1.Petroleum Resources of Nigeria

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A-0008 Preparedjo d+by theU S Depa ntof Energy U S Geological Survey\

- --y w y----- Am Ji . , -, l . k .:, ? - .? MUTER report on the .Petroleum Resa'ur~+& bf

the Federal Republicof NigeriaForeign EnergySupply AssessmentProgram SeriesOctober 1979


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DISCLAIMERThis report was prepared as an account of work sponsored by anagency of the United States Government. Neither the United StatesGovernment nor any agency Thereof nor any of their employeesmakes any warranty express or implied or assumes any legalliability or responsibility for the accuracy completeness orusefulness of any information apparatus product or processdisclosed or represents that its use would not infringe privatelyowned rights. Reference herein to any specific commercial productprocess or service by trade name trademark manufacturer orotherwise does not necessarily constitute or imply i ts endorsementrecommendation or favoring by the United States Government or anyagency thereof. The views and opinions of authors expressed hereindo not necessarily state or reflect those of the United StatesGovernment or any agency thereof.


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DISCLAIMERPortions of this document may be illegible inelectronic image products Images are producedfrom the best available original document


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Available fromNational Technical Infamation Service NTIS)U S Department of Carnmerce5285 Port Royal RoadSpringfield Virginia 22161

Rice : Rinfed copy:Microfiche: 3.00


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FOREWORD

This study of Nigerian oil and natural gasresobrces is. the first of proposed series of studiesunder the Foreign Energy Supply Assessment Program ofthe Department.of Energy. ~uture tudies will examinethe petrol eum resources of other world politicalentities, with a view to estimating the futureavailability of crude oil and natural gas.

Obviously, he economic and political decisionsof oil and.gas producing states, and those states whichhave potentially exploitable resources, will determinethe rate.at which oil and gas will be produced. Thelatitude of such decisions, however, will be constrainedby the physical limits of ultimately recoverable resources,and it is this latter dimension which these studieswill- ttempt to measure. .

There is no question that the supply of fossilfuel resources is limited. Thus, it is essential, fromboth a producerand from a consumer perspective, thatthese limits be defined as accurately as possible.With this knowledge in hand, it will then become possibleto plan more intelligently for our energy future.


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TABLE OF CONTENTS

Forewordxec u t iv e Summary i ve c t i o n I n t r o d u c t i o nO bj e ct iv e s of FESAP 3The L i m i t s o f FESAPP a r t i c i p a n t s 5D a ta S o u r c e s 6epor t Fo rmat 6S e c t i o n I B ack gr ou nd o f E x p l o r a t i o n andDeve lopmen t Hi s to ryA rea o f I n t e r e s tH i s t o r i c a l ~ x p l o r a t i o nand Developments 7Crude O i l P r o d u c t i o n 9E x p l o r a t i o n an d D ev e l o p m en tD r i l l i n g A c t i v i t yP r o d u c i n g O i l F i e l d sDomest ic Crude O i l Marke t and TradeN at u r a l Gas P ro du c t ion and Developmen t 18S e c t i o n 1 I I T h e F u t u r e P e t r ol e um P r o s p e c t sf N i g e r i a 20l t i m a t e l y R e c o ve r a bl e O i l 20u t u r e C r u d e O i l P r o d u c t i o n R a t e s 2 1R ema in in g R eco v e r ab l e N a t u r a las Resources 2 7F u t u r e N a t u r a l Gas P r o d u c t i o nC a p a b i l i t y 3 0S e c t i o n PV Geology and Resource Ana ly s i so f N i g e r i a 3 1Summary of Geology and ResourceA n a l y s i s 3 1G en e r a l O b s e r v a t i o n s 32T he Geol og y o f t h e N i g e r D e l t a 35Benin Form at ion 35Agbada Fo rm at io n 36Akata Form at ion 36The S u b s u r f a c e S t r u c t u r eo f t h e N i g e r D e l t a 37The Occur rence o f Hvdrocarbons 9G e o lo g ic a l C o n s id e r a t io n s i nR e s o u r c e A p p r a i s a l s 9P e r t i n e n t E x pl o r a t io n S t a t i s t i c s 43


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R e s o u r c e , A p p r a i s a l b y A n a l y s i sof F ind in g-Ra tes 45'B as ic S t a t i s t i c a l Data f o rt h e N i g e r D e l t a 50R es o u r ce A p p r a i s a l b y~ e o l o g i c a l n a l ys is 5 1Es t im ate s o f Remain ing O i l ResourcesUsing V ar iou s Methods 53Volu metr ic . Yie1.d by Pro vin ce 5 3Volumet r i c Yi e ld byProduc t ive Hydrocarbon B e l t s 53Gr id -average .Method 54F i n a l R e so ur ce A p p r a i s a l for O i lU s in g S u b j e c t i v e P r o b a b i l i t y M ethods 54R e ~ o u r c eA p p r a i s a l s f o r N a t u r a l G as 7E s e i m a t e s o f O i l F i e l d S i z e s a ndN\.mbers fo r Remaining Undiscovere dResources 0Appendices 63

FIGURES

F i g u r e 111 1F i g u r e 1 1 1 - 2F i g u r e 1 1 1 - 3

F i g u r e 1 1 1 - 4

F i g u r e I V - . lFigure IV-2

F i g u r e I V - 4Figure IV-5Figure IV-6

N i g e r i a L o ca t i o n Map w i t hP o p u l a t i o n C e n t e r s 8S e n s i t i v i t y of Maximum Pro duc t ionC a pa b i1 , i ty P r o f i l e s 2 2Maximum P r o d u c t i o n C ap ab i l i t y P r o f i l e sUsing Mean U lt im at e Recovery 23H i s t o r i c a l a nd P ro j e c t e d P r o d u c t io n .P r o f i l e s Based Upon t h e MeanUl t imate Recovery 2 4~ i s t o r i c a l ' a n d ro je c t ed C rude O i lP r o d u c ti o n f o r F i v e U l t i m a teRecover i es 28Gen era l G eo lo g ic a l Map ' o f t h eN i g e r D e l t a an d E n v i r o n s 3 3. F o r m a ti o n s o f t h e N i g e r D e l t aA r e a , N i g e r i a : 34D i f f e r e n t E v o l u t i o na l S t a g e s o f t h eT r ap s o f t h e N i g e r D e l t a 38Hydrocarbon Rich ' B e l t 4H i s t o r i c a l O i l F i e l d S i z e ~ i s t r i b u t i o n 6H i s t o r i c and P r o j e c t e d O i lF i n d i ng - R a t e s f o r N i g e r i a 48


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Figure IV-7 Frequency Distribution'of the Numberof Pays Per Field in the Niger Delta 52Figure IV-8 Probability Distribution of theRemaining Undiscovered Oil In-PlaceResources 56

Figure IV-9 Probability Distribution of theRemaining Undiscovered Gas In-PlaceResources 59

TABLESTable 11-1Table 11-2Table 11-3Table 11-4Table 11-5

Table 11-6Table 11-7Table 111-1Table IV-1Table IV-2Table IV-3Table IV-4Table IV-5Table IV-6Talbe IV-7

Crude Oil Production History of Nigeria 10Nigeria Historic Drilling Record 12Historical Peak Production ofNigerian Oil Fields 13The Major Oil Fields of Nigeria 15The Number of Producing Oil FieldsIdentified by Year of' iscovery andTheir Cumulative Production 16Nigeria's Crude Oil Exports, 1972-1977. 18Nigeria's Crude Oil ExportMarkets: 1977 19Alternative Production Schedulesfor Nigeria 26Ex poratory Footage Drilled in Nigeria. .44Probability Levels RemainingUndiscovered OilProbability Levels .RemainingUndiscovered Gas 58Resource Estimates Disaggregated by,Future Field Size ~ange'nd Number 60~isag~re~atedield Sizes 6Estimated Number of Small andand Intermediate Size Fields 61Estimated Number of Large Fields 62

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E X E C U T I V E SUMMARY

T he . R e pub l i c o f N ig e r i a r a nk s among t h e t e nl a r g e s t o i l p r o du c e rs of t h e w o rl d. P r od u c ti o n d u r i n gt h e f i r s t p a r t o f 1979 was a s h ig h a s 2 4 m i l l i o n b a r r e l sp e r d a y . I t i s a l s o on e o f t h e l e a d i n g e x p o r t e r s o fc ru de o i l , l l b u t thr t o f o u r p e r c e n t of N i g e r i a np r o d u c t i o n i s e xp o rt ed ; t h e r e s t i s u se d f o r d o m e st i cconsumption.S ev e r a l o f N i g e r i a s ~ f r i c a n e ig hb o rs a r ec r i t i c a l l y d ep e nd en t o n h e r o i l e x p o r t s . However, w e l lo v e r h a l f o f t h e ex p or te d o i l i s s o l d t o t h e Un ite d S t a t e s

a nd t o The Ne the r l a nds . A l though t h e U.S. s h a r e o fN i g e r i a n e x p o r t s i s e q u i v a l e n t t o o n l y t h r e e t o f o u rpe r c e n t o f U.S. dem and, t h e N ig e r i a n c r u de i s i m p o r t a n tbe c a us e o f i t s low s u l f u r q u a l i t y and hi g h g a s o l i n e y i e l d .T h i s cr u d e c h a r a c t e r i s t i c makes it d e s i r a b l e a l s o t oThe N e t h e r l a n d s s r e f i n e r i e s , w hich r e - ex p o r t r e f i n e dp r o duc t s t o We s te r n E ur ope an m a r ke t s .B ased o n g e o l o g i c a l an d e n g i n e e r i n g a n a l y s e s ,

it i s t h e o p i n i o n of t h e a d-hoc F o r ei g n ~ n e r g y u pp lyAssessment P rogram (FESAP) Task For ce t h a t N ig e r ia su l t i m a t e l y r e c o v e r a b l e o i l r e s o u r c e s may r a ng e from20.5 t o 4 1.5 b i l l i o n b a r r e l s . Through 1 97 7, 6 . 1 b i l l i o nb a r r e l s had b ee n p ro du ce d; t h u s , t h e r e m a in i n g r e c o v e r a b l eo i l r a n ge s f rom 1 4 4 t o 35.4 b i l l i o n b a r r e l s . About18:7 b i l l i o n b a r r e l s h av e b e en d i s c o v e r e d ; f ro m 1 . 8 t o22.8 b i l l i o n b a r r e l s r em ai n t o b e d i s c o v er e d . T he re i sa 95 p e rc e n t p r o b a b i l i t y t h a t a t l e a s t 1 .8 b i l l i o n b a r r e l sr em ain g t o b e di s c o v er e d , an d o n l y a 5 p e r c e n t p r o b a b i l i t yt h a t a t l e a s t 2 2.8 b i l l i o n b a r r e l s w i l l be foun d. Themean value (which i s a s t a t i s t i c a l a v er ag e) o f u n di sc ov er edr ec ov e ra b le o i l i s 8.4 b i l l i o n b a r r e l s , . an d h a s a 38p e r c e n t p r o b a b i l i t y of o c cu r re n c e.

t i s p o s s i b l e , w i t h an a c c e l e r a t e d e x p l o r a t i o na nd d ev elo pm en t e f f o r t , t h a t N i g e r i a s p r o d u c ti o n c ap a-b i l i t y c ou ld re a ch a peak l e v e l of 3.3 m i l l i o n b a r r e l sp e r d a y, o r a c o n s t a n t p r o d u c t i o n p l a t e a u o f a b o u t 3 .0m i l l i o n b a r r e l s p e r d ay . T h i s i s b a s ed o n e s t i m a t e s of


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u l t i m a t e r e co v e r a b le r e s o u rc e s o f 2 7.1 b i l l i o n b a r r e l sa nd t h e a s su m p t io n t h a t p r o d u c t i o n would b e c o n s t r a k n e do n l y by g e o l o g i c a l f a c t o r s . The p e r i o d o f p r o d u c ti o n a tt h i s l e v e l would be b r i e f , a p pr ox i ma te ly f i v e y e a r s .Lower c o ns t a n t p r od uc t i on p l a t e a u s , howe ve r, wh ic hr e f l e c t s l o w er r a t e s of e x p l o r a t i o n a nd de ve lo pm en t,a r e more l i k e l y . P r o du c ti o n p l a t e a u s g r e a t e r th a n2.0 m i l l i o n a nd l e s s t h an 2 .5 m i l l i o n b a r r e l s p e r dayc ou ld be m a in t a ine d f o r m ore t ha n a de c a de , a nd s uc hr a t e s would d e f e r s i g n i f i c a n t d e p l e t i o n o f N i g e r i a su l t i m a t e l y r e c o v e ra b l e o i l r e s o u r ce s t hr ou gh t h e 2 0thc e n t u r y .

N i g e r i a s e x p l o ra t i o n began e a r l y i n t h i s c e n tu r y ,a l t h o u g h t h e m odern e x p l o r a t i o n p h a s e be ga n i n 1 9 55 .Explora t ion and deve lopment may have peaked qu ick ly ,s 13 of 4 known, p r o b a b l e and p o s s i b l e g i a n t o i lf i e l d s w e r e d i sc o v er e d p r i o r t o 1 96 9, a nd t h e g r e a t e s tnumber o f f i e l d s w e r e d i sc o v e r e d i n t h e p e r i o d 1 96 5t h r o u g h 1 96 7. O ver t w o - t h i r d s o f t h e u l t i m a t e l y r e c o v e r -a b l e o i l o f N i g e r ia h a s b ee n d is c o v e re d .

Of t h e known pro duc ing f i e l d s , more th an two-t h i r d s h av e o r h a d s u s t a i n a b l e peak p r od u ct io n r a t e s( p ro d uc t i on f o r t h r e e s u cc e ss i ve y e a r s a t a s p e c i f i e dr a t e ) o f l e s s t h an f i v e m i l l i o n b a r r e l s o f o i l pe r y ea r ;n e a r l y .o n e -h a lf o f t h e f i e l d s l e s s t ha n t h r e em i l l i o n b a r r e l s p e r y e a r . Only s i x t e e n f i e l d s havep ro du ce d a t peak r a t e s r a n g i n g from 1 5 t o 45 m i l l i o nb a r r e l s p e r y e ar . I n e s se n ce , mo st o f N i g e r i a s o i lf i e l d s a r e s m a ll t o medium s i z e f i e l d s by w or ld s t a n d a r d s .F ut u re o i l d i s c o v er i e s a r e l i k e l y t o r e f l e c t t h i s t r e n d ,e ve n t hough s e v e r a l m ore g i a n t s may be f ound .

The n a t u r a l g a s r e so u r c e s o f N i g e r i a, u n l i k e t h eo i l r e s o u r c e s , a r e c o mp a ra ti ve ly u n d e ~ d e v e l o p e d . Never-t h e l e s s , s u f f i c i e n t e x p lo r a t io n h a s t ak e n p l a c e t o p er mi ta n as se ss m en t t o b e made of t h e p o t e n t i a l n a t u r a l g a sr e s o u r c e b a s e .The s t a t i s t i c a l mean e s t i m a t e o f u n di sc o ve re dn a t u r a l g a s i n d i c a t e s t h a t t h e r e r e 65 t r i l l i o n c u bi cf e e t ( T c f) o f r e c o v e r a b l e n a t u r a l g a s aw a i t i ng d is c o v e ry .

t i s 95 p e r c e n t pr o ba bl e t h a t a s l i t t l e a s 26 Tcf o,fa d d i t i o n a l r e c o v e r a b l e g a s may b e d i s c o v e r e d an d it i s


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five percent probable that as much as 130 Tcf of additionalnew gas discoveries may be found. Based on estimatesthat current proved reserves of natural gas are approxi-mately 50 Tcf, Nigeria s ultimately recoverable naturalgas resources may be in excess.of 100 Tcf. The NigerDelta, seaward from the cen.tra1 portion, may be the mostprospective for finding new natural gas resources.

Nigeria consumes about two to three percent, orless than 20 billion cubic feet, of its annual productionof natural gas. The remainder of the natural gas thatis produced along with crude oil, associated gas, Isflared, approximately three-quarters of a trillion (1012)cubic feet.

In summary, Nigeria has the capability to increaseoil production above its maximum historic level, assumingmore wells are drilled, and additional surface facili-ties .are installed. -However, t is likely that the yearly:av:er.ageroduction rate. will range from 2 millionbarrels to 2.5 million barrels per day over the next10 years or longer. In contrast, Nigeria s natural gasresources are underdeveloped and underutilized; a situationwhich is common among many oi1,producing countries of theworld.


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SECTION II n t r o d u c t i o n

Pe t ro leum* i s t h e b a s e l o ad ' e n er q y s o u r c e o f t h ewor ld . t s a t i s f i e s n e a r l y tw o -t hi rd s o f t h e w o r l d ' se n er g y n e e d s, w i t h c r u d e o i l a l o n e p r o v i d i n g o ne -h al fo f t h a t e ne rg y. I n a n e f f o r t t o r e du c e t h e, do m i na n ceo f c r u d e o i l i n t h e w o rl d en e rg y b a l a n c e , m os t i nd u s-t r i a l i z e d c o u n t r i e s , t hr ou gh c o ns e r va t i on and f u e ls u b s t i t u t i o n p ro gr am s , h a ve ha d n om in al s u c c e s s i nd e c r e a s i n g t h e i r c on su mp ti on o f o i l . N e v e r t h e l e s s ,e x c e p t f o r s e v e r a l r e c e s s i o n y e a r s , t h e demand f o r o i lh a s c on ti nu ed t o 'i n cr e as e , a l b e i t a t a s l ow er r a t e t h a nit d i d p r i o r t o 1974. I n a d d i t i o n , a g r e a t e r number o fd e v e l o p i n g c o . u n t r i e s a r e c om pe tin g f o r o i l i n t h e m ark et-p l a c e . M or eo ve r, s e v e r a l o f t h e p r o du c e r n a t i o n s h av ebecome g r e a t e r consumers of c ru d e o i l p r od u ct s .

C rude o i l p ro d uc e rs , and p a r t i c u l a r l y t h e e x p o rt -i n g n a t i o n s , a r e d et er mi ne d t o c o n t r o l t h e r a t e a t whicht h e i r r e m ai n in g p e tr o le u m r e s o u r c e s a r e de pl et ed . Byd e f e r r i n g de ve lo pm e nt , l i m i t i n g e x p o r t s , a nd r a . i s i n gp r i c e s , t h e p ro du ce r n a t i o n s a r e a b l e t o m a i nt a in t h ef o r e i g n e xc ha nge e a r n i n g s n e c e s sa r y t o a c h i e ve t h e i rr e s p e c t i v e econom ic and s o c i a l g o a l s . One o f t h e i rs t a t e d o b j ec t i ve s i s t o en c ou ra g e , t h r ou g h p r i c i n gp o l i c i e s , t h e i n d u s t r i a l n a t i o n s t o de ve lo p a l t e r n a t i v ef u e l fo rm s, and t h er e by s lo w t h e r a t e a t which t h e i rf i n i t e re s ou r ce s a r e d e p le t ed .

The co n s id e r a t io n o f p r o d u ce r co u n t r y ' s e con om icg o a l s a s t h e c r i t e r i a f o r d e t er m in in g r e s p e c t i v e produc-t i o n r a t e s and e x p o r t s i s t h e a n t i t h e s i s o f t h e h i s t o r i cr e l a t i o n s h i p o f s u p p l y a nd demand. H i s t o r i c a l l y , demandwas u n c o n s t r a i n e d a s s u p p l y re s po n de d t o b u y e r s ' n e e d s .D uring t h e 1 9 7 0 ' ~ ~o n s t r a i n t s h a v e . b e e n p l a c e d on s u p p lya v a i l a b i l i t y . The d e p a r t u r e from t h e t r a d i t i o n a l s up pl y/demand r e l a t i o n s h ip and t h e s h i f t i n t h e c o n t r o l of o i ls u p p l i e s , f rom t h e p r i n c i p a l l y we s te r n o i l com panies t on a t i o n a l g ov er nm en ts ,' h av e c r e a t e d a g r e a t d e a l o f ,u n c e r t a i n t y among t h e c on sum ing n a t i o n s a s t o t h e f u t u r ea v a i l a b i 1 i . t ~ nd p r i c e s of c ru de o il :

P et ro leum i n t h i s r e p o r t i n c l ud e s c ru de o i l , n a t u r a lg a s l i q u i d s .and n a t u r a l g a s .


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The uncertainty in the future market can besomewhat minimized if an insight can be developed as to:the quantities of discovered andundiscovered recoverable petroleumresources remaining among the respectiveproducers, and the feasible rates atwhich such resources can be developedand produced;the overall capital requirements of theoil exporting countries necessary toachieve their respective social, economicand political goals, and the oil andnatural gas resource development necessaryto sustain the production and exportsessential for maintaining foreign earn-ings; and finally,the events or political interests whichmight cause development, production rates,and exports to digress upward or downwardfrom the normal rate consistent withgoal achievement.

.O.f he., oints cited,.bove, the most fundamentalconcern facing the petroleum exporting nations isthe physical limits of the recoverable petroleum resourcebase. Each country has its own finite limit of crudeoil and natural gas. If the export of petroleum iscritical to its economy, succe'ss in achieving economic,social, and political goals will depend on the size ofits recoverable resource base and the capability toproduce and export petroleum.

The Foreign Energy Supply Assessment Program(FESAP) is the government's first systematic effort todetermine the quantities of conventional petroleuml/remaining and recoverable within each country of tEe world.

1/ Conventional petroleum includes crude oil and naturalgas recoverab1e.b~rilling, but excludes crude oilrecoverable by the use of tertiary recovery methods,or from deposits of tar.sands and shales and naturalgas associated with coal and geopressured water zones,etc.


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This study incorporates geological and engineeringanalyses with statistical techniques to estimate theremaining undiscovered recoverable resources and todetermine the rate at which such resources may be produced.

The Nigerian report is the first of a series ofFESAP country reports. The methodology and assumptionsused herein are described in the text or in the appropriateappendices.

The estimates represent the views of th ad hocstudy team consisting of Department of Energy and theU.S. Geological Survey (Department of the Interior)personnel, and should not be regarded as an officialDepartment of Energy or Interior position.Objectives of FESAP

The initial objective of the FESAP is to assessthe quantity of recoverable crude oil and natural gasresources, including the undiscovered recoverableresources, remaining within the petroleum.exporting,countries and the potential rate at which such resourcescan be produced.Petroleum resource assessments provide a basisfor determining a maximum production rate and the duration

petroleum may be available to world markets. Neverthe-less, in the short-term, the most likely rate may be afunction of capital requirements of the exporting countryand the importance of petroleum exports in satisfying thoserequirements.Nigeria was selected as the first country studybecause it has a comparatively homogenous geologicalenvironment for the occurrence of petroleum and it isfairly well explored and developed.The objectives of the FESAP country series are

achieved in the following manner:An assessment is made of the reported provedreserves2/ and the historical production rates;

2 ,~efinitions f Reserves and ~esources s well as ageological time and age chart is included in Appendix E.


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A geological analysis is made of thecountry sedimentary basin.(s) andgeological structures, which produceor have the potential to produceeconomic quantities.of petroleum;An estimate is made of the remainingundiscovered oil and natural gas in-place,the undiscovered recoverable petroleumresources, and the number of fields tobe discovered;A maximum production capability profileis determined using the total resourcebase; andFeasible production rates are projectedfor a per.iod until the .known proved reservesand the estimated remaining undiscoveredrecoverable resources near depletion.

The Limits of FESAPThe FESAP analytical process .is not a reservoirengineering study. However, a sufficient number ofgeological and engineering parameters are known to permit

reasonable estimates to be made 0.f the original oil in-place and the remaining proved reserves of many.fields.Also, the use of field-analogs. ermits judgments to bemade in instances when minimal information is available.It is acknowledged. hat national pol.itica1, socialand economic goals may influence exploration and develop-ment rates, thus ompounding the difficulties of estima-ting future production rates. However, the FESAPprojections of future production rates are based on thecontinuation of exploration and development, and on theperceived reservoir production capabilities , constrainedonly by geological factors.FESAP does not overlay non-engineering parame.terson the production factors, such. s an economic decision,which might result in slowing the rate of explorationand development, or reducing the optimum production of wells.


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The FESAP series is a product of cooperationbetween geologists, engineers, statisticians and.mathematicians, nd other skills in the Departments ofEnergy and of the ~nterior. The principals involvedin preparing the Nigerian report are:

Department of Energy:International Affairs-

Arthur J. Warner, FESAP Program ManagerJudith Reynolds, AssistantEnergy Information Administration-

Calvin Kilgore, Director, InternationalData AnalysisW. D. Dietzman, Supervisory,PetroleumEngineerHenry Weigel,, perations Research AnalystJohn wood, Petroleum EngineerVelton Funk, Petroleum EngineerLulli Crump, Mineral Sp,ecialist

Policy and Evaluation-Phyll is Kline,. Policy Alialyst

Department of the Interior, U.S. Geological Survey:Office of Eneryy Resources-

Oswald Girard, Petroleum GeologistHarold Krivoy, Physical ScientistResource Appraisal Group-

Betty Miller, Program Chief, InternationalResource AppraisalKurt Carlson, Mathematical GeologistRussell Allen, Geologist~ ~ n nears, Librarian


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Data SourcesThe data used in preparing the analysis conesfrom a variety of.pub1i.c sources including,the commercialinformation services of Petroconsultants, S.A.complete list of references is provided in the biblioqraphy.

Report FormatThe report is divided into four sections andfive appendices:Section I ~ntroductionSection I1 Background of Exploration

and Development HistorySection I The Future PetroleumProspects of NigeriaSection IV Geology and Resource~nalysis f Nigeria

Appendix A Analysis Report: NigeriaAn Assessment of Crude OilPotentialAppendix Petroleum Geology of theN,iger DeltaAppendix C Geologic Time Scale;Definitions; ReferencesAppendix D Statistical Data HistoricalResume of Oil Field,Production


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SECTION IBackground of E xp lo ra ti on and Development His to ry

A rea o f I n t e r e s tThe Republic of Niger ia i s l o c a t e d n o r t h o ft h e c e n t r a l p o r ti o n of t h e w e s t c o a s t o f A f r i c a . t sa r e a l s i z e i s ne ar ly 356.4 thousand square m i l e s (923thousand squa re k i lo me t e r s ) lo c a te d mos t ly betwe en

4 ON t o 13ON l a t i t u d e and 3OE t o 14OE longi tude . TheNiger De l ta i s t h e p r i n c i p a l p e t r o l e u m p r o v i n c e o fN i g er i a, and t h e a r e a o f i n t e r e s t i n t h i s s tu d y. TheDelta comprises some 4 thousand square m i l e s (106t ho us an d s q u a r e k i l o m e t e r s ) . O t he r a r e a s o f i n t e r e s ti n c l u d e t h e c on te rm i no us o f f s h o r e p o r t i o n o f t h e D e l t a ,approximate ly 33 thousand square m i l e s (85 thousands q u a r e k i l o m e t e r s ) , an d t h e s e d im e n ta ry b a s i n s a l o n gt h e Niger and Benue Riv ers . F ig ure 11 1 shows theN ig er D e l t a a r e a an d t h e i m p o r t a n t p o p u l a t i o n c e n t e r s .N i g e r i a s p o p u la t io n i s n e a r l y 67 m i l l i o n p e op l e.H is to r i c a l Exp lo ra t ion a nd De ve lopme n t s

The s e a r c h f o r o i l i n N i ge r ia b egan d u r i n g t h epe ri od 1908 t o 1914, when a German company, t h e Ni ge ria nBitumen Company, d r i l l e d 4 w e l l s i n t h e c o a s t a l r e g io n s ,55 mi le s eas t o f L ag os. The d r i l l s i t e s w e r e s e l e c t e don t h e b a s i s o f s u r f a c e s e e p s o f o i l w hich o c c u rr e da long C re tac e ous roc k ou tc rops . No s i g n i f i c a n t q u a n t i -t i e s of o i l were found.

A h i a t u s f o llo we d u n t i l t h e l a t e t h i r t i e s ,when t h e Shel l-D Arcy Pe tro le um Development Company bega nsu r f a c e mapping, s e i sm ic a nd g r a v i t y su rve ys , a nd a c o r ingprogram i n and sou th o f t h e Benue Va l l e y , \kh e re ge o log ic a ls t r u c t u r e s a r e mappa ble on ou tc ro ps o f C re ta ce ous a ge .The work was di sc o nt in u ed d u ri ng World War 11.t h i r d p e r i o d o f e x p l o r a t i o n began i n 1 94 7, w i t ha n e x t e n s i v e g e o l o g i c a l f i e l d s u rv e y and a e r i a l p ho to gr a-phy campaign. The e xp lo r a t io n progra m a l s o used g r a v i -me t r i c a nd se i smic su rve ys t hr ou gh ou t N i g er i a t o i d e n t i f yt h e o i l p r o s p e ct i v e g e o l o g i ca l s t r u c t u r e s . Most o f t h e


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ase503690 12 77

igure 11 1.


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d r i l l i n g w hich f o l l ow ed t oo k p l a c e i n t h e n o r t h e r n p a r to f t h e D e l t a a nd i n t h e C r o ss R i v e r V a l l e y o n C r e t a c eo u sa nd E oc e ne p r o s pe c t s . I n 1951 t h e f i r s t de e p w e l l wasd r i l l e d t o 11 ,228 f e e t . t was dry .

The f i r s t co m me rc ia l d i s c o v e r y o f o i l was madei n 19 56 , s o u t h o f t h e e a r l i e r p l a y s , a p p ro x i m at e ly 75k i l o m e t e r s w e s t o f P o r t H a rc ou rt . The O l o i b i r i f i e l dd i s c o v e r y w e l l was c o mp le te d i n a f o r m a t i o n o f T e r t i a r ya g e , a much yo un ge r f o r m a t i o n t h a n t h e e a r l i e r C r e t a c e o u st a r g e t s . A lth ou gh t h e O l o i b i r i f i e l d was a di s a p p o in t -m e n t , a s it n e v er p ro du ced i n e x c e s s o f m i l l i o n b a r r e l si n a ny y e a r , it pr oved t h e e x i s t e n c e o f c om me rc ia l accumu-l a t i o n o f o i l . A s ec on d f i e l d was d i s c o v e r e d d u r i n g t h esame y e a r a t Afam, a p p r o x i m a t e l y 30 k i l o m e t e r s n o r t h e a s to f P o r t H a r c o u r t ; it p r o d u c e d n e a r l y 4 m i l l i o n b a r r e l sp e r y e ar f o r s e v e r a l y e a r s . I n 1958 , t h e f i r s t g i a n to i l f i e l d , Bomu, l o c a t e d 75 k i l o m e t e r s s o u t h e a s t o f P o r tHa rco ur t , was d i sc ov er ed . The Bomu f i e l d p roduces ov er20 m i l l i o n b a r r e l s p e r y e a r an d u l t i m a t e l y i t c o u l dy i e l d o ve r 500 m i l l i o n b a r r e l s o f o i l . The f i r s t o f f -s h o r e g i a n t f i e l d , O kan, was d i s c o v e r e d i n 19 64 , on t h en o r t h e a s t ed ge o f t h e N i ge r i an c o n t i n e n t a l s h e l f .

S in c e t h e f i r s t commercial d i s co v e ry of o i l i nN i g e r i a , o v e r 200 o i l a nd n a t u r a l g a s f i e l d s h av e b e end i s c o v e r e d .Crude O i l P r o d u c t i o n

N i g e r i an o i l p r o d u c t io n b eg an i n 1958. I n o ve rtwo d e ca d es , o i l p r o du c t i o n h a s i n c r e a se d t o a r a t e i ne x c es s o f 2 m i l l i o n b a r r e l s p e r d a y, o v e r t h r e e - q u a r t e r so f a b i l l i o n b a r r e l s p e r y e a r ; m aking N i g er i a t h e s i x t hl a r g e s t o i l p ro du ce r i n t h e w o rld . A t o t a l o f 6 .1b i l l i o n b a r r e l s o f c r u de o i l h a s b ee n pro du ced t hr ou gh1 97 7. A p pr ox im at el y o n e - f o u r th o f c u r r e n t c r u d e o i lp r o d u c t i o n comes fro m o f f s h o r e f i e l d s . A s shown i nT a b le 11-1 N i g e r i a s a n n u al ,p r o d u c t io n h a s i n c r e a s e ds t e a d i l y , e x c e p t f o r two p e r i o d s o f d e c l i n e . Thef i r s t p r o d uc t io n r e v e r s a l o c c ur r ed i n 1967 an d 1 96 8,a s t h e r e s u l t o f t h e B i a f r a n War. The se co nd o c c u r r e di n 1 9 75 , a s t h e r e s u l t o f t h e c o mb in a ti on o f w o rld -w id ed e c l i n e i n c r u d e o i l demand, and t h e i n c r e a s e d a v a i l -a b i l i t y o f c r ud e o i l f ro m s uc h new s o u r c e s a s t h e N or thSea and Alaska .


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T a b l e 11 1

Year.

Crude O i l P r o d u c t io n H i s t o r y o f N i g e r i a(Thousa nd B a r r e l s )

D a i l y A ve ra ge T o t a l Cumula t ive

sour ce : Mi n i s t ry o f Mines and Power , Pe t ro leum Di v i s i on sAnnua l Repor t s Ce nt ra l Bank of N ige r ia -Economicand F inanc ia l Review i r e c t Communications t o t h eS e c r e t a r i a t .


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O v e r a l l , f ro m 1 95 8 t o 1 9 77 , N i g e r i a s p r o d u c t i o ni n c r e a s e d a t an av e r ag e an n u al r a t e of n e a r l y 37 p e r c e n t ,and a t a n av er ag e r a t e o f o v er 2 p e r c e n t p e r y e a r d u r i n gt h e l a s t t e n y e a r s . The h i g h e s t a n nu a l p r o d u c t io no c c u r r e d i n 1 9 74 , when N i g e r i a p r od u ce d 8 2 3 .1 m i l l i o nb a r r e l s .

E x ~ l o r a t i o n nd D e v e l o~ m en tD r i l l i . n s A c t i v i t yFrom 1956 th rou gh 1977 , 2 ,7 54 .h o le s have beend r i l l e d i n t h e s e a r ch an d d ev elo pm en t o f o i l an d n a t u r a lg a s i n N ig er ia . The h i s t o r i c a l d r i l l i n g a c t i v i t y i sshown i n Ta b le 11 2. Of t h e t o t a l , a p p r o x i m a te l y o ne -f o u r t h , o r 759 w e l l s w e r e d r i l l e d a s e x p l o r a t io n w e l ls .N e a r ly h a l f , 346 o f t h e e x p l o r a t o r y w e l l s , w e re s u c c es s -f u l i n f i n d i n g o i l o r n a t u r a l g a s. Of t h e s e , 304 w e l l s ,

o r n e a r l y 90 p e r c e n t , f ou nd o i l .A t o t a l o f 1 , 9 97 d ev el op m en t w e l l s h av e be end r i l l e d , o f which 85 p e r c e n t o r 1 , 69 9 w e l l s we r e s uc c e s s -f u l l y com pleted a s o i l o r n a t u r a l g a s w e l l s . Of th es e ,96 p e r c e n t o r 1 , 6 3 8 deve lopment w e l l s we re c om plet e d a so i l w e l l s ; 298 de ve lo pm en t w e l l s w e r e d r y .I n t h e a g g r eg a t e , N l g e r i a h as ha d a h i g h f i n d i n gs u c c e s s a v e r a g e , a s 2 ,0 4 5 e x p l o r a t o r y a n d d e ve lo p m en tw e l l s o r n e a r l y t h r e e - f o ur t h s o f t h e t o t a l w e l l s d r i l l e df ro m 1 95 6 t h r o u g h 19 7 7, f o u n d o i l a nd / or n a t u r a l g a s .D r i l l i n g a c t i v i t y d u ri ng t h e 21-year h i s t o r ypeaked i n 1972, when 258 w e l l s were d r i l l e d , o r 11 p e r -c e n t o f t h e t o t a l . However, e x p l o r a t i o n d r i l l i n g p eak ed5 y ea r s p r i o r , i n . 1 9 6 7 , when 79 e x p l o r a t o r y w e l l s 1 0p e r c e n t o f t h e t o t a l , were d r i l l e d .

P r oduc ina O i l F i e l d sA pp ro xim ate ly 1 30 f i e l d s p ro du ce o i l i n N i g e r i a .N e ar ly o n e- h al f o f t h e o i l f i e l d s ea ch ha ve p ro du ce d

l e s s t ha n 5 m i l l i on b a r r e l s o f o i l y e a r l y a t t h e i r peak-a nd o ve r o n e - t h i r d h av e pr od uc ed l e s s t h a n o ne m i l l i o nb a r r e l s p e r y e a r , a s shown i n T ab l e 11 -3 .

1 Produced a t t h e s p e c i f i e d r t e f o r a t l e a s t t h r e es u c c e s s i v e y e a r s .


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Table 11-2IN i g e r i a H i s t o r i c . D r i l l i n g R eco rd -(1956-1977)

E x p l o r a t o r y e l l s Development WellsY e a r i l Gas Dry T o ta l i l Gas Dry Tota l

TOTAL

GrandT o t a l

1 Source : A mer ican A sso c i a t i on o f Pe t ro l eum G eo l og i s t s ( exc ep t w here no t ed ) .2 / Source : Pe t ro co ns ul ta nt s SA Geneva Swi tzer land .-3/ T he t o t a l o f w e l l s shown i n 19 56 c o u l d n o t b e c l a s s i f i e d a s t o s t a t u s , t h u sa c c o u n t i n g f o r the d i sc r ep a n cy i n t h e t o t a l s .


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Table 11-3H i s t o r i c a l P ea k P r o d u c t io n R a te o f

N i g e r i a n O i l F i e l d s .

Year ly AverageNumber of Produc t ion RangeF i e l d s 2 / Gr e a t e r T ha n:

50 M i l l i o n B a r r e l s4 5 M i l l i o n a r r e l s40. M i l l i on ~ a r r e l s.35 Mil- l ion a r r e l s30 M i l l i on a r r e l s25, M i l l i o n B a r r e l s20 illio ion a r r e l s1 5 M i l l i o n B a r r e l s10 M i l l io n B a r r e l s5 illi ion B a r r e l s3 M i l l i o n a r r e l s1 M i l l i o n B a r r e l s0 .5 M i l l i o n a r r e l se 0 . 5 M i l l i o n B a r r e l s

105 TOTAL

1 Peak b as e d on a v e r a ge p r o d u c t i o n w i t h i n t h e r a n g e f o ra t l e a s t 3 s u c ce ss iv e y e a r s d u r in g t h e l i f e o f t h ef i e l d . S ee A pp en di x D f o r d e t a i l e d f i e l d p ro du c t io nd a t a .21 F i e l d s w i t h a tw o-y ea r p r o d u c t io n h i s t o r y o r l e s s a r en o t in c lu d e d ; t h u s , t h e r e i s a d i s c r e p a n c y b et we en t h ef i e l d t o t a l s o f t h i s t a b l e and Appendix D. A l s o ,a g gr eg a te d f i e l d p r o d u c ti o n i s c o n si d er e d a s one f i e l d


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Al th ou gh f i v e N ig e r ian f i e l d s had p ro du cedm ore t h an 30 m i l l i o n b a r r e l s y ea r ly , t h rou g h 19 77 ,none had p roduced more than 50 m i l l i o n b a r r e l s per yea r .t s e s ti m a t ed t h a t s e ve n of N i g e r i a s f i e l d sa r e known g i a n t f i e l d s . I n a d d i t i o t h e r e a r e t h r e ep r o b a b l e a n d f o u r p o s s i b l e g i a n t s . - . 3 he e a r l i e s tg i a n t , Bomu f i e l d , was d i scover ed i n 1958 , and t h e mostr e c e n t , Nembe Creek , was d isco ver ed i n 1973. A l l b u to ne of t h e g i a n t f i e l d s w ere d is c o ve r e d w i t h i n t h eper io d 1958 t o 1969 , a s shown i n Tab le 1 1 4 . The knowng i a n t f i e l d s ac co un t f o r o ve r on e- fo ur th of N i g e r i a sh i s t o r i c p r o d u c t i o n t h r ou g h 19 77 , b u t t h e y p r o vi d e d o n l yon e- f i f t h o f t h e o i l p roduced i n 1977. The seven knowng i a n t s and t h e s ev e n a p p a r e n t g i a n t s , i n c l u d i n g a f ew

a d d i t i o n a l f i e l d s whose p r o d u c ti o n r e c o r d s c a nn o t bed i s ag g reg a t ed f ro m th e g i a n t s , h av e prod uced ab o u t on e-h a l f o f N i g e r i a s h i s t o r i c pr o d uc t io n , and o v e r o n e - th i rdo f t h e 1977 p r o d u c t i o n , t h u s i n d i c a t i n g t h e i m p o rt a nc eo f t h e s e few m a jo r f i e1 d .s a s s o u rces o f o i l .t s l i k e l y t h a t a few more g i a n t o i l f i e l d s

w i l l b e d i s co v e red a s ex p l o r a t i o n p ro g re s s e s . However,t h e s t a t u s o f N i g e r i a s d ev elop me nt s wel l advanced ;t h u s , t h e p r o b a b i l i t y of f i n d i n g many more g i a n t f i e l d ss remote. t s a l s o p o s s i b l e t h a t a s d ev elo pm en tc o n t i n u e s , some of t h e g i a n t s i n t h e p r o b ab l e o r p o s s i b l eca t e g o ry may n o t ach i ev e t h a t r an k .

The pe ak number o f 1 7 o i l f i e l d d i s c o v e r i e so c c u r r e d i n 1 96 5, a nd n e a r l y o n e - t h i r d o f N i g e r i a sp ro du ci ng o i l f i e l d s w ere d is c o ve r e d d u r in g t h e t h r e e -ye ar pe r io d from 1965 through 1967. The cum ulat iv ep r o d u c t i o n t h r ou g h 19.77 fr om t h o s e d i s c o v e r i e s t o t a l so v e r two b i l l i o n b a r r e l s . S i n c e t h a t t i m e ; t h e numbero f o i l f i e l d d i s c o v e r i e s h av e d e c l i n e d . T a b le 11-5 showst h e number o f o i l f i e l d s d is c o ve r e d p e r y e a r and t h ecu m u la t i v e p ro d u c t i o n b ack d a ted t o t h e y ea r o f d i s co v e ry .

2 P a r t l y b as ed on t h e r e p o r t e n t i t l e d , G i an t O i l F i e l d sand World O i l Res ourc es, R icha rd Nehrin g, Rand,June 1978, p . 138.


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TABLE 11-4I/THE MAJOR OILFI ELDS OF NIGERIA-

1977 CUMULATIVE PRODUCTION DISCOVERYRANK/FIELD PRODUCTION THROUGH 1977 YEAR

2/ (MILLION BARRELS)GIANTS1. BOMU 10.92. IMO RIVER 21.23. OKAN* 17.44. MEREN* 26.75. JONES CREEK 30.56. FORCADOS YORKI 38.47. NEMBE CREEK 3 11.7

TOTAL 156.8 1,715.1

PROBABLE GIANTS:8. KOKORI 4/9. OLOMORO-lo. OBAGI?

TOTAL 55.9 714.3

POSSIBLE GIANTS:11. DELTA SOUTH* 13.712. M?BEDE~/ 20.113. EKPE* 12.814. ODIDI 17.7

TOTAL 64.3 577 4GRAND TOTAL 277.0 3,007.4

Indicates offshore fields.1/ Principal Source: Giant Oil F ields and Florld Oil Resources,Richard Nehring, Xand, June 1978, p 138.2/ Definition: Contains at least 500 million barrels of.recoverable oil3 Eianked on the basis of paper presented at AAPG-SEPM Annual ConventionApril 1-4, 1.979.4/ Also includes the production of the Afiesere, Eriemu and Oweh fields.5 Obagi field includes the production of the Erema field.6/ M.LBede ield i.n.cludes he production of th bvcha field...


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Table 11 5The Number of Producing i l F i e l d s I d e n t i f i e dBy Year of Disc overy and The ir Cumu lative Produc t ion

Year of ~ i e l d No. of Cumulat ive Produ ct ionDiscovery

TOTAL 1 2 9

Through 19772/( M i l l io n B a r r e l s )

1 Fi e l ds which have p roduced o r a r e on p roduc t i on:non-producers a r e not counted .2 Some d i s t o r t i o n s o c c ur a s a r e s u l t of t h e p r o d u ct i onof s e v e r a l f i e l d s w i t h v a r i o u s di s co v e ry - ye a rsbe ing aggrega ted .3/ Actua l cumula t ive produ c t ion s 6 1 b i l l i o n b a r re l s ;t h e d i f f e r e n c e s . i n p a r t due t o rounding of numbersb u t a l s o due t o minor e r r o r s i n f i e l d p r o du c ti onda t a which canno t be . account ed fo r . Th i s r e po r ts ho ul d n o t b e co n s id e re d t h e o f f i c i a l s o u r ce o f d a t a .


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Domest ic Crude O i l Marke t and TradeC rude o i l makes a s i g n i f i c a n t c o n t r i b u t i o n t ot h e N i g e r i a n e co no my .w The e x t e n t t o w hich c r u d e o i l

w i l l c o n t i n u e t o b e a n i m p o r t a n t e x p o r t com modity d e pe n dso n t h e q u a n t i t y o f c r u de o i l t h a t r em ai ns t o b e d i sc o v er e da nd d e v e l o p e d , t h e r a t e a t which t can be p roduced , andt h e a v a i l a b i l i t y of s u p p l y i n e x ce s s of d o me st ic c on su mp ti on .N i g e r i a s c ru de o i l i s m a rk et ed i n a l m o s t e v e r yp a r t o f t h e wo rl d. A p pr ox im at el y t h r e e p e r c e n t o f i t sp r o d u c t i o n i s consumed do m es t i ca l l y . Tab l e .T I-6 p r ov id esa s i x -y e a r h i s t o r i c a l resume o f t h e N i g er i an c r u d e o i le x p o r t s a nd m a r k e t s , D u ri ng t h e l a s t t h r e e y e a r s ,N i g e r i a c onsumed a n a v e r a g e o f 23.9 m i l l o n b a r r e l sa n n u a l l y , 6 5.5 t ho u sa n d b a r r e l s p e r d a y. D u ri ng t h esame p e r i o d , p r o d u c t i o n , a v e ra g e d 7 43 .8 m i l l i o n b a r r e l sa n n u a l l y , 2 .0 3 m i l l i o n b a r r e l s p e r d ay . The p r i n c i p a lm a r k et s f o r N i g e r i a n c r u d e i n 1977 w e r e t h e U n it ed S t a t e sa nd The Ne the r l a ndsZ / ; t he y i j ac c oun t f o r ov e r . 5 0 p e r c e n t .o f N i g e r i a s e x p o r t s . The p e r c e n ta g e t h a t N i g e r i a n c r u d er e p r e s e n t s o f t h e i m p o r ti n g c o u n t r i e s s t o t a l demand

i s shown i n Tab le 11-7.Na tu ra l Gas P r od uc t io n and Deve lopment

The n a t u r a l g a s i n d u s t r y o f N i g e r i a i s under -d e v e l o p e d b e c a u s e o f l i m i t e d d o m e s t i c demand a nd f o r e i g nm a r k e t i n g o p p o r t u n i t y . The o p p o r t u n it y t o u t i l i z en a t u r a l g a s f o r g r e a t e r . d o m e s t i c u s e and e x p o r t s h asf u t u r e p o t e n t i a l g

D o me st ic co n su m p ti on o f n a t u r a l g a s b e ga n i n1 96 3, when on e b i l l i o n c u b i c f e e t , ( B c f ) w e r e consumed.S i n c e t h e n , c o ns um p ti o n h a s i n c r e a s e d t o 1 8 .5 Bcf i n 1 97 6.T h i s r e p r e s e n t s a p p r o x im a t el y 2 p e r c e n t o f N i g e r i a n g a sp r o d u c t io n . T o t al n a t u r a l . g a s p r o d u c t i o n i n 1 9 77 wasa n e s t i m a t e d 7 57 B c f ; . n e a r l y 739 Bcf w e re f l a r e d u3 C rude o i l e x p o r t s a cc ou nt ed f o r 9 1 p e r c e n t o f N i g e r i a s-

f o r e i g n ex ch an ge e a r n i n g s , e q u i v a l e n t t o o ve r 9 b i l l i o nU .S.. d o l l a r s ( 1 9 7 8 ) .4 1974 - 24.6 m i l l i o n b a r r e l s o f o i l ; 1975 24.5 m i l l i o n- b a r r e l s ; an d ,1976 2 2 . 9 m i l l i o n b a r r e l s .5/ M ost o f The N e t h e r l a n d s s i m p o r t s a r e r e - e x p o r t e d , a s- r e f i n e d p r o du c t s.6/ The e x p o r t o f N i g e r i a n l i q u e f i e d n a t u r a l g a s ( L N G ) .t o- t h e U n i t e d . S t a t e s h a s b ee n p r op os ed .7 Not marketed.-


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TABLE 11-6NIGER IA S CRUDE OIL EXPORTS, 19 72 -1 97 7(THOUSAND BARRELS PER DAY

DESTINATIONNORTH AMERICAof wh ich :Canada

USALATIN AMERICA.o.f whichB r a z i lT r i n i d a d T o b a g oUruguayB r i t i s h T e r r i t o r i e sWESTERN EUROPEo f wh i c h :Belgium LuxembourgDenmarkF r a n c eGermany F .I t a l yN e t h e r l a n d sNorwaySwedenUni ted KingdomAFRICAo f wh i c h :GhanaI v o r y C o a s tS e n e g a lS i e r r a L e on eASIA AND .FAR EASTof wh ich :J a p a nTOTAL 2 ,030 .2 2 ,013 .2 1 ,7 13 . 3 2 ,179 .4 1 ,97 8 .1S o u r c e : OPEC A n n ua l S t a t i s t i c a l B u l l e t i n 1 9 77 S e p te m b e r 1 9 7 8 , p . 7 1.N o te : No e f f o r t h a s b ee n made t o r e c o n c i l e b a l a n c es .


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Table 11-7Nigerian Crude Oil Export Markets: 1977(Thousands Barrels Per Day)

Niger ianCrudeCrude TmpoEes As PercentImports Percent of TotalCrude :From. of Country s NigerianDestination ema an / ~i~eria+/ Demand Crude xportsUnited StatesBrazilBritish Terr. .Not Specified*BelgiumLuxembourgDenmarkFrance

. Germany F.R.ItalyNetherlandsNorwaySwedenUnited KingdomNot specified0GhanaIvory CoastSenegalSierra ~eoneNot specified+

Totals 2,030.2 81.421

NA:Not Available1/ International Petroleum Annual, June 1, 19792/ Organization of Petroleum Exporting countries,Sept. 78, p.71.3/ Because of unavailable data, this total is not complete.

* in Latin AmericaO in Western Europein Africa


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SECTION I11The Fu tu re Pe t ro leu m Pr o s p ec t s o f N ig e r i a

Ul t imate lv Recoverab le O i lP e tr o le u m e x p l o r a t i o n i n N i g e r i a t h r ou g h 1 977r e s u l t e d i n t h e d i sc o v e r y of a p pr o xi m a te l y 18.7 b i l l i o nb a r r e l s of r e c o v e r a b l e o i l ; c u m u l at iv e p r o du c t io nt o t a l l e d a pp ro xi m at el y 6 .1 b i l l i o n b a r r e l s . T h e r ef o r e,1 2 .6 b i l l i o n b a r r e l s o f p rov ed r e s e r v e s r em a in t o b er e c o ve r e d from t h e f i e l d s of N i g e r i a d i s c ov e r e dthrough 1977.Pos t-19 77 ex p lo ra t i o n and d ev elop m en t d r i l l i n g

w i l l r e s u l t (and h a s r e s u l t e d ) i n f u r t h e r d i s c o v e r i es anda d d i t i o n a l c a p a b i l i t y t o p ro du ce . An a n a l y s i s of t h eh i s t o r i c a l a c t i v i t y a n d t h e ge olo gy of t h e N ige r D e lt ap r o vi d e s a b a s i s f o r e s t i m a t i n g t h e u nd is co ve re d q u a n t i t i e so f c r u d e o i l t h a t may b e f ou nd a s e x p l o r a t i o n andd ev e lo p m en t c0 n t in u e .UThe a n a l y s e s of u n d is c o v er e d r e c o v e r a b l e o i lr e s o u r c e s i n d i c a t e t h a t from 1 .8 b i l l i o n t o 22.8b i l l i o n b a r r e l s o f o i l rem ain t o be d is co ve re d. Thelow e s t im a t e h as a 95 p e r c e n t . p r o b a b i l i t y and t h e h i g he s t i m a t e h as a 5 p e r ce n t p r o b a b i l i t y . The s t a t i s t i c a l

m e a n . e s t i m a t e o f u n di sc o ve r ed r e . c o v e r a b l e o i l s 8.4b i l l i o n b a r r e l s 2JB ased on t h e s t a t i s t i c a l mean v a l u e o f u n d is c ov e re do i l r e s o u rc e s and prove d r e s e r v e s , a s of t h e e n d o f . 1 9 7 7 ,21 . 0 b i l l i o n b a r r e l s , o f o i l rem ain t o be r ec ov er ed . S i x t yp e r c e n t o f t h e r e m a i n i n g , o i l s p r o v e d r e s e r v e s a s s o c i a t e dw i t h d i s c o v e r e d f i e l d s . The u nd is c ov e re d r e c o v e r a b l er e s ou r c es o f 8.4 b i l l i o n b a r r e l s w i l l b e fou nd i n new f i e l d s ,m o s t . b f whlich w i l l b e s m a l l , a l t h o u g h a few g i a n t orn e ar -g ia n t f i e l d s w i l l b e d i s co v e red .

1 The methodology o f es t i m at in g th e und iscove redr e c o v e r a b l e o i l r e s 0u r c e .s s d is cu ss ed i n S e c t i o n . 1 ~ .2 / The s t a t i s t i c a l mean v al ue h as a s t a t i s t i c a lp r o b a b i l i t y of 38 p e r c e n t .


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An' a l t e r n a t i v e s c e n a r i o t o t h e s i n g l e p o i n tp r o j e c t i o n o f u l t i m a t e l y r e c o v e r a b l e o i l may b e madeb y u s i n g a 30 p e r c e n t p l u s o r m in us v a r i a n c e f rom t h eu l t i m a t e r ec o v er a b le o i l volume ba se d on t h e s t a t i s t i c a lmean. N i g e r i a ' s r e m a in i n g r e c o v e r a b l e r e s o u r c e s i nt h i s i n s t a n c e would r a n g e from 1 8. 5 b i l l i o n t o 2 3.5b i l l i o n b a r r e l s . The r an ge i s i l l u s t r a t e d i n F ig u r e 111 1.The 30 p e r c e n t v a r i a n c e i s w i t h i n t h e n o r m a l l i m i t se x pe r ie n ce d i n h i s t o r i c a l r e v i s i o n s o f p ro ved r e s e r v e se s t i m a t e s .F u tu r e C r ude O i l p r o d u c t i o n R a t e s

The me th od s u se d h e r e i n t o d e v e l o p p o s s i b l emaximum p r o d u c t i o n p a t t e r n s a r e a m o d i f i c a t i o n o f t h ec o n c e p t s o f M King H u b b e r t . 3 The l o g i s t i c c u r ve si l l u s t r a t e d i n F ig u r e 111-2 d e p i c t a n nu a l p r o du c t io n o v e rt i m e ; t h e a r e a be n ea th t h e c u r ve r e p r e s e n t s t h e u l t i m a t e l ya v a i l a b l e o r r e c o v e r ab l e o i l . The m o d if ie d c u rv e i ss h i f t e d o r f o r c e f i t t o t h e r i g h t o f t h e f i t c u rv e.The, p u r p os e o f t h e m o d i f i c a t i o n i s t o c om pe nsa te f o r t h er e v e r s a l i n t h e h i s t o r i c a l p r od u ct io n t r e n d c au se d bymarke t demand d e c l i n e and subse quen t dampening of ex p l or a -t i o n and d ev el op me nt . The f i t l o g i s t i c c u r v e s u g g e s t st h a t N i g e r i a ' s p r o d u c t io n t h e o r e t i c a l l y .would h av epeaked a t 3 .8 m i l l i o n b a r r e l s i n t h e e a r l y 1 9 8 0 's a nd ,s u b s e q u e n t l y , p r o d u c t i o n w ou ld h av e d e c l i n e d t o a n a v e r a g ea nnua l r a t e o f more t h a n 20 pe r c e n t . The two c u r ve sassu me t h a t t h e s t a t i s t i c a l mean v al u, e o f u n d is c o ve r e dr e c o v e r a b l e o i l w ou ld b e f ou nd a nd d e v e lo p e d .

t i s assu med , b a s ed on t h e s t a t i s t i c a l mean,t h a t i f e x p l o r a t i o n a n d. de ve lo pm e nt w ere a c c e l e r a t e d a tt h i s t im e , a maximum pea k p r od uc t i on o f 3 . 3 m i l l i o nb a r r e l s p e r d ay c o u ld be a t t a i n e d i n t h e mi d- 19 80 's .The assumption i s i l l u s t r a t e d i n F i g ur e 111-3. F i g ur e11 1-3 a l s o shows t h e h i s t o r i c a l p ro d u c t i o n t r e n d f ro m1960 th ro ugh 1977 . The a r e a ben ea t h t h e asymmetr .i ca1b e l l - sh a p e d c u r ve r e p r e s e n t s t h e u l t i m a t e l y r e c o v e r a bl ec r u de o i l re s o u r c e s o f a pp ro xi ma te ly 2 7.1 b i l l i o n b a r r e l s ;t h e r e m a i n in g d i s c o v e r e d a nd u n d i sc o v er e d ( b a s e d o n t h es t a t i s t i c a l mean) r e c o v e r ab l e o i L , p l u s t h e c um ul at i 'v ep r o d u c t io n . The f u t u r e p r o d u c t io n l e v e l s t h a t m ig ht b ee x p e c t e d f r o m . N i g e r i a , d e t er m i ne d by r e s e r v o i r an dg e o l o g ic a l c o n d i t i o n s and v a r i o u s r a t e s ' o f e x p l o r a t i o n

3/ D i s cu s se d i n d e t a i l i n A ppend ix A


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. * * .. ULTI- 79 6 II UONMMean u n d i s c o v e r e d r e c o v e r a b le o i 1 + 30%3 . 0

I l L U UMean u n d i s c ov e r e d r e c o v e r a b l e o i l

Mean u n d i s c o v e re d r e c o v e r a b le o i l - 30%2.0

Note: The area

1960 1970 199E3 Z a 10YE R

F i g u r e 111-1 - S e n s i t i v i t y o f ma x imu m p r o d u c t i o n c a p a b i l l t y p r o f i l e s .


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and development efforts, are illustrated in Casesthrough 3. Case depicts a production growth rate of9.3 percent from the 1977 production of 2 million barrelsper day. That level of production could be sustainedthrough 1987. Production would decline thereafter atan assumed average annual rate of approximately 10percent, and in 1990 it would be about 2.23 millionbarrels; subsequently, declining to 1.35 million in1995, to 0.82 million'in the year 2000, and to 0.50million barrels per day in 2005. Before the .year 2010,95 percent of Nigeria's recoverable oil resources wouldbe depleted under the stated condition.

Table 111-1 shows that production rates.for thethree cases in five-year increments, the year in whichproduction would decline, and the year when 95 percentof Nigeria's ultimately recoverable crude oil would bedepleted.&/ h h lower rates of constant production areillustrated by Cases 1 and 2; the durations of thelower rates of production are sustained for a longerperiod of time, than for Case 3.Implicit in each of the three cases is.thatthe capital investment necessary to provide the ancillaryprocessing, storage and transportation facilities wouldbe available. Case 3 represents the optimum investmentrate. Cases 1 and 2 indicate lower rates of investment

and, therefore, decreased exploratiori and deve.lo.pment.Given that exploration and development activity hasslowed, -it is believed that Nigeria's future productiontrend is most likely to be in the range of Cases 1 and 2.The ultimate recoverable resource analysis,which drives the production estimates,, s based on theinformation available at this time and the ultimaterecovery value of the statistical mean. The production

estimates do not reflect .possible surprises or disap-pointments which cannot be predicted or built into theanalytical process. However, the sensitivity of a30 percent lower or higher ultimate recoverable resourceestimate changes the estimated maximum annualcapability only by a plus or minus six percent.

4 The methodology used to determine the productionrates is discussed in the Appendix A.


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Tab le 111-1 - A l t e r n a t e P r o d u c t i o n S c he du le s f o r N i g e r i a . .CASE 1 2 MM bopd)

l e v e l s , .-Probab i 1 y M i l l i o n B a rr e ls o f O i l Pe r Day Year Year

YEARpe rc en t 1980 1985 1990 1995 203 - b e g i n s d e p l e t e d

CASE I 2,5 MM bopd)

CASE I 3 .0 MM bopd)

9 5 2, 90 2.10 1.28 0.77 0.47 1981 20057 5 2.90 2,44 1.48 0.90 0.54 1983 200638 Mean) 2.90 3.00 2.23 . 1.35 0.82 1987 200825 2.90 3.00 2.81 1.70 1.03 1989 20092.90 3.00 3.00 3 . 0 0 . 2.98 2000 2017


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T h e r e f o r e , t h e maximum p r o d u c t i o n c a p a b i l i t y p r o f i l ei s n o t ve ry s e n s i t i v e t o a r e l a t i v e l y l a r g e p er ce n ta g ech an ge i n t h e u n d is co v er e d r e c o v e ra b l e o i l e s t i m a t e s .

l a r g e r u l t i m a t e re c ov e ry v a lu e i n f l u e n c e s t h e d u r a t i o no f t h e c o n s t a n t p r o d u c t io n p l a t e a u by e x t e n d i n g itC o n v e rs e ly , a l o w er u l t i m a t e r e c o v e r y e s t i m a t e f r om t h es t a t i s t i c a l mean, 2 7.1 b i l l i o n b a r r e l s , r ed uc es t h ed u r a t i o n of t h e c o n s t a n t p l a t e a u p r o d u ct io n r a t e .F i g u r e 1 1 1 4 i l l u s t r a t e s c o n s ta n t p l a t e a u d u r a t io n s byu s i n g a w id e r a n ge o f u l t i m a t e r e c o v e r y e s t i m a t e s a tt h e 2 .5 p r o d u c t i o n l e v e l . C urve i s b a s e d o n t h es t a t i s t i c a l mean e s t i m a t e o f u l t i m a t e r ec o v e ry ; C ur ve s2 and 4 r e p r e s e n t 75 p e r c e n t a nd 25 p e r c e n t p r o b a b i l i t yl e v e l s ; C u r v e 1 r e p r e s e n t s t h e u l t i m a t e r e c o v e ry ba se do n t h e 9 5 p e r c e n t p r o b a b i l i t y e s t i m a t e o f r em a in i ngu n d i s c o v e r e d r e c o v e r a b l e r e s o u r c e s , a nd C ur ve 5 i sb as ed o n t h e f i v e p e r c e n t p r o b a b i l i t y e s t i m a t e .Remaining Recoverable Natura l Gas Resour .ces

The l a c k o f d o m e s t i c m a r k e t s a nd e x p o r t o p p o r t u n i -t i s h ave l i m i t e d t h e i n t e r e s t i n n a t u r a l g a s e x p l o r a t i o nand deve lopment . Tha t which has been d i sco ve re d ha s beenfound i n c i d e n t a l t o t h e s e a r c h f o r c ru d e o i l .

I n t h e a b se nc e of a p e rf or ma nc e h i s t o r y f o r n a t u r a lg a s f i e l d p r o du c t io n , t h i s r e p o r t do e s n o t a n al y ze t h ee s t i m a t e s o f N i g e r i a s d i sc o v e re d n a t u r a l g a s r e c o ve r a b l er e s e r v e s . One p u b l i s h e d s o u r c e h a s r e p o r t e d N i g e r i a sproved r e s e r v e s t o 42 t r i l l i o n c ub i c f e e t ( T cf ) S anda no th e r s o ur c e r ep o r te d 51.4 ~ c f . / E i t h e r o f t h e s em a gn i tude s show t h a t t h e know inv e n to r y o f s upp ly i sc o n s i d er a b ly g r e a t e r t h an c u r r e n t p ro d uc t i on ; t h e r e s e r v et o p r o d u c t i o n r a t i o (R/P) i m p l i e s a 70 t o 86 y e a r s u p p l y .

The p r o p o r t i o n o f n a t u r a l g a s a s s o c i a t e d w i t hc r u de o i l i s r e l a t i v e l y h ig h i n t h e N ig er D e l t a . Theg a s - t o - o i l r a t i o a v e ra g e s a p pr o xi m at el y 800 c u b i c f e e tf o r ea c h b a r r e l o f o i l .The o c c u r r e n c e and d i s t r i b u t i o n o f n a t u r a l g a si n t h e N ig er D e l t a i s d e s c r i be d a s f o l l o w s :

5 O i l and G a s J o u r n a l , 1 9 7 8 .6/ DeGolyer and MacNaughton.


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Figure 111-4 Historical and projected crude oil production for five ultimate recoveriesCase 2 - 2 5 bopd).


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Large'deposits of natural gas are most likelyto be found south. f the main hydrocarbon-rich belt, which extends in a general south-east to northwest direction, where there isa narrow series of oil-rich zones; the centralpart of the Delta is predominantly a natural.gas province; andThe potential for finding natural gas vis-a-viscrude oil appears to increase seaward in asouth-easterly direction across the Delta.

Thus, it-would ppear that the opportunity forcontrolling exploration programs to selectively ordirectionally search for natural gas is'possible.Z/

The statistical mean estimate of undiscoverednatural gas indicates that there may be 81.3 Tcf ofnatural gas in-place. Based on a.recovery factor ofapproximately 80 percent, the undisco'vered recoverableresources may be 65 Tcf. Thus, the ultimate recoverablenatural gas supplies, discovered proved reserves p3.u~undiscovered recoverable resources, may total over 100 Tcf.The statistical analysis further indicates thatit is 95 percent pkobable that an estimated 32 Tcf remainto be discovered in-place, of which 25.6 Tcf are recover-able, 'and a five percent probability that as much as162 Tcf remain in-place, of which 130 Tcf are recoverab1e.g

7 The term directionality applies to an explorer's- capability to choose the objective of his search,either crude oil or natural ga's, based on geologicalevidence which favors the accurrence of.one or theother.8 The methodology used to arrive at these quantitiesis described in Section IV.


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F u t u r e N a t u r a l G as Pr o d u ct i o n C a p a b i l i t y

The r a t e a t w hich t h e N i g er i a n r e c o v e r a b l en a t u r a l g a s w i l l be produced i s d i f f i c u l t t o a s s e s s i nt h e a b s en c e o f n a t u r a l g a s w l l p e r f o r m a n c e h i s t o r y .The q u a n t i t y o f g a s a s s o c i a t e d w i th c ru d e o i l , t h er a t e a t - w h i c h t h e c ru de i s p ro du ce d, a nd f i n a l l y , t h et i m i n g o f t h e blow-down p e r i o d a r e some o f t h e f a c t o r swhich w i l l a f f e c t t h e p r od uc ti on r a t e o f a s s o c ia t e dn a t u r a l g as .The d e p l e t i o n o f 95 p e r c e n t o f N i g e r i a su l t i m a t e l y r e c ov e r ab l e n a t u r a l g a s r e so u r c e s w i t h i nt h e same p e r i o d a s t h e r e c o v er a b le o i l r e s o u r c e s ,30 t o , 3 5 , y e a r s , would r e q u i r e t h a t n a t u r a l g a s p r o d uc t io n

a v e ra g e s l i g h t l y o v e r 3 Tcf a n n u a l l y . The a c t u a lp r o d u c t i o n , h ow ev er , w ould be c o n t r o l l e d by s a l e s c on -t r a c t s a s w l l a s t h e r e s e r v o i r y i e l d r a t e s . A lso ,n a t u r a l g as d e p l e t i o n would t en d t o l a g o i l d e p l e t io nb e c a u s e o f p r e s s u r e m a i n te n a n ce p r o gr a ms , e t c

9/ The p r o d u c t i o n and d e p l e t i o n o f t h e g a s c a p o f ac ru d e o i l r e s e r v o i r f o l l o w in g t h e u l t i m a t e r e c o v e ryo f t h e o i l .


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SECTION I VGeo logy a nd R es ou rc e Ana ly s i s o f N i ge r i a

Summary of Geology and Resource AnalysisThe known pe t r o l e um p o t e n t i a l o f N ige r i a i sc o n c e n t ra t e d p r i m a r i l y i n t h e s o u t h er n p a r t o f t h ec o u n t r y an d p e tr o le u m o cc u r s f o r t h e most p a r t i n t h eT e r t i a r y s e d i m e n t s o f t h e N i g e r D e l t a . The N i g e rD e l t a c o v e r s a n a r e a o f a p p r o x i m a t e l y 4 t hous a nds qu ar e m i le s a n d , i t i s u n d er l a i n by t h i c k d e l t a i cs e d im e n t s r e a c h i ng a n e s t im a te d maximum th i c kn e s s o f3 0,0 00 t o 40 ,0 00 f e e t .The Agbada Formattion i s t h e main o b j e c t i v e i nt h e e x p l o r a t i o n f o r o i l a nd g a s i n s o u t h e rn N i ge r i aand p r ob a bl y e x t en d s a c r o s s t h e e n t i r e D e l t a .The m os t i m p o r t a n t g e o l o g i c s t r u c t u r a l f e a t u r e si n t h e N i ge r D e l t a a r e t h e l a r g e c re s ce n t- s h ap e d g ro wthf a u l t s . E lo ng at ed a n t i c l i n e s h av e formed i n f r o n t o ft h e f a u l t p l a n e , c r e a t i n g r o l l o v e r a n t i c l i n e s , i nw hic h m ost o f t h e l a r g e f i e l d s h av e b ee n d i s c o v e r e d .Through 1 97 5, a t l e a s t 203 f i e l d d i s c o v e r i e shave been r e p o r t ed , many of which have mul t i -pay rese rv o i r s . The e s t i m a t e d number o f o i l f i e l d s t h a t may b ed i s c o v e r e d a f t e r 1977 r a n g e f ro m 2 t o 123 , a t t h e

95 p e r c e n t t o 5 p e r c e n t s t a t i s t i c a l p r o b a b i l i t y l e v e l s ,r e s p e c t i v e l y , w i t h a mean e s t i m a t e o f 77 f i e l d s . S i g n i f i -c a n t u n di sc ov er ed o i l p o t e n t i a l s t i l l r emains i n some oft h e d e e p er f a u l t b l o c k s o n s h or e , a nd t h e r e i s a p r o s pe c -t i v e p a t t e r n o f g ro wth f a u l t s w hich o cc ur o f f s h o r e t h a tmay be h ig h l y p r o du c t i v e .The g as i n d u s t r y i n N i g e r i a r em a in s r e l a t i v e l yu nd er de ve lo pe d. The p o t e n t i a l f o r f i n d i n g a d d i t i o n a ln a t u r a l g a s a p pe a rs l i k e l y a s de ve lopm e n t e x t e ndss ea wa rd i n t h e d e ep e r s e d im e n t s a nd i n a s o u t h e a s t e r l yd i r e c t i o n a c r o s s t h e D e l t a .


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G e n e r a l O b s e r v a t i o n sThe knowle dge o f N ig e r i a s ge o logy ha s r e a c he d

a n ad van ced s t a g e a s t h e r e s u l t of t h e work o f i n t e r -n a t i o n a l o i l c om pa ni es , t h e N i g e r i a n N a t i o na l O i lC o r p o r a t i o n , a nd t h e G e o l o g i c a l S u r ve y o f N i g e r i a .One- ha lf o f N i ge r i a s composed of marine andc o n t i n e n t a l s ed im e nt ar y r o c k s o f C r e t ac e o us , T e r t i a r yan d Q u a t e r n a ry a ge w hich o v e r l i e : t h e c r y s t a l l i n e r o c k so f P r e ca m b r ia n a g e , a nd t h e o t h e r o n e -h a l f s made upo f i gne ous a nd m e ta m or phic r oc k s . Over t h r e e - f o u r th so f t h e i g n e o u s an d m et am o rp hi c r o c k s a r e P r e ca m b r ia ni n a g e , w h i l e t h e r em a in in g a r e y ou ng er i n t r u s i v e s a ndv o l c a n i c l a v a s .The s e d im e n t ar y r o c k s a r e c o n c e n t r a t e d p r i n c i -p a l l y i n t h e s o u th e rn p a r t o f N i g er i a and i n t h e N ig erand Benue t ro ug hs (Anambra B a s i n ) , a s shown i n F ig ur e

I V - 1 . The t r o u g h s a r e f i l l e d w i t h C r e t ac e o us s e di m en ta nd have a b r e a d th o f 95 t o 190 m i l e s . T h e o l d e s tknown s e d i m e n t a r y r o c k s i n N i g e r i a a r e o f t h e l o w e rC r e t a c eo u s ( A l b i a n A g e ) . The s t r a t i g r a p h i c c ol um na rs e c t i o n of N i g e r i a s shown i n F ig ur e IV-2. . Thed e e p l y f o l d e d s e d im e n t s a r e c o n c e n t r a t e d m a in l y i n t h em i dd le b a s i n o f t h e C r o s s R i v e r , l o c a t e d o n ~ ee a s t e r n e dg e o f t h e . D e l t a . They c o n s i s t o f s a n d s t o n e ,s h a l e and t h i n s t r i a t i o n s o f l im es to ne . l l d r i l lt e s t s i n t h e n o r th e rn a nd e a s t e r n p a r t s o f N i g er i a ,which pe n e t r a t e d Upper C r e t a c e ou s s e d im e n t s , w e r e d r yo r r e v e a l e d o n ly m inor o i l a nd n a t u r a l g a s d e p o s i t s .Lower Cre ta ceo us sed i me nts have shows of pe t ro leum i no u t c r o p s an d i n w e l l s , b u t no ma jo r d i s c o v e r i e s h av ebe e n made t o d a t e i n t h e Upper a nd Lower C r e t a c e o us .The C r e ta c e o u s i n s o u t h e r n N i g e r i a , a l t h o u g h n o tc o ns id e re d hi g h ly f a v or a b le f o r o i l , 1 c a nno t ber u l e d o u t a s o i l p r o sp e ct iv e .

1 S c h a t z l , L . H . P e t r o l e um i n N i g e r i a , O x f o r dUn iv e r s i t y P r e s s , I da de n , 1969 , pp. 1 -45 a nd198-210.


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Niger Delta

Figure IV - 2. Formations of the Niger Delta, Nigeria Modified from Short and Staihle, 1967)

GeologicPer i od

QuaternaryTer t i a ry

UpperCretaceous

owerCretaceous

SubsurfaceYoungestKnown Age

Recent

Recent

Recent

YoungestKnown AgePl io ,

Pl e is oceneMiocene

EoceneL EocenePaleocene

Maestri cht ia nCampani an

Camp. /MaesConi ac ian /Santonian

TuronianA1bian

Equivalents not known

Benin Fo m at i on

Agbada Formati on

Akata Formation

Surface Outcrops

Baniiti:iFarmationOgwashi -AsabaForm ati onAmeki Form ati on

I OForm ati onNsukka FmAjal i FormationMamu Form ation

Nkporo ShaleAwgu Shale

Eze Aku Shalesu River Group

01 desKnown Age

01i gocene

Eocene

Eocene

01 desKnown Age

Miocene?01i gocene

EocenePaleocene

Maestri c ht i anMaestri ch t i an

Campani anSan toni an

TuronianTuroni an

A1b ian


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F or ma ti on s o f T e r t i a r y ag e a r e e x t e n s i v e i ns o u t h e r n N i g e r i a a s s i g n i f i c a n t volum es o f s uc hsed imen t s have been depo s i t ed i n th e De l t a . The mostp ro m is in g c r u d e o i l a c c um u la ti o ns i n t h e T e r t i a r y h a veb een foun d a t d e p t h s b etw een 9 000 t o 1 1 0 00 f e e t i nt h e M iocene a g e. G e n e r a l l y t h e T e r t i a r y s e d im e n t sh av e p ro v en t o b e t h e m os t p r o d u c t i v e t h u s e x p l a i n i n gt h e c o n c e nt r at i on of d r i l l i n g i n T e r t i a r y f o rm a ti on so f t h e N ig er D e l t a . B eca us e t h i s i s t h e m o st p r o s p e c t i v ea r e a i n N ig er i a t h i s r e p o r t w i l l h e r e a f t e r c o n c e r ni t s e l f s p e c i f i c a l l y w i t h t h e geo lo gy of t h e Nig er D e l t aThe Geology of t h e Niger De lta

The 4 thousand square m i l e s of th e Nige rD e l ta a r e u n d e r la i n by d e l t a i c d e p o s i t s of T e r t i a r yage which may re ac h an est im ate d t hi ck ne ss of 30 000t o 40 000 f e e t . These d e p o s i t s a r e d i v id e d i n t o t h r e esubs ur f ace fo rma t ions from th e su r f ac e downward: t h ec o n t i n e n t a l s an dy B en in F or ma ti on ; t h e d e e p er t r a n s i -t i o n a l Agbada F o rm a ti on o f a l t e r n a t i n g s a n d s a nd s h a l e s ;and th e lower mar ine sh a l y Akata Format ion .Benin Formation:The Ben in Forma t ion cons i s t s of predominant lymass ive h i g h l y porous f r e shwa te r -bea r ing s a n d s t o n e sl o c a l l y in te rbedded w i t h t h i n s h a l e beds . The sands

and s a n d s t o n e s of t h e s e upper d e l t a i c d e p o s i t s mayr e p r e s e n t po in t -ba r d e p o s i t s channe l f i l l s o rn a t u r a l l e v e e s . The s h a l e s may be i n t e r p r e t e d a sbackswamp d e p o s i t s and oxbow f i l l s o r d e p o s i t s o fbra ided-s t ream o r i g i n . The depocen te r o f t h e BeninFormation i s i n t h e c e n t e r of t h e Niger D e l t a where ta t t a i n s a maximum t h i c k n e s s of t l e s t 6 000 f e e t .The Benin Formation was d e p o s i t e d a c r o s s t h ee n t i r e Niger D e l t a from t h e Benin-Onitsha a r e a i n t h en o r t h t o beyond t h e p r e s e n t c o a s t l i n e . The s h a l l o w e s tm a r i n e s h a l e u n d e r l y i n g t h i s sandy c o n t i n e n t a l sequence

h a s been d a t e d a s e a r l y Miocene Age. Thus t h e t o t a lage span i s Miocene t o Recent. To d a t e v e r y fewhydrocarbon d e p o s i t s have been found i n t h i s h i g h l yporous g e n e r a l l y f r e shwa te r -bea r ing format ion .


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Agbada Formation:The Agbada Formation is the main objective in

the exploration for oil in southern Nigeria. Hydro-carbons have been found in the sand intervals fromEocene to probably Pliocene age.The Agbada Formation underlies the Benin andextends throughout the Niger Delta subsurface. Itconsists of alternating sandstone and shales ofdelta-front distributary-channel and deltaic-plainorigin. The alternating sequence of sandstones andshales of the Agbada Formation are cyclic sequencesof marine and fluvial deposits. The upper part of theformation has a higher sandstme percentage than the

lower part demonstrating th progressive but highlyirregular seawaxd advance of the Niger Delta throughgeologic time despite the numerous transgressivesequences found in the Agbada Formation. In the centrapart of the Delta the formation attains a maximumthickness of 12 000 feet. The age of the formationdecreases from Eocene to possible Plio-Pleistoceneoffshore from the present coastline. The base of theAgbada Formation is defined as the deepest significantsandstone body in all vertical sections throughout theDelta.Akata Formation:The main source rock of the Niger Delta oilprovince is thought to be the shale of the AkataFormation. The Akata Formation is characterized by auniform shale development. The prodelta shales aremedium to dark gray sandy or silty undercompactedand may contain lenses of abnormally high-pressuredsiltstone or fine-grained sandstone. The AkataFormation is a marine sedimentary sequence laid downin front of an advancing delta front. Intervals ofvariable thickness ranging from 4 500 to 5 000 feethave been penetrated by some wells. The base has been

reached only along the Delta margin; thus th maximumdepth is not known. However its maximum thicknesshas been estimated at over 18 000 feet. The shale ofthe Akata Formation probably extends across the entireDelta area. The known age of the formation rangesfrom Eocene to Recent.


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The Subsurface Structure of the Niger DeltaThe Niger Delta began to build seaward over theedge of the African continent in middle to late Eocenetime. The Oligocene and younger Delta sediments arevery thick beyond the continental edge. Geophysicalevidence indicates a possible thickness of 30,000 to40,000 feet. Recent marine deposition on the forwardslope, represented by the continental slope off theNiger Delta, is a depositional feature and not a primarystructural feature.2/The thick, rapid deposition of sediments acrossthe Delta area created conditions which resulted inthe movement of large masses of sediment under the

influence of gravity. Much of the resultant faultmovement is contemporaneous with deposition, producinga thickening of the sedimentary section across thefault plane on the downthrown blocks. Faults whichcause such increases in thickness are called growthfaults. They are known to occur also in the Gulf ofMexico coastal area. In general, faults play an impor-tant role in the distribution and accumulation ofhydrocarbons in the Niger Delta, as shown in Figure IV-3.Many of the growth faults are crescent-shaped,both in cross-section and in plan view, with the

concave side toward the downthrown block. Due to thiscurvature, the downthrown block tends to slump orrotate along an axis roughly paralleling the fault.If sufficient movement has taken place along a curvedfault plane, an elongated anticline is formed in frontof the fault, which is called a rollover structure.In the Niger Delta such rollover anticlines are small,ranging from 4 to 5 miles along the long axes and 2 to3 miles across the short axes. Structural mappingshows that in many places a series of growth faultson strike with one another may form a continuous trendextending for tens of miles, roughly parallel with thecoastline.

2/ Hospers, J., ~he eology of the Niger Delta Area,nInstitute of Geological Sciences, Report No. 70/16,pp. 123-142.


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Figure I V 3i f ferent Evolutional Stages of the Traps

of the Niger elta

mr Fmm: K.J.WEBERand E.DAUKURU in 9th.World1 m k j w ~mcv r n m r rrur ~ h oong. pmd4) TOLVO 1 9 7 3

]PETROCONSULT NTS S A FRO 1337


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The Occurrence of HydrocarbonsMost of the hydrocarbon accumulations in the

Niger Delta have been found in the sandstones of theAgbada Formation mostly in traps formed by rolloveranticlines. The Benin and Akata Formations have yieldedsome oil and gas in minor amounts in such structures.The extent of petroleum accumulation in the AgbadaFormation may or may not be restricted by subsidiarygrowth faults or antithetic faults cutting the anticline.Such fault-formed restrictions are most evident inthe larger anticlines that normally are expected tobe effective traps for oil. The efficiency of suchtraps are limited by the faults. In addition to theanticlinal traps hydrocarbons have also been foundin fault traps that are not closed on all sides byregional dip.Many of the oil fields particularly those inthe rollover anticlines have multiple reservoirs.Few of these reservoirs are full to the structuralspill-point and many contain no hydrocarbons at all.Although multiple reservoir fields are common their exist-ence may not be apparent at the time of a field discovery.Subsequent drilling may reveal that the reservoirsare not stacked vertically but have been dislocatedlaterally. This is particularly true in the case offault traps associated with a low angle fault or in

a rollover anticline whose crest has shifted withdepth. This and the fact that minor faults oftencontrol the actual distribution of hydrocarbons withina structural closure require constant subsurfaceanalysis when developing a field.Geological Considerations in Resource Appraisal

A brief review of the geology and structuralconditions related to the occurrence of hydrocarbonsin the Niger Delta is summarized here as a part of thebasic input necessary for an appraisal of the undiscov-ered oil and gas resources in Nigeria.


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A general pattern concerning the hydrocarbondistribution throughout the Delta has been observedand summarized by Evamy, et al, 1978) as follow^:A hydrocarbon-rich belt cuts across thedepositional and structural trends of theDelta from southeast to northwest, asshown in Figure IV-4. North and east ofthe hydrocarbon-rich belt, the gas-to-oilratio3/ is higher, and the recoverable oilreserves of the accumulations found to dateare smaller. South of the main hydrocarbon-rich belt is a series of narrow oil-richzones; otherwise, a predominantly gasprovince occupies a fairly wide part ofthe central Delta.Known commercial oil accumulations occurpredominantly in the structurally highestpart of a given macrostructure in the strikesense, despite viable trapping conditionsdown plunge.Dry holes and marginal oil and gas findsare located predominantly on the southernflanks of the macrostructures.In a given macrostructure, the gas-to-oilratio increases down plunge and in a gener-ally seaward direction. Hence northernblocks with pronounced landward dips areregarded as being highly prospective for oil.The more downdip a macrostructure is withina megastructure, the greater is the probabilityof a higher gas-to-oil ratio;

3/ Gas-to-oil ratio denotes the ratio of the volumeof gas-bearing reservoir rock to the volume ofoil-bearing reservoir rock and ot solution gasvolume to recoverable oil GOR)


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. ... . . . . .

Figure IV 4. Hydrocarbon Rich BeltSource: Petroconsultants S.A.


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Because of the intensity of faulting andsteeply dipping reservoirs of collapsedcrest structures, the recoverable reservescan'be rather low. Exceptions are reser-voirs such as that of the Forcados Estuaryfield, where a reservoir with a long oilcolumn and concomitantly large arealextend exists at shallow depth. Hydro-carbons in collapsed-crest structurestend to be trapped behind crestal andantithetic faults, whereas the collapsedcrest itself is usually barren;Although the probability is high of findinghydrocarbons behind the numerous faults inmajor structures, commercial discoverieshave not been made as yek.Miocene age rocks contain the greaterpercentage of the total known reserves.Most of the large fields produce fromrollover anticlines associated withlarge regional growth faults. The smallerfields are generally associated withsmaller growth faults and non-growthfaults. There may be a correlation betweenthe magnitude of the throw of a fault and

the size of the fields.From the coast to the continental slopethe main producing formation (Agbada)becomes progressively thinner. The bulkof the total stratigraphic section offshoreis shale, with less of a chance for highquality reservoir rocks.The most important geological features arethe growth fault patterns which form theoil and gas field structures and which SOmay contribute to the migration route ofthe hydrocarbons from the source beds ofthe Akata Formation into the paralic sandlayers of the Agbada Formation. The paraliccyclic sedimentation pattern is well estab-lished.


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P e r t i n e n t E x pl o ra t i o n S t a t i s t i c sSome o f t h e d r i l l i n g , a n d f i e l d s t a t i s t i c s

u se d i n p r e p a r in g t h e o i l a nd g a s r e s o u r c e a ss es sm e nt sa r e shown below.t o t a l o f 759 e x p l o r a t o r y w e l l s w e r e d r i l l e di n N i g e r i a f ro m 1 9 5 1 t h r o u g h 1977.. The t o t a l e x p l o r a -t o r y f o o t a ge of 8.4 m i l l i o n f e e t d r i l l e d . s i n c e 1 95 1

i s shown o n a n a n n u a l b a s i s , i n T ab l e I V 1 .The t o t a l number o f f l o w i n g w e l l s i n N i g er i aa s o f J u l y 1 1978 , was 1 , 299 . T we n ty- th re e o i l w e l l sr e q u i r e g a s - l i f t , and 305 w e l l s a r e s h i t i n . Thea v er ag e p r od u c ti o n f o r t h e f i r s t s i x m onths o f 197 8was 1 , 6 71 , 9 68 b a r r e l s p e r d a y. The t o t a l c u m u l a t i v eo i l pr o d u ct i on t h ro u gh J u l y 1 1 9 78 , f o r N i g e r i a w as6 , 4 1 6 , 8 0 7 , 5 8 9 b a r r e l s .The t o t a l e s t i m a t e d pro ved r e s e r v e s a s r e p o r t e dby t h e O i l and Gas ~ o u r n a l ere : 1 8.2 b i l l i o n b a r r e l so f o i l and 42 t r i l l i o n c u b i c f e e t o f g a s. DeGolyer andM acN aug hton , i n 1 97 7 , r e p o r t e d e s t i m a t e d p r ov e d r e s e r v e so f 12.24 b i l l i o n b a r r e l s o f o i l and 51.42 t r i l l i o nc u b i c f e e t o f g a s a s o f J a n u ar y 1 1977.O i l and g a s f i e l d d a t a w e r e p a r t l y c om pil edf ro m t h e P e t r o c o n s u l t a n t s , S.A. W orld F i e l d F i l e s ,

w hich i n c l u d e 203 f i e l d r e c o r d s o f d i s c o v e r i e s up t oJ a n u a r y 1 19 75. Of t h e s e , 1 50 o i l f i e l d r e c o r d s w e r eu se d by t h e e n g i n e er s i n t h e DOE E n e r g y I n f o r m a t i o nA d m i n is t ra t io n t o c a l c u l a t e t h e e s t i m a t e d re m ai ni ngr e s e r v e s from p r o d u c t i o n d e c l i n e d a t a , r e co v e r y d a t ap e r ' w e l l , r e s e r v o i r d r i v e mechanism i n f o r m a t i o n , a ndp r e s s u r e d a t a . 4 / The o r i g i n a l o i l - i n - p l a c e was c a l -c u l a t e d by u s in g r e c ov e ry f a c t o r s , o r w a s d e t e r m i n e dv o l um e t r i c a l l y . T hese f i e l d da ta ., p l u s t h e d a t a f o r 1 7 .a d d i t i o n a l f i e l d s , r e p o r t e d s s h u t i n , s t a n d i ng o ra w a i t i n g d e ve lo p m en t , w e r e u se d i n t h e r e s o u r c e a s s e s & -ment s tu d y. t o t a l o f 36 f i e l d s r e p o r t ed i n t h eWorld F i e l d F i l e s d i d n o t have s u f f i c i e n t d a t a t o .make e s t i m a t e s o f r e m a i n in g r e s e r v e s . . T w e nt y -f iv e o f t h et h i r t y - s i x f i e l d s a r e o i l f i e l d s , f i v e a r e g a s f i e l d s ,and s i x a r e c o mb i na ti o n o i l an d g a s f i e l d s . Many g a sf i e l d s and pr o ba b ly some o i l f i e l d s d i sc o v e re d s i n c e '

4 / D is cu ss ed i n d e t a i l i n A ppendix A .


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T a b l e I V -1E x ~ l o r a t o r v o o t a s e D r i l l e d i n ~ i s e r i a

Year1 9 5 1 - 5 31 9 5 41 9 5 51 9 5 61 9 5 71 9 5 81 9 5 91 9 6 01 9 6 11 9 6 21 9 6 31 9 6 4 1 /1 9 6 5 -1 9 6 61 9 6 71 9 6 81 9 6 91 9 7 01 9 7 11 9 7 21 9 7 31 9 7 41 9 7 51 9 7 6 2 /1 9 7 7 -

F o o t a g e2 9 , 0 0 03 3 , 0 0 05 2 , 0 0 01 0 , 2 0 03 3 , 5 0 01 7 7 , 5 0 03 9 5 , 9 0 0

2 8 7 , 0 0 01 6 3 , 3 0 09 2 , 8 0 02 4 4 , 5 0 04 6 0 , 3 4 56 9 9 , 3 3 27 5 3 , 1 9 58 2 7 , 2 7 73 3 3 , 6 3 62 6 1 , 5 6 63 3 3 , 2 6 15 8 0 , 1 0 66 5 2 , 9 6 65 0 1 , 4 1 85 5 7 , 3 6 54 1 7 , 7 0 72 1 9 , 6 9 42 9 0 , 2 3 0

C u m u l a t i v e F o o t a g e2 9 , 0 0 06 2 , 0 0 0114,O.OO1 2 4 , 2 0 01 5 7 , 7 0 03 3 5 , 2 0 07 3 1 , 1 0 0 .

1 , 0 1 8 , l O O1 , 1 8 1 , 4 0 01 , 2 7 4 , 2 0 01 , 5 1 8 , 7 0 01 , 9 7 9 , 0 4 52 , 6 7 8 , 3 7 73 , 4 3 1 , 5 7 24 , 2 5 8 , 8 4 94 , 5 9 2 , 4 8 54 , 8 5 4 , 0 5 15 , 1 8 7

1.Petroleum Resources of Nigeria

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