Petrophysicist (Geologist)

For Practical Use and References

Quick Look Log Analysis Well Summary Regional geology Well History Problem and Objectives of drilling Strathigraphy of well Hydrocarbon Show Profile of Test Pressure Analysis (MW, Mud Pressure, Formation Pressure) Regional over pressure Bit data/properties Reservoir review (by pass) Manual petrophysist Porosity Vs Depth Source rock evaluation (TOC, Ro) Maturity (Ro, Pyrolisis) Conclusion

Well Summary Well name : L 40-1 Well type : Exploration Block Location : Central Lombok block (put some picture of

well location) Location : Lat 7˚ 20’ 28.10” S

Long 116˚ 15’ 18.52” E Water Depth : 1300’ MSL RKB to sea floor : 1339’ Actual TD : 11.860’ TVD (side tracks) Spud date : 25 February 1984 Test : DST @ 4412’ – 4528’ (zone of

perforated) Recover of mud and water formation

Objectives : objectives of formation that will be drilled Status : P & A as dry hole Well Diagram : picture of well schematic (Cassing,

perforated, cassing shoe, deviated well, etc)

Example of well summary

Well Strathigraphy Strathigraphy regional of the

block or basin Strathigraphy of the well, put

every formations that was penetrated by the well and the elevation and objectives too

Combined the formation log with GR log to make the review lithology of every formation

GR

1800190020002100220023002400250026002700280029003000310032003300340035003600370038003900400041004200430044004500460047004800490050005100520053005400550056005700580059006000610062006300640065006600670068006900700071007200730074007500

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Series1Series2

Early Pliocene

Earliest Pliocene Latest Miocene

Late Miocene

Middle Miocene

Early Miocene

Late Oligocene

Early Oligocene

Late Eocene

Objectives

Hydrocarbon Show Hydrocarbon show that was occur at cutting sample, core, DST, RFT and SWC Also from mud log or composite log Put the display of HC show with log (GR, resistivity, density and neutron) Don’t forgot to put the depth, description and in which formation that the HC show occur

OIL SHOWS SUMMARY on TAF

1610

1615

1620

1610 – 1611 : No Fluorescence, very s low bluish white streaming cut, pale yel low residual, t race oi l show.

1611 – 1612 : 2% yel lowish orange f luorescence, very s low bluish s treaming cut, t race to poorly oi l show.

1613 – 1614 : 2-5 % dul l brown f luorescence, no to very slow bluish whi te streaming cut, pale yel low residual, poor oi l show.

1614 – 1615 : 5% dul l brown f luorescence, s low to moderate bluish streaming cut, no odor, no residual, fair oi l show.

1618 – 1619 : 5% dull orange f luorescence, s low to moderate bluish white streaming cut, milky white crushed cut, fair oi l shows.

Example

If iC4, nC4 occurs related to oil !-Gas Chromatogram analyses : CH,WH,BH

Range interpretation : light gas

Heavy residual oil

OIL SHOW-Oil Flow, oil on shaker, oil in mud-Oil stain ( on grains/cuttings)-Direct/Fluorescence, streaming cut-Direct/no fluorescence, crushed, streaming cut, dead oil-Smell/Odor :

Aromatic probably by degraded Normalsour smells of rotten egg, lots of H2S

Relationship between Gas show & maturity depend on :- Permeability/Porosity- mud weight versus fm. Pressure (over/under balance)

-Tutorsity --> O-I (gampang susahnya larutan keluar)-The Higher of MW the difficult the liquid will be extract-Overbalance No Gas Influx

Hawboth et. all?

GAS SHOWTotal Gas >>> Background GasCan also be associated with C2+If C3+ occurs thermogenic (biogenic has no C3+)Fluorescence & cut apples

Usually blooming cut (crushed or not)Also accompany oil shows

Oil Show Explanation

• Oil Shaker (Floating Oil)

• Oil in Mud (Oil inside the mud)

• Oil Stain ( oil stain in grain of the rock)

Live Oil

Dead Oil → black stick in the grain, dull fluorescence

• More lighter the oil, the fluorescence more bright

• Fluorescence Color :

Light-bright: white & Yellow

Heavy-dull : Brown & Black

• Qualitative shows parameters: Fluorescence cut quantity and fluorescence cut quality

1. Excellent oil show

2. Good : all yellow

3. Fair : dark yellow

4. Poor

5. Trace: only pin point

• Put CL4 (Chloroform) into the cut to separated oil from the grain

• Streaming : Fast slow (it effected to productivity)

• OBM : rely on crushed cut ( if it crushed, it will streaming. Oil show)

Gas Show explanation

• Blooming Cut : difenetly Gas

• Biogenic Gas : C1, C2 at least 2 %

• Thermogenic gas : present of C3

• If C3 present in porous zone or sandstone probably migrated

• If C3 present in shale probably oil in the fracture zone in the shale

• Maturity = present of C3, if it not migrated it must be mature

• Ro = 0.6 → Type II in North Sea, Jurassic in Indonesia

• Ro = 0.5 – 0.45 → already mature in Indonesia, because coaly deltaic source PS-1 PS-2 Regional shale

• Plot Total Gas Vs Depth

• Smell:

1. Aromatic : By degraded (due bacterial activity/ water wash ate normal alkaline)

2. The bad more heavy

3. The good is more normal

• Power Plant only need C1

• LPG must have C4 and C5

• Biogenic need fermentation, example in the swamp

GAS OCCURRENCES (C1, C2, C3, nC4, C5+)

Palembang

Telisa

Baturaja

Talang Akar

LowerTalang Akar

Lemat

Basement

Gas peaks were encountered during drilling in Lower TAF

interval

Example

TEST PROFILETEST PROFILE

Test ProfileSome Test are: Drill Steam Test (DST), Repeat formation Test (RFT) or any

Production testPut the result of test, description of lithology, Put also log (GR, ILD, RHOB and NPHI) for display Put some petrophysis analysis to justified the result of test

Good porosity but absent of C1-C4

Presence of C1-C4 but no porosity

Presence of C1-C4, good porosity in shale stone, probably fractured

DST # 1, 4412’ – 4528’ MD

Recover of 30 BBLS of water formation and minor gas 90% C1, no liquid Hydrocarbon recover

Limestone : light tan, tan-white to white, variable mottled, fragment dom micrire with micro clastic dom over micro crystallin (range very fine – tine micro) with rare extremely soft, crypto crystalline, white rock fluorescence; micro-clastic dom white to tan – white, extremely hard, brittle and dense with rare light and white mottling; all explosively calcitic with approx 100% HCL digestion; abundant fragments with foraminifer (especially globigerina) and oolites and rare pelecypoda fragments; rare free relic coral tabulae and algal laminate; rare free crinoids steams; abundant light to medium green, irregular glauconitic; abundant very fine to fine micro-pyrite aggregates (cubes) in large fragments and abundant free aggregates of very fine micro-pyritohedra; visible porosity absent; crush cuts absent.

No Hydrocarbon recovery due the bad facies EXAMPL

E

Pressure Analysis Pressure analysis can be use to determine of reservoir content (oil, gas or water). The

data that was used are from RFT and DST pressure during the test Pressure analysis from Mud pressure and formation pressure can be used to determine

the over pressure zone. Leak Of Test (LOT) can be used to determine the value of MW can be use during the

drilling

TYPE OF PRESSURE IN DRILLING ACTIVITY IH/IHP : Initial Hydrostatic Pressure ISIP : Initial Shut In Pressure (can be use as formation pressure

parameters) IF/IFF FP*) : Flowing Pressure (IF-FF) FP**) : Formation Pressure FSIP : Final Shut In Pressure (can be use as formation pressure parameters) FHP : Final Hydrostatic Pressure BHP : Bottom Hole Pressure FLP : Flow line Pressure IHP/FHP : Tool as Formation Pressure control BHP : correlated to formation pressure

PFP

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PFP

(gas)0.099 psi/ ft

(oi l)0.248 psi/f t

(water)>0.43 psi/ ft

GOC

OWC

From RFT pressure can be use to determine the content of reservoir using equation:

(X2-X1)(Y2-Y1)

X= pressure Y= depth

the result :

Gas <0.2 psi/ft

Oil < 0.433 psi/ft

Water = 0.433 psi/fet

From the liner line pattern we also can determine the content. Gas pattern more steep than oil and oil more steep than water

In gas the line usually more vertical (90°), if the line less than 90° it probably caused by C02 content

The line more steep than oil or water. The line less than 90° due the high CO2 content in this formation

The line more shallow than oil or gas.

Usually the used of Mud weight bellow 11.5 ppg consider as under balance situation. But some times the usage of MW over 11.5 ppg to counter the high pressure formation so no kick were experience.

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ppg

Dep

th f

eet

Series1

Formation ppg

Formation pressure convert to ppg

Over balance

The usage of MW more heavy than formation pressure, this situation consider an over balance situation

To combined the MW data with formation pressure we need to chance ppg to psi. the equation is

PSI= Dept x MW X 0.052

It’s better to put also water gradient. The equation is

WG= (depth x 0.043) +14Pressure Plot

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psi

dep

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eet Mud press

water grad

IHP

IFPWater gradient

Mud pressure

Initial Hydrostatic Pressure

Formation pressure

Mud pressure can be over than formation pressure, but not over than 200 psi

Mud in and Mud out

• Pay attention about the viscosity of MW after coming and out from the borehole

• If Mud in < Mud out it’s normal caused there is contribute from cutting rocks during the drilling

Example: MW in = 8.5 ppg; MW out = 8.6 ppg

• If Mud in > Mud out, there contribute fluid from bore hole (gas/oil) “Mud Cut”

• Mud Cut = mud that mixed with water and gas from formation

Mud Flow in and out

• Mud flow in and out is about the volume of mud that was circulated

• If there is mud flow out that were more less then they were in (and there is no spill in the circulated tanks) probably there are zones that sucking the mud. (porous zone, fracture, etc)

Mud Temperature in and out

• If there is no temperature data in the subsurface, than mud temperature data can be use as temperature data in subsurface

• The mud was to used to cooling the formation

• With circulate it. The measurement of Mud temperature will be more cooler than the original

• Bottom Hole Temperature (BHT) that were measured were not the real formation temperature, it must be corrected with time and distance → Heat lose

• The usage: if there is changing of the temperature in the chart, probably there is something in the sub surface → induce from faulting or un conformity

LOT was conduct to determine the fracture gradient , it used to monitor the usage of mud weight so the mud will not penetrated in to the formation.

Example: in the depth 3650 m the MW is 14.2 ppg. The pressure in the surface are 410 psi. what the value of LOT

Equation: LOT = (MW x Depth x 0.052) + 410 psi

= (14.2 x 3650 x 0.052) + 410 psi

= 2695.16 + 410 psi

= 3105.16 psi

EMW = 3105.16 / (3650 x 0.052)

= 3105.16 / 189.8

= 16.3 ppg

Maximum MW can be used in this dept

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Psi

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th Mud Press

Water Grad

Fracture Gradient

MASP

Maximum Alloweder Surface Pressure

LOT

MW

To determine regional Over pressure we can use Sonic shale ploting

Regional Over pressure was happen due the tectonic activity or rapid sedimentation that caused of disequilibrium compaction.

This information can be use by driller to avoid drilling hazards such a kick or blow out .

Also for mud engineer to calculate of MW that will be used in the drilling

Sonic

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al o

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Regional overpressure at 5300 ft

EXAMPLE

Drilling data often doesn’t use in Formation Evaluation because it only used only by drilling engineer NOT by geologist

Example : Mud weight will be affect on HC show (balance or not)

Not every geologist can correlated between drilling data and geological data in the surface

Drilling data that usually use are:

RPM : Rotation per minutes

ROP : Rate Of Penetration

WOB : Weight On Bit

WHO : Weight on Hook

SPP : Stand Pipe Pressure

CP : Casing Pressure

Interpretation of ROP data usually correlated with RPM, WOB and Torge

ROP usually use some unit parameters such minute/ feet, feet/hour, feet/minute. From ROP data we can interpret the lithology by measureing the speed of drilling

The faster of the drilling it means the rock is more easily to penetrate , it means the lithology is soft or porous or fault zone.

The rock with high pressure gas also easily penetrate.

1. Does the Formation contain Hydrocarbon ?

Clean ? GR and SP

3. Recoverable

Resistivity

Rt un invaded zone

Rxo invaded zone

2. Quantity

ФCan ?

Density

Neutron

Sonic

Ф(1-Sw)F (Rt,Ф)

This is a schematic representation of the logging measurement used and the petrophysical parameters determined for answering the basic questions of well site

interpretation (Schlumberger)

Rock

Reservoir

Non-Reservoir

Hydrocarbon Bearing

Water Bearing

Gas Bearing

Oil Bearing

Evaluate

Evaluate

1. Locate reservoir

2. Detected hydrocarbons

3. Distinguish oil and gas

4. Evaluate Ф, Rw, Shc

Basic Steps for Quick look Evaluation

Schlumberger

Nomenclature: Borehole: Rm = Resistivity of mud.

Rmc = Resistivity of mud cake.

Flushed Zone: Rmf = Resistivity of mud filtrate.

RXO = Resistivity of flushed zone.

SXO = Water Saturation of flushed zone.

Uninvaded or Virgin Zone: RT = True resistivity of formation.

RW = Resistivity of formation water.

SW = Formation Water Saturation.

RS = Resistivity of adjacent bed or shoulder bed resistivity.

di = Diameter of invasion.

dh = Borehole diameter.

h = Bed thickness.

Looking for Productive Zones ?

Log SP or GR for interpreted a permeable zone :

“Shale base line” in the right side in GR log showing of shale (not permeable and not productive).

deflected SP and GR curve to the left showing of “Clean Zones” (sand or limestone) that probably productive.

Log-log Resistivitay :

High resistivity showing HC or “tight zones” or very low porosity/ bad porous zones.

Low resistivity showing of water bearing.

Log-log Porosity

showing of porous zones or non porous zone “tight”.

Log that showing of permeable zone are :

1. Spontaneous Potential (SP)

2. Gamma Ray (GR)

Log that measured formation resistivity

1. Log Induction

2. Log Lateral

Log that measured formation porosity

1. Log Neutron

2. Log Density

3. Log Sonic

Gamma Ray usually use to :

• reference to all logging data

• to separated between permeable and non permeable layer

• Correlation well to well

•Measurement of radioactive mineral such K, Na, Th

• the rock with Thorium content, the GR will be higher (Shaly)

•GR doesn’t correlated with grain size

•Coal included as high GR

Cut off

Shale

Sand

If the gamma ray line move to the left (value more lower) the lithology more porous and permeable or shale free but if the line move to the right (value more higher) the lithology more shaley or non permeable

The GR zone bellow cut off can be consider as a good reservoir

SP log used to:

• Differentiate potentially porous and permeable reservoir rocks from impermeable clays

• Define bed boundaries.

•Give an indication of shaliness (maximum deflection is clean; minimum in shale)

• Determine water formation resistivity (Rw) in both salt and fresh water mud's

oil

OWC

SPILD

Hydrocarbon suppression due the

present of HC

NOTE : Water formation more saline than mud

0 1-1

Salinity of mud or water

formation affecting SP

SP curve go to the right due Water formation more

saline than water base mud

SP curve go to the left due Water formation more

fresher than water base mud

SP DEFLECTION

Figure 4.

•In permeable rocks that contain of water, Thanif Rmf > Rw SP curve def lected to the left (SP negati f).i f Rmf < Rw SP curve def lected to the right (SP posit i f ).

•SP usually constant, but i t wil l be def lected to another level i f crossing between 2 formation boundary

RxoRt

Rm

Rm

Rxo

Rt

Laterolog

Response

Induction Response

Logging Tool

Borehole

Un invaded Zone

Invaded Zone

There are two main techniques for measuring resistivity:

Laterolog : Current is injected into the formation

Induction : Current loops are induced in the formation

Resistivity

To detected HC it’s best to take the data from un invaded zone

Logarithmic Resistivity Scale0.2 2.0 20

1.0 10

GR Resistivity

Sand Body

OWC

Increasing resistivity in short distance or in one sand body can indicated of OWC or hydrocarbon present.

Differentiation in water if there is no SB or Fs, it should be gradation, if not there must be HC or others.

NOTE :

In some places the value of hydrocarbon are different

In Kalimantan area resistivity value > 3 ohm for oil

In Sumatra area resistivity value > 10 ohm for oil

Fluid resistivity (measured from log)

Saline water : < 1 ohm

Brackish water : 1-10 ohm

Fresh water : > 10 ohm

Hydrocarbon : more higher than water

Higher porosity rock has lower resistivity than lower porosity rock, given the same Sw.

Archie Equation :

F x Rw Ro Swn = ---------- = -----

Rt Rt

if n = 2, Ro

Sw = √ -------- Rt

This equation can be use if we already know the zone that contain water or water bearing without known the porosity data.

SW : Water Saturation

F : Formation resistivity factor

RW : Resistivity of Formation water

Rt : true resistivity of formation

RO : Rock resistivity

Grain packing and sorting

Density of Sand is 2.65, if density of sandstone less than 2.65 it had pores

Value of density more than 2.6 indicated of tight

porosity

Value of density less than 2.6 indicated of porous

rock

This area was consider porous

The more porous of the rock, the curve more to the left

DENSITY LOG

How to measure porosity from the log ?

Р ma – P log

P ma – P FluidФ = P ma = density value of the rock

P log = value of density from log

P fluid = value of fluid inside the rock

Fresh water = 1

Salt water 1.08

Oil = 0.6-1 (API)

Gas = 10 – 50 (H2 Index)

P log Carbonate = 2.7

P log Sand = 2.65

P log Dolomite = 2.87

P log shale = 2.3 or 2.4

The equation

NOTE :

DENSITY LOG WILL BE USEFULL IF CALIPER DATA SHOWING OF GOOD HOLE CONDITION

example

HOW MUCH THE POROSITY OF THIS SAND ?

P ma 1P ma 2P ma 3P ma 4

P ma 5

P ma 1 + P ma 2 + P ma 3 + P ma 4 + P ma 5

5P log =

2.2 + 2.27 + 2.18 + 2.19 +2.02

5P log =

P log = 2.172

Р ma – P log

P ma – P FluidФ =

Ф = 2.65 – 2.172

2.65 – 1

0.478

1.65 Ф =

Ф = 0.28 28 %

POTENTIAL SOURCE ROCK

TOC VS Depth

Total Organic Content shows fair to good source rock potential of Lower TAF interval.

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TOC (weight %)

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th (

ft M

D)

TOC VS Depth Fm. Top

Palembang

Telisa

Baturaja

Talang Akar

LowerTalang Akar

LematBasement

Poor Fair GoodVeryGood

Excelent

T max

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(C)

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Vitrinite Reflectance %

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th

Ro

Oil window @ 8130’ RKB

Immature mature

From Vitrinite reflectance analysis. Mean VR determinations recorded range from 0.43% Ro (7660-7670ft) showing of early mature for oil

generation. Mean VR at 8130-9100 ft 0.5-0.53% showing of mature state of Oil generation. Oil window @ 8130 ft RKB

T-max & Virinite Reflectance

S3B

S3C

CASE: KMO Field in SE Asia

S7A

S7B

S7C

CASE: KMO Field in SE Asia

From many Sources

Reference