KZO Office Presentation_IOR-4_May 2015

STUDY ON THE STRUCTURAL STYLES OF PYAY OIL FIELD

1. Introduction, Objectives and Methods

2. Regional Geologic Setting

3. Stratigraphy

4. Field Geological Observations

5. Subsurface Structural Interpretations

6. Structural Relations

7. Pyay Thrust and Cross-faults

8. Time of Deformation

9. Hydrocarbon Implication

10. Conclusions and Suggestions

Contents

1. Describe the geometry of major fold and faults

2. Structural relations on three structures (Namayan, Pyay N and Pyay S)

3. Timing and tectonic history of folding and faulting

Methods

» Surface → Image interpretations and field observations

» Subsurface → Well data and 2D/3D seismic data

» Conclusion Integrated surface mapping and subsurface interpretations

Objectives

Location and Size

PYAY

Shwedaung

Inn ma

Kyangin

Pyay

South

Pyay

North

Namayan

Padaung

» Pyay oil field is located in the Bago Division, Pyay District, south of Pyay city and the east of Ayeyarwaddy river.

» Area boundary is covered by approximately 380 km2 (145 mile2).

» All of the Namayan, Pyay South and Pyay

North structures are located in the south of Pyay city.

N

MYANMAR

3D Seismic Area

2D Seismic Lines

Valleys (looking N)

Well-40

Well-20

Sharp topography (looking E)

Topography

PYAY

N

Trellis network

1 km

Drainage

Namayan

Pyay North

Pyay South

Tectonic sketch map of Myanmar(Modified from Pivnik et al., (1998), Kyi Khin & Myitta (1999), Soe Thura Tun (2007) and Bertrand & Rangin (2003).

N » Pyay Embayment (Pyay sub-basin) is one of the Tertiary sub-basin of the Central Myanmar Basin (CMB) (Bender; 1983, GIAC; 1996-1999, Pivnik et al., 1998).

» CMB is characterized by strike-slip movement of Burma plate against the Shan Plateau along the N-S striking Sagaing Fault (Gross; 1985, Win Swe; 1972).

» N-S running Kabaw Fault delimits the Pyay Embayment from Yakhine Yoma to the west (Win

Swe; 1972, Khan; 2012).

» At the east, the boundary between Pyay Embayment and Bago Yoma, is marked by Central Volcanic Line (Bender; 1983, Pivnik et al., 1998).

» Pyay Embayment and Salin sub-basin are separated by 20° N uplift (Bender; 1983, Pivnik et al.,

1998).

» The Pyay-Aunglan earthquake (1858) indicated as the Pyay thrust is still active since the Plio-Pleistocene

(Chhibber; 1934, Lin Thu Aung; 2014).

Regional Geologic Setting


N

Anticline

Syncline

Gas Show

Gravity map of the part of Pyay Embayment(MGOE; 1966)

N

» Roughly parallel N-S trending folds are commons

» NNW-SSE orientation of the major syncline is steadily widen towards South (Bender; 1983, Le Dain et al.,

1984).

» (Pyay oil field (Pyay structure) located between the western margin of the Pyay Embayment east of Shwedaung Syncline.

Shwedaung Syncline

PYAY

Regional geology map (Modified from Bender; 1983, MGS, Soe Thura Tun; 2014)

Gravity map of the part of Pyay Embayment (MGOE; 1966)

Anticline

Syncline

Gas Show

PYAY

Myanaung

Thayet

N

Shwedaung Syncline

Regional geology map (Modified from Bender; 1983, MGS, Soe Thura Tun; 2014)


» Eocene to Quaternary Sediments are exposed at the surface in Pyay Embayment.

» Dolerite rocks exposed about 20 miles east of Zegone (Chhiber; 1934, Win Swe; 2012).

» Depth of magnetic basement is about 15 km which rises towards the east between 17°N and 23° 50'N (Banner et al., 2011).

PYAY

Myanaung

Thayet

N

Generalized stratigraphy of Pyay Embayment, modified from Wandery (2006) and Bender (1983).

PE

RIO

D

EP

OC

H

GR

OU

P

F OR M A T IONA PPR OX IM A T E

T HIC KN ESS ( f t .)

Holocene - P leistocene

Pliocene

1475 - 2950

1215 - 1970

1510

T ert iary

Jain

tia

Oligocene

Pegu

Quaternary

> 3930

- Eocene

3445 - 8200

1280 - 4100M iocene

3935 - 8530

785 - 820

Irraw

addy

Alluv ium

Irrawaddy

Obogon

Ky aukkok

Py awbwe

Okhmintaung

Padaung/Tiy o

Shwezetaw/ Ky aukpon

Yaw

Pondaung

Taunggale

Kanbala

PYAY

Myanaung

Thayet

» Eocene to Recent sediments are exposed and filled (?) in the Pyay Embayment.


PE

RIO

D

EP

OC

H

GR

OU

P




Pliocene

1475 - 2950

1215 - 1970

1510

T ert iary

Jain

tia

Oligocene

Pegu

Quaternary

> 3930

- Eocene

3445 - 8200

1280 - 4100M iocene

3935 - 8530

785 - 820

Irraw

addy

Alluv ium

Irrawaddy

Obogon

Ky aukkok

Py awbwe

Okhmintaung

Padaung/Tiy o


Yaw

Pondaung

Taunggale

Kanbala

EOCENE

PYAY

Myanaung

Thayet

The upper Eocene of Taunggalaylime-stone and Yaw shale were deposited in the western part of Pyay Embayment


PE

RIO

D

EP

OC

H

GR

OU

P




Pliocene

1475 - 2950

1215 - 1970

1510

T ert iary

Jain

tia

Oligocene

Pegu

Quaternary

> 3930

- Eocene

3445 - 8200

1280 - 4100M iocene

3935 - 8530

785 - 820

Irraw

addy

Alluv ium

Irrawaddy

Obogon

Ky aukkok

Py awbwe

Okhmintaung

Padaung/Tiy o


Yaw

Pondaung

Taunggale

Kanbala

PYAY

Myanaung

Thayet

OLIGOCENE

The Oligocene sandstone and black shale alterations of Lower Pegu Groups are exposed at the west of Pyay and north of Thayet in northwestern part of Pyay Embayment.


PE

RIO

D

EP

OC

H

GR

OU

P




Pliocene

1475 - 2950

1215 - 1970

1510

T ert iary

Jain

tia

Oligocene

Pegu

Quaternary

> 3930

- Eocene

3445 - 8200

1280 - 4100M iocene

3935 - 8530

785 - 820

Irraw

addy

Alluv ium

Irrawaddy

Obogon

Ky aukkok

Py awbwe

Okhmintaung

Padaung/Tiy o


Yaw

Pondaung

Taunggale

Kanbala

PYAY

Myanaung

Thayet

MIOCENE

The Miocene age of sand and shale alterations of Upper Pegu Groups are exposed at the Pyay oil field, and Thayet area (especially in northwestern part of Pyay Embayment).


PE

RIO

D

EP

OC

H

GR

OU

P




Pliocene

1475 - 2950

1215 - 1970

1510

T ert iary

Jain

tia

Oligocene

Pegu

Quaternary

> 3930

- Eocene

3445 - 8200

1280 - 4100M iocene

3935 - 8530

785 - 820

Irraw

addy

Alluv ium

Irrawaddy

Obogon

Ky aukkok

Py awbwe

Okhmintaung

Padaung/Tiy o


Yaw

Pondaung

Taunggale

Kanbala

PYAY

Myanaung

Thayet

PLEISTOCENE

PLIOCENE

The Miocene age of sand and shale alterations of Upper Pegu Groups are exposed at the Pyay oil field, and Thayetarea (especially in northwestern part of Pyay Embayment).


PE

RIO

D

EP

OC

H

GR

OU

P




Pliocene

1475 - 2950

1215 - 1970

1510

T ert iary

Jain

tia

Oligocene

Pegu

Quaternary

> 3930

- Eocene

3445 - 8200

1280 - 4100M iocene

3935 - 8530

785 - 820

Irraw

addy

Alluv ium

Irrawaddy

Obogon

Ky aukkok

Py awbwe

Okhmintaung

Padaung/Tiy o


Yaw

Pondaung

Taunggale

Kanbala

PYAY

Myanaung

Thayet

HOLOCENE

The Holocene age Quaternary and Alluvium sediments are exposed at the South of Pyay city and especially in the Basin center.

3900

4800

3600

4200

4500

5100

5400

5700

6000

6600

6900

OB

Fm

(3085 f

t)

63002700

2100

1800

900

300

0

600

1200

1500

2400

3000

Lowest exposed horizon

Low

er A

lter

nat

ion U

nit

(85

0 f

t)

Feet

3300

350 f

tK

K F

m(3

815 f

t)

7200

IRR

Fm

(510 f

t)

8100

Feet

Lithological descriptions

Alluvial

No exposure

Alternations

Shale/Clay

Silt

Sand

Gravel

3600

PY

Fm

Stratigraphy of Pyay Oil Field

Shwedaung

PYAY

0 3 6km

N

Stream section location

» The Upper Pegu Groups of Pyawbwe, Kyaukkok, Obogon formations and Plio-Pleistocene Irrawaddy Formation is exposed in the Pyay oil field.

Source; MOGE 1965

Well 1 (Supra-T)

1990

Well 1 (Sub-T)

1990

Stream Section

1966

Burma Geological

Note No. 561, 1975

Holocene Quaternary - - - -

Plio-Pleistocene Irrawaddy 1850 - 510 > 5200

Miocene (Upp) Obogon 3085 2500

Miocene (Mid) Kyaukkok 3815 2600

Miocene (Low) Pyawbwe 950 > 1080 350 > 2500

Thickness in feet

Age Formation

1200 950

1

1

Pyay S Well-140

IRR Fm

OB Fm

KK Fm

PY Fm

?

Pyay Syncline Bago Yoma

?

?

Oligocene Fm ?10 km

Nodular Shale in Pyawbwe Fm. Rounded concretion in Kyaukkok Fm.

Convolute structure (?) in Obogon Fm. Large-scale cross-bedding in Irrawaddy Fm.

STRUCTURAL INTERPRETAIONS, RERLATIONS AND HYDORCARBON POTENTIAL

» Structural interpretations are mainly focus on the structural styles of the current hydrocarbon producing area of Pyay North, Pyay South anticline and also on the new prospect of Namayan Structures.

Namayan Structure

» The narrow and parallel north to south ridges and valleys outcrops indicate the different formations or rock units.

» Sharp topography suggesting the surface fault traces of Pyay thrust along the west of Namayan structure from Pyay to south of Shwedaung.

» The Pyay thrust is probably bifurcated near the Shwedaung.

STRUCTURAL INTERPRETAIONS, RERLATIONS AND HYDORCARBON POTENTIAL

» Google earth image show the right-lateral oblique view by topographic shifting near Shwedaung Reservoir and south of Shwedaung area.

Shwedaung

Reservoir

Generalized Geological map of Namayan monocline(modified from Wandery, 2006 and Bender,1983).

» The area is covered by the complete Miocene units of Pyawbwe, Kyaukkok and Obogon formations and Plio-Pleistocene Irrawaddy Formation from west to east.

» The east limb of monocline is thrusted and dips vary from the 80° to 20° and gradually gentle to the east in the Irrawaddy Formation.

» Right lateral strike-slip features observed near the Shwedaung reservoir (Google earth images interpretation).

» Stereographic projection of bedding data indicated as the south plunging feature about 12° and trending NW-SE (162°).

Field Geological Observation

12°/162°

12°/162°

N

Namayan Mud Volcanoes

» Active mud volcanoes found in Pyawbwe Formation (at the east of Namayan) » It comprises altogether 10 mud volcanoes, diameters of the observed cratrrs range from 3

inches to 2.5 ft.» The volcanoes are probably formed along the fault plane of the Pyay thrust, which forms the

contact of boundary between the PY/KK formations (MOGE; 1966).

100 ft

Largest CraterSmallest CraterN

--95° 13'

18°

45'

N

Subsurface Structural Interpretations

Ap

pro

xim

ated

Form

atio

ns

Boundar

ies

2.0

1.0

3.0

4.0

2.0

1.0

3.0

4.0

OB Fm.

1 km

KK Fm.

IRR Fm.

OB Fm.

IRR Fm.

KK Fm.PY Fm.

Shwedaung-1 (Projected)

TD-6500

1 km

OB Fm.

KK Fm.

Ap

pro

xim

ate

Form

atio

n B

oundar

y

2.0

1.0

3.0

4.0

Shwedaung-1 (Projected)

TD-6500

Generalized Geological map of Namayan monocline (modified from Wandery, 2006 and Bender,1983).

2.0

1.0

3.0

4.0

» The presence of steeply east dipping bed (~ 40°) along east side of monocline reveals the Pyay thrust Geometry).» In contrast, the west limb is <5° and structural

developed by forelimb of Shwedaung Syncline to the west.

» The conjugated-set of east-west striking and south hading faults are developed probably in the south plunge of structure.

SOUTHNORTH

EASTWEST

NN

12°/162°

Pyay North Structure

Inn Ma

N

Inn Ma

2 km

N

18

°3

5'

-

-95° 17'

» Both of DEM and Google Earth images significantly show the nearly north-south striking and south plunging anticline feature of the Pyay North anticline.

» Very sharp topography along the west of the area show the Pyay thrust fault traces.

Image Interpretations

Well-17

Well-20

Well-50

Well-17

Generalized geological map of the Pyay North anticline, modified from MOGE (1965).

» The area is covered by the north-south striking Miocene units of Kyaukkok and Obogon formations overlain by the Irrawaddy Formation (Plio-Pleistocene).

» Bedding data suggested that the Pyay North anticline is asymmetrical fold which gentle east-flank (10°-40°) and steep west-flank (25°-65°).

» The Stereographic projection indicates the axis of anticline is striking ~N-S and double plunging to the north (16°) and also to the south (08°).

» The major thrust fault (Pyay thrust) can be traced by the vertical to overturned beds along the west-flank of structure.

16°/360°

08°/174°



Vertical-overturned beds of OB Fm, (Facing S) (N 18°33' E 95°15')

Vertical-overturned beds of IRR Fm, (Facing S) (N 18°33'9.36" E 95°15')


N

1

2

3

TWTS

Ap

pro

xim

ate

Form

atio

n B

ou

nd

arie

s

EASTWEST


N

?

» The monoclinal character of fold layer is start developed in the Lower PY Fm and gradually changed to thrust-bounded anticlinal fold near the contacts of PY/KK and OB formations at the core of anticline.

» The fold is well developed in the KK and OB formations by the thrust related and the west-vergent asymmetrical anticline.


OB/KK Fm.

PY Fm.

IRR Fm.

OKH Fm?


» In the seep west-flank, northeast-southwest striking and southeast hading extensional cross faults are developed.

» These faults are penetrated from the surface to the deeper part of Miocene Formations which suggested that the tectonic history of extensional cross-faults are developed after the Irrawaddy deposition time.

1

2

3

TWTS

4 Ap

pro

xim

ate

Form

atio

n B

ou

nd

arie

s

SOUTHNORTH


N

OB/KK Fm.

PY Fm.

IRR Fm.

OKH Fm?

Pyay South Structure

» DEM and Google Earth images can be interpreted the major structural features of the Pyay thrust by abrupt changed topography in the west.

Image Interpretations

-95° 19'

Inn Ma

4 km

18

°2

9'

-

N

DEM image (30 m resolution) Google Earth image (2015)

N

Well-17

» The area is exposed only the Irrawaddy Formation and recent alluvium.

» Dip of 10° to 35° were measured on the east-flank and west-flank dips are ranging 25° to 45°(Asymmetrical anticline).

» The axis is striking approximately NW-SE (~340°) direction and double plunging to the North (06°) and to the South (08°).

» Most of the area is covered by loosely Irrawaddiansand and recent alluvium where no mesoscopic indicators are observed in the present study for the major thrust fault.

» But the cross-faults and surface fractures are observed in Pyay South area.


Generalized geological map of the Pyay South anticline, modified from MOGE (1965).

06°/348°

08°/162°

N


~100 ft

3 ft

SE

1 ft

NW

Vertical and equal spacing joints in conglomerate beds of Irrawaddy Formation.

SN

N

Subsurface structural interpretations


» The amplitude of fold layer is generally start developed in the Lower PY Fm (~ 3 sec) and gradually changed to thrust-bounded anticlinal fold near the contact of PY/KK formations at the core of anticline.

1

2

3

TWTS

EASTWEST

Ap

pro

xim

ate

Form

atio

n B

ou

nd

arie

s

IRR Fm.

OB/KK Fm.

PY Fm.

N


» The NE-SW striking and southeast heading en-echelon parallel faults (in the west-flank) and minor graben of two parallel NE-SW striking conjugated normal faults (in east-flank) are approved the NW-SE extension.

DC

Ap

pro

xim

ate

Form

atio

n B

ou

nd

arie

s

BA

1

2

3

TWTS

1

2

3

TWTS

D

C

B

A

N

» The Pyay oil field structure lie along the trend of the

Pyay anticline including Namayan, Pyay North and

Pyay South structures.

» These structures are separated by two saddles to each anticline.

» The north saddle is located between south plunge (12°) of Namayan structure and north plunge (16°) of Pyay North structure.

» The south saddle is located between south plunge (08°) of the Pyay North structure and north plunge (06°) of the Pyay South structures.

16°/360°

08°/174°

06°/348°

08°/162°

12°/162°

Structural Relations on

North Saddle

South Saddle

Namayan, Pyay S & Pyay NNamayanMonocline

Pyay North

Pyay South

N

» The mean fold axes is trending 346° and mean compression is generally from 255°(W-E).

» The fold is slightly asymmetrical, the gentle east-flank is linked by the major Pyay Syncline and the steep west-flank is connected with the Shwedaung Syncline.

» Along the crest of the structure is broken by the Pyay thrust from the west-flank and the whole fold of three are compartmentalized by the E-W cross normal faults.

Joints-rose diagram

Mean fold axes and compression direction

Structural Relations onNamayan, Pyay S & Pyay N

NamayanMonocline

Pyay North

Pyay South

N

Bel

ow

1.6

sec

Pyay North

Pyay South

Bel

ow

1.2

sec

Below 3.5 sec

N

Below 2.6 secTime Slices Interpretations » The amplitude of the folded features are

quite different in the each subsurface units and the saddle feature disappear below the 1.6 sec.

» Sharp topography, nearly vertical-overturned bedding, short and straight drainage features are the surface fault traces of Pyay thrust.

» Namayan monocline, Pyay North and Pyay South anticlines are due to the propagating of Pyay thrust.

» Pyay thrust is bifurcated in the Miocene formations and terminated in the southern end of Pyay oil field.

» One of the bifurcated thrust is probably terminated near the formation boundary of the PY and KK formations. The other thrust sheet is terminated as nearly vertical in the PY Fm with no significant displacement.

Pyay Thrust

Generalized dip cross-sections across the Pyay oil field.

NamayanMonocline

PyayNorth

PyaySouth

Generalized dip cross-sections across the Pyay oil field.

» Changes in the amplitude of the anticline may preserve profile compression as the thrust displacement decrease towards the south.

» The Pyay thrust geometry is pure thrust features in the Namayan monocline, high angle thrust or reverse fault in the Pyay North anticline and also Pyay South anticline.

» The stratigraphic throws or vertical displacement of thrust are up to ~ 6000 ft in Namayan monocline,

~ 5000 ft in Pyay North anticline,

~ 3000 ft in Pyay South anticline and decreased towards the south of Pyay oil field.

NamayanMonocline

PyaySouth

PyayNorth

Cross Faults

» NE-SW direction and southeast hading normal faults are common.

» South-east dipping en-echelon normal faults are commons and some north-west dipping fault have been observed.

» These tow-sets of dipping faults are most likely form conjugate set that indicates NW–SW extension.

DNORTH

1

2

3

TWTS

NamayanMonocline

PyayNorth

PyaySouth

SOUTH

» At least two time of deformations (NW-SE extension) can be interpreted on cross faults (before and after deposition of IRR Fm).

DNORTH

1

2

3

TWTS

NamayanMonocline

PyayNorth

PyaySouth

SOUTH

1

2

3

TWTS

SOUTHNORTH

Time of Deformation

» The upper part of Irrawaddy Formation is involved in the folding (= folding is younger than IRR Fm deposition time).

» Pyay thrusting is believed to be after folding (seismic evidence).

1

2

3

TWTS

EASTWEST

NamayanMonocline

PyayNorth

PyaySouth

IRR

Fm

Hydrocarbon Implication» HC occurs in both of supra-thrust (east-flank) and sub-

thrust (west-flank) structure of exposed formations (PY, KK, OB and IRR Fm).

» Source may be Lower Miocene (so-call Pyawbweshale) and can also be the Oligocene age of Okhmintaung Formation (Assuming).

» Commercial accumulation of oil is found in the sub-thrust KK Fm and gas in PY Fm.

» HC bearing sands are trapped by fault bounded closure at the crest and plunge of the anticline and seal by shale layer of OB Fm.

SOUTHSOUTH

Generalized structural contour map of the near contact of KK/OB formation (4200‘ Sand)

NORTH

OB Fm.

KK Fm.

PYAY SOUTH PYAY NORTHNAMAYAN

5 km

CONCLUSION

SOUTH NORTH

OB Fm.

KK Fm.

PYAY SOUTH PYAY NORTH

NAMAYAN

5 km

1. The Namayan monocline, Pyay North and Pyay South anticlines are due to the

propagating of west verging major Pyay thrust in the steep west-flank.

2. All three structures have disharmonic features within the Pyawbwe Formation,

double plunging and separated by tow saddles structure.

3. The mean fold axes is trending 346° and the compression form 255°.

4. The area was probably raised (uplifted) to the North, started form the Pyay South

anticline. It is evident by the facts that some HC producing sands (4200‘ of Pyay

South anticline are exposed in the Pyay North anticline, and the whole thickness

of Irrawaddy sediments are absent in the Pyay North anticline.

PY Fm.

1

2

3

TWTS

4

Ap

pro

xim

ate

Form

atio

n B

ou

nd

arie

s

TD 12335 ft

PSC-2

TD 9020 ft

Well-1

TD 6500 ft

SDG-1 (Projected)

5. The Pyay thrust is bifurcated and terminated within the Pyawbwe Formation at

the southern end of the Pyay South anticlines.

6. Cross faults are occurred to have formed at least two times of extension before

and after deposition of Irrawaddy formation.

SUGGESTIONS

1. Needs to correlate the surface and subsurface structures (Exposure is very poor).

2. East-flank fault and west-flank faults also need to correlate (continuous or

different faults). If the cross-faults of the two flanks are able to correlate, the

definite timing of deformation on cross-faults and timing of hydrocarbon

migration can be estimated.

3. Stratigraphic correlation between THREE STRUCTURES on east-flank and west-

flank of the are crucial to better understand the reservoir continuity for the future

exploration activities in the studied area.

4. Detailed geochemical analysis of the potential source rocks are also

recommended for the future studies.

THANKYOU

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