A REVIEW OF GROWTH FAULTS AND ROLLOVER ANTICLINES (A CASE STUDY OF NIGER DELTA)

A REVIEW OF GROWTH FAULTS AND ROLLOVER ANTICLINES

(A CASE STUDY OF NIGER DELTA )

PRESENTED BY

JAMES OPEMIPO OLOMO

9 October 2014Undergraduate Seminar

IntroductionAims And ObjectivesThe Niger Delta AreaGrowth Faults And Rollover AnticlinesGrowth Faults And Rollover Anticlines In The Niger DeltaHydrocarbon Trapping Mechanism Of Growth Faults And Rollover Anticlines In The Niger Delta Identification Of Growth Faults & Rollover Anticline The Niger DeltaEconomic ImportanceConclusion Thanks


PRESENTATION OUTLINE

INTRODUCTION Growth faults and rollover anticlines are generally

syndepositional structural features

They result from diastrophism which was contemporaneous with sedimentation

They are special structures which occur abundantly in the Niger Delta & constitute one of the most important hydrocarbon traps in the region


AIMS AND OBJECTIVES

The presentation is aimed at reviewing growth faults and rollover anticlines, especially as they occur in the Niger Delta basin.

The Objectives includes: Radius where these structures are seen in the

Niger Delta Identification of growth faults and rollover

anticlines Hydrocarbon trapping mechanism of these

structures 9 October 2014Undergraduate Seminar

THE NIGER DELTA AREA

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Niger Delta is a sedimentary basin, located at the apex of the gulf of Guniea, Southern Nigeria

It is a prolific hydrocarbon basin

It is composed of three main megasequences; the Benin, Agbada and Akata Formations.

Geological Map of Nigeria’s Sedimentary Basins (Obaje, 2009)

Undergraduate Seminar

WHAT ARE GROWTH FAULTS ?

Growth faults are normal faults that develop during sedimentation

Sediment accumulation on the downthrown block exceeds that on the upthrown block

The throw of the fault increase with depth and the fault plane becomes flatter

There is differential compaction on both sides of the fault


Rollover Anticlines are syndepositional structures developed at the downthrown sides of growth faults

They are formed when sedimentation along growth faults cause rotation

They grow concurrently with growth faults

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Listric Fault

Current direction

Current direction

Direction of Movement

Rollover Anticline

WHAT ARE ROLLOVER ANTICLINES ?


GROWTH FAULTS AND ROLLOVER ANTICLINES IN THE NIGER DELTA

Thick sediments overlying Agbada Formation exerts pressure on it, deposition direction is N-S (Hosper, 1971)

This pressure causes flowing of the Agbada Formation

Thus, results in growth faults and rollover anticlines

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Benin Fm.Agbada Fm.

Akata Fm.

Basement

Rollover Anticline


GROWTH FAULTS AND ROLLOVER ANTICLINES IN THE NIGER DELTA

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Diagram showing the regional structure distribution in the Niger delta (AAPG Bulletin, November 2005, v. 89, p.1475-1491)


HYDROCARBON TRAPPING MECHANISM BY GROWTH FAULTS AND ROLL OVER ANTICLINES IN THE NIGER DELTA

A trap is a geologic structure or phenomenon that stops the movement of hydrocarbon in reservoir rocks and enable hydrocarbon to accumulate in pools

Most traps in the Niger Delta are structural traps (i.e growth faults and rollover anticlines)

The primary seal rock in the N. Delta is the interbedded shale within the Agbada Formation (Duncan, Townsend 1997).


HYDROCARBON TRAPPING MECHANISM BY GROWTH FAULTS AND ROLL OVER ANTICLINES IN THE NIGER DELTA

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Diagram showing a rollover anticline trapping mechanismUndergraduate Seminar

IDENTIFICATION OF GROWTH FAULTS AND ROLLOVER ANTICLINES IN THE NIGER DELTA

SIESMIC DATA: Seismic profiles provide a view of the subsurface by defining its geometry and providing an estimation of the acoustic impedance of the Formation. Using kinematic tools such as T-Z plot, D-L plot and Expansion index plot.



STRUCTURE CONTOUR MAPS: Anticlinal and fault closures regarded as good hydrocarbon prospect areas can be delineated in structure contour maps.



WELL LOGS: This gives a vertical view of the subsurface but are limited laterally and in their definition of structures.

The accuracy of studying or identifying these structures in the Niger Delta is improved by combining seismic and well log data (Barde et al., 2002; Adejobi & Olayinka 1997)


IMPORTANCE OF GROWTH FAULTS AND ROLLOVER ANTICLINES

Growth faults are associated with rollover anticlines which acts as trap structures

Growth faults and rollover anticlines are easy to find through seismic method

The fault throw of these structures can produce migration pathway for hydrocarbon (If >150m in the Niger delta, (Weber and Daukoru, 1975 ).

Anticlinal traps are the most common type of petroleum trap, as about 80% of the world’s hydrocarbon are found in Anticlines.


CONCLUSION

The goal of oil and gas exploration is to identify and locate structural traps that constitute profitable exploitable accumulations and delineate the extent of discovery.

It has been established that growth faults and rollover anticlines are target structures in the accumulation of oil and gas but these structures can also be destructive especially if they are reactivated after hydrocarbon accumulation.

Hence the need for the petroleum explorationist to identify, study their development, trapping mechanism, and delineate their extent before exploration.


REFERENCES

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Aizebeokhai A.P. and Olayinka I. (Feb. 2011); Structural and stratigraphic mapping of Emi Field offshore Niger delta. Journal of Geology and Mining Research. Aminu B.M. and Olorunniwo M,O. 2012; Seismic paleo-Geomorphic system of the extensional province of the Niger Delta: An example of the Okari field. Intech open science journal. p.79-86. Bjerkvik, A. S. (2012); "Seimic analysis of Carboniferous rift basin and Triassic growth-fault basins of Svalbard; analysis of seismic facies patterns with bearing on basin geometry and growth-strata successions (Doctoral dissertation, Norwegian University of Science and Technology". Earth Sciences and Petroleum Engineering. Cazes, C. A. 2004; Overlap Zones, Growth Faults, and Sedimentation: Using High Resolution Gravity Data, Livingston Parish, LA.". Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfilment of the requirements for the degree of Master of Science in The Department of Geology and Geophysics; Louisiana State University, Thesis. p. 147. Doust, H. and Omatsola, E. 1990; Niger Delta. In Edwards, J.D and Santogrossi, P.A. (Eds.), Divergent/passive margin basins. Mem.AAPG, No.48, p.201-338E.K Nyantakyi et al (2013); Structural and stratigraphic mapping of Niger delta field, Agbada Formation, offshore Niger delta, Nigeria. American journal of Engineering ResearchProf. C.S. Nwajide. 2013; Geology of Nigeria’s sedimentary Basins p.456-460. Sebastien Castelltort et al (2004); Using T-Z plots as a graphical method to infer lithological variation for growth strata. Journal of structural Geology.


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