Growth faults and its associated rollover anticlines are generally syndepositional sedimentary structures that 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 . Despite this abundance, their occurrence is however restricted to the extensional zone of the Niger delta. These structures can be identified from outcrops, seismic data , structure contour maps and well logs. While their propagation history can be constrained by the use of key kinematic tools, such as t-z, d-l and expansion index plots. Although, it has been identified that these structures are target structures in the accumulation of oil and gas, they can also be destructive, especially if they are reactivated after hydrocarbon accumulation. Hence, it is important for the petroleum explorationist to identify, map their extent and constrain the propagation history of these structures, in order to minimise exploration risk.

1. A REVIEW OF
GROWTH FAULTS AND ROLLOVER ANTICLINES
(A CASE STUDY OF NIGER DELTA )
PRESENTED
BY
JAMES OPEMIPO OLOMO
9 October 2014Undergraduate Seminar

2. 9 October 2014Undergraduate Seminar
PRESENTATION OUTLINE

3. 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
9 October 2014Undergraduate Seminar

4. 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

5. 9 October 2014
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

6.  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
9 October 2014Undergraduate Seminar

7.  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
9 October 2014
Listric Fault
Current direction
Current direction
Direction of
Movement
Rollover Anticline
WHAT ARE ROLLOVER ANTICLINES ?
Undergraduate Seminar

8.  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
9 October 2014
Benin Fm.
Agbada Fm.
Akata Fm.
Basement
Rollover Anticline
Undergraduate Seminar

9. 9 October 2014
Diagram showing the regional structure distribution in the Niger delta (AAPG Bulletin, November 2005, v. 89, p.1475-1491)
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10.  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).
9 October 2014Undergraduate Seminar

11. 9 October 2014
Diagram showing a rollover anticline trapping mechanism
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12. 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.
9 October 2014Undergraduate Seminar

13. STRUCTURE CONTOUR
MAPS: Anticlinal and
fault closures
regarded as good
hydrocarbon
prospect areas can
be delineated in
structure contour
maps.
9 October 2014Undergraduate Seminar

14. 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)
9 October 2014Undergraduate Seminar

15.  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.
9 October 2014Undergraduate Seminar

16.  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.
9 October 2014Undergraduate Seminar

17. 9 October 2014
.
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.201-338
E.K Nyantakyi et al (2013); Structural and stratigraphic mapping of Niger delta field, Agbada
Formation, offshore Niger delta, Nigeria. American journal of Engineering Research
Prof. 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.
Undergraduate Seminar

18. THANKS
FOR
LISTENING
9 October 2014Undergraduate Seminar

19. QUESTIONS/COMMENTS
9 October 2014Undergraduate Seminar