international journal of modern applied physics, 2020, 10

Copyright © 2020 by Modern Scientific Press Company, Florida, USA

International Journal of Modern Applied Physics, 2020, 10(1): 54-68

International Journal of Modern Applied Physics

Journal homepage:www.ModernScientificPress.com/Journals/ijmep.aspx

ISSN: 2168-1139

Florida, USA

Article

Structural Interpretation of Three-dimensional Seismic Data

from B-field, Located in the Niger Delta Area, Nigeria

Bright C. Abanum.1, Egbo D. Okechukwu.2

1Department of Physics, University of Benin, Benin City, Nigeria

2Department of Physics, Ambrose Alli University, Ekpoma, Nigeria

* Author to whom correspondence should be addressed; E-Mail: [email protected]

Article history: Received 29 May 2020, Revised 5 August 2020, Accepted 15 August 2020, Published

24 August 2020.

Abstract: In this research work, a three-dimensional(3-D) seismic data from B-field, located

in the Niger Delta, Nigeria has been interpreted with the aim of generating a structural model

of the subsurface of the area with a view to reveal special features favorable to the

hydrocarbon prospectivity of the study area. The 3-D seismic volume data was interpreted

using OpendTect 4.3.0 software. Faults were delineated in field but only four was of interest

F1, F2, F3, F4. The fault F3 is the major growth fault in the field. Its setting tips it as a good

reservoir sealing structure. We have the faults F2 and F4 described as the antithetic faults.

Fault F1 can be describe as normal fault. Two seismic reflection horizons H1 and H2 were

mapped based on their reflection patterns. The seismic section reveals the structural

configuration of the field as an anticlinal dip closure. Since anticlinal and fault assisted

closures are regarded as good hydrocarbon prospect areas in the Niger Delta. It can be

therefore suggested that the trapping potential of the field are attributed to faults, acting as

fault assisted closures which have been perceived to be responsible for high retentive

capacity of the reservoirs and the hydrocarbon trapping mechanism in the studied area.

Keywords: 3-D (Three Dimensional), seismic data, Fault, Horizon, OpendTect 4.3.0

software, B-field, Niger Delta

mailto:[email protected]

Int. J. Modern App. Physics. 2020, 10(1): 54-68


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1. Introduction

The increasing population and standards of living of people globally has caused a growing

demand for energy source and despite the many efforts made to exploit `new' energy sources such as

solar energy and bio-mass in other to containing this increasing demand, oil and gas has continue to be

the primary sources of energy. In Nigeria, oil almost constitutes exclusively the revenue base for national

development and as such, demands greater efforts from both the Government and the research

institutions to ensure that this non-renewable resource is adequately and optimally tapped.

In view of the exploration of the huge deposits of the natural resources, particularly the

hydrocarbon deposits, the study of exploration geophysics has been of great relevance to the oil and gas

industry as this helps the exploration industry in identifying and delineating structural features that could

serve as possible traps for the accumulation of hydrocarbons Owing to the fact that this lucrative natural

resource has become the major source of the Nigerian economy, all efforts have been intensified over

the years to ensure the continuous exploration and production of this hydrocarbon deposits.

The production of oil and gas is from accumulation in the pore spaces of reservoir rocks usually

sandstone, limestone and dolomite. The formation is characterized by alternating sandstone and shale

units varying in thickness from 100ft to 1500ft [8].

There are various geophysical exploration methods applicable in tapping this great natural

resource which includes; the gravity, magnetic, seismic, electrical method and others. However, the

biggest breakthrough in petroleum and natural gas exploration came through the use of seismic method

while magnetic and gravity methods are used for reconnaissance surveys to delineate areas of interest

[11].

The goal of oil and gas exploration is to identify and delineate structural and stratigraphic traps

suitable for economically exploitable accumulations and delineate the extent of discoveries in field

appraisals and development [2].

[4] worked on the Reservoir characterization and structural interpretation of seismic profile: A

case study of Z-field, Niger Delta, Nigeria, showed that detailed study of the petrophysical results of the

field will provide an understanding of the geometric properties of the reservoirs, lateral variation in

thickness and possible hydrocarbon accumulations.

Three-dimensional (3-D) seismic exploration is capable of providing the most complete

subsurface picture of any surface-based geophysical technique. The essence of the method is a real

deployment of sources and receivers on a 2-D grid, followed by processing and interpretation of the

resulting densely sampled volumetric data [1].

Fundamentally, however, the greatest benefit of 3-D resides in its spatial resolving power both in

terms of absolute spatial resolution and relative accuracy in image positioning [20]. Features such as



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fault systems can now be mapped in much more detail than with 2-D seismic data, with its inherent

limitations of spatial aliasing [10].

[12] worked on feature detection algorithms using a Hough transform, and deduced that 3D fault

surfaces can automatically be extracted.

[3] worked on Emi Field of Niger Delta region, they showed that Anticlinal closures and fault

assisted closures which are regarded as good hydrocarbon prospect areas were found in the study area

and apart from the structural traps delineated, other stratigraphic pays including pinch-outs,

unconformities, sand lenses and channels were also suspected.

Other related contribution to knowledge in the context of 3-D structural interpretation of seismic

data can be seen in [1-20]

2. Theory

GEOPHYSICAL TECHNIQUES

Natural resources which are buried underneath the subsurface of the earth requires the application

of certain geophysical methods which reveals the possibilities of hydrocarbon presence and other

essential minerals at the subsurface of the earth and these methods have been of great relevance to the

oil and gas industries.

There are various methods which are available for geophysical survey which provides us with a

higher resolution picture of the subsurface geological features. The geophysical methods are basically

categorized into two which includes:

(1). The natural methods. This comprises of the following:

Magnetic

Gravity

Radiometric

Electrical method comprising of the resistivity, electromagnetic, self and induced potential

method and the telluric methods.

(2). Artificial methods:

Seismic

Electrical method comprising of the resistivity, electromagnetic, self and induced potential

method and the telluric methods.

Seismic survey method consists of creating a mechanical disturbance somewhere at the surface

of the earth or deep in a well and observing its effects at a number of locations along the surface or inside

the well. The objective of seismic exploration is to deduce information about the rock especially about



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the attitude of the beds, from the observed arrival time and from variation in amplitude, frequency and

waveform [16]. This survey method encompasses two methods which includes;

Reflection method

Refraction method.

There are two groups of seismic waves, body waves and surface waves [13]. Body waves are

waves that can propagate through the body of an elastic solid. They are of two types P-waves and S-

waves. S-waves are slower than P-waves and can only move through solid rock, not through any liquid

medium. [13] showed that the velocity of propagation of a body wave in any material is given by

𝑉 = [𝑎𝑝𝑝𝑟𝑜𝑝𝑟𝑖𝑎𝑡𝑒 𝑒𝑙𝑎𝑠𝑡𝑖𝑐 𝑚𝑜𝑑𝑢𝑙𝑒𝑠 𝑜𝑓 𝑚𝑎𝑡𝑒𝑟𝑖𝑎𝑙

𝑑𝑒𝑛𝑠𝑖𝑡𝑦 𝑜𝑓 𝑚𝑎𝑡𝑒𝑟𝑖𝑎𝑙 ]

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The general purpose of seismic survey is to give exploration knowledge about the various strata

beneath the earth’s surface. The three major components of the survey are data acquisition, data

processing and interpretation.

Seismic data acquisition refers to field procedures as well as the operational principles of

instruments used in obtaining information about the subsurface structure. The acquisition of seismic data

can either be done by reflection method or refraction method which is either carried out on land (land

survey), transition zones or at sea (marine survey).

The purpose of seismic data processing is to manipulate the acquired data into an image that can

be used to infer the sub-surface structure. Only minimal processing would be required if we had a perfect

acquisition system. Processing consists of the application of series of computer routines to the acquired

data guided by the preference of the processing geophysicist. The interpreter should be involved at all

stages to check that processing decisions do not radically alter the interpretability of the results in a

detrimental manner. From good quality data it is possible to estimate lithology in terms of velocity

information and pore content from amplitudes of reflections. Processing is carried out in time domain,

common midpoint (C.M.P) domain and stack domain [14].

The aim of seismic reflection surveying is to reveal as clearly as possible the structure of the

earth. Seismic interpretation which is part of seismic surveying is the process of determining information

about the subsurface of the earth as well as the geologic significance of seismic reflection data. Seismic

interpretation also involves the construction of a geological model of the subsurface using all available

data such as seismic section, check short data and well log. The interpreter’s job is to extract geological

meaning, both structural and stratigraphic, from these geophysical data.



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3. Methodology

The data for this paper consist of a 3-D volume of seismic reflection data having a large number

of inlines and crosslines. The interpretation of the 3-D seismic volume was carried out using

interpretation software called ‘Opendtect 4.3.0 version’. This software is a C++ programme which is

designed as an open source seismic interpretation programmed software used in interpreting structural

features (faults and horizons) of the earth subsurface from the 3-D seismic volume.

4. Results and Discussion

Results are listed in tables and figures below. Seismic interpretation of Bright-field (B-field)

revealed that the structural style that characterizes the field contains some interesting features. The

seismic section reveals the structural configuration of the field as an anticlinal dip closure as shown in

Figure 7, which is a fault assisted dip closure. This anticlinal configuration has a time structure increasing

in depth from N-E to S-W with colour increasing from dark red to dark blue. That is, these colors on the

time structure map indicate the travel times of depth. It can also be deduced that the blue portion of the

interpreted data have a greater depth than the red portion, that is the red part is shallower than the blue,

thereby making an anticlinal structure.

Seismic attribute analysis (RMS amplitude slices) performed on the interpreted section, shows

that the structural configuration observed (anticline and faults combination) in the field have

hydrocarbon trapping capacities as illustrated by Figures (2-8) and Figures (10-13).

From the seismic interpretation, a number of faults were identified and mapped which are

displayed on Figures (2-3) and table 1. The fault F3 (Royal blue) is a major growth fault which have a

main trend from the North-East direction to South-West direction and main dip towards southward

direction, which can however be inferred to as a good trap and we have the faults F2 (Dark Sea green)

and F4 (Dark green) described as the antithetic faults which have a main trend from the South-East

direction to north-East direction and a main dip towards Northward direction. Fault F1 (Orchide) dips in

the south direction and it can be described as the normal fault.

From the interpretation of the seismic volume with several horizons, two seismic reflecting

horizons were mapped based on their reflection patterns on every ten in-line and every five cross-line

where data quality was adequate to confidently follow reflectors, thereby generating a 10x5 grid. These

horizons were identified as H1 (Dark Magenta), and H2 (Dark Turquoise) as shown in Figure (6).

Horizon 1(H1) has a good continuity from N-E until truncated by a major fault and later

continued towards S-W and was truncated again by another fault as shown in Figure (7). An Amplitude

attribute was generated for horizon 1 (H1) with a time window of 25ms and 50ms time window and from



59

this attribute, it shows from the color key that H1 has an high amplitude at the north direction and south-

west which represent a very large sand body and an intercalated shale body of low amplitude as shown

in Figure (10-11).

Above the H1, is Horizon 2 (H2), which is also continuous from N-E until truncated by a major

fault and later continued towards S-W and was truncated again by another fault as shown in Figure 8.

An Amplitude attribute was generated for horizon 2 (H2) with a time window 25ms and 50ms. From the

color key, H2 has a low amplitude towards North-East direction which shows that the portion is made

up shale body and high amplitude at South-West direction which represent a sand body as displayed by

Figure (12- 13).

Figure 1: Perspective view of the 3-D seismic volume used for this study

Table 1: Different interpreted faults, their dip direction and the fault types

FAULTS FAULT DIRECTION FAULT TYPE

F1 SOUTH Minor growth fault

F2 NORTH Antithetic fault

F3 SOUTH Major growth fault

F4 NORTH Antithetic fault



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Figure 2: The four faults displayed on 11600 inline on the seismic section

Figure 3: A 3-D view of the faults with planes displayed on the seismic section



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Figure 4: A 3-D view of the horizons display (with Z-values) showing the depth characteristics

Figure 5: A 3-D display of two Horizons on inline 11600 (H1 represented by the Dark Magenta

colour that passes through the horizon and H2 represented by the Dark Turquoise colour

that passes through the horizon)



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Figure 6: A 3-D view of the horizons display (without Z-values)

Figure 7: A 3-D view of the horizon one (H1) display and faults



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Figure 8: A 3-D view of the horizon two (H2) display and fault planes

Figure 9: shows that the interpreted seismic section which reveals Anticlinal structure



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Figure 10: A display of amplitude attribute of Horizon 1 (H1) on the seismic section with

time window of 25ms

Figure 11: A display of amplitude attribute of Horizon 1 (H1) on the seismic section with a

window of 50ms



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Figure 12: A display of amplitude attribute of Horizon 2 (H2) on the seismic section with

time window 25ms

Figure 13: A display of amplitude attribute of Horizon 2 (H2) on the seismic section with a

window of 50ms



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5. Conclusion

The seismic data volume resulted in better understanding of the structural styles. The seismic

volume used for this study was interpreted using the software opendtect 4.3.0. From the interpretation,

four faults, were identified which has a major growth fault trending south, two antithetic fault trending

north and a normal fault having a dip direction in the southward.

The seismic section reveals the structural configuration of the field as an Anticlinal dip closure

as shown in Figure 9, which is a dip assisted fault closure where apparent fault dependent element of

closure is less than 50ft, dissected anticlinal dip closure: a pure dip closure dissected by non-sealing

synthetic and antithetic faults. About 50% of hydrocarbon bearing reserves in Nigeria appears to be dip

closed [20]. Furthermore, they also stated that the trapping styles in the Niger Delta are mostly structural.

Therefore, it can be deduced that the growth fault F3 and the normal fault F1 may have acted as migratory

paths for hydrocarbon flow from the underlying Akata Formation. Also, since Anticlinal and fault

assisted closures are regarded as good hydrocarbon prospect areas in the Niger Delta. It can be therefore

suggested that the trapping potential of the field are attributed to faults, acting as fault assisted closures

which have been perceived to be responsible for high retentive capacity of the reservoirs and the

hydrocarbon trapping mechanism in the studied area. It is therefore inferred that large areas covered by

the growth fault, antithetic faults and the normal fault are suggested to be the controlling factors

responsible for economic hydrocarbon accumulation in this particular study area of the Niger Delta.

The horizons H1 and H2 are associated with strong reflections and high amplitudes toward the

S-W direction. These results indicate that the hydrocarbon boundary is close to the strong or high

amplitudes representing a sand body as illustrated by the seismic attributes.

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