RESERVE ESTIMATE OF IMERI BITUMEN DEPOSIT (A CASE STUDY OF IMERI, OGUN STATE, NIGERIA)
There has been tremendous interest in the exploration in the production activities of readily available alternatives to conventional oil. Oil seeps observed in Imeri, Ijebu-Imushin, Ogun state, south-western Nigeria, serve as an indication of the occurrence of bituminous sand-a nonconventional hydrocarbon resource-in the area. Vertical Electrical Sounding techniques were employed to map the occurrence and extent of this black gold deposits in the study area. Three Vertical Electric Sounding were carried out using schlumberger array configuration. Modeling the likely subsurface structures indicates a likely maximum depth to basement of 13.4m for the bituminous sand across the study area. The constructed strata from the electrical methods revealed that bituminous sand deposit are likely to be present and substantial in the study area with a reserve estimate of more than one million barrels of bituminous sand in place.
TABLE OF CONTENT
TITLE PAGE - - - - - - - - i
CERTIFICATION - - - - - - - - ii
DEDICATION - - - - - - - - iii
ACKNOWLEDGEMENT - - - - - - - iv
TABLE OF CONTENT - - - - - - - v
LIST OF TABLES - - - - - - - - viii
LIST OF FIGURES - - - - - - - - ix
ABSTRACT - - - - - - - - - x
1.0 INTRODUCTION - - - - - - - 1
1.2 AIM AND OBJECTIVE - - - - - - 2
1.3 SCOPE AND LIMITATION - - - - - 3
1.4 LOCATION AND ACCESIBILITY - - - - 3
1.5 RELIEF AND DRAINAGE - - - - - - 3
1.6 CLIMATE AND VEGETATION - - - - - 4
1.7 DURATION - - - - - - - - 4
1.8 JUSTIFICATION - - - - - - - 4
1.9 GEOLOGICAL DISCRIPTION OF IMERI BITUMEN DEPOSIT- 8
1.10 REGIONAL GEOLOGY - - - - - - 8
2.0 DEFINITIONS AND LITERATURE REVIEW - - - 13
2.1 DEFINITIONS - - - - - - - 13
2.1.1 BITUMEN: - - - - - - - - 13
2.1.2 ASPHALT: - - - - - - - - 13
2.1.3 TAR: - - - - - - - - - 14
2.2 LITERATURE REVIEW - - - - - - 15
2.3 PROSPECTING HISTORY - - - - - 16
2.4 ENGINEERING STUDIES - - - - - 19
2.5 DETAILED SURVEY HISTORY OF BITUMEN IN THE
SOUTHERN PART OF NIGERIA - - - - 20
2.5.1 NIGERIA BITUMEN CORPORATION - - - - 20
2.5.2 SHELL D'ARCY - - - - - - - 21
2.5.3 SHELL BP - - - - - - - - 21
2.5.4 MOBIL OIL -- - - - - - - - 23
2.5.5 UNIVERSITY OF IFE (OBAFEMI AWOLOWO UNIVERSITY)- 23
2.5.6 NIGERIAN NATIONAL PETROLEUM CORPORATION - 24
2.5.7 JEREZ ENERGY - - - - - - - 24
2.5.8 BITUMEN PROJECT IMPLEMENTATION COMMITTEE (BPIC) -25
2.6 OGUN STATE NATURAL BITUMEN DEPOSITS - - -25
2.7 A PRELIMINARY ESTIMATE OF WORLD HEAVY OIL
AND BITUMEN RESOURCES - - - - - 26
3.0 EVALUATION OF IMERI BITUMEN DEPOSIT - - 30
3.1 THEORY - - - - - - - - 30
3.2 MATERIALS AND METHODS - - - - - 34
4.0 RESULTS AND INTEPRETATION OF DATAS - - 38
4.1 INTEPRETATION OF DATA (VERTICAL ELECTRIC
SOUNDING)- - - - - - - - 38
4.3 RESERVE ESTIMATE OF IMERI BITUMINOUS
SAND DEPOSIT - - - - - - - 34
5.0 CONCLUSION AND RECOMMENDATION - - - 43
5.1 CONCLUSION - - - - - - - 43
5.2 RECOMMENDATION - - - - - - 43
REFRENCES - - - - - - - - 44
LIST OF FIGURES
FIG. 1.1: Global demand for oil and gas
FIG. 1.2: Base map of the study area
FIG. 1.3: Topographical Map of the study Area
FIG. 1.4: General geological framework of the Dahomey Basin
FIG. 1.5: Geological map of south-western Nigeria showing the tar sands outcrop belt.
FIG. 2.1 Classification of Bituminous materials
FIG. 2.2: Historical Well and Borehole Data, Block 474 Vicinity
FIG. 2.3: Possible Hydrocarbon plays on block 474
FIG. 3.1: Equipotentials and current lines for a pair of current electrodes A and B on a homogeneous half-space.
FIG. 3.2: Schlumberger Array Configuration
FIG. 3.3: Resistivity range for various rock types (Palacky, 1987)
FIG. 3.4: Computer iterated curve of apparent resistivity against electrode spacing .
FIG. 4.1: Lithological correlation across the two (VES) points; the last lithological units in the two sections are manually inferred to infinity.
LIST OF TABLES
TABLE 1.1: The lithostratigraphic units of the Cretaceous to Tertiary sedimentary sequence of eastern margin of Dahomey basin
TABLE 2.1: Details of Asphalt production at the Kaduna Refinery, 1980 - 1992
TABLE 2.2: Estimated reserves for major Bitumen deposits in the world
TABLE 2.3: A preliminary estimate of the world heavy oil and bitumen resources (in barrels)
Table 3.1: Electrode spacing and Resistivity values for VES 1 and VES2
TABLE 4.1: Summary of VES results in the study area.
The Petroleum industry has become the mainstay of the overall economy of Nigeria, accounting for about 90 per cent of the country’s foreign exchange earrings, about 20 per cent of the Gross Domestic Product, and about 85 per cent of the Federal Government collectable revenue. The demand for this back gold is fast increasing worldwide. Figure 1.1, from Purvin & Gertz' most recent Global Petroleum Market Outlook study, shows how petroleum product demand has grown since 1995 and how it is expected to continue to grow through 2015. The study shows a 1.7 % per annum growth in worldwide demand and that this growth rate will continue over the next 15 years. The Purvin & Gertz study also states that the growth in crude supplies from 60 million barrels per day in 1990 to 75 million barrels in 2005 will continue up to 95 million barrels per day in 2020. The current growth in transportation fuel demand is outpacing the supply of traditional crude oil sources.
This gap can be filled through increased production of non-traditional hydrocarbon deposits, such as Canadian oil sands, Venezuelan heavy oils. It is apparent that increasing amounts of petroleum will come from nonconventional sources. Hence the need for the development of our heavy crude deposits. Therefore, in order to ensure continuity and orderly development of the industry, the Federal Government put in place a Petroleum Policy. Prominent among the objectives of the Policy is the development of the large deposit of tar sands in the country.
The extensive geological studies carried out largely by the staff of the University of Ife (now Obafemi Awolowo University) IIe Ife, confirmed the existence of the natural bitumen in Western Nigeria in commercial quantities. Similarly, the limited engineering studies of the naturally occurring bitumen in the Okitipupa area of Ondo State. Also, reference to various reports, newspaper publications and other information media in Nigeria within the last two decades is a pointer to the fact that petroleum crude, generally a major source of bitumen, has been aptly described as Nigeria's "black gold". But can this "black gold" concept of petroleum crude oil be extended to bitumen? Perhaps the second phase of Nigeria's economic breakthrough is round the corner!
It is in the light of the foregoing that the title of this research work has been chosen to read: "the reserve estimate of Bitumen deposit in Imeri, Southwestern Nigeria?" to find out if the natural bitumen can be mined in commercial quantity as a nonconventional petroleum to support Nigeria' s economic sector .
At the end of this project, we hope to be able to find solution to some pertinent questions like:
1) What is the meaning of bitumen?
2) What is its reserve estimate of bitumen in the study area?
3) What is its economic viability?
1.2 AIM AND OBJECTIVE
This project work aimed at determining:
The reserve estimate of bitumen deposit in Imeri, Ogun State, South-western Nigeria.
Its objective is to use this reserve in evaluating its commercial viability.
1.3 SCOPE AND LIMITATION
This project work covers:
I. The determination of the depth of burial, thickness and aerial extend of deposition of bitumen in the study area.
II. The estimation of bitumen reserve using the values gotten from above in the study area.
As a result of the short duration coupled with financial constraint this project will be limited to the study area.
1.4 LOCATION AND ACCESIBILITY
The study area lies within latitude 06046´-06049´N and longitudes 003058´-003060´E, on an area extent of approximately eighteen square kilometers (~18sq. km), a sedimentary terrain in the Dahomey Basin of Southwestern, Nigeria. The village has good road network that link it to the express. (Fig. 1.2)
1.5 RELIEF AND DRAINAGE
Imeri is almost a flat plain ground with extremely low relief with elevation between 100ft and 250ft above sea level, the drainage pattern is sub-dendrite-like with an average annual temperature of 310C and mean annual rainfall of 1200mm to 2300mm.
1.6 CLIMATE AND VEGETATION
The climate of Imeri is of moderately high humidity, the vegetation include shrubs, grasses and forest with agriculture being the predominant occupation of the dwellers.
This project work is expected to be done within six (6) months in accordance with the school calendar and should be ready latest September, 2011.
This project work when completed will boost the nation’s economy by preserving our conventional oil reserves while attention is focused on bitumen development, if all the recommendations proposed are implemented.
Fig. 1.1: Global Demand for Oil and Gas
Fig. 1.2: Base map of the study area
Fig. 1.3: Topographical Map of the study Area
1.9 GEOLOGICAL DESCRIPTION OF IMERI BITUMEN DEPOSIT
The bitumen seepages in Imeri were influenced by the presence of a fault and absence of a good cap rock. The fault is thought to serve as a conduit for the migration of the bitumen to the surface. Further fault seal analyses may incorporate the determination of the Shale Gouge Ratio (SGR) along the fault zones.
Faults play an important role in controlling the accumulation and migration of hydrocarbons. They can act as barriers to fluid flow i.e. seal reservoirs and stop migration of the hydrocarbon, and can also provide lateral and vertical migration paths for fluid. The general characteristic of oil sands (Bitumen) reservoirs is that they lack appropriate cap rock to keep the hydrocarbon in place which usually is responsible for their biodegradation. Other than this, wherever oil seepages are recorded the question in the mind of most structural geologists is to what is responsible for the seepage, whether there is a fault in place to structurally keep the hydrocarbon in the reservoir or the ability of such faults to act as conduits for the passage of the Hydrocarbon to the surface of the earth.
1.10 REGIONAL GEOLOGY
The Benin (Dahomey) Basin constitute part of a system of West African pericratonic (margin sag) basin (Kingston et al 1983) developed during the commencement of the rifting, associated with the opening of the Gulf of Guinea, in the Early Cretaceous to the Late Jurassic (Burke et al, 1971;Whiteman, 1982).
The crustal separation, typically preceded by crustal thinning, was accompanied by an extended period of thermally induced basin subsidence through the Middle – Upper Cretaceous to Tertiary times as the South American and the African plates entered a drift phase to accommodate the emerging Atlantic Ocean (Storey, 1995; Mpanda, 1997).
On the western part, the basin is bounded by the Ghana Ridge, which is presumably an offset extension of the Romanche Fracture Zone while the Benin Hinge Line, a Basement escarpment which separates the Okitipupa Structure from the Niger Delta basin binds it to the east. The Benin Hinge Line supposedly defines the continental extension of the Chain Fracture Zone, Figure 1.4.
The onshore part of the basin covers a broad arc-shaped profile of about 600 km2 in extent. The onshore section of the basin attains a maximum width, along its N-S axis, some 130 km around the Nigerian – Republic of Benin border. The basin narrows to about 50 km on the eastern side where the basement assumes a convex upwards outline with concomitant thinning of sediments. Along the northeastern fringe of the basin where it rims the Okitipupa high is a brand of tar (oil) sands and bitumen seepages (Nwachukwu et al 1989). The lithostratigraphic units of the Cretaceous to Tertiary sedimentary sequence of eastern margin of Dahomey basin is summarized in Table 1.1 below..