--> Investigating the Sealing Properties of a Major Growth Fault and its roles in Hydrocarbon Distribution - A Case Study of JEGE Field Southeastern Niger Delta, Nigeria, by Ayodele Ariyo; #90037 (2005)

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Investigating the Sealing Properties of a Major Growth Fault and its roles in Hydrocarbon Distribution - A Case Study of JEGE Field Southeastern Niger Delta, Nigeria

Ayodele Ariyo
Federal University of Technology Owerri, Imo State, Nigeria

Seals are an important and commonly overlooked component in the evaluation of a potential hydrocarbon accumulation. Effective seals for hydrocarbon accumulations are typically thick, laterally continuous, ductile with high capillary entry pressures. A number of statistical algorithms were employed in the bid to critically estimate the distribution and relative amount of shale along the stated fault zone which penetrated wells 1 and 5 at 8000 ft and 10,725 ft respectively. In a well illustrated relationship, the clay smear potential (CSP) values obtained increased from top to bottom of the fault plane but decreased drastically at about 11,325 ft to as small as 10 ft indicating an inverse relationship between the clay smear potential and fault throw, which the latter at this point is as much as 204 ft, hence increase in fault throw led to increase in the CSP values at that point. The general variation of the CSP values obtained showed that hydrocarbon bearing sands D - 07; C _01; A- 09 are trapped in windows that that have high to medium CSP values respectively. The oil/water contact seen in SAND_D_07_W_1, at 11,435 ft in the hanging wall may be as a result of the loss of critical clay-smear seals. Low CSP values obtained in the study represent very minute chance for the presence of continuous clay smear seals that can trap hydrocarbon. The increase in CSP values below 10,956 ft reflects an increase in fault seal from smearable clay as well as from juxtaposition against impermeable strata. The smear gouge ratio obtained at chosen positions equally rose steadily from 0.043 to as much as over 0.76 as we move basin ward, indicative of greater amount of smearable shale available for the proper sealing of the closures, hence, a more detailed knowledge of reservoir compartmentalization and communication will result in a more optimum development development of the field.