Assessment of Sealing Potential of Fault-Bounded Hydrocarbon Prospect in Gabo Field, Niger Delta, Nigeria

Abstract

Sealing potentials of faults are an important exploration risk to consider in the assessment of fault-bounded hydrocarbon prospects. This technique has been used for predicting potential hydrocarbon columns for mitigating risk in exploration and appraisals. Hence, the objective of the paper is to assess the sealing potential of the fault-bounded hydrocarbon prospects of the Gabo Field in the Niger Delta basin using seismic, well-log, and X-ray diffraction data. Three faults were interpreted as normal and syn-depositional faults. The well-log correlation showed that the shale sequence was inter-bedded with sands and showed a good spread with a relative thickness ranging between 12-105m from shallow to intermediate depth intervals. Results of the rock property analysis showed that the volume of shale ranged from 18 – 73.72% with an average of 63.59%. The total porosity ranged from 15.9 – 31.7 (good to excellent) with an average of 16.7 (good) in the shales and 27.2 (very good) in the sand. The effective porosity of the field ranged from 3.58 – 22.71 with an average of 6.028 in the shales and 20.13 in the sand. The estimated pore pressure ranged from 42.13 – 47.62psi with an average of 47.0psi in the shales and 42.8psi in the sand. The results of the X-ray diffraction analysis showed that the predominant minerals were kaolinite, rutile, gypsum, albite, microcline and quartz, which constitute the caprock sequence and the faulted rocks. Results of the sealing potential showed poor sealing in the shale sequence while the fault analysis showed good sealing along the fault planes. These results deduced the sealing uncertainty of the field and may be applied to similar siliciclastic trap configurations in deltaic environments.

Keywords

• Shale, Caprock, Seal, Trap, Niger Delta Basin