3-D SEISMIC INTERPRETATION AND FAULT SEALING ASSESSMENT OF ‘X’-FIELD OFFSHORE NIGER DELTA

Abstract

3-D seismic interpretation and fault-sealing assessment of ‘X’-Field, Offshore Niger Delta is an important topic to embark on in reservoir management because geologic structures accumulating hydrocarbon could be fault assisted or fault dependent, and these faults could be described as sealing or leaking in nature. In ‘X’-Field, it is important to know the sealing integrity of faults in order to improve on the economic viability of reservoirs. Several studies have been done to predict seals and leakages of faults along fault planes. Among the different methods applied in mapping fault integrity are: Clay Smear Potential (CSP), Shale Smear Factor (SSF) and Shale Gouge Ratio algorithm. This research was aimed at using Shale Gouge Ratio algorithm (SGRa) and the Manzocchi empirically derived fault-flow equations to assess the sealing capacity of faults in the ‘X’-Field. The objectives adopted are: identifying lithologies and reservoirs, estimating reservoir petrophysical parameters, determining the environment of deposition and age of sediments, examining the applicability of SGRa in predicting fault-seal, and delineating the mechanisms that affects the sealing capacity of faults in the study area. The methods employed for this research include: reservoir evaluation to understand the composition of the fault gouge and computation of fault gouge parameters (SSF, SGR, Fault permeability, and Fault transmissibility). Two reservoirs B and C were identified and they showed a good/excellent permeability of 100-10000 mD and a low shale volume<15 %. The permeability model of the faults is <10 mD in some regions along the fault plane while their transmissibility values range between 0 and 0.2. The SGR value is between 20 – 59 % which reveals a good percentage of faults that are sealed and will eventually prevent the migration of fluid out of the reservoir.