Parameterization of Fault Seal Analysis as Input to In-Place Volume Assessment

Abstract

Abstract This paper presents an integrated approach for addressing uncertainty in hydrocarbon column based on fault seal analysis and column-height prediction for a target reservoir ‘F’ in a field in the Niger Delta area. The target field is in the shallow offshore of the Nigerian delta, about 20km south of the present-day coastline. The field was discovered in the sixties by an exploration well; Further appraisal wells confirmed hydrocarbon in a footwall block, but with uncertainty in fluid contact. ‘F’ reservoir is a highly faulted collapsed crest structure sandwiched between regional and counter regional faults. Numerous antithetic and synthetic faults dissect the reservoir to form several compartments. Seismic data covering the area was shot in the late nineties and is deemed to be of relatively low quality leading to suboptimal imaging of the faults. To address structural framework uncertainty, two structural model realizations were built for ‘F’ reservoir, focusing on the trapping mechanism, namely, a fault assisted 3-way dip closure (i.e. closure is bound by a major antithetic fault). This trapping mechanism has major impact on the hydrocarbon column height that can be held by the fault. The column heights for the model realization was estimated from two different fault seal analysis methods: – i.) Bretan et al., 2003; and ii.) Yielding et al., 2010. The results viz., column heights from each of the two methods for the structural model realization were presented as one of the input parameters for the volumetric uncertainty assessment carried out to determine an optimal development plan for the reservoir.