Reservoir Evaluation of Hydrocarbon Bearing Sands of “X” Field in Niger Delta

The reservoir characteristics of hydrocarbon bearing sands of ‘X’ field in offshore Niger Delta, were evaluated and studied using wireline logs, core photos and seismic data. The method of study involved both qualitative and quantitative analysis of well data, with the aim to access the quality, potential and the performance of the reservoirs for hydrocarbon productivity. The main petrophysical parameters evaluated were, porosity, permeability, hydrocarbon & water saturation, and fractional pore spaces filled by hydrocarbon. A total number of (8) reservoirs labelled; A,B,C1,C2,C3,D1,D2 and E within the depth interval 11325ft to 13525ft, were identified and evaluated from (5) wells, among which sand units A,C3,D2 and E are gas bearing sands while sand units B,C2,D1,D2 and E are oil bearing sands. These reservoir sands lies within the paralic Agbada Formation of the Niger Delta. The wireline logs used are Gamma ray (GR) log, Resistivity log (ILD), Compensated Neutron log (CNL) and Bulk density log. The estimated petrophysical parameters from the log analysis such as porosity shows, a value range of 22- 29.7%, permeability value of 59 - 304 mD, which are considered good for hydrocarbon production, with a high hydrocarbon saturation of 56- 94% and a total fractional pore spaces filled by hydrocarbon of 15.2 - 25.9%. The interpreted faults and the anticlinal structures from seismic structural analysis serves as hydrocarbon migration traps in the field. The lithofacies identified from the core analysis are Bioturbated Heterolithic sandstone, Cross bedded fine to medium sandstone, Cross bedded and bioturbated sandstone, Parallel laminated sandstone and Laminated mudstone. Studies on the environments of deposition from the intergrated core analysis and GR log shapes of the reservoir sands, reveals different facies in different environments that includes;beach, tidal channel, upper shoreface , lower shoreface and tidal flat, this implies that overall depositional enviroments of the ‘X’ field lies within the marginal marine environments.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California