Well log petrophysics and interpretation of 3D seismic profiles of reservoirs in the Southern Field, Rio Del Rey Basin, Cameroon

Abstract

This work principally involves the petrophysical evaluation and the determination of hydrocarbon saturation of potential reservoirs in the Rio del Rey basin. Petrel 2017 software was used to interpret the obtained data well logs and seismic. Illustrator CS was used to find tune and arrange the maps and figures. From the studies, four reservoirs (S1A1, S1A2, S1A3 and RB) in total were successfully detected from two target wells: S-C1 and S-FB. Porosity, permeability and water saturation ranged between 17 to 22%, 149 to 193.5 mD and 60 to 100%, respectively. Good reservoirs were discovered based on the petrophysical studies at multiple zones, but only two were of interest to this work. The most prolific zones are those with less than 80% saturation of water and porosity of 17% and 22%. The remaining zones had the same porosity and permeability range but were not considered prolific zones due to high shale volume and more than 80% water saturation. Seismic interpretation revealed the presence of seven listric faults, two major faults (F9 and F19 trending in the NE-SW and E-W direction, respectively) and five minor faults (F7, and F2, and F6 which appear in the two wells). Faults F9, F2 and F6 trend in the same direction as the major faults: Eastern to Western. Four major horizons (S1A1, S1A2, S1A3, RB) were identified in well S-C1, and only one of these major horizons was identified in well S-FB (S1A3). All these horizons correspond to the five reservoir tops to be studied in the two target wells. Rollover anticlinal structures and fault closures between the listric faults were identified. All three types of environments of deposition of sediments were found in the reservoirs: progradational (sediment shift landward), aggradational (deposition far away from shore) and retrogradational (sediment shift seaward) sequences. Rollover anticline or four-way structural closure constitutes the main mechanism for trap formation. STOOIP of the reservoirs have been determined with S1A3 and RB zone being more prolific. The STOOIP of S1A3 is given by 11.2 MMbbls high case, 8.5 MMbbls base case and 7.4 MMbbls low case, while the STOOIP of RB is given by 8.6 MMbbls for the base case and 10.8 MMbbls for the high case.