PREDICTION OF RESERVOIR QUALITY WITH SEISMIC ATTRIBUTES OVER “XAVIEK” FIELD, NIGER DELTA, NIGERIA

Abstract

The sole reliance on structural interpretation for hydrocarbon exploration has sometimes resulted into drilling of dry holes, under estimation of the volume of hydrocarbon in place and the consequent economic loss in the Niger Delta. Hence the needs to compliment structural interpretation with attribute analysis in formation evaluation and proper reservoir characterization so as to enhance optimum well placement and accurate reserve estimation. 3D seismic data, checkshot data and suite of well logs for FOUR wells located in the study area were analysed for prediction of reservoir quality of the field. The study involved delineation of lithology from Gamma ray log, identification of reservoirs from the Resistivity log, well correlation, determination of petrophysical parameters, horizon and fault mapping, time to depth conversion, attribute analysis and reservoir estimation. Four reservoirs were mapped from the well logs with their tops and bases at depth ranging from 1934.39 m to 2335.28 m. The petrophysical analysis gave porosity values ranging from 0.23 to 0.39 across the reservoirs. The permeability values range from 645 md to 9565 md. The water saturation (Sw) values for reservoir 1 are from 22 % in well 2, 27 % in well 5, 29 % in well 4, while for reservoir 2, Sw values for well 2,5 and 4 are 38 %, 40 % and 55 %, while for reservoir 3, Sw values for well 2, 5 and 4 are 25 %, 43 % and 38 %, while for reservoir 4, Sw values for well 2, 5 and 4 are 39 %, 68% and 80% respectively. The volume of shale ranges from 0.07 to 0.42. The hydrocarbon saturation ranged from 0.2 to 0.78 across the four reservoirs. Four horizons were mapped and six faults named F1-F6 were mapped in the field. Two major faults F1 and F4 were identified. The depth structure maps generated showed anticlinal structures at the centre of the surfaces and that of the map. Envelope and Interval Average attributes were extracted which showed the location of the bright spots. The reserve estimate of reservoir 1 was 291.8 mmbls, reservoir 2 was 27.8 mmbls, reservoir 3 was 223.6 mmbls and reservoir 4 was 18.4 mmbls. The results of the petrophysical analysis revealed the presence of hydrocarbon in the FOUR reservoirs at quantities favorable for commercial exploitation. The result of this analysis has demonstrated that the integration of attribute with structural interpretation is a reliable and efficient way to carry out the prediction of reservoir quality