Impact of Depositional Facies and Petrophysical Parameters on the Estimated Hydrocarbon-in-place Volume of a Producing Field in the Niger Delta Basin, Nigeria

Abstract

The need to identify the major parameter with an overwhelming impact on estimated hydrocarbon volume has been a challenge for stakeholders in the oil and gas industry. To address this challenge, an investigation of the impact of depositional facies and petrophysical parameters on estimated oil volume was carried out on an oil field located within the Niger Delta using 3D geologic models. Different modeling techniques were employed in the study; each technique produced an estimated volume of hydrocarbon. Uncertainty analysis was carried out based on Facies and their petrophysical parameters by varying each parameter at a time while repeating the volumetric estimation to check their impact on the estimated volume. Thereafter, sensitivity was run on the parameters to determine the parameter with the most impact Three lithofacies; clean sand, shaly sand, and shale, and three sands bodies; D_1000, D_2000, and D_3000 were identified using the available gamma ray log. Results from the Petrophysical evaluation showed that the average porosity values of the reservoirs ranged between 0.20% and 0.225%, while average water saturation for the three reservoirs ranged from 21% to 40%, respectively. The major fault that cuts through the reservoirs may have caused the disappearance of reservoir D_3000 in wells X-002 and X-014. Reservoir D_3000 has the largest accumulation of about 952 MMSTB, while reservoir D_1000 gave the least accumulation of about 727MMSTB. Interestingly, the three reservoirs in this study presented porosity as the parameter with the biggest influence on the estimated hydrocarbon-in-place volume.