Study on probabilistic distribution model of reserves calculation coefficient in the fractured-vuggy reservoir of Tahe Oilfield, Tarim Basin, China

Due to the strong heterogeneity of fractured-vuggy reservoirs in Tahe Oilfield, the results of reserves calculated using the Volumetric Method are not ideal. To improve the calculation accuracy of reserves, this study selected 524 evaluation Wells of the fractured-vuggy reservoir in Tahe Oilfield, and adopt the probability method (or Monte Carlo method) to establish the characteristics and distribution model of reserves per unit coefficient (RPUC) based on the reservoir geological conditions, crude oil density, and development process. From the mathematical test, the Beta function is more applicable to represent the probability model of the RPUC parameters. The RPUC of reservoirs controlling by weathering crust is found to be the greatest, and proved to be the most favorable reservoir in this area. The calculation results obtained using the probability method are more reliable, compared to the other three methods, which are in line with the estimated reserves during oil and gas exploration. The RPUC values of reservoirs reveal that Aidingbei, and Yuqi porous reservoirs were relatively developed with better resource prospects. The above research can provide a reference for the calculation of the reserves for the fractured-vuggy carbonate reservoir of the new area in the Tarim Basin.