Geomechanical parameter-driven evaluation of ultra-deep reservoirs: An integrated methodology and its application to the Kuqa depression, Tarim Basin

Abstract

Reservoir evaluation is important in identifying oil and gas sweet spots in sedimentary basins. This also holds true in the Tarim Basin, where the ultra-deep oil and gas-bearing formations have high present-day in situ stress and geothermal temperature in addition to their considerable depth as a result of multiple stages of tectonic evolution. Traditional reservoir evaluation methods are based mainly on analyses of reservoir parameters like porosity, permeability, and pore throat structure; these parameters can sometimes vary dramatically in areas with complex Structures. Geomechanics-based reservoir evaluations are favored as they adequately capture the impact of tectonic processes on reservoirs, especially those in the Tarim Basin. This study evaluates the ultra-deep clastic reservoirs in the Kuqa Depression of the Tarim Basin by integrating the geomechanical parameters including elastic modulus, natural fracture density, and present-day in situ stress into a 3D geological modeling-based reservoir evaluation. The entropy weight method is introduced to establish a comprehensive index (Q) for reservoir evaluation. The results show that the positive correlation of the daily gas production rate of representative wells in the study area with this indicator is an effective way of reservoir evaluation in ultra-deep areas with complex structures.