Wu, Yu-ShuZhang, Chi2020-02-032022-02-032020-02-032022-02-032019https://hdl.handle.net/11124/174015Includes bibliographical references.2019 Fall.Data from a pilot test imply substantial water production after gas injection, which may impede oil production, but the underlying mechanisms are poorly understood. A compositional model is developed to study possible mechanisms for high water-cut pilot results. First, eight pseudo-components were used to match the PVT lab results of a typical oil sample from the Wolfcamp shale. A lab-scale model was then established in our simulation study to match the results of gas huff-n-puff experiments in cores, in which key parameters were identified and tuned. A half-stage field model consisting of five fractures was built, where stress-dependent permeability was represented by compaction tables. In addition, a sensitivity analysis was conducted to examine the roles of different mechanisms behind the abnormal high water-cut phenomenon. Our simulation results have shown that initial water saturation, IFT-dependent relative permeability, reactivation of water-bearing layers, and re-opening of unpropped hydraulic fractures may affect the water-cut after gas injection. Among them, re-opening of unpropped hydraulic fractures was the most critical factor. This study also optimized the period of injection and soaking phases and well bottom-hole pressure to improve the economic benefits of production operations.born digitalmasters thesesengCopyright of the original work is retained by the author.Text