Influence of three-dimensional tectonic stress field on natural gas migration and accumulation within Tianhuan Depression, Ordos Basin, China

Stress field controls the macroscopic distribution of oil and natural gas in the process of hydrocarbon generation, migration and accumulation, particularly during the peak of hydrocarbon generation period and oil and gas migration period. The Tianhuan Depression in the Ordos Basin is taken as an example to analyse the characteristics of tectonic evolution and stress field in this area. This process is performed to study the influence of tectonic stress field on natural gas migration and accumulation in tight sandstone reservoirs. The present-day tectonic stress field and flow potential field in different strata are studied through numerical simulation. The influence of tectonic stress on hydrocarbon migration and accumulation is summarised. The relatively low area of in situ stress and flow potential is the easy enrichment area of natural gas. This observation is consistent with the test results. The stress and the flow potential in the middle part of the Tianhuan Depression are relatively high, thus leading to migration and enrichment of natural gas on the two sides. The enrichment degree of natural gas in gentle slope areas is better than that in steep slope areas. The low-stress zone surrounded by the high-stress zone is a favourable gas storage structure. Thus, stress field analysis serves as the basis for the study of natural gas migration and accumulation.