EXPERIMENTAL INVESTIGATION ON THE RESERVOIR CHARACTERISTICS AND GAS-BEARING PROPERTIES OF ORGANIC-RICH SHALE

In this study, the reservoir characteristics and gas-bearing properties of organic-rich shales in the Wufeng-Longmaxi Formations were systematically studied. The results of petrographic analysis showed that the early Wufeng Formation was dominated by clay and clay-siliceous mixed shale facies, while in the middle and late periods, the siliceous shale fades was mainly developed. It proves that in the early period of the Ordovician-Silurian transition, the tectonic activity in the study area was violent, and the terrestrial source input was large; however, when the Wufeng Formation entered the middle and late depositional periods, the structure tended to be stable, and the bio-siliceous shale was mainly deposited. The lithofacies of the Longmaxi Formation are dominated by siliceous shale deposits, and no clay shale deposits were found. It reflects the stable structure and depositional environment in the early deposition stage of Longmaxi Formation. The TOC content of Wufeng and Longmaxi Formations are generally greater than 2%. Moreover, the type of adsorption and desorption curve of Wufeng-Longmaxi Formation shale is mainly type IV. Organic pores are the main pore types in shale reservoirs in the study area, and TOC content has the most important effect on the gas content of shale reservoirs.