Study on the seepage characteristics and influencing factors of low permeability reservoir based on microscopic seepage experiments in real sandstones-taking Dongsheng gas field in Hangjinqi area as an example

¹ Sinopec North China Oil &. Gas Branch, Zhengzhou, Henan 450006, China
² State Key Laboratory of Continental Dynamics/Department of Geology, Northwest University, Xi’an, 710069, China

Corresponding author: Yushuang Zhu, Professor, Doctoral Supervisor, Northwest University, China.E-mail address: petroleum_gas@163.com

Abstract

Taking the dense sandstone gas reservoirs of Shibang Group and Shanxi Group in Dongsheng area of Ordos Basin as an example, based on the characterization of the dense sandstone reservoirs in the study area in terms of petrological features, pore structure and diagenesis, we carried out real sandstone microscopic seepage experiments to analyze the gas-water seepage law and fluid storage state of different types of reservoirs, and systematically evaluated the efficiency of gas-water repulsion from the dense sandstone reservoirs and the microscopic influencing factors. The results show that the study area has strong non-homogeneity and different degrees of pore density, so a variety of fluid transportation channels are formed, and different transportation channels represent different types of evacuation. When the residual pore space and dense sandstone microporous space exist at the same time, gas and water are mainly transported along the residual pore space, and the microporous space of the dense particles almost does not enter; gas and water transport is very much affected by permeability, and the transport resistance will increase with the decrease of permeability; the pressure has a certain effect on the efficiency of the replacement, but it can only improve the efficiency of the replacement to a certain extent; the fluids in the process of rock transport, there will be varying degrees of bubbles stuck off In the process of fluid transport in the rock, there will be different degrees of bubble jamming phenomenon, resulting in the transport needs to overcome a large capillary resistance, which greatly increases the replacement pressure; for the low-permeability sandstones in Hangjinqi area, the good homogeneity of the pore structure of the conductor does not mean that the transport effect is good, in the area of the conductor pore space is strongly developed, the gas-water transport will form an advantageous channel, and its transport effect is better.