Abstract:

The shale has content is one of the most important indicators to evaluate shale reservoirs，and of great significance to forecast reserves. As adsorbed has content plays an important proportron in shale has content the evaluation of adsorptive capacity in shale reservoirs is very necessary.Through methane isothermaladsorption experiments of Paleozoic shale samples from three different sets of strata in Subei Area，the shale isothermal adsorption curves are obtained to analyze the main affecting factors of adsorption gas contents in shale reservoirs.  The results show that the saturated adsorption(VL)are 1.18-4. 85 m³/t with an average of 2. 89 m³/t，and the Langmuir pressure constant(PL)are2.01一4. 24 MPa with an average of 2. 67 MPa.The adsorption capacity varies among these three different sets of shale strata.  Mufushan，Dalong and Longtanformations have much more adsorption gas contents than Wufeng-Gaojiabian and Gufeng formations. The main affecting factors of adsorption gas contents are concluded as follows:(1)TOC directly affects the maximumadsorption gas content，the higher the organic carbon，the greater the maximum adsorption gas content;(2)with similar values of the organic matter content，organic maturity and the same pressure，the shale with high clay contents adsorbs more gas;in the shale with low organic carbon，illite plays a vital role in the adsorption， and the adsorbed gas contents is relatively high in those shales with high contents of illite;(3)the recruired minimum pressure(critical pressure)making shale saturated with adsorbed gas will decrease with the increase of TOC.The experiments  also  show  that the organic maturity has no obvious relation with the  saturated adsorbed gas contents.

Key words: shale, adsorbed gas content, affecting factor, Paleozoic, Subei Area