Abstract

It is necessary to know the reservoir property and the isothermal adsorption characteristics of shale for the exploratory development of shale gas. Aimed at the shale reservoir in lower section of Shahejie 3 Group in Shengli Oilfield, total mineral composition and relative content of clay mineral are analyzed by X-ray diffraction, porosity and specific surface area are tested by nitrogen adsorption method, ultra-low permeability are measured by differential pressure pulse decay and the pore structures are evaluated by using 3H-2000PS1 full automatic aperture analyzer of shale. Results show that the average content of fragile mineral (quartz, feldspar, calcite) is up to 65%, the average content of clay mineral mainly composed of illite is 27%, porosity distribution of this shale is from 0.62% to 2.68%, the average Langmuir specific surface area is 0.94m2/g, the permeability is in range of 0.008mD-0.022mD, the aperture is between 1.7nm and 77nm. The isothermal adsorption experimental results indicate that the adsorption of methane gas on this shale surface accords with Langmuir isothermal adsorption equation, increasing pressure and decreasing temperature are beneficial for shale to adsorb methane gas, and the adsorption of methane gas are in positive correlation with TOC content and specific surface area of shale.

Keywords: Shale reservoir; Isothermal adsorption; Porosity; Permeability; TOC; Specific surface area