Based on an analysis of the present geo-temperature field and the thermal conductivity (K) of 62 samples from the central-south area of the Huaibei coalfield in eastern China, we calculated the heat flow and plotted its distribution map. The results show that the average heat flow in the research area is about 60 mW/m2. It is different from other major energy basins in the North China Plate, but has close relationship with the regional geology and the deep geological setting. The heat flow is comparatively higher in the southeastern, central, and northwestern areas than in the northeastern and southwestern areas. The geo-temperature distribution map of the bottom interface of the Permian coal measure was drawn by calculating its embedding depth and geo-temperature gradients. Finally, the present gas generation condition of the Permian coal measure is discussed by associating with the temperature condition, the vitrinite reflectance (Ro), the metamorphism of coal and tectonic-burial evolution. The study indicates all present characters of the Permian coal measure, such as lower present temperature, higher Ro value, middle-high rank coals, and uplift and extension events after the coal measure sediment, are favorable for the generation of secondary biogenic gas, but not thermogenic gas or primary biogenic gas.
TAN JingQiangJU YiWenZHANG WenYongHOU QuanLinTAN YongJie
The physical and chemical texture of tectonically deformed coals produced by various formational mechanisms are different from those of primary coals,thus resulting in major differences among the physical properties of the reservoirs of these coals. We have studied the adsorption/desorption be-havior of tectonically deformed coals by the use of isothermal adsorption/desorption experiments un-der equilibrium moisture condition. Experiments of isothermal adsorption/desorption of methane or multi-component gases have indicated that,the adsorption curves of coals with a low degree of tec-tonic deformation conform to the type of isothermal adsorption curve described by the Langmuir equation; the methane adsorption curves of coals with strong tectonic deformation cannot be de-scribed by the Langmuir equation. The adsorption/desorption process of methane and multi-compo-nent gases in the deformed coals is not consistent with primary coals,which form an effect of hys-teresis in different kinds of tectonically deformed coals. With the change of pore structure of tectoni-cally deformed coals at reservoir condition,the added adsorbed CH4 in the experiments is desorbed on the pore surface of coals during the pressure reduction process. Thus,the result shows that the ad-sorption volume in the process of desorbing is greater than that in adsorbing. Because of the defor-mation,structural change,and transformation of the adsorption potential field of coals,it is essential to form a new kind of isothermal adsorption curve and the hysteresis effect of the desorption process.
JU YiWenJIANG BOHOU QuanLinTAN YongJieWANG GuiLiangXIAO WenJiao
