| Coal Measures Gas(CMG)resources in Linxing area,eastern margin of Ordos Basin,are abundant.However,the results of joint-mining test for CMG were not satisfactory due to prominent heterogeneity of natural gas geological conditions.It is urgent that geological research achievements such as division of geological units are needed to guide the well and layer selection.Therefore,the author in the paper suggests the prediction models of physical properties and fluid-bearing characteristics of different lithologic reservoirs in coal measures,and then makes comprehensive evaluation of reservoirs.Based on the structural,sedimentary and deep geological conditions,combined with the results of the evaluation and compatibility indentification,the geological boundary of each parameter is quantitatively analyzed.Finally,the geological units of CMG development are divided.The results show that the two main coal seams of Lower Paleozoic in the study area are stable and well-developed,the coal quality and physical properties are better,and the gas content is higher;Some strata,such as the sandstone gas reservoir of Tai 2 Member,have good development,large pore radius,good sorting of pore throat and physical conditions,and are favorable sandstone reservoirs;Shale is widely distributed with general brittleness.The average TOC content of Taiyuan Formation shale is slightly higher than that of other strata,and the average gas-measured total hydrocarbon content of Tai 2 Member shale is the highest.Based on the above knowledge,the variation coefficient method is used to give weight to the influencing factors,and the development potential grades of different types of reservoirs are determined according to the comprehensive evaluation results.At the same time,the permeability and pressure coefficient difference between different types of reservoirs are taken as key parameters to judge the compatibility of CMG joint-mining.Based on the comprehensive analysis of the above results,the parameters and method system of geological units division for CMG development are established.Ward’s minimum variance method is used to quantitatively analyze the geological boundaries of each parameter.The geological units for CMG single mining in the study area are divided into three categories by plane overlapping method of boundary conditions.The geological units for CMG joint-mining are divided into six categories,and the regional distribution of geological units for CMG development is predicted. |
