Shale gas content calculation of Chang-7 oil layers in central and southern Ordos basin

Chang-7 oil layers of Yanchang formation in central and southern Ordos basin is rich in shale gas,and it is of great importance to precisely calculate the shale gas content in non-coring wells with logging interpretation data.Firstly,by considering the logging characteristics of hydrocarbon source rocks,the overlap method was used to identify the shale of Chang-7 oil layers.Secondly,by multi-linear regression method,the logging interpretation model of organiccarbon content was established and the logging data were used to calculate the volume of adsorbed gas.Finally,by using the established porosity model and Hossin formula,the volume of free gas was indirectly calculated.Study results indicate the total volume of Chang-7 shale gas in the central and southern Ordos basin is 3.09 ~ 5.55m3/t,with the average value of 4.11m3/t,the volume of adsorbed gas is 2.83~3.77m3/t,with the average value of 2.97m3/t,and the volume of free gas is 0.07~2.51m3/t,with the average value of 1.14m3/t.