Construction of mineral component calculation model for tight carbonate reservoirs——by taking Ma5 X sub member of Majiagou formation in Ordos basin as an example

The carbonate reservoirs in the Ma5 X sub member of Majiagou formation in the east of Ordos basin are mainly karst residual hills type gas reservoirs with high filling degree of calcite and argillaceous, dense lithology and low porosity and permeability of reservoir matrix. In order to accurately calculate the volume content of various mineral components by using conventional logging data, so as to provide a basis for reservoir lithology identification, reservoir division and effectiveness evaluation, three methods, i.e. PE method, complex mineral component analysis method(including the CNL–DEN cross-plotting method and the CNL–AC cross-plotting method) and method of combined parameter regression model, were developed to establish mineral component content calculation model. And then the comparative study of calculation accuracy analysis was carried out and the results show that the accuracy of the CNL–DEN cross-plotting method based on the complex mineral composition analysis method is the highest and it has a good applicability for the calculation of the mineral composition of the Ma5 X sub member reservoir. The application of this method in exploration and development can provide an accurate basis for later reservoir division and effectiveness evaluation.