基于铸体薄片资料的砂岩储层孔隙度演化定量计算方法--以鄂尔多斯盆地环江地区长8储层为例

利用铸体薄片资料进行储层孔隙度演化定量计算是一项重要的成岩演化和储层模拟技术，但由于参数确定和计算方法存在的问题，导致结果准确性较差。基于此，在分析前人计算方法及其误差的基础上，确定了计算参数的选用，改进和完善了计算方法与结果检验方法的应用。在初始孔隙度的确定上，相对赋一固定值作为所有样品初始孔隙度或Scherer拟合公式，根据Beard和Weyl湿砂填集实验恢复初始孔隙度具有较高的精度；在考虑压实过程中岩石表观体积缩小的情况下，推导了压实、胶结损失孔隙度与溶蚀增加孔隙度计算公式，并给出了忽略岩石表观体积变化时孔隙度演化分析的误差来源和可能的误差大小范围；结果检验方面，摒弃了以往忽略溶蚀增加孔隙度而简单进行粒间孔隙度与和氦孔隙度对比的较为粗略的方法，建立了考虑各种成岩作用结果和成岩过程中岩石表观体积变化情况下的结果检验方法。应用该方法对鄂尔多斯盆地环江地区长8储层孔隙度演化进行计算，结果与岩芯氦孔隙度相比，绝对误差-1.1%，相对误差15.3%，取得了良好的应用效果。

Quantitative Calculation of Sandstone Porosity Evolution Based on Thin Section Data: A case study from Chang8 reservoir of Huanjiang area,Ordos Basin

The quantitative calculation of sandstone porosity evolution based on casting section data is one of important techniques for  diagenetic change and reservoir simulations. Because of the problems in parameters determination and calculation process, the results are not accurate in many cases. For this reason, based on the analysis of previous  computation process and their errors, the original porosity determination method is decided, and COPL, CEPL and CRPI (corrosional porosity increase) calculation formula are deducted. To the determination of original porosity, Beard and Weyl’s wet packing experiment is more accurate than the method of assigning a constant value for all the samples according to the sedimentary facies or the Scherer’s equation based on the relationship between original porosity and coefficient of sorting. Under the consideration of rock bulk volume’s reduction in the compacting process, COPL, CEPL and CRPI calculation formula are deducted, and the errors in situation that the bulk volume’s reduction is neglected is analysed, and the errors’ extent is calculated. Instead of the method contrasting the intergranular porosity and Φ_He without calculation of CRPI, the approach considering all diagenesis sorts and rock bulk volume’s reduction in the compacting process is established in calculation result accuracy check-out. The application of the above-mentioned calculation methods of sandstone porosity evolution in Chang8 reservoir of Huanjiang area, Ordos Basin, is satisfying with 1.1% absolute error and 15.3% relative error of porosity.