基于核磁测井孔喉分布的致密砂岩储层评价方法——以四川盆地Q地区沙溪庙组二段为例

Evaluation Method of Dense Sandstone Reservoir Based on NMR Logging Pore and Throat Distribution Taking the second member of Shaximiao Formation in Q Area of Sichuan Basin as an Example

四川盆地Q地区是致密气勘探开发的重要区块,但该区储层孔隙结构复杂、纵向变化快、储层品质评价难度大,给水平井箱体选择带来较大困难,同时传统的岩心孔渗关系、核磁测井Timur-Coates和SDR公式计算渗透率精度较差,难以满足生产实践需要。为了利用测井资料评价储层类型及渗透性,通过分析四川盆地Q地区沙溪庙组二段储层核磁测井响应特征,结合不同储层的常规测井、阵列感应等资料,优选有效孔隙井分级评价、优选优质储层提出水平井箱体设计建议,根据不同喉道占比与渗透率关系分析结果,提出了基于核磁测井孔喉分布的渗透率计算方法评价储层渗透性。应用结果表明:储层测井分类方法有效评价了储层内部非均质性,同时基于核磁测井孔喉分布计算渗透率与岩心渗透率吻合性较高,计算精度高于岩心孔渗相关性法及Timur-Coates和SDR法。

Q area in Sichuan Basin is an important area for exploration and development of tight gas,however the reservoir pore structure is complex,the vertical variation is fast and the reservoir quality evaluation is difficult,which makes it difficult in choosing the box of horizontal wells.At the same time,the traditional core pore-permeability relationship,the permeability formulas of TimurCoates and NMR logging are not accurate enough to meet the needs of production practice.In order to evaluate reservoir type and permeability with logging data,this paper analyzes the response characteristics of NMR logging in the second member of Shaximiao Formation in Q area of Sichuan Basin,combines the conventional logging and array induction data of different reservoirs and optimizes reservoir classification parameters such as effective porosity,shale content,resistivity increase rate and macropore ratio.Furthermore,suggestions on horizontal well box design are put forward for reservoir classification evaluation and optimization of highquality reservoir in the target formation of the second member of Shaximiao Formation.According to the results analyzed through the relationship between throat proportions and permeability,a permeability calculation method based on pore throat distribution of NMR logging is proposed to evaluate reservoir permeability.The application results show that reservoir logging classification method effectively evaluates the heterogeneity of reservoir,and the permeability calculated by the method based on the pore throat distribution of NMR logging is in good agreement with the pore permeabiltiy,the accuracy of calculation is higher than that of core porepermeability correlation method and Timur-Coates and SDR methods.