页岩气层“双甜点”评价方法及工程应用展望

Evaluation Methods and Engineering Application of the Feasibility of“Double Sweet Spots”in Shale Gas Reservoirs

页岩气层“双甜点”(地质甜点和工程甜点)评价是衡量页岩地层是否具有开采价值的有效方法,定量化评价“双甜点”有利于优化钻井和压裂施工,提高页岩气开发效率。针对甜点参数众多及甜点评价精度低的问题,利用相关系数法优选了主要甜点参数,采用独立性权系数法对地质甜点和工程甜点进行了定量表征。以涪陵页岩气田焦石坝区块地层为研究对象,优选出了5个地质甜点参数和4个工程甜点参数,地质甜点表征的相关系数为0.89,工程甜点表征的相关系数为0.85。研究结果表明,页岩气层“双甜点”及可压裂性可以用于钻井和压裂层位优选、水平钻进方位优化及套管工程安全管理方面。在此基础上,分析并展望了页岩气层的可压裂性、水平钻进方位优化技术对套管安全和大体积压裂的积极作用和优势。

The determination of“double sweet spots”(the geological and engineering sweet spot)in shale gas reservoirs is an effective method to determine whether it economically worthy of drilling,and the quantitative study of“double sweet spots”is also conducive to the optimization of drilling and fracturing,hence improving the development efficiency of shale gas.In view of the problems of numerous sweet spot parameters and low accuracy of sweet spot evaluation,the main sweet spot parameters were optimized by using the correlation coefficient method,whereby the independent weight coefficient method was adopted to quantitatively characterize both the geological sweet spot and the engineering sweet spot.Taking the strata of Jiaoshiba Block in the Fuling Shale Gas Field as the research object,five primary geological sweet spot parameters and four primary engineering sweet spot parameters were selected.The correlation coefficient of geological sweet spot was 0.89,and that of engineering sweet spot was 0.85.The research results showed that the“double sweet spots”and fracturing ability of shale gas could be used to optimize drilling and fracturing layers,horizontal drilling azimuth and casing engineering safety management.On this basis,the positive role and advantages of horizontal drilling azimuth optimization for casing safety and large volume fracturing as well as determining fracability in shale gas reservoir were analyzed and deemed feasible.