基于多元线性回归及模糊综合评判的平桥南区页岩气井压裂效果评价体系

A fracturing evaluation system based on multiple linear regression and fuzzy com-prehensive evaluation:Examples from shale gas wells,southern Pingqiao area,eastern Sichuan Basin

针对页岩气井的压裂效果受众多地质及工程影响因素联合作用的特点,为探究各影响因素的权重大小,分析影响压裂效果的主控因素,以四川盆地东部平桥南区页岩气井为研究对象,在常规单影响因素分析的基础上,使用多元线性回归方法对压裂效果影响因素进行权重分析,引入模糊综合评判法对压裂主控因素排序,建立一套新的压裂效果评价体系。应用结果表明:①压裂施工效果的影响因素权重由大到小依次为每米砂量、每米液量、埋深、曲率、应力夹角;②压后试气试采效果的影响因素权重由大到小依次为游离气、总含气、压裂效果、渗透率、试气段长、气测全烃;③通过模糊数学评判法建立的区块压裂改造评价体系与现有的压裂改造系数法以及单井EUR等评价结果较吻合。结论认为:模糊综合评判压裂改造评价体系对后续重复压裂施工具有重要参考意义,其中压裂施工效果对压后试气试采效果起着关键作用。

For shale gas wells,the fracturing effect is related to many geologic and engineering factors.To estimate the weight of each factor and major controls on fracturing,some shale gas wells,southern Pingqiao area,eastern Sichuan Basin,were taken as objectives.And then,a methodology of fracturing evaluation was established,involving not only multiple linear regression based on single-factor analysis to estimate the weight of each factor but also fuzzy comprehensive evaluation to sort major controlling factors.Results show that(1)sand volume per meter has the largest weight among fracturing controls,followed by liquid volume per meter,buried depth,curvature,and included angle of stress;(2)free gas has the largest weight among post-frac gas/production testing controls,followed by total gas content,fracturing effect,permeability,section length for gas testing,and total hydrocarbon in gas logging;and(3)the fracturing evaluation system based on fuzzy mathematical judgment and existing methods,e.g.fracturing stimulation coefficient and individual-well EUR,may yield similar evaluation results.This system based on fuzzy comprehensive evaluation is important to subsequent refracturing in view of the crucial effect of fracturing on post-frac gas testing and production testing.