基于分类方法的煤层气井压裂开发效果评价

煤层气井分类评价是指导煤层气藏开发调整的基础。煤层气井的分类存在干扰因素多,评价界限主观性强等问题;并且受煤层气井排水降压产气特点的影响,其压裂效果无法从压后短期内的产量来判定。基于数据挖掘中的分类方法,结合渗流力学理论,首先将煤层气井产量及井数做归一化处理,建立煤层气井产量分布曲线,提出以产量分布曲线的导数值作为划分低产井与高产井的评判准则,建立煤层气井分类方法。然后,采用现代生产分析的方法,分类评价煤层气井压裂开发效果。最后,通过对韩城某区块的深层煤层气井进行分类及压裂开发效果评价,结果表明,低产井HS16井形成的裂缝短,生产过程中表皮系数增大,裂缝导流能力降低,渗流通道堵塞,预测重复压裂可获产量300 m3/d;高产井HS14压裂裂缝长,裂缝导流能力与生产初期相当,生产过程中渗流通道未受影响,预测重复压裂可获产量1 300 m~3/d。

Evaluation on fracturing effect based on classification method

Classification evaluation of CBM wells provides a basis for the adjustment of coalbed methane reservoirs.However,there exist some disadvantages such as interfering with various factors,and subjectivity of choosing classification rule during classification evaluation.Besides,it is hard to assess the immediate effect of fracturing on CBM production,as methane recovery involves a process of drainage,depressurization and desorption.In this paper,an improved classification evaluation method of CBM wells was presented,based on data mining and seepage theory.CBM production distribution curve was plot using data through normalization,with normalized well number on horizontal axis and normalized production on vertical axis,whose derivative value was recognized as the criterion of classifying CBM wells.Method of production analysis was then used to evaluate the fracturing effect on different kinds of CBM wells.Classification was carried out in a gas field of Hancheng as well as assessing fracturing effect.Results show that the hydraulic fracture length of low yield well HS16 was short,skin factor increased during recovery,fracture conductivity was damaged and flow channels was blocked.Possible production after repeated fracturing was 300 m3/d.High yield well HS14 had a long fracture length and uninfluenced fracture conductivity.Production after fracturing was predicted to be 1 300 m3/d.