煤层气钻井固相物污染特征及评价

Pollution characteristics and evaluation of solid-phase materials in CBM drilling

钻井液配方和密度是储层污染和评价的关键参数。通过对寺河矿区煤层气井的开挖解剖,观测了煤储层中钻井固相残留物的污染特征,并建立了钻井液密度与固相侵入深度的关系。研究结果认为煤储层大裂隙系统,尤其是外生裂隙系统是钻井液固相运移通道和储存空间,煤层气井的钻井液污染范围达几米;钻井液密度越高,煤储层裂隙中泥饼厚度越大,滤液侵入深度相对减小。并以此为依据预测了新疆白杨河矿区煤层气钻井污染范围,新疆煤储层由于煤体结构破碎和采用顺煤层钻井工艺,钻井液滞留时间长,钻井固相物污染会相对严重。

Drilling fluid formulation and density are key parameters of pollution and evalution in coal reservoir.Through the dissection of the CBM wells in Sihe mining area,the paper observed the pollution characteristics ofthe drilling solid-phase material and established the relationship between drilling fluid density and depth ofsolid-phase invasion.The results showed that for large fracture system of coal reservoir,especially exogenousjoints system as migration pathways and storage space of solid-phase materials in drilling fluid,the range of coalbedmethane well pollution was up to several meters.The higher the drilling fluid density,the thicker the mud cakein the coal reservoir fractures,the invesion depth of filtrate was reduced relatively.On this basis,the range of CBMdrilling was predicted in Baiyanghe mining area,Xinjiang.Because of the broken coal texture of coal reservoir andadoption of along seam drilling technology in Xinjiang,the residence time of drilling fluid is long,the pollution ofthe solid-phase materials is relatively severe.