沁水盆地在用煤层气钻井液伤害沁水3#煤岩室内评价

Lab evaluation on formation damage of No.3 coalbed methane reservoir by drilling fluids in Qinshui basin

研究沁水3#煤岩储层钻井液储层伤害机理,对沁水煤层气开发至关重要。室内对比测定了清水、绒囊、膨润土聚合物等3类钻井液伤害端氏煤矿3#煤岩柱塞前后渗透率值。结果表明,清水、绒囊钻井液、膨润土聚合物钻井液伤害煤岩柱塞平均渗透率恢复值为70.88%、84.22%和49.26%。结合渗透率恢复实验数据、煤岩柱塞伤害时漏失情况,分析钻井液储层伤害的主要因素有钻井液滤液及颗粒伤害、煤岩自身煤粉及微粒运移、某些表面活性剂与地层不配伍等。建议钻井使用无固相控制煤粉运移的钻井液,适当使用处理剂封堵地层控制滤液与煤层接触机会,根据具体煤岩情况优选表面活性剂避免煤岩与表面活性剂不配伍造成储层渗透率降低。

It is virtually important for high and stable yield of CBM to research the damage mechanism of No.3 CBM reservoir by drillingfluids in Qinshui basin.Using clear water,bentonite-polymer drilling fluid and fuzzy-ball based drilling fluid separately to contaminate 20 core plugswhich were got from the drilling site of No.3 CBM in Duanshi coal mine,the permeability of core plugs was measured and compared.It is concludedthat the permeability recovery rate of core plugs after contaminating with the three solutions were 70.88%,84.22% and 49.26% separately.Throughlaboratory tests and observing leak off of core plugs,the main factors of damage mechanism by drilling fluids were analyzed to be solid phase ofdrilling fluid,migration of coal fine and incompatibility between some surfactant in drilling fluid and the formation.The paper suggests that we shouldtake non-solid coal fine migration controllable drilling fluid,properly use some treating agent to plug formation to decrease the contacting chance offiltration and formation,and optimize surfactant to avoid the formation permeability decrease by the incompatibility between coal bed and surfactant.