A hydrophilically inhibitive water base drilling fluid has been developed to drill shale gas wells penetrating the Longrnaxi Formation.This drilling fluid was formulated with a hydrophilically inhibitive agent CQ-SIA and a high performance lubricant CQLSA.CQ-SIA,the core additive of the formulation,is amphoteric in nature,and can render wettability reversal to the surface of rocks.It forms on the surface of rocks a hydrophilic film,thereby encapsulating and inhibiting the rocks from disintegration by water invasion.Hot rolling test results showed that 1％ CQ-SIA gave percent cuttings recovery of 83.72％,remarkably higher than that obtained with KPAM,AP-1 and KCl.CQ-LSA,thanks for its special molecular groups and structure,can form lipophilic film on the hydrophilic surfaces of drilling tools,mud cakes and formation rocks,thereby greatly decreasing frictional resistance experienced in drilling.Sticking coefficient of a 5％ bentonite slurry treated with 1％ CQ-LSA was 0.0507,lower than the 5％ bentonite slurries treated with two commonly used lubricants RH-220 and BARALUBE.The formulated drilling fluid had good rheology,high inhibitive capacity and good lubricity that were equivalent to oil base drilling fluid.Addition of 1％-3％ anti-sloughing plugging agent,1％-2％ poly glycol and 0.8％-1.6％ nano plugging agent rendered the formulation good plugging performance.It also had good contamination resistance.Success has been gained in the first use of this formulated drilling fluid on the well Changning H25-8.Mud properties in the horizontal fourth interval (3,079 m open hole length and 1,500 m horizontal section) were all maintained stable.No downhole problems have ever occurred.Tripping,wireline logging,casing running and well cementing were all done smoothly.%针对龙马溪组页岩气水平井钻井井壁失稳问题,研制出一种疏水抑制剂CQ-SIA和一种液体润滑剂CQ-LSA,并形成一套疏水抑制水基钻井液体系.CQ-SIA具有双亲特性,能使亲水的岩石表面发生润湿反转,在岩石表面形成一层疏水膜,具有强化抑制与包被的作用,实验测得岩屑在1％CQ-SIA中的滚动回收率为83.72％,明显高于KPAM、AP-1以及KCl.CQ-LSA具有特定的基团与结构,能在亲水的钻具、泥饼和地层岩石表面形成亲油膜,降低摩阻,实验测得加有1％CQ-LSA的5％膨润土浆黏附系数为0.050 7,低于加有RH-220和BARALUBE的膨润土浆.该疏水抑制水基钻井液的抑制性和润滑性能与油基钻井液相当,具有良好的流变性能和抗污染性能,加有1％～3％防塌封堵剂、1％～2％聚合醇和0.8％～1.6％纳米封堵剂,封堵能力强.该体系在长宁H25-8井进行了首次现场试验,在1 500 m水平井段的钻井过程中,该体系各项性能稳定,配制维护工艺简单,井下未出现任何复杂,起下钻、电测、下套管、固井作业顺利,表明该体系能满足长宁页岩气水平井的钻井需要.
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