摘要：
Borehole wall destabilization has long been a problem that needs to be solved.A high temperature bridging formation stabilizer QFT,has been developed based on the working mechanism under which formation stabilizers are adsorbed on clay particles and formation minerals.Monomers used in synthesizing QFT were AM,AMPS and a strong absorbent monomer M,and potassium persulfate was used as the initiator.The polymerization lasted for 4 hours at 60 °C.QFT is a white viscous liquid with 10％ active content.The molecular weight of QFT is ca.(8-60) × 104 g/mol.QFT is a drilling additive of high inhibitive capacity,good filtration control and weak effect on the viscosity of base mud.The highest temperature for QFT to function is 150 °C.Laboratory evaluation and analyses showed that,compared with fresh water,the rate of linear expansion of 3％QFT water solution (tested on shale cores) was reduced by 44.56％,and the percent recovery of shale core in hot rolling test was increased by 34.1％ at 150 °C.The percent recovery of shale cuttings tested with QFT was greater than KC1,KPAM and FA-367.Cores thoroughly disintegrated in fresh water after soaking for 10 min remained integrity after soaking 24 hours in QFT solution.X-ray diffraction showed that the low molecular weight QFT can enter the space between the crystal layers of clay,thereby prevent water molecules from entering the clay.Base mud treated with QFT had fine clay particles with higher specific surface area,indicating that QFT had been adsorbed onto the surface of clay particles through bridging,and this inhibited the agglomeration of clay particles at high temperatures and ensured that there were fine particles in the base mud to form a thin tight mud cake.The API filter loss of a 4％ bentonite base mud treated with 3％ QFT was reduced by 48.33％ after aging.Drilling fluid containing potassium and calcium,when treated with QFT,had reduced filtration rate.With the same drilling fluid,the percent recovery of shale cores (samples taken from field) was more than 95％,and the strength of artificial cores soaked at 120 °C in the potassium calcium drilling fluid with QFT treatment was 14％ higher than the cores soaked in potassium calcium drilling fluid with no QFT treatment.Application of QFT on the well H 160 in Hongshanzui demonstrated that potassium calcium drilling fluid treated with QFT successfully inhibited borehole wall instability.Meanwhile,the drilling time of this well was reduced by 43％ than the adjacent well H170-X.Monthly drilling rate was increased by 70％,and drilling cost was thus remarkably reduced.%井壁失稳一直是钻井过程中未能彻底解决的问题.根据防塌剂与钻井液中的黏土及地层矿物吸附联结的作用机理,采用AM、AMPS和一种强吸附单体M,通过以过硫酸钾作引发剂,在60°C反应4h,合成了一种抗温达150°C的高温桥联型防塌剂QFT,产物为白色黏稠状,QFT分子量约为(8～60)×104g/mol,有效含量为10％.该防塌剂具有强抑制、降滤失及对基浆黏度影响小的特点,对其进行了性能评价和机理分析,并介绍了其现场应用情况.与清水相比,3％QFT水溶液使泥页岩岩心线性膨胀量降低44.56％,泥页岩岩屑150°C滚动回收率提高34.1％,回收率大于KC1及KPAM和FA-367;在清水中浸泡10 min后完全分散开的岩心,在QFT溶液中浸泡24 h仍保存完整.X-射线衍射分析结果说明,QFT由于分子量较小,可以进入黏土层间,阻止水分子进入黏土层.含有QFT的基浆老化后黏土颗粒粒径较小,比表面积较大,说明该防塌剂可以通过与黏土的桥联吸附,阻止基浆中固相颗粒高温聚集,保证基浆中具有一定量的细颗粒,有利于形成薄而致密的滤饼,老化后3％ QFT可以使4％基浆的API滤失量降低48.33％.钾钙基钻井液体系中引入QFT后,有效地降低了滤失量,现场的泥岩岩屑滚动回收率在95％以上,且120°C下浸泡后的人造岩心强度比原体系提高14％以上.通过在红山嘴H160井的应用,表明该防塌钻井液体系能够防止井塌等复杂事故.此外,由于该体系有良好的降滤失及抑制性,试验井钻井周期比邻井H170-X井缩短43％,钻机月速提高了70％,显著提高了钻井时效,降低钻井成本.
