川西地区油基钻井液井壁强化技术

Borehole Strengthening Technology with Oil-Based Drilling Fluid in the Western Sichuan Basin

王星媛 陆灯云 袁志平

WANG Xingyuan LU Dengyun YUAN Zhiping

油气田应用化学四川省重点实验室，四川广汉 618300 中国石油集团川庆钻探工程有限公司钻采工程技术研究院，四川广汉 618300

Oil and Gas Field Applied Chemistry Key Laboratory of Sichuan Province, Guanghan, Sichuan, 618300, China Drilling and Production Technology Research Institute, Chuanqing Drilling and Exploration Engineering Company, Ltd., CNPC, Guanghan, Sichuan, 618300, China

钻进川西地区深部地层时，井漏、井眼垮塌和卡钻问题频发，如采用油基钻井液钻进，则不易形成厚滤饼且滤饼致密性差，井筒压力穿透能力强。针对该问题，根据钻井液成膜机理，采用核壳结构设计，以苯乙烯、丙烯酸酯类等为原料，合成了一种适用于该地区深井钻井中地层温度≤150 ℃中部层位的致密膜护壁剂CQ-NFF；根据风险地层的地质特性、工程特性分析结果和d90规则，选用超细碳酸钙、弹性石墨、高强度树脂和高分散纤维复配形成了内充填封堵剂。采用扫描电镜分析了钻井液的成膜机理及形貌，通过高温高压滤失、高温渗透失水、高温渗透失油试验评价了钻井液的成膜效应，通过高温高压砂床滤失试验评价了充填材料的承压封堵能力。结果表明，CQ-NFF可在油包水乳状液和油基钻井液中形成致密薄膜，并有效吸附在滤饼表面，薄膜承压封堵能力达到2.0 MPa；将内填充封堵剂加入油基钻井液后，内滤饼的承压能力可提高至3.5 MPa以上。以上述处理剂为核心的川西地区油基钻井液井壁强化技术，在双探6井和中江2井进行了现场试验，深层井漏、井眼垮塌、卡钻等井下故障时间大幅缩短，试验效果显著。

Wellbore collapse, lost circulation and sticking frequently happen in deep formations when drilling in the western Sichuan Basin. When drilling with oil-based drilling fluids, it is difficult for a thick filter cake to form. Plus, the low density of the filter cake leads to high pressure penetration ability at the wellbore. To solve this problem, based on the mechanism of drilling fluid film forming, a wellbore protection agent with the compact film, CQ-NFF, was synthesized from styrene, acrylate and other raw materials using the core-shell structural design, which is suitable for the middle layer with a temperature no more than 150 °C in deep well drilling in the area. According to the analysis results of the geological characteristics and engineering characteristics of high-risk formations and the d90 rule, an inner-filling plugging agent was formed from ultra-fine grains of calcium carbonate, elastic graphite, high strength resin and highly dispersed fiber. The film-forming mechanism and morphology of drilling fluid were analyzed by scanning electron microscope (SEM). Film forming effects were evaluated in filtration tests under high temperature and high pressure along with water and oil loss tests during drilling penetration at high temperature. By means of the sand bed filtration experiments under high temperature and high pressure, the plugging capacity of the filling material was evaluated. Experimental results show that CQ-NFF can form a compact film in water-in-oil emulsion and oil-based drilling fluid, and the film can be adsorbed on the surface of the filter cake effectively. The pressure resisting and plugging capacity of the film can reach 2.0 MPa. After the inner-filling plugging agent was added to the oil-based drilling fluid, the pressure bearing capacity of the inner filter cake was increased to over 3.5 MPa. The borehole strengthening technology with oil-based drilling fluid, treating chemicals as the core, was applied in Well Shuangtan 6 and Well Zhongjiang 2. The results show a remarkable application effect that the downhole downtime due to lost circulation in deep formations, wellbore collapse or drill pipe sticking were greatly reduced.

国家科技重大专项“四川盆地大型碳酸盐岩气田开发示范工程”（编号：2016ZX05052）、川庆钻探工程有限公司钻采工程技术研究院科技项目“220 ℃抗高温高密度油基钻井液技术研究与应用”（编号：ZCY-19-01）联合资助

https://doi.org/10.11911/syztjs.2020116