陈古1井钻井液技术

Drilling fluid technology for well Chengu-1

陈古1井是1口近5000 m的重要科学探井。主要目的层为元古界,兼探S_3、S_4油层。岩性主要为砾岩、泥岩、碳质泥岩、硬脆性泥岩、玄武岩、泥化玄武岩、石英岩及花岗岩等。由于地层复杂,存在多套压力层系,钻井液技术是该井的关键技术。根据地层特点、钻井工程要求和满足保护油气层的需要,一开使用膨润土浆;二开采用MMH钻井液体系,该体系具有携岩能力强、不冲蚀井壁的特点,保证了大井眼井段的防塌;三开使用聚合醇无毒钻井液体系,解决了复杂井段的防塌、防卡、扭方位等复杂问题;四开采用KCl-石灰分散型钻井液体系,该体系抑制能力强,性能稳定,维护处理简单,满足了陈古1井沙河街组地层钻进需要,井壁稳定、井下安全、井径规则,具有明显的防塌效果;五开使用水包油钻井液,该钻井波密度在0.95～0.99 g/cm^3之间可调,在150℃条件下乳化稳定性好,具有良好的流变性及高温热稳定性,完全满足4000～5000 m超深井欠平衡钻井的需要。现场施工表明,该井钻井液技术满足了常规钻井工程需要及欠平衡钻井施工要求,很好地保护了油气层。

Well Chengu-1 is an important scientific exploration well, with a total depth of 4264 m and the main target of the Proterozoic Era. The lithology consists of conglomerate, shale, carbonolite, hard brittle shale, basalt, pelitized basalt, quartzite and granite, etc. Multiple pressure layers are penetrated, thus drilling fluid technology is the key for the successful drilling of this well. Proper drilling fluid systems arc selected based on the formation characteristics and drilling requirements for reservoir protection. In the surface 562 mm hole, bentonite mud is used. In the 444. 5 mm hole, MMH drilling fluid is adopted. This system has good cuttings transportation capability and without washing the wall, which is good for the drilling in large size borehole. Non-toxic polyol drilling fluid system is used in the 311 mm hole, this minimize such troubles as sloughing, sticking and orientation correcting in the complicated deep well, and ensures the safety of completion, especially the case of heavy load casing cementing. In the 216 mm hole. KCl-lime dispersing drilling fluid system is used, this system has good inhibition and stability, and it is easy of field conditioning Using of it in this section results good well stability and downholc safety, the hole is regular and few sloughing problems are encountered. In the bottom 177. 8 mm hole, oil-in-water drilling fluid is used. Its density is adjustable between 0. 95-0. 99 g/cm3,and has better emulsifying and rheologi-cal property, and high temperature stability in 150 C . which meets the requirements of under-balanced drilling of ultra-deep wells of 4000 - 5000 m. Field drilling shows that this drilling fluid technology meets the requirements of both under-balanced drilling and conventional drilling operations, and achieves good formation protection results.