陆相页岩气水平井段井壁失稳机理及水基钻井液对策  

Mechanism of wellbore instability in continental shale gas horizontal sections and its water-based drilling fluid countermeasures

作　　者：王波[1,2] 孙金声 申峰 李伟 张文哲 WANG Bo;SUN Jinsheng;SHEN Feng;LI Wei;ZHANG Wenzhe(School of Petroleum Engineering,China University of Petroleum,Qingdao,Shandong 266580,China;Research Institute,Shaanxi Yanchang PetroleumCo.Ltd.,Xi'an,Shaanxi 710075,China;CNPC Engineering Technology R&D Co.Ltd.,Beijing 102206,China)

机构地区：[1]中国石油大学(华东)石油工程学院 [2]陕西延长石油(集团)有限责任公司研究院 [3]中国石油集团工程技术研究院有限公司

出　　处：《天然气工业》2020年第4期104-111,共8页Natural Gas Industry

基　　金：国家科技重大专项“陆相页岩气水平井高效低成本钻完井技术”(编号:2017ZX05039-003)。

摘　　要：鄂尔多斯盆地陆相页岩气井水平段井壁失稳问题,是制约该盆地延长区块中生界上三叠统延长组页岩气资源勘探开发的重大工程技术难题。为此,采用X射线衍射分析获取页岩矿物组分特征,并分析其理化特征、比表面积及微观结构,在此基础上研发了基于纳米封堵的低自由水活度页岩水基钻井液体系(PSW-2),并现场应用于5口陆相页岩气水平井,保障了其长水平段钻进井眼的稳定性。研究结果表明:①该区延长组页岩黏土矿物含量高,属弱膨胀、易分散、多层理裂缝地层,井壁失稳是力学、物理化学、钻井机械扰动等因素综合作用的结果;②页岩平均孔径为4.494~8.502 nm,毛细管作用明显、吸水能力较强、水化不均匀,导致页岩局部强度下降,易形成突发性垮塌;③研制的PSW-2体系API滤失量低于2.8 mL、滚动回收率为95.15%(接近于油基钻井液98.25%的回收率)、线性膨胀率低至1.38%,润湿角由干岩样的26°增大为56.5°;④该钻井液体系浸泡后抗压强度增加至95.806MPa,接近于原岩的强度(110.70MPa)。结论认为,该水基钻井液体系通过微纳米成分封堵页岩孔隙、降低液相活度提高抑制性、减弱页岩毛细管自吸效应的多元协同,破解了井壁失稳的难题。The wellbore instability in the horizontal sections of continental shale gas wells in the Ordos Basin is a major engineering and technical problem that restricts the exploration and development of the shale gas resources in the Yanchang Formation of Upper Triassic of Mesozoic in the Yanchang Block. To solve this problem, this paper analyzed the characteristics of mineral components in shale by means of X-ray diffraction. In addition, its physical and chemical characteristics, specific surface area and microstructure were analyzed. On this basis, a shale water-based drilling fluid system(PSW-2) of low free water activity based on nano plugging was developed. And it was applied on site at five horizontal wells in continental shale gas reservoirs to ensure the wellbore stability of their long horizontal sections. And the following research results were obtained. First, the Yanchang Formation shale in this area has a high content of clay mineral, and it is a fractured formation of weak expansion, easy dispersion and multiple bedding, so the wellbore instability here is the result of the comprehensive action of mechanical factors, physical and chemical factors, drilling mechanical disturbance, etc. Second, the shale has average pore diameter is 4.494-8.502 nm and is characterized by obvious capillary action, strong water absorption capacity and uneven hydration, which result in the decrease of local shale strength, so sudden collapse tends to happen easily. Third, the API loss of PSW-2 system is less than 2.8 mL, the rolling recovery rate is 95.15%(close to the recovery rate of oil-based drilling fluid 98.25%), the linear expansion rate is as low as 1.38%, and the wetting angle increases from 26° of dry rock samples to 56.5°. Fourth, the compressive strength of the system after immersion increases to 95.806 MPa, which is close to the original rock strength(110.70 MPa). It is concluded that this water-based drilling fluid system can effectively ensure wellbore stability by blocking the pores of shale with micro nano

关 键 词：鄂尔多斯盆地 陆相页岩气 晚三叠世延长期 水平井 井壁失稳 水基钻井液 抑制性 

分 类 号：TE243[石油与天然气工程—油气井工程] TE377TE254