关键词: 油气井固井, 长封固段, 大温差, 降失水剂, 缓凝剂, 水泥浆, 固井质量

Abstract: With oil and gas exploration and development unfolded continuously, the targets for exploration and development are becoming more and more complicated. The wells with a long open-hole, a large temperature differential, and co-existence of a multiple of pressure systems pose a stern challenge for safety of cementing service and guarantee of cementing quality. A series of problems often appear in cementing service, such as extra retarded set and poor cementing quality, thus affecting safe and high-efficiency development of deep-layer oil and gas resources. Focusing on the technological bottleneck in long-cementing interval of deep well under the large temperature differential condition, CNPC developed special cement slurry fluid loss agents and retarders suitable for cementing under large temperature differential condition, following study of the cement hydrogen mechanism and molecular structural design of cement admixtures. Meanwhile, CNPC also designed a cement slurry system suitable for different temperature ranges. The systematic process technology for large temperature differential cementing was developed by integration of the latest applicable technologies, such as large temperature difference cement slurry system, high efficient flushing spacer, improving displacement efficiency, antichanneling cementing, and safe tripping-in of casing. The process technology has been successfully used for more than 1100 wells in the oil and gas fields of Tarim, Southwest, Changqing and Huabei as well as CNPC’s overseas oilfields in Central Asia, providing the necessary technology for simplification of wellbore structure, cost reduction and improvement of cementing quality. As exploration and development is extending into deep and complicated layers, cementing technology for long cementing interval under large temperature difference condition shows a prominent technological advantage, with a bright prospect for wide application.