The lithology of the shale gas horizontal well in the Jiaoshiba block is clay shale. Excessive water loss of the cement slurry will cause wellbore instability. Therefore, the cement slurry needs sufficient thickening time, and the thickening time needs to be adjusted accordingly. By optimizing the monomer ratio, the water loss agent ZYJ-1, and the retarder ZYH-1 were prepared. The elastic agent, toughening agent, and expansion agent are optimized, and the compatibility is evaluated to form a high-strength and elastic cement slurry system. For this cement slurry system, the thickening time is adjustable, and other properties of the cement slurry are good.
The Jiaoye 1HF well was successfully deployed in the Jiaoshiba block in 2012 and an industrial gas flow of 20.3 × 104 m3/d was obtained. The Jiaoshiba block in Fuling is in the Jiaoshiba structure of the Baoluan - Jiaoshiba anticline, a high and steep fold belt in eastern Sichuan. which opened the prelude of Marine shale gas exploration in Fuling area (Zhou,2013; Li et al, 2011). In June 2013, an industrial gas flow of 11 × 104 m3/d was obtained in the Jiaoye 1-3HF well, which further confirmed that the Jiaoshiba block shale gas in the Fuling area has a good prospect for exploration and development.
However, poor cementing quality seriously affects the development efficiency of shale gas wells in this area. The design of cementing slurry for shale gas horizontal wells in the Jiaoshiba block faces the following challenges (Niu,2014; Ai et al, 2014; Ma,2017):
(1) Since the lithology of producing layer is mud shale, excessive water loss in cement slurry will cause borehole wall instability, and potentially causing different types of faults including in the cementing pump;
(2) The cement slurry is required to return to the ground at one time, the construction time is long. Therefore, the cement slurry must have enough thickening time, and the thickening time can be adjusted to meet the design requirements of the collar and tailing slurry.
