The Development of High-Performance Elastic-Floating Float Collars and Their Applications in Shale Gas Wells

Existing float collars exhibit low reliability in cementing operations of horizontal wells for shale gas development. Consequently, the failure of floating collars for casing may frequently induce negative impacts on quality of cementing operations. To solve these problems, a review was conducted of the root causes for failures of float collars together with technical solutions to enhance reliability of such collars. The feasibility of such solutions had been analyzed through simulation tests. On bases of combination of lab test results and assessments of overall performances, high-performance elastic-floating type float collars were developed. Laboratory test results showed that the newly developed float collar might endure pressures up to 60 MPa with resistance to temperature 180℃. In addition, these collars might experience no damage for 72 h under displacement erosion rate of 2.0 m3/min. High performance elastic floating float collars were applied in more than 200 shale gas horizontal wells in the Jiaoshiba Block of the Fuling Shale Gas Field with outstanding resistance to high pressures, high temperatures, erosion and excellent reliability,with a one-time setting success rate up to 100%. Research results suggested that these float collars may be widely used in cementing operations in wells with significant differential pressures, horizontal wells, high-temperature deep wells and wells under complicated conditions.