Key Technologies for Casing Running with Double Floating Collars in Middle and Deep Horizontal Wells

There are problems of excessive drag and restriction while running production casing into medium and deep horizontal wells. In addition, the conventional floating collar has a complex structure and complicated running procedure, and multiple floating collars in series have high risk. In order to improve floating collars' performance, reliability, and the pipe string trafficability of casing running, the immediate rupturing disc floating collar and eccentric self-rotating pressure bearing float shoes were developed, and key tools such as integral non-weld centralizer and elastic floating collar were selected. The determination method for drag coefficient and position of drag floating collar was established, and the technical procedure of casing running with floating collar were created, forming the key technologies for casing running with double floating collars suitable for middle and deep horizontal wells. The technologies have been successfully applied in nine horizontal wells in Zhongjiang Gas Field, and the casing was safely run to the designed depth. The maximum liquid column pressure bearing of the floating collar is 62.5 MPa, and the maximum floating length is 1811 m. The results of research and field application show that the casing running technologies with double floating collars can solve the problem of difficult casing running in middle and deep horizontal wells and provides a new technical method for casing running in middle and deep horizontal wells.