Study and Application of Gel-time Controllable Lost Circulation Material

In the development of theshale gas in Jiaoshiba, Fuling, Chongqing, mud losses into solution cavities or fractures have occurred frequently during the whole drilling process, and the mud losses were very difficult to be stopped. A gel-time controllable lost circulation material (LCM) has been developed for use in this area to try to control the severe mud losses. This LCM is formulated with gel materials, thixotropic agents, fibers, swelling agents, microcapsules and surfactants. The performance and mechanism of this LCM in mud loss control have been evaluated and analyzed. This gel-time controllable LCM is suitable for controlling mud losses into formations with high permeability, large-sized pores, fractures, or solution cavities. This LCM works in a temperature range of 30-80℃, and has adjustable gel time. When solidified, the LCM has compressive strength of 5.0 MPa (4 h) and 10 MPa (8 h). Pressure bearing capacity of the set LCM is 14 MPa. The set LCM is striongly resistant to water corrosion and has strong thixotropy. 80% of mud losses in 45 wells have been successfully brought under control. This gel-time controllable LCM has played a great role in controlling mud losses into solution cavity and fracture.