Development and Application of Anti-Sloughing Fluid System during Salvage in Borehole

In Bohai Oilfield, all horizontal wells and some directional wells are completed by using high quality sieve tube within borehole in order to control sand. During well work-over operation, if the working fluid system is not anti-sloughing, the system will cause wellbore lose stability, which will lead drilling pipe to stick. In addition, the system will destroy the reservoir structure in the near-wellbore area, which will do great damages to oil production and next well completion. We develop a new kind of antisloughing working fluid system on the basis of old system. The new system has good performance in anti-sloughing, which has been confirmed by laboratory tests and application. The anti-sloughing working fluid system can guarantee that fishing can be conducted smoothly.