Disposing Waste Oil Base Drilling Fluid from the Wei202H3 Platform

Waste oil base muds (OBMs) are disposed of presently by burial or reinjection. Potential pollution to environment and waste of large amount of mineral oil are the problems inusing these disposal methods. A study has been conducted on the recycling of waste OBMs from the Platform 202H3. The waste mud had apparent viscosity of 100-120 mPa·s, plastic viscosity (PV) of 80-100 mPa·s, yield point (YP) of 20 Pa, and 10"/10' gel strengths of 20/35 Pa/Pa The particle sizes of the mud lied between 5.59 μm and 13.74 μm. Studies showed that injection of 2 m³ waste oil base mud back into the well We202H3-3, which penetrated the Longmaxi formation, the final gel strength of the oil base mud in use was increased and the YP/PV ratio became uncontrollable. Use the low quality solids from the waste OBMs, a lost control slurry (LCM muds) was prepared and successfully used in controlling mud losses occurred in the well Changning-H12-3. From these practices, it was concluded that the troubles in recycling waste OBMs lied in the large amount of particles with sizes less than 20 μm, which were difficult to remove with the solids control equipment currently available. Technologies currently available in disposing of waste OBMs will be faced with problems such as safety, large spaces required, energy consumption, transportation, environment protection, and cost. It is thus suggested that the waste OBMs be used in formulating LCM muds, which can be used in controlling mud losses in shale gas drilling, thereby reducing economic losses to some extent. It is also suggested that if supercritical CO₂ fluid extraction technology can be used in cost control, it will be an important technology in waste OBMs disposal.