Application of Reverse Osmosis Drilling Fluid in H6-1 Well in the East China Sea

The East China Sea basin is located in the East China Sea, where a large number of low-porosity and low-permeability oil and gas reservoirs with deep-buried and heavy water block formation need to be developed on a large scale. Huagang group and Pinghu group have long section of mud shale and thin coal seam, so borehole wall instability occurred easily in the drilling process, which is a serious challenge for drilling safety and reservoir protection. Reverse osmosis drilling fluid technology is based on low free water drilling fluid and the theory of activity balance and semipermeable membrane. By drawing in a nano-micron sealing and bonding water technology, the drilling fluid has the function of reverse osmosis. The system was successfully applied in the high temperature deep well H6-1 in the East China Sea, and the average hole diameter expansion rate of the applied section was only 1.93%. The drilling was smooth, and the electrical test and casing were in target place in one trip. The drilling fluid system has strong inhibition, so the cuttings are in good shape. There is no drag pressure and pump in the drilling process. The invasion of drilling fluid and filtrate is greatly reduced, and the resistivity of logging while drilling is basically unchanged compared with that of logging (after the completion of drilling in 3 days. The system has the characteristics of low activity and low surface tension, which effectively protects low-porosity and low-permeability reservoirs. The successful application of reverse osmosis drilling fluid system meets the needs of safe and efficient developments of oil and gas fields in the East China Sea.