Novel Water-Based Mud for Low-Permeable Reservoir in South China Sea

Abstract

Conventional reservoir drill-in fluids used for drilling reservoirs in Weizhou Oilfield encounter rheological problems that result in technical problems such as hole-cleaning in openhole horizontal intervals. Hence, novel drill-in fluid was developed by optimizing the additive quantity and particle size distribution. Lab tests showed that novel drill-in fluids boast high low shearing rate viscosity, and provide promising cutting, carrying, and suspension capabilities. Furthermore, the novel drill-in fluids performed well in reservoir protection, with a permeability recovery rate of more than 90%. The novel drill-in fluids also have high inhibition capabilities with a linear expansion rate of mud shale as low as 10%, with a rolling recovery rate of up to 96.48%. Field application results showed no pipe-stuck was encountered during tripping in the horizontal interval when using the novel drill-in fluid. Moreover, by using the novel drill-in fluids, skin factor was reduced from 20.0 to −3.0, and daily oil production was double what was expected. It was concluded that novel drill-in fluids meets the demand of horizontal drilling intervals in Weizhou Oilfield and improves hole-cleaning and reservoir protection in the horizontal well.