Application of High-Performance Water-Based Drilling Fluid for Horizontal Wells in Tight Reservoirs of Daqing Oilfield

During the drilling of middle-shallow tight oil reservoirs in the Daqing Oilfield, mud making, hole shrinkage, caving and other downhole complications are frequently observed. To evaluate the problem, SEM and cast slice analyses were performed on core samples taken from tight reservoirs, and synergistic effects of polyamine and polyalcohol were used to enhance the inhibition performances of drilling fluids. By jointly using conventional physical plugging techniques and chemical plugging using polyalcohol, the plugging performances of drilling fluids in micro-fractures were enhanced significantly. By using assessment techniques with a combination of macrofacies and microfacies, polyamine inhibition additives with optimal performances were identified. In addition, with deployment of polyalcohol and other additives with satisfactory compatibility, a high-performance water-based drilling fluid with outstanding inhibition and plugging performance was generated. Lab test results showed that the high-performance water-based drilling fluid had rolling recovery rates above 95% for shale, with total fluid production from micro-fractures with sizes of 10-50 μm less than 2 mL, and with lubrication coefficients under extreme pressures at merely 0.10. The new drilling fluid was then deployed in 9 wells drilled in tight oil reservoirs in the Daqing Oilfield where it achieved outstanding performance.In Well Long26-Ping9, an expansion of the borehole diameter was no more than 9.31%, whereas the highest ROP was 10.58 m/h. Research results showed that the high-performance water-based drilling fluid could meet demands for development of tight oil reservoirs in the Daqing Oilfield.