Drilling fluid wall protection technology for loose and fractured strata in the Shenjing exploration area in Zhongwei City， Ningxia

Abstract:

At the initial stage of drilling in the coal resource exploration project of the Shenjing exploration area in Zhongwei City， Ningxia， the complexity of the geological conditions， characterized by loose， fractured， and loss-prone strata， presented significant challenges in borehole wall stabilization. This led to substandard core recovery rates， reduced construction efficiency， and increased costs， with the drilling rig's monthly efficiency reaching only 353 m. By analyzing the geotechnical engineering characteristics and rock physical-mechanical properties of the exploration area， adjustments were made to the construction techniques and drilling parameters. The drilling fluid formula was optimized， and a low-solid-phase polymer film-forming wall stabilization drilling fluid system was adopted. These measures improved both the wall stabilization and core protection effectiveness of the drilling fluid. The filtration loss of the drilling fluid decreased from 25 mL/30 min to 9 mL/30 min， a reduction of 64%. The average core recovery rate increased from 53% to 84.41%， an improvement of 31.41%. The average monthly rig efficiency increased to 757.87 m， an increase of 115%. Subsequent construction of 9 boreholes proceeded smoothly， achieving a cumulative drilling footage of 4774.6 m. This experience provides a valuable reference for drilling in similar regions.