Research and development of high-temperature drilling fluid for complex strata in deep geothermal wells

Abstract:

In recent years， the geothermal sector in China has witnessed rapid growth， and the significance of the development and utilization of geothermal resources has significantly escalated. To effectively drill medium-deep geothermal wells in complex strata， this paper focuses on the technical drilling issues that arise in medium-deep geothermal wells when penetrating water-sensitive strata， water-gushing strata， fractured and loose complex strata， as well as high temperatures within the boreholes. Based on a large number of experiments， an initial selection of high-temperature-resistant drilling fluid formulations was made. The optimal formulation was determined through orthogonal experiments. Through effective tests， the water loss of the drilling fluid at a high temperature of 120℃ in the well was 8.4mL， the funnel viscosity was 24s， the yield point was 1.43Pa， the apparent viscosity was 14.5mPa·s， the plastic viscosity was 13.1mPa·s， the pH value was 8， the density was 1.04g/cm³， and the anti-aging performance of the drilling fluid flowing for 48 hours at 120℃ was excellent. It indicates that the high-temperature-resistant drilling fluid developed for medium-deep geothermal well drilling （around 3000m） can meet the requirements of medium-deep geothermal well drilling， featuring good rheological properties， high-temperature resistance， anti-aging properties， and water loss and wall-building properties， and can effectively address the problems encountered during the drilling of medium-deep geothermal wells in complex strata.