Study on Rapid Evaluation Method and Application of Sedimentation Stability for Oil Testing Working Fluid Under High-Temperature

Long-term static placement of oil testing working fluid under high-temperature may result in severe sedimentation, causing downhole tubing obstructions during running down or difficulties in starting pumps, thus increasing operational risks. Currently, the indoor evaluation time for sedimentation stability of oil testing working fluid under high temperature is determined based on the running down process of tubing, typically ranging from 7 to 15 days, which is time-consuming and inefficient, severely limiting the oil testing efficiency of deep and ultra-deep well. Taking the PL block in the Sichuan basin as an example, a multi-parameter correlation model for sedimentation stability prediction under high temperature based on laboratory experimental data was successfully established using dimensional analysis and multivariate nonlinear regression methods in this paper, achieving rapid evaluation of sedimentation stability within 3 days. Field applications on three wells showed that the prediction model for sedimentation stability of testing fluid under high-temperature has high accuracy with a relative error of less than 1%. Additionally, a sedimentation stability chart for viscosity-static shear force of testing fluids was developed for this block, and rapid evaluation indicators and value ranges for sedimentation stability were proposed. The testing period was significantly reduced from the original 15 to 3 days, greatly enhancing the evaluation efficiency of sedimentation stability for testing fluids under high-temperature. The rapid evaluation method provides theoretical support for shortening the testing period and reducing complexities and failures during testing operations.