Effect of Fluid Rheology on the Performance of Fibrous Fluid in Horizontal Well Cleanout

Abstract

The deposition of solids in the wellbore is a widely known problem encountered during drilling, completion, and intervention operations. Innovative cleanout fluids alleviate problems associated with inefficient hole cleaning. Various methods are known to provide efficient cleanout; however, their effectiveness drops as the wellbore geometry becomes more complex. One of the innovative ways of resolving this issue is to add fibers to the drilling fluid and improve its lifting capacity by reducing the settling velocity of the solids. This study is aimed at evaluating the cleanout performance of fibrous fluids in horizontal wells using a large-scale flow loop. The flow loop has a 48-ft long annular test section that has a 5-inch wellbore and 2.375-inch drill pipe. In each experiment, the solids bed is initially formed in the annulus with natural sand that has similar particle size distribution as solids found in oil and gas wells. Low-viscosity and high-viscosity polymeric suspensions were used with and without fiber. During the investigation, flow rate and fluid rheology were varied while measuring the equilibrium bed height. The bed height was measured starting at the lowest flow rate. Then, the flow rate was increased step by step until the bed was completely cleaned. The measured test parameters include flow rate and pressure loss, which were monitored and recorded using the data acquisition system. The pipe section was used to monitor the rheology of the fluids before the completion of the test. The results demonstrated the effectiveness of fiber in improving hole cleanout in horizontal wellbores. When a small amount of fiber (0.04% wt.) was added, the cleanout performance of the high-viscosity fluid did not show a noticeable change while that of the low-viscosity improved significantly. Even though the addition of fiber had minimal impact on the rheological characteristics of the fluids, the fiber improved the solid carrying capacity of the low viscosity fluid. In the horizontal configuration, the cleaning process of solids requires resuspension of deposited solids and transportation of the suspended particles from one location to another. Fiber particles are more effective in improving the carrying capacity of the fluids than their resuspension capability. Hence, the low-viscosity fluid which has a better resuspension capacity as compared to the high-viscosity fluid exhibited better cleanout performance when the same amount of fiber was introduced. In the absence of pipe rotation during coiled tubing operations, wellbore cleanout after drilling and milling operations require efficient and optimized hole cleaning, especially in horizontal wells. The presented large-scale flow loop study provides a unique analysis of the dynamics of hole cleanout in horizontal wells using novel fibrous fluids. Copyright 2022, Society of Petroleum Engineers.