Self-Removing Fracturing Plugs: A Study of Initial Adoption in the Williston Basin

摘要

Research and development of hydraulic fracturing plug materials has shifted to materials that degrade upon exposure to wellbore fluids, thus eliminating the typically necessary post-fracturing millout operations. This paper provides an overview of the field trials and initial commercialization of a dissolvable metal alloy fracturing plug in the Williston Basin. The paper also discusses the alloy’s reaction with wellbore fluids and degradation prediction based on wellbore fluid constituents. During several months of degradable fracturing plug field trials, performance metrics were established, monitored, and analyzed for each stage of the completion process. Tests were conducted using samples of the alloy submerged in actual wellbore fluids from a given field trial to predict wellbore degradation. The test results were correlated to the field trial results, which helped enable prediction of degradation in future field trials. The conventional design and mechanics of the degradable alloy fracturing plug allow it to be set similar to the industry-standard composite plugs because no special tools or processes are necessary. More than 1,500 successful runs have been completed in the Williston Basin alone. Installation performance has been predictable since the field trials began; however, estimating degradation time has been more challenging because fluid-related variables are difficult to control. Degradation can vary significantly, even in similar fluids, because of specific fluid constituents’ effects on the reaction that occurs at the plug-fluid interface. The approach of relating test results to field results helps correlate many of these variables and helps identify specific constituents that affect degradation. Strong production figures allowed an operator to skip post- fracturing treatment millout operations in a few cases, thus saving more than USD 200,000 and several days of millout operations in one particular case. Additional field results and tests should help predict with a higher degree of certainty whether a well can be put on production after the fracturing treatment. This paper summarizes an approach for establishing performance standards, implementing testing methods, and predicting degradation of a degradable alloy fracturing plug designed to help eliminate post- fracturing treatment interventions altogether.