A Detailed Evaluation of Coiled Tubing Drillouts of Composites and Dissolvable Plugs In Permian Basin and Eagle Ford Fields

Abstract

Abstract Coiled tubing (CT) operations in Texas are distributed in the Permian Basin and Eagle Ford plays supporting unconventional completion of horizontal wells using plug-and-perf technology. CT drillouts are a key step in performing the plug removal and achieving full production potential. From a wide variety of plugs available, the most common plugs are composite and dissolvable. This study presents an evaluation of both plugs for CT drillout. The analysis gathers post-drillout data from CT interventions in the Permian basin and the Eagle Ford: 63 wells completed exclusively with 2,664 composite plugs, 60 wells completed with a combination of both type of plugs for a total of 382 dissolvable plugs and 1,792 composite plugs, and 16 wells completed with 543 dissolvable plugs. Data were analyzed for correlations between well geometry; lateral length; plugs used; dissolvable plug location in the lateral (heel, toe, full lateral); and key performance indicators (KPIs) such as time in well, average milling, wash times, plugs spacing and total number of plugs. The evaluation was conducted by comparing wells completed with only composite plugs, only dissolvable plugs, or a combination of both types, and it included a review of dissolvable plug dissolution performance. Composite plugs show a consistent milling performance for laterals of 1 and 1.5 miles, with an average milling time of 4 to 5 min and a variance of 3 min and wash times of 26 min; for laterals longer than 1.5 miles, the performance declines. When evaluating laterals completed with dissolvable plugs average milling time is 7 to 9 min, and the variance increases with the lateral length, with wash times of 26 to 36 min. Wells completed with a combination of dissolvable plugs on the toe and composites in the rest of the lateral show an improved overall performance, with constant milling times of 4 to 5 min regardless of the lateral length and variance of 1 to 3 min; the overall time in the well when plugs are combined is reduced by 46% compared to laterals completed with dissolvable only. The analysis also determined that at least 45% of dissolvable plugs did not dissolve and required CT intervention. The aim of this is study is to give operators a tool to assess the costs and benefits of using different plug technologies with a strategic placement to execute interventions in the safest and most efficient manner. Additionally, dissolvable plugs are commonly associated with cost reduction related to eliminating the need for CT milling. However, the data shows that inconsistent dissolution of the dissolvable plugs adds an uncertainty factor, which can only be dissipated with intervention using CT.