Water Shutoff With a Thixotropic Treatment in Offshore Well Increases Gas Production

Abstract

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 209889, “A Successful Water Shutoff Using a Thixotropic Treatment in a Subhydrostatic and Highly Aromatic Well Results in Increased Gas Production of 30% and Reduced Water Production of 63% in Vietnam,” by Tuanangkoon Daohmareeyor, Tran Thang Nguyen, and Reawat Wattanasuwankorn, Halliburton, et al. The paper has not been peer reviewed. _ An offshore operator in Vietnam faced high water production in a subhydrostatic and highly aromatic gas well. In addition to low productivity, the high water cut also strained the water-treatment facility. Previous treatment attempts to shut off the high-water-producing zones have been unsuccessful because of challenging well conditions. A customized solution using a thixotropic organically crosslinked polymer (TOCP) with extensive laboratory testing was found to be the most suitable treatment design for this well. The new placement technique provided prevention of losses to the depleted zones. The thixotropic treatment provided higher viscosity when pumping stopped, allowing the polymer to seal off at the target zone. Introduction Excessive water production in mature wells is a major challenge for oil and gas operators worldwide, causing numerous economic issues for hydrocarbon production. In this case, the operator faced concerns with handling the water at the production facility, which had almost reached its capacity limit and would soon result in well abandonment. Furthermore, the well discussed in the complete paper was one of the highest-producing gas wells on the platform. The trend of gas production in this well was decreasing year over year, however, and the previous chemical water-shutoff treatment was not successful because of reasons that included the following: - The highly depleted formation created difficulties for well-intervention activities and treatment placement. - A complex well-completion setup was not ideal for well intervention, especially for mechanical isolation applications. - High aromatic content from the reservoir created incompatibility with mechanical isolation packer elements, risking operational failure. To achieve a shutoff objective, prejob considerations should include proper candidate selection, root-cause investigation, placement selection, tailored treatment design, and risk-mitigation planning, all of which are important factors of a successful operation. The complete paper presents the design and operational execution to serve as a guideline for future wells with similar issues. The operation’s objective was to shut off the top interval (Interval A) of five intervals in the well to reduce water production and increase gas production.