First Successful Deployment of Nonmetallic Casing Strings: A Case History

Abstract

For the first time, two different sizes of nonmetallic casing strings were installed in water wells to cover shallow potable aquifers. This paper describes the reasons for deployment, planning and design, logistics, operational challenges, lessons learned, and the way forward for this newly deployed technology. In the initial stages of the project, fiberglass-reinforced thermoset resin (RTR) pipes manufactured locally were evaluated in terms of ratings, dimension, and method of connection and feasibility for downhole applications. Two nonmetallic casing strings, 19.7″ and 11″, were selected to be run in hole. Design consideration also included compatibility with available casing running and handling tools to ensure safe and efficient field handling and running. At this stage, carbon steel casings were still needed to connect the nonmetallic casing to the surface wellhead equipment and to the float equipment at the bottom of the string. Specially designed crossovers were manufactured and tested prior to enabling combination of nonmetallic and carbon steel casing. All manufactured casing joints and crossovers were tested based on the best available criteria for the nonmetallic industry. Different challenges were encountered in the design stage, such as overcoming the buoyancy force while running and cementing the nonmetallic casing, all of which to be tackled. Cement slurry design and casing accessories were modified based on the simulations scenarios that were run. These designs were subsequently modified in response to issues, i.e., total losses, encountered while drilling. Successful evaluation of the nonmetallic casing deployment was conducted from multiple aspects, including running efficiency, casing wear, and cement quality. Drillpipe protectors were utilized to reduce the possible casing damage due to wear. The nonmetallic casing joints were connected through crossovers to a top metallic casing and float equipment at bottom. Both casing strings were successfully run to depth and cemented in place. Both casings were pressure tested successfully after performing the logging jobs that indicated the level and quality of cement pumped around the strings. Logs showed no considerable change in both nonmetallic casing thickness. The well was completed with open hole, tested and flowed naturally to surface. A conventional power water injector wellhead was installed before release. The design, review and assessment processes, as well as several lessons learned from the first ever deployment of the nonmetallic casing in a water supply well, are the key takeaways from this paper.