This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 159848, ’High-Reliability Gas Lift Flow-Control-Device Technology and Erosion/Endurance Tests,’ by Jun Xu, Stuart L. Scott, SPE, and Wayne Mabry, SPE, Shell E&P, and Jose Gamboa, SPE, The University of Tulsa, prepared for the 2012 SPE Annual Technical Conference and Exhibition, San Antonio, Texas, USA, 8-10 October. The paper has not been peer reviewed.
High-reliability gas lift flow-control devices (GLFCDs) enable gas lift for wells with the potential for H2S in the produced gas and where casing is not qualified for H2S service. Valve specifications are such that no leakage is allowed at both high (8,000-psi) and low (1-psi) differential pressures across the valve. A series of tests was designed using the environmental-stress-screen (ESS) concept and a harsh test standard that greatly exceeds API specifications for GLFCDs.
Introduction
GLFCDs are usually incorporated into the production conduit and used to inject high-pressure natural gas from the injection conduit to the interior of the production conduit. Commercially available GLFCDs typically contain one-way check systems comprising a ball, hemisphere, or cone, which is pressed against a valve-seating ring by a spring. Unfortunately, many GLFCDs are prone to wear and damage because of fluid cut during the operation.
Some of Shell’s Gulf of Mexico deepwater wells commonly produce sour fluids, which the casing program was not designed to tolerate. When sour production enters casing that is not qualified to National Association of Corrosion Engineers standards, the wells cannot be produced. Therefore, a family of high-reliability GLFCDs has been developed for use in deepwater/subsea associations. This technology is viable for any gas lift well because of significant cost savings in change-out of GLFCDs and the ability to maintain well integrity. Fig. 1 presents schematics of the GLFCD through which liquids are unloaded from the casing annulus into the tubing, while Fig. 2 details several types of high-reliability GLFCDs.
High-Reliability-GLFCD Design Validation and Qualification Procedures
A series of design validation and qualification tests has been established and executed to determine whether high-reliability GLFCDs meet the acceptance criteria of API or ISO standards and Shell specifications and qualifications. Shell’s test program for these GLFCDs comprises three parts: factory acceptance, qualification, and endurance. Every individual GLFCD that has passed all factory-acceptance tests would be deemed accepted for installation and service. If the prototype of a GLFCD has passed Shell tests, it is deemed qualified to be a high-reliability GLFCD. Currently, three gas lift manufacturers have developed GLFCDs and products that have been tested using Shell’s test program; these test results are described in the following sections.
