One Innovative Intelligent Completion Intermediate String Design for Deepwater Gas Well Completions: The Installation Case Study from L Gas Field, China

Abstract

An intelligent completion design was installed in two wells in China's L field deepwater project. Both wells have dual-zone stack-pack sand-control lower completions. To handle critical well control concerns and enable production from each zone, an innovative intermediate string was installed to temporarily isolate the reservoir in each zone. The key components of the intermediate string were two types of temporary well barrier valve. One in-line barrier valve isolated tubing flow, which produced the lower zone, and another annular barrier valve isolated the annulus flow from upper zone. Both valves were installed permanently by the intermediate string. Before the intermediate string was deployed, the lower completion was completed by a stack-pack sand-control method. The intermediate string used one long tail pipe with a seal assembly to snap into the lower completion to separate the flow from the two zones. Both barrier valves were in the closed position after installation of the intermediate string. A safe and isolated casing environment was established before the upper completion was run in hole. After the upper completion was done, the two barrier valves were opened by applied pressure at the surface. The well could be tested safely, and the entire completion process was accomplished. In 2021, the intelligent well intermediate string completions were installed successfully in two wells in the southern coastal area of China. The two types of barrier isolation valve were installed, and pressure tested successfully. To separate the flow from the two zones, the space out of the intermediate string tail pipe was achieved by successfully running a seal assembly into a polished bore pre-installed between the sand-control completions of the two zones. After the intermediate completion was done, the upper completion was deployed safely in an isolated casing environment. In both wells, the two types of isolation valve were successfully opened by applied surface pressure, which verified a high reliability of barrier valve design. No through-tubing intervention was used in this project to open the valves. After completion installation, the wells were brought into production testing. Each zone of each well was tested separately, and a significantly different pressure response was observed by the downhole gauge, which verified the intelligent well zonal isolation was successfully achieved by the installed intermediate string per plan. This innovative intelligent well intermediate string completion design and the two types of barrier valve design/features represent an industry innovation. The project required new techniques for installation design and execution. This practice will benefit upcoming deepwater well completion designs, especially for high-pressure and high-temperature gas field development projects, where a temporary well suspension or well control is critical and essential for the project success.