Pilot Installation of a Deep Gas Lift System Conveyed with Coiled Tubing Catenary Method Increases Production of an Idle Well in Brunei

摘要

An oil well located offshore Southeast Asia, was completed with a dual string and after 20 years of production the drawdown decreased significantly even with gas lift mandrels located in the long string, 480m (1575ft.) above the lowest producing zone. A deep gas lift (DGL) system was installed based on field data that indicated the production could be improved by increasing the drawdown to optimize the gas lift performance. One of the main limitations was the depth of the production packer for the gas injection production. The deep gas lift system was selected as it enables the gas injection point to be moved deeper into the well, which in turn results in the ability to create a greater drawdown. The lowermost gas lift mandrel was straddled with two packers and a crossflow assembly that provided dual flow paths in a single system as well as suspending 350m (1148ft.) of 1.5in coiled tubing (CT) that acted as the injection string to a predetermined depth. The operation was the first of its kind in which the DGL system was conveyed with a CT Catenary system on board a dynamically positioned vessel (DP2); this enabled flexibility in deployment of the long bottomhole assemblies in small offshore platforms without the presence of a crane. For this operation, modifications were required in the original CT equipment to maintain well integrity, providing double barriers at every step of the installation. The DGL system was successfully and safely installed in a live well in 3 days. After its installation, the production rate increased tremendously. Similar operations will benefit from understanding the rationale in the selection of the solution, the details of the installation with the CT catenary system, the barrier systems put in place during the open-hole installation, the depth correlation methods and the lessons learned.