Well commissioning operations offshore encounter multiple organizational, operational and technical challenges that must be safely overcome to efficiently deliver high-quality service. Coiled tubing (CT) perforation and commissioning performed in hostile reservoir conditions and high pressure is one of the most complicated multiservice operations, especially in a sensitive aquifer ecosystem like the shallow Caspian basin. A comprehensive approach used to deploy an innovative solution to the challenges provided experience in such operations and lessons learned.
An innovative perforation technique was selected for the project: electric-line-enabled CT for precise depth control in combination with an advanced gun deployment system for conveyance of long gun strings under pressure. New techniques were incorporated to improve equipment efficiency and reliability: detonation shock-resistant bottomhole assembly, two independent emergency disconnects, software to predict and evaluate shock load and dynamic underbalance, high-pressure H2S-rated and conventional connectors for a specialized tool deployment stack (TDS), rounded scallop guns, and high-tensile CT logging-head-disconnect weak points.
To date, more than 10 well commissioning operations were successfully completed with this innovative method. Integrated service project management was a key approach to achieving successful results by effectively integrating multiple service lines. The technique proved to effectively minimize operational time, associated risks, improper equipment use, and interface failures between different service lines. The developed solution is a seamless integration of electric-line-enabled CT, the CT logging head, the gun deployment system for pressurized well conditions, and a set of wireline tools and specialized perforation equipment. The design was optimized to perforate the well in three or four runs at overbalanced condition (squeeze mode) in one rig-up job instead of the more than 20 wireline runs typical in conventional operations. Additionally, the use of CT provided the flexibility to perform pumping operations for well displacement, injection of an H2S scavenger, and stimulation, as per the operator's plan, without or with only partial rig-down.
This was the first time that integrated service project with the described CT perforation technique was performed in the Caspian region. The acquired experience will facilitate design, preparation, and execution stages for such type of jobs with multiple services involved.