Ravva is a mature field located offshore east coast of India with over 20 years of production history from Middle Miocene sandstone reservoirs. During the development phase of the field, Late Miocene (LM) sands were intersected in few wells at shallow depths. Due to the presence of more promising and critical zones below, these sands were not completed and fell above the production packer and behind the production casing. The marginal reserves in these sands did not justify workover operation to complete it. Rigless options were studied and a shut-in well was selected for implementation.
In order to safely complete and access the bypassed shallow sands, a vessel based pumping operation was planned to place a cement packer in the tubing – casing annulus. The slurry was circulated into the production casing/tubing annulus through a circulation SSD installed above the production packer.The cement packer was thus placed across the zone of interest. Designing of the cement slurry was based on reservoir parameters and the setting time was optimized to prevent reversing of the slurry back into the tubing. The cement mix had a bonding agent to exhibit good metal-cement bonding providing prolonged endurance of the cement with the capability of holding the expected pressure differential. The cement packer emulated a production packer providing zonal isolation for the new completion.
Size of the platform precluded spotting of the complete Coil Tubing spread on the platform. High cost prohibited catenary coil tubing operations. As an alternative, the pump spread was placed on a DP vessel and the coil tubing unit was spotted on the platform. A high pressure hose running up from the vessel to a standpipe on the main deck of the platform formed the main conduit for fluids being pumped from the vessel into the CT or wells. Onsite mixing of the cement slurry on the vessel required detailed planning and execution. The well was activated & tested at rates of 1500 bopd with no integrity concerns till date.
This paper will emphasize on the operational procedure and challenges of successfully completing the zone and bringing the shut-in well online. The execution of this operation was done at 1/10th of the cost of a rig based workover. This has also opened up new opportunities to access similar bypassed reserves resulting in incremental production from reservoirs which would have otherwise been left untapped.