CT real-time perforating service
Ensure target zone coverage with selective perforating, and achieve accurate depth control in a single run.
Total is developing a 17-well deepwater field offshore Congo. The field is prone to asphaltene deposition and rapid water breakthrough, requiring a high level of well interventions. Because of the strong need for well access, dry head installation was the preferred option from a TLP. To achieve the high level of interventions while producing and drilling, a special frame was required to enable coiled tubing, perforating, electric line, and slickline operations simultaneous with drilling and production. The limited deck space, heaves, and TLP moment, and requirements to be able to perform operations underneath the mast equipment package (MEP) added complexity to the project.
Schlumberger and Total designed a motion-compensated intervention tower to enable perforating and other CT, wireline, and slickline operations separate from the drilling activity. Designed to fit on the limited-space deck of the TLP, the tower can skid easily from one well slot to another and convey a long string of perforating guns even while working below the drilling MEP.
To enable perforating operations without killing the well, the remotely operated CIRP equipment was used from the tower to insert and retrieve long gun strings under wellhead pressure. A 5/16-in braided wireline cable for gun deployment was integrated with the tower while an A-frame gin pole crane facilitated gun deployment in the live well to meet the working height limitations. A custom CT well control stackup that worked within the tower's dimensional limits was rigged up on top of the Christmas tree and enabled by the motion-compensation system.
To accurately deliver the gun assemblies and verify depth and performance in real time, engineers used ACTive real-time downhole coiled tubing services and tools.
After drilling the first well and running the completion, the MEP was moved to drill the second well and the tower moved into place to prepare the first well for production. Slickline was deployed from the tower to remove plugs, and then the ACTive service used the tower to perform a cement bond log.
For the first perforating operation, 81.8 m [268 ft] of perforating guns and spacers were deployed from the tower on braided line into the live well. The perforating guns were conveyed to depth using the ACTive Perf service with a gamma ray tool and a casing collar locator for real-time depth correlation. The guns were activated on the first attempt and verified in real time with ACTive services downhole data acquisition.
After perforating, the tower was used for an acid wash operation on coiled tubing and a massive stimulation operation followed by flow profiling on slickline during the well cleanup and well testing.
In all, Total estimated that the new tower equipment saved 15 days of rig time by enabling the rigless well intervention work to be performed simultaneous with drilling operations.
Challenge: Perforate long reservoir intervals (up to 200 m [656 ft]) offshore from a tension-leg platform (TLP) with limited deck space and simultaneous production and drilling operations.