Real-Time Downhole Measurements During Coiled Tubing Campaign Brings Wells Back to Life

Abstract

Coiled tubing (CT) was used on a field on the Norwegian continental shelf to intervene in four separate wells. The campaign objectives were to restore injectivity to two injector wells, prepare a well for plugging and abandonment (P&A), and bring a newly drilled well onto production. The use of CT was a prerequisite because previous wireline interventions had failed to reach target depths due to ingress of fill into the wellbore. Three main challenges were faced during that campaign: demanding cleanout conditions, precision required on downhole weights, and critical perforations. The demanding cleanout conditions were due to the large completions and sensitive formations, which required accurate control of slighty underbalance conditions. The precise measurement of downhole weight and torque was required to effectively manage milling operations and accurately cut a hanger. Finally, the perforations required a depth accuracy within 0.5 m of the target depth, accuracy that was beyond the limits of what surface depth measurements can provide. Real-time downhole measurements quickly appeared as the common denominator to address all those challenges at once. To address the demanding cleanout conditions, real-time measurements of downhole pressures allowed controlling the pumping conditions at depth, whilst still allowing high pumping rates. This enabled handling high pumping rates, so the cleanouts could be performed effectively. To obtain precise downhole weights during milling and cutting operations, the exact downhole weight on the bottomhole assembly (BHA) and torque was monitored, which, in turn, opened possibilities for adjusting and optimizing the mill and motor use during the operations. For critical perforations, a selective activation firing head was used along with the full array of pressure, temperature, and depth control modules, which allowed multiple guns to be positioned precisely on depth and separately fired in a single run. The application of real-time downhole measurements resulted in objectives being met. Increased injectivity was achieved, while rig days were saved with the P&A preparations.