Cement Packer Installation in Highly Deviated Well Using the BalancedHydrostatic Plug Concept through Coiled Tubing: Offshore Niger Delta

摘要

The "balanced cement plug" concept has long been a standard industry practice for setting plugs in awellbore. This requires setting a hydrostatic plug consisting of a column of brine, spacers, and cement slurrypumped into the annulus of a tubing/drillstring to create a balanced U-Tube that equates the hydrostatichead in the drillstring/tubing and annulus. Fluid volumes are calculated accounting for fluids both insideand outside the pipe at the given gradient, thus resulting in a hydrostatically "balanced system." Recently, this technology has been successfully deployed for cement packer design and execution usingcoiled tubing (CT) at a depth of 1,899 ft above the production packer with 111 bbl of calcium chloride brineexisting (cement accelerator) below the tubing punch interval in the tubing-casing annulus. The cementpacker installation design was for accessing bypassed hydrocarbon in high-angle (65 to 72°) deviated wellsoffshore the Niger Delta. Design considerations are reviewed and precautions for placement of high anglecement packer through CT are discussed. Initial designs to isolate the lower depleted zone were futile because of failed zonal isolation withmechanical plugs. Thus, an attempt to isolate the lower interval by pumping cement with 15% excess(openhole volume) led to having 17 bbl (1,899 ft) of cement within the 3.5-in. production tubing, and abovethe production packer. The CT deployed cement packer installation without a cement retainer presentsunconventional solutions for placing cement at the height of 1,899 ft. The operation was successfullyexecuted and the temperature log confirmed top of cement as proposed during the design phase. The holdupdepth in the tubing was also tagged as expected with no cement U-tubing from the annulus. Post-job shut-in tubing and casing pressures, quantity of cement pumped, and flow testing have proven the success of thedesign and procedure implemented in challenging wellbores.