Abstract
Well completion design is critical for the life cycle of the well. Any failure or delay in the operation can jeopardize well integrity, delay production and potentially impact the economics of the field development plan. The well completion preparation, wellbore cleaning operation and the line top inflow testing are time consuming, especially in challenging well environments. The paper documents executed two case studies that illustrate how a Systematic Risk Control Approach enables the execution of drilling out cement, negative Test, Wellbore clean out, and Casing Pickling and Displacement in one run. The results of the cost savings are compared to the conventional approaches.
The procedure employed for the deployment is to RIH with bit, Wellbore Clean out tools with inflow test Packer, perform the positive/negative tests as per the requirements, pickle the casing ID by pumping fluid loss control additive spacer (pH 11), followed by solvent/surfactant spacer, and another fluid loss control additive spacer (pH 11). That was followed by filtered water at a controlled pumping rate and RPM rotating speed. Circulation with the filtered water at maximum rate continued until desired fluid quality are met (NTU < 50 and TSS < 0.05%), the well displaced to completion fluid and pulled out of the hole while laying down the drill pipe for the upper completion run.
The Torque and Drag and Hydraulic simulation results were used during the preplanning phase. The successful results of two field case studies are presented; the operation on the first well is to perform 4 ½-in. Inflow Test, Wellbore clean out with Polish mill, Casing Pickling and Displacement and the second well is to drill 4-1/2-in. landing collar with mud motor using 10 surface rpm, 3bpm, 420 rpm @bit, 1700 ft-lbs torque, max 5klbs WOB performed 4-1/2-in. inflow test on TOL at 9818 ft vertical with 3000 psi differential pressure. drawdown with 215 bbl of water.
The most significant challenge during the deployment operation is cleaning out of cement and setting the inflow test Packer at high differential pressure or high torque and manipulation to achieve the desired fluid clarity with high pressure and low flow rate. However, this was overcome by proper operational designed to operate at the optimum RPM, flow rate and contact time allowable for the safe operation of the wellbore cleanup process. In addition, selection of efficient cleaning systems is important, along with a detailed displacement procedure to achieve optimum results. Finally, we recommend that higher RPM, flow rate (using an annular velocity booster tool to achieve optimum flow rate) and optimum contact time results in higher cleaning efficiency.
The results of this approach eliminate multiple runs and provide effective wellbore cleanouts under any wellbore conditions. All wells were successfully cleaned out and indirectly displaced to completion fluid in one trip to demonstrate the effectiveness of systematic risk approached, saving approximately 36 hours of rig time valued at approximately USD 270,000.
