Innovative Technology in Producing Operations

Abstract

Hearn, D.D.,* ARCO Oil and Gas Co.; Blount, C.G.,* and Hightower, C.M.,* ARCO Alaska Inc.; Coleman, D.R., Exxon Co. U.S.A.; Carlberg, B.L., retired; Wolf, N.O., Conoco Inc.; Clayton, C.K., Nalco Chemical Co.; Blevins, B.A., Turner, J.M., Knight, R.M., and Nethers, J., Xytec;Eatwell, W.D., Camco Inc.; Craig, D.R., McClintock, P., and Krause, L., Damson Oil Corp.; Andrew, J.H.,* and Hall, J.W., Conoco Inc.; and Hamouda, A.A., Phillips Petroleum Co. Norway Phillips Petroleum Co. Norway *SPE Members The Innovative Technology in Producing Operations Forum is designed to allow the discussion of and dissemination of information about technical innovations and solutions in production engineering that are of immediate practical use but do not warrant a full-scale paper. Each subject is presented in a five to eight minute period with a discussion period of seven to ten minutes. A wide range of subjects is encompassed in the session. Abstracts of the presentations follow. presentations follow. I. Successful Application of Coiled Tubing Underreamers by D.D. Hearn, Arco Oil and Gas Co.; C.G.Blount and C.M. Hightower, Arco Alaska Inc. This is an overview of the evolutionary development, the testing, and the application of a coiled tubing system capable of underreaming cement, scale, or fill below production tubing. Using downhole motors, this system performs cleanout operations that normally require rig workovers. Recent jobs successfully completed at Prudhoe Bay have shown order of magnitude cost reductions over conventional operations. This project was conceived as part of an effort to lower workover costs through the innovative use of coiled tubing. The goal was to assemble a system capable of underreaming below production tubing using coiled tubing units available on the North Slope. Not only would such a system reduce direct cost, it would eliminate possible formation damage encountered when killing a well. To have the greatest utility in Prudhoe Bay wells, the system had to be capable of passing through a 3.725 inch restriction in the production tubing and of underreaming either 7 inch or 9-5/8 inch casing. Work on coiled tubing underreaming began in 1984 as part a coiled tubing cement squeeze program. The part a coiled tubing cement squeeze program. The underreamer design was derived from a casing cutter, and though it was not reliable enough for general field application, it showed the potential and feasibility of the operation. An alternate method for removing cement during the squeeze operation lowered the priority for continued underreamer development, and little work was done in the area until spring of 1987. The market was surveyed for improvements in underreamer and motor design, and a test program was begun to evaluate the various components and how well they worked together. Test targets constructed at Arco's laboratory facilities simulated cased wells cemented from target depth, past the 3.725 inch XN nipple, and up into the tailpipe. The design goal was a system to clean cement from the tailpipe and nipple then open and clean cement from the casing. Available motor/underreamer combinations tested in the initial 1987 trials were unable to do this reliably. Typical problems were a lack of torque, erratic extension and retraction of cutting blades, and excessive vibration and wear. Potentially damaging vibration was a persistent problem. The underreamers were developed primarily for workover rigs and snubbing units, and had difficulty with the higher speed of even the slowest downhole motors. This testing showed the critical importance centering and fully supporting the underreamer has in controlling vibration, and that two blades cannot provide adequate support. provide adequate support. Using the best features of two blade underreamers currently on the market, new designs were developed with improved lateral support. One approach was to use three blades in place of two. Another approach was to add a second pair of blades just above the first and rotated 90 deg. The first pair cuts the cement and supports the underreamer in one direction while the second pair is only to provide support in the other lateral direction. P. 737