Eight subsea wells were drilled and completed in Eugene-Island Block 175 Field from 1966 through 1968. Average water depth of the field is 85 feet. Service work, similar to wireline service on conventional wells, has been performed using thru-flowline pumpdown techniques. Workovers were required on three wells because of normal depletion and mechanical problems.
Three phases of the workover operation will be presented: I. Planning phase, II. Actual performance of the work, and III. Evaluation and conclusions of the job success. The planning phase will include rig selection, subsea inspection prior to moving in the rig, and formulating a particular plan of attack as in any workover. The second phase or work phase will include subsea inspection while moving in the rig and establishing contact with the wellbores. The removal and reinstallation of the subsea tree and installation of blowout preventers will be covered. Diver assist operations are documented by 16 mm color underwater photography. Once the blowout preventers have been installed, the problems of normal workovers will be excluded.
Three subsea wells were approved as workover candidates. One well did not require removal of the subsea tree, because problems were solved by conventional wireline and 1 inch pipe fishing operations through the tubing bores once contact with the well was established. The other two wells required removal of subsea Christmas tree and installing of 10" high pressure riser to repair the wells. Once the well was worked over the subsea trees were reinstalled.
Atlantic Richfield Company is now operating eight subsea wells in offshore Louisiana waters. These wells are located in Eugene Island Block 175 Field, approximately 70 miles southwest of Morgan City, Louisiana. Average water depth for the field is 85 feet. These wells were among the first to be installed as subsea completions in the Gulf of Mexico. These wells were drilled and completed as string completions between 1966 and 1968. All of the wells are producing from multiple pay zones and are flowing to a common production platform located from one to three miles from the wells. Routine service work on these wells, such as pulling and inspecting storm chokes, cutting paraffin, etc., is done by the flowline pumpdown techniques from the production platform. The wells were-originally completed with special cross-over ports that allow the tubing strings to communicate in the well just above the top packer in the well. This feature allows tools, similar to wireline tools, to be pumped down the flowline and into the tubing strings of the wells and to be pumped back out of the wells and returned to the production platform.