Coiled Tubing Workovers in Deep, Hot Wells

Abstract

ABSTRACT Mobil Oil Indonesia Inc. has successfully utilized a 1-1/2" OD coiled tubing unit in a well workover to isolate the upper portion of the producing zone. This isolation is necessary to produce gas, richer in condensate, from the lower producing zone. It was proved that the coiled tubing unit was able to perform squeeze cementing and drilling out of same at a depth of 10,000 ft and bottom hole temperature (BHT) of 350 °F. Ottawa sand was pumped to temporarily block the lower zone. A 3-3/8" down hole drilling motor with a 4-1/2" flat bottom mill was used to drill out cement. The cost of the workover using the coiled tubing unit was approximately US $ 400,000. Had a conventional drilling or workover rig been used, the workover cost would have been significantly higher. Furthermore, this operation requires less well shut down time as the wellhead and flowlines do not need to be dismantled for the workover. One Arun Field gas well has been worked over with this technique. Before the workover, the well produced with a condensate to gas ratio (CGR) of 34 bbl/MMSCF. Post workover results indicate that the well is currently producing with a CGR of 60 bbl/MMSCF. There were some problems in the first job associated with the high temperature of the reservoir. These problems have been overcome which will result in lower workover costs on subsequent jobs.