Using coiled tubing in HP/HT corrosive gas wells
High-yield-strength (100,000 psi) coiled tubing (CT) material has allowed for CT intervention in Mobile Bay Norphlet completions. These wells are approximately 22,000-ft-vertical-depth, high-pressure, hydrogen sulfide (H{sub 2}S) gas wells. Operations performed on the Norphlet wells include a scale cleanout to approximately 22,000 ft, a hydrochloric acid (HCl) job at 415 F, and buildup removal from a safety valve. The scale cleanout was performed first with a spiral wash tool. The well was killed with 10-lbm/gal sodium bromide (NaBr) brine; the same brine was used for cleanout fluid. Cost savings of 60% were realized. A HCl matrix acid job at 415 F was performed next, followed by a scale cleanout across the downhole safety valve. The safety valve was cleared of debris in 1 operational day. Estimated cost of the CT operation was 5 to 10% less than that of a rig workover. The 100,000-psi-yield Ct material used for the Mobile Bay operations does not comply with the (NACE) Standard MR-0175. But on the basis of extensive laboratory testing by the CT manufacturer, the decision was made that the material would pass a modified test performed with decreased H{sub 2}S levels. A maximum level of 400 ppm H{sub 2}S was determined as the safe working limit. Because the maximum H{sub 2}S content in the wells described later was 120 ppm, the risk of sulfide-stress cracking (SSC) was considered acceptably low. Elevated bottomhole temperatures (BHT`s) increase the corrosion rate of metals exposed to corrosives. Extensive laboratory testing of corrosion inhibitors allowed for design of a matrix-acidizing treatment to remove near-wellbore damage caused by lost zinc bromide (ZnBr) completion brine.
- OSTI ID:
- 504921
- Journal Information:
- JPT, Journal of Petroleum Technology, Vol. 49, Issue 6; Other Information: PBD: Jun 1997
- Country of Publication:
- United States
- Language:
- English
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