Case Study Tubing Repair in a Gas Well Patch set with Coiled Tubing
On a gas producer well, a leak was detected between the 4.5in #13.5 production tubing and the 7in casing. It was located with a thermo-log at a collar at 988m (3240ft). The major concern for the customer was to repair the zone and be able to run a downhole safety valve (storm choke) with an OD of 84mm (3.31in) through the repaired zone.
The workover of the Cr13 tubing string would have been very expensive and a tubing patch was determined to be the most reliable and cost effective solution. In order to cover the collar with a reasonable sealing length, a 6m (20ft) 4.5in reinforced patch was selected. The patch was conveyed using a 1-3/4in Coiled Tubing with optical fiber inside. Due to unpredictable CT behavior under pressure (elongation, helical buckling), a tension-compression sub was added in the BHA, to enable real time monitoring of the forces applied on the setting tool and the patch. It was also equipped with temperature and pressure sensors. The initial positioning of the patch was performed with a GR-CCL log. Prior to the patch operation, the well was killed with 1.27sg CaCl2 brine.
The patch was successfully set and drifted real time with the 3.4in OD setting tool (86.36mm, on 2m60=8.5ft long). After the POOH, a slick line gauge (OD=87mm=3.425in) was run through the patch without weight variation. The safety valve was then run through the patch and the well put back in production. No pressure increase in the 7in annulus confirmed the patch sealing capability. This job was a major success for the client and saved a costly workover.
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