Sonatrach DP encountered water production in the lower zone of one of its oil and gas wells, resulting in an overall production decline. After reperforating the upper zone failed to achieve the expected production, the operator decided to isolate the lower zone at 3,460 m, lift the column with coiled tubing, and then perform a flow test to assess performance of the upper zone.
Because there was no nipple profile available at the desired depth, a gas-tight V0-rated mechanical bridge plug was required to isolate the lower zone, but the 4½-in completion string contained a restriction at the landing nipple profile with a minimum ID of 3.450 in. The operator contacted a third-party supplier, but its proposed conventional 4½-in retrievable bridge plug had an OD of 3.65 in, which could not pass through the restriction.
SLB deployed the SIMextra plug using nonexplosive digital slickline services to ensure accurate correlation and reliable setting. The plug was successfully deployed with its integrated junk catcher at the desired depth of 3,460 m in a single run. During retrieval, again in a single run, a real-time downhole pressure gauge on the digital slickline toolstring helped the operations team monitor the downhole pressure during the entire equalization process. The unique seal element and barrel slip design of the plug was then completely retracted to the initial running OD of 3.375 in and the complete assembly passed successfully through the RN nipple profile without incident.
The plug maintained a 3,000-psi differential pressure during the entire 7-day operation, including the coiled tubing lifting and upper zone pressure survey. After the flow assessment was performed, the plug was removed to enable both zones to produce again.
The SLB solution helped Sonatrach finish the job in the shortest possible time at a significant cost saving when compared with the alternative, which would have included setting a millable high-expansion plug or umbrella plug, dumping cement, and then milling the assembly to recover wellbore access.
