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Three-Zone Completion Increases Recoverable Gas Reserves and Production in Indonesia Subsea Project
Published: 05/01/2012
Three-Zone Completion Increases Recoverable Gas Reserves and Production in Indonesia Subsea Project
Published: 05/01/2012
Drilling in subsea Indonesia
A large subsea development located in the Natuna Sea offshore Indonesia was producing from with three gas-bearing intervals that had an estimated 198 Bcf of gas in place.
A well was drilled with a 60° well inclination to strategically intersect all three gas-bearing intervals. The well log showed three distinctive sand lobes within a 195-m [640-ft] interval. The three lobes were separated by thick shale barriers. The 9 5/8-in production casing was cemented in preparation for completion operations.
Customizing completion technologies
Several possible sandface completion scenarios were investigated. After careful consideration, engineers selected the MZ Alternate Path and QUANTUM PERFPAC system.
Gravel and frac pack design for the three-zone Well A-01 completion.
Increasing reserves and adding revenue
After the production tubing was installed, the well produced sand free at an initial rate of 55 MMcf/d under 2.8 MPa [406 psi] of pipeline pressure, in excess of the predrill estimates of 47 MMcf/d.
Penetrating the three sand lobe reservoirs with one borehole resulted in an additional 6 to 10 Bcf in recoverable gas reserves and 10 MMcf/d in production. The well came in under budget and added USD 20 million in projected revenue and operational savings.
The effectiveness of the three-zone treatment was evaluated postjob by merging surface and downhole pressure, temperature, slurry rate, and proppant concentration data. The screenout can be clearly identified at the approximate time of 20:18:20.
A single treatment consisting of ClearFRAC XT viscoelastic surfactant was pumped to simultaneously frac pack the upper and middle intervals through the shunt tubes. After these zones were fully packed, the pump rate was reduced and the lower zone was gravel packed.
After the entire annulus was successfully packed, excess slurry was reversed from the wellbore. The DST equipment, QUANTUM service tool, and washpipe were then removed from the wellbore.
The number and length of shunt tubes were varied to create the proper diversion into each zone. Postjob pressure gauge data indicated an effective frac pack into the upper and middle zones and an effective gravel pack of the lower zone.
Sandface completion times were compared for a three-zone stacked completion and Multizone Alternate Path completions with and without the QUANTUM PERFPAC system. The stacked com-pletion time estimate of 18 days resulted from the time required to perform multiple perforating, cleanout, sand control tool deployments, and pumping treatments. The much shorter time for the Multizone Alternate Path completion—an estimated 6 days—resulted from the elimination of a cleanout run and only a single sand control tool run and single pumping treatment, saving 12 days of deepwater rig time. Ultimately, the multizone Alternate Path technique, combined with the QUANTUM PERFPAC system, resulted in a total sandface completion time of just 4 days.
Rig time savings
Use of the MZ Alternate Path system saved an estimated 12 days compared with a conventional stacked sand control method. The time savings was a result of perforating all the zones together, installing all of the sandface tool hardware in a single trip, and pumping simultaneous gravel- and frac pack treatments. Risks were also reduced by eliminating multiple trips in and out of the borehole.
An estimated 2 days of additional rig time savings resulted from combining the perforating and sandface tool assemblies (that is, using the QUANTUM PERFPAC system) into a single trip into the well. In one trip, all three intervals were perforated, the toolstring repositioned, the packers set, and the single pumping treatment performed. The need to remove the perforating string from the wellbore before running the sand control tool assembly was eliminated. In addition to reducing the completion time associated with an additional trip to remove the perforating string, this technique eliminated the cost and time to place and eventually remove a fluid loss control pill and productivity impairment resulting from the fluid loss control pill.
Increasing reserves and adding revenue
After the production tubing was installed, the well produced sand free at an initial rate of 55 MMcf/d under 2.8 MPa [406 psi] of pipeline pressure, in excess of the predrill estimates of 47 MMcf/d.
Penetrating the three sand lobe reservoirs with one borehole resulted in an additional 6 to 10 Bcf in recoverable gas reserves and 10 MMcf/d in production. The well came in under budget and added USD 20 million in projected revenue and operational savings.
Location
Indonesia, Asia, Offshore
Details
Challenge: Maximize deliverability and longevity of 195-m [640-ft] interval with three widely separated gas-bearing zones in a highly deviated well.
Solution: Combine Multizone Alternate Path system and QUANTUM PERFPAC system to frac pack and gravel pack multizones with a single perforating and pumping operation.
Results: Came in under budget and added USD 20 million in projected revenue through an additional 6 to 10 Bcf in recoverable reserves and 10 MMcf/d in production.
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