Schlumberger

Case Study: Combined Completions Technologies Add USD 20 Million in Projected Revenue

Three-zone Alternate Path and QUANTUM PERFPAC completion increases recoverable gas reserves and production in Indonesia subsea project

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.

Result: 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.

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 95/8-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.

The bottomhole assembly with perforating hardware, the multizone sandface tools, and the drillstem testing (DST) equipment were all run into the well. The perforating hardware consisted of the perforating packer, firing head, automatic gun release, and perforating guns. The sandface tools consisted of the Alternate Path screens, multizone Alternate Path packers, and QUANTUM packer and service tool. The DST equipment included gauges and the IRIS intelligent remote implementation system.

The assembly was positioned so that the perforating guns were at the desired depth across all intervals. The perforating packer was set, and the guns were detonated and expelled into the rate hole. The perforating packer was then unset, and the assembly was lowered to place the screens across the perforated intervals. The perforating packer was reset, then serving as the sump packer. Pressure was applied to the workstring to set the QUANTUM packer. Service tool positions were established. Next, the QUANTUM PERFPAC plug was dropped down the workstring and into the service tool, allowing the gravel-pack treatment to be diverted through the crossover port body.

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.

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 tool string 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.


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