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.

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 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.