Welltec® adapted the standard metal sleeve design of the WAB by incorporating a mixture of non-elastomeric seals to withstand the high temperatures. Isolation valves in the WAB provide pressure compensation from above and isolate the setting port. Additionally, and uniquely for this application, Welltec incorporated dual burst-disc assemblies above the WAB for bleeding off high-pressure steam build-up behind the casing in the event that free-water / un-cured cement-slurry causes high-pressure steam buildup between the expanded WAB and the 2nd-stage Cement-collar placed above the WAB. This design prevents the initial issues these high-temperature geothermal wells typically experience.
The WAB was run just above the 9 5/8” casing tailpipe and set inside the existing 13 3/8” casing using a third-party cementing tool. Subsequently, second-stage cementing operations were performed above the installed WAB, which provided annular protection for the operation. During deployment, water was flooded into the well to keep temperatures ≤ 212°F (100°C). Full production temperatures will be at least 545°F (285°C).
The WAB forms a life-of-well platform to initially support the cement column during curing and subsequently prevent free-water with acid (20%) from contaminating the cement or migrating to the surface.
This operation set a new precedent as the first time a WAB has been used to revive a geothermal well. Additionally, this job was the first time Welltec® worked within the geothermal industry in the Philippines and deployed the WAB with second-stage cementing equipment in Asia.
To drill a new well would have cost the client between $9 million and $12 million. Welltec’s solution enabled the client to execute a life-of-well repair, with low CAPEX and cost-effective well-rejuvenation measures, proving the value of engineered well remediation. The client initially responded to the WAB’s high-temperature capabilities as well as its robustness, as this allowed it to be installed through a milled window and to pass through milled casing sections without damage to its seals. In addition, it could also be set using third-party equipment as part of the 2nd-stage cementing procedures, which reduced rental tool volume and overall cost to the client.
This job required extensive collaboration between Welltec® and the third-party cementing company, with Welltec® appointed as the contractual focal point to ensure that tools, procedures, and personnel were aligned in terms of the objective. The operation went smoothly, and the client has since opted for another WAB based solution for use in a smaller-architecture well (9 5/8” re-lining) to address a similar issue.
FIRST GEOHERMAL WELL
WORKED ON IN THE PHILIPPINES.