WORLD’S FIRST WELL REPAIR VIA HIGH-TEMPERATURE WAB TO REVIVE GEOTHERMAL PRODUCER

Background

In May 2018, a Geothermal Operator in the Philippines expressed interest in taking well-repair measures on a well that has been shut-in for the last two years due to loss of integrity and mechanical failures of the completion/casing architecture. The 13 -3/8” casing had severe corrosion and caliper-logs / cameras had identified multiple holes and ‘bulges’ caused by free-water passage behind the casing – which is primarily caused by large expansion/contraction of the string due to thermal cycling and are secondary indications of cement-failure. The casing deformation (bulges) are a thermally-induced phenomenon due to free-water causing a high-pressure steam build-up after being exposed to production temperatures in excess of 300C.  Additional damage was due to the loss of the 7” slotted production liner from acidic corrosion. These failure-modes are a common issue within the geothermal industry and often result in the total loss and abandonment of the well. The operator will then usually have to drill another production well to replace this loss of electricity production. The same operator had been forced to shut-in many wells for similar issues however this particular well is one of the operator’s most prolific producers, contributing to over 12 Megawatts of power.

The client required a life-of-well, cement-assurance solution run on the new 9 5/8” production casing, which would be used to re-line the existing corroded 13 3/8” casing string as part of a well-remediation program.

Welltec® presented the Welltec® Annular Barrier (WAB) as a life-of-well repair solution. The WAB would provide a solid base for hydrostatic support to the column of cement slurry placed above it and would prevent the curing cement from becoming contaminated by the cross-flow of produced fluids and steam from below the production casing. Additionally, the WAB would offer anchoring support to the casing string in the event of thermal contraction or expansion of the casing string during production or shut-down operations.

Upon learning of the high-temperature capabilities of the WAB, the operator allowed Welltec® to use it in an attempt to revive the well.

The client required a life-of-well, cement-assurance solution run on the new 9 5/8” production casing, which would be used to re-line the existing corroded 13 3/8” casing string as part of a well-remediation program.

OPERATION

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.

ACHIEVEMENTS

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.

 

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Welltec’s solution enabled the client to execute a life-of-well repair, with low CAPEX and effective well-rejuvenation measures, proving the value of engineered well remediation saving them between $9 million and $12 million.