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Unocal Oil and Gas operates a number of offshore platforms located between Anchorage and Kenai, Alaska in the Cook Inlet.
Natural gas and crude oil production are the products produced by Unocal in Alaska. When oil or gas are produced a void is left in the reservoir and that void must be filled in order to maintain reservoir pressures and enhance oil recovery in the formation. In Alaska seawater is the product that is readily available to help fill the void left from oil and gas production.
The seawater is injected into the formation at very high pressures (2000-5000
psig). Large multi-stage centrifugal pumps are commonly used to boost
the pressure of the seawater and deliver the required volume. In the case
of Unocal’s Steelhead platform large 11-stage Bingham Type “CP” barrel
pumps are used in series to boost pressures. The pumps are double ended
and require two seals per pump. The pumps are driven by motors and gearboxes
to speeds over 6000 rpm.
Originally the pumps were fitted with a single seal that utilized a rotating
spring assembly. The surface speeds on the seal combined with very high
seal chamber pressures (up to 600 psig max.) limited the seal performance
in this service. The seal repair cost was high due to the outdated technology.
So, the decision was made by Unocal to “try” the AESSEAL® CAPI Type A1 single seal fitted with Antimony Impregnated Carbon vs. Silicon Carbide faces. The CAPI seals have been a terrific success and have operated without leakage for over a year.
The cost of the CAPI seals was significantly less than the cost of the old style seals and the performance appears to be better with the CAPI. AES has made its entry into the API market in Alaska and the results are extremely positive. Unocal is pleased with the cost savings and performance of this latest development from AES. Three more of these pumps are slated for a change to AES mechanical seals.
Over the last 12 months the plant has lost four competitor seals while
the AESSEAL® CAPI seals are still running.
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