U.S. Geothermal announces 28 MW initial capacity for Geysers project

Drilling rig on The Geysers project site of Western GeoPower (probably around 2007/ 2008) (source: Western GeoPower)
Alexander Richter 21 Sep 2015

U.S. Geothermal reports that already drilled wells at its WGP Geysers geothermal project could provide an initial 28 MW of power generation capacity with potential up to 44 MW with additional wells.

In an announcement this morning, geothermal developer and operator U.S. Geothermal Inc. (GTH) reports it has received the reservoir engineering report for the WGP Geysers project from third party engineering firm GeothermEx Inc..

As previously announced, the Company successfully completed a flow test program in June on the three largest production wells at the WGP Geysers project in northern California confirming that the wells were still open and ready for production. GeothermEx Inc. (a Schlumberger company) designed the isochronal (step-rate) flow test program, and monitored the testing of the wells.

GeothermEx reports that the four production wells are capable of delivering an initial capacity of 28.1 MW (gross) or 25.4 MW (net) based on current power plant steam conversion rates from a detailed design for a 28.8 MW (net) power plant. These longer term tests show the wells would initially produce a combined total of 458,000 pounds per hour of steam compared to 462,000 pounds per hour of steam from short term tests performed when the wells were first drilled, demonstrating that the capacity of the wells is virtually unchanged. Using the average steam production rate from these wells and an assumed interference factor of 30%, GeothermEx estimates that an additional 2-3 production wells would be needed to support the long term operation of a 28.8 MW (net) plant.

Two methods were used by GeothermEx to estimate the long term capacity of the WGP project, and both support a high probability that a 28.8 MW (net) plant can be operated for 25 years, given the modern plant design and the available productive area. The first is the p/z method, an established natural gas reservoir engineering calculation that is routinely used at The Geysers. Based on the plant design and the increase in available injection that would result from WGP’s planned hybrid cooling system, GeothermEx estimates that the reservoir could support the 28.8 MW (net) plant for up to 54 years. The second method, which is an empirical approach based on GeothermEx’s extensive experience at The Geysers, is used to estimate the steam production capacity per acre within the productive area of a geothermal leasehold. On this basis, GeothermEx reports that the productive acreage within the WGP leasehold has steam reserves sufficient to supply up to 44 MW (net) with a conventional injection level of 25%, and potentially more at the higher injection levels associated with the planned hybrid cooling system.

“The results of this analysis from our test program clearly shows that the WGP Geysers project has approximately 30 megawatts of steam, drilled, tested and ready for production, and that, with the higher injection rates provided by hybrid cooling, it has the reservoir to support long term generation,” said Dennis Gilles, CEO of US Geothermal. “We are pleased with last week’s passage of SB-350 in California, which now raises the Renewable Portfolio Standard for the state to 50% renewable energy by 2030, the highest in the country, and we anticipate this will increase the interest in a power purchase agreement for our WGP Geysers project. We are also pleased to announce that the recent forest fires reported in The Geysers area did not impact our geothermal wells, project equipment, or project site.”

Source: Company release via Marketwatch