Geothermal Energy Generation Using Shut-in High-Temperature Shale Gas Wells

Classical geothermal energy technology requires subsurface temperatures so high it is limited to less than 10 areas in the U.S., while enhanced geothermal works at lower temperatures but requires drilling wells with subsurface connections that are so expensive that projects struggle to be economic. Bottomhole temperatures are adequately high for enhanced geothermal in the Haynesville shale underlying Louisiana and Texas, which has over 11,000 existing wells and growing - a tenth of those are depleted and dormant with little or even negative value, thus could be acquired quickly at low cost. Some of these wells have subsurface connections and could be readily and quickly converted to enhanced geothermal wells with good project economics. (Cool water is injected down the well, is heated at bottomhole by the hot shale, and then hot fluid is produced.) But some of the wells are isolated in the subsurface, and thus additional technology is required to enable continuous production at adequately high rates. This project brings new technology adapted from proven techniques in the field of petroleum engineering that enables all dormant elevated-temperature shale wells to quickly and economically be converted to geothermal wells, each of which will produce clean continuous baseload electrical power at the surface by virtue of modern compact power plants that fit on each existing well pad. Complex analytical models were developed for 1) heat- and fluid-flow in the wellbore, 2) subsurface flow behavior, and 3) surface electricity generation. Then, these models were applied in a coupled fashion to various scenarios of flow rates, configurations of wellbore tubing and casing, etc., to ascertain range of expected surface rates and temperatures. The results demonstrated the feasibility of the new technology to continuously produce adequate surface flow rates and temperatures at an expected 0.5 MW net electricity for each well pair. Suitable Haynesville shale wells were identified and their operators were contacted, who are highly motivated and agreed to partner with us. Design for wellsite set-up and operations was done and relationships with vendors of needed equipment and services were developed, including for the geothermal power plant. This allowed work-up of a costs and business plan, which indicated that this project has attractive economics for investors and is widely scalable in the U.S. Project initiation and expansion requires investment, and investors first want to see results from a field demonstration project. Phase II comprises execution of such field operations, converting Haynesville wells on a well pad into geothermal wells, and generating and locally selling the resulting electrical power. Readily upscalable with large running room.