Geothermal Energy Generation Using Dormant Wells in High-Temperature Shale Sedimentary Areas

C55-13a-270233The project embodies a field demonstration of a novel geothermal process via water injection into a shut- in existing well (already drilled & hydraulically fractured, and shut-in) for a short period, and then that injected water, having been heated by contacting the subsurface rock, is produced back to the surface (via the same well through which it was injected). This intermittent process of alternating injection/production in each well is repeated many times. The hot water/steam that is produced by the well cluster via this process will feed an on-site portable small-scale (0.5-1 MW) geothermal power plant. While one well of the cluster is undergoing injection, its neighbor will be undergoing production, thereby providing continuous feed for the power plant, which will in turn provide continuous renewable power. Multiple well clusters can simultaneously be served with multiple power plants using this process. This geothermal project is unique in that it merely recycles already-existing shale wells that sit dormant, instead of drilling new wells which all other geothermal projects do. This project produces no oil or gas and addresses the creation of Enhanced Geothermal Systems in a selected sedimentary area with large temperature-gradients, which is of particular interest to DOE. The Haynesville shale area (TX & LA) has over 10,000 wells with over 1,000 already shut-in, many of them with temperatures in excess of 390?F. However, rather than containing adequately large amounts of native hot water to act as its own hydrothermal resource, the reservoir’s heat must be “mined” using cold water that is injected from the surface, is consequently heated by the rock at the bottom of the wellbore, then flows back to the surface. Moreover, accessing these geothermal resources requires a complex well- completion strategy designed such that the injected water contacts a large surface area of rockface for efficient heat conduction, while still providing a hydraulically conductive subsurface pathway both for the injected cold water to enter the formation, and for the heated water to flow back to the surface. To enable a quick and economical start of the geothermal power generation project, we take advantage of the following current conditions: 1) these shale reservoirs have thousands of wells already drilled and currently inactive, that can be used for geothermal projects, and can quickly be accessed at low cost; 2) these shale wells have already undergone expensive completion programs connecting them to a large fracture network with intimate connection to the rock volume in the reservoir; and 3) modern technology for geothermal power plants includes small portable units, each of which can be used aggressively for a few years to serve one small cluster of wells, and then moved to the next cluster of wells. The principals of Renascent Energy Management LLC, and Ivan E. Terez (PI) & Kenneth R. Kibodeaux, will conduct the research in the company’s office. Ramsgate Engineering Inc. will be engaged as a consultancy to help evaluate downhole tubing/packer changes, and fluid lift design. The overall market opportunity is quite substantial as a large portion of the current 10,000+ Haynesville shale wells are already depleted and have approached their economic limit after only 4-6 years of production, and many of their bottomhole temperatures are above 390?F. Furthermore, there are other shale basins that exhibit similar high temperatures. Thus, conversions of these numerous older shut-in wells may become quite a viable option for generating electricity. Estimated electricity production will be about 1 GW with the modular development and using 1,000 wells, which is a low-side estimate of the already shut-in wells in the Haynesville field.