| Title | In-situ Stresses and Fractures Inferred from Image Logs at Utah FORGE Site |
|---|---|
| Authors | Pengju XING, Andy WRAY, Edgar IGNACIO VELEZ ARTEAGA, Aleta FINNILA, Joseph MOORE, Clay JONES, Erik BORCHARDT, John MCLENNAN |
| Year | 2022 |
| Conference | Stanford Geothermal Workshop |
| Keywords | FORGE, image logs, fractures, in-situ stresses |
| Abstract | One injection well and five monitoring wells have been drilled at the Utah FORGE site. One of these, well 16A(78)-32 was directionally drilled at an inclination of 65o to the vertical. This highly deviated well will serve as the injection leg in a doublet interconnected by hydraulic fracturing. The well was drilled to a total depth of 10,987 ft (true vertical depth 8,560 ft) and the measured static bottomhole temperature is close to 220 oC. For the offset monitoring wells; three are moderately deep with true vertical depths between ~7500 and 9500 ft. Formation Micro-Imager (FMI) and Ultrasonic Borehole Imager (UBI) logs were acquired during or after drilling these wells. These image logs were acquired under higher temperature conditions than are usually experienced in oil and gas operations. Geothermal reservoir characterizations, such as natural fractures, and in-situ stresses can be obtained from the interpreted data sets. Induced tensile fractures from the image logs suggest/confirm the orientation of the horizontal maximum principal stress. Prominent breakouts, indicating compressive failure of the near-wellbore region, were also observed in the UBI logs. These image logs were further analyzed to constrain the magnitude of maximum horizontal principal stress and assess if there was any potential principal stresses rotation at the FORGE site. The inference/estimation of the maximum horizontal principal stress largely depends on the formation’s compressive strength. The inferred maximum “horizontal†principal stress is smaller in the case of principal stress rotation than the case of non-rotation. Geomechanical properties were also inferred from evaluation of the Slim Dipole Sonic data, helping as well with the fracture characterization using Stoneley waves and the borehole images results .Furthermore the acquisition of the slim dipole tool was modified to extend the recording times and record the information at each of the 4 azimuthal geophones in the 12 receivers of the tool which is mean to be used in sonic imaging applications, the 3D Far Field workflow was used to extract the quantitative dip and azimuth information of the acoustic reflection from azimuthal sonic data in two key steps; a) automated time pick and b) automated ray tracing and 3D STC, the evaluation delineated some reflectors at up to 30 ft from the wellbore and these are attributed to significant natural fractures. |