Stanford University
Frontier Observatory for Research in Geothermal Energy
Wellbore Fracture Imaging Using Inflow Detection Measurements
Stanford University
Roland N. Horne and Avery (Zack) Cashion, Co-PIs
Summary
“Show me the fractures”. One of the most striking measurements taken during DoE’s EGS Collab project at the 4850 depth location was the so-called ‘sewer cam’ which enabled direct visualization of flow of water into the production well through fractures during the stimulation. The ability to see directly which fractures were flowing, and (roughly) how much was a breakthrough in understanding the topology of the created fracture network. Achieving this kind of fracture flow imaging at FORGE will be equally valuable if it can be achieved.
The goal of this research is to make measurements in the FORGE wells, both before and after fracturing experiments, to map the fractures and estimate their flow magnitudes. Although indirect modeling of fractures has many useful functions, a direct visualization of the presence and magnitude of outflow from a fracture is an unambiguous indicator of a successful stimulation. Such visualization is also an important source of physical evidence to help refine numerical models. The ‘sewer cam’ images (and video) at EGS Collab were remarkable sources of information. We hope to be able to achieve similarly detailed inflow analysis based on precise chloride (and/or other ion) concentration measurement. The advantage is robustness of the device and the ability to run it at high temperature and pressure.
Characterizing the network of fractures that has been created during an EGS stimulation treatment allows us to determine whether the stimulation proceeded as planned and the extent to which the stimulation was effective. The outcome of this research would be to determine the location and relative (flow) importance of fractures created during FORGE stimulation. The same technique would also provide a way of monitoring the evolution of the fracture network over time.
The Stanford Geothermal Program has established the technical background to complete the proposed planning, scientific and engineering work, based on 45 years of experience and achievements in geothermal research. The major objectives of the Stanford Geothermal Program have been to serve the energy community by: (1) conducting practical and fundamental research in geothermal reservoir engineering; and (2) graduating geothermal reservoir engineers. More than 300 papers have been published and more than 140 geothermal engineers have graduated from the Stanford Geothermal Program since its inception in 1966. Under earlier US Department of Energy funding, the Stanford Geothermal Program has focused on problems related to analysis of fractured reservoirs. Stanford has been an active participant in the Department of Energy’s EGS Collab project, 2017-2020.
Sandia’s geothermal program brings experience and engineering expertise in novel downhole tool development and deployment. Laboratory development capabilities include a fully equipped electronics laboratory, ovens, pressure vessels, and part modification shop. Sandia is also in possession of a wireline truck, equipped with high temperature wireline, which has been used to test the existing electrochemical assessment tool in a shallow wellbore. This equipment will save cost on equipment rental, decrease operational risk by enabling integrated system testing, and simplify field deployment. Sandia has also been a central participant in the Department of Energy’s EGS Collab project, 2017-2020.
Data
Thermal Earth Model for the Conterminous United States This study presents a data-driven spatial interpolation algorithm based on physics-informed graph neural networks used to develop national temperature-at-depth maps for the conterminous United States. The model was trained to approximately satisfy the three-dimensional heat conduction law by simultaneously predicting subsurface temperature, surface heat flow, and rock thermal conductivity. In addition to bottomhole temperature measurements, we incorporated other physical quantities as model inputs, such as depth, geographic coordinates, elevation, sediment thickness, magnetic anomaly, gravity anomaly, gamma-ray flux of radioactive elements, seismicity, and electric conductivity. We constructed surface heat flow, and temperature and thermal conductivity predictions for depths of 0-7 km at an interval of 1 km with spatial resolution of 18 km2 per grid cell. Our model showed superior temperature, surface heat flow and thermal conductivity mean absolute errors of 4.8? C, 5.817 mW/m2 and 0.022 W/(C-m), respectively. The predictions were visualized in two-dimensional spatial maps across the modeled depths. This thorough modeling of the Earth's thermal processes is crucial to understanding subsurface phenomena and exploiting natural underground resources. The thermal Earth model is made available as an application programming interface (API) at stanford-temperature-model.com. It is also available as feature layers on ArcGIS at https://arcg.is/nLzzT0.
Videos
- Stanford 2023 Utah FORGE Annual Workshop Presentation
- Stanford 2024 Utah FORGE Annual Workshop Presentation
Well 58-32 Well 78-32 Well 78B-32 Well 68-32 Well 56-32 Well 16A(78)-32 Well 16B(78)-32 Wells General