Understanding the relationship between stress state, strain state and fracture initiation and propagation is critical to the improvement of fracture simulation capability if it is to be used as a tool for guiding hydraulic fracturing operations. The development of fracture prediction tools is especially critical for geothermal applications such as EGS because the opportunities to build understanding empirically will be limited due to the high costs associated with field trials. There is a significant body of experimental work associated with hydraulic fracture investigation, but past efforts are typically hampered by an inability to accurately and comprehensively measure strains within the sample mass near critical regions of interest. This work aims to develop non-destructive neutron diffraction based strain measurement techniques that can be used to interrogate the internal volume of geological specimens subjected to tri-axial stress states resembling geothermal application conditions. Demonstrating the ability of the technique to generate useful quantitative data is the primary focus at this stage of the effort. Details of the experimental setup and diffraction technique will be presented in this communication, including the description of a custom designed high-pressure, neutron scattering

Hydraulic shearing is an appealing reservoir stimulation strategy for Enhanced Geothermal Systems. It is believed that hydro-shearing is likely to simulate a fracture network that covers a relatively large volume of the reservoir whereas hydro-fracturing tends to create a small number of fractures. In this paper, we examine the geomechanical and hydraulic behaviors of natural fracture systems subjected to hydro-shearing stimulation and develop a coupled numerical model within the framework of discrete fracture network modeling. We found that in the low pressure hydro-shearing regime, the coupling between the fluid phase and the rock solid phase is relatively simple, and the numerical model is computationally efficient. Using this modified model, we study the behavior of a random fracture network subjected to hydro-shearing stimulation.

Lab-scale stimulation work on non-porous fused silica (similar mechanical properties to igneous rock) was performed using pure water, pure CO2 and water/CO2 mixtures to compare back to back fracturing performance of these fluids with PNNL's StimuFrac.

This is a report that describes the modelling of fracture nucleation and propagation in the near-wellbore region to understand the relationship between in situ stress and fracture patterns. A novel phase field formulation is described here, which represents fractures as a diffuse variable, eliminating the need for re-meshing or an element insertion algorithm in modelling. Brief numerical results are also provided to demonstrate the capability of this method. Traditional phase field formulations focused only on fracture propagation; however, this formulation models both nucleation and propagation, extending previous work to hydraulic fracturing and implementing it in the GEOS simulation framework. This work was done as part of Utah FORGE Project 2-2446: "Closing the Loop Between In-situ Stress Complexity and EGS Fracture Complexity."

This dataset includes data from injection/fall-off experiments conducted in controlled laboratory settings. The aim is to investigate the physics governing fracture closure and the associated stress measurements during hydraulic fracturing. These time series data include flow rate, pressure, and volume measurements. These experiments were conducted as part of Utah FORGE Project 5-2615: Thermo-poromechanical Response of Fractured Rock.

This report provides insights into Utah FORGE well 58-32's hydraulic fractures. It utilizes both electrical borehole scans from Schlumberger's Formation Micro-scanner Image tool (FMI) and Stoneley waves from a borehole sonic tool. These methods are combined in a comprehensive workflow, leveraging the advantages of each technique to characterize fractures intersecting the well and to estimate their effective width. The report compares separate fracture width estimates from both FMI and Stoneley wave analyses, drawing conclusions about their respective merits. A subsequent workflow was developed where FMI-derived fracture locations informed the Stoneley wave analysis, with results showcased alongside reference FMI images. The culmination of this study is an optimized workflow that offers a robust estimation of hydraulic fracture width, incorporating all collected data.