This project seeks to establish new geophysical and computational methods to image fluid migration through induced and natural hard rock fracture systems. Fluid flow imaging of fracture systems can be used to help eliminate irrelevant microfracture events and establish production borehole connectivity to induced fractures. A few existing microseismic techniques attempt to employ fluid flow metering (not imaging) and microseismic event correlation in an effort to reduce uncertainty in connectivity to the production borehole. However, this method is insufficient to adequately reduce uncertainty in fracture localization solutions and determining fracture connectivity to the production well. Recent industry efforts have been focused on improving microseismic performance, but direct imaging of subsurface fracture systems using non-seismic, or multisensor approaches using fluid flow related phenomenology has not been pursued. Hydrogeophysics, Inc. believes that a new integrated multisensor approach will enhance the subsurface fracture system characterization process and reduce uncertainty in the site characterization results, thus reducing project related risks. Based on this, Hydrogeophysics, Inc. considers that additional data from different, measurable signals, generated by physical interactions with fractured systems (e.g., seismic, electrical, fluid flow) is required to further constrain fracture localization solutions, while using as much a priori information as possible in fracture localization models and computations. Fluid motion in fractures generates a lesser known, but vitally important electrical signal (i.e., streaming potential) within fractured systems. This type of signal can be exploited as a critical part of the multisensor system approach. Hydrogeophysics, Inc. proposes to develop new geophysical streaming potential technology that exploits fluid flow to generate 4D images of fracture systems in our multisensor approach. We base our approach on the physics of fluid flow dynamics in fractured media, streaming potential phenomenology, and a priori information on subsurface structure details. This effort employs advanced analog and digital signal processing methods, along with knowledge- guided forward model development and joint inversion processing in a phased, risk-reduction process. Specifically, Phase I of this effort is to model the streaming potential effect in fractures, and to determine its order of magnitude using various scale finite element multiphysics-based numerical models. This modeling effort will use published measured material parameters to formulate numerical models. Importantly, boreholes and discrete fracture network constructs will be incorporated into 3D models that approximate different levels of complexity of near realistic environments. Various signal processing methods will be evaluated relative to the required signal to noise ratio improvements needed to extract very small signals from high noise levels. Phase I will be used to validate the scaled viability of this new geophysical method through numerical modeling and signal analysis of fracture network responses that is worthy of continued development in Phase II. Three geoscience based industry segments, geothermal, carbon sequestration, and oil and gas industries (listed under this topic by the Department of Energy) can benefit from the development of this new technology. All of these industry segments need to be able to image fracture systems, establish fluid flow patterns, determine hydraulic connectivity to production boreholes, and track fracture system and fluid flow changes over time. There continues to be a substantial level of dissatisfaction and frustration in these industries with existing subsurface fracture imaging technology. Resolving the problems with fracture and fluid flow imaging is crucial to meeting and sustaining critical industry objectives of energy production and waste sequestration. In addition to the stated primary industry interest areas in this Funding Opportunity Announcement, other applications for the proposed technology, including subsurface injection of liquid waste for disposal (minimizing or preventing induced seismicity), and mining industries are plausible. Therefore, this technology has a broad geophysical and industrial application potential.
