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ENERGIX-Stort program energi

Era-Net Seismoelectric Effects for Geothermal Resources Assessment and Monitoring - See4Geo

Awarded: NOK 2.0 mill.

Being able to identify pre-existing water-filled fracture networks greatly helps to assess geothermal resources and targets and inform on and monitor stimulation successes and risk mitigation, by mapping newly activated fracture networks. Monitoring of geothermal resources rely predominantly on seismic techniques, which alone do not capture fluid-phase properties. On the other hand, electromagnetic (EM) measurements add constraints to the fluid-phase properties, such as resistivity and permeability, but with little sensitivity to the rock structure. Here we are introducing the use of seismoelectric effects (SEE), which arise from seismic-to-electromagnetic conversion in naturally charged porous media with a certain degree of fluid saturation. The SEE technique provides the benefits of both EM and seismic technologies, with estimated field survey costs that are similar to data acquisition of only a single data type, keeping operations affordable. This project relies on a fully integrated approach to assess the potential of SEE for the exploration and development of geothermal systems, based on numerical simulations, and experimental and field analysis. The SEE4GEO French team and the US team have developed codes to model SEE signals. The codes are based on the same formulas, but one is time domain and one is frequency domain. Initial lab tests are performed with a new set of experiments to target SEE, Preliminary results shows that the set-up is able to generate and detect coseismic electric signals and interface electric conversion in a layered model. Both is required for using the SEE technique for identify water filled fractures NORCE performed a field experiment to test seismoelectric acquisition at Svelvik CO2 Field Lab in September. Analysis of these datasets is in progress to identify the coseismic electric signal by comparing the downhole recorded SEE signal with seismic signals recorded using DAS (Distributed Acoustic Sensing) technology.

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The main question we want to address with SE4GEO is: can we map fluid-saturated fracture networks for geothermal resource assessment and monitoring down to the relevant reservoir depth? Traditional seismic imaging techniques fail to resolve fluid-phase properties, while purely electromagnetic (EM) approaches typically provide limited, low-resolution constraints on the rock structure. Seismoelectric effects (SEE) arise from seismic-to-electromagnetic conversion in naturally charged porous media with a certain degree of fluid saturation. SEE are highly sensitive to fluid properties, such as resistivity and dynamic fluid viscosity. Since the coupling between seismic and electromagnetic fields is purely natural, the coupling coefficient between seismic and electromagnetic energy is sensitive to permeability, porosity, salinity, and other crucial geothermal reservoir properties. We propose a fully integrated approach to assess the potential of SEE for the exploration and development of geothermal systems, by creating a SEE numerical package to be used for improved subsurface imaging and characterization, supported and validated by laboratory experiments and field surveys for practical application. The main challenges anticipated will arise from the signal-to-noise ratio of the converted electromagnetic signals. We will develop dedicated data acquisition and data processing techniques to both extract and enhance the SEE converted signals. The inversion capabilities of the software will focus on extracting key geothermal subsurface properties such as permeability as well as the location of the fluid and its properties (e.g. resistivity, salinity, and viscosity). Combining laboratory experiments and tests in controlled environments, with actual field data acquisition and validation, will enable us to optimize SEE technology for realistic geothermal scenarios.

Funding scheme:

ENERGIX-Stort program energi