Dynamic Fracture Network Evolution: Monitoring and Characterizing using a Geomechanically Constrained Time-lapsed Windowed Microseismic Imaging

To create an efficient subsurface heat exchanger in an EGS, it is essential to have a thorough understanding of the subsurface characteristics along with an effective real-time system to monitor and characterize the evolution of induced and natural fractures during stimulation and production. The temporal evolution of fractures in geothermal reservoirs determines the efficacy of an EGS in the long term. The ability to monitor the variation in fracture network characteristics over time is necessary for assessment of reservoir performance over time. These updated assessments provide valuable information and an opportunity to optimize stimulation schemes for maximum heat production. We propose to develop an innovative methodology for monitoring temporal fractures evolution that significantly reduces the cost of monitoring in Enhanced Geothermal Systems (EGS) by using readily available microseismic data only. We analyze microseismic data through a novel “Time Lapsed Microseismic (TLM)” combined with geomechanical modeling to detect, locate and mechanically characterize seismic events in different time window to monitor the changes in fractures geometry and conductivity over time without imposing any additional data acquisition or monitoring cost to EGS or other geothermal projects. This technology translates microseismic data to the source fractures’ location, orientation, and mechanical status with respect to conductivity and heat-flow using a geomechanically constrained TLM in conjunction with an artificial neural network (ANN) model. We accomplish this by combining the extensive past experience of Petrolern LLC and FACT Inc. in advanced geomechanical and microseismic analyses. Considering the extent of geothermal energy capacity in the United States, access to an intelligent system to monitor, check and improve the health of the subsurface heat exchanger under the influence of well stimulation, maintenance, and other ad-hock operating conditions is required. Since cost is a major challenge in widespread use of geothermal energy, it is crucial to consider developing new technologies that reduce the cost of production of energy from geothermal sources. Subsurface monitoring is considered to be a large cost component of any geothermal complexes; thus, the proposed technology has potential to significantly reduce this cost by eliminating the needs for expensive monitoring sensor technologies or additional data acquisition.