Abstract
Hydraulic fracturing (HF) is a well-known stimulation method used to increase production from conventional and unconventional hydrocarbon reservoirs. In recent years, HF has been widely used in Enhanced Geothermal Systems (EGS). HF in EGS is used to create a geothermal collector in impermeable or poor-permeable hot rocks (HDR) at a depth formation. Artificially created fracture network in the collector allows for force the flow of technological fluid in a loop between at least two wells (injector and producer). Fluid heats up in the collector, then is pumped to the surface. Thermal energy is used to drive turbines generating electricity. This paper is a compilation of selected data from 10 major world’s EGS projects and provides an overview of the basic elements needed to design HF. Authors were focused on two types of data: geological, i.e., stratigraphy, lithology, target zone deposition depth and temperature; geophysical, i.e., the tectonic regime at the site, magnitudes of the principal stresses, elastic parameters of rocks and the seismic velocities. For each of the EGS areas, the scope of work related to HF processes was briefly presented. The most important HF parameters are cited, i.e., fracturing pressure, pumping rate and used fracking fluids and proppants. In a few cases, the dimensions of the modeled or created hydraulic fractures are also provided. Additionally, the current state of the conceptual work of EGS projects in Poland is also briefly presented.
Highlights
The XXI century is a time of global change in the approach in the field of energy acquisition
The current existing methods of energy production, based on conventional resources such as coal, natural gas and radioactive materials, are gradually being replaced by environmental-friendly, low-emission technologies, such as hydrogen, wind and sun farms, biomass combustion and geothermal systems. Among these modern green technologies, great potential is exhibited by so-called enhanced geothermal systems (EGS) [1]
The idea of the EGS system thermal collector is to use thermal energy of the hot dry rocks (HDR) formation to heat up the process fluid in situ, extract it to the surface and use it to drive a turbine generating electricity on a commercial scale
Summary
The XXI century is a time of global change in the approach in the field of energy acquisition. The current existing methods of energy production, based on conventional resources such as coal, natural gas and radioactive materials, are gradually being replaced by environmental-friendly, low-emission technologies, such as hydrogen, wind and sun farms, biomass combustion and geothermal systems. Among these modern green technologies, great potential is exhibited by so-called enhanced geothermal systems (EGS) [1]. Biodegradable chelating agents do not dissolve clay minerals and quartz This technology was developed and used in the oil and gas industry and was adapted to deep geothermal wells to enhance the fracture network, in EGS projects [5]. The polymer-based fluids, due to their ical stimulation consists of injecting an acid fluid to dissolve materials around the wellbore, increased viscosity, are characterized by better carrier properties
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