A critical review of the experimental and theoretical research on cyclic hydraulic fracturing for geothermal reservoir stimulation

Abstract

Hydraulic fracturing is necessary to stimulate deep geothermal reservoirs. Compared with traditional hydraulic fracturing (THF), cyclic hydraulic fracturing (CHF) decreases the breakdown pressure (BP), generates a more complex crack network and reduces the induced seismicity; thus, it has attracted increasing attention. In this work, state-of-the-art studies on CHF are comprehensively reviewed for the first time. Six CHF cyclic loading schemes are clarified, and their stimulation results are discussed. It is difficult to assess which loading schemes are the most advantageous because the reservoir boundary conditions and properties of rock specimens vary. The effects of critical influential factors on the stimulation results of CHF are reviewed in detail. A higher confining pressure generally produces longer cracks, and a lower-viscosity fracturing fluid more easily connects micropores and widens cracks. The existing theoretical and numerical models of CHF, which are based mainly on fracture mechanics and damage mechanics, are summarized and discussed. Based on this comprehensive review, some aspects through which the failure mechanism of CHF can be further understood are suggested. This work can benefit the application of CHF to exploit deep geothermal resources. Article Highlights• Six different cyclic hydraulic fracturing schemes are classified, and the corresponding stimulated effects are discussed. • The effects of the primary influencing factors on cyclic hydraulic fracturing are summarized. • Recommendations for further studying cyclic hydraulic fracturing are suggested.

Energy dissipation mechanisms in fluid driven fracturing of porous media

“…The model provides physics-based grounds for hydraulic production from tight reservoirs featuring low permeability (Clark 1949;Gidley 1989;Bunger Lecampion 2017). The hydraulic fracturing technique involves pumping a fracturing fluid at high rates with the aim of increasing the permeability in the fracture zone, which eventually allows for a more economic oil production (Montgomery and Smith 2010;Li et al 2022). The energy used in the pumping is transferred to the porous domain as: (i) elastic (potential) energy stored in the deformed domain, (ii) fracture energy used to create new damage surfaces, thus leading to energy dissipation through solid skeleton disintegration (damage), and (iii) kinetic energy used to move the fluid through the pores, leading to dissipation through fluid viscous flow (Goodfellow et al 2015).…”

Hydraulic stimulation strategies in enhanced geothermal systems (EGS): a review

“…To relate this approach to other methods, Zhuang et al (2020) and Li et al (2022) presented a summary of several fluid injection schemes, both injection-rate controlled and pressurization controlled, as shown in Fig. 6.…”

Approaches of Combining Machine Learning with NMR-Based Pore Structure Characterization for Reservoir Evaluation

“…As the global demand for sustainable energy grows rapidly, the utilization and storage of deep green energy resources (conventional and unconventional gas resources, geothermal energy, etc.) are becoming more and more significant [1][2][3]. Reservoirs, as one of the underground spaces, are not only a development and production area, but also regarded as a favorable place for geological energy storage and greenhouse gas sequestration [4][5][6].…”