This work aims to study the propagation of fractures during hydraulic fracturing operations to determine the conditions that lead to the most extensive network of secondary fractures along with the primary fractures at the pore scale. We investigate the occurrence and propagation of 3D fractures, considering the mineral composition and complex texture of elastic-plastic rock such as tight rocks and organic-rich mudstones. We work with a set of micro- and nano-scale digital rock models of the tight-gas Lower Berezov Formation. The simulation allowed us to calculate fracture networks for various loading conditions. We propose a method enabling the calculation of hydraulic fracturing fluid injection pressure from the obtained numerical conditions of loading and regional stress in the target reservoir rock. Results of numerical simulation and recalculation of the obtained loading conditions into the fluid injection pressure would allow geomechanical engineers to determine and justify stress-strain conditions required for obtaining the most significant degree of formation fracturing.
Unconventional hydrocarbon reservoir rocks, including oil and gas shales, have a specific storage capacity in terms of fluid saturation and critical absolute and phase permeability. One of the mainstream methods to increase drainage zones around producing wells is artificial hydraulic fracturing (HF). However, HF field efficiency is still poorly predicted and thus often does not sufficiently improve fluid flow to the wellbore. One of the essential ways to increase the HF efficiency of unconventional tight reservoir rocks is to create an extensive network of secondary feathers originating from the primary mainstream fractures.
Modern software simulators of hydraulic fracturing implement a variety of mechanical approaches (Shetty·and·Lin·2014, Morales·and·Abou-Sayed·1989, Erofeev·et·al.·2019), allowing assessment and prediction of possible propagation scenarios of either single fracture or a network of fractures at the field scale. However, degraded storage and transport properties (mainly porosity and permeability) of the reservoir rocks require the application of methods and approach accounting micro- and nano-mechanics at the pore scale that would provide explicit modeling of fracture-fracture and fracture-void interactions (Onwumelu et al. 2019, Sharma et al. 2013).