Speaker
Description
Stress-induced deformation of microfractures governs the evolution of reservoir permeability and, consequently, the rate of production. To research the effect of thermo-mechanical loading on microfracture’s morphology and permeability in ultra-deep and extra-deep reservoirs under ultra-high temperature (>200 °C) and ultra-high stress (>140 MPa), a discrete element method (DEM) model was developed. To simulate surface interlocking and interfacial wear during shear and normal loadings, the model incorporates a true three-dimensional irregular fracture topography together with a multi-generation particle breakage/replacement mechanism. Simulation results reproduced the coupled evolution of interlocked surfaces, localized stress, progressive crushing and frictional smoothing of asperities, and production and migration of gouge in the microfracture. On the shear modulus of the fractured medium, results revealed the competition between the strengthening effect of the normal stress and the weakening effect induced by crushing and frictional smoothing. A transitional critical stress was quantified. The model also captured continuous shear-induced changes in fracture’s morphology. Changes in the permeability of the fracture were computed using a lattice Boltzmann method coupled to the DEM model. Results demonstrate that flow within the fracture and that in the adjacent damaged are strongly affected by the morphological evolution of the fracture. These findings provide quantitative support for studies of coupled thermal-hydrological-mechanical (THM) processes, benefiting stimulation design and production optimization of the ultra-deep reservoir.
| Country | China |
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