A Coupled Elastoplastic Damage Model for Clayey Rock and Its Numerical Implementation and Validation

Jia, Shanpo; Zhao, Zhenyun; Wu, Guisheng; Wu, Bisheng; Wen, Caoxuan

doi:10.1155/2020/9853782

Cited by 5 publications

(2 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…When the reservoir is injected with a fluid or a gas, the general reduction in the effective stress might lead to the damage of the caprock and reduce its sealing capacity, thus triggering the risk of gas leakage [31]. When the effective stress is lower than the tensile strength, tensile failure will occur.…”

Section: Numerical Simulation Of Maximum Injection Pressurementioning

confidence: 99%

Simulation and Prediction of Injection Pressure in CO2 Geological Sequestration Based on Improved LSO Algorithm and BP Neural Networks

Liu

Jia

et al. 2022

Geofluids

View full text Add to dashboard Cite

In order to avoid the occurrence of caprock integrity damage and gas escape due to injection pressure overrun in CO2 sequestration, an optimized back propagation (BP) neural network model based on Monte Carlo simulation (MCS) and an improved lion swarm optimization (ILSO) algorithm is proposed for the maximum sustainable injection pressure prediction. Firstly, a hydromechanical model is constructed to simulate the damage changes of the reservoir caprock during injection by ABAQUS. Secondly, in view of the uncertainties of formation parameters that could lead to deviations between the model calculation results and actual geological condition, the MCS method is used, and then, the probability distribution interval of the maximum injection pressure with high probability of caprock failure under different formation parameters is obtained by MATLAB. This effectively reduces the uncertainty and improves the calculation accuracy. Finally, based on the numerical simulation results, the maximum injection pressure prediction model is constructed. Aiming at the problems of the sensitivity of the BP neural network to initial weights and its poor convergence, tent chaotic mapping and difference mechanism are introduced to improve the LSO algorithm. Following this, the neural network is optimized by ILSO algorithm whose superiority is verified through 8 benchmark functions, and the maximum injection pressure is effectively predicted according to porosity, permeability, and other parameters. Experimental results show that, compared to the other three optimization methods, the ILSO_BP model has a faster convergence speed, higher prediction accuracy, and stability, which can provide a powerful guide for the safe injection of CO2 and efficient sequestration management.

show abstract

Section: Numerical Simulation Of Maximum Injection Pressurementioning

confidence: 99%

Simulation and Prediction of Injection Pressure in CO2 Geological Sequestration Based on Improved LSO Algorithm and BP Neural Networks

Liu

Jia

et al. 2022

Geofluids

View full text Add to dashboard Cite

show abstract

“…The numerical analysis is based on the integration of damage models, which fully describe the nonlinear behavior of rock (Mazars et al 2015;Jia et al 2020). However, Mazars' material model is initially isotropic and the damage retains this isotropy with no dominating orientation (21) 5.7 (± 1.4) 3 9.4 T = CI_TD/12 3.7 (± 1.5) 2.4 5.9 T = BTS 6.5 (± 2.6) 3.7 8.9 9 T = 0.7 BTS 4. of cracks.…”

Section: Progressive Brittle Failure In Multiaxial Loadingmentioning

confidence: 99%

An Extension Strain Type Mohr–Coulomb Criterion

Staat

2021

Rock Mech Rock Eng

View full text Add to dashboard Cite

Extension fractures are typical for the deformation under low or no confining pressure. They can be explained by a phenomenological extension strain failure criterion. In the past, a simple empirical criterion for fracture initiation in brittle rock has been developed. In this article, it is shown that the simple extension strain criterion makes unrealistic strength predictions in biaxial compression and tension. To overcome this major limitation, a new extension strain criterion is proposed by adding a weighted principal shear component to the simple criterion. The shear weight is chosen, such that the enriched extension strain criterion represents the same failure surface as the Mohr–Coulomb (MC) criterion. Thus, the MC criterion has been derived as an extension strain criterion predicting extension failure modes, which are unexpected in the classical understanding of the failure of cohesive-frictional materials. In progressive damage of rock, the most likely fracture direction is orthogonal to the maximum extension strain leading to dilatancy. The enriched extension strain criterion is proposed as a threshold surface for crack initiation CI and crack damage CD and as a failure surface at peak stress CP. Different from compressive loading, tensile loading requires only a limited number of critical cracks to cause failure. Therefore, for tensile stresses, the failure criteria must be modified somehow, possibly by a cut-off corresponding to the CI stress. Examples show that the enriched extension strain criterion predicts much lower volumes of damaged rock mass compared to the simple extension strain criterion.

show abstract

Thermodynamic Characterization of Chemical Damage in Variably Saturated Water-Active Shales

Siddiqui¹,

Roshan²

2022

Rock Mech Rock Eng

View full text Add to dashboard Cite

A constitutive framework is developed for variably saturated water-active swelling rocks undergoing chemical damage using modified mixture theory and continuum damage mechanics. The Helmholtzian thermodynamic potential for the skeletal system is derived as a function of the state variables including deformation, damage, two-phase fluid pressures, and chemical potential. Using this, in addition to chemo-poroelastic constitutive equations, a thermodynamically consistent first-order estimation of the damage variable is developed. The working of the theory is shown through the numerical example of water uptake in clay-rich shale rocks solved by the finite element method. The numerical results portray the significance of including variably saturated conditions in constitutive equations as a unique damage-dependent poroelastic behavior was observed for wet and dry regions. The theoretical-based damage estimation corroborated by previous experimental observations illustrates that the rock strength is dominantly controlled by the time of exposure to water rather than the level of water saturation. Contrary to what was perceived, the results show that poroelastic and chemo-poroelastic responses do not coincide even in less reactive shales due to the time-dependent water-induced microstructural deterioration of the rock. The microstructural deterioration increases the storage and flow capacity in the water-saturated region giving rise to substantive spatio-temporal changes in matrix stresses. The research findings provide valuable insights to understand how poromechanics plays a role in causing water uptake in water-sensitive rocks and how such behavior is coupled with associated microstructural chemical damage.

show abstract

A Coupled Elastoplastic Damage Model for Clayey Rock and Its Numerical Implementation and Validation

Cited by 5 publications

References 27 publications

Simulation and Prediction of Injection Pressure in CO2 Geological Sequestration Based on Improved LSO Algorithm and BP Neural Networks

Simulation and Prediction of Injection Pressure in CO2 Geological Sequestration Based on Improved LSO Algorithm and BP Neural Networks

An Extension Strain Type Mohr–Coulomb Criterion

Thermodynamic Characterization of Chemical Damage in Variably Saturated Water-Active Shales

Contact Info

Product

Resources

About