A realistic and integrated model for evaluating oil sands development with Steam Assisted Gravity Drainage technology in Canada

Influence of gravel on the propagation pattern of hydraulic fracture in the glutenite reservoir

Brittleness evaluation of coal based on statistical damage and energy evolution theory

Evaluating the ability of coal seams to form fracture networks by hydraulic fracturing is important for the development of coalbed methane (CBM) reservoirs. In this paper, a new index for evaluating coal brittleness was established from the perspective of energy evolution during coal failure. Uniaxial and triaxial compression tests of coal monitored by an acoustic emission (AE) system were carried out and the applicability of the new index and the influence of the confining pressure and cleat orientation on the coal brittleness were analyzed. The pre-peak and post-peak dissipated energies were the essential factors in determining the coal brittleness. The new index can characterize the influence of the external stress and cleat orientation on coal brittleness, and can also comprehensively reflect the mechanical properties of the coal during the pre-peak and post-peak stages. The corresponding AE energy curves can be divided into Rapid Fracture Type, Stable Fracture Type and Plastic Fracture Type. For the Rapid Fracture Type, the accumulation rate of AE energy showed sudden changes when reaching the yield stress and peak strength, which represented high brittleness. The Plastic Fracture Type represented low brittleness, and the accumulated AE energy curves were smooth—first concave and then convex. The brittleness index of coal studied in this paper can provide a new method for selecting the optimal CBM reservoir and optimizing the fracturing scheme.

Energy-Based Brittleness Index and Acoustic Emission Characteristics of Anisotropic Coal Under Triaxial Stress Condition

Water-weakening effect is one of the most important causes triggering large deformation and failure of soft-rock engineering; however, few studies have paid attention to damage evolution and constitutive relationship of rock in water-weakening process In this paper, laboratory tests are first carried out to estimate the evolution of mechanical properties along with changes of immersion time for shale samples Then with the aid of X-ray diffraction and scanning electron microscope, mechanism of parameter degradation for shale under immersion conditions is investigated from the microscopic perspective Based on the generalized strain equivalent principle and the theory of statistical microscopic damage mechanics, a damage constitutive model of rock subjected to water-weakening effect and uniaxial loading is established by considering the influence of void-compression stage, and the proposed model is verified to be in good agreement with the experiment results This paper provides an effective approach to analyze the constitutive relationship of rock subjected to water-weakening effect and uniaxial loading

Mechanical Behavior and Damage Constitutive Model of Rock Subjected to Water-Weakening Effect and Uniaxial Loading

Evaluation method of rock brittleness based on statistical constitutive relations for rock damage

Poor shelling quality degrades the performance and profit of the peanut industry. The Hertz theory and the wear resistance experimental method were applied to identify a highly wear-resistant material guaranteeing a low mechanical damage rate (MDR) of peanut kernels. The Box–Behnken design method was applied in the experiment to illustrate the influence of the material’s elastic modulus (X1), radius of curvature of the key parts (X2), rotating speed of the shelling drum (X3), and clearance between the shelling drum and concave screen (X4) on MDR and shelling efficiency (SE). Depending on the analysis of variance, the weights of the influential factors were observed as X1 > X3 > X4 > X2. The mathematical models of MDR and SE were derived from the least squares’ method, and four-dimensional slice diagrams of the three most significant factors were used to illustrate the trends of MDR and SE. A multi-objective analysis provided the optimal combination of parameters as: X1 = 10 MPa, X2 = 12.77 mm, X3 = 277.48 r/min, and X4 = 24.24 mm, yielding MDR = 4.89% and SE = 97.91%. The results were further verified by a production trial test, proving that the proposed solution with the selected material, machine design, and working parameters were effective in improving peanut shelling quality.

https://www.mdpi.com/2077-0472/12/2/146/pdf?version=1643013680

Jiyong Peng

Papers

Evaluation method of rock brittleness based on statistical constitutive relations for rock damage

Optimization of Material for Key Components and Parameters of Peanut Sheller Based on Hertz Theory and Box–Behnken Design