Study on rock mechanics characteristics of deep shale in Luzhou block and the influence on reservoir fracturing

Abstract

This paper aims to study the influence of deep formation conditions on the mechanical properties of shale, which is of great significance for the engineering application of efficient development of deep shale gas. In this study, a real-time high-temperature (25°C-170°C) triaxial compression experiment was first carried out on shale samples. Then, based on the analysis results of rock mineral components and discrete element numerical simulation technology, a thermo-mechanical coupling model (TMCM) was constructed, and the accuracy of the numerical model was verified. Finally, based on the micromechanical parameters, a numerical fracturing mechanism model considering the influence of temperature, natural fracture density, and fracture length was established, and the influence of current reservoir conditions on hydraulic fracturing was discussed. The results show that confining pressure has a greater effect on rock mechanics than temperature.When the temperature exceeds 110°C, the plasticity of rock samples increases, and the fracture morphology becomes complex. In addition, the increase in temperature promotes the fracture of microcracks to a certain extent. The research results are expected to provide a sufficient theoretical basis for the development and utilization of deep shale gas resources. K E Y W O R D Sdeep shale gas, PFC, rock mechanics, temperature, XRD | INTRODUCTIONShale gas, an unconventional energy source with abundant reserves, is a clean and environmentally friendly natural gas that has become an important strategic resource in China. 1,2 Deep shale gas in China has a great potential for exploitation. 3 However, a series of technological difficulties exist. 4 In particular, the high-temperature (HT) and high-pressure (HP) geological environment of deep reservoirs results in the transformation of rock mechanical properties, 5 which has a significant impact on geological evaluation, drilling technology, and fracturing. [6][7][8][9] Therefore, this requires considerable attention.In recent decades, several studies have focused on understanding the mechanical behavior of progressive damage and microscopic damage mechanisms of rocks

Study on the induced effect of bedding weakness in deep shale gas reservoir on hydraulic fractures propagation

“…Frontiers in Energy Research frontiersin.org 04 Duan et al 10.3389/fenrg.2024.1392298 constant normal and tangential stiffness uniformly distributed on the contact surface between particles (Fairhurst and Hudson, 2000;Han et al, 2022;Martin et al, 2013). It is defined by the five parameters of normal stiffness, normal strength, tangential stiffness, tangential strength and connection radius, and then characterise the force-deformation behavior of the rock, as shown in Figure 6.…”

“…Ren et al (2023) derived the criteria for determining the propagation of threedimensional hydraulic fractures and natural fractures from the perspective of stress field at the crack tip through theoretical derivation, and verified them through experiments. Li et al (2022) established a mathematical model for complex fractures in shale gas and simulated the effects of different rock mechanics parameters, stress, fracture parameters, and structural parameters on fracture networks. Although experimental results and theoretical deductions can explain the induction mechanism of natural fractures in hydraulic fracturing, they cannot comprehensively and systematically reflect the fracturing fracture propagation behavior in underground reservoirs under the comprehensive influence of multiple factors.…”

Study on the Difference of Fracture Extension in Hydraulic Fracturing of Marine and Continental Shales Based on Optical Scanning Technology

“…However, shale reservoirs are characterized by low porosity and low permeability, with almost no natural production capacity. To realize the economic development of shale gas resources, it is necessary to modify the reservoirs through volumetric fracturing to form effective flow channels [6][7][8][9][10][11][12]. Based on hydraulic fracturing technology, the exploitation of marine shale gas has achieved significant success, and three major shale gas fields, including Fuling, Changning, and Weiyuan-in the Wufeng and Longmaxi Formations 2 of 16 of the Sichuan Basin of China, which are particularly large marine shale gas-producing areas-have realized the industrialized exploitation of shale gas by using hydraulic fracturing technology [13][14][15].…”