Glutenite reservoir is a special rock type with sandstone and gravels in different proportions, the significant mechanical anisotropy make the drilling, completion and stimulation methods for glutenite reservoir as a tough challenges. The scope of paper is to conduct triaxial compression tests for glutenite specimens from Mahu depression at Junggar Basin, China. Moreover, the effects of gravel on the failure modes of glutenite were discussed. According to complete stress vs. strain curves, the post peak stress drop rate is relatively low comparing to tight sandstones, indicating glutenite samples are more ductile than sandstone samples Thus, there are mainly three types of rock failures for glutenite, namely fracture termination, deflection and penetration, which all controls by combining effects of gravel strength and confining pressures. Fracture deflection and penetration modes dominate the failure modes at the low confining pressure conditions whereas the fracture termination and deflection modes dominate the fracture modes at high confining pressure condition. The experimental results can provide more insights for rock mechanisms of glutenite.
Glutenite reservoir is defined as a special oil and gas accumulation since the presence of different sizes of gravels embed with sandstones. As a special hydrocarbon reservoir, glutenite reservoirs are of a small scale in the total volume of fossil fuels but are abundant in some sedimentary basins (Zhang et al., 2014). The Mahu sag, which is located in the Junggar Basin, has rich oil and gas resources in glutenite formation. Glutenite reservoirs are commonly deeply buried, while the permeability and porosity of glutenite reservoirs are super low. Thus, the commercial oil and gas production cannot be successfully achieved without applying advanced stimulation techniques (Shimizu et al., 2011; Ju et al., 2016). To increase the efficiency of well completion and hydraulic fracturing, characterizing the mechanical properties for glutenite formation is necessary.
The rock mechanical properties and failure behaviors of sedimentary rocks are fundamental for better understanding a series of engineering problems, but researches related to mechanical properties of glutenite is still rare. High-pressure servo test system can be used to measure mechanical behavior and analyze the failure modes of under different confining pressure or complex loading conditions. In this paper, we performed triaxial tests on standard glutenite cores while the complete stress-strain response and failure behavior of glutenite was discussed. Furthermore, the relationships between gravels and mechanical properties were investigated. This study can provide basic mechanical data for drilling or hydraulic fracturing in glutenite reservoirs