Formation conditions and evolution of fractures in multiple tight rocks: Implications for unconventional reservoir exploitation

Novel triangle method for evaluation of fracability in transitional shale: Case study from well ZXY-1 in the southern North China Basin

“…The components of shales, such as minerals and OM have their own Young's modulus and Poisson's ratio, indicating that different mineral types and content influence shale fracability differently (Huo et al, 2018). As typical brittle minerals, quartz and pyrite have strong fracability (Chen et al, 2021b; Gholami et al, 2016; Jin et al, 2015; Simmons and Birch, 1963), whereas clay minerals and OM have poor fracability (Lawal et al, 2021; Mews et al, 2019; Walles, 2004; Yasin et al, 2017). Calcite, dolomite, and siderite have similar Young's moduli and Poisson's ratios, are non-brittle minerals, and contribute moderately to fracability (Mathia et al, 2016; Christensen, 1972).…”

“…The approximately 2.5 × 10 5 µm 2 of the area of each sample were polished by the argon-ion milled (AIM) technology first and then used Hitachi SU8010 scanning electron microscope (SEM) in secondary-electron mode to identify the type and geometry of pores, fractures and minerals. For more experiments, details can see (Chen et al, 2016(Chen et al, , 2021b. The stress-strain experiment adopts the WEP-600 microcomputer-controlled screen display, a universal rock mechanical experimental instrument, strictly in Maccoby the recommended method of the International Society of Rock Mechanics (Rock characterization testing and monitoring-ISRM suggested method), and the samples are processed under different conditions.…”

“…The approximately 2.5 × 10 5 µm 2 of the area of each sample were polished by the argon-ion milled (AIM) technology first and then used Hitachi SU8010 scanning electron microscope (SEM) in secondary-electron mode to identify the type and geometry of pores, fractures and minerals. For more experiments, details can see (Chen et al, 2016, 2021b).…”

“…A high Young's modulus and low Poisson's ratio suggest good reservoir fracability (Kang et al, 2020; Rickman et al, 2008). Quartz, which is a typical brittle mineral, has a high Young's modulus and low Poisson's ratio, showing good brittleness and fracability (Chen et al, 2021b). Jin et al (2015) and Simmons and Birch (1963) illustrated that pyrite also has good fracability and is a brittle mineral, with a high Young's modulus and low Poisson's ratio.…”

“…The types of fractures and pores in shale also influence the fracability of reservoirs. Some pores and fractures between brittle minerals can be preserved during strong compaction and are connected with artificial fractures during fracturing, which is conducive to shale fracability (Chen et al, 2021b). Most pores and fractures, particularly those developed in ductile minerals, are usually closed during compaction (He and Hayatdavoudi, 2018; Oluwadebi et al, 2018; Renard et al, 2018), which is not conducive to fracability.…”