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- Title
Effect of Liquid Nitrogen Freezing on the Mechanical Strength and Fracture Morphology in a Deep Shale Gas Reservoir.
- Authors
Qu, Hai; Li, Chengying; Qi, Chengwei; Chen, Xiangjun; Xu, Yang; Jun, Hong; Wu, Xiaoguang
- Abstract
Liquid nitrogen (LN2) can dramatically deteriorate the rock and create more fractures in high-temperature reservoirs, such as deep hydrocarbon reservoirs. The present study systematically investigates the mechanical strength change and fracture morphology evolution in a deep shale gas reservoir subject to LN2 freezing. The mineral components of three shales were measured by X-ray diffractometry (XRD). The uniaxial compressive and tensile experiments studied the mechanical strengths of shales under different LN2 freezing parameters. Scanning electron microscope (SEM) and nuclear magnetic resonance (NMR) analyse microstructural changes. The results indicated that LN2 freezing could effectively increase pore volume and induce bedding planes and longitudinal fractures in the deep shale at a high temperature. The freezing cycle will generate complex fracture networks at micro and macro levels. Intergranular cracks easily occur between quartz particle boundaries. The shale with fewer clay minerals is a rational target for LN2 fracturing. Two regression models were developed to predict the uniaxial compressive and tensile strengths of deep shale after LN2 freezing. The crucial findings are expected to provide fundamental guidance for developing deep shale resources in a feasible and environmentally acceptable way. Highlights: LN2 freezing can expand pore space and induce complex fractures in deep shale reservoirs. LN2 freezing has more damage effect on the deep shale with more clay minerals The brittle shale is a rational target for LN2 fracturing. Two models are developed to predict the uniaxial compressive and tensile strengths of deep shale by LN2 freezing.
- Subjects
SHALE gas reservoirs; FRACTURE strength; SHALE gas; LIQUID nitrogen; NUCLEAR magnetic resonance; HYDROCARBON reservoirs
- Publication
Rock Mechanics & Rock Engineering, 2022, Vol 55, Issue 12, p7715
- ISSN
0723-2632
- Publication type
Article
- DOI
10.1007/s00603-022-03035-y