Evaluating the Microstructure Evolution Behaviors of Saturated Sandstone Using NMR Testing Under Uniaxial Short-Term and Creep Compression

Chu, Zhaofei; Liu, Quansheng; Weng, Lei; Wang, Zhiyang; Zhou, Yuan

doi:10.1007/s00603-021-02538-4

Cited by 46 publications

(9 citation statements)

References 73 publications

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“…In single injection, injection time is varied to fracture coal rock. In cyclic injection, the number of freeze–thaw cycles is varied; coal rock is weakened as it is repeatedly frozen and thawed. − Coal rock pore structure is clearly changed by cyclic injection, while the effect of single injection is less clear. − As a coal rock fracturing fluid, LN 2 produces no waste or water pollution; the fracturing process is more stable and has few unintended consequences. − As a new means to fracture coal rock, LN 2 fracturing can increase coal rock permeability and enhance unconventional oil and gas production while avoiding the shortcomings of traditional fracturing. − …”

Section: Introductionmentioning

confidence: 99%

Advances in Liquid Nitrogen Fracturing for Unconventional Oil and Gas Development: A Review

et al. 2022

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Liquid nitrogen (LN 2 ) fracturing is an anhydrous fracturing technology that enhances coal permeability and supports unconventional oil and gas exploitation. In this Review, we provide a systematic review of five aspects of LN 2 fracturing. They are the history of the technology's development, research topics, factors influencing fracturing efficiency, fracturing mechanism, and engineering processes and systems. Liquid nitrogen fracturing transforms coal and rock pore structure through mechanisms such as low temperature, freeze−thaw damage, and gas expansion. It changes coal and rock mechanical properties and improves the pore penetration and efficiency of unconventional oil and gas extraction. However, in-depth studies are still required in many areas. They include theoretical studies of twophase nitrogen flow in coal and rock, development of technical equipment to support field operations, and plans to monitor and evaluate fracturing efficiency. On the basis of the advances in LN 2 fracturing research and the challenges, we conclude that future research should focus on multiphase flow and field equipment and technology.

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Section: Introductionmentioning

confidence: 99%

Advances in Liquid Nitrogen Fracturing for Unconventional Oil and Gas Development: A Review

et al. 2022

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“…e rock mass strength parameter is a vital factor for the stability of the surrounding rock, the numerical simulation calculation, and the support design of the tunnel [1][2][3][4]. e strength of the layered rock mass is lower than that of the intact rock mass due to the existence of weak structural planes.…”

Section: Introductionmentioning

confidence: 99%

Application of the Slope Coefficient of the Equivalent M–C Criterion in Layered Rock Mass Engineering

Liu

Zhang

et al. 2022

Advances in Civil Engineering

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The slope coefficient ω is defined based on the insufficiency of the area equivalent method, the slope of the equivalent M–C criterion obtained from the instantaneous equivalent, and the optimal first-order approximation to reduce the error between the simulated value and the measured value of the surrounding rock and ensure the safety of the project. Different ω conditions are set to obtain multiple equivalent M–C strength parameter combinations. The above combinations are input to the ubiquitous joint model of FLAC3D, and the surrounding rock strength of layered tunnels with different inclination angles (0°, 30°, 45°, 60°, and 90°) is corrected. The results show that (1) after the tunnel excavation is completed, the displacement of key points (e.g., the vault and waist) increases when the slope coefficient is increased and the deviator stress decreases when the slope coefficient is increased. (2) After the area equivalent method is revised, the displacement and the deviator stress are more significantly affected by the inclination of the rock strata than the uncorrected ones, suggesting that the equivalent area can more effectively highlight the anisotropy characteristics of the layered surrounding rock. (3) After the simulation results of the displacement and the deviator stress at the respective key point are comprehensively modified, the optimal slope coefficient corresponding to each rock layer inclination is obtained, and the area is optimized by ensuring reasonableness to reduce the error between the simulated value and the measured value. (4) The layered surrounding rock at a dip angle of 30° is studied. The development of the plastic zone is promoted when the slope coefficient is increased, and the rock shear failure and the joint shear failure occur simultaneously on both sides of its axis.

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“…Then, parameters such as porosity, pore size distribution, and pore fractal dimension of rock blocks are obtained through various algorithms around T 2 spectrum [4,5], so as to master pore distribution and crack development characteristics inside rock under frozen-thawed cycles. In terms of macroscopic mechanics, mechanical test experiments of frozen-thawed rocks were carried out to obtain the physical and mechanical parameters of rocks under frozen-thawed cycles and study the mechanical behavior laws of rocks under frozen-thawed cycles [6,7]. Finally, combined with the theories of damage mechanics, fracture mechanics, and the principle of NMR, the influence law of crack space characteristics, initial damage, and frozen-thawed action on rock damage was analyzed, the relationship between crack space characteristics and macroscopic mechanical parameters was found out, and a rock damage model considering frozen-thawed effect was established.…”

Section: Introductionmentioning

confidence: 99%

Study on Prediction Model of Mechanical Parameters of Rock Frozen-Thawed Damage based on NMR Technology

Tai

2022

Geofluids

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In order to establish prediction models for the mechanical parameters of rock freeze-thaw damage based on nuclear magnetic resonance (NMR) technology, with reference to the laboratory test of rock mechanical parameters after freeze-thaw, combined with low-field NMR and multivariate analysis methods, PLSR and PCR prediction models for the peak stress, peak strain, and elastic modulus of frozen-thawed rocks were established. The results show that the correlation coefficient of calibration set ( R 2 cal ) and validation set ( R 2 val ) of the PLSR and PCR prediction models are both greater than 0.9, and the residual prediction deviation (RPD) of each model is greater than 3, indicating that the established prediction models have good stability, small relative error, and high prediction accuracy. The application evaluation results show that the peak stress and peak strain of frozen-thawed rocks can be accurately predicted using these models. In this paper, only the NMR tests are performed on the frozen-thawed rocks, and no rock mechanics experiments are performed. The research results provide a new method for the research of rock freeze-thaw damage.

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Evaluating the Microstructure Evolution Behaviors of Saturated Sandstone Using NMR Testing Under Uniaxial Short-Term and Creep Compression

Cited by 46 publications

References 73 publications

Advances in Liquid Nitrogen Fracturing for Unconventional Oil and Gas Development: A Review

Advances in Liquid Nitrogen Fracturing for Unconventional Oil and Gas Development: A Review

Application of the Slope Coefficient of the Equivalent M–C Criterion in Layered Rock Mass Engineering

Study on Prediction Model of Mechanical Parameters of Rock Frozen-Thawed Damage based on NMR Technology

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