Changes of pore structures and permeability of the Chang 73 medium-to-low maturity shale during in-situ heating treatment

Wei, Zhao; Sheng, James J.

doi:10.1016/j.energy.2022.123609

Cited by 32 publications

(18 citation statements)

References 35 publications

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“…The dilation of pores and dehydration of clay minerals is the major mechanism enhancing the permeability. Wei and Sheng (2022) also reported that only a slight growth in permeability was observed at 100–300 °C, and even a small part of the permeability drop was witnessed due to the closure of thermal fractures or compaction of nanopores . However, at the higher heat treatment temperatures (400 and 600 °C), thermal fracturing and pyrolysis-induced fracturing play the dominating role.…”

Section: Resultsmentioning

confidence: 99%

“…Wei and Sheng (2022) also reported that only a slight growth in permeability was observed at 100−300 °C, and even a small part of the permeability drop was witnessed due to the closure of thermal fractures or compaction of nanopores. 76 However, at the higher heat treatment temperatures (400 and 600 °C), thermal fracturing and pyrolysis-induced fracturing play the dominating role. Newly formed microfracture networks provide additional transport pathways.…”

Section: Enhancement Of Diffusivity and Permeabilitymentioning

confidence: 99%

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Heating-Induced Enhancement of Shale Gas Transport and Its Application for Improving Hydraulic Fracturing Performance

et al. 2022

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Enhancing the gas transport capacity of shale is essential to obtain economical gas production. Thermal stimulation has been theoretically and experimentally proven as a feasible technology for improving shale gas extraction. In this work, Longmaxi organic-rich shale samples were heated at 200−1000 °C for 240 h to investigate the feasibility of heating-induced generation of additional gas transport pathways and improvement of gas transport capacity (diffusivity and permeability) within the shale matrix. Results show that the mass loss of shale samples is basically unchanged after 200 °C, while a significant mass loss ranging from 3.5 to 14.4% can be observed in the heat treatment at 400−1000 °C. Decomposition (e.g., organic matter, calcite, and dolomite) and clay dehydration are the primary causes of shale mass loss. The organic matter in the shale remained unchanged after 200 °C heat treatment but greatly reduced, until almost disappeared, after 400 and 600 °C heat treatments, and the content of carbonate minerals dropped sharply, until almost disappeared, after 600−1000 °C heat treatment. Nitrogen adsorption experiments and in situ scanning electron microscopy observations show a significant improvement of pore volume and pore size after 400−600 °C heat treatment. However, the mineral melt and recrystallization after the heat treatment at 800 and 1000 °C can cause pore destruction and densification, resulting in pore volume decrease, indicating that the best heating temperature in Longmaxi shale samples is around 600 °C to enhance the pore volume and connectivity in the shale matrix. The methane adsorption decreased by 63.0%, the effective diffusion coefficient in the macropore increased by 263 times after 600 °C, and the permeability increased by 212.8 times at 5 MPa confining pressure. The newly formed transport pathways derived from 600 °C heat treatment may also improve shale matrix permeability at a high effective stress ranging from 30 to 65 MPa, which is a typical stress condition in the shale formations 2000−4500 m in depth. Based on the experimental results in this study, we proposed the heat treatment to improve hydraulic fracturing performance by mitigating fracturing-induced formation damage (e.g., water blockage, clay swelling, and secondary precipitation) within the fracture−matrix interface. In situ combustion of shale gas in hydraulic fractures may be a possible method to heat the shale formations and generate heating-induced transport pathways on the wall surfaces of hydraulic fractures.

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Section: Resultsmentioning

confidence: 99%

Section: Enhancement Of Diffusivity and Permeabilitymentioning

confidence: 99%

Heating-Induced Enhancement of Shale Gas Transport and Its Application for Improving Hydraulic Fracturing Performance

et al. 2022

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“…Academic- and industry-based research and development efforts have demonstrated that the comprehensive characterization and modeling of unconventional reservoirs influence the evaluation and selection of sweet spots, since the reservoir property directly controls the migration, percolation, occurrence, accumulation, and extraction of shale oil and gas. − The reservoir property of mudrocks mainly comprises the porosity, permeability, surface area, pore size distribution, connectivity, heterogeneity, and brittleness. The permeability of mudrock strata is within the range of the nano-Darcy scale. − Zou et al first discovered nanosized pores with diameters of 5–300 nm in shale gas reservoirs in China . Since then, the birth of many new technologies or the application of interdisciplinary technologies has enabled the effective observation, quantification, and reconstruction of these nanosized pores.…”

Section: Introductionmentioning

confidence: 99%

“…Since then, the birth of many new technologies or the application of interdisciplinary technologies has enabled the effective observation, quantification, and reconstruction of these nanosized pores. These techniques primarily include scanning electron microscopy (SEM), computed tomography (CT), low-temperature gas adsorption, fluid invasion porosimetry (FIP), mercury intrusion porosimetry (MIP), nuclear magnetic resonance (NMR), spontaneous imbibition (SI), (ultra)small-angle neutron scattering ((U)SANS), and (ultra)small-angle X-ray scattering ((U)SAXS). ,− Unfortunately, the pore structure is difficult to quantify due to its nanoscale size, complex origin, distribution, and assembly, as well as strong heterogeneity. Therefore, multiple characterization techniques are often needed to validate and complement each other .…”

Section: Introductionmentioning

confidence: 99%

Advances in Microscopic Pore Structure Characterization of Fine-Grained Mudrocks

Wang

Cheng

2023

Energy Fuels

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The microscopic structure of the pore system in fine-grained mudrocks provides spaces for hydrocarbon percolation, migration, and occurrence. It exhibits strong heterogeneity due to the intimate mingling of organic matter (OM) and inorganic minerals and the intricate architecture of the internal network and dynamic changes along the diagenetic pathway and OM thermal maturation. The present review critically summarizes the advances in structure characterization, geological controlling factors, and heterogeneity of the pore system in mudrocks. The pore system in mudrocks can be divided into micro-, meso-, and macropores by diameters, OM-hosted, interparticles, and intraparticle pores by origin and distribution and connected and nonconnected pores according to whether they are connected. The commonly used pore structure characterization techniques can be classified into three categories: i.e., imaging, fluid invasion, and ray-related techniques. Their principles, experimental conditions, applicability, required sample sizes, detectable pore types and diameter ranges, advantages, and disadvantages have been comparatively summarized. To obtain more precise and comprehensive structural properties, multiple techniques are highly recommended to validate and complement each other. The depositional environment, diagenetic events, and OM thermal maturation jointly control the formation and evolution of the pore system. Differences in provenance and depositional background affect primary grain assemblages and thus changes in physical properties during burial depth. Diagenetic transformations mainly change the morphology and structure of mineral-related pores, while OM thermal maturation mainly controls that of OM-hosted pores. Furthermore, the pore structure of mudrocks generally shows strong heterogeneity, which can be effectively assessed by a point-counting porosity quantification and multifractal theory. Finally, we propose the challenges and prospects of microscopic pore structure characterization of mudrocks. More attention needs to be paid to quantifying OM-hosted and mineral-related pore volume fractions, effectively distinguishing connected and nonconnected pores, and comprehensively quantifying the coupled effect of diagenesis and hydrocarbon generation on pore network evolution. In conclusion, the most important aspect of this review is to summarize modern characterization methods and geological controls on pore structure development and propose prospects for unconventional reservoir characterization, with the hope of providing the ultimate knowledge to researchers engaged in unconventional shale oil and gas resources.

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“…According to the research of Bishan granite treated at various temperatures of Chen et al [8], permeability declined after treatment at 300°C, and when the temperature exceeded 400°C, permeability rose significantly with the increase in temperature. Wei et al [9], using real-time measurements, determined the permeability of middle and low mature shale cores in Chang 73 Submember at various temperatures and effective stresses. The results of the experiment revealed that porosity and permeability, respectively, increased by 3.13 times and 624.09 times on average at the 400°C threshold temperature.…”

Section: Introductionmentioning

confidence: 99%

Experimental study on mechanical properties and porosity and permeability of rock in high temperature environment

Hou

Sun

Xue

et al. 2022

J. Phys.: Conf. Ser.

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In order to explore the mechanical characteristics and porosity and permeability parameter of three kinds of rock (sandstone, granite and limestone) in high temperature environment, conventional triaxial compression experiments and porosity and permeability tests were conducted on three kinds of rocks under 25°C, 300°C and 500°C. The experimental results show that the high temperature environment increases the development degree of microcracks and pore structures in sandstone and limestone. As the temperature rises, the interpenetration length of triaxial compression shear crack of sandstone decreases gradually, and the angle between shear crack and horizontal direction increases gradually. Change of damage mode from single shear damage to tension shear damage (shear-dominated) in granite and limestone. The three rocks’ permeability and porosity increase as ambient temperature rises, and the permeability exhibits clear pressure-constricting sensitivity in a range of temperature settings. The results provide a reference for understanding and predicting the mechanical properties and porosity and permeability characteristics of rocks in high temperature environment.

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Changes of pore structures and permeability of the Chang 73 medium-to-low maturity shale during in-situ heating treatment

Cited by 32 publications

References 35 publications

Heating-Induced Enhancement of Shale Gas Transport and Its Application for Improving Hydraulic Fracturing Performance

Heating-Induced Enhancement of Shale Gas Transport and Its Application for Improving Hydraulic Fracturing Performance

Advances in Microscopic Pore Structure Characterization of Fine-Grained Mudrocks

Experimental study on mechanical properties and porosity and permeability of rock in high temperature environment

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