Adsorption characteristics and controlling factors of marine deep shale gas in southern Sichuan Basin, China

Shi, Xuewen; Zhou, Shangwen; Wu, Wei; Tian, Chong; Li, Du; Li, Dingyuan; Li, Yang; Cai, Changhong; Chen, Yulong

doi:10.1016/j.jnggs.2022.04.001

Cited by 12 publications

(14 citation statements)

References 14 publications

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“…Some scholars’ studies also mentioned that, at present, in southern China marine shale gas wells, the burial depth of the exploited formation section is generally >3500 m, the pressure is generally >70 MPa, and the temperature is generally >80 °C. The temperature–pressure settings in this paper restore the in situ conditions. − …”

Section: Methodsmentioning

confidence: 97%

Occurrence Characteristics of Water in Nano-Slit Pores under Different Solution Conditions: A Case Study on Kaolinite

Zhou

Song

et al. 2023

ACS Omega

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The presence of water in narrow pore spaces affects the occurrence and flow of methane, which in turn affects shale gas production. Therefore, studying the occurrence and distribution characteristics of water is of great significance to predict gas production. Based on molecular dynamics simulations, this study investigated the occurrence characteristics and influencing variables of liquid water in kaolinite nanopores in situ. Owing to its widespread distribution, kaolinite is the most prevalent clay mineral with two surfaces with different characteristics. Three systems of pure water, a CaCl 2 solution, and a H 2 O/CH 4 mixed phase were created at varied temperatures (80−120 °C) and pressures (70−120 MPa). The presence of gas and water in the nanopores was investigated thoroughly. The results showed that the adsorption of water on the Al−O octahedral surface of kaolinite was not affected by external conditions under in situ conditions, whereas the adsorption of water on the Si−O tetrahedral surface decreased with increasing temperature, but the change was small. When ions were present in the system, the water capacity decreased. Based on the aforementioned results, external conditions, such as temperature and pressure do not affect the basic state of water. However, if there are more than two fluid types in the system, the adsorption of water on the mineral surface is reduced owing to competitive adsorption. In addition, a CH 4 −H 2 O mixed system was simulated, in which methane molecules were distributed in clusters. There are two types of adsorptions in pores: gas−solid interactions and solid−liquid−gas interactions. CH 4 molecules are thought to be clustered in water molecules because of the strong hydrogen bonding interactions among the water.

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Section: Methodsmentioning

confidence: 97%

Occurrence Characteristics of Water in Nano-Slit Pores under Different Solution Conditions: A Case Study on Kaolinite

Zhou

Song

et al. 2023

ACS Omega

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“…Pores in shale reservoirs range from several nanometers to several hundreds of microns in size. This wide range presents a challenge to the use of a single measurement method to fully characterize the pore size distribution and pore structure of shale reservoirs . Currently, the pore structure of shale reservoirs is primarily examined through imaging and quantitative tests. − The main imaging methods include high-resolution focused ion beam scanning electron microscopy (FIB–SEM), transmission electron microscopy, atomic force microscopy (AFM), small-angle X-ray scattering, and nanocomputed tomography (CT). − FIB–SEM, known for its high-resolution capabilities, can be used to image nanopores and is primarily employed in two-dimensional (2D) observations. , High-resolution CT can be used for nondestructive scanning and three-dimensional (3D) reconstruction of nanopores in samples.…”

Section: Microstructural Characterization Tecniques For Shale Reservoirsmentioning

confidence: 99%

“…This wide range presents a challenge to the use of a single measurement method to fully characterize the pore size distribution and pore structure of shale reservoirs. 13 Currently, the pore structure of shale reservoirs is primarily examined through imaging and quantitative tests. 14 − 17 The main imaging methods include high-resolution focused ion beam scanning electron microscopy (FIB–SEM), transmission electron microscopy, atomic force microscopy (AFM), small-angle X-ray scattering, and nanocomputed tomography (CT).…”

Section: Microstructural Characterization Tecniques For Shale Reservoirsmentioning

confidence: 99%

Multiple Gas Seepage Mechanisms and Production Development Research for Shale Gas Reservoirs from Experimental Techniques and Theoretical Models

Duan

Chang

et al. 2023

ACS Omega

Self Cite

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Shale gas seepage theory provides a scientific basis for dynamically analyzing the physical gas flow processes involved in shale gas extraction and for estimating shale gas production. Conventional experimental techniques and theoretical methods applied in seepage research are unable to accurately illustrate shale gas mass transfer processes at the micro-and nanoscale. In view of these scientific issues, the knowledge of seepage mechanisms and production development design was improved from the perspective of experimental techniques and theoretical models in the paper. First, multiple techniques (e.g., focused ion beam scanning electron microscopy and a combination of mercury intrusion porosimetry and adsorption measurement techniques) were integrated to characterize the micro-and nanopore distribution in shales. Then, molecular dynamics simulations were carried out to analyze the microscale distribution of gas molecules in nanopores. In addition, an upscaled gas flow model for the shale matrix was developed based on molecular dynamics simulations. Finally, the coupled flow and productivity models were set up according to a long-term production physical simulation to identify the production patterns for adsorbed and free gas. The research results show that micropores (diameter: <2 nm) and mesopores (diameter: 2−50 nm) account for more than 70% of all the pores in shales and that they are the primary space hosting adsorbed gas. Molecular simulations reveal that microscopic adsorption layers in organic matter nanopores can be as thick as 0.7 nm and that desorption and diffusion are the main mechanisms behind the migration of gas molecules. An apparent permeability model that comprehensively accounts for adsorption, diffusion, and seepage was developed to address the deficiency of Darcy's law in characterizing gas flowability in shale reservoirs. The productivity model results for a certain gas well show that the production in the first three years accounts for more than 50% of its estimated ultimate recovery and that adsorbed gas contributes more to the annual production than free gas in the eighth year. These research results provide theoretical and technical support for improving the theoretical understanding of shale gas seepage and optimizing shale gas extraction techniques in China.

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“…Rani et al 20 pointed out that the adsorption of methane from waterbearing shales decreases and that organic-rich matter has a great effect on the adsorption of methane. Shi et al 21 used comprehensive experimental methods such as isothermal adsorption and low-temperature nitrogen adsorption to perform comparative analysis of the high-pressure isothermal adsorption characteristics of shale and considered that the adsorbed gas of deep shale accounts for about 30% of the total gas. However, the above isothermal adsorption studies of shale gas are based mainly on its application to shales at depths shallower than 3500 m, where the experimental pressure is less than 40 MPa.…”

Section: Introductionmentioning

confidence: 99%

Quantitative Studies on the Characterization and Evaluation of Adsorbed Gas and Free Gas in Deep Shale Reservoirs

Shen

Zuo

et al. 2023

Energy Fuels

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The quantitative characterization of adsorbed gas and free gas in shale reservoirs is a key issue in exploration and development of shale gas. Thus, the aforementioned topic is of great significance to the evaluation of reserves, the screening of favorable target areas, and the formulation of development plans. However, research on our current understanding of the quantities of adsorbed gas and free gas in deep shale gas reservoirs is still lacking. To address this problem, deep shales from the Longmaxi Formation in southern China were collected to conduct high-pressure isothermal adsorption experiments. The high-pressure isothermal adsorption model was used to describe the adsorption behavior of methane in deep shales, and the adsorbed gas and free gas in the deep shales were characterized quantitatively. The effects of temperature, pressure, and moisture on the adsorbed gas and the density of the free gas were analyzed. The results indicated that the excess adsorption isotherm curve for methane in deep shales increased and then decreased with the increase of pressure, and the modified Langmuir adsorption model may be used to describe the high-pressure adsorption behaviors. The adsorbed gas in shales decreases gradually with the increase of pressure, and the proportion of adsorbed gas and free gas is between 23 and 74% when the pressure reaches 50 MPa. The adsorbed gas in deep shales decreases with an increase of temperature, and the presence of water greatly reduces the adsorption capacity of the deep shale. The pore space occupied by the free gas in shale increased with the increase in the density of the free phase, and the ratio of the adsorbed gas to the free gas decreased. This research provides a useful reference for explaining how to best evaluate shale gas reservoirs, estimate the reserves in deep shales, and evaluate the adsorption and flow capacity of deep shale gas.

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Adsorption characteristics and controlling factors of marine deep shale gas in southern Sichuan Basin, China

Cited by 12 publications

References 14 publications

Occurrence Characteristics of Water in Nano-Slit Pores under Different Solution Conditions: A Case Study on Kaolinite

Occurrence Characteristics of Water in Nano-Slit Pores under Different Solution Conditions: A Case Study on Kaolinite

Multiple Gas Seepage Mechanisms and Production Development Research for Shale Gas Reservoirs from Experimental Techniques and Theoretical Models

Quantitative Studies on the Characterization and Evaluation of Adsorbed Gas and Free Gas in Deep Shale Reservoirs

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