Abstract
The exploration and development of unconventional resources have been of growing interest in the industry in recent years. It is widely known that the adsorption and desorption mechanisms of unconventional gas have great significance for gas accumulation and exploration. However, major researches based on the mechanism of solid-gas interface have failed to reveal it completely, which introduce large discrepancies between actual and predicted production. In this paper, the mechanism of solid-liquid-gas adsorption and desorption interface is enlightened to describe the characteristics of unconventional gas. The validity of the proposal was verified preliminarily by building a conceptual model which redefines the gas-water distribution. Furthermore, the possibility of production of gas trapped in micropores was first investigated. The findings of this study can help for better understanding of the adsorption, desorption, and production mechanisms and in unconventional gas system. Accordingly, the explanation of variation between experiment result and actual production rate even with physical parameters was reasonable in theory. Therefore, this work should provide a basis for improving the accuracy of production predictions in actual reservoirs and should assist analysts in determining reasonable unconventional gas target.
Highlights
The worldwide boom in unconventional oil and gas, wellknown as unconventional energy resource revolution, has a significant impact on the balance of hydrocarbon production in the field of energy [1]
The abundant resources contained in gas-bearing shale and coalbed have received renewed attention as important unconventional natural gas resources with worldwide distribution [2,3,4], especially after a breakthrough made in the development of the Barnett Shale gas in 1997 [5,6,7,8] and followed by the development of the Haynesville, Marcellus, and Fayetteville shale gases [9, 10]
Unconventional natural gases are derived from the organic matter through biogenic or thermogenic processes [11,12,13]
Summary
The worldwide boom in unconventional oil and gas, wellknown as unconventional energy resource revolution, has a significant impact on the balance of hydrocarbon production in the field of energy [1]. With the deepening of research, scholars have a relatively clear understanding about the factors affecting unconventional gas adsorption capacity, including the physical and chemical properties of organic matter (abundance, type, maturity, mineral composition, water content, etc.) and external conditions (temperature, pressure, etc.) [21,22,23]. Adsorption and desorption mechanisms are important for the unconventional gas and are mainly studied through high-pressure experiments with methane [28, 29]. Some scholars noticed that there are significant differences between the actual production and experimental results based on adsorption and desorption mechanisms of solid-gas interface, which is expressed by the Langmuir isotherms. Some scholars have analyzed the occurrence of water and the reason of variation between experiment result and actual production rate preliminarily, some details of the mechanisms are not well understood. This work should provide a basis for improving the accuracy of production prediction and determining reasonable targets in actual unconventional gas reservoirs
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