A review of gas adsorption on shale and the influencing factors of CH4 and CO2 adsorption

The escalating levels of carbon dioxide emissions (CO 2 ) and the detrimental consequences of global warming have spurred extensive research into identifying secure and reliable storage sites with ample capacity. Depleted gas reservoirs emerge as a promising option for CO 2 sequestration, solidifying their position as a viable carbon sink. These conventional or unconventional reservoirs retain substantial pore space after natural gas extraction and depressurization. Furthermore, their impermeable top layers ensure the long-term containment of hydrocarbons, enhancing the safety of this choice. Consequently, the cost of the process can be reduced through the incremental recapture of excess gas after carbon dioxide (CO 2 ) injection. This article is a comprehensive review of multiple published papers exploring the enhancement of shale gas recovery through CO 2 injection. It aims to present a thorough understanding of the concept of this technology, highlighting its benefits and drawbacks, comparing existing studies, and encouraging further research into the CO 2 -EGR principle.

Section: Introductionmentioning

confidence: 88%

“…Insights from refs , − , and were used as examples in ref work to show how supercritical CO 2 affects shale gas reservoirs, especially when it comes to enhanced gas recovery (EGR).…”

Section: Introductionmentioning

confidence: 99%

Review on Carbon Capture, Utilization, and Storage for Enhancing Gas Recovery

AL-khulaidi,

Sun,

Alareqi

et al. 2024

Section: Gas Adsorption In Shalesmentioning

confidence: 99%

Advances and Prospects of Supercritical CO₂ for Shale Gas Extraction and Geological Sequestration in Gas Shale Reservoirs

Shen,

Ma,

Zuo

et al. 2024

The advancements in hydraulic fracturing and horizontal drilling techniques have substantially facilitated the large-scale extraction of natural gas from shale gas reservoirs. However, the use of fracking water poses several potential drawbacks including the contamination of groundwater, surface water, and soil, as well as risks to air quality. Due to the unique physical properties of supercritical CO2, shale gas exploitation using this method has been considered a promising technology that can not only improve gas recovery but can also enable CO2 geological storage. This paper clarifies the gas adsorption mechanism in shale formations, including the factors influencing the adsorption of CH4, the differences between CH4 and CO2 adsorption, and various adsorption models. We show that shale inherently exhibits a preference for CO2 adsorption over CH4. Then, the supercritical CO2 fracturing mechanism, including the shale fracking pressure and the factors influencing CO2 fracturing, is analyzed. The mechanisms of CO2 extraction in shale gas and the key factors influencing CO2 geological storage are discussed. The main challenges and future prospects regarding the use of supercritical CO2 for shale gas recovery and geological sequestration in gas shale reservoirs are finally summarized. A more detailed understanding is required to evaluate the efficiency of shale gas recovery and CO2 geological sequestration in shale formations using supercritical CO2. This work provides a basis and serves as a reference for future research investigating the mechanisms of shale gas exploitation using supercritical CO2, as well as the limitations and advantages of CO2 geological sequestration in unconventional shale gas reservoirs.

“…Mudrocks, commonly as mere source rock in conventional petroleum systems, are self-sourced reservoirs in unconventional shale oil and gas systems. 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 .…”

Section: Introductionmentioning

confidence: 99%

Advances in Microscopic Pore Structure Characterization of Fine-Grained Mudrocks

Wang

Cheng

2023

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.