Characteristics of natural fractures in the upper Paleozoic coal bearing strata in the southern Qinshui Basin, China: Implications for coalbed methane (CBM) development

Shi, Jinxiong; Zeng, Lianbo; Zhao, Xiangyuan; Zhang, Yunzhao; Wang, Jipeng

doi:10.1016/j.marpetgeo.2019.104152

Cited by 26 publications

(18 citation statements)

References 63 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Fracture-filling calcite belongs to epigenetic minerals arising from precipitations of hydrothermal fluids or groundwater. ,, The direction of fluid migration is controlled by fracture, so that calcite is mainly deposited and filled in a coal fracture system. The observation results using a microscope or a scanning electron microscope confirmed that the fracture can be completely or partially filled with calcite. − In reality, fracture-filling calcite was commonly found in Chineselow-permeability coal seams with a high methane content, such as Carboniferous-Permian coal seam in northern China (especially in Qinshui Basin), , Late Permian coals in southwestern China (such as the coal mines in Furong, Junlian, Shiping, Huayingshan, Nantong, Liulong, and Xintian), − and low-rank coals in the Fuxin basin , and southern margin of Junggar Basin . Compared with the oxidation stimulation, coal seam-acidizing treatment may have more advantages, which include: (1) acid-soluble minerals infilled in fractures are beneficial to achieve larger stimulated reservoir volumes than that by coal matrix dissolution; (2) the rate of acid–mineral reactions is much faster than that of the coal matrix oxidation reaction; and (3) acid stimulation methods have been widely used in conventional oil and gas reservoirs, and risks associated with coal acidizing can be minimized.…”

Section: Introductionmentioning

confidence: 80%

Permeability Enhancement via Acetic Acid (CH₃COOH) Acidizing in Coals Containing Fracture-Filling Calcite

Chen

Wang

2021

Energy Fuels

View full text Add to dashboard Cite

Calcite is one of the most common fracture-filling minerals in low-permeability coal seams and can be dissolved easily by acid. Although much attention has been paid recently to coal seam acidizing, only few studies have focused on the permeability evolution during the injection of organic acid, which has a very different reaction rate and dissolution structure morphology from those of conventional strong acids (e.g., HCl and HF). In this study, 0.25−1.0 mol/L acetic acid (CH 3 COOH) was injected into the coal plug samples from the Fuxin Basin in China, whose fractures were completely infilled by calcite. The evolution of plug permeability during CH 3 COOH flooding was monitored. Before and after flooding experiments, the coal plugs were characterized using micro-computed tomography imaging, scanning electron microscopy, and nuclear magnetic resonance. The results showed that fracture-filling calcite exhibits high reactivity after exposure to CH 3 COOH at the temperatures of 20, 30, and 40 °C, and the macro-/microscale highly conductive flow channels between the inlet and the outlet of coal plugs can be formed in several hours. Thus, a significant permeability improvement from less than 0.02 mD to over 27 mD was observed during CH 3 COOH flooding. These increases ranging from 131 to 2720 times of the initial permeability are mainly due to the presence of fracture-filling calcite with high connectivity and the absence of fine migration, clay swelling, and secondary Fe-rich precipitation in the CH 3 COOH environment. The results also suggested that the minimum volume of CH 3 COOH required for a highly conductive flow channel breakthrough can be less than 1.0 PV. This investigation demonstrated the potential of deep matrix-acidizing treatment using CH 3 COOH for improving the permeability and enhanced coalbed methane recovery in coal seams containing fracture-filling calcite.

show abstract

Section: Introductionmentioning

confidence: 80%

Permeability Enhancement via Acetic Acid (CH₃COOH) Acidizing in Coals Containing Fracture-Filling Calcite

Chen

Wang

2021

Energy Fuels

View full text Add to dashboard Cite

show abstract

“…Meso-and small-scale fracture parameters, including strike, dip, density, aperture, and length, are obtained through outcrops, cores, and imaging logs (Hennings et al, 2000;Khoshbakht et al, 2012). The density of meso-and small-scale fractures refers to linear density, which is the number of fractures per unit length in the normal direction of the fracture surface (Shi et al, 2020). Micro-scale fracture parameters such as length, aperture, and density are derived from thin section observation (Ameen and Hailwood, 2008).…”

Section: Data Set and Methodologymentioning

confidence: 99%

The Effect of Multi-Scale Faults and Fractures on Oil Enrichment and Production in Tight Sandstone Reservoirs: A Case Study in the Southwestern Ordos Basin, China

et al. 2021

Self Cite

View full text Add to dashboard Cite

The Chang 8 Member of the Upper Triassic Yanchang Formation in the southwestern Ordos Basin is a typical tight sandstone reservoir and has an average porosity of 8.60% and air permeability 0.20 mD. Multi-scale faults and fractures are widely developed in these reservoirs. In this study, three-dimensional seismic data, outcrops, cores, imaging logs, and thin sections were used to classify faults and fractures at multiple scales. Combined with the oil production data, the influence of multi-scale faults and fractures on the oil enrichment and production was analyzed. The results show multi-scale faults and fractures can be divided into six levels: type-I faults, type-II faults, large-scale fractures, mesoscale fractures, small-scale fractures, and micro-scale fractures. As the scale decreases, the number of fractures increases in a power function. Type-I faults cut the caprocks and are not conducive to the preservation of oil. Type-II faults connect the source rocks and reservoirs and are migration channels of the oil source. Large-scale fractures cut the mudstone interlayer and are the seepage channel inside the reservoir. Mesoscale fractures are controlled by thick interlayers, and small-scale fractures are restricted by thin interlayers or layer interfaces. These fractures are the main seepage channels and effective storage spaces. Micro-scale fractures serve as important storage spaces for these reservoirs. The case study of oil reservoir development proves that type-I faults have the greatest impact on fluid flow, while wells drilled into the type-II faults zone have a higher oil production capacity. The oil production changes with the development degree of fractures in different scales, strikes, and positions of faults. Meso- and small-scale fractures are the key to influencing the early single-well production, and micro-scale fractures are conducive to the stable production of single wells. Consequently, multi-scale faults and fractures have significantly different effects on the oil enrichment and production of tight sandstone reservoirs, and the research conclusions can guide to the exploration and development of such similar reservoirs.

show abstract

Section: Cbm Exploitation Statusmentioning

confidence: 99%

Current Status and Effective Suggestions for Efficient Exploitation of Coalbed Methane in China: A Review

Zhang

Zhou

et al. 2021

Energy Fuels

View full text Add to dashboard Cite

The commercial production of coalbed methane (CBM) in China has made significant achievements. To further improve the production of CBM and realize its development, it is necessary to establish a unique, high-efficiency CBM production method that considers the characteristics of coal reservoirs in China. This paper presents the current status of China's CBM exploitation over the past 15 years from three aspects: reservoir characteristics, production mode, and exploitation technology. The achievements, in terms of exploration and development of CBM resources in China, were summarized. The CBM reservoirs in China are characterized by high coal rank, low permeability, high gas content, and low reservoir pressure gradient. Strategic measures for coal and CBM co-mining were proposed creatively as "Huainan", "Jincheng", and "Songzao" modes. CBM production enhancement measures have achieved significant innovations and breakthroughs in drilling and completion technologies and reservoir reconstruction, effectively reducing development costs and increasing single well production. Finally, based on existing basic research, this study proposes efficient CBM exploitation technologies suitable for the characteristics of CBM reservoirs in China. In particular, the uniform permeability enhancement measures of hydraulic grid slotting and fracturing have the advantages of safety, high efficiency, economy, feasibility, and broad application prospects under complex mining conditions. It is of great strategic significance to improve the CBM recovery rate and optimize China's energy structure.

show abstract

Characteristics of natural fractures in the upper Paleozoic coal bearing strata in the southern Qinshui Basin, China: Implications for coalbed methane (CBM) development

Cited by 26 publications

References 63 publications

Permeability Enhancement via Acetic Acid (CH₃COOH) Acidizing in Coals Containing Fracture-Filling Calcite

Permeability Enhancement via Acetic Acid (CH₃COOH) Acidizing in Coals Containing Fracture-Filling Calcite

The Effect of Multi-Scale Faults and Fractures on Oil Enrichment and Production in Tight Sandstone Reservoirs: A Case Study in the Southwestern Ordos Basin, China

Current Status and Effective Suggestions for Efficient Exploitation of Coalbed Methane in China: A Review

Contact Info

Product

Resources

About

Characteristics of natural fractures in the upper Paleozoic coal bearing strata in the southern Qinshui Basin, China: Implications for coalbed methane (CBM) development

Cited by 26 publications

References 63 publications

Permeability Enhancement via Acetic Acid (CH3COOH) Acidizing in Coals Containing Fracture-Filling Calcite

Permeability Enhancement via Acetic Acid (CH3COOH) Acidizing in Coals Containing Fracture-Filling Calcite

The Effect of Multi-Scale Faults and Fractures on Oil Enrichment and Production in Tight Sandstone Reservoirs: A Case Study in the Southwestern Ordos Basin, China

Current Status and Effective Suggestions for Efficient Exploitation of Coalbed Methane in China: A Review

Contact Info

Product

Resources

About

Permeability Enhancement via Acetic Acid (CH₃COOH) Acidizing in Coals Containing Fracture-Filling Calcite

Permeability Enhancement via Acetic Acid (CH₃COOH) Acidizing in Coals Containing Fracture-Filling Calcite