Experimental investigation of propagation mechanisms and fracture morphology for coalbed methane reservoirs

Ai, Chi; Li, Xiaoxuan; Zhang, Jun; Jia, Dechang; Tan, Wen-Jing

doi:10.1007/s12182-018-0252-z

Cited by 23 publications

(9 citation statements)

References 49 publications

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“…The loading and unloading during and after blasting or fracturing shake the coal seam and relieve stress on local portions of the seam, however, these stress-relief zones are much smaller than those of cavities or slots. Hydraulic fracturing and pre-splitting blasting can achieve considerable stimulation in coal seams, but the creation of enhanced permeability area is easily influenced by the principle stress difference (Chen et al, 2017;Chi et al, 2018;Cheng et al, 2018;Huang et al, 2019) and thus CMM drainage is restricted. To better connect conventional boreholes to coal cleats and to create a large stress relief zone around a conventional borehole, a new method, tree-type borehole drainage (TTBD), was introduced by Lu et al (2015) and Lu et al (2019) (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

Optimum Layout of Multiple Tree-type Boreholes in Low-Permeability Coal Seams to Improve Methane Drainage Performance

Zhang

Deng

et al. 2021

Front. Energy Res.

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Extracting coal mine methane (CMM) is important for underground mining safety. The tree-type borehole drainage (TTBD) technique can effectively remove methane from coal seams. Determining a suitable drilling pattern for multiple tree-type boreholes will promote the efficient application of this technique in coal mines. Aimed at solving the problem that the optimum methane extraction layout for multiple tree-type boreholes is unclear, this study first constructed a full-coupled thermo-hydro-mechanical model to simulate methane flow in coal. This model and data from a coal mine were used to investigate the effect of multiple tree-type borehole layouts, tree-type borehole spacing, different Langmuir volume and different Langmuir pressure constants, and initial coal permeabilities on CMM drainage. The results show that the different tree-type borehole layouts result in significant differences in drainage and that the use of a rhombic sub-borehole layout can reduce the methane pre-drainage time by up to 44.4%. As the tree-type borehole spacing increases, the total time required for pre-drainage increases as a power function. As the Langmuir pressure constant, the fracture permeability, or the matrix permeability increases, the effective drainage zone expands. The effective drainage zone also expands when the Langmuir volume constant decreases but all these changes are accompanied by a shortening of the drainage completion time. These results can provide a reliable basis for optimizing tree-type borehole drilling layouts.

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Section: Introductionmentioning

confidence: 99%

Optimum Layout of Multiple Tree-type Boreholes in Low-Permeability Coal Seams to Improve Methane Drainage Performance

Zhang

Deng

et al. 2021

Front. Energy Res.

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“…Hydraulic fracture is essential in unconventional oil and gas exploration such as the exploration of shale gas. Despite significant accomplishments in successful applications of hydraulic fracturing in the oil industry, there are still some fundamental questions that need to be resolved (Ai et al 2018;Tan et al 2019). Hydraulic fracturing process is essentially a dynamic process.…”

Section: Introductionmentioning

confidence: 99%

Experimental study of multi-timescale crack blunting in hydraulic fracture

et al. 2020

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Hydraulic fracture is important in unconventional oil and gas exploration. During the propagation of the hydraulic fracture, the crack tip is blunted due to the development of the process zone in the near-tip area. In this study, the blunting of the hydraulic fracture in polymethyl methacrylate specimens due to multi-timescale stress concentration is investigated. The ratio of the initiation toughness to the arrest toughness of the blunted hydraulic fracture is measured using both the dynamic and the static methods. Results show that a hydraulic fracture can be blunted with the time span of stress concentration from 1 ms to 600 s. It is also shown that the blunting of hydraulic fracture is a highly localized process. The morphology of the blunted crack depends on the stress distribution in the vicinity of the crack tip.

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“…At present, the following methods are commonly used both in China and elsewhere: fracturing and stimulation technology, heat injection and stimulation technology, multiple gas displacement technology, acoustic shock methods, and microbial stimulation technology. Ai et al [5] studied the connection between the pressure fracture network generated by hydraulic fracturing and the original structure of coal reservoirs and fundamentally defined the stimulation mechanism of coal-bed gas produced by hydraulic fracturing. Dong et al [6][7][8][9] studied the effect of hydraulic fracturing on coal-bed methane wells.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Coal Permeability Variation during Microwave Radiation

Yao

Shang

et al. 2020

Advances in Materials Science and Engineering

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Coal-bed methane (CBM) is a new type of clean energy, which is abundant in China. Rational development and use of CBM can not only reduce the occurrence of mine disasters but also alleviate energy shortages. However, the "high storage capacity and lowpermeability" characteristics of China's CBM have hindered the realization of industrialized CBM production. To study the effect of microwave radiation on the permeability of coal reservoirs, a seepage experiment under different stress and microwave radiation conditions was carried out by using the seepage experiment system of gas-bearing coal under microwave radiation developed by the authors. e relationship among different microwave powers, different irradiation times, different energy inputs, and coal permeability was explored. e results show that the microwave power effect and the temperature effect promote coal permeability. Under microwave radiation, the relationship between permeability and effective stress followed a negative exponential function, and all R-squared values were greater than 0.97. e permeability increased monotonically with increasing microwave power and irradiation time, and the linear fitting slope of the rate of increase in the low-effective-stress area was greater than in the high-effective-stress area. Under the same energy input, permeability increased with rising microwave power. e peak temperature of the coal sample also increased with increasing power. When the microwave power increased to a certain range, the permeability growth of the coal sample was the greatest, and the temperature gradient of the coal-sample temperature field was the steepest. e coal sample experienced the optimum microwave radiation power under the action of microwaves to achieve the permeability enhancement effect of microwaves on the coal sample. e experimental results provide a theoretical reference for applying microwave radiation technology in coal-bed methane extraction.

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Experimental investigation of propagation mechanisms and fracture morphology for coalbed methane reservoirs

Cited by 23 publications

References 49 publications

Optimum Layout of Multiple Tree-type Boreholes in Low-Permeability Coal Seams to Improve Methane Drainage Performance

Optimum Layout of Multiple Tree-type Boreholes in Low-Permeability Coal Seams to Improve Methane Drainage Performance

Experimental study of multi-timescale crack blunting in hydraulic fracture

Experimental Study on Coal Permeability Variation during Microwave Radiation

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