The impact of the coal macrolithotype on reservoir productivity, hydraulic fracture initiation and propagation

Liu, Yulong; Tang, Dazhen; Mathews, Jonathan P.; Zhai, Yue; Hou, Wei; Li, Song; Tao, Shu; Xiong, Xiaohui; Wang, Wei

doi:10.1016/j.fuel.2018.10.150

Cited by 48 publications

(14 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The more cleavage system developed in the reservoir, the more obvious the anisotropy of reservoir. When fracturing the heterogeneous reservoir, the artificial fracture is easier to communicate with natural fracture system, forming crisscross fracture network and improving the reservoir permeability (Blanton, 1982; Fan et al., 2014; Jeffrey et al., 2009; Liu et al., 2019; Valko and Economides, 1994). Therefore, when formulating a CBM well network deployment plan, the well network arrangement should be carried out based on the degree of permeability coal anisotropy as combined with the distribution of artificial fractures (Agarwal et al., 1998; Chaianansutcharit et al., 2001; Salehi and Nygaard, 2015; Xu et al., 2014).…”

Section: Introductionmentioning

confidence: 99%

“…The gas in coal reservoirs is mainly seepage in the natural fracture system, and the hydraulic fracturing has the function of communicating the cleavage systems, and modifying the reservoir permeability (Adachi et al., 2007; Li et al., 2009; Tan et al., 2017). The researchers determined that the geometry of fractures is complicated and the initiation and propagation behaviors are mainly controlled by the cleavage system (Beugelsdijk et al., 2000; Close, 1993; Dean and Schmidt, 2009; Liu et al., 2019). The CT tomographic scans show that the bright coal has the most developed pore-fracture system, and only a few filamentous micron-scale cracks develop in dull coal.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Analysis of hydraulic fracture behavior and well pattern optimization in anisotropic coal reservoirs

Liu

Tang

Hou³

et al. 2020

Energy Exploration & Exploitation

Self Cite

View full text Add to dashboard Cite

Macrolithotypes control the pore-fracture distribution heterogeneity in coal, which impacts stimulation via hydrofracturing and coalbed methane (CBM) production in the reservoir. Here, the hydraulic fracture was evaluated using the microseismic signal behavior for each macrolithotype with microfracture imaging technology, and the impact of the macrolithotype on hydraulic fracture initiation and propagation was investigated systematically. The result showed that the propagation types of hydraulic fractures are controlled by the macrolithotype. Due to the well-developed natural fracture network, the fracture in the bright coal is more likely to form the “complex fracture network”, and the “simple” case often happens in the dull coal. The hydraulic fracture differences are likely to impact the permeability pathways and the well productivity appears to vary when developing different coal macrolithtypes. Thus, considering the difference of hydraulic fracture and permeability, the CBM productivity characteristics controlled by coal petrology were simulated by numerical simulation software, and the rationality of well pattern optimization factors for each coal macrolithotype was demonstrated. The results showed the square well pattern is more suitable for dull coal and semi-dull coal with undeveloped natural fractures, while diamond and rectangular well pattern is more suitable for semi-bright coal and bright coal with more developed natural fractures and more complex fracturing fracture network; the optimum wells spacing of bright coal and semi-bright coal is 300 m and 250 m, while that of semi-dull coal and dull coal is just 200 m.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Analysis of hydraulic fracture behavior and well pattern optimization in anisotropic coal reservoirs

Liu

Tang

Hou³

et al. 2020

Energy Exploration & Exploitation

Self Cite

View full text Add to dashboard Cite

show abstract

“…To close this gap, researchers are redefining coal permeability estimations based on fracture models [e.g. Discrete Fracture Network models described in Liu et al (2019), Zhang et al (2015), Zhi et al (2018)]. Equating fracture parameters with resultant permeability requires certain analytical solutions like the 'cubic law' (details in Sect.…”

Section: Introductionmentioning

confidence: 99%

Dependence of fluid flow on cleat aperture distribution and aperture–length scaling: a case study from Gondwana coal seams of Raniganj Formation, Eastern India

Bandyopadhyay

Mallik

Ghosh

2019

Int J Coal Sci Technol

View full text Add to dashboard Cite

Dimensions and mutual relationships amongst fracture (cleat) parameters such as maximum aperture width, average aperture width, length, spacing etc. control the connectivity within a fracture network and the fluid flow in a coal seam as the matrix permeability, here, is negligible. In this paper, we document cleat size distributions and investigate lengthaperture relationships from coals of Raniganj coalfield in Eastern India. This coalfield has a proven extractable reserve of six billion tons of coal and holds immense potential to be one of the largest coal bed methane fields serving India's growing energy needs. Here, cleat length (L) correlates with corresponding maximum aperture width (D max) in a power-law function with an exponent of 0.84 (D max a L 0.84) instead of the commonly observed exponents of 1 or 0.5 applicable for other natural 'opening-mode' fractures. The conventional wisdom pertains that laminar fluid flow (Q) through an isolated, smooth-walled, parallel-plate fracture, embedded in an impermeable matrix, is directly proportional to the cube of its aperture width (b, equivalent to D avg ; cubic law: Q a b 3). This assumes a linear relationship between length and fracture aperture. However, the modified relationship between cleat length and average aperture width changes the cubic law applicable for Raniganj coal seam and now fluid flow correlates with aperture width in a power-law function with an exponent of 4.25 (Q a b 4.25) instead of 3 (cube). Such simplifications will come handy for the modeling and estimation of fluid flow as it will reduce the effort of cleat length measurement which is anyway difficult and can be misleading due to the risk of undersampling.

show abstract

“…1) and deep mining has become increasingly important. [3][4][5] However, deep mining carries significant risks including coal gas outburst and gas explosion, therefore attention has turned to the exploitation of coalbed methane (CBM). 6 On one hand, CBM exploitation can mitigate the risk caused by gas in deep mining [8][9][10][11] operations and on the other hand, is a type of relatively clean energy, conducive to environmental protection.…”

mentioning

confidence: 99%

“…For example, the world's largest CBM field (the Qinshui Basin) has been steadily exploited for years. 12,13 To enhance the gas permeability in the reservoirs during CBM production, many different fracturing techniques may be applied including hydraulic fracturing, 5,14 hydraulic slotting, 15,16 hydraulic punching, 17 hydraulic explosion, 18,19 hydraulic flushing, 20,21 and water jet. 22,23 Water is present in coal both as inherent moisture in the matrix and as free water in the fracture system.…”

mentioning

confidence: 99%

Permeability evolution in tectonic coal: The roles of moisture and pressurized water‐injection

et al. 2021

View full text Add to dashboard Cite

Water often influences the exploitation of Coalbed methane (CBM) as well as the hydraulically enhanced permeability; it is therefore useful to objectively quantify the permeation properties of a CBM reservoir with different moisture contents. Based on the occurrence of CBM and the laws governing gas flow in CBM reservoirs, gas seepage experiments were carried out on the coal collected from the Baijiao mine in Sichuan, China. Various moisture contents were evaluated using natural coal samples, dry coal samples heated in an oven for various periods, and coal samples wet by soaking them in different pressure water under a constant effective confining stress. Results showed that: (1) The coal moisture decreased gradually with the drying time and increased with the soaking time. When coal is soaked in high pressure water (5-20 MPa), the moisture content in coal will increase from 2.60 to 3.85% with the increasing of water pressure. (2) The permeability of soaked coal decreased with the increasing of gas pressure, while the permeability of natural coal firstly decreased and then increased with the pore pressure decrease. (3) For the coal with higher moisture contents, gas permeability is more sensitive to the reduction of pore pressure, which may be due to the alteration of fracture structure induced by high-pressure water injection. (4) Moisture content of coal affects the slippage effect in coal pores, and a higher moisture in coal will result in the decrease effective pore throat, incurring a stronger slippage flow and a higher apparent permeability of coal.

show abstract

The impact of the coal macrolithotype on reservoir productivity, hydraulic fracture initiation and propagation

Cited by 48 publications

References 44 publications

Analysis of hydraulic fracture behavior and well pattern optimization in anisotropic coal reservoirs

Analysis of hydraulic fracture behavior and well pattern optimization in anisotropic coal reservoirs

Dependence of fluid flow on cleat aperture distribution and aperture–length scaling: a case study from Gondwana coal seams of Raniganj Formation, Eastern India

Permeability evolution in tectonic coal: The roles of moisture and pressurized water‐injection

Contact Info

Product

Resources

About