TY - JOUR
T1 - Coal wettability in coalbed methane production
T2 - A critical review
AU - Wang, Ziwei
AU - Liu, Shimin
AU - Qin, Yong
N1 - Funding Information:
The first author gratefully acknowledges financial support from China Scholarship Council [Grant Numbers CSC201906420044].
Publisher Copyright:
© 2021 Elsevier Ltd
PY - 2021/11/1
Y1 - 2021/11/1
N2 - Coalbed methane (CBM) has been extracted on a commercial basis for more than six decades. The low permeability of coal and ineffective dewatering are key challenges in some CBM reservoirs. Coal is a naturally fractured rock with an extremely high organic content. Under in situ conditions, the reservoirs are typically saturated with formation water. The majority of gas is stored as sorbed gas in water saturated CBM formations, which leads to complex dual-phase flow during reservoir depletion. A review of the coal wettability characteristics is the focus of this article. Coal wettability directly influences the irreducible water content which can significantly alter the relative permeability of the gas and water during gas depletion. The technical challenge of the hydraulic fracturing operation is how to achieve an effective flowback when the coal is wet, given that the residual water can be hard to remove. During the initial CBM dewatering, water blocking and the Jamin effect are expected to occur more frequently in the pore throats and narrow cleats with hydrophilic surfaces, resulting in permeability damage. Currently, such technical problems may be solved in part by using surfactants to adjust the coal wetting characteristics. The coal wettability performance should be characterized in terms of selection of both the fracturing fluids and CBM formation cleaning to maximize gas production.
AB - Coalbed methane (CBM) has been extracted on a commercial basis for more than six decades. The low permeability of coal and ineffective dewatering are key challenges in some CBM reservoirs. Coal is a naturally fractured rock with an extremely high organic content. Under in situ conditions, the reservoirs are typically saturated with formation water. The majority of gas is stored as sorbed gas in water saturated CBM formations, which leads to complex dual-phase flow during reservoir depletion. A review of the coal wettability characteristics is the focus of this article. Coal wettability directly influences the irreducible water content which can significantly alter the relative permeability of the gas and water during gas depletion. The technical challenge of the hydraulic fracturing operation is how to achieve an effective flowback when the coal is wet, given that the residual water can be hard to remove. During the initial CBM dewatering, water blocking and the Jamin effect are expected to occur more frequently in the pore throats and narrow cleats with hydrophilic surfaces, resulting in permeability damage. Currently, such technical problems may be solved in part by using surfactants to adjust the coal wetting characteristics. The coal wettability performance should be characterized in terms of selection of both the fracturing fluids and CBM formation cleaning to maximize gas production.
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U2 - 10.1016/j.fuel.2021.121277
DO - 10.1016/j.fuel.2021.121277
M3 - Review article
AN - SCOPUS:85108415566
VL - 303
JO - Fuel
JF - Fuel
SN - 0016-2361
M1 - 121277
ER -