Fracturing in coals with different fluids: an experimental comparison between water, liquid CO 2 , and supercritical CO 2

Published on Oct 29, 2020in Scientific Reports3.998
· DOI :10.1038/S41598-020-75787-Y
Jianfeng Yang6
Estimated H-index: 6
(Xi'an University of Science and Technology),
Haojie Lian13
Estimated H-index: 13
(TUT: Taiyuan University of Technology),
Li Li4
Estimated H-index: 4
(UW: University of Waterloo)
The present work conducted laboratory experiments of fracturing in fat coals, anthracites, and mudstones. Three different fluids were selected as the fracturing fluids, including water, liquid CO2 (L-CO2), and supercritical CO2 (Sc-CO2). The resulting fracture morphologies and fracture apertures of the coal specimens were investigated using 3D morphological scanning, and the permeabilities of the samples were measured before and after fracturing. The experimental results showed that the breakdown pressures of Sc-CO2 fracturing were the lowest among the three fracturing fluids, and the average single fracture apertures of the ScCO2-induced cracks were the smallest amongst the three fracturing fluids. In addition, the number of cracks and the roughness coefficients induced by Sc-CO2 fracturing were larger than those caused by water and liquid CO2. The viscosity of the fracturing fluid and the capillary effect are key factors that affect the crack propagation path and fracture surface topography. The results suggest that Sc-CO2 has the largest diffusion length, and thus is capable of permeating the coal matrix through small pores and causing more extensive fractures. Additionally, the effective hydraulic apertures of coal specimens produced by Sc-CO2 fracturing were wider than those induced by water and liquid CO2. The experimental results indicate that Sc-CO2 fracturing has huge potential to enhance coalbed methane recovery.
📖 Papers frequently viewed together
53 Citations
176 Citations
8 Citations
#1Maria Mastalerz (IU: Indiana University)H-Index: 60
#2Agnieszka Drobniak (IU: Indiana University)H-Index: 20
Abstract Over the last several decades, coalbed methane (CBM) has emerged as an important energy source in the United States as well as worldwide and is expected to play a significant role in the energy portfolio of the future. This chapter opens with a discussion of the origins of CBM and follows with an overview of current world CBM resources and production. Past and present CBM exploration and production activities in coal-producing countries are also discussed, and they are the basis for pre...
8 CitationsSource
#1Linsen Wang (SDUST: Shandong University of Science and Technology)H-Index: 3
#2Zhongwei Chen (SDUST: Shandong University of Science and Technology)H-Index: 92
Last. Weitao Liu (SDUST: Shandong University of Science and Technology)H-Index: 3
view all 5 authors...
Abstract Steady-state flow methods are widely applied in the laboratory where permeability evolution is typically evaluated assuming a uniform pressure gradient along the sample. The accuracy of this approach is questionable for tight geomaterials when gas is used as the injecting fluid, due to: (i) the nonlinear distribution of pore pressure and gradient along the sample, suggesting that (ii) both slip and viscous flow may occur concurrently within samples containing nano-pores. The following p...
44 CitationsSource
#1Gan Feng (WHU: Wuhan University)H-Index: 2
#2Yong Kang (WHU: Wuhan University)H-Index: 17
Last. Yaoqing Hu (TUT: Taiyuan University of Technology)H-Index: 6
view all 5 authors...
Abstract This paper investigates variation in the failure behavior of shale in a ScCO2-immersion environment with different adsorption periods and layering orientations. Eight types of specimens are investigated, where the inclination of the layering to the applied force θ is 0°, 15°, 30°, 45°, 60°, 75°, 90°, and Divider type. The period of immersion ranges up to 60 days. The results indicate that after 60 days of ScCO2 adsorption, the Brazilian splitting strength (BSS), splitting modulus (E) an...
38 CitationsSource
#1Jianfeng Yang (TUT: Taiyuan University of Technology)H-Index: 6
#2Haojie Lian (TUT: Taiyuan University of Technology)H-Index: 13
Last. Stéphane Bordas (Cardiff University)H-Index: 65
view all 5 authors...
Abstract The present work develops cohesive zone models (CZM), i.e. cohesion-separation laws, for mode I fractures in different rank coals, including weakly caking coals, gas coals, fat coals, meager-lean coals and anthracite, through disk-shaped compact tension tests. Firstly, the experiments show that with the coal rank rising, the critical crack separation displacements and the degrees of the nonlinearity of the softening function decline gradually. By fitting the experimental data with the f...
14 CitationsSource
#1Shu Tao (China University of Geosciences)H-Index: 25
#2Zhejun Pan (CSIRO: Commonwealth Scientific and Industrial Research Organisation)H-Index: 57
Last. Shida Chen (China University of Geosciences)H-Index: 9
view all 4 authors...
Abstract Coalbed methane (CBM) drilling technology is critical in achieving efficient CBM development. The geological conditions for CBM development in China are complex, including special terrain, high-rank coal areas, deep coal seams, multiple superposed coal seams and coal measure gas symbiosis areas, steeply inclined coal seam areas, and tectonic coal seam areas. Therefore, it is critical to apply the optimum drilling technology in each different area. This paper first reviews the current CB...
88 CitationsSource
#1Yuedu Chen (TUT: Taiyuan University of Technology)H-Index: 5
#2Haojie Lian (TUT: Taiyuan University of Technology)H-Index: 13
Last. Stéphane Bordas (Cardiff University)H-Index: 65
view all 6 authors...
Abstract To investigate the influence of geometric characteristics of deformable rough fractures under confining stresses on the behaviors of non-Darcy flow, four fractured sandstone specimens were used for hydraulic tests in the experiments. According to the experimental results of the relationships between the hydraulic gradient and the flow rate, it is demonstrated that the Forchheimer's equation can offer a good description of the non-Darcy flow in rough fractures. In addition, the coefficie...
43 CitationsSource
#1Dawei Zhou (China University of Petroleum)H-Index: 4
#2Guangqing Zhang (China University of Petroleum)H-Index: 17
Last. Yuekun Xing (China University of Petroleum)H-Index: 5
view all 4 authors...
Abstract Supercritical carbon dioxide (SC-CO 2 ) fracturing has broad application prospects due to its potential to increase production, to reduce water requirements, and to minimize environmental impacts. To date, lowering fracture breakdown pressure and inducing multi-fractures using SC-CO 2 as fracturing fluid have been recognized, but the process of fracture propagation has been poorly studied. Therefore, acoustic emission (AE) system with 12 channels is used to monitor the SC-CO 2 fracturin...
29 CitationsSource
#1Yitong Han (Dalian Polytechnic University)H-Index: 3
#2Huanda Zheng (Dalian Polytechnic University)H-Index: 2
Last. Laijiu Zheng (Dalian Polytechnic University)H-Index: 10
view all 4 authors...
Abstract The present study aimed to investigate the effects of different supercritical CO2 conditions on the swelling of polyester. We employed a Box-Behnken design to discuss three variables governing the polymer swelling: system temperature, system pressure and treatment time. The obtained results showed that the system temperature and pressure played significant influence on the swelling of polyester samples. The second-order polynomial formula developed provided accurate predictions for the ...
9 CitationsSource
#1Hangyu Li (Royal Dutch Shell)H-Index: 10
#2Hon Chung Lau (NUS: National University of Singapore)H-Index: 13
Last. Shan Huang (Royal Dutch Shell)H-Index: 6
view all 3 authors...
Abstract Commercial development of coalbed methane (CBM) in China has lasted for a decade. However, in 2015 annual CBM production in China was less than 5 Bcm and lagged far behind those in US (35 Bcm) and Australia (18 Bcm). In this paper, we review the published literature to determine the engineering challenges and opportunities of CBM production in China. Our review has identified seven major engineering challenges to CBM development in China. They are low cleat permeability and underpressur...
47 CitationsSource
#1Can Cai (WHU: Wuhan University)H-Index: 8
#2Yong Kang (WHU: Wuhan University)H-Index: 17
Last. Yang Cai (WHU: Wuhan University)H-Index: 1
view all 7 authors...
Abstract Supercritical Carbon Dioxide (SC-CO2) hydro-jet fracturing can increase gas production and reduce carbon dioxide emission, and is considered as a promising alternative for shale gas exploration. SC-CO2 hydro-jet fracturing technology has resulted in multi-fracture network in the YanChang Well of Ordos Basin, China. However, the mechanism of SC-CO2 hydro-jet fracturing is still not clear. To address the problem, experiments and specimens were designed based on Orthogonal Experimental Des...
28 CitationsSource
Cited By5
The stress disturbance effect will significantly affect the propagation path of hydraulic fractures in the composite rock reservoir. To reveal the influence mechanism of stress disturbance effect on the hydraulic fracture propagation, several groups of laboratory tests and simulation tests were carried out. The test results showed that the hydraulic fracture tip formed a disturbing stress field because of the pore water pressure. Before the hydraulic fracture was extended to the bedding plane, t...
2 CitationsSource
According to the relationship between the development of hydraulic fracture and the distribution of different rock and mineral fabrics, digital image technology was used in this study based on the discrete element particle flow method. An SCGM numerical model, which can control fabric and refine mesoscopic crystal defects, was constructed. The tensile strength test of granite specimens with different component contents and polymerization conditions was conducted, with the monitorization of damag...
#1Liu Zhenghe (TUT: Taiyuan University of Technology)H-Index: 1
#2Shaohua Wang (TUT: Taiyuan University of Technology)
Last. Yang Dong (TUT: Taiyuan University of Technology)
view all 7 authors...
Directional hydraulic fracturing by prefabricating longitudinal (axial) cracks on the sides of boreholes is an effective technique to control hard roof and ensure mining safety. In the present work, a true triaxial hydraulic fracturing experimental device was used to study the influence of prefabricated crack (pre-crack) parameters (including inclination angle and crack length), fracturing fluid viscosity, and mechanical characteristics of rocks on directional hydraulic fracturing with axial pre...
2 CitationsSource
#1Jianfeng Yang (Xi'an University of Science and Technology)H-Index: 6
#2Haojie Lian (TUT: Taiyuan University of Technology)H-Index: 13
Last. Vinh Phu Nugyen (Monash University, Clayton campus)
view all 3 authors...
Abstract The present work studies the Park–Paulino–Roesler (PPR) model, a unified potential-based cohesive zone model (CZM), for mixed mode I/II fractures in different ranked coals, including weakly caking coals, fat coals and anthracite, by using disk-shaped compact tension (DC(T)) tests and punch-through shear (PTS) tests. The PTS experiments showed that with the increase in coal rank, the initial shear stiffness and shear peak loads grow and the maximum tangential crack opening displacement (...
2 CitationsSource
#1Jianfeng Yang (Xi'an University of Science and Technology)H-Index: 6
#2Haojie Lian (TUT: Taiyuan University of Technology)H-Index: 13
Last. Li Li (UW: University of Waterloo)H-Index: 4
view all 3 authors...
Abstract The present paper investigates the effects of CO2-saturation and confining pressures on the fracture toughness of carbon dioxide saturated bituminous coals. Three-point bending experiments were performed with semi-circular coal specimens (SCB) after they were immersed in different CO2 pressures. The experimental results show that the pure modes I and II fracture toughnesses of coal samples gradually decrease with the growth of CO2-saturation pressure. Additionally, the fracture toughnes...
4 CitationsSource