Experimental study on fracture propagation and induced earthquake reduction by pulse hydraulic fracturing in shale reservoirs

Pei, He; Lu, Zhaohui; Zhang, Ye; Huang, Yongkui; Pan, Linhua; Ouyang, Liming; Zhou, Jiankun

doi:10.1016/j.jgsce.2023.204908

Cited by 11 publications

(1 citation statement)

References 34 publications

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“…Unconventional hydrocarbon has become a reliable resource globally, which is of great significance for meeting the growing demand for energy and achieving low-carbon solutions [1][2][3][4][5]. Due to their intrinsic low-porosity and low-permeability features, the natural productivity of such reservoirs is generally quite low as compared to conventional reservoirs.…”

Section: Introductionmentioning

confidence: 99%

Microstructure Imaging and Characterization of Rocks Subjected to Liquid Nitrogen Cooling

Wu,

Zou,

et al. 2024

Processes

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Liquid nitrogen (LN2) fracturing is a potential stimulation method in unconventional hydrocarbon recovery, showing its merits in being water free, creating low formation damage and being environmentally friendly. The microstructure evolution of rocks subjected to LN2 cooling is a fundamental concern for the engineering application of LN2 fracturing. In this paper, pore-scale imaging and characterization were performed on two rocks, i.e., tight sandstone and coal specimens subjected to LN2 cooling using computed tomography scanning. The digital core technique was employed to reconstruct the microstructures of rocks and give a quantitative analysis of the pore structure evolution of both dry and water-saturated rocks. The results indicate that LN2 cooling has a great effect on the pores’ morphology and their spatial distribution, leading to a great improvement in pore diameter and aspect ratio. When compared to the sandstone, coal is more sensitive to LN2 cooling and thermal stresses, having a more noticeable growth in pore–throat size. The porosity growth of coal is 291% higher than that of sandstone. There is a growing trend in the irregularity and complexity of pore structures. After LN2 cooling, the fractal dimensions of the pores of sandstone and coal grow by 11.7% and 0.87%, respectively, and the proportion of pores with a shape factor > 100 increases. More bundle-like and strip-shape pores with multiple branches are generated, which causes a significant growth in the throat size and the proportion of connected pores with a coordination number ≥ 1, enhancing the complexity and connectivity of pore structures dramatically. Additionally, pore water plays an important role in aggravating rock damage during LN2 cooling, enhancing the pore space and connectivity. The porosities of the saturated sandstone and coal samples grow by 22.6% and 490.4%, respectively, after LN2 cooling, which are 5.6% and 186.6% higher than dry samples. The generation of macropores ≥ 70 μm is the primary contributor to porosity growth during LN2 cooling, although such pores account for only a small proportion of the total. These findings contribute to our understanding of the microscopic mechanism of LN2 cooling on rock damage and may provide some guidance for the engineering application of LN2 fracturing.

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Section: Introductionmentioning

confidence: 99%

Microstructure Imaging and Characterization of Rocks Subjected to Liquid Nitrogen Cooling

Wu,

Zou,

et al. 2024

Processes

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Effect of proppant injection condition on fracture network structure and conductivity

Bai,

Li,

et al. 2024

Energy Science & Engineering

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The hydraulic fracturing of shale reservoirs is an important topic, and adjusting the fracturing process can enhance fracturing efficiency. To analyze the effect of injection conditions on the fracture network structure and conductivity, numerical simulations and theoretical calculations are carried out based on the construction data, and the variation patterns of the fracture network parameters are determined. During the theory study, a fracture network conductivity model was obtained by combining the fracture network expansion model and the fracture diversion model. Then a numerical model was set up according to the analysis results of monitoring data. The numerical simulation results showed the fracture network structure and proppant distribution under different conditions. Throughout the simulation process, the structural parameters and conductivity of the fracture network can be determined by controlling the injection amount and adjusting the injection method, speed, and sand ratio. Results indicated that the proppant pulse frequency during the injection process was a major factor affecting the structure and conductivity of the fracture network. At the same time, a comparison of the distribution structure of the proppant revealed that although the intermittent injection of the proppant improved the flow channel, the efficiency of fracture utilization can still be improved.

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Field investigation of multi-stage pulse hydraulic fracturing for improving permeability of coal seam in directional long borehole in underground coal mines

Zhao,

Huang,

et al. 2023

Environ Earth Sci

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Experimental study on fracture propagation and induced earthquake reduction by pulse hydraulic fracturing in shale reservoirs

Cited by 11 publications

References 34 publications

Microstructure Imaging and Characterization of Rocks Subjected to Liquid Nitrogen Cooling

Microstructure Imaging and Characterization of Rocks Subjected to Liquid Nitrogen Cooling

Effect of proppant injection condition on fracture network structure and conductivity

Field investigation of multi-stage pulse hydraulic fracturing for improving permeability of coal seam in directional long borehole in underground coal mines

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