Investigating heterogeneous distribution of fluid pressure in hydraulic fractures during pulsating hydraulic fracturing

Hou, Yuguang; Peng, Yan; Chen, Zhangxin; Tian, Yingying

doi:10.1016/j.petrol.2021.109823

Cited by 16 publications

(9 citation statements)

References 49 publications

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“…Hydraulic slotting, loose blasting, and hydraulic fracturing are generally considered suitable for hard coal seams. For soft single coal seams, the fractures induced by these methods tend to compact under the impact of high stress. − Hydraulic flushing technology has emerged prominently for stress relief-induced permeability enhancement in deep single soft and low-permeability coal seams. Through cyclic high-pressure water flushing of boreholes, this methodology effectively enlarges the borehole radius, achieving stress relief-induced permeability enhancement in the surrounding area. , Liu et al formulated a gas flow-geomechanics coupling model, delving into the influence of hydraulic flushing on the permeability and gas migration of coal through numerical simulations.…”

Section: Introductionmentioning

confidence: 99%

Effect of Stress Relief on Coal Seam Gas Migration: Experiment and Application Discussion

Zhao,

Zhang,

Liu

et al. 2024

ACS Omega

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Stress relief-induced enhanced permeability is one of the crucial measures for promoting gas desorption flow and strengthening gas extraction. In order to examine the impact of stress relief and its magnitude on gas migration, this article explores the gas desorption flow during the stress relief process and elucidates the influence of stress relief degree on gas extraction. The results indicate that considering the analysis of the pore structure effect on gas seepage, the four coal samples' permeability is ranked as PDS > CSL > JZS > GHS. Throughout the stress relief process, the gas desorption rates of different coal samples under various stress paths exhibit varying degrees of increase. As an illustration, following 3600 s of stress alterations, the gas desorption rate of CSL1# experiences a notable increase, surging by 2.57 times; PDS2# shows 55.93 times increase after 4200 s, and JZS3# exhibits 3.13 times increase after 5400 s. A stress relief degree model is established to investigate the variation of horizontal stress and stress relief degrees under different borehole spacings, vertical stresses, cohesion, and internal friction angles for various borehole diameters (coal output). Optimal stress relief is achieved with a borehole diameter greater than 1.52 m with a borehole spacing set at 4 m. When the stress relief degree exceeds 30%, the corresponding borehole diameter ranges for different vertical stresses are 1.49−1.6 m. Similarly, for cohesion, the ranges are 1.25−1.68 m, and for internal friction angles, the ranges are 1.39−1.53 m. The research results can provide valuable insights for determining parameters in the on-site construction of stress relief boreholes.

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Section: Introductionmentioning

confidence: 99%

Effect of Stress Relief on Coal Seam Gas Migration: Experiment and Application Discussion

Zhao,

Zhang,

Liu

et al. 2024

ACS Omega

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“…It is an effective technique for increasing gas production in a variety of rock formations, such as coal seams. However, issues still exist in the understanding of the fatigue damage by the PHF in CBM formations. − PHF was initially proposed to improve the permeability of reservoirs based on its intrinsic property of fatigue damage impact. , However, existing experimental studies usually cannot directly observe the fatigue damage occurrence by hydraulic pulse pressure within a short testing time. An investigation of the effect of fatigue damage by the hydraulic pulse pressure on coal has been conducted in this work to better understand the fundamental mechanisms in CBM production.…”

Section: Introductionmentioning

confidence: 99%

Prediction of the Effects of Pulsating Hydraulic Fracturing on the Porous Structure and Permeability of Coal Based on NMR and AE Spectra

Yu,

Cheng,

Hong

et al. 2024

ACS Omega

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Pulsating hydraulic fracturing has been an environmentally friendly method to improve the permeability of rock formations to stimulate gas production and reduce hazard risks. It has the advantage of fracturing the reservoir with lower cracking pressure and less water volume, as the mechanical strength of rock materials has been reduced by the hydraulic pulse pressure. Many researchers have found significant changes in hard rocks after cyclic loading. However, the existing work still cannot clearly explain the mechanism of the rock damage by pulsating hydraulic fracturing within a short-time experiment. To solve the issue, an investigation of the effects of pulsating hydraulic fracturing on CBM production has been carried out in lab and field applications. Results indicate that the long-term hydraulic pulse pressure can cause a linear decline in cracking pressure directly measured in the lab. It plays an essential role in the permeability enhancement by generating more flow channels for CBM production. The low-field NMR quantitatively evaluates the increase in porosity, which reveals significant incremental ratios of over 20% in the porosity of macropores, mesopores, and micropores of coal caused by fatigue damage. It is first proven that hydraulic pulse pressure has a significant influence on the porosity components of macropores, mesopores, and micropores. To validate the effectiveness of the technique on the field scale, a field application of pulsating hydraulic fracturing has been carried out in a coal mine. It shows that gas production has been largely enhanced with a long and stable production stage and higher gas flux after the applied pulsating load. The gas concentration and gas flux of the fractured boreholes are about 2 times that of the nonfractured boreholes. This work provides an investigation of the effects of pulsating hydraulic fracturing on CBM production, which gives a better understanding of the mechanism for the engineers in the field.

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“…In the latest study (Hou et al, 2022), a multi-fracture geometry calculation model based on the G-function graph of the pressure drop data after fracturing was proposed. It can obtain the fracture length and width by considering the proportional function of fracture length.…”

Section: Introductionmentioning

confidence: 99%

Fracture size inversion method based on water hammer signal for shale reservoir

Zeng,

Wei,

et al. 2024

Front. Energy Res.

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Hydraulic fracturs size inversion plays an important role on evaluating hydraulic fracturing efficiency. Fracture size can be calculated by microseism events or all the pressure data generated by hydraulic fracturing stimulations. These methods are time-consuming. However, the sudden shutoff of pumping can induce a special data known as the water hammer signal. The size of this data is much fewer than others so using it to calculate fracture size is efficient. This study proposes a method of using water hammer signal to work out the hydraulic fracture size. The numerical simulation model is proposed based on the transient flow model to describe the water hammer behavior. The impacts of fracture on water hammer behavior are represented by three parameters (R,C and I). Through these parameters, the fracture size can be calculated. The accuracy of this method is validated by comparing fracture size inversion results between different methods. The results show that the parameter C and R have obvious impacts on water hammer signal and they can cause the amplitude of water hammer signal alternate from 5 to 2 MPa. In addition, this method is accurate for fracture size calculation and the overall error between its results and ones from normal methods is about 6.28%. This method is more suitable for fractures away from horizontal well toe than ones near to well toe. The mean error of fractures away from well toe is only 3.49% but it is 12.75% for fracture near well toe. It is because that the fracture structure is complex near well toe. It indicates that the more accurate relationship between fracture size and parameters (R,C and I) is required for fracture with complex structure.

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Investigating heterogeneous distribution of fluid pressure in hydraulic fractures during pulsating hydraulic fracturing

Cited by 16 publications

References 49 publications

Effect of Stress Relief on Coal Seam Gas Migration: Experiment and Application Discussion

Effect of Stress Relief on Coal Seam Gas Migration: Experiment and Application Discussion

Prediction of the Effects of Pulsating Hydraulic Fracturing on the Porous Structure and Permeability of Coal Based on NMR and AE Spectra

Fracture size inversion method based on water hammer signal for shale reservoir

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