Numerical Investigation of the Time-Dependent and the Proppant Dominated Stress Shadow Effects in a Transverse Multiple Fracture System and Optimization

Zhou, Lei; Chen, Junchao; Gou, Yang; Feng, Wentao

doi:10.3390/en10010083

Cited by 10 publications

(4 citation statements)

References 21 publications

(32 reference statements)

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“…The fluid net pressure during the propagation of hydraulic fractures has contributed to the increase in the stress of the rock matrix around the fractures along the height direction. This important behavior of fractures is defined as "stress shadow effect", which has non-negligible impacts on the extension directions, opening degrees and shapes [66][67][68]. Especially in the situation of multiple injection wells in the reservoir, the interaction of the stress shadows for the adjacent hydraulic fractures becomes more intense and complicated.…”

Section: Analysis Of Stress Shadow Effectmentioning

confidence: 99%

Numerical Investigation of Injection-Induced Fracture Propagation in Brittle Rocks with Two Injection Wells by a Modified Fluid-Mechanical Coupling Model

et al. 2020

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Hydraulic fracturing is a key technical means for stimulating tight and low permeability reservoirs to improve the production, which is widely employed in the development of unconventional energy resources, including shale gas, shale oil, gas hydrate, and dry hot rock. Although significant progress has been made in the simulation of fracturing a single well using two-dimensional Particle Flow Code (PFC2D), the understanding of the multi-well hydraulic fracturing characteristics is still limited. Exploring the mechanisms of fluid-driven fracture initiation, propagation and interaction under multi-well fracturing conditions is of great theoretical significance for creating complex fracture networks in the reservoir. In this study, a series of two-well fracturing simulations by a modified fluid-mechanical coupling algorithm were conducted to systematically investigate the effects of injection sequence and well spacing on breakdown pressure, fracture propagation and stress shadow. The results show that both injection sequence and well spacing make little difference on breakdown pressure but have huge impacts on fracture propagation pressure. Especially under hydrostatic pressure conditions, simultaneous injection and small well spacing increase the pore pressure between two injection wells and reduce the effective stress of rock to achieve lower fracture propagation pressure. The injection sequence can change the propagation direction of hydraulic fractures. When the in-situ stress is hydrostatic pressure, simultaneous injection compels the fractures to deflect and tend to propagate horizontally, which promotes the formation of complex fracture networks between two injection wells. When the maximum in-situ stress is in the horizontal direction, asynchronous injection is more conducive to the parallel propagation of multiple hydraulic fractures. Nevertheless, excessively small or large well spacing reduces the number of fracture branches in fracture networks. In addition, the stress shadow effect is found to be sensitive to both injection sequence and well spacing.

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Section: Analysis Of Stress Shadow Effectmentioning

confidence: 99%

Numerical Investigation of Injection-Induced Fracture Propagation in Brittle Rocks with Two Injection Wells by a Modified Fluid-Mechanical Coupling Model

et al. 2020

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“…In the 1980s, researchers found that earlier formed hydraulic fractures can increase the stress of subsequent fractures, and that the geometry of the hydraulic fractures and the elastic effect of the pores can affect the growth of nearby hydraulic fractures (Adachi et al, 2007;Pan et al, 2014;Lecampion et al, 2018;Gao and Ghassemi, 2020a). Bunger et al (2011) further verified this phenomenon in their research of Barnet shale gas in 2010 and defined it as a stress shadow (Zhou et al, 2017;Ju et al, 2020;Wang et al, 2022;Bunger et al, 2011). With the innovation and progress of hydraulic fracturing methods, the stress shadow effect can be used to improve the effect of reservoir stimulation through zipper fracturing or simultaneous fracturing methods.…”

Section: Introductionmentioning

confidence: 95%

Proactive stress interference mechanism and its application in the Mahu oil area, Junggar basin

Wang

Li²,

Líu³

et al. 2022

Front. Earth Sci.

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There exists a large horizontal principal stress difference (11–38 MPa) in the tight conglomerates in the Mahu oil area, China. It is difficult to form a complex fracture network via hydraulic fracturing under these conditions. To improve reservoir stimulation, the fracture formation mechanism of the complex conglomerate fracture networks was explored. Based on the geomechanics theory of fracture formation, the mechanism of the “stress wall” formed by fracturing in horizontal wells was analyzed in this paper. The inhibitory effect of the stress wall on the formation of tensile and shear fractures was studied. The reason for the decrease in the stress difference coefficient caused by fracturing fluid was analyzed through numerical simulation, which suggested that the complexity of a fracturing network is mainly controlled by the interference of externally applied stress and the reduction in the coefficient of internal stress difference. In this paper, innovative technologies were developed by proactively introducing stress interference in the application of the Ma131 small-well-spacing pilot area. The core technologies include optimization of the 3-D staggered small-well-spacing pattern, and synergetic optimization of multiple elements and zipper fracturing. The positive effects of proactive stress interference on improving fracturing volume, reserve utilization rate and recovery were discussed. Based on the concept of proactive stress interference, the “serial fracturing mode” of horizontal wells was proposed to reduce drilling and fracturing interference and improve the development effect.

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“…Stress interference can not only affect fracture geometry, but also the geometry of other hydraulic fractures in the adjacent area. This leads to the smaller adjacent fracture hydraulic fracture width, the increase in bending degree, and premature sand removal, which restricts proppant spreading and mesh fracture formation (He et al, 2017;Yoon et al, 2015;Zangeneh et al, 2015;Zhou et al, 2017). Therefore, a full understanding of the stress interference between multiple parallel fractures can help to optimize the fracturing section spacing and perforation spacing during the completion design phase.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation on the simultaneous stress interference of parallel multiple hydraulic fractures

2021

Energy Exploration & Exploitation

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During horizontal well staged fracturing, there is stress interference between multiple transverse fractures in the same perforation cluster. Theoretical analysis and numerical calculation methods are applied in this study. We analysed the mechanism of induced stress interference in a single fracture under different fracture spacings and principal stress ratios. We also investigated the hydraulic fracture morphology and synchronous expansion process under different fracture spacings and principal stress ratios. The results show that the essence of induced stress is the stress increment in the area around the hydraulic fracture. Induced stress had a dual role in the fracturing process. It created favourable ground stress conditions for the diversion of hydraulic fractures and the formation of complex fracture network systems, inhibited fracture expansion in local areas, stopped hydraulic fractures, and prevented the formation of effective fractures. The curves of the maximum principal stress, minimum principal stress, and induced principal stress difference with distance under different fracture lengths, different fracture spacings, and different principal stress ratios were consistent overall. With a small fracture spacing and a small principal stress ratio, intermediate hydraulic fractures were difficult to initiate or arrest soon after initiation, fractures did not expand easily, and the expansion speed of lateral hydraulic fractures was fast. Moreover, with a smaller fracture spacing and a smaller principal stress ratio, hydraulic fractures were more prone to steering, and even new fractures were produced in the minimum principal stress direction, which was beneficial to the fracture network communication in the reservoir. When the local stress and fracture spacing were appropriate, the intermediate fracture could expand normally, which could effectively increase the reservoir permeability.

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Numerical Investigation of the Time-Dependent and the Proppant Dominated Stress Shadow Effects in a Transverse Multiple Fracture System and Optimization

Cited by 10 publications

References 21 publications

Numerical Investigation of Injection-Induced Fracture Propagation in Brittle Rocks with Two Injection Wells by a Modified Fluid-Mechanical Coupling Model

Numerical Investigation of Injection-Induced Fracture Propagation in Brittle Rocks with Two Injection Wells by a Modified Fluid-Mechanical Coupling Model

Proactive stress interference mechanism and its application in the Mahu oil area, Junggar basin

Numerical simulation on the simultaneous stress interference of parallel multiple hydraulic fractures

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