Investigation on the effect of pore pressure gradient on fracture propagation in rock materials

Li, L. C.; Xia, Yingjie; Tang, Chun An

doi:10.1179/1432891715z.0000000001477

Cited by 7 publications

(5 citation statements)

References 8 publications

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“…Tang in 1995. As a numerical simulation code, the RFPA code can simulate the progressive failure process of materials, and it has been widely used and recognized by scholars worldwide [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. e simulation results of jointed shale on hydraulic fracturing can also provide relevant reference about the formation of complex fracture networks in jointed shale.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation on the Hydraulic Fracture Evolution of Jointed Shale

Men

Jin

2021

Advances in Materials Science and Engineering

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Joints are a common structure of heterogeneous shale rock masses, and in situ stress is the environment in which heterogeneous rock masses can be found. The existence of joint plane and confining pressure difference influences the physical properties of shale and propagation of fractures. In this study, jointed shale specimens were simulated under different confining pressures to explore the failure patterns and fracture propagation behavior of hydraulic fracturing. Different from the common research of hydraulic fracturing on signal parallel joint rock mass, the simulations in this study considered three points (parallel joint, multi-dip angle joint, and no-joint points). The effects of the single-dip angle joint, multi-dip angle joint, and confining pressure difference on the hydraulic fracture evolution and stress evolution of the jointed shale were studied comprehensively. The confining pressure difference coefficient proposed in this study was used to accurately describe the confining pressure difference. Results indicate that the larger is the confining pressure difference, the stronger is the control of the maximum principal stress on fracture evolution; by contrast, the smaller is the confining pressure difference, the stronger is the control of the joint plane on fracture evolution. Under the same confining pressure difference, the hydraulic fracture propagates more easily along the small dip angle joint plane. As the value of the confining pressure difference coefficient moves closer to zero, the hydraulic fracture propagates randomly, the tensile stress region around the fracture tip widens, and the joint planes fractured by tensile increase. This study can offer valuable guidance to the design of unconventional reservoir reconstruction.

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Section: Introductionmentioning

confidence: 99%

Numerical Investigation on the Hydraulic Fracture Evolution of Jointed Shale

Men

Jin

2021

Advances in Materials Science and Engineering

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“…Some scholars have studied the propagation rule of hydraulic fractures under the action of the symmetric or uniform pore pressure field, and then a hydraulic fracturing propagation model that considers pore pressure is proposed (Gao et al., 2019c; Gholami et al., 2017; Renshaw and Pollard, 1994). It is obtained from the results of non-uniform pore pressure field on the expansion rules of hydraulic fractures that the existence of pore pressure field can increase the stress intensity factor at the tip of hydraulic fractures, inducing the expansion of hydraulic fractures along the direction of high pore pressure (Li et al., 2015; Shou et al., 2015; Tang et al., 2003). The expansion of hydraulic fractures is not only affected by the local pore pressure at the fracture tip but also controlled by the macroscopic distribution of pore pressure gradient (Rahul et al., 2017).…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation on the effect of pore pressure gradient on the rules of hydraulic fracture propagation

2021

Energy Exploration & Exploitation

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To clarify the influence of pore pressure gradient on hydraulic fracture propagation, the stress distribution in and around the borehole is explained by theoretical analysis method in this paper. A mechanical model of hydraulic fracture initiation under the action of pore pressure gradient is established. Then coupled seepage-stress-damage software is used to simulate the initiation and propagation of hydraulic fractures in rock samples under the action of pore pressure gradient. Finally, the influence of the number and spatial position of the induction holes on the initiation and propagation of hydraulic fractures is analyzed. It is shown that: (1) Pore pressure gradient can effectively reduce the initiation pressure of hydraulic fractures. (2) The greater the pore pressure gradient is, the easier the hydraulic fracture is to spread to the region with high pore pressure. (3) With the action of pore pressure gradient, the hydraulic fracture is shaped as ‘丨’, ‘丿’ and ‘S’ types and can be represented by the four abstract conceptual models.

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“…Different from metal and glass materials, rock is a heterogeneous natural geological material [16]. erefore, the traditional calculation method based on material homogeneity and isotropy is not suitable for rocks.…”

Section: Brief Introduction To the Numerical Rfpa-flow Codementioning

confidence: 99%

Numerical Investigation of Fracture Network Formation under Multiple Wells

Men

2020

Mathematical Problems in Engineering

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A two-step fracturing method is proposed to investigate the hydraulic fracture evolution behavior and the process of complex fracture network formation under multiple wells. Simulations are conducted with Rock Failure Process Analysis code. Heterogeneity and permeability of the rocks are considered in this study. In Step 1, the influence of an asymmetric pressure gradient on the fracture evolution is simulated, and an artificial structural plane is formed. The simulation results reflect the macroscopic fracture evolution induced by mesoscopic failure; these results agree well with the characteristics of the experiments. Step 2, which is based on the first step, investigates the influence of preexisting fractures (i.e., artificial structural planes) on the subsequent fracturing behavior. The simulation results are supported by mechanics analysis. Results indicated that the fracture evolution is influenced by pressure magnitude on a local scale around the fracture tip and by the orientation and distribution of pore pressure on a global scale. The constant pressure in wellbore H2 can affect fracture propagation by changing the water flow direction, and the hydraulic fractures will propagate to the direction of higher local pore pressure. Furthermore, the artificial structural planes influence the stress distribution surrounding the wellbores and the hydraulic fracture evolution by altering the induced stresses around the preexisting fractures. Finally, fracture network is formed among the artificial structural planes and hydraulic fractures when multiple wells are fractured successively. This study provides valuable guidance to unconventional reservoir reconstruction designs.

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Investigation on the effect of pore pressure gradient on fracture propagation in rock materials

Cited by 7 publications

References 8 publications

Numerical Investigation on the Hydraulic Fracture Evolution of Jointed Shale

Numerical Investigation on the Hydraulic Fracture Evolution of Jointed Shale

Numerical simulation on the effect of pore pressure gradient on the rules of hydraulic fracture propagation

Numerical Investigation of Fracture Network Formation under Multiple Wells

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