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

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Abstract
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.
Funding Information
  • Special Project of 2019 Plan for the Introduction of High-level Scientific and Technological Talents in Development Zone of Lvliang City (2019102)
  • Transformation of Scientific and Technological Achievements Programs of Higher Education Institutions in Shanxi (2020CG050)
  • Science and Technology Project of Lvliang City in 2019 (Pressure relief and permeability (GXZDYF2019080)
  • School-Level Teaching Reform and Innovation Projects of Luliang University in 2020 (JXGG202039)

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