0 INTRODUCTION Pressure-stress coupling(PSC)refers to the bidirectional mechanical interaction between pore pressure and in-situ stress within subsurface formations(Hillis,2000).Variations in pore pressure redistribut...0 INTRODUCTION Pressure-stress coupling(PSC)refers to the bidirectional mechanical interaction between pore pressure and in-situ stress within subsurface formations(Hillis,2000).Variations in pore pressure redistribute the stress field,while evolving stress states in turn alter pore pressure.This reciprocity,governed by poroelasticity and multiphysics interactions,underlies a wide spectrum of geomechanical processes,including fracture initiation,fluid migration,reservoir evolution,and fault slip or seismicity(Xu et al.,2020).Conventional theories often treat pressure and stress as independent variables.展开更多
The fracture behavior of natural fracture in the geological reservoir subjected to filling property,affects the crack initiation and propagation under stress perturbation.Partial filling flaws were intermediate betwee...The fracture behavior of natural fracture in the geological reservoir subjected to filling property,affects the crack initiation and propagation under stress perturbation.Partial filling flaws were intermediate between open fractures and filled fractures,the fracture response may be worth exploring.In this work,the effect of the filling property of sandstone with partial filling flaws on the fracture behavior was systematically investigated based on three-point bending tests and the numerical approach of discrete element method(DEM).In the laboratory,semi-circular three-point bending tests were carried out with partial filling flaws of various filling strengths.Based on this,numerical simulations were used to further investigate the effect of the filling ratio and the inclination of the partial filling flaw on the mechanical and fracture responses,and the effect of the partial filling flaw under mixed-mode loading on the fracture mechanism was elucidated coupled with acoustic emission(AE)characteristics.The obtained results showed that the increase in filling strength and filling ratio of partial filling flaw led to an increase in peak strength,with a decreasing trend in peak strength with the inclination of partial filling flaw.In terms of crack propagation pattern,the increasing filling strength of the partial filling flaw induced the transformation of the fracture mechanism toward deflection,with a tortuosity path,while the filling ratio and inclination of partial filling flaw led to fracture mechanism change from deflection to penetration and attraction,accompanied with a larger AE event source in filler.Accordingly,the b-value based on the Gutenberg-Richter equation fluctuated between 5 and 4 at low filling ratio and inclination and remained around 5 at high filling ratio and inclination of partial filling flaw.Related results may provide an application prospective for reservoir stimulation using the natural fracture system.展开更多
Triaxial testing serves as a fundamental method for evaluating the elastic and strength properties of rocks,crucial for developing accurate 3D geomechanical models.This paper presents a novel method for determining st...Triaxial testing serves as a fundamental method for evaluating the elastic and strength properties of rocks,crucial for developing accurate 3D geomechanical models.This paper presents a novel method for determining strength parameters by incorporating the dependence of uniaxial compressive strength(UCS)on P-wave velocity into the Hoek-Brown criterion.Additionally,a new approach is introduced to process triaxial test data efficiently using Python libraries such as SciPy,NumPy,Matplotlib,and Pandas.Furthermore,the paper addresses challenges in determining elastic parameters through triaxial testing.A Python script is developed to automate the calculation of elastic modulus and Poisson's ratio,over-coming subjectivity in selecting the linear portion of stress-strain curves.The script optimally identifies the linear region by minimizing the fit error with appropriate constraints,ensuring a more objective and standardized approach.The proposed methodologies are demonstrated using limestone specimens from Central Asian gas fields.These innovations offer faster,more reliable results,reducing error and enhancing the comparability of analyses in geomechanics,with potential applications across various geological settings.展开更多
基金supported by the National Natural Science Foundation of China(Nos.U24B6002,42488101)the Key R&D Program of Shandong Province,China(No.2024CXPT076)the Independent innovation research program of China University of Petroleum(East China)(No.21CX06001A)。
文摘0 INTRODUCTION Pressure-stress coupling(PSC)refers to the bidirectional mechanical interaction between pore pressure and in-situ stress within subsurface formations(Hillis,2000).Variations in pore pressure redistribute the stress field,while evolving stress states in turn alter pore pressure.This reciprocity,governed by poroelasticity and multiphysics interactions,underlies a wide spectrum of geomechanical processes,including fracture initiation,fluid migration,reservoir evolution,and fault slip or seismicity(Xu et al.,2020).Conventional theories often treat pressure and stress as independent variables.
基金supported by the National Key R&D Program of China(Grant No.2022YFE0128300).
文摘The fracture behavior of natural fracture in the geological reservoir subjected to filling property,affects the crack initiation and propagation under stress perturbation.Partial filling flaws were intermediate between open fractures and filled fractures,the fracture response may be worth exploring.In this work,the effect of the filling property of sandstone with partial filling flaws on the fracture behavior was systematically investigated based on three-point bending tests and the numerical approach of discrete element method(DEM).In the laboratory,semi-circular three-point bending tests were carried out with partial filling flaws of various filling strengths.Based on this,numerical simulations were used to further investigate the effect of the filling ratio and the inclination of the partial filling flaw on the mechanical and fracture responses,and the effect of the partial filling flaw under mixed-mode loading on the fracture mechanism was elucidated coupled with acoustic emission(AE)characteristics.The obtained results showed that the increase in filling strength and filling ratio of partial filling flaw led to an increase in peak strength,with a decreasing trend in peak strength with the inclination of partial filling flaw.In terms of crack propagation pattern,the increasing filling strength of the partial filling flaw induced the transformation of the fracture mechanism toward deflection,with a tortuosity path,while the filling ratio and inclination of partial filling flaw led to fracture mechanism change from deflection to penetration and attraction,accompanied with a larger AE event source in filler.Accordingly,the b-value based on the Gutenberg-Richter equation fluctuated between 5 and 4 at low filling ratio and inclination and remained around 5 at high filling ratio and inclination of partial filling flaw.Related results may provide an application prospective for reservoir stimulation using the natural fracture system.
文摘Triaxial testing serves as a fundamental method for evaluating the elastic and strength properties of rocks,crucial for developing accurate 3D geomechanical models.This paper presents a novel method for determining strength parameters by incorporating the dependence of uniaxial compressive strength(UCS)on P-wave velocity into the Hoek-Brown criterion.Additionally,a new approach is introduced to process triaxial test data efficiently using Python libraries such as SciPy,NumPy,Matplotlib,and Pandas.Furthermore,the paper addresses challenges in determining elastic parameters through triaxial testing.A Python script is developed to automate the calculation of elastic modulus and Poisson's ratio,over-coming subjectivity in selecting the linear portion of stress-strain curves.The script optimally identifies the linear region by minimizing the fit error with appropriate constraints,ensuring a more objective and standardized approach.The proposed methodologies are demonstrated using limestone specimens from Central Asian gas fields.These innovations offer faster,more reliable results,reducing error and enhancing the comparability of analyses in geomechanics,with potential applications across various geological settings.
