Study On Hydraulic Fracture Propagation Behavior Of Deep Marine Shale

Deep marine shale gas is rich in resources,which can be used as a replacement field to maintain stable shale gas production in the future,and it’s also the main body of future production growth.The development technology of middle-shallow shale gas has been relatively mature,while the exploitation of deep shale gas is still in the initial stage,so it is of great significance to study the fracture propagation behavior of deep marine shale.Firstly,based on the new planar 3D fracturing model,the influences of different construction techniques and formation parameters on the 3D fracture propagation morphology are analyzed according to the geological characteristics of deep marine shale.The induced stress field model of hydraulic fracture was established and the influence of main controlling factors on the degree of stress inversion was analyzed.The 3D propagation morphology of multistage fracture in deep marine shale reservoir is simulated.It is found that,due to the characteristics of high elastic modulus,Poisson’s ratio and high horizontal stress difference,deep marine shale will lead to insufficient propagation of fracture width and length,difficult to improve fracture conductivity,and stress reversal trend is not obvious,difficult to steer fractures and other problems.With the increase of the number of clusters,the fracture length,width and height of each cluster decrease to some extent.Simultaneous fracturing of multiple clusters will present the phenomenon that the fracture length and width on both sides are short and narrow in the middle,leading to the increase of fracture heterogeneity.With the increase of cluster spacing,the effect of induced stress induced by each fracture on adjacent fractures is weakened,and the fracture length,width and height of each cluster fracture are increased.Secondly,according to the high temperature characteristics of deep marine shale reservoir,the temperature field characterization model of the near-fracture formation was established,the influence of different construction process parameters and geological parameters on the temperature variation along the near-fracture formation was analyzed,and the three-dimensional fracture propagation morphology under different temperature differences was simulated.The results show that the formation temperature near the fracture decreases with the increase of the distance from the fracture.The formation temperature at a certain fracture position increases with the increase of formation density and specific heat capacity,but decreases with the increase of formation porosity,fracturing fluid density and specific heat capacity.With the increase of fracture fluid fracture temperature,the fracture length and width showed an upward trend,while the fracture height showed a downward trend.Compared with the three-dimensional fracture expansion morphology without considering the influence of temperature difference,the fracture length and width both decreased,while the fracture height increased.The larger the temperature difference,the more pronounced the trend.Finally,according to the rich bedding characteristics of deep marine shale reservoir,the interaction criterion of hydraulic fractures and bedding is derived,and the influence of various geological factors on the interaction between fractures and bedding is analyzed.It is found that under a certain stress difference,the greater the tensile strength of rock mass,the more easily the fractures turn to bedding propagation.Under a certain tensile strength of rock mass,the smaller the stress difference is,the more easily the fracture turns to bedding propagation.Under a certain bedding inclination β,the smaller the angle α is,the more easily fracture turns to bedding propagation.The research method in this paper can provide a certain theoretical basis for the follow-up research on fracture propagation behavior of deep shale,and the research results can provide further understanding of fracture propagation behavior of deep Marine shale.