Papers by Keyword: Induced Stress

Abstract: The continental shale of Yanchang Formation in Ordos Basin is in complex facies. Being high in mud and low in brittle mineral, the reservoir quality is poor. Therefore multi-stage fracture stimulation has been applied there in horizontal wells. The fracture interval in horizontal well is a critical parameter and it has a great influence on the fracture interaction. Since the fracture interaction can directly determine the extent to which the stimulated reservoir volume (SRV) expands, its most necessary to study the mechanism of the effect. For this, a mathematical model based on elastic mechanics would be given. By using this model, we analyzed the influences on the fracturing work. An analysis of field data from Yanchang Oilfield shows that proper fracture interval can take good advantage of the fracture interaction so as to reduce the horizontal differential principal stress. However, exceeded fracture interaction may raise the fracture pressure. So the effect must be controlled by optimizing the fracture interval. To optimize the fracture interval, the results can be used to instruct the application of multi-stage fracture stimulation.

Abstract: Reorientation fracturing of post-phase development of conventional low productive formations and pro-phase development of unconventional reservoirs such as shale gas plays and coalbed methane formations has been and will always be of considerable significance for oil/gas development. Conventional reorientation trajectory prediction results cannot exactly match the field actual fracture mapping propagation ones. Based on the discrepancy, this research focuses on the dominant factors influencing re-fracture propagation path and re-recognizes the disturbed stress field. Taking advantage of the proposed Principle of Maximum Circumferential Tensile Stress, the fracture propagation path is numerically modeled, which is more in conformity with the fracture mapping compared with the conventional one. Finally, the importance of proper estimation of reorientation fracturing propagation trajectory is analyzed.

Abstract: In accordance with equilibrium differential equations and compatibility conditions of deformation, the partial differential equation of induced stress is achieved for elastic surrounding rocks of tunnels and chambers of round section. By method of the superposition principle, elastic analytical solutions of induced stress of surrounding rocks is derived from the partial differential equation, which is based on stress functions and boundary conditions.

Abstract: In order to accurately simulate the distribution of complicated in-situ stress filed of reservoir using the method of numerical simulation. In this paper, firstly, we have established the injection-production pore pressure model around refracturing well using potential additive principle; secondly, we have established primary fracture induced stress field model, considering that the weakly compressible fluid is filled with the injection-production primary fracture and introducing the elastic coefficient of fluid; finally, we have calculated the distribution of stress around a production well using ANASYS software. The calculating result is accurate and agrees well with practical ones. This method can solve the problem of calculating complicated in-situ stress filed using analytical method, and provides a new method for the subsequent study of stress field.

Abstract: In order to accurately describe the impact is on the redirection of the secondary fracturing caused by stress field distribution of the reservoir , according to the superposition principle of the potential, builds the pore pressure induced model around refracturing wells ; introduces the fluid influence factor coefficient , builds initial artificial crack induced stress field model. Finally, the three stress applies the linear superposition principle .Obtaining the total stress field before the refracturing , provides a reliable theoretical calculation basis for the induced stress calculation

Abstract: Explosive welding of two dissimilar metallic sheets is accomplished by the exhaustive deformation owing to high pressure and high temperature created at the collision place. This study addresses the analytical estimation of the dissipation of potential energy of the explosive initially to mechanical energy and then to thermal energy in dissimilar Copper – Low carbon steel combination. The emanating pressure in the region of detonation front is transmitted to flyer surface as compressive stress wave and a reflective tensile wave is generated at the bottom surface of the flyer. A dilational wave and shear wave are generated. As the flyer plate moving with the transmitted wave collides with the parent, the available kinetic energy is converted into thermal energy to produce adequate heat to induce plastic deformation thus resulting into a strong metallurgical bond.