Stress field

About: Stress field is a research topic. Over the lifetime, 11926 publications have been published within this topic receiving 226417 citations.

Numerical Investigation on Stress Shadowing in Fluid Injection-Induced Fracture Propagation in Naturally Fractured Geothermal Reservoirs

Abstract: In low permeability shale reservoirs, multi-stage hydraulic fracturing is largely used to increase the productivity by enlarging the stimulated rock volume. Hydraulic fracture created alters the stress field around it, and affects the subsequent fractures by the change of the stress field, in particular, mostly increased minimum principal stress at the area of subsequent fracturing. This is called stress shadow which accumulates as the fracturing stages advance from toe to heel. Hydraulic fractures generated in such altered stress field are shorter and compact with orientation deviating significantly from the far-field maximum horizontal stress orientation. This paper presents 2D discrete element-based numerical modeling of multi-stage hydraulic fracturing in a naturally fractured reservoir and investigates stress shadowing. The stress shadowing is tested with two different injection scenarios: constant and cyclic rate injections. The results show that cyclic injection tends to lower the effect of stress shadow as well as mitigates the magnitude of the induced seismicity. Another modeling case is presented to show how the stress shadow can be utilized to optimize a hydraulic fracture network in application to Gros Schonebeck geothermal reservoir, rather than being mitigated. The modeling demonstrated that the stress shadow is successfully utilized for optimizing the geothermal heat exchanger by altering the initial in situ stress field from highly anisotropic to less or even to isotropic.

On the anti-plane shear of an elliptic nano inhomogeneity

Abstract: The elastic field of an elliptic nano inhomogeneity embedded in an infinite matrix under anti-plane shear is studied with the complex variable method. The interface stress effects of the nano inhomogeneity are accounted for with the Gurtin–Murdoch model. The conformal mapping method is then applied to solve the formulated boundary value problem. The obtained numerical results are compared with the existing closed form solutions for a circular nano inhomogeneity and a traditional elliptic inhomogeneity under anti-plane. It shows that the proposed semi-analytic method is effective and accurate. The stress fields inside the inhomogeneity and matrix are then systematically studied for different interfacial and geometrical parameters. It is found that the stress field inside the elliptic nano inhomogeneity is no longer uniform due to the interface effects. The shear stress distributions inside the inhomogeneity and matrix are size dependent when the size of the inhomogeneity is on the order of nanometers. The numerical results also show that the interface effects are highly influenced by the local curvature of the interface. The elastic field around an elliptic nano hole is also investigated in this paper. It is found that the traction free boundary condition breaks down at the elliptic nano hole surface. As the aspect ratio of the elliptic hole increases, it can be seen as a Mode-III blunt crack. Even for long blunt cracks, the surface effects can still be significant around the blunt crack tip. Finally, the equivalence between the uniform eigenstrain inside the inhomogeneity and the remote loading is discussed.

Earthquake Triggering along the Xianshuihe Fault Zone of Western Sichuan, China

Abstract: Western Sichuan is among the most seismically active regions in southwestern China and is characterized by frequent strong (M ≥ 6.5) earthquakes, mainly along the Xianshuihe fault zone. Historical and instrumental seismicity show a temporal pattern of active periods separated by inactive ones, while in space a remarkable epicenter migration has been observed. During the last active period starting in 1893, the sinistral strike–slip Xianshuihe fault of 350 km total length, was entirely broken with the epicenters of successive strong earthquakes migrating along its strike. This pattern is investigated by resolving changes of Coulomb failure function (ΔCFF) since 1893 and hence the evolution of the stress field in the area during the last 110 years. Coulomb stress changes were calculated assuming that earthquakes can be modeled as static dislocations in an elastic halfspace, and taking into account both the coseismic slip in strong (M ≥ 6.5) earthquakes and the slow tectonic stress buildup associated with major fault segments. The stress change calculations were performed for faults of strike, dip, and rake appropriate to the strong events. We evaluate whether these stress changes brought a given strong earthquake closer to, or sent it farther from, failure. It was found that all strong earthquakes, and moreover, the majority of smaller events for which reliable fault plane solutions are available, have occurred on stress–enhanced fault segments providing a convincing case in which Coulomb stress modeling gives insight into the temporal and spatial manifestation of seismic activity. We extend the stress calculations to the year 2025 and provide an assessment for future seismic hazard by identifying the fault segments that are possible sites of future strong earthquakes.

Stress: Perspectives and Processes

Abstract: Stress and health an historical view of the stress field frameworks for studying stress phenomena the variables involved in the stress process the role of stress in health and illness a cognitive-phenomenological perspective.

On the Three-Dimensional Theory of Cracked Plates

Abstract: This paper discusses a method for solving three-dimensional mixed-boundary-value problems which arise in elastostatics. Specifically, the method is applied to a plate of finite thickness which contains a finite, through the thickness, line crack. The analysis shows that (a) in the interior of the plate only the stresses sigma-x, sigma-y, sigma-z, and tau-xy are singular of order 1/2; (b) in the vicinity of the corner point all the stresses are singular of order ((1/2) plus 2 nu); as the thickness h approaches infinity the plane strain solution is recovered and; (d) as nu approaches o the plane stress solution is recovered. Finally, it is found that in the neighborhood of the corner points, even though the displacements are singular for certain values of the Poisson's ratios, the derived stress field satisfies the condition of local finite energy. /Author/