Geomechanical Modeling of Stress and Fracture Distribution during Contractional Fault-Related Folding

Abstract

Understanding and predicting the distribution of fractures in the deep tight sandstone reservoir are important for both gas exploration and exploitation activities in Kuqa Depression. We analyzed the characteristics of regional structural evolution and paleotectonic stress setting based on acoustic emission tests and structural feature analysis. Several suites of geomechanical models and experiments were developed to analyze how the geological factors influenced and controlled the development and distribution of fractures during folding. The multilayer model used elasto-plastic finite element method to capture the stress variations and slip along bedding surfaces, and allowed large deformation. The simulated results demonstrate that this novel Quasi-Binary Method coupling composite failure criterion and geomechanical model can effectively quantitatively predict the developed area of fracture parameters in fault-related folds. High-density regions of fractures are mainly located in the fold limbs during initial folding stage, then gradually migrate from forelimb to backlimb, from limbs to hinge, from deep to shallow along with the fold uplift. Among these factors, the fold uplift and slip displacement along fault have the most important influence on distributions of fractures and stress field, meanwhile the lithology and distance to fault have also has certain influences. When the uplift height exceeds approximately 55 percent of the total height of fold the facture density reaches a peak, which conforms to typical top-graben fold type with large amplitude and high-density factures in the top. The overall simulated results match well with core observation and FMI results both in the whole geometry and fracture distribution.

Mechanical Response of Shallow Crust to Groundwater Storage Variations: Inferences From Deformation and Seismic Observations in the Eastern Southern Alps, Italy

“…The transformation of rainfall into GWS raises the question on how the aquifer connected to the BVBT fracture is recharged. It is likely that the water feeding the fracture mainly comes from the top of the MCCV mountain chain: the higher fracture density at the hinge zone of the anticline (e.g., Feng & Gu, 2017) and the well‐developed epikarst in the exposed rock formations (Maiolica and Rosso Ammonitico) suggest the presence of an epikarst circulation on the top of MCCV chain (Klimchouk & Sauro, 1996). The combined effect of the epikarst and the presence of a shallow, low permeable layer (the Fonzaso formation, located at ∼200 m of depth from the surface) facilitates the rapid infiltration of precipitation water and its convergence flow toward the back thrust, following the northward inclination of rock layers and stratification.…”

Mechanical Response of Shallow Crust to Groundwater Storage Variations: Inferences from Deformation and Seismic Observations in the Eastern Southern Alps, Italy

“…The transformation of rainfall into GWS raises the question on how the aquifer connected to the BVBT fracture is recharged. It is likely that the water feeding the fracture mainly comes from the top of the MCCV mountain chain: the higher fracture density at the hinge zone of the anticline (e.g., Feng and Gu, 2017) and the well-developed epikarst in the exposed rock formations (Maiolica and Rosso Ammonitico) suggest the presence of an epikarst circulation on the top of MCCV chain (Klimchouk and Sauro, 1996). The combined effect of the epikarst and the presence of a shallow, low permeable layer (the Fonzaso formation, located at ~200 m of depth from the surface) facilitates the rapid infiltration of precipitation water and its convergence flow toward the back thrust, following the northward inclination of rock layers and stratification.…”