Browsing by Subject "Stress reorientation"
Now showing 1 - 2 of 2
- Results Per Page
- Sort Options
Item A comprehensive study on three-dimensional stress evolution in unconventional reservoirs and implications for infill drilling and completion(2021-08-12) He, Jia Joanna; Sepehrnoori, Kamy, 1951-With increasing energy demand around the globe comes an increase in infill well drilling activities. Ideally, infill wells are placed in the undrained region of the unconventional reservoir, producing from where the horizontal parent wells were unable to produce. Geomechanics play a critical role in infill well operations, because production alters the initial in-situ stresses abiding to the theory of poroelasticity, and the change will inevitably impact child fracture growth and hydraulic fracturing efficiency. Despite the numerous existing literature on the topic of poroelastic stress change and infill well strategies, numerical studies on the effects of well and fracture designs on stress change are limited, and it is even more rare to seek literature regarding the stochastic of hydraulic fracture and natural fracture distributions when modeling stress evolution. Therefore, the purpose of this research is to provide a comprehensive sensitivity study on the most prominent well and fracture designs, and the effects of stochastic fracture property distributions on stress reorientation in unconventional reservoirs. A three-dimensional (3D) reservoir model is built with fluid flow and geomechanics iteratively coupled. The first part of this study characterized hydraulic fractures using the local grid refinement (LGR) approach, and the infill region is in between a pair of horizontal wells. Effects of well spacing, minimum bottom-hole pressure (BHP), and cluster spacing on stress reorientation are investigated. Stress evolution in space and time are observed, as well as stress reversal at the infill region. The stress reversal onset time is most susceptible to changes in the BHP, followed by cluster spacing and well spacing. The second and third parts of this study involve a multi-layer reservoir, and the hydraulic and natural fractures are characterized by the Embedded Discrete Fracture Model (EDFM). The parent well is in the middle layer of the reservoir, and there are two prospective locations for the infill well, where one is in the top layer, and another in the producing layer. Hydraulic fracture properties and natural fracture properties are stochastically distributed in the effort to identify and quantify their impacts on in-situ stress evolution. The simulation results show that stress reversal only occurred in the producing layer, while stress reorientation reached a peak value in the top layer before commencing to return to its initial state. The stochastic distributions of hydraulic fracture half-length and height demonstrate highest level of influence on stress reorientation in the producing and top layers, respectively. Natural fractures in general accelerates stress rotation; natural fracture length presents to be the most influential property on stress change. Specific infill well fracturing times are provided on a case-by-case scenario. Overall, this work is based on the theory of poroelasticity in the hope to extend on the current knowledge of flow-induced stress alteration. It provides a detailed investigation on several factors that will affect in-situ stresses. The highlights of the simulation outputs should shed light on infill well strategiesItem A new reservoir scale model for fracture propagation and stress reorientation in waterflooded reservoirs(2016-12) Bhardwaj, Prateek; Sharma, Mukul M.It is now well established that poro-thermo-elastic effects substantially change the magnitude and orientation of in-situ stresses. Fractures induced in injectors during water injection for waterflooding or produced water disposal have a profound impact on waterflood performance. These effects, coupled with injectivity decline due to plugging caused by injected particles, lead to permeability reduction, fracture initiation and propagation. Models are available for fracture propagation in single injection wells and single layered reservoirs that account for these effects. However, the impact of fluid injection and production on fracture growth in multiple wells and multi-layered reservoirs with competing fractures, has not been systematically modelled at a field scale. In this work, a three-dimensional, two-phase flow simulator with iteratively coupled geomechanics has been developed and applied to model the dynamic growth of injection-induced fractures. The model is based on a finite volume implementation of the cohesive zone model for arbitrary fracture propagation coupled with two-phase flow. A dynamic filtration model for permeability reduction is employed on the fracture faces to incorporate effects of internal damage and external filter cake build-up due to the injection of suspended solids and oil droplets. All physical phenomena are solved in a single framework designed for multi-well, field-scale simulation. The pressure distribution, saturation profile, thermal front, mechanical displacements and reservoir stresses are computed as fluids are injected and produced from the reservoir. Simulation results are discussed with single as well as multiple fractures propagating. Stress reorientation due to poroelastic, thermoelastic and mechanical effects is examined for the simulated cases. The orientation of the fractures is controlled primarily by the orientation of the stresses, which in turn depends on the pattern of wells and the rates of injection and production. The sweep efficiency of the waterflood is found to be impacted by the rate of growth of injection-induced fractures. Heterogeneities in multi-layered reservoirs strongly govern the expected vertical sweep and fluid distribution, which impacts the cumulative oil recovery. This is the first time a formulation of multiphase flow in the reservoir has been coupled with dynamic fracture propagation in multiple wells induced by solids plugging while including poro-thermo-elasticity at the reservoir scale. The model developed in this work can be used to simulate multiple water injection induced fractures, determine the reoriented stress state to optimize the location of infill wells and adjust injection well patterns to maximize reservoir sweep.