A Novel Hydraulic Fracturing Model Fully Coupled With Geomechanics and Reservoir Simulation

Abstract

Unconventional fracturing techniques, such as high-rate waterfracs, waterflooding, or steam stimulation, produced water and cuttings reinjection, CO 2 sequestration, and coalbed methane stimulation, are difficult to model because of strong interactions among the fracturing process, geomechanical changes in the porous media, and reservoir fluid flow. The resulting strong poroelastic/thermoelastic effects, permeability and porosity changes, and possible rock failure make current conventional fracturing models inadequate in such circumstances. Therefore, it is necessary to develop new models that include all of these mechanisms and that are capable of conducting integrated data analysis.This paper presents a new fracturing model with all of these mechanisms included. The model fully couples fracture mechanics with reservoir and geomechanics simulation. This methodology allows us to model fracture initiation and propagation, post-frac multiphase cleanup in the reservoir and fracture and pre-frac and post-frac well performance in a changing stress and pressure environment, all within the same system.The model couples a 3D finite element geomechanics model with a conventional 3D finite difference reservoir flow simulator. The geomechanics module implicitly models fracture propagation via displacements on the fracture face. The flow and geomechanics/fracturing are coupled in an iterative manner that is equivalent to full coupling of geomechanical and reservoir flow modeling. The 3D (planar) fracture geometry and the pressures in it are the common dynamic boundary conditions for the flow and stress modules. The new iterative process yields smooth fracture propagation, and the model has been tested on classical fracturing problems.A field example demonstrates the validity and advantages of the approach. To illustrate the model capabilities, we model a waterfrac stimulation performed in Bossier tight-gas sands. The model results show that the model is capable of matching complex injection history and calibrating the stress-dependency of formation permeability.

Ways to Minimize Water Usage in Engineered Geothermal Systems

“…The ability to maintain an acceptable level of purity of the working fluid and the heating fluid needs to be understood, giving engineers the tools to place limits on contaminant level based on performance parameters and risk assessment (Bruel 2002). Robust systems that have flexibility in fluid purity combined with materials developed to handle high salinity flows may allow non-potable or brackish water to be used for heat extraction, as has been done for shale gas recovery and hydraulic fracturing (Ji, Settari et al 2009), reducing the stress on potable and fresh water resources.…”

Fracture Propagation, Fluid Flow, and Geomechanics of Water-Based Hydraulic Fracturing in Shale Gas Systems and Electromagnetic Geophysical Monitoring of Fluid Migration

“…Then, considering vertical fracture propagation, we can simplify the node-splitting scheme into a method that updates outer boundary conditions (i.e., from the Dirichlet condition to the Neumann condition, as shown in Fig. 3 (right)), not introducing an internal boundary (this scheme was previously used in Ji et al (2009)). We then can reduce computational resources and code management effort.…”

“…Even though such models can provide numerical efficiency and reduce computational cost, full coupling in 3D between flow and geomechanics is required for rigorous modeling of fracture propagation and more reliable risk assessment. Recently, Ji et al (2009) and Dean and Schmidt (2009) performed numerical modeling of full 3D hydraulic fracturing in the context of coupled flow and geomechanics. Furthermore, Kim and Moridis (2013) incorporated the double porosity approach as well as simultaneous tensile and shear failure.…”

Investigation of possible wellbore cement failures during hydraulic fracturing operations

“…Permeability is also a strong function of the failure status, because material failure increases permeability significantly by several orders. For example, hydraulic fracturing increases nanodarcy of the reservoir permeability to an order of darcy, creating opening the fracture (Ji et al, 2009). …”