Saeed Salimzadeh

Fully Coupled XFEM Model for Flow and Deformation in Fractured Porous Media with Explicit Fracture Flow

AbstractA hydromechanical model with explicit fracture flow is presented for the fully coupled analysis of flow and deformation in fractured porous media. Extended finite-element method (XFEM) was utilized to model the fracture discontinuity in the two-dimensional plane-strain mechanical model. Two flow models, a one-dimensional laminar flow within the fracture and a two-dimensional Darcy flow through porous media, were considered. The flow domains were coupled through a mass exchange term (leak-off) accounting for discontinuous Darcy flow velocity across the fracture. Particular attention was given to the coupling of the flow domains with the mechanical model. Spatial and temporal discretization was achieved using the standard Galerkin method and the finite-difference technique, respectively. Unlike the successive coupled models in which the results of the mechanical model are used to update the fracture flow model and vice versa, the fully coupled hydromechanical formulation is solved simultaneously. Th...

Three-Dimensional Numerical Model for Double-Porosity Media with Two Miscible Fluids Including Geomechanical Response

AbstractThe finite-element formulation of a coupled fluid flow and geomechanics for two-phase fluid flow through fractured porous media are presented. Two porosities, pores and fractures, and five phases are introduced. The two fluids are taken as wetting and nonwetting. The governing equations are derived based on the theory of poroelasticity, the effective stress principle, and the balance equations of mass and momentum, taking into account the solubility of nonwetting fluid into wetting fluid. Spatial and temporal discretization of the governing equations has been realized through the Galerkin method and the finite-difference technique, respectively. A three-dimensional numerical code has been developed and validated based on previously published data. Various applications of the model have been demonstrated through three field-scale examples.

Consolidation of unsaturated lumpy clays

Coupled flow-deformation analysis of consolidation in unsaturated lumpy clays is presented. The governing differential equations are discretised using the Galerkin method and the finite difference technique for space and time, respectively. Particular attention is given to the cross coupling coefficients arising from the pore scale deformation compatibility between micro and macro voids. Two examples are analysed: a one-dimensional soil column, and a strip footing acting on a two-dimensional medium of lumpy clay. A range of sensitivity analyses are preformed using different values of degree of saturation and volume fraction of macro voids. All results are carefully analysed and salient features of consolation in lumpy clays are highlighted. The significance of the cross coupling coefficients in the numerical results obtained are also examined.

Finite-Element Modeling of the Growth and Interaction of Hydraulic Fractures in Poroelastic Rock Formations

Abstract This chapter presents a finite element–based method for simulating the hydraulic fracturing process in porous rocks. The finite-element method is used to compute the mechanical deformation of the rock, and it accounts for the effects of poroelasticity, thermoelasticity, and fluid flow in both the fractures and the rock matrix, in a fully coupled manner. The fractures are represented in the mesh as fully three-dimensional objects, with evolving local apertures that are computed as part of the solution. Fracture growth is modeled using stress intensity factors, and the direction and rate of growth is evaluated individually at each fracture tip node. Specifically, the direction of fracture growth at each tip node is governed by the maximum circumferential stress criterion, and the extent of fracture growth is approximated using a Paris-type growth law. Contact between opposing fracture surfaces is handled using a gap-based augmented Lagrangian approach. Fracture growth is computed independently of the underlying mesh, and the fracture path is not constrained to follow the mesh. Instead, a new mesh is constructed after each time step, if the fracture has grown in that time step. This numerical framework is then applied to the growth of multiple hydraulic fractures in impermeable and permeable formations to investigate the effects of matrix permeability, matrix poroelasticity, and temperature contrast (between the rock and the injected fluid) on the growth and interaction of hydraulic fractures.

Experimental and Numerical Study of the Stability of Radially Jet Drilled Laterals in Chalk Reservoirs

One way of increasing hydrocarbon production is to extend the lateral reach of the wellbore by lateral holes. The approach bypasses the potentially damaged near-wellbore area, thus improving the productivity of the well and enhancing the swept area. This has become feasible by a new technology called Radial Jet Drilling (RJD) technology, in which, relatively long, small-diameter laterals can be jetted radially from the main wellbore. However, the success of this technology very much depends on the long-term stability of the laterals under dynamic reservoir conditions. The objective of the present work is to evaluate which geometry of the lateral hole provides the most stable production as well as to define the limit of the rock material properties that withstands lateral hole collapse. To do so, a set of advanced laboratory experiments are performed on two distinct outcrop chalks from Austin (US) and Welton (UK) that are analogues to the reservoir chalk in the North Sea. Based on rock mechanics and jetting experiments, numerical modelling of jetted hole behaviour is implemented and analysed for the stability in the finite element (FE) software Abaqus.

Stability Analysis of Radial Jet Drilling in Chalk Reservoirs

In this work, the stability of Radial Jet Drilled (RJD) laterals in both injection and production wells are studied. Thermo-elastoplastic and poro-elastoplastic finite element models are developed in a robust software (ABAQUS) and used to simulate the injector and producer laterals. Several cases with varying in situ stresses are considered. The temperature and pressure gradients of 60°C and 10 MPa are applied. The simulation results show that both hydraulic and thermal stresses can affect the stability of a lateral by increasing the plastic region near the lateral. The thermal effect increases the plastic region around the producer, while the hydraulic effect increases the plastic region and its magnitude at the producer.