Showing papers by "Maurice B. Dusseault published in 2010"

Fully Coupled THMC Modeling of Wellbore Stability with Thermal and Solute Convection Considered

Abstract: Wellbore stability analysis is an important topic in petroleum geomechanics. Analytical and numerical analysis of wellbore stability involves the study of interactions among pressure, temperature and chemical changes, and the mechanical response of the rock, a coupled thermal–hydraulic–mechanical–chemical (THMC) process. Thermal and solute convection have usually been overlooked in numerical models. This is appropriate for shales with extremely low permeability, but for shales with intermediate and high permeability (e.g., shale with a disseminated microfissure network), thermal and solute convection should be considered. The challenge of considering advection lies in the numerical oscillation encountered when implementing the traditional Galerkin finite element approach for transient advection–diffusion problems. In this article, we present a fully coupled THMC model to analyze the stress, pressure, temperature, and solute concentration changes around a wellbore. In order to overcome spurious spatial temperature oscillations in the convection-dominated thermal advection–diffusion problem, we place the transient problem into an advection– diffusion-reaction problem framework, which is then efficiently addressed by a stabilized finite element approach, the subgrid scale/gradient subgrid scale method (SGS/GSGS).

Geomechanics Effects in Thermal Processes for Heavy-oil Exploitation

Abstract: THEOR processes, such as steam injection, generate large changes in amplitude and travel time in the complicated signature of a reservoir’s seismic response. Conventionally, pressure, temperature, and saturation changes induced by thermal recovery are examined to study their complex and often counteracting effects on the seismic attributes of the reservoir and bounding rocks. The effects of geomechanical changes in stress and stiffness are less often considered, though they may dominate seismic property changes. Thus, seismic data interpretation to deconvolve in situ rock properties is non-unique and it also varies with time as these physical parameters change with the maturity of the THEOR process. A fuller understanding of the effects of these changes will lead to better interpretation of changes of seismic attributes, hence better project management.

Process for sequestration of fluids in geological formations

Abstract: A process for geo-sequestration of a water-soluble fluid includes selection of a target water-laden geological formation bounded by an upper formation of low permeability, providing an injection well into the formation and injecting the fluid into the injection well under conditions of temperature, pressure and density contrast selected to cause the fluid to enter the formation and rise within the formation. This generates a density-driven convection current of formation water which promotes enhanced mixing of the water-soluble fluid with formation water.

Fully Coupled Numerical Modelling of Ground Surface Uplift in Steam Injection

Abstract: In enhanced oil recovery, steam injection involves high stresses, pressures, temperatures and volume changes. Traditional reservoir simulation fails to predict associated transient ground surface movements because it does not consider coupled geomechanical effects. We present a fully-coupled, thermal half- space model using a hybrid DDFEM method, in which a simultaneous finite element method (FEM) solution is adopted for the reservoir and the surrounding thermally affected zone, and a displacement discontinuity (DD) method used for the elastic, non-thermal zone. This approach provides transient ground surface movements in a natural manner.

Natural Cross-flow Rate Modeling in Complex Reservoirs

Abstract: During fluid injection into a complex reservoir, different pressure gradients are generated in the sandface of each layer because of differences in reservoir properties such as permeability, compressibility, thickness, porosity and depletion. Upon shut-in, these differences cause flow from high-pressure layers, usually of lower permeability, to low-pressure layers, usually of higher permeability, a process known as natural cross-flow. Cross-flow may lead to sanding problems [e.g. Santarelli et al. 1998]. In this study, one-dimensional (axisymmetric) natural cross-flow in a complex reservoir is simulated using a finite difference approach. The problem is solved for multiple layers with different permeabilities, separated by impermeable layers. In the paper we emphasize various means of establishing input parameters and apply the model to several well-documented field cases, demonstrating its capacity to predict accurately measured cross-flow.