This paper shows that numerical upscaling of permeability and elastic stiffness tensors can be applied to a very heterogeneous and deformable reservoir system. Fluid flow in deformable porous medium is a multiphysics problem that considers flow physics and rock physics simultaneously. This problem is computationally demanding since we need to solve different types of governing equations such as the mass balance and the equilibrium equations. Numerical upscaling of the transport properties and the mechanical properties using flow and mechanics solvers will provide a coarse reservoir model that represents fine scale contribution of fluid flow and geomechanics. This would help us perform more efficient modeling and simulation of coupled flow and geomechanics in a petroleum reservoir.
Coupled flow and geomechanics play an important role in the analysis of gas-hydrate reservoirs under production. The stiffness of the rock skeleton and the deformation of the reservoir, as well as porosity and permeability, are directly influenced by (and interrelated with) changes in pressure and temperature and in fluid- (water and gas) and solid- (hydrate and ice) phase saturations. Fluid and solid phases may coexist, which, coupled with steep temperature and pressure gradients, results in strong nonlinearities in the coupled flow and mechanics processes, making the description of system behavior in dissociating hydrate deposits exceptionally complicated.
In previous studies, the geological stability of hydrate-bearing sediments was investigated using one-way coupled analysis, in which the changes in fluid properties affect mechanics within the gas-hydrate reservoirs, but with no feedback from geomechanics to fluid flow. In this paper, we develop and test a rigorous two-way coupling between fluid flow and geomechanics, in which the solutions from mechanics are reflected in the solution of the flow problem through the adjustment of affected hydraulic properties. We employ the fixed-stress split method, which results in a convergent sequential implicit scheme.
In this study of several hydrate-reservoir cases, we find noticeable differences between the results from one- and two-way couplings. The nature of the elliptic boundary value problem of quasistatic mechanics results in instantaneous compaction or dilation over the domain through loading from reservoir-fluid production. This induces a pressure rise or drop at early times (low-pressure diffusion), and consequently changes the effective stress instantaneously, possibly causing geological instability. Additionally, the pressure and temperature regime affects the various phase saturations, the rock stiffness, porosity, and permeability, thus affecting the fluid-flow regime. These changes are not captured accurately by the simpler one-way coupling. The tightly coupled sequential approach we propose provides a rigorous, two-way coupling model that captures the interrelationship between geomechanical and flow properties and processes, accurately describes the system behavior, and can be readily applied to large-scale problems of hydrate behavior in geologic media.
Kim, Jihoon (Lawrence Berkeley National Laboratory) | Yang, Daegil (Texas A&M University) | Moridis, George J. (Lawrence Berkeley National Laboratory) | Rutqvist, Jonny (Lawrence Berkeley National Laboratory)
Coupled flow and geomechanics play an important role in gas hydrate reservoirs because the stiffness of the rock skeleton, porosity and permeability are directly influenced by changes of the fluid (water and gas) and solid (hydrate and water) phase saturations, and the deformation of the reservoir. The fluid and solid phases coexist, yielding a high nonlinearity for flow and mechanics, so the coupled problem for hydrates is exceptionally complicated.
In previous study, the stability of hydrate-bearing sediments was assessed by one-way coupled analysis, where the change of fluid properties affects mechanics, but there is no feedback from mechanics to flow. In this paper, we develop and test rigorous two-way coupling between fluid flow and mechanics, where the solutions from mechanics are used to solve the flow problem. We employ the fixed-stress split for a convergent sequential implicit scheme.
We have found noticeable differences between one- and two-way couplings for several cases. The nature of the elliptic boundary problem of quasi-static mechanics results in instantaneous compaction or dilation over the domain by loading from reservoir fluid production. This yields the pressure rise-up or drop at early time (low pressure diffusion), which changes the effective stress instantaneously and geological instability may occur. Also, the change of pressure or temperature affects the solid saturation, rock stiffness, porosity, and permeability fields, changing the fluid flow regime. These behaviors cannot be captured by one-way coupling.
In conclusion, we developed, verified, and demonstrated the applicability of the tightly coupled sequential approach. It provides a rigorous two-way coupled simulator which is ready to be applied to large scale problems to hydrate-bearing sediments.
Flow in porous media highly interacts with the mechanics of surrounding porous media, which results in strongly coupled fluid flow and mechanics. For example, reservoir engineering has several issues related to coupled flow and geomechanics such as stability of borehole and surface facilities, hydraulic fracturing, reservoir compaction, heavy oil or oil sand production, CO2 sequestration, and gas hydrate production (e.g., Bagheri and Settari (2008); Merle et al. (1976); Lewis and Schrefler (1998); Kosloff et al. (1980); Freeman et al. (2009); Morris (2009); Rutqvist and Moridis (2009)). Hydrate reservoirs are considered as potentially substantial future energy resources due to its huge quantity of hydrocarbon gas hydrates (Moridis, 2003). Coupled fluid flow and geomechanics play an important role in hydrate reservoirs because the change of fluid phases directly affect the stiffness of the solid skeleton, and the deformation of the reservoirs changes porosity and permeability. The geomechanical stability of hydrate-bearing sediments (HBS) also affects the integrity and stability of the wellbore due to the hydrate formation and dissociation, which interact with mechanics (Rutqvist and Moridis, 2009).
This paper presents the experimental and simulation study of E-Beam hydrocarbon upgrading process which shows the efficiency of E-Beam process and radiation energy transfer mechanism for single and multiphase fluid. Society's growing demands for energy results in rapid increase in oil consumption and motivates conversion of unconventional resources to conventional resources. There are enormous amounts of heavy oil reserves in the world but the lack of cost effective technologies either for extraction, transportation, or refinery upgrading hinders the development of heavy oil reserves. The traditional problem of conventional heavy oil upgrading is that it takes large amounts of thermal energy and expensive chemicals or catalysts to upgrade. Using E-Beam technology we may lower the energy requirement and reduce the use of specific chemicals or catalysts.
The design of facilities can be simpler and will contribute to lowering the costs of transportation and processing of heavy oil and bitumen.
A theoretical aquifer model predicts time-lapse mineral carbonation and isotope fractionation of injected CO2 in sediment. Geologic sequestration of CO2 has become one of the promising ways to reduce atmospheric emission of CO2 from human activity. However, the current and future effects of geologic storage after injecting CO2 are not known well. We developed a simple mathematical model based on a transport-reaction equation and calculated the abundance of carbon stable isotope in the reservoir with respect to time which allows us to predict CO2 saturation in sediment or CO2 flume distribution by ground reservoir water. These results indicate significant potential of the theoretical aquifer model for monitoring and verification of CO2 sequestration into the sediment.
Electron beam (E-Beam) heavy oil upgrading, which uses unique features of electron beam irradiation, can be a solution to minimize the critical problem of upgrading heavy oil. Enormous amounts of heavy oil reserves exist in the world, but the lack of cost-effective technologies hinders the development of heavy oil reserves. One of the critical problems of heavy oil or bitumen is that it takes large amounts of thermal energy and expensive catalysts to upgrade. E-Beam processing will allow lowering the thermal energy and sharply reduce the investment in catalysts. The design can be simpler and will contribute to lowering the production and transportation cost of heavy oil and bitumen.