Τίτλος:
Reservoir Modeling for Flow Simulation by Use of Surfaces, Adaptive
Unstructured Meshes, and an Overlapping-Control-Volume Finite-Element
Method
Περίληψη:
We present new approaches to reservoir modeling and flow simulation that
dispose of the pillar-grid concept that has persisted since reservoir
simulation began. This results in significant improvements to the
representation of multiscale geologic heterogeneity and the prediction
of flow through that heterogeneity. The research builds on more than 20
years of development of innovative numerical methods in geophysical
fluid mechanics, refined and modified to deal with the unique challenges
associated with reservoir simulation.
Geologic heterogeneities, whether structural, stratigraphic,
sedimentologic, or diagenetic in origin, are represented as discrete
volumes bounded by surfaces, without reference to a predefined grid.
Petrophysical properties are uniform within the geologically defined
rock volumes, rather than within grid cells. The resulting model is
discretized for flow simulation by use of an unstructured, tetrahedral
mesh that honors the architecture of the surfaces. This approach allows
heterogeneity over multiple length-scales to be explicitly captured by
use of fewer cells than conventional corner-point or unstructured grids.
Multiphase flow is simulated by use of a novel mixed finite-element
formulation centered on a new family of tetrahedral element types,
P-N(DG)-PN+1,which has a discontinuous Nth-order polynomial
representation for velocity and a continuous (order N +1) representation
for pressure. This method exactly represents Darcy-force balances on
unstructured meshes and thus accurately calculates pressure, velocity,
and saturation fields throughout the domain. Computational costs are
reduced through dynamic adaptive-mesh optimization and efficient
parallelization. Within each rock volume, the mesh coarsens and refines
to capture key flow processes during a simulation, and also preserves
the surface-based representation of geologic heterogeneity.
Computational effort is thus focused on regions of the model where it is
most required.
After validating the approach against a set of benchmark problems, we
demonstrate its capabilities by use of a number of test models that
capture aspects of geologic heterogeneity that are difficult or
impossible to simulate conventionally, without introducing unacceptably
large numbers of cells or highly nonorthogonal grids with associated
numerical errors. Our approach preserves key flow features associated
with realistic geologic features that are typically lost. The approach
may also be used to capture near-wellbore flow features such as coning,
changes in surface geometry across multiple stochastic realizations,
and, in future applications, geomechanical models with fracture
propagation, opening, and closing.
Συγγραφείς:
Jackson, M. D.
Percival, J. R.
Mostaghiml, P.
Tollit, B. S.
and Pavlidis, D.
Pain, C. C.
Gomes, J. L. M. A.
El-Sheikh,
A. H.
Salinas, P.
Muggeridge, A. H.
Blunt, M. J.
