Decoupled overlapping grids for modelling transient behaviour of oil wells
Abstract
This research presents a new method, the decoupled overlapping grids method,
for the numerical modelling of transient pressure and rate properties of oil wells.
The method is implemented in two stages: a global stage solved in the entire
domain with a point or line source well approximation, and a local (post-process)
stage solved in the near-well region with the well modelled explicitly and boundary
data interpolated from the global stage results. We have carried out simulation
studies in two- and three- dimensions to investigate the accuracy of the method.
For homogeneous case studies in 2D, we have demonstrated the convergence
rate of the maximum error in the quantities of interest of the global and local stage
computations by numerical and theoretical means. We also proposed a guideline
for the selection of the relative mesh sizes of the local and global simulations
based on error trends. Comparison to other methods in the literature showed
better performance of the decoupled overlapping grids method in all cases.
We carried out further investigations for heterogeneous case studies in 2D and
partially-penetrating wells in 3D which show that the error trends observed for the
2D homogeneous case deteriorate only slightly, and that a high level of accuracy
is achieved. Overall the results in this thesis demonstrate the potential of the
method of decoupled overlapping grids to accurately model transient wellbore
properties for arbitrary well con gurations and reservoir heterogeneity, and the
gain in computational e ciency achieved from the method.