Date

2015

Author

Rza Guliyev, Ulvi

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Reservoir simulations are computer models that can imitate real world reservoir behavior under different circumstances, therefore making it possible for reservoir engineers to make sensitivity studies in order to assess different scenarios. These models discretize the reservoir into smaller blocks either using structured grids or unstructured grids. The application of regular structured grids to correctly map reservoir's geological structure can be very difficult, if not nearly impossible. Unstructured grids can be more convenient for those cases. Voronoi gridding technique creates unstructured grids such that the boundary of two grids is normal to the line connecting Voronoi particles that represents the grids. So that it would be convenient to calculate the transmissibility on the block boundaries. In this study instead of placing the Voronoi particles randomly, or in a regular fashion, the properties of the reservoir such as permeability anisotropy, orientation of the permeability vectors, heterogeneity of the petrophysical properties, and well locations and types were taken into consideration in the placement of Voronoi particles. A three-step algorithm, created in this thesis and written using Matlab software, takes into account the high resolution petrophysical properties in a finer static mesh, together with permeability anisotropy ratio and orientation and well location. This algorithm generates initial distribution of grid points that honors permeability anisotropy, then assigns each grid point an error value, which is dependent on grid point placement, and tries to minimize this error by moving bad points onto better locations. The error gets lower as the Voronoi grids and the background finer static mesh agrees with each other. Finally, after each grid point's location is chosen grid points related to vertical and horizontal wells and fault are added. Algorithm was implemented on six cases of different complexity and then generated Voronoi grid blocks were used in a simple, single phase simulator to show the effects of the optimized grids. It was seen that the developed code during the study can match the given input static model and can reduce the number of grid blocks required to model a hydrocarbon reservoir.

Subject Keywords

Hydrocarbon reservoirs., Voronoi polygons., Gas reservoirs., Oil fields.

URI

http://etd.lib.metu.edu.tr/upload/12619250/index.pdf
https://hdl.handle.net/11511/25050

Collections

Graduate School of Natural and Applied Sciences, Thesis