A Method for General Reservoir Behavior Simulation on Digital Computers

A large-scale computer method for reservoir simulation in two dimensions is described. The physical effects taken into account are gravity component parallel to bedding plane, solubility and compressibility for two flowing phases, which may be oil and water or oil and free gas. Fluid flow is treated optionally as either homogeneous or segregated. A new numerical method for treating gravity in the two-phase flow equations is presented. The member to be simulated is described in terms of cells. A material balance is obtained for each cell. The cells may be chosen of variable size so that small cells can be used in the oil-bearing regions and large cells in the aquifer. A data-handling system to facilitate problem preparation and display of results is described. Applications of the simulator, particularly to the Arab-D member of Saudi Arabia, are discussed. Introduction Reservoir Behavior Simulation We define reservoir behavior simulation to be the response of an analogous model to disturbances corresponding to fluid withdrawals and infections. The model we call the reservoir simulator. In this paper, our main interest is to describe a particular reservoir behavior simulator. We also describe an example of production member behavior. However, this is only for illustration. Our main interest is the simulator itself. A Discussion of Reported Methods of Simulation Reports of reservoir behavior simulation appear frequently in the Journal of Petroleum Technology. The incentive for all this work is economic. The engineer believes he can plan more efficiently development of a reservoir when its behavior can be simulated. Probably the earliest attempts at simulation are characterized by the term "case histories". Here, the investigators report the behaviors of reservoirs together with a description of the reservoirs. These reports are of interest to other persons if they have a similar reservoir at hand. The first quantitative simulation of reservoir behavior seems to have been gained by omitting all consideration for spatial behavior. Only the principles of thermodynamics (temperature-pressure-volume relations) and conservation of matter are employed. No flaw dynamics are simulated. This model is now called the "Schilthuis" equations.