IPARS Introduction

The Implicit Parallel Accurate Reservoir Simulator (IPARS) provides a framework and a growing number of physical models suitable for research and practical calculations. Both oil reservoirs and aquifers can be simulated with the program. IPARS runs on parallel and single processor computers and can solve problems involving a million or more grid elements. It can handle multiple fault blocks with unaligned grids and problems that involve different physical models in various regions of the reservoir. This document is a second draft of a user’s manual for IPARS; it covers the capabilities, configuration, and application of the simulator.

The elements of IPARS can be combined in many different ways (more than 50) so the first task a user faces is to decide which elements he needs and which he does not need. He may want to track a contaminant in a faulted aquifer using a pc running Microsoft Windows and a multigrid linear solver, or he may want to conduct a history matching study on a 30 well unfaulted oil reservoir using a network of workstations running Linux with line successive over relaxation as the linear solver. The IPARS configurations for these two problems are quite different. Fortunately, IPARS is portable with respect to machines and operating systems, and includes a compiler preprocessor that automates configuration.

Preparation of input data is the next user’s task. The simulator employs a free-form keyword input with default values supplied for most of the input variables. There are two categories of input, initial data and transient data. In general, the input variables are different for the two categories. However, some variables can be input in both categories; for example, a well may be initially specified to be a production well but half way through the simulation may be converted to a water injection well. Various physical models and elements of the IPARS framework each require different sets of input variables; these sets are documented separately herein.

Execution of the simulation comes next. Inevitability, the first attempt at execution will produce error messages due perhaps to misspelled keywords or omission of required data. If at all possible, IPARS will process all of the initial data before terminating due to an error condition. Execution may be broken up into time segments so that intermediate results can be examined and transient data can be modified if necessary. IPARS can be restarted with the original input data; a specially prepared restart file is not required.

Both during and after execution, the user will want to visualize results. IPARS currently supports a commercial plotting package, Tecplot, by writing plot files in the appropriate format. Eventually, other plotting packages may be supported.