A Next-Generation Parallel Reservoir Simulator for Giant Reservoirs

Abstract

Abstract Giant reservoirs of the Middle East are crucial for the supply of oil and gas to the world market. Proper simulation of these giant reservoirs with long history and large amount of static and dynamic data requires efficient parallel simulation technologies, powerful visualization and data processing capabilities. This paper describes GigaPOWERS, a new parallel reservoir simulator capable of simulating hundreds of millions of cells to a billion cells with long production history in practical times. The new simulator uses unstructured grids. A distributed unstructured grid infrastructure has been developed for models using unstructured or complex structured grids. Unconventional wells such as maximum reservoir contact wells and fish-bone wells, as well as faults and fractures are handled by the new gridding system. A new parallel linear solver has been developed to solve the resulting linear system of equations. Load balancing issues are also discussed. A unified compositional formulation has been implemented. The simulator is designed to handle n-porosity systems. An optimization-based well management system has been developed by using mixed integer nonlinear programming. In addition to the core computational algorithms, the paper will present the pre- and post-processing software system to handle large amount of data. Visualization techniques for billions of cells are also presented. Introduction For many oil and gas reservoirs, especially large reservoirs in the Middle East, availability of vast amount of seismic, geological and dynamic reservoir data result in high-resolution geological models. But despite the many benefits of parallel simulation technology for large reservoirs, average cell size still remains in the order of hundreds of meters for large reservoirs. In order to fully utilize the seismic data, smaller grid blocks such as 25 to 50 meters in length are required. This size of grid blocks results in billion (Giga) cell models for giant reservoirs. In order to simulate such models with reasonable turnaround time, new innovations in the main components of the simulator such as linear equation solvers and equation of state computations are essential. Also, next generation pre- and post-processing tools are needed in order to build and analyze giga-cell models in practical times.