A Next-Generation Parallel Reservoir Simulator for Giant Reservoirs

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.

Toward building green computing environment for reservoir simulation

“…Each simulation model takes hours and sometimes days to finish execution so we deemed the 30 minutes to be a reasonable sampling rate. The sampling over 3 months allowed simulation engineers to run production simulation models, part of their daily work, including black oil, compositional and dual porosity dual permeability production models [11,12,13]. Our data center scheduler assigns GigaPOWERS run to either system based on the requested number of nodes and availability.…”

“…There are POWERS [12] (i.e., predecessor version of GigaPOWERS) reservoir simulation models with characteristics that limit models scalability for certain reservoir model with high number of wells. We call nonscalable models "Class B" models because of this limiting property.…”

“…Giant reservoir models with more than billion cells have been built recently [11,12]. Simulations of such large models pose a challenge to computing resources.…”

“…Simulations of such large models pose a challenge to computing resources. To perform accurate high resolution reservoir modeling using simulation, Saudi Aramco has developed a state-of-the-art simulator, POWERS™ [11] and GigaPOWERS™ [12,13]. GigaPOWERS is capable of simulating multi-billion cell reservoir models.…”

A multi-continuum multi-phase parallel simulator for large-scale conventional and unconventional reservoirs

“…Since 1980s, various of parallel simulators were developed (Li et al, 1995;Wheeler and Smith, 1989;Rutledge et al, 1991;Shiralkar et al, 1997;Parashar et al, 1997;Kaarstad et al, 1995;Killough and Bhogeswara, 1991;Killough et al, 1997). In (Dogru et al, 2002(Dogru et al, , 2009), Dogru et al developed a parallel simulator, GigaPOWERS, which has been successfully applied to a case with one billion gird cells, and a truncated Neumann series preconditioner is developed. In (DeBaun et al, 2005), an objectoriented, component-based architecture is designed, built on which a black oil simulator and a compositional simulator are developed.…”