Background on Reservoir Simulation

Today’s competitive economic climate requires cost-effective production technology to profitability produce marginal petroleum reservoirs. Reservoir simulation studies allow efficient exploitation of hydrocarbon reserves. Typically reservoir simulation is restricted to large companies which can afford mainframe computer or sophisticated workstation and wasn't feasible for the small independent producer.

Recent advances in PC computational speed and memory, the release of U.S. DOE BOAST3 (3D, 3 phase simulator) makes PC-based simulation feasible for small companies.

Pre & post processing tools such as MS Office97 & Geographix reduces simulation cost & time to assemble simulation input data. Output data can be manipulated by software packages such as B3plot2, Colorgrid of Boast3, MS Office97 & CorelDraw.

The reservoir simulator solves a system of partial differential equations, describes multiphase fluid flow (oil, water, gas) in a porous reservoir rock, estimates performance of reservoir, predicts future performance of a user defined reservoir based on its current state and past performance and explores methods for increasing the ultimate recovery of hydrocarbons. The program does require geologic & engineering judgement for proper use.

Simulator Classifications

• 1, 2, & 3-phase model (gas, oil and/or water)
• Reservoir components modeled - black oil, compositional, or enhanced oil recovery simulator
• direction of fluid flow - one, two, or three dimensional
• type of flow equations used
  • IMPES (implicit in pressure - explicit in saturation) model
  • fully implicit model
  • adaptively implicit model

Mechanics of Simulation

• reservoir is divided into grid cells using a X, Y, & Z coordinate system
• rock and fluid properties are assigned to each cell
• computations are carried out for all phases in each cell at discrete time steps
• simulation output consists of production volumes and rates, pressure and saturation distributions & material balance errors
• Other process specific information provided at selected time steps

Application of Black Oil Simulators

• aquifer behavior
• up-dip gas injection
• flank water injection
• vertical water influx
• single well operations
• simulation of large multi-well structures
• effects of reservoir heterogeneity
• simulation of large reservoirs of several non-communicating producing horizons
• analysis of lease unitization 

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Updated January 1999
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