Simulation Process
History Matching Procedure

The objective is to reproduce past reservoir performance which is achieved by 1) adjusting reservoir parameters of the model, 2) iterative simulation runs (sensitivity analysis), 3) matching simulated performance with history and determines 1) poorly known or unknown physical parameters, 2) critical parameters for improving quality of data.

The simulation process is a 4-step procedure:

1. Initialization - verify reliability and completeness of field data, problems encountered are corrected by examination of data errors, pressure distribution, saturation distribution and volumetrics - original and current gas, oil & water in place.
2. Pressure Match - match reservoir and well pressures before matching production rates which is achieved by adjusting 1) size of aquifer, 2) rock compressibility, 3) permeability distribution and 4) pay thickness and porosity.
3. Saturation Match - match WOR & GOR after matching reservoir and well pressures which is achieved by adjusting; 1) vertical and horizontal permeabilities, 2) relative permeability curves and 3) water-oil and gas-oil contacts. If pressure match is disturbed, then repeat pressure match with new data from saturation match.
4. Productivity Index Match - finally well flowing pressures are matched which is achieved by adjusting (within geologic & engineering reality) 1) productivity index of wells, 2) value of layer flow index for rates in STB/DAY, 3) PID = (.00708 K h)/ [ln .121 ((DX*DY)^.5/Rw) + S]

Performance Prediction

Prediction runs 1) predict future performance of reservoirs under existing operating conditions, 2) evaluate and compare alternative field development and operation plans and 3) objective is to maximize the recovery of hydrocarbon from reservoir.

For example performance prediction can show the need for:

• need for pressure maintenance
• placement of infill drilling locations
• types of wells (vertical - horizontal - slanted)
• >changes to well productivities (pump capacity - tubing size)