Abstract

Oil production declines under two processes:

  1. pressure depletion and

  2. decreasing oil relative permeability as the oil saturation declines.

The literature offers derivations of Arps' exponential and hyperbolic decline equations for pressure depletion decline; these derivations apply to single phase flow or solution gas drive recovery only. This paper proceeds to derive Arps' hyperbolic decline equation from the principles of relative permeability. The results indicate that hyperbolic decline rigorously applies for relative permeability dominated secondary and tertiary oil recovery processes. Arps' exponential and harmonic declines apply only under very special conditions. The results further emphasize that history matched decline constants apply only during the recovery process under which they were determined. A method of translating between field scale oil relative permeability curves and oil decline is provided. The physical basis for the decline exponent, b, for these processes is revealed along with expected value ranges.

P. 245

Keywords:
pressure depletion, production monitoring, permeability, exponent, fluid dynamics, relative permeability, decline analysis, reservoir surveillance, exponential decline, permeability curve
Subjects:
Well & Reservoir Surveillance and Monitoring, Reservoir Fluid Dynamics, Improved and Enhanced Recovery, Reservoir Simulation, Formation Evaluation & Management, Reserves Evaluation, Flow in porous media, Production forecasting
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1998. Society of Petroleum Engineers
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