Accurate Oil and Gas Production Decline Curve Fit Using Cumulative Production-Production Rate- Time Linearized Form of Arp’s Hyperbolic Decline Equation

Authors: Nwankwo KO* and Nwankwo PC

DOI: 10.23880/ppej-16000400

Volume 8, Issue 4

Abstract

Production forecasting is a crucial process in the Oil and Gas Business. Arps decline curves are the most common of these forecasting tools. The Exponential, Hyperbolic and Harmonic declines originated by J.J. Arps are three main decline profile types widely used in the industry. Exponential and Harmonic curves are more common because of the ease of fitting production profiles with them. Exponential and Harmonic, which rarely occur, are special cases the general Arps Decline curve. However, hyperbolic is the principal Decline curve equation. The difficulty in hyperbolic Decline fitting is in the prediction of the second decline parameter (Decline exponent). A hyperbolic decline fit of oil and gas production using a linear form has been demonstrated earlier on, and this worked well except for the estimation of initial production rate which was obtained by data regression. This paper shows yet another linear form of hyperbolic decline using Cumulative Production, Production Rate and Time. The novel form was found to be a better representation of the hyperbolic form than even the earlier linear model if Cumulative productions, production Rate with time data are available. This model will improve remaining reserves estimation, production rate forecasting and cumulative production trending. It should be noted, at this point, that the linear form presented here only replicates the exact Arp’s hyperbolic Decline form but cannot account for the decline pattern exhibited by wells due to drastic changes in reservoir fluid or rock properties like Gas-oil-ratio, water cut, porosity, permeability and changes caused by introduction of Artificial Lift or enhanced recovery scheme. The explicit determination of Initial Production Rate, Decline Exponent and Decline Constant using this derived linear form, in this paper, is the strength of this method over and above other methods.

Keywords: Oil and Gas Production; Cumulative Production; Hyperbolic Decline Equation

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