Gas Well Testing Handbook
Offering a thorough understanding of gas well test analysis basics, this book focuses on practical field application, where over 100 field examples are presented to illustrate basic methods for analysis.
TABLE OF CONTENTS Gas Well Testing Handbook
6.9: Average Reservoir Pressure Estimating Techniques
6.9 Average Reservoir Pressure Estimating Techniques
Average reservoir pressures are used for characterizing a reservoir, computing its oil/gas in place, and predicting future behavior. In addition to these uses, the average reservoir pressure is required to find a quantitative use in volumetric-balance calculations of oil/gas in place in a reservoir. In this section we will present various methods to calculate average reservoir pressure in a gas reservoir.
Horner MBH Method
The average reservoir pressure for a finite or bounded reservoir may be estimated as shown below using the values of m and ? 
obtained from the Horner plot and the MBH curves.3 From Equation 6 21 for 
,
where Eq. 6 22 is the defining equation ? . The material balance equation may be written in terms of pseudopressure with substitution for dimensionless quantities as
Subtracting Eq. 6 22 from Eq. 6 24 gives
or
m is the absolute value of the slope of the straight-line section of the Horner plot:
F is the MBH dimensionless pressure at t DA, and the t DA is the dimensionless time:
t P is a pseudoproduction time in hours and is calculated using Eq. 6 17; ?( p*) is the value of ?( p ws) corresponding to 
, from the extrapolated semilog straight line. F may be obtained from Table B 1 or Figures B 1 through B 5 corresponding to the appropriate well reservoir configuration and reservoir shape. Values of t DA may be calculated from Eq. 6 28.
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