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Appendix A: Use of SI Units in Gas Well Testing Equations

By Amanat Chaudhry
From Gas Well Testing Handbook

Example A 1 Converting Metric to English Gas Field Units

Equation A 1 describes the gradual decline in flowing bottom-hole pressure (atmospheres) in a gas or water well as related to time in seconds, when the rate of production is q (reservoir cc/sec). This liquid flow equation is useful generally even when gas is present. The following conversion factors and arithmetic will convert Eq. A 1 to A 2 from metric to English gas field units (however, leaving the t D parameter in Darcy units).

  • 1 foot = 30 .48 cm

  • 1 day = 86 ,400 sec

  • 1 B/D = 1 .84 cm 3/sec

  • 1mD = 0 .001 D

  • 1 psi = 1 /14 .65 atm

  • in x = 2 .303 log x

Change q to (q ? o ), so that q = tank barrels

Darcy units

English units

h

cm

ft

r w

cm

ft

t

sec

day

q

cm 3/sec

bbl/day

cP

cP

k

D

mD

p

atm

psi



Table A 1: Conversion of Common Field Units to Metric (SI) Units (Base conditions: Field 60 F, 14.65 psia; Metric (SI) 15 C, 101.325 kPa)

Field unit

Multiplication factor

Metric (SI) unit

Symbol

Acre

4.046 856 E+03

Square meter

m 2

Acre

4.046 856 E-01

Hectare

ha

Acre-foot

1.233 482 E+03

Cubic meter

m

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