Q. Jiang et al., EFFECTS OF SOME SIMPLIFYING ASSUMPTIONS ON INTERPRETATION OF TRANSIENT DATA, Journal of Canadian Petroleum Technology, 37(6), 1998, pp. 32-35
Citations number
4
Categorie Soggetti
Energy & Fuels","Engineering, Chemical","Engineering, Petroleum
Fluid low in porous media is described by the diffusional type of part
ial differential equation. In deriving the flow equation for the const
ant compressibility fluids, an important assumption is made regarding
the magnitude of the pressure gradient is assumed that this gradient i
s small enough that the square of this term becomes negligible. In thi
s study, an attempt is made to quantify the effect of this simplificat
ion. Data generated by numerical simulator and analytical solutions ar
e compared in order to determine the conditions under which this simpl
ification is justified. Except for extreme conditions (non-linear coef
ficient greater than 0.01), in is justifiable to ignore the square of
the pressure gradient term in oil diffusional equation. The drawdown s
olution on gas wells contains gas properties, which are pressure depen
dent. As the system is being depleted. the average reservoir pressure
declines. Although it seems logical to consider the gas properties at
the prevailing reservoir pressure, the gas viscosity and compressibili
ty are usually evaluated at the initial pressure level. Comparison of
the analytical solutions with numerical solutions obtained for a varie
ty or typical well rest conditions indicates the magnitude of inaccura
cy incurred by using standard approach to data interpretation. Based o
n this investigation, several pressure levels for properties calculati
on are considered. In applying analytical equations for pseudo-steady
state flow conditions, gas properties should be evaluated at an averag
e value of the initial and current reservoir pressures.