design flowline of simultanous oil-gas flow

[confidential]

Dear friends


i want to design flowline of simultanous oil-gas flow
(from well head to storage and proccessing facilities)

the first thing in the design is the correlation that relate the fluid properties with pressure temperature (such properties is the dissolved gas and formation volume factor)


for that purpose i used the The Vasquez-Beggs Equation,published in 1980 in jpt forum.this equation is as follows

Rs = C1 x gamma(gas) x p ^ C2 x exp [ C3 ( gamma(oil) / T + 460 ) ] --1

gamma(gas):gas gravity(air=1) that would result from seperator conditions of 100 psig

c1,c2,c3 are constants depend on api

to use this equation , the specific gravity of gas must be known.
Vasquez in his published stduy(1980),decided to use a value of of gas gravity at particular conditions of seperator pressure, so he took 100 psig as a reference pressure,and hence he gave this equation to calculate this value

gamma(gas)=gamma1(gas)(1+0.00005912*gama(oil)*t*log(p/114.7)) ---2



where
gamma1(gas):gas gravity obtained at seperator pressure(p)
and seperator temperature(t)

gamma(oil)=api gravity



snice its difficult to calculte gamma(gas) from equation 2,for the pipeline,hence how one could obtain the value of
gamma1(gas) at given pressure and temperature ?


so if i use the average surface gas gravity as gamma(gas)
instead of calculating , gamma(gas) from equation 2

the value of Rs from equation 1 would be accurate enough.

and if there is other correlation simpler than this for
calcualting fluid properties, i would be appreciated if you mention it , at what journal published by year and volume

thanks