Differential Vaporisation.pptx

Differential vaporisation • Objective : To generate PVT data below bubble points • This type of liberation is characterized by a varying composition of the total hydrocarbon system. • The experimental data obtained: 1. Amount of gas in solution as function of pressure 2. The shrinkage in oil volume as a function of pressure 3. Density of remaining oil as function of pressure

• Considered to be the representative of gas-liquid separation process in reservoir below bubble point • Flash liberation is considered to take place between reservoir and through the separator • To obtain oil formation factor and GOR that can be used to predict the behaviour of reservoir when pressure drop below bubble point

Procedure • The test is carried out on reservoir oil samples and involve charging a visual PVT cell with a liquid sample at bubble point pressure and at reservoir pressure • The pressure is reduced in steps, usually 10 to 15 pressure levels, and all the liberated gas is removed and its volume is measured at standard conditions • The volume of remaining oil VL is measured at each pressure level • Final stage is reduced the cell to 60 F keeping pressure at atmospheric pressure. Final oil volume is measured as residual oil.

Parameters Calculation of Bod, differential oil volume factor • The above procedure is continued to atmospheric atmosphere where oil remaining is measured and converted to standard condition, 60⁰F (Vsc) • Bod are calculated by dividing the recorded oil volumes VL by volume residual oil , Vsc

Calculation of Rsd and Btd • Rsd, the differential solution gas oil ratio is calculated by dividing the volume of gas in solution by residual oil volume. • Rsdb, differential gas oil ratio at the bubble point pressure • Btd, relative total volume calculated from

Calculation of Z and Bg • Gas deviation z-factor of liberated solution gas at the specific pressure is calculated from recorded gas volume measurement as

• Psc = standard pressure, ⁰R

• Tsc = standard temperature, psia • P = pressure, psia • T= temperature, ⁰R

• Gas formation volume ,Bg

• • • • •

Bg= gas formation volume Psc = standard pressure, ⁰R Tsc = standard temperature, psia P = pressure, psia T= temperature, ⁰R