西安石油大学：《油藏物理（油层物理学）Petro-physics》精品课程教学资源（英文课件）Physics property of reservoir rock 1.4 quantitative use of porosity

4 quantitative use of porosity Xuanqi Zhang Petroleum engineering college Xi'an shiyou university

4 quantitative use of porosity Xuanqi Zhang Petroleum engineering college Xi’an shiyou university

One of the simplest methods of calculating reservoir oil content is called the volumetric method.The mathematical expression for the initial oil-in-place by this method is:

One of the simplest methods of calculating reservoir oil content is called the volumetric method. The mathematical expression for the initial oil-in-place by this method is:

N=7.758 A,hosi u.s.A N=AhoSoi china where: As surface area of the reservoir,acres/m2. h thickness of the formation,ft/m. porosity,fraction. Soi initial oil saturation,fraction

N 758As hSoi  7. where: As = surface area of the reservoir, acres/m2 . h = thickness of the formation, ft/m. Φ = porosity, fraction. Soi = initial oil saturation, fraction. N  As hSoi china U.S.A

the equation gives the volume of oil contained in the porous rock at reservoir conditions of pressure and temperature

the equation gives the volume of oil contained in the porous rock at reservoir conditions of pressure and temperature

However,the surface or "stock tank'oil as finally sold by the producer is different from the liquid volume that existed underground. The difference is due to the changes in the oil properties as the pressure is decreased from high underground pressure and temperature to surface pressure and temperature

However, the surface or “stock tank” oil as finally sold by the producer is different from the liquid volume that existed underground. The difference is due to the changes in the oil properties as the pressure is decreased from high underground pressure and temperature to surface pressure and temperature

This reduction in p and T causes some of the volatile components to come out of solution (evaporate),causing the liquid volume to shrink.This reduction in volume is expressed by the oil formation volume factor,Bo.Thus, the stock tank oil initially in place is:

This reduction in p and T causes some of the volatile components to come out of solution (evaporate), causing the liquid volume to shrink. This reduction in volume is expressed by the oil formation volume factor, Bo. Thus, the stock tank oil initially in place is:

W=7.758 Ahooi U.S.A Boi where Boi is oil volume factor in reservoir barrels per stock tank barrel or bbl/STB.dimensionless N-< hooi china Boi

o i s o i B A h S N   7.758 where Boi is oil volume factor in reservoir barrels per stock tank barrel or bbl/STB. dimensionless oi s oi B A h S N   china U.S.A

In this equation,Soi is replaced by (1 Swi),where Swi is the irreducible or connate water saturation.This implies that no free gas is present in the pore space

In this equation, Soi is replaced by (1 - Swi), where Swi is the irreducible or connate water saturation. This implies that no free gas is present in the pore space

Because no petroleum reservoir is homogenous,the factors As,h,Φ，and Swi must be averaged

Because no petroleum reservoir is homogenous, the factors As, h, Φ, and Swi must be averaged

EXAMPLE Calculate the initial oil-in-place (N) of an oil reservoir.If As 1,600 acres,h=32ft,Φ=22%，Swi=20%, and Boi 1.23 bbl/STB

EXAMPLE Calculate the initial oil-in-place (N) of an oil reservoir. If As = 1,600 acres, h = 32 ft, Φ = 22%, Swi = 20%, and Boi = 1.23 bbl/STB