Reservoir Characterization.pdf

Reservoir

Reservoir

Characterization (Part I)

ƒ Reservoir stratification (reservoir lithology) ƒ Reservoir geometry

ƒ Porosity, permeability, and water saturation ƒ Adjoining aquiferj g q

Reservoir stratification

Reservoir stratification

Most reservoirs are layered because of variations that existed Most reservoirs are layered because of variations that existed in the depositional environment.

Porosity

V

_{p b ma}

V

V

V

V

V

Porosity

=

φ

=

=

−

b b

V

V

Rock Matrix and Pore Space

Rock Matrix and Pore Space

P

S

Cl

ifi ti

Pore-Space Classification

z Total porosity, φ_t = Space Pore Total z Effective porosity, φ_e = Volume Bulk p y, φ_e

Space

Pore

cted

Interconne

Volume

Bulk

Space

Pore

cted

Interconne

Permeability

z Permeability is a property of the porous

medium and is a measure of the capacity medium and is a measure of the capacity of the medium to transmit fluids

Absolute Permeability

z When the medium is completely

saturated with one fluid then the saturated with one fluid, then the permeability measurement is often referred to as

specific

or

absolute

referred to as

specific

or

absolute

permeability

Effective Permeability

Effective Permeability

z When the rock pore spaces contain

more than one fluid, then the permeability to a particular fluid is called the

effective permeability

z Effective permeability is a measure of

the fluid conductance capacity of a the fluid conductance capacity of a porous medium to a particular fluid when the medium is saturated with when the medium is saturated with more than one fluid

Relative Permeability

z

Relative permeability

p

y

is defined as the

ratio of the effective permeability to a fluid at a given saturation to theg effective permeability to that fluid at 100% saturation

Calculating Relative Permeabilities

z Oil

_k

k

eo z Oil

k

k

_ro

=

eo z Water

k

k

=

ew

k

k

_rw

=

z Gas

_k

k

=

eg

k

k

_rg

=

In-Situ Saturation

In-Situ Saturation

Fluid Saturation

Fluid Saturation

z The saturation of the fluid is the fraction of

the pore volume occupied by that fluid

fluid

of

Volume

volume

Pore

fluid

of

Volume

S

=

Fluid Saturations

Fluid Saturations

z Basic concepts of hydrocarbon

accumulation

– Initially, pore space filled 100% with water – Hydrocarbons migrate up dip into trapsy g p p p

– Hydrocarbons distributed by capillary forces and gravity

– Connate water saturation remains in hydrocarbon zone

Determining Fluid Saturations

Determining Fluid Saturations

z Core analysis

z Capillary pressure measurementsp y p z Electric openhole logs

Adjoining Aquifer

Adjoining Aquifer

The aquifer is the total volume of porous water-bearing rock in

Areal View Vertical view

g pressure communication with a hydrocarbon reservoir.

Areal View Vertical view

Gas

reservoir

Gas reservoir

B tt t

reservoir _{Bottom water}

Aquifer water

h f h

encroaches from the side

Reservoir Fluid Properties

Reservoir Fluid Properties

The fluid properties of interest to the Reservoir Engineer are

th th t ff t th bilit f fl id ithi th i

those that affect the mobility of fluids within the reservoirs these are used in material balance calculations

Properties at surface conditions for transportation and sales (API, viscosity, oil quality)

Reservoir Fluid Properties

Reservoir Fluid Properties

Oil Properties

– Bubble Point Pressure – Bo – Rs – Bt – Co and μo Gas properties Gas properties – z – Bg and μg

Compositions oil & gas

Real Gas in Reservoir

Real Gas in Reservoir

nZRT

pV

=

Equation of State:

pV

=

nZRT

Quantity Description Unit/Value

p Pressure psia

V Volume ft^3

V Volume ft 3

n Mole number lb-moles

Z G ibilit di i l Z Gas compressibility factor dimensionless T Temperature Rankine R Universal Gas 10.73 constant

Calculating Z (1)

Calculating Z (1)

0 1 2 3 4 5 6 7 8 0 1 2 3 4 5 6 7 8 3,0 2,8 2,6 2,4 2,2 2,0 1,9

NHIEÄT ÑOÄ GIAÛ GIAÛM

1,5 1,3 1 1 1,0 1,1 1,0 1,1

Step 1: Calculate pseudo-critical pressure and temperature (Sutton) 1,8 1,7 1,6 1,5 1,45 1,4 1,4 1,1 1,05 1,1 1,2 1 6 1,7 0,9 0 7 0,8 0,9 2 6 . 3 0 . 131 8 . 756 _{g g} pc p = − γ − γ 2 0 74 5 349 2 169 T = − γ − γ 1,35 1,3 1,25 1,2 1,3 1,4 1,5 1,6 1,7 1,8 _{1 4} 1,5 1,6 0 5 0,6 0,7 HEÄ SOÁ LEÄ CH KH Í, Z 0 . 74 5 . 349 2 . 169 _{g g} pc T γ γ

Step 2: Calculate pseudo-reduced pressure and temperature: 1,15 1,1 , 1,9 2,0 2,2 2,4 2,6 3,0 1,2 1,3 1,4 0,3 0,4 0,5 pc pr pc pr T T T p p p = ; = 1,05 1,2 1,1 1 71,8 1,9 2,0 2,2 2,4 2,6 3,0 2,8 1,0 1,1 1,0 1,1 pc pc p

Step 3: Use Standings-Katz plot to determine Z 7 8 9 10 11 12 13 14 15 , 1,05 1,4 1,3 1,6 1,7 0,9 0,9

Exercise 1

Exercise 1

Calculate z-factor according to the given data as follows

Quantity Value Unit

Specific gravity 0.665 Dimensionless g y Reservoir temperature 213 °F temperature Reservoir pressure 3250 psia pressure

Solution to Exercise 1

Solution to Exercise 1

0 1 2 3 4 5 6 7 8 0 1 2 3 4 5 6 7 8 3,0 2,8 2,6 2,4 2,2 2,0 1,9

NHIEÄT ÑOÄ GIAÛ GIAÛM

1,5 1,3 1 1 1,0 1,1 1,0 1,1

Step 1: Calculate pseudo-critical pressure and temperature (Sutton) 1,8 1,7 1,6 1,5 1,45 1,4 1,4 1,1 1,05 1,1 1,2 1 6 1,7 0,9 0 7 0,8 0,9 668 ) 665 (. 6 . 3 ) 665 (. 0 . 131 8 . 756 − − 2 = = pc p 369 ) 665 (. 0 . 74 ) 665 (. 5 . 349 2 . 169 − − 2 = = pc T 1,35 1,3 1,25 1,2 1,3 1,4 1,5 1,6 1,7 1,8 _{1 4} 1,5 1,6 0 5 0,6 0,7 HEÄ SOÁ LEÄ CH KH Í, Z pc

Step 2: Calculate pseudo-reduced pressure and temperature: 1,15 1,1 , 1,9 2,0 2,2 2,4 2,6 3,0 1,2 1,3 1,4 0,3 0,4 0,5 82 . 1 ; 87 . 4 = = _pr pr T p 1,05 1,2 1,1 1 71,8 1,9 2,0 2,2 2,4 2,6 3,0 2,8 1,0 1,1 1,0

1,1 Step 3: Use Standings-Katz plot to determine

Z 7 8 9 10 11 12 13 14 15 , 1,05 1,4 1,3 1,6 1,7 0,9 0,9

AÙP SUAÁT GIAÛ GIAÛM

Calculate Z using Dranchuk and

Abou-Kassem Correlation

Abou-Kassem Correlation

2 11 2 11 5 5 4 2 3 2 1 r r (1 r ) exp( r ) 1 0 r r Z R R R A A R R F = − + ρ − ρ + + ρ − ρ + = ρ ρ 5 5 4 4 3 3 2 1 1 / 27 0 / / / / ) /( 27 . 0 pr pr pr pr pr pr r T p R T A T A T A T A A R ZT p = + + + + = = ρ 2 8 7 9 4 2 8 7 6 3 2 ) / / ( / / / 27 . 0 pr pr pr pr pr pr T A T A A R T A T A A R T p R + = + + = = 5339 . 0 ; 0700 . 1 ; 3265 . 0 _{2 3} 1 = A = − A = − A 3 10 5 A / T pr R = 1056 . 0 ; 1844 . 0 ; 7361 . 0 5475 . 0 ; 05165 . 0 ; 01569 . 0 9 8 7 6 5 4 = = − = = − = = A A A A A A 7210 . 0 ; 6134 . 0 ₁₁ 10 = A = A

Exercise 2: PVT Analysis

Exercise 2: PVT Analysis

Using the data in the table below and assuming real gas behavior, calculate the density of the gas phase under initial reservoir conditions. Compare the results with that of ideal gas behavior.

Critical Critical Component Mole Percent Molecular Weight

Critical Critical Press. Temp. (psia) (R) (1) (2) (3) (4) C1 0.85 16.043 666.4 343.00 C2 0 04 30 070 706 5 549 59 C2 0.04 30.070 706.5 549.59 C3 0.03 44.097 616.0 665.73 iC4 0.03 58.123 527.9 734.13 nC4 0.02 58.123 550.6 765.29 iC5 0.00 72.150 490.4 828.77 nC5 0.00 72.150 488.6 845.47 C6 0.00 86.177 436.9 913.27 C7 0.00 100.204 396.8 972.37 C8 0.00 114.231 360.7 1023.89 C9 0 00 128 258 331 8 1070 35 C9 0.00 128.258 331.8 1070.35 C10 0.00 142.285 305.2 1111.67 H2S 0.00 34.080 1300.0 672.12 CO2 0.02 44.010 1071.0 547.58 N2 0.01 28.013 493.1 227.16 H 0 00 4 003 33 0 9 36 He 0.00 4.003 33.0 9.36 Air 0.00 28.960 546.9 238.36 O2 0.00 31.999 731.4 278.24