Distribution of Formation

Properties

What properties to distribute for reservoir

simulation?

• Gross thickness

• Net reservoir thickness

• Absolute permeability

• Effective porosity

• Other: shale beds, fractures…

Use of geologic model data in reservoir simulation

Property Use in Simulation Status

Structure top Reservoir depth

Initial reservoir pressure

Original oil in place (OOIP) and original gas in

place (OGIP) calculations

Required for top layer

Net reservoir thickness, hn Assignment of cell net thickness values

Horizontal-transmissibility calculations

PV calculations

Calculation of well geometric factors, Gw

OOIP and OGIP calculations

Required

Gross reservoir thickness, hg Assignment of cell gross thickness values

Gravity head calculations

Initial reservoir pressures

Transition-zone calculations

Initial saturation distributions

Vertical-transmissibility calculations

Optional (default may be obtained from net

thickness)

Net-to-gross ratio Assignment to cell hn/hg values Optional(default may equal one, hn/hg=1)

Porosity Assignment of cell values

Development of porosity/permeability transforms

Pore volume (PV) calculations

OOIP and OGIP calculations

Required for all layers

Horizontal permeability Assignment of cell permeability values

Horizontal-transmissibility calculations

Development of porosity/permeability transforms

Calculation of well geometric factors, Gw

Required for all layers

Vertical permeability Assignment of cell permeability values

Vertical-transmissibility calculations

Optional(default may be obtained from kv/kh=1)

Initial saturations Initial saturation distributions

Transition-zone heights

OOIP and OGIP calculations

Optional(default may be obtained from Pc data)

Endpoint saturations Saturation normalization

Assignment of cell critical saturation values for

saturation unnormalization

Optional(default may be obtained from kr curves)

Fluid Contacts OOIP and OGIP calculations

Initial saturation distributions

Initial reservoir pressures

Required

Porosity Distribution

Porosity AveragingPorosity - thickness-weighted average

n

ii

h

n

ii

hi

1

1

h1

h2

h3

1

2

3

Water saturation - volume weighted average

n

i

n

iw

S

1i

hi

φ

1i

hi

φwi

S

Permeability Distribution & Averaging

Measures of Heterogeneity

50

1.8450

k

kkV

ADCAArea

ABCAAreak

L

Dyksta-Parsons Coefficient Lorenz Coefficient

Pitfalls of statistical approaches

• Data in sequential order…reservoir is not

• relies on permeability variations for estimating

layers, however the speed of fluid traveling

through a layer is dependent on the phase

mobility, pressure gradient, and the k/ ratio.

dep

th

arranged un-arranged

Hydraulic Flow Unit

}{0314.0}{

mdkmRQI

zk

gvS

FZI1

1r

0.010

0.100

1.000

10.000

0.010 0.100 1.000

Porosity Ratio

RQ

I

Classic Problem

How to distribute interwell properties?

How?

Porosity-Permeability Transforms

1E-03

1E-02

1E-01

1E+00

1E+01

1E+02

1E+03

1E+04

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35

porosity

pe

rme

ab

ilit

y

Core Porosity vs Permeability

0.1

1

10

100

1000

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0

Porosity

Pe

rm

eab

ilit

y, m

d

Clastic example:

Burbank Sandstone, Oklahoma

Carbonate example:

San Andres, West Texas

Good Bad

Upscaling of detailed geology

Geostatistics

Kriging

Conditional Simulation

Distributed Values

Data Points

k, Sw, , Net Pay, Gross

Variogram

Model

Poor Example: Final isotropic permeability

distribution after history matching

Note: “bullseye effect”

Excellent example: top of structure

Structure Map Grid/Kriged results

Geostatistics:

Base Case Double the block size and reduce the

number of grid blocks.

3D Seismic: Anticlinal Structure - North Field, Qatar: Recoverable

reserves 500 trillion ft3. Largest single accumulation of unassociated

gas in the world.

Application of seismic data

Application of seismic data