IEA Collaborative Project on EOR - 30th Annual Workshop and Symposium - 21-23 September 2009, Canberra, Australia

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Controlled CO2 | Diversified fuels | Fuel-efficient vehicles | Clean refining | Extended reserves

How In-Situ Combustion Process Works in a Fractured System

Two-Dimensional, Core and Block Scale Simulation

H. Fadaei G. Renard

M. QuintardG. Debenest

A.M. Kamp

30th Annual IEA Collaborative Project on EOR - 21-23 September 2009, Canberra, Australia 2

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Outline

IntroductionCombustion in fractured mediaLiterature resultsObjectives & methodology

Core-scale simulationsPreliminary workPropagation/extinction, front shape

Matrix block-scale simulationsTemperature, Oil saturation, Oil production

Analysis (dimensionless numbers) Conclusion Perspectives

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Combustion in fractured media

Is combustion feasible in a fractured medium? How does it scale between lab and field? Can it be controlled? Is it of practical interest?

Matrix blockFracture

Air

Combustion front

Gravity-drained oil+ combustion gases

The idea

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Literature results

At a lab scale it is feasible:Schulte et de Vries (1985)Greaves et al (1991)

Field experience is rareCraig & Parrish, COFCAW (1974)

In numerical simulations it seems to work

Tabasinejad et al (2006)Fadaei et al (2008)

Heating elements

Annular fissure

Stack of limestone plugsDiameter 25 mmLength 40 cm

Sample temperature measurement

Control temperature of vessel

S & de V, ‘85SPE10723

1 mm gapC

oke

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Context and objectives

Obtain propagation/extinction condition maps Reach understanding of the physics of the processes

Is air diffusion the rate limiting factor or is the kinetics of the oxidation process?

Up-scaling strategy from single medium to dual medium

Model for mass and energy transfer between matrix blocks and fracture

Be able to say something useful concerning the potential of field application

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Become familiar with the reservoir simulatorComparison with analytic results and previous works

Single-medium simulations forcore with surrounding fracture

propagation/extinction conditions

one matrix block with surrounding fracturesseveral matrix blocks separated by fractures

Calculate average properties on grid blocks Try to develop expression for transfer terms

between matrix blocks and fracturesCan semi-analytical solutions help?

Run lab experiments for validation (Stanford)

Methodology

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CORE SCALE

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Preliminary work

Numerical reservoir simulation of conventional combustionComparison to analytical results by Aldushin et al (2000)Gas/solid combustionExcellent agreement on fronts-speed

Simulation of Kumar’s data set (SPE16027)26 °API oilGood agreement with Kumar’s simulations and with experimental

data

This gave some hands-on experience with simulation of combustion

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Propagation/extinction at core scale

Kumar’s data set26 °API

Permeability12.7 D matrix (base)1270 D fracture

Sw=0.178, Sg=0.168

Dair=0.667×10-5 m2/s (base)

jair= 4.52 m3/m2/hr

1.5cm

0.2 cm .67 cm

1.5 cm

AirAir

6.4 cm

13x1x37

51 cm

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Propagation/extinction diagram

332.5

21.5

10.5

0

2.52

1.510.5

0 0

1

2

3

x 10 -4

- Log(D/Dref)- Log(K/Kref)

Np(m3)

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Effect of diffusion coefficient on front shape

1 0.1 0.01 0.001D/Dref

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BLOCK SCALE

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Geometry

Matrix block scale (2-D slab) Same data set as before

Except: viscosity = 4000 cPk = 1.27 D

No heat losses to surrounding 0.5 x 0.05 x 0.5 m system 20 x 1 x 20 grid Fracture is 4 grid blocks wide

Air injection

Oil production

0.5m

0.5m

1mm

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Temperature

Cone shaped front Front temperature

increases with time Front speed decreases

with time

480°C

38°C

550°C

38°C

420°C

38°C

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Oil saturation

1

0

1

0

10hrs 30hrs

50hrs70hrs

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Oil production

0.0E+00

5.0E-04

1.0E-03

1.5E-03

2.0E-03

2.5E-03

3.0E-03

0 20 40 60 80 100 120 140 160

Time (hr)

Cu

mu

lati

ve o

il p

rod

ucti

on

(m

3)

K=1270 mD

K=127 mD

K=12.7 mD

331025.3 mOOIP

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Analysis

Diffusion processes usually scale with 1/L2

We need to find out how the whole process scales as function of block size

02.0K

LvCPe gg

g

45.0)1(

K

LuCPe cs

c

front from far027.0front to close109.0

~3

*Lv

Pe ooil

Negligible heat transfer by gas phase

Important heat transfer by moving front and by conduction

Little contribution to heat transfer by moving oil

08.0* D

LvPe g

gasDiffusion is the determining factor for air delivery to the front

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Upscaling challenges

Grid block

Matrix block

From single to dual porosity modelNeed of modelling transfer terms between matrix and

fracture, knowing only statistical parameters of the fractures (pdf of width, orientation, fracture density, ...)

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Conclusion Numerical simulation shows that combustion in a fractured

system can be initiated and maintained at core and block level

We tested a medium oil (26°API) at core scale, and a “synthetic” heavy oil (4000 cP) at block size

Testing with more realistic data is needed

A cone-shaped front is observed, a shape which is emphasized at low diffusion coefficient

Air diffusion will likely be a rate limiting parameter A substantial amount of oil is recovered from a single block

(~75% of OOIP for 1.27 D permeability)

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Perspectives

3-D single-block single-medium simulations Use a more realistic oil-system

Looking for Wolf Lake data (especially kinetics) for history matching of experiments by Greaves et al.

Interpretation of experiments done at Stanford

Scaling of the processes at single-block level Development of expression for matrix-fracture

transfer functions based on: Semi-analytical model development Averaging of the numerical results

Multi-block single-medium simulations

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QUESTION/DISCUSSION

ITOHOS 2008, SPE/PS/CHOA 117645 (PS2008-117645)