AN OVERVIEW OF HEAVY OIL RECOVERY STUDIESiea-eor.ptrc.ca/2012/assets/s4/4- Sohrabi_Session...

Institute of Petroleum Engineering,

Heriot-Watt University

Edinburgh, UK

Contact:

Mehran.Sohrabi@pet.hw.ac.uk

+44(0)131 451 3568

AN OVERVIEW OF HEAVY OIL RECOVERY STUDIES AT THE CENTRE FOR ENHANCED OIL RECOVERY AND CO2 SOLUTIONS OF

HERIOT-WATT UNIVERSITY

IEAEOR 33rd Annual Symposium, Regina, Saskatchewan, Canada

Prof. Mehran Sohrabi

28 August 2012

1

Outline 2

Introduction & Objectives

Experimental Facilities

Visualization Experiments

Coreflood Experiments

Conclusions

3

Heavy Oil Recovery

Thermal methods are applied in the field but there

are limitations: - thin and deeper reservoirs - energy intensive - environmental issues e.g. carbon footprint

Non-thermal recovery methods provide a solution for reservoirs in which thermal methods are impractical or uneconomical also offer advantages on capital cost, energy consumption, environmental pollution etc.

Very low primary production (5% to 10%) and

poor waterflood performance.

Objective 4

The objective of the Non-Thermal Enhanced Oil Recovery JIP

at Heriot-Watt is to investigate potential of improving heavy

oil recovery by:

Water/CO2 combinations (focus of this presentation)

Chemical Injection, and

Mobility control techniques.

Mechanisms of Oil Recovery by CO2 Injection

5

Light Oil Systems Heavy Oil Systems

Klins, 1984

Interactions of CO2 and crude oil are different in heavy oil

compared to conventional oil

CO2 Dissolution and Viscosity Reduction

6

While miscibility would be absent, large drops in heavy oil

viscosity takes place upon mixing with CO2.

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0% 20% 40% 60% 80% 100%

Vis

co

sit

y R

ati

o (

% v

isc

os

ity o

f o

il/C

O2

mix

ture

to

ori

gin

al o

il v

isc

os

ity)

CO2 content, saturation frac.

Crude "J"

Crude "C"

7

Our research approach:

Investigate pore-scale physics by performing visualization experiments

Quantify level of additional oil recovery by each method by core flood

experiments under reservoir conditions.

Performed simulation and modelling at core and field scales.

Outline 8

Introduction & Objectives

Experimental Facilities

Visualization Experiments

Coreflood Experiments

Conclusions

Work Reported in Thesis

Eight heavy crude oil samples were provided by sponsor companies from reservoirs

around the world. The viscosity range was from 5 to 10000 cp at their test

conditions. The focus of this presentation is on the following two heavy oils.

Experimental Work

Fluid Characterization: Viscosity, composition, Wettability, IFT, Acid number , etc

Flow Visualization Experiments: Using the transparent micromodels to investigate the

displacement mechanisms at the pore scale,

Displacement Experiments: Using Sandpack and consolidated cores to up-scale

and quantify the observations in the micromodel.

9

Crude APIº Viscosity

(cp)

Pressure

(psig)

Temperature

(ºC)

“C” 10 8700 600 50

“J” 16 617 1500 28

Flow Visualization Rig 10

High-pressure micromodels allow detailed investigation of

pore-scale mechanisms under reservoir conditions.

Coreflood Rig 11

Outline 12

Introduction

Experimental Facilities

Visualization Experiments

Coreflood Experiments

Conclusions

Low Pressure (gaseous) Application of CO2 (Crude C)

Initial Waterflood Flood – poor oil recovery CO2 Flood at CO2 Breakthrough

CO2 Flood after 2 days – note change of

colour of oil due to dilution with CO2

Water injection after CO2 flood resulted in

significant additional oil recovery

Initial Oil saturation Initial Water Flood

CO2 Flood at Breakthrough CO2 Flood after 1 day 2nd Waterflood (post CO2 Flood)

High Pressure (Super Critical) Application of CO2 (crude J)

Initial Oil Saturation

CO2-Foam, 2 hrs CO2-Foam, 10 hrs

Water Flood Surfactant Flood CO2-Foam BT

CO2-Foam, 5 hrs CO2-Foam, 1 day

CO2-Foam, 1 hr

Mobility Control by CO2-Foam (Crude C)

Oil Recovery Comparison (Crude C)

CO2 Flood after 2 days CO2-Foam injection 1 day CO2 and Water injection (slugs)

Outline 17

Introduction

Experimental Facilities

Visualization Experiments

Coreflood Experiments

Conclusions

Oil Recovery by Waterflood (Heavy Oil vs. Light Oil)

18

0

10

20

30

40

50

60

70

80

0 0.5 1 1.5 2 2.5

Oil R

ec

ove

ry (

%O

OIP

)

Inj Brine (PV)

Heavy oil - 617 cp

Light Oil - 1 cp

Water BT

Crude J – 617 cp

Heavy Oil Recovery by CO2 Injection (Tertiary Vs Secondary)

19

0

10

20

30

40

50

60

70

80

0 1 2 3 4 5

Oil R

ec

ove

ry (

%O

OIP

)

Inj Fluids (PV)

Tertiary CO2 Flood

Secondary CO2 Flood

CO2 BT

Tertiary CO2 Flood

Secondary CO2 Flood

Secondary Waterflood

Crude J – 617 cp (medium heavy oil)

Mobility Control by CO2-Foam (CO2 inj Vs CO2Foam)

20

0

10

20

30

40

50

60

70

80

90

0 1 2 3 4 5 6 7

Oil R

ec

ove

ry (

%O

OIP

)

Inj Fluids (PV)

Tertiary CO2 Flood

CO2-Foam Flood

Waterflood

CO2/CO2-Foam Flood

Crude C – 8670 cp (extra heavy oil)

CO2 storage in light vs. heavy oil Reservoirs

21

While in conventional oil reservoirs the amount of CO2 that can be stored

in water flooded reservoirs (tertiary) is much lower than secondary. In

heavy oil systems, CO2 storage capacity is almost the same for secondary

and tertiary CO2 injection.

0

0.1

0.2

0.3

0.4

0.5

0.6

0 0.5 1 1.5 2

Ave

rag

e G

as

Sa

tura

tio

n

Gas Injected (Core PV)

2Phase, Gas Injection

3 Phase, 1st Gas Injection

Secondary Gas Injection

Tertiary Gas Injection

0

0.1

0.2

0.3

0.4

0.5

0.6

0 0.5 1 1.5 2

CO

2 S

tora

ge

(P

V)

Inj Fluids (PV)

Secondary CO2 Flood

Tertiary CO2 Flood

Heavy Oil (Crude J )

617 cp

Light Oil

µ <1 cp

Mobeen Fatemi and Mehran Sohrabi, Water Alternating Gas Injection

JIP, Steering meeting Oct. 2011

Outline 22

Introduction

Experimental Facilities

Visualization Experiments

Coreflood Experiments

Conclusions

Conclusions 23

The results of this study show significant potential for

enhanced oil recovery and CO2 storage in heavy oil

reservoirs.

The coreflood results show that the performance of

CO2 is, to a large extent, dependent on reservoir

conditions, the state of CO2 under reservoir

conditions, and physical properties of the heavy

crude oil.

Conclusions 24

Comparison of recovery data during secondary and

tertiary injection of CO2 reveals that secondary CO2

injection provides much better recovery efficiency at

early injection times.

While CO2 storage capacity in light oil systems is a

strong function of injection mode (pre- or post-

waterflood), heavy oil systems show much less

sensitivity to CO2 injection strategy.

Conclusions 25

The results of micromodel and coreflood experiments

revealed that when the CO2 flood process is boosted

by a appopriate mobility control technique (e.g. in-

situ formation of foam), heavy oil displacement

process takes place in a much shorter time period and

more efficiently.

Acknowledgment 26

This work was carried out as part of the ongoing Enhanced

Heavy Oil Recovery joint industry project (JIP) at the Institute

of Petroleum Engineering of Heriot-Watt University and was

equally supported by: Total Exploration and Production UK,

ConocoPhillips, Petrobras, PEMEX, and PTT Ltd. which is

gratefully acknowledged.