Post-Cold Production EOR: In-Situ Combustion (an Overview) and

PTRC/SRC’s Air Injection ProjectCarolyn Preston

Petroleum Technology Research Centre

Norm FreitagSaskatchewan Research Council

(with Bernard Tremblay and Ray Exelby)

IEA EOR 30th Annual Symposium and Workshop

C b A t liCanberra, Australia

September 21-23, 2009

Conventional In-Situ Combustion

M. Szeoke, In Situ Combustion Research Group, University of Calgary

Overview of History in Canada

• Many early field trials, with very few successes• Athabasca bitumen (Gregoire Lake): Unable to obtain ( g )

communication between injectors and producers• Cold Lake bitumen (Wolf Lake): Obtained communication through

pre-steaming, but field responses were unpredictablep g, p p• Required constant monitoring and adjustment of individual well

operations

• Lloydminster heavy oil: Many uneconomic pilots from 1960s into• Lloydminster heavy oil: Many uneconomic pilots from 1960s into 1980s

• Included pilot with injection of pure oxygen (Golden Lake)

O l j i di il (B tt )• Only major success was in a medium oil (Battrum)

Overview of History (Cont’d.)

• General field performances in heavy oils• Poor/reduced air injectivityj y

Gas channelling problems at higher oil viscosities

• Gas-blocking of oil productionW ll t t i i j t ft d d i l flWells nearest to air injectors often produced mainly flue gas Much of the oil production appeared at offset wells outside the

main injection patterns• Stable water-in-oil emulsions• Relatively high oil recoveries when oil could be produced

New Air Injection Processes

• THAITM

• Being piloted in bitumen by Petrobank at Whitesands• Depends on gravity drainage of oilp g y g• Overcomes low oil mobility through short-path oil production• Range of operation for stable combustion front still uncertain

• COSHCOSH• Air injected into a horizontal well• Uses gravity drainage of oil to a horizontal producer

U ff t ti l ll t d fl th t ld bl k il• Uses offset vertical wells to produce flue gas that would block oil• No field tests, yet

• AIR INJECTION IN POST-COLD-PRODUCED HEAVY OIL• CHOPS (Cold Heavy Oil Production with Sand) sand production has

created “wormholes” that could be used for short-path oil production• Intended for thin sands in which gravity drainage is ineffective• No field tests, yet

THAI: Current Technologies

Technical Challenges in Heavy Oils• Main obstacles in heavy oils:• Main obstacles in heavy oils:

1) Moving mobilized oil to producing wells through a cold formation2) Low heavy oil prices ― some earlier projects could have been

economic with current prices3) Failure to maintain a combustion front.

• Generally caused by either poor oil mobility, or decisions to reduce y y p y,air injection rates to cut costs

• In bitumens and very viscous heavy oils, ignition was troublesome

• Consequences of loss of combustion front:• Loss of recovery mechanisms (distillation, cracking, less steam)• Low-temperature oxidation occurs, which causes:

1) Increased oil viscosity/ loss of oil productivity2) Organic acid production → corrosion3) Stable water-in-oil emulsions → treatment problems

Requirements for SuccessRequirements for Success

• Maintain a stable combustion front!• Deep (warm) light-oil reservoirs ignite spontaneously (usually)• Deep (warm) light-oil reservoirs ignite spontaneously (usually)• In heavy oil reservoirs, combustion front can go out

• Predict conditions (injection rate, well locations, etc.) at which the front is stable

• Not yet achievableyProbably requires numerical simulation (available?) and a reliable

reaction model (not yet available)

Basic Process ChemistryBasic Process Chemistry

Three main types of reactions:1. Combustion

Hydrocarbon Fuel + O CO + H O + COHydrocarbon Fuel + O2 → CO2 + H2O + CO

2. Pyrolysis (coking)Hydrocarbons → Coke + Lighter Hydrocarbons

• With heavy oils, coke is main fuel for combustion• With light oils, other fractions contribute to fuel

3. Low-Temperature Oxidation (LTO)p ( )Hydrocarbons + O2 → Residue + Some [CO2, H2O & CO]• Residue contains much oxygen (especially ketonic)• Residue is highly viscous, and contains acids/surfactantsResidue is highly viscous, and contains acids/surfactants

Reaction ModellingReaction Modelling

Crude oil not uniform → must divide into pseudocomponentspseudocomponents

• Earliest methods used distillation cuts• More recent alternative uses SARA analysis Saturates Aromatics Resins A h lt Asphaltenes

SARA-Based Reaction Model

• Spits oil into SARA-based fractions• Saturates, aromatics, resins, asphaltenes

• Intended to replace distillation-cut modelsAl d h b d l i l f• Already have sub-models in place for combustion and pyrolysis reactions

• Low-temperature oxidation (LTO) reactions are more complex

• Active research topic

SARA fractions from a bitumen sample

Post Cold Production EOR: Air InjectionA N Ai I j ti P f Ll d i t H Oil tA New Air-Injection Process for Lloydminster Heavy Oils may prove to be one EOR process that succeeds in some reservoirs following CHOPS.

4 ha 8 ha

Air Injection

Installed in Existing Patterns

New Air Injection WellInjection Well

Inner PatternOuter Pattern

Objectives of the Project

1) Gather oil producers into a plan under which a field pilot test of air injection will be implemented soon.

2) Pre-determine the potential for suitable oil and gas flow rates in a2) Pre-determine the potential for suitable oil and gas flow rates in a “wormholed” field.

3) Conduct LTO kinetic tests on saturates and whole oil.

Hydrocarbon Oxidation Rates

Schematic of Lab EquipmentSchematic of Lab Equipment

Air SupplyGasometer

Air Supply

Flow

Tubular Reactor

Controller

Computer-Controlled Oven Gas Chromatograph

O2 Concentrations at Reactor OutletBaseline Test

25

70 % t t & 30% ti i d

20

(mol

%) 70 % saturates & 30% aromatics on reservoir sand

15

entr

atio

n

5

10

gen

Con

ce

Conditions: 160OC & 164 kPaAir Flux = 29.6 cm3/(cm2•min)

0

5

0 5 10 15 20 25

Oxy

g

0 5 10 15 20 25

Run Time (h)

O2 Concentrations at Reactor OutletBaseline Test

25

70 % t t & 30% ti i d

20

(mol

%) 70 % saturates & 30% aromatics on reservoir sand

15

entr

atio

n

5

10

gen

Con

ce

Conditions: 160OC & 164 kPaAir Flux = 29.6 cm3/(cm2•min)

0

5

0 5 10 15 20 25

Oxy

g

Measured Hypothetical Single Reaction

0 5 10 15 20 25

Run Time (h)

Causes of Induction Periods

1) Buildup of an essential free-radical reaction intermediate• Will likely be consumed if oxygen supply stops

2) O id ti i hibit2) Oxidation inhibitors• Free-radical scavengers that interrupt chain reaction• Are consumed by reaction with free radicals

If O2 supply is temporarily interrupted: Explanation 1 → Induction period re-occursp pExplanation 2 → Induction period resumes/never lengthens

Comparison of Test Results

25

20

n (m

ol%

)

15

ncen

trat

ion

5

10

xyge

n C

on

Inlet Air, First Interrupted Test

Reactor Outlet, Baseline Test

0

5

0 5 10 15 20 25

Ox

Reactor Outlet, First Interrupted Test

Reactor Outlet, Second Interrupted Test

0 5 10 15 20 25

Cumulative Time Air Injected (h)

Results of History Match

25

20

(mol

%)

15

cent

ratio

n (

5

10

ygen

Con

c

Inlet AirProduced Gas - Measured

0

5

Oxy Produced Gas - Simulated

0 5 10 15 20 25 30Run Time (h)

Discussion: So What?

Effect of inhibitors is less apparent in crude oils Already known: Saturates LTO faster only when other fractions are nearly

absentabsent• Rapid LTO occurs only when concentrations of both the inhibiting

saturates and other fractions are low Where/when does this occur?Where/when does this occur? Answer: During air/gas injection

• Aromatic-based compounds generally less volatile Inhibiting saturates probably have a polyaromatic core (?) Inhibiting saturates probably have a polyaromatic core (?)

• Already postulated to explain why deep light-oil reservoirs can ignite spontaneously

Main benefit: Have a way to simulate LTO repression!y p

Future Plans

Retain the services of a consultant to provide a generalized budget and schedule for field pilot.

Develop simulation techniques for testing against the pilot’s Develop simulation techniques for testing against the pilot s performance.

Assess the accuracy of chemical reaction models in regard to the y gformation of liquid/solid residues during LTO.

Continue field-scale simulations to determine whether wormholes can provide level of fluid mobility required for ISC.

PTRC-Supported Initiatives

• Collaboration between SRC and University of Calgary to promote aCollaboration between SRC and University of Calgary to promote a field pilot in post-cold produced heavy oil• Invitation for JIP

• Research contracts at SRC and University of Regina into better method to predict combustion front stability• Focus on reaction chemistry and kinetics• Focus on reaction chemistry and kinetics

Acknowledgements

Some of these slides originally appeared in the following presentation, presented at the CIPC conference, June, 2009:

• Freitag, N.P. 2009. Evidence That Naturally Occurring Inhibitors Affect the Low-Temperature Oxidation Kinetics of Heavy Oil. Paper SPE-2009-182 presented at the Canadian International Petroleum Conference, Calgary, Alberta, Canada, 16-18 June.

© 2009 Society of Petroleum Engineers© 2009 Society of Petroleum Engineers