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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
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Conventional In-Situ Combustion
M. Szeoke, In Situ Combustion Research Group, University of Calgary
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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)
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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
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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
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THAI: Current Technologies
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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
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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)
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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
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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
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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
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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
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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.
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Hydrocarbon Oxidation Rates
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Schematic of Lab EquipmentSchematic of Lab Equipment
Air SupplyGasometer
Air Supply
Flow
Tubular Reactor
Controller
Computer-Controlled Oven Gas Chromatograph
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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)
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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)
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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
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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)
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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)
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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
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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.
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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
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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