ENHANCED OIL RECOVERY PROCESSES docx

ENHANCED OIL RECOVERY PROCESSES -Polymers and Surfactants -4-GAS INJECTION as a promising EOR process - Specificities,Mechanisms,Efficiencies,Selection criteria,Ratios,Methodology to

ENHANCED OIL RECOVERY PROCESSES

-Polymers and Surfactants

-4-GAS INJECTION as a promising EOR process

- Specificities,Mechanisms,Efficiencies,Selection criteria,Ratios,Methodology to conduct a GI project

Typical Oil Field Performances

WATER INJ.

Ultimate Reserves and Recovery mechanism sequence

N pu =N 1 +N 2 +N 3 at economical abandonment conditions

=N 1 +(N i -N 1 )[E d xE vol ] water +(N i -N 1 -N 2 )[E d xE vol ] gas

How to optimise N pu ?How to combine N 1 ,N 2 ,N 3 ?

Main parameters?

N 1 (nat.depl.) :identification-limitations-duration

N 2 (water inj.) :limitations-implementation-duration

N (EOR) :process selection-implementation

Tertiary Recovery Objectives

PRODUCE- ECONOMICALLY - PART OF OIL LEFT BY CONVENTIONAL RECOVERY METHODS

– Improvement of displacement efficiency

– Improvement of volumetric sweep efficiency

lowering mobility ratio by increasing m w

chemical flood - polymers

reducing m o

thermal flood

Microscopic and Volumetric Sweep Efficiencies

Example of Five Spot Injection

Pore Level Mechanisms - Microscope Efficiency

· Competition between viscous and capillary forces capillary number:

· Competition between gravity and capillary forces Dombrowski

PORE SIZE DIST'N

WIDE AVERAGE NARROW

Water Injection Efficiency

Water-flood efficiency = Areal sweep efficiency

x Vertical sweep efficiency xDisplacement efficiency Limitations: Ed<1

Eareal<1

Evertical<1

f(pattern,mobility ratio) vs.layer contrast

Sorw = 0

Limitations of conventional

methods-Recovery by conventional methods=

Natural depletion +Water injection recovery

=N 1 +N 2

=N 1 +(N i -N 1 ) x Edispl X Evol.

Ed= Oil left in swept zones

Evol<1 ~0.4 to 1 Oil left in unswept zones

S oi -S orw 1-S wi <1 ~60%

Enhanced Oil Recovery Methods

Enhanced Oil Recovery

IMPROVEMENT OF VOLUMETRIC EFFICIENCY Evol

IMPROVEMENT OF DISPLACEMENT EFFICIENCY Ed

INCREASE WATER VICOSITY

HEAVY OIL

STEAM INJECTION POLYMER

SURFACTANT MISCIBLE NEAR MISCIBLE GAS INJECTION

HC,CO2,N2,AIR,… IMMISCIBLE LEAN

GAS INJECTION STEAM INJ.(LIGHT OIL)

II- Gas reservoirs

EOR contribution in the world oil production

World Oil reserves estimates( P.R.Bauquis-2000-)

-Conventional reserves ( billion stb )

Initial 1800 to 2500

Cumulative production 800 800

Remaining to be produced 1000 to 1700

-Non conventional reserves

(economically recoverable at year 2030 horizon)

Deep offshore (below 500m water depth) 100 100

Ultra heavy oil (50/50 Orinoco and Athabasca) 600 600 GasToLiquids conversion 100 100 -Overall reserves 1800 to 2500

TENTATIVE ESTIMATE of EOR POTENTIAL

YEAR 2000 ROUGH WORLD RESERVE‘’GUESTIMATE’’

(for an initial oil in place of >3500billion stb)

1% recovery factor improvement~35 billion stb !

Deep offshore:100 billion stb

Heavy oil :600 billion stb

*onshore+offshore( less than 300 meters water depth)

TENTATIVE ESTIMATE of EOR POTENTIAL

CASE of MATURE or AGEING OIL FIELDS

(more than 20 years old and/or in declining phase)

-75% of the conventional reserves located in mature fields

-70% of the world production from fields of >20years

old,majority of them started their decline phase(generally increasing water-cut)

ENHANCED OIL RECOVERY

F Methods:Increase reservoir temperature

Steam Injection In-situ Combustion

F Effect

Reduction of oil viscosity due to heating effect

Thermal Flood

Fundamentals of Reservoir Engineering

HEAVY OIL(°API<20-25)=HIGH VISCOSITY(10 to > 10 6 cpo)

=LOW PI =LOW or VERY LOW RATE

Confusing heterogeneous denominations :

- Heavy Oil, Extra Heavy Oil, Oil Sands, Tar Sands, Bitumen,

….

è need for a simple classification

4 Classes based mainly on downhole viscosity :

0 A Class : Medium Heavy Oil 25°> d°API > 18°

100 cPo > m > 10 cPo, mobile at reservoir conditions

0 B Class : Extra Heavy Oil 20°> d°API > 7°

10 000 cPo > m > 100 cPo , mobile at reservoir conditions

0 C Class : Tar Sands and Bitumen 12°> d°API > 7°

m > 10 000 cPo, non mobile at reservoir conditions

0 D Class : Oil Shales

Reservoir = Source Rock, no permeability Mining Extraction only

Heavy Oil : a mix of heterogeneous denominations

Heavy Oil (excluding Oil Shales) : 3 Main Categories

Heavy Oil Classification

Duri

Wabasca Athabasca

Peace river Cold lake

Lloyminster

Cat canyon

Kern river

Mount poso Midway

Yorba linda Belridge Poso creek

Pilon Morichal Eljobo Boscan

Grenade

Varadero

Boca de Jaruco Bechraji

Upper & Lower Ugnu

Fazenda belem Alto do rodrigues 2

C Class : Tar Sands & Bitumen

A Class : Medium Heavy Oil

u

Canada

Steam Injection

F Steam : Good Heat Carrier

T ö mo ø Oil Mobility Increases

Steam Distillation Process in Zone 1 :

Light Oil Vapor Condenses and Enriches Existing Oil

Reduction on Sor Thanks to Solvent Slug

Cyclic Steam Injection Process Scheme

Produced fluids Soak period

Water Viscous oil

Heat Steam

Thermal Methods

Fundamentals of Reservoir Engineering

Cond.

water

Cyclic Steam Injection

Cyclic Steam Stimulated Producers with Drainage Area

Thermal Methods

Fundamentals of Reservoir Engineering

In Situ Combustion

F Oil is Ignited around Well Bore

F Burning Front Sustained by Continuous Injection of Air

F A Small Portion of the Oil is Burned

F The Heat Generated

F Continuous Air Injection Develops Efficient Gas Drive Mechanisms

Thermal Methods

Fundamentals of Reservoir Engineering

Air Injection

Schematic Representation of in Situ Combustion Process and

the Various Zones as Formed in the Oil Reservoir

Air Injection

Mechanisms : Oil + Flue Gas

F Reservoir Pressure Maintenance / Repressurization

F Gravity Stable Displacement

F Oil Swelling

F Miscibility - Flue Gas / Reservoir Oil

Air Injection

Mechanisms Air + Oil + Water

N 2 + Oil Oil Stripping Hc Gas + Stripped Oil

STEAM

FLUE GAS

Air Injection

F Oxygene Oil Reactivity vs Reservoir Temperature

F Possible Spontaneous Oil Ignition and Complete Comsumption

F Two Classes of Oxidation Reactions :

Polar Compounds : Alcohol, Ketone, Aldehyde, Ester

Air Injection

Experimental Programme : Simulations

F Simulations with Therm (SSI)

F Reaction Stoichiometry for Combustion

1- C 11+ + 23.54 O 2 21.66 CO X + 11.91 H 2 o + Heat 2- PS4 + 8.39 O 2 7.72 CO X + 4.25 H 2 o + Heat 3- PS3 + 4.35 O 2 4 CO X + 2.2 H 2 o + Heat

F Reaction Rates Based on Arrhenius Equation

Model Therm Features

Temperature, Composition computed for each cell at each time step

- Heat from surrounding cells by CONVECTION

- Heat from surrounding cells by CONDUCTION

- Heat from surrounding cells by RADIATION

- Heat from the cell itself

Heat of Reaction in the grid block (reaction r)

Chemical Reactions

O 2 + flue gas + heavy ends

Thermal front (water + oil vaporisation

fuel oil Condensed oil + flue gas + condensed water + fuel oil

Oil rim + flue gas

S orw + flue gas

Flue gas (N 2 + CO + CO 2 + HC)

Oil Steam Water

"Heavy Oils" : Wordwide OiI In Place

Worlwide Oil in Place : # 4,600 Gb

"Heavy Oils" : Resources of 4000 to 5000 Gb (OIP) Potential Reserves depends on recovery factors

Light Oil Reserves

270

Considerable Potential Reserves : # 500 to 1000 Gb

equivalent to 50-100% of worldwide conventional oil reserves

5 to 10 times (?) the ultra-deep offshore potential reserves mainly (80%) in extra heavy oil, tar sands and bitumens mainly (80%) in North and South America

less than 1% produced or under active development

Heavy Oil Reserves

Huge Untapped Resources in Orinoco and Athabasca

Tar Sands & Bitumen

(µ > 10,000 cPo)

Oil in place: 1,300 Gb (EUB estimates)

The Orinoco Belt Deposits:

a New Saudi Arabia?

First exploration campaigns in the 1930’s

One of the largest extra heavy crude oil deposits in the world

Recoverable reserves

• 100 Bbls

• Estimated potential reserves of around 300 Bbls (post 2020)

• Extra heavy crude oil (8 - 10° API), with high sulfur content

• Shallow sand reservoirs

Saudi Arabia conventional oil reserves estimated around

Orinoco

1,200 Bbls oil in place

Cold Production Scheme

550 m

1 400 m

20 0 m

Electrical Submersible pump

SINCOR FIELD - Reservoir model parameters

Parameters (fluvial) Permeability : 20 D Kv/Kh: 0.1

Cp 10 E-6psi-1 Viscosity @ Pbp 2000 cP

Constraints

SAGD Process

SAGD Process

Bitumen is solid at reservoir conditions

Preheating phase needed to establish hydraulic communication Steam injection and production of condensed water and mobile oil

Oil reservoir

Steam injection well

Heated oil and condensate flow

to well

Production well, oil and condensate are drained continuously

Steam flows to interface and condenses

Horizontal well pair

ENHANCED OIL RECOVERY

F The Process is Conducted in Two Steps :

Injection of the Surfactant Slug Injection of the Polymer Mobility Buffer

Surfactant - Polymer Injection

Fundamentals of Reservoir Engineering

F Method

Addition of Polymers to Water Being Injected This is Done in Conjunction with Surfactants Polymers : Organic Materials Soluble in Water

F Effect

Increase of Water Viscosity

Chemical Flood Polymers

Fundamentals of Reservoir Engineering

Fundamentals of Reservoir Engineering

Water Injection Sweep Efficiency

Effect of Polymer Flooding

Water Flooding

Polymer Flooding

Schematic View of Polymer Flood

Water

Oil

Fresh Water

Fresh Water

Polymer solution

Chemical Methods

Fundamentals of Reservoir Engineering

WATER INJECTION + SURFACTANTS

Not Efficient

Difficult at High Temperature with High Salinity

In Carbonate Reservoirs

Water Injection + Chemicals

Fundamentals of Reservoir Engineering

ENHANCED OIL RECOVERY PROCESSES

Gas Injection:Objectives

Ø Analyse the traditional misgivings against Gas Injection

Ø Show the decisive improvements in 3 domains :

F Lean Gas Injection

F Near Miscible Gas Injection

F Air Injection

Thanks to : - R & D Achievements

- Gas Injection Active Project Review and Re-study

Gas Injection = a Promising Future for E.O.R.

Optimum Technical Recovery

INJECTION EFFICIENCY =

= E volumetric x E microscopic

OIP left after injection

Swept zones : E MIC =

Gas Injection = a Promising Future for E.O.R.

OIP before injection - OIP after injection

OIP before injection

in swept zones (Ev) = Sorg

in unswept zones (1 - Ev) = Soi

Soi - Sorg Soi

EOR by Gas Injection - Volumetric and Microscopic Sweep Efficiencies

S org

Gas Injector

Oil Producer

Oil Producer

Oil

Producer

S oi

Nature of Gases and Injection Conditions

Ø Nature :

F Hydrocarbon (Lean, Rich, Enriched)

F Non Hydrocarbon : CO 2 , N 2 , Air, Flue Gas

Ø Injected Gas / Rock Fluids Reactions :

F Exchanges (Mass Transfert) = Important or Not

F Thermal Effects or Not (O 2 Presence)

Ø Conditions : Secondary or Tertiary Conditions

(Nb : Fractured Reservoirs : Specific Mechanisms)

Gas Injection = a Promising Future for E.O.R.

HYDROCARBON GAS COMPOSITION

Methane Ethane Propane Butane Pentane …

CH 4 C 2 H 6 C 3 H 8 C 4 H 10 C 5 H 12 …

C 1 C 2 C 3 C 4 C 5 +

LEAN GAS: lean in intermediate components

low liquid content(LPG+CONDENSATES)

C

RICH GAS: rich in intermediate components

fairly high liquid content(LPG+CONDENSATES)

60%<C

Gas Injection = a Promising Future for E.O.R.

– Majority of IOR projects in the world:

Ù Water injection (for conventional oil)

Ù Steam injection (for heavy oil)

– Gas injection: traditional misgivings

Ù Poor sweep efficiency( g/o mobility ratio >>1) and unstable displacements

Ù High compression cost (vs Water pumping)

Ù Gas availability (demanding gas market)

– Exception to this "Ostracism":

Ù Us = CO 2 injection

Ù Canada = rich gas/Lpg injection

Ù Venezuela (Oriente), Iran (Asmari), Libya (Intissar)

Ù Algeria (Hassi-Messaoud)

Injected fluids:Gas Specificities( vs.Water)

Ø Exchanges with Oil Need for Equation Of

Ø Higher Sensitivity to Reservoir Heterogeneities

Ø Need More Design Optimization

F Enhanced Understanding of Mechanisms

F Sophisticated Lab Experiments

F Compositional Modelling

F Reservoir Characterization

Gas Injection = a Promising Future for E.O.R.

Benefits of Gas Injection

F Good Macroscopic Efficency if :

-Gravity Stable Displacement

-Possible Mobility Control by WAG (water alternating gas)

Gas Injection = a Promising Future for E.O.R.

Tertiary Oil Recovery by Gas Injection

Thermodynamic conditions during oil displacement

– Miscibility

– Partial miscibility

· Vaporizing gas drive

· Condensing gas drive

– Immiscibility

Reservoir conditions

– Secondary

– Tertiary

Miscibility Diagram for a Reservoir Oil Vs Injected Gas Composition and Pressure

(At reservoir temperature)

1 2 3 4

Gas injection-Two Domains :

Gas Injection = a Promising Future for E.O.R.

Microscopic Oil Displacement by Water and Gas

S oi

Miscible Gas Injection

Water Injection

Lean Gas Injection

Pore Level Mechanisms - Microscope Efficiency

· Competition between viscous and capillary forces capillary number:

· Competition between gravity and capillary forces Dombrowski

PORE SIZE DIST'N

WIDE AVERAGE NARROW

Miscibility Diagram for a Reservoir Oil Vs Injected Gas Composition and Pressure

(At reservoir temperature)

1 2 3 4

EOR by Gas Injection:MMP(Minimum Miscibility Pressure)

Graphical laboratory determination

Slim tube experiments(42ft lenght)

Actual reservoir temperature and actual gas(fixed composition)

6 to 8 points increasing pressure

EOR by Gas Injection:MMR(Minimum Miscibility Richness)

Graphical laboratory determination

Slim tube experiments(42ft lenght)

Actual reservoir temperature and actual gas(fixed pressure)

6 to 8 points increasing enrichment

100%

>90%

MMR

Benefits of Gas Injection

EFFICIENCY = Microscopic Sweep Efficency

x Macroscopic Sweep Efficency

Good Microscopic Efficency (S oi -S org )/S oi if :

-Swelling

-Phase Behaviour

-Miscible or Near Miscible Displacements

Sorg lower than Sorw or Sorg= 0 ?

Gas Injection = a Promising Future for E.O.R.

Main R & D Achievements

Ú Pre and Post Processing

Gas Injection = a Promising Future for E.O.R.

R & D : Practical Effects

Ø Better Predictions

Ø Possibility to Perform Numerous Sensitivity Runs

Nature of Gas Richness of Gas Pressure

Injection / Production Scheme Optimum Development : Mmp or Mmr ?

Ø Efficiency of Gravity Drainage in Tertiary Conditions

Gas Injection = a Promising Future for E.O.R.

E x E VOL MIC

MMP

Gas Injection = a Promising Future for E.O.R.

Optimum Technical Recovery

E MIC =

If E MIC = 1 E VOL x E MIC Maximum ?

Ø Example : Case 1 : E MIC = 1, E VOL = 0.6

Case 2 : E MIC = 0.8, E VOL = 0.8

Case 2 better than Case 1!

Gas Injection = a Promising Future for E.O.R.

Soi - Sorg Soi

1 at miscible conditions (Sorg = 0)

< 1 at non miscible conditions (Sorg ¹ 0)

Gas Injection = a Promising Future for E.O.R.

GRAVITY DRAINAGE MECHANISM

None or limited thermodynamical exchanges at fairly low

pressure

Gravity drainage in the gas invaded zone may be very efficient

Gravity drainage is a recovery process in which the gravity force

is the main mechanism

gravity forces > capillary forces

h Dr og g > 2 s og cos q / r

Gravity drainage must be efficient within an economical time scale

Immiscible Lean Gas Injection