© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
SURFACE PROCESSING
A – CRUDE OIL TREATMENT
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-SEPARATION – Contents
1- Well effluents Generalities
2- Gas/liquid separation
-equilibrium calculations
-influence of the process recovery rate
3- Separator sizing principles
-diphasic vertical separator
-diphasic horizontal separator
4- Gas/Liquid Separator different types
5- Foaming (difficult gas/liquid separation)
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-WELL HEAD EFFLUENTS
WELLHEAD
WELLHEAD
EFFLUENTS
EFFLUENTS
GAS
GAS
OIL
OIL
WATER
WATER
FORMATION SAND AND SILT
FORMATION SAND AND SILT
COLLOID STATE CLAY
COLLOID STATE CLAY
CORROSION PRODUCT
CORROSION PRODUCT
WAXES
WAXES
ASPHALTENES
ASPHALTENES
MINERAL CRYSTALS
MINERAL CRYSTALS
NaCl
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
SEPARATION CHAIN
EMULSION EMULSION INTERMINGLED WATER/OIL INTERMINGLED WATER/OIL FOAMS FOAMS LIQUID DROPLETS LIQUID DROPLETS IN GAS IN GAS WELLHEAD EFFLUENTS WELLHEAD EFFLUENTS CONDENSATE CONDENSATE FREE WATER FREE WATER GASGAS--LIQUIDLIQUID SEPARATION SEPARATION GAS TREATMENT GAS TREATMENT DEHYDRATION DEHYDRATION CONDENSATE CONDENSATE RECUPERATION RECUPERATION EMULSION EMULSION TREATMENT TREATMENT WATER WATER EMULSION EMULSION GAS GAS WATER WATER OPERATIONS SOMETIMES OPERATIONS SOMETIMES CARRIED OUT CARRIED OUT export crude OIL
OIL--WATERWATER
SEPARATION
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-SOURCE OF WATER
WATER AND OIL ZONES IN RESERVOIR
WATER AND OIL ZONES IN RESERVOIR
OIL
OIL
OIL
OIL
* Active Water Reservoir
* Active Water Reservoir
* Water Injection : Injection of 1
* Water Injection : Injection of 1
-
-
2 volumes of water
2 volumes of water
Production of 1
Production of 1
-
-
5 volumes of water per oil volume
5 volumes of water per oil volume
* Faulty Cementing Job
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
SOURCE OF SALT
SALT SALT RESERVOIR WATER RESERVOIR WATERINJECTED WATER (SEA WATER)
INJECTED WATER (SEA WATER)
*If Salt Content>10mg/l , Reservoir Water INGRESS
*If Salt Content>10mg/l , Reservoir Water INGRESS
Produced Water Not Detected; only salt content is measured
Produced Water Not Detected; only salt content is measured
*HASSI MESSAOUD : CAMBRIEN WATER 370g/l
*HASSI MESSAOUD : CAMBRIEN WATER 370g/l
Low Water Cut
Low Water Cut HIGH SALT CONTENTHIGH SALT CONTENT 0,1%
0,1% SALT CONTENT 370 mg/lSALT CONTENT 370 mg/l
*Sometimes HIGH SALT CONTENT without Water EAST BAGDAD As much as 265ppm of salt *** * Same for Hassi Messaoud - Fateh - ABK -Zadco This Phenomenon is limited in Time
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-OIL , BSW and GOR EVOLUTION WITH TIME
Production 106 m3 / an 3 2 1 GOR GOR OIL OIL BSW % 30 30 20 20 10 10 300 300 200 200 100 100 YEARS BSW BSW 1 1 22 33 44 55 66 77 88 99 1010 1111 1212 GOR
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
CONTRACTUAL WATER AND SALT CONTENTS
TRANSPORTERS
TRANSPORTERS
: LIMITATION FOR WATER CONTENT
: LIMITATION FOR WATER CONTENT
*PIPELINE
*PIPELINE
-
-
PIPE OVER LOADING
PIPE OVER LOADING
BSW <= 0.5%
BSW <= 0.5%
--
CORROSION ( WATER + SALT )
CORROSION ( WATER + SALT )
*BY SEA NO FIXED CONSTRAINTS
*BY SEA NO FIXED CONSTRAINTS
BUT
BUT
--
ACCIDENTAL CONTAMINATION
ACCIDENTAL CONTAMINATION
--
LOAD ON TOP CONTAMINATION
LOAD ON TOP CONTAMINATION
AGREEMENT
AGREEMENT
PRODUCERS
PRODUCERS
TRANSPORTERS
TRANSPORTERS
REFINERS
REFINERS
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-1 ELECTROSTATIC DESALTER
1 ELECTROSTATIC DESALTER
SALT CONTENT <5mg/l
SALT CONTENT <5mg/l
* SCALE DEPOSIT INSIDE EXCHANGERS
* SCALE DEPOSIT INSIDE EXCHANGERS
* DISTILLATION UNITS CORROSION
* RESIDUAL QUALITY DEGRADATION
* RESIDUAL QUALITY DEGRADATION
95 % EFFICIENCY
95 % EFFICIENCY
INLET SALT CONTENT < 100 mg/l
INLET SALT CONTENT < 100 mg/l
INLET SALT CONTENT < 100 mg/l
EUROPEAN REFINERIES
REFINERY : Salt...100 mg/l
REFINERY : Salt...100 mg/l
Water....0,2%
Water....0,2%
TRANSPORT : Salt...60 mg/l
TRANSPORT : Salt...60 mg/l
Water....0,5%
Water....0,5%
BSW in Production Fields < 0.5 %
BSW in Production Fields < 0.5 %
BSW in Production Fields < 0.5 %
PRODUCTION FIELD SPECIFICATIONS
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
DEHYDRATION
TO WITHDRAW WATER DISPERSED IN CRUDE STRESSING
THE WATER CONTENT
DESALTING
TO GET THE SALT SPECIFICATION WHEN THIS IS NOT THE
DIRECT RESULT OF COMPLYING THE WATER SPEC.
DESALTING IS A DEHYDRATION TRT SET
PREVIOUSLY WITH WASH WATER SOFTER
THAN RESERVOIR WATER
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-DEHYDRATION/DESALTING
With Reservoir Water at 350 g/l expressed as NaCl equivalent
0.1 % of Water Content
350 mg/l ( 123 PTB ) Salt Content
Salt Content < 60 mg/l
Water Content < 0.017 %
SALINITY IS THE MOST RESTRICTING SPECIFICATION
With Reservoir Water at 40 g/l expressed as NaCl equivalent
0.1 % of Water Content
40 mg/l ( 14 PTB ) Salt Content
Salt Content < 60 mg/l
Water Content < 0.15 %
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
2- Gas/liquid separation
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-GAS/LIQUID SEPARATION - Generalities
Hydrocarbon reservoir :
at reservoir conditions, generally one monophasic fluid
at surface conditions (P &T decrease), different components appear : monophasic polyphasic (gas + liquid)
hydrocarbon gas condensation of heavier hydrocarbons liquid water vapour liquid water
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
TREATMENT UNIT
AIM OF A TREATMENT UNIT
to recover all the different constituents
Process specific to each development to treat oil so that it is free of gas
to produce a gas as dry as possible (no water nor heavy hydrocarbons) to remove water (and solids) from oil
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e -Pr Pw Pf Pc Pr Reservoir Ps Storage Shipping Separation
Hydrocarbon production scheme
Pr: Reservoir pressure Pf: Bottomhole flowing pressure Pw: Wellhead pressure Pc: Choke pressure Ps: Processing pressure
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
Phase diagram
P Liquid Pr Vapour T 0 Pf 0 % 100 % Ps Pc Pw Bubble Point mole % liquid 30 % 15 % 5 % 1 %© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e -at Constant composition
1. Flash process
If T constant = flash liberation P1 V1 T1 P2 V2 T2 with P1 > P2 P1 V1 T1 P2 V2 T1 P1 > P2 P1 V1 T1 P2 V2 T2 P1 > P2 T1 > T2 If T varies = flash separation
G1 L1 P1 T1 G2 L2 P2 T2
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
total composition varies : there is draw off
2. Differential process
If T = constant = differential liberation P1 > P2 G1 L1 G2 L2 Gi Li GS P1 T1 P2 T2
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-3. Composite process : combination of the two
G L L G1L1 G2L2 GSLS PG TG PF TG P1 T1 P2 T2 Pa Ta Differential Liberation (T cst)
Flash Flash Flash
Reservoir Separators Storage
PG PF P1 P2 Pa Ta T2 T1 TG P T
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
OPTIMAL SEPARATION PRESSURE IN HYDROCARBON PRODUCTION FIELDS IS AN APPLICATION OF PHASE EQUILIBRIUM IN
THERMODYNAMICS
AMOUNT OF LIQUID RECOVERED IS DEPENDENT OF THE COMPOSITE PROCESS SEPARATION EFFICIENCYYIELD (R) = final stock tank oil mass / mass of hydrocarbons entering the processing unit
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-Influence of the Process Recovery rate
Separation P Pb 1 3 15° TG T Liberation 2 1 Rs P Flash Differential Pb Rs = V gas produced V oil at Pb
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
QUANTITIES OF FREE GAS ARE MORE IMPORTANT IN FLASH LIBERATION THAN IN DIFFERENTIAL LIBERATION
SIMILARLY, VOLUME OF LIQUID IS GREATER IN A DIFFERENTIAL PROCESS THAN IN A FLASH PROCESS
THE RELATIVE DIFFERENCE BETWEEN THE TWO CURVES DEPENDS ON THE NATURE OF THE OIL : SLIGHT FOR HEAVY OILS AND
GREATER FOR VOLATILE OILS
the higher the number of separation stages, the greater the liquid recovery but P at 1st stage is governed by well head P (i.e. reservoir P) number of stages is a compromise between costs of installation and liquid recovery© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e -G L G L Pi T1 Ps T1 Flash liberation
max gas & min liquid
One stage Application / Field Several stages P1 T1 P2 T1 L P3 T1 L Ps T1 G Separators Storage G L L G G
Influence of the process Recovery rate
in each separator : flash liberation
but the whole chain of separators represents a differential separation
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri Rule of thumb
Separation pressure at the different stages
n = number of stages + storage Examples GOR < 20 m3/m3 1°: 3-7 bara 2°: Storage GOR < 150 m3/m3 1° :10-20 bara 2°: 2-6 bara 3°: Storage P sep. HP P storage n - 1
R =
GOR > 200 1°: 20-40 bara 2°: 5-15 bara 3°: 2-5 bara 4°: Storage© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-PALANCA FIELD (ANGOLA)
Separation efficiency = final stock tank oil mass / mass of hydrocarbons entering the processing unit
at P = 25, 20, 15 & 10 bar
at T = 105°C, 90°C, 75°C
Determination of the optimal P & T and number of separation stages to get the higher separation efficiency
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri Sep. Efficiency (%) 74 73.5 73 72.5 0 10 20 105 Pressure (bars) 25 90 75° C 75 74.5 75.5 76 76.5 5 15
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e -Sep. Efficiency (%) 74.5 74 73.5 73 0 6 12 105 Pressure (bars)15 90 75° C 75.5 75 76 76.5 77 3 9
Low pressure separator pressure 77.5
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri Sep. Efficiency (%) 75.5 75 74.5 0 6 12 105 Pressure (bars) 15 90 75° C 76.5 76 77 77.5 3 9
Medium pressure separator pressure
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e -Pressure (bar) Output (%) 76.5 76 75.5 0 10 20 25 4 stages 77.5 77 78 5 15 3 stages 2 stages
PALANCA separation – output T=
75°C
significant gain between 2 & 3
less gain between 3 & 4 ECONOMICS COMPROMISE
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
Influence of separation temperature
Temperature
+
-Low Average High • Liquid • Economy • Water • Gas • H2S treatment • Gas Price EFFECT ON RECOVERY ( )
in general, the lower the T the higher the liquid recovery
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e -ASHTART Gas 13b - 110 °C 1b - 85 °C Gas Oil Gas 5b - 40 °C 1b - 35 °C Gas Oil
GAIN 9 % OIL at
lower T
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri BREME Flare 4b 40° C 1b Gas Oil Flare 4b 40° C 1b Gas Oil
GAIN 2.6 % OIL
from flare gas recovery
3.5 b 30° C
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-3- Separator sizing
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
Sizing of a separator
INCREASING COMPLEXITY OF FIELD INSTALLATIONS WITH THE AIM TO MAXIMISE RECOVEY AND OPTIMISE ALL PRODUCTION UNITS
INTRODUCTION TO GENERAL PRINCIPLES AND METHODS OF SIZING AND TYPICAL VALUES
SPECIFIC INSTALLATIONS AS HEATER-TREATER, CYCLONIC SEPARATORS, etc. ARE DETERMINED BY MANUFACTURERS
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-Sizing of a separator
DIMENSIONS FOR GAS AND LIQUID FLOWRATES ARE CALCULATED SEPARATELY
FOR GAS FLOWRATE, SPEED LIMITED TO PREVENT GAS FROM ENTRAINING DROPLETS OF LIQUID smallest diameter possible
FOR LIQUID FLOWRATE, RETENTION TIME SIZE TO ENSURE THAT
THE GAS IS COMPLETELY RELEASED FROM IT DEPENDS ON OIL CHARACTERISTICS
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri Basic data
Sizing of a separator
Gas : Flow rate - composition - specific mass Oil : Flow rate - composition - specific mass Retention time
1
Sizing for gas Sizing = passage cross-section
Passage cross-section = f (limit velocity gas) Limit velocity gas = liquid not drawn with it 2
Sizing for liquids Sizing = f (retention time)
Retention time = time needed for degassing Retention time = f (oil characteristics)
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-Vertical separator GAS
Aim : PREVENT WATER BEING DRAWN ALONG P T P = ΠΠΠΠD3 6 Lg Condition : P > A + R fixed D limit = 20 µm A = ΠΠΠΠD 3 6 Vg R = K ΠΠΠΠD2 4 V2 V V < K D L - V V 1 GOR L V ) = m/s Kv = f ( at D (Ø) L Liquid V V (velocity) Gas A R P
Sizing of a separator
weight aerodynamic force buoyancy liquid
max speed not to carry over D
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
Calculation of V (P and T) from M • Let M = 30 (0° C - 1013 mb) o = 22.430 Kg/m3 = MP ZRT • If T = 50° C and P = 20 bar V = o x P P0 x T0 T x 1 Z A few values of Kv
• Flare drum (horizontal) 0.04 m/s • Column head separator (horizontal) 0.07 m/s • Compressor suction (vertical) 0.04 m/s
= 22.430 x 1.01320 x 273323 x 0.931 = 24 kg/m3 Vertical separator GAS
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
Vertical separator LIQUID Transit time through the vessel
Concerns water and oil (Gas : pm) T = V Q = Π ΠΠ Π D2 4 x h Q
Sizing of a separator
T:transit time© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e -Gas Outlet GAS Oil outlet Water outlet OIL WATER Feed Water droplet Gas bubble Oil droplet
VERTICAL Separator / Liquid : liquid sizing
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
Vertical separator LIQUID Decantation time
STOKES' law
D=O.1 mm (around 20 to 30 µm in general) V = g D
2 ( L - V)
18 µµµµ
Sizing of a separator
V = settling velocity of the liquid droplet D = diameter of the droplet
L = specific gravity of droplet
V = specific gravity of the gas at P&T g = gravitational acceleration
µ = viscosity of the continuous phase
note : Decantation time is very dependant of the crude and water characteristics ( emulsions)
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-Vertical separator LIQUID Retention time (practical reference)
Sizing of a separator
corresponds to the value obtained by taking the volume
measured between the mean level and the low level, where the mean level usually is located in the middle of the drum
Often varies with the crudes from 2" to 5" in most cases
but can reach 10" or even 30" or 60" for "problematic" crude, i.e. heavy oils or acid crudes
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri Vertical separator
• Gas passage velocity :
V critical = 0.048 in m/s Common practices L - G G • Internal diameter : D = D in m Q in m3/h V in m/s Q 900. ΠΠΠΠ . V • Height of separator : 1.5 < Height/Diameter < 3 • Max. oil level :
Hoil < 0.65 D • Low oil level :
at 10 inches from the bottom • Retention time
Oil + water = 2" to 5"
If foaming or high viscosity : 10"
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e -Horizontal separator
Sizing of a separator
Demister Flow straightened cross sectionGas Liquids Secondary chamber Decantation chamber A R P liquid Horizontal separator Gravity Gravity Vertical separator Resultant Entrainment Entrainment Resultant Kv horiz. = 1.25 Kv vertical
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri L l Vh h D Water
h = continuous water height (water)
vh = decantation velocity of an oil droplet (rising)
vwater = displacement velocity of the continuous water phase (horizontal)
l = minimum decantation length
t = decantation time.
Oil droplet Vwater
Horizontal separator
Sizing of a separator
Decantation time with Stokes law
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-Sizing of a separator: Summary
GAS IS THE PRIORITY PARAMETER TAKEN INTO ACCOUNT IN THE DESIGN OF SEPARATORS
LIQUID TRANSIT TIME (often referred as Retention time) IS MORE EMPIRIC AND IS MORE BASED ON EXPERIENCE WITH SAFETY MARGINS MORE OR LESS IMPORTANT
DECANTATION TIME FOR LIQUIDS IS GENERALLY BASED ON LAB EXPERIMENTS
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
4- Gas/Liquid Separator
different types
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-Vertical 2 phase separator
Drainage duct Pressure valve Safety seal Mist extractor Pressure gauge Déflector Oil and gas inlet Primary chamber Visual level monitor Decantation chamber Base Purge Oil outlet Manhole Isolation partition Centrifugal effect in a vertical separator Gas flow Liquid flow 3 2 1 1. body of separator 2. gas outlet (high point) 3. fluid input
Deflector action
well adapted for low GOR
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
Horizontal 2 phase separator
Mist extractor Settling section Secondary chamber Primary chamber Diffuser Gas + liquids inlet Decantation chamber Separation partition Purge Anti-wave partition Chassis Oil outlet Gas Liquid Gas outlet well adapted for high GOR
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-gas outlet Inlet
liquid outlet
High-pressure horizontal separator with liquid retention capacity
large capacity high P
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
Spherical 2 phase separator
Fluids inlet Gas outlet Oil outlet Level regulation Scrubber Deflector rare
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-Cyclone effect separator
Gas outlet
Gas + Liquid inlet
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
Multi-cyclone separator
Multi-cyclones Gas outlet Liquid outlet Diffuser Gas inletLiquid level Secondary drain Retention
volume
Liquid outlet
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-Other types
of gas/liquid separators
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
Gas SCRUBBER
Mist extractor Sifter© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-VAPE SORBER
Absorbent material Porous filters© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
Components
of a gas/liquid separator
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-Horizontal 2 phase separator components/internals
Mist extractor Settling section Secondary chamber Primary chamber Diffuser
Gas + liquids inlet
Decantation chamber Separation partition Purge Anti-wave partition Chassis Oil outlet Gas outlet
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
5- Foaming
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-Foaming
Origin• Gas expansion + oil / gas surface tension
• Pure liquids do not foam A surfactant is needed
Mixtures of isomers in hydrocarbons are surfactants • Foams are unstable (state of least energy)
• The internal viscosity of the oil stabilises the foam, leading to drawing along of the gas (foaming)
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
FOAMS
–
FOAMS are oil + gas "emulsions"
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-–
INCONVENIENTS :
•
oil entrainments in gas (affecting scrubbers, flares,
compressors protection, gas treatment solvents ...),
and gas entrainments in oil ( pump cavitation, later
degassing...)
•
loss of control of levels in separators
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri GAZ
• the speed of drainage is
dependant of the viscosity of
the oil
•the max width is dependant
of the liquid interfacial
tension
INTERFACIAL FILM© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e -•
• NATURAL SURFACTANTSNATURAL SURFACTANTS •
• ADDED SURFACTANTS (PRODUCTION CHEMICALS)ADDED SURFACTANTS (PRODUCTION CHEMICALS) •
• SOLID PARTICULESSOLID PARTICULES •
• WATER DROPLETSWATER DROPLETS
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
Foaming is dependant on crude characteristics
BUT
• If asphaltene content > 1 %, higher foaming and stability
• if acid index >0.2 mg KOH/l, lower quantity of foam & higher stability
• The % of water and additives (anticorrosion etc… ) do not appear to have any effect on the phenomenon
Tendency to foam
API 40 = .825 API 30 = .876 Increase in % vol.
Foam breaking in seconds
API > 40 30 < API < 40 API < 30
10 - 20 20 - 40 > 50 30 30 - 60 > 60
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-• THE VERTICAL SPEED OF GAS BUBBLES IS HIGH DUE TO THE
HIGH DENSITY DIFFERENCE WITH THE OIL (STOKES LAW)
• GAS BUBBLES FLOCCULATE AT THE SURFACE AND CREATE A
"MATTRESS"
• COALESCENCE BECOMES THE LIMITING FACTOR
– THE LIQUID IS DRAINED OUT OF THE INTERFACIAL FILM
DECREASING ITS WIDTH UNTIL A MINIMUM VALUE IS REACHED WHERE IT BREAKS
– BREAKING WIDTHS ARE MUCH THINNER THAN FOR EMULSIONS
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
•
•
IT IS POSSIBLE TO :
IT IS POSSIBLE TO :
–– increase the breaking width of the foam by adding a chemicalincrease the breaking width of the foam by adding a chemical –
– increase the speed of drainage by lowering the liquid increase the speed of drainage by lowering the liquid viscosity (HEAT)
viscosity (HEAT)
–
– install separator internals acting on install separator internals acting on wettabilitywettability –
– use separators equipped with specific cyclonic inlet devicesuse separators equipped with specific cyclonic inlet devices
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e -Treatment • Mechanical - Washing
- longer time spent in installation • Chemical - anti-foam
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri Chemical Treatment Action:
• displace the foam stabilizing element from the bubble walls • or cause bubbles to burst locally
Necessary conditions:
• be soluble in the foaming system • disperse satisfactorily
• have surface tension < that of the foam
ANTI-FOAMS
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-anti
anti
-
-
foam additives
foam additives
– MOSTLY USED : SILICONE OILS ( POLYSILOXANES )
– EFFICIENT AT 2/3 ppm (4 to 5 ppm if diluted )
– HAVE TO BE INJECTED UPSTREAM THE SEPARATOR BUT THE
CLOSER FROM THE INLET
• LOSS OF EFFICIENCY AFTER A CERTAIN PERIOD OF TIME)
• LOOSE THEIR EFFICIENCY WHEN TOO MUCH MIXED WITH THE CRUDE
THESE PRODUCTS ARE REFINERY CATALYSTS POISONS their dosage have to be strictly controlled
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
OTHER PRODUCTS
OTHER PRODUCTS
:
:
–
Heavy Alcohols, cheap but weak efficiency
–
fluoro-Silicones, very efficient but expensive
•
to be used in severe cases
Selection implemented in the Flash Foaming Test (Lab)
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-CRUDE OIL FOAMING TENDENCIES
FLASH FOAMING TEST
FLASH FOAMING TEST
M
PI TR TR OIL STORAGE NITROGEN BUTANE TO WATER BATH CALIBRATED CYLINDER ADJUSTABLE CONTROL VALVE ( 35 L/H) PROCEDUREP = 10 BARS with N2 / BUTANE T = 60 ° C
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
Gutter separator
for foam treatment
Diffuser Oil Inclined plates Inlet Mist extractor Gas
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri Section X-X
FOAMS TREATMENTS : mechanical
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
-Foam treatment
by heating
in salt water bath
Mist extractor Inlet Burner LC (water) Water LC (water) oil Gas Gas PC (gas) Oil Heating Salt water
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri
•
•
FOAMS ARE SIMILAR TO EMULSIONS
FOAMS ARE SIMILAR TO EMULSIONS
•
•
HEAVY OILS (viscous) OR ACID/NAPHTENIC CRUDES
HEAVY OILS (viscous) OR ACID/NAPHTENIC CRUDES
(natural surfactants) ARE CREATING STRONG FOAMS
(natural surfactants) ARE CREATING STRONG FOAMS
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•
IF FOAMING HAS BEEN ANTICIPATED, OVERSIZING
IF FOAMING HAS BEEN ANTICIPATED, OVERSIZING
OF SEPARATORS OR SEPARATOR INTERNALS CAN
OF SEPARATORS OR SEPARATOR INTERNALS CAN
BE CHOSEN TO LIMIT INCONVENIENTS
BE CHOSEN TO LIMIT INCONVENIENTS
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•
IF NOT, FOAM TREATMENT USUALLY REQUIRES
IF NOT, FOAM TREATMENT USUALLY REQUIRES
HEAT + CHEMICAL TREATMENT
HEAT + CHEMICAL TREATMENT
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e
© 2 0 0 7 E N S P M F o rm a tio n In d u s tri Pressure (bars) 300 250 200 150 100 50 0 0 50 100 150 200 100 % 98.4 97.2 96 94.4 91.7 88.9 85.1 80 T(° C) TG P1 Bubble curve 88.9 %
Flash liberation
Yield (R)© 2 0 0 7 E N S P M F o rm a tio n In d u s tri e -Pressure (bars) 300 250 200 150 100 50 0 0 50 100 150 200 100 % 95.0 88.1 86.2 T(° C) TG P1 Initial bubble curve in the reservoir 83.7 92 % Elimination of gas Bubble curve at perforations
Differential liberation
Yield (R)© 2 0 0 7 E N S P M F o rm a tio n In d u s tri Pressure (bars) 300 250 200 150 100 50 0 0 50 100 150 200 100 % 91.0 88.9 T(° C) P1 Initial bubble curve in the reservoir 84.7 90 % 1st stage separation gas elimination Perforations 86.7 Well head Bubble curve at perforations