1 - Crude Oil Treatment - Separation 556z3x
This document was ed by and they confirmed that they have the permission to share it. If you are author or own the copyright of this book, please report to us by using this report form. Report 3l3c15
Overview 3z723u
& View 1 - Crude Oil Treatment - Separation as PDF for free.
More details 2i4a6q
- Words: 4,593
- Pages: 85
SURFACE PROCESSING
A – CRUDE OIL TREATMENT I- SEPARATION © 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
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
5- Foaming (difficult gas/liquid separation) Next course: Oil/Water separation PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
4- Gas/Liquid Separator different types
1- Well head effluents © 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
WELL HEAD EFFLUENTS
GAS WELLHEAD EFFLUENTS
OIL WATER FORMATION SAND AND SILT COLLOID STATE CLAY
MINERAL CRYSTALS NaCl CaCO3 BaSO4 SrSO4
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
CORROSION PRODUCT WAXES ASPHALTENES
SEPARATION CHAIN
FOAMS LIQUID DROPLETS IN GAS
WELLHEAD EFFLUENTS
GAS
GAS TREATMENT DEHYDRATION CONDENSATE RECUPERATION
GAS-LIQUID SEPARATION
CONDENSATE WATER
EMULSION INTERMINGLED WATER/OIL
OIL-WATER SEPARATION OPERATIONS SOMETIMES CARRIED OUT in 1 PROCESS EQUIPMENT PRO01198 – CRUDE OIL TREATMENT - Separation
EMULSION TREATMENT
EMULSION FREE WATER
WATER
© 2007 ENSPM Formation Industrie - IFP Training
export crude
SOURCE OF WATER
WATER AND OIL ZONES IN RESERVOIR
OIL OIL
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
* Active Water Reservoir * Water Injection : Injection of 1-2 volumes of water Production of 1-5 volumes of water per oil volume * Faulty Cementing Job
SOURCE OF SALT RESERVOIR WATER SALT
INJECTED WATER (SEA WATER)
*HASSI MESSAOUD : CAMBRIEN WATER 370g/l Low Water Cut 0,1%
HIGH SALT CONTENT SALT CONTENT 370 mg/l
*If Salt Content>10mg/l , Reservoir Water INGRESS *Sometimes HIGH SALT CONTENT without Water EAST BAGDAD As much as 265ppm of salt ***
Produced Water Not Detected; only salt content is measured
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
* Same for Hassi Messaoud - Fateh - ABK -Zadco This Phenomenon is limited in Time
OIL , BSW and GOR EVOLUTION WITH TIME Production 3
difficulty to design separation equipment
106 m3 / an
OIL
2
BSW
GOR
%
1
1
300
20
200
10
100
BSW 2
3
PRO01198 – CRUDE OIL TREATMENT - Separation
4
5
6
7
8
9
10
11
12
YEARS
© 2007 ENSPM Formation Industrie - IFP Training
GOR
30
CONTRACTUAL WATER AND SALT CONTENTS
CRUDE OIL MARKETING
AGREEMENT
$
Business is business!!
$
PRODUCERS TRANSPORTERS REFINERS
TRANSPORTERS : LIMITATION FOR WATER CONTENT *PIPELINE
BSW <= 0.5% NO FIXED CONSTRAINTS - ACCIDENTAL CONTAMINATION - LOAD ON TOP CONTAMINATION
PRO01198 – CRUDE OIL TREATMENT - Separation
BUT
© 2007 ENSPM Formation Industrie - IFP Training
*BY SEA
- PIPE OVER LOADING - CORROSION ( WATER + SALT )
CONTRACTUAL WATER AND SALT CONTENTS
EUROPEAN REFINERIES 1 ELECTROSTATIC DESALTER SALT CONTENT <5mg/l * SCALE DEPOSIT INSIDE EXCHANGERS * DISTILLATION UNITS CORROSION * RESIDUAL QUALITY DEGRADATION 95 % EFFICIENCY INLET INLETSALT SALTCONTENT CONTENT<<100 100mg/l mg/l PRODUCTION FIELD SPECIFICATIONS Salt...100 mg/l
TRANSPORT :
Salt...60 mg/l
BSW BSWin inProduction ProductionFields Fields<<0.5 0.5% % PRO01198 – CRUDE OIL TREATMENT - Separation
Water....0,2% Water....0,5%
© 2007 ENSPM Formation Industrie - IFP Training
REFINERY :
DEHYDRATION/DESALTING
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.
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
DESALTING IS A DEHYDRATION TRT SET PREVIOUSLY WITH WASH WATER SOFTER THAN RESERVOIR WATER
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 40 mg/l ( 14 PTB ) Salt Content
Salt Content < 60 mg/l
Water Content < 0.15 %
WATER CONTENT IS THE MOST RESTRICTING SPEC. PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
0.1 % of Water Content
2- Gas/liquid separation
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
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
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
THERMODYNAMIC BEHAVIOUR
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
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
to remove oil and solids from water (Water Treatment specific courses)
Hydrocarbon production scheme Pw
Pc Separation Storage
Shipping
Ps
Pr
Pr
PRO01198 – CRUDE OIL TREATMENT - Separation
Pr: Pf:
Reservoir pressure Bottomhole flowing pressure Pw: Wellhead pressure Pc: Choke pressure Ps: Processing pressure
© 2007 ENSPM Formation Industrie - IFP Training
Pf
Reservoir
Phase diagram
P Pr Liquid Pf Bubble Point
100 %
30 %
Pc
Ps
PRO01198 – CRUDE OIL TREATMENT - Separation
5%
1%
0% mole % liquid T
© 2007 ENSPM Formation Industrie - IFP Training
15 %
0
Vapour
Pw
METHANE - ETHANE MIXTURE PHASE DIAGRAM
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
GAS PHASE ENVELOPPE SHAPE VERSUS GAS COMPOSITION
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
1. Flash process
P1 V1 T1
P2 V2 T2
with P1 > P2
at Constant composition If T constant = flash liberation P1 V1 T1
P2 V2 T1
P1 > P2
P2 V2 T2
P1 > P2 T1 > T2
If T varies = flash separation
G1 L1 P1 T1 PRO01198 – CRUDE OIL TREATMENT - Separation
G2 L2 P2 T2
© 2007 ENSPM Formation Industrie - IFP Training
P1 V1 T1
2. Differential process P1 > P2 G1 L1
GS Gi Li
P1 T1
G2 L2 P2 T2
total composition varies : there is draw off
If T = constant = differential liberation © 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
3. Composite process : combination of the two Separators
Reservoir
Storage
PG TG
PF TG
P1 T1
P2 T2
Pa Ta
L
G L
G1 L1
G2 L2
GS LS
Differential Liberation (T cst)
Flash
Flash
Flash
P PG PF
P2 Pa
T Ta
PRO01198 – CRUDE OIL TREATMENT - Separation
T2
T1
TG
© 2007 ENSPM Formation Industrie - IFP Training
P1
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 EFFICIENCY
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
YIELD (R) = final stock tank oil mass / mass of hydrocarbons entering the processing unit
Influence of the Process Recovery rate P 1
Pb
Liberation 3
1
Separation 2
15°
TG
T
Rs FROM PVT LAB EXPERIMENTS
Differential Rs =
V gas produced V oil at Pb
PRO01198 – CRUDE OIL TREATMENT - Separation
Pb
P
© 2007 ENSPM Formation Industrie - IFP Training
Flash
Influence of the Process Recovery rate
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 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
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
recovery
Influence of the process Recovery rate Application / Field One stage G L Pi T1
Flash liberation
G L Ps T1
max gas & min liquid
Several stages G
G
G
L
L P2 T1 Separators
L P3 T1
L Ps T1 Storage
P1 T1
in each separator : flash liberation but the whole chain of separators represents a differential separation max of liquid recovery for an infinite number of separation stages
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
G
Separation pressure at the different stages Rule of thumb n-1
R=
P sep. HP P storage
n = number of stages + storage Examples GOR < 20 m3/m3
PRO01198 – CRUDE OIL TREATMENT - Separation
1° :10-20 bara 2°: 2-6 bara 3°: Storage
GOR > 200 1°: 20-40 bara 2°: 5-15 bara 3°: 2-5 bara 4°: Storage
© 2007 ENSPM Formation Industrie - IFP Training
GOR < 150 m3/m3
1°: 3-7 bara 2°: Storage
EXAMPLE OF APPLICATION
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
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
Determination of the optimal P & T and number of separation stages to get the higher separation efficiency
PALANCA separation – output 2nd stage Sep. Efficiency (%) 76.5 75° C
76 75.5 75
90
74.5 74 73.5
105
72.5 0
5
PRO01198 – CRUDE OIL TREATMENT - Separation
10
15
20
25 Pressure (bars)
© 2007 ENSPM Formation Industrie - IFP Training
73
PALANCA separation – output 3rd stage Sep. Efficiency (%) 77.5 77 76.5 75° C
76 75.5 75
90
74.5 74 105
73 0 3 6 Low pressure separator pressure
PRO01198 – CRUDE OIL TREATMENT - Separation
9
12
15 Pressure (bars)
© 2007 ENSPM Formation Industrie - IFP Training
73.5
PALANCA separation – output 4th stage Sep. Efficiency (%) 77.5 75° C
77
76.5
76
90
75.5
74.5
105
3 0 6 Medium pressure separator pressure
PRO01198 – CRUDE OIL TREATMENT - Separation
9
12
15 Pressure (bars)
© 2007 ENSPM Formation Industrie - IFP Training
75
PALANCA separation – output T=75°C Output (%) 78
77.5 4 stages
77
significant gain between 2 & 3
76.5
less gain between 3&4 ECONOMICS COMPROMISE
2 stages
75.5 0
5
PRO01198 – CRUDE OIL TREATMENT - Separation
10
15
20
25 Pressure (bar)
© 2007 ENSPM Formation Industrie - IFP Training
76
3 stages
Influence of separation temperature EFFECT ON RECOVERY (
)
+
Temperature • •
Liquid Economy
Average
•
Water
• •
Gas H2S treatment
High
•
Gas
Price
in general, the lower the T the higher the liquid recovery (but other parameters interfere on final Process T chosen : e.g. oil/water separation which is enhanced by high T°C) PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
Low
-
Influence of separation T & P : example 1
ASHTART Gas
13b - 110 °C
Gas
1b - 85 °C Oil Gas
5b - 40 °C
Gas
1b - 35 °C
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
GAIN 9 % OIL at lower T
Oil
Influence of separation T & P : example 2 BREME Flare Gas
4b 40° C 1b
Oil
Flare
3.5 b 30° C Gas
4b 40° C
GAIN 2.6 % OIL from flare gas recovery PRO01198 – CRUDE OIL TREATMENT - Separation
Oil
© 2007 ENSPM Formation Industrie - IFP Training
1b
3- Separator sizing
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
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 © 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
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
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
DEPENDS ON OIL CHARACTERISTICS
Sizing of a separator 1
Basic data Gas : Flow rate - composition - specific mass Oil : Flow rate - composition - specific mass Retention time
2
Sizing for gas Sizing = age cross-section age cross-section = f (limit velocity gas) Limit velocity gas = liquid not drawn with it Sizing for liquids Sizing = f (retention time) Retention time = time needed for degassing Retention time = f (oil characteristics)
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
3
Sizing of a separator Vertical separator
GAS
Aim : PREVENT WATER BEING DRAWN ALONG A at
P T
R
D (Ø) L
Liquid
liquid
ΠD3 P= 6 weight
R= K
ΠD2
4
V2
A=
V
aerodynamic force
P>A+R
V
fixed D limit = 20 µm 1 Kv = f ( GOR PRO01198 – CRUDE OIL TREATMENT - Separation
ΠD3
6
Vg
buoyancy
D
L- V V
L ) = m/s V
max speed not to carry over D
© 2007 ENSPM Formation Industrie - IFP Training
Condition :
Gas
P Lg
V V (velocity)
Sizing of a separator Vertical separator
GAS
Calculation of V (P and T) from M • Let M = 30 (0° C - 1013 mb) o=
30 22.4
MP ZRT
Kg/m3 =
• If T = 50° C and P = 20 bar V= ox 30 22.4
x
20 x 1.013
T0 T
x
273 x 323
A few values of Kv • Flare drum (horizontal) • Column head separator (horizontal) • Compressor suction (vertical) PRO01198 – CRUDE OIL TREATMENT - Separation
0.04 m/s 0.07 m/s 0.04 m/s
1 Z
1 x 0.93
= 24 kg/m3
© 2007 ENSPM Formation Industrie - IFP Training
=
P P0
Separator value of Kv in m/s versus GOR
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
Sizing of a separator Vertical separator
LIQUID
Transit time through the vessel Concerns water and oil (Gas : pm) T:transit time
T=
V Q
=
Π D2 4
x
h Q
T:transit time fonction of decantation time and retention time
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
VERTICAL Separator / Liquid : liquid sizing
Gas Outlet
GAS
Decantation time refers to liquids
Feed
Water droplet Oil outlet OIL Water outlet
Gas bubble Oil droplet
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
WATER
Sizing of a separator Vertical separator
LIQUID
Decantation time STOKES' law
V=
g D2 ( L - V) 18 µ
D=O.1 mm
(around 20 to 30 µm in general)
note : Decantation time is very dependant of the crude and water characteristics ( emulsions) PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
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
Sizing of a separator Vertical separator
LIQUID
Retention time (practical reference) 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 © 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
Sizing of a separator Vertical separator Common practices • Gas age velocity : V critical = 0.048 • Internal diameter :
D=
L- G G Q 900. Π . V
PRO01198 – CRUDE OIL TREATMENT - Separation
D in m Q in m3/h V in m/s
© 2007 ENSPM Formation Industrie - IFP Training
• 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" (heavy oil ROSPO MARE : 35")
in m/s
Sizing of a separator Horizontal separator Flow straightened cross section
Demister Gas Liquids
Secondary chamber Decantation chamber Horizontal separator
A
Entrainment
Entrainment
P Resultant
Kv horiz. = 1.25 Kv vertical Gravity
PRO01198 – CRUDE OIL TREATMENT - Separation
Resultant
Gravity
© 2007 ENSPM Formation Industrie - IFP Training
liquid
R
Vertical separator
Sizing of a separator Horizontal separator L
Decantation time D
with Stokes law
l Water Vh
h
Oil droplet
Vwater
=
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.
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
h
Sizing of a separator: Summary
GAS IS THE PRIORITY PARAMETER TAKEN INTO 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
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
DECANTATION TIME FOR LIQUIDS IS GENERALLY BASED ON LAB EXPERIMENTS
4- Gas/Liquid Separator different types © 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
Vertical 2 phase separator Pressure
Safety seal
well adapted
valve Mist extractor Déflector
Oil and gas inlet
for low GOR
Deflector action 1
Pressure gauge
2
Drainage duct Primary chamber
Isolation partition Manhole
Visual level monitor
1. body of separator 2. gas outlet (high point) 3. fluid input
Purge Base
PRO01198 – CRUDE OIL TREATMENT - Separation
Gas flow Liquid flow
Centrifugal effect in a vertical separator
© 2007 ENSPM Formation Industrie - IFP Training
Oil outlet Decantation chamber
3
Horizontal 2 phase separator
Primary chamber
Settling section
Secondary chamber
Mist extractor
Diff Gas outlet
Gas + liquids inlet
Purge
Oil outlet
Chassis
Decantation chamber
Anti-wave partition
Separation partition
well adapted
Liquid
Inlet diff PRO01198 – CRUDE OIL TREATMENT - Separation
for high GOR
© 2007 ENSPM Formation Industrie - IFP Training
Gas
High-pressure horizontal separator with liquid retention capacity
gas outlet
Inlet
large capacity high P
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
liquid outlet
Spherical 2 phase separator
rare Fluids inlet
for very high GOR Deflector
Scrubber
Level regulation
Gas outlet
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
Oil outlet
Cyclone effect separator Gas outlet
Gas + Liquid inlet
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
Liquid outlet
Multi-cyclone separator Gas outlet
Multicyclones
Gas inlet
Diff
Liquid level
Liquid outlet Secondary drain
Retention volume
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
Liquid outlet
Other types of gas/liquid separators
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
Gas SCRUBBER
Mist extractor Sifter
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
VAPE SORBER
Absorbent material
Porous filters © 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
Components of a gas/liquid separator © 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
Horizontal 2 phase separator components/internals Settling section Mist extractor Secondary chamber
Primary chamber
Diff Gas outlet
Gas + liquids inlet
Purge
Decantation chamber
PRO01198 – CRUDE OIL TREATMENT - Separation
Separation partition
Anti-wave partition
© 2007 ENSPM Formation Industrie - IFP Training
Chassis
Oil outlet
5- Foaming difficult gas/liquid separation
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
Foaming Origin • Gas expansion + oil / gas surface tension Theory • Pure liquids do not foam A surfactant is needed Mixtures of isomers in hydrocarbons are surfactants • Foams are unstable (state of least energy)
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
• The internal viscosity of the oil stabilises the foam, leading to drawing along of the gas (foaming)
FOAMS
– FOAMS are oil + gas "emulsions"
T=15mn
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
FOAMS – Inconvenience
– INCONVENIENTS : • oil entrainments in gas (affecting scrubbers, flares, compressors protection, gas treatment solvents ...), and gas entrainments in oil ( pump cavitation, later degassing...)
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
• loss of control of levels in separators
FOAMS – Schematic representation
INTERFACIAL FILM
GAZ
• the speed of drainage is dependant of the viscosity of the oil •the max width is dependant of the liquid interfacial tension © 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
FOAMS STABILISATION
• NATURAL SURFACTANTS • ADDED SURFACTANTS (PRODUCTION CHEMICALS) • SOLID PARTICULES • WATER DROPLETS © 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
Foaming is dependant on crude characteristics
Tendency to foam API 40 = .825 Increase in % vol. Foam breaking in seconds
API 30 = .876
API > 40
30 < API < 40
API < 30
10 - 20
20 - 40
> 50
30
30 - 60
> 60
BUT • If asphaltene content > 1 %, higher foaming and stability
• The % of water and additives (anticorrosion etc… ) do not appear to have any effect on the phenomenon
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
• if acid index >0.2 mg KOH/l, lower quantity of foam & higher stability
FOAMS : separation / breaking
•
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
– BREAKING WIDTHS ARE MUCH THINNER THAN FOR EMULSIONS PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
– THE LIQUID IS DRAINED OUT OF THE INTERFACIAL FILM DECREASING ITS WIDTH UNTIL A MINIMUM VALUE IS REACHED WHERE IT BREAKS
FOAMS TREATMENT
•
IT IS POSSIBLE TO : – increase the breaking width of the foam by adding a chemical – increase the speed of drainage by lowering the liquid viscosity (HEAT) – install separator internals acting on wettability
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
– use separators equipped with specific cyclonic inlet devices
FOAMS TREATMENT
Treatment
• Mechanical
- Washing - longer time spent in installation
• Chemical
- anti-foam
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
FOAMS TREATMENTS : anti-foams Chemical Treatment
ANTI-FOAMS Action: • displace the foam stabilizing element from the bubble walls • or cause bubbles to burst locally
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
Necessary conditions: • be soluble in the foaming system • disperse satisfactorily • have surface tension < that of the foam
FOAMS TREATMENTS : anti-foams
anti-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
their dosage have to be strictly controlled
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
THESE PRODUCTS ARE REFINERY CATALYSTS POISONS
FOAMS TREATMENTS : anti-foams
OTHER PRODUCTS :
– Heavy Alcohols, cheap but weak efficiency – fluoro-Silicones, very efficient but expensive
Selection implemented in the Flash Foaming Test (Lab)
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
• to be used in severe cases
CRUDE OIL FOAMING TENDENCIES
OIL STORAGE
FLASH FOAMING TEST PI
M
TR
NITROGEN BUTANE
TO WATER BATH PROCEDURE
TR
PRO01198 – CRUDE OIL TREATMENT - Separation
CALIBRATED CYLINDER
© 2007 ENSPM Formation Industrie - IFP Training
ADJUSTABLE CONTROL VALVE ( 35 L/H)
P = 10 BARS with N2 / BUTANE T = 60 ° C 600 CC OIL
FOAMS TREATMENTS : mechanical
Gas
Mist extractor
Gutter separator for foam treatment Diff Inlet Inclined plates
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
Oil
FOAMS TREATMENTS : mechanical
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
FOAMS TREATMENTS : mechanical
Section X-X
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
DIXON PLATES
FOAMS TREATMENTS : mechanical Inlet PC (gas) Gas Mist extractor
Gas
LC (water) oil
Oil
Salt water Heating
PRO01198 – CRUDE OIL TREATMENT - Separation
LC (water)
Water
© 2007 ENSPM Formation Industrie - IFP Training
Burner
Foam treatment by heating in salt water bath
FOAMS - CONCLUSIONS
• FOAMS ARE SIMILAR TO EMULSIONS • HEAVY OILS (viscous) OR ACID/NAPHTENIC CRUDES (natural surfactants) ARE CREATING STRONG FOAMS
• IF NOT, FOAM TREATMENT USUALLY REQUIRES HEAT + CHEMICAL TREATMENT PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
• IF FOAMING HAS BEEN ANTICIPATED, OVERSIZING OF SEPARATORS OR SEPARATOR INTERNALS CAN BE CHOSEN TO LIMIT INCONVENIENTS
CRUDE OIL PROCESSING - SEPARATION
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
Flash liberation Pressure (bars) 300
Yield (R) 250
Bubble curve
98.4
200
100 % 97.2 96 94.4 91.7 88.9
150
85.1
100 80 88.9 %
50
0 0
50
PRO01198 – CRUDE OIL TREATMENT - Separation
100
TG 150
200
T(° C)
© 2007 ENSPM Formation Industrie - IFP Training
P1
Differential liberation Pressure (bars) 300
250
Initial bubble curve in the reservoir
Elimination of gas
200
Bubble curve at perforations
Yield (R) 100 %
150
95.0 88.1
100
86.2 92 %
83.7
50
0 0
50
PRO01198 – CRUDE OIL TREATMENT - Separation
100
TG 150
200
T(° C)
© 2007 ENSPM Formation Industrie - IFP Training
P1
Composite liberation Pressure (bars) 300 Initial bubble curve in the reservoir
250
gas elimination
200
Yield (R) 100 %
150 Bubble curve at perforations
Well head
Perforations
91.0 88.9
100
86.7 84.7
90 % 1st stage separation
50
0 0
50
PRO01198 – CRUDE OIL TREATMENT - Separation
100
TG 150
200
T(° C)
© 2007 ENSPM Formation Industrie - IFP Training
P1
A – CRUDE OIL TREATMENT I- SEPARATION © 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
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
5- Foaming (difficult gas/liquid separation) Next course: Oil/Water separation PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
4- Gas/Liquid Separator different types
1- Well head effluents © 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
WELL HEAD EFFLUENTS
GAS WELLHEAD EFFLUENTS
OIL WATER FORMATION SAND AND SILT COLLOID STATE CLAY
MINERAL CRYSTALS NaCl CaCO3 BaSO4 SrSO4
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
CORROSION PRODUCT WAXES ASPHALTENES
SEPARATION CHAIN
FOAMS LIQUID DROPLETS IN GAS
WELLHEAD EFFLUENTS
GAS
GAS TREATMENT DEHYDRATION CONDENSATE RECUPERATION
GAS-LIQUID SEPARATION
CONDENSATE WATER
EMULSION INTERMINGLED WATER/OIL
OIL-WATER SEPARATION OPERATIONS SOMETIMES CARRIED OUT in 1 PROCESS EQUIPMENT PRO01198 – CRUDE OIL TREATMENT - Separation
EMULSION TREATMENT
EMULSION FREE WATER
WATER
© 2007 ENSPM Formation Industrie - IFP Training
export crude
SOURCE OF WATER
WATER AND OIL ZONES IN RESERVOIR
OIL OIL
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
* Active Water Reservoir * Water Injection : Injection of 1-2 volumes of water Production of 1-5 volumes of water per oil volume * Faulty Cementing Job
SOURCE OF SALT RESERVOIR WATER SALT
INJECTED WATER (SEA WATER)
*HASSI MESSAOUD : CAMBRIEN WATER 370g/l Low Water Cut 0,1%
HIGH SALT CONTENT SALT CONTENT 370 mg/l
*If Salt Content>10mg/l , Reservoir Water INGRESS *Sometimes HIGH SALT CONTENT without Water EAST BAGDAD As much as 265ppm of salt ***
Produced Water Not Detected; only salt content is measured
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
* Same for Hassi Messaoud - Fateh - ABK -Zadco This Phenomenon is limited in Time
OIL , BSW and GOR EVOLUTION WITH TIME Production 3
difficulty to design separation equipment
106 m3 / an
OIL
2
BSW
GOR
%
1
1
300
20
200
10
100
BSW 2
3
PRO01198 – CRUDE OIL TREATMENT - Separation
4
5
6
7
8
9
10
11
12
YEARS
© 2007 ENSPM Formation Industrie - IFP Training
GOR
30
CONTRACTUAL WATER AND SALT CONTENTS
CRUDE OIL MARKETING
AGREEMENT
$
Business is business!!
$
PRODUCERS TRANSPORTERS REFINERS
TRANSPORTERS : LIMITATION FOR WATER CONTENT *PIPELINE
BSW <= 0.5% NO FIXED CONSTRAINTS - ACCIDENTAL CONTAMINATION - LOAD ON TOP CONTAMINATION
PRO01198 – CRUDE OIL TREATMENT - Separation
BUT
© 2007 ENSPM Formation Industrie - IFP Training
*BY SEA
- PIPE OVER LOADING - CORROSION ( WATER + SALT )
CONTRACTUAL WATER AND SALT CONTENTS
EUROPEAN REFINERIES 1 ELECTROSTATIC DESALTER SALT CONTENT <5mg/l * SCALE DEPOSIT INSIDE EXCHANGERS * DISTILLATION UNITS CORROSION * RESIDUAL QUALITY DEGRADATION 95 % EFFICIENCY INLET INLETSALT SALTCONTENT CONTENT<<100 100mg/l mg/l PRODUCTION FIELD SPECIFICATIONS Salt...100 mg/l
TRANSPORT :
Salt...60 mg/l
BSW BSWin inProduction ProductionFields Fields<<0.5 0.5% % PRO01198 – CRUDE OIL TREATMENT - Separation
Water....0,2% Water....0,5%
© 2007 ENSPM Formation Industrie - IFP Training
REFINERY :
DEHYDRATION/DESALTING
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.
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
DESALTING IS A DEHYDRATION TRT SET PREVIOUSLY WITH WASH WATER SOFTER THAN RESERVOIR WATER
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 40 mg/l ( 14 PTB ) Salt Content
Salt Content < 60 mg/l
Water Content < 0.15 %
WATER CONTENT IS THE MOST RESTRICTING SPEC. PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
0.1 % of Water Content
2- Gas/liquid separation
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
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
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
THERMODYNAMIC BEHAVIOUR
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
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
to remove oil and solids from water (Water Treatment specific courses)
Hydrocarbon production scheme Pw
Pc Separation Storage
Shipping
Ps
Pr
Pr
PRO01198 – CRUDE OIL TREATMENT - Separation
Pr: Pf:
Reservoir pressure Bottomhole flowing pressure Pw: Wellhead pressure Pc: Choke pressure Ps: Processing pressure
© 2007 ENSPM Formation Industrie - IFP Training
Pf
Reservoir
Phase diagram
P Pr Liquid Pf Bubble Point
100 %
30 %
Pc
Ps
PRO01198 – CRUDE OIL TREATMENT - Separation
5%
1%
0% mole % liquid T
© 2007 ENSPM Formation Industrie - IFP Training
15 %
0
Vapour
Pw
METHANE - ETHANE MIXTURE PHASE DIAGRAM
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
GAS PHASE ENVELOPPE SHAPE VERSUS GAS COMPOSITION
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
1. Flash process
P1 V1 T1
P2 V2 T2
with P1 > P2
at Constant composition If T constant = flash liberation P1 V1 T1
P2 V2 T1
P1 > P2
P2 V2 T2
P1 > P2 T1 > T2
If T varies = flash separation
G1 L1 P1 T1 PRO01198 – CRUDE OIL TREATMENT - Separation
G2 L2 P2 T2
© 2007 ENSPM Formation Industrie - IFP Training
P1 V1 T1
2. Differential process P1 > P2 G1 L1
GS Gi Li
P1 T1
G2 L2 P2 T2
total composition varies : there is draw off
If T = constant = differential liberation © 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
3. Composite process : combination of the two Separators
Reservoir
Storage
PG TG
PF TG
P1 T1
P2 T2
Pa Ta
L
G L
G1 L1
G2 L2
GS LS
Differential Liberation (T cst)
Flash
Flash
Flash
P PG PF
P2 Pa
T Ta
PRO01198 – CRUDE OIL TREATMENT - Separation
T2
T1
TG
© 2007 ENSPM Formation Industrie - IFP Training
P1
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 EFFICIENCY
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
YIELD (R) = final stock tank oil mass / mass of hydrocarbons entering the processing unit
Influence of the Process Recovery rate P 1
Pb
Liberation 3
1
Separation 2
15°
TG
T
Rs FROM PVT LAB EXPERIMENTS
Differential Rs =
V gas produced V oil at Pb
PRO01198 – CRUDE OIL TREATMENT - Separation
Pb
P
© 2007 ENSPM Formation Industrie - IFP Training
Flash
Influence of the Process Recovery rate
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 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
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
recovery
Influence of the process Recovery rate Application / Field One stage G L Pi T1
Flash liberation
G L Ps T1
max gas & min liquid
Several stages G
G
G
L
L P2 T1 Separators
L P3 T1
L Ps T1 Storage
P1 T1
in each separator : flash liberation but the whole chain of separators represents a differential separation max of liquid recovery for an infinite number of separation stages
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
G
Separation pressure at the different stages Rule of thumb n-1
R=
P sep. HP P storage
n = number of stages + storage Examples GOR < 20 m3/m3
PRO01198 – CRUDE OIL TREATMENT - Separation
1° :10-20 bara 2°: 2-6 bara 3°: Storage
GOR > 200 1°: 20-40 bara 2°: 5-15 bara 3°: 2-5 bara 4°: Storage
© 2007 ENSPM Formation Industrie - IFP Training
GOR < 150 m3/m3
1°: 3-7 bara 2°: Storage
EXAMPLE OF APPLICATION
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
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
Determination of the optimal P & T and number of separation stages to get the higher separation efficiency
PALANCA separation – output 2nd stage Sep. Efficiency (%) 76.5 75° C
76 75.5 75
90
74.5 74 73.5
105
72.5 0
5
PRO01198 – CRUDE OIL TREATMENT - Separation
10
15
20
25 Pressure (bars)
© 2007 ENSPM Formation Industrie - IFP Training
73
PALANCA separation – output 3rd stage Sep. Efficiency (%) 77.5 77 76.5 75° C
76 75.5 75
90
74.5 74 105
73 0 3 6 Low pressure separator pressure
PRO01198 – CRUDE OIL TREATMENT - Separation
9
12
15 Pressure (bars)
© 2007 ENSPM Formation Industrie - IFP Training
73.5
PALANCA separation – output 4th stage Sep. Efficiency (%) 77.5 75° C
77
76.5
76
90
75.5
74.5
105
3 0 6 Medium pressure separator pressure
PRO01198 – CRUDE OIL TREATMENT - Separation
9
12
15 Pressure (bars)
© 2007 ENSPM Formation Industrie - IFP Training
75
PALANCA separation – output T=75°C Output (%) 78
77.5 4 stages
77
significant gain between 2 & 3
76.5
less gain between 3&4 ECONOMICS COMPROMISE
2 stages
75.5 0
5
PRO01198 – CRUDE OIL TREATMENT - Separation
10
15
20
25 Pressure (bar)
© 2007 ENSPM Formation Industrie - IFP Training
76
3 stages
Influence of separation temperature EFFECT ON RECOVERY (
)
+
Temperature • •
Liquid Economy
Average
•
Water
• •
Gas H2S treatment
High
•
Gas
Price
in general, the lower the T the higher the liquid recovery (but other parameters interfere on final Process T chosen : e.g. oil/water separation which is enhanced by high T°C) PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
Low
-
Influence of separation T & P : example 1
ASHTART Gas
13b - 110 °C
Gas
1b - 85 °C Oil Gas
5b - 40 °C
Gas
1b - 35 °C
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
GAIN 9 % OIL at lower T
Oil
Influence of separation T & P : example 2 BREME Flare Gas
4b 40° C 1b
Oil
Flare
3.5 b 30° C Gas
4b 40° C
GAIN 2.6 % OIL from flare gas recovery PRO01198 – CRUDE OIL TREATMENT - Separation
Oil
© 2007 ENSPM Formation Industrie - IFP Training
1b
3- Separator sizing
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
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 © 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
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
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
DEPENDS ON OIL CHARACTERISTICS
Sizing of a separator 1
Basic data Gas : Flow rate - composition - specific mass Oil : Flow rate - composition - specific mass Retention time
2
Sizing for gas Sizing = age cross-section age cross-section = f (limit velocity gas) Limit velocity gas = liquid not drawn with it Sizing for liquids Sizing = f (retention time) Retention time = time needed for degassing Retention time = f (oil characteristics)
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
3
Sizing of a separator Vertical separator
GAS
Aim : PREVENT WATER BEING DRAWN ALONG A at
P T
R
D (Ø) L
Liquid
liquid
ΠD3 P= 6 weight
R= K
ΠD2
4
V2
A=
V
aerodynamic force
P>A+R
V
fixed D limit = 20 µm 1 Kv = f ( GOR PRO01198 – CRUDE OIL TREATMENT - Separation
ΠD3
6
Vg
buoyancy
D
L- V V
L ) = m/s V
max speed not to carry over D
© 2007 ENSPM Formation Industrie - IFP Training
Condition :
Gas
P Lg
V V (velocity)
Sizing of a separator Vertical separator
GAS
Calculation of V (P and T) from M • Let M = 30 (0° C - 1013 mb) o=
30 22.4
MP ZRT
Kg/m3 =
• If T = 50° C and P = 20 bar V= ox 30 22.4
x
20 x 1.013
T0 T
x
273 x 323
A few values of Kv • Flare drum (horizontal) • Column head separator (horizontal) • Compressor suction (vertical) PRO01198 – CRUDE OIL TREATMENT - Separation
0.04 m/s 0.07 m/s 0.04 m/s
1 Z
1 x 0.93
= 24 kg/m3
© 2007 ENSPM Formation Industrie - IFP Training
=
P P0
Separator value of Kv in m/s versus GOR
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
Sizing of a separator Vertical separator
LIQUID
Transit time through the vessel Concerns water and oil (Gas : pm) T:transit time
T=
V Q
=
Π D2 4
x
h Q
T:transit time fonction of decantation time and retention time
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
VERTICAL Separator / Liquid : liquid sizing
Gas Outlet
GAS
Decantation time refers to liquids
Feed
Water droplet Oil outlet OIL Water outlet
Gas bubble Oil droplet
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
WATER
Sizing of a separator Vertical separator
LIQUID
Decantation time STOKES' law
V=
g D2 ( L - V) 18 µ
D=O.1 mm
(around 20 to 30 µm in general)
note : Decantation time is very dependant of the crude and water characteristics ( emulsions) PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
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
Sizing of a separator Vertical separator
LIQUID
Retention time (practical reference) 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 © 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
Sizing of a separator Vertical separator Common practices • Gas age velocity : V critical = 0.048 • Internal diameter :
D=
L- G G Q 900. Π . V
PRO01198 – CRUDE OIL TREATMENT - Separation
D in m Q in m3/h V in m/s
© 2007 ENSPM Formation Industrie - IFP Training
• 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" (heavy oil ROSPO MARE : 35")
in m/s
Sizing of a separator Horizontal separator Flow straightened cross section
Demister Gas Liquids
Secondary chamber Decantation chamber Horizontal separator
A
Entrainment
Entrainment
P Resultant
Kv horiz. = 1.25 Kv vertical Gravity
PRO01198 – CRUDE OIL TREATMENT - Separation
Resultant
Gravity
© 2007 ENSPM Formation Industrie - IFP Training
liquid
R
Vertical separator
Sizing of a separator Horizontal separator L
Decantation time D
with Stokes law
l Water Vh
h
Oil droplet
Vwater
=
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.
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
h
Sizing of a separator: Summary
GAS IS THE PRIORITY PARAMETER TAKEN INTO 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
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
DECANTATION TIME FOR LIQUIDS IS GENERALLY BASED ON LAB EXPERIMENTS
4- Gas/Liquid Separator different types © 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
Vertical 2 phase separator Pressure
Safety seal
well adapted
valve Mist extractor Déflector
Oil and gas inlet
for low GOR
Deflector action 1
Pressure gauge
2
Drainage duct Primary chamber
Isolation partition Manhole
Visual level monitor
1. body of separator 2. gas outlet (high point) 3. fluid input
Purge Base
PRO01198 – CRUDE OIL TREATMENT - Separation
Gas flow Liquid flow
Centrifugal effect in a vertical separator
© 2007 ENSPM Formation Industrie - IFP Training
Oil outlet Decantation chamber
3
Horizontal 2 phase separator
Primary chamber
Settling section
Secondary chamber
Mist extractor
Diff Gas outlet
Gas + liquids inlet
Purge
Oil outlet
Chassis
Decantation chamber
Anti-wave partition
Separation partition
well adapted
Liquid
Inlet diff PRO01198 – CRUDE OIL TREATMENT - Separation
for high GOR
© 2007 ENSPM Formation Industrie - IFP Training
Gas
High-pressure horizontal separator with liquid retention capacity
gas outlet
Inlet
large capacity high P
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
liquid outlet
Spherical 2 phase separator
rare Fluids inlet
for very high GOR Deflector
Scrubber
Level regulation
Gas outlet
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
Oil outlet
Cyclone effect separator Gas outlet
Gas + Liquid inlet
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
Liquid outlet
Multi-cyclone separator Gas outlet
Multicyclones
Gas inlet
Diff
Liquid level
Liquid outlet Secondary drain
Retention volume
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
Liquid outlet
Other types of gas/liquid separators
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
Gas SCRUBBER
Mist extractor Sifter
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
VAPE SORBER
Absorbent material
Porous filters © 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
Components of a gas/liquid separator © 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
Horizontal 2 phase separator components/internals Settling section Mist extractor Secondary chamber
Primary chamber
Diff Gas outlet
Gas + liquids inlet
Purge
Decantation chamber
PRO01198 – CRUDE OIL TREATMENT - Separation
Separation partition
Anti-wave partition
© 2007 ENSPM Formation Industrie - IFP Training
Chassis
Oil outlet
5- Foaming difficult gas/liquid separation
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
Foaming Origin • Gas expansion + oil / gas surface tension Theory • Pure liquids do not foam A surfactant is needed Mixtures of isomers in hydrocarbons are surfactants • Foams are unstable (state of least energy)
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
• The internal viscosity of the oil stabilises the foam, leading to drawing along of the gas (foaming)
FOAMS
– FOAMS are oil + gas "emulsions"
T=15mn
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
FOAMS – Inconvenience
– INCONVENIENTS : • oil entrainments in gas (affecting scrubbers, flares, compressors protection, gas treatment solvents ...), and gas entrainments in oil ( pump cavitation, later degassing...)
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
• loss of control of levels in separators
FOAMS – Schematic representation
INTERFACIAL FILM
GAZ
• the speed of drainage is dependant of the viscosity of the oil •the max width is dependant of the liquid interfacial tension © 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
FOAMS STABILISATION
• NATURAL SURFACTANTS • ADDED SURFACTANTS (PRODUCTION CHEMICALS) • SOLID PARTICULES • WATER DROPLETS © 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
Foaming is dependant on crude characteristics
Tendency to foam API 40 = .825 Increase in % vol. Foam breaking in seconds
API 30 = .876
API > 40
30 < API < 40
API < 30
10 - 20
20 - 40
> 50
30
30 - 60
> 60
BUT • If asphaltene content > 1 %, higher foaming and stability
• The % of water and additives (anticorrosion etc… ) do not appear to have any effect on the phenomenon
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
• if acid index >0.2 mg KOH/l, lower quantity of foam & higher stability
FOAMS : separation / breaking
•
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
– BREAKING WIDTHS ARE MUCH THINNER THAN FOR EMULSIONS PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
– THE LIQUID IS DRAINED OUT OF THE INTERFACIAL FILM DECREASING ITS WIDTH UNTIL A MINIMUM VALUE IS REACHED WHERE IT BREAKS
FOAMS TREATMENT
•
IT IS POSSIBLE TO : – increase the breaking width of the foam by adding a chemical – increase the speed of drainage by lowering the liquid viscosity (HEAT) – install separator internals acting on wettability
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
– use separators equipped with specific cyclonic inlet devices
FOAMS TREATMENT
Treatment
• Mechanical
- Washing - longer time spent in installation
• Chemical
- anti-foam
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
FOAMS TREATMENTS : anti-foams Chemical Treatment
ANTI-FOAMS Action: • displace the foam stabilizing element from the bubble walls • or cause bubbles to burst locally
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
Necessary conditions: • be soluble in the foaming system • disperse satisfactorily • have surface tension < that of the foam
FOAMS TREATMENTS : anti-foams
anti-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
their dosage have to be strictly controlled
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
THESE PRODUCTS ARE REFINERY CATALYSTS POISONS
FOAMS TREATMENTS : anti-foams
OTHER PRODUCTS :
– Heavy Alcohols, cheap but weak efficiency – fluoro-Silicones, very efficient but expensive
Selection implemented in the Flash Foaming Test (Lab)
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
• to be used in severe cases
CRUDE OIL FOAMING TENDENCIES
OIL STORAGE
FLASH FOAMING TEST PI
M
TR
NITROGEN BUTANE
TO WATER BATH PROCEDURE
TR
PRO01198 – CRUDE OIL TREATMENT - Separation
CALIBRATED CYLINDER
© 2007 ENSPM Formation Industrie - IFP Training
ADJUSTABLE CONTROL VALVE ( 35 L/H)
P = 10 BARS with N2 / BUTANE T = 60 ° C 600 CC OIL
FOAMS TREATMENTS : mechanical
Gas
Mist extractor
Gutter separator for foam treatment Diff Inlet Inclined plates
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
Oil
FOAMS TREATMENTS : mechanical
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
FOAMS TREATMENTS : mechanical
Section X-X
PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
DIXON PLATES
FOAMS TREATMENTS : mechanical Inlet PC (gas) Gas Mist extractor
Gas
LC (water) oil
Oil
Salt water Heating
PRO01198 – CRUDE OIL TREATMENT - Separation
LC (water)
Water
© 2007 ENSPM Formation Industrie - IFP Training
Burner
Foam treatment by heating in salt water bath
FOAMS - CONCLUSIONS
• FOAMS ARE SIMILAR TO EMULSIONS • HEAVY OILS (viscous) OR ACID/NAPHTENIC CRUDES (natural surfactants) ARE CREATING STRONG FOAMS
• IF NOT, FOAM TREATMENT USUALLY REQUIRES HEAT + CHEMICAL TREATMENT PRO01198 – CRUDE OIL TREATMENT - Separation
© 2007 ENSPM Formation Industrie - IFP Training
• IF FOAMING HAS BEEN ANTICIPATED, OVERSIZING OF SEPARATORS OR SEPARATOR INTERNALS CAN BE CHOSEN TO LIMIT INCONVENIENTS
CRUDE OIL PROCESSING - SEPARATION
© 2007 ENSPM Formation Industrie - IFP Training
PRO01198 – CRUDE OIL TREATMENT - Separation
Flash liberation Pressure (bars) 300
Yield (R) 250
Bubble curve
98.4
200
100 % 97.2 96 94.4 91.7 88.9
150
85.1
100 80 88.9 %
50
0 0
50
PRO01198 – CRUDE OIL TREATMENT - Separation
100
TG 150
200
T(° C)
© 2007 ENSPM Formation Industrie - IFP Training
P1
Differential liberation Pressure (bars) 300
250
Initial bubble curve in the reservoir
Elimination of gas
200
Bubble curve at perforations
Yield (R) 100 %
150
95.0 88.1
100
86.2 92 %
83.7
50
0 0
50
PRO01198 – CRUDE OIL TREATMENT - Separation
100
TG 150
200
T(° C)
© 2007 ENSPM Formation Industrie - IFP Training
P1
Composite liberation Pressure (bars) 300 Initial bubble curve in the reservoir
250
gas elimination
200
Yield (R) 100 %
150 Bubble curve at perforations
Well head
Perforations
91.0 88.9
100
86.7 84.7
90 % 1st stage separation
50
0 0
50
PRO01198 – CRUDE OIL TREATMENT - Separation
100
TG 150
200
T(° C)
© 2007 ENSPM Formation Industrie - IFP Training
P1
Related Documents g842
1 - Crude Oil Treatment - Separation 556z3x
October 2019 77
Crude Oil 144pk
December 2020 0
Unit 1 Crude Oil Properties.pdf 6o3u5w
October 2019 47
Crude Oil Specifications 1k1w2x
December 2019 151
Crude Oil Washing 5w183z
November 2019 85
Crude Oil Washing 5w183z
November 2019 105More Documents from "Haider" j6667
Oxford Ib Programme Geography Textbook 516a55
November 2019 2,987
1 - Crude Oil Treatment - Separation 556z3x
October 2019 77
Sample Chapter On Optical And Surveying Instruments d6yq
October 2019 91
Oxford Geography Study Guide For Ib Diploma 4m2t4d
October 2019 303
Shahkar By Riffat Siraj-urduinpage.com 3j636r
October 2019 72