V06d Fluid Recovery 1206

7/30/2019 V06d Fluid Recovery 1206

1/46

Floating Production Technology

Fluid Recovery Gas Lift, Gas Injection,

Water Injection

Specialist Diploma in Marine & Offshore Technology


2/46

FPSO Layout


3/46

Falcon FPSO - Layout


4/46

Primary Production System


5/46

Gas Lift Principle


6/46

Gas Lift Operating Principle

An artificial-lift method in which gas is injected into theproduction tubing to reduce the hydrostatic pressure of the

fluid column.

The resulting reduction in bottomhole pressure allows thereservoir liquids to enter the wellbore at a higher flow rate.

The injection gas is typically conveyed down the tubing-casing

annulus and enters the production train through a series of

gas-lift valves.

The gas-lift valve position, operating pressures and gas

injection rate are determined by specific well conditions.


7/46

Gas Lift Principle

Gas-Lift is used whenlarge supply of natural gas

is available.

Natural gas is introduced

into the well in theannular space between

the tubing and casing.


8/46

Gas Lift Principle

Gas lift valves close as thegas enters the lowest

valve.

As the gas enters the

production zone, it isdispersed within the oil

phase, which makes it

lighter reducing static

head.


9/46

Gas Injection Gas Flooding

A reservoir maintenance orsecondary recovery method

that uses injected gas to

supplement the pressure in

an oil reservoir or field.

In most cases, a field will

incorporate a planned

distribution of gas-injection

wells to maintain reservoirpressure and effect an

efficient sweep of

recoverable liquids.


10/46

Gas Injection or Gas Flooding

Gas is injected into the

gas cap above the oil

layer.

It essentially builds uppressure to push the oil

up once the natural

pressure decreases.


11/46

Water Injection Water Flooding

A method of secondary recovery in

which water is injected into the

reservoir formation to displace

residual oil.

The water from injection wells

physically sweeps the displaced oil

to adjacent production wells.


12/46

Water Injection Water Flooding

Potential problems associated with

waterflood techniques include

inefficient recovery due to variable

permeability, or similar conditions

affecting fluid transport within thereservoir, and early water

breakthrough that may cause

production and surface processing

problems.


13/46

Tertiary Recovery - Water Injection


14/46

Specification of Water Injection

Flowrate : 80,000 BWPD

Temperature : 10 to 30C

Pressure : 205 bara at FPSO

Pressure 201 bara at well

Oxygen concentration : 0.10 mg/l (without O2 Scavenger)

O2 concentration : 0.01 mg/l (with O2 Scavenger)

Solids content : 95% removal of 5microns


15/46

Water Injection

Two Sources

What are the two

sources?

Sea water (plentiful, all

around)

Produced water (good

to inject them back into

reservoir, otherwisethey have to be

disposed off)


16/46

Seawater Injection Greater Plutonio


17/46

Seawater Treatment for Water Injection

Coarse and fine filters

Electro-Chlorination

Sulphate removal

reduce scale production inwells and separation

equipment.

Vacuum de-aeration

High Pressure Injection pumps Sterilization


18/46

Seawater Injection

Sea-water Lift Pumps

A large amount of seawater is used for cooling various

processes and in providing seawater for injection.

The seawater lift pumps may be located within the ship takingsuction from sea-chests or be large electric submersible

pumps located in caissons.

These pumps are usually high-volume, low-head pumps.

Seawater for water injection and cooling medium cooling is

normally supplied by three (3) units of 50% seawater lift

pumps located in seawater lift caissons or sea chests.


19/46

Seawater Lift Pumps


20/46

Water Injection Process

Filtration

Filtration of the seawater will be carried out in two stages.


21/46

Seawater Filters


22/46


Filtration

The first stage will be through a

coarse filter package. This will

remove particulate matter down to

300 microns. The coarse filter

package will be located on the

discharge of the seawater lift

pumps.

All the seawater required for

process indirect cooling and for

injection will pass through the

course filter package.


23/46

Water Injection System

Coarse Filtration

The coarse filters are usually

automatic back-washable

basket filters.

During the bloom period, these

filters may require more

frequent backwashing to dealwith the high levels of plankton.


24/46


Filtration

The second stage of filtration after

the seawater has passed through

the cooling medium/seawaterplate cooler will be through a fine

filter package.

This package normally comprises of

single or dual media back washable

filters which will remove 95% of all

solids down to and including 5

microns.


25/46


Fine Filtration The package normally contains a number, approximately 6

filter pods, which provide the correct flux rate to be able to

remove virtually all particulate matter.

The filters are backwashed using an air scour system to lift

and break up the bed in order to remove the solids contained

on the media.

Fine filters take up quite a bit of space and are heavy. Forthese reasons, careful analysis of the reservoir rock porosity is

necessary to ascertain what level of filtration is required.

(There is a big space and weight bonus if fine filters are not

required.)


26/46

Electro-Chlorination

This occurs immediately after filtration has taken place

This process will kill off marine organisms remaining in the

seawater so as to reduce marine fouling in piping or

equipment.


27/46

Sulphate Reduction

Intent : reduce the sulphate ion concentration in the sea water

Method: dose the low sulphate water with chemicals

Effect : prevent corrosion, scaling and reservoir souring wheninjected

Performance specification:

Sulphate content 20 mg/litre Max particle size 10 micron


28/46

Sulphate Reduction Package


29/46


Deaeration

Vacuum deaeration is the most common method used to

remove dissolved oxygen from the seawater.

The warm filtered seawater will then be routed to the

deaerator where the oxygen content of the seawater will be

reduced to 0.1 mg/litre by vacuum stripping.

Injection of an oxygen scavenger into the base of thedeaerator will reduce the oxygen content down to 0.01

mg/litre or less.


30/46

Vacuum Deaeration

Tower


31/46


Deaerationcontinued

A vacuum package made up of a combination of vacuum

pumps and ejectors which creates a vacuum at each stage

within the tower.

Each stage is separated from the next by a water seal. This

means that as the water travels down the tower it will pass

through two or three different levels of vacuum (2 or 3 stage

vacuum tower) depending on the number of stages of thedesign.


32/46


Deareator Tower


33/46


The treated seawater from the deaerator will then bepumped up to the required injection pressure by a two-stage

process:

booster pump (to 10 bara)

injection pump (to 200 bara)

Booster pump Injection pump


34/46


Booster Pumps

Two 50% booster pumps will take water from the deaerator

tower and boost the pressure up to around 10 bara.

Booster pumps provided the necessary net positive suction

head (NPSH) for the high-pressure injection pumps.


35/46


Injection Pumps

The booster pumps will then feed straight into the suction

side of two 50% injection pumps which will further boost the

pressure up to its final injection pressure normally around200 bara.


36/46


Injection Pumps - continued

The filtered and oxygen-free seawater is then finally pumped

up to the required injection pressure by multi-stage injection

pumps.

These high-pressure pumps are normally one of the biggest

power users. Their power requirement is of the order of

several megawatts.

Water Injection manifold


37/46


Sterilisation

Sterilisation of the injection water will be carried out using a

UV sterilisation package or by use of chlorinating chemicals,

downstream of the injection pumps.


38/46


Principal Items of Water Injection Equipment

Seawater Lift Pumps 3 50%

Seawater Coarse Filters 3 50%

Seawater Fine Filters 6

20%Deaerator Tower 1 100%

Booster Pumps 2 50%

Injection Pumps 2 50%

Sterilisation Package 1 100%


39/46

Produced Water System

The other type of water for injection is Produced water.

Produced water from the HP Separator and LP Separator is

normally treated in a produced water treatment package.

This package normally consists of a bank of hydrocyclonesand a degassing vessel.


40/46



41/46


Produced water from the electrostatic coalescer can either be pumped up to the pressure of the HP Separator,

commingled with the HP Separator water and prepared for

re-injection or

sent to the ships slop oil system and treated as part of theships oily water system.


42/46


Treatment for Re-Injection

Hydrocyclones / Centrifuges

The level of oil in the produced water is reduced by

hydrocyclones where the g-forces are increased byhundreds

Degassers

The level of gas in the produced water may be reduced by

vacuum stripping in a degasser


43/46

Hyrdocyclones Working Principle

Liquid/Liquid Hydrocyclones

Based on the physics of enhanced gravity separation and free

vortex action

a cylindrical inlet, a tapered tube with the liquids entering

tangentially via inlets

These forces & differential pressures, set up across the

hydrocyclone, allow:

the heavy phase to exit at the underflow

the lighter phase reverses flow and exits the overflow at

the opposite end


44/46

Produced Water

Disposal of Unwanted Water

As oily water (water for disposal overboard):

The treated produced water will contain a maximum 40 ppm

free oil and will have been degassed down to atmosphericpressure before disposal to the sea via a produced water

disposal caisson or appropriate sea chest.


45/46

Oil Content Criteria

Less than 15 ppm Will not produce an oil sheen on the

water

Between 15 to 100 ppm

Produce a sheen (but not a slick) whichwould be absorbed by the sea orevaporate within 3 to 4 hours.

15 ppm can be smelled but not seen

100 ppm may be seen as a sheen withslight discolouration

More than 100 ppm

Produce an oil slick which would

eventually reach shore


46/46

Produced Water

Specification for Produced Water for discharge into sea:

Handling capacity : 70,000 BWPD

Discharge temperature range : 50 to 80C

Oil content : 40 ppm (free oil)

Documents

V06d Fluid Recovery 1206