TEKNA SEPARATION CONFERENCE 2013

A methodology to diagnose liquid carry over

in gas processing and action to reduce the problem.

Creation of sub-micron droplets (mechanism) Diagnostic method Chemical effects

Jon Berntsen, Managing Director

KANFA Mator AS, Norway

Liquid carry over in gas process

According to NORSOK requirement, liquid carry over shall not exceed 13 L (liquids)/MSm3 (gas).

Verification is typically done by the use of radiotracers. Oil resp. water soluble tracers.

Operation of gas processes sometimes require use of anti-surge valve. Will that or other operational problems influence scrubber performance?

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Typical gas process

The sample equipment are prefilled with a reference fluid; one for

collection of oil and one for collection of water.

After a defined sampling time the gas flow is stopped,

the equipment disconnected, and droplets accumulated in the

reference fluid is analysed.

For the fluids absorbed by the reference-fluid it is possible to find:

Droplet size distribution. Type of carry over (oil/condensate/water)

Sampling equipment

Hook-up in the field

Creation of sub-micron droplets

Result from initial field testing.

Sampling 1 st. separator @ 50 barg.

4 different tests.

Is it possible to generate sub-micron and micron

droplets in a 50 bar separator?

Creation of sub-micron droplets

This presentation was our reference point about expected oil droplet sizes!

FIELD DATA

Creation of sub-micron droplets

Verification of our sampling and analytical method versus technologies that are reliable in the

Sub-micron and micron area.

Creation of sub-micron droplets

Generating of droplets in test

rig.

Testing @ 1 bar and 10 min

sampling time.

Testing @ 3.3 bar and 25 min

sampling time.

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Typical gas process

Typical gas process, high pressure

This sample presents the conditions after 5 minutes sampling

at a pressure of approx. 50 barg.

Note that the volume of crude oil is significant.

The reference fluid had a high concentration of dispersed oil

droplets > 1000 ppm. Note that all these oil droplets are very

small with an average droplet size of 2.6 microns.

The total volume of oil is dominated by free oil.

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Typical gas process

Typical gas process, low pressure

This sample presents the conditions after 5 minutes sampling

at a pressure less than 10 barg.

Note that the volume of free crude oil is low.

The reference fluid had a concentration of 870 ppm oil. Note

that all these oil droplets are less that 100 microns.

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Typical gas process, high pressure scrubber

Typical gas process, high pressure scrubber

These two samples indicate that

process variations influence the

degree and type of liquid carry over.

After conducting many tests a better

understanding of operation was gained.

Drainage of the liquid level in the scrubber

might result in more carry over.

Use of anti-surge might influence.

Typical gas process. Tracking of droplets

High pressure separator

Lower pressure separator

High pressure scrubber

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Anti-surge operation

SAMPLEPOINT

Anti-surge operation

Three different samples collected at the same sample point.

The center picture show condensate in reference fluid creating something that can

be expressed as slurry while the right picture is oil comingled with condensate.

Is this a result of anti-surge use or ???

Determination of type of hydrocarbons

The laser diffraction instrument identify droplets of crude oil and condensate dispersed

in the reference fluid and gives information about their droplet sizes and concentration (ppm).

Further use of different analytical methods is needed to differentiate between oil and

condensate.

Fine dispersed droplets are trapped in the reference fluid, while large droplets and free oil are collected at the top.

Condensate droplets

Crude oil droplets

The laser detects both oil and condensate

droplets dispersed in the reference fluid.

The other technique detects only crude

oil.

Results from the reference fluid and total volume sample.

The light brown fluid on top is condensate mixed with

crude oil. At first sight an impression of large volume

crude oil carry over might be the case, but when analyzing

the different phases a more correct picture is drawn.

Results downstream scrubber

Results downstream scrubber

Laser diffraction measurement show a concentration of 401 ppm in the sample

When analyzing the same sample for crude oil 13 ppm is reported in the reference liquid.

Testing of chemicals for improved separation

In different processes it might be possible to gain some assistance by

use of chemicals.

It is normal procedure to use a defoaming chemical to reduce foaming

tendencies in separators to minimize liquid carry over.

We normally use neutron scanning to determine efficiency of defoaming

chemicals, but this time testing of gas quality was carried out.

Very interesting results!

Defoamer test gas from 1.st separator

Injection of 6 l/h

Injection of 12 l/h

Injection of 24 l/h

Defoamer test: After high pressure scrubber

Result from standard defoamer Note concentration and distribution

Result with newdefoamer Note concentration and distribution

New defoaming chemical improved performance in the scrubbers significantly.

Final touch

Technology and methodology is available for better

understanding of gas processes!

Final touch

And

A special thank to my colleague

Kristin S. Nomme

who has provided me with good data, information

and interesting discussion based on all the field

work conducted