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Subsea processing boosts and speeds offshore oil production

The world’s first full field subsea separator, developed as a result of the EUREKA E! 3040 SUBSEA SEPARATOR project, is a key component in a subsea processing system that will be installed in the Norwegian Statoil Tordis field in the North Sea in the 3rd quarter of 2007. Carrying out part of the processing on the sea floor and re-injecting the separated water avoids the flow of water up from the subsea well to the production platform, leaving a much larger part of the system – pipelines and processing equipment – for the oil and gas content. This technology will enable higher recovery rates of already scarce oil reserves and increase production rates. Such highly innovative European equipment is already attracting worldwide interest.

“By installing a full field subsea separation

facility, Statoil expects to improve the

Tordis field’s recovery factor from 49 to 55

per cent”, explains Rune Mode Ramberg,

Statoil’s subsea processing discipline

adviser. Along with other upgrades to

the field, the separation system will allow

Statoil to extract roughly 35 million extra

barrels of oil from the Tordis field. This is

achieved by reducing the back pressure

towards the Tordis field by separating

water and sand from the wellstream

subsea, re-injecting the water and sand

in a separate well subsea, boosting the

wellstream with a subsea pump and

reducing the receiving pressure at the

topside production platform.

Separation equipment plays a crucial role

in the oil and gas production process

by splitting the wellstream, which may

comprise of oil, gas, water and sand,

into their individual constituents.

Only through effective and efficient

separation is it possible to carry out the

subsequent processing steps – from gas

dehydration and/or gas compression to

oil treatment and water cleaning before

disposal. Moreover, as oilfields age, the

total production flow is often limited by

the process system, outputs decrease and

more water and/or gas mixes with the oil.

This leads to a decrease in the amount of oil

produced. Better equipment is necessary

to debottleneck the existing separators.

In this way, the decision to shut down an

oilfield can be postponed and reserves can

be more fully exploited. Oil companies

therefore need more innovative, efficient

and compact separators. The capital

investment required to exploit a new

field can be reduced and it is easier to

economically exploit marginal fields with

smaller separation equipment.

Compact subsea separator with inte-grated sand management system

The EUREKA SUBSEA SEPARATOR project

set out to qualify a compact subsea

water separator with an integrated sand

management system. The developed

separation technology allows for a

40 to 50% size reduction compared

to conventional separators. Subsea

separation makes it possible to minimise

the water flowrate to existing platforms

and ensures that produced water can be

directly re-injected with subsea pumps

into water injection reservoirs. Oil

production can be increased by reducing

the back pressure towards the producing

wells and flowlines to a topside platform

are dedicated to only oil and gas. There

is also a reduced need for topside water

cleaning. This is a strong ecological

advantage, drastically reducing the load

on platforms as produced water can be

pumped back to where it came from.

CDS, now an FMC Technologies subsidiairy, was a small company and this was an expensive project. Without the EUREKA funding it would have been quite difficult.

Toine Hendriks - CDS Engineering, the Netherlands

Compact, highly reliable subsea separation equipment will improve the economics of offshore oil and gas production and ensure better use of increasingly scarce resources.

Shaping tomorrow’s innovations today

“The consortium was very logical,” explains

Philip van Dessel, managing director of

project leader CDS Engineering. “CDS

provided the core separation technology,

FMC Technologies – a company big

in subsea oil production equipment

– strongly cooperated in the subsea

separator development, marinised and

built the equipment and put it together

with other key building blocks like subsea

pumps for boosting into a complete

subsea processing system. Norwegian oil

company Statoil, as an end user closely

involved in the development work,

could tell us with what characteristics

the equipment should comply and also

provided important knowledge of field

specific fluid characteristics. Moreover

Statoil was keen to use the equipment

which was particularly important because

you can develop nice technology but in a

sector such as the oil industry finding a

first user is essential.”

CDS designs and develops state-of-

the-art separators for use in upstream

and downstream activities of the oil

and gas industry. Over the years, it has

established a reputation for supplying

highly-innovative separation solutions to

the offshore industry. It modelled the gas/

liquid and liquid/liquid flows inside the

subsea separator using computational

fluid dynamics (CFD) calculation tools.

Reliability and compactness

“Reliability is crucial as you need to make

sure that such equipment will continue

to function for 20 years,” says Steinar

Eriksen, process lead Tordis for FMC

Technologies. “Retrieving equipment

from the seafloor is very costly; if you

need to do that several times, you

will kill the economics of the project.

And compactness is crucial because

everything that you install subsea is

very expensive – and the bigger it is, the

more expensive it becomes, both from a

manufacturing and installation point of

view.”

Separation and sand handling performance

was optimised using CFD simulations,

followed by extensive small- and large-

scale testing under both atmospheric

and high-pressure conditions. The tests

measured gas/liquid, liquid/liquid and

sand separation performance. “CDS,

now an FMC Technologies subsidiairy,

was a small company and this was an

expensive project: we literally had to

build a 1:1 scale model in our test lab –

and we had to extend the test lab for the

project,” explains Toine Hendriks, CDS

Engineering’s senior process engineer.

“Without the EUREKA funding it would

have been quite difficult.”

The initial result of this EUREKA

project was a demonstration pilot

separator installed in the CDS testlab

in the Netherlands. The developed

separation technology is currently being

implemented in the Statoil Tordis Subsea

Separation, Boosting and Injection (SSBI)

project. Statoil is the largest operator

on the Norwegian continental shelf.

This application is a first but Statoil is an

innovative company, highly motivated

to improve oil recovery in its offshore

fields. “By using this technology, you can

exploit an oilfield much deeper – so for

instance you can recover five to 10%

more from the original reserves, an

enormous advantage,” insists Hendriks.

“It is also expected that this technology

will facilitate new oil field developments

at deeper and more remote areas, an

advantage for the future as most of

the easy accessible oil has already been

produced. And, as only the relevant

constituents run through the topside

platform, the production rate can be

increased, so that you can produce

quicker, normally considered as a big

advantage!”

The future for this EUREKA-developed

technology is bright. “We are already

looking at applying similar technology in

several offshore fields”, adds Hendriks. Oil

companies realise that with oil reserves

becoming scarcer it is important to

exploit these reserves as efficiently as

possible.

By using this technology, you can exploit an oilfield much deeper – so for instance you can recover five to 10% more from the original reserves, an enormous advantage.

Toine Hendriks - CDS Engineering, the Netherlands

Project participants:The Netherlands, Norway

Budget: 1.9 MEuro

Duration: 14 months

ContactCDS Engineering BVDelta 101, 6825 MNlArnhem, The Netherlands Toine HendriksTel : +31 26 799 9140Fax: +31 267 99 9119toine.hendriks@cdsengineering.comwww.cdsengineering.comwww.fmctechnologies.com/subsea

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