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Compact, inline separation technology – what and why? - NTNU

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<strong>Compact</strong>, <strong>inline</strong> <strong>separation</strong><br />

<strong>technology</strong> – <strong>what</strong> <strong>and</strong> <strong>why</strong>?<br />

Olav Kristiansen<br />

Statoil RDI, Subsea Separation Technologies<br />

<strong>NTNU</strong>, Flerfaseteknikk guest lecture, February 11 2013<br />

2013-02-11


Outline<br />

• Process challenge<br />

• <strong>Compact</strong> separators, working principle<br />

• <strong>Compact</strong> <strong>separation</strong> applications in Statoil<br />

• Future applications, challenges <strong>and</strong> new technical requirements<br />

• R&D in Statoil to meet new technical challenges<br />

• Summary<br />

2 -<br />

2013-02-11


Statfjord B produced water challenge<br />

>60 bar<br />

18’’<br />

(vertical)<br />


Working principle<br />

Gas/liquid stream<br />

Separation<br />

chamber<br />

Separated gas<br />

Gas free liquid<br />

Swirl element<br />

Gas extraction<br />

Increasing <strong>separation</strong> by inducing swirling flow – increasing g-forces<br />

Enable <strong>separation</strong> of two phases with different densities<br />

4 -<br />

2013-02-11


Videos – working principle<br />

• Phase splitter liquid film <strong>and</strong> carry over into gas extraction pipe<br />

− Bulk <strong>separation</strong><br />

− Induce two-phase flow spin ~100g<br />

• Axial cyclone<br />

− Fine <strong>separation</strong>, removing droplets down to a ~30 to 50 microns<br />

− Induce flow spin <strong>and</strong> apply tangential force<br />

The videos are courtesy of FMC Separation Technology<br />

5 -<br />

2013-02-11


Statfjord B - Produced water slugging<br />

Challenge solution<br />

Major problem with slugs <strong>and</strong> strong vibrations in the<br />

Statoil Statfjord B platform produced water system.<br />

• Capacity limitation of the system<br />

• Safety concern due to the vibrations.<br />

• Solution: 18” De-gasser. Since 2003, gas has been<br />

exported instead of flared. Slugging stopped.<br />

Statfjord B<br />

6 -<br />

2013-02-11


Veslefrikk slugging problem<br />

• Production through 150m flexible hoses between Veslefrikk A <strong>and</strong> B<br />

• Two-phase (3phase) flow<br />

• Slugging, pressure fluctuations <strong>and</strong> production instabilities<br />

• Solution?<br />

7 -<br />

2013-02-11


Veslefrikk slugging problem<br />

Phase splitter<br />

Solution: Split gas <strong>and</strong> liquid using a Phase Splitter, produce outside slug flow<br />

region. 2-4000 BOPD production increase (1-2 MNOK/day)<br />

8 -<br />

2013-02-11


Sleipner T – Scrubber Overload<br />

• Scrubber overloaded with liquid due to a<br />

very high gas velocity through the vessel (Kfactor<br />

>0.2 m/s).<br />

• Massive carry-over of condensate with the<br />

outlet gas that is used to superheat the gas<br />

to the amine absorbers.<br />

• Solution: De-liquidiser to<br />

remove the bulk of the<br />

liquid condensate in the<br />

feed stream prior to<br />

entering the scrubber.<br />

• This improves the<br />

operating conditions for<br />

the suction scrubber <strong>and</strong><br />

thereby the <strong>separation</strong><br />

efficiency.<br />

9 - 2013-02-11


Kvitebjørn – huge production increase<br />

• Objective: Increase production capacity<br />

• Solution: Installation of a 20” Phase Splitter<br />

upstream the inlet separator <strong>and</strong> route some of the<br />

gas (30 to 35%) directly to the scrubber.<br />

• New application for Statoil – high pressure, gas<br />

dominated flow (less than 5% liquid by volume in the<br />

incoming flow).<br />

• Qualification tests at K-LAB 2007 (8” unit)<br />

• Gas capacity increase by 35% from 18.5 to<br />

25MMSm 3 /d<br />

10 - 2013-02-11


Hydrocarbon resources<br />

11 - 2013-02-11


Where are the hydrocarbon resources?<br />

Source: Wikipedia ’Peak Oil’<br />

12 -<br />

2013-02-11


Deepwater potential<br />

13 - 2013-02-11


What are the challenges?<br />

Development of new discoveries<br />

• Colder (Arctic)<br />

• Deeper (Gulf of Mexico, West<br />

Africa, Brazil….)<br />

• Longer (Barent region, Arctic)<br />

Enhanced Oil Recovery<br />

• Norwegian Continental Shelf (NCS)<br />

– old fields with steeply declining<br />

production<br />

− Increased reservoir depletion<br />

− Tie-in of marginal fields to existing<br />

infrastructure<br />

New <strong>technology</strong> is required!<br />

14 -<br />

2013-02-11


Deep water boosting – new field development<br />

<strong>and</strong> enhanced oil recovery<br />

• Long tie-ins (Pazflor/Angola)<br />

• Deep water <strong>and</strong> low reservoir pressure<br />

− High static head to be overcomed<br />

− Single-phase pumps required (MPPs give dp


How large separator can we put subsea?<br />

• Tordis separator <strong>and</strong> boosting station<br />

− Diameter 2.1m<br />

− Skid dry weight 1 300 tons.<br />

− Water depth 200m<br />

− Possible <strong>and</strong> in operation<br />

Max 1000m<br />

w.d.<br />

• A Tordis separator at 3000m w.d.<br />

− 17cm wall thickness due to outer<br />

pressure.<br />

− Difficult to produce<br />

− Difficult (if possible) to heave!<br />

Max weight<br />

300tons at<br />

3000m w.d.<br />

16 -<br />

2013-02-11


Conventional vs. compact separators<br />

17 - 2013-02-11


<strong>Compact</strong>, <strong>inline</strong> separators – <strong>what</strong> <strong>and</strong> <strong>why</strong>?<br />

Caltec iSep<br />

Operating principle:<br />

• Cyclonic separators<br />

• Low-G operation (typically


Now <strong>and</strong> the future<br />

Today: De-bottlenecking<br />

• Performance requirement for one outlet phase<br />

• Performance knowledge: “Sufficient”<br />

• Empirical <strong>and</strong> experienced designs.<br />

Increased fundamental<br />

underst<strong>and</strong>ing of the fluid mechanical<br />

processes is required!<br />

New applications<br />

• Replace traditional separators<br />

• Enable ultra deep water subsea processing for boosting<br />

Two/Three/Four-phase <strong>separation</strong> systems<br />

New <strong>and</strong> stricter requirements<br />

• Stricter requirements for both outlet phases<br />

• Exact performance knowledge <strong>and</strong> operational envelope<br />

required.<br />

• Must h<strong>and</strong>le start-up/shut-down, slug flow, large<br />

turndown<br />

• Challenging process controls<br />

19 -<br />

2013-02-11


Tehcnical challenge: performance compared to<br />

conventional separators<br />

<strong>Compact</strong><br />

• Turndown 50 to 120% of design<br />

operational rate. Swirl breakdown at too<br />

low rate.<br />

• Pressure drop 0.5-2 bar<br />

• Optimised for one outlet stream, e.g. low<br />

liquid carry over<br />

Conventional<br />

• Turndown 0 to >100%<br />

• Pressure drop very low<br />

• Two or three clean output streams<br />

• Can h<strong>and</strong>le transients<br />

• Homogenous inflow is required (no stratified<br />

or slug flow)<br />

Systems will be needed to<br />

overcome these limitations –<br />

single-units are not sufficient<br />

20 -<br />

2013-02-11


Slug flow performance – single Phase Splitter<br />

Hydrodynamic slugs upstream<br />

Incoming slugs propagate through the separator<br />

(little or no slug damping)<br />

1<br />

1<br />

0,9<br />

0,9<br />

0,8<br />

0,8<br />

0,7<br />

0,7<br />

Hold-up<br />

0,6<br />

0,5<br />

0,4<br />

GVF Hold-up<br />

0,6<br />

0,5<br />

0,4<br />

GVF liq<br />

GVF gas<br />

Hold-up<br />

GVF liq avrage=0,34<br />

GVF gas avrage=0,78<br />

0,3<br />

0,3<br />

0,2<br />

0,2<br />

0,1<br />

0,1<br />

0<br />

15 17 19 21 23 25 27 29 31 33 35<br />

Time (s)<br />

0<br />

15 17 19 21 23 25 27 29 31 33 35<br />

Time (s)<br />

21 -<br />

2013-02-11


<strong>Compact</strong> separator systems<br />

– to overcome the limitations of single <strong>inline</strong> separators<br />

Positive:<br />

• Can h<strong>and</strong>le turndown 0-100%(+)<br />

− Start-up <strong>and</strong> shutdown<br />

• H<strong>and</strong>les hydrodynamic slugs<br />

• Can be optimised for both outlet streams<br />

• Weight <strong>and</strong> footprint lower than traditional<br />

separator<br />

Negative:<br />

• Pressure drop (several bars)<br />

• Complex process<br />

• Challenging (but manageble) process<br />

control<br />

<strong>Compact</strong>Sep JIP <strong>separation</strong> system<br />

Development project with<br />

Statoil, Petrobras <strong>and</strong> Chevron<br />

Patent Application priority filing date 22-12-2012<br />

PCT/EP2011/073881<br />

22 -<br />

2013-02-11


Turndown problem solved<br />

Production start-up<br />

100% liquid<br />

100% gas<br />

Flow rate (Am 3 /hr)<br />

100% liquid<br />

50% gas<br />

250<br />

200<br />

150<br />

100<br />

50<br />

Inlet liquid flow rate<br />

Inlet gas flow rate<br />

Gas flow rate, Phase Splitter liquid outlet<br />

Liquid flow rate, De-liquidiser gas outlet<br />

Shut-down<br />

100% liquid<br />

100% gas<br />

100% liquid<br />

50% gas<br />

0% production<br />

0<br />

1000 1060 1120 1180 1240 1300 1360 1420 1480 1540 1600 1660 1720 1780 1840 1900 1960 2020<br />

Relative time (s)<br />

Liquid carry over <strong>and</strong> gas entrainment within acceptance criteria during<br />

startup <strong>and</strong> shutdown<br />

0% production<br />

23 -<br />

2013-02-11


Slug flow (rapid transient) problem solved<br />

Variation in<br />

gas quality<br />

Incoming<br />

slugs 5±4m<br />

Variation in<br />

liquid quality<br />

24<br />

2013-02-11


Summary<br />

• Inline, compact separators – working principle<br />

• Examples, <strong>inline</strong> <strong>separation</strong> in Statoil – troubleshooting <strong>and</strong> de-bottlenecking<br />

• Where are the future resources<br />

• Special attention to deep-water developments <strong>and</strong> new technical requriements<br />

• Technology development of compact <strong>separation</strong> systems – solving limitations<br />

related to <strong>inline</strong> separators. Ongoing JIP with one vendor <strong>and</strong> four oil companies.<br />

25 2013-02-11


<strong>Compact</strong>, <strong>inline</strong> <strong>separation</strong> <strong>technology</strong> –<br />

<strong>what</strong> <strong>and</strong> <strong>why</strong>?<br />

Olav Kristiansen<br />

Principle Researcher, Statoil RDI,<br />

Subsea Separation Technologies<br />

olakri@statoil.com<br />

Tel: +4790213317<br />

www.statoil.com<br />

26<br />

2013-02-11

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