CO 2 transport i rør Flow assurance

Transcription

1 Kursdagene i Trondheim Januar 2009 CO 2 håndtering Er vi i rute? CO 2 transport i rør Flow assurance Oddmund Kvernvold < >

2 Content What is flow assurance? CO 2 characteristics and related flow assurance aspects Available software capabilities and limitations Storage of CO 2 from Kårstø and Mongstad - Storage concepts - Operational requirements - OLGA simulation steady state and blow down - Impact/dispersion analysis Concluding remarks Slide 2

3 Flow Assurance

4 Flow Assurance Introduced by Petrobras in the early 1990 s as 'Garantia de Fluxo' which literally translates as 'Guarantee the Flow', or "Flow Assurance". The term originally covered the thermal hydraulic and production chemistry technical issues faced when exploiting deepwater oil reserves. Now, it is generally understood under a much broader definition: "Flow Assurance" includes all issues important maintaining the flow from reservoir/export to reception facilities "Flow Assurance" is a multi-discipline activity, requiring engineers with detailed technical backgrounds to "follow the flow" from export through to reception. Slide 4

5 Flow assurance Covers Pipeline sizing/capacity Thermohydraulic Insulation design Flow characteristics Slugging Corrosion Hydrate, wax and scale formation Blow down Transient operation - start up and shut downs Sand accumulation in pipeline Erosion due to solids production Impacts on Well growth Pipe sizing and schedule Insulation Weight coating Trenching/backfill requirements Upheaval buckling Snaking Pipeline creep Free span Slide 5

6 CO 2 characteristics and FA related issues

7 Pressure (bara) CO 2 characteristics Mol weight 44kg/kmol Critical point 31 o C and 73.3bara Triple point -56 o C and 5.2bara Sublimation temperature at 1bara o C Latent heat of sublimation 570kJ/kg Density of dry ice kg/m3 Latent heat of evaporation 285kJ/kg Phase diagram CO Solid Tripple point Temperature (DegC) Liquid/dense phase Critical point Gas CO2 Slide 7

8 CO 2 /flow assurance aspects Capacity pipe dimensioning - Export pressure - Reservoir pressure - Injection requirement Hydrate formation Dense phase Corrosion Transient operation/blow down - Feasibility - Low temperature in pipe line - Solid formation Dispersion impact evaluation - Impact on property/environment - Humans - Safety zones Slide 8

9 Software capacity and limitations

10 OLGA flow simulations OLGA commercial code - Developed for analysis of analysis of multi component systems - Gets problems for single component systems and operation close to the boiling curve - Applicable in dense phase and in gas phase - Not able to predict solid formation OLGA new module not commercial - Able to treat single component CO 2 systems. - Not able to predict solid formation, but can be assessed from temperature results Slide 10

11 PHAST dispersion of CO 2 from blow down PHAST commercial code - Developed for simulation of dispersion of gas in atmosphere - Not able to handle gas jets with solids - Sublimation in jet - Solid drop out and accumulation at ground PHAST next generation - Work is ongoing to develop a code which may handle also solid behaviour in jet - Commercial code available mid next year Slide 11

12 Water in stream

13 Consequences of water in CO 2 gas Hydrate Corrosion Will require automatic shut down if water content exceeds set value Slide 13

14 Storage of CO 2 from Kårstø and Mongstad

15 Alternative storage solutions Pipeline from Kårstø to subsea templates and storage in the reservoirs at either the Utsira or Johansen formation Pipeline from Mongstad to subsea templates and storage in the reservoirs at either the Utsira or Johansen formation Johansen formation Mongstad Via Sleipner platform Kårstø Plant/CO2 source Impermeable soil/rock Reservoir Utsira formation Sleipner Slide 15

16 Depth (m) Elevation (m) System specifications Pipeline length - Kårstø Utsira 230km - Kårstø Johansen 235km - Mongstad Utsira 352km - Mongstad Johansen 98km Kårstø to Utsira Reservoir conditions KP (km) Utsira Johansen Horizontal well - Utsira formation Depth (m) Pressure (bara) Temperature ( o C) Horizontal deviation (m) Slide 16

17 Operational requirements Three injection rates Maximum export pressure Minimum design temperature ( Million tons/year) 200bar -25/50 o C normal operation -40/50 o C during blow down System operated in dense phase Slide 17

18 Case example Operation and blow down Pipeline from Kårstø to Utsira (10 ) Base case injection requirements Will be showing - Steady state operational conditions - Shut down of pipeline followed by settle out for 24houres - Blow down of pipeline through constant size vent Simulations performed with new OLGA module - Simulation work performed by SPT Slide 18

19 Steady state - pipeline Holdup Pipeline profile Pressur e Temperature Note: Two phase flow from approximately KP = 200 Required export pressure approximately 100bara Slide 19

20 Steady state - well Note: Two phase flow from approximately 500m into the well Slide 20

21 Settle out conditions 24hours after shut down Slide 21 21

22 1day after initiation of blow down Boil off close to Utsira Pushes liquid to low point in Buknafjorden Some liquid transported uphill from bottom of Buknafjorden to Kårstø Note: Pipeline topography acts as water lock Balance between boil of rate/volume and release rate at Kårstø Minimum temperature -30 o C Slide 22 22

23 2days after initiation of blow down Boil off at close to Utsira Pushes liquid to low point in Buknafjorden Gas flow high enough to transport liquid uphill to Utsira Slide 23 23

24 4days after initiation of blow down CO 2 boiled off close to Utsira No liquid transported uphill to Kårstø Slide 24 24

25 5.5days after initiation of blow down Nearly all liquid has boiled off Slide 25 25

26 8days after initiation of blow down Blow down finalised Slide 26 26

27 Blow down rate Mixture of CO 2 in liquid and gas phase released during the first two days After two days only gas is released Maximum vent rate 60kg/s (only for a short period after initiation of blow down Reduces to 15-30kg/s for the next 4-5days Total 9000 ton of CO 2 released during blow down Slide 27

28 Pressure and temperature upstream/downstream of vent Minimum temperature upstream of vent -35 o C Temperature downstream of vent -79 o C for the first two days Release of a mixture and CO 2 in both solid and gas phase in first two days After two days CO 2 will be released to atmosphere in gas phase Total blow down time 7-8days Slide 28

29 Impact evaluation

30 CO2 Hazards Above 25% can cause quick death! Above 10% can cause unconsciousness Not able to escape! Safe distance is assumed with a maximum of 5% concentration 0.5-1% is the concentration for the workplace, for a 10-hr work shift (NIOSH CO 2 exposure limits) Slide 30

31 Proposed venting solution Vent directed at 45 o with vertical - High momentum/velocity will result in violent mixing with air and no critical concentration of CO 2 at ground level - Solid CO 2 will deposit in dedicated area - Sublimation of CO 2 onshore is a very slow process 0.5% concentration curves Direct the venting towards the sea - Solid CO 2 will deposit on the sea and sublimate - Will result in violent boiling from the sea - Safety zones at sea have to be established Slide 31

32 Concluding remarks The concept of transporting CO 2 in pipelines from onshore plants at Kårstø and Mongstad for storage into reservoirs has been demonstrated to be feasible both with respect to normal operation and pipeline blow down scenarios A design case is to be selected and detail engineering to be initiated Shortcomings (handling of CO 2 in solid form) of existing codes to be emphasized. Development work is required "Flow Assurance" is a multi-discipline activity Slide 32

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