Near Field Behavior of Oil & Gas Plumes

Transcription

1 Near Field Behavior of Oil & Gas Plumes Effects of bubble/ droplet sizes Eric Adams and S. Socolofsky A. Chow G. Chan 1

2 Phase Separation Socolofsky & Adams (2002) Bubbles & droplets can separate from plume (and fractionate) due to stratification or crossflow DWH was stratification dominated DeepSpill was crossflow dominated

3 oil and gas released in a current Gas bubbles create plume, but currents blow oil and entrained seawater 3 downstream, leaving gas to rise separately. Socolofsky & Adams (2002)

4 gas released in linear stratification Density stratification is caused when lighter (warmer) water overlies heavier (colder) water. Light gas and heavy seawater rise to a level of neutral buoyancy causing oil and seawater to separate from the gas and intrude laterally. Gas bubbles continue to rise, causing plume to restart, with lesser quantities of oil 4 Socolofsky & Adams (2003)

5 Correlations Principal independent variables: B, N, u s, z, U a ( m) ( ) (~ m 3 /s) ( m) ( m) Socolofsky & Adams (2003, 2005), Akar and Jirka (1995) Stratification dominated; weak crossflow

6 Peak CDOM measurements vs Predicted trap height

7 Tang, Gorgas & Masutani (2003) D max ~ (s/r) 3/5 e -2/5 ; e ~ U 3 /D; D max /D ~ rq o /sd 3 ) -0.6 High jet velocity (high e), and chemical dispersants (low s) produce small droplets (right)

8 Oh Atomization Large drops 8 Re Tang, Gorgas & Masutani (2003)

9 Oh Atomization Large drops 200 W = rq o2 /sd o 3 20 DH 9 Re Tang, Gorgas & Masutani (2003)

10 Oh Atomization Large drops 200 W = rq o2 /sd o 3 20 D/D o ~ W -3/5 DH 10 Re Tang, Gorgas & Masutani (2003)

11 Simulated & Observed Cumula2ve Gas BSD from DeepSpill Field Experiment (cm; Data from SINTEF: average of near and far measurements Fig ; Model 2: D o = 6 cm, n = 3) Mod2G (DS) Obs G (DS ave N/F)

12 Simulated & Observed Cumula2ve Oil DSD from DeepSpill Field Experiment (cm; data from SINTEF: ave of close and far measurements Fig ; (Model 2; D o = 6 cm, n = 3) Mod2 O (DS) Obs O (DS ave N/F)

13 Applying Chemical Dispersants to Sub-Surface Oil Spills Chevron-MIT study also involving TAMU and U. Hawaii

14 z hp ht Plume behavior depends on B, N, u s, z U ~ (B/z) 1/3 h p, h t ~ (B/N 3 ) 1/4 U c ~ (BN) 1/4 Expect droplets to detrain/intrude as function of U N = w s /(BN) 1/4 14

15 Plume Classification Socolofsky and Adams (2005) U N < < U N < < U N Socolofsky & Adams (2005): U U N > 0.6 no intrusion (bubbles) Chow (2004): U N < ~ 0.1 significant intrusion (glass beads & brine motivated by CO 2 storage )

16 Ballo2ni glass beads (PoVers Industries Dawson- MacDonald Co.) Bead Median Diameter (cm) U s (cm/s)* U N * A B (GC) C D (GC) AD AE (AC) AG (GC) AH (AC, GC) *SG = 2.5; B = 3 x 10-5 m 4 /s 3 ; N = 0.3 s -1

17 Experimental water tank

18 Two-tank stratification method 500 gallons freshwater mixed with 80lbs evaporated salt Pump 1000 gallons water tank

19 Release mechanism Water surface

20 Collec2on trays Each cell measures 4cm by 5cm Longer piece: 35 cells (total length: 140 cm) Shorter piece: 14 cells (each measures: 56cm) Two measurements per loca2on

21 Experiments with beads AH, AG, D, B 1000g per release, water depth = 190cm AH AG D B u s (cm/s) Q b (m 3 /s) 1.94E E E E- 6 B (m 4 /s 3 ) 2.77E E E E- 5 N (1/s) U N Type 1* (intrusion) 1* (intrusion) 1* (detrainment) 1*/2 (borderline)

22 Mass Distribution Mass faction (g/g) B B fit D D fit AG AG fit AH AH fit distance from 'center' (cm)

23 σ/h vs. UN y = ln(x) R² = σ/h 0.1 Detrainment/intrusion Detrainment/no-detrain UN

24 Deepwater Horizon* Diameter (um) U s (cm/s) U N to to to to to Preliminary conclusion: Droplets smaller than at least 300 mm should intrude Spherical oil droplets with density = 0.85 g/cm 3 ; B = 0.5 to 1.0 m 4 /s 3 ; N = to s -1

25 Droplet rise through non-entraining intrusion layer z Q i r h i r(z) r i t i = h i /u s V i = Q i t i = πr i2 h i r i = (Q i /πu s ) 1/2 Q i =0.9B 3/4 /N 5/4 r i = 0.5B 3/8 /(N 5/8 u s 1/2 ) ~D -1 Plume source

26 Correlations Principal independent variables: B, N, u s, z, U a ( m) ( ) (~ m 3 /s) ( m) ( m) Socolofsky & Adams (2003, 2005), Akar and Jirka (1995) Stratification dominated; weak crossflow

27 New data s Data from Chow (2004)

28 New data s Deepwater Horizon Data from Chow (2004) 300 mm drop: 180 < s r < 800 m 30 mm drop: 5.5 km < s r < 24 km Much of the oil was found on surface within 1 km of source (must have been large droplets; dispersants not totally effective)

29 Ongoing and future work Add l exp ts being conducted low & intermediate U N poly-dispersed buoyancy source (oil/gas, large/small oil) Stratification & current (towing release) Transport & fate within intermediate field (intrusion layer & open ocean above layer) Interfacing particles with Lagrangian transport models

30 30 Near Field oil distribution can be used in simple 1-D models of advection, diffusion, dissolution/degradation

31 SABGOM: data-assimilating 3D ocean circulation model LTRANS: 3D particle-tracking with advection, diffusion, and oil transformations Multi-phase oil plume model LTRANS transports/transforms droplets. Droplets with different size, DOB, decay properties transported independently; concentration distributions can be computed during post-processing

32 Questions?