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Gulf of Mexico Deepwater Current Structure Observations
Presenter and Author: Andy Brown
Co-Authors: Dick Crout, Pak Leung,
Jordan Krumm, Chunyan Li 1
Gulf of Mexico Deepwater Current Structure Observations
+ Location of 42370
Yucatan Straits
Florida Straits Loop Current
Loop Current Eddy
Cyclonic Eddies
Gulf Stream
• Background Information
• Station 42370
• Data Time Series
• Spectral Analysis
• Conclusions
• Future Applications
2
Background • The Notice to Lessees (NTL) established in 2005, requires the collection of current
profile data from oil and gas production platforms and drilling rigs operating in the Gulf of Mexico deep waters
• Data are obtained from an average of 30 rigs or platforms (stations) at any given time since 2005. Maximum number of reporting stations was over 40 in 2009
• Length of data set from each station varies from a few weeks to years
• Quality of data collected is dependant on the operators requirements • This talk presents high quality current data obtained from a single location in the
North Central Gulf of Mexico and the findings of inertial motions and Topographic Rossby Wave signatures
• Excellent example of a long term oceanographic data set obtained for operational purposes that can also be used as research data
• We conclude with suggestions for future measurement programs
3
Technical Details
• The National Data Buoy Center (NDBC) Station 42370 is a Production Drilling and Quarters Truss Spar permanently moored in 1325m of water in Green Canyon block 645, 150 miles South of New Orleans, Louisiana
• A real time, high quality, current profiling system was designed and engineered in
2004 for the operator of the Spar. Installation was in 2005. The purpose of the system was to support daily marine operations including input to the riser management system and meet or exceed the anticipated 2005 NTL requirements
4
Technical Details • Operator desire for accurate data, design requirements and quality control during the
engineering phase have been key to the success of the system • A near surface deployed 38kHz ADCP and a seabed mounted 75kHz ADCP
• 75kHz ADCP interface to the surface via dual fiber optic data and power cable
running along catenary riser
• Seabed terminal for fly-lead connection utilizes hybrid ROV Wet mateable connectors. Prizm fiber optic multiplexer & 220v/48v convertor in subsea electronics housing
• Continuous operation for almost 7 years
• Data every 20 minutes since May 2005
• No instrument recovery or servicing
5
Average (annual) currents near seabed at GC645 Annual Average Speed 1000 m Depth 1200 m Depth
2006
5.4 cm/s 5.0 cm/s
2007
5.3 cm/s 4.2 cm/s
2008
5.5 cm/s 4.0 cm/s
2009
5.2 cm/s 4.2 cm/s
2010
5.4 cm/s 3.8 cm/s
6
Selected Eddy Events 1000m Depth 10 May 2006 – 9 May 2007
7
Eddy Yankee
0
5
10
15
20
25
30
35
40
13
92
78
31
17
41
56
51
95
62
34
72
73
83
12
93
52
03
91
14
30
24
69
35
08
45
47
55
86
66
25
76
64
87
03
97
43
07
82
18
21
28
60
38
99
49
38
59
77
61
01
67
10
55
81
09
49
11
34
01
17
31
12
12
21
25
13
12
90
41
32
95
13
68
61
40
77
14
46
81
48
59
15
25
01
56
41
16
03
21
64
23
1200 m
8
Selected Eddy Events 1000m Depth 10 May 2007 – 9 May 2008
9
0
5
10
15
20
25
30
35
40
45
1
47
7
95
3
14
29
19
05
23
81
28
57
33
33
38
09
42
85
47
61
52
37
57
13
61
89
66
65
71
41
76
17
80
93
85
69
90
45
95
21
99
97
10
47
3
10
94
9
11
42
5
11
90
1
12
37
7
12
85
3
13
32
9
13
80
5
14
28
1
14
75
7
15
23
3
15
70
9
0
5
10
15
20
14
64
92
71
39
01
85
32
31
62
77
93
24
23
70
54
16
84
63
15
09
45
55
76
02
06
48
36
94
67
40
97
87
28
33
58
79
8
Eddy Albert
Eddy Albert
10
1200 m
Selected Eddy Events 1000m Depth 10 May 2008 – 9 May 2009
11
0
2
4
6
8
10
12
14
16
18
14
53
90
51
35
71
80
92
26
12
71
33
16
53
61
74
06
94
52
14
97
35
42
55
87
76
32
96
78
17
23
37
68
58
13
78
58
99
04
19
49
39
94
51
03
97
10
84
91
13
01
11
75
31
22
05
12
65
71
31
09
13
56
11
40
13
14
46
5
0
5
10
15
20
25
30
35
40
45
1
44
4
88
7
13
30
17
73
22
16
26
59
31
02
35
45
39
88
44
31
48
74
53
17
57
60
62
03
66
46
70
89
75
32
79
75
Eddy Darwin
Eddy Darwin
12
1200 m
Selected Eddy Events 1000m Depth 10 May 2009 – 9 May 2010
Great data set, average currents are higher and very periodic
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Spectral Analysis 1000m Depth May 2005 – May 2010
Full Spectrum Smoothed
0 0.2 0.4 0.6 0.8 1 1.2 1.40
1
2
3
4
5
x 104
Frequency - Cycle Per Day (CPD)
Pow
er
Power Spectrum of Motion
0 0.2 0.4 0.6 0.8 1 1.2 1.40
1
2
3
4
5
x 104
Frequency - Cycle Per Day (CPD)
Pow
er
Power Spectrum of Motion
14
Spectral Analysis 1200m Depth May 2005 – May 2010
Full Spectrum Smoothed
0 0.2 0.4 0.6 0.8 1 1.2 1.40
0.5
1
1.5
2
2.5
3
3.5
x 104
Frequency - Cycle Per Day (CPD)
Pow
er
Power Spectrum of Motion
0 0.2 0.4 0.6 0.8 1 1.2 1.40
1
2
3
4
5
6
x 104
Frequency - Cycle Per Day (CPD)
Pow
er
Power Spectrum of Motion
15 Inertial waves have degenerated with depth
Power Spectrum 5 Years
Spectral Analysis
1000 meter Depth 1200 meter Depth
Time Period May 2005 – April 2010
Frequency (cpd) Period Frequency (cpd) Period
Near-inertial 0.9045 26.53 hours
Near-inertial 0.9025 26.59 hours 0.90 26.67 hours
Low-frequency 0.0102 98.04 days
Low-frequency 0.0450 22.22 days 0.0495 20.20 days
Low-frequency 0.0580 17.24 days 0.0576 17.36 days
16
26.08 Near Inertial Oscillation for this latitude
5 Year Power Spectrum Animation
17
Further Investigation - Eddy Ekman June 2009 – Feb 2010
18
Eddy Ekman June 2009 – February 2010
0
2
4
6
8
10
12
14
16
18
20
13
95
78
91
18
31
57
71
97
12
36
52
75
93
15
33
54
73
94
14
33
54
72
95
12
35
51
75
91
16
30
56
69
97
09
37
48
77
88
18
27
58
66
99
06
39
45
79
85
11
02
45
10
63
91
10
33
11
42
71
18
21
12
21
51
26
09
13
00
31
33
97
13
79
11
41
85
14
57
91
49
73
15
36
71
57
61
16
15
51
65
49
1000 m
0
2
4
6
8
10
12
14
16
18
13
95
78
91
18
31
57
71
97
12
36
52
75
93
15
33
54
73
94
14
33
54
72
95
12
35
51
75
91
16
30
56
69
97
09
37
48
77
88
18
27
58
66
99
06
39
45
79
85
11
02
45
10
63
91
10
33
11
42
71
18
21
12
21
51
26
09
13
00
31
33
97
13
79
11
41
85
14
57
91
49
73
15
36
71
57
61
16
15
51
65
49
Eddy Ekman
1200 m
19
Power Spectrum June 2009 – February 2010
1000 m 1200 m
0 0.5 1 1.5 2 2.5 30
2000
4000
6000
8000
10000
12000
14000
16000
Frequency (CPD)
m2/s
0 0.5 1 1.5 2 2.5 30
0.5
1
1.5
2
2.5
3x 10
4
Frequency (CPD)
m2/s
20
Power Spectrum Energy Eddy Ekman
Depth
Peak NIO Frequency Peak TRW Frequency
1000 m
1.75 x 104 m2/s 1.30 x 104 m2/s
1200 m
0.70 x 104 m2/s 1.35 x 104 m2/s
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Conclusions
• Currents in excess of 35 cm/s were detected at 1200 m depth as Loop Eddies Yankee, Albert, and Darwin pass south of the GC 645 location
• Wind generated near-inertial oscillations are observed at 1000 and 1200 m depths with more energy present at 1000 m
• Topographic Rossby Waves impact on near-bottom currents is shown during the period from May 2005 through May 2010. They appear consistently at approximately 17 -20 day intervals
• Five year power spectra
• Significant peaks at near-inertial frequencies (near 26.06 hours) and Topographic Rossby Wave TRW frequencies (10 - 100 days)
• Single peak near the inertial frequency at 1200 m and a double peak at 1000 m • Energy at both depths is approximately the same in the TRW frequency range • Energy in the near-inertial band at 1000 m is nearly twice that at 1200 m
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Future Applications • High quality data is the result of the operators desire for quality data exceeding NTL
requirements • Unique long term oceanographic data set obtained for operational purposes
providing a unique opportunity to study deepwater current and events from different oceanographic phenomena
• Review of NTL related current measurements suggests that a more rigorous approach
to the data collection is required in order to standardize quality, data return and usability
• Cost of NTL related measurements over 5 years and public access to data
• Alternative - Installation of a Gulf of Mexico observing system utilizing existing platform and fiber optic networks
• Include the need for long term site specific measurements at new development sites
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Thank You