Gas Hydrate System of Shenhu Area, Northern South China Sea: Geochemical Results
Table 1
Gas composition and methane/ethane ratio in sediments of Shenhu Area, northern slope of SCS.
Sample no.
Depth (mbsf)
Gas composition
C1/C2
CH4 (%)
C2H6 (ppm)
C3H8 (ppm)
SH2-1
70.73
96.10
440
LD
2185
SH2-2
73.31
96.72
477
LD
2027
SH2-3
146.46
98.49
646
97
1524
SH2-4
146.89
98.02
632
88
1551
SH2-5
150.00
99.53
552
67
1804
SH2-6
150.00
96.60
494
LD
1956
SH2-7
181.65
99.36
675
65
1473
SH2-8
182.07
97.75
533
LD
1833
SH2-9
185.39
99.21
581
61
1708
SH2-10
185.54
99.32
824
53
1205
SH2-11
195.40
99.32
1611
LD
616
SH2-12
197.50
99.82
1737
LD
575
SH2-13
197.50
99.80
1974
LD
506
SH2-14
197.50
99.77
2330
LD
428
SH2-15
197.50
99.72
2778
LD
359
SH2-16
197.50
99.57
3015
LD
330
SH2-17
221.71
99.68
1559
LD
639
SH2-18
228.00
99.70
1653
LD
603
SH2-19
238.58
99.06
1346
LD
736
SH3-1
68.63
99.12
632
ND
1569
SH3-2
71.32
99.78
692
LD
1443
SH3-3
74.55
99.77
640
LD
1560
SH3-4
117.01
99.77
644
LD
1548
SH3-5
117.60
99.80
658
LD
1516
SH3-6
119.85
99.69
618
LD
1613
SH3-7
121.15
99.83
703
LD
1419
SH3-8
125.00
99.91
659
LD
1516
SH3-9
125.00
99.89
695
LD
1438
SH3-10
128.71
99.80
696
LD
1434
SH3-11
129.06
99.73
661
ND
1510
SH3-12
132.34
99.78
726
LD
1374
SH3-13
132.80
99.79
721
LD
1385
SH3-14
190.50
99.87
1241
ND
805
SH3-15
190.50
99.87
1237
ND
807
SH3-16
190.50
99.21
1051
ND
944
SH3-17
192.95
99.21
3587
ND
277
SH3-18
201.31
99.85
1376
ND
718
SH3-19
201.70
99.73
2209
ND
451
SH7-1
97.52
97.52
158
84
6161
SH7-2
99.53
98.19
188
67
5233
SH7-3
100.83
97.40
139
70
6989
SH7-4
104.00
99.86
159
67
6286
SH7-5
131.81
96.44
80
LD
11995
SH7-6
132.84
95.56
102
LD
9377
SH7-7
135.00
99.68
88
55
11315
SH7-8
135.00
99.47
124
61
8009
SH7-9
155.00
99.89
1066
ND
937
SH7-10
155.00
99.85
1042
ND
958
SH7-11
155.00
99.84
1017
ND
981
SH7-12
155.00
99.81
1137
ND
878
SH7-13
155.00
99.74
1078
ND
925
SH7-14
168.67
99.55
2912
ND
342
SH7-15
176.12
99.21
7621
ND
130
SH7-16
185.00
99.76
2182
ND
457
SH7-17
185.00
99.54
2277
LD
437
Note. Mbsf: meters below seafloor; % of original gas, mole percent of each gas in the original sample: depressurization samples and void gas samples; ethane and propane (ppm), detection limit 50 parts per million; LD means lower than detection limit; ND means not detectable; C1/C2 is the molecule ratio of methane to ethane.