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Table T17. Carbon isotopic composition and concentration of methane in mud gas analyzed during on-line mud-gas monitoring using the methane carbon isotope analyzer (MCIA), Hole C0020A.
Depth of on-line
monitored mud
gas MSF (m)
|
δ13C-methane
(‰ vs. VPDB)
|
SD δ13C-methane
(‰ vs. VPDB)
|
Methane
(ppm)
|
SD methane
(ppm)
|
|
648.0
|
–67.3
|
0.1
|
1,190
|
47
|
|
649.0
|
–67.1
|
0.4
|
1,460
|
61
|
|
649.5
|
–67.0
|
0.3
|
1,540
|
166
|
|
650.0
|
–66.1
|
0.9
|
1,220
|
143
|
|
650.5
|
–66.2
|
0.9
|
1,740
|
211
|
|
651.5
|
–67.2
|
0.3
|
2,290
|
81
|
|
652.0
|
–67.5
|
0.1
|
2,530
|
84
|
|
652.5
|
–67.1
|
0.1
|
2,790
|
129
|
|
653.0
|
–67.0
|
0.2
|
3,840
|
386
|
|
654.0
|
–66.2
|
0.1
|
4,730
|
126
|
|
654.5
|
–66.2
|
0.2
|
5,120
|
125
|
|
655.0
|
–66.2
|
0.1
|
5,430
|
88
|
|
655.5
|
–66.3
|
0.1
|
5,780
|
148
|
|
656.0
|
–66.3
|
0.1
|
6,180
|
132
|
|
656.5
|
–66.1
|
0.2
|
7,100
|
402
|
|
656.6
|
–66.0
|
0.2
|
7,970
|
429
|
|
657.0
|
–66.0
|
0.1
|
8,580
|
47
|
|
657.5
|
–66.2
|
0.2
|
8,730
|
55
|
|
658.0
|
–66.2
|
0.1
|
8,900
|
62
|
|
658.5
|
–66.0
|
0.1
|
9,110
|
30
|
|
659.0
|
–66.2
|
0.1
|
9,290
|
110
|
|
660.0
|
–66.0
|
0.1
|
9,620
|
105
|
|
660.5
|
–66.1
|
0.1
|
10,000
|
185
|
|
661.5
|
–66.2
|
0.1
|
12,600
|
834
|
|
662.5
|
–66.1
|
0.0
|
13,300
|
105
|
|
663.5
|
–66.1
|
0.1
|
16,000
|
1,170
|
|
664.0
|
–66.2
|
0.2
|
29,500
|
8,880
|
|
664.5
|
–66.3
|
0.1
|
20,500
|
839
|
|
665.5
|
–66.2
|
0.3
|
17,900
|
1,880
|
|
666.5
|
–66.1
|
0.1
|
17,000
|
3,480
|
|
667.0
|
–67.8
|
0.5
|
398,000
|
257,000
|
|
667.5
|
–66.6
|
0.1
|
138,000
|
93,400
|
|
668.0
|
–66.0
|
0.1
|
81,900
|
23,900
|
|
668.5
|
–66.7
|
0.1
|
260,000
|
36,400
|
|
669.5
|
–66.1
|
0.1
|
86,800
|
6,630
|
|
670.0
|
–66.3
|
0.0
|
164,000
|
37,500
|
|
671.0
|
–66.2
|
0.1
|
126,000
|
37,200
|
|
671.5
|
–66.3
|
0.3
|
96,800
|
13,800
|
|
672.5
|
–66.5
|
0.2
|
157,000
|
5,540
|
|
673.5
|
–66.1
|
0.3
|
96,400
|
18,500
|
|
674.5
|
–66.1
|
0.1
|
121,000
|
34,300
|
|
675.5
|
–66.2
|
0.4
|
123,000
|
29,000
|
|
676.5
|
–66.1
|
0.0
|
92,300
|
15,500
|
|
678.0
|
–66.3
|
0.0
|
134,000
|
32,600
|
|
678.5
|
–66.1
|
0.3
|
95,100
|
28,100
|
|
679.0
|
–66.3
|
0.2
|
123,000
|
44,200
|
|
679.5
|
–66.2
|
0.1
|
91,600
|
26,400
|
|
680.5
|
–66.3
|
0.1
|
114,000
|
38,300
|
|
681.0
|
–66.3
|
0.2
|
83,600
|
18,400
|
|
682.0
|
–66.4
|
0.1
|
127,000
|
38,000
|
|
682.5
|
–66.2
|
0.2
|
78,600
|
9,230
|
|
683.0
|
–66.5
|
0.1
|
147,000
|
20,400
|
|
684.0
|
–66.1
|
0.3
|
89,300
|
22,500
|
|
685.0
|
–66.2
|
0.1
|
99,400
|
27,300
|
|
685.5
|
–66.4
|
0.3
|
170,000
|
2,750
|
|
686.5
|
–66.1
|
0.2
|
79,200
|
11,200
|
|
687.0
|
–66.7
|
0.0
|
172,000
|
39,800
|
|
687.5
|
–66.3
|
0.2
|
145,000
|
49,300
|
In general, 100–200 data points were recorded by MCIA per meter of drilled sediment. The actual number of data points per depth interval depends on the rate of penetration. The table reports average values and standard deviations (SDs) for 0.5 m depth intervals. Methane contents in the on-line monitored flow of extracted mud gas are reported as well, but it is important to note that they depend on several factors (rate of penetration, mud flow, mud/headspace ratio in the separator, gas flow into the gas monitoring lab, etc.) and do not directly reflect the in situ concentration of methane in the formation. VPDB = Vienna Peedee belemnite. Only a portion of this table appears here. The complete table is available in ASCII.
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