Methane and carbon at equilibrium in source rocks

Table 1 Hydrocarbon ingestion, Mowry Shale, 75°C, 200 hours

	Weight Concentrations in gas over time
VIAL A	1	2	3	4	5	6
μg C2/g	83.993	13.629	4.720	1.239	0.114	0.028
μg C3/g	101.548	11.542	3.113	0.693	0.036	0.010
μg iC4/g	124.533	13.942	4.059	1.032	0.065	0.020
μg nC4/g	86.679	4.290	1.051	0.184	0.007	0.007
VIAL B	1	2	3	4	5	6
μg C2/g	69.046	32.556	8.803	5.489	2.623	1.595
μg C3/g	93.766	44.174	12.430	7.606	3.249	1.558
μg iC4/g	119.893	59.328	19.538	12.789	5.971	3.032
μg nC4/g	114.537	57.104	17.266	11.075	5.403	2.734
VIAL C	1	2	3	4	5	6
μg C2/g	106.474	54.830	12.063	7.282	4.088
μg C3/g	149.244	73.379	10.149	5.855	3.118
μg iC4/g	191.697	92.384	10.637	6.208	3.464
μg nC4/g	177.661	83.205	3.061	1.749	1.080
	Percent wt Compositions in C₂-C₄over time
VIAL A	1	2	3	4	5
% C2/g	21.17	31.40	36.47	39.36	51.16
% C3/g	25.59	26.59	24.05	22.00	16.12
% iC4/g	31.39	32.12	31.36	32.80	29.38
% nC4/g	21.85	9.88	8.12	5.83	3.34
VIAL B	1	2	3	4	5
% C2/g	17.38	16.85	15.17	14.85	15.21
% C3/g	23.60	22.87	21.42	20.58	18.84
% iC4/g	30.18	30.71	33.66	34.60	34.62
% nC4/g	28.83	29.56	29.75	29.96	31.33
VIAL C	1	2	3	4	5
% C2/g	17.03	18.05	33.59	34.52	34.79
% C3/g	23.88	24.15	28.26	27.76	26.54
% iC4/g	30.67	30.41	29.62	29.43	29.48
% nC4/g	28.42	27.39	8.52	8.29	9.19

Sample preparation and experimental procedures are described elsewhere [10]. Each 5 ml. vial was charged with 1 g shale and gas composed of a 2 ml. mixture of ethane, propane, isobutane, and n-butane, equal volumes, and about 2 ml. of either methane (Vials B & C) or argon (Vial A). 2 ml. gas was removed and analyzed 5 times over 200 hours and replaced with argon (Vial A), or methane (Vials B & C). Concentrations are gas concentrations in the vials prior to each dilution calculated from the concentrations in the 2 ml. samples removed with each dilution.

ISSN: 1467-4866