Scientific results from the deepened Lopra-1 borehole, Faroe Islands: Hydrocarbon gases in Palaeogene volcanic rocks from the Lopra-1/1A well, Faroe Islands
Hydrocarbon gases were monitored in the drilling fluid during deepening of the Lopra-1 well from 2178–3565 m, in which thermogenic, methane-rich gases had been found previously. The mud gas concentration, up to 105 ppm of methane, was generally higher in the hyaloclastite sequence, 2470 m – terminal...
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| Format: | Article |
| Language: | English |
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Geological Survey of Denmark and Greenland
2006-07-01
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| Series: | Geological Survey of Denmark and Greenland Bulletin |
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| Online Access: | http://www.geus.dk/publications/bull/nr9/nr9_p79-90.pdf |
| _version_ | 1811221845790162944 |
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| author | Laier, Troels |
| author_facet | Laier, Troels |
| author_sort | Laier, Troels |
| collection | DOAJ |
| description | Hydrocarbon gases were monitored in the drilling fluid during deepening of the Lopra-1 well from 2178–3565 m, in which thermogenic, methane-rich gases had been found previously. The mud gas concentration, up to 105 ppm of methane, was generally higher in the hyaloclastite sequence, 2470 m – terminal depth (TD), than in the overlying lavas of the lower basalt formation. The highest concentrations of mud gas in the lower basalt formation were associated with the more porous tuffaceous zones, whereas no simple relationship could be established between measured mud gas concentrations and porosity of the hyaloclastic rocks, which showed less marked porosity variations than the lavas.Chemical (C2+ < 1%) and isotopic (δ13C1: –34 to –39‰) compositions of seven samples of mud gas collected at peak gas concentrations between 2657 m and 3442 m compare well with those of the hydrocarbon gases which had been seeping more or less continuously into the existing well since 1983, suggesting a common origin of the gases. Headspace methane concentrations measured in 135 canned samples of cuttings were scattered between 10 ppm and 6 × 103 ppm, with the exception of six samples from a short interval, 2685–2745 m, which showed consistently high values > 104 ppm. No particularly gas-rich zones were indicated, however, by the mud gas, nor was any significant change in lithology noted for this interval. It is possible that the technique of turbo-drilling, that had been attempted over a short interval, 2657–2675 m prior to collection of the high-level methane samples, may have caused enhanced degassingdue to the very fine cuttings produced. Chemical and isotopic composition of headspace gas and mud gas indicated the same type of gas throughout the well, although headspace methane tended to bemore enriched with respect to the 13C isotope.The origin of the Lopra-1 gas is discussed in the light of recent information obtained from source rock studies of central East Greenland and the Faroe–Shetland Basin. |
| first_indexed | 2024-04-12T08:07:12Z |
| format | Article |
| id | doaj.art-e1bda6c55be34be8bd8df7146710866d |
| institution | Directory Open Access Journal |
| issn | 1604-8156 |
| language | English |
| last_indexed | 2024-04-12T08:07:12Z |
| publishDate | 2006-07-01 |
| publisher | Geological Survey of Denmark and Greenland |
| record_format | Article |
| series | Geological Survey of Denmark and Greenland Bulletin |
| spelling | doaj.art-e1bda6c55be34be8bd8df7146710866d2022-12-22T03:41:07ZengGeological Survey of Denmark and GreenlandGeological Survey of Denmark and Greenland Bulletin1604-81562006-07-01097990Scientific results from the deepened Lopra-1 borehole, Faroe Islands: Hydrocarbon gases in Palaeogene volcanic rocks from the Lopra-1/1A well, Faroe IslandsLaier, TroelsHydrocarbon gases were monitored in the drilling fluid during deepening of the Lopra-1 well from 2178–3565 m, in which thermogenic, methane-rich gases had been found previously. The mud gas concentration, up to 105 ppm of methane, was generally higher in the hyaloclastite sequence, 2470 m – terminal depth (TD), than in the overlying lavas of the lower basalt formation. The highest concentrations of mud gas in the lower basalt formation were associated with the more porous tuffaceous zones, whereas no simple relationship could be established between measured mud gas concentrations and porosity of the hyaloclastic rocks, which showed less marked porosity variations than the lavas.Chemical (C2+ < 1%) and isotopic (δ13C1: –34 to –39‰) compositions of seven samples of mud gas collected at peak gas concentrations between 2657 m and 3442 m compare well with those of the hydrocarbon gases which had been seeping more or less continuously into the existing well since 1983, suggesting a common origin of the gases. Headspace methane concentrations measured in 135 canned samples of cuttings were scattered between 10 ppm and 6 × 103 ppm, with the exception of six samples from a short interval, 2685–2745 m, which showed consistently high values > 104 ppm. No particularly gas-rich zones were indicated, however, by the mud gas, nor was any significant change in lithology noted for this interval. It is possible that the technique of turbo-drilling, that had been attempted over a short interval, 2657–2675 m prior to collection of the high-level methane samples, may have caused enhanced degassingdue to the very fine cuttings produced. Chemical and isotopic composition of headspace gas and mud gas indicated the same type of gas throughout the well, although headspace methane tended to bemore enriched with respect to the 13C isotope.The origin of the Lopra-1 gas is discussed in the light of recent information obtained from source rock studies of central East Greenland and the Faroe–Shetland Basin.http://www.geus.dk/publications/bull/nr9/nr9_p79-90.pdfFaroesLopra-1/1Avolcanics hydrocarbon gasisotopesheadspace methanecuttings |
| spellingShingle | Laier, Troels Scientific results from the deepened Lopra-1 borehole, Faroe Islands: Hydrocarbon gases in Palaeogene volcanic rocks from the Lopra-1/1A well, Faroe Islands Geological Survey of Denmark and Greenland Bulletin Faroes Lopra-1/1A volcanics hydrocarbon gas isotopes headspace methane cuttings |
| title | Scientific results from the deepened Lopra-1 borehole, Faroe Islands: Hydrocarbon gases in Palaeogene volcanic rocks from the Lopra-1/1A well, Faroe Islands |
| title_full | Scientific results from the deepened Lopra-1 borehole, Faroe Islands: Hydrocarbon gases in Palaeogene volcanic rocks from the Lopra-1/1A well, Faroe Islands |
| title_fullStr | Scientific results from the deepened Lopra-1 borehole, Faroe Islands: Hydrocarbon gases in Palaeogene volcanic rocks from the Lopra-1/1A well, Faroe Islands |
| title_full_unstemmed | Scientific results from the deepened Lopra-1 borehole, Faroe Islands: Hydrocarbon gases in Palaeogene volcanic rocks from the Lopra-1/1A well, Faroe Islands |
| title_short | Scientific results from the deepened Lopra-1 borehole, Faroe Islands: Hydrocarbon gases in Palaeogene volcanic rocks from the Lopra-1/1A well, Faroe Islands |
| title_sort | scientific results from the deepened lopra 1 borehole faroe islands hydrocarbon gases in palaeogene volcanic rocks from the lopra 1 1a well faroe islands |
| topic | Faroes Lopra-1/1A volcanics hydrocarbon gas isotopes headspace methane cuttings |
| url | http://www.geus.dk/publications/bull/nr9/nr9_p79-90.pdf |
| work_keys_str_mv | AT laiertroels scientificresultsfromthedeepenedlopra1boreholefaroeislandshydrocarbongasesinpalaeogenevolcanicrocksfromthelopra11awellfaroeislands |