L'étude reprise sur http://www.eia.gov/analysis/studies/worldshalegas/pdf/chaptersviii_xiii.pdf?zscb=30305606 (XIII 12 à XIII 16 ou pages 117 à 121).
Voici les paragraphes (hors images) relatifs au Sud est de la France, sachant que cette étude concernait l'ensemble des ressources susceptibles d'être exploitées dans le monde.
Cette étude étant rédigée en anglais, si vous avez un peu de temps, n'hésitez pas à nous faire parvenir votre traduction que nous mettrons en ligne.
2. SOUTH-EAST BASIN
The South-East Basin is the thickest sedimentary basin in France, containing up to 10 km of Mesozoic to Cenozoic sediments. The basin is bounded on the east and south by the Alpine thrust belt and on the west by the Massif Central, an uplifted section of the Paleozoic basement, Figure XIII-9. Local oil and gas seeps discovered in the 1940’s encouraged hydrocarbon exploration in the South-East Basin. However, despite the drilling of 150 wells in the onshore and offshore portions of the basin, no significant oil and gas deposits have been found. Recent re-evaluations of the basin’s potential have stimulated a further look at this complex basin and its shale formations.
We estimate that the South-East Basin contains 37 Tcf of risked shale gas in-place, with 7 Tcf as the risked, technically recoverable shale gas resource, Table XIII-4. We have limited our shale resource assessment to the western portion of the basin and its deep dry gas potential area. In addition, given considerable uncertainty as to the location of the higher TOC (>2%) portions of the basin, we have assumed that only 30% of the overall dry gas prospective area will meet the 2% TOC criterion used by the study.
2.2 Geologic Setting
This study examined the shale gas potential of two formations in the South-East Basin, the Upper Jurassic "Terres Niores" black shale, and the Lower Jurassic Liassic black shale, Figure XIII-10. These shales are composed of Type II marine organic matter and were deposited during a time of subsidence and rifting, when the "Liguro-Piemontais" ocean covered portions of what is now southern France6 As such, this shale was excluded from further assessment. The Lower Jurassic Lias Shale, while thermally mature and present in much of the South-East Basin contains a wide spectrum of TOC values, ranging from 0.4% to 4.1%, Figure XIII-11.6. However, the Upper Jurassic "Terres Niores" black shale has low TOC, not exceeding 1%.7 Because of the presence of some higher TOC values, we have included the Lias Shale in our resource assessment but have highly risked this shale play.
We have mapped an unrisked, 4,000-mi2 area prospective for shale gas in the eastern portion of the South-East Basin, Figure XIII-12. The prospective area is bounded on the west by the dry gas maturity limit, on the south by the onshore portion of basin, and on the east by the available data on the TOC of the Lias Shale.
2.3 Reservoir Properties (Prospective Area)
Uplifting along the western margin of the South-East Basin has brought the Lias Shale to a more favorable depth for exploration. Depth to the Lias Shale ranges from 3,300 feet to 16,300 feet deep over the basin, with most of the shale in the prospective area at an average depth of 12,300 feet, Figure XIII-12. The organic-rich gross interval of the shale is estimated at 525 feet with 158 feet of net shale. Total organic content (TOC) in the risked prospective area averages 2%. Thermal maturity in the Lias Shale increases with depth, ranging from 1.3% Ro in the shallower western areas to over 1.7% Ro in the deeper central area. Average vitrinite reflectance (Ro) over the prospective area is 1.5%.
2.4 Resource Assessment
We estimate a moderate resource concentration in the dry gas prospective area of the Lias Shale, South-East Basin of 54 Bcf/mi2. The risked shale gas in-place is estimated at 37 Tcf, with 7 Tcf as the risked, technically recoverable shale gas resource.
2.5 Recent Activity
A number of firms are beginning to examine the shale gas potential of the South-East Basin; the initial permit award deadline was delayed due to the large numbers of applications. The French Ministry of Energy and the Environment awarded several exploration permits, covering over 4,000 mi2, to companies interested in investing in the drilling and exploration of shale formations in the South-East Basin of France.
Article mis en ligne par Christian Dépret (Adm.)
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