Quaternary
1.8
Neogene
24 Palaeogene
Cenozoic
m. years
65
(65 m. years-present)
Fig. 1.2 Stratigraphic chart
Mesozoic
142
Jurassic
205
(250-65 m. years)
Cretaceous
Triassic
250 292
Palaeozoic
(545-250 m. years)
Precambrian
(4556-545 m. years)
Carboniferous
354
417 Silurian
440 Ordovician
495 Cambrian
545 Proterozoic
2500 Archean Hadean
4000
For organic matter in the source rock to transform into hydrocarbons, it must be exposed to the right temperature and pressure conditions. Consequently, the source rock must be buried at a certain depth. A source rock not buried at a sufficient depth is termed immature. However, if it is buried at too great a depth, it is over-mature. If the source rock is over-mature, hydrocarbons can no longer form. Any amount of oil or gas formed in the source rock will presumably have seeped up towards the surface during the millions of years since its formation. Because of the lower burial depth of source rock in the Open Door Area, it is uncertain whether sufficient amounts of oil and gas have been formed. Examples of potential source rocks are claystone with beds of coal from the Carboniferous period or shale with a high organic content from the Cambrian and Ordovician periods; see figure 1.2. Data on the extent of source rocks is scarce for large parts of the Open Door area. Intensified exploration activity is required to interpret the geological formation history of hydrocarbons and their subsequent migration from source rocks to reservoir rocks.
Permian
Devonian
Potential source rocks The greatest uncertainty concerning exploration in the Open Door area is associated with source rock.
4556
Potential reservoirs In most of the Danish subsoil, there are one or more porous sandstone formations that could contain oil or gas accumulations under the right conditions. In the Danish Basin, the most important reservoirs consist of sandstone from the Triassic and Jurassic periods; see figures 1.2 and 1.3a. During the Triassic and early Jurassic periods, large parts of Denmark and the North Sea were land areas. In the uppermost (youngest) section of the Triassic the sea level began rising. It continued to rise up through the Jurassic, and the sea covered most of Denmark at that time. Some of the most important reservoirs from this period were formed by sand deposited in the coastal zone or in rivers in the areas still covered by land. Sandstone formations from the Triassic and Jurassic have good reservoir potential, due to relatively high porosity of up to 30 per cent and thicknesses of up to 100 metres. Carbonates in the Upper Permian can also function as reservoirs and can have a porosity of up to 15 per cent. In the North German Basin and the Danish Basin, such carbonates might function as reservoirs; see figure 1.3a. AMENDED LICENCES Approved transfers All contemplated transfers of licences and the relevant transfer conditions must be submitted to the DEA for approval. In 2007, DONG Energy took over the company ConocoPhillips Petroleum International Corporation Denmark, incorporating it as a DONG Energy subsidiary. Thus, DONG also took over ConocoPhillips’ shares and operatorships of licences 4/98, 5/98 and 1/06. With effect from 21 May 2007, the name of the subsidiary was changed to DONG Central Graben E&P Ltd. Subsequently, the DEA approved the
Licences and exploration