BackgroundThe Gridded SurfacesThe products of the interpretation are time structure maps in the form of gridded time surfaces (10 km node spacing) in units of milliseconds two way travel time. A total of 12 horizon grids are presented, in digital format and as pre-prepared maps. The horizons are generally defined as the bases of sediment sequences of a given age. The extent of the horizon grid defines the extent of the associated sediments. However, in the cases of H101 Top Triassic and H108 Top Zechstein, these horizons are defined in accordance with their top. A number of horizons are mapped as basin-wide regional events i.e.
The alternative to this approach would have been to define every horizon consistently as a top. However, this would have made it more difficult to construct the regional events at Base Eocene, Base Palaeocene and Base Upper Cretaceous. The time structure maps have been created in a level of detail suitable for display at a scale of 1:1,000,000. A UTM projection has been used with a central Meridian of 3°00’E. The Line InterpretationsThe original interpretation was constructed from either paper sections at a scale of 5 cm/s or from an interpretation workstation. Approximately 80 % of this interpretation was derived from paper sections. The location and extent of the seismic lines employed are shown in Figure 1. In order to show the relationship between the interpreted horizons and lithostratigraphic terms, which vary widely over the basin, a number of correlation diagrams are included within this brochure (Figure 3, Figure 4, Figure 5, Figure 6). Figure 2 shows the location of these correlations. The Well DatabaseThe well database was originally derived from within the NSDA-2.0. The NSDA-Public Licence package sees a revised database structure and design, which is provided in a Microsoft Access 2000 and Microsoft Access 97 formats. The number of wells with both location and formation top information total 920. These are distributed, according to country, as follows:
The database has been organised into two tables. The headers table contains information relating to well location, well status, elevation and depth. The tops table contains the two-way-times for the interpreted horizons on each seismic line that is intersected by a well. The government well ID has, where available, been added to the headers table. A report has been prepared for both tables and provides all information relevant to each well on separate pages. Links to Government websites used are listed below and database tables for each country can be found in the Government_Database.mdb file.
Prepared mapsThe NSDA-Public Licence package presents the digital grids and associated files as a number of pre-prepared maps in pdf format. These have been contoured at either 50 ms or 100 ms intervals, dependant on the level of detail recognised and required. They are presented at a scale of 1:1,000,000. The location and extent of the basemap can be observed in Figure 8. |