GeoQube 2D to 3D

Click to enlarge

The GeoQube process is essentially a 2D to 3D seismic data conversion package. It is not a replacement for a 3D survey but can be a very useful product in the exploration phase when the overall benefits are considered:

• It is an inexpensive process that converts 2D data so it can be viewed in a 3D sense.
• A matched dataset is produced prior to 3D interpolation and gridding.
• A velocity field is constructed for the 3D volume.
• The regularised 2D data volume is 3D-migrated.
• The final 3D-migrated volume can be loaded to a 3D workstation.

• Data Matching
• Dip Interpolation
• 3D Migration

Data Matching
Where datasets of differing vintages are concerned the first phase of the process is to match the phase and character and resolve any apparent positional errors. A dataset is chosen as the 'master' dataset and all intersections with it are examined. Optimal matching operators are derived to ratify phase/character/amplitude misties and applied to all datasets and the intersections reconfirmed to ensure data similarity. Intersections are not purely taken from the navigation data but are assessed over a number of CDP's surrounding the intersection for the strongest cross-coherency seismic fit.

Dip Interpolation
This was originally based on a mathematical approach devised by Pennzoil (USA) which has subsequently been re-designed to incorporate modern dip intelligent algorithms. The method involves a structural reconstruction of the data within each polygon based on the original 2D lines that form the edge of the polygon. Specific horizons are projected as surfaces within each polygon and a regular set of data points are produced.

3D Migration
The matched, interpolated 3D volume, is 3D migrated either using a one pass finite difference solution or one or two pass Kirchhoff.

Feasibility
A minimum line density can be calculated from Fresnel zone calculations at differing times down the section, 80% of the Fresnel diameter is usually required. It can be advantageous to have a variety of line directions, as these assist in dip estimation. Previously processed filtered and migrated stacks are useful for Q.C.

Results of a completed GeoQube project (Click to enlarge)

A typical GeoQube project will require the following data items:

• Raw SEGY stack tapes for all lines
• Positioning data in UK00A format
• Velocity information for the area
• Paper sections to act as QC and to confirm SP/CMP relationship
• Background knowledge of the target zone and structural geological information