About GUNDALF

GUNDALF is a state of the art airgun modelling package based on many years of research. Airgun array computer modelling is an enormously cost-effective exercise given the cost of downtime of a seismic survey vessel for signature tests or concerns about the effects of drop-out. In the processing centre, simple knowledge of the acquisition geometry and gun types allows an accurate signature to be generated for sophisticated signature deconvolution.

It has taken a number of years to refine understanding of the physics of airgun bubble interaction to its current level but it now offers a genuine alternative to the very costly experimental approach or even worse, guessing or the use of 'library' signatures because acquisition deadlines are so short.

GUNDALF is capable of modelling arrays of up to 128 guns in its present form with full interaction allowed between them. Linear superposition of sub-arrays or even individual guns as is often used is rejected in favour of proper modelling. The power of modern desktop and laptop computers means that this is now entirely feasible. No scientific compromise is made here, the physics at the heart of GUNDALF is capable of accurately modelling the phase locking observed in closely-interacting airguns right down to the edge of the super-foam region. It contains arguably the most advanced physics of its kind anywhere.

GUNDALF is available in two forms both of which use the same state of the art physical modelling engine:

GUNDALF Designer

• Enables the geophysicist to model the signature of up to 128 interacting airguns in an array quickly and accurately.

• Includes most common gun types including injector and sleeve guns in its array construction palette.

• Simple graphical interface to add, edit or delete guns, change the depth of all guns and numerous other shortcuts. Each gun is individually set in position, gun type, volume and operating pressure allowing complete flexibility.

• Signature characteristics such as peak to peak, primary to bubble and bubble period are produced on demand.

• Amplitude spectra and any filtering can be done at the click of a button. The resulting plots are interactive giving an instantaneous check on the amplitude and position with just a click of the mouse.

• Sophisticated handling of the surface reflection ghost using rough sea surface modelling.

• Import and export of signatures in both text and SEGY format.

• Import and export of arrays in text format allowing full arrays with symmetric sub-arrays to be built quickly and easily, (noting that all interactions are always used when actually modelling the array).

• Zoom in and out and postscript (Unix versions only) output facilities.

• Intranet reporting with comprehensive array report produced in a form suitable for a company Intranet.

• Basic drop-out analysis based on signature criteria such as maximum drop in peak-to-peak integrated into the Intranet reporting.

• Two-click re-modelling of an array signature if a particular dropout occurs. In effect, this means that if a gun goes down during a survey, the effects on the signature can be accurately modelled within a minute. In clustered arrays, this is often non-intuitive.

GUNDALF Optimiser

As above but includes additionally:-

• The unique ability to define an inventory of guns and then using sophisticated global optimisation techniques, to design the best array 'ground-up' within the constraints of spectral flatness in a certain region, maximal primary to bubble ratio or a number of other optimisation criteria. This can take a little time but the resulting arrays are often far superior to those resulting from simple intuition.

• The unique ability to overdraw an inventory and then report on any additional guns necessary to meet a specification.

• The ability to design an array to satisfy complex modern array specifications with just a few mouse clicks and a coffee break. This takes most of the effort out of one of the most time-consuming of all array design activities.

• More sophisticated dropout modelling schemes based on spectral impact.

• Generation of sophisticated Intranet format reports.

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