2D, 3D AND 4D SEISMIC NAVIGATION QA & QC
We believe that the quality (and fidelity) of seismic data is strongly correlated with the quality of navigation data and that the best total quality will be achieved when navigation and seismic quality control (QC) are carried out as an integrated process.
We think that the navigation data should be quality-assured in conjunction with every seismic reprocessing project. In the event that quality control of a navigation data set should indicate that there is a potential for improving the quality, we are able to offer the comprehensive solution, ensuring that our clients receive a high quality in navigation data.
We will always ensure that our clients receive a high quality in our final products.
2D & 3D Navigation Data Re-processing/Re-computation
Processing of 2D/3D marine seismic navigation data is performed using the ResProc software, which is one of the components compromised in Geograf's in-house ResTool package. ResProc has a variety of processing techniques. Choice of technique will vary upon complexity and vintage of the survey to be processed. ResProc uses Kalman filtering in the calculation process and has comprehensive functionality for defining observation weighting and process noise (system dynamics). The final result is a UKOOA P1 s/r data set together with a processing and QC report.
Furthermore, Geograf also provides re-processing services for older data. In the last few years there has been an increased emphasis on ensuring the quality of the navigation data in realtion to data processing. This is strongly related to newer and better advancements in seismic data processing routines and increased use of 4-D seismic. We believe that the navigation data should be considered for re-processing and re-computation from raw data in conjunction with every seismic re-processing projects.
Prior to processing, any raw navigation data not in the UKOOA P2/91 (94) format needs to be converted. Geograf has wide experience handling “all” types of formats. Navigation data is then checked for data conditioning, i.e. editing, filtering and pre-processing might be carried out before actual processing.
MARINE SEISMIC GEOSPATIAL DATA UTILITIES AND TOOLS
AS Geograf has the knowledge and expertise in spatial data handling. Spatial data can be retrieved from many different sources. We are able to retrieve spatial attributes from any source, whether it is a standard formatted UKOOA file or a proprietary binary file. We extract, generate, analyze, concatenate and present attributes.
Depending on type of job we will use the most appropriate tool. AS Geograf typically utilize the ESRI family GIS products, and our own proprietary ResTool package.
We have a variety of standard products like:
- PrePlot generation
- QC of PrePlot
- Extraction of data within certain limits
- Extraction of attributes for datasets
Topo and Coordinate Reference System QC
The coordinates used to understand the position of a field is only correct when the Coordinate Reference System has been identified and maintained through all processes seismic data has been used.
Seismic data goes through a chain of value adding from seismic acquisition, to seismic processing, to seismic interpretation and ends up in a reservoir model. High precision navigation data is a critical factor at all levels of the chain.
Based on our knowledge of both seismic data and navigation data AS Geograf has developed the knowhow, procedures and software to perform quality control of seismic data at any level of the value adding chain. Navigation QC of seismic data (Topo QC) is an integral part of our ResTool/ResProg software. We have more than a decade of experience carrying out this service on a consultancy basis or as an enterprise for our clients.
Topo QC is applicable to 2D as well as to 3D seismic data.
NavSeis Merge is a process which involves writing position data to seismic trace headers, prior to seismic processing / reprocessing.
Why is NavSeis Merge by Geograf recommended?
By using NavSeis Merge whilst copying, transcribing or re-formatting the seismic data, you will obtain a quality controlled SEG-Y dataset with confidence that the navigation data is correct and ready for any processing/re-processing.
The objective of performing NavSeis Merge, prior to the potential use of the data, is to obtain valuable knowledge about its quality, hence saving time and avoiding data positioning problems during processing. Geograf ensures that there is no ambiguity for the match of seismic and positioning data. Geograf’s experts use a unique approach to QC using spatial data attributes to ensure that the merge is correct. It is the spatial analysis approach to QC of the merge which differentiates the Geograf method.
The geophysical QC during and after NavSeis Merge consists of:
- For each line, plotting and checking of offsets, gun codes, near traces, far traces, first and last shot
- Extraction of navigation data from merged SEG-Y file into P1 format
- Comparison of “reverse-engineered” P1 against original P1 data
When to do NavSeis Merge?
Prior to any seismic processing/re-processing, particularly of legacy data, when data is undergoing input reading, copying or transcription. Also, during a tape transcription clean-up project, NavSeis Merge SEG-Y data could be output as an additional tape dataset to the bit-to-bit SEG-D output.