Our marine seismic services constitute quality control services, project management, technical audits and HSSE advisory consultancy. The former can subdivided into general acquisition QC, navigation processing QC and seismic processing QC, all working independently of the contractor’s quality control processes. Our marine surveys are variations of either towed streamer or transition zone surveys and are acquired in 2D, 3D and 4D (click here for details on 4D seismic).
Marine operations can present various challenges. For example, North Sea conditions often switch quickly from flat water to high swells and waves. On another note, complex OBC projects near the coast involve attending to high fishing levels and busy shipping lanes.
In addition to leveraging technical skills, we ensure that our consultants are in good physical health, possess a positive attitude, and have the ability to communicate frequently and effectively. For crew members to work constructively, often in a confined space, can be a challenge in itself, especially where crews are multinational and contractors with varied cultures are working together for long periods. The Geo People understands the potential pitfalls and knows how to prevent or solve them.
There is always a key influential factor for each survey – be it logistical, economical, contractual or scientific. All these factors play a part to varying extents and can be successful in their own right. However, for the overall project to be fruitful, the right combination of these factors has to be obtained. The performance of the survey is tracked daily by our project managers and includes HSSE management system adherence; monitoring geophysical or geological targets; cost efficiency and exploration milestones. The Geo People's consultants always have access to advice from a team of professional experts with experience in the field, when required. For reasons of support, this is helpful and is also reassuring for our consultants and our clients.
Marine seismic acquisition QC/QA
Acquisition QC consultants for 2D/3D/4D towed streamer, OBC/OBS and marine VSP surveys are all provided through The Geo People, all of whom understand the importance of effective and constructive communication between themselves, the client and the contractor. A knowledge of both navigation processing and geophysics together with field experience enables them to understand the project holistically. They understand what affects the final dataset and how, thereby increasing the value of the data. Emphasis is put on the client representatives to involve themselves with pre-survey planning. The consultants are then able to study the contracts in good time and carry out their work more effectively, not least their HSSE responsibilities. Experience with a variety of contractors and clients provides acquisition QCs with comprehensive of a wide variety of ways in which surveys are acquired, enabling them to provide solutions to problems more knowledgeably and efficiently.
Navigation processing QC/QA & surveying
The Geo People provides navigation processing, surveying and QC/QA services for 2D, 3D & 4D towed streamer and OBC/OBZ seismic projects as well as for rig moves. Marine site survey QC and marine pipeline inspection services are provided for both seismic and renewable energy projects. Navigation positioning data are independently processed to check processing flow parameters against acquisition offsets, recording parameters and appropriate processing requirements. Navigation positioning data are analysed in detail and comparisons are made between the raw P2 data and the processed P1 datasets highlighting any incorrect offsets, non-robust networks resulting from lack of data and/or geometry, inappropriate filters for ranges and bearings etc. For OBC surveys, receiver positions are checked ensuring that the correct source receiver pairings are selected. It is important that the QC data are processed at the time of acquisition to validate the positioning data using the information from the crew, enabling any adjustments to be made close to the time of acquisition, when the crew is still in the prospect area.
Seismic data processing & QC/QA for marine
In addition to towed streamer and OBC seismic processing QC, The Geo People provide specialist seismic processing, in-house seismic data processing QC and in-house seismic processing management QC. Recorded SEGD data is input and converted to internal format. Bad traces are edited and tidal corrections input to the trace headers. Following this, the geometry from navigation is applied along with tidal statics and the data output. Following swell noise attenuation, linear noise including direct arrival, cable tug, and back-scattered noise is attenuated. Any externally generated noise (for example from platforms) can be attenuated using f-x algorithms. Subsequent to linear noise attenuation, deconvolution is tested for the purpose of short-period multiple attenuation. Thereafter, velocity analysis is run at intervals in both inline and crossline directions. Trace summation and Q filters may be applied and finally a QC stack mute is designed whereby stacks are generated for the purpose of selecting an appropriate mute. This is chosen from CMP gathers and applied to eliminate the far-offset stretch noise.
Marine technical audits
The Geo People provides technical audit engineers able to make independent investigative analyses of the performance of marine seismic survey crews. Often carried out by the acquisition QC, technical audits are conducted to confirm that all the recording and source equipment operates to the standard specified by the manufacturer prior to allowing the crew to commence the recording of seismic data. These include stringent quality control tests and analysis of all recording, source and positioning equipment and a thorough review of the systems and start-up test procedures. Systems tested may include for example: the Sercel Seal recording system, Spectra navigation system, Reflex binning system, Sprint navigation QC, ProMAX and the seismic source. Verification of the offsets and antenna calculations, echo sounders, acoustic positioning, recording system, navigation and GPS positioning systems e.g. Multifix and Skyfix and evaluation of the seismic personnel then take place. The instrument tests and the quality of the positioning are checked and raw and processed UKOOA files are read and compared. Testif-i, VisualVoxAT, ITA, SeisPos, P1Tools, Geometis, Omni 10 and Vista are software which may be used to carry out the technical audit on the vessel. In addition to carrying out technical audits at the start of a survey during the preparation period, follow-up audits are often required at regular intervals or when there is a crew change or change of client.