Being responsive to new product/application requirements as well as continuously focusing on optimising support and service processes have been key challenges and success factors in this exciting, demanding and rapidly moving business.
How does it work?
What a current meter mounted underneath the vessel hull will measure is basically the vessel speed through water, i.e. a high precision speed log. However, what the navigation crew typically is interested in is the net ocean current speed and direction relative to ground. This is obtained by connecting the vessel gyro and DGPS and subtract the vessel speed over ground from the speed through water value.
What are the benefits of installing a current meter on a seismic survey vessel? There are four major concerns making a current meter a vital part of the navigators positioning setup.
- Feather angles. Currents crossing the vessel track will cause streamer - and geophone - deflection . Knowing and predicting this angle improves the positioning precision and the ability to determine the actual point of data acquisition.
- In-fills. Turning a seismic rig around takes hours, and the operational cost for a seismic vessel is considerable. Thus the ability to plan ahead, reducing the number of “extra” runs is crucial.
- Knowledge about local currents improves the ability to avoid costly entanglements during streamer deployment, handling and recovery.
- Close passes. Today so called 4D runs are becoming increasingly more in demand. This basically means doing new surveys on existing reservoirs in order to determine changes and remaining volumes. These reservoirs usually have existing installations, and predicting streamer path is vital in order to avoid collisions. Streamers can be repositioned vertically in the water column into a layer with more favorable currents.
The basic hardware product offered to the seismic business today is the bronze housing VM AWAC current profiler, developed from the well proven AWAC hardware platform.
The system is delivered with a marine certified computer, a power/communication interface unit and cables at customized lengths.
The user interface software being shipped with the system is the SurveyVM, which has been virtually unchanged for a decade, ever since the introduction of the VM current profiler concept. The basic SurveyVM software has a broad reputation for being an intuitive and easy-to-use product providing useful information even to personnel without basic training or previous introduction.
The ExploreP software package, designed for post processing, analysis and quality control also comes standard with the system.
Current data is becoming increasingly important both in terms of navigational issues and as key oceanographic information made available to the market in a broader perspective.
Keeping pace with this rapidly changing business is encouraging and a continuous challenge in terms of both transducer hardware technology and concept development.
At Nortek we appreciate the fact that working in this professional, competitive and demanding environment has its rewards – it helps us improve – ensuring innovative and reliable solutions also for the future.