Steerable Marine Source Array Control
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Solution Overview
Problem
Existing marine geophysical surveying systems face challenges in accurately steering seismic source arrays, particularly in harsh marine environments, which hinders the effectiveness of four-dimensional surveys that require precise repetition of three-dimensional scans over time.
Innovation Solution
A marine survey apparatus comprising towed cables with deflected tow cables, a spread rope, and a controllable drag device, allowing for precise positioning of seismic sources through adjustable elongate flexible members and winches, enabling accurate repositioning of survey tools for repeat surveys.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a capstan is used on the rig to steer the streamer cables, then the cable position can be controlled, but the capstan operates in a harsh marine environment and is liable to breakdown
Solution Approach 1:
The capstan is removed from the rig and relocated to the towing vessel. This extraction eliminates the harsh environment problem while maintaining cable control capability, as the capstan now operates in the protected environment of the vessel rather than exposed to marine conditions.
Solution Approach 2:
A cable connection system acts as an intermediary between the capstan on the vessel and the streamer cables on the rig. This intermediary mechanism transmits control forces without requiring the capstan to be physically attached to the rig, solving both reliability and control needs.
2Ease of operation
If the rig steers by changing the length of cables forming part of the rig, then the streamer array position can be adjusted, but the cable length must be precisely controlled for repeat surveys
Solution Approach 1:
The system uses depth sounders to continuously monitor the actual position of the streamer array and feeds this information back to the control system. This feedback loop enables precise cable length adjustment to maintain the array at the desired location for repeat surveys.
Solution Approach 2:
The mechanical cable length adjustment system is supplemented by electronic control mechanisms including winches with precise control systems and electronic depth sounders. This substitution enables more accurate and reliable position control compared to purely mechanical methods.
3Quantity of substance
If a three dimensional survey system is used, then multiple slices through mineral deposits can be obtained, but the system complexity increases significantly
Solution Approach 1:
The three-dimensional survey system is divided into multiple independent cable groups, each supporting a subset of seismic sources. This segmentation allows the complex rig to be managed through modular units, reducing overall system complexity while maintaining the capability to obtain multiple survey slices.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances the ability to conduct four-dimensional surveys by allowing precise repositioning of seismic sources, improving the accuracy and efficiency of resource depletion assessments in oil and gas fields.
Implementation Method 1
at least one water engaging drag device, the at least one drag device attached to and trailed behind the at least one spread rope
Data Source
AI summary
A marine survey apparatus comprises a plurality of cables towed by a vessel, the plurality of cables including two deflected tow cables each connected to the towing vessel. A primary surveying tool is attached to a cable, which cable is attached to the towing vessel and a spread rope. The deflected cables are connected to one another by the spread rope. The apparatus further comprises a water engaging drag device, which is attached to and trailed behind the spread rope. An elongate flexible element extends between the drag device and the vessel. The apparatus includes a control means for controlling the elongate flexible member and the drag device attached thereto. The survey apparatus is steerable to position the at least survey tool in a desired location by controlling the at least one drag device.