Long-Wire Electromagnetic Receiver for Deep CSEM Survey Navigation
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Solution Overview
Problem
Current marine controlled source electromagnetic (CSEM) surveys face limitations in detecting deep resistivity targets due to noise floor issues, transmitter waveform stability, and navigation challenges, which restrict the depth capability and accuracy in identifying hydrocarbon reservoirs.
Innovation Solution
The system enhances CSEM surveys by using a modified long-wire electromagnetic (LEM) receiver with increased discrete antennae on a single long wire, allowing precise measurement of electric field amplitude and phase gradients, and incorporates an intelligent ranging long-line baseline acoustic transceiver for improved navigation and noise rejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional CSEM surveys are used, then shallow water reservoir detection is achieved, but deep resistivity target detection capability is limited due to noise floor issues
Solution Approach 1:
The patent segments the long wire into multiple discrete antenna elements (at least two) positioned at different locations along the wire. This segmentation allows the system to measure electric field gradients between adjacent antennas, which enhances the signal-to-noise ratio for deep resistivity targets by differential measurement techniques that reject common-mode noise.
Solution Approach 2:
The patent extends the measurement dimension by deploying a long wire with multiple antennas along a spatial dimension (length of the wire), enabling gradient measurements in the direction parallel to the wire. This dimensional extension provides additional measurement information that improves detection capability beyond single-point measurements.
2Measurement precision
If traditional navigation methods are used, then basic positioning is achieved, but navigation accuracy is insufficient for precise gradient measurements
Solution Approach 1:
The patent introduces an acoustic transceiver system as an intermediary for navigation and positioning. The transceiver communicates between the vessel and the seafloor instruments, providing precise location data for the long wire deployment. This intermediary system enables accurate tracking of instrument positions without requiring complex direct satellite or radio navigation systems.
3Measurement precision
If single antenna measurements are used, then simple measurement setup is achieved, but signal-to-noise ratio is insufficient for ultra-deep target detection
Solution Approach 1:
The patent segments the receiving system into multiple discrete antennas along the long wire, each measuring the electric field at its specific location. This segmentation enables gradient calculations by comparing measurements from adjacent antennas, significantly improving the signal-to-noise ratio through spatial differentiation that enhances weak signals from ultra-deep targets.
Solution Approach 2:
The patent adds spatial dimension to the measurement system by distributing multiple antennas along the length of the wire, enabling measurement of electric field gradients in addition to absolute field values. This dimensional enhancement provides more information for detecting ultra-deep resistivity targets while managing system complexity through shared measurement infrastructure.
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 approach significantly improves signal-to-noise ratio and detection thresholds, enabling the identification of ultra-deep hydrocarbon reservoirs lacking seismic direct hydrocarbon indicators, with enhanced accuracy and resolution in measuring electric field gradients and phase velocities.
Implementation Method 1
a vessel and an electromagnetic transmitter mounted on the vessel
Implementation Method 2
modified long-wire electromagnetic (LEM) receiver with increased discrete antennae on a single long wire, allowing precise measurement of electric field amplitude and phase gradients
Implementation Method 3
intelligent ranging long-line baseline acoustic transceiver for improved navigation
Data Source
AI summary
An acoustic navigation system includes a vessel and an interrogation unit towed behind the vessel below the surface of the water, a tail acoustic transponder trailing behind the interrogation unit, and a pair of surface acoustic transponders towed behind the vessel on the surface of the body of water. The interrogation unit generates an acoustic interrogation signal and receives responses from each of the tail acoustic transponder and the surface acoustic transponders from which it triangulates its position. The surface acoustic transponders may further include GPS receivers for receiving positioning information from GPS satellites. Additional acoustic transponders on instruments located on the floor of the body of water respond to the interrogation signal to allow triangulation of the location of the instruments.