Marine Controlled Source Electromagnetic Surveying for Deep-Water Resistivity

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Solution Overview

Problem

Current geophysical survey methods, such as seismic and magnetotelluric techniques, face challenges in accurately discriminating between water and hydrocarbon deposits at sea-beds, particularly in deep-water settings, due to limited depth of investigation and sensitivity issues with resistive targets.

Innovation Solution

The use of ultra-low and extremely low-frequency (ULF/ELF) electromagnetic signals, generated by remote transmitters on land or sea, to measure sea-bed resistivity, allowing for deeper penetration and improved sensitivity through 3D conductivity distribution determination and correlation with geological formations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If magnetotelluric methods are used to survey sea-bed resistivity, then regional electromagnetic field coverage is achieved, but sensitivity and resolution for thin horizontal resistive targets are very limited

Engineering Contradiction:

Improveelectromagnetic field coverage areaVSAvoidsensitivity to thin horizontal resistive targets

Core Design Contradiction:

Area of stationary objectVSMeasurement precision

Solution Approach 1:

The patent transitions from regional magnetotelluric surveying to localized marine controlled source electromagnetic (MCSEM) methods. By placing transmitters in direct proximity to targets and using focused electromagnetic sources, the system achieves high sensitivity to thin horizontal resistive targets while maintaining practical survey capabilities through controlled local illumination rather than broad regional coverage

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the electromagnetic field parameters by using specific frequency ranges and source configurations optimized for detecting resistive hydrocarbon targets. By adjusting transmitter power, frequency, and receiver sensitivity parameters, the system achieves enhanced measurement precision for thin horizontal targets while maintaining operational feasibility

Inventive Principle:

Principle #35Parameter changes

2Length of stationary object

If large transmitter/receiver offsets are used to increase depth of electromagnetic field penetration, then investigation depth is improved, but technological difficulties and survey cost increase

Engineering Contradiction:

Improvedepth of investigationVSAvoidtechnological difficulty

Core Design Contradiction:

Length of stationary objectVSDevice complexity

Solution Approach 1:

The patent employs time-domain electromagnetic methods with pulsed transmitters, using periodic excitation signals to penetrate deep into the earth. By transmitting electromagnetic pulses and measuring the decaying response over time, the system achieves deep investigation depth while using manageable transmitter powers and standard receiver equipment, avoiding the need for continuously high-power transmitters or excessively large offsets

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent uses dynamic time-domain measurements where receivers capture the temporal evolution of electromagnetic fields after pulsed excitation. This dynamic approach allows deep penetration by exploiting the diffusion nature of electromagnetic fields in conductive media, achieving depth without requiring static large offsets or continuously high power levels

Inventive Principle:

Principle #15Dynamics

3Area of stationary object

If magnetotelluric field is used for deep-water surveys, then regional electromagnetic coverage is achieved, but the field attenuates rapidly within the conductive layer of sea water limiting practical application

Engineering Contradiction:

Improveelectromagnetic field coverageVSAvoidsignal attenuation in deep water

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The patent introduces specialized electromagnetic transmitters as intermediaries that generate fields specifically optimized to penetrate seawater. These transmitters use frequencies and source configurations that minimize attenuation in conductive seawater, acting as mediators between the survey system and the deep-sea targets, enabling reliable measurements in deep-water environments where natural magnetotelluric fields fail

Inventive Principle:

Principle #24Intermediary (Mediator)

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 enables direct deposit imaging and quantitative evaluation of geoelectrical parameters, enhancing the ability to detect and characterize hydrocarbon deposits even in deep-water environments where traditional methods fail.

Implementation Method 1

An electromagnetic field is generated by an electromagnetic transmitter

Methodology Applied

Scientific EffectElectromagnetic field generation: Electromagnetic Induction

Implementation Method 2

at least one component of the electromagnetic field is measured by a receiver to determine a conductivity distribution

Methodology Applied

Scientific EffectElectromagnetic field detection: Electromagnetic Induction

Data Source

PatentUS7969152B2Systems and methods for measuring sea-bed resistivity

Publication Date: 2011.06.28 TECHNOIMAGING LLC

AI summary

A method for measuring the resistivity of sea-bed formations is described. An electromagnetic field is generated using at least one stationary long-range transmitter. The frequency of the electromagnetic field is between and/or including the ULF/ELF range. At least one component of the electromagnetic field is measured. A conductivity distribution is determined based on the at least one measured component. The determined conductivity distribution is correlated with geological formations and/or hydrocarbon deposits.