Marine Electrical Survey Using Joint Time-Space Inversion
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Solution Overview
Problem
Current marine geo-electrical survey methods, such as CSEM, face limitations in accuracy due to inability to measure strata chargeability and low spatial resolution, especially at shallow and great depths, which hampers the prognosis of hydrocarbon deposits effectively.
Innovation Solution
A method involving a generator of alternative-sign electric pulses, synchronized with sea-bottom stations, measuring time and space-domain data arrays of electric field signals, and performing joint data inversion to determine strata resistivity and polarization characteristics, allowing for more accurate hydrocarbon deposit prognosis across varying water depths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If CSEM method is used for marine electrical survey, then survey can be executed at sea depths up to 3 km, but the method cannot obtain data on strata chargeability which significantly decreases prognosis accuracy
Solution Approach 1:
The patent combines two different measurement approaches (frequency-domain CSEM measurements and time-domain transient electromagnetic measurements) into a single integrated survey method. By simultaneously acquiring both chargeability data (from transient decay measurements) and resistivity data (from frequency-domain measurements), the method resolves the contradiction by obtaining comprehensive electrical properties without sacrificing survey depth capability
Solution Approach 2:
The patent creates a multi-functional survey system that can perform multiple types of measurements (chargeability, resistivity, and electromagnetic properties) using the same sea-bottom stations and generator line configuration. This universal approach allows the system to provide both deep penetration capability and detailed electrical property characterization, resolving the limitation of single-function methods
2Adaptability or versatility
If conventional marine electrical survey methods are used, then survey equipment can operate at various water depths, but spatial resolution remains relatively low especially at shallow and great depths
Solution Approach 1:
The patent employs dynamic measurement strategies where the generator line is towed at different speeds and positions, and sea-bottom stations are deployed at varying distances from the generator line. This dynamic approach allows optimization of spatial resolution for different water depth conditions, resolving the contradiction between broad adaptability and high resolution by adjusting measurement parameters in real-time
Solution Approach 2:
The patent adds the time dimension to traditional spatial measurements by incorporating transient electromagnetic measurements. By measuring the temporal decay of electromagnetic fields after the generator is turned off, the method extracts additional information about subsurface properties, effectively adding a time domain dimension that enhances spatial resolution without compromising depth adaptability
3Device complexity
If single-domain data inversion is performed, then data processing is simpler, but the accuracy of determining both resistivity and chargeability is insufficient
Solution Approach 1:
The patent merges frequency-domain and time-domain data into a unified inversion framework. By combining measurements from both domains and performing joint inversion, the method simultaneously determines resistivity and chargeability parameters with high accuracy. The integrated approach leverages complementary information from both measurement types, resolving the contradiction between processing simplicity and determination accuracy
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 method enhances the accuracy and applicability of hydrocarbon deposit prognosis by providing detailed resistivity and chargeability data, improving spatial resolution and usability in both shallow and deep water conditions.
Implementation Method 1
The field excitation is carried out by periodical electromagnetic pulses of different polarity with pauses between them
Implementation Method 2
measuring time series of the signals of electric field by the sea-bottom stations during both the on and off periods of the electric current pulses
Data Source
AI summary
A method for survey of hydrocarbon deposits in a researched profile of sea-bottom comprises providing a generator generating pulse electric current with a generator frequency in a towable generator line exciting electric field signals measured by sea-bottom stations synchronized with the generator, forming space-domain data arrays for the generator frequency and for higher odd harmonics frequencies nearest thereto, forming time-domain data arrays for selected offsets, inversion of the time-domain and space-domain data, and determining a bottom strata resistivity and polarization characteristics for the researched profile, based the inversion's results. The inversion preferably encompasses synchronizing and adjusting the generator line and electric field signals, dividing them into a frequency branch, including a fast Fourier transform and a robust summation producing the space-domain arrays, and a time-domain branch, including a robust summation producing the time-domain arrays. Embodiments include transient field analysis with spatial derivatives, special towing configurations, generator line types choices, etc.