Electromagnetic Telemetry Using Subsurface Conductive Electrodes
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Solution Overview
Problem
Electromagnetic telemetry signals used in measurement while drilling (MWD) and logging while drilling (LWD) are significantly attenuated by subsurface formation resistivity, drilling fluid resistivity, and depth, making reliable high-data-rate communication challenging.
Innovation Solution
The method involves using a conductive electrode or signal wire disposed in the subsurface, either as a telemetry well or signal wire, to bypass conductive overburden formations and reduce noise, allowing for enhanced signal transmission by creating an electrically conductive channel to the surface, measuring voltages between the signal wire and electrode, or using an insulated signal wire to transmit signals directly to the surface via an electrical cable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electromagnetic telemetry signals are transmitted through subsurface formations, then communication between wellbore instruments and surface is achieved, but signal attenuation increases due to formation resistivity, drilling fluid resistivity, and depth
Solution Approach 1:
The patent introduces a conductive electrode or signal wire disposed in the subsurface as an intermediary element to facilitate electromagnetic signal transmission. This intermediary creates a more conductive pathway through the subsurface formations, reducing signal attenuation caused by resistive formations and drilling fluids while enabling reliable communication between wellbore instruments and the surface.
2Loss of information
If conventional electromagnetic telemetry is used with surface electrodes, then signal communication is possible, but noise from drilling operations and conductive overburden formations degrades signal quality
Solution Approach 1:
The patent positions the conductive electrode or signal wire at a selected depth below the surface at a selected lateral distance from the wellbore, moving the measurement point to a different spatial dimension. This depth and lateral positioning places the electrode below conductive overburden formations and at a distance from drilling noise sources, thereby reducing electrical noise and interference while improving signal quality.
3Productivity
If higher data communication rates are achieved, then more information can be transmitted, but signal attenuation and noise make reliable communication challenging
Solution Approach 1:
The conductive electrode or signal wire acts as an intermediary that creates a lower-resistance transmission path for electromagnetic signals. This intermediary structure enables higher data communication rates by improving signal strength and reducing attenuation, while simultaneously maintaining communication reliability through consistent signal quality and reduced noise interference.
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 minimizes signal attenuation and noise, enabling higher data communication rates and more reliable signal transmission between wellbore drilling instruments and the Earth's surface, particularly in multi-well drilling environments.
Implementation Method 1
generating an electromagnetic field in an instrument disposed in a drill string used to drill a wellbore. The electromagnetic field includes encoded measurements from at least one sensor associated with the instrument
Implementation Method 2
using an insulated signal wire to transmit signals directly to the surface via an electrical cable
Implementation Method 3
A time varying voltage impressed across the insulated gap (or the toroid) generates an electromagnetic field which can be used to communicate between a surface electric dipole receiver antenna or a plurality of differently oriented electric dipole antennas and the MWD/LWD instrument
Data Source
AI summary
A method for signal communication between a well drilling instrument and the Earth's surface includes generating an electromagnetic field in an instrument disposed in drill string used to drill a wellbore. The electromagnetic field includes encoded measurements from at least one sensor associated with the instrument. A signal corresponding to an amplitude of the electromagnetic field is measured and the measurements from the measured signal are decoded. The signal comprises a voltage measured across electrodes or a voltage induced in an electromagnetic receiver disposed at a selected depth below the Earth's surface. The selected depth is at least the depth of a formation below the water table having a highest resistivity within 500 meters of the surface.