Downhole Telemetry Using Pulsed Drill String Signals
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Solution Overview
Problem
Current downhole telemetry systems face challenges in accurately determining the location of a drill bit due to signal attenuation and noise interference, particularly in deep wells, limiting data transmission rates and reliability.
Innovation Solution
A telemetry apparatus that uses coded, time-wise spaced pulses of high voltage, short duration charges on the drill string, leveraging the drill string's conductivity to transmit signals with repeater stations and a power source, such as batteries, to enhance signal strength and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electromagnetic signals are transmitted through the drill string, then data can be transmitted from the drill bit to the surface, but signal attenuation and noise interference limit transmission rates and reliability in deep wells
Solution Approach 1:
The patent applies periodic pulsed electromagnetic signals instead of continuous signals. The system transmits data using coded pulses at optimized intervals, allowing the drill string to fully discharge between pulses. This periodic action reduces signal attenuation and noise interference while maintaining reliable data transmission from the drill bit to the surface.
Solution Approach 2:
The patent changes key signal parameters including using high voltage short-duration pulses with voltages up to 20,000V and durations less than 10ms. The pulse width, amplitude, and spacing are optimized to match the drill string's electrical characteristics and the surrounding geological formation's time constant, thereby maximizing signal penetration and reducing attenuation.
2Stress or pressure
If high power continuous signals are used to overcome attenuation, then signal strength increases, but power consumption increases significantly
Solution Approach 1:
The system uses periodic pulsed signals instead of continuous high-power signals. By transmitting energy in short bursts followed by discharge periods, the system achieves sufficient signal strength for deep well transmission while dramatically reducing average power consumption from the downhole battery.
Solution Approach 2:
The patent converts the drill string's natural electrical discharge characteristic, which was previously a source of signal loss, into a beneficial feature. The discharge of the drill string into the surrounding geological formation is timed to occur between pulses, allowing the system to reset the electrical baseline and prepare for the next high-voltage pulse, thereby reducing overall power requirements.
3Productivity
If pulse spacing is reduced to increase data rate, then transmission speed increases, but signal overlap and interference increase
Solution Approach 1:
The patent optimizes pulse spacing parameters to match the electrical time constant of the drill string-formation system. By carefully selecting the interval between pulses, the system ensures complete discharge and signal decay before the next pulse, preventing overlap and interference while maximizing the data transmission rate within the physical constraints of the medium.
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 allows for more accurate drill bit location determination and higher data transmission rates with reduced power consumption, overcoming signal attenuation and noise issues in deep wells.
Implementation Method 1
A drill string is an electrically conductive object that extends from a well head to a downhole location
Implementation Method 2
The signal transmitter is operable to place coded electrical charge pulses on the drill string
Implementation Method 3
The receiver is mounted in operative connection to detect transmitted electrical pulses
Data Source
AI summary
A well-bore downhole data logging signal transmission apparatus having: a signal transmitter at a drill bit on a drill string; a receiver at a drill bore head, a generator places a carrier current on the drill string with the drill bit; the transmitter places signal pulses; the receiver senses the pulses; the pulses have a duration less than 10 ms.