Drillstring Tool for Detecting Nearby Conductive Pipes
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Solution Overview
Problem
Existing passive ranging techniques for directed drilling near existing wells are limited by the need for pre-polarization of well casing, which disrupts production and cannot be applied to wells already in service, and struggle to detect conductive formations at significant depths.
Innovation Solution
A drillstring tool that induces a current flow along a conductive tubular in a borehole, using azimuthally-sensitive antennas to detect the magnetic fields generated by secondary currents in nearby conductors, allowing for precise steering and distance estimation without interrupting well operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pre-polarization of well casing is used to enable passive ranging detection, then detection capability is improved, but production is interrupted and the method cannot be applied to wells already in service
Solution Approach 1:
The patent applies preliminary action by pre-polarizing the drillstring before insertion into the borehole. The drillstring is polarized to a magnetic moment at least 10 times greater than the well casing, enabling passive ranging detection without requiring pre-polarization of the existing well casing. This allows the drilling operation to proceed without interrupting production in existing wells.
Solution Approach 2:
The patent introduces the drillstring as an intermediary carrier of magnetic moment. Instead of polarizing the well casing directly (which would interrupt production), the drillstring serves as a mobile polarized element that interacts with the well casing during drilling operations. This intermediary approach enables detection capability while maintaining production continuity in existing wells.
2Measurement precision
If electromagnetic source is placed in existing well for active ranging, then directional control is improved, but operations on existing well must be interrupted
Solution Approach 1:
The patent inverts the traditional active ranging approach by placing the electromagnetic source on the drillstring (moving element) rather than in the existing well (stationary element). The drillstring carries a polarized element that generates the electromagnetic field, while sensors on the drillstring detect the response from the well casing. This inversion eliminates the need to interrupt operations in the existing well.
Solution Approach 2:
The drillstring serves dual functions: it carries both the electromagnetic source (polarized element) and the sensors for detection. This self-service approach eliminates the need for separate operations in the existing well, allowing directional control to be achieved without interrupting production in the producing well.
3Measurement precision
If sensors are placed on drillstring for passive ranging, then continuous monitoring is improved, but detection depth is limited without pre-polarization
Solution Approach 1:
The patent changes the magnetic moment parameter by polarizing the drillstring to a magnetic moment at least 10 times greater than the well casing. This parameter enhancement enables sensors on the drillstring to detect the well casing at greater depths and distances, extending detection depth while maintaining continuous monitoring capability during drilling operations.
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
Enables detection of conductive formations up to 150 feet away, improving measurement signal-to-noise ratio and allowing for precise directional control of the drill bit relative to existing wells without disrupting ongoing production.
Implementation Method 1
A drillstring tool induces a current flow along a conductive tubular in a borehole. The current flow disperses into the surrounding formation and induces a secondary current flow in a nearby conductor.
Implementation Method 2
The magnetic field from the secondary current flow can be detected using one or more azimuthally-sensitive antennas. Direction and distance estimates may be obtainable from the azimuthally-sensitive measurements.
Data Source
AI summary
Downhole tools and techniques acquire information regarding nearby conductors such as pipes, well casing, and conductive formations. At least some method embodiments provide a current flow along a drill string in a borehole. The current flow disperses into the surrounding formation and causes a secondary current flow in the nearby conductor. The magnetic field from the secondary current flow can be detected using one or more azimuthally-sensitive antennas. Direction and distance estimates may be obtainable from the azimuthally-sensitive measurements, and can be used as the basis for steering the drillstring relative to the distant conductor. Possible techniques for providing current flow in the drillstring include imposing a voltage across an insulated gap or using a toroid around the drillstring to induce the current flow.