Tilted Antenna Casing Detection for Drilling
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Solution Overview
Problem
Existing passive ranging techniques for drilling near existing wells are limited by the need for pre-polarization of the casing, which interrupts well operations and cannot be applied to wells already in commercial service, and they rely on magnetic 'hot spots' that are not always present.
Innovation Solution
The method involves using a downhole logging tool with tilted antennas to transmit and measure electromagnetic signals, analyzing the azimuthal dependence of the response signals to determine the diagonal and cross components, which are used to accurately estimate the distance and direction of nearby conductive features like well casing without interrupting well operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pre-polarization of casing is used to enable passive ranging, then casing detection capability is improved, but well operations are interrupted
Solution Approach 1:
The patent applies preliminary action by pre-polarizing the casing during construction before the well enters commercial service. This allows the casing to have the necessary magnetic properties for passive ranging detection without requiring interruption of ongoing well operations. The polarization is performed once during the well construction phase, enabling continuous operation thereafter.
2Ease of operation
If magnetic hot spots are relied upon for casing detection, then detection simplicity is improved, but detection reliability deteriorates due to absence of hot spots
Solution Approach 1:
The patent changes the magnetic parameter of the casing by applying pre-polarization during construction, transforming the casing from a non-magnetic or weakly magnetic state to a strongly magnetic state with detectable hot spots. This ensures reliable passive ranging detection without depending on random or absent magnetic anomalies, thereby improving both detection reliability and maintaining operational simplicity.
3Productivity
If passive ranging is applied to wells in commercial service, then operational continuity is improved, but casing polarization becomes impossible
Solution Approach 1:
The patent resolves this contradiction by performing the casing polarization action preliminarily during the well construction phase, before the well enters commercial service. This timing allows the polarization to be completed without interrupting production, enabling passive ranging to be applied to existing producing wells while maintaining operational continuity.
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 precise directional drilling without interrupting existing well operations, as it can detect and measure the distance and direction of nearby casing using electromagnetic signals, improving the accuracy and efficiency of drilling operations.
Implementation Method 1
a first antenna on a downhole logging tool transmits an electromagnetic signal and a second antenna on the downhole logging tool measures a response signal
Data Source
AI summary
Methods and apparatus for detecting nearby conductors such as pipes, well casing, etc., from within a borehole. A nearby casing string can be detected by transmitting an electromagnetic signal from a transmit antenna on a downhole logging tool and measuring a parallel response signal with a first receive antenna parallel to the transmit antenna and a perpendicular response signal with a second receive antenna perpendicular to the transmit antenna, both receive antennas on the downhole logging tool. As the tool rotates, the transmitting and measuring are repeated to determine the azimuthal dependence of the parallel and perpendicular response signals. The azimuthal dependence is analyzed to determine a diagonal component of said azimuthal dependence for each response signal. Distance to a casing string can be estimated using the diagonal component of each response signal. At least one of the antennas is preferably tilted.