EM Ranging in Oil-Based Mud Using Conductive Bridges
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing passive ranging techniques for 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 are ineffective in identifying conductive anomalies in oil-based mud boreholes.
Innovation Solution
A system that uses axially-spaced conductive bridges on a drillstring to inject current into the formation, generating a secondary current in nearby conductors, detectable by azimuthally-sensitive magnetic field sensors, allowing for direction and distance estimation and precise steering without interrupting well operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pre-polarization of well casing is used for passive ranging, then ranging capability is improved, but production is interrupted and application to existing wells is prevented
Solution Approach 1:
The patent applies preliminary action by pre-polarizing the well casing during the drilling and completion phase, before the well enters production. This allows the ranging system to be prepared in advance so that no production interruption occurs during actual ranging operations. The polarization is performed once during construction, enabling continuous production thereafter while maintaining ranging capability.
2Measurement precision
If conventional passive ranging is used, then ranging is possible, but it is ineffective in identifying conductive anomalies in oil-based mud boreholes
Solution Approach 1:
The patent applies parameter changes by utilizing the high electrical resistivity characteristic of oil-based mud as a beneficial parameter. The electromagnetic ranging system is specifically designed to operate in high-resistivity environments, where conventional electrical methods fail. The system transmits electromagnetic signals at frequencies and power levels optimized for penetrating oil-based mud, enabling detection of conductive anomalies like casing that would be invisible to conventional methods.
3Measurement precision
If active ranging with electromagnetic source in existing well is used, then ranging precision is improved, but operations on existing well must be interrupted
Solution Approach 1:
The patent applies preliminary action by installing the electromagnetic source and polarization infrastructure during the drilling and completion operations, before production begins. This preliminary setup eliminates the need to interrupt existing production for ranging operations, as the system is already in place and can operate continuously during production without requiring well intervention.
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 features like well casings deep within oil-based mud boreholes, improving measurement signal-to-noise ratio and allowing for precise steering of the drill bit relative to existing wells without disrupting production.
Implementation Method 1
A system that uses axially-spaced conductive bridges on a drillstring to inject current into the formation, generating a secondary current in nearby conductors
Implementation Method 2
detectable by azimuthally-sensitive magnetic field sensors, allowing for direction and distance estimation
Data Source
AI summary
Nearby conductors such as pipes, well casing, etc., are detectable from within a borehole filled with an oil-based fluid. At least some method embodiments provide a current flow between axially-spaced conductive bridges on a drillstring. 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 are 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.