Passive Magnetic Telemetry Well Positioning Uncertainty Quantification
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Solution Overview
Problem
Conventional Passive Magnetic Ranging (PMR) methods for identifying the position of a wellbore with respect to an existing wellbore lack precision, resulting in arbitrary margins of error and unknown confidence levels, which can lead to risks such as underestimation of distance and collision avoidance during drilling operations.
Innovation Solution
A method that quantifies and identifies uncertainties by capturing magnetic field measurements, modeling the wellbore using a distribution of poles, calculating positional uncertainties, and determining a three-dimensional region of uncertainty using a variance-covariance matrix, allowing for a more accurate determination of the wellbore's position and orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional PMR methods are used to identify wellbore position, then the identification process is simple and quick, but the measurement precision and reliability are poor with arbitrary margins of error
Solution Approach 1:
The patent applies preliminary action by pre-defining multiple candidate positions for the target wellbore around the measurement location, and pre-calculating the theoretical magnetic field signatures for each candidate position. This preparation work is done before the actual matching process, enabling faster and more accurate position identification during drilling operations.
Solution Approach 2:
The patent replaces the conventional arbitrary error estimation method with a systematic computational approach. Instead of using arbitrary percentage-based margins of error, the invention uses numerical modeling and magnetic field theory to calculate precise probability distributions and confidence regions, substituting mechanical estimation with computational analysis.
2Reliability
If arbitrary margins of error are used in conventional PMR, then the calculation is simple, but the reliability and confidence level are unknown
Solution Approach 1:
The patent calculates and stores the theoretical magnetic field signatures and their associated probability distributions for each candidate position in advance. This preliminary computation enables rapid reliability assessment during actual drilling operations, as the matching process only requires comparing measured fields against pre-computed reference data rather than performing complex real-time calculations.
Solution Approach 2:
The patent changes the parameter representation from arbitrary percentage margins to probability-based confidence levels. By using statistical parameters such as standard deviations and confidence intervals derived from the magnetic field matching process, the system provides quantifiable reliability metrics that can be directly interpreted in terms of confidence levels.
3Measurement precision
If precise position identification is achieved through numerical modeling, then measurement precision improves, but the calculation complexity increases
Solution Approach 1:
The patent segments the continuous space around the measurement point into a discrete set of candidate positions arranged in a grid or radial pattern. This segmentation transforms the continuous position identification problem into a discrete comparison task, where the measured magnetic field is matched against pre-computed signatures at each discrete candidate location, simplifying the computational approach.
Solution Approach 2:
The patent creates theoretical copies of the magnetic field signature for each candidate wellbore position based on magnetic field theory and the known or assumed wellbore geometry. These copied theoretical signatures are then compared with the actual measured field, allowing precise position identification through pattern matching rather than complex inverse modeling.
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 method provides a reasonable calculation time compatible with drilling operations, offering results within minutes, and minimizes differences between theoretical and measured magnetic fields to accurately approximate the wellbore's position, reducing the risk of collisions and improving positional accuracy.
Implementation Method 1
a principle of the presence of a magnetic field generated by a ferromagnetic structure
Implementation Method 2
The first well denotes here a borehole that already exists. Such a well conventionally comprises ferromagnetic parts, for example a casing string, a casing, a drill string
Data Source
AI summary
A method for the identification of the position of a first well, modelled by a distribution of poles, includes, after having determined an optimum position of each pole, determining a three-dimensional region of uncertainties around the optimum position of each pole, by applying a numerical method characterizing the differences between at least one measurement of the magnetic field and a disturbed theoretical magnetic field by varying the position of at least one pole and comparing a result of the numerical method with a threshold value. If the result is less than or equal to the threshold value, the disturbed position of the pole is considered in the region. The region is thus defined with a centre corresponding to the optimum position of the pole and the radii of which have a length at least equal to the maximum difference between the acceptable positions of the poles and the optimum position.