Electromagnetic Tool Sensitivity Range for Confident Geosteering
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Solution Overview
Problem
Existing methods for monitoring subsurface formation resistivity in energy exploration are limited by tool sensitivity uncertainties, leading to inaccurate resistivity models and reduced confidence in drilling decisions.
Innovation Solution
A method and system that determine the sensitivity range of an electromagnetic tool by iteratively positioning an artificial layer in the resistivity model, calculating a modified tool response, and assigning confidence levels to resistivity model information beyond the sensitivity range, allowing for improved drilling control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the electromagnetic tool is used to monitor subsurface formation resistivity, then resistivity data is obtained for drilling decisions, but tool sensitivity uncertainties lead to inaccurate resistivity models and reduced confidence in drilling decisions
Solution Approach 1:
The patent applies preliminary action by pre-determining the tool sensitivity range through iterative positioning of an artificial layer in the resistivity model before actual drilling decisions are made. The system calculates where the tool response changes by a threshold amount (e.g., 10%) when an artificial layer is added, establishing confidence levels for different depth intervals in advance. This allows operators to know which resistivity model information is reliable before making drilling decisions.
Solution Approach 2:
The patent uses an artificial layer as an intermediary element to probe and determine the tool's sensitivity range. By iteratively adding and positioning this artificial layer at different depths in the resistivity model and observing when the tool response changes significantly, the system indirectly measures the tool's effective sensing range. This intermediary approach allows quantification of sensitivity without requiring direct measurement of the tool's physical limitations.
2Length of stationary object
If the resistivity model is used beyond the tool sensitivity range, then more depth information is obtained, but the confidence level in the information decreases
Solution Approach 1:
The patent applies local quality by assigning different confidence levels to different depth intervals within the resistivity model based on the tool's sensitivity characteristics. Rather than treating the entire resistivity model uniformly, the system identifies the sensitivity range through artificial layer positioning and marks regions beyond this range with reduced confidence levels. This allows operators to selectively trust and use resistivity information only from depth intervals where the tool has demonstrated sensitivity.
3Productivity
If the tool sensitivity range is not determined, then drilling decisions can be made quickly, but inaccurate resistivity models lead to poor drilling control
Solution Approach 1:
The patent resolves this contradiction by performing the sensitivity range determination as a preliminary calculation that can be done in advance or in real-time with minimal impact on drilling operations. The iterative artificial layer positioning method establishes confidence levels for the resistivity model before drilling decisions are made, ensuring that operators have reliable information without delaying productivity. The system efficiently calculates sensitivity ranges using the resistivity model and tool response data already available from normal 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
Enhances the accuracy of resistivity model interpretations and confidence levels, facilitating more precise geosteering and well placement by identifying reliable and unreliable data ranges, thereby improving drilling efficiency and decision-making.
Implementation Method 1
the induction tool transmits a magnetic field into the formation and measures a magnetic field induced by the eddy currents in the formation
Implementation Method 2
measures a magnetic field induced by the eddy currents in the formation
Data Source
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AI summary
A system and method to control drilling based on determining a sensitivity range of an electromagnetic tool include obtaining a resistivity model over an interval of depths, obtaining an original tool response from the resistivity model over the interval of depths for a tool configuration, and positioning an artificial layer in the resistivity model to generate a modified resistivity model. The method also includes obtaining a modified tool response from the modified resistivity model and iteratively performing the positioning the artificial layer and the obtaining the modified tool response, estimating the sensitivity range according to a position of the artificial layer when a normalized difference between the original tool response and the modified tool response reaches a threshold value, and assigning a different confidence level to information obtained from the resistivity model beyond the sensitivity range and controlling the drilling based on the resistivity model and the confidence level.