Downhole EM Tool Volume of Investigation Calculation
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Solution Overview
Problem
In the oil and gas industry, existing methods for monitoring formation resistivity using electromagnetic tools face challenges in accurately determining the volume contributing to measured responses, leading to increased uncertainty in geo-steering decisions.
Innovation Solution
A downhole system and method that calculates a volume of investigation using various approaches such as skin depth, response-based, and field decay methods to define the radial detection range and shape of the volume of investigation, enhancing the accuracy of resistivity measurements and geo-steering operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electromagnetic tools transmit electromagnetic field into formation to measure multi-component magnetic field, then resistivity values can be obtained, but measured responses from remote areas have increased levels of uncertainty
Solution Approach 1:
The patent segments the formation space into discrete cells and calculates a contribution metric for each cell to the measured EM response. By identifying and isolating the specific volume of formation that contributes most to the measurement, the system separates relevant information from remote areas with high uncertainty, thereby improving measurement precision and reliability for geo-steering decisions.
2Area of stationary object
If inversion process is used to obtain resistivity model from measured magnetic field, then complete space coverage is achieved, but uncertainty in remote areas increases
Solution Approach 1:
The patent applies local quality by calculating a contribution metric that varies spatially across different cells in the formation. Each cell is evaluated individually to determine its contribution to the EM measurement, allowing the system to identify regions of high confidence (near the tool) versus low confidence (remote areas). This enables selective use of inversion results based on their reliability.
3Reliability
If volume of investigation is not evaluated, then entire formation space is analyzed, but geo-steering decision accuracy decreases due to uncertainty
Solution Approach 1:
The patent performs preliminary evaluation of the volume of investigation by calculating contribution metrics for each cell before conducting the full inversion process. This preliminary step identifies which cells contribute significantly to the measurement, allowing the inversion to focus computational resources on relevant regions and improving confidence in the resulting model while managing complexity.
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
The system improves the confidence in inversion models and reduces uncertainty in geo-steering by determining the volume of investigation effectively, allowing for more precise resistivity measurements and better decision-making during drilling.
Implementation Method 1
the induction tool transmits an electromagnetic field into the formation and measures a multi-component magnetic field induced by the currents in the formation
Data Source
AI summary
A downhole system performs a method of operating a downhole device. The downhole system includes a downhole device configured to obtain measurements of a formation parameter at a measure point along a trajectory of the downhole device, and a processor. The processor defines an initial volume surrounding the downhole device, calculates a first radial parameter value using a predetermined formation parameter value distribution in the initial volume, the first radial parameter value representing a distance from the measure point and defining a volume of investigation, and performs the operation of the downhole device using the volume of investigation.