COMET Formation Evaluation Optimizing Water Saturation
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Solution Overview
Problem
Conventional methods for evaluating subsurface formations, such as LRLC formation evaluation, are inaccurate in quantifying total and effective porosities and associated water saturations due to difficulties in accurately estimating shale volume and incorporating conductive rock components.
Innovation Solution
The COMET technique (Conductive rock component Optimization Matrix Enhancement Technique) evaluates conductivity, total shale porosity, effective porosity, and total porosity from logging tool measurements, calculates total and effective water saturation values, and adjusts dry clay density to optimize water saturation evaluation without requiring rock core data calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional LRLC formation evaluation methods are used to estimate shale volume and incorporate conductive rock components, then the evaluation process can be performed using standard well logs, but the accuracy of total and effective porosity and water saturation calculations deteriorates
Solution Approach 1:
The patent changes the approach by introducing a new parameter (conductive rock component volume, Vcrc) that is directly calculated from resistivity and porosity logs without requiring core calibration. This parameter transformation allows the system to maintain ease of operation while improving measurement precision by eliminating the inaccuracies associated with conventional shale volume estimation methods.
Solution Approach 2:
The patent replaces the mechanical/core-based calibration system with an electrical/resistivity-based calculation system. Instead of relying on physical core samples to calibrate shale volume and porosity parameters, the method uses electrical resistivity measurements and porosity logs to directly compute conductive rock component volume, thereby improving accuracy while maintaining operational simplicity.
2Measurement precision
If rock core data calibration is used to calibrate conductivity and porosity measurements, then measurement precision can be improved, but the complexity and cost of the evaluation process increases
Solution Approach 1:
The patent extracts the calibration requirement from the evaluation process. By taking out the need for rock core data calibration, the method simplifies the evaluation process while maintaining precision through direct calculation of conductive rock component volume from standard log measurements. This extraction eliminates the complex calibration steps while preserving measurement accuracy.
Solution Approach 2:
The patent implements a self-service approach where the evaluation system uses its own standard log measurements (resistivity and porosity) to calculate the conductive rock component volume without requiring external core calibration data. This self-service capability allows the system to maintain measurement precision independently, reducing both complexity and cost.
3Ease of operation
If conventional methods estimate water saturation using standard equations, then the evaluation process remains simple, but the reliability of water saturation values deteriorates due to inaccurate shale volume estimation
Solution Approach 1:
The patent introduces a feedback mechanism where the calculated conductive rock component volume (Vcrc) is used to correct and refine the water saturation calculation. By incorporating the accurately determined Vcrc value back into the water saturation equation, the system maintains operational simplicity while significantly improving the reliability of water saturation values through iterative refinement.
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 COMET technique provides more accurate and reliable results for component volumes and attributes in subsurface formations, improving the estimation of total and effective porosities and water saturations, and enhancing the evaluation of hydrocarbon reservoirs.
Implementation Method 1
evaluating conductivity, total shale porosity, effective porosity and total porosity based on logging tool measurements
Implementation Method 2
The logging tool is typically a string of instruments that may measure the natural gamma ray, electrical, acoustic, stimulated radioactive responses, electromagnetic, nuclear magnetic resonance, density, pressure and/or other properties of the probed formation interval
Data Source
AI summary
Formation evaluation methods and apparatuses use a COMET technique to cross-calibrate the total porosity and effective porosity approaches using logging tool measurements. The COMET technique minimizes the difference between total water saturation value and effective water saturation value assuming that non-conductive pore volume calculated using total porosity and using effective porosity is the same.