Sonic Log Deviation and Dispersion Correction in Laminated Formations
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Solution Overview
Problem
Existing methods for correcting deviation and dispersion effects on sonic log measurements in deviated wells in laminated formations are limited, often requiring advanced logging suites and assuming constant anisotropy parameters, and fail to validate corrected measurements accurately, leading to inaccurate mechanical property interpretations.
Innovation Solution
A method that defines Thomsen parameters using formation constituents and constraints, calculates corrected velocities and dispersion using a non-linear solver, and plots actual and calculated measurements to validate the corrections using rock physics cross-plots, allowing simultaneous correction of deviation and dispersion effects on sonic log measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional deviation correction techniques are used, then correction can be applied to sonic log measurements, but the methods fail to account for dispersion effects and require expensive advanced logging suites or neighboring well data
Solution Approach 1:
The patent transforms the correction problem from requiring complex hardware or additional wells to a parameter-based computational approach. By defining Thomsen anisotropy parameters (epsilon, gamma, delta) and using a non-linear solver to calculate corrected velocities and dispersion, the method changes the problem from physical measurement complexity to mathematical parameter optimization, achieving accurate correction without advanced logging suites or neighboring well data
Solution Approach 2:
The patent creates a virtual model of the formation's anisotropic properties through Thomsen parameters and uses this model to generate corrected velocity data. Instead of requiring physical measurements from vertical wells or complex logging equipment, the method copies the essential geological characteristics into a computational model that can be processed independently
2Ease of operation
If interval-based correction methods are used, then correction can be applied to each lithological layer, but the assumption of constant anisotropy parameters within each interval reduces accuracy in real earth conditions
Solution Approach 1:
The patent transitions from static interval-based correction with constant parameters to a dynamic approach where Thomsen parameters can vary continuously with depth. The non-linear solver allows parameters to be optimized at each depth point rather than being fixed for entire intervals, capturing the dynamic nature of real earth anisotropy while maintaining computational feasibility
3Reliability
If sonic log measurements from neighboring vertical wells are used for validation, then corrected measurements can be validated, but the process becomes expensive and is not often practiced
Solution Approach 1:
The patent makes the correction method self-validating by using the measured deviated well data itself to constrain and verify the Thomsen parameters through the non-linear solver. The rock physics cross-plots provide internal consistency checks without requiring external data from neighboring wells, allowing the system to validate its own corrections through the physical relationships encoded in the Thomsen parameter framework
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 approach enables accurate and cost-effective simultaneous correction and validation of sonic log measurements in deviated wells, improving the accuracy of mechanical property interpretations by accounting for anisotropy and dispersion effects.
Implementation Method 1
In laminated rocks such as shales, compressional and shear waves propagate with different velocities in different directions. Therefore, when wells are drilled with an angle different from 0 or 90 degrees with respect to the lamination or bedding (i.e. deviated wells), the wave velocities measured along the wells are different from the velocities parallel or perpendicular to the bedding or lamination.
Implementation Method 2
some of these techniques also assume a group velocity is being measured instead of the more preferred phase velocities. Nevertheless, such techniques do not correct the effects of dispersion on sonic log measurements of deviated wells in laminated formations.
Data Source
AI summary
Systems and methods for simultaneously correcting the effects of deviation and dispersion on sonic log measurements of deviated wells in laminated formations and validating the corrected sonic log measurements using rock physics cross-plots.