Cased Hole Stress Estimation via Sonic Dispersion Analysis
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Solution Overview
Problem
Current methods face challenges in accurately estimating changes in subterranean formation stresses caused by reservoir depletion or injection using time-lapse borehole sonic data, particularly in cased holes, due to complexities in processing sonic data and accounting for factors like cement bonding quality and fluid mobility.
Innovation Solution
A method involving the collection of baseline and subsequent sonic data, calculation of cased hole Stoneley and cross-dipole dispersions, estimation of minimum and maximum horizontal stress magnitudes, and calculation of pressure, which utilizes inversion algorithms to transform sonic data into formation stress changes, accounting for fluid mobility and structural anisotropy effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If sonic data is processed in cased holes to estimate formation stress parameters, then stress estimation can be performed in production wells, but the processing becomes more challenging due to cement bonding quality and fluid mobility effects
Solution Approach 1:
The patent segments the complex cased-hole sonic data processing into distinct components: (1) measuring Stoneley and dipole dispersions, (2) estimating shear moduli from each dispersion type, (3) calculating stress parameters from the shear moduli. This segmentation allows each component to be handled separately, reducing overall processing complexity while maintaining applicability to cased holes.
Solution Approach 2:
The patent introduces shear modulus estimation as an intermediary step between raw sonic data measurement and final stress parameter calculation. By first estimating shear moduli from Stoneley and dipole dispersions, the method creates intermediate parameters that simplify the final stress calculation, thereby reducing processing complexity.
2Measurement precision
If inversion algorithms are used to transform sonic data into formation stress changes, then stress estimation accuracy is improved, but the processing complexity increases
Solution Approach 1:
The patent replaces complex full-waveform inversion algorithms with a simplified mechanical approach based on dispersion analysis. By measuring Stoneley and dipole dispersions and using established relationships between dispersion characteristics and shear moduli, the method achieves accurate stress estimation without requiring computationally intensive inversion algorithms.
Solution Approach 2:
The patent changes the parameter space from direct stress estimation to shear modulus estimation via dispersion analysis. By transforming the problem into estimating shear moduli from measurable dispersion parameters first, then calculating stresses from these moduli, the method achieves accuracy while reducing algorithmic complexity.
3Reliability
If multiple dispersion types are calculated from baseline and subsequent sonic data, then stress estimation reliability is improved, but the processing time increases
Solution Approach 1:
The patent performs preliminary estimation of shear moduli from Stoneley and dipole dispersions before calculating final stress parameters. This preliminary action allows the use of established relationships between dispersion characteristics and shear moduli, reducing the computational burden of the final stress calculation and overall processing time.
Solution Approach 2:
The method uses the measured dispersion data itself to directly estimate shear moduli without requiring additional external data or complex iterative processes. The Stoneley and dipole dispersions self-containedly provide the information needed to calculate shear moduli and subsequent stress parameters, reducing processing time.
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 reliable estimation of formation stress changes, helping to maintain reservoir integrity and prevent unwanted fractures by accurately monitoring pressure and stress changes, thereby reducing the risk of CO2 leakage.
Implementation Method 1
A standard sonic measurement system consists of placing a piezoelectric source and an array of hydrophone receivers inside a fluid-filled borehole
Implementation Method 2
A logging device that has been used to obtain and analyze sonic logging measurements of formations surrounding an earth borehole... Parameters of compressional, shear and Stoneley waves, such as their velocity
Implementation Method 3
The headwaves are caused by the coupling of the transmitted acoustic energy to plane waves in the formation that propagate along the borehole axis. An incident compressional wave in the borehole fluid produces critically refracted compressional waves in the formation
Implementation Method 4
In contrast, a dipole source primarily excites the lowest-order flexural borehole mode together with compressional and shear headwaves
Data Source
AI summary
An apparatus and a method for recovering hydrocarbons from a subterranean formation including collecting baseline and subsequent sonic data. Either open or cased hole Stoneley and cross dipole dispersions are calculated using the baseline and subsequent sonic data, the minimum and maximum horizontal stress magnitudes are calculated using the calculating dispersions, a pressure is calculated and hydrocarbons are recovered.