Multicomponent VSP Seismic Inversion for Deviated Wells
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Solution Overview
Problem
Current seismic inversion methods for Vertical Seismic Profile (VSP) data are underutilized and produce inaccurate results due to assumptions about normal incidence angles and downgoing wavefields, lacking shear impedance and density information, and are ineffective for deviated wells.
Innovation Solution
The method involves obtaining an initial velocity model, determining acquisition geometry, performing seismic surveys, analyzing direct arrival signals, and using tomographic inversion to generate an updated velocity model, which is then used for multicomponent seismic inversion to create an elastic model of the subterranean formation, including both acoustic and shear impedance and density information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If normal incidence angle assumption is used in VSP seismic inversion, then the processing is simplified, but the acoustic impedance estimation accuracy deteriorates when actual angle differs more than 15 degrees
Solution Approach 1:
The patent changes the parameter of incidence angle from a fixed normal incidence assumption to a variable parameter that can take different values. The system calculates seismic responses for multiple incidence angles and selects the angle that provides the best match between observed and synthesized VSP data, thereby resolving the contradiction between processing simplicity and estimation accuracy.
2Device complexity
If downgoing wavefield is used as input wavelet, then the workflow is simplified, but the inversion result accuracy deteriorates due to wavelet rotation issues
Solution Approach 1:
The patent creates a synthetic copy of the VSP data by forward modeling seismic responses using the updated velocity model and testing different wavelets. The system compares these synthetic copies with the actual observed data to identify the correct wavelet, avoiding the inaccuracies of using the downgoing wavefield directly while maintaining a systematic workflow.
Solution Approach 2:
The patent implements an iterative feedback mechanism where the inversion results are used to update the velocity model, which then generates new synthetic data for comparing with observed data. This feedback loop continues until convergence, allowing the system to correct wavelet rotation issues and improve inversion accuracy through successive approximations.
3Ease of operation
If 1D corridor stack VSP data is used with normal incidence assumption, then the processing is straightforward, but shear impedance and density information is lost
Solution Approach 1:
The patent transitions from 1D corridor stack processing to multi-dimensional processing by incorporating multiple incidence angles and both downgoing and upgoing wavefields. This dimensional expansion allows the system to recover and utilize shear impedance and density information that would be lost in conventional 1D processing, while maintaining operational feasibility through automated algorithms.
4Adaptability or versatility
If conventional VSP-seismic inversion workflow is applied to deviated wells, then the method should be versatile, but the results are unsuccessful
Solution Approach 1:
The patent introduces dynamic adjustments to accommodate different well configurations. The system adaptively modifies the processing parameters, incidence angle ranges, and geometric corrections based on whether the well is vertical or deviated. This dynamic approach maintains versatility across different well types while ensuring reliable results by optimizing the inversion workflow for each specific case.
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 generates more accurate 2D and 3D seismic images, providing comprehensive information about subterranean formations, improving the precision of seismic inversion and enabling effective analysis for both vertical and deviated wells.
Implementation Method 1
modifying the initial velocity model to generate an updated velocity model by performing a tomographic inversion of the transit time data
Implementation Method 2
Seismic inversion is the process of transforming seismic reflection data into a quantitative rock property description of a reservoir
Implementation Method 3
generating an elastic model of the subterranean formation by performing the seismic inversion of the VSP data using the updated velocity model
Data Source
AI summary
A method for seismic inversion of vertical seismic profile (VSP) data in an oilfield. The method includes obtaining an initial velocity model of a subterranean formation including acoustic velocities of wave propagation in proximity to the wellbore, determining an acquisition geometry for obtaining the VSP data including receiver locations within the wellbore and a source location, performing a seismic survey to obtain the VSP data based on the acquisition geometry, analyzing arrival signals of the VSP data to generate transit time data for wave propagation from the source location to the receiver locations, modifying the initial velocity model to generate an updated velocity model by performing a tomographic inversion of the transit time data, generating an elastic model of the subterranean formation by performing the seismic inversion of the VSP data using the updated velocity model, and adjusting the operations of the oilfield based on the elastic model.