Look-ahead VSP Workflow Using Time and Depth Variant Q
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Solution Overview
Problem
Vertical seismic profile (VSP) data experiences energy loss due to fluid movement and friction with grain boundaries, leading to attenuation of seismic waves, which complicates the acquisition of high-resolution seismic images and accurate formation characteristics ahead of a drilling bit.
Innovation Solution
A method is developed to calculate the time and depth variant quality factor (Q) of a subterranean formation using VSP data, employing a spectral ratio method with a ground force signal as the reference trace to compensate for attenuation, thereby improving the accuracy of seismic data inversion and reducing uncertainties in geological modeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If seismic waves propagate through the formation to acquire VSP data, then formation characteristics can be estimated ahead of the drilling bit, but energy loss occurs due to fluid movement and friction with grain boundaries causing attenuation
Solution Approach 1:
The patent converts the harmful attenuation effect into a beneficial measurement tool by calculating the quality factor Q from the attenuated seismic waves. The attenuation, caused by fluid movement and friction, is no longer treated as mere noise but as a source of information about formation properties. By measuring the energy loss and frequency changes, the system derives Q values that characterize the formation's attenuation properties, turning the harmful effect into useful data for improved depth estimation and formation characterization.
Solution Approach 2:
The patent applies parameter changes by introducing the quality factor Q as a new parameter to describe and compensate for attenuation effects. The system calculates Q as a function of frequency and depth, then uses these parameter variations to correct the seismic data. By modeling attenuation as an exponential decay function with Q-dependent parameters, the system transforms the raw attenuated signals into corrected data with improved amplitude and phase characteristics, enabling more accurate depth estimation.
2Productivity
If standard VSP processing is used without attenuation compensation, then processing is simpler and faster, but resolution of seismic images and quality of AVO analysis deteriorate
Solution Approach 1:
The patent applies preliminary action by calculating the quality factor Q and determining attenuation compensation parameters before the main seismic image processing and interpretation steps. The system pre-computes the attenuation correction functions based on the measured seismic waves, then applies these corrections to the VSP data before inversion and imaging. This preliminary compensation ensures that subsequent processing works with already-corrected data, improving final resolution without significantly increasing overall processing time.
3Device complexity
If Q is calculated using traditional methods, then computation is straightforward, but uncertainties in depth estimation ahead of the drilling bit increase
Solution Approach 1:
The patent implements feedback by using the calculated quality factor Q to iteratively refine the depth estimation process. The system calculates Q from the seismic waves, uses Q to correct attenuation in the data, then uses the corrected data to improve depth estimates, which in turn refine the Q calculation. This feedback loop continues until convergence, systematically reducing uncertainties in depth estimation ahead of the drilling bit while maintaining manageable computational complexity through automated iteration.
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 enhances the amplitude and phase compensation of seismic data, leading to improved resolution and faster turnaround times for look-ahead VSP applications, allowing for more accurate estimation of formation characteristics and safer drilling operations.
Implementation Method 1
calculating, using the ground force signal, a time and depth variant quality factor (Q) of the subterranean formation
Implementation Method 2
compensating, based on the time and depth variant Q, attenuation in the seismic data
Data Source
AI summary
Disclosed are methods, systems, and computer-readable medium to perform operations including: receiving seismic data acquired by at least one receiver of a geologic survey system configured to perform a geologic survey of a subterranean formation, wherein the seismic data is associated with reflected acoustic signals generated by at least one source of the geologic survey system; calculating a ground force signal by stacking the acoustic signals generated by the least one source; calculating, using the ground force signal, a time and depth variant quality factor (Q) of the subterranean formation; and compensating, based on the time and depth variant Q, attenuation in the seismic data.