Amplitude-versus-angle analysis using virtual sources
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional marine seismic surveys face challenges in resolving near-surface structures due to coarse shot density and lack of primaries in the near-offset range, leading to inadequate angular illumination and difficulty in imaging shallow targets.
Innovation Solution
The use of separated wavefield imaging and multi-sensor seismic receivers to construct angle gathers that span a range of incidence angles, incorporating both up-going and down-going wavefields, and leveraging sea surface reflections as modeled seismic sources to improve angular illumination and provide near-offset range data for amplitude-versus-angle analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional marine towed-streamer acquisition with point sources is used, then the acquisition setup is simple and cost-effective, but the shot density is coarse leading to inadequate angular illumination
Solution Approach 1:
The patent creates virtual point sources by processing sea surface reflection data, effectively copying the source function to multiple locations on the sea surface. This allows dense angular sampling without physically deploying dense shot arrays, resolving the contradiction between simple acquisition setup and adequate angular illumination.
Solution Approach 2:
The sea surface reflections act as intermediaries that carry information from the original point source to multiple virtual source locations. By using these reflected wavefields as mediators, the system achieves dense shot density equivalent without actual dense physical source deployment.
2Measurement precision
If primary-only imaging is used for shallow targets, then the processing is straightforward, but near-offset range data is missing leading to poor resolution of shallow structures
Solution Approach 1:
The patent converts sea surface reflections, which are traditionally considered harmful multiples to be removed, into beneficial virtual point sources. These reflected wavefields provide the missing near-offset range data for shallow target imaging, transforming a problem into a solution.
Solution Approach 2:
Instead of trying to acquire near-offset primary data directly (which is geometrically impossible with towed streamers), the patent inverts the approach by using far-offset reflected data to synthesize near-offset information through virtual source construction.
3Quantity of substance
If sea surface reflections are used as virtual sources, then dense shot density and full angular coverage are achieved, but the processing complexity increases
Solution Approach 1:
The patent makes the sea surface a universal source plane where every location can serve as a virtual point source. This multi-functional approach allows a single acquisition pass to generate dense shot density equivalent data for all angular ranges, managing complexity through unified processing methodology.
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 resolution of shallow targets, enables accurate velocity modeling, and provides improved amplitude-versus-angle analysis, allowing for the detection of hydrocarbons and better characterization of subsurface properties, overcoming the limitations of primary-only imaging.
Implementation Method 1
The seismic source control may cause the one or more seismic sources, which can be air guns, marine vibrators, etc., to produce acoustic signals at selected times. Each acoustic signal is essentially a sound wave called a wavefield that travels down through the water and into the subterranean formation.
Implementation Method 2
At each interface between different types of rock, a portion of the wavefield may be refracted, and another portion may be reflected, which may include some scattering, back toward the body of water to propagate toward the sea surface.
Implementation Method 3
At each interface between different types of rock, a portion of the wavefield may be refracted, and another portion may be reflected, which may include some scattering, back toward the body of water to propagate toward the sea surface.
Implementation Method 4
Pressure and particle motion variation as a function of time and position caused by an acoustic signal from a seismic source or modeled as being emitted by a modeled seismic source is called the source wavefield. Pressure and particle motion variation as a function of time and position measured by a seismic receiver or modeled as being received by a modeled seismic receiver is called the receiver wavefield.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Amplitude-versus-angle analysis for quantitative interpretation can include creation (1190) of a plurality of angle gathers from imaging a subsurface location with multiples in a near-offset range and imaging primaries outside the near-offset range and application (1192) of an amplitude-versus-angle analysis to the plurality of angle gathers to produce a quantitative interpretation pertaining to the subsurface location.