Layer | Fill | Outline |
---|
Map layers
Theme | Visible | Selectable | Appearance | Zoom Range (now: 0) |
---|
Fill | Stroke |
---|---|
Collaborating Authors
Results
Wave-Equation Angle-Based Illumination Weighting Study: Thunder Horse, Gulf Of Mexico
Gherasim, Mariana (EPT BP) | Albertin, Uwe (EPT BP) | Nolte, Bertram (EPT BP) | Etgen, John (EPT BP) | Vu, Phuong (EPT BP) | Jilek, Petr (EPT BP) | Trout, Matt (GOM BP) | Hartman, Ken (GOM BP)
We begin by comparing by slant -stacking, gives illumination information in the our wave-equation illumination weighting workflows, angle direction (Askim et al., 2010). We then use these explain the differences between the one-way and two-way illumination gathers to generate corresponding illumination methods and describe the well tie procedure. We then weight gathers, which improve subsalt structural images demonstrate the impact of our illumination weighting when applied to migrated angle gathers.
- North America > United States > Gulf of Mexico > Central GOM > East Gulf Coast Tertiary Basin > Mississippi Canyon > Block 822 > Thunder Horse Field (0.99)
- North America > United States > Gulf of Mexico > Central GOM > East Gulf Coast Tertiary Basin > Mississippi Canyon > Block 778 > Thunder Horse North Field (0.99)
- North America > United States > Gulf of Mexico > Central GOM > East Gulf Coast Tertiary Basin > Mississippi Canyon > Block 778 > Thunder Horse Field (0.99)
- (3 more...)
Wave-equation Angle-based Illumination Weighting For Optimized Subsalt Imaging
Gherasim, Mariana (EPT BP) | Albertin, Uwe (EPT BP) | Nolte, Bertram (EPT BP) | Askim, OJ (EPT BP) | Trout, Matt (GOM BP) | Hartman, Ken (GOM BP)
Summary We design a wave-equation based demigration-remigration workflow that computes a measure of uneven seismic illumination effects on angle-gather amplitudes. We then use the workflow to generate a set of illumination weights, which, when applied to migrated gathers, improves the structural imaging in subsalt areas. We demonstrate the effectiveness of our method with narrow-azimuth 3D subsalt examples from Gulf of Mexico. Introduction Illumination effects such as shadow zones in subsalt imaging have been a challenging problem since the early stages of such imaging. Since imaging in general cannot remove all the effects of seismic wave propagation through overburden, some degradation of the image in subsalt areas is to be expected, even with the use of sophisticated imaging algorithms such as reverse-time migration. Hence, the mitigation of these effects is of significant interest to subsalt exploration. Historically, the mitigation of illumination effects has largely focused on the structural image below salt. However, as technology for depth imaging advances towards the determination of rock properties under salt, estimating the effects of illumination on migration gathers will become of interest as well. In this paper we present a technique for computing a measure of illumination along angle gathers in waveequation migration using a demigration-remigration technique. We first outline the theoretical basis for the technique, and then proceed to give several examples from Gulf of Mexico illustrating the effectiveness of the method in structural subsalt imaging. Theory Current measures of illumination in wave-equation migration are based on a linearization of the least-squares migration problem. In this case, the adjoint of the migration operator, which we refer here to as demigration is thought of as a modeling operator. This concept can be extended in a natural way to provide illumination information as a function of opening angle when the angle gathers are generated via slant-stacking of nonzero-spatial lagged migrated data. The idea is to feed into the demigration process a set of ‘perfect’ angle gathers, with no AVA signature, which follow an interpreted event. Since such a perfect angle gather corresponds to a pointdiffractor in subsurface offset domain via inverse slantstacking, the result of demigration-remigration is a distorted subsurface-offset diffractor, which when followed by slant –stacking, gives illumination information in the angle direction (Askim et al, 2010). In this paper we refer to gathers obtained in this way as ‘illumination gathers’, which we subsequently use to determine a set of weights as a function of angle. We then apply these weights in appropriate ways to improve the structural image. Narrow-azimuth application We initially developed our workflow using a Narrow- Azimuth Towed Streamer (NATS) data set from BP operated Thunder Horse field, GOM, which was shot along 3 azimuths: NS, EW and NW-SE. Thunder Horse subsalt development currently consists of two structural traps referred to as Thunder Horse North (THN) and Thunder Horse South (THS). THN consists of three-way dip closure near the salt wall and THS consists of a faulted four-way dip closure related to salt withdrawal (Ray et al., 2005).
- North America > United States > Gulf of Mexico > Central GOM (0.35)
- North America > Canada > Alberta (0.25)
- North America > United States > Gulf of Mexico > Central GOM > East Gulf Coast Tertiary Basin > Mississippi Canyon > Block 822 > Thunder Horse Field (0.99)
- North America > United States > Gulf of Mexico > Central GOM > East Gulf Coast Tertiary Basin > Mississippi Canyon > Block 778 > Thunder Horse North Field (0.99)
- North America > United States > Gulf of Mexico > Central GOM > East Gulf Coast Tertiary Basin > Mississippi Canyon > Block 778 > Thunder Horse Field (0.99)
- (3 more...)