Daniele Colombo

Near-surface and anisotropy modeling for efficient land seismic depth imaging in low-relief geology

AbstractPrestack depth migration of land data presents unique characteristics and challenges that distinguish it from the workflows applied for marine data. Such unique characteristics are primarily related to the near surface. In areas of low-relief geology, near-surface velocity variations can obscure the reservoir structure. The remaining deeper earth model section has good lateral continuity and can be described effectively by smooth velocity fields. Strategies for estimating the near-surface effects and incorporating them into a processing workflow are of primary importance for the successful depth imaging of land seismic data. The second important aspect of a depth imaging workflow is that the seismic image must honor the well markers or formation tops. The subhorizontal fine-scale layering of low-relief structures can cause anisotropy that needs to be taken into account to achieve accurate well ties and good image quality. We have evaluated the application of an efficient workflow to achieve fast a...

Gaussian Beam Migration: Prestack, Common-shot, TTI, True Amplitude In Angular Domain

Gaussian beam prestack depth migration (GB-PSDM) represents an excellent tool for the migration of seismic data in complex velocity fields, as it is an implicit multiarrival migration algorithm. With the turning waves feature, it is also appropriate for imaging of steep dips. Application in common-shot domain makes it suitable for irregular acquisition geometries. In addition, an anisotropic acoustic approximation of the raypath as the central ray of the beam can be easily parameterized for handling complex anisotropy (e.g., tilted transversely isotropic (TTI)). Implementation of the Gaussian beam migration in angular domain gives additional value for post-migration processing and true amplitude normalization by means of hit counter equalization.

Feasibility study for long offset seismic acquisition in a thrust‐belt

A new approach is used to define the optimal parameters for long offset acquisition in a thrust belt. The feasibility study makes use of ray-tracing, tomography, FD acoustic modelling and PSDM to determine the maximum offsets that could be used for imaging purposes and for velocity model building. The optimal acquisition parameters are then sought in terms of source spacing, maximum offset and actual coverage in the offset range that would provide the best imaging potential for the target.

Microseismicity As a Deep Seismic Source For Reservoir Fluid Characterization

Enhanced Oil Recovery (EOR) procedures, such as water, steam and CO2 injection, generate MicroEarthQuake (MEQ) events due to the pressure gradients induced in the reservoir. The variations in Vp and Vs as a result of fluid substitution (e.g. steam substituting oil) can be detected via Vp, Vs or Vp/Vs tomography, where MEQs are used as seismic sources. The steam-saturated volume in a geothermal reservoir and the water flooding effects are successfully identified via 3D Vp/Vs tomographic analysis of MEQ data.

Seismic long offsets for imaging below complex overburden

The feasibility of using seismic long offsets for imaging targets located below complex overburden is investigated by using synthetic modeling procedures based on a real geologic model of the central Apennines, Italy. Illumination through ray tracing, acoustic modeling and depth imaging through PSDM are the techniques used. The results indicate that extended offsets up to two times the depth of the target can be successfully used for imaging without introduction of artifacts and that the imaging results are substantially better than those obtained with a conventional seismic layout.