Robert Wiley

Marmousi2 An elastic upgrade for Marmousi

The original Marmousi model was created by a consortium led by the Institut Francais du Petrole (IFP) in 1988. Since its creation, the model and its acoustic finite-difference synthetic data have been used by hundreds of researchers throughout the world for a multitude of geophysical purposes, and to this day remains one of the most published geophysical data sets. The advancement in computer hardware capabilities since the late 1980s has made it possible to perform a major upgrade to the model and data set, thereby extending the usefulness of the model for, hopefully, some time to come. This paper outlines the creation of an updated and upgraded Marmousi model and data set which we have named Marmousi2.

Next-generation Numerical Modeling: Incorporating Elasticity, Anisotropy And Attenuation

A new effort has been initiated between the Department of Energy (DOE) and the Society of Exploration Geophysicists (SEG) to investigate what features the next generation of numerical seismic models should contain that will best address current technical problems encountered during exploration in increasingly complex geologies. This collaborative work is focused on designing and building these new models, generating synthetic seismic data through simulated surveys of various geometries, and using these data to test and validate new and improved seismic imaging algorithms. The new models will be both 2- and 3-dimensional and will include complex velocity structures as well as anisotropy and attenuation. Considerable attention is being focused on multi-component acoustic and elastic effects because it is now widely recognized that converted phases could play a vital role in improving the quality of seismic images. An existing, validated 3-D elastic modeling code is being used to generate the synthetic data. Preliminary elastic modeling results using this code are presented here along with a description of the proposed new models that will be built and tested.

Reverse VSP Prestack Depth Migration with Multiples

Summary Reverse VSP (RVSP) can lead to good subsurface images, although the corresponding data processing is quite challenging due to the presence of strong down-going waves and multiples. We have modified a pseudospectral prestack depth migration (Hou and Zhou, 1999a,b) for the case of RVSP. This method uses a numerical solution of full wave equation to propagate forward wavefield from each source and backward wavefield from each receiver. The depth imaging of RVSP is achieved by one step, without the often tedious preprocessing of multiple attenuation and separation of up-going and down-going waves. We use synthetic reflection gathers and RVSP data to test the concepts and algorithm. Prestack depth migration of synthetic reflection data shows that internal multiples can make significant contribution to depth imaging. The synthetic RVSP image verified that the multiples (and down-going waves) can be used for imaging, including the subsurface structures above the source location. As a field data test, a RVSP data set from Michigan shows that the up-going and down-going waves can not be separated in a reliable fashion due to a narrow range of source depths. Nevertheless, the depth imaging using the full wave method reveals the structures above the sources.

Using seismic attributes to detect vertical fractures: A physical model study

Understanding fracture density and orientation is key to producing many carbonate reservoirs. Over the years many methods have been used to extract this information from seismic data. These methods include shear wave birefringence and velocity variations of P-wave data resulting from the anisotropy due to the fracturing. We want to investigate the class of geometrical attributes and the class of spectral attributes as a means of detecting fractures. This will avoid the time consuming process of picking P-wave data and the expense of multi-component data for shear wave analysis. To conduct a controlled experiment, we constructed a fracture model and acquired a various sets of data employing differing offsets and azimuths. Some of the geometrical attributes were able to identify the fractures while others were not. Of the spectral attributes, the dominant frequency was used to identify the fractures.

Next-Generation Seismic Modeling and Imaging project: summary of elastic modeling results

Summary A collaborative industry-US national laboratory-university research project has focused on increasing our understanding of elastic wave propagation in complex Earth structures. The project also followed up and extended the a highly successful 3-D SEG/EAEG acoustic modeling effort. Though considerable additional computing resources have become available in the past decade, it is still a major undertaking to compute a full 3-D elastic survey. Most of the project’s work has been devoted to carrying out calculations of 2-D and 3-D elastic model data sets in existing models that were modified and extended to make them more generally useful. The 3-D elastic modeling is described here. The model and data calculated from it are available to interested researchers. Several new 2-D and 3D models were identified and the work of adapting them for elastic modeling is underway, but will not be completed within this project.

3-D imaging of seismic data from a physical model of a salt structure

Seismic data from a physical model of the SEG/EAGE salt structure were imaged to evaluate the quality of imaging of a complex structure and benchmark imaging codes. The physical model was constructed at the University of Houston. Two simulated marine surveys were collected from it: a conventional towed streamer survey, and a vertical receiver cable survey.

Imaging and modeling seismic data from a physical model of the SEG/EAGE salt structure

Seismic data collected from a physical model of the SEG/EAGE salt structure provides a test of imaging in a complex and highly variable velocity structure. The physical model was constructed to simulate most of the features of the numerical model used to calculate the large SEG/EAGE synthetic seismic data set. The physical model is slightly simplified, since it could not be constructed with the velocity gradients used in the numerical model. Two data sets were collected from the model, one a simulation of a traditional marine survey, the other a simulation of a survey with vertical arrays of receivers. The main reason for collecting the two data sets was to compare images obtained from the marine survey with those obtained from the vertical receiver arrays.