FEW 04FE02

Project Goal
The project is developing realistic and workable approaches for amplitude-preserving Kirchhoff migration and Amplitude vs. Angle (AVA) analysis to delineate reservoir physical properties. The project effort will focus on (1) obtaining more information from images by implementing "Amplitude-Preserving Migration" through the use of more realistic imaging conditions and proper accounting for transmission loss, wave conversions, anisotropy, (2) the use of AVA to evaluate formation properties and to carry out velocity analysis and (3) the use of limited-aperture Kirchhoff migration to obtain better trace weights for use in amplitude-preserving migration, and (4) investigation of the effects of various implementations of Kirchhoff migration on the resolution of the seismic image; e.g. how small an object can be resolved and how is this influenced by the migration approach.

Performer
Los Alamos National Laboratory
Los Alamos, NM

Project Results
New methods for amplitude preserving Kirchhoff migration processing are being developed, which will lead to improved images and increase the amount and reliability of information that can be obtained from the images and will improve reservoir interpretation.

Benefits
With increased prices of petroleum, increased global demand for petroleum as a source of energy, the large expense of drilling for oil, and the expanded effort to search for oil in geologically more complex regions, there is a great need to obtain better images of the Earth's subsurface for reliable identification of new reservoirs and for optimizing production from existing reservoirs.

Background
Seismic imaging for petroleum exploration is a critical step in the process of reservoir identification and characterization. While Kirchhoff migration continues to be widely used in the petroleum industry, there are several areas where development of improved Kirchhoff migration has not been pursued. Our work addresses some of the issues that are not being addressed. We are addressing some of the important issues that our industry partners have recommended need to be addressed to allow them to use Kirchhoff migration in the future. This project builds on a previous project where we developed a fast and reliable approach for Kirchhoff migration and demonstrated its viability. We are now extending our work to better understand the reliability of the images (image resolution) and to use information obtained from the images to make quantitative estimation of reservoir properties.

Project Summary

• Seismic image resolution is better when using only first arrivals in Kirchhoff migration
• Use of ray-based amplitudes in ray-based Kirchhoff migration leads to cleaner images

In this first year's efforts, the project was initiated with investigations of the impacts of seismic data acquisition parameters on the resolution of the resulting seismic images. We have developed a formalism for understanding the influence of data acquisition parameters, the velocity model, and the migration propagator on the migration resolution. Previous investigators have focused their evaluation only on the effects of data acquisition parameters. We are in the process of making direct calculations of image resolution using our formalism. As part of this work, we have made numerical calculations that have allowed us to evaluate the effect of migration propagator on image resolution. Our numerical experiments to date have led us to the surprising conclusion that using only first arrivals in Kirchhoff migration leads to a slightly better image resolution than is obtained when using multiple arrivals. However, the image obtained when using only first arrivals contains significantly more artifacts away from an image point than we obtain when using multi-valued traveltime tables with ray-based amplitudes. We are in the process of evaluating this result. Results of this work were presented in talks at two professional meetings.

Current Status (August 2005)
The project obtained funding in approximately May, 2004. It is anticipated that this will be a three-year effort. However, the project is discontinued. It was not funded in FY 05 and FY 06.

Project Start: April 8, 2004
Project End: June 14, 2006

Anticipated DOE Contribution: $433,000
Performer Contribution: $0

Contact Information
NETL - Purna Halder (purna.halder@netl.doe.gov or 918-699-2083)
LANL - Michael C. Fehler (Fehler@lanl.gov or 505-667-1925)