Exploration and Production Technologies

Advanced Reservoir Imaging Using Frequency-Dependent Seismic Attributes

DE-FC26-04NT15503

Project Goal
The project goal is to develop seismic-based technology that quantifies a reservoir’s fluid-saturation and fluid-mobility properties. The research work will provide a mechanism and frequency-dependent amplitude-versus-offset (AVO&F) techniques to recognize, delineate, and validate new hydrocarbon reserves and assist in the development of producing fields.

Performers 
University of Houston, Houston, TX 
University of California, Berkeley, CA 
Lawrence Berkeley National Laboratory, Berkeley, CA

Results
The project has developed an asymptotic model and governing equations describing seismic wave propagation in dual-permeability media and reflectivity of such media at different incident angles and frequencies. The project has developed algorithms for preserving the wavelet frequency content and applied a low-frequency asymptotic approach to deriving algorithms for reflection/transmission coefficients and attenuation that are dependent on frequency and fluid mobility.

Physical modeling is one technique employed to investigate wave propagation in dual-porosity media. Several diagnostic methodologies for evaluating fractures were identified. The methodologies involved head waves, reflections, and coda.

The project has formulated and developed rock-property transforms that allow conventional seismic horizon maps to be converted into reflectivity maps. With these transforms and the AVO gathers at the prospect and at the downdip water-equivalent reservoir, a pore fluid saturation can be estimated without a calibration well that ties the seismic unless the bed thickness is desired.

A spectrum cross-plot technique was developed based on AVO&F analysis and applied this technique to separate wet- and gas-saturated zones.

During 2006, the results of the project performers’ activity related to this project were presented to representatives of 32 oil industry companies.

Benefits 
The project expects to develop technologies that will assist in the recognition of hydrocarbon accumulations from 3-D seismic data and that will predict reservoir rock type, pore-fluid properties, and the delineation of hydrocarbon distribution. These technologies will assist in the more complete and economic recovery of the reservoir’s hydrocarbons.

The results will help to find new hydrocarbon prospects in areas that have subtle to no seismic expression, those being deeper and more costly to find and drill. The analysis of frequency-dependent AVO attributes and frequency-dependent imaging will lead to accurate predictions of pore-fluid production by mapping fluid contacts and mobility. This will represent a major step in the goal of developing a seismic-based method of mapping reservoir permeability. Thus the research work will provide a mechanism to recognize, delineate, and validate new hydrocarbon reserves and assist in the development of producing fields.

Background 
The DHI (direct hydrocarbon indicator) based on “bright-spot” recognition of hydrocarbons became routine during the 1970s. Shortly after, 3-D acquisition more accurately delineated the structure of bright-spot reservoirs. However, most large bright-spot reservoirs have been drilled. Energy companies are now drilling prospects in areas that have subtle to no seismic expression of hydrocarbons. During the last 5 years, spectral decomposition of 3-D data has renewed interest in frequency-dependent analysis for recognition of hydrocarbon reservoirs. Most of these frequency studies are done with normal-incident post-stack seismic data. In the mid-1990s, the birth of anisotropic seismic imaging allowed data with source-receiver offsets greater than twice the depth of investigation to be routine. The results from far-offset data provided detailed images of hydrocarbon reservoirs not seen on conventional data. Many results were not explained by elastic wave theory. Thus simultaneous research began, using long-offset seismic data in the areas of non-elastic wave propagation with fluid flow, target-oriented processing, and the development of geologic workflows for multi-trace seismic attributes. This multi-discipline study was the reason for the research collaboration between the universities of Houston and California (Berkeley).

Summary
The project is developing innovative seismic-based technology that correlates with and quantifies a reservoir’s fluid saturation and fluid mobility properties and their spatial distribution to frequency and angle-dependent reflectivity. The project involves theory and processing algorithms development, numerical and physical modeling, laboratory experiments, and field verification using seismic, well logs, and engineering data.

During the second year period, from January 1, 2006, through December 31, 2006, the project focused on the following tasks:

  • Develop an asymptotic model and governing equations describing seismic wave propagation in dual-permeability media,
  • Formulate reflectivity equations and develop algorithms and computer codes for numerical modeling of frequency-dependent seismic imaging for porous permeable layered medium,
  • Develop frequency-preserved target-oriented seismic migration and algorithms for extracting low-frequency signal from seismic data,
  • Undertake 3-D anisotropic fractured physical modeling for investigation of azimuth- and frequency-dependent reflectivity of the porous model surfaces.
  • Build the geologic models of reservoirs and calibrate the seismic attributes against the geologic models and reservoir parameters determined from petrophysical and engineering data.

The result of the research provides a new mechanism to discover and validate new hydrocarbon reserve.

Current Status (July 2007) 
The project has finished the second year of a 3-year term successfully. The project is not been funded for the third year by the DOE. The project ended and produced the Final Report.

Funding 
The project was selected in response to DOE’s Oil and Gas Master Solicitation DE-PS-04NT15450, focus area Advanced Diagnostics and Imaging Technology.

Project Start: January 1, 2005 
Project End: May 31, 2007

Anticipated DOE Contribution: $472,532
Performer Contribution: $252,000

Contact Information
NETL - Purna Halder (purna.halder@netl.doe.gov or 918-699-2083)
U. of Houston - Fred Hilterman (fhilterman@uh.edu or 713-743-5802)

Publications 
G. Goloshubin, C. VanSchuyver, V. Korneev, D. Silin, and V. Vingalov, “Reservoir imaging using low frequencies of seismic reflections,” The Leading Edge, Vol. 25, No 5, pp. 527-531, 2006.

D. Silin, V. Korneev, G. Goloshubin, and T. Patzek, “Low-Frequency Asymptotic Analysis of Seismic Reflection From a Fluid-Saturated Media,” Transport in Porous Media, Vol. 62, No. 3, pp. 283-305, 2006.

Silin, D., Goloshubin, G., “Asymptotic analysis of seismic reflection from a fractured reservoir: Part I. Biot-Barenblatt dual-porosity medium,” presented for publication, 2006.

Silin, D., Goloshubin, G., “Asymptotic analysis of seismic reflection from a fractured reservoir: Part II. Transmission and reflection coefficients,” presented for publication, 2006.

Gennady Goloshubin and Dmitriy Silin, “Frequency-dependent reflection from a permeable boundary in a fractured reservoir,” 76th SEG Meeting, New Orleans, LA, 2006.

G. Goloshubin, D. Silin, “Dual porosity Biot-Barenblatt model,” 68th EAGE Meeting, Vienna, Austria, 2006.

Zhengyun Zhou, Fred Hilterman, and Haitao Ren, “Stringent assumptions necessary for pore-fluid estimation,” 76th SEG Meeting, New Orleans, LA, 2006.

Haitao Ren, Fred Hilterman, Zhengyun Zhou, and Mike Dunn, “AVO Equation without velocity and density,“ 76th SEG Meeting, New Orleans, LA, 2006.

Mingya Chen, Fred Hilterman, and Julius Doruelo, “3-D common-offset migration on a vertically aligned fracturing model,” 76th SEG Meeting, New Orleans, LA, 2006.

Julius Doruelo, Fred Hilterman, and Gennady Goloshubin, “Head waves as mechanism for azimuthal PP AVO magnitude anomalies,” 76th SEG Meeting, New Orleans, LA, 2006.


Modeling data: AVO&F responses from water-saturated reservoir (left) and gas-saturated reservoir (right).


Modeling data: Spectral amplitudes cross-plot (left) and illuminated gas reservoir on the seismic section (right).


Field data: Frequency decomposition of near-offset data (left) and far-offset data (right).


Field data: Spectral amplitudes cross-plot (left) and illuminated gas reservoir on the seismic section (right).

Time slice through the Most-Positive curvature volume within the Devonian interval of the West Texas 3-D seismic data.

The common-mid-point gather in the left panel has common-offset migration and normal moveout (NMO) corrections. The panel on the right started with the same input data but was target-oriented migrated and NMO corrected. The amplitude of the event at 2.250 s on the left panel contains useful amplitude information past the 14,000-ft source-to-receiver offset trace.

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