|Natural Fracture Diagnostics Validation
The goal of this project is to evaluate the ability of modern seismic methods to detect, map and analyze naturally fractured gas reservoirs, and assess future research needs in this area.
During the last ten years there has been considerable research in developing and evaluating various seismic techniques for fracture characterization for petroleum and gas applications as well as for mining, geothermal and nuclear waste disposal. Current methods rely on gross definition of fracture properties using attributes such as P-wave anisotropy, AVO (Amplitude versus Offset) or AVA (Amplitude versus Angle). While useful for gross fracture detection, these approaches have not been able to define the specific fracture sets that control permeability. This effort investigated high-resolution seismic methods (including vertical seismic profiling [VSP] and single well seismic) for their ability to provide useful information on fracture properties. A key focus of this effort was to combine the surface seismic information with current borehole seismic methods. Field studies in the San Juan Basin in New Mexico were conducted to validate the most promising seismic characterization methods, and a validation well was drilled. The final stages of the work were to synthesize project data and information to produce a handbook of the best methods for fracture characterization using seismic and well data in the San Juan Basin.
Study area (red box) in relation to the fault structure as determined by 2-D and 3-D seismic
Lawrence Berkeley National Laboratory (project management, VSP and modeling)
ConocoPhillips (3-D surface seismic and data processing)
Schlumberger (single well seismic)
Schlumberger Reservoir Technologies (reservoir modeling and simulation)
Lynn, Inc (data processing)
Virginia Tech (modeling)
Stanford University (modeling)
Sandia National Laboratory (analysis of cores from the San Juan basin)
Berkeley, CA 94720
The San Juan Basin is the second largest gas field in the conterminous United States, with an estimated 50.6 trillion cubic feet of undiscovered natural gas, according to the U.S. Geological Survey. Nearly all of the non-coalbed gas in the basin has come from naturally fractured tight sandstones, including those of the Mesaverde Group. The location, extent, and geometry of the fractures in these reservoirs have been poorly understood in the past, but studies such as this one have improved fracture prediction and fracture quantification. The success of the Newberry well indicates that seismic waveform modeling, seismic anisotropy analysis, VSP and single-well seismic analysis, specialized borehole logging and imaging techniques, and production history matching are powerful tools for targeting areas where natural fractures are abundant and gas production is likely to be high.
Results from 1-D tomography applied to 20 shots from the San Juan 3-D VSP data sets
- Investigated the effects of water filled and gas filled fractures on seismic signature. The results show a conclusive change in P-wave signal in very small fracture widths, <1mm. A combination of VSP offset and crosswell techniques can be used to verify fractures and their orientations in a reservoir utilizing high frequency seismic signals.
- Completed crosswell seismic data at a ConocoPhillips well test site showed that reflection waves are a potential methodology of identifying fractures in seismic data.
- Completed downhole seismic on the NIPSCO Royal Center Gas Field in north-central Indiana and evaluated the surface seismic data for the reflection wave signatures. The effort consisted of integrating all the geology, reservoir modeling and seismic interpretation of the test site to determine the extent of fractures distribution and its effect on gas deliverability.
- ConocoPhillips drilled and completed successful validation wells (the Newberry and Moore wells) in June 2002 based on earlier project findings. The well site recommendations were based on the following: (1) reprocessing and azimuthal anisotropy analysis of a 20-square-mile, 3-dimensional seismic reflection data set and (2) modeling of seismic wave propagation through fractured media. The Newberry well showed initial gas production of 1 million cubic feet per day and decline curves indicative of sustained high production.
- Confirmation of fractures in the Newberry well using high-resolution vertical seismic profiling (VSP), single-well seismic imaging, and specialized well-logging techniques, including Formation Micro Imager logging has been completed.
Layout of 9-C VSP for Newberry and Moore Wells
Current Status and Remaining Tasks:
The success of the Newberry well indicates that seismic waveform modeling, seismic anisotropy analysis, VSP, single-well seismic data analysis, specialized borehole logging and imaging techniques, and production history matching are powerful tools for targeting areas where natural fractures are abundant and gas production is likely to be high. Detailed project results are included in the project’s final report: “A Handbook for the application of seismic methods for quantifying naturally fractured gas reservoirs in the San Juan Basin, New Mexico".
Project Start Date: February 2, 1995
Project End Date: September 30, 2004
DOE Contribution: $ 4,191,000
Performer Contribution: $ 0
Lawrence Berkeley National Laboratory – Ernest Majer (510-486-6709 or firstname.lastname@example.org)
NETL – Frances Cole Toro (304-285-4107 or email@example.com)
Project Final Report: A Handbook for the Application of Seismic Methods for Quantifying Naturally Fractured Gas Reservoirs in the San Juan Basin, New Mexico [PDF-31MB]