NASA, Geosat to conduct sensor research probe

An estimated 46.9 tcf of natural gas remains in the major Cretaceous-age reservoirs in the Greater Green River and Wind River basins of the U.S. Rocky Mountains. This figure does not include coalbed methane and low permeability sandstone and shale reservoirs.

Researchers from the National Aeronautics and Space Administration and the Geosat Committee will apply an airborne hyperspectral instrument to help find these reserves in a program open to industry participants (OGJ, Oct. 5, 1998, p. 113).

Hyperspectral, an exciting new remote sensing technology, slices electromagnetic light energy into extremely fine windows, measuring the actual chemical constituents of soil, rock, and vegetation. Target minerals and hydrocarbons are identified by the way their molecules reflect and absorb light.

Economic benefits

Numerous economic gains should accrue from this work:

Structure and stratigraphic analysis pinpoints minerals like gypsum, calcite, dolomite, kaolinite, smectite, illite, goethite, hematite, and analcime.
Fracture mapping-correlating these with tight gas sandstone and shale production in the Greater Green River basin.
Direct detection of gas seeps and associated soil and vegetative surface alterations.
Adding new information to the integration of basin analysis, ground-truth surveys, and gas exploration models.
Conduct accurate coalbed methane environmental monitoring programs.
Move high technology from a theoretical basis into proven problem-solving, time- and money-saving commercial application; design short-course training.

Industry participants will guide final selection of test sites to be studied, but it makes sense to revisit NASA test site areas in the Greater Green River and Wind River basins: They are relevant to current industry exploration models and extensive ground-truth databases are at hand.

The project will fully leverage what was learned during the historic 1977-84 joint NASA/Geosat Test Case Project: This groundbreaking research developed exploration models using remote sensing methods that directly detected surface hydrocarbon alterations related to reservoirs at depth.

Cretaceous Mesaverde sand

East-northeast and northeast-trending basement faults, fractures, and joint sets are important for production in Upper Cretaceous rocks. East-northeast-trending basement faults, reactivated during Tertiary basin extension, formed east-northeast striking joints. These are apparent in current imagery, will be further delineated, and correlated with sedimentary facies to enhance gas production models.

In addition, "sweet spots" (areas of enhanced permeability in reservoir rocks) are critical to producing from tight gas sandstones. We can map fracture orientation, delineate the tectonic regimes, interpret lithofacies, and detect gas seeps directly.

Lewis shale gas resource model

More than 1 tcf of this infill-based, low-cost, undiscovered resource will be found at moderate drilling depths in sweet spots. Exploration and development strategies are easily applied and combine to make the Lewis shale worthy of further study.

Spectral stratigraphy is an excellent tool for mapping the lateral and vertical distribution of lithofacies. NASA's Analysis of Sedimentary Basins Project pioneered spectral stratigraphic analysis of sedimentary basins for delineating marine and continental lithofacies.

Deep-basin gas resource model

Prime exploration targets are deep-basin compartmentalized gas accumulations at 10,000-20,000 ft in existing Greater Green River basin fields. One theory about these deep-basin gas targets describes the formation and destruction of anomalously pressured, compartmentalized gas accumulations. The orientation and timing of fractures and faults that bound these compartments are critical factors.

Data from this project will provide the necessary spatial and spectral resolution to correlate fracture density studies with lithofacies. Collected at a ground sample distance of 3-10 m, the hyperspectral data will approximate the in-line spacing of modern 3D seismic data.

Three-dimensional geologic models developed from this project will then be compared to subsurface reservoir models developed from 3D seismic data. Linking these correlations with 3D models of basement faults (and pressure models for deep-basin gas resources) will provide insight into downward continuation of linear features mapped at the surface.

Coalbed methane producibility

The USGS estimates 700 tcf gas in place from coalbed methane in the U.S. Producing it involves cost-effective treatment and disposal of produced water; measuring the migration of methane into shallow aquifer systems; defining the basin framework depositional settings; and predicting productive play fairways.

Deliverables to participants

Digital hyperspectral datasets collected over selected test sites; copies of all digitally processed image data, basin-scale, and reservoir-scale models developed for study areas.
Templates for planning hyperspectral and ground-truth projects.
Instruction on techniques for integrated basin analysis and 3D visualization of geologic models.
Short-courses on the integration of remote sensing and GIS data for geoscience and environmental programs.

The project will benefit oil and gas exploration companies and related research foundations interested in the economic development of oil and gas reservoirs. The Geosat Committee Inc. serves as the primary fundraiser organization and administers the project.

Data collection is to start in spring 1999. The instrument, the ESSI Probe 1, will be available to industry participants for proprietary airborne projects in the vicinity.

Hyperspectral data at spatial resolutions of 3-10 m-unavailable in earlier studies-are a step forward in mapping structural orientation.

The Authors

Dave Koger is proprietor of Koger Remote Sensing, Fort Worth, and past chairman of the Geosat Committee. E-mail: [email protected]

Dr. Rebecca L. Dodge is Geosat research and training director at the Pan American Center for Earth and Environmental Studies, University of Texas at El Paso. E-mail: [email protected]