This paper is a progress report that briefly summarizes the concepts and procedures being implemented for basin analysis to develop an integrated GIS and expert system to aid in assessing energy resources. This knowledge-based system will include information that would allow policy makers to deal more efficiently with energy and mineral exploration and development issues at regional, State, and national levels.
The concepts and methods for conducting sedimentary basin analysis have evolved from fairly simplistic geological studies that employed primarily qualitative and semiquantitative techniques to studies of ever- increasing complexity that employ quantitative evaluations from total basin systems. Complex quantitative methods require enormous amounts of diverse and multivariate spatial data necessary to quantify the geological, geophysical, geochemical, and hydrologic processes reacting during the history of a sedimentary basin.
Such an integrated analysis for a sedimentary basin is a difficult task to accomplish without computer assistance. It requires a multidisciplinary approach that draws on many areas of geologic expertise supported by the integration and analysis of large volumes of multivariate spatial data. This extensive data base requires the use of a computer to analyze effectively the data within the three-dimensional framework of a basin. However, new applications of knowledge-based computer mapping techniques, known as geographic information systems (GIS), and computer diagnostic programs, known as expert systems, may provide the tools needed to define strategies and technologies for conducting the complex tasks common to sedimentary basin analysis. These techniques, when applied to basin analysis, may be particularly useful for conducting energy and mineral resource assessments.
The USGS is currently exploring the feasibility of applying GIS and expert systems technologies to a prototype system that provides the framework for analyzing sedimentary basins primarily to assess their energy and mineral resources. This paper, in the nature of a progress report, briefly summarizes the concepts and procedures being implemented in basin analysis to develop an integrated GIS and expert system to help assess energy resources. This knowledge-based system will include information that allows resource managers to deal more efficiently with issues related to energy and mineral exploration and development at regional, State, and national levels.
GIS were originally designed and developed nearly 20 years ago as a method to overlay and combine diverse kinds of data into a single map to summarize geographic, cultural, and scientific attributes. Since that time, these systems have evolved to serve many diverse applications, such as inventory mapping of forests, water, and other natural resources; lease management; topographic mapping; exploration; marketing and facility information; municipality planning; land-use planning; military applications; teaching; and scientific research. With the growing interest in three-dimensional geologic modeling and the importance of subsurface geologic analysis, new applications of GIS are currently being investigated. These GIS provide data integration to link surface and subsurface geology with associated rock attributes, such as those from geochemical and geophysical data (Loudon, 1986; Bak and Mill, 1989). A GIS typically links different data sets. Figure 1 illustrates in a spatial context the linking of related surface and subsurface data bases that can be represented as a number of data layers, or map coverages, useful to the assessment of natural resources. Present-day GIS data models can analyze geographic (and geologic) data and provide users with the ability to view and to analyze data relationships as well as to map, query, and manipulate spatial information (Chrisman, 1987).
GIS technology allows the integration of mapping and data-base functions that enable the user to integrate and manipulate spatial (coordinate) data with attribute (thematic) data to combine complex geographic, geologic, and geophysical data bases into resultant overlay and composite maps. It also permits the user to conduct multivariate spatial data analysis and to have access to a variety of options for analyzing these data bases.
The demands for detailed three-dimensional subsurface data are especially crucial in such applications as petroleum reservoir characterization (Jones, 1988), ground- water contamination modeling, ore-body delineation, and geotechnical site characterization for complex construction projects. The same needs and demands are also recognized for the characterization of three-dimensional subsurface data to (1) conduct studies on sedimentary basin evolution and (2) evaluate potential energy and mineral resources.
Some of the major information sources used to develop the surface and subsurface cartographic data bases for the San Juan Basin are listed below. The U.S. GeoData System from the USGS's National Mapping Program is one of the cartographic data bases used for surface mapping in the investigation of this basin. It includes the Digital Cartographic Data Base (DCDB), which contains the digital elevation models (DEM) for terrain elevations and the digital line graphs (DLG) for planimetric information on boundaries, transportation, and hydrography. Other cartographic data bases used in the study are the U.S. Public Land Survey System, land-ownership data from the Bureau of Land Management (BLM), and land use and land cover (LULC) data. Additional data bases incorporated for use in the GIS for surface coverages include those concerning surficial geology, locations of oil and gas wells, well status, and oil and gas fields. Data bases created for subsurface mapping include structure contour, isopach, and facies information for the major oil- and gas-producing formations; stratigraphic information for cross sections, fence diagrams, and paleogeographic reconstructions; and various composited map products. The Petroleum Information-Well History Control System (PI-WHCS) data base (Petroleum Information, 1990) provided the major source for well information, depth and thickness information for identified formations within the basin, and a variety of data on productive reservoirs.
GIS technology applied in the San Juan Basin study was initially directed to the development and integration of the multivariate spatial data base needed for the analysis of these large volumes of surface and subsurface data. This technology, when applied to sedimentary basins, is used to establish a three- dimensional perspective of the basin's fundamental geologic, stratigraphic, and structural framework on the basis of subsurface data. Surface data are also used for information pertinent to the project, such as land ownership, surficial geology, topography, hydrography, and location of oil and gas wells (Miller, 1988, 1989b, 1992; Miller and others, 1990a,b).
GIS, featuring the integration of mapping and data-base functions, allow the geologist to generate maps and to apply a variety of options for analyzing and manipulating geographic and geologic information. Subsurface data coverages, representing geological surfaces and attributes, are used by the GIS as a part of the geographically referenced data base. The GIS, through its ability to carry out spatial operations, typically links the related surface and subsurface data sets by using the geographic locations (x and y coordinates) as the common key. The major advantage of using a GIS is that it allows the geologist to identify the spatial relationships existing between surface and subsurface features. Thus, complex spatial operations are possible with a GIS that would be difficult, time consuming, or impracticable otherwise.
Current GIS technology and mapping software being used by the USGS in this pilot study for the three- dimensional analysis of the San Juan Basin include ESRI's ARC/INFO GIS software (Environmental Systems Research Institute, 1987, 1990) and the Interactive Surface Modeling (ISM) mapping software package (Dynamic Graphics, 1984). Both software systems are run on the PRIME computer in Reston, Va.
Earth-science applications for expert systems include diagnosing drilling problems and problems with producing oil wells, interpreting and correlating well data, enhancing oil-recovery techniques, acquiring seismic data, and making geophysical interpretations. Expert systems are also used as exploration tools in mineral prospecting, such as Stanford Research Institute's PROSPECTOR (Duda, 1980) and Schlumberger's DIPMETER ADVISOR system (Baker, 1984). Some applications of expert systems in the USGS include use of the muPETROL program to classify sedimentary basins for petroleum-resource assessment (Miller, 1986, 1987a,b) and use of a microversion of PROSPECTOR for mineral exploration (McCammon and others, 1984; McCammon, 1986).
The capability of expert systems to deal with reasoning under uncertainty is essential to the geologist for various applications in the earth sciences. Assessing undiscovered energy and mineral resources within sedimentary basins is a prime example of reasoning under uncertainty. Typically, geologists deal with information that is usually incomplete, inferred or interpretive in nature, often uncertain, and sometimes unreliable. Frequently, the geologist must extrapolate from the known to the unknown when working in frontier areas for which there is little or no information.
It is important to the long-term strategic planning of energy and mineral resource projects to compile and document knowledge-based systems for sedimentary basins that are permanent and have continuity. Each basin system can be used as an ongoing decision-making tool by the team of experts building it as they encode and document their expertise as a reference for those who may need it in the future. Thus, expert systems provide a knowledge base that can be continuously updated and is amenable to changing geologic interpretations and exploratory conditions within the basins. Such a knowledge-based expert system can also provide for in-house training of new staff.
Knowledge-based expert systems can be used to document USGS expertise on all of the significant basins or energy and mineral provinces of the United States. Such systems could incorporate new concepts in basin analysis, along with the application of old and new methods for resource appraisal methodology.
The USGS is investigating the feasibility of using expert systems and knowledge acquisition techniques in two areas of sedimentary basin analysis: the design and construction of a global system for classifying sedimentary basins, as discussed by Miller (1986, 1987a,b, 1989a), and geological analysis of sedimentary basins to assess their petroleum potential.
The primary objective in this basin analysis project is to design a prototype expert system and knowledge- based GIS that captures both the logic used to define geologic basin concepts and the reasoning that enables the geologist to understand and reconstruct the geologic evolution of a sedimentary basin (Miller, 1986, 1987a,b, 1989a). Such a system can provide these capabilities through documentation of major basin analysis components such as stratigraphy, structural geology, and sedimentology. The system is being designed to analyze the traditional concepts of source, reservoir, and trapping mechanisms; to help in the diagnosis of geological conditions favorable for the occurrence of petroleum or other energy resources; and to assess these resources.
Findings from this study are critical to the long-term objective. For example, information from the pilot study can be used as input for the selection of energy-resource appraisal methods. These methods are used to calculate the remaining undiscovered energy resources in the basin, or to limited areas, such as an exploration play or tracts relevant to land ownership.
Such a procedure gives the user insight into the tasks needed to perform the following: (1) analysis of a sedimentary basin geologically by incorporating all known and analogous basin information; (2) interpretation and relation of these basin characteristics to the genetic occurrence and location of energy resources; and (3) development, selection, and application of the most credible resource appraisal methods for estimating the energy resources of a basin. The system would also provide for complete documentation of the information used (including any maps derived by GIS), the geologic assumptions made, and the methods applied for any particular assessment.
The functional requirements of a national resource LIS would fall into three categories: (1) data-base development, management, and inventory; (2) spatial analysis; and (3) map and report generation.
Initially, most of the effort to establish and operate such a resource information system would be related to data-base and knowledge-base development (surface and subsurface data capture, transformation, and registration), management (map and attribute storage and retrieval), and inventory (area and volume estimations). Data-analysis tasks, such as basin analysis in which a rule-based expert system and spatial data analysis are used, would then be conducted in response to the questions posed to the data base. Finally, computer and digital displays would provide the geologist with the capability to evaluate the results of the analyses interactively and to produce hard-copy maps and reports documenting results for interpretive or planning purposes.
Preliminary work conducted to date on a knowledge- based GIS for the San Juan Basin provides the geologist with the capability to manipulate essential surface and subsurface data layers, to interpret the basic geology of the basin, and to locate known energy resources. Integrating these GIS capabilities with a knowledge-based expert system provides the geologist with an "intelligent" data- management system for processing and interpreting the spatial data relationships. This integration creates an efficient system for the geologist to rapidly explore and view spatial data bases and provides the methods and algorithms for exploratory data-analysis and resource-appraisal procedures. The expert system also provides the geologist with a diagnostic tool to interpret, analyze, and forecast the occurrence of additional energy resources on the basis of the basin's geologic history.
Several national projects have been initiated by various Federal agencies that involve the application of GIS techniques to land information systems. Sturdevant and Kleckner (1984) report on one such project for the development of the Federal Mineral Land Information System (FMLIS), a GIS that would permit rapid retrieval, display, and analysis of mineral information on Federal lands throughout the United States. A pilot project was conducted on the Medford, Ore., (1 degree by 2 degree) quadrangle, and mineral occurrence and potential data were taken from the Conterminous United States Mineral Assessment Program (CUSMAP) and the Mineral Resource Data System (MRDS). A national FMLIS, however, has not yet been completed (R.L. Kleckner, oral commun., 1990). Some of the difficulties are attributed to the fact that land- status data, complete mineral-assessment data by geologic tract locations and their associated attributes from CUSMAP, and mineral-deposit and occurrence data from MRDS were available to FMLIS for only a limited number of areas in the United States.
A second national project using GIS technology has been initiated to develop LIS support for the BLM's oil and gas program. An oil and gas data-base system that is currently being designed will coordinate, within the BLM's LIS architecture, with those being developed for the Automated Lands and Minerals Record System (ALMRS) and the Public Land Survey/Geographic Coordinate Data Base (PLS/GCDB). This oil and gas automated-resource data base (ARD), in conjunction with the ALMRS data base, will be utilized to support a majority of the automated requirements of BLM's oil and gas program (Gazewood, 1989).
All of these automated national resource land information systems (such as FMLIS, BLM's LIS, and the basin resource information system discussed in this paper) have merit, are needed, and are technically feasible. They can increase access to energy and mineral resource information and provide effective use of natural resources, better service to the public, and more efficient decision making to support better resource management on public lands. "Whether for the government or private enterprise, managing thousands of acres of resources is a natural GIS application" (Ballou and Varney, 1990, p. 25). However, these large, automated information systems require the development of major data bases to be effective, and this effectiveness can only be achieved with considerable effort and dedication to the task.
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