GIS in Natural Resources

U.S. Oil and Gas Meets ArcView GIS

John D. Grace, Ph.D.,
President, Earth Science Associates

For the last 25 years, the USGS has periodically assessed the oil and gas resources of the onshore United States. These studies, paired with parallel analyses covering the offshore by the U.S. Minerals Management Service, form a comprehensive analysis of domestic energy supplies from these two critical commodities.

In 1995, the USGS issued the findings of their most recent National Oil and Gas Assessment. These data cover three types of hydrocarbons—oil, gas, and natural gas liquids—in three resource categories.

Proved Reserves are volumes in discovered fields that have been measured and are known to be economically producible. Field Growth includes those volumes expected to be added to already-discovered fields through new drilling and technology. The final category is Undiscovered. As these volumes are expressed as probability distributions, the means are reported, representing the central tendencies of the distributions.

Earth Science Associates (ESA) assisted the USGS in the 1995 National Oil and Gas Assessment in the areas of assessment methodology and economic analysis and assisted ESRI in the design of the GIS that supported the project. GIS played a critical role in providing custom map products to the dozens of USGS geologists responsible for analysis of specific geographic regions.

Goal to Spread Data on Which Analysis was Based

An important goal of this Assessment was dissemination of the data on which the analysis was based, as well as the results that characterized the undiscovered hydrocarbon resources of the 458 plays (groupings of genetically linked oil and gas fields and prospects) defined in the United States. Specifically, there were three types of data released from the three-year study.

Tabular data describe the discovered resources of the 458 plays. These include the volumes of oil and gas discovered, field sizes, historical data on discoveries, and other characteristics of fields. Most of these data were summarized from NRG Associates' Significant Oil and Gas Field database. The USGS's estimates of the volume and characteristics of undiscovered hydrocarbons in each play were also recorded in tables.

Spatial and Text Data Released

There were two types of spatial data. First were polygons outlining the geographic extent of all 458 plays. The second type was over 1.5 million point-data observations summarizing all oil and gas drilling in the United States on the basis of a 40-acre grid. The USGS used Petroleum Information's Well History Control System as the basis of this data set. For each 40 acre cell, the number of wells in the cell is given, whether the drilling resulted in oil or gas production, or if they were "dry" (nonproductive); the stratigraphic intervals penetrated; when the wells were drilled; and the depth of drilling and type of wells in the cell (e.g., exploration, production).

The third class of data was a 500 plus page text report describing the petroleum geology and resource base of each of the 458 plays and the USGS's methodology. The individual play descriptions in the report contained very valuable information that was not captured in either the tables or spatial data.

Huge Volume of Data Leads to Accessibility Issues

Because of the volume of data, the USGS released these data sets on two compact discs. However, because of federal data standards requiring accessibility from a wide range of software systems, the tabular and spatial data were recorded as simple flat files. This format is very user-unfriendly, severely undermining the accessibility of the most valuable U.S. oil and gas data set ever released to the public.

ESRI Helps Develop GIS-Based Way to Make Data Accessible

Recognizing a better GIS-based solution, ESA, with the help of ESRI, developed an integrated software/data system using ESRI's ArcView Data Publisher program. The resulting product, called the U.S. Oil and Gas Resource System, combines the power of ArcView GIS software with the data and report released by the USGS.

The 1.5 million, 40-acre drilling summary records were organized into 72 provinces covering the onshore United States. Polygons delimiting all the plays were also recorded. These data allow the user to map all drilling within a single play, group of plays, or the whole province. This provides "query-able" maps of oil or gas production, "dry" wells, drilling depth, well type, and the development of drilling and production over time.

Accessible while viewing the maps is a catalog of about three dozen premade charts on the resources of each province and all of the plays within it. Three dozen charts times 458 plays is an extremely large number. So rather than hard-coding thousands of charts, they are made on the fly, executing Avenue scripts. For this programming finesse and the parallel mapping solutions, ESA worked with ESRI's Rent-a-Tech group to develop the scripts and interface.

Combining Information Is Key to Using It Successfully

Combination of information is the key. The user may examine a map of drilling over time and simultaneously display corresponding histograms showing the number of wells drilled per year and the history of oil and gas field discoveries. Similarly, map themes can be turned on, showing the location of fields by play, a histogram indicating the size of discovered fields, and line graphs of the probability distribution of undiscovered oil and gas remaining in the play. As with any other ArcView GIS project, each point on the map, polygon, and chart element can be queried with the identify tool for the underlying data.

Incorporating data developed by the U.S. Department of Energy (DOE), each county in the country was hot linked to a list of each county's oil and gas fields. There are about 50,000 oil and gas fields in the United States, with each field record providing basic data such as the discovery year.

Accessing the USGS report required reaching beyond ArcView GIS. The report was converted to a hypertext document and installed as a Window's Help file, which can be "surfed" and searched at any time from within ArcView GIS. Blue Sky's WinHelp Office95 software was the authoring environment for this conversion. "Hyperindices" were also created for the report, allowing the user to list individual plays with common geologic characteristics (e.g., the same trap type, similar reservoir porosities).

ArcView Data Publisher Takes Data to Next Level

While ArcView Data Publisher format limits the user to the data on the CD-ROM, its capabilities allow full access to all of the original USGS map and tabular data, reports, and the U.S. DOE field database. However, as a fully functional GIS, it goes far beyond the original data.

Users with their own ArcView GIS systems can integrate their own data with those in the U.S. Oil and Gas Resource System and use the Avenue scripts and project (.apr) file. The underlying data were put in the public domain by the USGS for free. Coupled with ESRI's ArcView Data Publisher, ESA's project gives small companies and individual geologists and engineers economic access to the data and analytic power that was once reserved to only a dozen major oil companies.

Getting More Information

For more information, contact John Grace, Earth Science Associates, 201 East Abram St., Suite 750, Arlington, Texas 76010 (tel.: 817-469-8218, fax: 817-795-3562).