Evaluation Techniques for Identifying Underdeveloped Areas
An approach combining the strengths of GIS software, spatial analysis, waterflood analysis, and petrophysical analysis is being used to group reservoirs within representative formations in the Illinois Basin into play portfolios. The digitization and integration of several data sources maintained at the ISGS have resulted in the development of new evaluation techniques for the identification of pay zone trends and potential underdeveloped areas. These techniques have generated new maps and data models.
Color-Coded Pay Maps
The ISGS produces a series of Oil and Gas Development Maps showing current well status, derived from information contained in basic well data files stored in the Oracle database. The basic well data files contain information for over 180,000 wells in Illinois and include fields for location, status, operator, formation tops, and API identification number. The Development Map series covers the entire oil producing region of Illinois. Producing formation data for approximately 83,000 wells have been updated and integrated with the well data files. The producing formation data can now be displayed on the Oil and Gas Development Maps, resulting in a series of color-coded pay maps. An obvious application of this technology is the capability it creates to visually recognize reservoir trends and geometries within individual formations and the potential of projecting these characteristics into under- and undeveloped areas for possible development. Digitizing these maps has enabled faster data updates and greater analytical flexibility by permitting separation and layering of each pay zone. Digitzing also has increased the array of data delivery options.
Historic Injection Wells
A basic well data file contains a substantial amount of information relevant to the exploration and development of reservoirs in the Illinois Basin. Records that identify historical injection wells no longer classified as such on Oil and Gas Development Maps, because their status has changed, are useful in the identification of UDAs. Mapping all injection wells, historic and current, on a single base identifies possible underdeveloped and resource-depleted areas.
The ISGS has collected data regarding injected and produced fluids from over 2,000 waterflood units in Illinois. Waterflood boundaries delineating acreage of the waterflood projects and fluid volumetric data are often available. Volumetric analysis using these data can be used to determine the efficiency and extent to which reservoir compartments have been drained. Therefore, this is a technique for evaluating potential UDAs. These types of analyses are commonly used to compare similar reservoirs to determine possible future reservoir performance and economic potential.
Grouping reservoirs with similar petrophysical characteristics is accomplished by extracting and analyzing porosity and permeability data from the ISGS core analysis database, which contains about 30,000 wells. Permeability and porosity cross-plots for core-defined flow units in the Aux Vases Sandstone, Cypress Sandstone, and Ste. Genevieve Limestone are used to establish unique petrophysical flow units for each of these formations. Identifying flow units and mapping their locations and thicknesses will aid in the grouping of reservoirs that exhibit similar characteristics into play portfolios.
Updated 12/10/2009 SLD