The goal is to develop a better understanding of reservoir character as it effects efficient utilization for gas storage.

University of Illinois – Project management and all research products
Peoples Energy Corporation – Well and reservoir data
First Data Services – Digitizing of well logs

The objective was to develop 3-D visualization models for two natural gas storage fields in the Mt. Simon Sandstone of the Illinois Basin, in order to characterize the formation and determine how to store and withdraw gas more efficiently.

• Prepared regional structure maps of the top of the Galena (Trenton) Group, the St. Peter Sandstone and the Mt. Simon Sandstone,
• Prepared a new regional salinity map of the Mt. Simon waters from northern and northwestern Illinois to the deeper parts of the Illinois Basin,
• Compiled digital well log and core data and prepared formation and internal Mt. Simon correlations, cross sections, structure and isopach maps for the Manlove Field,
• Determined the depositional environment, lithologic facies and mineralogy, and their relationship to porosity in the Manlove Field,
• Prepared cross-sections and interval slice maps to visualize the heterogeneity of the reservoir in the Manlove Field,
• Developed an alternative empirical method to estimate porosity due to the lack of modern wireline logs in the Herscher Field,
• Prepared 3-D visualization models for both fields

In northern Illinois, the Cambrian Mt. Simon Sandstone is used for natural gas storage by utilities. This project examined the Mt. Simon in the Manlove Gas Storage Field, Champaign County, Illinois, and the Herscher Gas Storage Field in Kankakee County, Illinois, in order to improve understanding the reservoir's character and geometry. The University of Illinois's Illinois State Geological Survey partnered with natural gas storage companies to carry out the project.

The 3-D porosity model of Manlove Field was well constrained by porosity and permeability measurements from 35 cores and calculated porosity values from modern FDC-CNL logs run in half of the 170 wells in the field. The resulting 3-D model indicated a heterogeneous reservoir with channel-confined, vertically discontinuous, high-porosity compartments.

Modeling of Herscher Field was less constrained, but still provided insight into reservoir compartments. Only six wells had reservoir core data and two wells had FDC-CNL logs at Herscher Field, while the remaining wells had only 1960s-era gamma ray-neutron logs, many of which were useless for neutron porosity determination. An alternative modeling approach was developed using a Vshale-porosity transform. This 3-D model indicated the presence of sand bodies with more lateral continuity than at Manlove Field, although vertical continuity remains fairly poor at both fields. Thus, although well-constrained models are preferable, models built with older, less-constrained data can provide improved understanding of the heterogeneous Mt. Simon reservoir's geometry and potential flow units.

Regional structure maps of the top of the Ordovician Galena Group (Trenton), the St. Peter Sandstone and the Mt. Simon Sandstone, developed for this project, delineate present and prospective locations for Mt. Simon gas storage reservoirs. A new regional salinity map of the Mt. Simon waters shows the transition from potable water in northern and northwestern Illinois to a brine-filled formation in the deeper parts of the Illinois Basin.

Methodologies used in this project can be applied to other natural gas storage reservoir characterization projects where data quality is an issue and also to potential use of these formations for carbon sequestration.

This project is complete and a final report is available from the Illinois State Geological Survey, online at http://www.isgs.illinois.edu/.

$180,000

$199,886

NETL – Thomas Mroz (thomas.mroz@netl.doe.gov or 304-285-4071)
University of Illinois – David G. Morse (morse@geoserv.isgs.uiuc.edu or 217-333-4747)

DOE Techline, November 1, 1999 - "3-D Modeling of Mt. Simon Gas Storage Fields Could Enhance Winter Gas Availability from the Illinois Basin"