Addressing Geologic and Geophysical Uncertainties in Developing a CO2 Sequestration Site
Characterization of the target reservoir is an intrinsic part of all geologic CO2 sequestration site evaluations. Prior to drilling an injection well, a reservoir characterization study has inherent uncertainties that may not be obvious in the initial evaluation of a site. A saline reservoir sequestration project at Decatur, Illinois, funded by the U. S. Dept. of Energy, is used as a case study of the underlying uncertainty of the geological and geophysical data used to define the target reservoir, the Cambrian Mt. Simon Sandstone. The nearest well penetrating the Mt. Simon is 17 miles to the southeast, and this well penetrated only the top 400 feet of the formation that may be over 1,500 feet thick. Seismic reflection data are difficult to acquire and are of reduced quality due to noise from nearby industrial plants. The lack of close proximity to well control increases the uncertainty of the geological interpretation.
The Decatur sequestration site is located in an urban setting with adjacent industrial, residential, and educational properties. Acquisition of geologic and geophysical data is more difficult and costly in such an urban setting. FEP analysis (Features, Events, and Processes) is used to develop a workflow for the acquisition and interpretation of data. Numerical flow simulation of different subsurface reservoir models is used to address the consequences of data uncertainty. Determination of risk management priorities must include a quantitative and qualitative approach to understanding uncertainties in site characterization data.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009