These documents present the means by which theoretical maximum storage resource can be refined by mathematically considering the real-world characteristics of a geologic formation (e.g., formation dimensions and porosity distribution, etc.) that limit its storage resource, thereby allowing evaluators to develop more accurate storage resource/capacity estimates.
At the heart of the matter is the fact that only a fraction of the pore space within any given geological formation will be available or amenable to CO2 storage. The purpose of a storage coefficient is to assign a value to that fraction of a given formation in which CO2 can be effectively stored.
The concept is derived and applied in much the same way that the concept of sweep efficiency has been for secondary and tertiary enhanced oil recovery operations.