Personally, would avoid the term “extrapolation” here big time. As Jeff explains your prediction on where any geological parameters are thought to be reasonably similar (where the risk is common (I like the term CRS – but let’s not go there)) should be guided by data & observations and models & analogues. The boundaries between CR segments should be informed by your GDE maps which are products of interpretation and geological insight.
“Extrapolation” takes you dangerously into the world of geostats and variograms. Rather the try to be over quantitative on the “CoS” that you ascribe to any one segment – the important conversation is around what is required to make a business decision and what data can be acquired or studies performed to give you more confidence in being able to inform that decision.