 |
 |
 |
 |
 |
 |
Why did I learn about relative permeability in school?
The predicament is that sometimes fracture stimulation, as a remedial solution, does not necessarily guarantee a highly productive well again. Numerous studies have
been
done on just about every gas sand in North America which demonstrate that
gas sands with mid-high clay content are often seriously impacted when they
make contact with fresh water drilling and completion fluids because the
clays swell. Clay swelling can fill or plug the pore throats of the porosity
and permeability channels and create restrictions, which cause irreversible
damage to the reservoir. Many times we make considerable effort to keep water-based fluids away from gas sands that are high in clay content, but give no consideration to the potential damage that oil-based fluids may cause on those same gas sands. While oil-based fluids may not cause clays to swell, they can cause irreversible damage to a gas reservoir by simply altering the relative permeability characteristics if the fluid is allowed to penetrate very deeply into the gas reservoir. Changing the relative permeability characteristics of the reservoir may be as significant a culprit to damaging our gas reservoirs as using water-based fluids.
Relative permeability is when more than one fluid occupies the pore space in reservoir rock, and the fluids compete for the ability to flow. Permeability is affected by interfacial tension that exists between two immiscible fluids, and the wettability of the formation. While that is a very academic description, the bottom line is that if you introduce oil or water during the drilling or completion phase of operations into a reservoir whose relative permeability is favorable to gas, you may irreversibly alter the relative permeability characteristics of the reservoir.
If you use your mapping software to identify relative permeability and clay swelling problems, you will be surprised at the number of mistakes operators have made over the years. If you are unsure how to drill or complete a gas zone in an area, compare completion types and performance with log and reservoir analysis to determine if any anomalies exist that might indicate relative permeability and/or clay swelling problems before you start pumping fluid in the ground. These comparisons can easily be done with industry mapping software in a matter of minutes. Finally, these comparisons can help you identify opportunities for acquisition and drilling prospects.
Back to November 2003 Newsletter
| CEC Energy Consultants Home | Newsletter | News Release | Services | Credentials | Contact | Download | Site Map | ||
| Copyright © 2004-2008 CEC Energy Consultants | ||
| updated 01.06.08 | website design by tevadesign.com | ||