cat is outta the bag, page-4

sorry for length ,but this is all I have found so far---Liquid carbon dioxide holds potential for use in Marcellus Shale development. The carbon dioxide can be pumped in as a liquid and will vaporize as a gas. The carbon dioxide is mixed with a proppant, usually sand. The carbon dioxide can transport smaller volumes of sand than can water, and it requires a closed system blender to mix together. This type of mixture can be used in less permeable, lower pressure dry gas formations. In the northern half of Pennsylvania, the Marcellus shale is slightly geopressured while the southern half is underpressured. Generally speaking, all Marcellus shale in the state has low permeability. The western part of the state contains wet gas formations while central and eastern Pennsylvania contains dry gas formations. The initial cost of using liquid carbon dioxide is higher than using water due to the higher cost of carbon dioxide. The benefit is that it causes no formation damage, and well cleanup is faster and more economical. One potential problem is that carbon dioxide is less viscous than water and much less viscous than water when gels are added. This lack of viscosity causes the gas to stray from the fracture into the surrounding rock, reducing its ability to transport proppant.

Additional concerns would need to be addressed when implementing carbon dioxide as a fracking medium. When the liquid carbon dioxide returns from the well, it is vaporized into carbon dioxide gas. The gas needs to be captured and stored in order to prevent it being released into the atmosphere. It can be stored underground in deep, non-permeable geologic formations. In Canada, carbon dioxide plants can liquefy carbon dioxide from naturally produced gas streams and be used in hydraulic fracturing. These type of plants are very expensive, approximately $35 million to build. A major problem with using carbon dioxide is the current lack of infrastructure to currently transport the carbon dioxide from production to consumption area. The carbon dioxide can be transported in by truck but with the rising cost of fuel and logistics, it may not be a viable option.

"the institute for energy and inviromental research" (wilks ) pensilvania