*CO2 Foam as an Improved Fracturing Fluid System for Unconventional Reservoir DOI: http://dx.doi.org/10.5772/intechopen.84564*

 height of the pay zone. In addition to the aforementioned factors, chemical usage in the fracturing process is also adjusted depending on its environmental impacts and economics. On the other hand, there are several constraints associated with shale hydraulic fracturing processes that include usage of high volume of water, aquifer contamination, and methane infiltration in aquifers.

In general, fracturing fluid is composed of 99.5% of water and sand proppant, and 0.5% of chemical additives [17]. Potential additives for enhancing the performance of fracturing fluid include surfactant, friction reducers, biocides, and scale inhibitors [18]. In order to optimize fracture treatment for improving overall recovery efficiency, reservoir characterization is essential as specific treatment is required depending on the rock and fluid properties. Besides hydraulic fracturing, other techniques such as explosive fracturing and dynamic loading that do not utilize water-based fluid have been taken into consideration [19]. Nonetheless, these aforementioned techniques are not extensively implemented due to their performance and environmental concerns.
