*Exploitation of Unconventional Oil and Gas Resources - Hydraulic Fracturing...*

consumption [1]. Most growth is found in the consumption of renewable energy and natural gas. However, energy from the renewable and sustainable resources cannot compete with the nonrenewable and cheap fossil fuel energy in technical and economic aspects. Therefore, unconventional reservoir is considered as an immediate alternative for overcoming the production decline of the conventional reservoirs. These unconventional reservoirs originally come in different forms which include shale gas and oil, tight gas and oil, coal bed methane (CBM), shale oil, and natural gas hydrates as shown in **Figure 1(a)** [2]. The illustration of global gas resources including the general features and the worldwide endowment for each resource is presented in **Figure 1(b)**. Endowment is the sum of undiscovered gas, reserves, and the cumulative gas production. The endowment for the natural gas as shown in **Figure 1(b)** is about 68,000 trillion cubic feet (Tcf) and 70% of it is approximately in shale gas and tight gas reservoir [2].
