During the past two decades, the oil and gas industry in North America has been successfully evolved into the era of commercially developing unconventional oil and gas plays. In this talk, “unconventional reservoirs” mainly refers to shale gas, tight gas, and tight oil reservoirs. Currently, about three quarters of the natural gas production and more than one third of the total petroleum liquids produced in the U.S. were contributed by unconventional reservoirs. These numbers are predicted to keep increasing in the next few decades. Meanwhile, great success in North America enables unconventional resources to gain more and more attention in other countries, e.g., China and Argentina. Nonetheless, the estimated ultimate recovery (EUR) of unconventional reservoirs is very low, i.e., less than 10% for tight oil and less than 30% for shale gas. The fractured horizontal wells generally decline to 10-20% of their initial production rates in 1-2 years, leaving neither the hydrocarbon recovery nor the investment utilization maximized. Therefore, in the past few years, some traditional and new improved oil recovery (IOR) and enhanced oil recovery (EOR) methods have been studied worldwide. In this talk, we will discuss the following topics: (a) Unconventional Petroleum Resources; (b) Fluid Storage, Flow and Simulation Approaches; and (c) IOR/EOR Practice.