Modular approach has penetrated oil and gas industry in various ways. In this chapter, we examine five topics of importance for oil industry. First, we examine how modular approach has improved oil well performance. Modular approach has also streamlined offshore oil well construction and thereby reduced its cost and construction time. Modular approach has also been used in heavy oil recovery and refining processes. Modular refineries have gained more prominence. Finally, modular approach has also been used for waste oil cleaning and upgrading processes. For each topic, specific examples of successful modular systems are outlined.