Microbiologically influenced corrosion (MIC) is a major problem that impacts crude oil production transportation and storage infrastructures. Indigenous microorganisms that naturally reside in oil reservoirs are able to induce localized changes in the aqueous environment and lead to catastrophic damages. The study herein applies molecular techniques to investigate the microbial communities associated with corrosion products collected from crude oil pipelines. Small subunit ribosomal rRNA gene pyrosequencing was used to identify microbial communities present in each system. The results indicated that that the microbial communities in the corrosion products obtained from both the sour oil pipeline and sweet crude pipeline were dominated by bacteria though archaeal sequences (predominately Methanobacteriaceae and Methanomicrobiaceae) were also identified in the sweet and sour crude oil samples respectively. The dominant bacterial phylotypes in the sour crude sample include members of the Thermoanaerobacterales Synergistales and Syntrophobacterales. In the sweet crude sample the dominant phylotypes include members of Halothiobacillaceae. Interestingly common bacterial phylotypes that are related to Thermotogaceae were identified in all investigated samples. The impacts of these microorganisms in MIC are presented in this paper. This work will increase the knowledge related to the complex microbial diversity associated with crude oil systems and guide future MIC research.