Chapter 2 - Microbiology and Microbial Products for Enhanced Oil Recovery

Abstract

Microbial enhanced oil recovery (MEOR) is an attractive, alternative oil recovery approach that involves the use of indigenous or exogenous microorganisms to promote microbial by-product production that have the ability to benefit oil production. Therefore, the success of MEOR depends on the adequate understanding of the microbial community structure and the oil reservoir environments. Abundance and diversity of microbial communities in nature are determined by presence of nutrients (foods for microorganisms) and various environmental conditions, such as temperature, pressure, pH, salinity, and oxygen availability. Microbial habitats, the environment in which microbial communities thrive, can either be favorable for living for some species or be threatful to other species. In nature, microorganisms metabolite using resources from the ecosystem to keep generating new cells and to adapt to the environment; thereby, they also excrete by-products back to the environments. Therefore, microorganisms can even change the ecosystem depending on the resource availability and the environmental conditions for metabolism. Temperature, pH, salinity, and oxygen availability are the most influential factors for bacterial growth. Oil reservoirs are extreme environments for microbial life associated with high toxicity, high temperature, high salinity, and high pressure. This chapter describes the environment factors affecting growth and survival of microorganisms and explores diverse types of microorganisms that live in hydrocarbon reservoir environments. Then the representative bacterial species that produce microbial by-products for MEOR practices such as biosurfactants, biopolymers, extracellular polymeric substances (EPS), gas, solvents, and acids producing bacteria are introduced.