Abstract
The depletion of oil resources, increasing global energy demand, the current low, yet unpredictable, price of oil, and increasing maturity of major oil fields has driven the need for the development of oil recovery technologies that are less costly and, where possible, environmentally compatible. Using current technologies, between 20 and 40% of the original oil in a reservoir can be extracted by conventional production operations (e.g., vertical drilling), with secondary recovery methods yielding a further 15–25%. Hence, up to 55% of the original oil can remain unrecovered in a reservoir. Enhanced oil recovery (EOR) is a tertiary recovery process that involves application of different thermal, chemical, and microbial processes to recover an additional 7–15% of the original oil in place (OOIP) at an economically feasible production rate from poor-performing and depleted oil wells. EOR can significantly impact oil production, as increase in the recovery rate of oil by even a small margin could bring significant revenues without developing unconventional resources. Microbial enhanced oil recovery (MEOR) is an attractive, alternative oil recovery approach, which is claimed to potentially recover up to 50% of residual oil. The in situ production of biological surface-active compounds (e.g., biosurfactants) during the MEOR process does not require vast energy inputs and are not affected by global crude oil prices. Compared to other EOR methods, MEOR can be an economically and more environmentally friendly alternative. In this review, the current state of knowledge of MEOR, with insights from discussions with the industry and other stakeholders, is presented and in addition to the future outlook for this technology.
Highlights
Global energy demand and consumption are expected to grow as fast-growing economies, such as China, India, and Brazil, are expected to account for over half of the increase in energy demand
Gassara et al (2017) injected different concentrations of three carbon sources and nitrate into model upflow bioreactors to determine the effect of amount of carbon source on oil production
They established that to produce a significant amount of oil – up to 36% of residual oil in place – during incubation of nitrate-reducing bacteria Pseudomonas and Thauera, high concentrations of both the carbon source and nitrate were required – 17 mM of glucose/molasses or 57 mM acetate and 80 mM nitrate, respectively
Summary
Global energy demand and consumption are expected to grow as fast-growing economies, such as China, India, and Brazil, are expected to account for over half of the increase in energy demand. Microbial-Enhanced Oil Recovery to remain as the dominant sources of energy and accounting for more than three-quarters of total energy supplies in 2035 (BP, 2017). Global proved oil reserves (over 1.6 trillion barrels of oil) have more than doubled over the past 35 years; 67% of the total petroleum reserves in the world comprise the residual crude oil in reservoirs that is difficult to recover (Shibulal et al, 2014). Secondary recovery of oil can achieve a further 15–25%, leaving behind up to 55% unrecoverable residual oil in oil reservoirs (Shibulal et al, 2014). The current low, yet unpredictable, price of oil, the increasing maturity of major oil fields (e.g., the North Sea), and the decreased number of newly developed oil fields are drivers to the industry for maximizing the efficiency of oil recovery in the current petroleum industry
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