A Review on Microbial Enhanced Oil Recovery With Special Reference to Marginal/Uneconomical Reserves

Abstract

Abstract Oil and natural gas are vital for any economy and the importance of these resources in determining the social stability and economic viability of a nation is enormous. As the search for petroleum continues, recovery of known reserves must be improved if the goal of avoiding shortages is to be met. In today's energy sector, the high oil prices have driven the oil companies to recover the maximum amount of oil with the lowest production costs. Thus, economic production of oil and gas resources requires carefully engineered recovery projects of increasing technical complexity and sophistication. One of the promising recovery methods is the microbiological enhanced oil recovery (MEOR). MEOR technology has the potential to be one of the reliable technologies that suits best the economic constraints of the current oil markets. The technology is a potential alternative to other EOR/ IOR methods, as it is being implementing in most parts of the world with satisfactory results not only form economics point of view but also from having lesser environmental impact. The paper provides a review on MEOR technology and discusses it with special reference to marginal and/or uneconomical reserves. The goal of cost reduction, which is a major objective in any recovery methods, can be met by using MEOR technology which involves injecting a small amount of a solution containing microorganisms to spread through the reservoir and consequently produce desirable chemicals and gases that will enhance oil recovery and therefore profit. The paper also outlines the strategies to identify and meet the challenge of recovering large proportions of oil using MEOR techniques which could be very helpful in closing the energy gap by draining large proportions of oil which is left behind and minimizing the supply and demand difference in today's "energy hungry world". Introduction Typically much of the oil remains in the reservoir after conventional recovery methods. To produce the remaining oil different improved and enhanced oil recovery methods are used. One of the major factors in the selection of any recovery method is the economic potential of the remaining reserves. In the past, much of the oil was left behind in the reservoir especially in the marginal and mature reserves due to the absence of a cost effective method. But, in today's energy sector where oil prices are at their highest level ever reached, the development of marginal and/or uneconomical reserves cannot only brings such reserves to production but could also help the operators to get maximum profit from these reserves. One of the recovery methods which have the vast potential of bringing such reserves to production is the Microbial Enhanced Oil Recovery. It is an enhanced and/or improved oil recovery method in which different microorganisms and their products are used to enhance the production and/or recovery from a reservoir. It is a chemical enhanced oil recovery method but with chemicals generated in situ. It has been a main topic of interest and research for last few years. A few years back when the oil prices were not as high as today, the use of other recovery methods in small fields was a question whether they should be applied or the field should be abandoned as their economic limits were approached in that low oil price regime. So, MEOR processes which have long been expected to offer a low-cost approach for improving oil recovery once again become the area of interest for the oil industry. The concept of using microorganism to recover oil is not new and the idea of using them and their products as an oil recovery method was first suggested by Beckman 1 in 1926 when he analyzed the action of bacteria on mineral oil and proposed that bacterial enzymes could be used in oil recovery. Later on in 1947, ZoBell conducted a series of field tests and discovered that bacteria can release oil from sedimentary materials. From those tests ZoBell found that the mechanism by which bacterial oil release could occur areproduction of gaseous CO2production of organic acids and detergentsdissolution of carbonates in the rockphysical dislodgement of the oil 4,5