Application of a Microbial Selective-Plugging Process at the North Burbank Unit: Prepilot Tests

Abstract

Summary Microbial enhanced-oil-recovery (MEOR) nutrients were injected in an injection well at North Burbank unit (NBU) in Oklahoma to plug off high-permeability layers through the growth of indigenous microorganisms and to divert injection fluid to lower-permeability, higher-oil-saturation zones. Several different types of treatments were performed using both sequential and co-injection of nutrients. Pressure falloff/injection tests and vertical injection profiles were conducted before and after nutrient injection. The results of pressure injection tests following co-injection of nutrients and an incubation period indicated a 33% drop in the effective permeability to the injection fluid and a negative skin factor, while injection profile surveys showed a 33% reduction in the zone taking water. Swabbed samples from the injector following shut in revealed abundant bacterial concentrations and products as well as oil and inorganic solids. Although significant in-depth permeability reduction was observed following nutrient co-injection tests, the unstable behavior of the plug suggested that insufficient biomass was being formed to effectively seal off the higher-permeability zones. Introduction The NBU located in Osage County, OK has been the target of numerous enhanced-oil-recovery (EOR) efforts over the past 25 years. It is estimated of the 671 MMbbl of original oil in place (OOIP), over 300 MMbbl of oil remain. In 1980, a freshwater polymer flood was initiated in a 1,440 acre section of NBU, and this project accounted for an additional 2.5 MM STB of oil over that attributable to waterflooding alone. However, declining oil prices and the costs associated with procuring fresh water have made the further expansion of freshwater polymer flooding in NBU only marginally attractive. For these reasons, Phillips Petroleum Co. began to look to MEOR as an alternative method to chemical EOR for increasing oil production at NBU. MEOR has several potential advantages over chemical EOR. Microbial processes can use inexpensive feedstocks (e.g., molasses) and convert them to products, such as solvents, surfactants, acids, polymers, and gases, that have potential for increasing oil recovery. Microbial processes can be applied in situ so that products are produced in the reservoir, avoiding some of the problems of product retention by the reservoir rock. Also, MEOR processes are environmentally friendly because they use only biodegradable chemicals and nonpathogenic microorganisms.

Recent Advances in Petroleum Microbiology

“…Nutrient-stimulated microbial growth produced a 33% drop in the effective permeability in an injection well at North Burbank Unit in Oklahoma, plugging off high-perme- (287). In contrast to the poor experience with exogenous organisms for bioremediation (bioaugmentation), injection of selected microbial species into oil field plots in Japan and China resulted in improved oil recoveries of 15 to 23% (248,680).…”

Microbial Enhanced Oil Recovery

“…Likewise, several reports discussing in-situ uses of MEOR in field trials with analysis of the results are published elsewhere (Portwood, 1995;Clark et al, 1981;Dennis, 1998;Kleppe, 2001;Youssef et al, 2007). For example, in an MEOR field trial in the Southeast Vassar Vertz Sand Unit saltcontaining reservoir in Oklahoma, nutrient injection motivated the growth of the indigenous microbial populations, which reduced the effective permeability by 33% (Jenneman et al, 1996). A biosurfactant flooding process using a very low concentration of biosurfactant, which was produced by the Bacillus mojavensis strain JF-2, was reported to be very effective in recovering residual oil from Berea sandstone cores (Bailey et al, 2001).…”

Investigation of spore forming bacterial flooding for enhanced oil recovery in a North Sea chalk Reservoir

“…Injection of nutrients/and or bacteria into these preferential pathways and stimulation of the bacterial growth in situ will block the water channels, either with bacterial cells or polymers produced in situ by the growing bacteria. Blocking of these channels will alter the water pathways to the previously unswept pore space (Crescente et al, 2005;Jenneman et al, 1996;Li et al, 2012;Nagase et al, 2002;Yakimov et al, 1997). This concept is known as microbial selective plugging as illustrated in Fig.…”