This is an article in a series reviewing 2016 patents focused on Enhanced Oil Recovery (EOR). In particular, this article relates to the technology area of Microbial Enhanced Oil Recovery (MEOR), which concerns the use of microbes to extract oil from oil-containing formations, and Enzyme Enhanced Oil Recovery (EEOR) which similarly concerns the use of enzymes.

MEOR generally involves injecting microbes and nutrients into a well followed by closure of the well for a period of time to allow the microbes to do their work. The microbes are designed to produce various gases, organic acids, solvents, polymers and surfactants. Typical microbes include Bacillus, Clostridium, Pseudomonas, Eurobacterium, Fusobacterium, Bacteroides, Leuconostoc mesenteroides, Desulfovibrio, Mycobacterium, and Peptococcus. Typical nutrients include materials such as molasses, corn syrup, and sucrose. MEOR increases well production in a number of ways. The production of gas and biomass by the microbes displaces oil, pushing it toward the surface. The surfactants and polymers lower the surface interfacial tension between the oil and the rock/water surface, which causes emulsification and a more comprehensive oil/water split. The solvent, acids and surfactants remove heavy long chain hydrocarbons from the pores of the formation to enhance permeability.

In EEOR, the enzyme cleaves carbon bonds to produce a lower carbon-number product with lower viscosity that flows more easily. It is different than MEOR in that the enzyme is nonliving, and does not require a pretreatment of the reservoir with a nutrient fluid.

Review of patents issued in 2016 in the MEOR/EEOR areas indicate that research efforts are ongoing, at least of the type for which patent protection is sought, and is generally comparable in number and scope to those issued in 2015. Three patents issued in 2016. One of these patents (U.S. 9,238,842), is directed to a method for detecting the genus of Bacillus in samples from oil reservoirs. Another patent, (U.S. 9,290,688) relates to water-flooding an oil reservoir with an alkaline fluid or a fluid containing a compound toxic to indigenous microbes, and then inoculating the reservoir with microbes that are alkaliphilic, halo-alkaliphilic or alkaline tolerant. A third patent, (U.S. 9,528,358) relates to an EOR system having an enzyme storage equipped with temperature control capability. This compares to last year’s patents, where a total of five issued; with one of the patents being directed to particular types of microbe systems, two of the patents being directed to the microbe-containing injection fluid, one patent being directed to an MEOR process for wells that have undergone a CHOPS process, and a final patent directed to a process for delivering oxygen to the microbes in the well bore. Thus, the pace of development in this area appears stable.

Attached Table 1 lists relevant information on the MEOR/EEOR patents reviewed. Table 2 contains a representative independent claim from each.

U.S. Patent No. 9.238,842 generally relates to a quick process for detecting microbe Bacillus in samples from oil reservoirs. The specification points out that Bacillus is a potential microbial group for MEOR, but that current methods for detection of this particular bacteria are not sufficient. The ‘842 Patent has a single independent claim, and a total of 6. The ‘842’s method for detecting Bacillus includes collecting a sample from the oil reservoir, inactivating the microbes with high temperature, collecting spores from the inactivated sample, incubating the collected spores and stimulating to resurrect the Bacillus, and then detecting the resurrected Bacillus using molecular biological techniques, where the procedures are particularly specified.

U.S. Patent No. 9,290,688 generally relates to a process to maximize oil recovery by combining an MEOR process with alkaline flooding. Alkaline flooding takes advantage of acid compounds naturally found in some petroleum streams. The alkaline chemicals react with the acid compounds, also referred to as naphthenic acid, of the crude petroleum oil to form in situ surfactants on the surface of the oil. MEOR dislodges micro-trapped oil from the rock. The patent contains a single independent claim and 26 total claims. The process includes water-flooding an oil reservoir with an alkaline fluid or a fluid containing a compound toxic to indigenous microbes, to reduce the concentration of microbes that have the ability to utilize short chain hydrocarbons of 12 carbons or less. The oil reservoir is then inoculated with microbes that are alkaliphilic, halo-alkaliphilic or alkaline tolerant to utilize hydrocarbons of 12 carbons or less. The microbes then proliferate and degrade the hydrocarbons under alkaline conditions to obtain enhanced oil recovery.

U.S. Patent No. 9,528,358 generally relates to an enhanced oil recovery system using enzymes, where the enzymes are stored using a temperature control system. The advantage of such a system is that the enzyme is most effective within a certain temperature range, and depending on the location of the oil reservoir, temperature control could be useful. The patent contains a total of 22 claims with 2 independent claims, directed to an enhanced oil recovery system and a method for operating an underground oil reservoir. The recovery system includes an injection well that is connected to an underground oil reservoir, an enzyme storage equipped with a temperature controller, and an injector for creating an injection stream containing enzymes from the enzyme storage unit to the underground oil reservoir through the injection well.

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Table 1 EOR Patents - MEOR/EEOR

Patent Number Inventor Assignee Title Issue Date
U.S. 9,238,842 Zhang et al. China University of Geosciences Method For Detecting The Genus Of Bacillus In Samples From Oil Reservoirs January 19, 2016
U.S. 9,290,688 Kohr et al. GEO Fossil Fuels, LLC Alkaline Microbial Enhanced Oil Recovery March 22, 2016
U.S. 9,528,358 Soren Frank Maersk Olie og Gas A/S Enhanced Oil Recovery System And A Method For Operating An Underground Oil Reservoir December 27, 2016

Table 2 Enhanced Oil Recovery — MEOR/EEOR

Patent Number Independent Claim
U.S. 9,238,842 Claim 1. A quick method for detecting the genus Bacillus in samples from oil reservoirs, which comprises: (a) collecting a sample from an oil reservoir; (b) inactivating microbes through high temperature; (c) collecting spores from the inactivated sample; (d) incubating the collected spores in an appropriate medium, and stimulating to resurrect the Bacillus under the in situ temperature of the oil reservoir; and (e) detecting the resurrected Bacillus in the cultures using molecular biological techniques, wherein said step of inactivating microbes through high temperature comprises transferring 500 ml of the sample into a sterile flask in a sterile condition, sealing the flask with a sterile ventilate membrane, and placing the flask on an electric heater and boiling the sample for 10 minutes, then cooling the sample at room temperature, wherein said step of collecting spores from the inactivated sample comprises, after the cooling step, transferring the inactivated sample into 50 ml sterile centrifuge tubes in a sterile condition and centrifuging at 10,000xg for 15 minutes to produce a supernatant and a pellet, transferring the supernatant to a sterile container for medium preparation, resuspending the pellet with 1 ml sterile water, and combining the suspension from all the centrifuge tubes into a 10 ml mixture, the mixture containing spores, wherein said medium is compatible with the environment from which the sample was collected, and can provide nutrients for stimulating spores, the medium prepared by solving 2 g molasses, 0.16 g (NH4)2HPO4, 0.2 g KNO2 and the supernatant from the collecting step to obtain a 100 ml solution, followed by adding 2 g crude oil from the reservoir from which the sample was collected to the 100 ml solution, and autoclaving at 121°C. for 20 minutes.
U.S. 9,290,688 Claim 1. A method of enhancing oil recovery comprising (a) water-flooding an oil reservoir with an alkaline fluid or a fluid containing a compound toxic to indigenous microbes to reduce the concentration of microbes that have the ability to utilize short chain hydrocarbons of about 12 carbons or less, (b) inoculating said oil reservoir with a consortium comprising microbes that naturally are, or are engineered to be, obligatory alkaliphilic, halo-alkaliphilic or alkaline tolerant and naturally are, or are engineered to be, deficient in their ability to utilize short chain hydrocarbons of 12 carbons or less but have the ability to convert hydrocarbons into fatty acids, (c) allowing the consortium to proliferate and degrade hydrocarbons of greater than 12 carbons, and (d) obtaining enhanced oil recovery from the oil reservoir, wherein step (c) is performed under alkaline conditions.
U.S. 9,528,358 Claim 1. An enhanced oil recovery system, comprising an underground oil reservoir comprising oil having an oil temperature, an injection well in fluid communication with said underground oil reservoir, an enzyme storage comprising a temperature controller, wherein said temperature controller is adapted for controlling the temperature of enzymes in said enzyme storage in relation to an operative temperature range of said enzymes, and an injector for creating an injection stream comprising enzymes from said enzyme storage to said underground oil reservoir through said injection well.