This is another article in a series reviewing Enhanced Oil Recovery (EOR) patents granted in approximately the last year.  In particular, the patents highlighted here relate to CO2 injection to improve oil recovery:

Carbon Dioxide injection has been used effectively for enhanced oil recovery from reservoirs, since at high pressures it forms a miscible mixture with oil, increasing the volume of the oil, and allowing it to dislodge additional material from the rock as it pushes through the formation.[1]  CO2 injection is often used in a process known as water alternated with gas (WAG), where the gas and water are alternately injected into the well, thereby mitigating the tendency of the lower density gas to migrate to the top of the reservoir and bypass other sections.[2]  Interest in CO2 injection continues, not simply in conventional oil reservoirs, but in unconventional reservoirs as well.[3]  Not surprisingly, aspects of CO2 injection find their way into patent claims.

Five patents are summarized below which illustrate the range of patented technologies in which CO2 is used.  The first relates to a type of swing gas use of CO2 involving a first CO2 stream and a second stream containing CO2 and a light hydrocarbon.  The second relates to CO2 recycle in EOR where purification of the recycled CO2 stream is avoided by adding a thickener.  The third again generally relates to a system for alternating CO2 and water injection, however, it directs the injections to different “lenses” of oil retained in varying levels of the reservoir.  The fourth relates to a method for an economic assessment of treating a residual oil zone with CO2.  The fifth relates to a CO2 foam and its use.  It contrasts with the swing gas injection method technique to prevent segregation.

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

U.S. Patent No. 10,024,149  has three independent claims (claims 1, 10 and 11), and generally relates to a method for enhanced oil recovery using CO2 injection.  The technique is an embodiment of the so-called composition swing injection method for reducing the viscosity and density differences between the injected phase and the reservoir fluid, for reducing reservoir segregation.  The claim requires injecting a first CO2-containing stream at or near its supercritical state, for a period of time, then injecting a second composition containing CO2 and a hydrocarbon, again, at or near its supercritical state for another period of time, extracting oil from the formation, and cycling between the injection steps.  The period of time for injection is preferably longer than a month.

U.S. Patent No. 10,030,483 has two independent claims (claims 1 and 7), and generally relates to CO2 recycling/recovery of a hydrocarbon enriched stream of condensed CO2 from an EOR well or fracturing well.  The technique avoids the added step of purifying the CO2 stream prior to recycle, and involves adding one or more particularly defined polymeric thickeners to the hydrocarbon enriched stream.

U.S. Patent No. 10,066,469 has two independent claims (1 and 5), and generally relates to a method for enhanced oil recovery where the oil resides in the reservoir within multiple “lenses” at various levels that extend between the injection well and the producing well.  The claim recites recovering oil (primary oil) from the producing well by injecting water into the injection well and then into a primary set of the lenses.  Then, carbon dioxide is injected into the injection well and then into a secondary set of the lenses to recover a first amount of secondary oil, where the secondary set of lenses is different than the primary set.  Water is introduced into the injection well so that a second amount of secondary oil is recovered from the producing well.  Recovering secondary oil with the injection of carbon dioxide and water is repeated.  In the next step, carbon dioxide is injected into the producing well and then into a tertiary set of lenses to recover a first amount of tertiary oil, where the tertiary set of lenses is different than the first and secondary set.  A second amount of tertiary oil is recovered from the injection well by injecting water into the producing well.  Finally, third and fourth amounts of tertiary oil are recovered by repeating the carbon dioxide injection into the tertiary set of lenses step and subsequent injection of water into the producing well.

U.S. Patent No. 10,087,720 has a single independent claim, (claim 1) and generally relates to a method for economic assessment of residual oil zones (ROZ).  The ROZ assessment using microbial self limitation (MSL) increases the footprint and locations into which CO2 can be injected.

U.S. Patent No. 10,214,680 has five independent claims (claims 1, 10, 13, 14, and 16) and generally relates to a foam of CO2 in a supercritical state, and its uses.  Such foams can be used as an alternative to the water alternating gas systems described above.  The foam has a non-liquid phase which is the CO2 in a supercritical state and a liquid dispersion phase containing polyelectolyte and surfactant in water with a surfactant/polyelectrolye ratio of 3:1 to 9:1.  The polyelectrolyte material forms nanoparticles by the electrostatic interaction of a cationic and an anionic polyelectrolyte, where the nanoparticles are located at lamellae of the liquid dispersion phase to stabilize the foam.  The polyelectrolyte is present in an amount of 0.1 to 5% by weight of the liquid phase.  From 60 to 90% of the total foam volume is occupied by the non-liquid state.

Table 1

EOR Patents  —  CO2 Injection 

Patent Number Inventor Assignee Title Issue Date
U.S. 10,024,149 Nazarian et al. STATOIL PETROLEUM AS Method For CO2 EOR And Storage And Use Thereof July 17, 2018
U.S. 10,030,483 Hancu et al. GENERAL ELECTRIC COMPANY Carbon Dioxide And Hydrocarbon Assisted Enhanced Oil Recovery July 24, 2018
U.S. 10,066,469 Graff et al. Inventors Multi-Directional Enhanced Oil Recovery (MEOR) Method September 4, 2018
U.S. 10,087,720 Vance ARCADIS CORPORATE SERVICES, INC. Method For Petroleum Recovery And Carbon Dioxide Sequestration In Residual Oil Zones October 2, 2018
U.S. 10,214,680 Ghahfarokhi The University of Kansas Stability Improvement Of CO2 Foam For Enhanced Oil Recovery Applications Using Polyelectrolytes And Polyelectrolyte Complex Nanoparticles February 26, 2019

Table 2.  —  Enhanced Oil Recovery  —  CO2 Injection

Patent Number Independent Claim
U.S. 10,024,149 Claim 1.  A method of Enhanced Oil Recovery (EOR) from paleo or residual oil zones in a subterranean geological formation; the method comprising: a first injecting step of injecting a first composition comprising CO2, the first composition being injected at or near its supercritical state, into the subterranean geological formation for a period of time; a second injecting step of injecting a second composition comprising CO2 and a hydrocarbon, the second composition being injected at or near its supercritical state, into the subterranean geological formation for a period of time, wherein the first composition and the second composition are different and have viscosity and density at the site of injection that are different; extracting oil from the subterranean geological formation; and cycling alternately between the first injecting step and the second injecting step.

 
U.S. 10,030,483 Claim 1.  A process for carbon dioxide recycling comprising: recovering a hydrocarbon enriched stream of condensed carbon dioxide from an enhanced oil recovery (EOR) well or a fracturing well; adding to said stream one or more thickeners; and directing the thickened stream to the EOR well or fracturing well for recycled usage in EOR, wherein a thickener of the one or more thickeners is a polymer comprising at least one functional group as follows:

 

 

 

wherein bonds indicated by a dotted line are absent; ring A is absent; X is C1-C8 alkyl; p is an integer from 2 to 6; R7 is independently, at each occurrence, hydrogen; R8 is independently, at each occurrence, R10; R10 comprises repeating units of structure IIB:

 

MaDbTcQd (IIB)

 

wherein M has the formula R13SiO1/2; D has the formula R2R3SiO2/2; T has the formula R4SiO3/2; Q has the formula SiO4/2; and wherein each of R1, R2, R3, and R4 is independently C1-C5 alkyl; and a=1-10, b=0-30, c=0-10; and d=0-10.

 

 
U.S. 10,087,720 Claim 1  A method of assessment, management and monitoring of the sequestration of carbon dioxide associated with CO2 enhanced oil recovery (EOR) operations by characterizing conditions within a residual oil zone (ROZ) to assess if it is a viable commercial CO2 EOR target, comprising; identifying and obtaining one or more samples of media from an ROZ; quantitatively and qualitatively evaluating how in situ microbial self limitation (MSL) conditions govern the microbial processing of petroleum in the one or more samples obtained from the ROZ by a process comprising; identifying specific microbial consortia and associated metabolic pathways within the one or more samples obtained from the ROZ, wherein identifying the specific microbial consortia and associated metabolic pathways within the one or more samples comprises identification by domain and species and by heterotrophic and autotrophic metabolic pathways; determining the effects of microbial processes of the microbial consortia on mineral species within one or more of the samples obtained from the ROZ; thereafter determining how in situ MSL conditions govern the microbial processing of petroleum by the microbial consortia in the one or more samples taken from the ROZ to effect biogenic mineral production of amorphous, nano-crystalline and chaotic mineral forms having enhanced reactivity towards CO2 by a process comprising: determining the activity of the indigenous or introduced microbial consortia to the presence of petroleum hydrocarbons based on selective degradation and modification of native hydrocarbons species in the one or more samples; determining whether the modification of the native hydrocarbon species generates charged or polar species that interact with mineral surface charges to stimulate adsorption of petroleum hydrocarbons to mineral surfaces within the one or more samples; determining the effect of biosurfactants on the one or more samples obtained from the ROZ; determining the capacity for stimulation of iron reduction by the microbial consortia within the one or more samples; determining the effect of sulfate reduction, methanogenic and labile elemental systems, and processes and effects of microbial inhibition that prevent the substantially complete degradation of petroleum in the one or more samples; and combinations thereof; determining the ability of the amorphous, nano-crystalline and chaotic mineral forms having enhanced reactivity towards CO2 that were effected by the processing of petroleum by the microbial consortia in the one or more samples taken from the ROZ to sequester and store at least some injected CO2; and, thereafter determining if the sampled ROZ can be economically developed using CO2 EOR techniques based in part on the determination of the effects of the microbial consortia on mineral species and the determination of how in situ MSL conditions govern the microbial processing of petroleum by the microbial consortia to effect biogenic mineral production of amorphous, nano-crystalline and chaotic mineral forms having enhanced reactivity towards CO2 within one or more of the samples obtained from the ROZ, wherein if it is determined that the ROZ can be economically developed using CO2 EOR techniques, thereafter injecting CO2 into the ROZ and monitoring the sequestration of injected CO2 associated with the CO2 EOR operation.
U.S. 10,214,680 Claim 1  In a foam including a non-liquid fluid phase and a liquid dispersion phase, the improvement comprising: the foam having a foam quality ranging from 60% to 90% determined as a percentage total foam volume occupied by the non-liquid fluid phase; the liquid dispersion phase being a dispersion of polyelectrolyte material and surfactant in water, the polyelectrolyte material and the surfactant being combined in a ratio of surfactant to polyelectrolyte material ranging from 3:1 to 9:1; the polyelectrolyte material forming nanoparticles by electrostatic interaction of a cationic and an anionic polyelectrolyte, the nanoparticles being located at lamellae of the liquid dispersion phase in an effective amount to stabilize the foam; the polyelectrolyte material being present in an amount ranging from 0.1% to 5% of the liquid phase by weight; and the non-liquid fluid phase being CO2 in a supercritical state.

 

 

[1] Raymond, M. et al. (2006). Oil and Gas Production in Nontechnical Language, Tulsa, OK: PennWell Corporation, p. 185.

[2] Id. at 186.

[3] Kokai, Sunil (2019). CO2. Journal Of Petroleum Technology, 71(7), p. 68.  This edition of JPT also contains several articles describing such CO2 injection work: Carpenter, Chris Laboratory Investigation Targets EOR Techniques for Organic-Rich Shales, pp 69-71; Carpenter, Chris Gas Injection Evaluated for EOR in Organic-Rich Shale, pp 72-73; and Feder, Judy, The Feasibility of CO2 Injection for IOR in Shale Reservoirs, pp 74-75.

-William Reid

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