This is an article in a series reviewing Enhanced Oil Recovery (EOR) patents granted in approximately the last year.  In particular, the patents highlighted here relate to fluids injected into the well to improve oil recovery: specifically, co-solvent systems and systems containing multicarboxylates.

Primary oil recovery from a well relates to the recovery of oil from its reservoir using the differential pressure between the reservoir and the wellbore.  Secondary recovery normally denotes the injection of water or gas into the well to maintain its pressure.  Together, these account for only about 20-40% of the oil originally contained in the reservoir.  Enhanced oil recovery techniques (tertiary recovery) can boost the total recovery to about 40-60% through a variety of techniques selected based on the morphology of the reservoir, the physical and chemical nature of its rock and contained fluids, and the characteristics of the available water supply.  One such technique is chemical injection, which can be very effective, however, it requires an assessment of the interaction between the injected chemicals, the fluids in the reservoir and the water used in recovery.

Four patents are summarized below.  Three are related and assigned to the University of Texas.  They are directed to systems especially designed to deal with situations where the available water supply is hard, which can cause problems due to the resultant precipitation of calcium or magnesium-containing materials.  The fourth patent relates to the use of multicarboxylate compositions in oil recovery.  As the document notes, alkylaryl carboxylates are known as surfactants in oil recovery.

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

U.S. Patent No. 10,106,725 contains a single independent claim (claim 1), and generally relates to a process for displacing material from a reservoir using a non-surfactant aqueous composition, where the composition contains a particularly defined light co-solvent (see Table 2); a water soluble polymer such as polyacrylamide, 2-acrylamido 2-methyl propane sulfonate, N-vinyl pyrrolidone, xanthan gum, scleroglucan or polyethylene oxide; and an alkali agent such as sodium carbonate and metaborate.  The method excludes adding a surfactant to the aqueous composition.

U.S. Patent No. 10,167,421 has a single independent claim (claim 1), and generally relates to a process for converting the petroleum acids contained in a reservoir into a surfactant using an aqueous composition.  The composition contains water; an anionic surfactant such as an alkoxy sulfate, alkoxy carboxylate, an olefin sulfonate, an alkyl benzene sulfonate, an alkyl sulfonate or an aryl sulfonate; an alkali agent such as sodium, potassium, ammonium or lithium hydroxide, sodium carbonate, bicarbonate, metaborate, silicate or orthosilicate; and a particularly defined co-solvent (see Table 2).  The alkali in the aqueous composition reacts with the acid, thus forming a soap (surfactant) in situ.

U.S. Patent No. 10,190,035 has four independent claims (1, 11, 14, and 24), and generally relates to an aqueous composition containing water; one or more anionic surfactants that are not alcohol phosphate surfactants or phosphate alkyl ester surfactants; an alkali agent such as such as sodium, potassium, ammonium or lithium hydroxide, sodium carbonate, bicarbonate, metaborate, silicate or orthosilicate; and a particularly defined co-solvent (see Table 2).  Independent claims are also directed to emulsions containing a petroleum phase and an aqueous phase containing the aqueous composition; and a process for displacing petroleum material using the aqueous composition.

U.S. Patent No. 10,233,382 has two independent claims (claims 1 and 7) generally relates to an additive composition for oil recovery operations containing a particularly defined multicarboxylate (see Table 2); a polymer such as xanthan gum, scleroglucan, water soluble unhydrolyzed or partially hydrolyzed polyacrylamides, hydrophobically-modified associative polymers, co-polymers of polyacrylamide, 2-acrylamido 2-methylpropane sulfonic acid and its sodium salt, and N-vinyl pyrrolidone; a Group IA alkali metal; and a lower carbon chain alcohol co-solvent.  Independent claims are also directed to a process for enhancing oil recovery where the composition is injected into a reservoir

 

Table 1: EOR Patents  —  Co-Solvent & Multicarboxylate Systems

 

Patent Number Inventor Assignee Title Issue Date
U.S. 10,106,725 Weerassoriya et al. Board of Regents, The University of Texas System Light Co-Solvent Compositions October 23, 2018
U.S. 10,167,421 Weerasooriya et al. Board of Regents, The University of Texas System Phenol-Alkoxylate Co-Solvent Surfactant Composition January 1, 2019
U.S. 10,190,035 Weerasooriya et al. Board of Regents, The University of Texas System Phenol-Alkoxylate Co-Solvent Surfactant Composition January 29, 2019
U.S. 10,233,382 Shong et al. Chevron U.S.A. Inc. Method Of Using Multicarboxylate Compositions In Enhanced Oil Recovery March 19, 2019

 

Table 2.  —  Enhanced Oil Recovery  —  Co-Solvent & Multicarboxylate Systems

Patent Number Independent Claim
U.S. 10,106,725 Claim 1. A method of displacing an unrefined active petroleum material in contact with a solid material, the method comprising: (i) injecting a non-surfactant aqueous composition into a petroleum reservoir to form a mixture, wherein the non-surfactant aqueous composition comprises a light co-solvent, a water-soluble polymer, and an alkali agent, wherein the light co-solvent is defined by the formula: wherein R1A is unsubstituted C1-C6 alkylene, unsubstituted phenylene, unsubstituted cyclohexylene, unsubstituted cyclopentylene, or methyl-substituted cyclopentylene; R2A is independently for each occurrence hydrogen, methyl, or ethyl; R3A is hydrogen or R4A is independently for each occurrence hydrogen, methyl, or ethyl; n is an integer from 1 to 30; and m is an integer from 0 to 3; wherein R3A together with R1A include six or less carbon atoms, wherein the alkali agent is selected from sodium carbonate, sodium metaborate, and combinations thereof and is present in an amount of from 0.6 to 4.5 wt %, based on the weight of the non-surfactant composition, and wherein the unrefined active petroleum material is in contact with a solid material; (ii) allowing the unrefined active petroleum material to separate from the solid material thereby displacing the unrefined active petroleum material in contact with the solid material, and (iii) recovering the unrefined active petroleum material, and wherein the method does not include adding a surfactant to the aqueous composition.
U.S. 10,167,421 1. A method of converting an unrefined petroleum acid into a surfactant, the method comprising: (i) contacting a petroleum material with an aqueous composition comprising water, an anionic surfactant, an alkali agent, and a co-solvent having the formula wherein R1 is independently hydrogen or unsubstituted C1-C4 alkyl; R2 is independently hydrogen or unsubstituted C1-C2 alkyl; and n is an integer from 1 to 30, thereby forming an emulsion in contact with the petroleum material; wherein the co-solvent is present in an amount of from 0.25% to 3% by weight, based on the weight of the aqueous composition, wherein the aqueous composition has a salinity of at least 5,000 ppm and a pH of from 9.5 to 12, and wherein the anionic surfactant consists essentially of one or more anionic surfactants that are not alcohol phosphate surfactants or phosphate alkyl ester surfactants, and (ii) allowing the unrefined petroleum acid within an unrefined petroleum material to enter into the emulsion, thereby converting the unrefined petroleum acid into the surfactant.
U.S. 10,190,035 Claim 1.  An aqueous composition comprising water, an anionic surfactant, an alkali agent, and a co-solvent having the formula: wherein R1 is independently hydrogen or unsubstituted C1-C4 alkyl; R2 is independently hydrogen or unsubstituted C1-C2 alkyl; and n is an integer from 1 to 30, wherein the aqueous composition has a salinity of at least 5,000 ppm and a pH of from 9.5 to 12, wherein the co-solvent is present in an amount of from 0.25% to 3% by weight, based on the weight of the aqueous composition, and wherein the anionic surfactant consists essentially of one or more anionic surfactants that are not alcohol phosphate surfactants or phosphate alkyl ester surfactants.
U.S. 10,233,382 Claim 1  An aqueous stream for injecting into a subterranean reservoir for enhanced oil recovery applications, the aqueous stream having a composition comprising: a) 0.01-20% by weight of an additive compound comprising the chemical formula: R1–R2–R3, wherein: R1 comprises a branched or unbranched, saturated or unsaturated, cyclic or non-cyclic, hydrophobic carbon chain having 7-150 carbon atoms and an oxygen atom linking R1 and R2; R2 comprises an alkoxylated chain comprising at least one oxide group selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide, and combinations thereof wherein R2 is selected from the group

consisting of –(BO)m–(PO)n-(EO)o–, –(BO)p–(PO)q–(BO)r-(EO)s–, and –(BO)t-(EO)u–, wherein m through u≠0, m+n+o=8-190, p+q+r+s=8-190, and t+u=8-190; and R3 consists of a branched or unbranched hydrocarbon chain comprising 2-12 carbon atoms and 2-5 –COOH or 2-5 –COOM groups wherein M is a monovalent, divalent, or trivalent cation; b) 250 to 5000 ppm of a polymer selected from the group consisting of xanthan gum, scleroglucan, water soluble unhydrolyzed or partially hydrolyzed polyacrylamides, hydrophobically-modified associative polymers, co-polymers of polyacrylamide, 2-acrylamido 2-methylpropane sulfonic acid and its sodium salt, and N-vinyl pyrrolidone; c) 0.3 to 20 weight percent of a basic salt of a Group IA alkali metal; and d) 0.5 to about 6.0 weight percent of a lower carbon chain alcohol co-solvent.

-William Reid

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