Abstract: A method is provided for locating non-aqueous phase liquid in an aquifer. An aqueous solution having the capacity to solubilize the contaminating liquid to concentrations greater than the solubility of the contaminant in water is injected and produced through a well. Chemical concentrations in produced fluid samples are interpreted to locate the contaminating liquid. Produced fluid samples are chemically analyzed to determine composition of the contaminant.

Abstract: A method for treating a formation having zones of varying permeabilities to improve the sweep efficiency of a drive fluid through the formation. At least one radial, relative horizontal bore is formed from a relative vertical wellbore and extends outward into a high-permeability zone of said formation. A gelant is injected into said formation through the radial bore(s) and flows into the higher-permeability zones of the formation. After the gelant is in place, the wellbore is shut-in to allow the gelant to set to form a flow-blocking gel in the treated zones of formation. Secondary recovery operations are then resumed and the drive fluid (e.g. water) will now flow through the previously unswept (i.e. less-permeable zones) of the formation.

Abstract: Disclosed are processes for treating a subterranean formation to improve the permeability distribution by reducing the permeability in high permeability zones, so fluids injected for oil recovery purposes will sweep more uniformly through the formation. The processes involve injecting a polymerizable compound, preferably a monomer or oligomer of furfuryl alcohol, together with a diluent, preferably an ester such as butyl acetate, and a suitable acid catalyst for the formation conditions, generally toluenesulfonic acid. The fluid may be injected in a liquid phase or mixed with steam or non-condensable gas to form an aerosol, which is injected then into the formation prior to the injection of the oil recovery fluid, which may be water, surfactant fluid, polymer fluid, or steam.

Abstract: A method for safely disposing of a waste gas from produced hydrocarbons. The waste gas is mixed with a surfactant to form a foam which, in turn, is placed within a disposal zone of a subterranean formation. The waste gas is effectively "trapped" within the foam thereby substantially reducing the mobility of the gas in the formation which, in turn, restricts the ability of the waste gas to readily flow out of the disposal zone and into the producing zone of the formation. The waste gas foam can be placed into the formation by coinjecting the surfactant and the waste gas or it can be formed in situ by first injecting the surfactant and then injecting the waste gas.

Abstract: A method and composition for controlling the profile of a formation where temperatures higher than 400.degree. F. are encountered. An aqueous solution of an organoammonium silicate, alkali metal or ammonium silicate is injected into a zone of higher permeability in a formation. Subsequently, a spacer volume of a water-immiscible organic solvent is directed into said zone. Afterwards, a water-miscible organic solvent containing an alkylpolysilicate and an inorganic salt or a chelated calcium compound are injected into the higher permeability zone. A silicate cement is formed in-situ thereby substantially closing the higher permeability zone to fluid flow. Thereafter, a steam-flooding, water-flooding, carbon dioxide-flooding, or fire-flooding EOR operation is commenced in a lower permeability zone.

Abstract: Water injection wells are fractured by a proppant-laden fracturing fluid to create a propped fracture and wherein the proppant-laden fluid is followed by injection of a substantially proppant-free fluid so that the near wellbore portion of the fracture is free of proppant to minimize pressure drop during water injection and to produce higher injection rates for a given injection pressure. The fracture treatment may include the use of viscous fracturing and displacement fluids which are degraded by the injection of acid-bearing fluids at the end of the fracture treatment cycle. Stimulation or displacement liquid (water) injection may commence immediately after the fracture treatment and may be alternated with miscible gas injection.

Abstract: Polymers (and especially hydroxyethylcellulose) are crosslinked using a lanthanide as a crosslinking agent. The crosslinked polymers have utility in well completion, well stimulation, enhanced oil recovery, and subterranean fluid containment operations.

Abstract: A variant strain of Agrobacter radiobacter has been found to produce a unique heteropolysaccharide containing D-galactose, D-glucose and pyruvic acid in approximate molar ratios of 2:15:2 in a seventeen member repeat unit having the structure shown below, wherein Glc represents D-glucose, Gal represents D-galactose and Pyr represents pyruvic acid, with the numerals indicating the positions of linkage in these ring structures. The heteropolysaccharide is useful in mobility control in oil reservoir formations, especially when crosslinked with trivalent metal cations (Cr.sup.3+, Al.sup.3+, Fe.sup.3+ or Ti.sup.3+) to form a gel which preferentially fills high permeability zones in such reservoirs.

Abstract: A method for the disposal of waste water in a formation having varying permeability zones therein where a higher permeability zone is first closed to fluid flow via a solidifiable gellable mixture. This mixture forms a solid gel in the higher permeability zone. Afterwards, waste water is injected into a zone of lesser permeability which allows increased amounts of water to be placed into the formation.

Abstract: A method for selectively closing an intermediate zone of a near wellbore area in a formation. Initially, a drillable mechanical packer is placed into the wellbore below the intermediate zone. The wellbore area adjacent to the intermediate zone is cooled to a critical temperature between about 130.degree. to about 180.degree. F. Subsequently, a novolac or resole-type phenolformaldehyde resin containing an acid catalyst is placed into the wellbore where it forms a solid platform over the packer and intermediate zone in about 2 hours. The critical temperature is maintained in the wellbore and intermediate zone while placing a second resinous material containing an alkaline catalyst into the wellbore and intermediate zone. Thereafter, the second material forms a steam resistant solid gel in the intermediate zone, thereby closing it.

Abstract: A method for forming a gravel pack in a washed-out interval is provided where a borehole penetrates an unconsolidated or loosely consolidated oil or gas reservoir which is likely to introduce substantial amounts of sand into the borehole. After perforating the borehole's casing at a washed-out interval of the formation, sand is introduced into the interval. Afterwards, an aqueous silicate solution is injected into said interval. Next, a spacer volume of a water-immiscible hydrocarbonaceous liquid is introduced into the interval. Thereafter, a water-miscible organic solvent containing an alkylpolysilicate is injected into the interval. A permeability retaining silica cement is formed in the interval thereby making a gravel pack. Injection of the aqueous silicate and organic solvent containing an alkylpolysilicate is continued until the interval has been consolidated by the silica cement to an extent sufficient to exclude sand and formation fines.

Abstract: A method for controlling the profile of a formation where temperatures higher than 200.degree. F. are encountered. Initially, an aqueous solution of an alkali metal hydroxide, ammonium hydroxide or organoammonium hydroxide is injected into a zone of greater permeability in a formation. Thereafter, a spacer volume of a water miscible organic solvent is injected into said zone. Afterwards, a water-miscible organic solvent containing an alkylpolysilicate is injected into the greater permeability zone. A silica cement is formed in-situ thereby substantially closing off the higher permeability zone to fluid flow. Thereafter, a steam-flooding, water-flooding, carbon dioxide stimulation or fire-flooding EOR operation is commenced in a lower permeability zone.

Abstract: A sand consolidating method is provided for use in a borehole within an unconsolidated or loosely consolidated oil or gas reservoir which is likely to introduce substantial amounts of sand into the borehole and cause caving. After perforating the borehole's casing at an interval of the formation where sand will be produced, an aqueous silicate solution is injected into said interval. Next, a spacer volume of a water-immiscible hydrocarbonaceous liquid is introduced into the interval. Thereafter, a water-miscible organic solvent containing an alkylpolysilicate and inorganic salt or chelated calcium is injected into the interval. A permeability retentive silicate cement is formed in the interval. Injection of the aqueous silicate and organic solvent is continued until the interval has been consolidated by the silicate cement to an extent sufficient to prevent sand migration and thereby prevent caving.

Abstract: A method and composition for controlling the profile of a formation where temperatures higher than 200.degree. F. are encountered. An aqueous solution of an organoammonium silicate, alkali metal or ammonium silicate is injected into a zone of higher permeability in a formation. Subsequently, a spacer volume of a water-immiscible organic solvent is directed into said zone. Afterwards, a water-miscible organic solvent containing an alkylpolysilicate is injected into the higher permeability zone. A silica cement is formed in-situ thereby substantially closing the higher permeability zone to fluid flow. Thereafter, a steam-flooding, water-flooding, carbon dioxide-flooding, or fire-flooding EOR operation is commenced in a lower permeability zone.

Abstract: Pathway-containing foamed gels enhance the recovery of the nonaqueous fluids from subterranean formations by selectively reducing the flow of aqueous fluids with respect to the flow of nonaqueous fluids.

Abstract: Disclosed are processes for treating a subterranean formation to improve the permeability distribution by reducing the permeability in high permeability zones, so fluids injected for oil recovery purposes will sweep more uniformly through the formation. The processes involve injecting a polymerizable compound, preferably a monomer or oligomer of furfuryl alcohol, together with a diluent, preferably an ester such as butyl acetate, and a suitable acid catalyst for the formation conditions, generally toluenesulfonic acid. The fluid may be injected in a liquid phase or mixed with steam or non-condensable gas to form an aerosol, which is injected then into the formation prior to the injection of the oil recovery fluid, which may be water, surfactant fluid, polymer fluid, or steam.

Abstract: A method for imparting selectivity to an in-situ gel-forming composition for placement within a subterranean oil-bearing formation having relatively high permeability zones and relatively low permeability zones, comprising the steps of: preparing an aqueous-based mixture, the mixture comprising: a first stage gel-forming composition in an amount effective to selectively enter the relatively high permeability zones of the formation, the first stage composition including a heteropolysaccharide prepared by growing Xanthomonas campestris NCIB 11854 in an aqueous nutrient medium by aerobic fermentation and recovering the heteropolysaccharide and a crosslinking agent for the heteropolysaccharide; and at least one second stage in-situ gel-forming composition comprising a water-dispersible polymer and a crosslinking agent for the water-dispersible polymer in an amount effective to form a stable gel; and gelling the first stage gel-forming composition ex-situ by reacting the Xanthomonas campestris NCIB 11854 heteropol

Abstract: Liquid composition for the production of a gel in a well drilled in the ground which is comprised of a hydrophilic polymer. Its liquid medium consists of an organic liquid at least partially miscible with water.

Abstract: Gels containing gas precursors and/or pathways are used to selectively reduce the flow of aqueous fluids with respect to the flow of nonaqueous fluids to enhance the recovery of the nonaqueous fluids from subterranean formations. The gels, while stable at reservoir conditions, are also readily degraded by gel degrading agents such as acids and therefore are also employed as fail-safe gels in subterranean gel treatments. In another embodiment, selective permeability is restored to a previously treated well by injecting a gas into the previous treated portions of the subterranean formation to displace any aqueous fluid obstructing the passage of the nonaqueous fluid through the polymer-coated pores or gel.

Abstract: A conformance improvement treatment process is provided for reducing the permeability of a higher-permeability zone in a subterranean hydrocarbon-bearing formation which is in fluid communication with a lower-permeability zone of the formation. The process includes preparing a gel precursor solution at the surface, injecting the solution into a wellbore penetrating the formation, placing the solution in the higher-permeability zone and gelling the solution therein. In situ gelation of the solution results in substantial permeability reduction to the higher-permeability zone. A specific gel precursor solution is utilized which contains a gelling agent and a polymer formed from at least two distinct monomers wherein the first monomer has a relatively faster, yet controlled, rate of hydrolysis and the second monomer has a relatively slower rate of hydrolysis. Gelation of the solution is delayed until a substantial number of carboxylate groups are formed in situ on the polymer.

Abstract: A gellable aqueous compositions able to reduce the permeability of high-permeability zones in an oil reservoir is a aqueous solution containing metered quantities of:a) a water-soluble organic polymer cross-linkable by the effect of a polyvalent metal ion cross-linking agent;b) a Cr(III) ion cross-linking agent; andc) a ligand for the cross-linking agent chosen from water-soluble organic alpha-hydroxy acids and alpha-amino acids.

Abstract: A method for controlling the permeability of a petroleum-bearing subterranean formation including the steps of producing from biomass, a water-insoluble viscous biomass oil, and injecting the biomass oil into the petroleum bearing formation to decrease the permeability of at least some of the formation for altering flow paths through the formation to increase petroleum yield.

Abstract: A foam is provided having utility for improving sweep efficiency in subterranean oil-bearing formations and having specific utility for conformance improvement treatments and mobility control in such formations. The foam is a gel medium having a gas dispersed therein. The gel medium is made up of a crosslinkable polymer, a crosslinking agent, a surfactant and a liquid solvent.

Abstract: Oil recovery method using polymer solutions in which highly permeable strata are made significantly less permeable while less permeable strata are not made significantly less permeable. This is accomplished by heating more permeable strata by injection of hot fluids, and then injection of a crosslinkable vinyl aromatic-conjugated diolefin polymer and a temperature activated crosslinking agent. A crosslinked gel is formed in the initially more permeable strata, permitting recovery of oil from the initially less permeable strata.

Abstract: A process for improved delivery of mobility control agents. The drive solvent is designed such that the plugging agent, e.g. surfactant or polymer, is soluble in the drive solvent under the injection conditions of temperature and pressure but is substantially insoluble under the conditions of temperature and pressure in the formation. Typically, miscible drive solvents have more favorable solvent properties at the low injection temperature than at the higher formation temperature. Preferably, solute solubility in miscible drive solvents is increased by the use of appropriate cosolvents. Cosolvent concentration is maintained below the amount needed for solute solubility at reservoir temperatures so that the solute will drop out of solution at some increased temperature depending on the concentration of the cosolvent added to the primary drive solvent.

Abstract: Improved methods of correcting the vertical permeability contrast of a subterranean formation to improve the sweep efficiency of waterflooding operations carried out therein wherein the subterranean formation contains at least one high permeability zone lying adjacent and in fluid communication with at least one low permeability zone are provided. In accordance with the methods, a near well bore portion of the high permeability zone is plugged and a crosslinked gel is formed at least at the boundary between the low permeability zone and the high permeability zone whereby fluid communication between the zones is reduced.

Abstract: Undesirable fluid flow is inhibited between a near well bore interval and an underlying aquifer in fluid communication therewith. A permeability-reducing material is injected into the near well bore interval and a portion of the material is selectively overdisplaced out into the formation by means of a low density gas subsequently injected into the interval. The gas desirably restores hydrocarbon productivity or fluid injectivity to the interval while the permeability-reducing material remaining in the interval inhibits fluid communication between the interval and the aquifer.

Abstract: An aqueous alkaline flood for recovering oil from a reservoir containing acidic oil is improved by adding to the injected aqueous alkaline solution both a stoichiometric excess of the alkaline material and a kind and amount of preformed cosurfactant material that increases the salinity of that solution so that, in contact with the oil in the reservoir, it will form a surfactant system having a salinity requirement which minimizes the interfacial tension between it and the oil.

Abstract: A surfactant composition, suitable for enhanced oil recovery comprising in a 60:40 to 10/90 weight ratio a) (o,m)- and/or (o,p)-dialkylbenzene alkali sulfonate and b) polyalkoxyphenyl ether alkali sulfonate.

Abstract: A stable aqueous gel is formed from a polyvinyl alcohol or vinyl alcohol copolymer and a partially methylated melamine-formaldehyde resin in the presence of a pH regulating agent which provides an initial acid pH during the formulation of the gel.

Abstract: A profile control method for closing off a more permeable zone of a formation where water, high fluid flow, or high perssures are encountered. A water-external emulsion containing a monomer, a cross-linker, free radical initiators and reaction inhibitors is injected into the formation. There they react to form plastic-like solid spheres in the more permeable formation zone. Because the spheres are not water soluble and have high compressive strength, they can be used in severe flow applications. Ethylene, propylene and styrene monomers can be utilized to form solid spheres of polyethylene, polypropylene or polystyrene.

Abstract: Alkaline earth metal scales, especially barium sulfate scale deposits are removed from oilfield pipe and other tubular goods with a scale-removing composition comprising an aqueous alkaline solution having a pH of about 8 to about 14, preferably about 11 to 13, of a polyaminopolycarboxylic acid, preferably EDTA or DTPA and a catalyst or synergist comprising thiosulfate or nitriloacetate anions. When the scale-removing solution is contacted with a surface containing a scale deposit, substantially more scale is dissolved at a faster rate than is possible without the synergist.

Abstract: A method of microbial enhanced oil recovery includes introducing, into an underground carbonate-containing rock formation that defines an anaerobic environment, denitrifying microorganisms, water, and a source of nitrate ion. The microorganisms reduce the nitrate and produce sulfuric acid which dissolves the rock formation, releasing oil. The microorganisms can be denitrifying Thiobacilli, such as T. denitrificans.

Abstract: A metal-containing oxidizing solution is injected through wellbores which reacts in a subterranean reservoir which has naturally-ocurring reduction capacity to form a slightly soluble compound of metal having a valence of +3. Thereafter, the metal crosslinks a water-soluble polymer which is injected into the metal-containing pore volume resulting in a decreased flow in the treated portion of the reservoir.

Abstract: An aqueous polymeric gel-forming composition of improved stability for selectively plugging highly permeable zones in subterranean oil-bearing formations. The composition comprises an aqueous solution of a water-dispersible polymer present in a viscosifying amount, a crosslinking agent present in an amount sufficient to cause gelation and a stabilizing agent in an amount effective to reduce syneresis of the gelled composition.

Abstract: A method for minimizing well recompletions in a multiple zone hydrocarbonaceous fluid containing formation. A steam flooding enhanced oil recovery (EOR) is conducted in the upper zone of said formation via fluidly communicating injector and producer wells which penetrate the upper and lower zones. The wells are unperforated and do not communicate with each other in the lower zone. Thereafter, a temperature activated gellable composition is injected into the upper zone where it forms a solid gel. Afterwards, both wells are perforated so as to fluidly communicate with each other in the lower productive interval. Subsequently, a steam-flooding EOR operation is conducted in the lower level and hydrocarbonaceous fluids are removed therefrom. Polymers utilized in the gellable composition include polyvinyl alcohol and polyacrylamide cross-linked with phenol and an aldehyde producing compound sufficient to form a phenolic resin in situ.

Abstract: A composition for use in enhanced oil recovery procedures comprises steam, carbon dioxide, carbonic acid, and a corrosion inhibitor. In one version of the invention, the corrosion inhibitor is a carbonate-containing buffering agent and in another version of the invention, the corrosion inhibitor is a pH-adjusting agent.

Abstract: A method for recovering viscous oil from a formation having a bottom water zone below an oil containing zone. Steam is directed into the bottom water zone thereby heating this zone and an oil containing zone thereabove. Afterwards, steam injection is ceased and a gellable composition is directed into the bottom water zone where it forms a solid gel. Once the solid gel has formed, steam is injected into the bottom water zone where the solid gel causes it to flow upwardly into the oil containing zone. Oil, water, and steam are removed via a recompleted producer well.

Abstract: A composition of matter wherein amino resins such as melamine formaldehyde ("MF") resins co-gel and crosslink with polymers useful for profile control where said polymers have amine, amide, hydroxyl and thiol functionalities. Resulting gels are useful as permeability control agents for high temperature reservoirs during a water-flooding operation.

Abstract: Water supply contamination is reduced within a formation or eliminated in a flooding procedure utilizing an alkaline aqueous solution. Biodegradable polymer provides a desired viscosity and mobility. Biodegradable surfactant and alkali provide any needed interfacial tension reduction. Additives, e.g., chelating agents, can be utilized for solubilization of insoluble contaminants.

Abstract: A nonflowing crosslinked polymer gel is employed as a well kill material in a process for preventing or minimizing the intrusion of formation fluid into a wellbore while preventing or minimizing wellbore fluid leakoff in the formation during conventional oil field wellbore operations in the wellbore. The gel comprises an a carboxylate-containing polymer and a chromic carboxylate crosslinking agent.

Abstract: A method and composition for altering the permeability of a high temperature subterranean formation are provided. The composition of the invention is comprised of water, at least one water dispersible acrylamide containing polymer, and a water dispersible crosslinker for bringing about the delayed crosslinking of the polymer comprised of the combination of an aldehyde and a salicylic acid derivative.

Abstract: A composition capable of selectively plugging highly permeable zones in a subterranean formation. The composition forms a gel subsequent to its injection into the formation via an injection wall. The composition comprises an aqueous solution of a welan gum heteropolysaccharide biopolymer produced by the fermentation of a microorganism of the genus Alcaligenes, a phenolic compound, an aldehyde and water. The compositions of this invention will form stable gels even in low salinity brines. Also provided is a process for selectively plugging regions of higher permeability within an oil-bearing subterranean formation to improve sweep efficiency during a fluid flood oil recovery process using the gel-forming compositions of this invention.

Abstract: A water-soluble graft copolymer of lignin-(2-propenamide)-(2-methyl-N7,N7-dimethyl-7-ammonium-3-oxo-4-oxyoct- 1-e ne chloride or methylsulfate) having a central lignin network and at least one grafted side chain, R, having randomly repeating units of the formula: ##STR1## such that the central lignin network has a molecular weight of about 1,000 to 150,000 and the total number of randomly repreating units in the grafted side chain or chains is in the range of 50 to 300,000 such that the total copolymer molecular weight is in the range of 15,000 to 30,000,000.

Abstract: A process is described to direct heat towards a productive interval of a reservoir during a thermal enhanced oil recovery (EOR) operation. A chemical composition suitable for producing a rigid polymer foam is injected above or below the productive interval. Once in place the temperature of the composition is increased and it reacts to produce a foamed polymer thermal barrier. The temperature can be increased by steam injection or in-situ combustion. After a rigid foam is formed, thermal efficiency is increased by reducing heat losses to non-producing zones during a thermal stimulation.

Abstract: An alkaline flooding oil recovery process is enhanced by injection of aqueous solutions of foam-forming surfactant and gases, or pre-formed foams, either ahead of or behind conventional alkaline slugs. In a preferred embodiment, a slug of an aqueous solution containing an alkaline agent followed by a driving fluid is injected into the formation that displaces oil through the relative high permeability zones of the formation and oil is recovered via the production well. Thereafter, a slug of an aqueous solution of a foam-forming surfactant is coinjected into the formation with a gas creating a foam when the gas mixes with the foam-forming surfactant in the aqueous solution. The foam created from the aqueous surfactant and gas will go preferentially into the formation zones of relatively high permeability and low oil saturation substantially plugging these zones.

Abstract: A method is disclosed for increasing the recovery of oil in enhanced oil recovery operations employing anionic surfactant by blending a taurine with said anionic surfactant. The taurine may also increase the salt and divalent ion tolerance of the anionic surfactant.

Abstract: A process for selectively plugging zones of high permeability within an oil-bearing subterranean formation. The process of the present invention comprises the steps of injecting into the formation a high temperature selective gel-forming composition comprising an aqueous solution of a high molecular weight polyacrylamide having 30 percent or less hydrolysis, and an effective amount of a crosslinking agent which is a mixture of a phenolic component and an aldehyde, and gelling the solution in-situ by thermally reacting said gel-forming composition at a temperature effective to promote gelation. The resultant gel is exceptionally thermally stable and, therefore, can be used as an effective profile control agent in all thermal enhanced oil recovery operations, including steam flooding. Also provided is a process for recovering oil from a subterranean oil-bearing formation.

Abstract: A process for use with a polymer which is crosslinkable by reaction with an amino resin, which comprises the steps of determining a period of time within which full gelation of the polymer is to be achieved; preparing a gel-forming aqueous-based mixture comprising the polymer, a rapid amino resin crosslinking agent and a delayed amino resin crosslinking agent, the gel-forming aqueous-based mixture capable of complete gelation within the period of time so determined; partially gelling the aqueous-based mixture by reacting the polymer with the rapid amino resin crosslinking agent which is effective to complete the partial gelation by crosslinking the polymer within four hours; and fully gelling the aqueous-based mixture by reacting the polymer with the delayed amino resin crosslinking agent which is effective to complete the full gelation by crosslinking the polymer within the period of time so determined. A method of enhancing the recovery of oil from a subterraean oil-bearing formation is also provided.

Abstract: A gel-forming composition capable of plugging highly permeable zones in a subterranean formation. The composition comprises water, a viscosifying amount of a water-dispersible polyvinyl amine copolymer and a crosslinking agent which is a mixture of an aldehyde and a phenolic component in an amount effective to cause gelation of the aqueous solution of the copolymer. The resultant gel is exceptionally thermally stable and, therefore, can be used as an effective profile control agent in all enhanced oil recovery operations, including steam flooding.