Abstract: This invention is directed to a composition comprising expandable cross linked polymeric microparticles having an unexpanded volume average particle size diameter of from about 0.05 to about 10 microns and a cross linking agent content of from about 9,000 to about 200,000 ppm of labile cross linkers and from 0 to about 300 ppm of non-labile cross linkers and to the use of the composition for modifying the permeability of subterranean formations and increasing the mobilization and/or recovery rate of hydrocarbon fluids present in the formations.

Abstract: A water-soluble branched polyhydroxyetheramine, wherein the branched polyhydroxyetheramine is prepared by reacting an amine having two reactive hydrogen atoms with a diepoxide to form a polyhydroxyetheramine and then reacting the polyhydroxyetheramine with an N-alkylating agent, an aqueous composition comprising the branched polyhydroxyetheramine and use of the branched polyhydroxyetheramine to modify the permeability to water of a subterranean formation are disclosed.

Abstract: A method for controlling the rheology of aqueous systems, particularly for those intended for underground use, includes injecting an aqueous viscoelastic fluid containing a surfactant gelling agent into the system. The viscoelastic surfactant composition of the invention comprises, as a gelling agent, at least one fatty aliphatic amidoamine oxide in a glycol solvent. The composition also maintains the levels of free fatty acid and free amine within critical parameters in order to achieve superior performance. The additives may be incorporated in the viscoelastic fluid to tailor its use in stimulation fluids, drilling muds, fracture fluids, and in applications such as permeability modification, gravel packing, cementing, and the like.

Abstract: For extracting a liquid (such as oil) from a porous medium, the liquid is subjected to pulses that propagate through the liquid flowing through the pores of the medium. The pulses cause momentary surges in the velocity of the liquid, which keeps the pores open. The pulses can be generated in the production well, or in a separate excitation well. If the pulses travel with the liquid, the velocity of travel of the liquid through the pores can be increased. The solid matrix is kept stationary, and the pulses move through the liquid. The pulses in the liquid can be generated directly in the liquid, or indirectly in the liquid via a localised area of the solid matrix.

Abstract: Selectively cross-linked starches are disclosed that are useful as fluid loss control additives in subterranean treatment fluids comprising starches that cross-linked to a Brabender peak viscosity of about 800 to about 1250 Brabender units after about 40 to about 70 minutes at about 92° C. and provide good fluid loss control over a temperature range of from about 20° C. to about 160° C. (68° F. to 320° F.).

Abstract: A process for the selective and controlled reduction of permeability to water in oil-bearing formations made up of sandstone or limestone, the process comprising the injection of a slug of polymer aqueous solutions having a polarity opposite to the polarity of the rock, followed by the injection of a spacing slug of alkaline halide and then a fresh slug of polymer aqueous solution, the polarity of which is opposite to the polarity of the first polymer slug, and then a slug of aqueous solution of trivalent metal crosslinking agent to effect the partial crosslinking of the polymer charges, the polymer layers being successively added until the injection pressure of the polymer aqueous solutions show that the desired Residual Resistance Factor RRF was attained, and well production may be resumed.

Abstract: This invention is directed to a composition comprising expandable cross linked polymeric microparticles having an unexpanded volume average particle size diameter of from about 0.05 to about 10 microns and a cross linking agent content of from about 9,000 to about 200,000 ppm of labile cross linkers and from 0 to about 300 ppm of non-labile cross linkers and to the use of the composition for modifying the permeability of subterranean formations and increasing the mobilization and/or recovery rate of hydrocarbon fluids present in the formations.

Abstract: A foam drive method for enhancing oil recovery efficiently is initiated by injecting into a subterranean oil-bearing formation, an aqueous polymer solution as a preceding-slug. This is followed by periodically injecting simultaneously or alternately a non-condensible gas and an aqueous solution of foaming composition to form a combined foam under ground or periodically injecting the combined foam formed beforehand by the gas and said aqueous solution above ground. The aqueous solution of foaming composition comprises an alkali, a surfactant and a polymer. Thereafter, an aqueous polymer solution used as a protecting-slug is injected into the formation; followed by continuing water-flooding.

Abstract: A wellbore method which, in certain aspects, includes providing with a primary system a fluid with microorganisms, the primary system including introduction apparatus, with the introduction apparatus introducing the fluid with microorganisms into an earth formation bearing hydrocarbons, the microorganisms for facilitating removal of the hyrdrocarbons from the earth formation bearing hydrocarbons, effecting heat exchange between the fluid with microorganisms and heat transfer fluid that has traversed an earth loop of an earth loop heat exchange system, the earth loop heat exchange system with an earth loop extending from an earth surface down into the earth with the heat transfer fluid flowable through the earth loop and heat transfer apparatus for transferring heat between the fluid with the microorganisms and the heat transfer fluid; and, in certain asepcts wherein effecting the heat exchange between said fluid with microorganisms and the heat transfer fluid prolongs life of and/or enhances activity of the m

Abstract: For extracting a liquid (such as oil) from a porous medium, the liquid is subjected to pulses that propagate through the liquid flowing through the pores of the medium. The pulses cause momentary surges in the velocity of the liquid, which keeps the pores open. The pulses can be generated in the production well, or in a separate excitation well. If the pulses travel with the liquid, the velocity of travel of the liquid through the pores can be increased. The solid matrix is kept stationary, and the pulses move through the liquid. The pulses in the liquid can be generated directly in the liquid, or indirectly in the liquid via a localized area of the solid matrix.

Abstract: A method of precipitating or depositing material within an underground reservoir which comprises introducing into the reservoir in aqueous solution (i) an isolated enzyme and (ii) a substrate for the enzyme, such that the action of the enzyme on the substrate leads to the precipitation or deposition of material within the underground reservoir.

Abstract: Improved methods of treating water and hydrocarbons producing subterranean formations to reduce the water permeabilities of the formations without substantially reducing the hydrocarbons permeabilities thereof are provided. The methods basically comprise introducing into the formation a chemical which does not resist water flow and attaches to adsorption sites on surfaces within the porosity of the formation but slowly washes off the sites as another fluid flows through the treated formation. Thereafter, a water flow resisting polymer is introduced into the formation so that it flows deeply into the porosity of the formation before the previously introduced chemical washes off and attaches to the adsorption sites as the chemical washes off.

Abstract: The remediation treatment creates environmentally neutral species from hydrocarbon contaminants. For soils having a low porosity, fissures are created in the site by, for example, fluid, i.e., hydraulic or pneumatic, fracturing. A catalyst is injected into the site and is permitted to diffuse through the site. An oxidizing agent is then introduced into the site to release a free radical in a Fenton-type reaction. The compounds react to release a free radical, which acts upon the contaminants to form environmentally neutral species. Diffusion of both compounds is aided by turbulence induced in the groundwater. A pH-adjusting compound is added to optimize reaction conditions. Reaction vapors are collected above ground, filtered, and vented to the atmosphere, reducing the chance for gas pressure buildup and possibly dangerous, potentially explosive conditions.

Abstract: A process is disclosed for stimulating the activity of microbial consortia in a subterranean formation to convert hydrocarbons to methane, which can be produced. Fluid and rock of the formation are analyzed. The presence of microbial consortia is determined and a characterization made (preferably genetic) of at least one microorganism of the consortia, at least one being a methanogenic microorganism. The characterization is compared with at least one known characterization derived from a known microorganism having one or more known physiological and ecological characteristics. This information, together with the information obtained from the analysis of the fluid and rock, is used to determine an ecological environment that promotes in situ microbial degradation of formation hydrocarbons and promotes microbial generation of methane by at least one methanogenic microorganism of the consortia. This information is then used as the basis for modifying the formation environment to produce methane.

Abstract: The present invention is related to an aqueous composition of at least one hydrophobically associating polymer and at least one surfactant, the mixture's viscosity being substantially constant or increased over temperatures ranging from about 20° C. to about 100° C. In another embodiment, the invention is related to a method for recovering oil from a subterranean reservoir by injecting into the reservoir a mixture of at least 100 to 25,000 ppm of a hydrophobically associating polymer per million parts by weight of water, about 25 to about 7,500 parts by weight per million parts by weight of water of one or more surfactants; and from about 0.5 wt. % to about 10 wt. %, based on the weight of water, of salts selected from the group consisting of alkali and alkaline earth metal halides and mixtures thereof.

Abstract: A proactive conformance method for a well includes selecting a well either in a completion phase or early in a production phase of the well and performing a conformance treatment on the well in the completion phase or early in the production phase. The conformance treatment preferably is performed before the well is completed (i.e., sometime during the completion phase between the well having been drilled and the well being placed in production), such as after running open hole logging or before setting casing. Another preferred aspect is the use of magnetic resonance imaging, such as using magnetic resonance imaging to analyze the well to determine where unwanted mobile fluid is in a reservoir intersected by the well. Such a well is completed in response to using the magnetic resonance imaging, including treating the well to confine at least part of the unwanted mobile fluid determined to be in the reservoir.

Abstract: The invention relates to processes for treating acidic crudes or fractions thereof to reduce or eliminate their acidity by addition of effective amounts of crosslinked polymeric amines having a pKa of greater than 9 such as polyvinyl amine and anionic exchange resins having amino groups. The process has utility for crude processing.

Abstract: A method for strengthening a subterranean formation by injecting an aqueous gellable composition containing a cross-linkable polymer into the subterranean formation through a wellbore to increase the strength of the subterranean formation while retaining the ability of the subterranean formation to produce fluids.

Abstract: A CO2-foamable gelling composition and use of said composition for conformance control operations are described The gelling fluid comprises a decomposing agent to counteract the detrimental effect of CO2 on the gelling process.

Abstract: For extracting a liquid (such as oil) from a porous medium, the liquid is subjected to pulses that propagate through the liquid flowing through the pores of the medium. The pulses cause momentary surges in the velocity of the liquid, which keeps the pores open. The pulses can be generated in the production well, or in a separate excitation well. If the pulses travel with the liquid, the velocity of travel of the liquid through the pores can be increased. The solid matrix is kept stationary, and the pulses move through the liquid. The pulses in the liquid can be generated directly in the liquid, or indirectly in the liquid via a localised area of the solid matrix.

Abstract: A method for controlling the rheology of aqueous systems, particularly for those intended for underground use, includes injecting an aqueous fluid containing a surfactant gelling agent into the system. The surfactant gelling agents are, for example, fatty aliphatic amidoamine oxides, salts of an alkoxylated monoamine with an aromatic dicarboxylic acid, and salts of an alkyldiamine with an aromatic dicarboxylic acid. The surfactant gelling agents can be adsorbed onto particulate supports to facilitate delivery of the gelling agent. The additives may be incorporated in the viscoelastic fluid to tailor its use in hydraulic fluids, drilling muds, fracture fluids, and in applications such as permeability modification, gravel packing, cementing, and the like.

Abstract: An encapsulated breaker slurry composition for reducing the viscosity of a fracturing fluid. The slurry has a flashpoint above 93° C., and the liquid of the slurry does not facilitate release of the breaker from the coating. Methods of using the slurry composition are also described.

Abstract: The remediation treatment creates environmentally neutral species from hydrocarbon contaminants. A catalyst is injected into the site and is permitted to diffuse through the site. An oxidizing agent is then introduced into the site to release a free radical in a Fenton-type reaction. The compounds react to release a free radical, which acts upon the contaminants to form environmentally neutral species. Diffusion of both compounds is aided by turbulence induced in the groundwater. A pH-adjusting compound is added to optimize reaction conditions. Reaction vapors are collected above ground, filtered, and vented to the atmosphere, reducing the chance for gas pressure buildup and possibly dangerous, potentially explosive conditions.

Abstract: A method of making surfactants from lignin is disclosed by reducing lignin in the presence of a metal oxide or iron based catalyst in an organic hydrogen donor solvent to produce lignin phenol and subjecting the lignin phenol to one or a combination of several reactions such as alkoxylation, alkylation, sulfonation, sulfation, alkoxysulfation, and sulfomethylation. The lignin surfactants so produced can be employed in a surfactant system to recover oil from underground formations.

Abstract: Methods and compositions for reducing the permeabilities of subterranean zones are provided. The methods of the invention are basically comprised of introducing an aqueous composition comprised of a chelated organic gelling agent and a copolymer of an ethylenically unsaturated polar monomer and an ethylenically unsaturated ester or a terpolymer or tetrapolymer of an ethylenically unsaturated polar monomer, an ethylenically unsaturated ester and a monomer selected from AMPS® and/or N-vinylpyrrolidone into the zone and then allowing the aqueous composition to form a cross-linked gel in the zone.

Abstract: A process is provided for reducing the permeability of or fluid mobility within a carbonate-containing treatment region in or proximate to a hydrocarbon-bearing formation below an earthen surface penetrated by a well bore. The process is initiated by preparing a gelation solution at the earthen surface which includes an acrylamide polymer, a crosslinking agent, a stabilizing agent and an aqueous solvent. The stabilizing agent is an acid additive, acidic pH buffer system, or delayed acid generator. The crosslinking agent is a chromium(III) complex having one or more chromium(III) cations and one or more carboxylate anions. The gelation solution is injected into the well bore and displaced into the treatment region where it is gelled in situ to form a gel which substantially reduces the permeability of or fluid mobility within the treatment region.

Abstract: A method for reducing the permeability of a region of an underground formation by injecting a gelant solution that forms a stable gel into the region is disclosed. The gelant solution includes an aqueous solvent, about 2% to about 16% by weight of a lignosulfonate-acrylic acid graft copolymer and a sufficient concentration of a crosslinking agent to crosslink the copolymer. The lignosulfonate-acrylic acid copolymer used in the invention has an acrylic acid content of about 10% to about 50% by weight and the crosslinking agent is a complex of one or more positively charged chromium (III) species and one or more negatively charged carboxylate species. Preferably, the chromium (III) species used in the invention has a concentration of about 0.1% to about 8.0% by weight. In one preferred embodiment, the carboxylate species of the crosslinker may be selected from formate, acetate, propionate, lactate, oxalate and malonate.

Abstract: This invention is a process for improving the rheological properties of oil well drilling fluids particularly useful for oil-based invert emulsion types of drilling fluids. The process is particularly useful when drilling in deep water from an off-shore drilling rig. The new process uses as a rheological viscosifier, for such fluids, a composition which is a mixture of organoclays and castor wax and/or castor was type rheological additives, which when added to a drilling fluid at from about 0.5 and 5% by weight, creates an inventive drilling fluid compositions less sensitive to the variety of different and varying, very hot and very cold temperatures found in the drilling hole, and in the long stem of drilling pipe. The present invention also relates to the discovery of oil based invert emulsion drilling fluids that exhibit greater efficiency and provides more stable drilling fluid viscosity and anti-settling performance over varying temperatures when compared to conventional fluids containing organoclays.

Abstract: A method for strengthening a subterranean formation by injecting an aqueous gellable composition containing a cross-inkable polymer into the subterranean formation through a wellbore to increase the strength of the subterranean formation while retaining the ability of the subterranean formation to produce fluids.

Abstract: A wellbore service fluid comprising polymers having cross-linking groups capable of forming chemical bonds with other polymers without additional monomeric cross-linking agents is described, and related methods, particularly applicable to water control operations.

Abstract: The invention relates to processes for treating acidic crudes or fractions thereof to reduce or eliminate their acidity by addition of effective amounts of crosslinked polymeric amines. The process has utility for crude processing.

Abstract: The disclosed invention provides a method for recovering hydrocarbons from a subterranean formation by injecting an emulsion, comprising oil and water, into the formation. More specifically, the emulsion is stabilized using undissolved solid particles, which are preferably at least partially oleophilic. The solids-stabilized emulsion may be used either as a drive fluid for displacing hydrocarbons from the formation or to produce a barrier for diverting flow of fluids in the formation. Such solid particles may be either formation solid particles (i.e., indigenous to the formation) or nonformation solid particles (i.e., obtained from outside the formation). Nonformation solid particles may either be naturally occurring or synthetic. Some preferred solids include clays, quartz, feldspar, gypsum, coal dust, asphaltenes, and polymers.

Abstract: A method for improving the a real sweep efficiency of a waterflood process is described. Reservoir heterogeneity results in the waterflood being diverted to the thief zones, bypassing much of the in-place hydrocarbon fluids. Existing remedial options are sensitive to water chemistry and temperature and are mostly effective near the wellbore. The unique advantages of this process is that it is insensitive to the water phase, in-depth in its placement, and can be triggered by pressure change which no other existing process offers.

Abstract: The remediation treatment creates environmentally neutral species from hydrocarbon contaminants. A catalyst is injected into the site and is permitted to diffuse through the site. An oxidizing agent is then introduced into the site to release a free radical in a Fenton-type reaction. The compounds react to release a free radical, which acts upon the contaminants to form environmentally neutral species. Diffusion of both compounds is aided by turbulence induced in the groundwater. Reaction vapors are collected above ground, filtered, and vented to the atmosphere.

Abstract: The present invention relates to improved methods and compositions for performing well completion or remedial procedures in subterranean zones having temperatures below about 70.degree. F. or above about 170.degree. F. The methods basically include the steps of introducing into the zone an aqueous solution of a polymerizable monomer, a polymerization initiator and a low temperature polymerization activator or a high temperature polymerization inhibitor. Thereafter, the polymerizable monomer is allowed to polymerize in the zone.

Abstract: A process for mitigating the effects of gas migration through channels in a cement sheath in a hydrocarbon production well by injecting a mixture of a carrier fluid with a dissolved polmer into the sheath and dropping the polymer out of solution to form polymers to plug the channels. The process utilizes the phase transition parameters of the mixture coupled with well conditions and/or injection parameters to cause the polymer to drop out of solution within the gas migration channels. The mixture can be injected through well perforations in the producing zone or perforations made in the wellbore adjacent the gas migration zone or directly into the cement sheath at the wellhead.

Abstract: A water-soluble polymer and a process for using the polymer for applications in a subterranean formation are provided. The polymer comprises repeat units derived from a nitrogen-containing olefinic monomer and optionally an olefinic comonomer. The polymer can be used in drilling fluids, workover fluids, completion fluids, permeability corrections, water or gas coning prevention, fluid loss prevention, matrix acidizing, fracture acidizing, and combinations of any two or more thereof.

Abstract: Thermosetting compositions with improved latency are obtained by addition of a molten aromatic polyamine type curing agent to a liquid epoxy resin followed by cooling the mixture, causing the curing agent to form a suspension of fine particles in the epoxy resin by recrystallisation thereof. The compositions obtained can be used for the manufacture of prepregs with high latency for their use in processes requiring intermediate steps at 80.degree. C. over several hours.

Abstract: A method for consolidating unconsolidated mineral particles in a subterranean petroleum formation penetrated by a well in fluid communication with at least a portion of the formation, including:a) introducing an effective amount of preflush into the formation sufficient to invade substantially all of the pore spaces of a portion of the formation to be consolidated, said preflush including an ester, and an oligomer or monomer of the compound from which the resin to be used in the consolidation is obtained, an ester, and an effective amount of a coupling agent;b) introducing a sand consolidating fluid into substantially the same portion of the formation as the preflush fluid, the sand consolidating fluid containing a polymerizable compound, a diluent for the polymerizable compound and an acid catalyst capable of causing condensation polymerization of the compound at fluid injection temperatures; andc) allowing the injected fluid to remain in the formation for a period of time sufficient to accomplish at least p

Abstract: This invention relates generally to methods of measuring interfacial areas, and more specifically to flow-based methods for measuring the area of the interfaces between two immiscible fluids. The immiscible fluids of interest are various oils and gases that do not have significant solubility, and thus form a distinct fluid phase and exist as agglomerations of varying sizes of blobs or ganglia when added to aqueous solutions. Our invention permits the measurement of such fluid-fluid interface areas for two immiscible fluids present in flow systems. The flow-based method involves the introduction of an interfacial tracer chemical into the flow system in one of two modes: (1) step input, and (2) pulse input. The tracer is soluble to appreciable extent in only one of the two fluids, designated as the carrier fluid phase.

Abstract: An apparatus for testing a shear thickening plugging fluid that is an emulsion of two components which react with each other to provide a thickening of the fluid when subjected to high stress, such apparatus comprising a cylinder (1) having an inlet (2) with an inlet valve (3) for the plugging fluid and an outlet (4) with an outlet valve (5) for the plugging fluid, a moveable piston (6) sealing against the chamber walls, so that the piston by being moved rearward in the cylinder can suck plugging fluid into the cylinder through the inlet (2), and in a retrograde movement can press the plugging fluid out through the outlet (4), a shear valve (7) connected with the outlet (4), which shear valve (7) is adjustable for adjusting a desired shear stress to be subjected upon the plugging fluid, a means (8, 9) for measuring the pressure drop over the shear valve (7), a receiver means (10) for collecting plugging fluid that has been pressed through the shear valve, and one or more means for measuring properties of the

Abstract: The present invention provides a method for restricting a fluid flow path in subterranean geological formations to facilitate the removal of hydrocarbons from the subterranean geological formation during enhanced oil recovery techniques. The method includes the steps of injecting a first water volume into the fluid flow path thereby displacing fluids present in the fluid flow path. The next step is injecting an alkaline volume into the fluid flow path thereby displacing the first water volume ahead of the alkaline volume. The injections create a first water and alkaline mixed continuum between the first water volume and the hydroxide volume wherein the relative concentrations of water and hydroxide vary along a length of the first water and hydroxide mixed continuum wherein the relative concentrations of water and alkaline are conducive to the formation of scale upon the surfaces of the subterranean geological formation.

Abstract: A process is provided for selectively placing a permeability-reducing material in an interval of a subterranean hydrocarbon-bearing formation penetrated by a well bore to inhibit the vertical flow of fluid between the well bore and an aquifer underlying the interval. The process is performed by simultaneously injecting a pair of fluids into the well bore, wherein one fluid has a density substantially less than the density of the other, and displacing the fluids out into the interval. The two fluids directly contact one another as they are displaced, however, the density difference between the fluids causes the first fluid to preferentially enter an upper portion of the interval and the second fluid to preferentially enter a lower portion of the interval under the force of gravity stratification or gravity segregation.

Abstract: A method for enhanced oil recovery from a low permeability diatomaceous reservoir by imbibition is described. In this method, oil is displaced from a single injection well, or series of injection wells into a single producer or series of producing wells by a combination of applied fluid pressure, plus "enhanced imbibition." Enhanced imbibition is accomplished by adding chemical additives to the injection fluid so that rock in the tight reservoir has a stronger affinity for the water present therein, thus releasing oil from the rock.

Abstract: A gelable composition and process are disclosed that delay the gelation and increase the gel strength of gelled water soluble acrylamide-containing polymers contains: (1) a water dispersible first crosslinking compound selected from the group consisting of p-aminosalicylic acid, furfuryl alcohol, RArOC(O)R' and HOArC(O)OR" wherein Ar represents a phenyl group which can be substituted or non-substituted; R is a hydrogen or a carboxylic group; R' is a C.sub.1 -C.sub.6 alkyl; R" is a hydrogen, a phenyl group, or a C.sub.1 -C.sub.6 alkyl; and when R is a carboxylic group, R and C(O)OR" can be at ortho, meta, or para position with respect to the OC(O)R' group and the OH group, respectively; (2) a water dispersible second crosslinking compound selected from the group consisting of aldehydes and aldehyde-generating compounds; (3) a water soluble acrylamide-containing polymer; and (4) water.

Abstract: A gelling composition and a process for wellbore treatment comprising injecting the composition into reservoirs are disclosed wherein the composition comprise a water-soluble polymer such as, for example, polyacrylamide; an iron compound such as, for example, ferric acetylacetonate or ammonium ferric oxalate; a ketone compound such as, for example, 2,4-pentanedione; and a liquid such as, for example, a produced brine.

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 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: A method for emplacing a silicate gel to improve the sweep efficiency of a water, gas, or steam flood operation by reducing the permeability of high-permeability thief zones is disclosed. Controlled quantities of a silicate solution and either a gas or a gas and an organic acid are injected into a well to infiltrate and generate a controlled amount of a silicate gel of a controlled SiO.sub.2 concentration in the high-permeability thief zones, to reduce the permeability thereof. Base agents and weak acids may be added to control gel generation rate. Methods for selective emplacement of silicate gels into thief zones through a well without selective injection facilities are also disclosed.

Abstract: A method for the injection of a pre-determined volume of gel below a fracture pressure limit is described. The fracture pressure limit for an unfractured formation is the fracture initiation pressure. The pressure limit for a previously fractured formation is the fracture extension pressure. Initially, a desired gel is injected into a thief zone at a constant rate while maintaining the injection pressure below the limiting fracture pressure. When the injection pressure reaches the formation fracture pressure limit, gel injection is halted for a period of about 3 hours. Afterwards, the bottom hole pressure is allowed to decline and stabilize. Next, gel injection is resumed at the same rate and pressure used prior to halting the injection. If necessary gel injection can be halted when the formation's pressure limit is again reached. After a period of about 3 hours, injection of gel can be again commenced. These steps can be repeated until a pre-determined volume of gel has been placed into the thief zone.