Abstract: Zero discharge processing methods for the treatment of agricultural drainage water (ADW) are disclosed. The disclosed methods are capable of meeting the three critical issues in treating ADW: (1) selective removal of sulfate scale-prone species and toxic species; (2) production of usable water that at least meets irrigation water quality; and (3) recovery of sodium sulfate and sodium chloride as valuable commodities.

Abstract: A process is described for replacing at least a portion of the liquid within the annular volume of a casing system within a wellbore with a second liquid. The second liquid is preselected to provide a measure of control of the pressure within the annular volume as the fluid within the volume is being heated.

Abstract: An economic method for in situ maturing and production of oil shale or other deep-lying, impermeable resources containing immobile hydrocarbons. Vertical fractures are created using horizontal or vertical wells. The same or other wells are used to inject pressurized fluids heated to less than approximately 370° C., and to return the cooled fluid for reheating and recycling. The heat transferred to the oil shale gradually matures the kerogen to oil and gas as the temperature in the shale is brought up, and also promotes permeability within the shale in the form of small fractures sufficient to allow the shale to flow into the well fractures where the product is collected commingled with the heating fluid and separated out before the heating fluid is recycled.

Abstract: A dual use fluid filtration tool to separate both solids and gas from a fluid. The fluid filtration tool is suspended from and connected to downhole equipment, such as a downhole submersible pump having a motor, which rotates a shaft. The tool includes a housing having a cylindrical wall with a plurality of perforations therethrough and m interior chamber therein. A removable cylindrical filter surrounds the interior chamber of the housing in order to filter solid particles. At least one centralizer bearing within the interior chamber of the housing centralizes the shaft which passes therethrough. The fluid in the interior chamber is radially induced in order to separate gas from fluid. The gas separated from the fluid is directed out of the chamber while the fluid remaining in the interior chamber is directed to the intake of the downhole pump.

Abstract: Substances to stimulate the extraction of crude oil and a method, of processing them: This invention is about substances to stimulate the extraction of crude oils, especially the ponderous and paraffin one, not clogging the route and the abutting deposits of the oil derrick by changing the deposit's reology and also about solubility of the aggregates which were made from paraffin resins on the oil derrick's circulation route, using a similar chemical vector to the prodrugs from the medicine industry. The substance to stimulate the extraction of crude oil by increasing the fluidization characterized by the fact that 90% from the volume is made by mixing three fractions oil types from the distilled mineral coal: ?20-30% phenol oil (fraction distilled from 170-190° C.); ?20-40% absorption oil (fraction distilled from 250-270° C.); ?20-40% polymerized oil (fraction distilled from 320-350° C.

Abstract: A process for the selective controlled reduction of the relative water permeability in high permeability, oil-bearing formations, with negligible reduction of the permeability to oil. The process comprises, for sandstone reservoir rocks, a first layer of cationic polymer, followed by a brine spacer slug and a second polymer layer made up of a suspension of anionic polymer and an anionic or non-ionic microgel, optionally this configuration being repeated. As a result the thickness of the polymer layer is considerably increased, which permits the process to be used in high permeability formations. For limestone rocks the first layer is made up of anionic polymer, while the second layer involves a suspension of cationic polymer/cationic or non-ionic microgel. The polymers are all injected as aqueous suspensions in brine or seawater.

Abstract: Methods are disclosed for the selective separation of sulfate from a saline stream such as seawater to produce nearly sulfate-free saline stream for oil-fields water injection operations. The separated sulfate in the form of gypsum from the treated saline stream can be used in different applications.

Abstract: A method for determining the extent of recovery of materials injected or otherwise introduced into oil wells or subsurface formations is practiced using a portable device. The portable device can also be used to determiner the occurrence of a predetermined condition in an oil well such as water break through in a production zone, or the opening or closing of a sliding sleeve. When, for example, water breakthrough is detected, the zone producing too much water can be plugged, using, for example, a flow-through bridge plug, if there are other producing zones further downhole.

Abstract: A formulation and method to enhance recovery from an oil wherein the method supplies a mixture of petroleum distillates and terpenoid compounds, and a salt extraction formulation comprising a mixture of humic acid and fulvic acid. The method discontinues the extraction of materials from the oil well, disposing the mixture of petroleum distillates and terpenoid compounds into the oil well, and disposes the salt extraction formulation into the oil well. The method recirculates the oil well, and then returns the oil well to service.

Abstract: Certain embodiments provide a method for treating a subsurface formation. The method includes using heaters to form a heated portion of the subsurface formation. A production conduit is used to direct formation fluid in a vapor phase from the heated portion of the subsurface formation towards a surface of the subsurface formation. Condensate of the vapor phase formation fluid is formed in or near the production conduit. Condensate of the vapor phase formation fluid is diverted to a desired location.

Abstract: Treating fluid production and subterranean formation treating methods as well as treating fluid compositions that reuse at least part of a prior treating fluid, particularly a fluid having one or more constituents that can be relinked. This includes conditioning a selected at least partially delinked flow-back fluid recovered from a first treating fluid pumped into a well, such that the conditioned selected at least partially delinked flow-back fluid provides a constituent for a second treating fluid. Also included are pricing considerations. A composition for a treating fluid includes a treating fluid residual recovered from a well, preferably a conditioned treating fluid residual. Examples of such compositions include fracturing fluids and gravel pack fluids.

Abstract: A method for releasing gas from a gas hydrate without melting the gas hydrate by substituting the gas with a releasing agent that forms a more stable hydrate structure than the gas.

Abstract: Hydrocarbon solids are removed from an oil well by feeding into the oil well a composition comprising at least 40 vol. % dense phase carbon dioxide and at least 30 vol. % of a C1–C3 alkanol component and optionally one or more surfactants, under a pressure of 300 to 10,000 psia and a temperature of 90° F. to 120° F., holding the composition in the well to solubilize hydrocarbon solids, and then removing from the well a liquid composition comprising solubilized hydrocarbon solids and alkanol.

Abstract: The present invention may be used as an apparatus and method for extracting oil from a hydrocarbon material bearing formation. A well may be positioned in a formation having hydrocarbon material with a well casing extending into the formation that may have a number of apertures formed in the casing wall adjacent to multiple zones of interest in the formation. A hydrostatic separator may have a specific gravity approximately equal to an oil that may be extracted from the formation and may be positioned and anchored in the well casing above and adjacent to an upper level of said formation. An extraction pipe may be disposed interior to the well casing with a lower end positioned above and adjacent a separator top and may have an upper end attached at a well head. The well head may be in fluid communication with an oil storage unit and in communication with a pressure application apparatus.

Abstract: A method for inhibiting formation of hydrocarbon hydrates in mixtures of water and a hydrate-forming guest molecule involves adding a reaction product to the mixtures in an effective amount to inhibit formation of the hydrocarbon hydrates under conditions otherwise effective to form the hydrocarbon hydrates in the absence of the reaction product. The product is made by the reaction of first reactant that is an amine or polyamine, or alcohol or polyalcohol, with a second, aldehyde reactant and a third reactant that is an alcohol or polyalcohol or, an amide or polyamide. Preferably, if the first and third reactants are both an alcohol or both a polyalcohol, they are not the same. A non-limiting example of a suitable amine would be a fatty alkyl amine, while formaldehyde would be a non-limiting of a suitable aldehyde and polyacrylamide would be a suitable third reactant.

Abstract: A new class of sulfur scavenging or converting compositions is disclosed comprising diamine terminated, amine-aldehyde adducts, where the adducts are substantially bimolecular amine-aldehyde adducts and the composition is substantially free of trimer and/or triazines. Methods for making and using the new class of sulfur scavenging or converting composition are also disclosed.

Abstract: Methods for the removal of alkaline and sulfate scales from aqueous saline streams such as seawater, oil-gas fields produced waters, formation waters, and the like. Such processing methods can also be extended for the simultaneous removal of hydrogen sulfide, and/or sulfur dioxide, and/or oxides of nitrogen, and/or carbon dioxide from gaseous streams. The same processing concept with modified methods can further be employed for the removal of gases such as radon, hydrogen sulfide, sulfur dioxide, oxides of nitrogen, and carbon dioxide from gaseous streams.

Abstract: The present invention relates to acidic treatment fluids that comprise an acid fluid and an ester-containing quaternary ammonium compound (“esterquat”) and methods of their use. One embodiment of the present invention provides a method of inhibiting metal corrosion during a subterranean treatment operation comprising using an acidic treatment fluid comprising an acidic fluid and an esterquat. Another embodiment of the present invention provides a method of reducing sludge formation during a subterranean treatment operation formation comprising the step of using an acidic treatment fluid comprising an acidic fluid and an esterquat. Another embodiment of the present invention provides a method of inhibiting the formation of emulsions during a subterranean treatment operation comprising using an acidic treatment fluid comprising an acidic fluid and an esterquat. Another embodiment of the present invention provides an acidic subterranean treatment fluid comprising an acidic fluid and an esterquat.

Abstract: Compositions and methods for the inhibition of salt formation in oil and gas wells are disclosed. In particular, nitrilotriacetamide and its salts are effective at treating existing salt formations, and in inhibiting formation of new deposits.

Abstract: Method is provided for increasing the productivity of gas wells producing from reservoirs where retrograde condensation occurs around the wells. An oil-wetting surfactant is injected in a solvent to oil wet the formation for a selected distance around a well or a hydraulic fracture intersecting the well. A pre-flush liquid, such as carbon dioxide, alcohol or similar products and mixtures thereof, may be used to reduce water saturation before injection of the surfactant. The method may also be applied to increase the productivity of oil wells producing from reservoirs where breakout of solution gas occurs near the well.

Abstract: This invention is directed to treating fluid production and subterranean formation treating methods as well as compositions for treating fluids that reuse at least part of a prior treating fluid, particularly a fluid having one or more constituents that can be relinked. This includes conditioning a selected at least partially delinked flow-back fluid, recovered from a first treating fluid pumped into a well, such that the conditioned selected at least partially delinked flow-back fluid provides a constituent for a second treating fluid. Also included are pricing considerations. A composition for a treating fluid includes a treating fluid residual recovered from a well, preferably conditioned as described. Examples of such fluids include fracturing fluids and gravel pack fluids.

Abstract: A wellbore completion includes a plurality of longitudinal gravel pack sections disposed within a well, the gravel pack sections being capable of imposing a predetermined substantially radial flow restriction upon fluid production flowing radially through the gravel pack section. At least one of the gravel pack sections creates a radial flow restriction that is different from the radial flow restriction of at least one other gravel pack section. The gravel pack sections may comprise graded gravel material having an effective permeability within a predetermined range when placed in the well.

Abstract: A method for in situ forming of an unstable oil in water emulsion includes the steps of providing a mixture of an aqueous alkali salt solution and a surfactant, and pumping the mixture down a well containing a crude hydrocarbon having an API gravity of less than or equal to 26 so as to provide an unstable emulsion in the well, the unstable emulsion having the hydrocarbon as a dispersed phase and the solution as a continuous phase and having a ratio by weight of the hydrocarbon to the solution of at least about 50:50.

Abstract: This invention aims to provide a gas-hydrate extracting device and method whereby a high-performance jet fluid is injected from a nozzle at the tip of an extraction pipe inserted into a gas-hydrate stratum, and whereby said jet fluid breaks said stratum so as to form a gas-hydrate mixed fluid that is transferred to surface of the earth, and whereby the void resulting from the removal of said gas hydrate is filled with the components of said high-performance jet fluid and a void-refilling fluid.

Abstract: A method of recovering oil or contaminants from subterranean reservoirs using a surfactant system where an adsorption reducing agent is injected before, after, and/or with the surfactant system. The adsorption reducing agent is formed by the reaction of an olefin sulfonic acid and phenol/aldehyde resin, the structure which is shown below where M may be Hydrogen or any cation, R is hydrogen, alkyl, alkenyl, etc., X is methylene or other aldehyde derived bridge, Y is hydrogen, ethylene oxide, propylene oxide, butylene oxide or mixtures of two or more of these, x+y is greater than 2 and n is equal or greater than 1.

Abstract: An oil well capsule to reduce the paraffin and asphaltene which accumulate on the walls of the pipes which are used to bring the oil up from underground deposits, and a method of using the oil well capsule. An oil well capsule having a shell encapsulating a chemically active mass wherein the chemically active mass consists essentially of alkaline or alkaline earth metal.

Abstract: A brine for use during drilling operations, preferably a completion brine, comprising an amount of a low molecular weight water-soluble organic compound effective to reduce the crystallization point of the brine. The low molecular weight water soluble organic compound can be a variety of compounds, with preferred compounds being ethylene glycol, tripropylene glycol bottoms, and combinations thereof. A method of lowering the crystallization point of the brine using a low molecular weight water soluble organic compound also is provided.

Abstract: Compositions and methods for the inhibition of salt formation in oil and gas wells are disclosed. In particular, nitrilotriacetamide and its salts are effective at treating existing salt formations, and in inhibiting formation of new deposits.

Abstract: A method to increase the production of oil from an oil reservoir is described. The method includes injecting a magnetic or magnetostrictive material through an oil well into the oil reservoir, vibrating the material with the aid of an alternating electric field and removing oil from the oil well.

Abstract: Pumpable multiple phase compositions for carrying agents and components downhole and controllably releasing them by breaking the suspensions are described. The multiple phase composition may have an external or third phase, which in turn has a first pumpable emulsion internally. The first pumpable emulsion has a second phase containing a first phase which bears the agent to be controllably released. The entire pumpable multiple phase composition may thus be an oil phase-in-aqueous phase-in-oil phase emulsion, or an aqueous phase-in-oil phase-in-aqueous phase emulsion. The agent may be released by one or more of a variety of mechanisms. For example, a water-soluble shale stabilizer could be delivered downhole in an aqueous phase-in-oil phase-in-aqueous phase multiple phase emulsion by injecting the multiple phase composition into a water-based drilling fluid, and then the suspension broken by rotary bit nozzles under high shear stress to release the shale stabilizer at the drilling zone.

Abstract: A method is provided for expanding an expandable steel tubular including the steps of: flattening the unexpanded tubular; transporting the flattened unexpanded tubular to a location at or near the site where the tubular is to be installed; unflattening the tubular before positioning the tubular at said site; and expanding the tubular along at least a substantial part of its length before or after the tubular has been positioned at said site.

Abstract: Method and apparatus for delivery of chemical reagents to a subterranean body of soil and groundwater to destroy or enhance mobility of organic compounds using a riser insertable in a borehole having spaced permeable sections separated by a non-permeable section and wherein the reagents are introduced from a source by a pressurization apparatus.

Abstract: A method for treating a gas well to prevent any fresh water, which may have condensed out of the gas stream, from damaging the gas producing formation during the shut-in period. The well is shut-in and then an additive, e.g. a salt, alcohol, etc., is injected into the well to convert any accumulated fresh water into an aqueous solution which will not damage the formation. The additive can be injected in solid form or as a solution.

Abstract: A method for inhibiting the formation of gas hydrates in a petroleum fluid having hydrate-forming constituents is claimed. More specifically, the method can be used to treat a petroleum fluid, such as natural gas conveyed in a pipe, to inhibit the formation of a hydrate flow restriction in the pipe. The hydrate inhibitors used for practicing the method comprise substantially water soluble homopolymers and copolymers of N-acyldehydroalanine derivatives which are esters or amides of N-acyldehydroalanine.

Abstract: A system for hydrocarbon production and water disposal utilizing a displacement liquid having a specific gravity less than that of water and immiscible with water. One embodiment of the apparatus comprises an outer well casing having an inlet for reservoir fluid, an outlet for water disposal, and an outlet for produced hydrocarbon fluid; and a tube disposed within the casing having an upper passageway for connection with a supply of a displacement liquid and an inlet having a one-way valve for allowing entry of reservoir fluid from within the casing, and a lower outlet having a one-way valve for allowing egress of water. One embodiment incorporates a downhole separator to allow a higher production rate.

Abstract: The use of high flash point, low vapor pressure compositions for injection into, and coating of, gas and oil wells and surrounding underground hydrocarbon bearing formations and processing equipment for the purpose of removing scale, paraffins, tars, and other viscous constituents. Treatment results in increased flow of gas and/or oil and decreased adhesion of soils and scale in all aspects of oil and gas recovery, including hydrocarbon bearing formations, casings, lines, and pumping equipment. The composition contains about 40 to 99 wt. % of a fatty acid alkyl ester blend and about 1 to 25 wt. % of at least one lower alkyl glycol ether.

Abstract: A method for inhibiting or preventing the deposition of metals onto metallic surfaces, particularly the metal surfaces in an oil or gas well is disclosed.

Abstract: The present invention provides a method for suppressing the formation of hydrates during drilling operations under conditions that are conducive to hydrate formation comprising using a water based fluid selected from the group consisting of a drilling, a drill-in, and a completion fluid, wherein said water based fluid comprises as an integral component a hydrate suppressing amount of a water-soluble organic compound having a molecular weight below about 800 and said fluid has effective rheology and fluid loss control properties.

Abstract: A method of inhibiting or retarding formation of hydrates from water and a lower alkane, such as methane or ethane, involves adding additives which comprise (i) a corrosion inhibitor and (ii) a salt which is of formula [R.sup.1 (R.sup.2)XR.sup.3 ].sup.+ Y.sup.-, wherein each of R.sup.1, R.sup.2 and R.sup.3 is bonded directly to X, each of R.sup.1 and R.sup.2, which may be the same or different is an alkyl group of at least 4 carbons, X is S, NR.sup.4 or PR.sup.4, wherein each of R.sup.3 and R.sup.4 which may be the same or different represents hydrogen or an organic group, with the proviso that at least one of R.sup.3 and R.sup.4 is an organic group of at least 4 carbons, and Y is an anion, the additives being added in an amount effective to inhibit or retard hydrate formation, to a medium susceptible to hydrate formation.

Abstract: A process for the thermo-hydraulic control of gas hydrates in subsea production and injection wells as well as pipelines which transport liquid or gaseous hydrocarbons is described, the process making use of a Nitrogen Generating System foamed or in solution. The control may signify the prevention of the formation of the gas hydrates or the dissolution of the gas hydrate plug already formed. Under conditions of use designed for the prevention of the formation of gas hydrates the SGN fluid prevents the thermal conditions leading to the gas hydrate plugs. Under conditions of use designed to dissolve the already formed gas hydrate plugs, the SGN fluid alters the thermo-hydraulic conditions which favor the gas hydrate plugs, so that they are dissolved and return to the water+gas phase.

Abstract: A method for inhibiting the formation of clathrate hydrates in a fluid having hydrate forming constituents is claimed. More specifically, the method can be used in treating a petroleum fluid stream such as natural gas conveyed in a pipe to inhibit the formation of a hydrate restriction in the pipe. The hydrate inhibitors used for practicing the method comprise substantially water soluble polymers having N-vinyl amide or N-allyl amide units. Specific examples of such copolymers include, N-vinyl-N-methylacetamide (VIMA) copolymerized with acryloylpyrrolidine (APYD) or acryloylpiperidine (APID), and more preferably, VIMA copolymerized with N-substituted methacrylamides, such as N-isopropylmethacrylamide (iPMAM) and methacryloylpyrrolidine (MAPYD) to produce inhibitors for practicing the claimed method.

Abstract: The present invention provides a process for continuously producing clathrate hydrate. This process includes comprising the steps of:(a) pressurizing a hydrate-forming gas to an elevated pressure and cooling the hydrate-forming gas below the gas-water-hydrate equilibrium point at the elevated pressure;(b) cooling liquid water below the gas-water-hydrate equilibrium temperature for the elevated pressure;(c) charging hydrate-forming gas at the elevated pressure into a reaction zone which contains a movable surface;(d) atomizing water in the reaction zone in contact with the hydrate-forming gas to form gas hydrates in the reaction;(e) depositing the gas hydrates on the movable surface; and(f) collecting the gas hydrates from the movable surface.

Abstract: A composition for and an improved process of, enhancing petroleum recovery from a petroleum reservoir by injecting said composition into the reservoir through a wellbore are provided. The aqueous composition is derived from a concentrate which includes a defoaming agent, a demulsifying agent, and optionally a stabilizing agent suitable for stabilizing the concentrate as an aqueous emulsion. In one embodiment, the defoaming agent is dispersed in carrier solvent and the concentrate further includes an emulsifying agent suitable for emulsifying the carrier solvent in water. The composition is preferably injected at a high pumping rate directly into the formation through the tubing-casing annulus and allowed to permeate into the reservoir surrounding the wellbore before oil production commences. The composition and method are particularly suited for used in conjunction with steam injection oil recovery techniques.

Abstract: A method for separating hydrocarbons from a soil, e.g. to separate bitumen from oil sands, involves mixing the soil thoroughly with water and a supply of buoyant beads having surfaces that are of oleophilic material and coated with a surface layer of hydrocarbon solvent. The beads, soil and water are agitated for a period during which hydrocarbons from the soil become adhered to the solvent coated beads. After the mixture has been allowed to settle the beads separate towards the top and are removed and treated with solvent to recover the adhered hydrocarbons therefrom. Suitable solvents are oil refinery products such as naphtha, kerosine, gasoline, varsol, toluene and diesel fuel.

Abstract: A method for inhibiting the formation and/or agglomeration of clathrate hydrates in a petroleum fluid stream containing water is disclosed. The disclosed method uses predetermined inhibitors having a guest group, a polymer backbone, and an anchor group positioned between the guest group and the polymer backbone. The inhibitor predetermination method comprises selection of the polymer backbone, anchor group and guest group using several types of criteria. The polymer backbone should produce a substantially water soluble polymer in combination with the anchor group and the guest group. The anchor group should be a hydrophilic moiety with between one and four hydrogen bonding atoms. The guest group should be either a hydrophobic or amphiphilic moiety with a carbon atom to heteroatom ratio greater than or equal to about two to one and an average van der Waals diameter between about 3.8 angstroms and about 8.6 angstroms.

Abstract: Discussed is a process for preventing clathrate hydrate masses from detrimentally impeding the possible flow of a fluid susceptible to clathrate hydrate formation. The process is particularly useful in the natural gas and petroleum production, transportation and processing industry where gas hydrate formation can cause serious problems. Additives preferably contain one or more five member, six member and/or seven member cyclic chemical groupings. Additives include polymers having lactam rings. Additives can also contain polyelectrolytes that are believed to improve conformance of polymer additives through steric hinderance and/or charge repulsion. Additional additives include alkoxy compounds, and particularly those comprising ethoxy and or propoxy polymer blocks. Further additives include alcohols and oxazoline polymers which are preferably used in combination with polymers having lactam rings. Additives are useful in controlling clathrate hydrates in highly saline aqueous liquids.

Abstract: A method for inhibiting the formation of clathrate hydrates in a fluid having hydrate forming constituents is disclosed. More specifically, the method can be used in treating a petroleum fluid stream such as natural gas conveyed in a pipe to inhibit the formation of a hydrate restriction in the pipe. The hydrate inhibitor used for practicing the method is selected from the family of substantially water soluble copolymers formed from N-methyl-N-vinylacetamide (VIMA) and one of three comonomers, vinylpyrrolidone (VP), vinylpiperidone (VPip), or vinylcaprolactam (VCap). VIMA/VCap is the preferred copolymer. These copolymers may be used alone or in combination with each other or other hydrate inhibitors. Preferably, a solvent, such as water, brine, alcohol, or mixtures thereof, is used to produce an inhibitor solution or mixture to facilitate treatment of the petroleum fluid stream.

Abstract: The invention concerns a process for inhibiting or retarding hydrate formation, growth and/or agglomeration in a fluid comprising water and gases, by addition of a hydrosoluble copolymer which does not contain a heterocycle but contains at least one sulphonate group.The copolymer is generally introduced at a concentration of 0.05% to 5% by weight with respect to the quantity of water in the medium.The copolymer can also be mixed with an alcohol (monoalcohol or polyol). In this case, the proportions are generally 0.5% to 20% by weight of alcohol with respect to the water content, for 0.05% to 3% by weight of copolymer with respect to the quantity of water content of the medium.

Abstract: The present invention provides methods of decomposing gas hydrates in subsea or subterranean wells, the equipment associated with the wells and in subterranean reservoirs containing gas hydrates. The methods basically comprise the steps of combining an acidic liquid with a basic liquid which chemically react exothermically to form a hot salt solution, contacting the gas hydrates with the hot salt solution to decompose at least a portion of the gas hydrates whereby natural gas and water are released therefrom and recovering the released natural gas, water and salt solution.

Abstract: Discussed is a process for preventing clathrate hydrate masses from detrimentally impeding the possible flow of a fluid susceptible to clathrate hydrate formation. The process is particularly useful in the natural gas and petroleum production, transportation and processing industry where gas hydrate formation can cause serious problems. Additives preferably contain one or more five member, six member and/or seven member cyclic chemical groupings. Additives include polymers having lactam rings. Additives can also contain polyelectrolytes that are believed to improve conformance of polymer additives through steric hinderance and/or charge repulsion. Also, polymers having an amide on which a C.sub.1 -C.sub.4 group is attached to the nitrogen and/or the carbonyl carbon of the amide may be used alone, or in combination with ring-containing polymers for enhanced effectiveness.