Mobil Oil Corporation

John L Hen

Earl S Snavely, Jr

Alfred R Jennings, Jr

David C Calabro

Eleanor R Fieler

An improvement in a method for the inhibition of scale deposition on the surfaces of a well coproducing oil and scale forming brines, said method comprising injecting into the well reservoir an acidic aqueous solution at a first pH containing dissolved therein a scale inhibitor, multivalent metal cations, and a heat-sensitive pH-increasing substance which decomposes at elevated temperatures liberating an alkaline compound such that the solution is inherently heated by the higher ambient reservoir temperature to a temperature at which the alkaline compound is liberated from the heat-sensitive substance thus raising the pH of the solution to a point at which a sparingly soluble multivalent metal salt of the scale inhibitor is phase separated from the solution on the porous surfaces of the reservoir rock formation, providing for a slow release of inhibitor into the produced brines when the well is in its production phase. Such improvement comprises injecting as a preflush before said injection of inhibitor solution and/or as an afterflush after said injection of inhibitor solution, a solution of a heat sensitive pH-increasing substance and multivalent metal cations.

Inhibition of scale from oil well brines utilizing a slow release

A method for the inhibition of scale deposition on the surfaces of a well coproducing oil and scale forming brines comprising injecting into the well reservoir an acidic aqueous solution at a first pH containing dissolved therein a scale inhibitor, multivalent metal ions, and a heat-sensitive pH-increasing substance containing no more than 10 carbon atoms, which decomposes at elevated temperatures liberating an alkaline compound such that the solution is inherently heated by the higher ambient reservoir temperature to a temperature at which the alkaline compound is liberated from the heat-sensitive substance thus raising the pH of the solution to a point at which a sparingly soluble multivalent metal salt of the scale inhibitor is phase separated from the solution on the porous surfaces of the reservoir rock formation, providing for a slow release of inhibitor into the produced brines when the well is in its production phase.

Inhibition of scale formation from oil well brines utilizing a slow

A method for placement of a long life scale inhibitor into a formation where variable density scale inhibitors are utilized. A substantially low density non-reactive fluid is loaded into an interval of the formation to be treated. Afterwards, a high density first stage scale inhibitor is injected into the interval. Thereafter, a low density spacer fluid is injected into the interval being treated. Next, a second stage high density scale inhibitor having a density lower than the first stage inhibitor is injected into said interval. Subsequently, a low density spacer is injected into the interval. Volume increments are repeatedly injected with decreasing fluid densities until a desired zone has been treated. The entire treatment is then overflushed with an inert high density fluid. Use of this method allows even inhibitor distribution in intervals of a formation with permeability variations thereby preventing scale build-up.

Method for effective placement of a long life scale inhibitor

There is provided a method for preparing crystalline ultra-large pore oxide materials. The materials are formed from reaction mixtures comprising an amphiphilic compound, such as a cetyltrimethylammonium compound, a source of at least one oxide, such as silica, and water. The concentration of amphiphilic compounds in these reaction mixtures is rather low. The addition of an inorganic salt, such as sodium bromide, to the reaction mixture may result in the increased thermal stability of the as-synthesized form of the crystalline material and may also alter the crystalline phase of the product.

Synthesis of crystalline ultra-large pore oxide materials

A method for the inhibition of scale deposition on the surfaces of a well coproducing oil and scale forming brines comprising injecting into the well reservoir an acidic aqueous solution at a first pH containing dissolved therein a scale inhibitor, multivalent metal ions, and a heat sensitive pH increasing substance which decomposes at elevated temperatures liberating an alkaline compound such that the solution is inherently heated by the higher ambient reservoir temperature to a temperature at which the alkaline compound is liberated from the heat sensitive substance thus raising the pH of the solution to a point at which a sparingly soluble multivalent metal salt of the scale inhibitor is phase separated from the solution on the porous surfaces of the reservoir rock formation, providing for a slow release of inhibitor into the produced brines when the well is in its production phase.

A novel method of injecting or squeezing a cross-linked scale inhibitor down a well into a subterranean formation which significantly lengthens its effective life is accomplished by cross-linking a carboxylic acid-containing polymeric or organophosphorus-containing inhibitor with a polyalcohol. The significant extension of life afforded by cross-linking with a polyalcohol improves the overall economics of oil production in fields prone to mineral scale.

Method of increasing retention of scale inhibitors in subterranean

The invention provides for the use of compositions to dissolve sulfate scales from surfaces containing these scales, comprising an aqueous solution of an aminopolycarboxylic acid (APCA) containing 1 to 4 amino groups, e.g., diethylenetriaminepentaacetic acid (DTPA) or ethylenediaminetetraacetic acid (EDTA), or a salt thereof, and a second component which is diethylenetriaminepenta (methylenephosphonic acid) (DTPMP) or a salt thereof, or aminotri(methylenephosphonic acid) (ATMP), or a salt thereof. More particularly, the invention encompasses a method of removing sulfate scales from surfaces on which they have formed utilizing the foregoing solutions, particularly the removal of scales from equipment and wellbore surfaces associated with the operation of crude oil and gas wells.

Dissolution of sulfate scales

The invention provides for the use of compositions to dissolve sulfate scales from surfaces containing these scales, comprising an aqueous solution of an aminopolycarboxylic acid (APCA) containing 1 to 4 amino groups, e.g., diethylenetriaminepentaacetic acid (DTPA) or ethylenediaminetetraacetic acid (EDTA), or a salt thereof, and 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC) or a salt thereof. More particularly, the invention encompasses a method of removing sulfate scales from surfaces on which they have formed utilizing the foregoing solutions, particularly the removal of scales from equipment and wellbore surfaces associated with the operation of crude oil and gas wells.

A method and composition for improving high temperature and high pressure filtration control in a water base drilling fluid is described. Polyanionic cellulose is combined with a synthetic sulfonate containing vinyl polymer into a drilling fluid to provide for unexpectedly improved filtration control.

Sulfonate-containing polymer/polyanionic cellulose combination for high

A method for inhibiting the formation of scale in a well penetrating a subterranean formation for the production of fluids from the formation comprising injecting into the formation an acidic aqueous solution having a pH effective to form a water-soluble complex of the inhibitor and the polyvalent cation, preferably in the range of 2 to 3, containing a mixture of a polyacrylate scale inhibitor having a molecular weight range from 500 to 10,000 and a polyvalent cation wherein the equivalent ratio of polyvalent cation to polyacrylate scale inhibitor is less than or equal to 0.5 in the acidic aqueous solution and allowing natural conditions in the formation to raise the pH of the solution an amount sufficient to cause controlled precipitation and increased deposition of the scale inhibitor in situ in the form of the polyvalent cation-polyacrylate complex. The scale inhibitor solution employed in this method avoids premature plugging of the formation, substantially extends the lift of the treatment and the polyvalent cation complex of the polyacrylate is fully inhibitive.

Method of increasing retention of scale inhibitor in subterranean

Low viscosity copolymers of ethylene and higher olefins are prepared with Ziegler-Natta catalysts in the presence of an aliphatic-aromatic solvent mixture, e.g., 1:1 (by volume) of hexane:toluene. The copolymerization can be conducted without hydrogen and subsequent cracking or dewaxing steps are not necessary to obtain oils with high VI and low pour point suitable for use as basestocks, blendstocks and as shear stable VI improvers.

Process for preparing ethylene-higher olefin copolymer oils with

A method for inhibiting the formation of scale and corrosion in a well penetrating a subterranean formation for the production of fluids from the formation comprising injecting a predetermined amount of microparticles of a basic anion exchange resin providing a source of polycations into the formation about the well and that are trapped and retained by the interstices of the formation without rendering the interstices or the formation impermeable to the flow of fluids. Thereafter a predetermined amount of an aqueous solution of scale and corrosion inhibitor is injected into the formation about the well that contacts the basic anion exchange resin and becomes fixed in a slightly soluble state either by complexation with the polycations or is precipitated by the polycations in the exchange resin. The scale and corrosion inhibitor is released slowly at effective concentration into fluids produced by the well to inhibit scale formation and corrosion.

Method for scale and corrosion inhibition in a well penetrating a

A method for inhibiting the formation of scale and corrosion in a well penetrating a subterranean formation for the production of fluids from the formation comprising injecting a predetermined amount of microparticles of a cation exchange resin loaded with the desired cations into the formation about the well that are trapped and retained by the interstices of the formation without rendering the interstices or the formation impermeable to the flow of fluids. Thereafter a predetermined amount of an aqueous solution of scale and corrosion inhibitor is injected into the formation about the well that contacts the cation exchange resin and becomes fixed in a slightly soluble state either by complexation with the cations or is precipitated by the cations in the exchange resin. The scale and corrosion inhibitor is released slowly at effective concentration into fluids produced by the well to inhibit scale formation and corrosion.

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Skillman, NJ, United States of America

John L Hen