NL8103326A - SALT WATER CEMENT SLICES AND WATER LOSS REDUCING ADDITIVES THEREFOR. - Google Patents

Description

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Salt water cement slurries and water loss reducing additives therefor.

In drilling and finishing oil, gas and water wells, cement slurries are commonly used to perform cementation work such as applying cemente® coatings to the wells, sealing subterranean zones penetrated by the wells, and so forth. In most cases, the cement slurries are pumped into the wells and allowed to set in the wells or desired zones in formations on site.

A number of different additives have been heretofore developed and used to improve the properties of cement slurries and to obtain desired results, including additives to reduce water loss from such slurries during or after application. Excessive water loss from cement slurries can prevent proper hydration of the cement, and in cementing wells excessive water loss as the slurries flow through the wells and lead to dehydration of the slurries at the point where bridging of the cement and other solids the wells occur, preventing completion of cement displacement, and so on. While the water loss reducing additives which have been used heretofore have an effect in cement slurries formed from fresh water or from water containing very low concentrations of salts, such additives are substantially ineffective in cement slurries containing high concentrations of salts and in particular in cement slurries, which are saturated with salts. For example, a number of cellulose derivatives have been used to control fluid loss from cement slurries containing little or no salts. However, such hitherto used cellulose derivatives are substantially ineffective in reducing water loss from salt water cement slurries. Top 8103326 * · ^

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In addition, other water loss reducing additives previously used for freshwater cement slurry such as polyacrylic acid amides, polyethylene imines mixed with naphthalene sulfonic acid and poly-2-acrylamide-3-propyl sulfonic acid salts are ineffective in reducing water loss from salt water cement slurry.

The present invention now relates to water loss reducing additives for salt water cement slurries which are effective over a wide temperature range in reducing water loss from the slurries.

The invention also relates to methods of using the additives and salt water cement slurries containing the additives. The term "salt water" as used herein refers to sea water, brine and other materials. and 15 release of water from salts including ammonium, alkali and alkaline earth halides and nitrates with salt concentrations to saturation. Salts other than the above may be included in; some degree in the cement slurry of the invention;

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; · Taught, even though they might respond with or | • can make changes in the behavior of the slurries, for example bicarbonates, phosphates and sulphates. The term "salt water cement slurry" as used herein refers to a cement slurry composed of water, cement, one or more salts and other components or additives to provide:. · · I 25 desired properties or operating results. The salt amounts, or concentrations, in the cement slurry included below; given are expressed as a percentage by weight of the water in the cement slurry and. The amounts of water loss-reducing additives in the cement slurry, which are mentioned below, are expressed in the weight percent of the dry cement in the slurries. >

The water-loss additives for salt water cement slurries. of the present invention are composed of very low molecular weight carboxymethylhydroxyethyl cellulose polymers I-35. The particular carboxymethyl 8103326 or t-3-hydroxyethyl cellulose polymers which can be used according to the invention have in particular a carboxymethyl degree of substitution (DS) of 0.1 to 0.7 and a ratio of ethylene oxide mill to anhydroglucose units ( MS) from 0.6 to 2.8.

The carboxymethylhydroxyethyl cellulose polymers are derived from the cellulose class, which is represented as a series of anhydroglucose units of the formula 1.

The portion of the above structural formula in brackets consists of two anhydroglucose units each having three reactive hydroxyl groups. n Is an integer that gives the desired length of the polymer molecule. When the polymer is treated with sodium hydroxide and reacted under controlled conditions with chloroacetic acid and ethylene oxide, carboxymethylhydroxyethyl cellulose having the formula II is produced.

The above-mentioned sodium salt of carboxymethyl hydroxyethyl cellulose has hydroxyl groups substituted on one side by carboxymethyl and the carboxymethyl substitution degree (D.S.) is therefore 0.5 per anhydroglucose unit. As already stated, the degree of carboxymethyl substitution for the carboxymethylhydroxyethyl cellulose used according to the invention is preferably 0.1 to 0.7. At a carboxymethyl substitution degree of less than 0.1, the earboxymethylhydroxyethyl-25 cellulose is sparingly soluble in water, and at a carboxymethyl substitution degree of more than 0.7, the carboxymethylhydroxyethyl cellulose has too strong anionic character and, when combined with a cement slurry, causes the formation of a precipitate.

The above structural formula also shows that the mole ratio of ethylene oxide to anhydroglucose units (M.S.) is 1 mole per two units or 0.5. Preferably, the ethylene oxide is M.S. for the carboxymethylhydroxyethyl cellulose used according to the invention 0.6 to 2.8. Carboxymethylhydroxyethylcellulose with an ethylene oxide 8103326 f * *

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M.S. outside the above range, a salt water cement slurry does not provide sufficient water loss reducing properties. ] | The molecular length of the carboxymethylhyd; Hydroxyethyl cellulose polymers, that is, the molecular weight of the polymers, must be very low in order to give a low viscosity salt water cement slurry with which the polymers are combined. More specifically, the carboxymethylhydroxyethyl cellulose polymers, which have been used for 1 | 10 use '. according to the invention are suitable, such a low molecular weight, that a 1 wt% aqueous solution of the carboxymethylhydroxyethyl cellulose at a temperature of 25.6%. ° C has a viscosity of 10 to 225 centipoise measured on a FANN viscometer at 300 rpm using a number 1 spring, standard pin and standard sleeve. At molecular weights higher than those falling within the above range, the viscosity is | the salt water cement slurry with which the carboxymethyl- hydroxyethyl cellulose is combined is too high, so that the! (! J 20 resulting slurry cannot be pumped or otherwise treated. The FAUN viscometer listed here is a FANN Model j 35 viscometer manufactured by Fann Instrument Co. of Houston, Texas.:

Although the above-described carboxymethyl hydroxyethyl cellulose polymers the water loss from salt water: | effectively reduce cement slurries when the salt concentrates; in the slurries amounts to more than 18% by weight of the water,! the action of the polymers itself decreases. However, when a hydroxycarboxylic acid is combined with the carboxymethylhydroxyethyl cellulose polymers, the resulting additive is a very effective agent for reducing water loss from salt water cement slurries with high salt concentrations. More particularly, in salt water, cement slurry and with a salt concentration of 18% by weight of the water is converted to Saturation uses an additive consisting of the disclosed 8103326% t-5-carboxymethylhydroxyethylcellulose polymers and a hydroxy carboxylic acid present in the additive in an amount of 50% by weight of the carboxymethylhydroxyethyl cellulose in the additive. Particularly suitable hydroxycarboxylic acids to be used are gluconic, tartaric, lactic, citric, maleic and mixtures of such acids. Of these, gluconic, tartaric and citric acids were preferred, with citric acid being most preferred.

A preferred water loss reducing additive for 10 salt water cement slurries with a salt concentration of less than 18% by weight consists of carboxymethylhydroxyethylcellulose with a carboxymethyl D.S. of 0.1 to 0.7, an ethylene oxide of M.S. from 0.6 to 2.8 and a molecular weight such that a 1 wt% aqueous solution of the carboxymethylhydroxyethyl cellulose at a temperature of 25.6 ° C has a viscosity of 10 to 225 cemtipoise, measured on a FANN fish cosimeter at 300 revolutions per minute using a spring number 1. The most preferred type additive is 20 carboxymethylhydroxyethylcellulose with a carboxymethyl DS of 0.4, an ethylene oxide MS of 2.0 and a molecular weight, wherein the viscosity of a 1 wt% aqueous solution is between 10 and 200.

A preferred water loss reducing additive for 25 salt water cement slurries with a salt concentration of more than 18% by weight of the water to saturation is carboxymethylhydroxyethyl cellulose with a carboxymethyl D.S. of 0.1 to 0.7, an ethylene oxide M.S. from 0.6 to 2.8 and a molecular weight such that a 1 wt% aqueous solution of this carboxymethylhydroxyethyl cellulose at a temperature of 25.6 ° C has a viscosity of 10 to 225 centipoise, measured on a FANN viscometer at 300 revolutions per minute using a spring number 1 and hydroxycarboxylic acid, gluconic acid, tartaric acid, lactic acid, citric acid, maleic acid or a mixture thereof, 8103326%

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Which acid is present in the additive in a weight amount of 50% by weight of carboxymethylhydroxyethyl cellulose in the additive.

The additive of this type, which most; Preferred consists of carboxymethylhydroxyethylcellulose with a carboxymethyl D.S. of 0.4, an ethylene oxide M.S. of 2.0 and a molecular weight such that a 1% w / w aqueous solution thereof at a temperature of 25.6 ° C has an 'I' | j has a viscosity of 10 to 200 centipoise, measured on an i; 10 FANN viscometer at 300 rpm using a spring number 1, and citric acid, which is present in the additive in an amount of 50% by weight of carboxymethylhydroxyethyl cellulose in the additive.

A preferred salt water cement slurry, which exhibits little water loss when in contact with permeable earth formations, of the invention consists of salt water, cement and water loss. reducing additive consisting of carboxymethylhydroxyethyl cellulose with a carboxymethyl D.S. of 0.1 to 0.7, one | ethylene oxide M.S. from 0.6 to 2.8 and a molecular weight such that a 1 wt% aqueous solution thereof at a temperature • • "i | temperature of 25.6 ° C and a viscosity of 10 to 225 centipoise '; measured on a FANN fish cosimeter at 300 revolutions | i | 25 per minute using a spring timing 1. j

Another salt water cement slurry, that little! exhibits preferred water loss upon contact with permeable earth formations, * consisting of salt water, cement, a water loss reducing additive, consisting of carboxymethyl-30 hydroxyethyl cellulose with a carboxymethyl D.S. from 0.1 to; 0.7, an ethylene oxide M.S. from 0.6 to 2.8 and molecular weight such that a 1 wt% aqueous solution thereof at a temperature of 25.6 ° G has a viscosity of 10 to 225 centipoise, measured on a FANN fish cosimeter at 300: 35 revolutions per minute using a spring number 8103326-7 mer 1, which is present in the slurry in an amount of 0.2 to 2.0 wt% of the dry cement in the slurry and a hydroxy carboxylic acid namely gluconic, tartaric, lactic, citric, maleic, or a mixture of such acids, which is present in the slurry in an amount of 0.1 to 1.0 wt% of the dry cement in the slurry.

The salt water cement slurry, which exhibits little water loss and is most preferred, consists of salt water, cement and a water loss reducing additive consisting of carboxymethylhydroxyethyl cellulose with a carboxymethyl D.S. of 0.4, an ethylene oxide of M.S. of 2.0 and a molecular weight such that a 1 wt% solution in water at a temperature of 25.6 ° C has a viscosity of 10 to 200 centipoise, measured on a FANN viscometer 15 at 300 rpm using a spring number 1, wherein the carboxymethylhydroxyethyl cellulose is present in the slurry in an amount of 0.25 to 1.8% by weight of the dry cement in the slurry and the citric acid is present in the amount of 0.1 to 0 .9% by weight of the dry cement in the slurry.

When using the water loss reducing additives of the present invention in a salt water cement slurry used for cementing wells, the additive is combined with the salt water cement slurry before using it. Preferably, the water loss reducing additive is mixed dry with other dry components and added to the mixing water used to prepare the cement slurry. If the mixing water does not already contain salts, the salt or salts used are preferably also mixed dry with other dry components, after which the mixture is combined with the mixing water. Once thoroughly mixed, the slurry is introduced into a wellbore and / or subterranean formations which are penetrated therewith and allowed to cure to a hard, permeable mass. The water loss reducing additive -----—_- - - 8103326

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- 8 - .------- 1 I i and cement slurries containing such additives cause a significant reduction in water loss over a wide temperature range, ie from 38 to 182 i; The salt water cement slurries of the invention 1 may, of course, contain a wide variety of other components and additives to achieve desired results, including solid fillers such as sand, curing time retarders, accelerators, etc. ! The following examples illustrate the invention. to. '

Example I

Cement slurries are prepared using fresh water containing various concentrations of sodium chloride, cement and water loss reducing additives of the invention consisting of very low molecular weight carboxymethylhydroxyethyl cellulose polymers (DS 0.4, MS 2.0 and such molecular weight that a 1 wt% aqueous solution thereof at a temperature of 25.6 ° C has a viscosity of 10 to 200 centipoise, measured on a FANN viscosimeter at 300 revolutions per minute under Use a Number 1 and tartaric acid. The slurries and: additives are mixed at high speed for 35 seconds in a Waring Blender. The surface mixing viscosities of the slurries are determined at 38 ° C, 49 ° C, 66 ° G and 88 ° C. Using a Halliburton consistometer as described in U.S. Patent 2,122,765.

The liquid loss properties of the slurries are measured according to API standard methods (API RP-10B) on a 0.044 ml sieve at 7000 kPa at 100 ° C, 49 ° C, 66 ° C and 88 ° C. j

The results of these tests are given in Table A below.

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Example II

The procedure of Example 1 is repeated. Using water loss reducing additives; "Consisting of the described low molecular weight carboxymethylhydroxyethyl cellulose polymers and various hydroxy carboxylic acids.

The results of these tests are given in Table B below.

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Table B shows that a good reduction in fluid loss is obtained using the additives of the invention at temperatures from 38 to 182 ° C. It is further seen that additives containing hydroxycarboxylic acids are more effective in salt water cement slurries with a salt concentration of more than 18% by weight of the water than those containing only CMHEC.

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Claims (19)

Additive according to claim 1, characterized in that it also contains a hydroxycarboxylic acid. J Additive according to claim 3, characterized in that the hydroxycarboxylic acid is gluconic, tartaric, lactic, citric, maleic or a mixture thereof. ï. Additive according to claim 4, characterized in that the hydroxycarboxylic acid is present in the additive! [50] in an amount of 50% by weight of the carboxymethylhydroxyethyl-hydroxylose present in the additive. 6. Water loss reducing additive for use in salt water cement slurry and characterized in that the J carboxymethylhydroxyethyl cellulose with a carboxymethyl D.S. j from 0.1 to 0.7, an ethylene M.S. from 0.6 to 2.8 and a molecular weight such that a 1 wt% aqueous solution thereof at a temperature of 25.6 ° C has a viscosity of 10 to 225 centipoise, measured on a FANN fish cosimeter at 300 revolutions per minute using a spring number 1 and a hydroxycarboxylic acid in the form of gluconic acid, tartaric acid, lactic acid, citric acid, maleic acid or a mixture thereof, the acid being present in the additive amount of 50% by weight of the carboxymethyl-hydroxyethyl cellulose in the additive. Additive according to claim 6, characterized in that the carboxymethylhydroxyethyl cellulose has a carboxymethyl D.S. of 0.4, an ethylene oxide of M.S. of 2.0 and has a molecular weight such that said viscosity is from 10 to 225 centipoise and the hydroxycarboxylic acid is citric acid. 8. Salt water cement slurry which loses little water on contact with permeable earth formations, characterized in that the slurry contains: salt water, cement and a water loss reducing additive, consisting of carboxymethylhydroxyethyl cellulose with a carboxymethyl DS of 0.1 to 0, 7, an ethylene oxide MS from 0.6 to 2.8 and molecular weight such that a 1 wt% solution thereof in water at a temperature of 25.6 ° C has a viscosity of 10 to 225 centipoise, measured on a FAUN fish cosimeter at 300 revolutions per minute using a spring number 1. Cement slurry according to claim 8, characterized in that the carboxymethylhydroxyethylcellulose has a carboxymethyl D.S. of 0.4, an ethylene oxide M.S. of 2.0 and has a molecular weight such that said viscosity is 10 to 250 t centipoise. Cement slurry according to claim 8, characterized in that the carboxymethylhydroxyethylcellulose is present in the cement slurry in an amount of 0.2 to 2.0% by weight of the dry cement in the slurry. Cement slurry according to claim 7, characterized in that this slurry also contains a hydroxycarboxylic acid. Cement slurry according to claim 11, characterized in that the hydroxycarboxylic acid is gluconic acid, tartaric acid, lactic acid, citric acid, maleic acid or a mixture thereof. Cement slurry according to claim 12, characterized in that the hydroxycarboxylic acid is present in the slurry in an amount of 0.1 to 1.0% by weight of the dry cement in the slurry. 14. Salt water cement slurry which, on contact with | for water permeable earth formation loses little water, characterized in that this slurry contains: j 10 salt water, 1; cement and a water loss reducing additive consisting of carboxymethylhydroxyethylcellulose with a carboxymethyl D.S. from 0.1 to 0.7, an ethylene oxide M.S. from 0.6 to 2.8 and a molecular weight such that a 1 wt% aqueous solution thereof at a temperature of 25.6 ° C has a viscosity of 10 to 225 centipoise, measured on a FAffl fish cosimeter at 300 revolutions per minute below ge; using a spring number 1 and a hydroxycarboxylic acid 20 in the form of gluconic, tartaric, lactic, citric, maleic or a mixture thereof, which acid is present in the additive in an amount of 50% by weight of carboxymethylhydroxyethyl cellulose in the additive. Cement slurry according to claim 14, characterized in that the carboxymethylhydroxyethyl cellulose has a carboxymethyl D.S. of 0.4, an ethylene oxide M.S. of 2.0 and a molecular weight such that said viscosity is 10 to 200 µ centipoise and is present in the slurry in an amount of 0.2 to 2.0 wt% of the dry cement in the i. .. · I mash. 16. A method for reducing the water loss from a salt water cement slurry used in cementing a well, characterized in that the slurry is combined with a water before use 8103326 a 5 * - 17 groin-reducing additive, consisting of carboxymethylhydroxyethylcellulose with a carboxymethyl DS of 0.1 to 0.7, an ethylene oxide MS from 0.6 to 2.8 and a molecular weight such that a 1 wt% aqueous solution thereof at a temperature of 25.6 ° C has a viscosity of 10 to 225 centipoise, measured on a FAUN fish cosimeter at 300 revolutions per minute using a spring number 1. 17. Process according to claim 16, characterized in that the carboxymethylhydroxyethylcellulose has a carboxymethyl D.S. of 0.4, an ethylene oxide M.S. of 2.0 and has a molecular weight such that the viscosity is 10 to 200 centipoise. A method according to claim 16, characterized in that the additive also contains a hydroxycarboxylic acid. Process according to claim 18, characterized in that the hydroxycarboxylic acid is included in the slurry in an amount of 50% by weight of the carboxymethylhydroxyethyl cellulose e combined with the slurry. 20. Method for reducing the water loss from a salt water cement slurry used in cementing a well, characterized in that the slurry is combined with a water loss reducing additive prior to use, consisting of carboxymethyl hydroxyethyl cellulose with a carboxymethyl DS of 0.1 to 0.7, an ethylene oxide MS from 0.6 to 2.8 and a molecular weight such that a 1 wt% aqueous solution thereof at a temperature of 25.6 ° C has a viscosity of 10 to 225 centipoise, measured on a FANN viscometer at 300 revolutions per minute using a spring number 1, which carboxymethylhydroxyethylcellulose is included in the slurry in an amount of 0.2 to 2.0 wt% of the dry cement in the slurry and a hydroxycarboxylic acid in the form of gluconic, tartaric, lactic acid citric acid, maleic acid or a mixture thereof, which acid is included in the slurry in an amount of 0.1 to 1.0 wt% of the dry cement in the slurry. Process according to claim 20, characterized in that the carboxymethyl hydroxyethyl cellulose has a carboxymethyl D.S. of 0.4, an ethylene oxide M.S. of 2.0 and one; 5 has molecular weight such that said viscosity is 10 to 200 centipoise and the hydroxycarboxylic acid is citric acid. ! 10 f i i I: l i "1 j, 1: | t i. I j i • i i J j 8103326