NL8103669A - METHOD FOR PREPARING WELL TREATMENT FLUIDS - Google Patents

Description

. ff 1T.0. 30,266 -1- 'f

Process for Ae 'preparation of utility treatment liquids.

The present invention relates to the preparation of polymer-containing salt solutions, which are suitable for various applications, in which an increase in viscosity, filtrate control or other functional property is derived from the polymer preparation present there.

Polymer-containing saline solutions are useful as well treatment fluids, such as drilling fluids, recovery fluids, completion fluids, packer fluids, well handling fluids, subsurface formation fluids, spacer fluids and well abandonment fluids and in other applications where thickened aqueous media are required. It is known to use hydrophilic polymers, such as, for example, hydroxyethyl cellulose (HEC) as thickeners for aqueous media, such as those used in well treatment fluids. However, such polymers are not readily hydrated, containing one or more water-soluble salts of polyvalent cations, are hydrated, dissolved or dispersed, such as the saline solutions for heavy oil fields with a density greater than about 1.39 kg / dm @ 2 at preference for the preparation of well treatment fluids. Elevated temperatures and / or high shear mixing for extended periods of time are required to effectively thicken such brines with hydrophilic polymeric materials to obtain a homogeneous mixture. In many cases, such as, for example, in repair operations, the equipment available for the preparation of well treatment fluids does not really lend itself to such conditions. Consequently, when it is desired to use such thickened saline solutions, it is usually necessary to prepare them outside the well site or to circulate the liquid in the hot borehole.

It is therefore an object of the present invention to provide a process for the preparation of thickened polymer containing salt solutions, in particular heavy salt solutions with a density greater than 1.39 kg / dm 2 under conditions of low shifting mixing without the application of heat.

Other objects and advantages of the invention will be apparent. -2- are apparent from the following description thereof, together with the appended claims.

According to the invention, a suspension of a hydrophilic polymer and water is formed by generally dispersing the polymer uniformly in the water. An inorganic salt with a positive heat of dissolution is then added to the slurry in the absence of external heating, the amount of salt added being sufficient to raise the temperature of the dispersion above 71 ° C due to the heat of dissolution of the salt. Depending on the desired density, this suspension can be used directly as a well treatment liquid.

In another embodiment of the invention, a sufficient amount of a heavy aqueous saline is added to the polymer liquid suspension to provide an amount of well treatment fluid of the desired density.

The hydrophilic polymers suitable for carrying out the invention are particulate organic polymers which are generally water-soluble or water-dispersible and which, after dissolution or dispersion in an aqueous medium, have a viscosity of enlarging the system, but which do not readily hydrate, dissolve or disperse upon addition to heavy salt solutions with a density greater than 1.39 kg / dm 2 and which contain soluble salts of polyvalent cations. Such polymers are selected from the group consisting of cellulose derivatives, water-dispersible starch derivatives, polysaccharide gums and mixtures thereof. Examples of cellulose derivatives are the carboxyalkyl cellulose ethers, such as carboxymethyl cellulose and carboxyethyl cellulose; Hydroxyalkyl cellulose ethers such as hydroxyethyl cellulose and hydroxypropyl cellulose and mixed cellulose ethers such as: carboxyalkylhydroxyalkyl cellulose, ie carboxymethylhydroxyethyl cellulose; alkyl hydroxyalkyl cellulose; that is, methyl hydroxyethyl cellulose, methyl hydroxypropyl cellulose; alkyl carboxyalkyl cellulose, i.e., ethyl carboxymethyl cellulose. See U.S. Patent 4 * 110,230. Examples of starch derivatives are the carboxyalkyl starch ethers such as carboxymethyl starch and carboxyethyl starch; hydroxyalkyl starch ethers, such as hydroxyethyl starch and hydroxypropyl starch, and mixed starch ethers such as: carboxyal-40-kylhydroxyalkyl starch, that is, carboxymethylhydroxyethyl starch-8103669 flour; alkylhydroxyalkyl starch, i.e. methylhydroxyethyl starch; alkylcarboxyalkyl starch, i.e. ethylcarboxymethyl starch. Examples of polysaccharide gums include: the bio-polymers such as Xanthomonas (xanthan) gum; galactomannan gums, such as guar gum, locust bean gum, tara gum; glncomannan gums and derivatives thereof, in particular the hydroxyalkyl derivatives. See U.S. Pat. Nos. 4 * 021,355 and 4-105 * 461. Other polymers that can be used include pre-gratinized starch powder and stabilized, partially dextrinized polysaccharide-10 powder, toxic nonionic.

Especially preferred are the HEC polymers, which are generally high yield water-soluble, nonionic polymers prepared by treating cellulose with sodium hydroxide followed by reaction with epoxyethane. Each anhydroglucose unit in the cellulose molecule has three reactive hydroxyl groups. The average number of moles of the epoxyethane bound to each anhydroglueose unit in cellulose is called the number of moles of the combined substituent. In general, the greater the degree of substitution, the greater the water solubility. In general, it is preferred to use HEC polymers with the greatest possible molar substitution.

Usually, after the addition of any of the above-described dry particulate hydrophilic polymers to aqueous media, such as saline solutions, the polymer particles undergo surface hydration, which prevents the interior of the particle from easily hydrating, dissolving or otherwise dispersing in the water containing environment. As a result, high shear, long mixing times and / or elevated temperatures must be used to achieve a homogeneous system. Using the method of the present invention, the hydrophilic polymers are easily hydrated, dissolved or dispersed in the aqueous salt solution at a relatively low shear and low ambient temperatures.

At the initial stage of the process, the hydrophilic polymer and the water, such as, for example, fresh water, distilled water, etc., are mixed under such conditions that an even dispersion of the polymer in the water is obtained. The term "uniform dispersion" as used herein refers to a state in which the polymer and water form a generally homogeneous system, whether the state is a solution or a mixture, in which discrete polymer particles are generally evenly distributed through the suspension of polymer and water. The polymer and it. water can be mixed by conventional mixing techniques and no special conditions of temperature, mixing times or other such parameters are required. It is sufficient only that the polymer and water are mixed sufficiently to provide the uniform dispersion of the polymer slurry in the water.

In the next step of the process, one or more inorganic salts in dry form are added to the suspension of the polymer and the water, the salt being of a type having a positive heat of dissolution and brine heat, develops after dissolving in water. The amount of the inorganic salt added to the polymer slurry will be such that a temperature above about 40 ° C is provided due to the heat of dissolution of the salt and without the addition of external heating. Dissolution of the salt in the polymer slurry can be performed by conventional mixing techniques.

The inorganic salt or inorganic salts which can be used in the second step of the process are all water-soluble salts which generate heat after dissolving in water and which preferably form saline solutions suitable for hydrocarbon recovery operations. Preferred salts are salts selected from the group consisting of calcium chloride, calcium bromide, zinc chloride, zinc bromide and mixtures thereof. As mentioned, preferably the amount of added salt should be such that the temperature of the polymer / water slurry is raised above about 70 ° C. It is preferred, however, that the amount of salt added is such that the temperature is raised to at least 82 ° C and most preferably to at least 93 ° C. It will be understood that different salts have different positive heat of dissolution and therefore the amount of added salt or added salts will depend on the special salt or salts selected or selected.

The polymer / water suspensions prepared as above can themselves be used as well treatment fluid feh, when the amounts of inorganic salts added are sufficient to achieve the desired density. Except, for example, in a particular case, the amount of mixed polymer, 40 water and inorganic salt may be sufficient to form a thickened salt solution of the desired density. More frequently, however, an aqueous salt solution of a given density is added to the polymer / water suspension containing the dissolved salt, the aqueous salt solution being added in such an amount that a. well treatment fluid of a predetermined density is provided. In this latter embodiment of the process of the invention, the polymer, water and inorganic salt are mixed as described above to hydrate the polymer and form the polymer / water slurry. After this, the aqueous salt solution is mixed with the polymer / water slurry containing the inorganic salt and the well treatment liquid is thus prepared. The aqueous saline solutions which can be mixed with the polymer / water suspensions generally contain soluble salts such as, for example, a soluble salt of an alkali metal, an alkaline earth metal, a metal of the group Ib of the Periodic System, a metal of the group lib of the Periodic System as well as water-soluble salts of ammonia and other cations. Generally speaking, such aqueous saline solutions contain soluble salts of polyvalent cations, for example, zinc and calcium. In addition, aqueous saline solutions containing a salt selected from the group consisting of calcium chloride, calcium bromide, zinc chloride, zinc bromide and mixtures thereof are particularly preferred. The aqueous saline solutions will generally have densities ranging from about 1.39 kg / dm 2 to about 2.30 kg / dm 2.

The amount of hydrophilic polymer used in the method of the present invention will be such as to provide a final concentration of from about 0.28 to about 28.5 kg / m 2 regardless of whether the final well treatment liquid (a) prepared the polymer / water suspension by mixing the polymer, water and the inorganic salt or (b) the polymer, water, inorganic salt and an amount of an aqueous salt solution.

While the mechanism of the method of the present invention is not fully understood, it has been found that saline solutions prepared by this method have improved rheological and filtration properties as opposed to saline solutions, which are prepared simply by dispersion of the hydrophilic polymer 8103669 V - '_ .....

* · V

-6- in dry form in saline and then heating the mixture to dissolve the polymer. The application of artificial heat to the mixture of a hydrophilic polymer and a salt solution, while giving some improved results, does not achieve the remarkable results obtained by the method, wherein the polymer is first dispersed in water and then this suspension at an elevated temperature is introduced through the natural heat of dissolution mechanism of the one or more inorganic salts, which dissolve in the polymer / water suspension. In order to more fully illustrate the present invention, the following nonlimiting examples are given. Unless otherwise specified, all physical property measurements were performed according to the test methods set forth in STANDARD PROCEDURE FOR TESTING DRILLING ELUID, API HP 13B, 7th Edition, April 1978. In the following examples, the following hydrophilic polymers were used:

Hi Yis CELLEK (carboxymethyl cellulose marketed by BARAZAN (zanthan gum marketed by NATRASOL 230 HHR (hydroxyethyl cellulose marketed 20 by Hercules Chemical Company) DRISPAC (polyanionic cellulose powder marketed by B0HRAJyiYL (cross-linked hydroxyethyl starch) brought by 25 IMPERHEX (pregelatinized starch powder marketed by DEXTRID (stabilized partially dextrinized polysaccharide powder, toxic nonionic marketed by Example I.

Various hydrophilic polymers were used to prepare the thickened aqueous saline solutions described below. About 2 g of the polymer were mixed in 204.4 S water using a "multimixer" for about 1.0 minutes. Next, to the pre-hydrated polymer were added 114 g of CaCl 4 granules (94 - 97%) and 280.5 g of CaBr (91%), followed by 16.8 ml of a CaBr 3. ZnBr 2 saline of 2.3 kg / cLur to bring the density of the resulting saline to 1.82 kg / dm 2. The heat of dissolution of the added salts brought each sample to boiling point (100 ° C). The resulting thickened mixtures were left overnight at 8103669. The ambient temperature was kept and the rheological and filtration properties of each mixture were then determined. Rheological properties were measured using a Farm Model 35A Yisco meter and a Brookfield BYT Yiscometer. The filtration properties were measured on an API filter press. The properties listed are 2 plastic viscosity (PY) cP, yield strength (ïP) kg / m, apparent viscosity (AY) cP, gel strength at 10 seconds (GEL 10 s) kg / m and API filtrate (ΑΡ ^ -Ί ^ ΐι) ml. All filtration tests were performed after adding 28.5 kg / m 2 as a backing. Results of 10 measurements performed are presented in Table A. Table B gives the same information for identical samples after being rolled at 66 ° C for 16 hours.

(see tables A and B).

Image II.

Control solutions of thickened aqueous saline solutions were prepared by adding 2 g of each of the dry polymers used in Example I to a pre-prepared saline of 1.82 kg / dm prepared by mixing 214> 2 g of water , 119 µf CaClg, 294> 0 8 CaBr2 and 16.2 ml of a CaBrg / ZnBrg saline 20 of 2.30 kg / dm 2. Data on the rheological and filtration properties of the control samples after overnight storage are presented in Table C, while similar data on identical samples after being rolled at 66 ° C for 16 hours are presented in Table D. These data compared to those of the Tables A and B show that the salt solutions prepared according to the method of the invention (Example i), in which the polymer is first hydrated and the dry salts are added thereto, exhibit better viscosity and give lower filtrates in any case before rolling takes place in the heat and in almost all cases after rolling in the heat.

(see Tables C and D),

Figure III.

Using the method described in Example I, polymer-containing aqueous salt solutions of several different densities were prepared. 5 ff Hi Yis Cellex were pre-hydrated in water by mixing for 10 minutes. Dry CaCl 2 beads were added to the pre-hydrated polymer with mixing to obtain a Hi Yis Cellex concentrate with a density of 1.39 kg / dm 2. 140 ml of the concentrate were added to 210 ml of an aqueous saline solution with a density of 8103669 "-8" of 1 kg / m 2 to achieve a polymer concentration of 5> 7 kg / m ^. In the same manner, heavy water-containing salt solutions of 1.70 and 2.0 kg / dm 2 were prepared. 33rd composition of each of the aqueous saline solutions is shown in Table E.

5 (see Table E).

Control samples of thickened aqueous saline were prepared by mixing 2 g of the dry Hi Yis Cellex with pre-prepared saline with densities of 1.39, 1.70 and 2.04 kg / dm 2, respectively. Eological and filtration measurements of the 10 samples prepared according to the method of Example I and the control samples were performed as described in the previous examples. The results are presented in Table E. Table G presents the data obtained from all samples after hot rolling at 66 ° C for 16 minutes. It is clear from these data that the apparent viscosities of the salt solutions prepared according to the method of the invention have values twice or more than those of the control samples. The better filtration properties of the samples prepared according to the method of the present invention are also readily apparent from a comparison of these data.

(see Tables E and G).

Yoorbeeld 17.

Saline solutions with a density of 1.85 kg / dm 2 and containing 2.85 kg / m 2 carboxymethyl cellulose, either Hi Yis Cellex 25 (high viscosity grade) or DEISPAC, were prepared by adding the polymer to 176 ml of water and mixing until the polymer dissolved. Thereafter, 114 g of CaCl- (95%) and 180 g of GaBrg (91%) (equivalent to 329 and 798 kg / n) were added with mixing. The heat of dissolution of these salts raised the temperature to 100 ° C. The API rheology and the fluid loss were determined in these viscous solutions after cooling to ambient temperature. The data obtained are shown in Table H.

(see table ïï).

Yoorbeeld Y.

Saline solutions of varying density containing hydroxyethyl cellulose (NATE0S0L 250 HER) of 4 28 kg / m 2 were prepared by mixing the polymer with the amount of water indicated in Table B. When the polymer hydrated in the water, the viscosity increased. Then the indicated amount of CaClg (95% active) 40 was added with mixing. The heat of dissolution of the CaClg raised the temperature about 82 ° C to 8103669-9 and the solution became more viscous. The indicated amount of 44.5 kg / m2 of CaBr2 solution was added slowly followed by the indicated amount of ZnBr2 / CaBr2 solution of 2.30 kg / dm * *. After cooling to ambient temperature in one hour, the API rheology and fluid loss were obtained. The solutions were then rolled at 66 ° C for 16 hours, cooled to ambient temperature, and the API rheology and fluid loss were determined. The data are included in Table I.

(see Table I.).

10 Example VI.

Three Hi Yis Cellex polymer concentrates were prepared by dispersing 2 g of the polymer in 3.89 ml of water. One concentrate (control sample) was diluted with 155.5 nil water, followed by the addition of 114.0 g CaClg, 280.5 g CaBr2 and 16.8 ml of a 2.30 kg / dm CaBr2 / ZnBr2 saline. ^. The temperature of this sample reached 100 ° C.

A second concentrate (sample A) was added to saline at ambient temperature. The saline was prepared with 155.5 nil water, 114.0 g of CaClg, 280.5 g of CaBr2 and 16.8 ml of a 2.30 kg / dm 2 CaBr2 / ZhBr2 saline. The addition of the concentrate under mixing caused heat to develop, bringing the sample temperature to 45 ° C. It was noted that insoluble lumps of carboxymethyl cellulose were immediately formed. On overnight cooling, a large amount of suspended tapes 25 were formed, which optionally floated to the surface. It did not appear that some of the polymeric concentrate went into the saline solution.

A third concentrate (sample B) was prepared as in the case of sample k and heat was redeveloped when the eon-50 centrate was added with mixing, the temperature reaching 45.5 ° C. After this, sample B was rolled in an aging cell at 100 ° C for 3 hours. The sample temperature after aging was measured as 71 ° C. Although some suspended polymer bands formed and floated to the surface, most of the polymer concentrate appears to have been dispersed.

The previous three samples were then rolled at 66 ° C for 64 hours. After cooling, they were placed on a Brookfield viscometer at 50 rpm. The control sample had a reading of 1590 cP and showed a flat consistency, such as 40 before rolling.

8103669 * «-10-

Most of the insoluble clumps and all suspended bands dissolved in Sample A. The Brookfield reading was nevertheless only 180 cP.

Sample B, which appeared homogeneous, showed a Brookfield reading of 250 cP.

From the foregoing results, it is apparent that simple prehydration of the polymer in water only (Sample A) is not the mechanism of the salt-activated method of the present invention. In other words, it is also necessary, after dispersion of the polymer in water, that the dry salt or the dry salts, with positive heat of dissolution, are added to the polymer concentrates. While the application of artificial heat (rolling at 100 ° C) produces some reaction (the Brookfield reading of 250 cP on sample B, compared to the Brookfield reading of 180 cP on sample A), the effect is nothing in compared to the Brookfield reading of 1590 cP used in the control sample prepared by the salt activation method.

8103669 5- * -11-

Table A.

GEL API

PT XP AT 10 a PIL

CELLEX HT - 0 150+ 1.18 1.5 BARAZAN 92 1.44 109 0.12 6.5 LRISPAC - - 150+ 1.97 0.5 BOHRAMXL 80 0.19 82 0.10 3.0 IMPERMEX 72 0 .29 74 0.10 100 LEXTRIL 75 0.29 76 0.07 53-

Table B.

GEL API

PT XP AT 10 a PIL

CELLEX HT 150+ 0.53 0.5 BARAZAN - - t50 + 0.29 4.5. LRISPAC - - 150+ 0.43 0.5 BOHRAMYL 76 0.19 78 0.10 1.0 IMPERMEX 62 0.19 64 0.10 77 LEXTRIL 68 0.29 71 0.10 89

Table C.

GEL API

FT XP AT 10 3 · PIL

CELLEX HT 54 0 54 0.10 180 B ΑΡΑΖΑΝ 46 0 46 0.07 201 LRISPAC 55 0.05 55 0.07 174 BOHRAMXIi 49 0.05 49 0.05 190 IMPERMEX 51 0.05 52 0.10 172 LEXTRIL 51 0.05 51 0.07 170.

Table L.

GEL API

PT XP AT 10 3 PIL

CELLEX HT 49 0 50 0.10 250 BARAZAN 67 - 67 0.07 1 LRISPAC 50 0.14 52 0.07 262 BOHRAMXL 73 - 71 0.07 6 IMPERMEX 67 0.29 70 0.10 42 LEXTRIL 65 - 64 0 , 07 6.

8103669 -12-

Table E.

_. 20 ml of water, ml 299.6 234> 2 112.2

CaCl2, g 197.7 137.9 62.6

CaBr-, g - 224.3 154.1

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2.30 kg / dnr saline, ml - 166.6.

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Claims (15)

1. Process for "preparing a liquid suspension of a hydrophilic polymer in a water" containing saline, characterized in that a hydrophilic polymer and water are mixed under conditions which give a generally uniform dispersion of the polymer in To provide the water, dissolves in the dispersion an inorganic salt with a positive heat of dissolution, which salt is added in an amount such that a temperature in the dispersion is reached above 71 ° C as a result of the heat of dissolution of the salt. 2. Process according to claim 1, characterized in that the hydrophilic polymer is selected from the group "consisting of carboxyalkyl cellulose ethers, hydroxyalkyl cellulose ethers, mixed cellulose ethers, carboxyalkyl starch ethers, hydroxyalkyl starch ethers, mixed starch ethers, polysaccharide gums, pre-gelatinized -Tinated starch powder, stabilized, partially dextrinized polysaccharide powder, toxic nonionic and mixtures thereof. 5. Process according to claim 1 or 2, characterized in that the inorganic salt used is a salt selected from the group consisting of calcium chloride, calcium bromide, zinc chloride, zinc bromide and mixtures thereof. 4. Process according to claims 1-3 », characterized in that a temperature higher than 82 ° 0 is developed by the heat of dissolution of the inorganic salt. 5 5. Method according to claims 1-4? characterized in that a temperature higher than about 93 ° C is developed by the heat of dissolution of the inorganic salt. 6. Process according to claims 1-5 », characterized in that the hydrophilic polymer in the suspension is used in an amount of from about 0.285 to about 28.5 kg / m 2. 7. Process according to claims 1-6, characterized in that a hydrophilic polymer is used, which contains hydroxyethyl cellulose. 8. A process for the preparation of an aqueous salt solution suitable as a well-handling liquid, characterized in that a hydrophilic polymer and water are mixed under conditions which give a generally uniform dispersion of the polymer. to provide the water, dissolves in the dispersion an inorganic salt with a positive heat of dissolution, which salt is added in an amount of 8103669% - 4 · 1 -1 -16 - such that a temperature in the dispersion is reached above about 71 ° C as a result of the heat of dissolution of the salt and adding to the dispersion an aqueous salt solution of a given density in an amount sufficient to give a. well treatment fluid. to produce a predetermined density. Process according to claim 8, characterized in that the hydrophilic polymer used is a polymer selected from the group consisting of carboxyalkyl cellulose ethers, hydroxyalkyl cellulose, ether ethers, mixed cellulose ethers, carboxyalkyl starch ethers, hydroxyalkyl starch ethers, mixed starch ethers, polysaccharide gums, pregelatinized starch powder, stabilized, partially dextrinized polysaccharide powder, toxic, nonionic and mixtures thereof. 10. Process according to claim 8 or 9, characterized in that the inorganic salt used is a salt selected from the group consisting of calcium chloride, calcium bromide, zinc chloride, zinc bromide and mixtures thereof. 11. Process according to claims 8-10, characterized in that the process is continued. the heat of dissolution of the inorganic salt develops a temperature higher than about 82 <> C. Process according to claim 11, characterized in that a temperature higher than about 95 ° C is developed by the heat of dissolution of the inorganic salt. 1. Process according to claim 8, characterized in that an aqueous salt solution is used, which contains at least one salt, selected from the group consisting of water-soluble salts of alkali metals, alkaline earth metals, metals of group Ib of the Periodic System, metals of group lib of the Perio-50 dieke System and mixtures thereof. 14. Process according to claim 15, characterized in that an aqueous salt solution is used, which as water-soluble salt contains a salt selected from the group consisting of calcium chloride, calcium bromide, zinc chloride, zinc bromide and mixture thereof. 15. Process according to claims 8 - 1.4, characterized in that a hydrophilic polymer is used, which contains hydroxyethyl cellulose. 16. Process according to claims 8-15, characterized in that the polymer is used in an amount of about 0.285 to about 28.5 kg / m 2. 17. Process according to claims 8-16, characterized in that a well preparation liquid is prepared having a density of about 1.59 to about 2.30 kg / dm 3. The authorized representative hereby sends in duplicate a sheet with corrections for page 6, lines 17, 18, 22, 24, 26 and 28, page 8, lines 1, 28 and 37 and page 9, lines 1 and 2 of the Dutch description regarding the above-mentioned patent application. The authorized representative requests you to enclose the attached sheet with the printed documents to be made available for inspection and to deduct the required page tax of authorized representatives from you. ςμί e ^ 8103669% Associated with OA 8103669 T.n.v. HL Industries Ine. Amendment sheet Page 6: add line 17 "HL Industries Ine." add line 18 "NL Industries Ine." line 22 add "Drilling Specialties" line 24- add "Auebe N.V." line 26 add "HL Industries Ine." line 28 add "HL Industries Ine." rule 18 change zanthan to xanthan. P. 8: line 1 change 33.1 to 1.39 line 28 798 change to 513 line 37 B change to I Page. 9: add line 1 after temperature "to" change line 2 44.5 to 1.70 8103669