DE3003747A1 - METHOD FOR DRILLING HOLES - Google Patents

Description

The invention relates to the use of a copolymer

(1) a (Meth-J-Acrylamidoalkylsulfonic acid or its Alkali metal salt and

(2) a (meth) acrylamide or N-alkyl (meth) acrylamide

or a crosslinked copolymer of components (1) and (2) to effectively reduce the filtrate losses of aqueous drilling fluids used in drilling underground wells or shafts.

It is generally accepted that rotary systems are an acceptable form of drilling oil or gas wells. These systems are built on the rotation of a drill pipe with a multi-pronged cutting edge attached to the bottom is. The cutting edge cuts into the earth and causes the accumulation of cut materials, if drilling continues »A drilling fluid must therefore be used to cut it off To bring materials to the surface for removal so that the bit can function continuously and the borehole can be kept clean and free of loose material at all times. at Drilling operations, drilling systems other than rotary systems are sometimes used. However, these also require Systems a drilling fluid to remove the loose material and other functions perceive the drilling fluid.

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Oil producing formations are generally porous Layers with different permeability to the flow of flowable media, e.g. oil, water or Gas. The speed of oil production therefore depends heavily on the flow rate through this permeable Formations, which in turn depend on the porosity or permeability of the existing sand or stone depends. When drilling through such a porous layer, it is desirable to have a drilling fluid with such characteristics to use that prevents large amounts of liquid or solids from flowing through the porous Penetrate formation. The ability of the drilling fluid to excessively penetrate the formation Preventing through the liquid is known as filtration control. .

Materials hitherto used to control the filtration rates of aqueous drilling fluids Forming pegs, making cakes, or similar methods have been used to have materials such as pregelatinized starch, sodium carboxymethyl cellulose, Sodium polyacrylates and lignites, including · All however, these materials have certain limitations. For example, lignite is formed at high salt concentrations ineffective.

Acrylic and methacrylic acid derivatives, for example those made with styrenes substituted with hydrocarbons, such as alpha-methylstyrene, para-methylstyrene, 2,4-dimethylstyrene and the like, copolymerized, have heretofore been used in drilling fluids · So for example, U.S. Patent No. 2,718,497 uses it of polymers of these materials with a relatively high

03G037 / Q614- "/ ■ ■ . \

Molecular weight to control water release properties of aqueous sludges and clay dispersions. In US Pat. No. 2,650,905, the use of water-soluble sulfonated polystyrene derivatives for the filtration control of water-based drilling fluids described *

According to the prior art acrylic acid derivatives are already as thickeners for numerous technical © Anwendungssweek © with inclusion of drilling fluids verwandet vordea _o For example, in US Pat h 059 552 describes the use of Acrylamidnatriumacrylat or substituted acrylic acid acrylates "A similar Verdikkungsmaterial is in the US-PS 4 O37 O35 _s besehrisben wherein a Acrylamidnatriumacrylat component is used with a Acrylamidacrylsäurealkanolamin _o Similarly, copolymers of acrylamide and Natriumaerylat and acrylate derivatives thereof which have been formed by Bestrahlungspolymeri "organization, used as thickeners, as for example, in U.S. Patent 3,926,576. US Pat. No. 3,897,404 describes the use of substituted acrylamide acrylic acid acrylate derivatives as thickeners for printing pastes and the like. - ... - '- ■'. '

It has been shown that hydrophilic gels ₀ which are derived from 2-hydroxyethyl methacrylate, for a number of medical applications purposes as a material for the gel filtration are "Examples thereof are copolymers of acrylamide, Acrylester-hydroxyethyl methacrylate 2-, as described in US-PS 3 948 841.

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Crosslinked acrylamide-sodium acrylate-2-hydroxyethyl acrylate materials with a relatively high molecular weight are used as soil stabilizers according to US Pat. No. 3,651,002 »

Acrylic acid derivatives such as copolymers of acrylamide and sodium acrylate derivatives are frequently and technically used as flocculants for drilling fluids. you will be for example in U.S. Patents 3,558,545 and 3,472 described. Similarly, U.S. Patent 3,323,603 a copolymer of acrylic acid and acrylamide is described as a flocculant for aqueous drilling fluids.

Acrylamide / 2-acrylamido-2-methylpropanesulfonate and polymers of N-sulfohydrocarbon-substituted acrylamides have been used as viscosity agents in water flooding processes for secondary and tertiary oil production (see e.g. US Pat. No. 3,679,000, ^B A Comparative Evaluation of Polymers For Oil Recovery - Theological Properties "by Miklos T. Szabo, Society of Petroleum Engineers, AIME, Paper Number SPE 66OI-A, and" Recent Advances In Ion-Containing Polymers ⁿ by MF Hoover and GB Butler (J. Polymer SCL: Symposium No. 45, 1 to 37, 1974)).

The present invention relates to an aqueous drilling fluid, a filtration control agent for use in this aqueous drilling fluid and "a method for forming a filter cake on the wall of a borehole to reduce the filtrate of the drilling fluid. According to the invention, a copolymer of (i) a (meth -) - acrylamidoalkylsulfonic acid or alkali metal salt thereof and (2) a (meth -) - acrylamide or N-alkyl (meth -) -.. using acrylamide The copolymer can with a quaternary ammonium salt crosslinking agent be crosslinked -ί '' ■ * ■ ^r \

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According to the invention there is an improved filtration control obtained by incorporating into an aqueous drilling fluid a filtration control agent which is essentially from a copolymer of (i) a (meth -) - acrylamidoalkylsulfonic acid or an alkali metal salt thereof and (2) a (meth -) acrylamide or N-alkyl (meth) acrylamide consists · The copolymer of (1) and (2) can be reinforced by crosslinking with a quaternary ammonium salt be. It is believed that the copolymer along with the other components of the drilling fluid make one Filter cake along the borehole to provide effective filtration control while the drilling fluid is circulating in the borehole.

The object of the invention is to provide a filter cake _r available, which remains practically unaffected by relatively high temperatures and pressures of the wellbore. The invention is also intended to provide a filtration control means which does not significantly affect the viscosity of the drilling fluid system used. Furthermore, the invention is intended to provide a comparatively cheap and easily manufactured filtration control agent for use in aqueous drilling fluids.The invention is also intended to provide a filtration control agent for aqueous drilling fluids which works in salt environments within the aqueous system. The invention is also intended to provide a filtration control means which can be used in weighted drilling fluids.

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The invention produces a filter cake Substance provided that is effective after exposure to high temperatures and that is effective in salt environments works which are found in aqueous drilling fluids. According to the invention, a copolymer is made from

(1) a fatty) - acrylamidoalkylsulfonic acid or its Alkali metal salt and

(2) a (meth-) acrylamide or N-alkyl- (meth- ^ acrylamide

or a crosslinked copolymer of the above components (1) and (2) are used.

During the preparation of the copolymer used according to the invention two monomer materials are used, namely (1) a (meth-γ-acrylamidoalkylsulfonic acid or its alkali metal salt and (2) a (meth -) acrylamide or N-alkyl (meth) acrylamide. The copolymer can be crosslinked with a quaternary ammonium salt crosslinking agent.

In the preparation of the copolymer used according to the invention any acrylamidoalkylsulfonic acids or their alkali metal salts can be used. So can e.g., 1,3-acrylamidopropylsulfonic acid or preferably their sodium salt can be used. Sodium 2-acrylamido-2-methylpropanesulfonate is preferred used. In the preparation of the copolymer, the 2-acrylamido- 2-methylpropanesulfonic acid or its alkali metal salt in a range of about 8 to about 70 mole # can be used. In the preferred composition using the sodium salt of 2-acrylamido-2-methylpropanesulfonate an amount of about 20 mol- ^ fe as an initial starting material incorporated. . ... _ ^ _, ".-, -.-

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According to the invention, as starting raw materials are also any (meth -) - acrylamides or JM-alkyl = (raeth -) - acrylamides which are capable of doing so with the acrylamidoalkylsulfonic acid or its alkali metal salt to enter into a polymerization. Acrylamide is preferred because of its relatively cheap price, its good quality Availability and good reactivity with reagents other than monomer selected if this monomer is used, it should be employed in amounts of between about 30 to about 91 moles. Preferably about 80 M0I-5 & acrylamide are used as the starting material used·

Under certain circumstances, © s suitably be ₉ to provide the copolymer as a filtration control agent, and drilling fluid in crosslinked form, to obtain isi SaIzumgebungen, such as sea water, © ine more effective filtration * In the preparation of a crosslinked Cop "lymeren ©, the crosslinking agent is a quaternary ammonium salt, E.g. _e 3-Methacryloylo: sy-2-hydrQxypropyltrime · »thylammonium chloride, 3-acrylamido-3 = ™ © thylbutyltrim © thyI-ammonium chloride, diallyldira © thylammonium chloride ₍ N-Ms = thyl-2-vinylpyridinium methyl sulfate, N-methyl- ^ fr- vinylpyri ° diniummethylsulfat, N-Propylaerylaniidotrisaethy! ammonium · "chloride or preferably 2-Methacryloyloxyäthyltrimethylammoniummethosulfat, _o be the (meth ~) acryloyloxy = 'alkyltrimethylammonium can see in © in © r lot of Zvi => about 0.2 and about h _t k Mol- $ are used «Preferably about 0.2 mol% methacryloylosyäthyltrimethylammoniummethosulfat are used.

In making a crosslinked copolymer you can can be used: Between about 8 and about 70

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(Meth -) - Acrylaniidoalkylsulfonic acid or its alkali metal salt, between about 30 and ^ Λ mol% of (meth -) - acrylamide or N-alkyl- (meth -) - acrylamide and between about 0.2 and k _t h mol- quaternary Ammonium salt. Preferably, the crosslinked copolymers containing from about 9 _f $ 8 mol (meth -) - acrylamidoalkylsulfonic acid or its alkali metal salt, about 90 mole / £ (meth -) - acrylamide or N-alkyl (meth -) - acrylamide, and about 0.2 Molar quaternary ammonium salt.

The polymerization can be initiated by typical initiators used in aqueous systems, such as peroxides, Persulfates, persulfate sulfites and the like will. It has been found that the copolymer can be made with small amounts of the initiator, when the starting materials are heated to about 60 C. the initiator used in such conditions is closely impaired the properties of the copolymer as a filtration control agent not.

The polymerization of the above starting materials can be carried out using a variety of techniques will. For example, an emulsion, suspension, Solution or bulk polymerization can be carried out. The preferred technique is solution polymerization.

As an effective filtrate control agent, the copolymer can be added to the aqueous based drilling fluid in an amount of between about 0.25 to about 5 parts per million. (pounds per kZ gallon barrel) may be added. The amount required naturally varies according to the particular type of aqueous drilling fluid used, for example saline solution, seawater or the like, the weight of the drilling fluid used, the clay-like substances present therein and the presence

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and the amount of other chemical additives, e.g. of lignosulfonate deflocculants and the like. Simple and off-the-shelf test techniques can be used at the The location of the borehole can be easily applied to determine the amount of filtration control additive that will be applied must be added to the circulatory drilling fluid in order to ensure effective filtration control in the subsurface Get borehole. Because of material losses in the borehole, for example through adsorption on the Surface of the drilled solids and the like, it may be necessary to add in increments of the Make copolymers to the drilling fluid from time to time, to maintain the required concentration.

The effectiveness of the copolymer in controlling fluid loss drilling fluids can be determined using a simple filtration test. A standardized procedure for determining the rate of filtration is given in "A.P.I. Recommended Practice RP 13 B Standard Procedure for Testing Drilling Fluids ", 2nd Edition (April 1969).

The invention is illustrated in the examples. These describe the preparation and use of the copolymers to control fluid loss in aqueous drilling fluids

example 1

In this example, the production of a copolymers used described, with acrylamide, sodium 2-acrylamido-2-methylpropane as initial monomer starting materials with and without a crosslinking agent

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be used. A solution was made by 3O, 2 g of water and 12.3 g of 50% sodium hydroxide mixed became. The solution was cooled in an ice water bath and then in portions with 31 »8 g of 2-acrylam ± do-2-methylpropanesulfonic acid offset. The acid was added at a rate that the temperature the solution was kept below about 3 ° C. The pH of the solution was adjusted to and held between about 6.8 and about 7 * 0 ". A 64.3 g batch of Acrylamide was then added. The solution was warmed to about 30 C to dissolve the starting materials to effect. The solution was poured into a 250 ml dropping funnel convicted.

A 1-1 jacketed flask fitted with a mechanical stirrer, thermometer, reflux condenser, and 250 ml addition funnel containing the monomer mixture was charged with 263 grams of deionized keg. The water was heated to 6O ⁰ C. About 1/10 of the monomer solution was added and then 1 ml of an aqueous solution containing 18 mg of potassium persulfate was added. An exothermic reaction was observed approximately 10 minutes after the initiator had been added. The remaining monomer mixture was added dropwise over 1 hour. Every 6 minutes, 1 ml aliquots of the aqueous solution containing 18 mg potassium persulfate were added. The reaction mixture was kept at a nearly constant temperature by circulating water in the jacket of a constant temperature water bath of about 60 ° C. The temperature of the reaction mixture rose to about 65 ^° C. during the first half hour. Thereafter, it took place during the next 3 b- gradually to 6O ⁰ C.

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The very viscous gel-like reaction mixture was slowly added to 2 l of acetone and quickly stirred with it. The product precipitated into small, filterable particles as the mixing and addition technique was optimized. The product was filtered on a Buchner funnel, washed with small amounts of a 1: 1 mixture of water and acetone. The product was dried to constant weight at 105 C, which took about 2k hours. The yield of the product was almost quantitative. The product was analyzed for sulfur, which was calculated to be 4.87%. An amount of $ 4.9 was found.

A crosslinked copolymer was prepared as above by 1.8 g of 80% methacryloyloxyethyltrimetnylammonium methosulfate in lasser were reacted with the monomeric reagents before heating the reagents to 30 ° C. Otherwise the same procedure was used for the preparation of the non-crosslinked copolymers.

The monomer compositions of the samples given in Table I are for the copolymer used in the present invention (Samples G to L) and the crosslinked copolymer (Samples A to F) are representative.

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Table I.

sample

Acrylamide
(MoI- ^ j

Sodium 2-acryl-2-methacryloyl-methacrylamide-2-methyloxyethyl trimeamide propane (mol%) thylammonium (mol%)

methosulfate (Mol - ??.)

A. 73.2 24.4 2.4 B. 78.3 19.5 2.2 C. 75.0 24.8 O, 2 D. 90.0 9.8 0.2 E. 75.0 24.5 0.5 F. 90.0 9 _t 5 0.5 G 70.0 30.0 H 68.3 31.7 I. 50.0 50.0 J 50.8 49.2 K 30.0 70.0 L. 50.0 example 2

50.0

In this example and in the following examples the copolymer used according to the invention in simulated Drilling fluid environments tested, ta the filtration control properties to determine. The specified amount of the copolymer was slowly converted into barrel equivalents of one Basic sludge is sieved in, while this is subjected to a shear action on an electrical mixer was subjected to moderate speed. The shear action was then continued for a period of 30 minutes. The pH of the sample was measured through in aliquots necessary addition of sodium hydroxide

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if necessary set to about 9 »5. Thereafter, each sample was hot-rolled hours in an oven of 65.6 ⁰ to C 16. Each sample was then allowed to cool to room temperature and the pH readjusted to about 9-5 if necessary. Flow property and API filtrate tests were performed. Some of the samples were then hot-rolled again at temperatures between and 177 ° C. for the specified time and then cooled to room temperature. If necessary, the pH was readjusted to about 9-5. The flow properties and the API «filtrate were then determined again.

In this example, a mud system was made to simulate a seawater mud. The sample sludge had the following composition: 9 * 1 kg / bbl bentonite, 5 * 0 kg / bbl commercial seawater salt and 0.7 kg / bbl chromium lignosulfonate. The pH of the slurry was adjusted with sodium hydroxide to about 9 $. 5 A typical filtrate analysis of the basic sludge is as follows: 1500 mg / l chloride ions, 900 mg / l total hardness, measured as calcium ions, and 400 mg / l calcium ions.

In this example, a sludge sample and a base sludge without additive with the specified in the example " N copolymers are treated to determine the effectiveness of the filtration control and the rehological behavior to measure the liquid. The results of these tests are shown in Table XX.

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Example 3

In order to determine the effect of this temperature on the maturity of the filtration control agent according to the invention to effectively control the filtration in a sea water mud sample, sample D according to Table I of Example 1 was converted into the simulated sea water mud according to Example 2 in a concentration of 0 , 5 and 0.9 kg / bbl given. «Each sample was first hot-rolled for 16 hours at 65.6 C and then the rheological properties and the AP * I. Filtrate were measured * Then each sample was again for 10 hours at one temperature Hot rolled from I63 C. The samples were then allowed to cool. The pH was adjusted and the rheological properties and API filtrate readings were taken. The results of this test showed that the filtration control agent according to the invention continues to perform a filtration control even at temperatures above 149.degree. The results of these tests are shown in Table III.

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BATH ORIGINAL

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This example demonstrates the ability of the filtration control agent of the present invention to provide effective filtration control in fresh water and saturated salt water sludge environments. A fresh water sludge system (sludge IV-A) contained deionized water and 7.9 kg / bbl bentonite, 0.5 kg / bbl gypsum, 0.9 kg / bbl sodium chloride and 0.7 kg / bbl chromium lignosulfonate. The other fresh water sludge (sludge TV-B) contained 10.0 kg / bbl bentonite and 4.9 kg / bbl sodium chloride. The pH was adjusted to about 9 »5. A typical filtrate analysis of the first sludge was as follows: chloride ion content 3800 mg / l, 300 mg / l calcium ions and total hardness of 350 mg / 1 / bbl contained attapulgite. The rheological properties and API filtrates of these slurries were measured as in the previous tests. Table IV summarizes the results of these tests.

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Table IV A.

Conc
tration
kg / bbl , 2 sample
No. Fresh water sludge Fann replacements
600 300 200 at 65 5 »Ο * C 100 6th 5 1 , 5 3 , 5 IV-A 5 10 min
Gel value pH
value 7th API
Filtrate 0 , 5 16 h 7, 5 5, , 5 5 1 7th 0 1 , 7 A. 13.5 8th, 5 6th hot rolled 5 1 1 At first
gel value 1.5 9, 9 19 8th ο, , 2 A. 16 10, 8th, , 5 3 5 1 , 5 1 1.5 9, 8th 16, 6th Λ. ο .5 A. 18.5 6th 5 4th 3, 1 1 1 1.5 9. 6th 11 4th ν ' ¹ ·' ¹ O , 7 B. 11 8th, 6, • o 4, 5 1 O, , 5 1 5 1 9, 1 18 k O , 2 B. 15.5 11 8th, • ο 2, 1 1 1 1 9, 9 14, 8th ^; ο O , 5 B. 20th 8th 5 , 5 3, 5 1 1 , 5 0, 5 1.5 10, 9 11 6th O , 7 C. 14th 10 5 7th 5 3 1 1 1 9, 5 17, 0 ö O » ² C. 18th 17, 5 13th 3, 5 1 1 1 5 1 9, 9 13, 2 O , 5 C. 31 7, 5 5 4th 2 2 1 5 7th 9, 6th 14, 2 . ο O , 7 D. 13.5 10, 8th 8th, 1 1 1 1 9, 1 27 6th ■ Ξ O , 2 D. 18th 12th 8th .5 3 1 1 2, 4th 9, 4th 18 Λ * «· O , 5 D. 22nd 13th 9 , 5 5, 1 1 .5 1 1.5 10, 6th n. , 0 •,. O , 7 E. 23 12th 8th , 5 5 5 2 , 5 1 1, 3 9, 9 12, ,8th O , 2 E. 20th 17th 13th 6th , 5 1 1 .5 1 3 9, 9 9, ,8th ο »5 E. 28 7th 5 , 5 5 0 1 1, 5 9, 8th 6, , 4 ο , 7 F. 13th 9 , 5 6th 8th 1 1 1, 3 9, 9 12, > 2 ν. O reason
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.0300.37 / 0614

Claims (1)

PATENT LAWYERS A. 3RUNLICKER D) Pt_-ING. H. KINKELDEY cK-ΐΝα W. STOCKMAIR DR-INa ■ AaE! CA.! ECH) K. SCHUMANN DR RER NAT. APl_-PHva P. H. JAKOB D (PU-ING G. BEZOLD DR RER NAT-OPL-OCM. 8 MUNICH 22 MAXIMILIANSTRASSE 43 Feb. 1, 1980 P 14 557 MILK INCORPORATED Essex Lane, Houston, Texas 77027, USA. Method of drilling boreholes Claims 1. Method of drilling boreholes in underground Formations in which an aqueous drilling fluid is circulated in the borehole, forming a filter cake the wall of the borehole to reduce fluid loss from the drilling fluid, thereby marked that one (1) the drilling fluid a copolymer of (a) a (Meth -) - Aerylara £ doalkylsulph © nic acid or one 037 / 06U TELEPHONE (OSO) 3220 QS TELEX OS-2G SSO ■ ·· TELEGRAMS ΜΟΝΔΡΔΤ TELECOPER Alkali metal salt thereof, and (b) a (meth -) - acrylamide or N-alkyl (meth) acrylamide in an amount of at least about 0.11 kg per 159-1 barrel (0.25 pounds per gallon barrel h2) is added , and that one (2) allows the drilling fluid to circulate in the borehole 2. The method according to claim 1, characterized in that the proportion of (meth) - acrylamidoalkylsulfonic acid or its alkali metal salt in the copolymer is between about 8 mole percent and about 70 mole percent. 3 · The method according to claim 1, characterized in that the proportion of (meth) -Acrylamidoalkylsulfonsäure or its alkali metal salt is about 20 mol%. H. Process according to Claim 1, characterized in that the proportion of the (meth) acrylamide or N-alkyl (meth) acrylamide in the copolymer is between about 30 mol% and about 91 mol%. 5 · The method according to claim 1, characterized in that the proportion of (meth -) - acrylamides or of the N-alkyl- (meth-) - acrylamide is about 80 mol- ^. 6. The method according to claim 1, characterized in that the proportion of (meth) - acrylamidoalkylsulfonic acid or its alkali metal salt is about 20 mol # and that the proportion of (meth -) - acrylamides or the N-alkyl (meth) acrylamide is about 80 mol #. 7 · The method according to claim 1, characterized in that the (meth -) - acrylamidoalkylsulfonic acid or its alkali metal salt is sodium 2-acrylamido- · 2-methylpropane. "~ - ■ ■ - .. 030037/0614 8. The method according to claim 1, characterized in that the (meth) - acrylamide acrylamide is. 9 · A method according to claim 1, characterized in that the (meth -) - acrylamidoalkylsulfonic acid or its alkali metal salt is sodium 2-acrylamido-2-methylpropane in an amount of about 20 m0i-5 and that the (meth -) - acrylamide acrylamide is in an amount of about 80 mole percent. 10. A method of drilling wells in subterranean formations in which an aqueous drilling fluid in is circulated in the borehole, thereby forming a filter cake on the wall of the borehole to reduce fluid loss from the drilling fluid marked, ■ that one (1) the drilling fluid a crosslinked copolymer of (a) a (meth -) - acrylamidoalkylsulfonic acid or its alkali metal salt and (b) a (meth) acrylamide or N-alkyl (meth) acrylamide in an amount of at least about 0.11 kg per 159-1 barrel (0.25 pounds per 42 gallon barrel) and that one (2) circulating the drilling fluid in the wellbore. 11. The method according to claim 10, characterized in that the proportion of (meth- ^ acrylamidoalkylsulfonic acid or its alkali metal salt in the crosslinked copolymer is between about 8 and about 70 mole percent. 030037/0614 12. Procedure according to. Claim 10, characterized in that the proportion of the (meth) - acrylamidoalkylsulfonic acid or its alkali metal salt in the crosslinked copolymer is between about 9 and about 10 mol $
lies. 13 · The method according to claim 10, characterized in that the proportion of (meth -) - acrylamide
or the N-alkyl (meth -) - acrylamide i _n the cross-linked copolymer is between about 3 ° void about 91 mole $ located. Ik, method according to claim 10, characterized in that the proportion of (Meth-J-Acry '^ - Exd ^
or the N-alkyl (meth) acrylamide is about 90 mol $. 15. The method according to claim 10, characterized in that the proportion of (meth -) - acrylamidoalkylsulfonic acid or its alkali metal salt is about 9 »8
Mol-56 and that the proportion of (meth -) - acrylamide
or the N-alkyl (meth) acrylamide is about 90 mol $. 16. The method according to claim 10, characterized in that the (meth) - acrylamidoalkylsulfonic acid or its alkali metal salt sodium 2-acrylamido-2-methylpropane is. 17 · The method according to claim 10, characterized in that the (meth -) - acrylamide acrylamide
is. 18. The method according to claim 10, characterized in that the (meth) - acrylamidoalkylsulfonic acid or its alkali metal salt sodium 2-acrylamido-2-methy! propane is in an amount of about 9.8 mole percent and 0300Oi // 0614 that the (meth -) - acrylamide acrylamide in an amount of about 90 M0I-5 & is. 19 · Procedure for drilling boreholes in underground Formations in which an aqueous drilling fluid is circulated in the borehole, forming a filter cake the wall of the borehole to reduce fluid loss from the drilling fluid, thereby marked that one (1) the drilling fluid is a cross-linked copolymer of (a) a (meth) - acrylamidoalkylsulfonic acid or an alkali metal salt thereof, (b) a (meth) - acrylamide or an N-alkyl (meth ) acrylamide and (c) a quaternary ammonium salt in an amount of 0.11 kg per 159-1 barrel (0.25 pounds per 42 gallon barrel) and that one (2) circulate the drilling fluid in the wellbore leaves. 20. The method according to claim 19 »characterized in that the proportion of (meth) - acrylamidoalkylsulfonic acid or its alkali metal salt in the crosslinked copolymer between about 8 and about 70 moles lies. 21. The method according to claim 19, characterized in that the proportion of (meth) - acrylamidoalkylsulfonic acid or its alkali metal salt is between about 9 and about 10 mole percent. 22. The method according to claim 19 »characterized in that the proportion of (meth) - acrylamides 0SO037 / 06H or the N-alkyl (meth) acrylamide in the crosslinked copolymer is between about 30 and about 91 mol- $ » 23. The method according to claim 19, characterized in that the proportion of (meth) - acrylamide or the N-alkyl (meth) acrylamide is about 90 mol #. 2k, method according to claim 19, characterized in that the proportion of the quaternary ammonium salt in the crosslinked copolymer is between about 0.2 and about k _t k mol%. 25. The method according to claim 19 »characterized in that the proportion of the quaternary ammonium salt in the crosslinked copolymer is about 0.2 mole $. 26. The method according to claim 19 »characterized in that the proportion of (meth) - acrylamidoalkylsulfonic acid or its alkali metal salt about 9.8 Mo1- $ is that the proportion of (meth -) - acrylamides or of the N-alkyl (meth) acrylamide is about 90 mol # and that the proportion of the quaternary ammonium salt is about $ 0.2 " 27. The method according to claim 19 * thereby marked draws that the (meth -) - acrylamidoalkylsulfonic acid or its alkali metal salt sodium-2-acrylamido-2-methylpropane is. 28. The method according to claim 19, characterized draws that the (math -) - acrylamide is acrylamide. 0300 37/0614 29. The method according to claim 19 »characterized in that the quaternary Atnmoniumsalz a Is (meth -) - acryloyloxyalkyltrimethylammonium salt. 30, method according to claim 19 »characterized in that the quaternary ammonium salt is 2-methacryloyloxyethyltrimethylammoniumethosulfate is. 31 · The method according to claim 19 »characterized in that the (meth -) - acrylamidoalkylsulfonic acid or its alkali metal salt sodium 2-acrylamido-2-methylpropane in an amount of about 9 »8 mol- ^ is that the (meth -} - acrylamide is acrylamide in an amount of about 90 mol%; and that the quaternary ammonium salt is 2-methylacryloyloxyethyltrimethylammonium methosulfate is in an amount of about 0.2 mole #. 32. Aqueous drilling fluid, characterized in that it contains water, a clay-like substance suspended in the water and at least about 0.11 kg per 159-1 barrel (0.25 pounds per kilo gallon barrel) of a copolymer of (a) a ( Meth -) - acrylamidoalkylsulfonic acid or its alkali metal salt and (b) a (meth -) - acrylamide or N-alkyl- (meth -) - acrylamide. 33. Drilling fluid according to claim 32, characterized in that the proportion of (meth) - acrylamidoalkylsulfonic acid or their alkali metal salt in the copolymer between about 8 and about 70 mol% lies. 3k, drilling fluid according to claim 32, characterized in that the proportion of (meth -) - 0 3 0 0 r: 7/0 6 U Acrylamidoalkylsulfonic acid or its alkali metal salt is about 20 mole percent. 35 · drilling fluid according to claim 32, characterized in that the portion of the (meth -) - acrylamide or the N-alkyl- (meth-) acrylamide in the copolymer is between about 3 ° and about 91 mol- #. 36. Drilling fluid according to claim 32 _t characterized in that the proportion of the acrylamide or N-alkyl of acrylamide is about 80 mole% - (meth -) - (meth -). 37 · drilling fluid according to claim 32, characterized in that the proportion of (meth -) - acrylamidoalkylsulfonic acid or its alkali metal salt is about 20 mol # and that the proportion of (meth -) - ' Acrylamides or the N-alkyl- (meth-) - acrylamide is about 80 - #. 38, drilling fluid according to claim 32, characterized in that the (meth -) - acrylamidoalkylsulfonic acid or its alkali metal salt is sodium 2-acrylamido-2-methylpropane. 39 · drilling fluid according to claim 32, characterized in that the (meth ) acrylamide Is acrylamide. k0. Drilling fluid according to claim 32 _t characterized in that the (meth -) - acrylamidoalkylsulfonic acid or its alkali metal salt of sodium 2- 03Ö037 / O6U 30037A7 acrylamido-2-methylpropane in an amount of about 20 and that the (meth -) - acrylamide is acrylamide in a lot of about 80 mole #. kl. Aqueous drilling fluid characterized by containing water, a clay-like substance suspended in the water, and at least about 0.11 kg per 159-1 barrel (0.25 pounds per 42 gallon barrel) of a crosslinked copolymer of (a) a (meth -) - Acrylamidoalkylsulfonic acid or its alkali metal salt and (b) a (meth -) acrylamide or an N-alkyl (meth) acrylamide contains kZ, drilling fluid according to claim kl, characterized in that the proportion of the (meth -) - acrylamidoalkylsulfonic acid or its alkali metal salt in the crosslinked copolymer is between about 8 and about 70 mol- #. 43. Drilling fluid according to claim kl, characterized in that the proportion of (meth) - acrylamidoalkylsulfonic acid or its alkali metal salt is between about 9 and about 10 mol. kkm drilling fluid according to claim kl , characterized in that the proportion of the (meth -) acrylamide or the N-alkyl (meth) acrylamide in the crosslinked copolymer is between about 30 and about 91 - #. k5. Drilling fluid according to claim kl, characterized in that the proportion of the (meth) acrylamide or the N-alkyl (moth) acrylamide is about 90 - #. 0 30037/0614 - 10 - k6. Drilling fluid according to claim kl, characterized in that - indicates that the proportion of (meth -) - acrylamidoalkylsulfonic acid or its alkali metal salt about 9.8 mol% and that the proportion of (meth -) acrylamide or N-alkyl (meth) acrylamide is about 90 mol% is. kjm Drilling fluid according to claim 4i, characterized in that the (meth -) - acrylamidoalkylsulfonic acid or its alkali metal salt is sodium 2-acrylamido-2-methylpropane 48. Drilling fluid according to claim kl, characterized in that the (meth) acrylamide is acrylamide. Λ9 · Drilling fluid according to claim * H, characterized in that the (meth -) - acrylamido-.alkylsulphonic acid or its alkali metal salt sodium 2-acrylamido-2-methylpropane in an amount of about 9.8 Mol% and that the @ 4eth-J-acrylamide is acrylamide in is an amount of about 90 mole percent. 50. Aqueous drilling fluid, characterized in that it is water, one in the water suspended clay-like substance and at least about 0.11 kg per 159-1 barrel (0.25 pounds per 42 gallon barrel) one crosslinked copolymers of (a) a (meth-J-acrylamidoalkylsulfonic acid or its alkali metal salt, (bj a (Meth -) - acrylamide or N-alkyl- (meth -) - acrylamide and (c) contains a quaternary ammonium salt. 51. drilling fluid according to claim 50, characterized in that the proportion of (meth-J- 0300 3 7/0614 - 11 - Acrylamidoalkylsulfonic acid or its alkali metal as in the crosslinked copolymer between about 8 and about
70 mol- # is located. 52. Drilling fluid according to claim 50, characterized in that the proportion of (meth) - Acrylamidoalkylsulfonsäurs or its alkali metal salt is between about 9 and about 10 moles = $. 53 · Drilling fluid according to claim 5O _9, characterized in that the proportion of the (meth-) acrylamide or the N-alkyl- (meth-) acrylamide in the crosslinked copolymer is between at about 30 and about 91%
lies. 5 ^ · drilling fluid according to claim 50, characterized in that the proportion of (meth = ·) -acrylamide or N-alkyl- (meth-) - acrylamide is about 90
-# is. 55 · drilling fluid according to claim 50 »characterized in that the proportion of the quaternary ammonium salt in the crosslinked copolymer is between about 0.2 and about k _t k mol- #. 56, drilling fluid according to claim 50, characterized in that g β - » denoting that the proportion of the quaternary Ammonium salt is about 0.2 mol - $>. 57 · drilling fluid according to claim 50, characterized in that the proportion of (meth -) - acrylamidoalkylsulfonic acid or its alkali metal salt is about 9.8 mol%, that the proportion of (meth -) - 03003 7 / ΟΘ14 .... Acrylamides or the N-alkyl- (meth-) - acrylamide about 90 Mol $ and that the proportion of the quaternary ammonium salt is about 0.2 mol $. 58. Drilling fluid according to claim 50, characterized in that the (meth) - acrylaraidoalkylsulfonic acid or its alkali metal salt sodium 2-acrylamido-2-methylpropane is. 59. drilling fluid according to claim 50, characterized in that the (meth) - acrylamide Is acrylamide. 60. drilling fluid according to claim 50, characterized in that the quaternary ammonium salt a (meth-J-acryloyloxyalkyltrimethylammonium salt is. 61. drilling fluid according to claim 50, characterized in that the quaternary ammonium salt a 2-methacryloyloxyäthyltrimethylammoniummethosulfat is. 62. drilling fluid according to claim 50, characterized in that the (meth) - acrylamidoalkylsulfonic acid or its alkali metal salt sodium 2-acrylamido-2-methylpropane in an amount of about 9 »8 mol-56 is that the (meth -) - acrylamide acrylamide in one Amount of about 90 Mo1- $ and that the quaternary ammonium salt 2-methacryloyloxyethyltrimethylammonium methosulfate is in an amount of about 0.2 mole $. 0300 37 / 06U