Terpolymer composition for aqueous drilling fluids
A method of improving high temperature fluid loss and rheology stabilization of high calcium brine clay-containing oil well drilling fluids which comprises adding thereto a stabilizing amount of a water-soluble terpolymer composition comprising:______________________________________ Ingredients % by weight ______________________________________ NaAMPS 72-3.8 N,N-dimethylacrylamide 13.5-0.7 Acrylonitrile 9.5-0.5 ______________________________________said composition containing lignin, modified lignin, brown coal or modified brown coal in an amount ranging between 5-95% with the lignin, modified lignin, brown coal or modified brown coal having been present during the polymerization of the water-soluble polymer.
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A serious problem is encountered when clay-based oil well drilling fluids are subjected to conditions of high temperature and high pressure in conjunction with utilization of high calcium-containing brines which are used to prepare these drilling fluids. When these conditions exist, conventional drilling fluid polymeric additives such as acrylamide polymers, when used as stabilizers for these fluids, tend to be rendered ineffective.
In U.S. Pat. No. 4,502,964, there is shown an improved high temperature fluid loss additive and rheology stabilizer for high temperature oil well drilling fluids which comprises a water-soluble terpolymer having the following compositions:
______________________________________
Mole %
Ingredients Preferred General
______________________________________
2-acrylamido-2-methylpropane-
53.5 51-59
sulfonic acid, sodium salt (AMPS.sup.1)
N,N-dimethylacrylamide
16.6 6-28
acrylonitrile 29.8 20-35
______________________________________
.sup.1 AMPS, a registered trademark of Lubrisol, Inc., is
2acrylamido-2-methylpropane sulfonic acid. Na salt.
These polymers are further described in this patent as having a molecular weight below one million. They preferably have a molecular weight range within the range of 10,000-500,000. The other properties of these polymers and their efficacy as high temperature fluid loss additives are further described in this patent. The disclosure of U.S. Pat. No. 4,502,964 is incorporated into this disclosure by reference and forms a part hereof.
Resinex, a sulfonated lignite complexed with a sulfonated phenolic resin, is a commercially available high temperature, high pressure fluid loss additive for drilling muds. It is effective in controlling filtration properties in both fresh sea water muds with high concentrations of soluble calcium.
If it were possible to provide high temperature fluid loss additives having superior activity to the activity of either the polymers described U.S. Pat. No. 4,502,964 or the Resinex additive, an advance in the art would be afforded.
THE INVENTIONIn accordance with the invention, there is provided a method for improving high temperature fluid loss and rheology stabilization of high calcium brine clay-containing oil well drilling fluids which comprises adding thereto a stabilizing amount of a water-soluble terpolymer composition comprising: polymer prepared by polymerizing the following monomer ingredients:
______________________________________
Ingredients % by weight
______________________________________
NaAMPS 72-3.8
N,N-dimethylacrylamide
13.5-0.7
Acrylonitrile 9.5-0.5
______________________________________
said compositions containing lignin, modified lignin, brown coal or modified brown coal in an amount ranging between 5-95% with the lignin, modified lignin, brown coal or modified brown coal having been present during the polymerization of the water-soluble polymer.
THE LIGNIN, MODIFIED LIGNIN, BROWN COAL OR MODIFIED BROWN COALA variety of material falling within this generic description may be used in the practice of the invention. One of the most common materials is lignite which is a brown coal in which the original structure of the wood is still recognizable. It is commonly known that lignite may be reacted with sulfuric acid or SO.sub.3 to produce a sulfonated lignite. A related product that may also be substituted is lignin which is a byproduct formed in the processing of wood for the manufacture of paper.
It can be modified to provide a lignosulfonate or a cyano derivative as described in U.S. Pat. No. 3,639,263.
Another related product is leonardite which is a naturally oxidized product with higher oxygen and moisture content than lignite.
Another brown coal-type material is humic acid which is a complexed polycyclic polycarboxylic acid which can be converted into its salt form e.g. alkali metal, ammonia or amine, or it can be sulfonated. Such products as well as other derivatives of humic acid are described in U.S. Pat. No. 3,266,887. The disclosure of which is incorporated herein by reference.
The polymer portion of the compostion used to practice the invention is prepared in accordance with the teachings of U.S. Pat. No. 4,502,964. The reaction temperature and times may be varied with the reaction time being temperature dependent, e.g. the higher the temperature the shorter the reaction time. Generally, temperatures within the range of about 35.degree.-80.degree. C. may be employed. Although, the temperature and reaction times vary, they are further governed by the amount of catalyst as well as the ratio of the reactants. Often, routine experimentation must be used to optimize the process.
As indicated, the compositions are prepared by conducting the polymerization in the presence of the lignin, modified lignin, brown coal or modified brown coal.
The amount of brown coal combined with the polymer as indicated ranges between 5-95%, preferably 20-50% and most preferably 20-35% by weight.
One of the surprising facts of the invention is that the entire broad range of lignin, modified lignin, brown coal or modified brown coal used shows excellent results are achieved in providing fluid loss control.
The composition of this invention provides good results at dosages ranging between 0.5-10 lbs. per barrel. A preferred dosage range is between 1-5 lbs. per barrel. The dosages are varied depending upon the conditions and type of formation being treated.
______________________________________
Method of Preparing the Compositions of the Invention
Composition I
Component Weight Percent
______________________________________
(1) Deionized Water 55.77
(2) Causticized Lignite
9.53
(3) 50% Na AMPS Solution
28.87
(4) Dimethylacrylamide
2.71
(5) Acrylonitrile 1.90
(6) EDTA .10
(7) Sodium Bisulfite
.56
(8) Ammonium Persulfate
.56
100.00
______________________________________
Charge (1) and (2) to reactor with stirring, heat to 60.degree. C. and continue stirring at 60.degree. C. for 30 minutes. Charge (3)-(6). Close in reactor, pull vacuum, break with nitrogen, repeat. Charge catalyst pair (7) and (8), portionwise (approximately 0.14 weight percent) at one hour intervals. A small exotherm (10.degree.-15.degree. C.) may occur and the solution should gain viscosity. It appears that a Brookfield viscosity greater than 200 centipoise is necessary for peak product performance. Continue adding catalyst doses until residual monomer levels are at acceptable levels (less than 1% for AMPS and dimethylacrylamide, and less than 25 ppm for acrylonitrile). Typical residuals for open pot laboratory reactions are as follows:
______________________________________
Monomer Residual
______________________________________
ACN 1.7 .mu.g/g
AMPS .07%
diMeAcAM <.05%
______________________________________
Using this general preparative method, the following compositions in Table I were prepared:
TABLE I
______________________________________
Product Compositions
Weight Percents
Composition N,N-dimethyl- Lig-
No. NaAMPS acrylamide Acrylonitrile
nite
______________________________________
1 50.5 9.5 6.7 33.3
2 60.7 11.4 7.9 20
3 72.0 13.5 9.5 5
4 3.8 0.7 0.5 95
5 54.3 12.4 -- 33.3
6 47.2 18.4 1.1 33.3
7 48.6 14.7 3.4 33.3
8 51.6 6.7 8.4 33.3
9 56.9 2.1 7.7 33.3
10 59.3 -- 7.4 33.3
11 66.7 -- -- 33.3
______________________________________
The following variations contain the same base polymer with different lignin/lignite variations:
NaAMPS (50.5%), N,N-dimethylacrylamide (9.5%), acrylonitrile (6.5%), lignin/lignite variation (33.3%).
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Composition No. Lignin/Lignite Variation
______________________________________
12 Ca lignosulfonate
13 Na lignosulfonate
14 Lignin
15 Sulfomethylated lignite
16 Sulfonated lignite
______________________________________
FLUID TEST PROCEDURES
The variations were tested in a high temperature, high pressure fluid loss additive test which is described in detail in the American Petroleum Institute publication RP13(B). Improved fluid loss control was observed for the variations tested. The results in both unaged muds and muds aged overnight at 350.degree. F. are shown in Table II. The base mud used for testing consisted of:
______________________________________
280 g water
15 g bentonite
40 g kaolinite
4 g chrome lignosulfonate
294 g barite
10.6 g sea salt
______________________________________
Using the above test procedures, the compositions of Table I were evaluated with the results being shown in Table II.
TABLE II
______________________________________
Composi-
Concentration
HTHP Fluid Loss (ml)
tion No.
(lbs/bbl Unaged Aged 350.degree. F.
______________________________________
Blank -- dry @ 27 min dry @ 28 min
1 2 80 70
2 2 64 62
3 2 76 66
4 2 142 134
5 2 90 70
6 2 78 60
7 2 74 62
8 2 96 66
9 2 98 94
10 2 112 94
11 2 84 70
12 2 dry @ 29 min 30 sec
82
13 2 134 102
14 2 dry @ 27 min 96
15 2 dry @ 29 min 30 sec
124
16 2 124 96
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The products of the invention, either in solution or in dry form, provided effective and improved performance as fluid loss additive in oil field drilling fluid. These products show especially improved performance at elevated temperatures. These additives may be used in a wide range of drilling fluid types including the following:
(1) fresh water muds
(2) fresh water muds contaminated with calcium or other multivalent ion
(3) sea water muds
(4) gypsum muds
(5) lime muds
Claims
20-35% by weight..]..Iadd.4. A composition comprising:
- terpolymer segments comprising units derived from acrylonitrile, N,N-dimethylacrylamide, and 2-acrylamido-2-methylpropane sulfonic acid, sodium salt wherein said acrylonitrile is present in an amount up to about 9.5%, said N,N-dimethyacrylamide is present in an amount up to about 18.4% and said 2-acrylamido-2-methylpropane sulfonic acid, sodium salt is present in an amount of about 3.8% to about 72%;
- from about 5% to about 95% by weight of a lignin, modified lignin, brown coal or modified brown coal selected from the group consisting of lignites, sulfonated lignites, lignins, leonardites, lignosulfonates, humic acids, sulfonated humic acids, and the salts of each;
- said terpolymer segments being formed in the presence of said material.
.Iaddend..Iadd.5. A composition comprising:
- terpolymer segments comprising units derived from acrylonitrile, N,N-dimethylacrylamide, and 2-acrylamido-2-methylpropane sulfonic acid, sodium salt wherein said acrylonitrile is present in an amount up to about 9.5%, said N,N-dimethylacrylamide is present in an amount up to about 18.4%, and said 2-acrylamido-2-methylpropane sulfonic acid, sodium salt is present in an amount of about 3.8% to about 72%;
- from about 20% to about 35% by weight of a lignin, modified lignin, brown coal or modified brown coal selected from the group consisting of lignites, sulfonated lignites, lignins, leonardites, lignosulfonates, humic acids, sulfonated humic acids, and the salts of each;
- said terpolymer segments being formed in the presence of said material.
.Iaddend..Iadd.6. A composition comprising:
- terpolymer segments comprising units derived from acrylonitrile, N,N-dimethylacrylamide, and 2-acrylamido-2-methylpropane sulfonic acid, sodium salt, wherein said acrylonitrile is present in an amount of at least about 0.5% to about 9.5%, said N,N-dimethylacrylamide is present in an amount of at least about 0.7% to about 13.5% and said 2-acrylamido-2-methylpropane sulfonic acid, sodium salt is present in an amount of at least about 3.8% to about 72%;
- from about 5% to about 95% by weight of a lignin, modified lignin, brown coal or modified brown coal selected from the group consisting of lignites, sulfonated lignites, lignins, leonardites, lignosulfonates, humic acids, sulfonated humic acids, and the salts of each;
- said terpolymer segments being formed in the presence of said material..Iaddend..Iadd.7. A composition comprising:
- terpolymer segments comprising units derived from acrylonitrile, N,N-dimethylacrylamide, and 2-acrylamido-2-methylpropane sulfonic acid, sodium salt, wherein said acrylonitrile is present in an amount of at least about 0.5% to about 9.5%, said N,N-dimethylacrylamide is present in an amount of at least about 0.7% to about 13.5% and said 2-acrylamido-2-methylpropane sulfonic acid, sodium salt is present in an amount of at least about 3.8% to about 72%;
- from about 20% to about 35% by weight of a lignin, modified lignin, brown coal or modified brown coal selected from the group consisting of lignites sulfonated lignites, lignins, leonardites, lignosulfonates, humic acids, sulfonated humic acids, and the salts of each;
- said terpolymer segments being formed in the presence of said material..Iaddend.
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- American Petroleum Institute, publication RP 13(B), 6th ed., Apr. 1976, pp. 1-33, "Standard Procedure for Testing Drilling Fluids".
Type: Grant
Filed: Dec 20, 1988
Date of Patent: Mar 24, 1992
Assignee: Nalco Chemical Company (Naperville, IL)
Inventors: David M. Giddings (Sugar Land, TX), Charles D. Williamson (Sugar Land, TX)
Primary Examiner: Robert L. Stoll
Assistant Examiner: Gary L. Geist
Law Firm: Arnold, White & Durkee
Application Number: 7/286,887
International Classification: C09K 702;
