JPH052716B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a dispersant for drilling fluids containing a water-soluble salt of an addition copolymer of an α,β-unsaturated monocarboxylic acid and a dicarboxylic acid monomer as an active ingredient. (Prior Art) As a method for drilling a well for extracting fluids such as oil, natural gas, geothermal fluid, and groundwater that exist underground, there is a swing drilling method that uses drilling fluid. In this method, drilling fluid is pumped into the pipe and squirted out of the pit nozzle to remove drilling debris. This muddy water has the role of cooling the high frictional heat generated in the pit, removing the cutting debris from the pit cutting edge, and transporting it to the surface.At the same time, the hydrostatic pressure of the underground muddy water maintains a balance with the formation pressure. It also plays a role in preventing the collapse of the pit and the inflow of formation fluids. The drilling fluid that plays such an important role in the rotary drilling method is generally a water-based mud prepared by adding various additives to a suspension of water and clay. One of these additives is a drilling fluid dispersant to prevent clay flocculation. Various compounds have been developed as dispersants for drilling fluids, such as lignin sulfonate, iron chromium lignin sulfonate, humate, polyacrylate, polyacrylamide, and poly-2-acrylamide-2. -Salts of methylpropanesulfonic acid, salts of styrenesulfonic acid-maleic anhydride copolymer, and the like are known. Among these, styrene sulfonic acid-maleic anhydride copolymer salt (hereinafter referred to as SSM) has excellent stability at high temperatures compared to other dispersants, and has excellent stability in fields where heat resistance is required (for example, deep It is also used as a well drilling agent (U.S. Patent No.
3730900 etc.). (Problem to be solved by the invention) However, in recent years, as the depth of wells has increased, the required performance for heat resistance has become even more severe. development was strongly desired. Therefore, the present inventors conducted intensive studies to meet this demand, and found that among many carboxylic acid polymers, only water-soluble salts of copolymers with specific compositions have uniquely excellent performance. The present invention was completed based on the discovery that (Means for Solving the Problems) An object of the present invention is to provide a dispersant for drilling fluids that has excellent dispersion stability under high temperatures. or 4
α, β-ethylenically unsaturated monocarboxylic acid 30~
95 mol%, preferably 40-90 mol% and (b) dicarboxylic acid monomer 5-70 mol%, preferably 10-90 mol%
This is achieved by using a water-soluble salt of an addition copolymer having a number average molecular weight of 500 to 100,000, preferably 1,000 to 50,000, consisting of 60 mol % as an active ingredient of a dispersant for drilling fluids. In the present invention, (a) constituting the copolymer
The composition of (b) and (b) are important requirements; if the proportion of (a) is too large or too small, the dispersibility at high temperatures will decrease. Specific examples of component (a) to be used include acrylic acid, methacrylic acid, crotonic acid, and the like. On the other hand, component (b) is an α,β-ethylenically unsaturated dicarboxylic acid having 4 or 5 carbon atoms or a sulfonic acid group-containing derivative derived from the dicarboxylic acid and a sulfonic acid group-containing amine, that is, an acid imide. Here, the sulfonic acid group includes not only a sulfonic acid group in the narrow sense represented by -SO ₃ H but also a sulfonic acid ester residue represented by -OSO ₃ H. Specific examples of such component (b) include α, β-ethylenically unsaturated dicarboxylic acids having 4 or 5 carbon atoms such as maleic acid, citraconic acid, itaconic acid, etc.; β−
Ethylenically unsaturated dicarboxylic acid and aminomethanesulfonic acid, aminoethanesulfonic acid, amino-2
-Methylpropanesulfonic acid, aminoptanesulfonic acid, aniline monosulfonic acid, aniline disulfonic acid, aminotoluenesulfonic acid, naphthylamine monosulfonic acid, naphthylamine disulfonic acid, naphthylamine trisulfonic acid, amidosulfuric acid, monoaminoethyl sulfate, monoamino sulfate Examples include acid imides with amino group-containing sulfonic acids containing 1 to 3 sulfonic acid groups, such as propyl, monoaminobutyl sulfate, monoaminohexyl sulfate, monoaminooctyl sulfate, and the like. Among these components (b), sulfonic acid group-containing derivatives, particularly acid imide type derivatives, are preferred, and acid imides with aliphatic or aromatic amino group-containing sulfonic acids having 1 to 10 carbon atoms are particularly preferred. In the case of acid imide derivatives, they have superior performance in terms of stability against polyvalent metal ions such as calcium ions, magnesium ions, etc. and stability against common salt, compared to when dicarboxylic acids are used. Furthermore, an acid imide type derivative and a dicarboxylic acid can be used together as component (b), and in this case, the heat resistance in a system containing a high concentration of polyvalent metal ions or common salt is further improved. From this point of view, 5% of the acid imide is contained in the entire composition.
A copolymer containing the dicarboxylic acid in an amount of 0 to 50 mol%, preferably 10 to 40 mol% is used. Further, the present invention may contain other copolymerizable comonomers as necessary, as long as they do not essentially impede the effects. The addition copolymer used in the present invention is not particularly limited as long as it functions as a dispersant for drilling fluids, but it usually has a number average molecular weight of 500 to 100,000, preferably 1,000 to 30,000; If the molecular weight is larger than this, the dispersion performance deteriorates, and conversely, if the molecular weight is too small, the dispersion performance becomes insufficient. In the present invention, at least a portion of the carboxyl groups and/or sulfonic acid groups present in the copolymer are converted into salts with monovalent or polyvalent cations, and the water-solubilizing ability is enhanced and the resulting mixture is used as a dispersant. be done. Specific examples of such salts include sodium, potassium, magnesium, calcium,
Examples include salts of alkali metals or alkaline earth metals such as barium, ammonium salts, amine salts such as trimethylamine, triethylamine, triethanolamine, etc. Among them, alkali metals such as barium, etc. Salt is also prized. The copolymer salt used in the present invention is not limited in any way by its manufacturing method, and can be appropriately manufactured according to conventional methods. For example, when the component (b) is an α,β-unsaturated dicarboxylic acid, the components (a) and (b) are radically polymerized according to a conventional method, and then
It can be easily obtained by neutralizing with a desired base, and when the component (b) is a sulfonic acid group-containing derivative, α, β formed in advance in an aqueous solution of an amino group-containing sulfonic acid group can be obtained. - A method in which a copolymer of an unsaturated monocarboxylic acid and an α,β-unsaturated dicarboxylic acid anhydride is added and reacted at high temperature (see British Patent No. 1246953), the copolymer is uniformly mixed in an alkaline aqueous solution. There is a method of adding amino group sulfonic acid after dissolving and reacting at high temperature. The water-soluble salt thus prepared may be applied to a dispersant in the form of an aqueous solution, but if necessary, after removing water, it may be obtained as a solid and used in that state. Such water-soluble salts are added as dispersants to aqueous drilling fluids consisting essentially of an aqueous base material, clay, and a dispersant. Here, the aqueous base material and clay material may be any commonly used materials, and the former is used in the form of fresh water, salt water, or seawater, and specific examples of the latter include:
Examples include Na-bentonite, Ca-bentonite, and attapulgite. The content in such clayey aqueous drilling fluid is selected as appropriate, but is usually about 5 to 15% by weight. The amount of the copolymer water-soluble salt to be used is appropriately selected depending on the type of drilling fluid and its usage conditions, but it is usually added to the aqueous drilling fluid.
The proportion is 0.1 to 5% by weight, preferably 0.3 to 1% by weight. In addition, when preparing drilling fluid, if necessary, commonly used compounding agents such as specific gravity adjusters such as barite, iron oxide, calcium carbonate, etc.
Viscosity modifiers such as etherified cellulose and polyacrylamide, general purpose chemicals such as sodium hydroxide, sodium carbonate, and calcium chloride, fluid loss control agents such as carboxymethyl cellulose, starch, and polyacrylates, lignin sulfonic acid, sodium phosphate, Other dispersants such as polyacrylates may be included as appropriate. (Effects of the Invention) The dispersant for drilling fluids of the present invention has excellent dispersibility at high temperatures compared to SSM, which has been used in the past, and in particular uses a sulfonic acid group-containing derivative as component (b). When used, it shows good performance in terms of stability against salt and polyvalent metal ions. Therefore, if drilling fluids containing such dispersants are used, it becomes possible to drill deep wells such as in offshore oil fields, and the service life of the fluids is longer than when drilling fluids containing other dispersants are used. It is extremely advantageous in terms of operation and economy. The drilling fluid of the present invention is particularly effective when used at high temperatures or in systems containing a high degree of polyvalent metal ions or salt, but it also has excellent properties when used for drilling under normal conditions. Of course, it is necessary to have one. The present invention will be explained in more detail with reference to Examples below. In addition, parts and percentages in the examples are based on weight unless otherwise specified. Example 1 The performance of the various sodium salts of carboxylic acid polymers shown in Table 1 as dispersants for aqueous drilling fluids was evaluated according to the following test conditions. The polymers used in experiment numbers (1-1) to (1-6) were prepared by adding aminoethanesulfonic acid to an aqueous solution of sodium salt of polymaleic acid or maleic acid-acrylic acid copolymer synthesized by radical polymerization. It was synthesized by heating and imidizing the maleic acid unit, and the polymer used in experiment number (1-7) was maleic acid, acrylic acid, and 2-acrylamido-2-methylpropanesulfone. Acid (hereinafter referred to as AMPS)
It was obtained by radical polymerization. 1 Heat resistance test After mixing 6.8 parts of 100% Wyoming bentonite, 18.1 parts of East Texas bentonite clay, and 241.3 parts of fresh water using a homogenizer,
1.7 parts of iron chromated lignin (based on solid content) and 0.57 parts of carboxylic acid polymer (based on solid content) were added as dispersion aids to 100 parts of aqueous mud prepared by standing at room temperature for 24 hours, and then 10% The pH of the system was adjusted to 10 with aqueous caustic soda solution. The flow characteristics of the thus obtained Matsudo composition at room temperature were measured using a rheometer (FANN Viscometer Model-35) before and after a heat resistance test (left in an autoclave at 500°C for 16 hours).
Measured using 2 Salt water resistance test 25% NaCl containing 2000ppm calcium ions
2 parts of the above copolymer in 350 parts of aqueous solution (based on solid content)
After adding 5% caustic soda aqueous solution under stirring, the pH of the system was gradually raised, and the pH value when cloudiness first appeared was measured and evaluated in three stages. ○: Does not precipitate even at PH = 10 △: Precipitates between PH = 7 and 10 ×: Precipitates at PH = 7 or less

[Table] *2 Number average molecular weight before imidization From this result, it can be seen that only when a copolymer of components (a) and (b) is used, uniquely excellent heat resistance is exhibited. Example 2 Maleic acid-acrylic acid copolymer (molar ratio =
N-substituted maleimide obtained by reacting sodium salt (1:1, molecular weight 3000) with various imidizing agents
Maleic acid-acrylic acid copolymer (molar ratio =
Example 1 for the sodium salt of 0.2:0.3:0.5)
Tests were conducted in the same manner as above, and the results are shown in Table 2.

[Table] Example 3 N-sulfoethylmaleimide-maleic acid-acrylic acid obtained by reacting sodium salts of maleic acid-acrylic acid copolymers with different molecular weights (molar ratio = 1:1) and aminoethanesulfonic acid The Na salt of the acid copolymer (molar ratio = 0.2:0.3:0.5) was tested in the same manner as in Example 1, and the results are shown in Table 3.

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[Table] Example 4 Regarding the sodium salts of various carboxylic acid polymers shown in Table 4 obtained by radical polymerization,
A heat resistance test was conducted in the same manner as in Example 1. The results are shown in Table 4. From the results in Table 4, it can be seen that among the various carboxylic acid polymers, only the copolymer used in the present invention has uniquely excellent heat resistance.

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Claims (1)

[Claims] 1 (a) 30 to 95 mol% α,β-ethylenically unsaturated monocarboxylic acid having 3 or 4 carbon atoms and (b) 4 carbon atoms
or at least one sulfonic acid group-containing derivative selected from α,β-ethylenically unsaturated dicarboxylic acids and sulfonic acid group-containing derivatives which are acid imides of the dicarboxylic acids and amino group-containing sulfonic acids having 1 to 3 sulfonic acid groups. Dicarboxylic acid monomer 5-70 mol%
A dispersant for drilling fluids, the active ingredient being a water-soluble salt of an addition copolymer having a number average molecular weight of 500 to 100,000.