CN101845295B - Drilling fluid tackifier favorable for protecting oil-gas layers - Google Patents

Abstract

The invention relates to a drilling fluid tackifier favorable for protecting oil-gas layers, which belongs to the technical field of oil-field drilling-fluid additives. The tackifier is obtained by mixing and preparing 5 to 95 parts of quadripolymer and 95 to 5 parts of bis-quaternary ammonium salt, wherein the quadripolymer is obtained by compounding three types of vinyl monomer and one type of hydrophobic monomer. The drilling fluid tackifier is a low molecular weight polymer and forms earthworm-shaped or long round rod-shaped micellar solution in aqueous solution through molecular association; when micelle concentration exceeds a critical value, space grid structure is formed among molecules and has strong suspending capability; gel can automatically break when meeting oil-gas, so the pollution of drilling fluid to oil layers can be removed without chemical gel breakers. The tackifier solves the problem that the prior water-soluble polymer tackifier for drilling fluid cannot thoroughly break gel. Compared with conventional drilling fluid tackifiers, the tackifier of the invention also contains long-carbon-chain hydrophobic groups besides hydrophilic groups, and can reduce the surface tension of drilling fluid, effectively prevent water locking and increase the productivity of oil wells.

Description

A Drilling Fluid Viscosifier Good for Protecting Oil and Gas Reservoirs

Technical field:

The invention relates to a drilling fluid viscosifier beneficial for protecting oil and gas layers, and belongs to the technical field of oilfield drilling fluid additives.

Background technique:

At present, conventional water-based drilling fluids are usually formulated with water-soluble polymers, such as hydrolyzed polyacrylamide, carboxymethyl cellulose, and modified guar gum, as thickeners. These water-based drilling fluids have the problem of not being able to completely break the gel in the later stage of well completion. Once the polymer is squeezed into the formation, it is easily absorbed and trapped in the pores, causing oil flow to be blocked and resulting in a decline in oil well productivity. To solve this problem, the current conventional solution is to use chemical gel breakers to completely break the gel, so as to prevent the water-soluble polymers in the water-based drilling fluid from being adsorbed by the formation and trapped in the pores, causing oil flow to be blocked. . However, the disadvantage of this solution is that the chemical breaker is usually an oxidant, and there are unsafe factors in the process of transportation and use, which cannot meet the engineering needs of safe drilling operations.

Invention content:

The object of the present invention is to: provide a kind of compound that is formed by tetrapolymer and bis-quaternary ammonium salt, form micelle solution in aqueous solution, when micelle concentration surpasses critical value, form space grid structure between molecules, thereby The viscosity of the solution is greatly increased, and it has a strong suspension ability. When encountering oil and gas, it will automatically break the gel, protect the oil and gas layers to the maximum extent, and increase the productivity of the oil well. It is a drilling fluid viscosifier that can completely solve the problem that existing drilling fluid water-soluble polymer viscosifiers cannot completely break the gel, and is beneficial to protect oil and gas layers.

The present invention realizes above-mentioned object through following technical scheme:

A drilling fluid viscosifier beneficial to protecting oil and gas formations is characterized in that it consists of the following components by weight:

Tetrapolymer 5～95 parts

Diquaternary ammonium salt 95-5 parts;

The tetrapolymer is formed by polymerizing three kinds of ethylenic monomers and one kind of hydrophobic monomer, and the mass ratio of three kinds of ethylenic monomers and one kind of hydrophobic monomer is: 20～30:30～20: 47～45: 3～5;

The three ethylenic monomers are acrylamide, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, sodium p-styrenesulfonate, N, N-dimethylacrylamide, and sodium propylenesulfonate Any three of , itaconic acid and fumaric acid;

Described hydrophobic monomer is 2-acrylamido dodecane sulfonic acid, N-dodecyl acrylamide, N-hexadecyl acrylamide, N-mono-maleic acid hexadecyl amide, N- Any one of stearylamide monomaleic acid;

The bis-quaternary ammonium salts are: N, N'-bis(tetradecyldimethyl)-1,3-dibromide propylene diammonium salt, N,N'-bis(hexadecyldimethyl base)-1,2-dibromide ethylenediammonium salt, N,N'-bis(dodecyldimethyl)-1,2-dibromide ethylenediammonium salt, N,N'-bis( Dodecyl dimethyl)-1,3-dibromide propylene diammonium salt, N,N'-bis(hexadecyl dimethyl)-1,3-dibromide propylene diammonium salt any kind.

The preparation method of the above-mentioned drilling fluid viscosifier that is beneficial to protect oil and gas formations is:

(1), preparation of tetrapolymer:

Take 300 ml of deionized water and pour it into a clean jar, add 5 grams of sodium hydroxide, stir to completely dissolve the sodium hydroxide, and then follow the mass ratio of 20-30:30-20:47-45:3 The ratio of ~5 is acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate, N,N-dimethylacrylamide, sodium propylenesulfonate, itaconic acid , any three raw materials in fumaric acid and 2-acrylamido dodecane sulfonic acid, N-dodecyl acrylamide, N-hexadecyl acrylamide, N-mono-maleic acid hexadecyl Any one of the raw materials in amides and N-mono-maleic acid octadecylamide, so that the total mass of the four monomers is 100 grams, is added to the jar, and stirred evenly until the four monomers are completely dissolved . Then use 10% sodium hydroxide solution to adjust the pH value of the mixed solution at 4-6. After passing nitrogen for 30 minutes at room temperature, polymerize with 0.4-0.8 grams of potassium persulfate and 0.2-0.4 grams of sodium sulfite as initiators. Reaction, after the reaction time reaches 6 hours, the polymerization reaction is completed to generate a low-molecular-weight polymer, which is then spray-dried, pulverized, and passed through a 40-mesh sieve to obtain a tetrapolymer for subsequent use;

(2) Preparation of drilling fluid viscosifier:

The tetrapolymer is uniformly mixed with the bisquaternary ammonium salt according to the above-mentioned ratio, crushed and passed through a 40-mesh sieve, and the drilling fluid viscosity increaser product of the present invention is obtained.

The beneficial effect of the present invention compared with prior art is:

1. This product is compounded by polymers of special ethylenic monomers and bis-quaternary ammonium salts. It is a low-molecular-weight polymer. It forms a micellar solution through molecular association in an aqueous solution, which acts as a thickening and cutting effect. The bundles are mainly in the shape of earthworms or oblong rods; due to the hydrophobic association, when the concentration of micelles exceeds the critical value, a space network structure is formed between the molecules, so that the viscosity of the solution is greatly increased and has a certain degree of elasticity and strong suspension capacity. To meet the engineering needs of drilling operations,

2. When oil and gas are encountered during production, the gel will be broken automatically, and the pollution of the drilling fluid to the oil layer can be removed without chemical gel breakers. The drilling fluid viscosifier is used to replace clay and high molecular weight polymers in conventional drilling fluids to construct a drilling fluid system, which is beneficial to protect oil and gas layers.

3. Compared with conventional drilling fluid viscosifiers, the drilling fluid viscosifier of the present invention contains not only hydrophilic groups but also hydrophobic groups with long carbon chains, which can reduce the surface tension of drilling fluids and effectively prevent water Lock, improve oil well productivity.

Detailed ways:

The present invention will be further described below in conjunction with specific embodiments.

Example 1:

Acrylic acid, sodium p-styrene sulfonate, 2-acrylamido-2-methylpropanesulfonic acid are used for ethylenic monomers; N-hexadecylamide monomaleic acid is used for hydrophobic monomers; N , N'-bis(hexadecyldimethyl)-1,3-dipropylenediammonium bromide salt.

(1), preparation of tetrapolymer:

Add an appropriate amount of 300 ml of deionized water and 5 grams of sodium hydroxide to the cleaned reaction vessel and stir evenly. Take 28 grams of acrylic acid, 22 grams of sodium p-styrenesulfonate, 2-acrylamido-2-methyl Add 47 grams of propanesulfonic acid and 3 grams of hexadecylamide N-monomaleic acid into a jar, stir evenly until the monomers are completely dissolved, then adjust the above mixture with 10% sodium hydroxide solution The pH value is at 4. After 30 minutes of nitrogen gas flow at room temperature, the polymerization reaction is carried out with 0.4 gram of potassium persulfate and 0.2 gram of sodium sulfite as an initiator. After 6 hours of closed reaction, a low molecular weight polymer is generated, which is then spray-dried, Pulverize and pass through a 40-mesh sieve to obtain the tetrapolymer, which is set aside;

(2) Preparation of drilling fluid viscosifier:

Get 50 parts by weight of the synthesized tetrapolymer and N, N'-bis(hexadecyldimethyl)-1,3-dibromide propylene diammonium salt 50 parts by weight and mix uniformly, pass through 40 parts after pulverizing. mesh sieve to obtain the drilling fluid viscosifier product of the present invention.

Example 2:

Acrylamide, N, N-dimethylacrylamide, sodium propylene sulfonate are used for ethylenic monomers; N-dodecyl acrylamide is used for hydrophobic monomers; N, N'-bis(dodecyl) Alkyldimethyl)-1,2-diethylenediammonium bromide salt.

(1), preparation of tetrapolymer:

Add an appropriate amount of 300 g of deionized water and 5 g of sodium hydroxide to the cleaned reaction vessel and stir evenly, then take 23 g of acrylamide, 27 g of N,N-dimethylacrylamide, 46 g of sodium propylene sulfonate, Add 4 grams of N-dodecylacrylamide into the jar, stir evenly until the monomer is completely dissolved, adjust the pH value of the mixture to 5 with 10% sodium hydroxide solution, and blow nitrogen at room temperature After 30 minutes, polymerize with 0.6 gram of potassium persulfate and 0.3 gram of sodium sulfite as initiators. After 6 hours of sealed reaction, a low molecular weight polymer is generated, which is then spray-dried, pulverized, and passed through a 40-mesh sieve to obtain a tetrapolymer ,spare;

(2) Preparation of drilling fluid viscosifier:

Get 80 parts by weight of the synthesized tetrapolymer and N, N'-bis(dodecyldimethyl)-1,20 parts by weight of ethylenediammonium dibromide salt and mix uniformly, and pass through 40 parts after pulverization. mesh sieve to obtain the drilling fluid viscosifier product of the present invention.

In order to further prove the beneficial effect of the drilling fluid viscosifier which is beneficial to protect oil and gas layers, the performance of the drilling fluid viscosifier was evaluated indoors, and the specific results are as follows:

1. Performance evaluation of drilling fluid viscosifier:

The viscosification of different additions of viscosifiers in seawater was evaluated indoors, and the experimental results are shown in Table 1:

Table 1 Viscosification properties of different additions of viscosifiers in seawater

increase AV(mPa·s) PV(mPa s) YP(Pa) Ф6/Ф3 0.2% 10 6 4 2/1 0.5% 18 12 6 4/3 0.8% 30 16 14 10/9 1.0% 35 19 16 12/11

Experimental data shows that the viscosifier of the present invention has a good viscosifying effect in seawater, and a network structure is formed due to the mutual association between molecular micelles, thereby having a relatively high dynamic shear force, which is beneficial to the development of branch wells. carry rock.

2. Basic performance evaluation of water-based drilling fluid:

With the viscosifier of the present invention as the core treatment agent, the formula of the water-based drilling fluid system constructed is as follows:

Seawater + 0.15% NaCO ₃ +0.3% NaOH + 1.0% ~ 1.5% viscosifier + 2% fluid loss reducer FL + 3% polymer alcohol JLX + 3% KCl + 5% plugging agent QWY (200 mesh).

Table 2 Basic properties of water-based drilling fluid system

Experimental conditions AVmPa.s PVmPa.s YPPa YP/PV Ф6/Ф3 FL _API ml FL _HTHP ml roll forward 33 14 19 1.36 12/10 Get out 36 17 19 1.12 14/12 4.8 10

Aging condition: 100℃×16h.

From the above experimental results, it can be seen that the constructed water-based drilling fluid has good rheology and good water loss and wall-building properties, which can meet the requirements of oil and gas drilling.

5. Performance evaluation of water-based drilling fluid oil and gas layer protection

The evaluation procedure is carried out in accordance with the China Petroleum and Natural Gas Industry Standard SY/T6540-2002 "Indoor Evaluation Method for Drilling Fluid and Completion Fluid Damage to Reservoir". The high temperature and high pressure dynamic water loss instrument is used to simulate the drilling conditions and the impact of the high temperature and high pressure core flow instrument on the drilling fluid. Evaluation of oil and gas reservoir protection performance. The experimental results in Table 3 show that the recovery values of the permeability of the two cores are both above 90%, indicating that the water-based drilling fluid system constructed by the viscosifier of the present invention has better oil and gas layer protection performance.

Table 3. Core flow test results of water-based drilling fluid system

Core No. 2984 2875 Ko, 10 ^-3 μm ² 85.8 96.4 K ₁ , 10 ^-3 μm ² 78.5 91.1 Permeability recovery value Krd, % 91.5 94.5

Note: The experimental conditions of drilling fluid dynamic pollution are temperature 100°C, pressure 3.5MPa, and time 125min.

Claims (2)

1. A drilling fluid viscosifier beneficial to protecting oil and gas reservoirs, characterized in that: it is made of the following components by weight: Tetrapolymer 5～95 parts Diquaternary ammonium salt 95~5 parts; The tetrapolymer is formed by polymerizing three kinds of ethylenic monomers and one kind of hydrophobic monomer, and the mass ratio of three kinds of ethylenic monomers and one kind of hydrophobic monomer is 20～30:30～20:47～ 45: 3~5; The preparation method of the above-mentioned drilling fluid viscosifier that is beneficial to protect oil and gas formations is: (1), preparation of tetrapolymer: Take 300 milliliters of deionized water and pour it into a cleaned wide-mouth bottle, add 5 grams of sodium hydroxide, stir to completely dissolve the sodium hydroxide, and then follow the mass ratio of 20～30:30～20:47～45: The ratio of 3 to 5 is acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate, N,N-dimethylacrylamide, sodium propylenesulfonate, itacan Acid, any three raw materials in fumaric acid and 2-acrylamido dodecane sulfonic acid, N-dodecyl acrylamide, N-hexadecyl acrylamide, N-mono-maleic acid hexadecane Any one of the base amide and N-mono-maleic acid octadecylamide, so that the total mass of the four monomers is 100 grams, add it to the jar, stir evenly, until the four monomers are completely dissolved ; then use 10% sodium hydroxide solution to adjust the pH value of the mixed solution at 4 to 6, and after nitrogen gas flow for 30 minutes at room temperature, carry out the process with 0.4 to 0.8 gram of potassium persulfate and 0.2 to 0.4 gram of sodium sulfite as an initiator Polymerization reaction, after the reaction time reaches 6 hours, the polymerization reaction is completed to generate a low molecular weight polymer, which is then spray-dried, pulverized, and passed through a 40-mesh sieve to obtain a tetrapolymer for subsequent use; (2) Preparation of drilling fluid viscosifier: Mix the tetrapolymer with the diquaternary ammonium salt evenly according to the above ratio, crush it and pass it through a 40-mesh sieve to obtain the drilling fluid viscosity increaser product. 2. the drilling fluid viscosifier that is beneficial to protect the oil and gas reservoir according to claim 1, is characterized in that: described two quaternary ammonium salts are: N, N '-bis(tetradecyldimethyl)- 1,3-dibromide propylene diammonium salt, N,N'-bis(hexadecyldimethyl)-1,2-dibromide ethylene diammonium salt, N,N'-bis(dodecane Dimethyl)-1,2-dibromide ethylene diammonium salt, N,N'-bis(dodecyl dimethyl)-1,3-dibromide propylene diammonium salt, N,N' - Any one of bis(hexadecyldimethyl)-1,3-dipropylenediammonium bromide salts.