JPH04126788A - Visocosity increasing agent for drilling fluid of well, finishing or repairing fluid and fluid containing the same - Google Patents

Abstract

PURPOSE:To obtain the subject viscosity increasing agent, composed' of a copolymer containing a cationic vinyl monomer and a specific vinyl monomer as constituent components and capable of sufficiently maintaining viscosity in brine solutions at a high concentration even in high-temperature environment without causing deterioration. CONSTITUTION:The objective viscosity increasing agent is composed of a copolymer containing (A) preferably a quaternary salt type or betaine type cationic vinyl monomer and (B) a vinyl monomer (preferred example; N-vinylpyrrolidone, N-vinylcaprolactam or N-methyl-N-vinylacetamide) expressed by formula I or II (R1 and R2 are 1-4C alkyl; R3 is trimethylene or pentamethylene) as constituent components.

Description

[Detailed description of the invention] a. Industrial application field The present invention is applicable to drilling fluids for wells such as oil and natural gas, finishing of wells such as oil and natural gas under high temperature and high pressure environments, and The present invention relates to thickeners added to fluids used during well workovers, and well drilling fluids, completions or workover fluids using the thickeners.

More specifically, the present invention relates to a thickener that is added to a drilling fluid using an inorganic salt solution (hereinafter referred to as brine) used when drilling wells for oil, natural gas, etc. When using brine to complete production wells for oil, natural gas, etc. under high temperature and high pressure environments,
Alternatively, when repairing an aging oil or natural gas well using brine, brine may enter the production layer when drilling holes in the production layer (hereinafter referred to as gun perforation work). Thickeners for finishing or repairing fluids in mines and their thickeners, which can prevent formation disturbances such as production failures, and can also prevent oil, natural gas, or underground water outburst accidents caused by drops in pressure in the mine. Relating to finishing or refurbishing fluids using agents.

b. Prior Art Currently, brine is used as part of the drilling fluid for oil and natural gas wells, and as a fluid for completing or renovating various wells. However, these brines are aqueous solutions of inorganic salts that do not contain any solids, and if they are used as they are during well drilling or gunbar foraging work, the expensive brines will be used in the excavation pit. There is a risk of water leaking into the well's geological formation or production layer, resulting in significant losses. In addition, when brine enters the production layer, the balance of ions in the strata that make up the production layer is disrupted.
It has a negative effect on the hydration and dispersion of clay minerals that make up the production layer, and can cause formation disturbances. Furthermore, there are many accidents in which oil, natural gas, or underground water erupts due to a drop in pressure inside a mine due to brine or the like.

On the other hand, in the repair work of aging wells, the pressure within the formation may have decreased due to the production of oil and natural gas, and there is a risk that an accident similar to the above may occur.

During the drilling, completion, or repair work of these wells, the following measures are taken to prevent accidents caused by brine leaking into the well's geological formation or production layer, or entering the production layer. is possible.

■ Thickeners are added to brine to increase its viscosity and prevent water from flowing into the formation or production layer due to flow resistance.

■ Add a thickener to the brine to prepare a brine solution (hereinafter referred to as brine fluid), and suspend a bridging agent with a particle size distribution that matches the pore size of the production layer. to prevent water loss.

The above-mentioned thickeners must be easily dissolved in aqueous solutions of highly concentrated salts, obtain high viscosity with a small amount added, and have a stable thickening effect in high temperature environments, acids, oils, or water. It is desirable that the material dissolves easily in any of the above and does not remain permanently in the production stratum. In addition, as a bridging agent,
It is desirable that the material has a particle size in the range of 1 to 3000 microns, which does not change its quality even in a high temperature environment, is easily dissolved in acid or oil, and does not remain permanently in the production stratum.

Traditionally, carboxymethyl cellulose,
Methyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, starch, guar gum, sodium polyacrylate, polyacrylamide, polyethylene oxide, fatty acid ester derivatives, polyurethane, etc. are used.

Bridging agents include solids that dissolve in hydrochloric acid but not in water, such as calcium carbonate, mixed solids that dissolve in acids, such as a mixture of calcium carbonate and lignin compounds, and salt. Water-soluble compounds and oil-soluble solids such as petroleum resins were used.

Conventional thickeners are capable of keeping brine concentrations relatively low when used in brine fluids for drilling fluids, and are capable of keeping brine concentrations relatively low when used in completion or workover fluids. Satisfactory viscosity can be maintained in wells with relatively low temperature conditions. However, when the brine concentration is high and/or in a high temperature environment, there are drawbacks such as the thickener itself being denatured and reduced in viscosity or denatured and gelled. Therefore, conventional thickeners are unable to adequately maintain the viscosity of brine fluids at high brine concentrations and/or in high temperature environments, and the brine concentrations and/or temperature ranges used are relatively low. Therefore, satisfactory characteristics could not be obtained in a high concentration brine solution and/or in a high temperature environment.

In other words, it is heat-resistant and salt-resistant, with no defects such as deterioration and thinning or denaturation and gelation even in high-concentration brine solutions and/or high-temperature environments, and exhibits excellent solubility and thickening properties. There was a need for a thickening agent with the same characteristics.

60 Means for Solving the Problems The present inventors have conducted intensive research on thickeners that can maintain sufficient viscosity and do not deteriorate even when used in high concentration brine solutions and/or in high temperature environments. , we have completed the present invention.

That is, the present invention provides a well drilling fluid, completion fluid, or workover fluid consisting of a copolymer of a cationic vinyl monomer and a vinyl monomer represented by the following general formula (hereinafter referred to as formula (1)). thickeners and drilling fluids using the thickeners;
A finishing or refurbishing brine fluid.

[In the formula, R+, Rz are CI"" C4 alkyl groups,
R3 is trimethylene or pentamethylene. ] Generally, the base brine has a specific gravity of 1.10 to 2.
An aqueous solution consisting only of 50 inorganic salts is used.

Also in the present invention, the specific gravity of the brine is 1.15 to 2.
50 is used.

The cationic vinyl monomer that is the raw material for the present invention includes N-
(meth)acryloxethyltrimethylammonium chloride, 3-(acryloylamino)propyltrimethylammonium chloride, N-(3-sulfopropyl)
-N-Methachloryloxyethyl-N, N-dimethylammonium betaine, N-(3-sulfoprovir)-N-
Methacryloylamide propyl-N,N-dimethylammonium betaine, 1-(3-sulfopropyl)-2-
Vinylpyridimium betaine, 1,1-dimethyl-1(
Quaternary salts or betaine type monomers such as 2-hydroxypropyl)amine methacrylimide, dimethyldiallylammonium chloride, 3-(methacryloxy)-2-hydroxypropyltrimethylammonium chloride:
Also, N,N-dimethylamine ethyl (meth)acrylate hydrochloride, N-ethyl-N-methylaminoethyl (
meth)acrylate Tertiary salt type monomers such as hydrochloric acid: and t-butylaminoethyl (meth)acrylate, N,
N-dimethylaminopropyl (meth)acrylamide,
Examples include amino type monomers such as aminoethyl vinyl ether, dimethylaminoethyl vinyl ether, and 2-vinylpyridine. These cationic vinyl monomers are
This component is selected to give the polymer excellent solubility in brine and thickening properties, and is preferably a quaternary salt type or betaine type monomer.

In addition, the vinyl monomer represented by formula (1) in the present invention includes N-vinylformamide, N-vinylpyrrolidone, N-vinylcaprolactam, N-methyl-N-vinylpropionic acid amide, N-methyl- Examples include N-vinylacetamide. These vinyl monomers are components selected for the purpose of imparting excellent heat resistance to the brine, and preferred examples include N-vinylpyrrolidone, N-vinylcaprolactam, and N-methyl-N-vinylacetamide. .

That is, the present invention provides the above cationic vinyl monomer,
Also, it is a brine fluid using as a thickener a copolymer made of one or a combination of two or more monomers selected from the vinyl monomers represented by the above formula (1). .

The composition ratio of the above cationic vinyl monomer and the vinyl monomer represented by formula (1) is 90/90 by weight of each monomer.
10 to 10/90, preferably 70/30 to 3
It is 0/70. If this composition ratio is exceeded, the copolymer's solubility in brine will deteriorate, the thickening effect will be lost, and the heat resistance of the copolymer itself will decrease. It becomes impossible to obtain a copolymer with the heat and salt resistance required as a thickener for brine fluids used in high temperature environments.

The copolymer of the present invention includes monomers copolymerizable with the monomers used in the present invention, such as carboxylic acid type monomers such as (meth)acrylic acid, maleic acid, and itaconic acid; acrylic acid esters, and methacrylates. Ester-type monomers such as acid esters and vinyl acetate; or copolymers with styrene, vinyl chloride, acrylamide, etc. can be mentioned. In addition, polyalkylene glycol mono(meth)acrylate, methylene bisacrylamide, divinylbenzene,
Suitable crosslinking of the polymer with a polyfunctional monomer such as trimethylolpropane acrylate is preferred as it improves the heat resistance of the polymer;
When using other monomers, they should be used within a range that does not pose a risk of deteriorating the water solubility or thickening effect of the polymer.

The copolymer used as the thickener of the present invention has a molecular weight (
weight average molecular weight) is 100.000 to 10,000,
Preferably, it is 000. More preferably, 50
0,000~5. It is OOO,000.

The brine fluid of the present invention contains the above-mentioned thickener in an amount of 0.1 to 5.0.
It is appropriate to use % by weight. Additionally, other thickeners,
For example, it may be used in combination with conventional general-purpose thickeners such as cellulose derivatives, polyacrylamide, starch, and polyethylene oxide.

In addition to the thickener described above, a bridging agent is added to the brine fluid of the present invention in order to prevent water loss of the fluid, etc.
This allows excavation, finishing or refurbishment work to be carried out more safely and effectively.

This bridging agent closes formation voids, forms well walls, prevents leakage of drilling fluid, completion fluid, or workover fluid, and prevents formation failure.

Bridging agents include calcium carbonate powder of various particle sizes that do not dissolve in water, petroleum resins of various particle sizes that dissolve in crude oil and light oil, calcium carbonate powder of various particle sizes, and water-soluble gluegenin that has the function of adjusting the amount of dehydration. Examples include mixtures with sodium sulfonate, pregelatinized starch, and the like.

These bridging agents are effective when added in an amount of 1.0 to 20.0% by weight. Preferably, it is in the range of 5 to 12% by weight.

The particle size of the bridging agent must be selected depending on the porosity of the formation. By providing a variety of particle sizes, excavation, completion or refurbishment operations can be carried out efficiently and successfully.

e. Function The thickener used in the present invention has both cationic and anionic properties, so it has high solubility in brine.
The thickening effect is excellent. In addition, it maintains its thickening effect without deteriorating even in a high concentration brine solution and/or in a high temperature environment, and can exhibit sufficient viscosity as a drilling fluid, finishing fluid, or repair fluid.

In production strata and permeable strata, bridging agents also fill the surface of voids in the strata and form pit walls, allowing drilling fluids, finishing fluids, remediation fluids, etc. to escape into the strata. Prevent formation disturbances.

Bridging agents that plug production strata and permeable strata may become an obstacle in oil and gas production. Therefore, the bridging agent must be able to be easily removed from the packed stratum by simple treatment according to the characteristics of the bridging agent.
Insufficient removal of bridging agents often causes production problems.

f. Examples Examples include pacebutyin solutions, thickeners,
A bridging agent was used.

(1) Base brine solution (BS-1 to 3) BS-1:
BS-2: NaCl aqueous solution with a specific gravity of 1.15 (about 20% by weight aqueous solution) BS-2: NaCl aqueous solution with a specific gravity of 1.35 (about 35% by weight aqueous solution) BS-3: CaClt/CaBrz mixed aqueous solution with a specific gravity of 1.70 (CaCl , is about 22%, and CaBr2 is about 3
(4% mixed aqueous solution) (2) Thickener (ZN-1 to 3) ZN-1: DMC, (70% by weight) /VP (30
superposition%) ZN-2: DMPQ (15fj it%)
) / MVAD (85111%) ZN-3: D
MH (50% by weight) / MVAD (50% by weight) PEG
M (0,01% by weight) DMC, N-methacryloxyethyltrimethylammonium chloride DMPQ; 3-(acryloylamino)propyltrimethylammonium chloride) DM)l; N, N-dimethylaminoethyl methacrylate hydrochloride MVAD; N -Methi71z -N-vinylacetamide VP, N-vinylpyrrolidone PEGM, polyethylene glycol dimethacrylate (3) Bridging agent BA-F, calcium carbonate, particle size distribution = 1-30μ Average particle size = 20.4μ The following implementation In an example, the performance of a brine fluid of the present invention and a conventional brine fluid were compared.

(1) Yield value (thickening property) When evaluating the thickening effect of a thickening agent,
On, the yield value (kl /
ton). The larger the yield, the greater the thickening effect.

This yield value was determined by adding a thickener to the baseline solution, stirring for 20 minutes in a Hamilton Beach mixer, leaving it to stand at room temperature for 16 hours, and stirring for an additional 10 minutes.
(7) The apparent viscosity (AV value) was measured and plotted to obtain a viscosity curve. From this curve, the concentration of 15 cp (g/100 d) was determined. , the yield value (je1/1on) was calculated using the following formula.

AV 1) CI4 mJX(g/lυυjlEJ(2)
Flow properties (flow properties of brine fluid) To the baseline solution, a thickener was added, stirred in a Hamilton Beach mixer for 20 minutes, left to stand at room temperature for 16 hours, stirred for an additional 10 minutes, and then mixed at 22-25 °C. The flow properties of the concentration (g/100d) were measured using a Fann model 35 viscometer.

(3) Put the brine fluid made in heat resistance (2) into the curing cell,
The fluid was left to heat and cure for 8 hours at temperatures of 1200°C and 230°C, and changes in the flow characteristics of the fluid before and after curing were investigated.The flow characteristics after curing were determined by cooling the fluid to 25°C. and measured using a Fann model 35 viscometer.

(4) In order to evaluate the effect of dehydration bridging agent, improved square PI
The amount of dehydration under high temperature and high pressure was measured using a high temperature and high pressure dehydration tester.

To measure the amount of dewatering, the finished fluid before and after addition of the bridging agent was placed in a modified API high temperature and high pressure dehydration tester cell set at a constant temperature, and a pressure of 100 psi was applied for 3.
Let stand for 0 minutes. Thereafter, the pressure was increased to 250 psi and the amount of water removed over 2 hours was measured.

The improved API high temperature and high pressure dehydration tester cell has a filter with an air permeability of 500ed (average pore diameter 9.8
μ), 2000md (average pore diameter 19.3μ), 5
Cores with different diameters of 000+++d (average pore diameter 38.4μ) were used. The core measures 1 inch in diameter and 1 inch in length.
It is 5 inches. Here, md is millidarcy (penetration rate), which is 1/1000 darcy (d). This value is unique to porous objects and is expressed by the following equation.

A-ΔP L::17 length (CI+)Q::I7
Flow rate of fluid penetrating into (jd!/sec) ^: Cross-sectional area of core (cifi) ΔP: Pressure difference (atmospheric pressure) K: Darcy (d) (5) Recovery rate Air permeability is 100ed (average pore diameter 1. 39),
Using a 500ed core, the oil penetration rate before the brine fluid was penetrated was taken as the initial penetration rate, and the core penetrated with the brine fluid was treated with a hydrochloric acid aqueous solution (concentration 7.5% by weight) to recover. The oil penetration rate was defined as the recovery penetration rate, and the ratio of this initial penetration rate to the recovery penetration rate was defined as the recovery rate.

A permeability measuring device was used to measure the oil permeability.

(Example-1) Baseline solution B5-1 (NaCl with specific gravity 1.15
The fluidity, heat resistance, and yield value of a brine fluid prepared by adding a thickener ZN-1 or ZN-2 to an aqueous solution were measured.

Table 1 shows the composition of the brine fluid, Table 2 shows the fluidity and heat resistance, and Table 3 shows the yield value.

Note that the yield value was measured at 22 to 25°C.

Table-1 Brine fluid composition Comparative Example 1 used hydroxyethylcellulose.

Table-2 Fluidity and heat resistance *Units = AV: cp, PV: cp, YV: lb/100
ft” Table-3 Yield value (Example-2) Base pline solution B5-2 (CaC with specific gravity 1.35
Fluidity, heat resistance, and yield value were measured for a brine fluid obtained by adding a thickener ZN-2 or ZN-3 to a 1z aqueous solution).

Table 4 shows the composition of the brine fluid, Table 5 shows the fluidity and heat resistance, and Table 6 shows the yield value.

Note that the yield value was measured at 22 to 25°C.

Table-4 Brine fluid composition - Comparative example 2 used xanthan gum.

Table-5 Fluidity and heat resistance unit = AV: cp, PV: cp, YV: lb/100f
t'' Table-6 Yield value (Example-3) Base pline solution B5-3 (CaC with specific gravity 1.70
1zl/CaBr, 'mixed aqueous solution) with thickener ZN-1
Alternatively, the fluidity, heat resistance, and yield value of the brine fluid to which ZN-3 was added were measured. Table 7 shows the composition of the brine fluid, Table 8 shows the fluidity and heat resistance, and Table 9
The yield values are shown in .

Note that the yield value was measured at 22 to 25°C.

Table-7 Brine fluid composition Comparative Example 3 used hydroxypropylcellulose.

Table-8 Fluidity and heat resistance unit = AVsep, PV: cp, YV: lb/100f
t2 Table-9 Yield value (Example-4) Base brine solution B5-1 (CaC with specific gravity 1.15
After adjusting the brine fluid by adding a bridging agent (BA-F) to the brine fluid in which the thickener ZN-3 was added to the B5-3 CaC1z/CaBrz mixed aqueous solution) or the B5-3 CaC1z/CaBrz mixed aqueous solution, Fluidity, heat resistance and yield value were measured. Furthermore, in order to evaluate the effect of the thickener on this brine fluid, the amount of water removed and the recovery rate of oil permeability were measured.

Table 10 shows the composition of the brine fluid, Table 11 shows the fluidity and heat resistance, and Table 12 shows the dewatering amount and recovery rate.

Table 10 Brine fluid composition Comparative Example 3 used hydroxyethyl cellulose thickener.

Table 11 Fluidity and heat resistance Table 12 Dehydration amount and recovery rate g0 Effect of the invention The thickener of the present invention exhibits an excellent thickening effect in brine consisting of a highly concentrated inorganic electrolyte solution. Drilling fluids, completion fluids, or workover fluids for wells that have been prepared with the addition of It exhibits superior effects not found in conventional drilling fluids, completion fluids, or workover fluids, such as making it possible to drill wells and not causing formation disturbances during completion or workover work of production wells under high temperature and high pressure conditions. .

Claims (4)

[Claims] (1) Thickening fluid for well drilling, finishing or workover fluids characterized by being composed of a copolymer consisting of a cationic vinyl monomer and a vinyl monomer represented by the following general formula. agent. ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [In the formula, R_1 and R_2 are C_1 to C_4 alkyl groups, and R_3 is trimethylene or pentamethylene. ] (2) A well characterized in that the thickener of claim (1) is added to a fluid consisting of an inorganic salt solution used as a circulating fluid in the drilling of wells for oil, natural gas, etc. drilling fluid. (3) The scope of the claims ( A well completion or workover fluid characterized by adding the thickener of 1). (4) The finishing or refurbishment fluid according to claim (3), characterized in that a bridging agent is added and mixed therein.