JP2592715B2 - Thickeners and fluids containing well drilling fluids, finishing or renovation fluids - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION a. Industrial Field of the Invention The present invention relates to drilling fluids for wells such as petroleum and natural gas, and finishing or aging of wells for petroleum and natural gas under high temperature and high pressure environment. The present invention relates to a thickener to be added to a fluid used at the time of rehabilitation of a well, and a drilling fluid, a finishing or a renovation fluid of the well using the thickener.

More specifically, the present invention relates to a thickener added to a drilling fluid using an inorganic salt solution (hereinafter, referred to as "brine") used for drilling a well such as petroleum and natural gas, and to use the thickener. Drilling fluids and oil and
In the case of using a brine to finish a production well for natural gas or the like, or to repair an aging oil or natural gas well using a brine, drilling holes in the production layer (hereinafter referred to as gun perforation work) ), It is possible to prevent geological disturbances such as the intrusion of brine into the production layer and the production failure, and also the prevention of oil, natural gas or groundwater eruption accidents due to a decrease in underground pressure. And a finishing or renovating fluid using the thickener.

b. Conventional technology At present, brine is used as a part of drilling fluid in wells such as oil and natural gas, and as a fluid for finishing or repairing various wells. However, these brines are aqueous solutions of inorganic salts that do not contain any solid components, and if they are used as they are at the time of well drilling work or gun perforation work, expensive brine will cause the formation of drilling well formations. There is a possibility that the water may be lost inside and in the production layer, causing a great loss. In addition, the invasion of brine into the production layer disrupts the balance of ions and other constituents in the stratum that forms them, adversely affects the hydration and dispersion of the clay minerals that compose the production layer, and can cause stratum damage. Become. Furthermore, there are not a few accidents in which oil, natural gas, groundwater, or the like is ejected due to pressure drop in the mine due to brine or the like.

On the other hand, in the repair work of an aging well, since the production of oil and natural gas has been performed, the pressure in the formation may decrease, and the same accident as above may occur.

In the drilling, finishing, or rehabilitation work of these wells, the following measures should be taken to prevent accidents caused by brine flowing into the well formation or production layer and entering the production layer. Can be considered.

A thickener is added to the brine to increase the viscosity of the brine and to prevent water loss into the formation or production layer due to flow resistance.

A thickening agent is added to the brine to prepare a brine solution (hereinafter referred to as "brine fluid"), and a bridging agent having a particle size distribution suitable for the pore diameter of the production layer is suspended in the solution. Fill to prevent water loss.

As the above-mentioned thickener, it can be easily dissolved in an aqueous solution of high-concentration salts, a high viscosity can be obtained with a small amount of addition, and it has a stable thickening effect under a high temperature environment, acid, oil or water. It is desirable that the compound easily dissolves in any of the above and does not remain permanently in the production stratum. In addition, as a bridging agent, even in a high-temperature environment, without causing a change in the material, easily dissolved by an acid or oil, etc., does not permanently remain in the production stratum, the particle size from 1 to 3000μ Is desirable.

Conventionally, as a thickener, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose,
Polyvinyl alcohol, starch, guar gum, sodium polyacrylate, polyacrylamide, polyethylene oxide, fatty acid ester derivatives, polyurethane and the like are used.

As a bridging agent, solids insoluble in water dissolved in hydrochloric acid such as calcium carbonate, solids in a mixture of acids such as a mixture of calcium carbonate and a lignin compound, solids such as salt, etc. Compounds that dissolve in water,
Solids soluble in oils such as petroleum resins have been used.

c. Problems to be Solved by the Invention Conventional thickeners, when used in brine fluid for drilling fluid, can keep the brine concentration relatively low,
When used in finishing or refurbishment 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 is a disadvantage that the thickener itself changes its quality to reduce the viscosity or to be denatured and gelled. Therefore, the conventional thickener cannot maintain the viscosity of the brine fluid sufficiently at a high brine concentration and / or in a high temperature environment, and the used brine concentration and / or temperature range is limited to a relatively low range. As a result, satisfactory characteristics could not be obtained in a high-concentration brine solution and / or in a high-temperature environment.

That is, even in a high-concentration brine solution and / or under a high-temperature environment, there is no defect such as denaturation and thinning, or denaturation and gelation, and excellent heat resistance and salt resistance showing excellent solubility and viscosity. There was a need for a thickener with it.

d. Means for Solving the Problems The present inventors have intensively studied a thickener which can maintain sufficient viscosity and does not deteriorate even when used in a high-concentration brine solution and / or under a high temperature environment. result,
The present invention has been completed.

That is, the present invention relates to a well drilling fluid, a finishing fluid, or a repair fluid comprising 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, finishing or renovation brine fluids using the thickeners.

Wherein R ₁ and R ₂ are a C ₁ -C ₄ alkyl group, and R ₃ is trimethylene or pentamethylene. In general, the base brine has a specific gravity of 1.10 to 2.50.
An aqueous solution consisting of only the inorganic salts of the above is used. Also in the present invention, brine having a specific gravity of 1.15 to 2.50 is used.

The cationic vinyl monomer used as a raw material of the present invention includes N
-(Meth) acryloxyethyltrimethylammonium chloride, 3- (acryloylamino) propyltrimethylammonium chloride, N- (3-sulfopropyl) -N-methacryloxyethyl-N, N-dimethylammonium betaine, N- (3 -Sulfopropyl) -N
-Methacryloylamidopropyl-N, N-dimethylammonium betaine, 1- (3-sulfopropyl) -2-
Vinyl pyridimium betaine, 1,1-dimethyl-1 (2
-Hydroxypropyl) amine methacrylimide, dimethyldiallylammonium chloride, quaternary salts such as 3- (methacryloxy) -2-hydroxypropyltrimethylammonium chloride or betaine type monomers: and N, N-dimethylaminoethyl (meth) acrylate Tertiary salt-type monomers such as hydrochloride and N-ethyl-N-methylaminoethyl (meth) acrylate hydrochloride are exemplified. These cationic vinyl monomers are components selected to give the polymer excellent solubility in brine, and to increase the viscosity, and are preferably quaternary salt types,
Alternatively, a betaine-type monomer can be used.

Further, the vinyl monomer represented by the formula (1) in the present invention includes N-vinylformamide, N-vinylpyrrolidone, N-vinylcaprolactam, N-methyl-N-vinylpropionamide, N-methyl- N-vinylacetamide and the like. These vinyl monomers are components selected for the purpose of imparting excellent heat resistance to brine, and preferably include N-vinylpyrrolidone, N-vinylcaprolactam, and N-methyl-N-vinylacetamide. .

That is, the present invention provides a combination of one or two or more monomers selected from the above-mentioned cationic vinyl monomers and the vinyl monomers represented by the above formula (1). Is a brine fluid using the resulting copolymer as a thickener.

The composition ratio of the cationic vinyl monomer and the vinyl monomer represented by the formula (1) is 90/1 by weight ratio of each monomer.
It is 0 to 10/90, preferably 70/30 to 30/70. If the composition ratio is out of this range, the solubility in brine becomes poor, and the thickening effect is lost. Also, the heat resistance of the copolymer itself decreases. Therefore, a copolymer having a heat-resistant salt property required as a thickener for a brine fluid used in a high-concentration brine solution and / or in a high-temperature environment cannot be obtained.

The copolymer of the present invention includes a monomer copolymerizable with the monomer used in the present invention, for example, a carboxylic acid type monomer such as (meth) acrylic acid, maleic acid, and itaconic acid: acrylic acid ester, methacrylic acid Ester type monomers such as acid esters and vinyl acetate: and copolymers with styrene, vinyl chloride, acrylamide and the like. Furthermore, appropriately cross-linking the polymer with a polyfunctional monomer such as polyalkylene glycol mono (meth) acrylate, methylenebisacrylamide, divinylbenzene, trimethylolpropane acrylate, etc., improves the heat resistance of the polymer. It is preferred. In any case, when another monomer is used, the polymer should be used within a range that does not reduce the water solubility or the thickening effect.

The molecular weight (weight average molecular weight) of the copolymer used as the thickener of the present invention is preferably from 100,000 to 10,000,000. More preferably, 500,000-5,000,000
It is.

The brine fluid of the present invention suitably uses 0.1 to 5.0% by weight of the above thickener. Further, it may be used in combination with other conventional thickeners such as cellulose derivatives, polyacrylamide, starch and polyethylene oxide.

To the brine fluid of the present invention, in addition to the above-mentioned thickener, a bridging agent is added to prevent the fluid from flowing out, etc., so that a drilling operation, a finishing operation or a renovation operation can be performed more safely and effectively. It can be performed.

The bridging agent blocks formation cavities, forms wellbore walls, prevents the escape of drilling, finishing, or refurbishment fluids and prevents formation failure.

Examples of the bridging agent include calcium carbonate powders of various particle sizes that are not soluble in water, petroleum resins of various particle sizes that are soluble in crude oil and light oil, and calcium carbonate powders of various particle sizes and water-soluble lignin having a dehydration control function. Mixtures with sodium sulfonate, pregelatinized starch and the like are included.

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 according to the porosity of the formation. By preparing those having various particle diameters, excavation work, finishing work or renovation work can be efficiently and successfully performed.

e. Action Since the thickener used in the present invention has both cationic and anionic properties, it has high solubility in brine and an excellent thickening effect. Further, even in a high-concentration brine solution and / or under a high-temperature environment, the thickening effect can be maintained without deteriorating, and sufficient viscosity can be exhibited as a drilling fluid, a finishing fluid, or a repair fluid.

In addition, the bridging agent, in the production stratum or permeable stratum, clogs the surface of the void portion of the stratum, further forms a pit wall, and drilling fluid, finishing fluid or renovation fluid, etc., escapes into the stratum, Prevent geological disturbance.

The bridging agent that clogs the production and permeable formations may be an obstacle to oil and gas production. Accordingly, the bridging agent must be one that can be easily removed from the clogged formation by performing a simple treatment according to the properties of the bridging agent. Insufficient removal of the bridging agent often causes production disturbances.

f. Examples In the examples, the following base brine solutions, thickeners, and bridging agents were used.

(1) Base brine solution (BS-1~3) BS-1 : NaCl aqueous solution having a specific gravity of 1.15 (about 20% by weight aqueous solution) _BS-2: NaCl 2 solution having a specific gravity of 1.35 (about 35% by weight aqueous solution) BS-3: CaCl ₂ / CaBr ₂ mixed aqueous solution of specific gravity 1.70 (CaCl ₂
22%, CaBr ₂ are mixed system an aqueous solution of about 34%) (2) a thickening agent (ZN-1~3) ZN-1 : DMC (70 wt%) / VP (30 wt%) ZN-2: DMPQ ( 15% by weight) / MVAD (85% by weight) ZN-3: DMH (50% by weight) / MVAD (50% by weight) PEGM (0.01% by weight) DMC; N-methacryloxyethyltrimethylammonium chloride DMPQ; 3- ( (Acryloylamino) propyltrimethylammonium chloride) DMH; N, N-dimethylaminoethyl methacrylate hydrochloride MVAD; N-methyl-N-vinylacetamide VP; N-vinylpyrrolidone PEGM; polyethylene glycol dimethacrylate (3) Bridging agent BA-F; calcium carbonate, particle size distribution = 1 to 30 µm Average particle size = 20.4 µm In the following examples, the performance of the brine fluid of the present invention and the conventional brine fluid was compared.

(1) Yield value (thickening) When evaluating the effect of thickening of a thickener, 1 ton
The yield capacity (kl / ton) was evaluated as the yield capacity of a brine fluid having an apparent viscosity (AV value) of 15 cp. The larger the yield value, the higher the thickening effect.

The yield value was determined by adding a thickener to the baseline solution, stirring with a Hamilton Beach mixer for 20 minutes, allowing to stand at room temperature for 16 hours, stirring for another 10 minutes, and then adjusting the concentration (g / g) at 22 to 25 ° C. (100 ml) was measured and plotted to obtain a viscosity curve. From this curve, the concentration of 15 cp (g / 10
0 ml) and the yield value (kl / ton) was determined by the following equation.

(2) Fluidity (Flow characteristics of brine fluid) A thickener was added to the baseline solution, stirred with a Hamilton Beach mixer for 20 minutes, allowed to stand at room temperature for 16 hours, and further stirred for 10 minutes, and 22 to 25. The flow characteristics of each concentration (g / 100 ml) were measured at ° C. using a Fann model 35 viscometer.

(3) Heat resistance Put the brine fluid prepared in (2) into the curing cell,
At each temperature of ℃, 200 ℃, and 230 ℃, it was heated and cured for 8 hours in a constant temperature bath, and the change in the flow characteristics of the fluid before and after curing was examined.
After curing, the fluid was cooled to 25 ° C and the Fann model
It was measured using a 35 viscometer.

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

For the measurement of the amount of dehydration, the finishing fluid before and after the addition of the bridging agent is placed in an improved API high-temperature and high-pressure dehydration test cell set at a constant temperature, and a pressure of 100 psi is applied, and the mixture is allowed to stand for 30 minutes. Thereafter, the pressure was increased to 250 psi, and the amount of dehydration for 2 hours was measured.

The improved API high-temperature high-pressure dehydration tester cell has a filter with air permeability of 500 md (average void diameter of 9.8 µ), 2000
md (average void diameter 19.3μ), 5000md (average void diameter 38.4μ)
Different cores were used. The size of the core is 1 inch in diameter and 1.5 inches in length. Here, md is millidarcy (permeability), which is 1/1000 darcy (d).
This value is specific to the porous object and is expressed by the following equation.

μ: Viscosity μ of liquid permeating core μ (CP) L: Length of core (cm) Q: Flow rate of fluid permeating core (ml / sec) A: Cross-sectional area of core (cm ² ) ΔP: Pressure difference (Atmospheric pressure) K: Darcy (d) (5) Recovery rate Using a core of 100 md (average void diameter 7.3 μ) and 500 md, the permeability of oil before permeating the brine is defined as the initial permeability. Further, the core that has been impregnated with the brine fluid is treated with an aqueous hydrochloric acid solution (concentration 7.5% by weight) and recovered, and the oil permeability is referred to as the recovery permeability, and the ratio between the initial permeability and the recovery permeability is referred to as the recovery rate. did.

 For measuring the oil permeability, a permeability measuring device was used.

(Example-1) Base brine solution BS-1 (NaCl aqueous solution of specific gravity 1.15)
The fluidity, heat resistance, and yield value of a brine fluid obtained by adding a thickener ZN-1 or ZN-2 to a fluid 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.

 The measurement of the yield value was performed at 22 to 25 ° C.

(Example-2) The fluidity, heat resistance and yield value of a brine fluid obtained by adding a thickener ZN-2 or ZN-3 to a base brine solution BS-2 (a CaCl ₂ aqueous solution having a specific gravity of 1.35) were measured.

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

 The measurement of the yield value was performed at 22 to 25 ° C.

(Example -3) based brine solution _{BS-3 (CaCl 2 1 /} CaBr 2 specific gravity 1.70
The fluidity, heat resistance, and yield value of a brine fluid obtained by adding a thickener ZN-1 or ZN-3 to a mixed aqueous solution) were measured. Table 7 shows the composition of the brine fluid, Table 8 shows the fluidity and heat resistance, and Table 9 shows the yield value.

 The measurement of the yield value was performed at 22 to 25 ° C.

(Example-4) Base brine solution BS-1 (CaCl aqueous solution with specific gravity of 1.15)
Or BS-3CaCl ₂ / CaBr ₂ mixed system aqueous thickener ZN-3 to the added brine fluid respectively, bridging agent (BA
After adding -F) to adjust the fluid, the fluidity, heat resistance and yield value of the brine fluid were measured. Further, in order to evaluate the effect of the thickener on the brine fluid, the amount of dewatering and the recovery rate of the 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 dehydration amount and recovery rate.

g.Effect of the Invention The thickener of the present invention exhibits an excellent thickening effect in brine composed of a high concentration of inorganic electrolyte solution. Alternatively, refurbishment fluids and, if necessary, fluids obtained by adding bridging agents to these fluids, make it possible to drill wells safely and without accidents, and to use wells for production wells under high temperature and high pressure. It shows excellent effects not found in conventional drilling fluids, finishing fluids or renovation fluids, such as no formation failure during finishing or renovation work.

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Claims (4)

(57) [Claims] 1. A well drilling fluid, a finishing fluid or a refurbishment fluid comprising a copolymer comprising a cationic vinyl monomer and a vinyl monomer represented by the following general formula: Thickener. Wherein R ₁ and R ₂ are a C ₁ -C ₄ alkyl group, and R ₃ is trimethylene or pentamethylene. ] 2. A fluid comprising an inorganic salt solution used as a circulating fluid in drilling a well such as oil and natural gas,
A drilling fluid for a well, wherein the thickener according to claim 1 is added. 3. A finishing or repairing fluid comprising an inorganic salt solution used for finishing or repairing a production well for oil, natural gas or the like under high-temperature and high-pressure circulation. A finishing or refurbishment fluid for a well, characterized by adding a thickener according to (1). 4. The finishing or modifying fluid according to claim 3, wherein a bridging agent is added and mixed.