JPS6215279A - Chemical for petroleum third recovery use - Google Patents

Abstract

PURPOSE:To obtain the titled chemical of high injectability into oil strata, improved in shear degradation resistance, by radical copolymerization in an aqueous solution between acrylamide-based monomer(s), methacrylic acie salt and water-soluble anionic monomer followed by drying the resultant gel of specific anionic modification degree to effect pulverization. CONSTITUTION:A radical copolymerization is carried out in an aqueous solution between (A) acrylamide or a monomer mixture made up chiefly of acrylamide, (B) 5-40wt%, based on the component A, of a methacrylic acid salt, and (C) 0-35wt%, based on the component A, of a water-soluble anionic vinyl monomer (e.g., sodium acrylate) followed by, if neded, partial hydrolysis of the resulting copolymer gel. The copolymer gel thus formed with an anionic modification degree 5-35mol% is dried to effect pulverization, thus obtaining the objective chemical consisting of copolymer powder.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a tertiary petroleum recovery agent that has good injectability into oil reservoirs and improved mechanical shear degradation characteristics.
IP, -+4 j 1 [Background technology] When an acrylamide polymer aqueous solution used for tertiary oil recovery is injected into an underground oil layer to forcibly recover oil, the acrylamide polymer is used at an oil layer temperature of 30 ~9
At 0°C, in addition to being exposed to high salt concentrations, mechanical shearing during injection into the oil layer causes viscosity deterioration of the acrylamide polymer aqueous solution, resulting in a decrease in oil recovery rate and, in extreme cases, the objective In some cases, it may become impossible to use it for the intended purpose.

Therefore, it is required that the acrylamide polymer aqueous solution not only has excellent thermal stability and saltiness, but also has low mechanical shear even under high salt concentration.

When an acrylamide-based polymer aqueous solution is injected into an oil layer under severe conditions such as those mentioned above, it generally causes rapid mechanical shear deterioration and cannot exhibit sufficient efficacy as a tertiary oil recovery agent. .

Tertiary petroleum recovery agents generally use very high molecular weight acrylamide polymers in consideration of efficiency and economy, but if an acrylamide polymer aqueous solution with too high molecular weight is used, Injectability into the oil layer is poor, and in some cases it may even be difficult to inject, and even if it can be injected, it suffers from significant mechanical shear deterioration and is hardly effective.

On the other hand, in the case of a low molecular weight acrylamide polymer, mechanical shear deterioration is small, but a high concentration must be used to maintain a constant viscosity.

Therefore, in order to improve these characteristics, U.S. Patent No.
, 247,171 describes a method for partially crosslinking the polymer, and U.S. Pat. A method of using an acrylamide-based polymer containing butylammonium chloride (AMBTAC) etc. as a tertiary petroleum recovery agent is also described in US Pat. No. 4,432,881. A method using a tertiary petroleum recovery agent in combination with a polymer (eg, acrylamide-dodecyl acrylate copolymer) and a surfactant is disclosed.

However, it is difficult to say that any of these methods fully satisfies the above-mentioned requirements for tertiary petroleum recovery agents from the standpoint of practical application.

[Disclosure of the invention]

The object of the present invention is to exhibit high viscosity under high salt concentration.

An object of the present invention is to provide a tertiary petroleum recovery agent that has good injectability into an oil layer and is less susceptible to mechanical shear deterioration.

The tertiary petroleum recovery agent of the present invention comprises (a) acrylamide or a monomer containing a predominant amount of acrylamide, (b) methacrylate in an amount of 5 to 40% of the weight of monomer (a), and (c) a monomer containing a predominant amount of acrylamide. Aqueous radical copolymerization of 0 to 35% of the weight of polymer (a) of a water-soluble anionic vinyl monomer is carried out, and if necessary, the resulting copolymer gel is partially hydrolyzed, resulting in anionized degree is 5
It consists of copolymer powder obtained by drying ~35 mol% of copolymer gel and pulverizing it.

[Embodiments of the invention]

The methacrylate is used in an amount of 5 to 40% by weight, preferably 10 to 30% by weight, based on monomer (a).

If the content of methacrylate is 5% by weight or less, a tertiary petroleum recovery agent that has good injectability into an oil layer and low mechanical shear deterioration properties cannot be obtained. Moreover, at 40% by weight or more,
High molecular weight acrylamide polymers are difficult to obtain, and even if they are obtained, precipitation occurs due to divalent or higher valent metal salts contained in underground layers.

Examples of methacrylates are sodium, potassium, ammonium salts, etc. of methacrylic acid.

Examples of water-soluble anionic vinyl monomers are sodium salts, potassium salts, ammonium salts, etc. of acrylic acid or 2-acrylamido-2-methylpropanesulfonic acid, and mixtures thereof; vinyl monomer.

It is allowed to coexist in an amount of 0 to 35% by weight based on monomer (a).

V1 master! h・g /7'l'&
Shiba Kakuto ITI '7 ・h''/kk
l・+l・product Polymerize without or with JjLI+ coexisting.

The objective can also be achieved by subsequently partially hydrolyzing the acrylamide component or methacrylamide component.

The acrylamide copolymer obtained as described above has an anionization degree of 5 to 35 mol%.

If the degree of anionization is less than 5 mol%, the water-soluble polymer will adsorb onto the rock of the oil layer, which will not only make it difficult to inject the acrylamide polymer aqueous solution into the oil layer, but also cause further mechanical shear deterioration. Furthermore, if the degree of anionization is 35 mol% or more, precipitation of acrylamide polymer due to divalent or higher valent metal salts contained in the ground F layer will occur, which will fill the rock and reduce the tertiary oil recovery efficiency. The degree of anionization of the acrylamide polymer is from 5 to 35 mol%, preferably from 10 to 30 mol%, for reasons of 0 or more, which cause severe deterioration and mechanical shear deterioration.

A copolymer gel is obtained by radical polymerizing an aqueous solution of preferably 20 to 40% by weight of the above monomers (a) to (c) using a redox catalyst and/or an azo catalyst consisting of an oxidizing agent and a reducing agent. If necessary, this partial hydrolysis is performed, and the resulting copolymer gel having an anionization degree of 5 to 35 mol % is dried and powdered to obtain a copolymer powder. What are the molecular weights of these copolymers?

Although not particularly limited, the effects of the present invention are better exhibited in a copolymer having a relatively high molecular weight. Specifically, it is preferable to have a weight average molecular weight of at least 5 million. The weight average molecular weight can be measured by the light scattering method or the intrinsic viscosity [η] method (the value of [η] is 18-
This is a value measured using an Ubbelohde viscometer or a Cannon-Fenske viscometer in a constant temperature bath at 30°C using a sodium nitrate aqueous solution, and the weight average molecular weight in the case of an acrylamide homopolymer is [η] = 3. 73 XI
O″I0.68 [MW] (30°C, 1N-NaN03).

The redox catalyst consisting of an oxidizing agent and a reducing agent used in the present invention includes a water-soluble peroxide-hydroxy tertiary amine system, a water-soluble peroxide-water soluble sulfite, and a water-soluble peroxide-water soluble These include sulfite-based substances.

The azo catalyst is a water-soluble azo compound, such as 2.2'-
Examples include azobis(2-amidinopropane)hydrochloride and oil-soluble azo compounds such as azobisisobutyronitrile and 4,4'-azobis-4-cyanoparelic acid.

EXAMPLES The present invention will be further explained in detail with reference to Examples below, but these Examples should not be construed as limiting the present invention.

Example 1 Concentration of monomers consisting of 80% by weight of acrylamide (AND), 5% by weight of sodium methacrylate (MAANa), and 15% by weight of sodium acrylate (^ANa) 30
750 parts of aqueous solution (pH=7.5) at 10°C
After cooling to.

The reaction system was placed in a heat-insulated box, and the inside of the reaction system was sufficiently deoxidized with N2 gas. A solution of 0.25 parts of 7zobiscyanovaleric acid (AGVA) dissolved in 7.5 parts of methanol was added to this aqueous solution, and 0.002 parts of ammonium persulfate (APS) and sulfuric acid were added as polymerization initiators. 0.004 part of iron ammonium (FAS) was added, and adiabatic polymerization was carried out at a reaction initiation temperature of 5°C. The reaction was completed in about 5 hours.

The obtained polymer gel was cut into pieces with a diameter of 2 to 3 mm using a meat cutter, and dried and crushed to obtain a standard viscosity (SV value) (IN-NaCJ aqueous solution of 0.1% by weight). 80rp using a BBL type viscometer with
A water-soluble high molecular weight polymer powder having a value measured at m) of about 4.9 cps/25° C. was obtained.

500 pP1 of the acrylamide-based high molecular weight copolymer powder containing sodium methacrylate obtained as described above.
1 Dissolved in water as per aqueous concentration, 20-25 °C
After being left in a constant temperature bath for a day and night, 2% by weight of Ha (J) and 0.2% by weight of Ca (J2) were added to the aqueous solution and completely dissolved.

This solution was filtered through a 200me+h stainless steel gold foil, and a mechanical stability test was conducted using the method described below.

The mechanical stability test method is 3QQaj)
- Put 150tj of the above polymer aqueous solution in a ruby car (φ = 801■) and insert two plate-shaped blades (diameter = 18m).
layer x h = 11 mm) on both sides of a rod with a diameter of 8IllIl.
2000rpa using a stirring bar mounted on a 0° inclination.
Mechanical shear was applied to the polymer solution by stirring at + high speed for 5 minutes. The viscosity before and after stirring was measured using a BBL viscometer (Brookfield Viscosity), and the viscosity of the polymer solution before high-speed stirring (η) was calculated from the viscosity of the polymer solution after high-speed stirring (η).
The value obtained by subtracting the value is the polymer solution viscosity (η) before high-speed stirring.

) was calculated as the mechanical shear deterioration rate and used as an index of the mechanical stability of the polymer.

Another evaluation of mechanical stability was performed by the screen viscometer method. That is, five 100-mesh stainless steel wire meshes were stacked and attached to the bottom of a pipette-shaped glass tube, and the polymer aqueous solution before and after high-speed stirring was passed through a screen viscometer with markings on the top and bottom of the bulb at 25°C. The flow time (1) during which the liquid level passed between the marked lines was measured. Similarly, the flow time (70) of an aqueous solution containing 2% by weight of NaO and 20.2% by weight of Ca was measured, and the ratio between the two (
t / t o ) is called the screen factor and is used as an index, and the screen factor before high-speed stirring deterioration (SF
o) to screen factor after high-speed stirring deterioration (SF
) was divided by the screen factor (SFO) before high-speed stirring deterioration, and the percentage of the value was determined as the mechanical shear deterioration rate, and was used as an index of the mechanical stability of the polymer.

The results are shown in Tables 1 and 2.

Example 2 AND 80% by weight, NAANa 10% by weight, AAN
After cooling 750 parts of a 30% by weight aqueous solution (pH-7,5) of a monomer consisting of %alO by weight to 10°C, the reaction system was thoroughly degassed with N2 gas. It was oxygen. To this aqueous solution, 0.25 part of 7zobiscyanovaleric 7 seed/de (ACVA) was added to meta/-lua,
Then, 0.002 parts of APS and 0.004 parts of FAS O were added as polymerization initiators, and adiabatic polymerization was carried out at a reaction initiation temperature of 10°C. The reaction was completed in about 7 hours.

The obtained polymer gel was treated in the same manner as in Example 1 to obtain a water-soluble high molecular weight polymer powder. Standard viscosity (SV value)
was approximately 4.3 cps/25°C. A mechanical stability test was then conducted in the same manner as in Example 1.

The results are shown in Tables 1 and 2.

Example 3 AND 75% by weight 1MAANa 20% by weight, sodium 2-acrylamido-2-methylpropanesulfonate (
AMP! JNa) 5% by weight monomer concentration 30
750 parts of wt% aqueous solution (pH-7,5) 20"
After adjusting the position.

The reaction system was placed in a heat-insulated box No. 11, and the inside of the reaction system was sufficiently deoxidized with N2 gas. This aqueous solution contains 0.1 part of A(:VA dissolved in 7.5 parts of methanol) and 2.2'-azobis(
2-amidinopropane) hydrochloride (V-50
) 0.3 parts Naa p2o7a 10H200,0
and 1 part of APS as a polymerization initiator.
O,002 copies.

4 parts of FAS O.000 was added and adiabatic polymerization was carried out at a reaction temperature of 20°C. The reaction was completed in about 5 hours.

The obtained polymer gel was treated in the same manner as in Example 1 to obtain a water-soluble polymer powder. The standard viscosity (SV value) was approximately 4, lcpg/25°C. Below, Example 1
A mechanical stability test was conducted using the same procedure as above. The results are shown in Tables 1 and 2.

Example 4 Aqueous solution with a monomer concentration of 30% consisting of 70% by weight of AMo and 30% by weight of NAANa (pH-8.0) 75
After adjusting the temperature of 0 parts to 20° C., the mixture was placed in a heat-insulated box, and the reaction system was sufficiently deoxidized with N2 gas.

Polymerization was carried out under exactly the same polymerization conditions as in Example 3, except that 0.003 parts of APS O and 0.008 parts of FAS O were added.
The reaction was completed in time.

The obtained polymer gel was treated in the same manner as in Example 1 to obtain a water-soluble polymer powder. Standard viscosity (sv value) is approximately 4.2
cps/25°C. A mechanical stability test was then carried out in the same manner as in Example 1, and the results were as shown in Tables 1 and 2.

Example 5 Aqueous solution (PH-8,0) with a monomer concentration of 30% by weight, consisting of 80% by weight AND and 40% by weight MAANa 7
After adjusting the temperature to 20° C., 50 parts of the reaction mixture were placed in a heat-insulated box, and the inside of the reaction system was sufficiently deoxidized with N2 gas.

Polymerization was carried out under exactly the same polymerization conditions as in Example 3, except that 0.005 parts of APS O and 0.010 parts of FAS were added.
The reaction was completed in about 5 hours.

The obtained polymer gel was treated in the same manner as in Example 1 to obtain a water-soluble polymer powder. Standard viscosity (SV value) is approximately 3.7
cps/25°C. A mechanical stability test was then carried out in the same manner as in Example 1, and the results were as shown in Tables 1 and 2.

Comparative Example 1 An aqueous solution (p) with a monomer concentration of 30% by weight consisting of 80% by weight of AND and 2 parts by weight of AANa (p)I=7.
5) After cooling 750 parts to 5°C, the mixture was placed in a heat-insulated box, and the inside of the reaction system was sufficiently deoxidized with N2 gas. To this aqueous solution, 35 parts of AIBNo dissolved in 7.5 parts of methanol and 0.4 parts of isopropyl alcohol were added, and 0.007 parts of APS O and 0.007 parts of FAS O were added as polymerization initiators.
,005 parts were added, and adiabatic polymerization was carried out at a polymerization initiation temperature of 5°C. The reaction was completed in about 1 hour.

The obtained polymer gel was treated in the same manner as in Example 1 to obtain an aqueous solution of a high molecular weight polymer having a standard viscosity (SV value) of approximately 5.0 cps/25°C. The polymer obtained as described above was evaluated in the same manner as in Example 1 for aqueous solution viscosity and mechanical shear stability under high salt concentration. The results are shown in Tables 1 and 2.

Comparative Example 2 Aqueous solution with a monomer concentration of 30% by weight (pH = 7.5) consisting of 80% by weight of AMo and 20% by weight of AANa
After adjusting 750 parts to 5°C, 19. Place the reaction system in an insulated box with N? Oxygen was sufficiently removed using gas. To this aqueous solution, 35 parts of AIBNo dissolved in 7.5 parts of methanol and 0.75 parts of isopropyl alcohol were added, and 0.007 parts of APS O and FAS were added as polymerization initiators.
After adding 0.005 parts of O, adiabatic polymerization was carried out at a double polymerization initiation temperature of 5° C. The reaction was completed in about 1 hour.

The obtained polymer gel was treated in the same manner as in Example 1 to obtain an aqueous solution of a high molecular weight polymer having a standard viscosity (SV value) of approximately 4.4 cps/25°C. The polymer obtained as described above was evaluated in the same manner as in Example 1 for aqueous solution viscosity and mechanical shear stability under high salt concentration. The results are shown in Tables 1 and 2.

Comparative Example 3 Aqueous solution with a monomer concentration of 30% by weight consisting of 80% by weight of AMo and 20% by weight of AANa (pH = 7.5)
After adjusting the temperature of 750 parts to 5°C, the mixture was placed in a 1M insulation box, and the inside of the reaction system was sufficiently deoxidized with N2 gas. To this aqueous solution, 35 parts of AIBNo dissolved in 7.5 parts of methanol and 0.75 parts of isopropyl alcohol were added, and further 20 parts of AP'SO, 0.02 parts of FAS were added as polymerization initiators.
0.14 parts of O was added and adiabatic polymerization was carried out at a polymerization initiation temperature of 5° C. The reaction was completed in about 40 minutes.

The obtained polymer gel was treated in the same manner as in Example 1 to obtain an aqueous solution of a high molecular weight polymer having a standard viscosity (SV value) of approximately 3.8 cps/25°C. The polymer obtained as described above was evaluated in the same manner as in Example 1 for aqueous solution viscosity and mechanical shear stability under high salt concentration. The results are shown in Tables 1 and 2.

〔Effect of the invention〕

5-4 stabilized against mechanical shear according to the invention
A tertiary petroleum recovery agent consisting of an acrylamide polymer containing 0% by weight of methacrylate can be obtained from oil fields as well as from distilled water or city water.
It is recognized that it is less susceptible to mechanical shearing than conventional 7-ionic acrylamide polymers, even in highly saline waters such as ter" and "produced water." The reason for the low mechanical shear deterioration of acrylamide-based copolymers containing methacrylate is not clear, but C
When a methacrylate with an H3 group is introduced into an acrylamide polymer, the polymer collapses due to a radical reaction involving oxidizing substances or dissolved oxygen contained in the polymer, and the polymer itself This is thought to be due to the increased resistance to mechanical shear deterioration.

Patent applicant: Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Scope of Claims] 1. (a) acrylamide or a unit containing a predominant amount of acrylamide, (b) methacrylate in an amount of 5 to 40% by weight of monomer (a), and (c) monomer Aqueous radical copolymerization of 0 to 35% of the weight of body (a) of a water-soluble anionic vinyl monomer is carried out, and if necessary, the resulting copolymer gel is partially hydrolyzed to determine the degree of anionization obtained. is 5
A tertiary petroleum recovery agent consisting of a copolymer powder obtained by drying and powdering ~35 mol% copolymer gel.