JP2663145B2 - Oil layer preparation method using water-in-oil swellable emulsion - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for effectively recovering petroleum from a stratum, and more particularly, to an oil reservoir using a water-in-oil type water-swellable polymer emulsion. The present invention relates to a method for adjusting the penetration rate of a material.

[Prior Art] When a crude oil is produced from an underground oil reservoir, a large amount of water is produced together with the crude oil from a production well. The crude oil produced must separate the associated water and the economic cost of this separation is problematic. More importantly, the entrained water reduces crude oil production, as the total well production is limited by the equipment. Decreasing the amount of accompanying water increases the rate of crude oil production and reduces the cost of separation, which is extremely effective in producing crude oil.

The production of water from production wells is mainly based on the outflow of groundwater from the formation outside the reservoir (water coning) and the water or aqueous solution injected by water flooding or tertiary flooding in which another aqueous solution is injected. Through the high-permeability layer (a layer through which water easily passes) or the fracture existing in the oil layer. In other words, most oil layers are composed of layers with different water permeability (permeability). In the water flooding method or the third flooding method using other aqueous solutions, water or an aqueous solution is injected into these layers and each layer is pressed. It is intended to push out the crude oil present in the oil, but the crude oil is pushed out in preference to the high permeability portion, and the injection water in this portion flows out of the production well earlier, causing A large amount of water will be entrained. Further, the portion where the crude oil is extruded by the injection water becomes more easily permeable, and reduces the production rate of the crude oil from the house permeability portion where a large amount of the crude oil still remains.

One method of reducing the production of water is to treat the oil layer with a crosslinked product of an acrylamide copolymer and another water-soluble polymer. U.S. Pat.Nos. 3,749,172, 3,762,476, 3,785,437 as representative patents,
No. 3,909,423, No. 3,949,811, No. 3,952,806, No. 3,9
No. 78,928, No. 4,018,286, No. 4,076,628, No. 4,110,22
There is No. 6.

These techniques are characterized by using a water-soluble polymer and a crosslinking agent. That is, a crosslinking agent is added to the aqueous solution of the water-soluble polymer during the injection into the formation, or after the injection, the polymer is cross-linked in the underground formation, and the generated crosslinked product is used to fill the waterways and fractures in the water-easy layer. It is a technology that makes it difficult to pass water or makes it completely impermeable. By these techniques, the injection water flows to a low permeability layer where water has been difficult to pass so far, thereby increasing the production rate of crude oil.

These known techniques can be roughly classified into a chromium gel method and an aluminum citrate method.

The chromium gel method is mainly used to pack the fractures in the oil layer, and is a method in which a water-soluble polymer and a cross-linking agent are mixed and injected on the ground, or both are injected at the same time. As a molecule, a copolymer using acrylamide and acrylic acid, and as a crosslinking agent, one using sodium dichromate-sodium sulfite may be used.

The aluminum citrate method is mainly used to lower the permeability of an oil layer, and is a method of alternately injecting a water-soluble polymer and a crosslinking agent, that is, aluminum citrate, and crosslinking underground.

[Problems to be Solved by the Invention] The problem of these technologies lies first in the crosslinking method.
That is, since both methods employ a method of crosslinking underground, crosslinking does not occur depending on the conditions of the oil layer, so that the permeability of the oil layer cannot be reduced or the fracture cannot be packed. Furthermore, in the chromium gel method, if crosslinking occurs early, gelation occurs near the injection port of the oil layer, which may render the injection well unusable.

The second problem is a problem of the processing effect. When the oil layer is treated, the injected water-soluble polymer or the like enters not only the high-permeability layer but also the low-permeability layer, so that the permeability of this portion is reduced, and the treatment effect is reduced.

The above two points are fundamental problems when implementing the known technique, and an essential improvement method has been particularly demanded.

[Means for Solving the Problems] The present inventors have continued various studies on a method for improving an oil layer without the above-mentioned disadvantages, and as a result, have succeeded in finding an excellent method as described below and completed the present invention. I came to.

That is, in the conventional method, a method of injecting a water-soluble polymer and a cross-linking agent into the formation and performing cross-linking during or after the injection is used, but this requires direct underground treatment of the cross-linked polymer. This is because it is actually difficult to inject into the stratum.

The use of a pre-crosslinked high molecular weight polymer requires a remarkably high injection pressure, and furthermore, there is a high possibility that the injection wells will be packed and become unusable. Therefore, it is not practical to inject the crosslinked polymer directly into the formation, and it is difficult to actually try it.

However, the present inventors have surprisingly found that a water-in-oil type water-swellable polymer emulsion obtained by polymerizing a water-soluble vinyl monomer as a water-in-oil type emulsion in the presence of a crosslinking agent is surprising. It has been found that, like a cross-linked polymer, it can be easily injected into the formation as well as an uncross-linked water-soluble polymer.

In other words, this water-in-oil type water-swellable polymer can be uniformly dispersed in water because it is composed of fine emulsion particles, and is essentially insoluble in water while having an appearance and properties as a water-soluble polymer. Present as a dispersion with no difference. Therefore, it has been found that this dispersion can be pressed into the formation just as easily as the water-soluble polymer,
A completely new approach has been discovered in which a water-swellable polymer emulsion, which is a crosslinked polymer, which was completely unexpected from the prior art and known knowledge, is directly injected into the formation.

The present invention does not have the above-mentioned disadvantages at the time of crosslinking by using a water-soluble polymer and a crosslinking agent, and is characterized by using an already crosslinked water-in-oil type water-swellable polymer emulsion. The problems of cross-linking, which are drawbacks, and the effect of improving the permeability are greatly improved.
That is, the method of the present invention is a technique characterized by using a water-in-oil type water-swellable polymer emulsion which is formed into a crosslinked product by adding a crosslinking agent during polymerization.

That is, the present invention is characterized in that (1) directly using a water-in-oil swellable polymer emulsion or using a water-swellable polymer obtained by removing oil and water from the emulsion. (2) At least one of an acrylamide polymer, a copolymer of acrylamide and another monomer, a polymer of acrylic acid and a salt thereof, and a polymer of a cationic group-containing monomer as the water-swellable polymer (1) The method for preparing an oil layer according to (1), wherein a crosslinked product selected from the species is used. (3) When the water-swellable polymer emulsion is injected into the oil layer, the injection water containing the water-swellable polymer is used. (1) and (1) wherein the size of the water-swellable polymer particles is adjusted by changing the pH and / or salt concentration, and the water-swellable polymer is injected into the formation to be treated. Reservoir adjustment method), (4) is injected and held in the underground water-swellable polymers, pH
And / or changing the permeability by treating with an injection water whose salt concentration has been adjusted and expanding or reducing the same to change the permeability.

 Hereinafter, the present invention will be described in detail.

The water-in-oil type water-swellable polymer emulsion comprises, as a vinyl monomer, one or more water-soluble vinyl monomers, or one or more water-soluble vinyl monomers, and a water-soluble vinyl monomer. After emulsifying an aqueous dispersion containing at least one kind of vinyl monomer copolymerizable with a water-soluble vinyl monomer as a cross-linking agent into an organic dispersion medium containing a surfactant, , Obtained by radical polymerization.

As the water-soluble vinyl monomer, any water-soluble vinyl monomer or a salt thereof can be used. Specific examples include (meth) acrylamide, N, N-dimethylacrylamide, (meth) acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, vinylsulfonic acid, styrenesulfonic acid, itaconic acid, arylsulfonic acid, dimethyl Aminoethyl methacrylate methyl chloride quaternary salt, diethyldiallylammonium chloride, dimethyldiallylammonium chloride and the like can be mentioned. Preferred water-soluble vinyl monomers include one or more of acrylamide, acrylic acid (salt), and dimethylaminoethyl methacrylate methyl chloride quaternary salt.

Acrylic acid and the various acids mentioned above can also be used for the polymerization in salt form. Specific examples of salts include sodium, potassium,
Ammonium salts and the like can be mentioned.

As the cross-linking agent, one that can be copolymerized with a water-soluble vinyl monomer is used. Specific examples thereof include N, N-methylenebisacrylamide, diallyl phthalate, divinylbenzene, and (poly) ethylene glycol di (meth) acrylate. And the like. Preferred crosslinking agents include N, N-
Methylene bisacrylamide is exemplified. The amount of addition is 0.0005 to 5% by weight, preferably 0.001 to 1% by weight, based on the water-soluble vinyl monomer.

The oil component constituting the water-in-oil swellable emulsion is an organic dispersion medium, and examples thereof include saturated linear hydrocarbons, branched saturated hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons. These organic dispersion media usually have a boiling point of 30 to 350.
Those in the range of ° C are used.

In addition, the water-in-oil swellable emulsion usually contains
Surfactants are included. It emulsifies to form a water-in-oil emulsion, and Griffin's HLB for the purpose of keeping it stable
(Hereinafter simply referred to as HLB) 3 to 7, preferably 4 to 7
The surfactant of No. 6 is used. Specific examples include sorbitan monoesters.

According to the method of the present invention, the oil layer is adjusted by adding a water-in-oil water-swellable polymer emulsion to water used in a waterflooding method,
Injection is performed from an injection well or a production well, and a water-swellable polymer is used to pack a high permeability layer in an oil layer and a water-permeable layer such as a fracture.

Most of the water-swellable polymer injected into the oil layer is preferentially injected into a water-permeable layer such as a high-permeability layer and a fracture, and is retained in the layer by adsorption, trap, and the like. The channel in that layer is narrowed, making it harder for the water and aqueous solution subsequently injected to flow. On the other hand, the water-swellable polymer hardly penetrates into the low-permeability layer that is difficult to pass through water, and as a result, the injection water and the aqueous solution flow into the low-permeability layer where water has hardly flowed so far, and the crude oil in that part is removed. The speed of collection will be increased.

The water-in-oil type water-swellable emulsion to be injected into the oil layer is used by directly adding to the injection water or dissolving the water-swellable polymer obtained by removing oil and water from the emulsion into the injection water. . The concentration used is usually 0.001 to 1%, preferably 0.01 to 0.1%, as a water-swellable polymer.

Use at concentrations above 1% will damage the oil layer due to too high injection pressure. Also, use at a concentration of less than 0.001% is uneconomical due to the time required for processing.

The water swelling ratio of water-swellable polymer in water varies depending on the type of salt dissolved in water, its concentration, pH and the like. At high salt concentration, low pH and high pH, the water swelling ratio is small, the size of the water swellable polymer is small, and low salt concentration and pH =
In the vicinity of 7, the size of the water-swellable polymer increases. Utilizing this property, when injecting the water-swellable polymer into the oil layer, the salt concentration and / or the pH of the aqueous solution are adjusted according to the permeability of the formation, which has been sampled and measured in advance, to thereby obtain the water-swellable polymer. By adjusting the size of the coalescence, the water-swellable polymer can be more effectively injected into the high-permeability layer.

[Effect] The water-swellable polymer injected into the high-permeability layer and the fracture of the oil layer is retained in the oil layer, and thereafter, the permeability of the injected water to the injected water is lowered, thereby making it difficult for the water to flow through the injected water. Is made uniform. Also, the injection water pH
And / or changing the salt concentration can change the size of the retained water-swellable polymer and change the permeability,
The permeability of the entire oil layer becomes more uniform.

As a specific example, at a salt concentration or pH at which the particle size of the water-swellable polymer is relatively small, after sufficiently retaining the water-swellable polymer in the high-permeability layer, the salt concentration of the injection water is gradually reduced. Alternatively, by bringing the pH value closer to 7, it is possible to increase the particle size of the water-swellable polymer retained in the layer and more effectively reduce the permeability.

The oil layer treated by this method has a higher treatment rate of the high permeability layer than the oil layer treated by the aluminum citrate method, resulting in a more uniform permeability layer.

EXAMPLES Hereinafter, the present invention will be further described with reference to Examples.
The present invention is not limited by the following examples.

Example 1 Aqueous 50% aqueous solutions of acrylamide (AMD), sodium acrylate (AAC-Na), and dimethylaminoethyl methacrylate methyl chloride quaternary salt (DMQ) alone as vinyl monomers, and a mixture of AMD and AAC-Na Using 683 g of a 50% aqueous solution of the molar mixture, 0.15 g of methylene bisacrylamide as a cross-linking agent and 18 g of sorbitan monooleate as a surfactant, a ratio of paraffin 64% by weight, naphthene 35% by weight, and aromatic hydrocarbon 1% by weight. A water-in-oil type water-swellable polymer emulsion emulsified and polymerized in 240 g of an organic dispersion medium consisting of
Of water-swellable polymer aqueous solutions (4 types) were prepared. These solutions were adjusted to pH = 4 and a 1 inch diameter, 3 inch long Be
The resistance factor was investigated by injecting into the core of rea Sand Stone at a flow rate of 2 m / day. Thereafter, a 0.1% NaCl solution was injected to measure the permeability, and the permeability reduction coefficient was examined. Table 1 shows the results.

Example 2 A water-in-oil type water-swellable polymer emulsion of sodium acrylate obtained in Example 1 was dissolved in a 0.1% NaCl solution to prepare a solution having a concentration of 500 ppm of the water-swellable polymer. The pH of this solution was adjusted to 3, 5 and 7 and injected into the core of Berea Sand Stone to examine its resistance factor. Table 2 shows the results.

Example 3 The water-in-oil type water-swellable polymer emulsion of DMQ obtained in Example 1 was dissolved in a 0.1% NaCl solution to prepare a solution having a concentration of 500 ppm of the water-swellable polymer. Transfer this solution to 700 md Ber
ea Sand Stone, then add different concentrations of NaCl
Table 3 shows the results of examining the permeability reduction coefficient by injecting the solution.

Example 4 The water-swellable polymer solution prepared in Example 3 was connected in parallel to two BereaSand Stones (cores) having different permeability.
Ratio to both cores when injected into the core, and then 0.1% NaC
Tables 4 and 5 show the results of comparison of the injection ratio when water was injected with the aluminum citrate method and the chromium method.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hikotada Tsuboi 1900 Togo, Togo, Mobara-shi, Chiba Mitsui Saia Namid Co., Ltd.

Claims (5)

(57) [Claims] An oil layer preparation method comprising directly using a water-in-oil swellable polymer emulsion or using a water-swellable polymer obtained by removing oil and water from the emulsion. 2. A water-in-oil type swellable polymer emulsion comprising one or more water-soluble vinyl monomers, or one or more water-soluble vinyl monomers, and a water-soluble vinyl monomer. An aqueous solution containing one or more polymerizable vinyl monomers and a crosslinking agent copolymerizable with a water-soluble vinyl monomer is injected into an organic dispersion medium containing a surfactant, emulsified, and then radically polymerized. The oil layer adjusting method according to claim 1, wherein the oil layer is obtained. 3. A water swellable polymer comprising at least one of an acrylamide polymer, a copolymer of acrylamide and another monomer, a polymer of acrylic acid and a salt thereof, and a polymer of a cationic group-containing monomer. The method for adjusting an oil layer according to claim 1, wherein a selected crosslinked product is used. 4. The size of the water-swellable polymer particles is adjusted by changing the pH and / or salt concentration of the water containing the water-swellable polymer when the water-swellable polymer emulsion is injected into the oil layer. Claim 1, wherein the water swellable polymer is injected into the formation to be treated.
Item 4. The oil layer adjusting method according to Item 2 or 3. 5. The method according to claim 1, wherein the water-swellable polymer injected and held underground is expanded or reduced by treating it with injection water whose pH and / or salt concentration has been adjusted to change the permeability. Item 4. The oil layer adjusting method according to any one of Items 1, 2 and 3.