A selective water shutoff agent and its preparation method

Abstract

The present invention discloses a selective water shutoff agent and a preparation method thereof. The selective water shutoff agent, by weight, comprises 100 - 150 parts of cement, 10 - 15 parts of microsilica, 10 - 25 parts of density regulator, 1 - 6 parts of modifier, 0.5 - 4 parts of emulsifier, 1 - 5 parts of suspending agent, 1 - 4 parts of pore-forming agent, 1 - 2 parts of polyester fiber, and 150 - 200 parts of water. The preparation method comprises the following steps: S1: Weigh cement, microsilica, density regulator, suspending agent, and polyester fiber, mix them evenly to obtain a dry powder mixture; S2: Weigh water, add the dry powder mixture under stirring conditions, and stir evenly to obtain a first mixed solution; S3: Add the modifier and emulsifier to the first mixed solution under stirring conditions, and stir evenly to obtain a second mixed solution; S4: Add the pore-forming agent to the second mixed solution under stirring conditions, and stir evenly to obtain the selective water shutoff agent. The surface and interior of the selective water shutoff agent of the present invention are both hydrophobic and lipophilic, which can improve the relative permeability of oil, increase the flow resistance of water, and achieve the effect of water shutoff without oil blockage.

Description

Technical Field

[0001] The present invention relates to the technical field of reservoir development, and particularly relates to a selective water plugging agent and a preparation method thereof. Background Art

[0002] During the process of reservoir development, with the increasing prevalence of oilfield water injection development and over-exploitation, due to natural fractures in the rock reservoir or artificial induced fractures generated after development such as fracturing acidification, the formation morphology presents the characteristics of large size, large pore channels, and fissures. Oil well water production is an inevitable problem. The water content in the well increases significantly, and the two-phase flow of water and oil intensifies in the seepage channels and formation pores, resulting in an increase in reservoir energy consumption, a decrease in the production of a single well during exploitation, and a reduction in the effectiveness of measures and operations. Oil well water production will lead to a chain of effects: severe water production causes additional consumption of formation energy and a decrease in the ultimate recovery rate of the oil layer; the pump rate of pumping wells will decrease; the corrosion and scaling of equipment such as pipelines and equipment will intensify; the load of the oilfield dehydration station will increase; if the produced water is not reinjected, sewage discharge will also cause environmental pollution.

[0003] In the face of these problems, the general measure taken is to inject a water plugging agent to block old fractures and perforation holes or adjust the formation profile permeability. However, most of the existing water plugging agents are chemically synthesized substances, and there are certain problems with their environmental friendliness and economy. Moreover, the production and production efficiency of oil wells are both low, and their practical value and market prospects are insufficient.

[0004] In addition, cementing water plugging in oil wells is a technical measure often used in the later stage of oilfield exploitation. However, after the traditional water plugging cement is squeezed into the formation and solidifies, it will block the seepage pore throats of the formation, resulting in a decrease in the permeability of the oil and gas layer, seriously affecting the production of oil wells and their normal production. Summary of the Invention

[0005] In view of the above problems, the present invention aims to provide a selective water plugging agent and a preparation method thereof.

[0006] The technical solution of the present invention is as follows:

[0007] On the one hand, a selective water plugging agent is provided, which includes 100 - 150 parts by weight of cement, 10 - 15 parts of microsilica, 10 - 25 parts of density regulator, 1 - 6 parts of modifier, 0.5 - 4 parts of emulsifier, 1 - 5 parts of suspending agent, 1 - 4 parts of pore-forming agent, 1 - 2 parts of polyester fiber, and 150 - 200 parts of water.

[0008] Preferably, the density regulator is perlite.

[0009] Preferably, the particle size of the perlite is 80 - 100 mesh.

[0010] Preferably, the modifier is n-octyltriethoxysilane.

[0011] Preferably, the emulsifier is an oil-in-water emulsifier.

[0012] Preferably, the oil-in-water emulsifier is a surfactant with an HLB value in the range of 8 - 18.

[0013] Preferably, the suspending agent is xanthan gum.

[0014] On the other hand, a preparation method of the selective water shutoff agent according to any one of the above is also provided, including the following steps:

[0015] S1: Weigh 100 - 150 parts of cement, 10 - 15 parts of microsilica, 10 - 25 parts of density regulator, 1 - 5 parts of suspending agent, and 1 - 2 parts of polyester fiber, and mix them evenly to obtain a dry powder mixture;

[0016] S2: Weigh 150 - 200 parts of water, and add the dry powder mixture under stirring conditions, and stir evenly to obtain a first mixed solution;

[0017] S3: Add 1 - 6 parts of modifier and 0.5 - 4 parts of emulsifier to the first mixed solution under stirring conditions, and stir evenly to obtain a second mixed solution;

[0018] S4: Add 1 - 4 parts of pore-forming agent to the second mixed solution under stirring conditions, and stir evenly to obtain the selective water shutoff agent.

[0019] Preferably, in steps S2 - S4, the stirring rate used is 800 - 1000 r / min.

[0020] Preferably, in step S2, the stirring time is 30 - 40 min; in step S3, the stirring time is greater than 20 min; in step S4, the stirring time is 10 - 20 min.

[0021] The beneficial effects of the present invention are as follows:

[0022] After the selective water shutoff agent of the present invention is cured and formed, it has a multi-porous structure inside, and both its surface and inside are hydrophobic and oleophilic, which can improve the relative permeability of oil, increase the flow resistance of water, and achieve the effect of plugging water without plugging oil; at the same time, the selective water shutoff agent of the present invention has a low density, large fluidity, and small injection pressure, which can reduce the damage to the formation, and at the same time has a certain compressive strength, playing a role in sand prevention for sandstone formations. Detailed Embodiments

[0023] The present invention will be further described below in conjunction with embodiments. It should be noted that, without conflict, the embodiments in the present application and the technical features in the embodiments may be combined with each other. It should be pointed out that unless otherwise specified, all technical and scientific terms used in the present application have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs. As used in the disclosure of the present invention, words such as "including" or "comprising" and the like are intended to mean that the elements or items appearing before the word cover the elements or items listed after the word and their equivalents, without excluding other elements or items.

[0024] On the one hand, the present invention provides a selective water shutoff agent, which, by weight, comprises 100-150 parts of cement, 10-15 parts of microsilica, 10-25 parts of density regulator, 1-6 parts of modifier, 0.5-4 parts of emulsifier, 1-5 parts of suspending agent, 1-4 parts of pore-forming agent, 1-2 parts of polyester fiber, and 150-200 parts of water.

[0025] In the present invention, the microsilica can enhance the suspension stability of the selective water shutoff agent of the present invention; the density regulator can reduce the density of the selective water shutoff agent of the present invention, reduce the pressure on the formation, and avoid re-fracturing of the fissured and porous formation; the pore-forming agent can increase the porosity of the selective water shutoff agent of the present invention to ensure the oil throughput of the water shutoff agent material; the polyester fiber can utilize its three-dimensional disordered three-dimensional distribution in the system to connect pores, increase the permeability, and at the same time increase the compressive strength of the system; adding 150-200 parts of water can avoid the system stratifying and being unstable when too much water is added; when too little water is added, the fluidity of the system is poor and grouting is difficult.

[0026] In a specific embodiment, the density regulator is perlite. Optionally, the particle size of the perlite is 80-100 mesh. In this embodiment, using perlite with the above particle size can avoid the cement gel not being able to wrap the perlite with too large a particle size, which is easy to float up and cause the system to be unstable and stratified; it can also avoid the perlite with too small a particle size filling the pores of the system and reducing the porosity.

[0027] In a specific embodiment, the modifier is n-octyltriethoxysilane.

[0028] In a specific embodiment, the emulsifier is an oil-in-water emulsifier. Optionally, the oil-in-water emulsifier is a surfactant with an HLB value in the range of 8-18.

[0029] In a specific embodiment, the suspending agent is xanthan gum. In this embodiment, xanthan gum sol molecules can form a super-bound helical copolymer ribbon, constituting a fragile gel-like network structure that can support the morphology of solid particles, droplets, and bubbles, showing strong emulsifying stability and high suspension ability. In the system, it can suspend the modifier and the density regulator, making the system stable without stratification. At the same time, it has an adhesion effect on the bubbles generated by the pore-forming agent to prevent the bubbles from overflowing, playing a role in stabilizing the bubbles.

[0030] On the other hand, the present invention also provides a preparation method of the selective water plugging agent described in any one of the above, including the following steps:

[0031] S1: Weigh 100 - 150 parts of cement, 10 - 15 parts of microsilica, 10 - 25 parts of density regulator, 1 - 5 parts of suspending agent, and 1 - 2 parts of polyester fiber, and mix them evenly to obtain a dry powder mixture;

[0032] S2: Weigh 150 - 200 parts of water, and add the dry powder mixture under stirring conditions, and stir evenly to obtain a first mixed solution;

[0033] S3: Add 1 - 6 parts of modifier and 0.5 - 4 parts of emulsifier to the first mixed solution under stirring conditions, and stir evenly to obtain a second mixed solution;

[0034] S4: Add 1 - 4 parts of pore-forming agent to the second mixed solution under stirring conditions, and stir evenly to obtain the selective water plugging agent.

[0035] In the present invention, in step S2, hydroxyl groups are generated during the hydration of cement, and then the modifier is added in step S3. In this way, the hydroxyl groups generated by the hydration of cement can react with the long-chain alkyl groups of the modifier, and the modifier forms a chemical adsorption with the cement rather than a physical adsorption, thereby extending the validity period of the hydrophobic property of the water plugging agent; finally, the pore-forming agent is added in step S4, so that more fine bubbles can be generated; if it is added before step S2 (that is, adding the pore-forming agent first and then the dry powder), the bubbles are likely to overflow, and the bubbles remaining in the system are not uniform and less; if it is added before step S3 (that is, adding the pore-forming agent first and then the modifier), the bubbles generated by the pore-forming agent will hinder the contact and reaction between the modifier and the cement, making the modifier unable to be well dispersed in the overall system.

[0036] In a specific embodiment, in steps S2 - S4, the stirring rate used is 800 - 1000 r / min. Optionally, in step S2, the stirring time is 30 - 40 min; in step S3, the stirring time is greater than 20 min; in step S4, the stirring time is 10 - 20 min.

[0037] Example 1

[0038] A selective water shutoff agent is prepared through the following steps:

[0039] (1) Weigh 100 parts of cement (purchased from Jiahua Special Cement Co., Ltd.), 10 parts of microsilica (average particle size 0.1 - 0.3 μm), 15 parts of density regulator (perlite with a particle size of 80 - 100 mesh), 3 parts of suspending agent (xanthan gum), and 1 part of polyester fiber (equivalent diameter 10 - 25 μm, length 4 - 6 mm), and mix them evenly to obtain a dry powder mixture;

[0040] (2) Weigh 150 parts of water, add the dry powder mixture under stirring conditions with a stirring rate of 1000 r / min, and stir for 30 min to obtain a first mixed solution;

[0041] (3) Add 2 parts of modifier (n - octyltriethoxysilane) and 2 parts of emulsifier (OP - 10) to the first mixed solution under the same stirring conditions, and stir for 20 min to obtain a second mixed solution;

[0042] (4) Add 1 part of pore - forming agent (concentrated high - efficiency cement foaming agent, purchased from Henan Sitong Chemical Construction Concrete Admixture Co., Ltd.) to the second mixed solution under the same stirring conditions, and stir for 10 min to obtain the selective water shutoff agent.

[0043] Example 2

[0044] A selective water shutoff agent is prepared through the following steps:

[0045] (1) Weigh 100 parts of cement (purchased from Jiahua Special Cement Co., Ltd.), 15 parts of microsilica (average particle size 0.1 - 0.3 μm), 12 parts of density regulator (perlite with a particle size of 80 - 100 mesh), 2 parts of suspending agent (xanthan gum), and 0.5 part of polyester fiber (equivalent diameter 10 - 25 μm, length 4 - 6 mm), and mix them evenly to obtain a dry powder mixture;

[0046] (2) Weigh 150 parts of water, add the dry powder mixture under stirring conditions with a stirring rate of 1000 r / min, and stir for 30 min to obtain a first mixed solution;

[0047] (3) Add 4 parts of modifier (n - octyltriethoxysilane) and 2 parts of emulsifier (OP - 10) to the first mixed solution under the same stirring conditions, and stir for 20 min to obtain a second mixed solution;

[0048] (4) Add 1.5 parts of pore - forming agent (concentrated high - efficiency cement foaming agent, purchased from Henan Sitong Chemical Construction Concrete Admixture Co., Ltd.) to the second mixed solution under the same stirring conditions, and stir for 10 min to obtain the selective water shutoff agent.

[0049] Example 3

[0050] A selective water plugging agent is prepared through the following steps:

[0051] (1) Weigh 100 parts of cement (purchased from Jiahua Special Cement Co., Ltd.), 10 parts of microsilica (average particle size 0.1 - 0.3 μm), 15 parts of density regulator (perlite with a particle size of 80 - 100 mesh), 3 parts of suspending agent (xanthan gum), and 1 part of polyester fiber (equivalent diameter 10 - 25 μm, length 4 - 6 mm), mix them evenly to obtain a dry powder mixture;

[0052] (2) Weigh 150 parts of water, add the dry powder mixture under the stirring condition with a stirring rate of 1000 r / min, and stir for 30 min to obtain a first mixed solution;

[0053] (3) Add 4 parts of modifier (n - octyltriethoxysilane) and 2 parts of emulsifier (Tween 80) to the first mixed solution under the same stirring condition, and stir for 20 min to obtain a second mixed solution;

[0054] (4) Add 1 part of pore - forming agent (concentrated high - efficiency cement foaming agent, purchased from Henan Sitong Chemical Construction Concrete Admixture Co., Ltd.) to the second mixed solution under the same stirring condition, and stir for 10 min to obtain the selective water plugging agent.

[0055] Example 4

[0056] A selective water plugging agent is prepared through the following steps:

[0057] (1) Weigh 100 parts of cement (purchased from Jiahua Special Cement Co., Ltd.), 10 parts of microsilica (average particle size 0.1 - 0.3 μm), 15 parts of density regulator (perlite with a particle size of 80 - 100 mesh), 3 parts of suspending agent (xanthan gum), and 1 part of polyester fiber (equivalent diameter 10 - 25 μm, length 4 - 6 mm), mix them evenly to obtain a dry powder mixture;

[0058] (2) Weigh 150 parts of water, add the dry powder mixture under the stirring condition with a stirring rate of 1000 r / min, and stir for 30 min to obtain a first mixed solution;

[0059] (3) Add 2 parts of modifier (n - octyltriethoxysilane) and 2 parts of emulsifier (OP - 10) to the first mixed solution under the same stirring condition, and stir for 20 min to obtain a second mixed solution;

[0060] Add 1 part of pore - forming agent (NaHCO3) to the second mixed solution under the same stirring condition, and stir for 10 min to obtain the selective water plugging agent.

[0061] Example 5

[0062] A selective water shutoff agent is prepared through the following steps:

[0063] (1) Weigh 100 parts of cement (purchased from Jiahua Special Cement Co., Ltd.), 10 parts of microsilica (average particle size 0.1 - 0.3 μm), 15 parts of density regulator (perlite with a particle size of 80 - 100 mesh), 3 parts of suspending agent (xanthan gum), and 1 part of polyester fiber (equivalent diameter 10 - 25 μm, length 4 - 6 mm), and mix them evenly to obtain a dry powder mixture;

[0064] (2) Weigh 150 parts of water, and add the dry powder mixture under stirring conditions with a stirring rate of 1000 r / min, and stir for 30 min to obtain a first mixed solution;

[0065] (3) Under the same stirring conditions, add 2 parts of modifier (n - octyltriethoxysilane) and 2 parts of emulsifier (OP - 10) to the first mixed solution, and stir for 20 min to obtain a second mixed solution;

[0066] (4) Under the same stirring conditions, add 1 part of pore - forming agent (NH4HCO3) to the second mixed solution, and stir for 10 min to obtain the selective water shutoff agent.

[0067] Comparative Example 1

[0068] Different from Example 1, in this comparative example, the modifier in step (3) is octamethylcyclotetrasiloxane.

[0069] Comparative Example 2

[0070] Different from Example 1, in this comparative example, the modifier in step (3) is decamethylcyclopentasiloxane.

[0071] Comparative Example 3

[0072] Different from Example 1, in this comparative example, the modifier in step (3) is methyltriethoxysilane.

[0073] Perform performance tests on the water shutoff agents of each example and each comparative example. Some performance characteristics of the selective water shutoff agents of Examples 1 - 3 are shown in Table 1:

[0074] Table 1 Performance test results of the selective water shutoff agents of Examples 1 - 3 of the present invention

[0075] Example Flowability mm Initial setting time h Gas permeability mD Oil permeability mD Water permeability mD Compressive strength Mpa 1 185 6 314 82 15 6.5 2 190 5.5 323 83 18 7 3 185 5.5 334 84 14 6.8

[0076] As can be seen from Table 1, the fluidity of the selective water shutoff agents in Examples 1-3 is greater than 180 mm, the initial setting time is greater than 5 h, the gas permeability is greater than 300 mD, the oil permeability is greater than 80 mD, the water permeability is less than 20 mD, and the compressive strength is greater than 6 Mpa. The selective water shutoff agents obtained in each example have a high porosity, a setting time meeting the construction requirements, a high oil and gas permeability, and a low water permeability. At the same time, they have a certain compressive strength to ensure that the structure of the water shutoff agent can maintain a porous structure in the formation for a long time without being damaged.

[0077] The porosities of the selective water shutoff agents in Example 1 and Examples 4-5 are shown in Table 2:

[0078] Table 2 Test results of the porosity of the selective water shutoff agent

[0079] Different pore formers Cement foaming agent <![CDATA[NaHCO3]]> <![CDATA[NH4HCO3]]> Porosity (%) 68.5％ 63.1％ 61.8％

[0080] As can be seen from Table 2, after adding the pore-forming agent, the porosity of the selective water shutoff agent of the present invention can reach more than 60%, which can ensure the oil throughput of the selective water shutoff agent.

[0081] The test results of the maximum contact angle between the water shutoff agents in Example 1 and Comparative Examples 1-3 and the aqueous phase are shown in Table 3:

[0082] Table 3 Test results of the maximum contact angle between the water shutoff agent and the aqueous phase

[0083] Different modifiers n-Octyltriethoxysilane Octamethylcyclotetrasiloxane Decamethylcyclopentasiloxane Methyltriethoxysilane Maximum contact angle 151° 137° 140° 121°

[0084] As can be seen from Table 3, by using the modifier of the present invention, the maximum contact angle between the present invention and the aqueous phase can be greater than 150°, achieving a superhydrophobic effect, while other modifiers cannot make the water shutoff agent reach the superhydrophobic effect.

[0085] In summary, the selective water shutoff agent of the present invention can be hydrophobic and oleophilic, improve the relative permeability of oil, increase the flow resistance of water, and achieve the effect of water shutoff without oil blockage. Compared with the prior art, the present invention has made significant progress.

[0086] The above are only representative embodiments of the present invention, and do not impose any form of limitation on the present invention. Any person skilled in the art, without departing from the scope of the technical solution of the present invention, makes some modifications or decorations using the disclosed technical content, and such embodiments are equivalent embodiments of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change, and decoration made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A selective water plugging agent, characterized in that: The invention comprises, by weight, 100-150 parts of cement, 10-15 parts of microsilicon, 10-25 parts of density regulator, 1-6 parts of modifier, 0.5-4 parts of emulsifier, 1-5 parts of suspending agent, 1-4 parts of pore-forming agent, 1-2 parts of polyester fiber, and 150-200 parts of water, wherein the modifier is n-octyltriethoxysilane; The selective water plugging agent is prepared by the following steps: S1: Weigh 100-150 parts of cement, 10-15 parts of microsilica, 10-25 parts of density regulator, 1-5 parts of suspending agent, and 1-2 parts of polyester fiber, mix well, and obtain a dry powder mixture; S2: Weigh 150-200 parts of water, add the dry powder mixture under stirring, and stir evenly to obtain a mixed solution 1; S3: adding 1-6 parts of a modifier and 0.5-4 parts of an emulsifier to the mixed solution 1 under stirring conditions, stirring evenly, to obtain a mixed solution 2; S4: adding 1-4 parts of pore-forming agent to the mixed solution 2 under stirring conditions, stirring evenly, to obtain the selective water plugging agent.

2. The selective water plugging agent according to claim 1, characterized in that: The density regulator is perlite.

3. The selective water plugging agent according to claim 2, characterized in that: The particle size of the perlite is 80-100 meshes.

4. The selective water plugging agent according to claim 1, characterized in that: The emulsifier is an oil-in-water emulsifier.

5. The selective water plugging agent according to claim 4, characterized in that: The oil-in-water emulsifier is a surfactant with an HLB value in the range of 8-18.

6. The selective water plugging agent according to claim 1, characterized in that: The suspending agent is xanthan gum.

7. The method for preparing the selective water plugging agent according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1: Weigh 100-150 parts of cement, 10-15 parts of microsilica, 10-25 parts of density regulator, 1-5 parts of suspending agent, and 1-2 parts of polyester fiber, mix well, and obtain a dry powder mixture; S2: Weigh 150-200 parts of water, add the dry powder mixture under stirring, and stir evenly to obtain a mixed solution 1; S3: adding 1-6 parts of a modifier and 0.5-4 parts of an emulsifier to the mixed solution 1 under stirring conditions, stirring evenly, to obtain a mixed solution 2; S4: adding 1-4 parts of pore-forming agent to the mixed solution 2 under stirring conditions, stirring evenly, to obtain the selective water plugging agent.

8. The method for preparing the selective water plugging agent according to claim 7, characterized in that: In steps S2-S4, the stirring rate adopted is 800-1000 r / min.

9. The method for preparing the selective water plugging agent according to claim 8, characterized in that: In step S2, the stirring time is 30-40 min; in step S3, the stirring time is greater than 20 min; in step S4, the stirring time is 10-20 min.