阅读说明：本技术 一种油井水泥低粘度触变剂及其制备方法 (Oil well cement low-viscosity thixotropic agent and preparation method thereof ) 是由 黄熠 刘和兴 李磊 柳亚亚 梁继文 于 2020-07-28 设计创作，主要内容包括：本发明涉及油田化学及油气井固井材料领域,涉及一种油井水泥触变剂,具体涉及一种适用于油井水泥的低粘度触变剂及制备方法。本发明将粉煤灰与合成聚合物类触变剂有效结合,使粉煤灰吸附聚合物类触变剂。本发明利用了粉煤灰的“滚珠效应”,使水泥浆在泵注过程中低粘,当水泥浆静止时,粉煤灰表面吸附的聚合物快速形成网架结构,达到触变功能。当在外力作用下时,由于聚合物吸附在粉煤灰表面,只要外力使粉煤灰发生运动,则网架结构即被破坏,打破触变,可有效保证泵注过程的安全施工。(The invention relates to the field of oilfield chemistry and oil-gas well cementing materials, relates to an oil well cement thixotropic agent, and particularly relates to a low-viscosity thixotropic agent suitable for oil well cement and a preparation method thereof. The invention effectively combines the fly ash and the synthetic polymer thixotropic agent, so that the fly ash absorbs the polymer thixotropic agent. The invention utilizes the ball effect of the fly ash to ensure that the cement paste has low viscosity in the pump injection process, and when the cement paste is static, polymers adsorbed on the surface of the fly ash quickly form a grid structure to achieve the thixotropic function. When the polymer is adsorbed on the surface of the fly ash under the action of external force, the grid structure is damaged as long as the fly ash moves under the action of the external force, the thixotropy is broken, and the safe construction in the pump injection process can be effectively ensured.)

1. A low viscosity thixotropic agent for cement is prepared from powdered coal ash and synthetic polymer as thixotropic agent.

2. The cement low-viscosity thixotropic agent according to claim 1, wherein the synthetic polymer thixotropic agent is formed by polymerizing 2-acrylamide-2-methylpropanesulfonic Acid (AMPS) and Acrylamide (AM) in a ratio of (3-4) to (7-6).

3. A cement low viscosity thixotropic agent according to claim 2 wherein the crosslinking agent is N, N-Methylene Bisacrylamide (MBA) added in an amount of 0.5 to 3% by mass of the monomers.

4. The cement low viscosity thixotropic agent of claim 2 wherein the initiator is ammonium persulfate added in an amount of 1-4% by mass of the monomer.

5. The cement low viscosity thixotropic agent as claimed in claim 2, wherein the fly ash has a particle size of 200-500 mesh and is added in an amount of 800-900% by mass based on the mass of the monomer.

6. A method of making a cement low viscosity thixotropic agent as claimed in any one of claims 1 to 5, characterised in that it comprises the steps of:

(5) adding the fly ash into a synthetic polymer thixotropic agent solvent,

(6) stirring to form slurry;

(7) heating the slurry to make the fly ash adsorb and synthesize the polymer thixotropic agent;

(8) drying to obtain the product.

7. The method for preparing a low-viscosity thixotropic agent for cement according to claim 6, wherein the synthetic polymer-based thixotropic agent solvent of the step (1) is prepared by: 2-acrylamido-2-methylpropanesulfonic Acid (AMPS), Acrylamide (AM) and N, N-Methylenebisacrylamide (MBA) are dissolved in water to form a solution, and ammonium persulfate is added to the solution to form a solution.

8. The method for preparing a cement low viscosity thixotropic agent according to claim 7, wherein the heating in the step (3) is performed at 75 ℃ for 2 hours.

9. A cement slurry system comprising a cement slurry and the cementitious low viscosity thixotropic agent of any one of claims 1-5.

Technical Field

The invention relates to the field of oilfield chemistry and oil-gas well cementing materials, relates to an oil well cement thixotropic agent, and particularly relates to a low-viscosity thixotropic agent suitable for oil well cement and a preparation method thereof.

Background

The thixotropic cement paste system has good flowing property in the mixing and injection process, and can quickly form a special cement paste system with higher gel strength after the thixotropic cement paste system is static, so that the ideal cement paste thixotropy can effectively solve the problems of leakage and channeling in the well cementation process. At present, thixotropic agents used in thixotropic cement paste systems at home and abroad can be divided into inorganic thixotropic agents and organic thixotropic agents, wherein the inorganic thixotropic agents mainly comprise clay minerals, sulfates, metal carbonates or mixed metal hydroxides and the like, and the organic thixotropic agents mainly comprise cross-linked polymers and synthetic polymers. The cross-linking agent commonly used in the cross-linked polymer thixotropic agent comprises high-valence transition metal ions such as zirconium, yttrium, iron and the like and titanium chelates such as piperyldione, lactic acid, triethanolamine and the like. The synthetic polymers mainly include polymers of acrylamide monomers, and the like.

The thixotropic mechanism is generally considered to be that internal particles or molecules form a network space structure through certain acting force when a liquid is static, the network space structure can be destroyed under the action of external force, macroscopically, the network space structure is static thickened and shear-thinned, and the network space structure is reformed after the external force is removed for a period of time. According to the thixotropic mechanism, most of the prior common thixotropic agents have the side effect of tackifying, and the cement paste is difficult to pump due to overlarge viscosity, so that an oil well cement low-viscosity thixotropic agent needs to be researched, and the thixotropic agent has certain engineering significance for narrow annulus or small pipe grouting.

Disclosure of Invention

The invention mainly aims to provide a low-viscosity thixotropic agent for oil well cement, and a cement paste system prepared by adopting a conventional water-solid ratio has low viscosity and strong thixotropic property after the thixotropic agent is added.

In order to achieve the purpose, the invention adopts the following technical scheme:

a low viscosity thixotropic agent for cement is prepared from powdered coal ash and synthetic polymer as thixotropic agent.

Optionally, the synthetic polymer thixotropic agent is formed by polymerizing 2-acrylamide-2-methylpropanesulfonic Acid (AMPS) and Acrylamide (AM), and the proportion of the thixotropic agent is (3-4) to (7-6).

Optionally, the crosslinking agent is N, N-Methylene Bisacrylamide (MBA), and the addition amount of the crosslinking agent is 0.5-3% of the mass of the monomer.

Optionally, the initiator is ammonium persulfate, and the addition amount of the initiator is 1-4% of the mass of the monomer.

The optional fly ash has the particle size of 200-500 meshes, and the addition amount of the fly ash is 900 percent of the mass of the monomer.

Wherein the mass of the monomer is the sum of the mass of two monomers, namely 2-acrylamide-2-methylpropanesulfonic Acid (AMPS) and Acrylamide (AM).

The invention also provides a preparation method of the cement low-viscosity thixotropic agent, which comprises the following steps:

(1) adding the fly ash into a synthetic polymer thixotropic agent solvent,

(2) stirring to form slurry;

(3) heating the slurry to make the fly ash adsorb and synthesize the polymer thixotropic agent;

(4) drying to obtain the product.

Optionally, the synthesized polymer thixotropic agent solvent in the step (1) is prepared by the following method: 2-acrylamido-2-methylpropanesulfonic Acid (AMPS), Acrylamide (AM) and N, N-Methylenebisacrylamide (MBA) are dissolved in water to form a solution, and ammonium persulfate is added to the solution to form a solution.

Optionally, the heating in the step (3) is performed at 75 ℃ for 2 hours.

The invention further provides a cement paste system comprising a cement paste and the cement low-viscosity thixotropic agent. The cement slurry is prepared at a conventional water-to-solid ratio, such as 0.44.

Specifically, the method comprises the following steps: the invention provides an oil well cement low-viscosity thixotropic agent, which is prepared by the following steps:

2-acrylamido-2-methylpropanesulfonic Acid (AMPS), Acrylamide (AM) and N, N-Methylenebisacrylamide (MBA) were dissolved in water to form a solution, and ammonium persulfate was added to the solution to form a solution I. And adding a certain amount of fly ash into the solution I, and uniformly stirring to form slurry I. And (3) reacting the slurry I for 2h at 75 ℃. Then drying and crushing to obtain the product.

The mass ratio of the 2-acrylamide-2-methylpropanesulfonic Acid (AMPS) to the Acrylamide (AM) is 3:7-4: 6.

The addition amount of the N, N-Methylene Bisacrylamide (MBA) is 0.5-3% of the mass of the monomer.

The adding amount of the ammonium persulfate is 1-4% of the mass of the monomer.

The mass of water in the solution I is 350-400% of the mass of the monomer.

Preferably, the particle size of the fly ash is 200-500 meshes; the fly ash is divided into F grade and C grade, and if the influence on the cement performance is small, the F grade is mostly used in oil well cement.

The mass of the fly ash in the slurry I is 800-900% of the mass of the monomer.

The oil well cement low-viscosity thixotropic agent disclosed by the invention effectively combines the fly ash and a synthetic polymer thixotropic agent, so that the fly ash adsorbs the polymer thixotropic agent. The invention utilizes the ball effect of the fly ash to ensure that the cement paste has low viscosity in the pump injection process, and when the cement paste is static, polymers adsorbed on the surface of the fly ash quickly form a grid structure to achieve the thixotropic function. When the polymer is adsorbed on the surface of the fly ash under the action of external force, the grid structure is damaged as long as the fly ash moves under the action of the external force, the thixotropy is broken, and the safe construction in the pump injection process can be effectively ensured.

Drawings

FIG. 1 is a micrograph of a low viscosity thixotropic agent.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of the stated features, steps, operations, and/or combinations thereof, unless the context clearly indicates otherwise.

In order to make the technical solutions of the present invention more clearly understood by those skilled in the art, the technical solutions of the present invention will be described in detail below with reference to specific embodiments.