Low-density cement paste suspending agent and preparation method thereof

Abstract

The invention relates to a low-density cement paste suspending agent which comprises the following components in parts by weight: 100 parts of 2-acrylamide-2-methylpropanesulfonic acid; 5-10 parts of a temperature-sensitive monomer; 1-3 parts of a molecular weight regulator; 8 to 10 parts of an amide monomer; 0.5 to 1.0 part of a carboxylic acid monomer; and 300 to 400 parts of water. The low-density cement slurry suspending agent has the advantages that the low-density cement slurry suspending agent is especially suitable for a low-density cement slurry system, and low-density cement slurry prepared from the low-density cement slurry suspending agent has the characteristics of high cement discharging speed, good rheological property at low temperature, good suspension stability at high temperature and the like, has good comprehensive performance, and can effectively guarantee the safety of well cementation construction and improve the well cementation quality.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield drilling cement slurry application, in particular to a low-density cement slurry suspending agent and a preparation method thereof. Background Art

[0002] At present, the Fuman Oilfield of Tarim Oilfield is located between the two major oil and gas-bearing areas of Tazhong and Tabei in the Tarim Basin of Xinjiang Uygur Autonomous Region. The main target layer is buried at a depth of 8,000 meters, making exploration and exploitation difficult. The main wellbore structure is four openings and three completions. The second opening is for the Permian igneous rock (including basalt and tuff), and the pressure bearing capacity is about 1.35-1.45g / cm 3 The cementing loss risk is high, and some wells lose casing during cementing. The pressure bearing capacity of the Silurian formation in the third opening is low (pressure bearing capacity <1.48g / cm 3 ), the risk of leakage is high, and there is high-pressure brine (1.37-1.44 g / cm 3 ), narrow density window (0.03-0.08g / cm 3 Therefore, cement slurry is usually 1.35-1.38 g / cm 3 Low density + normal density cement slurry system. The temperature of the second open cycle is 80-100℃, and the pressure is 50-70MPa; the temperature of the third open cycle is 120-135℃, and the pressure is 80-120MPa.

[0003] The suspension stability of low-density cement slurry is different from that of conventional density and high-density cement slurry. The main reason for its poor stability is the upward movement of lightening materials such as hollow microspheres, rather than the sinking of weighting materials under the action of gravity. Especially after high-temperature (above 120°C) curing, its stability is more difficult to adjust. Once the suspension stability of low-density cement slurry is not good, lightening materials such as microspheres move upward. After the cementing construction is completed, it is very easy to find the upper plug, which seriously affects the sealing integrity of the cement ring and causes problems such as annular gas blowby and even pressure. At the same time, due to the light weight and poor surface wettability of the lightening material, the ash-laying time of its slurry is also a major problem. Some commonly used bio-colloid-containing suspending agents are mostly in the form of viscosity increase to improve the suspension stability, but this will further lead to the difficulty of ash-laying of the low-density system, resulting in the inability to increase the density of the cement slurry during on-site construction, poor slurry rheology, and difficulty in displacement. Therefore, there is an urgent need for a technology or product that can improve the shortcomings of low-density cement slurry. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a low-density cement slurry suspending agent, comprising the following components in parts by weight: 100 parts of 2-acrylamide-2-methylpropane sulfonic acid; 5 to 10 parts of a temperature-sensitive monomer; 1 to 3 parts of a molecular weight regulator; 8 to 10 parts of an amide monomer; 0.5 to 1.0 parts of a carboxylic acid monomer; and 300 to 400 parts of water.

[0005] Specifically, the 2-acrylamide-2-methylpropanesulfonic acid introduced into the suspending agent has good water solubility, and has a hydrophilic sulfonic acid group and a polymerizable vinyl group in its molecule, and can undergo copolymerization reaction with other components under certain conditions.

[0006] Preferably, the weight proportion of the water is 300 parts, 320 parts, 340 parts, 350 parts, 370 parts, 380 parts or 400 parts.

[0007] Furthermore, the molecular weight regulator is at least one of isopropanol and dodecanethiol.

[0008] Preferably, the weight proportion of the molecular weight regulator is 1 part, 1.3 parts, 1.5 parts, 2 parts, 2.3 parts, 2.5 parts or 3 parts.

[0009] Specifically, the molecular weight regulator is used to control the molecular weight and molecular weight distribution of the suspending agent, so as to ensure the suspension stability of the cement slurry while ensuring the ash laying time and rheological properties at low temperature.

[0010] Furthermore, the temperature-sensitive monomer is N-isopropylacrylamide.

[0011] Specifically, when the weight fraction of the thermosensitive monomer exceeds 10, the cement slurry prepared by the suspending agent provided by the above components has a high consistency and poor rheological properties, and the thickening line is prone to problems such as "bulging" and "core wrapping"; and when the weight fraction of the thermosensitive monomer is less than 5, the amount of the suspending agent needs to be increased, and the suspension stability of the system is relatively poor; therefore, preferably, the weight fraction of the thermosensitive monomer does not exceed 10; preferably, the weight fraction of the thermosensitive monomer is 5 to 10.

[0012] Preferably, the weight proportion of the temperature-sensitive monomer is 5 parts, 6 parts, 7 parts, 8 parts, 9 parts or 10 parts.

[0013] Specifically, by adding the thermosensitive monomer, as the temperature increases, the solubility of the monomer decreases, and phase separation will occur at a certain temperature, affecting the interaction between each functional group and water within the molecule and between molecules, so that the entire network structure changes, and then a volume phase change occurs, which compensates for the dilution effect of the polymer at high temperature, and at the same time binds the floating beads, microbeads and other lightening materials to prevent them from drifting upward, thereby playing a role in suspension stability.

[0014] Furthermore, the amide monomer is at least one of N,N-dimethylacrylamide and acrylamide.

[0015] Specifically, the N,N-dimethylacrylamide and acrylamide are easy to generate polymers with high polymerization degree, which can increase the viscosity of cement slurry and improve its stability.

[0016] Preferably, the weight proportion of the amide monomer is 8 parts, 8.2 parts, 8.5 parts, 9 parts, 9.3 parts, 9.5 parts or 10 parts.

[0017] Furthermore, the carboxylic acid monomer is at least one of itaconic acid and acrylic acid.

[0018] It should be noted that when the weight fraction of the carboxylic acid monomer exceeds 1.5, the cement slurry prepared by the suspending agent provided by the present invention will have a prolonged thickening time and slow strength development at low temperatures. Therefore, preferably, the weight fraction of the carboxylic acid monomer does not exceed 1.0; preferably, the weight fraction of the carboxylic acid monomer is 0.5 to 1.0.

[0019] Preferably, the weight proportion of the carboxylic acid monomer may be 0.5 part, 0.6 part, 0.7 part, 0.8 part, 0.9 part or 1.0 part.

[0020] Specifically, carboxylic acid monomers are introduced into the suspending agent to further enhance the adsorption performance of the suspending agent, so that it can be adsorbed on the surface of cement particles, support the cement particles, and further ensure its suspension stability.

[0021] Furthermore, the suspending agent is used to prepare low-density cement slurry.

[0022] The low-density cement slurry suspending agent of the present invention has the following advantages: the low-density cement slurry prepared by using the low-density cement slurry has the characteristics of fast ash removal, good rheological properties at low temperatures, good stability at high temperatures, etc., and has good comprehensive performance, which can effectively ensure the safety of cementing construction and improve the quality of cementing.

[0023] Another aspect of the present invention also provides a method for preparing a low-density cement slurry suspension agent, comprising the following steps:

[0024] Step 1, according to the preset weight proportions of each component, water, 2-acrylamide-2-methylpropanesulfonic acid, a molecular weight regulator, a temperature-sensitive monomer, an amide monomer and a carboxylic acid monomer are sequentially added into a reactor to obtain a mixed solution;

[0025] Step 2, after stirring until all components are dissolved, adjusting the pH value of the hydrogen ion concentration index of the mixed solution to a preset value, and raising the temperature of the reaction solution to a preset temperature;

[0026] Step three, adding an initiator to the reaction solution, reacting for a preset period of time, and then cooling to room temperature to obtain a low-density cement slurry suspension.

[0027] Furthermore, in the step 2, the stirring speed is 190 rpm to 210 rpm.

[0028] Furthermore, the preset value of the pH value is 6-7, and the preset value of the temperature is 50-60°C.

[0029] Furthermore, in the step three, the initiator is at least one of ammonium persulfate, potassium persulfate, azobisisobutylamidine hydrochloride and azobisisobutylimidazoline hydrochloride.

[0030] In summary, the beneficial technical effects of the present invention are as follows: the preparation method is simple, and the suspending agent prepared by the method is applied to low-density cement slurry, and has the following advantages: fast ash removal, good rheological properties at low temperatures, good stability at high temperatures, etc., and has good comprehensive performance, which can effectively ensure the safety of cementing construction and improve the quality of cementing. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings. The accompanying drawings are only used for the purpose of illustrating the preferred embodiment mode and are not to be considered as limiting the present invention. In addition, the same reference symbols are used to represent the same components throughout the accompanying drawings.

[0032] Figure 1 This is the shutdown thickening curve of the cement slurry prepared in Example 1 at 131°C. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below in conjunction with the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0034] The present invention discloses a method for preparing a low-density cement slurry suspension agent, which comprises:

[0035] Step 1: according to the weight proportions of the components, water, 2-acrylamide-2-methylpropanesulfonic acid, a temperature-sensitive monomer, a molecular weight regulator, a carboxylic acid monomer and an amide monomer are sequentially added into a reactor to obtain a reaction solution.

[0036] The weight proportions of the components are: 300-400 weight proportions of water, 100 weight proportions of 2-acrylamide-2-methylpropanesulfonic acid, 5-10 weight proportions of temperature-sensitive monomer, 1-3 weight proportions of molecular weight regulator, 8-10 weight proportions of amide monomer and 0.5-1.0 weight proportions of carboxylic acid monomer. The corresponding weight proportions of the components are sequentially added into the reactor.

[0037] The reactor can be a four-necked flask equipped with a thermometer, a stirrer and a reflux condenser.

[0038] Step 2: Stirring at a speed of 200 rpm, adjusting the pH of the reaction solution to 6-7, and raising the temperature of the reaction solution to 50-60°C.

[0039] In this step, the pH of the reaction solution can be adjusted by using a NaOH solution. The concentration of the NaOH solution can be set and changed as needed, and is not specifically limited in the embodiments of the present invention. For example, the concentration of the NaOH solution can be 0.05 mol / L, 0.1 mol / L, or 0.2 mol / L.

[0040] Step 3: After all components are dissolved, add an initiator to the reaction solution, react for 2 to 3 hours, and cool to room temperature to obtain a suspension.

[0041] One point that needs to be explained is that, in this embodiment, when the weight fraction of the thermosensitive monomer exceeds 10, the cement slurry prepared by the suspending agent provided by the embodiment of the present invention has a high consistency, poor rheological properties, and the thickening line is prone to problems such as "bulging" and "core wrapping". When the weight fraction of the thermosensitive monomer is less than 5, the amount of the suspending agent needs to be increased, and the suspension stability of the system is relatively poor. Therefore, in the embodiment of the present invention, the weight fraction of the thermosensitive monomer does not exceed 10. Preferably, the weight fraction of the thermosensitive monomer is 5 to 10.

[0042] Another point to be explained is that when the weight percentage of the carboxylic acid monomer exceeds 1.5, the cement slurry prepared by the suspending agent provided in the embodiment of the present invention will have a prolonged thickening time and slow strength development at low temperatures. Therefore, in the embodiment of the present invention, the weight percentage of the carboxylic acid monomer does not exceed 1.0. Preferably, the weight percentage of the carboxylic acid monomer is 0.5 to 1.0.

[0043] In step 3 of the present invention, an initiator is used to initiate a polymerization reaction of the components of the suspending agent to obtain a suspending agent. In an embodiment of the present invention, the initiator is at least one of ammonium persulfate, potassium persulfate, azobisisobutylamidine hydrochloride and azobisisobutylimidazoline hydrochloride. In an embodiment of the present invention, this is not specifically limited.

[0044] The suspension is a light yellow liquid with a certain viscosity.

[0045] The preparation method of the above suspension agent is simple. The suspension agent obtained by the method is used in low-density cement slurry to obtain cement slurry with the characteristics of fast ash removal, good low-temperature rheology and good high-temperature stability. Especially when used in cementing operations of low-density cement slurry, it can ensure that the cement slurry has fast ash removal (20-30s), good rheology (k<0.5), good stability at high temperature (the upper and lower density difference can be controlled within 0.03, and the free liquid is zero), good water loss, and fast compressive strength development, thereby ensuring the quality of cementing.

[0046] The technical solution of the present invention will be described in detail below through specific embodiments and comparative examples.

[0047] Example 1

[0048] According to the weight parts of each component, 300 parts by weight of water, 100 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid, 5 parts by weight of N-isopropylacrylamide, 1 part by weight of isopropanol, 8 parts by weight of acrylamide and 0.5 parts by weight of itaconic acid are sequentially added into a reactor to obtain a reaction solution; the reaction solution is stirred at a speed of 200 rpm, the pH value of the reaction solution is adjusted to 6, and the temperature of the reaction solution is increased to 60° C.; after all the components are dissolved, an initiator ammonium persulfate is added to the reaction solution, the reaction is carried out for 2 hours, and the reaction is cooled to room temperature to obtain a suspension.

[0049] Example 2

[0050] According to the weight parts of each component, 350 parts by weight of water, 100 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid, 8 parts by weight of N-isopropylacrylamide, 3 parts by weight of dodecanethiol, 10 parts by weight of N,N-dimethylacrylamide and 1 part by weight of acrylic acid are sequentially added into a reactor to obtain a reaction solution; the reaction solution is stirred at a speed of 200 rpm, the pH value of the reaction solution is adjusted to 7, and the temperature of the reaction solution is increased to 60° C. After all the components are dissolved, an initiator ammonium persulfate is added into the reaction solution, the reaction is carried out for 2 hours, and the reaction is cooled to room temperature to obtain a suspension.

[0051] Example 3

[0052] According to the weight parts of each component, 400 parts by weight of water, 100 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid, 10 parts by weight of N-isopropylacrylamide, 1.5 parts by weight of isopropanol, 1.5 parts by weight of dodecanethiol, 5 parts by weight of acrylamide, 5 parts by weight of N,N-dimethylacrylamide, 0.3 parts by weight of acrylic acid, and 0.3 parts by weight of itaconic acid are sequentially added into a reactor to obtain a reaction solution; the reaction solution is stirred at a speed of 200 rpm, the pH value of the reaction solution is adjusted to 7, and the temperature of the reaction solution is increased to 60° C.; after all the components are dissolved, an initiator ammonium persulfate is added into the reaction solution, the reaction is carried out for 2 hours, and the reaction is cooled to room temperature to obtain a suspension.

[0053] Comparative Example 1

[0054] According to the weight parts of each component, 300 parts by weight of water, 100 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid, 1 part by weight of isopropanol, 8 parts by weight of acrylamide and 0.5 parts by weight of itaconic acid are sequentially added into a reactor to obtain a reaction solution; the reaction solution is stirred at a speed of 200 rpm, the pH value of the reaction solution is adjusted to 6, and the temperature of the reaction solution is increased to 60° C. After all the components are dissolved, an initiator ammonium persulfate is added to the reaction solution, the reaction is carried out for 2 hours, and the reaction is cooled to room temperature to obtain a suspension.

[0055] Comparative Example 2

[0056] According to the weight parts of each component, 300 parts by weight of water, 100 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid, 5 parts by weight of N-isopropylacrylamide, 8 parts by weight of acrylamide and 0.5 parts by weight of itaconic acid are sequentially added into a reactor to obtain a reaction solution; the reaction solution is stirred at a speed of 200 rpm, the pH value of the reaction solution is adjusted to 6, and the temperature of the reaction solution is increased to 60° C. After all the components are dissolved, an initiator ammonium persulfate is added to the reaction solution, the reaction is carried out for 2 hours, and the reaction is cooled to room temperature to obtain a suspension.

[0057] According to the geological characteristics and cementing requirements of Fuman Oilfield in Tarim Oilfield, a 1.38g / cm 3 A set of low-density cement slurry, see Table 1 for details. The cement is Aksu G-grade oil well cement; the microsilica is Huli brand microsilica; the microbead is 3M0.6g / cm 3 microspheres; retarder is BCR-300L, fluid loss reducer is BCF-230L, defoamer is G603, drag reducer CF-40L are all purchased from Tianjin Sinopec Boxing Engineering Technology Co., Ltd.; water is tap water from Tanggu.

[0058] Table 1 Low density cement slurry system formula

[0059]

[0060]

[0061] The molecular weight and molecular weight distribution of the suspending agents of the above three examples and two comparative examples are shown in Table 2 below:

[0062] Table 2 Molecular weight and molecular weight distribution of the suspending agent of Examples 1-3 and Comparative Examples 1-2

[0063]

[0064] It can be seen from Table 2 that, compared with Comparative Example 2, Examples 1 to 3 all add a molecular weight regulator, so the suspending agent has a better molecular weight and distribution, which leads to the low-density cement slurry prepared therewith having the characteristics of fast ash laying time and good cold slurry rheology. The specific performance is shown in Table 3.

[0065] Table 3 Properties of low-density cement slurries prepared by suspending agents of Examples 1-3 and Comparative Examples 1-2

[0066]

[0067]

[0068] It can be seen from Table 3 that when the temperature-sensitive monomer is not added to the suspending agent, such as in Comparative Example 1, the low-density cement slurry prepared therefrom has poor sedimentation stability at high temperature, and the upper and lower density difference is 0.35 g / cm 3 , the free liquid is 0.2%, and the cement stone has stratification after curing, which does not meet the requirements of cementing construction. When the molecular weight regulator is not added to the suspending agent, such as in Comparative Example 2, when the low-density cement slurry is configured by it, the ash-laying time is slow, requiring 65s; and the rheological properties of the cold slurry are poor, the initial consistency is 35Bc, the fluidity is only 15.5cm, and the consistency coefficient reaches 1.28, which does not meet the requirements of cementing construction. At the same time, compared with Comparative Examples 1 and 2, the low-density cement slurry configured by Example 1, Example 2 and Example 3 has a fast recovery, which can be controlled within 30s; the rheological properties of the cold slurry are good, and the initial consistency can be controlled within 18Bc; the fluidity is greater than 21cm, and the consistency coefficient is less than 0.5; the sedimentation stability is good at high temperature, the upper and lower density difference can be controlled within 0.03, and the free liquid is zero; the comprehensive performance is good, the water loss can be controlled within 50mL, the thickening time is greater than 400min, and the 24h compressive strength is greater than 10MPa. Meet the stringent requirements of cementing construction in Tarim Fuman Oilfield. Figure 1 As shown, it is a shutdown experiment of Example 1 performed at 131°C. Curve A represents temperature, curve B represents pressure, and curve C represents consistency. It can be seen from the figure that the consistency hardly changes at the moment of startup, indicating that under high temperature curing conditions, the cement slurry has good sedimentation stability.

[0069] In summary, the beneficial technical effect of a low-density cement slurry suspending agent disclosed in this embodiment is as follows: the low-density cement slurry configured using the suspending agent has the characteristics of fast ash removal, good rheological properties at low temperatures, good stability at high temperatures, etc., and has good comprehensive performance, which can effectively ensure the safety of cementing construction and improve the quality of cementing.

[0070] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0071] Finally, it should be noted that: Obviously, the above embodiments are only examples for clearly explaining the present invention, and are not intended to limit the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the scope of protection of the present invention.

Claims

1. A low-density cement slurry suspending agent, characterized in that: The invention comprises the following components in parts by weight: 100 parts of 2-acrylamide-2-methylpropanesulfonic acid; 5-10 parts of a temperature-sensitive monomer; 1-3 parts of a molecular weight regulator; and 8-10 parts of an amide monomer. Carboxylic acid monomer, 0.5~1.0 part; Water, 300~400 parts.

2. The low-density cement slurry suspending agent according to claim 1, characterized in that: The molecular weight regulator is at least one of isopropanol and dodecanethiol.

3. The low-density cement slurry suspending agent according to claim 1, characterized in that: The temperature-sensitive monomer is N-isopropylacrylamide.

4. The low-density cement slurry suspending agent according to claim 1, characterized in that: The amide monomer is at least one of N,N-dimethylacrylamide and acrylamide.

5. The low-density cement slurry suspending agent according to claim 1, characterized in that: The carboxylic acid monomer is at least one of itaconic acid and acrylic acid.

6. The low-density cement slurry suspending agent according to any one of claims 1 to 6, characterized in that: The low-density cement slurry suspending agent is used for preparing low-density cement slurry.

7. A method for preparing a low-density cement slurry suspension agent, characterized in that: The steps include: Step 1, according to the preset weight proportions of each component, water, 2-acrylamide-2-methylpropanesulfonic acid, a molecular weight regulator, a temperature-sensitive monomer, an amide monomer and a carboxylic acid monomer are sequentially added into a reactor to obtain a mixed solution; Step 2, after stirring until all components are dissolved, adjusting the pH value of the hydrogen ion concentration index of the mixed solution to a preset value, and raising the temperature of the reaction solution to a preset temperature; Step three, adding an initiator to the reaction solution, reacting for a preset period of time, and then cooling to room temperature to obtain a low-density cement slurry suspension.

8. The method according to claim 7, characterized in that: In the step 2, the stirring speed is 190 rpm to 210 rpm.

9. The method according to claim 7, characterized in that In the step 2, the preset value of the pH value is 6-7, and the preset value of the temperature is 50-60°C.

10. The method according to claim 7, characterized in that: In the step three, the initiator is at least one of ammonium persulfate, potassium persulfate, azobisisobutylamidine hydrochloride and azobisisobutylimidazoline hydrochloride.

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