High-temperature-resistant oil well cement fluid loss agent as well as preparation method and application thereof

Abstract

The invention discloses a high-temperature-resistant oil well cement fluid loss agent. The high-temperature fluid loss agent mainly solves the problem that the existing high-temperature fluid loss agent product is insufficient in temperature resistance and cannot guarantee the stability of cement slurry in a shaft environment at the temperature of 200 DEG C or above. The invention is characterized in that the adhesive is prepared from the following components in parts by mass: 50 to 80 parts of 2-acrylamido-2-methylpropanesulfonic acid, 5 to 10 parts of acrylic acid, 1 to 10 parts of polyoxyethylene, 1 to 10 parts of diacetone acrylamide, 1 to 3 parts of N-vinyl pyrrolidone, 0.5 to 3 parts of initiator, 300 to 420 parts of deionized water and 45 to 75 parts of NaOH. The preparation method comprises the following steps: mixing and dissolving deionized water, 2-acrylamido-2-methylpropanesulfonic acid and acrylic acid, and dropwise adding NaOH to obtain a reaction solution; deionized water, polyoxyethylene, diacetone acrylamide and N-vinyl pyrrolidone are mixed and dissolved and then added into the reaction solution, and a prepolymerization reaction solution is obtained; and adding an initiator to obtain the fluid loss agent.

Description

Technical Field

[0001] This invention relates to cementing admixtures in the field of oilfield drilling, and particularly to a high-temperature resistant oil well cement fluid loss reducer, its preparation method, and its application. Background Technology

[0002] With the increasing demand for deep oil and gas resources in my country, the number of deep and ultra-deep wells is constantly increasing. Wells such as the Deepland Take 1 and Deepland Chuanke 1 in the Tarim Oilfield of China National Petroleum Corporation are currently exploring to depths exceeding 10,000 meters, where bottom-hole temperatures will exceed 200℃. Due to the greater depth and more complex downhole geological environment and working conditions, high-temperature and high-pressure formations will become increasingly common during exploration and development, placing higher demands on drilling and completion fluids, especially cement slurry, which will face severe challenges. Under high-temperature conditions, cement slurry has a severe dilution and viscosity-reducing effect, producing a large amount of cement particle sedimentation while releasing free fluid. During field construction, if a large amount of sedimentation occurs after the cement slurry is pumped to the bottom of the well, it can easily clog the wellbore, preventing further pumping and leading to cementing failure. As an important component of cement slurry, fluid loss reducer is a cement additive that prevents cement slurry filtrate from entering the formation and formation fluids from entering the cement slurry inside the wellbore, maintaining the water-to-ash ratio in the cement slurry, thereby reducing water loss and preventing cross-contamination. Domestic high-temperature fluid loss reducing agents are generally resistant to temperatures below 200℃ and often suffer from viscosity reduction or failure at high temperatures. The main reason is that their temperature resistance is insufficient and they cannot guarantee the stability of cement slurry in well environments with temperatures above 200℃, which no longer meets the needs of deep and ultra-deep well exploration. Summary of the Invention

[0003] This invention provides a high-temperature resistant oil well cement fluid loss control agent to overcome the problem in the prior art where existing high-temperature fluid loss control agents have insufficient temperature resistance and cannot guarantee the stability of cement slurry in wellbore environments above 200°C. The purpose of this invention is to propose a high-temperature resistant oil well cement fluid loss control agent that can guarantee the stability of cement slurry in wellbore environments above 200°C, meeting the needs of deep and ultra-deep well exploration. This invention also provides a method for preparing and applying the high-temperature resistant oil well cement fluid loss control agent.

[0004] To achieve the above objectives, the first aspect of the present invention provides a high-temperature resistant oil well cement fluid loss reducing agent, the components of which and the mass fractions of each component are as follows:

[0005] 50-80 parts of 2-acrylamido-2-methylpropanesulfonic acid, 5-10 parts of acrylic acid, 1-10 parts of polyethylene oxide, 1-10 parts of diacetone acrylamide, 1-3 parts of N-vinylpyrrolidone, 0.5-3 parts of initiator, 300-420 parts of deionized water, and 45-75 parts of 30% (w / w) NaOH.

[0006] Preferably, the initiator is an azobisisobutyrazoline hydrochloride (VA044) or ammonium persulfate (APS) thermal initiator to initiate monomer polymerization.

[0007] A second aspect of this invention provides a method for preparing a high-temperature resistant oil well cement fluid loss reducing agent, comprising the following steps:

[0008] (1) Add deionized water, 2-acrylamido-2-methylpropanesulfonic acid and acrylic acid to the reactor in proportion, turn on the cooling water circulation and stirring, stir until completely dissolved, and slowly add 30% (W / W) NaOH while stirring, control the temperature at 15-30℃ to obtain the reaction solution.

[0009] (2) Add deionized water, polyethylene oxide, diacetone acrylamide and N-vinylpyrrolidone to a container in proportion, stir until completely dissolved, and then add to the reaction solution of step (1) to disperse completely to obtain the prepolymer reaction solution.

[0010] (3) Nitrogen gas is introduced into the reactor and heated to increase the temperature. The initiator is dissolved in deionized water according to the ratio and added into the reactor to obtain the dehydration reduction agent product.

[0011] Preferably, in step (3), nitrogen gas is introduced into the reactor and heated for 30 minutes until the temperature reaches 60°C.

[0012] Preferably, the reaction time in step (3) in the reactor is 5 to 8 hours.

[0013] Preferably, the mass ratio of deionized water used in steps (1), (2) and (3) is 200-320:100:10.

[0014] The third aspect of this invention provides a high-temperature resistant oil well cement dehydration agent that can be used for cementing deep and ultra-deep wells.

[0015] Preferably, the applicable temperature range for high-temperature resistant oil well cement fluid loss reducing agent used in cementing deep and ultra-deep wells is 150–220℃.

[0016] Preferably, the water loss reducing agent, under the same dosage and different temperature conditions within the temperature range of 150-220°C, can form a dense mud cake with a water loss of less than 30 mL.

[0017] Preferably, when the high-temperature resistant oil well cement fluid loss reducing agent is used for cementing applications in deep and ultra-deep wells, the amount of fluid loss reducing agent added in the cement slurry preparation is 8%.

[0018] The functions or synergistic effects of the components in the high-temperature resistant oil well cement fluid loss reducer of this invention are as follows: polyethylene oxide serves as the grafted skeleton of the branched structure; 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, and N-vinylpyrrolidone serve as branches; simultaneously, the diacetone acrylamide functional unit introduced into the fluid loss reducer structure acts as an additional crosslinking functional monomer to enhance the temperature resistance of the fluid loss reducer; and the high-temperature induced post-crosslinking effect compensates for the energy loss of the fluid loss reducer at high temperatures, thereby improving the temperature resistance of the fluid loss reducer. It can also increase the viscosity of the cement slurry liquid phase, increase the resistance to liquid phase filtration into the formation, and reduce water loss in the cement slurry, enabling it to control water loss even at 220℃. Furthermore, the fluid loss reducer contains a large amount of -CH2-SO4. 3- and -COO - These groups have strong hydration and adsorption effects with cement particles, which can improve the structure of cement filter cake and form a network structure of "cement particles - linear polymer - water molecule adsorption layer" on the surface of cement particles. This can bind more free water and block the internal pores of cement to form a dense filter cake with low permeability, thereby further reducing water loss.

[0019] The present invention has at least the following beneficial effects:

[0020] (1) The present invention uses solution polymerization in the process of synthesizing the water loss reducing agent. Polyethylene oxide is used as the graft skeleton of the branched structure and various functional monomers are used as branches. The branched structure is used to improve the temperature resistance of the polymer. At the same time, the diacetone acrylamide functional unit introduced into the polymer structure can introduce ketone carbonyl groups into the polymer structure. The chemical properties of ketone carbonyl groups can make the polymer undergo cross-linking reaction at high temperature. The high temperature-induced post-cross-linking effect is used to compensate for the performance loss of the polymer at high temperature, improve the temperature resistance of the product, effectively ensure the liquid phase viscosity of cement slurry at high temperature, and increase the frictional resistance in the slurry.

[0021] (2) The fluid loss control agent of this invention has strong fluid loss control ability and excellent resistance to ultra-high temperature, and can meet the cementing use at a temperature of 220℃.

[0022] (3) The water loss reducing agent of the present invention has a small effect on the water loss under the same dosage and different temperature conditions within the temperature range of 150 to 220°C. It can form a dense mud cake and the water loss is less than 30 mL. It can inhibit gas migration to a certain extent and play a role in preventing gas channeling.

[0023] (4) This invention provides a novel fluid loss reducing agent, which expands the range of fluid loss reducing agents for cementing oil wells in ultra-deep wells. It requires a lower dosage and has a simple production process, which helps to reduce production costs. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present invention and, together with the specification, serve to explain the technical solutions of the present invention.

[0025] Figure 1 The image shows the thickening curve of cement slurry when the water loss reducing agent dosage is 8% (BWOC) prepared in Example 1 of this invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0027] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the materials and reagents used in the following examples are commercially available unless otherwise specified.

[0028] This invention is not limited to the specific embodiments listed below. Those skilled in the art can implement this invention using various other specific embodiments based on the content disclosed herein. Any modifications or alterations made to the design structure and concept of this invention fall within the protection scope of this invention. It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0029] The following describes the evaluation method for water loss reducing agents and the testing method for cement application performance in the examples:

[0030] The evaluation methods for fluid loss reducing agents in all the following examples are based on the existing standards for oil well cement – ​​the People's Republic of China Petroleum and Natural Gas Industry Standard SY / T 5504.2-2013 "Evaluation Methods for Oil Well Cement Admixtures Part 2: Fluid Loss Reducing Agents".

[0031] The following examples use the following instruments for evaluating cement slurry containing water loss reducing agents: a Warin 3170 mixer from Trinity Instruments, Inc., a Trinity 8240 high-temperature and high-pressure thickener from Trinity Instruments, Inc., a TG-71 high-temperature and high-pressure water loss tester from Shenyang Tiger Petroleum Instrument Equipment Manufacturing Co., Ltd., and a Trinity 1910 high-temperature and high-pressure curing autoclave from Trinity Instruments, Inc.

[0032] The following examples illustrate the preparation method of cement slurry containing a water loss reducing agent: Weigh a certain amount of oil well cement, quartz sand, suspending agent, liquid high-temperature water loss reducing agent, and mixing water, and then mix them evenly to obtain cement slurry. Other requirements for cement slurry preparation are specified in GB / T 19139-2012 "Test Methods for Oil Well Cement".

[0033] The following example shows the test scheme for cement slurry containing a fluid loss reducer: 600g oil well cement + 300g quartz sand (200 mesh) + 18g suspending agent + 60g retarder + Xg fluid loss reducer + (282-X)g water. The suspending agent is WH-2 suspension stabilizer produced by Weihui Chemical Co., Ltd.; the retarder is DHTR400 retarder produced by Daqing Drilling Engineering Co., Ltd., and both the oil well cement and quartz sand are commercially available products.

[0034] Example 1:

[0035] (1) Add 245.44g of deionized water to the reaction vessel, add 70.32g of 2-acrylamido-2-methylpropanesulfonic acid, and then add 15.42g of acrylic acid. Turn on the cooling water circulation and stirring. After stirring until completely dissolved, slowly add 53.77g of 30% (W / W) NaOH while stirring. Control the temperature at 15-30℃ to obtain the reaction solution (1).

[0036] (2) Add 100 parts of deionized water to the prepared container, add 5.23g of polyethylene oxide, 7.00g of diacetone acrylamide and 2.82g of N-vinylpyrrolidone, stir until completely dissolved and then add to the reaction solution (1) to disperse completely to obtain the prepolymer reaction solution;

[0037] (3) Introduce nitrogen into the reactor and heat for 30 minutes until the temperature reaches 60°C. Dissolve 1.20g of initiator VA044 in 10 parts of deionized water and add it into the reactor. The dehydration reducer is obtained after reacting for 8 hours.

[0038] Example 2:

[0039] (1) Add 245.44g of deionized water, 70.32g of 2-acrylamido-2-methylpropanesulfonic acid, and 15.42g of acrylic acid to the reactor. Turn on the cooling water circulation and stirring. Stir until completely dissolved. Then, slowly add 53.77g of 30% (W / W) NaOH while stirring, and control the temperature at 15-30℃.

[0040] (2) Add 100 parts of deionized water to the prepared container, add 5.23g of polyethylene oxide, 7.00g of diacetone acrylamide and 2.82g of N-vinylpyrrolidone, stir until completely dissolved and then add to the reaction solution (1) to disperse completely to obtain the prepolymer reaction solution;

[0041] (3) Introduce nitrogen into the reactor and heat for 30 minutes until the temperature reaches 60°C. Dissolve 1.20g of initiator APS in 10 parts of deionized water and add it into the reactor. React for 8 hours to obtain the dehydration reducer.

[0042] Comparative Example 1

[0043] (1) Add 245.44g of deionized water, 70.32g of 2-acrylamido-2-methylpropanesulfonic acid, and 15.42g of acrylic acid to the reactor. Turn on the cooling water circulation and stirring. Stir until completely dissolved. Then, slowly add 53.77g of 30% (W / W) NaOH while stirring, and control the temperature at 15-30℃.

[0044] (2) Add 100 parts of deionized water to the prepared container, add 5.23g of polyethylene oxide and 7.00g of diacetone acrylamide, stir until completely dissolved, and then add to the reaction solution (1) to disperse completely to obtain the prepolymer reaction solution;

[0045] (3) Introduce nitrogen into the reactor and heat for 30 minutes until the temperature reaches 60°C. Dissolve 1.20g of initiator APS in 10 parts of deionized water and add it into the reactor. React for 8 hours to obtain the dehydration reducer.

[0046] Comparative Example 2

[0047] (1) Add 245.44g of deionized water, 70.32g of 2-acrylamido-2-methylpropanesulfonic acid, and 15.42g of acrylic acid to the reactor. Turn on the cooling water circulation and stirring. Stir until completely dissolved. Then, slowly add 53.77g of 30% (W / W) NaOH while stirring, and control the temperature at 15-30℃.

[0048] (2) Add 100 parts of deionized water to the prepared container, add 5.23g of polyethylene oxide and 2.82g of N-vinylpyrrolidone, stir until completely dissolved, and then add to the reaction solution (1) and disperse completely to obtain the prepolymer reaction solution;

[0049] (3) Introduce nitrogen into the reactor and heat for 30 minutes until the temperature reaches 60°C. Dissolve 1.20g of initiator VA044 in 10 parts of deionized water and add it into the reactor. The dehydration reducer is obtained after reacting for 8 hours.

[0050] Comparative Example 3

[0051] (1) Add 245.44g of deionized water, 70.32g of 2-acrylamido-2-methylpropanesulfonic acid, and 15.42g of acrylic acid to the reactor. Turn on the cooling water circulation and stirring. Stir until completely dissolved. Then, slowly add 53.77g of 30% (W / W) NaOH while stirring, and control the temperature at 15-30℃.

[0052] (2) Add 100 parts of deionized water to the prepared container, add 7.00g of diacetone acrylamide and 2.82g of N-vinylpyrrolidone, stir until completely dissolved, and then add to the reaction solution (1) and disperse completely to obtain the prepolymer reaction solution;

[0053] (3) Introduce nitrogen into the reactor and heat for 30 minutes until the temperature reaches 60°C. Dissolve 1.20g of initiator VA044 in 10 parts of deionized water and add it into the reactor. The dehydration reducer is obtained after reacting for 8 hours.

[0054] The water loss reducing agent prepared in Examples 1-2 and Comparative Examples 1-3 was used in cement slurry tests in the following manner: 600g oil well cement + 300g quartz sand (200 mesh) + 18g suspending agent + 60g retarder + Xg water loss reducing agent + (282-X)g water. The suspending agent was WH-2, a suspension stabilizer produced by Weihui Chemical Co., Ltd.; the retarder was DHTR400, a retarder produced by Daqing Drilling Engineering Co., Ltd.; and both the oil well cement and quartz sand were commercially available products. The dosage of the water loss reducing agent, the test conditions, and the measured water loss in each example are shown in Table 1. Table 1 shows the experimental results of the water loss reducing agent obtained in each example.

[0055] Table 1

[0056]

[0057]

[0058] Table 1 shows that the water loss control agent prepared by solution polymerization using polyethylene oxide as the branched structure and diacetone acrylamide as the functional unit can effectively improve the temperature resistance of the water loss control agent up to 220℃. The water loss control agent obtained in Example 1, with its low dosage, exhibits the most significant water loss control ability, and the change in water loss is minimal with increasing temperature, indicating that temperature has little impact on it and it maintains good performance at high temperatures. When the dosage of the water loss control agent is 8%, the water loss is less than 30 mL, which can inhibit gas migration and play a role in preventing gas channeling.

[0059] Figure 1 The thickening curve of cement slurry prepared in Example 1 with an addition of 8% (BWOC) of water loss reducing agent is shown at 220°C and 110MPa.

[0060] The cement slurry formula is: 600g oil well cement + 300g quartz sand (200 mesh) + 18g suspending agent WH-2 + 60g retarder DHTR400 + 48g water loss reducing agent (water loss reducing agent prepared in Example 1) + 234g water.

[0061] from Figure 1It can be seen that the cement slurry mixed with the water loss reducing agent prepared in Example 1 has a normal thickening curve and no abnormal gelation phenomenon. The experimental results show that the water loss reducing agent of the present invention has met the conditions for field application, and the water loss reducing agent prepared by the formulation in Example 1 is relatively better.

[0062] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A high-temperature resistant oil well cement fluid loss reducing agent, characterized in that: The components and their mass fractions are as follows: 50-80 parts of 2-acrylamido-2-methylpropanesulfonic acid, 5-10 parts of acrylic acid, 1-10 parts of polyethylene oxide, 1-10 parts of diacetone acrylamide, 1-3 parts of N-vinylpyrrolidone, 0.5-3 parts of initiator, 300-420 parts of deionized water, and 45-75 parts of 30% (w / w) NaOH.

2. The high-temperature resistant oil well cement fluid loss reducing agent according to claim 1, characterized in that: The initiator is azobisisobutyrazoline hydrochloride (VA044) or ammonium persulfate (APS) thermal initiator to initiate monomer polymerization.

3. A method for preparing a high-temperature resistant oil well cement fluid loss reducing agent according to any one of claims 1 to 2, characterized in that: Includes the following steps: In a reaction vessel, deionized water, 2-acrylamido-2-methylpropanesulfonic acid and acrylic acid are added in sequence according to the proportion. The cooling water circulation and stirring are turned on. After stirring until completely dissolved, 30% (W / W) NaOH is slowly added dropwise while stirring. The temperature is controlled at 15-30℃ to obtain the reaction solution. In a prepared container, deionized water, polyethylene oxide, diacetone acrylamide and N-vinylpyrrolidone were added in sequence according to the proportion. After stirring and dissolving completely, the mixture was added to the reaction solution of step (1) and dispersed completely to obtain the prepolymer reaction solution. Nitrogen gas is introduced into the reactor and heated to increase the temperature. The initiator is dissolved in deionized water in a certain proportion and added to the reactor. The reaction yields the dehydration reduction agent product.

4. The preparation method of a high-temperature resistant oil well cement fluid loss reducing agent according to claim 3, characterized in that: In step (3), nitrogen gas is introduced into the reactor and heated for 30 minutes until the temperature reaches 60°C.

5. The preparation method of a high-temperature resistant oil well cement fluid loss reducing agent according to claim 3, characterized in that: The reaction time in step (3) in the reactor is 5 to 8 hours.

6. The preparation method of a high-temperature resistant oil well cement fluid loss reducing agent according to claim 3, characterized in that: The mass ratio of deionized water used in steps (1), (2) and (3) is 200-320:100:

10.

7. The high-temperature resistant oil well cement fluid loss reducing agent according to claim 1 can be used for cementing deep and ultra-deep wells.

8. The application according to claim 7, characterized in that: The applicable temperature range for high-temperature resistant oil well cement fluid loss reducing agent in cementing deep and ultra-deep wells is 150–220℃.

9. The application according to claim 7, characterized in that: The water loss reducing agent can form a dense mud cake under the same dosage and different temperature conditions within the temperature range of 150-220℃, with a water loss of less than 30mL.

10. The application according to claim 7, characterized in that: When the high-temperature resistant oil well cement fluid loss reducer is used for cementing applications in deep and ultra-deep wells, the amount of fluid loss reducer added in the cement slurry preparation is 8%.

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