Preparation method of water invasion preventing agent for low density cement slurry used in well cementing

Abstract

The application discloses a preparation method of a low-density cement slurry water invasion preventing agent for well cementation, and belongs to the technical field of well cementation materials for oil and gas wells, and comprises the following steps: a, adding 200 parts of deionized water, then adding silicon-oxygen polyether cellulose, starting stirring, then adding acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and sodium metaaluminate according to the formula amount, adjusting the pH value to 7, and continuously stirring by blowing nitrogen; b, adding an initiator and stirring to react; c, preparing a water invasion preventing main agent; and d, adding the water invasion preventing main agent, hydrated calcium silicate powder, a pozzolanic material, triethanolamine and gypsum into a non-gravity mixing machine according to the formula amount, mixing for 10-15 minutes at a rotating speed of 1500 rpm, and obtaining the low-density cement slurry water invasion preventing agent for well cementation. The low-density cement slurry water invasion preventing agent for well cementation prepared by the application has good water prevention effect and stability, is suitable for a low-density cement slurry system, can effectively prevent water invasion and water channeling of the low-density cement slurry filling in a well cementation section, and effectively improves the well cementation quality.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas well cementing materials, and particularly relates to a preparation method of a low-density cement slurry water invasion preventing agent for well cementing. BACKGROUND

[0002] At present, large platforms and well clusters are densely developed in major oilfields, well spacing is gradually shortened, the formation is easy to channel, drilling, fracturing reconstruction and oil production are simultaneously carried out in the same block, the pressure of the target layer is disordered, and water invasion and water channeling are serious in the annular space during the well cementing waiting-on-cement process, which affects the well cementing quality. The oil reservoir is shallow, the vertical depth of the horizontal well is 1700-2100m, the bottom hole static temperature is less than 75℃, the length of the horizontal section is continuously increasing, the cement slurry strength develops slowly under the conditions of medium-low temperature and long thickening time, and the conventional system cannot meet the well cementing requirements. Under the influence of the domestic stable and increased production tasks, water injection wells cannot be stopped for a long time.

[0003] The existing well cementing water invasion preventing agent is mainly used for conventional density cement slurry systems, most of which use natural high molecular materials to achieve the water prevention effect through physical plugging and chemical bonding. After well cementing construction, the cementing quality of the aquifer is poor, and the existing water invasion preventing agent cannot be applied to low-density cement slurry systems, and it is difficult to meet the well cementing requirements of low-density cement slurry filling in the well cementing section.

[0004] A kind of anti water invasion cement slurry for well cementing in aquifer is disclosed in Chinese patent document with publication number CN114516737A and publication date of May 20, 2022, which comprises, by mass fraction: high anti-sulfate type G-grade oil well cement and external additive material, total 100 parts; G-grade oil well cement: external additive material = 100:0-40:60; polymer fluid loss additive 0.5-5 parts; crosslinking agent 0.5-2.5 parts; delay agent 0.5-5 parts; retarder 0.5-4 parts; dispersant 0.1-1.5 parts; defoamer 0.05-0.1 parts and water 35-50 parts.

[0005] The anti water invasion cement slurry for well cementing in aquifer disclosed in the patent document has good pumping performance, controllable gel time, temperature resistance up to 150℃ or above, simple construction process, and can be applied to well cementing in adjustment wells in old areas and well cementing in deep wells with high-pressure water layers. However, it is not suitable for low-density cement slurry systems, the water prevention effect and stability are not good, and it cannot effectively prevent water invasion and water channeling of low-density cement slurry filling in the well cementing section, affecting the well cementing quality. SUMMARY

[0006] In order to overcome the defects of the above-mentioned prior art, the present application provides a preparation method of a low-density cement slurry water invasion preventing agent for well cementing. The low-density cement slurry water invasion preventing agent prepared by the present application has good water prevention effect and stability, is suitable for low-density cement slurry systems, can effectively prevent water invasion and water channeling of low-density cement slurry filling in the well cementing section, and effectively improves the well cementing quality.

[0007] The present application is realized by the following technical solutions:

[0008] A preparation method of a low-density cement slurry water invasion prevention agent for well cementing, characterized in that the method comprises the following steps:

[0009] a. In a closed enamel reaction kettle, 200 parts of deionized water is added according to the formula amount, then silicon-oxygen polyether cellulose is added, stirring is started, then acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and sodium metaaluminate are added according to the formula amount, sodium hydroxide is added to adjust the pH value to 7, and nitrogen is introduced for continuous stirring;

[0010] b. When the temperature of the closed enamel reaction kettle reaches 50-60 DEG C, an initiator is added according to the formula amount for stirring reaction;

[0011] c. Stopping heating, cooling, drying and powdering are performed to obtain a water invasion prevention main agent;

[0012] d. The water invasion prevention main agent, calcium silicate hydrate powder, pozzolanic material, triethanolamine and gypsum are added to a non-gravity mixer according to the formula amount, mixed for 10-15 minutes at a rotating speed of 1500 rpm to obtain a low-density cement slurry water invasion prevention agent for well cementing.

[0013] In the step a, the weight fraction of the silicon-oxygen polyether cellulose is 50 parts, the weight fraction of the acrylamide is 20 parts, the weight fraction of the 2-acrylamido-2-methylpropanesulfonic acid is 20-30 parts, and the weight fraction of the sodium metaaluminate is 2 parts.

[0014] In the step a, the weight fraction of the sodium hydroxide is 1-6 parts.

[0015] In the step a, the time for continuous stirring by introducing nitrogen is 0.5 h.

[0016] In the step b, the weight fraction of the initiator is 0.3 parts.

[0017] In the step b, the time for stirring reaction by adding the initiator is 2 h.

[0018] In the step d, the weight fraction of the water invasion prevention main agent is 15-25 parts, the weight fraction of the calcium silicate hydrate powder is 45-50 parts, the weight fraction of the pozzolanic material is 22-35 parts, the weight fraction of the triethanolamine is 0.1 parts, and the weight fraction of the gypsum is 2 parts.

[0019] In the step d, the particle size of the calcium silicate hydrate powder is 3-10 μm.

[0020] In the step d, the pozzolanic material is one or more of water-quenched slag, fly ash and steel slag.

[0021] The gypsum in step d is natural dihydrate gypsum.

[0022] The mechanism of the present application is as follows:

[0023] The low-density cement slurry water invasion preventing agent for well cementing is prepared by a free radical water solution polymerization method, a water-soluble hydrophobic association multi-polymer water invasion preventing agent is prepared, intermolecular association is used, supermolecular aggregates are formed in the cement slurry, the cohesion of the components of the cement slurry and the binding capacity to water molecules are improved, and thus the water invasion resistance of the cement slurry is enhanced. The principles of 'crystal nucleus induction' and 'accelerating hydration' are used to reduce the nuclear potential barrier in the cement hydration process, and thus the Gibbs free energy for the nucleation and growth of the cement hydration products is reduced, and the early strength of the cement stone is improved.

[0024] The beneficial effects of the present application mainly include the following aspects:

[0025] 1. In the present application, a, 200 parts of deionized water are added into a closed enamel reaction kettle according to the formula amount, then silicon-oxygen polyether cellulose is added, stirring is started, acrylamide, 2-acrylamido-2-methylpropane sulfonic acid and sodium metaaluminate are added according to the formula amount, sodium hydroxide is added to adjust the pH value to 7, and nitrogen is introduced for continuous stirring; b, when the temperature of the closed enamel reaction kettle reaches 50-60 DEG C, an initiator is added according to the formula amount for stirring reaction; c, the heating is stopped, cooling, drying and powdering are carried out, and the water invasion preventing main agent is prepared; d, the water invasion preventing main agent, calcium silicate hydrate powder, pozzolanic material, triethanolamine and gypsum are added into a non-gravity mixer according to the formula amount, mixed for 10-15 minutes, and the rotation speed is 1500 rpm, and the low-density cement slurry water invasion preventing agent for well cementing is obtained.

[0026] 2. The present application mainly uses the high-molecular copolymer generated by the free radical micellar polymerization reaction as the main agent, and pozzolanic material is added, which has excellent water resistance and stability when added into the low-density cement slurry system, can effectively improve the well cementing quality of the low-density filling section under the dynamic water condition, and prolong the service life of the oil and gas well.

[0027] 3. The present application has the advantages of simple and easy preparation method, low production cost, easy industrial production, wide application prospect and market prospect, and is suitable for different types and specifications of oil and gas well cementing operations.

[0028] 4. The present application solves the problems of slow development of the cement stone strength under medium and low temperature conditions, water invasion and water channeling in high water content oil and gas wells, and has good applicability. BRIEF DESCRIPTION OF DRAWINGS

[0029] The application will be further described in conjunction with the accompanying drawings and specific embodiments of the application:

[0030] Figure 1 The effect of the amount of the cement slurry on the cementing pressure is shown in the following schematic diagram. DETAILED DESCRIPTION

[0031] Embodiment 1

[0032] A preparation method of a low-density cement slurry water invasion prevention agent for well cementing, comprising the following steps:

[0033] a. 200 parts of deionized water is added into a closed porcelain reaction kettle according to the formula amount, then silicon-oxygen polyether cellulose is added, stirring is started, then acrylamide, 2-acrylamido-2-methylpropane sulfonic acid and sodium metaaluminate are added according to the formula amount, sodium hydroxide is added according to the formula amount to adjust the pH value to 7, and nitrogen is introduced for continuous stirring;

[0034] b. When the temperature of the closed porcelain reaction kettle reaches 50℃, an initiator is added according to the formula amount for stirring reaction;

[0035] c. The heating is stopped, and cooling, drying and powdering are performed to obtain the water invasion prevention main agent;

[0036] d. The water invasion prevention main agent, calcium silicate hydrate powder, pozzolanic material, triethanolamine and gypsum are added into a non-gravity mixer according to the formula amount, mixed for 10 minutes at a speed of 1500 rpm, to obtain the low-density cement slurry water invasion prevention agent for well cementing.

[0037] The embodiment is the most basic implementation. Compared with the prior art, the prepared low-density cement slurry water invasion prevention agent for well cementing has good water prevention effect and stability, is suitable for a low-density cement slurry system, can effectively prevent water invasion and water channeling of the low-density cement slurry filling in the cementing section, and effectively improves the cementing quality.

[0038] Embodiment 2

[0039] A preparation method of a low-density cement slurry water invasion prevention agent for well cementing, comprising the following steps:

[0040] a. 200 parts of deionized water is added into a closed porcelain reaction kettle according to the formula amount, then silicon-oxygen polyether cellulose is added, stirring is started, then acrylamide, 2-acrylamido-2-methylpropane sulfonic acid and sodium metaaluminate are added according to the formula amount, sodium hydroxide is added according to the formula amount to adjust the pH value to 7, and nitrogen is introduced for continuous stirring;

[0041] b. When the temperature of the closed porcelain reaction kettle reaches 55℃, an initiator is added according to the formula amount for stirring reaction;

[0042] c. The heating is stopped, and cooling, drying and powdering are performed to obtain the water invasion prevention main agent;

[0043] d. Add the waterproofing agent, hydrated calcium silicate powder, pozzolanic material, triethanolamine and gypsum to a zero-gravity mixer according to the formula and mix for 12 minutes at a speed of 1500 rpm to obtain a low-density cement slurry waterproofing agent for well cementing.

[0044] Preferably, in step a, the weight percentages of the siloxane polyether cellulose are 50 parts, the weight percentages of the acrylamide are 20 parts, the weight percentages of the 2-acrylamido-2-methylpropanesulfonic acid are 20 parts, and the weight percentages of the sodium aluminate are 2 parts.

[0045] In step a, the amount of sodium hydroxide is 1 part by weight.

[0046] In step a, nitrogen gas is introduced and stirring is continued for 0.5 hours.

[0047] In step b, the initiator is 0.3 parts by weight.

[0048] In step b, the initiator is added and the reaction is stirred for 2 hours.

[0049] This embodiment is a preferred implementation method, which mainly uses a polymer copolymer generated by free radical micellar polymerization, supplemented with volcanic materials, and adds it to a low-density cement slurry system. It has excellent waterproof performance and stability, and can effectively improve the cementing quality of low-density filled sections under dynamic water conditions and extend the service life of oil and gas wells.

[0050] Example 3

[0051] A method for preparing a waterproofing agent for low-density cement slurry used in well cementing includes the following steps:

[0052] a. Add 200 parts of deionized water to a sealed enamel-lined reactor according to the formula, then add silicone polyether cellulose, start stirring, then add acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and sodium aluminate according to the formula, add sodium hydroxide according to the formula to adjust the pH value to 7, and continue stirring after purging with nitrogen.

[0053] b. When the temperature of the sealed enamel-lined reactor reaches 55°C, add the initiator according to the formula and stir to react.

[0054] c. Stop heating, cool, dry, and grind into powder to prepare the waterproofing agent;

[0055] d. Add the waterproofing agent, hydrated calcium silicate powder, pozzolanic material, triethanolamine and gypsum to a zero-gravity mixer according to the formula and mix for 15 minutes at a speed of 1500 rpm to obtain a low-density cement slurry waterproofing agent for well cementing.

[0056] In step a, the weight percentages of the siloxane polyether cellulose are 50 parts, the weight percentages of the acrylamide are 20 parts, the weight percentages of the 2-acrylamido-2-methylpropanesulfonic acid are 28 parts, and the weight percentages of the sodium aluminate are 2 parts.

[0057] In step a, the amount of sodium hydroxide is 3 parts by weight.

[0058] In step a, nitrogen gas is introduced and stirring is continued for 0.5 hours.

[0059] In step b, the initiator is 0.3 parts by weight.

[0060] In step b, the initiator is added and the reaction is stirred for 2 hours.

[0061] In step d, the water-resistant agent is 15 parts by weight, the hydrated calcium silicate powder is 45 parts by weight, the volcanic ash material is 22 parts by weight, the triethanolamine is 0.1 parts by weight, and the gypsum is 2 parts by weight.

[0062] In step d, the particle size of the hydrated calcium silicate powder is 3 μm.

[0063] In step d, the pozzolanic material is water-quenched slag and fly ash.

[0064] This embodiment is another preferred implementation method. The preparation method is simple and easy to implement, the production cost is low, it is easy to industrialize, and it is suitable for cementing operations of oil and gas wells of different types and specifications. It has broad application prospects and market prospects.

[0065] Example 4

[0066] A method for preparing a waterproofing agent for low-density cement slurry used in well cementing includes the following steps:

[0067] a. Add 200 parts of deionized water to a sealed enamel-lined reactor according to the formula, then add silicone polyether cellulose, start stirring, then add acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and sodium aluminate according to the formula, add sodium hydroxide according to the formula to adjust the pH value to 7, and continue stirring after purging with nitrogen.

[0068] b. When the temperature of the sealed enamel-lined reactor reaches 60℃, add the initiator according to the formula and stir to react.

[0069] c. Stop heating, cool, dry, and grind into powder to prepare the waterproofing agent;

[0070] d. Add the waterproofing agent, hydrated calcium silicate powder, pozzolanic material, triethanolamine and gypsum to a zero-gravity mixer according to the formula and mix for 15 minutes at a speed of 1500 rpm to obtain a low-density cement slurry waterproofing agent for well cementing.

[0071] In step a, the weight percentages of the siloxane polyether cellulose are 50 parts, the weight percentages of the acrylamide are 20 parts, the weight percentages of the 2-acrylamido-2-methylpropanesulfonic acid are 30 parts, and the weight percentages of the sodium aluminate are 2 parts.

[0072] In step a, the amount of sodium hydroxide is 6 parts by weight.

[0073] In step a, nitrogen gas is introduced and stirring is continued for 0.5 hours.

[0074] In step b, the initiator is 0.3 parts by weight.

[0075] In step b, the initiator is added and the reaction is stirred for 2 hours.

[0076] More preferably, in step d, the water-resistant agent comprises 25 parts by weight, the hydrated calcium silicate powder comprises 50 parts by weight, the volcanic ash material comprises 35 parts by weight, the triethanolamine comprises 0.1 parts by weight, and the gypsum comprises 2 parts by weight.

[0077] In step d, the hydrated calcium silicate powder has a particle size of 10 μm.

[0078] In step d, the pozzolanic material is water-quenched slag, fly ash, and steel slag.

[0079] In step d, the gypsum is natural dihydrate gypsum.

[0080] This embodiment is the best implementation method, which solves the problems of slow strength development of cement stone under medium and low temperature conditions and water intrusion and water channeling in high water-content oil and gas wells, and has good applicability.

[0081] The invention will now be illustrated with specific examples:

[0082] Specific example 1:

[0083] For each 100g portion, first weigh out 15g of waterproofing agent, 50g of hydrated calcium silicate powder, 33.9g of volcanic ash material, 0.1g of triethanolamine, and 2g of gypsum. Mix them in the above proportions using a zero-gravity mixer for 15 minutes at a speed of 1500rpm to obtain a low-density cement slurry waterproofing agent for well cementing, which is designated as sample #1.

[0084] Specific example 2:

[0085] For each 100g portion, first weigh out 20g of waterproofing agent, 45g of hydrated calcium silicate powder, 32.9g of volcanic ash material, 0.1g of triethanolamine, and 2g of gypsum. Mix them in the above proportions using a zero-gravity mixer for 15 minutes at a speed of 1500rpm to obtain a low-density cement slurry waterproofing agent for well cementing, which is designated as sample #2.

[0086] Specific example 3:

[0087] For each 100g portion, first weigh out 25g of waterproofing agent, 50g of hydrated calcium silicate powder, 22.9g of volcanic ash material, 0.1g of triethanolamine, and 2g of gypsum. Mix them in the above proportions using a zero-gravity mixer for 15 minutes at a speed of 1500rpm to obtain a low-density cement slurry waterproofing agent for well cementing, which is designated as sample #3.

[0088] Test 1:

[0089] In an exemplary embodiment of the present invention, the water is drinking water for the well site, the low-density formula is 65% oil well cement + 25% lightening agent + 10% microsilica, the water-cement ratio is 1.05, and the cement slurry density is 1.35 g / cm³. 3 The process of formation water intruding into annular cement slurry under a certain pressure was simulated using a water intrusion simulation tester. The channeling pressure reflects the water intrusion resistance of the annular cement slurry and characterizes its anti-channeling ability. A water intrusion pressure of 3.5 MPa was used as the water intrusion pressure in the water channeling simulation tester. For the effect of dosage on the channeling pressure of cement slurry, please refer to [reference needed]. Figure 1 .

[0090] When the dosage of samples 1, 2, and 3 is 0%, the cement slurry leakage pressure is 0. When the dosage of samples 1, 2, and 3 is 1%, the leakage pressure of sample 3 reaches a maximum of 4.5 MPa, while that of sample 1 is 3 MPa. When the dosage of samples 1, 2, and 3 is 4%, the leakage pressure of sample 3 reaches a maximum of 7.8 MPa, while that of sample 1 is 6.2 MPa. The experiment shows that the low-density cement slurry water-resistant agent for cementing enhances the water-resistant ability of the cement slurry and improves its water-resistant leakage performance; the higher the dosage, the better the water-resistant leakage performance.

[0091] Test 2:

[0092] Cement grout formula used:

[0093] Formula 1: 65% oil well cement + 25% lightweighting agent + 10% microsilica, water-cement ratio 1.05, cement paste density 1.35 g / cm³ 3 .

[0094] Formula 2: 65% oil well cement + 25% lightweight agent + 10% microsilica + 3% waterproofing agent for low-density cement slurry used in cementing, with a water-cement ratio of 1.05 and a cement slurry density of 1.35 g / cm³. 3.

[0095] Cement slurry obtained using Formula 1 with the same dosage was recorded as blank cement slurry; cement slurry obtained using Formula 2 with added samples #1, #2, and #3 was recorded as #1 cement slurry, #2 cement slurry, and #3 cement slurry, respectively, with a dosage of 1.35 g / cm³. 3 For the performance of the low-density waterproof cement grout system, please refer to Table 1 below.

[0096] Table 1

[0097]

[0098] As shown in Table 1, the performance evaluation results of the cement slurry show that the waterproof low-density cement slurry has good engineering performance. The cement slurry becomes slightly thicker, but within a controllable range. After adding the waterproof agent for cementing low-density cement slurry, the strength of the cement stone is significantly improved under low-temperature conditions. Overall, the waterproof agent low-density cement slurry system has no impact on normal cementing operations.

[0099] In the specific examples 1-3 above, the stirrer is the CHANDLER3260 constant speed stirrer from CHANDLER Corporation of the United States, the digital display liquid density meter is the YMS1-5 digital display density meter produced by Qingdao Haitongda Special Instrument Factory, the high temperature curing chamber is the OWC-118 high temperature curing chamber from the Applied Technology Research Institute of Shenyang Aerospace University, and the pressure testing machine is the WHY-300 / 10 microcomputer fully automatic control pressure testing machine from Shanghai Hualong Testing Instrument Co., Ltd.

Claims

1. A method for preparing a waterproofing agent for low-density cement slurry used in well cementing, characterized in that, Includes the following steps: a. Add 200 parts of deionized water to a sealed enamel-lined reactor according to the formula, then add silicone polyether cellulose, start stirring, then add acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and sodium aluminate according to the formula, add sodium hydroxide according to the formula to adjust the pH value to 7, and continue stirring after purging with nitrogen. b. When the temperature of the sealed enamel-lined reactor reaches 50℃-60℃, add the initiator according to the formula and stir to react. c. Stop heating, cool, dry, and grind into powder to prepare the waterproofing agent; d. Add the waterproofing agent, hydrated calcium silicate powder, pozzolanic material, triethanolamine and gypsum to a zero-gravity mixer according to the formula and mix for 10-15 minutes at a speed of 1500 rpm to obtain a low-density cement slurry waterproofing agent for well cementing. In step a, the weight percentage of siloxane polyether cellulose is 50 parts, the weight percentage of acrylamide is 20 parts, the weight percentage of 2-acrylamido-2-methylpropanesulfonic acid is 20-30 parts, and the weight percentage of sodium aluminate is 2 parts. In step d, the water-resistant main agent is 15-25 parts by weight, the hydrated calcium silicate powder is 45-50 parts by weight, the volcanic ash material is 22-35 parts by weight, the triethanolamine is 0.1 parts by weight, and the gypsum is 2 parts by weight.

2. The method for preparing a waterproofing agent for low-density cement slurry used in cementing according to claim 1, characterized in that: In step a, the amount of sodium hydroxide is 1-6 parts by weight.

3. The method for preparing a waterproofing agent for low-density cement slurry used in cementing according to claim 1, characterized in that: In step a, nitrogen gas is introduced and stirring is continued for 0.5 hours.

4. The method for preparing a waterproofing agent for low-density cement slurry used in cementing according to claim 1, characterized in that: In step b, the initiator is 0.3 parts by weight.

5. The method for preparing a waterproofing agent for low-density cement slurry used in cementing according to claim 1, characterized in that: In step b, the initiator is added and the reaction is stirred for 2 hours.

6. The method for preparing a waterproofing agent for low-density cement slurry used in cementing according to claim 1, characterized in that: In step d, the particle size of the hydrated calcium silicate powder is 3-10 μm.

7. The method for preparing a waterproofing agent for low-density cement slurry used in cementing according to claim 1, characterized in that: In step d, the pozzolanic material is one or more of water-quenched slag, fly ash, and steel slag.

8. The method for preparing a waterproofing agent for low-density cement slurry used in cementing according to claim 1, characterized in that: In step d, the gypsum is natural dihydrate gypsum.

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