阅读说明：本技术 水泥浆组合物、固井用水泥浆及其制备方法与应用 (Cement slurry composition, cement slurry for well cementation and preparation method and application thereof ) 是由 陶谦 杜晓雨 苗霞 曾敏 陆沛青 李小江 于 2019-09-05 设计创作，主要内容包括：本发明提供了一种水泥浆组合物、包括所述水泥浆组合物的固井水泥浆体系及其制备方法。所述水泥浆组合物包括水泥、抗高温弹性材料、抗高温降失水剂、抗高温无机防窜乳液、高温强度稳定剂、加重剂和水。使用该水泥浆体系在高温高压环境以及后期的大型压裂施工过程中形成的水泥环具有较好的弹性性能并且具有良好的抗压强度,可以长久地保持自身完整性,有效地保证了层间密封,降低了页岩气井环空带压风险。(The invention provides a cement slurry composition, a well cementation cement slurry system comprising the cement slurry composition and a preparation method thereof. The cement slurry composition comprises cement, a high-temperature-resistant elastic material, a high-temperature-resistant fluid loss agent, a high-temperature-resistant inorganic anti-channeling emulsion, a high-temperature strength stabilizer, a weighting agent and water. The cement sheath formed in the large-scale fracturing construction process in the high-temperature and high-pressure environment and the later stage by using the cement slurry system has better elastic performance and good compressive strength, can keep self integrity for a long time, effectively ensures interlayer sealing, and reduces the risk of annulus pressure of the shale gas well.)

1. A cement slurry composition comprises cement, a high-temperature resistant elastic material, a high-temperature resistant fluid loss agent, a high-temperature resistant inorganic anti-channeling emulsion, a high-temperature strength stabilizer, a weighting agent and water.

2. The composition of claim 1, further comprising a dispersant, a slurry conditioner, and a retarder.

3. Composition according to claim 1 or 2, characterized in that the high temperature resistant elastic material is between 3 and 10 wt.%, preferably between 4 and 8 wt.%, based on the mass of cement; 4-8 wt% of high temperature resistant fluid loss agent, preferably 4-6 wt%; 5-10 wt% of high-temperature resistant inorganic anti-channeling emulsion; 30-60 wt% of high-temperature strength stabilizer; 60-90 wt% of weighting agent and 55-59 wt% of water; 0.8-1 wt% of dispersant; 0.8-1 wt% of slurry regulator; the retarder is 1-2 wt%.

4. The composition as claimed in any one of claims 1 to 3, wherein the high temperature resistant elastic material is nano-silicon-poly-p-phenylene diamide, preferably nano-silicon-poly-p-phenylene diamide with nano-silicon as a shell and poly-p-phenylene diamide as a core, more preferably the average particle size of the nano-silicon is 100-300nm, and the average particle size of the poly-p-phenylene diamide is 140-180 mesh.

5. Composition according to any one of claims 1 to 4, characterized in that the cement is an oil well cement, preferably a G-grade oil well cement;

and/or the high-temperature-resistant fluid loss agent comprises a 2-acrylamide-2-methylpropanesulfonic acid copolymer;

and/or, the high temperature resistant inorganic anti-channeling emulsion comprises a nano-silica emulsion;

and/or the high-temperature strength stabilizer comprises silicon powder, preferably the silicon powder with the particle size of 60-100 meshes;

and/or the dispersant comprises one or more selected from aldehyde ketone polycondensates and sulfonate salts, preferably comprises aldehyde ketone polycondensates;

and/or, the slurry conditioner comprises sodium silicate;

and/or, the retarder comprises acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer;

and/or the weighting agent comprises one or more of calcium carbonate, barite, iron ore powder and galena powder, preferably the iron ore powder, and more preferably the iron ore powder with the particle size of 100-150 meshes.

6. A cementing cement slurry comprising or prepared from a feedstock comprising a composition according to any one of claims 1 to 5.

7. The cementing cement slurry of claim 6, wherein the cementing cement slurry has a density of 2.0-2.5g/cm³。

8. A method of preparing the cementing slurry of claim 6 or 7, comprising the steps of:

s1: mixing cement, a high-temperature resistant elastic material, a weighting agent and a high-temperature strength stabilizer to obtain large sample ash;

s2: mixing the high-temperature-resistant fluid loss agent, the high-temperature-resistant inorganic anti-channeling emulsion, the dispersing agent, the slurry regulator, the retarder and water to obtain bulk water;

s3: and mixing the large sample ash obtained in the step S1 with the large sample water obtained in the step S2 to obtain the cement slurry for well cementation.

9. The method of claim 8, wherein step S1 is performed before step S25 days.

10. Use of the cementing cement slurry according to claim 6 or 7 or prepared according to the method of claim 8 or 9 for cementing, in particular shale gas cementing.

Technical Field

The invention belongs to the field of shale gas-solid wells, and particularly relates to a cement slurry composition, a cement slurry for well cementation comprising the cement slurry composition, and a preparation method and application thereof.

Background

When the perforation is completed, the cement sheath is subjected to larger impact load, and for the purposes of stabilizing and increasing yield, the production increasing measures such as water injection, fracturing, acidification and the like are carried out in each oil field in sequence, and different operation processes inevitably cause the change of the stress state of the underground casing and the cement sheath. The cement stone formed by the conventional oil well cement paste system is a brittle material, has poor deformation capability and low toughness, easily causes the cement sheath to be damaged, and has cracks or micro annular gaps in the later production or operation process of an oil well, so that the cement sheath loses the sealing capability and influences the later production. Meanwhile, the change of the underground temperature and pressure in the production process can also cause the change of the profit state of the cement sheath, and the cement sheath is easy to damage due to the defects of the conventional set cement to generate cracks and further expand, so that the channeling between underground oil, gas and water layers and the corrosion damage of a casing are caused, and the oil, gas and well are scrapped when the channeling is serious. The existing elastic and flexible cement paste system can effectively improve the brittleness of the set cement, effectively reduce the elastic modulus of the set cement, and simultaneously has larger compressive strength loss of the set cement. The elastic modulus and the compressive strength are in a contradictory relationship, so that the elastic modulus of the cement sheath cannot reach an optimal state. Therefore, there is an urgent need in the art to develop a new elastic-flexible cementing slurry system having higher flexibility without a significant decrease in strength.

Disclosure of Invention

In order to solve the problems in the prior art, on the premise of ensuring that the basic performance of a cement paste system meets the requirements, the invention adds a novel elastic material into the cement paste to provide an elastic and tough cement paste system, enables the corresponding set cement to have lower elastic modulus and enough compressive strength, meets the construction requirements of shale gas-solid wells, and ensures that a cement ring keeps integrity and the sealing capability of the shale gas-solid layer in the later large-scale fracturing construction process.

The invention provides a cement slurry composition, which comprises cement, a high-temperature-resistant elastic material, a high-temperature-resistant fluid loss agent, a high-temperature-resistant inorganic anti-channeling emulsion, a high-temperature strength stabilizer, a weighting agent and water.

According to some embodiments of the invention, the cement slurry composition further comprises a dispersant, a slurry conditioner, and a retarder.

According to some embodiments of the invention, the high temperature resistant elastomeric material is 3-10 wt%, preferably 4-8 wt%, such as 4%, 5%, 6%, 7% and 8% and any value in between, based on the mass of cement.

According to some embodiments of the invention, the high temperature fluid loss additive is 4-8 wt%, preferably 4-6 wt%, such as 4%, 4.5%, 5%, 5.5% and 6% and any value in between, based on the mass of the cement.

According to some embodiments of the present invention, the high temperature resistant inorganic anti-channeling emulsion is 5-10% by weight, such as 5%, 6%, 7%, 8%, 9%, and 10% by mass of the cement and any value therebetween.

According to some embodiments of the invention, the high temperature strength stabilizer is 30-60% by weight, e.g. 30%, 40%, 50% and 60% by mass of the cement and any value in between.

According to some embodiments of the invention, the weighting agent is 60-90% by weight, such as 60%, 70%, 78%, 80%, 85% and 90% by mass of the cement and any value in between.

According to some embodiments of the invention, the water is 55-59% by weight, such as 55%, 56%, 57%, 58% and 59% and any value in between, based on the mass of the cement.

According to some embodiments of the invention, the dispersant is 0.8 to 1 wt%, such as 0.8%, 0.85%, 0.9%, 0.95%, and 1.0% by mass of the cement and any value therebetween.

According to some embodiments of the invention, the slurry conditioner is 0.8-1 wt%, such as 0.8%, 0.85%, 0.9%, 0.95%, and 1.0% by mass of cement and any value therebetween.

According to some embodiments of the invention, the set retarder is 1-2 wt% based on the mass of the cement, such as 1.0%, 1.2%, 1.5%, and 2.0% and any value therebetween.

According to some embodiments of the invention, the high temperature resistant elastic material is 4 to 8 parts, the high temperature resistant fluid loss additive is 4 to 6 parts, the high temperature resistant inorganic anti-channeling emulsion is 5 to 10 parts, the weighting agent is 60 to 90 parts, the high temperature strength stabilizer is 30 to 60 parts, the dispersant is 0.8 to 1 part, the slurry regulator is 0.8 to 1 part, the retarder is 1 to 2 parts, and the water is 55 to 59 parts by 100 parts by mass of the G-grade oil well cement.

According to some embodiments of the invention, the high temperature resistant elastic material is nano silicon-poly terephthalamide.

According to some embodiments of the present invention, the high temperature resistant elastic material is nano silicon-poly-p-phenylene diamide with nano silicon as a shell and poly-p-phenylene diamide as a core.

According to some embodiments of the present invention, the average particle size of the nano-silicon is 100-300nm, and the average particle size of the poly-p-phenylene terephthalamide is 140-180 mesh.

According to some embodiments of the present invention, the nano silicon-poly-p-phenylene diamide composite particles are prepared using a particle composite system encapsulation process technology.

According to some embodiments of the present invention, the method for preparing the nano silicon-poly-p-phenylene diamide composite particles comprises the steps of: adding the poly-p-phenylene diamide particles and the nano-silicon into a mixer of a particle compounding system in proportion, adjusting experimental process parameters of a quantitative metering system to ensure that the nano-silicon and the poly-p-phenylene diamide particles are fully contacted and mixed in a host machine, and finally obtaining powder in a collecting device under the control of a control system to form a core-shell structure of the poly-p-phenylene diamide particles coated by the nano-silicon.

According to some embodiments of the invention, the cement is oil well cement, preferably grade G oil well cement.

According to some embodiments of the invention, the high temperature fluid loss additive comprises a 2-acrylamido-2-methylpropanesulfonic acid copolymer.

According to some embodiments of the present invention, the high temperature fluid loss additive is an AMPS (2-acrylamido-2-methylpropanesulfonic acid) multipolymer, wherein the raw materials for preparing the AMPS multipolymer comprise: 100 parts by mass of water, 40 to 80 parts by mass of 2-acrylamido-2-methylpropanesulfonic acid, 1 to 30 parts by mass of 3-allyloxy-2-hydroxy-1-propanesulfonic acid, 30 to 70 parts by mass of N' N-dimethylacrylamide, 1 to 20 parts by mass of acrylic acid, 1 to 20 parts by mass of acrylonitrile.

In one embodiment, the step of preparing the AMPS multipolymer is as follows: adding 40 to 80 parts by mass of 2-acrylamido-2-methylpropanesulfonic acid, 1 to 30 parts by mass of 3-allyloxy-2-hydroxy-1-propanesulfonic acid, 30 to 70 parts by mass of N' N-dimethylacrylamide, 1 to 20 parts by mass of acrylic acid, and 1 to 20 parts by mass of acrylonitrile to 100 parts by mass of water, stirring to dissolve, then adjusting the pH of the solution to 6 to 7, followed by holding at 60 to 75 ℃ for 1 to 1.5 hours under an inert atmosphere; then adding an initiator under the stirring state, continuously reacting under the stirring state at the temperature of between 60 and 75 ℃, and cooling to room temperature (for example, naturally cooling to 25 +/-5 ℃) to obtain the high-temperature-resistant fluid loss agent; wherein the initiator comprises an oxidizing agent and a reducing agent; the amount of the oxidizing agent is 0.1 to 0.3 part by mass based on 100 parts by mass of the water; the amount of the reducing agent is 0.1 to 0.3 part by mass; the oxidant is ammonium persulfate, and the reducing agent is sodium bisulfite.

According to some embodiments of the invention, the high temperature resistant inorganic anti-channeling emulsion comprises a nanosilica emulsion.

According to some embodiments of the invention, the high temperature strength stabilizer comprises silicon powder, preferably silicon powder having a particle size of 60-100 mesh.

According to some embodiments of the invention, the dispersant comprises one or more selected from the group consisting of aldehyde ketone polycondensates, sulfonates, and preferably comprises aldehyde ketone polycondensates.

According to some embodiments of the invention, the slurry conditioner comprises sodium silicate.

According to some embodiments of the invention, the retarder comprises acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer.

According to some embodiments of the invention, the weighting agent comprises one or more selected from the group consisting of calcium carbonate, barite, iron ore fines, and galena fines.

According to some embodiments of the present invention, the weighting agent is iron ore powder, preferably iron ore powder with a particle size of 100-150 mesh.

The term nano in the present invention means 1 to 1000 nm.

A second aspect of the invention provides a cement slurry for well cementing, the cement slurry comprising the above cement slurry composition or prepared from a raw material comprising the above composition.

According to some embodiments of the invention, the cementing cement slurry has a density of 2.0 to 2.5g/cm³。

The third aspect of the invention provides a preparation method of the cementing fluid cement slurry, which comprises the following steps:

s1: mixing cement, a high-temperature resistant elastic material, a weighting agent and a high-temperature strength stabilizer to obtain large sample ash;

s2: mixing the high-temperature-resistant fluid loss agent, the high-temperature-resistant inorganic anti-channeling emulsion, the dispersing agent, the slurry regulator, the retarder and water to obtain bulk water;

s3: and mixing the large sample ash obtained in the step S1 with the large sample water obtained in the step S2 to obtain the cement slurry for well cementation.

According to some embodiments of the invention, said step S1 is performed prior to step S20-5 days, preferably 5 days.

According to some embodiments of the invention, the large sample ash obtained in step 1) is stored in a closed container for use within 5 days before construction.

The cement paste system has the characteristics of low consumption of high-temperature resistant elastic materials and high-temperature resistant fluid loss additives, and simultaneously has the characteristic of high temperature resistance (such as 130-180 ℃), and in addition, the cement paste system is denseThe adjustable range of the degree is 2.0-2.50g/cm³. The cement stone (which can represent a cement sheath in actual working conditions) prepared under corresponding high-temperature and high-pressure curing has good elastic modulus, can be as low as 4GPa, and can completely meet the requirement that the current deep shale gas well cementing construction scheme is less than 6 GPa. The integrity of the cement sheath can be well guaranteed in the later-stage large-scale fracturing construction process, the purpose of effective interlayer packing is achieved, the annulus pressure risk of the shale gas well is reduced, and the shale gas interlayer packing capacity is guaranteed. The cement paste system also has sufficient compressive strength, for example, the compression strength of the set cement is more than 14MPa/48h, more than 18MPa/7d, and the compression strength at 200 ℃ for 60d is more than 30 MPa.

A large number of indoor experiments verify that the low-elasticity high-strength cement paste system has good rheological property and good sedimentation stability under the high-temperature experiment condition, and the difference of the upper density and the lower density of cement paste meeting the requirements of a construction scheme is less than 0.06g/cm³. Meanwhile, the lowest water loss of the cement paste system is 35mL under the high-pressure high-temperature experimental condition, the water loss is less than 50mL which completely meets the requirements of a construction scheme, and the cement paste system has zero water separation and high fluidity.

According to the field construction reflection, the cold mortar has better rheological property and good pumpability in the mortar stirring process, the field test density is consistent with the design density, and the requirements of field construction are met.

Detailed Description

The invention will now be further illustrated by means of specific examples, but it will be understood that the scope of the invention is not limited thereto.

The present invention is further illustrated by the following examples, which are intended to be purely exemplary of the invention and are not to be construed as limiting the invention in any way.

The starting materials used in the examples are all commercially available unless otherwise specified.

Unless otherwise specified, the high temperature resistant elastic material used in each of the examples and comparative examples of the present invention was SFP-3 available from Texas continental shelf oil engineering technology, Inc., which was nano-sized silicon-poly-p-phenylene diamide particles, and the preparation method thereof included the steps of: adding the poly-p-phenylene diamide particles with the average particle size of 160 meshes and the nano-silicon with the average particle size of 200nm into a mixer of a particle compounding system according to a certain proportion, adjusting experimental process parameters of a quantitative metering system to ensure that the nano-silicon and the poly-p-phenylene diamide particles are fully contacted and mixed in a host, and finally obtaining powder in a collecting device under the control of a control system to form a core-shell structure of the micro-silicon coated poly-p-phenylene diamide particles.

The grade G oil well cement used in the examples and comparative examples of the present invention was a grade Caragana grade G sulfate-resistant oil well cement purchased from Caragana Sichuan cement plants, unless otherwise specified.

Unless otherwise specified, the high temperature resistant inorganic anti-channeling emulsions used in the examples and comparative examples of the present invention were nano-silica emulsions, available from SCLS of continental shelf oil engineering, Inc. of Texas.

Unless otherwise specified, the high temperature fluid loss additives used in the examples and comparative examples of the present invention were AMPS multipolymers available from SCF200L, Dacron, Tex, Petroleum engineering, Inc.

Unless otherwise specified, the retarder used in the examples and comparative examples of the present invention was acrylic acid-2-acrylamido-2-methylpropanesulfonic acid copolymer available from SCR-3 of continental shelf oil engineering, Tex.

Unless otherwise specified, the dispersants used in the examples and comparative examples of the present invention were aldehyde ketone polycondensates available from DZS from continental shelf oil engineering, ltd, texas.

Unless otherwise specified, the slurry conditioner used in the examples and comparative examples of the present invention was sodium silicate, available from H-18 of continental shelf oil engineering, Tex.

Example 1

(1) 100 parts by mass of pure cement of the G-grade oil well, 60 parts by mass of weighting agent, 30 parts by mass of high-temperature strength stabilizer and 4 parts by mass of high-temperature resistant elastic material are dry-mixed and uniformly stirred to form large sample ash which is stored and put in a closed ash can for use.

(2) 4 parts by mass of high-temperature-resistant fluid loss additive, 5 parts by mass of high-temperature-resistant inorganic anti-channeling emulsion, 0.8 part by mass of dispersing agent, 0.8 part by mass of slurry regulator and 1 part by mass of retarder are added into 55 parts by mass of field water, and the mixture is fully circulated to ensure that the additive is completely dissolved and uniformly mixed to form large sample water, so that the construction and use can be carried out.

(3) And pouring the large sample ash into the large sample water, and fully and uniformly stirring to form the high-density cement slurry suitable for shale gas cementing.

The amounts of the components are shown in Table 1.

Example 2

(1) 100 parts by mass of pure cement of the G-grade oil well, 70 parts by mass of weighting agent, 40 parts by mass of high-temperature strength stabilizer and 5 parts by mass of elastic material are dry-mixed and uniformly stirred to form large sample ash which is stored and put in a closed ash tank for use.

(2) Adding 4 parts by mass of fluid loss additive, 6 parts by mass of high-temperature-resistant inorganic anti-channeling emulsion, 1 part by mass of dispersing agent, 0.8 part by mass of slurry regulator and 1.2 parts by mass of retarder into 57 parts by mass of field water, and fully circulating to ensure that the additive is completely dissolved and uniformly mixed to form large sample water, thus being capable of being constructed and used.

(3) And pouring the large sample ash into the large sample water, and fully and uniformly stirring to form the high-density cement slurry suitable for shale gas well cementation.

The amounts of the components are shown in Table 1.

Example 3

(1) 100 parts by mass of pure cement of the G-grade oil well, 78 parts by mass of weighting agent, 50 parts by mass of high-temperature strength stabilizer and 6 parts by mass of elastic material are dry-mixed and uniformly stirred to form large sample ash which is stored and put in a closed ash tank for use.

(2) Adding 5 parts by mass of fluid loss additive, 7 parts by mass of high-temperature-resistant inorganic anti-channeling emulsion, 1 part by mass of dispersing agent, 1 part by mass of slurry regulator and 2 parts by mass of retarder into 59 parts by mass of field water, and fully circulating to ensure that the additive is completely dissolved and uniformly mixed to form large sample water, thus being capable of being constructed and used.

(3) And pouring the large sample ash into the large sample water, and fully and uniformly stirring to form the high-density cement slurry suitable for shale gas cementing.

The amounts of the components are shown in Table 1.

Example 4

(1) 100 parts by mass of pure cement of the G-grade oil well, 85 parts by mass of weighting agent, 60 parts by mass of high-temperature strength stabilizer and 7 parts by mass of elastic material are dry-mixed and uniformly stirred to form large sample ash which is stored and put in a closed ash tank for use.

(2) 6 parts by mass of fluid loss additive, 9 parts by mass of high-temperature-resistant inorganic anti-channeling emulsion, 1 part by mass of dispersant, 0.8 part by mass of slurry regulator and 2 parts by mass of retarder are added into 57 parts by mass of field water, and the mixture is fully circulated to ensure that the additive is completely dissolved and uniformly mixed to form large sample ash, so that the construction and use can be carried out.

(3) And pouring the large sample ash into large sample water, and fully and uniformly stirring to form the high-density cement slurry suitable for shale gas cementing.

The amounts of the components are shown in Table 1.

Example 5

(1) 100 parts by mass of pure cement of the G-grade oil well, 90 parts by mass of weighting agent, 60 parts by mass of high-temperature strength stabilizer and 8 parts by mass of elastic material are dry-mixed and uniformly stirred to form large sample ash which is stored and put in a closed ash tank for use.

(2) 6 parts by mass of fluid loss additive, 10 parts by mass of high-temperature-resistant inorganic anti-channeling emulsion, 1 part by mass of dispersant, 1 part by mass of slurry regulator and 2 parts by mass of retarder are added into 59 parts by mass of field water, and the mixture is fully circulated to ensure that the additive is completely dissolved and uniformly mixed to form large sample water, so that the construction and use can be realized.

(3) And pouring the large sample ash into large sample water, and fully and uniformly stirring to form the high-density cement slurry suitable for shale gas cementing.

The amounts of the components are shown in Table 1.

Example 6

The procedure of example 1 was repeated except that the amount of the fluid loss control agent was 3.5 parts by mass.

The amounts of the components are shown in Table 1.

Example 7

The procedure of example 1 was repeated except that the amount of the fluid loss additive was 6 parts by mass.

The amounts of the components are shown in Table 1.

Example 8

The procedure of example 1 was repeated except that the amount of the fluid loss additive was 8 parts by mass.

The amounts of the components are shown in Table 1.

Example 9

The same procedure as in example 5 was repeated except that the elastic material was added in an amount of 3 parts by mass.

The amounts of the components are shown in Table 1.

Example 10

The same procedure as in example 5 was repeated except that 10 parts by mass of the elastic material was used.

The amounts of the components are shown in Table 1.

Comparative example 1

The same procedure as in example 5 was repeated except that the elastic material was added in an amount of 0 part by mass.

The amounts of the components are shown in Table 1.

TABLE 1

Performance testing

The cement paste systems prepared in examples 1 to 10 and comparative example 1 were subjected to performance tests according to the oil well cement test method (GB19139-2012), and the specific performance results are shown in table 2.

TABLE 2 shale gas cementing low-elasticity high-strength cement slurry system performance

As can be seen from table 2, the shear stress readings of the cement slurries in examples 1 to 10 and comparative example 1 are good, and no reading greater than 300 appears, which indicates that the cement slurries corresponding to the densities have good fluidity and have safe pumping conditions on the construction site; the minimum water loss amount is 28mL under the high-temperature and high-pressure condition, even if the maximum water loss amount is 40mL under the condition of 180 ℃, the maximum water loss amount meets the shale gas well cementation requirement and is less than 50 mL; the cement slurries in examples 1 to 10 and comparative example 1 all meet the requirements of zero water separation, high fluidity and good sedimentation stability.

In the cement paste formula of the embodiment 6, because the addition of the fluid loss reducer is lower than the minimum value of the recommended use amount of the system, the water loss amount of the formed cement paste is 56mL under the high-temperature and pressure test condition, and the water loss amount does not meet the requirement of a shale gas-solid well construction scheme and is less than or equal to 50 mL. The addition of the fluid loss agent in the cement paste formulas of the embodiments 7 and 8 meets the recommended usage amount, and the water loss amount of the cement paste system is well controlled and is far higher than the standard requirement of shale gas-solid well construction.

Examples 9-10 and comparative example 1 each evaluated the effect of different loadings of elastomeric material on the cement slurry system. According to the experimental result, the basic performance of the cement paste system is not obviously influenced by different adding amounts of the elastic material, the recommended adding amount of the elastic material is 4-8 parts by mass, and according to the example 10, the rheological performance of the paste is slightly influenced when the adding amount of the elastic material is higher than the recommended adding amount.

The mechanical properties of the set cements prepared from the cement slurry systems prepared in examples 1 to 10 and comparative example 1 were evaluated according to the oil well cement test method, GB19139-2012, and the results are shown in table 3.

TABLE 3 shale gas cementing low-elasticity high-strength set cement mechanical properties

As can be seen from Table 3, the cement paste systems prepared in examples 1 to 5 all have an elastic modulus of less than 6GPa, which is required by shale gas-solid well construction schemes.

In examples 6 to 8, the amounts of the elastic materials were all 4 parts by mass, and only the amount of the fluid loss additive was changed. The elastic modulus of the cement paste system formed by curing the prepared cement paste system under the high-temperature and high-pressure conditions is less than 6GPa, and the difference is small, which shows that the influence of different addition amounts of the fluid loss additive on the elastic modulus of a cement sheath formed by the cement paste system is small.

The elastic materials in examples 9-10 and comparative example 1 are different in addition, the formed set cement has a larger elastic modulus difference between the examples 9 and comparative example 1, and the elastic modulus difference between the examples 9 and comparative example 1 is mainly caused by the fact that the addition of the elastic materials is lower than the minimum value of the recommended usage amount of the system, so that the elastic modulus of the formed set cement is obviously increased and is higher than 6GPa required by a shale gas-solid well construction scheme, and therefore effective sealing of an annular space cannot be guaranteed in the later fracturing construction process, and the risk of the annular space under pressure is greatly increased.

The cement paste systems in examples 1 to 10 and comparative example 1 form cement stones 3d, 7d and 14d with compressive strength greater than 20MPa, which shows that the addition of the elastic material in the system not only can effectively reduce the elastic modulus of the cement stones, but also has no negative effect on the strength of the cement stones, and achieves the target of low elasticity and high strength

It should be noted that the above-mentioned embodiments are only for explaining the present invention, and do not set any limit to the present invention. The present invention has been described with reference to exemplary embodiments, but the words which have been used herein are words of description and illustration, rather than words of limitation. The invention can be modified, as prescribed, within the scope of the claims and without departing from the scope and spirit of the invention. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, but rather extends to all other methods and applications having the same functionality.