Ultra-high temperature resistant cement slurry system for cementing and preparation method and use thereof

Abstract

An ultra-high temperature resistant cement slurry system comprising cement, an ultra-high temperature strength stabilizer, an ultra-high temperature reinforcing material, a density regulator, an ultra-high temperature suspension stabilizer, a dispersant, a fluid loss additive, a retarder, a defoaming agent and water, wherein the ultra-high temperature suspension stabilizer comprises an ether-based starch, an aluminosilicate and a polyalcohol polymer. The method for preparing the cement slurry system includes dry mixing and wet mixing raw materials homogeneously, respectively, and then homogeneously mixing the dry mix and wet mix to obtain the cement slurry system. The cement slurry system can be used for cementing in deep wells and ultra-deep wells at high and ultra-high temperatures.

Claims

1. An ultra-high temperature resistant cement slurry system for cementing, comprising by weight: 100 parts of cement, 15-50 parts of an ultra-high temperature strength stabilizer, 15-50 parts of an ultra-high temperature reinforcing material, 0-140 parts of a density regulator, 1-6 parts of an ultra-high temperature suspension stabilizer, 0-2 parts of a dispersant, 2-9 parts of a fluid loss additive, 0.1-9 parts of a retarder, 0.1-0.5 part of a defoaming agent, and 40-120 parts of water, wherein the ultra-high temperature suspension stabilizer comprises by weight: 1-3 parts of an ether-based starch, 1-3 parts of an aluminosilicate, and 1-2 parts of a polyalcohol polymer.

2. The ultra-high temperature resistant cement slurry system for cementing according to claim 1, wherein the ether-based starch comprises one or more of carboxymethyl starch, carboxyethyl starch, carboxypropyl starch, carboxyhexyl starch, sulfoethyl starch, and sulfo-2-hydroxypropyl starch.

3. The ultra-high temperature resistant cement slurry system for cementing according to claim 1, wherein the aluminosilicate is a nano-sized aluminosilicate.

4. The ultra-high temperature resistant cement slurry system for cementing according to claim 3, wherein the nano-sized aluminosilicate comprises one or more of nano-sized orthoclase, nano-sized zeolite, nano-sized anorthite, and nano-sized halloysite.

5. The ultra-high temperature resistant cement slurry system for cementing according to claim 1, wherein the polyalcohol polymer comprises one or more of polyvinyl alcohol, polyethylene glycol, and polyethylene oxide.

6. The ultra-high temperature resistant cement slurry system for cementing according to claim 1, wherein the ultra-high temperature reinforcing material comprises one or more of halloysite, mullite and tricalcium phosphate.

7. The ultra-high temperature resistant cement slurry system for cementing according to claim 6, wherein the ultra-high temperature reinforcing material comprises a mixture of halloysite, mullite and tricalcium phosphate in a weight ratio of (1-2):(1-2):(1-2).

8. The ultra-high temperature resistant cement slurry system for cementing according to claim 1, wherein: the ultra-high temperature strength stabilizer comprises quartz sand; the density regulator comprises refined iron mine powder and/or glass microbead; the dispersant comprises an aldehyde-ketone polycondensate-based dispersant and/or a polystyrene sulfonate-based dispersant; the fluid loss additive comprises an acrylamide polymer-based fluid loss additive; the retarder comprises an acrylamide polymer-based retarder and/or a 2-acrylamide-2-methylpropanesulfonic acid polymer-based retarder; and the defoaming agent comprises one or more of an organic ester, polyoxypropylene glycerol ether and polydimethylsiloxane.

9. The ultra-high temperature resistant cement slurry system for cementing according to claim 8, wherein: the ultra-high temperature strength stabilizer comprises high purity acid-washed quartz sand of 100-1500 mesh and/or high purity quartz sand of 100-1500 mesh; the refined iron mine powder has a density of 5.05-7.20 g/cm.sup.3; and the glass microbead has a density of 0.44-0.65 g/cm.sup.3.

10. The ultra-high temperature resistant cement slurry system for cementing according to claim 8, wherein the organic ester comprises tributyl phosphate.

11. The ultra-high temperature resistant cement slurry system for cementing according to claim 1, wherein the cement comprises a class G oil well cement.

12. The ultra-high temperature resistant cement slurry system for cementing according to claim 1, wherein the cement slurry system has a density of 1.35-2.35 g/cm.sup.3, an applicable temperature of 30 C.-240 C., and a density variation of not more than 0.04 g/cm.sup.3 in the applicable temperature range.

13. The ultra-high temperature resistant cement slurry system for cementing according to claim 12, wherein the cement slurry system has an applicable temperature of 200 C.-240 C., and a density variation of not more than 0.04 g/cm.sup.3 in the applicable temperature range.

14. The ultra-high temperature resistant cement slurry system for cementing according to claim 13, wherein the cement slurry system has an applicable temperature of 220 C.-240 C.

15. A method for preparing the ultra-high temperature resistant cement slurry system for cementing according to claim 1, comprising the steps of: (1) homogeneously mixing by weight 100 parts of cement, 15-50 parts of the ultra-high temperature strength stabilizer, 15-50 parts of the ultra-high temperature reinforcing material, 0-140 parts of the density regulator, 1-6 parts of the ultra-high temperature suspension stabilizer, and 0-2 parts of the dispersant, to obtain a dry mix; (2) homogeneously mixing by weight 2-9 parts of the fluid loss additive, 0.1-9 parts of the retarder, 0.1-0.5 part of the defoaming agent and 40-120 parts of water, to obtain a wet mix; and (3) under stirring, uniformly adding the dry mix obtained from step (1) into the wet mix obtained from step (2), and continuing to stir for a period of time, to obtain the ultra-high temperature resistant cement slurry system for cementing.

16. The method for preparing the ultra-high temperature resistant cement slurry system for cementing according to claim 12, wherein in step (3), the dry mix obtained from step (1) is uniformly added into the wet mix obtained from step (2) at a rotational speed of 4,000200 r/min, and then the stirring is continued for 35-50 s at a rotational speed of 12,000500 r/min, to obtain the ultra-high temperature resistant cement slurry system for cementing.

17. A method of using the ultra-high temperature resistant cement slurry system for cementing according to claim 1, comprising the step of applying the slurry system to a deep well, an ultra-deep well, and/or an extra-ultra-deep well at high and/or ultra-high temperatures.

18. The method according to claim 17, wherein the high and/or ultra-high temperatures are 200 C.-240 C., the deep well has a depth of 4,500-6,000 m, the ultra-deep wells has a depth of 6,000-9,000 m, and the extra-ultra-deep wells has a depth of 9,000 m or more.

19. The method according to claim 18, wherein the high and/or ultra-high temperatures are from 220 C. to 240 C.

Description

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(1) In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present disclosure, the technical solution of the present disclosure is hereby described in detail below in conjunction with the following specific examples, which should not be construed as limiting the implementable scope of the present disclosure.

(2) The experiments are carried out in accordance with GB/T 19139-2012 Testing of well cements to evaluate the thickening performance, fluidity, API fluid loss, free water content, settlement stability, and compressive strength of the cement slurry systems prepared by the following Examples and Comparative Examples. The main experimental instruments include: Model 30-60 corrugation stirrer and Model 8240 high temperature and high pressure consistometer, products of CHANDLER: Model HH-420 constant temperature digital water tank, Changzhou YINENG Experimental Instrument Factory.

(3) The oil well cement used during the following experiments is High Sulfate Resistant (HSR) Class G oil well cement, produced by Jiahua Special Cement Co., Ltd. The experimental water was distilled water. The biopolymer-based suspension stabilizer DRK-3S, sulfonated aldehyde-ketone polycondensate-based dispersant DRS-1S, acrylamide polymer-based retarder DRH-2L, acrylamide polymer-based fluid loss additive DRF-2L and organic ester-based defoaming agent DRX-1L in the formulation of the cement slurry system are produced by China Petroleum Corporation Engineering & Technology Research Institute Co., Ltd.

Example 1

(4) This example provided an ultra-high temperature resistant cement slurry system for cementing, comprising by weight: 100 parts of Jiahua class G oil well cement, 50 parts of an ultra-high temperature strength stabilizer (acid-washed quartz sand of 600 mesh with a purity of 97% or more), 20 parts of an ultra-high temperature reinforcing material (a mixture of halloysite, mullite and tricalcium phosphate in a weight ratio of 1:1:1), 3 parts of an ultra-high temperature suspension stabilizer (a mixture of sodium carboxymethyl starch (i.e., carboxymethyl starch), nano-sized halloysite powder and polyethylene glycol in a weight ratio of 1:1:1, wherein the size of the nano-sized halloysite powder is 30-100 nm in diameter and 0.5-1 m in length), 1.2 parts of a dispersant DRS-1S, 4 parts of a fluid loss additive DRF-2L, 3 parts of a retarder DRH-2L, 0.2 part of a defoaming agent DRX-1L, and 58 parts of water.

(5) The ultra-high temperature resistant cement slurry system for cementing in this example was prepared by the following method: (1) the class G oil well cement, the ultra-high temperature strength stabilizer, the ultra-high temperature reinforcing material, the ultra-high temperature suspension stabilizer and the dispersant were homogeneously mixed in the above proportions to obtain a dry mix: (2) the fluid loss additive, the retarder, the defoaming agent and water were homogeneously mixed in the above proportions to obtain a wet mix: (3) the dry mix obtained from step (1) was uniformly added into the wet mix obtained from step (2) at a rotational speed of 4,000200 r/min, and after the dry mix was completely added to the wet mix, the mixing cup was covered with a lid, the rotational speed of the stirrer was adjusted to 12000500 r/min, and stirring was continued for 35 s, to obtain the ultra-high temperature resistant cement slurry system for cementing.

(6) The density of the ultra-high temperature resistant cement slurry system for cementing in this example is 1.90 g/cm.sup.3, and the results of various experiments are shown in Table 1.

Example 2

(7) This examples provided an ultra-high temperature resistant cement slurry system for cementing, comprising by weight: 100 parts of Jiahua class G oil well cement, 30 parts of an ultra-high temperature strength stabilizer (acid-washed quartz sand of 600 mesh with a purity of 97% or more), 20 parts of an ultra-high temperature reinforcing material (a mixture of halloysite, mullite and tricalcium phosphate in a weight ratio of 1:1:1), 35 parts of a density regulator (hollow glass microbead with a density of 0.60 g/cm.sup.3), 4.5 parts of an ultra-high temperature suspension stabilizer (a mixture of sodium carboxymethyl starch, nano-sized halloysite powder and polyethylene glycol in a weight ratio of 1:2:1, wherein the size of the nano-sized halloysite powder is 30-100 nm in diameter and 0.5-1 m in length), 1 part of a dispersant DRS-1S, 6 parts of a fluid loss additive DRF-2L, 4 parts of a retarder DRH-2L, 0.2 part of a defoaming agent DRX-1L, and 115 parts of water.

(8) The ultra-high temperature resistant cement slurry system for cementing in this example was prepared by the following method: (1) the class G oil well cement, the ultra-high temperature strength stabilizer, the ultra-high temperature reinforcing material, the density regulator, the ultra-high temperature suspension stabilizer and the dispersant were homogeneously mixed in the above proportions to obtain a dry mix: (2) the fluid loss additive, the retarder, the defoaming agent and water were homogeneously mixed in the above proportions to obtain a wet mix: (3) the dry mix obtained from step (1) was uniformly added into the wet mix obtained from step (2) at a rotational speed of 4,000200 r/min, and after the dry mix was completely added to the wet mix, the mixing cup was covered with a lid, the rotational speed of the stirrer was adjusted to 12000500 r/min, and stirring was continued for 35 s, to obtain the ultra-high temperature resistant cement slurry system for cementing.

(9) The density of the ultra-high temperature resistant cement slurry system for cementing in this example is 1.35 g/cm.sup.3, and the results of various experiments are shown in Table 1.

Example 3

(10) This examples provided an ultra-high temperature resistant cement slurry system for cementing, comprising by weight: 100 parts of Jiahua class G oil well cement, 50 parts of an ultra-high temperature strength stabilizer (acid-washed quartz sand of 600 mesh with a purity of 97% or more), 20 parts of an ultra-high temperature reinforcing material (a mixture of halloysite, mullite and tricalcium phosphate in a weight ratio of 1:1:1), 4 parts of an ultra-high temperature suspension stabilizer (a mixture of sodium carboxymethyl starch, nano-sized halloysite powder and polyethylene glycol in a weight ratio of 1:2:1, wherein the size of the nano-sized halloysite powder is 30-100 nm in diameter and 0.5-1 m in length), 1.2 parts of a dispersant DRS-1S, 3.2 parts of a fluid loss additive DRF-2L, 3.2 parts of a retarder DRH-2L, 0.2 part of a defoaming agent DRX-1L, and 58 parts of water.

(11) The method for preparing the ultra-high temperature resistant cement slurry system for cementing in this example was the same as that of Example 1.

(12) The density of the ultra-high temperature resistant cement slurry system for cementing in this example is 1.90 g/cm.sup.3, and the results of various experiments are shown in Table 1.

Example 4

(13) This examples provided an ultra-high temperature resistant cement slurry system for cementing, comprising by weight: 100 parts of Jiahua class G oil well cement, 50 parts of an ultra-high temperature strength stabilizer (acid-washed quartz sand of 600 mesh with a purity of 97% or more), 20 parts of an ultra-high temperature reinforcing material (a mixture of halloysite, mullite and tricalcium phosphate in a weight ratio of 1:1:1), 140 parts of a density regulator (iron mine powder with a density of 7.20 g/cm.sup.3), 5.5 parts of an ultra-high temperature suspension stabilizer (a mixture of sodium carboxymethyl starch, nano-sized halloysite powder and polyethylene glycol in a weight ratio of 1:2:1, wherein the size of the nano-sized halloysite powder is 30-100 nm in diameter and 0.5-1 m in length), 1.5 parts of a dispersant DRS-1S, 4.5 parts of a fluid loss additive DRF-2L, 3.5 parts of a retarder DRH-2L, 0.2 part of a defoaming agent DRX-1L, and 96 parts of water.

(14) The method for preparing the ultra-high temperature resistant cement slurry system for cementing in this example was the same as that of Example 2.

(15) The density of the ultra-high temperature resistant cement slurry system for cementing in this example is 2.35 g/cm.sup.3, and the results of various experiments are shown in Table 1.

Example 5

(16) This examples provided an ultra-high temperature resistant cement slurry system for cementing, comprising by weight: 100 parts of Jiahua class G oil well cement, 50 parts of an ultra-high temperature strength stabilizer (acid-washed quartz sand of 600 mesh with a purity of 97% or more), 20 parts of an ultra-high temperature reinforcing material (a mixture of halloysite, mullite and tricalcium phosphate in a weight ratio of 1:1:1), 4.5 parts of an ultra-high temperature suspension stabilizer (a mixture of sodium carboxymethyl starch, nano-sized halloysite powder and polyethylene glycol in a weight ratio of 1:2:1, wherein the size of the nano-sized halloysite powder is 30-100 nm in diameter and 0.5-1 m in length), 1.2 parts of a dispersant DRS-1S, 5.5 parts of a fluid loss additive DRF-2L, 5 parts of a retarder DRH-2L, 0.2 part of a defoaming agent DRX-1L, and 58 parts of water.

(17) The method for preparing the ultra-high temperature resistant cement slurry system for cementing in this example was the same as that of Example 1.

(18) The density of the ultra-high temperature resistant cement slurry system for cementing in this example is 1.90 g/cm.sup.3, and the results of various experiments are shown in Table 1.

Example 6

(19) This examples provided an ultra-high temperature resistant cement slurry composition for cementing, comprising by weight: 100 parts of Jiahua class G oil well cement, 50 parts of an ultra-high temperature strength stabilizer (acid-washed quartz sand of 600 mesh with a purity of 97% or more), 20 parts of an ultra-high temperature reinforcing material (a mixture of halloysite, mullite and tricalcium phosphate in a weight ratio of 1:1:1), 4 parts of an ultra-high temperature suspension stabilizer (a mixture of sodium carboxymethyl starch, nano-sized halloysite powder and polyethylene glycol in a weight ratio of 1:1:1, wherein the size of the nano-sized halloysite powder is 30-100 nm in diameter and 0.5-1 m in length), 1.2 parts of a dispersant DRS-1S, 3.2 parts of a fluid loss additive DRF-2L, 3.2 parts of a retarder DRH-2L, 0.2 part of a defoaming agent DRX-1L, and 58 parts of water.

(20) The method for preparing the ultra-high temperature resistant cement slurry composition for cementing in this example was the same as that of Example 1.

(21) The density of the ultra-high temperature resistant cement slurry composition for cementing in this example is 1.90 g/cm.sup.3, and the results of various experiments are shown in Table 2.

Example 7

(22) This examples provided an ultra-high temperature resistant cement slurry composition for cementing, comprising by weight: 100 parts of Jiahua class G oil well cement, 50 parts of an ultra-high temperature strength stabilizer (acid-washed quartz sand of 600 mesh with a purity of 97% or more), 20 parts of an ultra-high temperature reinforcing material (a mixture of halloysite, mullite and tricalcium phosphate in a weight ratio of 2:2:1), 4 parts of an ultra-high temperature suspension stabilizer (a mixture of sodium carboxymethyl starch, nano-sized halloysite powder and polyethylene glycol in a weight ratio of 1:2:1, wherein the size of the nano-sized halloysite powder is 30-100 nm in diameter and 0.5-1 m in length), 1.2 parts of a dispersant DRS-1S, 3.2 parts of a fluid loss additive DRF-2L, 3.2 parts of a retarder DRH-2L, 0.2 part of a defoaming agent DRX-1L, and 58 parts of water.

(23) The method for preparing the ultra-high temperature resistant cement slurry composition for cementing in this example was the same as that of Example 1.

(24) The density of the ultra-high temperature resistant cement slurry composition for cementing in this example is 1.90 g/cm.sup.3, and the results of various experiments are shown in Table 2.

Example 8

(25) This examples provided an ultra-high temperature resistant cement slurry composition for cementing, comprising by weight: 100 parts of Jiahua class G oil well cement, 50 parts of an ultra-high temperature strength stabilizer (acid-washed quartz sand of 600 mesh with a purity of 97% or more), 20 parts of an ultra-high temperature reinforcing material (a mixture of halloysite, mullite and tricalcium phosphate in a weight ratio of 1:1:1), 4 parts of an ultra-high temperature suspension stabilizer (a mixture of sodium carboxymethyl starch, nano-sized halloysite powder and polyethylene glycol in a weight ratio of 1:2:1, wherein the size of the nano-sized halloysite powder is 30-100 nm in diameter and 0.5-1 m in length), 1.2 parts of a dispersant DRS-1S, 3.2 parts of a fluid loss additive DRF-2L, 3.2 parts of a retarder DRH-2L, 0.2 part of a defoaming agent DRX-1L, and 58 parts of water.

(26) The method for preparing the ultra-high temperature resistant cement slurry composition for cementing in this example was the same as that of Example 1.

(27) The density of the ultra-high temperature resistant cement slurry composition for cementing in this example is 1.90 g/cm.sup.3, and the results of various experiments are shown in Table 2.

Example 9

(28) This examples provided an ultra-high temperature resistant cement slurry composition for cementing, comprising by weight: 100 parts of Jiahua class G oil well cement, 50 parts of an ultra-high temperature strength stabilizer (acid-washed quartz sand of 600 mesh with a purity of 97% or more), 20 parts of an ultra-high temperature reinforcing material (a mixture of halloysite, mullite and tricalcium phosphate in a weight ratio of 2:2:1), 4 parts of an ultra-high temperature suspension stabilizer (a mixture of sodium carboxypropyl starch, nano-sized halloysite powder and polyethylene oxide in a weight ratio of 1:2:1, wherein the size of the nano-sized halloysite powder is 30-100 nm in diameter and 0.5-1 m in length), 1.2 parts of a dispersant DRS-1S, 3.2 parts of a fluid loss additive DRF-2L, 3.2 parts of a retarder DRH-2L, 0.2 part of a defoaming agent DRX-1L, and 58 parts of water.

(29) The method for preparing the ultra-high temperature resistant cement slurry composition for cementing in this example was the same as that of Example 1.

(30) The density of the ultra-high temperature resistant cement slurry composition for cementing in this example is 1.90 g/cm.sup.3, and the results of various experiments are shown in Table 2.

Example 10

(31) This examples provided an ultra-high temperature resistant cement slurry composition for cementing, comprising by weight: 100 parts of Jiahua class G oil well cement, 50 parts of an ultra-high temperature strength stabilizer (acid-washed quartz sand of 600 mesh with a purity of 97% or more), 20 parts of an ultra-high temperature reinforcing material (a mixture of halloysite, mullite and tricalcium phosphate in a weight ratio of 2:2:1), 4 parts of an ultra-high temperature suspension stabilizer (a mixture of carboxyhexyl starch, nano-sized zeolite and polyethylene glycol in a weight ratio of 1:2:1, wherein the size of the nano-sized zeolite is 30-100 nm in particle diameter), 1.2 parts of a dispersant DRS-1S, 3.2 parts of a fluid loss additive DRF-2L, 3.2 parts of a retarder DRH-2L, 0.2 part of a defoaming agent DRX-1L, and 58 parts of water.

(32) The method for preparing the ultra-high temperature resistant cement slurry composition for cementing in this example was the same as that of Example 1.

(33) The density of the ultra-high temperature resistant cement slurry composition for cementing in this example is 1.90 g/cm.sup.3, and the results of various experiments are shown in Table 2.

Example 11

(34) This examples provided an ultra-high temperature resistant cement slurry system for cementing, comprising by weight: 100 parts of Jiahua class G oil well cement, 50 parts of an ultra-high temperature strength stabilizer (acid-washed quartz sand of 600 mesh with a purity of 97% or more), 20 parts of an ultra-high temperature reinforcing material (a mixture of halloysite, mullite and tricalcium phosphate in a weight ratio of 2:2:1), 4 parts of an ultra-high temperature suspension stabilizer (a mixture of sodium carboxymethyl starch, nano-sized zeolite and polyvinyl alcohol in a weight ratio of 1:2:1, wherein the size of the nano-sized zeolite is 30-100 nm in particle diameter), 1.2 parts of a dispersant DRS-1S, 4 parts of a fluid loss additive DRF-2L, 3 parts of a retarder DRH-2L, 0.2 part of a defoaming agent DRX-1L, and 58 parts of water.

(35) The method for preparing the ultra-high temperature resistant cement slurry composition for cementing in this example was the same as that of Example 1.

(36) The density of the ultra-high temperature resistant cement slurry composition for cementing in this example is 1.90 g/cm.sup.3, and the results of various experiments are shown in Table 2.

Comparative Example 1

(37) This comparative example provided a cement slurry system, comprising by weight: 100 parts of Jiahua class G oil well cement, 50 parts of an ultra-high temperature strength stabilizer (acid-washed quartz sand of 600 mesh with a purity of 97% or more), 2.5 parts of a biopolymer-based suspension stabilizer DRK-3S, 1.2 parts of a dispersant DRS-1S, 4 parts of a fluid loss additive DRF-2L, 3 parts of a retarder DRH-2L, 0.2 part of a defoaming agent DRX-1L, and 51 parts of water.

(38) The cement slurry system in this comparative example was prepared by the following method: (1) the class G oil well cement, the ultra-high temperature strength stabilizer, the suspension stabilizer and the dispersant were homogeneously mixed in the above proportions to obtain a dry mix: (2) the fluid loss additive, the retarder, the defoaming agent and water were homogeneously mixed in the above proportions to obtain a wet mix: (3) the dry mix obtained from step (1) was uniformly added into the wet mix obtained from step (2) at a rotational speed of 4,000200 r/min, and after the dry mix was completely added to the wet mix, the mixing cup was covered with a lid, the rotational speed of the stirrer was adjusted to 12000500 r/min, and stirring was continued for 35 s, to obtain the cement slurry system.

(39) The density of the cement slurry system in this comparative example is 1.90 g/cm.sup.3, and the results of various experiments are shown in Table 3.

Comparative Example 2

(40) This comparative example provided a cement slurry system, comprising by weight: 100 parts of Jiahua class G oil well cement, 50 parts of an ultra-high temperature strength stabilizer (acid-washed quartz sand of 600 mesh with a purity of 97% or more), 3 parts of a biopolymer-based suspension stabilizer DRK-3S, 1.2 parts of a dispersant DRS-1S, 4.5 parts of a fluid loss additive DRF-2L, 4 parts of a retarder DRH-2L, 0.2 part of a defoaming agent DRX-1L, and 51 parts of water.

(41) The method for preparing the cement slurry system in this comparative example was the same as that of Comparative Example 1.

(42) The density of the cement slurry system in this comparative example is 1.90 g/cm.sup.3, and the results of various experiments are shown in Table 3.

Comparative Example 3

(43) This comparative example provided a cement slurry system, comprising by weight: 100 parts of Jiahua class G oil well cement, 50 parts of an ultra-high temperature strength stabilizer (acid-washed quartz sand of 600 mesh with a purity of 97% or more), 3.5 parts of a biopolymer-based suspension stabilizer DRK-3S, 1.2 parts of a dispersant DRS-1S, 5.5 parts of a fluid loss additive DRF-2L, 5 parts of a retarder DRH-2L, 0.2 part of a defoaming agent DRX-1L, and 51 parts of water.

(44) The method for preparing the cement slurry system in this comparative example was the same as that of Comparative Example 1.

(45) The density of the cement slurry system in this comparative example is 1.90 g/cm.sup.3, and the results of various experiments are shown in Table 3.

Comparative Example 4

(46) This comparative example provided a cement slurry system, comprising by weight: 100 parts of Jiahua class G oil well cement, 50 parts of an ultra-high temperature strength stabilizer (acid-washed quartz sand of 600 mesh with a purity of 97% or more), 20 parts of an ultra-high temperature reinforcing material (a mixture of halloysite, mullite and tricalcium phosphate in a weight ratio of 1:1:1), 4 parts of a high temperature suspension stabilizer (a mixture of sodium carboxymethyl starch, aluminum sulfate and polyethylene glycol in a weight ratio of 1:2:1), 1.2 parts of a dispersant DRS-1S, 5.5 parts of a fluid loss additive DRF-2L, 5.5 parts of a retarder DRH-2L, 0.2 part of a defoaming agent DRX-1L, and 58 parts of water.

(47) The method for preparing the cement slurry system in this comparative example was the same as that of Comparative Example 1.

(48) The density of the cement slurry system in this comparative example is 1.90 g/cm.sup.3, and the results of various experiments are shown in Table 3.

Comparative Example 5

(49) This comparative example provided a cement slurry system, comprising by weight: 100 parts of Jiahua class G oil well cement, 50 parts of an ultra-high temperature strength stabilizer (acid-washed quartz sand of 600 mesh with a purity of 97% or more), 20 parts of an ultra-high temperature reinforcing material (a mixture of halloysite, mullite and tricalcium phosphate in a weight ratio of 1:1:1), 4.5 parts of a high temperature suspension stabilizer (a mixture of sodium carboxymethyl starch and nano-sized halloysite powder in a weight ratio of 1:2, wherein the size of the nano-sized halloysite powder is 30-100 nm in diameter and 0.5-1 m in length), 1.2 parts of a dispersant DRS-1S, 5.5 parts of a fluid loss additive DRF-2L, 5 parts of a retarder DRH-2L, 0.2 part of a defoaming agent DRX-1L, and 58 parts of water.

(50) The method for preparing the cement slurry system in this comparative example was the same as that of Comparative Example 1.

(51) The density of the cement slurry system in this comparative example is 1.90 g/cm.sup.3, and the results of various experiments are shown in Table 3.

Comparative Example 6

(52) This comparative example provided a cement slurry system, comprising by weight: 100 parts of Jiahua class G oil well cement, 50 parts of an ultra-high temperature strength stabilizer (acid-washed quartz sand of 600 mesh with a purity of 97% or more), 20 parts of a high temperature reinforcing material (metakaolin of 300 mesh), 4.5 parts of a high temperature suspension stabilizer (a mixture of sodium carboxymethyl starch, nano-sized halloysite powder and polyethylene glycol in a weight ratio of 1:2:1, wherein the size of the nano-sized halloysite powder is 30-100 nm in diameter and 0.5-1 m in length), 1.2 parts of a dispersant DRS-1S, 5.5 parts of a fluid loss additive DRF-2L, 5 parts of a retarder DRH-2L, 0.2 part of a defoaming agent DRX-1L, and 58 parts of water.

(53) The method for preparing the cement slurry system in this comparative example was the same as that of Comparative Example 1.

(54) The density of the cement slurry system in this comparative example is 1.90 g/cm.sup.3, and the results of various experiments are shown in Table 3.

(55) TABLE-US-00001 TABLE 1 Items Example 1 Example 2 Example 3 Example 4 Example 5 Density, g/cm.sup.3 1.90 1.35 1.90 2.35 1.90 Fluidity, cm 24 23 24 23 23 API fluid loss, ml 36 46 37 42 38 Free water, % 0 0 0 0 0 Stability (density variation), 0.01 0.02 0.02 0.03 0.03 g/cm.sup.3 Thickening Resting 200 220 220 220 240 properties temperature, C. Cycling 180 200 200 200 220 temperature, C. Thickening time, 227 268 282 274 275 min Thickening linerity normal normal normal normal normal Compressive 7 d compressive 42.5 36.4 40.8 43.6 46.2 strength strength, Mpa 28 d compressive 45.1 37.9 42.3 45.2 48.8 strength, Mpa

(56) TABLE-US-00002 TABLE 2 Example Example Example Example Example Example Items 6 7 8 9 10 11 Density, g/cm.sup.3 1.90 1.90 1.90 1.90 1.90 1.90 Fluidity, cm 24 23 24 23 24 24 API fluid loss, ml 38 36 39 37 38 40 Free water, % 0 0 0 0 0 0 Stability (density variation) g/cm.sup.3 0.04 0.02 0.01 0.03 0.03 0.03 Thickening Resting 220 220 220 220 220 220 properties temperature, C. Cycling 200 200 200 200 200 200 temperature, C. Thickening time, 277 286 291 272 281 298 min Thickening linerity normal normal normal normal normal normal Compressive 7 d compressive 42.5 43.2 41.6 42.7 41.8 41.1 strength strength, Mpa 28 d compressive 45.1 46.2 43.4 45.5 44.3 43.9 strength, Mpa

(57) TABLE-US-00003 TABLE 3 Com- Com- Com- Com- Com- Com- parative parative parative parative parative parative Example Example Example Example Example Example Items 1 2 3 4 5 6 Density, g/cm.sup.3 1.90 1.90 1.90 1.90 1.90 1.90 Fluidity, cm 21 21 20 22 23 18 API fluid loss, ml 36 39 44 39 36 37 Free water, % 0 0.01 0.02 0.01 0.01 0 Stability (density variation) g/cm.sup.3 0.26 0.34 0.40 0.19 0.17 0.03 Thickening Resting 200 220 240 240 240 240 properties temperature, C. Cycling 180 200 220 220 220 220 temperature, C. Thickening time, 209 162 263 275 275 198 min Thickening normal bulging stepping normal normal normal linerity Compressive 7 d compressive 35 30 25 46.20 46.20 34.70 strength strength, Mpa 28 d compressive 29.7 23.3 20.5 48.80 48.80 31.50 strength, Mpa

(58) As can be seen from the data in Table 1, the density of the ultra-high temperature resistant cement slurry system for cementing of the present disclosure is adjustable. For the ultra-high temperature resistant cement slurry systems for cementing of all the Examples, the fluidity is greater than 22 cm, the API fluid loss is less than 50 mL, and the free water content is 0, which meet the requirements for cementing construction. The test of thickening properties indicates that the thickening time of the ultra-high temperature resistant cement slurry systems for cementing of all the Examples of the present disclosure is adjustable, and the thickening curve is normal, with no abnormal phenomena such as bulging. The test of compressive strength of cement stone indicates that as for the cement stone cured from the ultra-high temperature resistant cement slurry system for cementing of all the Examples of the present disclosure, both the conventional density system and the high density system have a 7 d (7 days) compressive strength of more than 40 MPa, and the low density system has a 7 d (7 days) compressive strength of more than 35 MPa.

(59) The difference between the cement slurry system of Example 1 and that of Comparative Example 1 mainly lies in that in Example 1, 2.5 parts of the suspension stabilizer in Comparative Example 1 is replaced with 3 parts of the ultra-high temperature suspension stabilizer, and 20 parts of the ultra-high temperature reinforcing material is added. As can be seen from the comparison of the data in Tables 1 and 3, under the same experimental conditions, the fluidity of the cement slurry system of Comparative Example 1 is 21 cm, and the fluidity of the cement slurry system of Example 1 is 24 cm, indicating that the ultra-high-temperature suspension stabilizer of the present disclosure improves the fluidity of the cement slurry system. The 7 d compressive strength of the cement stone cured from the cement slurry system of Comparative Example 1 is 35 MPa, and the 7 d compressive strength of the cement stone cured from the cement slurry system of Example 1 is 42.5 MPa. The 7 d compressive strength of the cement stone is increased by 21.4%, indicating that the ultra-high temperature reinforcing material of the present disclosure effectively improves the mechanical properties of the cement stone under high temperature.

(60) The difference between the cement slurry system of Example 3 and that of Comparative Example 2 mainly lies in that in Example 3, 3 parts of the suspension stabilizer in Comparative Example 2 is replaced with 4 parts of the ultra-high temperature suspension stabilizer, and 20 parts of the ultra-high temperature reinforcing material is added. Under the same experimental conditions, the cement slurry system of Comparative Example 2 has a thickening curve with bulging, a density variation of 0.34 g/cm.sup.3, and a free water content of 0.01%: the cement slurry system of Example 3 has a normal thickening curve, a density variation of 0.02 g/cm.sup.3, and a free water content of 0. This indicates that the ultra-high temperature suspension stabilizer of the present disclosure effectively solves the problems of abnormal thickening curve, core wrapping and settling of cement slurry; and improves the stability of cement slurry. The 7 d compressive strength of the cement stone cured from the cement slurry system of Comparative Example 2 is 30 MPa, and the 7 d compressive strength of the cement stone cured from the cement slurry system of Example 3 is 40.8 MPa. The 7 d compressive strength of the cement stone is increased by 36%, indicating that the ultra-high temperature reinforcing material of the present disclosure effectively improves the mechanical properties of the cement stone under ultra-high temperature.

(61) Example 2, Example 3, and Example 4 are cement slurry systems with densities of 1.35 g/cm.sup.3, 1.90 g/cm.sup.3, and 2.35 g/cm.sup.3, respectively. The cement stone of Example 2 has a 7 d compressive strength of 36.4 MPa, a density variation of 0.02 g/cm.sup.3, and an API fluid loss of 46 mL. The cement stone of Example 3 has a 7 d compressive strength of 40.8 MPa, a density variation of 0.02 g/cm.sup.3, and an API fluid loss of 37 mL. The cement stone of Example 4 has a 7 d compressive strength of 43.6 MPa, a density variation of 0.03 g/cm.sup.3, and an API fluid loss of 42 mL. Under the same experimental conditions, the compressive strengths are effectively improved compared to that of the cement stone of Comparative Example 2: the density variations are less than or equal to 0.03 g/cm.sup.3: the density is adjustable; and other properties satisfy the performance of ultra-high temperature cementing construction.

(62) The difference between the cement slurry system of Example 5 and that of Comparative Example 3 mainly lies in that in Example 5, 3.5 parts of the suspension stabilizer in Comparative Example 3 is replaced with 4.5 parts of the ultra-high temperature suspension stabilizer, and 20 parts of the ultra-high temperature reinforcing material is added. Under the same experimental conditions, the cement slurry system of Comparative Example 3 has a thickening curve with stepping, a fluidity of 20 cm, a density variation of 0.40 g/cm.sup.3, and a free water content of 0.02%: the cement slurry system of Example 5 has a normal thickening curve, a fluidity of 23 cm, a density variation of 0.03 g/cm.sup.3, and a free water content of 0. This indicates that the ultra-high temperature suspension stabilizer of the present disclosure effectively solves the problem of poor fluidity and stability of the cement slurry system at a high temperature of 240 C.

(63) The difference between the cement slurry system of Example 5 and the cement slurry systems of Comparative Examples 4 and 5 mainly lies in that in Example 5, the specific formulations of the high temperature suspension stabilizers in Comparative Examples 4 and 5 are changed. Under the same experimental conditions, the cement slurry system of Comparative Example 4 has a density variation of 0.19 g/cm.sup.3, and a free water content of 0.01%; the cement slurry system of Comparative Example 5 has a density variation of 0.17 g/cm.sup.3, and a free water content of 0.01%; the cement slurry system of Example 5 has a density variation of 0.03 g/cm.sup.3, and a free water content of 0. This indicates that the problem of poor stability of the cement slurry system at a high temperature of 240 C. can be effectively solved only when the specific composition of the ultra-high temperature suspension stabilizer provided in the present disclosure is used. The difference between the cement slurry system of Example 5 and that of Comparative Example 6 mainly lies in that in Example 5, the ultrahigh-temperature reinforcing material, metakaolin in Comparative Example 6 is replaced with the ultra-high temperature reinforcing material. Under the same experimental conditions, the cement slurry system of Comparative Example 6 is thickened severely and the thickening time is shortened significantly. This is mainly due to the fact that although the metakaolin has an anti-decay effect at high temperature, its compatibility with the system is poor. On the other hand, The ultra-high temperature reinforcing material of the present disclosure has a good compatibility with the cement slurry system and effectively improves the mechanical properties of cement stone at high temperature.

(64) Thus, the ultra-high temperature resistant cement slurry system for cementing provided by the present disclosure has a strong temperature-resistance, a wide applicable range (an applicable temperature of 30 C.-240 C.), and an excellent settlement stability. The cement slurry system has a density of 1.35-2.35 g/cm.sup.3 and a density variation of not more than 0.04 g/cm.sup.3 (preferably not more than 0.03 g/cm.sup.3) when operating at the applicable temperature (particularly at 220 C. to 240 C.): the density is adjustable to meet the requirement on the density of the cement slurry system under different working conditions. Moreover, the cement slurry system of the present disclosure has excellent rheological properties, a small thixotropy, an adjustable thickening time within the applicable temperature range, low initial consistency during thickening, and a short ash time (within 50 s), which avoids the problems of bulging and stepping of the thickening curve. The thickening curve is normal, which solves the problem of poor stability and strength decline of the cement slurry system under the condition of 220 C.-240 C., and the linear relationship between the thickening time and the temperature, density, or the like is good. At the same time, the cement slurry system of the present disclosure can effectively prevent the decline of compressive strength of cement stone at high temperature and make the 28 d compressive strength of cement stone more than 35 MPa. Therefore, the ultra-high temperature resistant cement slurry system for cementing of the present disclosure can guarantee the safety of cementing construction in deep wells, ultra-deep wells and extra-ultra-deep wells under high temperature and ultra-high temperature, ensure the cementing and sealing effect, and improve the cementing quality.