CO2-proof spacer fluid system as well as preparation method and application thereof

Abstract

The invention discloses a CO2-proof spacer fluid system as well as a preparation method and application thereof. The CO2-proof spacer fluid system is mainly prepared by mixing the following components in parts by weight, 1-3 parts of a CO2 pollution preventing agent, 1-4 parts of a flow regulator, 1-3 parts of a suspension stabilizer, 2-4 parts of a flushing agent, 30-300 parts of a weighting agent, 0.5-1 part of a defoaming agent and 90-105 parts of water; wherein the CO2 pollution preventing agent is at least one of micromolecular organic amine, an ether compound and potassium carbonate. In the well cementation construction process, the CO2 prevention type spacer fluid system is added in advance, when drilling fluid containing CO2 invasion is encountered in the well cementation process, organic and inorganic components in the CO2 prevention type spacer fluid system can fully act with free CO2 in the drilling fluid to consume residual CO2, damage of CO2 to mixed fluid is prevented, the rheological property of the mixed fluid is further stabilized, and the well cementation effect is improved. And no negative influence is generated on the effects of other admixtures.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield chemistry, and in particular relates to a CO2-proof isolation fluid system and a preparation method and application thereof. Background Art

[0002] Cementing engineering is a process in drilling engineering and a key project that connects drilling operations and subsequent oil and gas production. In the cementing process, drilling fluid and cementing slurry are two fluids with completely different physical and chemical properties, so most drilling fluids and cement slurries are difficult to be compatible. Once the drilling fluid and cementing slurry come into direct contact, the cement slurry will produce agglomerated flocculent substances, and the slurry will become very viscous, which will lead to problems such as a sharp drop in flow properties. Effectively isolating drilling fluid and cement slurry and alleviating contact contamination between the two is one of the important functions of isolation fluid in cementing operations.

[0003] During the drilling process of the water-based drilling fluid, which is currently the most commonly used in China, it is very easy to be contaminated by CO2 contained in the formation. When the water-based drilling fluid is invaded by CO2, the performance of the drilling fluid will be severely damaged, mainly manifested as: pH value decreases, density decreases, rheological properties deteriorate, etc. After the drilling fluid is contaminated by CO2, it is easy to shorten the cement slurry thickening time after mixing with the spacer fluid and cement slurry used in cementing in different proportions, affecting the safety of cementing construction. In order to ensure the safety of cementing construction, the spacer fluid is required to have good compatibility with both cement slurry and drilling fluid. It is necessary to adjust the CO2-proof performance of the spacer fluid to ensure that the thickening time after mixing the spacer fluid with cement slurry and drilling fluid in different proportions meets the requirements of cementing construction. Therefore, it is of great significance to study a new type of CO2-proof spacer fluid and form a good compatibility system for the safe and efficient exploitation of oil and gas wells and the production life of the adjustment well. Summary of the invention

[0004] The technical problem to be solved by the present invention is that the existing isolation fluid does not have the performance of preventing CO2 pollution, which leads to CO2 contamination of drilling fluid. After the drilling fluid is contaminated by CO2, it is easy to shorten the thickening time of cement slurry after mixing with the isolation fluid and cement slurry used in cementing in different proportions, affecting the safety of cementing construction.

[0005] The first object of the present invention is to provide a CO2-proof isolation fluid system, which is mainly composed of the following components in parts by weight;

[0006] 1-3 parts of anti-CO2 pollution agent, 1-4 parts of flow regulator, 1-3 parts of suspension stabilizer, 2-4 parts of flushing agent, 30-300 parts of weighting agent, 0.5-1 parts of defoaming agent, 90-105 parts of water;

[0007] Wherein, the anti-CO2 pollution agent is at least one of small molecule organic amines, ether compounds and potassium carbonate.

[0008] As a possible design, the anti-CO2 pollution agent is a complex composed of small molecule organic amines, ether compounds and potassium carbonate; wherein the small molecule organic amines account for 60% to 80% of the total mass of the complex, the ether compounds account for 10% to 20% of the total mass of the complex, and potassium carbonate accounts for 10% to 20% of the total mass of the complex.

[0009] As a possible design, the small molecule organic amine is an alcohol amine compound, and the ether compound is polyethylene glycol dimethyl ether.

[0010] As a possible design, the fluidity regulator is at least one of sodium gluconate, ethylenediaminetetraacetic acid and AMPS-type multipolymer.

[0011] As a possible design, the suspension stabilizer is at least one of sodium bentonite, sepiolite and modified starch.

[0012] As a possible design, the flushing agent is at least one of alkylphenol polyvinyl ether, fatty acid methyl ester ethoxylate and secondary alkyl sodium sulfonate.

[0013] As a possible design, the weighting agent is barite powder and / or iron ore powder.

[0014] As a possible design, the defoaming agent is polydimethylsiloxane and / or tributyl phosphate.

[0015] The second object of the present invention is to provide a method for preparing a CO2-proof isolation liquid system, comprising:

[0016] After mixing the water and suspension stabilizer evenly, add the CO2 pollution prevention agent, fluidity regulator, weighting agent and flushing agent and mix evenly, and finally add the defoaming agent and mix evenly.

[0017] Beneficial effects of the present invention:

[0018] The CO2-proof isolation fluid provided by the present invention has good high temperature resistance, compatibility and stability through the synergistic effect of various components. During the cementing construction process, the CO2-proof isolation fluid system is added in advance. When the drilling fluid containing CO2 intrusion is encountered during the cementing process, the organic and inorganic components in the CO2-proof isolation fluid system will fully react with the free CO2 in the drilling fluid to consume the residual CO2, prevent CO2 from damaging the mixed fluid, further stabilize the rheology of the mixed fluid, and will not have a negative impact on the effects of other admixtures. DETAILED DESCRIPTION

[0019] Since the existing isolation fluid does not have the ability to prevent CO2 pollution, CO2 will contaminate the drilling fluid. After the drilling fluid is contaminated by CO2, it is easy to shorten the thickening time of the cement slurry when mixed with the isolation fluid and cement slurry used in cementing in different proportions, affecting the safety of cementing construction.

[0020] The present invention provides a CO2-proof isolation liquid system, which is mainly composed of the following components in parts by weight:

[0021] 1-3 parts of anti-CO2 pollution agent, 1-4 parts of flow regulator, 1-3 parts of suspension stabilizer, 2-4 parts of flushing agent, 30-300 parts of weighting agent, 0.5-1 parts of defoaming agent, 90-105 parts of water;

[0022] Wherein, the anti-CO2 pollution agent is at least one of small molecule organic amines, ether compounds and potassium carbonate.

[0023] Small molecule organic amines are dissolved in water and react with CO2 to generate water-soluble salts to eliminate residual CO2 in the slurry. Ether compounds can effectively isolate and clean the drilling fluid in the wellbore due to their surfactant properties. They are also an excellent organic solvent and have the function of adjusting the overall stability of the isolation fluid, so that the various components of the anti-CO2 pollution agent are compatible with the isolation fluid. Potassium carbonate reacts with CO2 in the downhole environment to generate potassium bicarbonate and dissolves in the slurry, making the slurry slightly alkaline, and has good compatibility with the drilling fluid and cement slurry in contact with its interface, ensuring good flow properties and ensuring construction safety.

[0024] Small molecule organic amines mainly include alcohol amine compounds. Ether compounds mainly include polyethylene glycol dimethyl ether.

[0025] As a possible implementation, the CO2 pollution prevention agent is a compound formed by mixing small molecule organic amine, ether compound and potassium carbonate, wherein the small molecule organic amine accounts for 60% to 80% of the total mass of the compound, the ether compound accounts for 10% to 20% of the total mass of the compound, and the potassium carbonate accounts for 10% to 20% of the total mass of the compound.

[0026] As a possible implementation, the fluidity regulator is at least one of sodium gluconate, ethylenediaminetetraacetic acid and AMPS-based multipolymers. It can quickly react with high-valent metal ions in the slurry to reduce Al 3+ and Fe 3+ The content of metal ions in the mixed slurry can alleviate the contact contamination between drilling fluid and cement slurry.

[0027] As a possible implementation, the suspension stabilizer is at least one of sodium bentonite, sepiolite and modified starch, which can effectively enhance the internal friction and adsorption between particles through hydrogen bonding after hydration reaction, and support and suspend the weighting material particles.

[0028] As a possible implementation, the flushing agent is at least one of alkylphenol polyvinyl ether, fatty acid methyl ester ethoxylate and secondary alkyl sodium sulfonate. By changing the wetting conditions of the casing and well wall surfaces in contact with the cement slurry, it is beneficial to improve the cleaning efficiency of the annulus interface and the cement ring interface bonding quality, enhance the penetration of the isolation fluid to the well wall, and accelerate the decomposition rate of the mud cake on the casing and the well wall.

[0029] As a possible implementation, the weighting agent is barite powder and / or iron ore powder, which can increase the friction force when the isolation fluid flushes the casing and the well wall, thereby improving the cleaning efficiency and displacement capacity.

[0030] As a possible implementation, the defoaming agent is polydimethylsiloxane and / or tributyl phosphate.

[0031] The present invention also provides a method for preparing the aforementioned CO2-proof isolation fluid system, comprising the following steps:

[0032] S1. Mix water and suspension stabilizer and stir evenly until the suspension stabilizer is completely hydrated and evenly distributed in the water. The stirring speed is generally 2000r / min~3000r / min, and the stirring time is generally about 30min;

[0033] S2. Add anti-CO2 pollution agent, flowability regulator, weighting agent and flushing agent to the system obtained in step S1 and stir evenly; stirring can be added while stirring, the stirring speed is generally 2000r / min~3000r / min, and the stirring time is generally 5-10min;

[0034] S3. Add a defoamer to the system obtained in step S2; the defoamer can be added while stirring. The stirring speed is generally 2000r / min to 3000r / min, and the stirring time is generally 1-2min.

[0035] Example 1

[0036] raw material:

[0037] Anti-CO2 pollution agent: triisopropanolamine, polyethylene glycol dimethyl ether and potassium carbonate, mass ratio is 80:10:10;

[0038] Fluidity regulator: sodium gluconate, ethylenediaminetetraacetic acid and 2-acrylamide-2-methylpropanesulfonic acid anionic polymer, mass ratio is 45:5:50;

[0039] Suspension stabilizer: sodium bentonite, sepiolite and modified starch, mass ratio is 25:25:50;

[0040] Flushing agent: alkylphenol polyvinyl ether, fatty acid methyl ester ethoxylate, sodium secondary alkyl sulfonate, mass ratio is 30:30:40;

[0041] Weighting agent: density 4.0g / cm 3 of barite powder;

[0042] Defoaming agent: dimethylsiloxane and tributyl phosphate, mass ratio is 50:50.

[0043] Preparation method:

[0044] According to the weight parts of each component in the anti-CO2 type isolation liquid, 100 weight parts of water and 3 weight parts of suspension stabilizer are added to the agitator, and stirred at a speed of 2000r / min for 30min to make the suspension stabilizer evenly distributed in the water and completely hydrated, and then 2 weight parts of anti-CO2 pollution agent, 4 weight parts of fluidity regulator, 86 weight parts of weighting agent, and 4 weight parts of flushing agent are added in sequence under the stirring state of the agitator at a speed of 2000r / min, and stirred at a speed of 2000r / min for 10min until all materials are evenly distributed in the water. During the stirring process, 1 weight part of defoaming agent is slowly added to prevent the generation of a large number of bubbles, and a density of 1.50g / cm 3 CO2 proof isolation fluid.

[0045] Example 2

[0046] raw material:

[0047] Anti-CO2 pollution agent: triisopropanolamine, polyethylene glycol dimethyl ether and potassium carbonate, mass ratio is 85:10:5;

[0048] Fluidity regulator: sodium gluconate, ethylenediaminetetraacetic acid, 2-acrylamide-2-methylpropanesulfonic acid anionic polymer, mass ratio is 45:5:50;

[0049] Suspension stabilizer: sodium bentonite, sepiolite, modified starch, mass ratio is 25:25:50;

[0050] Flushing agent: alkylphenol polyvinyl ether, fatty acid methyl ester ethoxylate, sodium secondary alkyl sulfonate, mass ratio is 30:30:40;

[0051] Weighting agent: density 4.0g / cm 3 of barite powder;

[0052] Defoaming agent: dimethylsiloxane or tributyl phosphate, mass ratio is 50:50.

[0053] Preparation method:

[0054] According to the weight parts of each component in the anti-CO2 type isolation liquid, 100 weight parts of water and 3 weight parts of suspension stabilizer are added to the agitator, and stirred at a speed of 3000r / min for 30min to make the suspension stabilizer evenly distributed in the water and completely hydrated, and then 2 weight parts of anti-CO2 pollution agent, 4 weight parts of fluidity regulator, 133 weight parts of weighting agent, and 4 weight parts of flushing agent are added in sequence under the stirring state of the agitator at a speed of 3000r / min, and stirred at a speed of 3000r / min for 5min until all materials are evenly distributed in the water. During the stirring process, 1 weight part of defoaming agent is slowly added to prevent the generation of a large number of bubbles, and a density of 1.70g / cm 3 CO2 proof isolation fluid.

[0055] Example 3

[0056] raw material:

[0057] Anti-CO2 pollution agent: triisopropanolamine, polyethylene glycol dimethyl ether and potassium carbonate, mass ratio is 85:5:10;

[0058] Fluidity regulator: sodium gluconate, ethylenediaminetetraacetic acid, 2-acrylamide-2-methylpropanesulfonic acid anionic polymer, mass ratio is 45:5:50;

[0059] Suspension stabilizer: sodium bentonite, sepiolite, modified starch, mass ratio is 25:25:50;

[0060] Flushing agent: alkylphenol polyvinyl ether, fatty acid methyl ester ethoxylate, sodium secondary alkyl sulfonate, mass ratio is 30:30:40;

[0061] Weighting agent: density 4.0g / cm 3 of barite powder;

[0062] Defoaming agent: dimethylsiloxane or tributyl phosphate, mass ratio is 50:50.

[0063] Preparation method:

[0064] According to the weight parts of each component in the anti-CO2 type isolation liquid, 100 weight parts of water and 3 weight parts of suspension stabilizer are added to the agitator, and stirred at a speed of 2500r / min for 30min to make the suspension stabilizer evenly distributed in the water and completely hydrated, and then 2 weight parts of anti-CO2 pollution agent, 4 weight parts of fluidity regulator, 188 weight parts of weighting agent, and 4 weight parts of flushing agent are added in sequence under the stirring state of the agitator at a speed of 2500r / min, and stirred at a speed of 2500r / min for 8min until all materials are evenly distributed in the water. During the stirring process, 1 weight part of defoaming agent is slowly added to prevent the generation of a large number of bubbles, and a density of 1.90g / cm 3CO2 proof isolation fluid.

[0065] Example 4

[0066] raw material:

[0067] Anti-CO2 pollution agent: triisopropanolamine, polyethylene glycol dimethyl ether and potassium carbonate, mass ratio is 90:5:5;

[0068] Fluidity regulator: sodium gluconic acid CO2 pollution prevention agent, ethylenediaminetetraacetic acid, 2-acrylamide-2-methylpropanesulfonic acid anionic polymer, mass ratio is 45:5:50;

[0069] Suspension stabilizer: sodium bentonite, sepiolite, modified starch, mass ratio is 25:25:50;

[0070] Flushing agent: alkylphenol polyvinyl ether, fatty acid methyl ester ethoxylate, sodium secondary alkyl sulfonate, mass ratio is 30:30:40;

[0071] Weighting agent: density 4.0g / cm 3 of barite powder;

[0072] Defoaming agent: dimethylsiloxane or tributyl phosphate, mass ratio is 50:50.

[0073] Preparation method:

[0074] According to the weight parts of each component in the anti-CO2 type isolation liquid, 100 weight parts of water and 3 weight parts of suspension stabilizer are added to the agitator, and stirred at a speed of 2200r / min for 30min to make the suspension stabilizer evenly distributed in the water and completely hydrated, and then 2 weight parts of anti-CO2 pollution agent, 4 weight parts of fluidity regulator, 256 weight parts of weighting agent, and 4 weight parts of flushing agent are added in sequence under the stirring state of the agitator at a speed of 2200r / min, and stirred at a speed of 2200r / min for 8min until all materials are evenly distributed in the water. During the stirring process, 1 weight part of defoaming agent is slowly added to prevent the generation of a large number of bubbles, and a density of 1.50g / cm 3 CO2 proof isolation fluid.

[0075] Comparative Example 1

[0076] The difference from Example 3 is that no CO2 pollution prevention agent is used;

[0077] raw material:

[0078] Fluidity regulator: sodium gluconate, ethylenediaminetetraacetic acid, 2-acrylamide-2-methylpropanesulfonic acid anionic polymer, mass ratio is 45:5:50;

[0079] Suspension stabilizer: sodium bentonite, sepiolite, modified starch, mass ratio is 25:25:50;

[0080] Flushing agent: alkylphenol polyvinyl ether, fatty acid methyl ester ethoxylate, sodium secondary alkyl sulfonate, mass ratio is 30:30:40;

[0081] Weighting agent: density 4.0g / cm 3 of barite powder;

[0082] Defoaming agent: dimethylsiloxane or tributyl phosphate, mass ratio is 50:50.

[0083] Preparation method:

[0084] Add 100 parts by weight of water and 3 parts by weight of suspension stabilizer to the stirrer, stir at a speed of 2500 r / minn for 30 minutes to make the suspension stabilizer evenly distributed in the water and completely hydrated, then add 2 parts by weight of anti-CO2 pollution agent, 4 parts by weight of flow regulator, 186 parts by weight of weighting agent, and 4 parts by weight of flushing agent in sequence under the stirring state of the stirrer at a speed of 2500 r / min, stir at a speed of 2500 r / min for 8 minutes until all materials are evenly distributed in the water, and slowly add 1 part by weight of defoamer during the stirring process to prevent the generation of a large number of bubbles, and obtain a density of 1.90 g / cm 3 Commonly used isolation fluid.

[0085] Performance Test:

[0086] Test Example 1: Isolation Fluid Suspension Stability

[0087] During the suspension stability test, the prepared isolation liquid of each embodiment and comparative example was poured into a standard thickening slurry cup and placed in a high-temperature and high-pressure thickener. The temperature and pressure were increased and cured under experimental conditions (90°C×40MPa×50min, 120°C×55MPa×55min, 150°C×70MPa×60min). After the temperature and pressure reached the set values, the constant temperature and pressure were continued for 120min. Then, the isolation liquid was poured into a measuring cylinder. After standing for 120min, the density difference between the upper and lower portions of the measuring cylinder and the free liquid were measured with a densitometer. The experimental results are shown in Table 1.

[0088] Table 1 Isolation fluid suspension stability test

[0089]

[0090] The experimental results show that within the test temperature range, the CO2-proof isolation liquid prepared by isolation liquid Examples 1 to 4 has good sedimentation stability in different temperature ranges, similar to the comparative example, and the density difference between the upper and lower limits of 120 min is within 0.02 g / cm 3Within the density range, the free liquid is 0. This indicates that the CO2 pollution prevention agent does not affect the sedimentation stability of the isolation liquid under different temperature conditions and different solid phase particle contents.

[0091] Test Example 2: Rheological properties of spacer fluid

[0092] During the rheological property test, the prepared isolation liquids of each embodiment and comparative example were poured into a thickening slurry cup and placed in a viscosifier at normal temperature and pressure. After curing for 30 minutes at 90° C. under normal pressure, the rheological parameters were measured using a six-speed rotary viscometer. The experimental results are shown in Table 2.

[0093] Table 2 Rheological properties test of isolation fluid

[0094]

[0095] The experimental results show that at room temperature and 90° C., the spacer liquids of Examples 1 to 4 and the comparative example all have good flow properties, indicating that the spacer liquid system of the present invention has good rheological properties.

[0096] Test Example 3: Isolation Fluid Compatibility

[0097] During the compatibility test, the isolation fluid was prepared using the methods of Example 3 and Comparative Example 1, and mixed with conventional drilling fluid / CO2-containing drilling fluid and cement slurry in a ratio of 1:2:7, and then a compatibility test was carried out using a high-temperature and high-pressure viscosifier at 120°C×55MPa×55min. The results are shown in Table 3.

[0098] Table 3 Compatibility of spacer fluid

[0099]

[0100] The experimental results show that after the spacer fluid, conventional drilling fluid and cement slurry are mixed in a ratio of 1:2:7, the thickening time of Example 3 and Comparative Example 1 is 240 minutes, which is longer than the thickening time of cement slurry 204 minutes, meeting the on-site cementing requirements; after the spacer fluid, CO2-containing drilling fluid and cement slurry are mixed in a ratio of 1:2:7, the thickening time of Example 3 is 240 minutes, meeting the on-site cementing requirements, while the thickening time of Comparative Example 1 is 67 minutes, which has cementing safety risks. This shows that the spacer fluid system of the present invention has good compatibility with CO2-containing drilling fluid and cement slurry.

[0101] The cement slurry formula is: 600g Jiahua G-grade oil well cement + 3% microsilicon + 4% toughening material + 2.5% fluid loss reducer + 1% retarder + 1% dispersant + 0.5% defoamer + 45% water, and the cement slurry density is 1.90g / cm 3 .

[0102] The conventional drilling fluid formula is: water + 3% organic bentonite + 0.5% viscosity enhancer + 2% fluid loss reducer + 1% wetting agent + 0.5% structural agent + 0.5% CaO + 3% ultrafine calcium carbonate + 61% barite. The drilling fluid density is 1.62g / cm 3 .

[0103] The formula of CO2-containing drilling fluid is: water + 3% organic bentonite + 0.5% viscosity enhancer + 2% fluid loss reducer + 1% wetting agent + 0.5% structural agent + 0.5% CaO + 3% ultrafine calcium carbonate + 0.25% CO2 (dry ice) + 61% barite. The drilling fluid density is 1.62g / cm 3 .

[0104] The spacer liquid formula is prepared according to the method of Example 3 and Comparative Example 1, and the density of the spacer liquid is 1.90 g / cm 3 .

[0105] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A CO2-proof isolation fluid system, characterized in that: It is mainly composed of the following components in parts by weight; 1-3 parts of anti-CO2 pollution agent, 1-4 parts of flow regulator, 1-3 parts of suspension stabilizer, 2-4 parts of flushing agent, 30-300 parts of weighting agent, 0.5-1 parts of defoaming agent, 90-105 parts of water; Wherein, the anti-CO2 pollution agent is at least one of small molecule organic amines, ether compounds and potassium carbonate.

2. The CO2-proof isolation fluid system according to claim 1, characterized in that: The anti-CO2 pollution agent is a complex composed of small molecule organic amine, ether compound and potassium carbonate; wherein the small molecule organic amine accounts for 60% to 80% of the total mass of the complex, the ether compound accounts for 10% to 20% of the total mass of the complex, and potassium carbonate accounts for 10% to 20% of the total mass of the complex.

3. The CO2-proof isolation fluid system according to claim 1 or 2, characterized in that: The small molecule organic amine is an alcohol amine compound, and the ether compound is polyethylene glycol dimethyl ether.

4. The CO2-proof isolation fluid system according to claim 1, characterized in that: The fluidity regulator is at least one of sodium gluconate, ethylenediaminetetraacetic acid and AMPS-based multi-polymer.

5. The CO2-proof isolation fluid system according to claim 1, characterized in that: The suspension stabilizer is at least one of sodium bentonite, sepiolite and modified starch.

6. The CO2-proof isolation fluid system according to claim 1, characterized in that: The flushing agent is at least one of alkylphenol polyvinyl ether, fatty acid methyl ester ethoxylate and secondary alkyl sodium sulfonate.

7. The CO2-proof isolation fluid system according to claim 1, characterized in that: The weighting agent is barite powder and / or iron ore powder.

8. The CO2-proof isolation fluid system according to claim 1, characterized in that: The defoaming agent is polydimethylsiloxane and / or tributyl phosphate.

9. A method for preparing the CO2-proof isolation fluid system according to any one of claims 1 to 8, characterized in that: The preparation method comprises: After mixing the water and suspension stabilizer evenly, add the CO2 pollution prevention agent, fluidity regulator, weighting agent and flushing agent and mix evenly, and finally add the defoaming agent and mix evenly.

10. An application of the CO2-proof isolation fluid system according to any one of claims 1 to 8 in oil field drilling, characterized in that: Used to isolate drilling fluid and cement slurry.

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