Background
In the process of oil exploitation, well cementation is a key link for connecting well drilling and later-stage oil exploitation. In the well cementation process, cement slurry is injected from a ground wellhead, pumped to an annular space between the casing and the stratum through the casing, and forms a cement sheath after being solidified, so that the cement sheath plays a role in supporting and protecting the casing and sealing and isolating oil, gas and water layers.
Currently, the exploration of oil and gas resources is mainly gradually shifted from conventional oil and gas resources which are easy to exploit to deep/ultra-deep layers which are complex and difficult to exploit, the formation conditions are complex, and well cementation is often confronted with the problems that the sealing section is ultra-long, the temperature difference between the top and the bottom of a cement sheath is large, and salt-containing formations, paste salt layers or brine layers are easy to leak and the like. Most natural gas wells face the difficult problem of long-seal-section well cementation operation under the condition of a huge thick salt layer, a paste salt layer or a composite salt layer. The ultra-long sealing section and the large top-bottom temperature difference must require enough cement paste retarder to ensure the injection safety at high temperature. But after returning to the top, the strength of the cement sheath develops slowly at low temperature, and even an over-retarding phenomenon appears. Cl in salt or paste-salt formations-、SO4 2-Can diffuse into a cement sheath, leads to later-stage cement stone corrosion damage and mechanical property reduction, and seriously threatens the long-term sealing integrity of the natural gas well. Therefore, the corrosion resistance and the top strength of the cement ring under the long sealing section of the stratum with the salt layer and the paste-salt layer are ensured to be rapidly developedThe later sealing integrity of the high cement ring is of great significance.
The long sealing section well is generally fixed under the condition of large temperature difference by adopting an early strength agent to improve the strength of cement slurry after returning to the top. At present, the commonly used oil well cement early strength agents are mainly inorganic salts and organic compounds, and related early strength agent patents also mainly adopt different inorganic salt compounding or inorganic salt and organic compound compounding, for example, Chinese patent CN105347716A, a dispersive chlorine-free oil well cement low-temperature early strength agent and cement paste containing the same; chinese patent CN106830744B, an early strength agent for well cementation and a preparation method thereof; chinese patent CN109943303A, a chlorine-free coagulation accelerator early strength agent for oil well cement, a preparation method and application thereof; chinese patent CN109943304A, an oil well cement coagulation accelerator early strength agent and a preparation method and application thereof; chinese patent CN110317589A, early strength agent and preparation method thereof, cement slurry for well cementation; chinese patent CN106746848B, a composite low-density cement early strength agent, a preparation method and application; chinese patent CN104194752A, a low-temperature early strength agent for coal bed gas well cementing and cement slurry for cementing containing the same.
The inorganic salt early strength agent mainly comprises chloride salts, aluminate salts, sulfate salts, lithium salts and nitrate salts, such as calcium chloride, lithium carbonate, sodium silicate, calcium sulfate, sodium nitrate, sodium aluminate and the like; the organic early strength agent comprises formamide, triethanolamine, calcium formate, sodium acetate and the like. However, these early strength agents all have certain disadvantages:
(1) the chloride and sulfate early strength agents can improve the early strength of the set cement, but can cause the corrosion of the set cement and a sleeve, increase the permeability of the set cement, aggravate the damage of a later-stage cement sheath and influence the long-term packing durability of the cement sheath;
(2) the lithium salt early strength agent has high cost and high reaction speed, and releases large amount of heat in a short time, if the heat is not consumed or released in time, microcracks are generated in the cement, so that the later strength is reduced;
(3) after the mixing amount of the inorganic salt early strength agent is larger, the slurry has strong thixotropy and high consistency, and the annular pressure loss is increased and the leakage risk is increased easily caused by cementing in a formation which is easy to leak;
(4) the addition of organic triethanolamine is sensitive when used alone, is extremely small and is not easy to control, and the excessive triethanolamine is easy to generate ultra-retardation;
(5) the addition of calcium formate and sodium acetate easily causes the loss of the later strength of the set cement;
(6) the early strength agent has the coagulation promoting effect, and the thickening time is shortened due to excessive addition, so that the operation safety is influenced; the addition amount is too small to exert the effect, which is also the deficiency of the prior early strength agent.
Disclosure of Invention
The invention aims to provide an oil well cement corrosion-resistant early strength agent suitable for cementing a salt-gypsum layer and a preparation method thereof, which solve the problem that chloride and sulfate early strength agents are easy to corrode and reduce the problems of cement sheath corrosion and later-stage mechanical property reduction caused by the existing early strength agent.
In order to achieve the purpose, the invention provides an oil well cement anticorrosion type early strength agent suitable for salt-gypsum layer cementing, which comprises the following components in parts by weight: 25-40 parts of layered mineral A, 40-50 parts of layered mineral B and 10-40 parts of nano SiO2(ii) a Wherein the lamellar mineral A contains NO between layers3 -(ii) a The interlayer of the layered mineral B contains an organic micromolecule early strength agent.
Preferably, the lamellar mineral a is prepared by the following method: mixing a high-valence metal nitrate more than trivalent and a low-valence metal nitrate less than divalent according to a molar ratio of 2: 1-4: 1 to form a mixed metal nitrate, putting the mixed metal nitrate in water, and adjusting the pH of the solution to 9-12; reacting at 70-90 ℃ in an inert gas atmosphere; after the reaction is finished, carrying out suction filtration, and freeze-drying or drying the solid at 50-70 ℃ to obtain the product containing NO between layers3 -The layered mineral A of (1).
The lamellar mineral B is prepared by the following method: mixing an organic small-molecule early strength agent and the layered mineral A according to the mass ratio of 0.3: 1-0.6: 1, and reacting the mixture in an organic solvent at 60-90 ℃ in an inert gas atmosphere; and after the reaction is finished, carrying out suction filtration, and carrying out freeze drying or drying at 50-70 ℃ on the solid to obtain the layered mineral B containing the organic small-molecule early strength agent between layers.
Preferably, the organic small-molecule early strength agent is selected from triethanolamine and/or triisopropanolamine.
Preferably, the high-valence metal nitrate is selected from Al (NO)3)3·9H2O and/or Fe (NO)3)3·9H2O。
Preferably, the low-valent metal nitrate is selected from Mg (NO)3)2·6H2O、Zn(NO3)2·6H2O、Zn(NO3)2·4H2O and Ca (NO)3)2·4H2And (4) in O.
Preferably, the organic solvent is ethylene glycol or a mixture of ethanol and water.
The invention also aims to provide a preparation method of the oil well cement anti-corrosion early strength agent suitable for cementing a salt-gypsum layer, which comprises the following steps: mixing the layered mineral A, the layered mineral B and the nano SiO2And (3) uniformly mixing to obtain the oil well cement corrosion-resistant early strength agent suitable for salt-gypsum layer cementing.
The preparation method of the layered mineral A comprises the following steps: mixing a high-valence metal nitrate with more than three valence and a low-valence metal nitrate with less than two valence according to a molar ratio of 2: 1-4: 1 to form mixed metal nitrate, adding 15-40 parts by weight of the mixed metal nitrate into 100 parts by weight of water, and adjusting the pH of the solution to 9-12; reacting at 70-90 ℃ in an inert gas atmosphere; after the reaction is finished, carrying out suction filtration, and freeze-drying or drying the solid at 50-70 ℃ to obtain the product containing NO between layers3 -The layered mineral A of (1).
The preparation method of the layered mineral B comprises the following steps: mixing an organic small-molecule early strength agent and the layered mineral A according to the mass ratio of 0.3: 1-0.6: 1, and reacting 15-35 parts by weight of the mixture in 100 parts by weight of an organic solvent at 60-90 ℃ in an inert gas atmosphere; and after the reaction is finished, carrying out suction filtration, and carrying out freeze drying or drying at 50-70 ℃ on the solid to obtain the layered mineral B containing the organic small-molecule early strength agent between layers.
Preferably, the high-valence metal nitrate is selected from Al (NO)3)3·9H2O and/or Fe (NO)3)3·9H2O; the low-valence metal nitrate is selected from Mg (NO)3)2·6H2O、Zn(NO3)2·6H2O、Zn(NO3)2·4H2O and Ca (NO)3)2·4H2And (4) in O.
Preferably, the organic small-molecule early strength agent is selected from triethanolamine and/or triisopropanolamine.
Preferably, the organic solvent is a mixture of ethylene glycol or ethanol and water, and the volume ratio of the ethylene glycol or the ethanol to the water is 1: 1.
The oil well cement corrosion-resistant early strength agent suitable for salt-gypsum layer cementing and the preparation method thereof solve the problem that chloride and sulfate early strength agents are easy to corrode, and have the following advantages:
(1) the oil well cement anticorrosive early strength agent does not contain Cl-、SO4 2-The problems of cement sheath corrosion and later-period mechanical property reduction caused by the early strength agent are fundamentally reduced;
(2) the oil well cement anticorrosive early strength agent utilizes the formation temperature and Cl in a salt-gypsum layer-、SO4 2-NO with early strengthening effect on layered minerals3 -And organic early strength agent molecules are released and replaced, so that the slow release effect of the early strength agent is realized, the environmental response and slow release characteristics avoid the shortening of thickening time caused by the early reaction of the early strength agent, and the contradiction between the long thickening time required by the safety of the injection cement at high temperature and the fast development requirement of the early strength at low temperature is overcome. Meanwhile, Cl which originally has corrosion effect can be replaced by interlayer anions-、SO4 2-Is inserted into the interlayer of the layered mineral to prevent diffusion and migration and reaction with set cement, and reduce Cl-、SO4 2-The ability to corrode set cement;
(3) the oil well cement anticorrosive early strength agent has nanometer level solid phase grains and may be used in producing cementThe crystal nucleus of the growth of the substance increases the compactness of the cement and further reduces Cl-、SO4 2-The diffusion capacity improves the corrosion resistance and the mechanical property of the set cement, and realizes the effect of one agent with multiple effects.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
An oil well cement anticorrosion early strength agent suitable for salt-gypsum layer cementing is prepared by the following steps:
(1) preparation of the layered mineral a:
mixing Al (NO)3)3·9H2O and Mg (NO)3)2·6H2Mixing O in a molar ratio of 3:1 to obtain mixed metal salt, adding 35 parts by weight of the mixed metal salt into a reactor filled with 100 parts by weight of deionized water, rapidly stirring, and adjusting the pH value of the solution to 9 by adopting NaOH. Then, N was introduced into the reactor2(prevention of CO in air)2Dissolved in the solution, carbonized), and reacted at 70 ℃ for 24 hours. After the reaction is finished, cooling the solution to room temperature, washing the solution by deionized water under the condition of suction filtration until the pH of the solution is neutral, and then freeze-drying the prepared solid phase for 24 hours to obtain the product containing NO between layers3 -The layered mineral A of (1).
(2) Preparation of layered mineral B:
mixing triethanolamine and the lamellar mineral A according to the mass ratio of 0.4:1, weighing 20 parts by weight of the mixture, adding the mixture into a reactor filled with 100 parts by weight of mixed solution of glycol and water according to the volume ratio of 1:1, and introducing N2After that, the reaction was stirred rapidly at 90 ℃ for 48 h. After the reaction is finished, cooling the solution to room temperature, washing for 3-5 times by using deionized water under the suction filtration condition, and freeze-drying the prepared solid phase for 24 hours to obtain the productTo obtain the layered mineral B containing triethanolamine between layers.
(3) Preparing an anticorrosive early strength agent:
25 parts of layered mineral A, 50 parts of layered mineral B and 25 parts of nano SiO2And (4) uniformly mixing to obtain the anticorrosive early strength agent.
Example 2
An oil well cement anticorrosion early strength agent suitable for salt-gypsum layer cementing is prepared by the following steps:
(1) preparation of the layered mineral a:
mixing Al (NO)3)3·9H2O and Zn (NO)3)2·6H2Mixing O in a molar ratio of 3:1 to obtain mixed metal salt, adding 30 parts by weight of the mixed metal salt into a reactor filled with 100 parts by weight of deionized water, rapidly stirring, and adjusting the pH value of the solution to 10 by adopting NaOH. Then introducing N into the reactor2The reaction was carried out at 85 ℃ for 15 h. After the reaction is finished, cooling the solution to room temperature, washing the solution by deionized water under the condition of suction filtration until the pH of the solution is neutral, and then freeze-drying the prepared solid phase for 24 hours to obtain the product containing NO between layers3 -The layered mineral A of (1).
(2) Preparation of layered mineral B:
mixing triethanolamine and the lamellar mineral A according to the mass ratio of 0.5:1, weighing 20 parts by weight of the mixture, adding the mixture into a reactor filled with 100 parts by weight of mixed solution of glycol and water according to the volume ratio of 1:1, and introducing N2After that, the reaction was stirred rapidly at 70 ℃ for 30 h. And after the reaction is finished, cooling the solution to room temperature, washing for 3-5 times by using deionized water under the suction filtration condition, and freeze-drying the prepared solid phase for 24 hours to obtain the layered mineral B containing triethanolamine between layers.
(3) Preparing an anticorrosive early strength agent:
32 parts of lamellar mineral A, 48 parts of lamellar mineral B and 20 parts of nano SiO2And (4) uniformly mixing to obtain the anticorrosive early strength agent.
Example 3
An oil well cement anticorrosion early strength agent suitable for salt-gypsum layer cementing is prepared by the following steps:
(1) preparation of the layered mineral a:
mixing Al (NO)3)3·9H2O and Mg (NO)3)2·6H2Mixing O in a molar ratio of 4:1 to obtain mixed metal salt, adding 25 parts by weight of the mixed metal salt into a reactor containing 100 parts by weight of deionized water, rapidly stirring, and adjusting the pH value of the solution to 11 by using NaOH. Then introducing N into the reactor2And reacting at 70 ℃ for 24 h. After the reaction is finished, cooling the solution to room temperature, washing the solution by deionized water under the condition of suction filtration until the pH of the solution is neutral, and then freeze-drying the prepared solid phase for 24 hours to obtain the product containing NO between layers3 -The layered mineral A of (1).
(2) Preparation of layered mineral B:
mixing triethanolamine and the lamellar mineral A according to the mass ratio of 0.35:1, weighing 30 parts by weight of the mixture, adding the mixture into a reactor filled with 100 parts by weight of mixed solution of glycol and water according to the volume ratio of 1:1, and introducing N2After that, the reaction was stirred rapidly at 80 ℃ for 24 h. And after the reaction is finished, cooling the solution to room temperature, washing for 3-5 times by using deionized water under the suction filtration condition, and freeze-drying the prepared solid phase for 24 hours to obtain the layered mineral B containing triethanolamine between layers.
(3) Preparing an anticorrosive early strength agent:
30 parts of a layered mineral A, 45 parts of a layered mineral B and 25 parts of nano SiO2Mixing uniformly to obtain the anti-corrosion early strength agent
Example 4
An oil well cement anticorrosion early strength agent suitable for salt-gypsum layer cementing is prepared by the following steps:
(1) preparation of the layered mineral a:
mixing Al (NO)3)3·9H2O and Ca (NO)3)2·6H2Mixing O in a molar ratio of 3:1 to obtain mixed metal salt, adding 30 parts by weight of the mixed metal salt into a reactor filled with 100 parts by weight of deionized water, rapidly stirring, and adjusting the pH value of the solution to 10 by adopting NaOH. However, the device is not suitable for use in a kitchenThen introducing N into the reactor2And reacting at 80 ℃ for 24 h. After the reaction is finished, cooling the solution to room temperature, washing the solution by deionized water under the condition of suction filtration until the pH of the solution is neutral, and then freeze-drying the prepared solid phase for 24 hours to obtain the product containing NO between layers3 -The layered mineral A of (1).
(2) Preparation of layered mineral B:
mixing triisopropanolamine and the lamellar mineral A according to the mass ratio of 0.55:1, weighing 25 parts by weight of the mixture, adding the mixture into a reactor filled with 100 parts by weight of ethanol and water mixed solution according to the volume ratio of 1:1, and introducing N2After that, the reaction was stirred rapidly at 85 ℃ for 20 h. And after the reaction is finished, cooling the solution to room temperature, washing for 3-5 times by using deionized water under the suction filtration condition, and freeze-drying the prepared solid phase for 24 hours to obtain the layered mineral B containing triisopropanolamine between layers.
(3) Preparing an anticorrosive early strength agent:
35 parts of lamellar mineral A, 45 parts of lamellar mineral B and 20 parts of nano SiO2And (4) uniformly mixing to obtain the anticorrosive early strength agent.
Experimental example 1 Performance test
1. Preparation of cement paste
Setting blank group cement paste, comparison group cement paste and embodiment cement paste, wherein the components of each cement paste are as follows:
the formula of the blank group cement slurry is as follows: 100 parts by weight of JH-G grade oil well cement, 20 parts by weight of silicon powder, 10 parts by weight of micro silicon, a density regulator, 6 parts by weight of a filtrate reducer, 5 parts by weight of a retarder and 1.0 part by weight of a dispersant
The formula of the cement paste of the control group is as follows: 100 parts by weight of JH-G grade oil well cement, 20 parts by weight of silicon powder, 10 parts by weight of micro-silicon, a density regulator and 3 parts by weight of CaCl2+6 parts by weight of fluid loss additive, 5 parts by weight of retarder and 1.0 part by weight of dispersant
The cement paste formula of the embodiment is as follows: 100 parts by weight of JH-G grade oil well cement, 20 parts by weight of silicon powder, 10 parts by weight of micro silicon, a density regulator and 4 parts by weight of anti-corrosive early strength agent, 6 parts by weight of filtrate reducer, 5 parts by weight of retarder and 1.0 part by weight of dispersing agent in the corresponding examples
2. Performance testing
The cement paste thickening time and compressive strength tests of the examples, the control group and the blank group are carried out according to GB/T19139-2012 oil well cement test method; in the corrosion resistance evaluation experiment, the prepared cement stone is preserved for 2 days at 100 ℃ and 20.7MPa in advance, and then is soaked in a medium containing corrosion (containing 5 mass percent of Na)2SO4NaCl with the mass fraction of 5 percent) is continuously maintained at 100 ℃ for 5 days under the condition of 20.7MPa, and then taken out to test the compressive strength; and curing the non-corroded sample at 100 ℃ and 20.7MPa for 7 days, and taking out the non-corroded sample to test the compressive strength.
Table 1 shows the effect of the corrosion-inhibiting early strength agent on the early strength and thickening time of the cement paste
Note: a: thickening time at 150 ℃ and 130 MPa; b: the compressive strength is under the conditions of 100 ℃, 20.7MPa and 24 h; c: the compressive strength is under the conditions of 90 ℃, 20.7MPa and 24 h; d is the compressive strength under the conditions of 80 ℃, 20.7MPa and 24 h;
table 2 shows the results of the experiment of corrosion resistance of the corrosion-resistant early strength agent to cement slurry
Note: compression strength at 100 ℃, 20.7MPa, 7 d.
As can be seen from the table, although the conventional calcium chloride early strength agent can improve the early strength of the cement paste, the effect on the thickening time of the cement paste is great, and the thickening time is shortened by 140-200 min. The corrosion-resistant early strength agent prepared by the invention is doped into cement paste, the thickening time influence is small, and compared with the thickening time in a blank group, the thickening time is shortThe shortening is only about 40 min. After high-temperature prefabrication at 150 ℃, the strength of the cement stone doped with the anticorrosive early strength agent develops rapidly under maintenance at different top temperatures. Meanwhile, compared with a control group sample, after the anti-corrosion early strength agent prepared by the invention is doped into cement slurry and soaked in a corrosive medium, the reduction of the compressive strength is inhibited, the strength reduction rate of 168 hours is only about 10 percent, which is obviously higher than that of the control group, and the set cement resists Cl-、SO4 2-The corrosion capability of the steel is obviously improved.
While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. Various modifications and alterations to this invention will become apparent to those skilled in the art upon reading the foregoing description. Accordingly, the scope of the invention should be determined from the following claims.