阅读说明：本技术 油井管柱防腐牺牲阳极合金、组分设计方法、制备方法及应用 (Oil well pipe column anticorrosion sacrificial anode alloy, component design method, preparation method and application ) 是由 李健 李天太 张明 杨玲 于 2020-05-28 设计创作，主要内容包括：本发明属于油田井下钢质管柱防腐的牺牲阳极合金技术领域,具体公开一种用于油井管柱防腐的牺牲阳极合金材料,由以下组分制成：铝、锌、铟、锡、镁、钛、硼和稀土元素铈。本发明提供的用于油井管柱防腐的牺牲阳极合金材料,改善了合金组织和电化学性能,在模拟中国西部油田高温、高矿化度地层水中,具有较负的工作电位和较高的电流效率,活化性能好,工作电位稳定,溶解均匀,腐蚀产物容易脱落,可应用于井下钢质管柱防腐。(The invention belongs to the technical field of sacrificial anode alloy for corrosion prevention of steel pipe columns in oil fields, and particularly discloses a sacrificial anode alloy material for corrosion prevention of oil well pipe columns, which is prepared from the following components in parts by weight: aluminum, zinc, indium, tin, magnesium, titanium, boron and the rare earth element cerium. The sacrificial anode alloy material for oil well pipe column corrosion prevention provided by the invention improves alloy structure and electrochemical performance, has relatively negative working potential and relatively high current efficiency in simulated high-temperature and high-salinity stratum water of western oil fields in China, has good activation performance, stable working potential and uniform dissolution, is easy for corrosion products to fall off, and can be applied to corrosion prevention of underground steel pipe columns.)

1. The oil well pipe column anticorrosion sacrificial anode alloy is characterized by comprising the following components in percentage by mass: 2.2 to 5.2 percent of zinc, 0.01 to 0.05 percent of indium, 0.02 to 0.05 percent of tin, 0.5 to 2.0 percent of magnesium, 0.01 to 0.05 percent of titanium, 0.02 to 0.04 percent of boron, 0.01 to 0.05 percent of cerium and the balance of aluminum.

2. The method for designing the components of the oil well pipe string anticorrosion sacrificial anode alloy as claimed in claim 1, wherein the components of the sacrificial anode alloy are screened and designed by using a molecular dynamics and density functional theory method, an interface between the alloy and an aqueous solution is modeled, and the components of the sacrificial anode alloy are screened and designed according to chemical affinity and change rules between the aqueous solution and different alloy components.

3. The method for designing the components of the oil well pipe string anticorrosion sacrificial anode alloy as claimed in claim 2, is characterized by comprising the following steps:

a. Establishing a series of aluminum alloy bulk phase models with different alloy element types and different alloy element contents and surface models thereof by using a molecular dynamics and density functional theory simulation calculation method;

Selecting a COMPASS force field and GGA-PBE (gas-insulated Gate Bipolar translator) super-soft pseudopotential based on a plane wave substrate, and optimizing an aluminum alloy bulk model and a surface model thereof by using a virtual crystal approximation method;

b. Establishing a water solution model of water molecules and various anions and cations by using a molecular dynamics and density functional theory simulation calculation method, further establishing an interface model between the water solution and the surface of the aluminum alloy, and inspecting the interface combination tendency between the water solution and the surface of the aluminum alloy;

c. Comparing the molecular dynamics and density functional theory simulation calculation results of the interface model between the aluminum alloy surface and the aqueous solution, wherein the aluminum alloy surface and the aqueous solution have different alloy element types and different alloy element contents, and screening out a series of target alloy components;

d. Based on the target components obtained by screening through theoretical simulation calculation, the final components of the aluminum-based sacrificial anode alloy are selected.

4. The method of designing the composition of the oil well pipe string corrosion protection sacrificial anode alloy as claimed in claim 3, wherein the cation is sodium ion, potassium ion or magnesium ion.

5. The method for designing the composition of the oil well pipe string corrosion protection sacrificial anode alloy according to claim 3 or 4, wherein the anion is chloride ion or sulfate ion.

6. The method for preparing the oil well pipe column anticorrosive sacrificial anode alloy according to claim 1, characterized in that industrial pure metals or intermediate alloys of aluminum, zinc, indium, tin, magnesium, titanium, boron and cerium are selected for proportioning, and mixed smelting is carried out by an induction heating mode under the protection of inert gas; and after complete melting, heating to 720-750 ℃, preserving heat for 10min, removing slag, and pouring and quickly cooling in a graphite casting mold to obtain the sacrificial anode alloy material.

7. Use of the oil well string corrosion protection sacrificial anode alloy of claim 1 in the cathodic protection of oil well down-hole string corrosion in high temperature, highly mineralized formation water.

Technical Field

The invention belongs to the technical field of sacrificial anode alloy for corrosion prevention of steel pipe columns in oil fields, and particularly relates to a sacrificial anode alloy material suitable for corrosion prevention of oil well pipe columns in high-temperature and high-salinity stratum water, and a component design method, a preparation method and application thereof.

Background

In the production process of an oil and gas field, an underground steel pipe column is in direct contact with high-temperature and high-salinity stratum water, in order to further improve the recovery efficiency, technological measures such as water-drive oil extraction, acid fracturing and the like are common yield increasing modes in the middle and later periods of oil well exploitation, and the corrosion of the underground pipe column is a serious problem frequently occurring in oil and gas field engineering. In order to ensure the safe production of oil exploitation, cost reduction and efficiency improvement, a certain anticorrosion measure is generally adopted at the same time, wherein cathodic protection is a common anticorrosion technology, and the method has a good protection effect on the corrosion of a steel pipe column.

There are two main methods for cathodic protection of steel components: one is an external power supply method; the other is a sacrificial anode method. The basic principle of the sacrificial anode method is as follows: and selecting a metal with more negative potential than the steel component as a sacrificial anode, establishing electrical connection between the protected component and the sacrificial anode, wherein the sacrificial anode is subjected to corrosion dissolution, and the protected component exists as a cathode, so that the protected component is prevented from being corroded.

Particularly, the sacrificial anode material for corrosion prevention of the steel pipe column In the well of the oil and gas field is mainly an aluminum-based sacrificial anode material which mainly comprises an Al-Zn-In system, an Al-Zn-Mg system and an Al-Zn-Sn system, and In addition, the sacrificial anode material also has related researches on other alloy systems (such as an Al-Zn-Ga system). Wherein, the Al-Zn-In alloy has better comprehensive performance without heat treatment, and is the most widely applied aluminum alloy sacrificial anode material at present.

China has already established a national standard aluminum-zinc-indium series alloy sacrificial anode (GB/T4948-2002), which mainly covers two types and five specific Al-Zn-In series sacrificial anode materials. But the standard is mainly suitable for corrosion prevention of steel members of ships, harbor work or ocean engineering facilities and the like in seawater media. Although the petroleum industry also references the use of the sacrificial anode, because the underground formation water is different from seawater, the temperature, the ion type, the content and the like are obviously different, and the novel Al-Zn-In sacrificial anode alloy is generally researched and designed by adjusting or adding alloy components and ingredients on the basis of the alloy listed In the standard.

Compared with a seawater medium corrosion environment, the working condition of the underground steel pipe column of the oil-gas field is high-temperature, high-pressure and high-salinity produced water, reinjection water or acidizing fracturing fluid. The aluminum-based sacrificial anode alloy used conventionally is easy to cause uneven anode dissolution and serious intergranular corrosion under the conditions; due to the influence of the extreme conditions such as high temperature and hypersalinity, the sacrificial anode alloy tends to be dissolved at a high rate in the initial stage, and corrosion products cannot be effectively dispersed and peeled off from the surface in time, so that severe polarization is easily caused after the sacrificial anode alloy is in service for a period of time, the current efficiency of the sacrificial anode alloy is reduced, the potential is shifted forward, even electrode inversion may occur, and the corrosion of a steel member is aggravated.

Disclosure of Invention

aiming at the corrosion protection problem of the underground steel pipe column of the oil and gas field, the invention provides the anticorrosive sacrificial anode alloy for the oil well pipe column, which is used in a stratum water environment simulating high temperature (more than or equal to 70 ℃) and high mineralization degree (about 50 g/L) of a certain oil field in the western region of China, and has the discharge current density of 1mA/cm ²Under the condition, the sacrificial anode alloy material has negative working potential (less than or equal to-1.10V) and higher current efficiency (about 85 percent), has good activation performance, uniform dissolution, easy shedding of corrosion products and stable working potential, and can be used for cathodic protection of the corrosion of the steel pipe column under the oil and gas field.

The oil well pipe column anticorrosion sacrificial anode alloy provided by the invention comprises the following components in percentage by mass: 2.2 to 5.2 percent of zinc, 0.01 to 0.05 percent of indium, 0.02 to 0.05 percent of tin, 0.5 to 2.0 percent of magnesium, 0.01 to 0.05 percent of titanium, 0.02 to 0.04 percent of boron, 0.01 to 0.05 percent of cerium and the balance of aluminum.

The invention also provides a component design method of the oil well pipe column anticorrosive sacrificial anode alloy, which comprises the following steps:

The method comprises the steps of screening and designing alloy components by using a molecular dynamics and density functional theory method, modeling an alloy and aqueous solution interface, adjusting and changing the alloy components in the model, and screening to obtain the components of the sacrificial anode alloy material according to the chemical affinity and the change rule between the aqueous solution and the alloy when the component alloy changes.

The specific process is as follows:

a. Establishing a series of aluminum alloy bulk phase models with different alloy element types and different alloy element contents and surface models thereof by using a molecular dynamics and density functional theory simulation calculation method;

Selecting a COMPASS force field and GGA-PBE (gas-insulated Gate Bipolar translator) ultra-soft pseudopotential based on a plane wave substrate, and optimizing an aluminum alloy bulk model and a surface model thereof by using a virtual crystal approximation method;

b. Establishing a water solution model of water molecules and various anions and cations by using a molecular dynamics and density functional theory simulation calculation method, further establishing an interface model between the water solution and the surface of the aluminum alloy, and inspecting the interface combination tendency between the water solution and the surface of the aluminum alloy;

c. Comparing the molecular dynamics and density functional theory simulation calculation results of the interface model between the aluminum alloy surface and the aqueous solution, wherein the aluminum alloy surface and the aqueous solution have different alloy element types and different alloy element contents, and screening out a series of target alloy components;

d. Based on the target components obtained by screening through theoretical simulation calculation, the final components of the aluminum-based sacrificial anode alloy are selected.

Preferably, the cation is a sodium ion, a potassium ion or a magnesium ion.

Preferably, the anion is chloride or sulfate.

The invention also provides a preparation method of the oil well pipe column anticorrosive sacrificial anode alloy, which comprises the following specific steps:

The sacrificial anode alloy material is prepared by adopting industrial pure metals of aluminum, zinc, indium, tin, magnesium, titanium, boron and cerium or intermediate alloy for proportioning, smelting in an inert environment, and pouring and quickly cooling in a graphite casting mold. The preparation process comprises the following steps: smelting the mixed metal material by using an induction heating mode under the inert gas protective atmosphere; and after complete melting, heating to 720-750 ℃, preserving heat for 10min, removing slag, and pouring and quickly cooling in a graphite casting mold to obtain the sacrificial anode alloy material.

The sacrificial anode alloy can be used for sacrificial anode cathodic protection of corrosion prevention of an underground steel pipe column of an oil field in high-temperature and high-salinity stratum water.

Compared with the prior art, the invention has the beneficial effects that:

1. The oil well pipe column anticorrosion sacrificial anode alloy provided by the invention has larger combination reaction tendency of the used boron element, the titanium element and the cerium element, so that the titanium element, the cerium element and the boron element preferentially form TiB in a high-temperature aluminum alloy melt ₂、CeB₆Boride particles with equal high melting point; then, when the temperature of the aluminum alloy melt is continuously reduced, Ti element and Ce element are in TiB ₂、CeB₆Local enrichment appears on the particle surface, and then the particle reacts with Al atoms in the aluminum liquid to generate Al ₃Ti、Al₃(Ti, Ce) and Al ₁₁Ce₃An isobinary or ternary compound to form an Al-coated film ₃Ti、Al₃(Ti, Ce) and Al ₁₁Ce₃Of TiB ₂、CeB₆granular compound, and finally, when the temperature of the aluminum liquid is further reduced to α -Al and crystallization and nucleation begin, Al is added ₃Ti、Al₃(Ti, Ce) and Al ₁₁Ce₃the lattice mismatch between the compounds and alpha-Al is extremely small, so that the coating layer is coated with Al ₃Ti、Al₃(Ti, Ce) and Al ₁₁Ce₃Of TiB ₂、CeB₆the grain refinement can obviously improve the structure and the component uniformity of the aluminum alloy, greatly reduce the potential difference of different microscopic regions of the aluminum alloy, slow down the self-corrosion effect of the aluminum alloy, improve the uniform dissolving capacity of the alloy surface and improve the current efficiency of the sacrificial anode alloy;

2. the oil well pipe column anticorrosion sacrificial anode alloy provided by the invention is used in a stratum water environment simulating high temperature (more than or equal to 70 ℃) and high mineralization degree (about 50 g/L) of a certain oil field in western China, and the discharge current density is 1mA/cm ²Under the condition of (1), the sacrificial anode alloy material has relatively negative working potential (lower than-1.10V) and relatively high current efficiency (higher than 85 percent), and has activation performance Good and uniform dissolution, easy shedding of corrosion products and stable working potential, and can be used for cathodic protection of steel pipe column corrosion in the well of oil and gas fields.

Drawings

FIG. 1 is a molecular dynamics model established during the composition screening design process of an alloy, simulating an interface model between an aqueous solution and an Al (111) surface; wherein, the graph a is an interface model schematic diagram of the Al (111) surface doped with Ce, and the graph b is an interface model schematic diagram of the Al (111) surface doped with Ti;

FIG. 2 is a metallographic structure of an alloy material prepared in example 3; wherein, the image a is an optical microscope image with 200 times, and the image b is a scanning electron microscope back scattering image with 1000 times;

FIG. 3 is a macro topography of the surface of an aluminum-based sacrificial anode alloy sample after electrochemical performance testing; wherein, the graphs a to c are the surface macro topography of the alloy material samples provided in the embodiments 3, 1 and 2 in sequence after the test; fig. d to g are surface macro-morphologies of the alloy material samples provided in comparative example 1, comparative example 2, comparative example 3, and comparative example 4 in this order;

FIG. 4 is a graph showing the change of the working potential of the electrode measured during the electrochemical performance test of the aluminum-based sacrificial anode alloy; wherein, a is the change curve of the working potential of the alloy material provided in example 3, and b is the change curve of the working potential of the alloy material provided in comparative example 1.

Detailed Description

The following detailed description of the preferred embodiments of the present invention is provided in conjunction with the accompanying drawings so that the objects, technical solutions and advantages of the present invention can be more easily understood by those skilled in the art, and thus the scope of the present invention can be clearly and clearly defined. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The oil well pipe column anticorrosive sacrificial anode alloy has the following components: firstly, theoretically designing and screening alloy components by a molecular dynamics and density functional theory simulation calculation method; secondly, preparing alloy components and smelting to prepare an alloy sample on the basis of obtaining a target alloy through theoretical screening, testing the electrochemical performance of the alloy sample according to GB/T17848 sacrificial anode electrochemical performance test method, and performing further optimization design on the alloy components according to experimental data so as to determine the final alloy components.

The method adopts a theoretical simulation method to carry out theoretical design and screening on the added elements of the alloy, and mainly comprises the following basic steps:

a. Establishing a series of aluminum alloy bulk phase models with different alloy element types and different alloy element contents and a (111) surface model thereof by using a molecular dynamics and density functional theory simulation calculation method; selecting a COMPASS force field and GGA-PBE (gradient-guided wave-based-PBE) ultra-soft pseudopotentials based on a plane wave substrate, and fully optimizing a volume phase model and a surface model by using a Virtual Crystal Approximation (VCA) method;

b. Establishing an aqueous solution model of water molecules, various anions (such as chloride ions, sulfate ions and the like) and cations (such as sodium ions, potassium ions, magnesium ions and the like) by using a molecular dynamics and density functional theory simulation calculation method, and further establishing an interface model between the aqueous solution and the surface of the aluminum alloy (111); observing the interface bonding tendency between the aqueous solution and the surface of the aluminum alloy, wherein the greater the bonding tendency, the greater the chemical affinity of the aluminum alloy and the aqueous solution, and the greater the anode alloy activity of the component;

c. Comparing the molecular dynamics and density functional theory simulation calculation results of the interface model between the aluminum alloy surface and the water solution with different alloy element types and different alloy element contents, and screening out a series of target alloy components;

The final components of the aluminum-based sacrificial anode alloy are selected according to the basis that the alloy is prepared and the electrochemical performance of the alloy is detected through experiments on the basis of target components obtained through screening in theoretical simulation calculation. The process is as follows: based on target components obtained by theoretical simulation screening, a series of alloy materials are prepared through experiments, and the electrochemical performance of the alloy materials is tested through experiments. On one hand, through the comparison of experimental results, the final composition of the sacrificial anode alloy material is preferably determined; on the other hand, whether the electrochemical performance of the electrochemical material meets the national standard and the actual engineering requirement is fully verified through experimental tests. The experimental study content comprises the following basic steps:

a. Preparing a series of different sacrificial anode alloy material components according to target alloy components obtained by theoretical simulation calculation and screening, and preparing materials by using pure metals (industrial purity, 99.8%) of aluminum, zinc, indium, tin and magnesium, an aluminum-titanium-boron intermediate alloy (titanium mass percent is 5%, boron mass percent is 1%) and an aluminum-cerium intermediate alloy (cerium mass percent is 12%);

b. Under the protective atmosphere of high-purity argon, avoiding introducing oxygen and nitrogen in the air, and smelting by using an induction heating crucible furnace; after complete melting, heating to 720-750 ℃, preserving heat for 10min, removing slag, pouring in a graphite casting mold, and quickly cooling the molten metal to obtain an ingot;

c. according to GB/T17848 sacrificial anode electrochemical performance test method, an anode electrochemical performance sample is obtained by mechanically processing an alloy cast ingot, and the electrochemical performance of the sample is tested in formation water which simulates the high temperature (70 ℃) and the high mineralization degree (more than or equal to 50 g/L) of an oil field in the west of China;

d. The electrochemical performance of the sacrificial anode alloy is measured according to GB/T17848 electrochemical performance test method for sacrificial anode, and the test parameter is current density of 1mA/cm ²Test time 240 h;

e. According to GB/T17848 'test method for electrochemical performance of sacrificial anode', measuring the working potential of the sacrificial anode alloy, calculating the current efficiency, and inspecting the dissolution rate and the surface dissolution appearance of the sacrificial anode alloy;

f. According to the experimental results, the current efficiency, the anodic dissolution rate and the surface dissolution morphology of different alloys are compared, and the final composition of the alloy is preferably determined.

Through the steps, the components of the sacrificial anode alloy material provided by the invention are 2.2% -5.2% of zinc, 0.01% -0.05% of indium, 0.02% -0.05% of tin, 0.5% -2.0% of magnesium, 0.01% -0.05% of titanium, 0.02% -0.04% of boron, 0.01% -0.05% of cerium and the balance of aluminum.

The following description will be given with reference to specific examples.