CN103045215A - Aluminate cement-based carbon dioxide corrosion resistant cement system for cementing of well - Google Patents

Abstract

The invention relates to an aluminate cement-based carbon dioxide corrosion-resistant cement system for well cementing, which is composed of: 100 parts of aluminate cement, 40 parts of water, 8-12 parts of sodium phosphate, and an oil well cement defoamer 0.4-0.6 parts, retarder 0-3.5 parts. The aluminate cement-based _CO2 corrosion-resistant cement system of the present invention has excellent _CO2 corrosion resistance under the conditions of high temperature, high pressure and high concentration _CO2 , and has good strength performance at high temperature, and the 3D compressive strength of cement stone It can reach 39.8MPa and can be used for long-term sealing of oil and gas wells eroded by high-concentration CO ₂ . It can not only seal the lost zone to a certain extent, but also reduce the occurrence of gas channeling.

Description

An aluminate cement-based carbon dioxide corrosion-resistant cement system for well cementing

technical field

The invention relates to a CO ₂ corrosion-resistant cementing cement system used in the field of oil and gas well drilling, which is especially suitable for technical applications such as the exploitation of high CO ₂ oil and gas reservoirs, CO ₂ flooding, and CO ₂ storage in depleted oil and gas reservoirs. Aluminate cement-based cement systems for the cementing of oil and gas wells containing high concentrations of _CO2 .

Background technique

At present, the cement used in oil and gas well cementing is mostly Portland cement system. In recent years, the _CO2 corrosion of Portland cement in well cementing has attracted much attention. This is because the source of the high concentration of CO ₂ in the formation is no longer just the associated gas of oil and natural gas, but also includes the large amount of CO ₂ injected by technologies such as CO ₂ flooding and CO ₂ storage, which greatly increases the concentration of CO ₂ in the formation . Under high temperature, high pressure and humid environment underground, high concentration of CO ₂ will cause serious corrosion to Portland cement in a short period of time, which is manifested by increased permeability and reduced strength of the cement, which will cause the cement to lose its seal. performance, resulting in the failure of the seal performance of the sealing system, which in turn leads to serious consequences such as the reduction of oil and gas recovery and the failure of _CO2 storage. Therefore, Portland cement can no longer meet the long-term sealing requirements of oil and gas wells in high-concentration CO ₂ formations. It is necessary to study a new type of CO ₂ corrosion-resistant cement system to replace the Portland cement system to improve the cementing performance. The CO ₂ corrosion resistance of cement stone ensures the successful application of technologies such as high CO ₂ oil and gas reservoir development, CO ₂ flooding and CO ₂ storage.

In the past few decades, with the development of high CO ₂ oil and gas reservoirs, the research and application of CO ₂ displacement technology and CO ₂ sequestration in depleted oil and gas reservoirs, CO ₂ corrosion-resistant cementing cements have been developed successively at home and abroad. Systematic research has yielded some results.

The article "Effect Analysis of Slag Micropowder in Cement" involves a low-density CO ₂ corrosion-resistant Portland cement system made by adding a certain amount of micro-silicon and floating beads to Portland cement, and the field application effect is good. There are two explanations for the corrosion resistance mechanism of the system: the pozzolanic action of micro-silicon changes the phase composition of cement stone, which can react with CH (Ca(OH) ₂ ) in the hydration product to form calcium silicate hydrate gel. The CH component in the cement stone is greatly reduced, and the corrosion resistance of the cement stone is enhanced; the remaining micro-silicon reacted with CH can be filled in the voids of _the mixed solid phase accumulation body and the micro-cracks of the cement stone, improving the corrosion resistance of the cement stone. Microstructure, optimize the pore size distribution of cement stone, greatly reduce the large pores, increase the number of small pores, poor pore connectivity, reduce the permeability of cement stone, which is not conducive to the intrusion of formation corrosive fluid into cement stone, and improve the cement stone. Corrosion resistance.

Portland cement-based CO ₂ corrosion-resistant cementing cement system can improve the CO ₂ corrosion resistance of cement stone to a certain extent, but the hydration product that determines the CO ₂ corrosion resistance of cement stone—calcium silicate hydrate gel ( CSH) will continue to corrode with CO ₂ at a certain rate, and there is still a great risk in long-term application, so the Portland cement-based CO ₂ corrosion-resistant cement system cannot meet the long-term sealing requirements of high CO ₂ oil and gas wells. Require.

The article "Advanced Cement Systems Used to Improve Geothermal Well Reliability in Java" involves a low-density cement slurry system prepared by compounding Portland cement and high-alumina cement and injecting a certain amount of nitrogen. It has good CO ₂ corrosion resistance, but The temperature resistance and anti-pollution performance are poor.

The patent "Carbon dioxide corrosion-resistant cement system for oil and gas well cementing" (publication number CN102559161A) relates to an aluminophosphate cement-based _CO2 corrosion-resistant cement system, which has good _CO2 corrosion resistance, but the aluminophosphate cement The mineral phase of cement clinker is mainly calcium aluminate solid solution and calcium phosphate solid solution, and the products formed by hydration are mainly apatite crystal minerals. The maximum compressive strength of cement stone can only reach 21MPa, and it has been used for high temperature and high pressure oil and gas wells for a long time There will be safety hazards in the environment.

The aluminate cement used in the present invention is different from the aluminophosphate cement used in the patent "carbon dioxide corrosion-resistant cement system for oil and gas well cementing", and the mineral phase composition and hydration products are also different. They are special cements with different properties. Aluminate cement will undergo crystal phase transformation at high temperature (>50°C), and its strength will shrink seriously. If it is used in cementing engineering, its high temperature performance needs to be improved.

The aluminate cement-based carbon dioxide corrosion-resistant cement system of the present invention is excellent in _CO2 corrosion resistance, and the compressive strength of the cement stone cured at high temperature can reach 39.8MPa, which solves the strength shrinkage problem of single-use aluminate cement, and has excellent mechanical properties. Far superior to aluminophosphate cement-based CO ₂ corrosion-resistant cement systems.

Contents of the invention

The purpose of the present invention is to solve the deficiency of the high temperature performance of the existing aluminate cement, and provide a kind of aluminate cement base carbon dioxide corrosion resistant cement system for well cementing, the cement stone of the cement system can be used under the conditions of high temperature, high pressure and high concentration _CO2 It has excellent corrosion resistance and can meet the long-term sealing requirements of high CO ₂ oil and gas wells, providing guarantee for exploration and development, efficient production and environmental protection.

In order to achieve the above object, the technical scheme adopted in the present invention is:

An aluminate cement-based carbon dioxide corrosion-resistant cement system for well cementing, which is composed of: 100 parts of aluminate cement, 40 parts of water, 8-12 parts of sodium phosphate, and 0.4-0.6 parts of oil well cement defoamer parts, retarder 0 to 3.5 parts.

The aluminate cement-based carbon dioxide corrosion-resistant cement system for well cementing is preferably composed of: 100 parts of aluminate cement, 40 parts of water, 10 parts of sodium phosphate, 0.5 parts of oil well cement defoamer, 3 parts retarder.

The above mineral phases of aluminate cement are mainly monocalcium aluminate (CA), monocalcium dialuminate (CA ₂ ), calcium aluminate feldspar (C ₂ AS), tricalcium aluminate (C ₃ A) and trace amounts of iron Aluminates, sulfides, etc. Aluminate cement is preferably composed of 50-60 parts by weight of monocalcium aluminate, 10-15 parts of monocalcium dialuminate, 8-15 parts of calcium aluminum feldspar, and 3-5 parts of tricalcium aluminate.

The sodium phosphate salt is any soluble phosphate or its compound, preferably one or more of sodium phosphate, sodium hexametaphosphate, sodium pyrophosphate, sodium tripolyphosphate, and sodium dihydrogen phosphate.

The oil well cement defoamer is an organic polyether defoamer, such as the SWX-1 type defoamer produced by Tianjin Zhongyou Boxing Engineering Technology Co., Ltd., and the described retarder is sodium silicate, tetraboric acid One or more of sodium and sodium lignosulfonate.

Adding a certain amount of soluble phosphate to aluminate cement can solve the strength shrinkage problem of aluminate cement at high temperature on the one hand, reduce the formation of minerals susceptible to _CO2 corrosion and promote the formation of _CO2 corrosion-resistant minerals on the other hand. Formation, optimize the mineral composition of cement stone, add defoamer to control the foam quantity of the system and improve the dispersion of slurry, add retarder to prolong the thickening time of cement system if necessary. The retarder not only has retarding effect, but also improves the rheology of the cement system and enhances the pumpability of the cement slurry.

The aluminate cement-based carbon dioxide corrosion-resistant cement system for well cementing of the present invention has excellent properties in the following three aspects:

(1) The aluminate cement-based CO ₂ corrosion-resistant cement system of the present invention has excellent CO ₂ corrosion resistance under the conditions of high temperature, high pressure and high concentration of CO ₂ , and can slow down the formation of high-concentration CO ₂ when used in oil and gas well cementing Corrosion of the cement sheath, prolonging the service life of oil and gas wells.

(2) The aluminate cement-based CO ₂ corrosion-resistant cement system of the present invention optimizes the strength performance of aluminate cement at high temperatures, and the 3d compressive strength of cement stone can reach 39.8MPa, which can be used for long-term sealing of high-concentration CO ₂ Eroded oil and gas wells.

(3) The aluminate cement-based CO ₂ corrosion-resistant cement system of the present invention has certain thixotropic properties, which can not only seal the leakage layer to a certain extent, but also reduce the occurrence of gas channeling. This is conducive to the success of cementing construction operations and the improvement of cementing quality.

Detailed ways

Below in conjunction with embodiment further illustrate.

Example 1

An aluminate cement-based carbon dioxide corrosion-resistant cement system for well cementing: 100 parts of aluminate cement, 40 parts of water, 10 parts of sodium hexametaphosphate, 0.5 part of oil well cement defoamer, and no retarder. The sample number of the cement system is 1#. Among them, the aluminate cement is produced by Zhengzhou Zhongfa Special Cement Melt Co., Ltd., and the model is CA-50. The influence of sodium hexametaphosphate on aluminate cement has not been tested, and no retarder is added to this system.

Example 2

An aluminate cement-based carbon dioxide corrosion-resistant cement system for well cementing: 100 parts of aluminate cement, 40 parts of water, 10 parts of sodium hexametaphosphate, 0.5 parts of oil well cement defoamer, and 3 parts of sodium silicate. The sample number of the cement system is Z1#. This system is compared with Example 1, in order to test the impact of retarder on the compressive strength of 1# system.

Comparative example 1

Cement system formula: 100 parts of aluminate cement, 40 parts of water, 0.5 parts of oil well cement defoamer. The sample number of the cement system is 2#. This system is compared with Example 1, in order to test the influence of sodium hexametaphosphate on the compressive strength of aluminate cement.

Comparative example 2

Cement system formula: Jiahua G grade cement 100 parts, water 44 parts, sodium hexametaphosphate 10 parts, oil well cement defoamer 0.5 parts. The sample number of the cement system is 3#. This system is combined with Example 1 to compare the carbon dioxide corrosion resistance of the two cement systems.

Performance Testing:

1. Evaluation of high temperature compressive strength

Prepare the cement slurry according to the oil well cement test method standard GB/T19139-2003 standard, wherein the water is proportioned according to the mass percentage based on the total weight of the aluminophosphate cement; Put it in the mold, put it in a 75°C water bath, and maintain it under normal pressure conditions. After a certain age, take it out and demould, and measure the compressive strength of one piece of cement stone in each cement slurry formula. The test results are shown in Table 1. Experimental results show that the aluminate cement-based _CO2 corrosion-resistant cement system of the present invention has higher compressive strength at high temperatures. There was no shrinkage in compressive strength. Evaluation of High Temperature Compressive Strength of Aluminate Cement Based _CO2 Corrosion Resistant Cement System of the Present Invention

Table 11# cement system and 2# cement system compressive strength comparison

2. Evaluation of corrosion resistance

Prepare cement slurry according to the oil well cement test method standard GB/T19139-2003 standard, wherein the water is proportioned by mass percentage based on the total weight of aluminophosphate cement and Portland cement; then pour the prepared cement slurry into a diameter of 2.6cm, 5cm high mold, placed in a 75 ℃ water bath box, curing under normal pressure conditions, after 12 hours, take out the mold, and then put the cement stone (column) into the high temperature and high pressure acid and alkali corrosion curing equipment for curing, curing The conditions were 130°C and the partial pressure of CO ₂ was about 5MPa; after curing for 3d, 7d, 21d and 40d, the test block was taken out to measure the compressive strength and corrosion depth. The test results are shown in Table 2. The experimental results show that the aluminate cement-based _CO2 corrosion-resistant cement system for well cementing of the present invention is compared with Portland cement, the cement stone compressive strength before and after corrosion of the former remains basically unchanged, and the corrosion depth is small, indicating that the cement The corrosion of the cement stone is small; the compressive strength of the cement stone before and after corrosion is significantly reduced, and the corrosion depth is obviously increased, indicating that the cement stone is subject to greater corrosion. It can be seen from the comparison that the aluminate cement-based CO ₂ corrosion-resistant cement system for well cementing of the present invention has better corrosion resistance.

Table 21# cement system and 3# cement system CO ₂ corrosion resistance comparison

3. Comprehensive performance evaluation

The cement slurry was prepared according to the oil well cement test method standard GB/T19139-2003, and the modified aluminophosphate cement slurry added to the sample was measured according to the Petroleum and Natural Gas Industry Standard SY/T5546-92 of the People's Republic of China "Test Method for Application Performance of Oil Well Cement". The thickening time at the specified temperature, the test condition is normal pressure, and the test results are shown in Table 3.

According to the oil well cement test method standard GB/T19139-2003, prepare cement slurry, pour the prepared cement slurry into a mold with a diameter of 2.6cm and a height of 5cm, and place it in a water bath at 75°C under normal pressure for 12 hours. Finally, take out the demoulding, and then put the cement stone (column) into the high temperature and high pressure acid and alkali corrosion curing equipment for curing. The curing conditions are 130°C and the partial pressure of _CO2 is about 5MPa; after curing for 7d, 21d and 40d, take out the test block The compressive strength and corrosion depth were measured, and the test results are shown in Table 3.

Table 3 Aluminate cement based CO of the present invention The comprehensive performance table of the corrosion _- resistant cement system

Claims (6)

1. An aluminate cement-based carbon dioxide corrosion-resistant cement system for well cementing, which is composed of: 100 parts of aluminate cement, 40 parts of water, 8 to 12 parts of sodium phosphate, and 0.4 parts of oil well cement defoamer ~0.6 parts, retarder 0~3.5 parts. 2. The aluminate cement-based carbon dioxide corrosion-resistant cement system for well cementing according to claim 1 is characterized in that its weight ratio consists of: 100 parts of aluminate cement, 40 parts of water, and 10 parts of sodium phosphate , 0.5 parts of oil well cement defoamer, 3 parts of retarder. 3. The aluminate cement-based carbon dioxide corrosion resistant cement system for well cementing according to claim 1, characterized in that the aluminate cement consists of 50-60 parts by weight of monocalcium aluminate, 50-60 parts of dialuminate 10-15 parts of calcium, 8-15 parts of calcium aluminate feldspar, and 3-5 parts of tricalcium aluminate. 4. Aluminate cement base carbon dioxide corrosion resistant cement system for well cementing according to claim 1, is characterized in that, described sodium phosphate salt is sodium phosphate, sodium hexametaphosphate, sodium pyrophosphate, sodium tripolyphosphate , one or more of sodium dihydrogen phosphate. 5. The aluminate cement-based carbon dioxide corrosion-resistant cement system for well cementing according to claim 1, wherein the oil well cement defoamer is a silicone emulsion defoamer. 6. Aluminate cement base carbon dioxide corrosion resistant cement system for cementing according to claim 1, is characterized in that, described retarder is one of sodium silicate, sodium tetraborate, sodium lignosulfonate species or several.