CN104774601A - Gypsum microspheres and low elasticity modulus expansion well cementation cement system - Google Patents

Abstract

The invention discloses a gypsum microsphere and a low elastic modulus expansion cement system suitable for medium and low temperature well cementing, wherein the gypsum microsphere is obtained by reverse-phase coagulation and hardening of a certain proportion of anhydrite, α-type hemihydrate gypsum and water product. The components of the low elastic modulus expansive cement system and their weight ratios are as follows: 100 parts of oil well cement, 10 to 40 parts of gypsum microspheres, 5 to 10 parts of micro silicon, and 65 to 75 parts of water , the addition of gypsum microspheres simultaneously realizes the functions of expanding the volume of cement stone and reducing the elastic modulus of cement stone. The invention is beneficial to the long-term demand for the integrity of the cement sheath, and has important engineering significance for ensuring the cementing quality and the long-term safe production of oil and gas wells.

Description

Gypsum microspheres and low elastic modulus expansion cement system

technical field

The invention relates to a gypsum microsphere and a low-elastic-modulus expansion cement system containing the gypsum microsphere, which can guarantee the cementing quality for a long time, and belongs to the field of oil and gas well cementing materials.

Background technique

The cementing sheath has the functions of supporting the casing and isolating the formation, and the latter is the main function. The cement sheath provides interlayer isolation to prevent interlayer channeling, avoid interlayer pollution, and ensure safe oil and gas production. To perform this function, the cement sheath must be continuous and impermeable. The volume shrinkage of annular cement stone after cement hardening is one of the main factors affecting the sealing performance of cement annulus. The volume shrinkage of cement stone mainly includes chemical shrinkage and drying shrinkage. Chemical shrinkage is a defect of cement itself; drying shrinkage is positively correlated with water-cement ratio. In cementing engineering, in order to ensure the pumpability of cement slurry, the water-cement ratio is high, so the drying shrinkage is serious. The most effective way to solve the volume shrinkage of cement stone is to add expansion agent to cement. Lattice expansion agent and gas expansion agent are commonly used types of expansion agent for oil well cement.

For the lattice expansion agent (gypsum and magnesia), the research shows (Bu Yuhuan, Liu Huajie, Song Wenyu. The experiment of the influence of lattice expansion agent on the cement-casing interface bonding performance [J]. Acta Petroleum Sinica, 2011,32(6) :1067-1071.), although the addition of lattice expansion agent can make up for the shrinkage of the cement stone volume, it cannot effectively improve the cementing quality and reduce the ability of the cement sheath to resist the stress and strain caused by temperature and pressure changes, resulting in cement sheath The bonding strength with the casing decreases greatly after temperature and pressure changes. This is due to the addition of gypsum and magnesium oxide lattice expansion agents, which will generate a large number of crystals in the cement sheath. The presence of a large number of crystals increases the elastic modulus of the cement stone and reduces the ability of the cement stone to resist temperature and pressure changes.

For the gas expansion agent, it was found through research (Liu Huajie, Bu Yuhuan, Wang Xueying, Guo Xinyang. The influence of pores on the strength of gas expansion cement stone[J]. Journal of China University of Petroleum (Natural Science Edition) 2014,38(2): 75-81.), the pores produced by the gas expansion agent have the dual functions of compensating the volume shrinkage of the cement stone and reducing the elastic modulus of the cement stone, but the gas expansion process is difficult to control, and the uneven distribution of the pores will affect the strength performance of the cement stone Therefore, when applying the gas expansion agent, a special process or the application technology of the gas expansion agent should be adopted to make the pore diameter distribution range more concentrated, and it is very difficult to implement these measures.

Volume shrinkage is a defect of cement stone itself. At the same time, various downhole operations in oil and gas wells will inevitably exert pressure and thermal stress on the cement sheath. Therefore, the cement sheath is required to have certain expansion properties and a low elastic modulus. process to prevent brittle failure. Therefore, the development of a low elastic modulus expansion cement system can ensure the long-term integrity of the cement sheath, which is of great engineering significance to ensure the quality of cementing and the long-term safe production of oil and gas wells.

Contents of the invention

The object of the present invention is to provide a gypsum microsphere and a low elastic modulus expansion cement system in order to solve one of the problems in the above-mentioned prior art.

The technical solution adopted by the present invention to solve its technical problems is:

One aspect of the present invention provides a method for preparing gypsum microspheres. After mixing anhydrous gypsum and hemihydrate gypsum evenly, they are added to water and stirred to obtain a gypsum suspension, and then the gypsum suspension is added to the oil phase dispersion medium to continue stirring , filtered to obtain gypsum microspheres; wherein the mass percent of the anhydrous gypsum, hemihydrate gypsum and water is (10-30%): (30-50%): (30-50%), and the gypsum suspension Accounting for 5%-25% of the volume of the oil phase dispersion medium.

The gypsum microsphere of the present invention is a product obtained by reverse-phase coagulation and hardening of a certain proportion of anhydrous gypsum, α-type hemihydrate gypsum and water.

Preferably, the hemihydrate gypsum is α-type hemihydrate gypsum.

Preferably, the mesh size of the anhydrous gypsum is 500-1000 mesh.

Preferably, the mesh size of the α-type hemihydrate gypsum is 500-1000 mesh.

Preferably, the stirring time of the gypsum suspension is no more than 5 minutes.

Preferably, the gypsum suspension is added to the oil phase dispersion medium with a stirring speed of 200-700 r/min and a stirring time of 1-2 hours.

Preferably, the oil phase dispersion medium is castor oil or rapeseed oil or soybean oil or corn oil or peanut oil.

Gypsum microspheres prepared by the above-mentioned preparation method of gypsum microspheres.

Preferably, the particle size range of the gypsum microspheres is 50-200 μm.

Another aspect of the present invention provides a low elastic modulus expansion cement system, comprising the following components and the weight ratio of each component: 100 parts of oil well cement, 10 to 40 parts of gypsum microspheres, 5 parts of micro silicon 1 to 10 parts, 65 to 75 parts of water.

Preferably, the components and their weight ratios are as follows: 100 parts of oil well cement, 25-30 parts of gypsum microspheres, 8-10 parts of micro-silicon, and 65-70 parts of water.

Preferably, the components and their weight ratios are: 100 parts of oil well cement, 25 parts of gypsum microspheres, 8 parts of micro silicon, and 65 parts of water.

Preferably, the components and their weight ratios are as follows: 100 parts of oil well cement, 30 parts of gypsum microspheres, 10 parts of micro silicon, and 70 parts of water.

The preparation method of the above-mentioned low elastic modulus expansive cementing cement system, first dry-mixes oil well cement, gypsum microspheres and micro-silicon, and then mixes the dry-blended system with water according to the standard.

The low elastic modulus expansion cement system of the present invention has micro-expansion performance under medium and low temperature conditions, and the cement slurry has a low elastic modulus after solidification and hardening, which can solve the problem of poor sealing quality caused by the volume shrinkage of the cement sheath It can effectively resist stress and strain, ensure the long-term integrity of the cement sheath, and better meet the needs of cementing engineering.

The invention adopts special components and techniques to develop gypsum microspheres with certain strength, then adds the gypsum microspheres into the cement and simultaneously introduces micro silicon into the cement to prevent the gypsum microspheres from settling. Gypsum is a commonly used lattice expansion agent for oil well cement, so gypsum microspheres can expand cement stone; at the same time, due to the introduction of more water in the process of developing gypsum microspheres, the microspheres have many pore structures, making their elastic modulus relatively low. Low, so the gypsum microspheres can also reduce the elastic modulus of the cement stone as a whole. However, as a lattice expansion agent for oil well cement, gypsum can be used at a temperature not exceeding 85° C. in theory, so the present invention is not suitable for high temperature well cementing.

The addition of the gypsum microspheres of the present invention simultaneously realizes the functions of expanding the volume of the cement stone and reducing the elastic modulus of the cement stone. The low elastic modulus expansion cement system of the present invention is beneficial to the long-term demand for the integrity of the cement sheath, and has important engineering significance for ensuring the quality of cementing and the long-term safe production of oil and gas wells.

Additional aspects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and comprehensible from the description of the embodiments in conjunction with the following drawings, wherein:

Fig. 1 is the micrograph of gypsum microsphere (G1) of the present invention;

Fig. 2 is the micrograph of gypsum microsphere (G2) of the present invention;

Figure 3 is a diagram of the volume change of cement stone.

Detailed ways

The embodiments described below by referring to the figures are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

Embodiment 1 gypsum microspheres and preparation method thereof

After mixing 6g of anhydrous gypsum (625 mesh) and 14g of α-type hemihydrate gypsum (625 mesh) evenly, add them into 16g of water, and stir evenly for 1.5min. Then, at room temperature, add the gypsum suspension into 200 g of corn oil, and stir while adding, at a stirring rate of 500 r/min. After adding the gypsum suspension into the corn oil, continue stirring for 2 hours. After stirring, the gypsum microspheres were filtered out, washed, and dried at room temperature to obtain gypsum microspheres with a particle size of about 100 μm, which were recorded as G1, as shown in Figure 1.

Embodiment 2 gypsum microspheres and preparation method thereof

Mix 4g of anhydrous gypsum (800 mesh) and 16g of α-type hemihydrate gypsum (800 mesh) evenly, add them into 14g of water, and stir evenly for 2 minutes. Then, at room temperature, add the gypsum suspension into 300 g of soybean oil, and stir while adding, at a stirring rate of 600 r/min. After adding the gypsum suspension into the soybean oil, continue stirring for 2 hours. After stirring, the gypsum microspheres were filtered out, washed, and dried at room temperature to obtain gypsum microspheres with a particle size range of about 50-80 μm, which were recorded as G2, as shown in Figure 2.

Example 3 Low elastic modulus expansion cement system

Cement slurry formula: 100 parts of G grade oil well cement + 25 parts of gypsum microspheres (G1) + 8 parts of micro silicon + 65 parts of water. The resulting cement stone sample is denoted as C1.

Preparation method: dry-mix oil well cement, gypsum microspheres and micro-silicon, and then prepare cement slurry with the dry-mixed system and water according to GB19139-2003 oil well cement test method.

Embodiment 4 Low elastic modulus expansion cement system

Cement slurry formula: 100 parts of G grade oil well cement + 30 parts of gypsum microspheres (G1) + 10 parts of micro silicon + 70 parts of water. The obtained cement stone sample is recorded as C2.

Preparation method: dry-mix oil well cement, gypsum microspheres and micro-silicon, and then prepare cement slurry with the dry-mixed system and water according to GB19139-2003 oil well cement test method.

Embodiment 5 Low elastic modulus expansion cement system

Cement slurry formula: 100 parts of G grade oil well cement + 30 parts of gypsum microspheres (G2) + 10 parts of micro silicon + 70 parts of water. The resulting cement stone sample is denoted as C3.

Preparation method: dry-mix oil well cement, gypsum microspheres and micro-silicon, and then prepare cement slurry with the dry-mixed system and water according to GB19139-2003 oil well cement test method.

Embodiment 6 Low elastic modulus expansion cement system

Cement slurry formula: 100 parts of H grade oil well cement + 30 parts of gypsum microspheres (G1) + 10 parts of micro silicon + 70 parts of water. The obtained cement stone sample is recorded as C4.

Preparation method: dry-mix oil well cement, gypsum microspheres and micro-silicon, and then prepare cement slurry with the dry-mixed system and water according to GB19139-2003 oil well cement test method.

For comparison, a conventional grout formulation was chosen:

G grade oil well cement 100 parts + micro silicon 10 parts + water 55 parts. The obtained cement stone sample is recorded as C5.

H grade oil well cement 100 parts + micro silicon 10 parts + water 55 parts. The obtained cement stone sample is recorded as C6.

Prepare cement slurry according to GB 19139-2003 oil well cement test method, and test the slurry density, compressive strength of cement stone, rheology and settlement stability of cement slurry. The volume change of cement stone is measured according to ANSI/API Recommended Practice 10B-5 standard. The elastic modulus of cement stone is measured by the dynamic elastic modulus test method. The addition of micro silicon in the formula is mainly to prevent the gypsum microspheres from settling. The cement sample C2 was selected for the rheological test first. The rheological test results are shown in Table 1. From the data in the table, it can be seen that the rheological properties of the cement slurry meet the requirements of the cementing project. Under the premise that the rheology of the cement slurry meets the requirements of the cementing project, the settlement stability of the cement sample C2 was tested. The test results are shown in Table 2. The percentage of the upper and lower density difference of the cement stone is 0.715%, which meets the requirements of the cementing project.

Table 1 Rheology of cement slurry

Table 2 Measurement results of cement slurry settlement stability

Measuring position 1 (bottom) 2 3 4 5 (topmost) Density of cement stone (g/cm ³ ) 1.678 1.675 1.670 1.669 1.666

The test results of cement slurry density, compressive strength and dynamic elastic modulus are shown in Table 3. The volume change of cement stone is shown in Figure 3.

Table 3 cement slurry density, compressive strength and dynamic elastic modulus

It can be seen from Table 3 and Figure 3 that the addition of gypsum microspheres simultaneously realizes the dual effects of micro-expansion of cement stone and reduction of elastic modulus of cement stone.

The addition of gypsum microspheres reduces the density and compressive strength of cement stones. This is mainly because gypsum microspheres have a more porous structure and their own density is low, which reduces the density of cement stones. At the same time, because gypsum microspheres do not have glue However, it can be seen from Table 3 that under the same amount of addition, the smaller the particle size of gypsum microspheres is added, the greater the compressive strength of cement stone. For a better explanation, the data in the literature (Wang Qun. my country's low-density cement research and application overview [J]. Drilling and Production Technology. 1991, 14(2): 1-8), as shown in Table 4 and Table 5 Show.

Table 4 The influence of bentonite on the compressive strength of cement stone

Note: "--" No relevant data provided in the original literature

Table 5 Effect of fly ash on the compressive strength of cement stone

It can be seen from Table 4 and Table 5 that the addition of bentonite and fly ash can reduce the density of cement stone, but the activity of bentonite and fly ash is very low in the absence of activator, so the compressive strength of cement stone Strength is reduced.

Rubber particles have the effect of reducing the elastic modulus of cement stone. For comparative analysis, references (Li Zaoyuan, Guo Xiaoyang. The influence of rubber powder on the mechanical properties of oil well cement stone[J]. Petroleum Drilling Technology, 2008,36(6): 52 -55.), as shown in Table 6.

Table 6 Effect of rubber particles on the mechanical properties of cement stone

It can be seen from Table 6 that the rubber particles reduce the elastic modulus of the cement stone, and also reduce the compressive strength of the cement stone, but the rubber particles do not have the effect of compensating the volume shrinkage of the cement stone.

Therefore, the present invention has significant advantages in realizing the volume expansion of cement stone and reducing the elastic modulus of cement stone at the same time.

Although the embodiments of the present invention have been shown and described, those skilled in the art can understand that various changes, modifications, substitutions and modifications can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the invention is defined by the claims and their equivalents.

Claims (10)

1. a preparation method for gypsum microballoon, is characterized in that, the stirring that is added to the water after dehydrated gyp-, semi-hydrated gypsum being mixed obtains gypsum suspension liquid, then gypsum suspension liquid is joined continuation stirring in oil phase dispersion medium, filters to obtain gypsum microballoon; The mass percent of wherein said dehydrated gyp-, semi-hydrated gypsum and water is (10 ~ 30%): (30 ~ 50%): (30 ~ 50%), and described gypsum suspension liquid accounts for 5% ~ 25% of described oil phase dispersion medium volume.

2. preparation method according to claim 1, is characterized in that, described semi-hydrated gypsum is alpha semi-hydrated gypsum.

3. preparation method according to claim 1, is characterized in that, described dehydrated gyp-order number is 500 ~ 1000 orders, and described alpha semi-hydrated gypsum order number is 500 ~ 1000 orders.

4. preparation method according to claim 1, is characterized in that, the churning time of described gypsum suspension liquid is no more than 5min, and it is 200 ~ 700r/min that described gypsum suspension liquid joins stirring velocity in oil phase dispersion medium, and churning time is 1 ~ 2h.

5. preparation method according to claim 1, is characterized in that, described oil phase dispersion medium is Viscotrol C or rapeseed oil or soya-bean oil or Semen Maydis oil or peanut oil.

6. gypsum microballoon prepared by the preparation method described in any one of claim 1-5.

7. gypsum microballoon according to claim 6, is characterized in that, its particle size range is 50 ~ 200 μm.

8. a low elastic modulus expansion cementing cement system, is characterized in that, comprises following component and its each ingredients weight parts ratio consists of: oil well cement 100 parts, gypsum microballoon 10 ~ 40 parts, micro-silicon 5 ~ 10 parts, 65 ~ 75 parts, water.

9. low elastic modulus expansion cementing cement system according to claim 8, it is characterized in that, the weight part ratio of described each component and each component thereof consists of: oil well cement 100 parts, gypsum microballoon 25-30 part, micro-silicon 8-10 part, water 65-70 part.

10. the preparation method of the low elastic modulus expansion cementing cement system described in claim 8 or 9, is characterized in that, first by oil well cement, gypsum microballoon and micro-silicon are dry mixed, and is then undertaken with slurry by the system after being dry mixed and water.