Low-cost high-temperature-resistant high-salt-resistant dissoluble environment-friendly water plugging cement and plugging removal method thereof

Abstract

The invention provides low-cost high-temperature-resistant high-salt-resistant dissoluble environment-friendly water plugging cement and a plugging removal method thereof, and belongs to the technical field of oilfield chemical water plugging. The environment-friendly water plugging cement is prepared from the following components in parts by weight: 20-40 parts of bluestone powder, 20-40 parts of fly ash, 10-15 parts of calcium hydroxide, 1-2 parts of potassium chloride, 5-15 parts of Portland cement and 9-15 parts of a modifier, the water-cement ratio of the environment-friendly water plugging cement is 5: 6. The content of organic components in the cement formula is less than 0.5%, and the cement can tolerate the high temperature of 120 DEG C. The cement formula disclosed by the invention can be normally solidified under the mineralization degree of 100000mg / L, and the compressive strength of 40MPa or above is maintained. The cement formula disclosed by the invention can be used for effectively removing blocking in an acid solution, and a blocking channel can be opened in a dissoluble and reversible manner.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield chemical water plugging, and in particular to a low-cost, high-temperature-resistant, high-salt-resistant, soluble, environmentally friendly water plugging cement and a plugging removal method thereof. Background Art

[0002] As the time of water injection development increases, high-permeability water channel will be formed inside the reservoir, resulting in ineffective water injection and wasting water injection cycle energy. In order to improve the efficiency of water injection development, using water-blocking cement to block high-permeability water flow channels is one of the effective technical means. However, in the high-temperature and high-salinity reservoir environment (120℃, 100000mg / L), the solidification effect of water-blocking cement is difficult to guarantee, resulting in poor water-blocking effect. However, there are few studies on the existing high-temperature and high-salinity cement formulas, and the existing formulas and technologies are costly, which cannot form a large profit margin, and their large-scale application in high-water-content, high-temperature and high-salinity reservoirs is limited. Therefore, low-cost, high-temperature and high-salinity water-blocking cement technology is one of the technical problems that need to be solved in this technical field. On this basis, some high-temperature and high-salinity reservoirs also have the need to reopen the plugging layer in order to carry out subsequent production activities. This requires that the water-blocking cement can be dissolved in addition to the characteristics of low cost, high-temperature resistance and high-salinity resistance, so as to unblock the blocked high-permeability water layer, and this technical problem has not yet been effectively solved.

[0003] On this basis, fly ash, as a waste product from coal combustion, is reused, which has environmental protection significance. Summary of the invention

[0004] The purpose of the present invention is to provide a low-cost, high-temperature, high-salt-resistant, soluble, environmentally friendly water-plugging cement and a method for removing water plugging, so as to solve the technical problems of high cost and poor water-plugging effect of existing water-plugging cement.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a low-cost, high-temperature-resistant, high-salt-resistant, soluble, environmentally friendly water-plugging cement, which is composed of the following components in parts by weight:

[0007]

[0008] 5-15 parts of Portland cement;

[0009] 9-15 parts of improver;

[0010] The water-cement ratio of the environmentally friendly water-blocking cement is 5:6.

[0011] Furthermore, the environmentally friendly water plugging cement is composed of the following components in parts by weight:

[0012] 20 parts of bluestone powder, 20 parts of fly ash, 10 parts of calcium hydroxide, 1 part of potassium chloride, 5 parts of portland cement, 9 parts of modifier.

[0013] Furthermore, the environment-friendly water-blocking cement is composed of components including the following parts by weight:

[0014] 30 parts of bluestone powder, 30 parts of fly ash, 13 parts of calcium hydroxide, 1.5 parts of potassium chloride, 10 parts of portland cement, 12 parts of modifier.

[0015] Furthermore, the environment-friendly water-blocking cement is composed of components including the following parts by weight:

[0016] 40 parts of bluestone powder, 40 parts of fly ash, 15 parts of calcium hydroxide, 2 parts of potassium chloride, 15 parts of portland cement, 15 parts of modifier.

[0017] Furthermore, the modifier comprises the following components: 30 - 50 parts of sodium chloride, 30 - 50 parts of magnesium chloride, 30 - 50 parts of calcium chloride, 30 - 50 parts of calcium silicate, 10 - 20 parts of sodium bentonite, 10 - 20 parts of calcium bentonite, 4 - 6 parts of additive.

[0018] Furthermore, the modifier comprises the following components: 30 parts of sodium chloride, 30 parts of magnesium chloride, 30 parts of calcium chloride, 30 parts of calcium silicate, 10 parts of sodium bentonite, 10 parts of calcium bentonite, 4 parts of additive.

[0019] Furthermore, the modifier comprises the following components: 40 parts of sodium chloride, 40 parts of magnesium chloride, 40 parts of calcium chloride, 40 parts of calcium silicate, 15 parts of sodium bentonite, 15 parts of calcium bentonite, 5 parts of additive.

[0020] Furthermore, the components in the modifier include: 50 parts of sodium chloride, 50 parts of magnesium chloride, 50 parts of calcium chloride, 50 parts of calcium silicate, 20 parts of sodium bentonite, 20 parts of calcium bentonite, 6 parts of additive.

[0021] Furthermore, the additive includes one or several of polyacrylamide, carboxymethyl cellulose and triethanolamine; the particle sizes of the components in the environment-friendly water-blocking cement are independently ≤ 74 μm.

[0022] The present invention also discloses a method for removing the blockage of the low-cost high-temperature resistant high-salt soluble environment-friendly water-blocking cement. The blockage removal liquid is injected into the plugging port in multiple segments to complete the blockage removal work; the blockage removal liquid comprises hydrochloric acid, acetic acid and water with a volume ratio of 2 - 3:7 - 9:10.

[0023] The beneficial effects of the present invention:

[0024] 1. In the cement materials, the bluestone powder and fly ash exceed 50%, with low cost and suitable for large-scale promotion.

[0025] 2. Fly ash, as a combustion waste of coal, has been reused, which has environmental protection significance.

[0026] 3. In the cement formula of the present invention, the organic component is less than 0.5%, and it can withstand high temperature of 120 °C.

[0027] 4. The cement formula of the present invention can normally solidify at a salinity of 100,000 mg / L and maintain a compressive strength of 40 MPa.

[0028] 5. The cement formula of the present invention can effectively remove blockage in acid solution, realizing dissolvable and reversible opening of the plugging channel. Detailed implementation mode

[0029] The present invention provides an environmentally friendly water plugging cement with low cost, high temperature resistance, high salt resistance and solubility, which is composed of components containing the following parts by weight:

[0030]

[0031] The water-cement ratio of the environmentally friendly water plugging cement is 5:6.

[0032] Preferably, the environmentally friendly water plugging cement is composed of components containing the following parts by weight:

[0033] 20 parts of bluestone powder, 20 parts of fly ash, 10 parts of calcium hydroxide, 1 part of potassium chloride, 5 parts of portland cement, 9 parts of modifier.

[0034] Preferably, the environmentally friendly water plugging cement is composed of components containing the following parts by weight:

[0035] 30 parts of bluestone powder, 30 parts of fly ash, 13 parts of calcium hydroxide, 1.5 parts of potassium chloride, 10 parts of portland cement, 12 parts of modifier.

[0036] Preferably, the environmentally friendly water plugging cement is composed of components containing the following parts by weight:

[0037] 40 parts of bluestone powder, 40 parts of fly ash, 15 parts of calcium hydroxide, 2 parts of potassium chloride, 15 parts of portland cement, 15 parts of modifier.

[0038] Preferably, the modifier contains the following components: 30-50 parts of sodium chloride, 30-50 parts of magnesium chloride, 30-50 parts of calcium chloride, 30-50 parts of calcium silicate, 10-20 parts of sodium bentonite, 10-20 parts of calcium bentonite, 4-6 parts of additive.

[0039] Preferably, the modifier contains the following components: 30 parts of sodium chloride, 30 parts of magnesium chloride, 30 parts of calcium chloride, 30 parts of calcium silicate, 10 parts of sodium bentonite, 10 parts of calcium bentonite, 4 parts of additive.

[0040] Preferably, the modifier comprises the following components: 40 parts of sodium chloride, 40 parts of magnesium chloride, 40 parts of calcium chloride, 40 parts of calcium silicate, 15 parts of sodium bentonite, 15 parts of calcium bentonite, and 5 parts of additive.

[0041] Preferably, the components in the modifier comprise: 50 parts of sodium chloride, 50 parts of magnesium chloride, 50 parts of calcium chloride, 50 parts of calcium silicate, 20 parts of sodium bentonite, 20 parts of calcium bentonite, and 6 parts of additive.

[0042] Preferably, the additive comprises one or more of polyacrylamide, carboxymethyl cellulose, and triethanolamine, preferably polyacrylamide; the particle size of each component in the environmentally friendly water shutoff cement is independently ≤74 μm.

[0043] The present invention also discloses a method for unplugging an environmentally friendly water shutoff cement with low cost, high temperature resistance, high salt resistance, and solubility. The unplugging fluid is injected into the plugging port in multiple segments to complete the unplugging work; the unplugging fluid comprises hydrochloric acid, acetic acid, and water in a volume ratio of 2-3:7-9:10.

[0044] Preferably in the present invention, the unplugging fluid comprises hydrochloric acid, acetic acid, and water in a volume ratio of 2:8:10.

[0045] In the present invention, to ensure that the water shutoff cement can be fully mixed and effectively enter the deep formation, all components should be able to pass through a 200-mesh sieve (≤74 μm). The water-cement ratio is 5:6 and is injected into the plugging layer after mixing, and the setting time is greater than 24 hours.

[0046] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0047] Example 1

[0048] In a certain tight sandstone reservoir, water channeling occurred due to fracturing. It is now required to temporarily plug the high-permeability water flow channel with water shutoff cement. Later, in order to develop the deep reservoir, unplugging is required 12 months after the plugging development. The reservoir temperature is 95°C and the salinity is 90,000 mg / L.

[0049] Prepare the cement system according to the raw material weight ratio: 30 parts of bluestone powder, 30 parts of fly ash, 13 parts of calcium hydroxide, 1.5 parts of potassium chloride, 10 parts of portland cement, and 12 parts of modifier. Prepare the modifier system according to the weight ratio: 40 parts of sodium chloride, 40 parts of magnesium chloride, 40 parts of calcium chloride, 40 parts of calcium silicate, 15 parts of sodium bentonite, 15 parts of calcium bentonite, and 5 parts of additive. The additive is selected as polyacrylamide. Before use, it should be ensured that the particle diameter of each component is ≤74 μm. The dosage of each material of the cement is shown in the following table.

[0050] Table 1 Formulation of Example 1

[0051]

[0052]

[0053] Example 2

[0054] Prepare cement system according to the weight composition of raw materials: 20 parts of bluestone powder, 20 parts of fly ash, 10 parts of calcium hydroxide, 1 part of potassium chloride, 5 parts of silicate cement, and 9 parts of improver. Prepare improver system according to the weight composition: 30 parts of sodium chloride, 30 parts of magnesium chloride, 30 parts of calcium chloride, 30 parts of calcium silicate, 10 parts of sodium bentonite, 10 parts of calcium bentonite, and 4 parts of additives. Carboxymethyl cellulose is selected as the additive. Before use, ensure that the particle diameter of each component is ≤74μm. The amount of each material used in cement is shown in the table below.

[0055] Table 2 Formulation of Example 2

[0056]

[0057] Example 3

[0058] Prepare cement system according to the weight composition of raw materials: 40 parts of bluestone powder, 40 parts of fly ash, 15 parts of calcium hydroxide, 2 parts of potassium chloride, 15 parts of silicate cement, and 15 parts of improver. Prepare improver system according to the weight composition: 50 parts of sodium chloride, 50 parts of magnesium chloride, 50 parts of calcium chloride, 50 parts of calcium silicate, 20 parts of sodium bentonite, 20 parts of calcium bentonite, and 6 parts of additives. Select triethanolamine as additive. Before use, ensure that the particle diameter of each component is ≤74μm. The amount of each material used in cement is shown in the table below.

[0059] Table 3 Formulation of Example 3

[0060]

[0061] In Examples 1 to 3, the water-cement ratio is 5:6. 834 g of water should be added to every 1 kg of cement. After sufficient stirring, the cement is injected into the plugging layer. After the injection is completed, the pressure is maintained for 24 hours. Then, water injection development is started.

[0062] When unblocking is required, use the unblocking acid formula with a ratio of hydrochloric acid: acetic acid: water of 2:8:10. Inject the unblocking liquid in multiple sections. That is, after injecting a part of the acid, maintain the pressure to unblock for a period of time, and then inject another part of the acid to continue unblocking. Repeat this process several times to complete the unblocking operation.

[0063] The environmentally friendly water plugging cement obtained in Examples 1 to 3 was tested for performance, and the results are shown in Table 1 below.

[0064] Table 1 Test data

[0065] Initial setting time / h Final setting time / h Waiting for setting / h 24h compressive strength / MPa Example 1 3 10 ＞24 43 Example 2 4 12 ＞24 42 Example 3 5 14 ＞24 41

[0066] As can be seen from the above embodiments, the present invention provides an environmentally friendly water plugging cement with low cost, high temperature resistance, high salt resistance and solubility, and a method for removing the plugging thereof. The cement formula of the present invention can normally solidify at a salinity of 100,000 mg / L and maintain a compressive strength of more than 40 MPa. The cement formula of the present invention can effectively remove the plugging in an acid solution, realizing the dissolution and reversible opening of the plugging channel.

[0067] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A low-cost, high-temperature, high-salt-resistant, soluble, environmentally friendly water-plugging cement, characterized in that: It is composed of the following components in parts by weight: The water-cement ratio of the environmentally friendly water-blocking cement is 5:

6.

2. The low-cost, high-temperature-resistant, high-salt-resistant, soluble, environmentally friendly water-plugging cement according to claim 1 is characterized in that: The environmentally friendly water plugging cement is composed of the following components in parts by weight: 20 parts of bluestone powder, 20 parts of fly ash, 10 parts of calcium hydroxide, 1 part of potassium chloride, 5 parts of silicate cement, and 9 parts of improver.

3. The low-cost, high-temperature, high-salt, soluble, environmentally friendly water-plugging cement according to claim 1 is characterized in that: The environmentally friendly water plugging cement is composed of the following components in parts by weight: 30 parts of bluestone powder, 30 parts of fly ash, 13 parts of calcium hydroxide, 1.5 parts of potassium chloride, 10 parts of silicate cement, and 12 parts of improver.

4. The low-cost, high-temperature-resistant, high-salt-resistant, soluble, environmentally friendly water-plugging cement according to claim 1 is characterized in that: The environmentally friendly water plugging cement is composed of the following components in parts by weight: 40 parts of bluestone powder, 40 parts of fly ash, 15 parts of calcium hydroxide, 2 parts of potassium chloride, 15 parts of silicate cement, and 15 parts of improver.

5. The low-cost, high-temperature, high-salt, soluble, environmentally friendly water-plugging cement according to any one of claims 1 to 4, characterized in that: The improver comprises the following components: 30-50 parts of sodium chloride, 30-50 parts of magnesium chloride, 30-50 parts of calcium chloride, 30-50 parts of calcium silicate, 10-20 parts of sodium bentonite, 10-20 parts of calcium bentonite, and 4-6 parts of additives.

6. The low-cost, high-temperature, high-salt, soluble, environmentally friendly water-plugging cement according to any one of claims 1 to 4, characterized in that: The improver comprises the following components: 30 parts of sodium chloride, 30 parts of magnesium chloride, 30 parts of calcium chloride, 30 parts of calcium silicate, 10 parts of sodium bentonite, 10 parts of calcium bentonite, and 4 parts of additives.

7. The low-cost, high-temperature-resistant, high-salt-resistant, soluble, environmentally friendly water-plugging cement according to any one of claims 1 to 4, characterized in that: The improver comprises the following components: 40 parts of sodium chloride, 40 parts of magnesium chloride, 40 parts of calcium chloride, 40 parts of calcium silicate, 15 parts of sodium bentonite, 15 parts of calcium bentonite, and 5 parts of additives.

8. The low-cost, high-temperature, high-salt, soluble, environmentally friendly water-plugging cement according to any one of claims 1 to 4, characterized in that: The components of the improver include: 50 parts of sodium chloride, 50 parts of magnesium chloride, 50 parts of calcium chloride, 50 parts of calcium silicate, 20 parts of sodium bentonite, 20 parts of calcium bentonite, and 6 parts of additives.

9. The low-cost, high-temperature-resistant, high-salt-resistant, soluble, environmentally friendly water-plugging cement according to claim 5, characterized in that: The additive comprises one or more of polyacrylamide, carboxymethyl cellulose and triethanolamine; and the particle size of each component in the environmentally friendly water plugging cement is independently ≤74 μm.

10. The method for removing plugging by using low-cost, high-temperature, high-salt-resistant, soluble, environmentally friendly water-plugging cement according to any one of claims 1 to 9, characterized in that: The unblocking liquid is injected into the plugging port in sections for multiple times to complete the unblocking work; the unblocking liquid contains hydrochloric acid, acetic acid and water in a volume ratio of 2 to 3:7 to 9:10.

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