High-density solid-free weighting liquid as well as preparation method and application thereof

Abstract

The invention discloses a high-density solid-free weighting liquid which comprises the following components in parts by weight: 100 parts of zinc salt, 1-50 parts of choline chloride, 1-50 parts of water and 0-10 parts of other components, wherein the zinc salt is zinc chloride and / or zinc bromide; the other component is at least one of a filtrate reducer, a corrosion inhibitor and a shear strength improving agent; the high-density solid-free weighting liquid is prepared by mixing a low-cost zinc salt and a composite solvent system prepared from choline chloride and water, the weighting limit of the zinc salt is enhanced, the cost is low, the density of the solid-free weighting liquid is adjustable between 1.8 g / cm < 3 > and 2.6 g / cm < 3 >, the problem that a solid-free weighting system in a high-density interval of 2.3 g / cm < 3 > and 2.6 g / cm < 3 > is not easy to prepare is solved, and the high-density solid-free weighting liquid is suitable for large-scale production. Meanwhile, the adding amount of zinc salt is reduced in the low-density interval range of 1.8 g / cm < 3 > to 2.2 g / cm < 3 >.

Description

Technical Field

[0001] The invention relates to the technical field of drilling fluid weighting and completion fluid weighting, and in particular to a high-density solid-phase-free weighting fluid and a preparation method and application thereof. Background Art

[0002] During the drilling and completion construction of oil fields, the drilling fluid and completion fluid need to be weighted to balance the formation pressure. The traditional method is to use barite for weighting. However, as the density demand increases, the amount of barite added also increases, which will cause a significant increase in the solid content of the drilling and completion fluids, causing serious damage to the reservoir and seriously affecting oil and gas production capacity. Subsequently, a solid-free weighting technology was developed, which uses potassium chloride, sodium chloride, sodium bromide, potassium bromide, sodium formate, potassium formate, cesium formate, calcium chloride, calcium bromide, zinc chloride, zinc bromide, sodium acetate, organic ammonium salts and other soluble salts for weighting. At the same time, in order to reduce the corrosion of salts to casing, drilling tools, and other types of downhole tools, various corrosion inhibitors are added thereto. The solid-free weighting fluid prepared by the above method effectively solves the problem of barite blocking the reservoir and has a very good effect on the stability of the well wall. However, the weighted density of the weighted fluid developed by the existing technology is very limited. As drilling conditions become increasingly complex, the existing technology is difficult to meet in some special cases, such as ultra-high density 2.3g / cm 3 ~2.6g / cm 3 The demand for solid-free drilling fluid or completion fluid; In addition, the current realization of 1.8g / cm 3 ~2.2g / cm 3 The weighting system for the density range generally uses cesium formate or zinc bromide, which is too expensive, limiting its promotion and use on site. The use of relatively low-cost zinc chloride for weighting has a maximum density of only 2.0g / cm 3 , cannot meet the requirements.

[0003] Therefore, in order to solve the above ultra-high density (2.3g / cm 3 ~2.6g / cm 3 ) No solid phase weighting problem, and the weighting range is reduced to 1.8g / cm 3 ~2.2g / cm 3 In order to reduce the weighting cost, it is necessary to design a new weighting system. Summary of the invention

[0004] The purpose of the present invention is to provide a super high density (2.3g / cm 3 ~2.6g / cm 3 ) No solid phase weighting problem, and the weighting range is reduced to 1.8g / cm 3 ~2.2g / cm 3 High density solid-free weighting fluid with minimal weighting cost.

[0005] Another object of the present invention is to provide a method for preparing the high-density solid-free weighting liquid.

[0006] Another object of the present invention is to provide an application of the high-density solid-free weighting liquid.

[0007] To this end, the technical solution of the present invention is as follows:

[0008] A high-density solid-free weighting liquid comprises 100 parts of zinc salt, 1 to 50 parts of choline chloride, 1 to 50 parts of water and 0 to 10 parts of other components in parts by weight; wherein the zinc salt is zinc chloride and / or zinc bromide; and the other components are at least one of a fluid loss reducer, a corrosion inhibitor and a shear enhancer.

[0009] Preferably, the weight ratio of choline chloride to water is (1.45-3.8):1.

[0010] Preferably, the fluid loss reducer is a polymer or copolymer obtained by polymerizing at least one monomer selected from the group consisting of acrylic acid, methacrylic acid, acrylamide, acrylonitrile, itaconic acid, and 2-acrylamide-2-methylpropanesulfonic acid.

[0011] Preferably, the fluid loss reducer is obtained by grafting acrylamide, methacrylic acid, 2-acrylamide-2-methylpropanesulfonic acid or acrylic acid onto starch or cellulose.

[0012] Preferably, the corrosion inhibitor is an organic amine corrosion inhibitor.

[0013] Preferably, the shearing agent is a water-soluble polymer shearing agent.

[0014] A preparation method of a high-density solid-free weighting liquid comprises the following steps: after choline chloride, water and zinc salt are uniformly mixed according to a certain proportion, the mixed system is heated to 50°C to 100°C so that the choline chloride, water and zinc salt form a co-solvent system more quickly; after the choline chloride, water and zinc salt are completely dissolved by stirring, other components (a fluid loss reducer, a corrosion inhibitor and / or a shearing agent) are added, and the stirring is continued to be uniform, so as to obtain a high-density solid-free weighting liquid.

[0015] The high-density solid-free weighting fluid is used as well repair fluid and well killing fluid in oil field exploitation; and as drilling fluid and cement slurry spacer fluid in oil field drilling.

[0016] Compared with the prior art, the high-density solid-free weighting liquid is prepared by mixing low-cost zinc salt (zinc bromide and / or zinc chloride) and a composite solvent system prepared by choline chloride and water. Choline chloride as a hydrogen bond acceptor and water as a hydrogen bond donor are mixed in a certain proportion to form a property similar to that of an ionic liquid. The weighting limit of the zinc salt is enhanced by compounding with a soluble zinc salt. The high-density solid-free weighting liquid is not only low in cost, but also has a density of 1.8 g / cm3 ~2.6g / cm 3 Adjustable between 2.3 and 2.6 g / cm 3 The high density range does not have the problem of being difficult to prepare a solid phase weighting system. 3 The amount of zinc salt added is also reduced in the low-density range; compared with the use of cesium formate to achieve high-density weighting in the prior art, the weighting cost is effectively reduced; based on this, the high-density solid-free weighting fluid can be widely used in the preparation of well repair fluid, well killing fluid, drilling fluid and cement slurry spacer fluid. DETAILED DESCRIPTION

[0017] The present invention will be further described below in conjunction with specific examples, but the following examples are by no means intended to limit the present invention in any way.

[0018] Example 1

[0019] After 1 kg zinc bromide, 160 g choline chloride and 45 g water are mixed evenly, the mixture is heated to 50 °C and stirred until completely dissolved to obtain a density of 2.61 g / cm 3 The high-density solid-free weighting liquid I is placed at 50° C. for 30 days and remains liquid without solid precipitation.

[0020] Example 2

[0021] After 1 kg zinc bromide, 175 g choline chloride and 45 g water are mixed evenly, the mixture is heated to 50 °C and stirred until completely dissolved to obtain a density of 2.56 g / cm 3 The high-density solid-free weighting liquid II is still liquid without solid precipitation when placed at 50°C for 30 days.

[0022] Example 3

[0023] After 1 kg zinc chloride, 145 g choline chloride and 100 g water are mixed evenly, the mixture is heated to 80 °C and stirred until completely dissolved to obtain a density of 2.20 g / cm 3 The high-density solid-free weighting liquid III is still liquid without solid precipitation when placed at 50°C for 30 days.

[0024] Example 4

[0025] After 1kg zinc chloride, 201g zinc bromide, 258g choline chloride and 116g water are mixed evenly, the mixture is heated to 50°C and stirred until completely dissolved, and then other components are added and stirred evenly to obtain a density of 1.98g / cm 3The high-density solid-free weighting liquid IV is placed at 50° C. for 30 days and remains liquid without solid precipitation.

[0026] Example 5

[0027] After 1kg zinc chloride, 150g choline chloride and 102g water are mixed evenly, the mixture is heated to 80°C and stirred until completely dissolved. Then 10g organic amine corrosion inhibitor is added and stirred evenly to obtain a density of 2.15g / cm 3 The high-density solid-free weighting liquid V is placed at 50° C. for 30 days and remains liquid without solid precipitation.

[0028] Since the high-density solid-free weighting liquid V is added with corrosion inhibitor, its corrosion performance is also tested using N80 steel sheet. The test method is: 50g of weighting liquid is placed in a hydrothermal kettle containing a polytetrafluoroethylene liner; then an N80 steel sheet with a specification of 40mm*13mm*2mm is placed in the weighting liquid, placed at 180°C for 7 days, taken out, and the corrosion condition is inspected; the test results show that the corrosion rate of the steel sheet is 0.06mm / year; compared with the weighting liquid without adding corrosion inhibitor, the corrosion rate is slowed down by 90%, indicating that the weighting system can have good compatibility with conventional corrosion inhibitors and does not affect the corrosion inhibition performance of the corrosion inhibitor.

[0029] Example 6

[0030] After 1kg zinc chloride, 150g choline chloride and 102g water are mixed evenly, the mixed system is heated to 50°C and stirred until completely dissolved. Then 10g of filtrate reducer prepared by grafting starch with acrylic acid is added and stirred evenly to obtain a density of 2.15g / cm 3 The high-density solid-free weighting liquid VI is still liquid without solid precipitation when placed at 50°C for 30 days.

[0031] Since the high-density solid-free weighting liquid VI is added with a filtrate reducer, the filtrate reduction performance is tested by a medium-pressure filter loss meter. The test method is: under a pressure difference of 0.7 MPa, the filtrate loss in 30 minutes is 2 mL; compared with the weighting liquid without adding the filtrate loss agent, under a pressure difference of 0.7 MPa, the filtrate loss in 30 minutes is reduced by 5 mL, indicating that the weighting system has good compatibility with conventional filtrate reducers and does not affect the filtrate reduction performance of the filtrate reducer.

[0032] Example 7

[0033] After 1kg zinc chloride, 150g choline chloride and 102g water are mixed evenly, the mixture is heated to 80°C and stirred until completely dissolved. Then 8g water-soluble polymer shearing agent is added and stirred evenly to obtain a density of 2.15g / cm 3 The high-density solid-free weighting liquid VII is placed at 50° C. for 30 days and remains liquid without solid precipitation.

[0034] Since a shearing agent is added to the high-density solid-free weighting liquid VI, the rheological properties are tested using a high-temperature and high-pressure rheometer. The experimental results at 150°C show that compared with the blank experiment of the weighting liquid without adding a shearing agent, the initial shearing performance is improved by 5 times, the final shearing performance is improved by 4 times, and the apparent viscosity is increased by 40%, indicating that the weighting system has good compatibility with conventional shearing agents and does not affect the shearing performance of the shearing agents.

[0035] Comparative Example 1

[0036] Take 200g of zinc chloride, gradually add water, and stir at 80℃ until the zinc chloride is completely dissolved to form a saturated solution. The density of the saturated zinc chloride aqueous solution is 1.99g / cm 3 The saturated zinc chloride aqueous solution was placed at 50°C for 24 hours, and solid precipitated.

[0037] Comparative Example 2

[0038] Take 200g of zinc bromide, gradually add water, and stir at 80℃ until the zinc bromide is completely dissolved to form a saturated solution. The density of the saturated zinc bromide aqueous solution is 2.30g / cm 3 The saturated zinc bromide aqueous solution was placed at 50°C for 24 hours, and solid precipitated.

[0039] It can be seen from the above Comparative Examples 1 and 2 that the maximum density of the zinc chloride aqueous solution alone at 80°C is 1.99 g / cm 3 Although zinc bromide has better solubility than zinc chloride, its maximum density in aqueous solution at 80°C can only reach 2.3 g / cm 3 Compared with the two comparative examples, the high-density solid-free weighting liquid prepared in Examples 1 to 7 achieves a density of 1.8 g / cm by compounding a zinc salt (zinc chloride and / or zinc bromide) with an aqueous solution of choline chloride. 3 ~2.6g / cm 3 Preparation of solid-free weighting liquid.

Claims

1. A high-density solid-free weighting liquid, characterized in that: The invention comprises 100 parts of zinc salt, 1 part to 50 parts of choline chloride, 1 part to 50 parts of water and 0 part to 10 parts of other components in parts by weight; wherein the zinc salt is zinc chloride and / or zinc bromide; and the other components are at least one of a fluid loss reducer, a corrosion inhibitor and a shear enhancer.

2. The high-density solid-free weighting liquid according to claim 1, characterized in that: The weight ratio of choline chloride to water is (1.45-3.8):

1.

3. The high-density solid-free weighting liquid according to claim 1, characterized in that: The fluid loss reducer is a polymer or copolymer obtained by polymerizing at least one monomer selected from acrylic acid, methacrylic acid, acrylamide, acrylonitrile, itaconic acid and 2-acrylamide-2-methylpropanesulfonic acid.

4. The high-density solid-free weighting liquid according to claim 1, characterized in that: The fluid loss reducer is obtained by grafting starch or cellulose with acrylamide, methacrylic acid, 2-acrylamide-2-methylpropanesulfonic acid or acrylic acid.

5. The high-density solid-free weighting liquid according to claim 1, characterized in that: The corrosion inhibitor is an organic amine corrosion inhibitor.

6. The high-density solid-free weighting liquid according to claim 1, characterized in that: The shearing agent is a water-soluble polymer shearing agent.

7. A method for preparing a high-density solid-free weighting liquid as claimed in any one of claims 1 to 6, characterized in that: The method comprises the following steps: uniformly mixing choline chloride, water and zinc salt according to a certain proportion, heating the mixed system to 50°C to 100°C, stirring to completely dissolve, adding other components, and continuing to stir uniformly to obtain a high-density solid-free weighting liquid.

8. Use of a high-density solid-free weighting liquid as claimed in any one of claims 1 to 6, characterized in that: It is used as workover fluid and well killing fluid in oil field exploitation.

9. Use of a high-density solid-free weighting liquid as claimed in any one of claims 1 to 6, characterized in that: Used as drilling fluid and cement slurry spacer fluid in oil field drilling.