Wellbore sand flushing fluid and its preparation method and application

Abstract

The present invention belongs to the field of oil and gas well repair operations, and specifically relates to a wellbore sand flushing fluid and its preparation method and application. The raw materials of the sand flushing fluid include tetradecyl primary amine, didodecylamine, hydrochloric acid, white oil and water. First, 2-5 parts of tetradecyl primary amine are added to 92-97 parts of water, and 1-3 parts of hydrochloric acid are added during stirring to adjust the pH to obtain solution B; then 2-8 parts of didodecylamine are added to 92-98 parts of white oil and stirred to obtain solution C; 40-50 parts of solution B and 50-60 parts of solution C are mixed, heated and stirred to obtain emulsion A; 1-4 parts of emulsion A are mixed with 96-99 parts of water to obtain sand flushing fluid. The sand flushing fluid and nitrogen are simultaneously introduced into the well for sand flushing, which has a simple process and low cost. Stable suspension of sand is achieved at a relatively low viscosity, and no defoaming is required. It can be quickly reused after standing or filtering.

Description

Technical Field

[0001] The invention belongs to the field of oil and gas well repair operations, and particularly relates to a wellbore sand flushing fluid and a preparation method and application thereof. Background Art

[0002] During the development of oil and gas reservoirs, sand production from the formation often occurs. If the fluid in the well cannot carry all the sand out of the wellbore, the sand will continue to accumulate in the wellbore, resulting in sand-buried reservoirs, increasing fluid flow resistance and reducing production. Therefore, wellbore sand cleaning operations are required for oil and gas wells that produce sand. Common sand cleaning methods include mechanical sand bailing and tubing sand flushing. Commonly used sand flushing fluids include clean water, glue, foam, etc. For wells with long-term production bottom layer deficits or wells with relatively low formation pressure coefficients, using clean water or glue to flush sand often results in serious leakage, inability to establish effective circulation, and difficulty in returning sand to the wellhead. Therefore, sand flushing is performed in wells or formations with low pressure coefficients.

[0003] Commonly used sand flushing media are water (including seawater) and foam. Foam fluids offer advantages such as low density, high viscosity, low fluid loss, and strong sand-carrying capacity. Furthermore, with long-term oilfield production, reservoir pressure decreases significantly, making foam a common medium for sand flushing. However, existing foam sand flushing processes generally fail to recycle the foam base fluid, resulting in significant waste from single-use foam and environmental pollution from returned foam. This not only increases the cost of foam sand flushing and well cleaning, but also poses a threat to environmental protection.

[0004] At present, methods such as changing the pH value of the foam base liquid and adding organic defoaming agents are commonly used in nitrogen foam sandblasting construction to achieve the purpose of defoaming and re-foaming. The method of changing the pH value of the foam base liquid is selective for the foaming agent and is limited to amphoteric foaming agents. In addition, corrosive strong acids and strong bases need to be repeatedly added during the circulation process to adjust the pH value. There are safety risks during transportation and construction, and the construction equipment requirements are high and the construction process is relatively complicated. Although the addition of conventional organic defoaming agents can quickly defoam, it is easy to affect the performance of the foaming agent, inhibiting its ability to re-foam, and cannot achieve the recycling of the foam base liquid.

[0005] Chinese invention patent application CN102031098A discloses a recyclable foam base fluid for sand flushing and well washing. This sand flushing and well washing fluid comprises an N-alkyl-β-aminopropionic acid-based amphoteric surfactant and water. By adjusting the pH of the base fluid, the amphoteric surfactant's sensitivity to acid and alkali allows for the recycling of the foam. While this invention achieves foam recycling, it requires the use of corresponding acid and alkali tanks, as well as mixing equipment. The repeated addition of strong acids and alkalis during the recycling process complicates the recycling process and results in high application costs.

[0006] Chinese invention patent application CN112240173A discloses a foam-cycle-based sand flushing system for oil and gas wells, as well as defoaming and foaming fluids used for this purpose. This invention involves adding a defoaming fluid to the sand-carrying foam fluid obtained after well flushing to remove the foam, separate the sand particles, and then adding a foaming agent to the resulting fluid for reuse. However, this invention suffers from the repeated addition of foaming and defoaming agents, requiring large amounts of chemicals, and the defoaming agent can inhibit the re-foaming properties of the sand flushing fluid.

[0007] Chinese invention patent application CN115725287A discloses a heat-resistant and salt-resistant nitrogen foam sand-flushing fluid and its preparation and use methods. The nitrogen foam fluid comprises a nitrogen foam stock solution, a settling aid, and a sand-carrying agent. The nitrogen foam stock solution includes: 0.01% to 0.2% sodium polyacrylate, 0.01% to 1% carboxymethyl cellulose, 0.01% to 0.1% carrageenan, 0.01% to 0.2% polyvinyl pyrrolidone, 0.1% to 1% sodium carbonate, 0.1% to 2% sodium bicarbonate, 0.01% to 0.1% triethanolamine, 0.01% to 0.5% sodium dodecylbenzenesulfonate, 0.01% to 0.5% octadecylphenol polyoxyethylene ether, 0.01% to 0.5% dodecyl dimethyl betaine, and the balance is water. The sand-flushing fluid in this invention has a strong sand-carrying capacity, can quickly separate sediment from the foam solution, and can be recycled multiple times. However, the large number of additives results in high costs.

[0008] Therefore, it is necessary to develop a sand flushing fluid that has a simple preparation process, low cost, can quickly separate liquid sand without defoaming treatment, and can be recycled. Summary of the Invention

[0009] To address the above-mentioned issues, the present invention provides a wellbore sand flushing fluid, its preparation method, and its application. The sand flushing fluid is quickly prepared by directly mixing an emulsion-type agent with clean water. This sand flushing fluid is mixed with nitrogen and injected into the wellbore. The sand flushing fluid flushes the sand within the wellbore, flushing the sediment to the surface at relatively low viscosity or flow rates.

[0010] In order to achieve the above-mentioned purpose of the present invention, the specific technical solution adopted by the present invention is:

[0011] A wellbore sand flushing fluid consists of emulsion A and water, wherein the raw materials of emulsion A include tetradecyl primary amine, didodecylamine, hydrochloric acid, white oil and water.

[0012] Preferably, the emulsion A comprises solution B and solution C, wherein the raw materials of solution B comprise tetradecyl primary amine, hydrochloric acid and water; the raw materials of solution C comprise didodecylamine and white oil.

[0013] Preferably, the sand flushing fluid comprises 1-4 parts of emulsion A and 96-99 parts of water, by weight.

[0014] Preferably, the emulsion A comprises 40-50 parts of solution B and 50-60 parts of solution C by weight.

[0015] Preferably, the raw materials of the solution B include 2-5 parts of tetradecyl primary amine, 1-3 parts of hydrochloric acid and 92-97 parts of water in parts by weight.

[0016] Preferably, the raw materials of the solution C include 2-8 parts of didodecylamine and 92-98 parts of white oil in parts by weight.

[0017] The present invention also relates to a method for preparing a wellbore sand flushing fluid, comprising the following steps:

[0018] (1) Tetradecyl primary amine was added to water and hydrochloric acid was added during stirring to obtain solution B;

[0019] (2) adding didodecylamine to white oil and stirring to obtain solution C;

[0020] (3) Mixing solution B and solution C, heating and stirring to obtain emulsion A;

[0021] (4) Emulsion A is mixed with water to obtain sand washing liquid.

[0022] Preferably, in step (1), hydrochloric acid is added to adjust the pH to 7-8, and the mass concentration of hydrochloric acid is 10-20%.

[0023] Preferably, the heating temperature in step (3) is 50-70° C., and the heating and stirring time is 8-10 min.

[0024] The present invention also relates to the use of the sand flushing fluid or the sand flushing fluid prepared by the above preparation method in sand flushing and well washing.

[0025] Preferably, during the sand flushing and well washing process, a sand flushing fluid or a sand flushing fluid and nitrogen are simultaneously introduced into the well to flush the sand, and the fluid returned from the well is sedimented or filtered to remove sand and then re-introduced into the well as the sand flushing fluid.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The present invention can achieve surface modification of sand deposited in the wellbore. Even in a static state, the sand adsorbed / encapsulated with nitrogen can still be suspended in the sand flushing fluid. The sand flushing fluid is mixed with an appropriate amount of sand and shaken thoroughly in a closed container. The suspension rate of the sand in clean water can reach 90% or more.

[0028] (2) The sand washing liquid has low viscosity and is easy to separate from the liquid sand. It does not require defoaming and can be quickly reused after standing or filtering.

[0029] (3) Compared with conventional foam sand washing, this technology has the advantages of simple process and low cost. It can achieve stable suspension of sand at a lower viscosity and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The conventional foam sand washing fluid (left) and the sand washing fluid of Example 1 (center and right). DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention are further clearly described. The described embodiments are only a part of the present invention and are used to explain the present invention, but not to limit the present invention. Therefore, other embodiments obtained by other technicians in this field without creative work all fall within the scope of protection of the present invention.

[0032] The experimental methods without specific conditions specified in the examples are generally based on conventional conditions. The materials and reagents used in the following examples are all commercially available unless otherwise specified.

[0033] Example 1

[0034] The raw materials of the wellbore sand flushing fluid in this embodiment are tetradecyl primary amine, didodecylamine, hydrochloric acid, white oil and water.

[0035] The preparation method of the wellbore sand flushing fluid is specifically performed as follows:

[0036] (1) Add 3 parts of tetradecyl primary amine to 95 parts of water, add 2 parts of hydrochloric acid (hydrochloric acid concentration is 15%), stir thoroughly until completely dissolved, and the pH is 7, to prepare solution B;

[0037] (2) Add 5 parts of didodecylamine to 95 parts of white oil and stir thoroughly to prepare solution C;

[0038] (3) 50 parts of solution B and 50 parts of solution C were heated at 60° C. for 10 min and stirred for 10 min to prepare emulsion A;

[0039] (4) Mix 97 parts of clean water with 3 parts of emulsion A to obtain a sand washing solution.

[0040] Weigh 10 parts of quartz sand (particle size < 0.5 mm) and mix it with 90 parts of sand washing liquid. Shake it thoroughly in a closed container and take a picture immediately. The suspension rate of sand in clean water can reach 95%. Figure 1 As shown in the middle figure, the lower clear liquid can be reused.

[0041] Weigh 10 parts of quartz sand (particle size < 0.5 mm) and mix with 90 parts of the above lower layer of clear water. Shake thoroughly in a sealed container and take a picture immediately. The suspended state of the sand can be seen. Figure 1As shown in the right picture, more than 60% of the sand can still float on the water surface.

[0042] Example 2

[0043] The raw materials of the wellbore sand flushing fluid in this embodiment are tetradecyl primary amine, didodecylamine, hydrochloric acid, white oil and water.

[0044] The preparation method of the wellbore sand flushing fluid is specifically performed as follows:

[0045] (1) Add 5 parts of tetradecyl primary amine to 92 parts of water, add 3 parts of hydrochloric acid (concentration is 20%), stir thoroughly until completely dissolved, pH is 8, to prepare solution B;

[0046] (2) Add 8 parts of didodecylamine to 92 parts of white oil and stir thoroughly to prepare solution C;

[0047] (3) 40 parts of solution B and 60 parts of solution C were heated at 70°C for 8 minutes and stirred for 8 minutes to prepare emulsion A;

[0048] (4) Mix 99 parts of clean water with 1 part of emulsion A to obtain a sand washing solution.

[0049] Example 3

[0050] The raw materials of the wellbore sand flushing fluid in this embodiment are tetradecyl primary amine, didodecylamine, hydrochloric acid, white oil and water.

[0051] The preparation method of the wellbore sand flushing fluid is specifically performed as follows:

[0052] (1) Add 2 parts of tetradecyl primary amine to 97 parts of water, add 1 part of hydrochloric acid (concentration is 10%), stir thoroughly until completely dissolved, pH is 7, to prepare solution B;

[0053] (2) Add 2 parts of didodecylamine to 98 parts of white oil and stir thoroughly to prepare solution C;

[0054] (3) 45 parts of solution B and 55 parts of solution C were heated at 50° C. for 10 minutes and stirred for 10 minutes to prepare emulsion A;

[0055] (4) Mix 96 parts of clean water with 4 parts of emulsion A to obtain a sand washing solution.

[0056] Comparative Example 1

[0057] The raw materials of the wellbore sand flushing fluid in this comparative example are hexadecyldimethylammonium chloride, didodecylamine, white oil and water.

[0058] The preparation method of the wellbore sand flushing fluid is specifically performed as follows:

[0059] (1) Add 3 parts of hexadecyldimethylammonium chloride to 97 parts of water and stir thoroughly until completely dissolved to prepare solution B;

[0060] (2) Add 5 parts of didodecylamine to 95 parts of white oil and stir thoroughly to prepare solution C;

[0061] (3) 50 parts of solution B and 50 parts of solution C were heated at 60° C. for 10 min and stirred for 10 min to prepare emulsion A;

[0062] (4) Mix 97 parts of clean water with 3 parts of emulsion A to obtain a sand washing solution.

[0063] Comparative Example 2

[0064] The raw materials of the wellbore sand flushing fluid in this comparative example are tetradecyl primary amine, dioctadecylamine, hydrochloric acid, white oil and water.

[0065] The preparation method of the wellbore sand flushing fluid is specifically performed as follows:

[0066] (1) Add 3 parts of tetradecyl primary amine to 95 parts of water, add 2 parts of hydrochloric acid (hydrochloric acid concentration is 15%), stir thoroughly until completely dissolved, and the pH is 7, to prepare solution B;

[0067] (2) Add 5 parts of dioctadecylamine to 95 parts of white oil and stir thoroughly to prepare solution C;

[0068] (3) 50 parts of solution B and 50 parts of solution C were heated at 60° C. for 10 min and stirred for 10 min to prepare emulsion A;

[0069] (4) Mix 97 parts of clean water with 3 parts of emulsion A to obtain a sand washing solution.

[0070] Comparative Example 3

[0071] The raw materials of the wellbore sand flushing fluid in this comparative example are tetradecyl primary amine, didodecylamine, hydrochloric acid, kerosene and water.

[0072] The preparation method of the wellbore sand flushing fluid is specifically performed as follows:

[0073] (1) Add 3 parts of tetradecyl primary amine to 95 parts of water, add 2 parts of hydrochloric acid (hydrochloric acid concentration is 15%), stir thoroughly until completely dissolved, and the pH is 7, to prepare solution B;

[0074] (2) Add 5 parts of didodecylamine to 95 parts of kerosene and stir thoroughly to prepare solution C;

[0075] (3) 50 parts of solution B and 50 parts of solution C were heated at 60° C. for 10 min and stirred for 10 min to prepare emulsion A;

[0076] (4) Mix 97 parts of clean water with 3 parts of emulsion A to obtain a sand washing solution.

[0077] Example 4 Sand flushing fluid effect test

[0078] Viscosity test

[0079] The sand flushing fluid and nitrogen are pumped into the well at the same time for sand flushing. After the sand flushing fluid is returned from the wellbore to the surface, the liquid and sand can be separated by standing or filtering without adding any chemicals. After the sand flushing fluid is returned to the surface storage tank and stood for 10 seconds, the viscosity of the lower layer of clear water is measured. The specific operation process is as follows:

[0080] Measure 350 mL of the lower layer of clear water and transfer it to a rotary viscosity measuring cup. Use a Fann-type six-speed rotary viscometer to measure the shear rate at 170 s. -1 The apparent viscosity at .

[0081] Sand blasting efficiency

[0082] Weigh m0 = 50 g of sand and spread it evenly in a simulated horizontal tube (inner diameter 3.67 cm). Use a PVC hose (inner diameter 2.00 cm) as the sand flushing tube. Prepare 200 L of sand flushing liquid and stir it evenly. Adjust the gas-liquid volume ratio to 3:7 and the sand flushing displacement to 3 L / min. Weigh the mass m1 of the sand flushed out and calculate the sand flushing performance of the sand flushing liquid. The calculation formula is as follows:

[0083]

[0084] Where: Ψ—sand washing efficiency, %;

[0085] m1—mass of sand flushed out, g;

[0086] m0—mass of sand filled in, g.

[0087] Liquid sand separation time

[0088] The time required for the sand to completely float to the surface of the sand flushing fluid or settle to the bottom of the sand flushing fluid after the sand is returned to the ground storage tank and allowed to stand.

[0089] Table 1 shows the test data of Examples 1-3 and Comparative Examples 1-3 at 25°C.

[0090] Table 1 Test results

[0091]

[0092] In combination with the above embodiments, it can be seen that after the sand flushing fluid of the present invention is returned from the wellbore to the surface, the gas, liquid and sand can be automatically separated quickly without adding any reagents. The sand particles float on the surface of the sand flushing fluid, and the viscosity of the lower clear night is measured to be ≤3mPa·s.

[0093] The above detailed description is a specific description of one feasible embodiment of the present invention. This embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not depart from the present invention should be included in the scope of the technical solution of the present invention.

Claims

1. A wellbore sand flushing fluid, characterized in that: The sand washing fluid comprises emulsion A and water, wherein the raw materials of emulsion A comprise tetradecyl primary amine, didodecylamine, hydrochloric acid, white oil and water.

2. The sand washing fluid according to claim 1, characterized in that The emulsion A comprises solution B and solution C, wherein the raw materials of solution B comprise tetradecyl primary amine, hydrochloric acid and water; the raw materials of solution C comprise didodecylamine and white oil.

3. The sand flushing fluid according to claim 1, characterized in that The sand flushing fluid comprises 1-4 parts of emulsion A and 96-99 parts of water in parts by weight.

4. The sand flushing fluid according to claim 2, characterized in that In parts by weight, the emulsion A includes 40-50 parts of solution B and 50-60 parts of solution C.

5. The sand flushing fluid according to claim 2, characterized in that In parts by weight, the raw materials of the solution B include 2-5 parts of tetradecyl primary amine, 1-3 parts of hydrochloric acid and 92-97 parts of water.

6. The sand flushing fluid according to claim 2, characterized in that In parts by weight, the raw materials of the solution C include 2-8 parts of didodecylamine and 92-98 parts of white oil.

7. A method for preparing the sand flushing fluid according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) Tetradecyl primary amine was added to water and hydrochloric acid was added to obtain solution B; (2) adding didodecylamine to white oil and stirring to obtain solution C; (3) Mixing solution B and solution C, heating and stirring to obtain emulsion A; (4) Emulsion A is mixed with water to obtain sand washing liquid.

8. The preparation method according to claim 7, characterized in that In step (1), hydrochloric acid is added to adjust the pH to 7-8, and the mass concentration of hydrochloric acid is 10-20%.

9. The preparation method according to claim 7, characterized in that The heating temperature in step (3) is 50-70° C., and the heating and stirring time is 8-10 min.

10. Use of the sand flushing fluid according to any one of claims 1 to 6 or the sand flushing fluid prepared by the preparation method according to any one of claims 7 to 9 in sand flushing and well washing.

11. The use according to claim 10, characterized in that During the sand flushing and well washing process, a sand flushing fluid or a sand flushing fluid and nitrogen are simultaneously fed into the well to flush the sand, and the fluid returned from the well is sedimented or filtered to remove sand and then re-entered the well as the sand flushing fluid.

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