High-temperature-resistant coring sealing fluid, preparation method and application thereof

Abstract

This invention provides a high-temperature resistant core sampling sealing fluid, its preparation method, and its application. The high-temperature resistant core sampling sealing fluid comprises the following components in parts by weight: 65-85 parts of polyol ester, 6-20 parts of thickener, and 1-7 parts of sealant; wherein the polyol ester includes neopentyl glycol diacetylpropionate and / or pentaerythritol oleate. This invention prepares a high-temperature resistant core sampling sealing fluid with high Brinell viscosity and long fiber length by dissolving the thickener in a polyol ester containing a sealant. Furthermore, the preparation method of this sealing fluid is simple, cost-controllable, and conducive to large-scale application. The sealing fluid prepared by this invention has good film-forming properties, excellent sealing effect, low filtrate intrusion, and effectively protects the core from drilling fluid contamination. It is also biodegradable and environmentally friendly.

Description

Technical Field

[0001] This invention relates to a high-temperature resistant coring sealing fluid, its preparation method and application, belonging to the field of petroleum coring technology. Background Technology

[0002] Closed core drilling is an important means of obtaining geological data in oil fields. By analyzing the extracted core samples, data such as oil saturation, porosity, and crude oil properties of the corresponding strata can be obtained. These data are of great significance for calculating oil and gas geological reserves and formulating reasonable and efficient exploration and development plans, and help improve oil and gas recovery rates.

[0003] In closed-loop coring, a sealing fluid is used in the coring cylinder. This sealing fluid must possess suitable viscosity, good fluidity, good film-forming properties, and strong adhesion. This is because: higher viscosity increases the thickness of the sealing film, enhancing the filling effect of the sealing fluid in the annulus; good fluidity facilitates the loading and unloading of the sealing fluid; and good film-forming properties and strong adhesion ensure that the formed sealing film is not easily damaged, improving its impermeability. These characteristics of the sealing fluid enable the core entering the coring cylinder to form a robust protective film in a timely manner, and throughout the coring process, it continuously fills the gap between the core and the inner cylinder, preventing drilling fluid from entering the inner core cylinder and ensuring effective protection of the core during coring, thus preventing drilling fluid contamination.

[0004] Currently, sealing fluids used in oil exploration drilling coring are mainly classified into three categories: oil-based, water-based, and synthetic-based. Oil-based sealing fluids, particularly those based on vegetable oils, typically use castor oil and chlorinated paraffin. This preparation process is difficult to control and involves the release of toxic gases such as chlorine and hydrogen chloride, resulting in unstable product performance and environmental pollution. Heavy oil-based sealing fluids, whose main raw material is heavy oil from crude oil, may affect the determination of oil saturation, oil and gas shows, and well logging interpretation when using this type of fluid for coring. Furthermore, at high temperatures (e.g., up to 100°C), the viscosity of the sealing fluid decreases, leading to poorer coring performance in high-permeability, loose formations and affecting the sealing effect. Water-based sealing fluids suffer from poor temperature resistance, limited applicability, and short storage time. Synthetic-based sealing fluids, whose main component is organic esters, offer good sealing performance but are expensive and complex to prepare.

[0005] In summary, core sealing fluids face three main challenges. First, as exploration and development move towards deeper formations, core sealing fluids need to withstand higher temperatures. Second, the environmental friendliness of sealing fluids used in oil drilling urgently needs attention. Third, the complex formulation process and high-cost raw materials increase the overall cost of sealing fluids, hindering cost reduction and efficiency improvement.

[0006] Therefore, it is of great significance to propose a biodegradable, environmentally friendly, high-temperature resistant, and well-sealing coring sealing solution. Summary of the Invention

[0007] To solve the above-mentioned technical problems, the purpose of this invention is to provide a high-temperature resistant coring sealing liquid, its preparation method and application, wherein the sealing liquid is resistant to high temperature and has good sealing properties.

[0008] To achieve the above objectives, in a first aspect, the present invention provides a high-temperature resistant coring sealing liquid, comprising the following components in parts by weight:

[0009] 65-85 parts of polyol ester, 6-20 parts of tackifier, and 1-7 parts of sealant;

[0010] The polyol esters include neopentyl diol diacetylpropionate and / or pentaerythritol oleate.

[0011] According to a specific embodiment of the present invention, preferably, the composition comprises the following components in parts by weight: 70-85 parts of polyol ester, 8-15 parts of tackifier, and 1-5 parts of sealant; more preferably, 77-83 parts of polyol ester, 8-12 parts of tackifier, and 1-4 parts of sealant.

[0012] According to a specific embodiment of the present invention, preferably, the polyol ester comprises neopentyl diol diacetylpropionate and pentaerythritol oleate in a mass ratio of 0.5-2:1.

[0013] The polyol esters of this invention are biodegradable, have minimal environmental impact, and meet the requirements of green chemistry. The ester groups of the polyol esters are polar, and the ester molecules readily adsorb onto the core surface to form a boundary oil film, protecting the core from drilling fluid contamination. The ester groups, while elongating the carbon chain, increase the number of ester groups, branches, and cyclic structures, thereby improving the viscosity and temperature resistance of the sealed fluid. Specifically, the neopentyl diol diacetylpropionate molecule does not contain hydrogen on its β-carbon atom, exhibiting good thermal stability and is less prone to chemical bond breakage and oxidation at high temperatures, thus improving the temperature resistance of the sealed fluid. This neopentyl diol diacetylpropionate is biodegradable, meeting environmental protection and geological testing requirements.

[0014] According to a specific embodiment of the present invention, preferably, the tackifier is selected from one or a combination of two or more of polymethyl methacrylate, polystyrene, and polyvinyl chloride. The tackifier of the present invention, dissolved and dispersed in a high-boiling-point polyol ester, can form a "three-dimensional network" or "sponge" framework. Its characteristic of adsorbing and fixing the polyol ester onto the framework to form a colloidal network structure endows the sealed liquid with good rheological properties, facilitating the filling and core exit of the sealed liquid, and achieving the purpose of drawing into a film. More preferably, the tackifier is a combination of polymethyl methacrylate and polystyrene in a mass ratio of 0.5:1 to 2.5:1, or a combination of polymethyl methacrylate and polyvinyl chloride in a mass ratio of 1:1 to 3:1.

[0015] According to a specific embodiment of the present invention, preferably, the sealant is selected from one or a combination of two or more of nano-clay, silica gel, fumed silica, nano-titanium dioxide, and boron nitride. The sealant of the present invention has a good sealing effect; at the moment the core contacts the drilling fluid, it assists in sealing the core with polyol esters, increasing the viscosity and stability of the sealing fluid to a certain extent.

[0016] As a preferred embodiment, the present invention provides a high-temperature resistant core-harvesting sealing liquid, comprising the following components in parts by weight:

[0017] 77-83 parts of polyol ester, 8-12 parts of tackifier, and 1-4 parts of sealant, wherein:

[0018] The polyol ester is selected from neopentyl diol diacetylpropionate and / or pentaerythritol oleate;

[0019] The tackifier comprises a combination of polymethyl methacrylate and polystyrene in a mass ratio of 0.5:1 to 2.5:1, or a combination of polymethyl methacrylate and polyvinyl chloride in a mass ratio of 1:1 to 3:1.

[0020] The sealant is selected from one or more of nano-clay, silicone, fumed silica, nano-titanium dioxide, and boron nitride.

[0021] As a preferred embodiment, the present invention provides a high-temperature resistant core-harvesting sealing liquid, comprising the following components in parts by weight:

[0022] 80 parts polyol ester, 8-10 parts tackifier, 1.5-3 parts sealant, wherein:

[0023] The polyol ester is neopentyl diol diacetylpropionate;

[0024] The tackifier is a combination of polymethyl methacrylate and polystyrene in a mass ratio of 0.5:1 to 2.5:1 (preferably 1.5:1);

[0025] The sealant is a combination of nano-clay, fumed silica and nano-titanium dioxide in a mass ratio of 0.5-1.5:0.5-1.5:0.5-1.5 (preferably 1:1:1).

[0026] As a preferred embodiment, the present invention provides a high-temperature resistant core-harvesting sealing liquid, comprising the following components in parts by weight:

[0027] 80 parts polyol ester, 9-12 parts tackifier, 1-2 parts sealant,

[0028] The polyol ester comprises neopentyl diol diacetylpropionate and pentaerythritol oleate (preferably 1:1) in a mass ratio of 0.5-2:1;

[0029] The tackifier includes polymethyl methacrylate;

[0030] The sealant is silicone and boron nitride in a mass ratio of 2-4:1.5-2.5 (preferably 3:2).

[0031] As a preferred embodiment, the present invention provides a high-temperature resistant core-harvesting sealing liquid, comprising the following components in parts by weight:

[0032] 80 parts polyol ester, 9-12 parts tackifier, 1-2 parts sealant, wherein:

[0033] The polyol ester is pentaerythritol oleate;

[0034] The tackifier is a combination of polymethyl methacrylate and polyvinyl chloride in a mass ratio of 1:1 to 3:1 (preferably 2:1);

[0035] The sealant is silicone, boron nitride and nano titanium dioxide in a mass ratio of 1-3:0.5-1.5:1-3 (preferably 2:1:2).

[0036] According to a specific embodiment of the present invention, preferably, the sealed liquid has a Brookfield viscosity of 16000-30000 mPa·s (more preferably 16000-20200 mPa·s) at 25±3℃ and a drawing length of 15-40 cm (more preferably 20-25 cm).

[0037] Secondly, the present invention also provides a method for preparing a high-temperature resistant coring sealing liquid, wherein the high-temperature resistant coring sealing liquid is the aforementioned high-temperature resistant coring sealing liquid, and the preparation method includes the following steps:

[0038] The polyol ester and sealant are heated to obtain the oil phase;

[0039] A thickener was added to the oil phase, and the mixture was heated and stirred to obtain the high-temperature resistant core-taking sealing liquid.

[0040] According to a specific embodiment of the present invention, preferably, the heating temperature of the polyol ester and the sealant is 60℃-100℃, more preferably 60℃-80℃.

[0041] According to a specific embodiment of the present invention, preferably, the temperature for heating is 100℃-150℃, more preferably 130℃-150℃.

[0042] According to a specific embodiment of the present invention, preferably, the stirring speed is 700 rpm / min-1100 rpm / min and the stirring time is 3h-6h; more preferably, the stirring speed is 700 rpm / min-900 rpm / min and the stirring time is 4h-5h.

[0043] As a preferred embodiment, the present invention provides a method for preparing a high-temperature resistant core-harvesting sealing liquid, comprising the following steps:

[0044] Mix 70-85 parts of neopentyl polyol ester and 1-5 parts of sealant evenly, and heat to 60℃-100℃ to obtain the oil phase;

[0045] Add 8-15 parts of thickener to the oil phase, heat to 100℃-150℃, and stir at 700-1100 rpm / min for 3-6 hours until the thickener is completely dissolved in the oil phase. Cool to room temperature to obtain the high-temperature resistant core-taking sealing liquid.

[0046] Thirdly, the present invention also provides a closed coring method using the high-temperature resistant coring sealing fluid described above. This closed coring method can be performed according to the method in SY / T 5347-2016 "Drilling Coring Operation Procedures".

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] This invention achieves a harmonious balance of fluidity, temperature resistance, environmental friendliness, and sealing properties through optimized formulation, resulting in a high-temperature resistant core-taking sealing fluid. Even after high-temperature aging, the sealing fluid maintains a high Brookfield viscosity and retains fluidity at -30°C. This invention also prepares a high-temperature resistant core-taking sealing fluid with high Brookfield viscosity and long fiber length by dissolving a thickener in a polyol ester containing a sealant. Furthermore, the preparation method is simple, cost-effective, and conducive to large-scale application.

[0049] The sealing liquid prepared by this invention has good film-forming properties, good sealing effect, low filtrate intrusion, and can effectively protect the core from drilling fluid contamination. It is also biodegradable and environmentally friendly. Detailed Implementation

[0050] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0051] Example 1

[0052] This embodiment provides a high-temperature resistant core-harvesting sealing solution, which is prepared through the following steps:

[0053] In a three-necked flask, add 240g of neopentyl diol diacetylpropionate, then slowly add 2g of nano clay, 2g of fumed silica, and 2g of nano titanium dioxide, stir well, and heat to 70°C to obtain the oil phase.

[0054] Slowly add 15g of polymethyl methacrylate and 10g of polystyrene to the oil phase while heating and stirring. Heat to 150℃ and stir at 800 rpm. After the addition is complete, continue stirring at a constant temperature for 4 hours until the thickener is completely dissolved in the oil phase. Cool to room temperature to obtain a high-temperature resistant core-taking sealing liquid, denoted as P1.

[0055] Example 2

[0056] This embodiment provides a high-temperature resistant core-harvesting sealing solution, which is prepared through the following steps:

[0057] In a three-necked flask, add 120g of neopentyl diol diacetylpropionate and 120g of pentaerythritol oleate, then slowly add 3g of silica gel and 2g of boron nitride, stir until homogeneous, and heat to 60°C to obtain the oil phase.

[0058] Slowly add 30g of polymethyl methacrylate to the oil phase while heating and stirring. Heat to 130℃ and stir at 800 rpm. After the addition is complete, continue stirring at a constant temperature for 5 hours until the thickener is completely dissolved in the oil phase. Cool to room temperature to obtain a high-temperature resistant core-taking sealing liquid, denoted as P2.

[0059] Example 3

[0060] This embodiment provides a high-temperature resistant core-harvesting sealing solution, which is prepared through the following steps:

[0061] In a three-necked flask, add 240g of pentaerythritol oleate, then slowly add 2g of silica gel, 1g of boron nitride, and 2g of nano titanium dioxide, stir until homogeneous, and heat to 60°C to obtain the oil phase.

[0062] Slowly add 20g of polymethyl methacrylate and 10g of polyvinyl chloride to the oil phase while heating and stirring. Heat to 130℃ and stir at 700 rpm. After the addition is complete, continue stirring at a constant temperature for 5 hours until the thickener is completely dissolved in the oil phase. Cool to room temperature to obtain a high-temperature resistant core-taking sealing liquid, denoted as P3.

[0063] Comparative Example 1

[0064] This comparative example provides a high-temperature resistant core-harvesting sealing solution, which is prepared through the following steps:

[0065] Add 240g castor oil and 5g bentonite to a three-necked flask, stir well, and heat to 60℃ to obtain the oil phase;

[0066] Slowly add 24g of chlorinated paraffin to the oil phase while heating and stirring. Heat to 160℃ and stir at 800 rpm. After the addition is complete, continue stirring at a constant temperature for 5 hours until the thickener is completely dissolved in the oil phase. Cool to room temperature to obtain a high-temperature resistant core-taking sealing liquid, denoted as E1.

[0067] Comparative Example 2

[0068] This comparative example provides a core-collecting sealing solution, which is prepared through the following steps:

[0069] In a three-necked flask, add 120g of neopentyl diol diacetylpropionate and 120g of pentaerythritol oleate, then slowly add 3g of silica gel and 2g of boron nitride, stir until homogeneous, and heat to 60°C to obtain the oil phase.

[0070] After the addition is complete, continue stirring at a constant temperature for 5 hours, then cool to room temperature to obtain the core-collecting sealed solution, denoted as E2.

[0071] Comparative Example 3

[0072] This comparative example provides a core-collecting sealing solution, which is prepared through the following steps:

[0073] In a three-necked flask, add 240g pentaerythritol oleate, then slowly add 10g silica gel, 3g boron nitride, and 4g nano titanium dioxide, stir until homogeneous, and heat to 60℃ to obtain the oil phase.

[0074] Slowly add 5g of polyvinyl chloride to the oil phase while heating and stirring. Heat to 130℃ and stir at 700 rpm. After the addition is complete, continue stirring at a constant temperature for 5 hours until the thickener is completely dissolved in the oil phase. Cool to room temperature to obtain the core-taking sealed liquid, which is denoted as E3.

[0075] Comparative Example 4

[0076] This comparative example provides a core-collecting sealing solution, which is prepared through the following steps:

[0077] In a three-necked flask, add 240g of neopentyl diol diacetylpropionate, then slowly add 2g of nano clay, 2g of fumed silica, and 2g of nano titanium dioxide, stir well, and heat to 70°C to obtain the oil phase.

[0078] Slowly add 15g of polymethyl methacrylate and 10g of polystyrene to the oil phase while heating and stirring. Heat to 160℃ and stir at 1000 rpm. After the addition is complete, continue stirring at a constant temperature for 4 hours until the thickener is completely dissolved in the oil phase. Cool to room temperature to obtain the core-sealing liquid, which is denoted as E4.

[0079] Experimental Example

[0080] The method of closed coring was used in accordance with the industry standard SY / T 5347-2016 "Drilling Coring Operation Procedures". Evaluation experiments were conducted on the appearance, viscosity value and wire drawing performance of the environmentally friendly coring sealing fluid before and after heating.

[0081] 1. Test of airtightness

[0082] The core samples were immersed in a sealing fluid, and the sealing effect of the sealing fluid in the examples and comparative examples was measured. The amount of filtrate intrusion was tested according to SY / T5343-2013 "Method for Determination of Filtrate Intrusion into Core". The room temperature viscosity, high temperature viscosity after aging at 135±5℃, and wire drawing length of the sealing fluid were tested according to SY / T 5347-2016 "Drilling Core Operation Procedure". The test results are shown in Table 1.

[0083] Table 1

[0084]

[0085] As can be seen from Table 1, the filtrate intrusion amount Vd ≤ 2 for the high-temperature resistant coring sealing fluids P1, P2, and P3 provided in Examples 1-3, indicating a good sealing effect. In contrast, the filtrate intrusion amount Vd = 8 for the coring sealing fluid E2 without thickener provided in Comparative Example 2, indicating a strong intrusion effect. This suggests that the coring sealing fluid cannot provide a good sealing effect, and the filtrate will intrude into the core. The high-temperature resistant coring sealing fluid of the present invention can form a film by adding a thickener, thereby providing a good sealing effect.

[0086] The core-taking sealing fluid E3 provided in Comparative Example 3 contained a large amount of sealant, and its corresponding filtrate intrusion amount Vd = 5, indicating a strong intrusion effect. This shows that the sealing fluid could not provide a good sealing effect. This indicates that the amount of sealant added was too large and the content of thickener was too small. The resulting core-taking sealing fluid had a low wire drawing length and poor sealing effect. This shows that controlling the amount of sealant added appropriately has an important impact on obtaining a high-performance, high-temperature resistant core-taking sealing fluid.

[0087] 2. High-temperature resistance test

[0088] Table 2 shows the viscosity values ​​and fiber drawing performance test results of the high-temperature resistant core-taking sealing liquid P1 prepared in Example 1 before and after heating at different aging temperatures for 16 hours. Among them, "Bruch's viscosity (mPa·s) at (25±3)℃" and "fiber drawing length (cm) at (25±3)℃" refer to the viscosity value and fiber drawing length measured after heating at the aging temperature for 16 hours and then standing at (25±3)℃. The viscosity value and fiber drawing length corresponding to the aging temperature of (25±3)℃ were obtained directly at (25±3)℃ without the need for heating at (25±3)℃ for 16 hours.

[0089] Table 2

[0090]

[0091] As can be seen from Table 2, after aging at 120-180℃, the Brookfield viscosity and wire drawing length of the sealing liquid at (25±3)℃ do not change much and can meet the standard requirements. At temperatures above 200℃, the viscosity and wire drawing length decrease significantly after aging. This indicates that the high-temperature resistant sealing liquid provided by this invention can withstand high temperatures below 180℃.

[0092] The viscosity values ​​and drawing performance test results of the core-collecting sealed liquid of the examples and comparative examples before and after heating at 180°C for 16 hours are shown in Table 3.

[0093] Table 3

[0094]

[0095]

[0096] As can be seen from Table 3, the high-temperature resistant core-taking sealing liquids P1, P2, and P3 provided in Examples 1-3, after being aged at 180℃ for 16 hours, showed a Brinell viscosity of over 16000 mPa·s when tested again at (25±3)℃. At 180℃, their viscosity values ​​all exceeded the standard of over 300 mPa·s. After drawing the fibers at room temperature and aging, the lengths reached over 17 cm. In contrast, the sealing liquids provided in the comparative example, after being aged at 180℃ for 16 hours, showed a Brinell viscosity of less than 5000 mPa·s when tested again at (25±3)℃. Their viscosity values ​​at 180℃ were also below the standard of 300 mPa·s. This indicates that the sealing liquids provided in the comparative example are no longer usable as sealing liquids at 180℃, while the high-temperature resistant core-taking sealing liquid provided by this invention still maintains good sealing performance at 180℃.

[0097] 3. Field Application

[0098] The high-temperature resistant coring sealing fluid provided in Example 1 was used for coring operations at oil well sites, specifically according to the methods in SY / T5347-2016 "Drilling Coring Operation Procedures". The application results are shown in Table 4. The sealing rate was calculated as follows: (Number of cores with sealing effect / Total number of cores) × 100%.

[0099] Table 4

[0100] hashtag Core section / m Core length / m airtightness / % Well 1 2820-2866 25 95 Well No. 2 3230-3378 43 92 Well No. 3 3105-3293 57 93.2 Well 4 3432-3512.8 14 100 Well No. 5 3622-3843 14.2 97

[0101] As can be seen from Table 4, when using the high-temperature resistant coring sealing liquid P1 provided in Example 1 for sealed coring, the sealing rate is above 92%.

Claims

1. A high temperature resistant coring sealant fluid, wherein, The composition comprises the following components in parts by weight: 65-85 parts of polyol ester, 6-20 parts of tackifier, and 1-7 parts of sealant; The polyol esters include neopentyl diol diacetylpropionate and / or pentaerythritol oleate.

2. The high temperature resistant coring seal fluid of claim 1, wherein, The composition comprises the following components in parts by weight: 70-85 parts of polyol ester, 8-15 parts of tackifier, and 1-5 parts of sealant.

3. The high temperature resistant coring seal fluid of claim 1, wherein, Composition of components comprising the following parts by weight: 77-83 parts of polyol ester, 8-12 parts of tackifier, and 1-4 parts of sealant.

4. The high temperature core retrieval sealant of claim 1, wherein, The polyol esters include neopentyl diol diacetylpropionate and pentaerythritol oleate in a mass ratio of 0.5-2:

1.

5. The high temperature core-retrieval sealant of any one of claims 1-3, wherein, The tackifier is selected from one or more of polymethyl methacrylate, polystyrene, and polyvinyl chloride.

6. The high temperature resistant coring seal fluid of claim 5 wherein, The tackifier is a combination of polymethyl methacrylate and polystyrene in a mass ratio of 0.5:1 to 2.5:1, or a combination of polymethyl methacrylate and polyvinyl chloride in a mass ratio of 1:1 to 3:

1.

7. The high temperature core-retrieval sealant of any one of claims 1-3, wherein, The sealant is selected from one or more of nano-clay, silicone, fumed silica, nano-titanium dioxide, and boron nitride.

8. A method for preparing a high temperature resistant coring sealant fluid, wherein, The high-temperature resistant coring sealing liquid is the high-temperature resistant coring sealing liquid according to any one of claims 1-7, and the preparation method includes the following steps: The polyol ester and sealant are heated to obtain the oil phase; A thickener was added to the oil phase, and the mixture was heated and stirred to obtain the high-temperature resistant core-taking sealing liquid.

9. The method of preparing a high temperature resistant coring seal fluid according to claim 8, wherein: The polyol ester and sealant are heated to a temperature of 60℃-100℃.

10. The method of preparing a high temperature resistant coring seal fluid according to claim 8, wherein: The temperature for the heating is 100℃-150℃.

11. The method for preparing the high-temperature resistant core-harvesting sealing liquid according to claim 8, wherein, The stirring speed is 700-1100 rpm / min, and the stirring time is 3-6 h.

12. A closed-loop coring method, wherein, The closed-loop coring method uses the high-temperature resistant coring sealing liquid as described in any one of claims 1-7.

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