High-temperature-resistant coring sealing liquid

Abstract

The invention relates to the technical field of well drilling and coring, and particularly discloses a high-temperature-resistant coring sealing liquid which comprises the following components in parts by mass: 50-70 parts of high-temperature-resistant vegetable oil, 10-15 parts of organic ester, 8-12 parts of a plasticizer, 5-8 parts of an emulsifier and 1-5 parts of a weighting agent. The high-temperature-resistant vegetable oil is used as a main base solution, and compared with traditional mineral oil or common vegetable oil, the molecular structure is more stable, the thermal decomposition temperature is high, and the chemical stability can be kept at high temperature; organic ester is introduced as a coalescing agent, has good compatibility with high-temperature-resistant vegetable oil and can participate in the film forming process, and the compactness and adhesive force of a film layer are improved; meanwhile, the flexibility and crack resistance of a protective film are remarkably improved by matching with a plasticizer, so that effective isolation of a rock core is maintained, and generally, the coring sealing liquid has excellent high-temperature resistance and is suitable for sealed coring operation of a deep well and an ultra-deep well.

Description

Technical Field

[0001] This invention relates to the field of drilling coring technology, and in particular to a high-temperature resistant coring sealing fluid. Background Technology

[0002] Closed coring is a crucial method for obtaining original formation parameters in oil and gas exploration. Its core lies in forming a dense, continuous protective film on the core surface in situ using a sealing fluid. This effectively isolates the drilling fluid from direct contact with the core, thus preserving the core's original physicochemical state to the greatest extent possible. This technology is crucial for accurately determining key parameters such as reservoir porosity, permeability, and oil saturation, and is widely used in important scenarios such as reservoir evaluation in new blocks, identification of remaining oil distribution in old oilfields, and optimization of development plans. The quality of coring directly affects the scientific understanding of reservoir characteristics and the reliability of subsequent development decisions; therefore, it occupies an irreplaceable position in the efficient exploration and development system of oil and gas resources.

[0003] However, as oil and gas exploration continues to advance into deeper formations, the downhole operating environment is becoming increasingly harsh, especially with a significant increase in bottom hole temperature—some ultra-deep wells have reached temperatures as high as 180°C, and even exceed 220°C. Under these high-temperature conditions, the technical limitations of existing sealing fluid systems are becoming increasingly prominent, becoming a major bottleneck restricting high-quality coring operations in deep and ultra-deep wells. Currently, the mainstream sealing fluid systems mainly include three categories: oil-based, water-based, and synthetic-based. Although they perform well under conventional temperature and pressure conditions, their high-temperature resistance is generally insufficient. The upper limit of temperature resistance for most commercial sealing fluids does not exceed 135°C. Although a few high-performance products can withstand 180°C, they are still prone to problems such as thermal degradation of polymer components, molecular chain breakage, or additive failure under higher temperatures or prolonged high-temperature exposure, leading to a significant decrease or even complete loss of film-forming ability. If the sealing fluid fails to form a complete and effective protective barrier on the core surface, solid particles, treatment agents, and filtrate in the drilling fluid will invade the core pore system, causing serious core contamination. This will result in the measured reservoir parameters deviating significantly from their true values, thereby affecting the accuracy of geological evaluation and the scientific nature of development plans.

[0004] Therefore, there is an urgent need to develop a new type of high-temperature resistant sealing fluid with excellent thermal stability and film-forming properties to meet the core sampling requirements under complex high-temperature conditions in deep and ultra-deep wells, ensure the originality and representativeness of core samples, and provide key technical support for the accurate evaluation and efficient development of deep oil and gas resources. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide an oil-based sealing fluid for closed coring operations, which has excellent high-temperature resistance.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solution: A high-temperature resistant core extraction sealing solution, characterized in that it comprises the following components in parts by weight: High-temperature resistant vegetable oil, 50-70 parts; Organic esters, 10-15 parts; Plasticizer, 8-12 parts; Emulsifier, 5-8 parts; Weighting agent, 1-5 parts.

[0007] Excellent high temperature resistance In one specific embodiment of the present invention, the high-temperature resistant vegetable oil is avocado oil, rice bran oil, refined olive oil, rapeseed oil, tea oil, peanut oil, or corn oil. These vegetable oils have high smoke points and good oxidative stability. To further improve their oxidative stability, antioxidants can be added to the vegetable oils.

[0008] In one specific embodiment of the present invention, the weighting agent is one of manganese ore powder, iron ore powder or barite powder, manganese tetroxide, barite or calcium carbonate.

[0009] In one specific embodiment of the present invention, the organic ester is diisodecyl phthalate or trioctyl trimellitate.

[0010] In one specific embodiment of the present invention, the plasticizer is one of epoxidized soybean oil, triethyl citrate, acetylated triethyl citrate, acetylated tributyl citrate, and 2-octyl phthalate.

[0011] In one specific embodiment of the present invention, the emulsifier is alkylphenol polyoxyethylene ether or polyether-modified silicone oil.

[0012] As one specific embodiment of the present invention, it also includes 1-5 parts of nano-graphene.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention uses high-temperature resistant vegetable oil as the main base liquid. Compared with traditional mineral oil or ordinary vegetable oil, its molecular structure is more stable and its thermal decomposition temperature is higher, allowing it to maintain chemical stability at high temperatures. Organic esters are introduced as film-forming aids, which not only have good compatibility with high-temperature resistant vegetable oil, but also participate in the film-forming process, improving the density and adhesion of the film. At the same time, plasticizers are used to significantly improve the flexibility and crack resistance of the protective film, thereby maintaining effective isolation of the rock core.

[0014] The core-taking sealing fluid of the present invention has excellent high-temperature resistance. It can still maintain a high viscosity after aging at 200°C, which meets the requirements of deep well core taking. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments.

[0016] Example 1 Mix 60 parts rapeseed oil, 12 parts diisodecyl phthalate, 8 parts triethyl citrate, 7 parts polyether-modified silicone oil, and 2 parts barite powder weighting agent and stir for 30 minutes to obtain a core-collecting sealed liquid.

[0017] Example 2 Mix 60 parts rapeseed oil, 12 parts trioctyl trimellitate, 8 parts triethyl citrate, 7 parts polyether-modified silicone oil, and 2 parts barite powder weighting agent and stir for 30 minutes to obtain a core-collecting sealed liquid.

[0018] Example 3 Mix 60 parts rapeseed oil, 12 parts trioctyl trimellitate, 8 parts triethyl citrate, 7 parts polyether-modified silicone oil, 2 parts barite powder weighting agent, and 2 parts graphene oxide, and stir for 30 minutes to obtain a core-collecting sealed liquid.

[0019] Test Example 1 (Viscosity Test) Take the core-collecting sealed liquids from Examples 1-3, measure their viscosity at room temperature, and then age them at 200°C for 12 hours. After aging, measure their viscosity again. The final results are shown in Table 1.

[0020] Table 1 Viscosities of various core-collecting sealing solutions before and after high-temperature aging As shown in Table 1, after 12 hours of high-temperature aging, the viscosity of the core-collecting sealing liquid is relatively high, which meets the requirements for core collection.

[0021] Test Example 2 (Filtrate Intrusion Test) Three core samples of the same size retrieved from the field were soaked in a container filled with kerosene. The container containing the core samples was placed in a vacuum device and evacuated until the core samples were saturated with kerosene. Drilling fluid containing ammonium thiocyanate tracer (API filtration loss not exceeding 6 mL, ammonium thiocyanate content 1.0 g / L) was added to the filter press of the high-temperature and high-pressure filtration analyzer. The treated core samples were then placed in the core-taking sealing fluid of Examples 1-3, ensuring they were evenly coated with a layer of core-taking sealing fluid. After removal, they were placed in the drilling fluid inside the filter press of the filtration analyzer, ensuring the drilling fluid completely submerged the core samples. The cylinder was then covered, and the filter press was placed in the heating chamber of the filtration analyzer. The temperature was adjusted to 200°C. Timing was started when the temperature reached the required level, and heating was stopped after 4 hours. The device was then removed. After cooling, the core samples were removed and cleaned. The core samples were broken up, and the central portion was removed and placed in a clean, dry glass bottle, which was then sealed and labeled. The titration experiment for the amount of filtrate intruding into the core was carried out in accordance with SY-T5343-1994 "Method for Determination of the Amount of Filtrate Intruding into the Core". The experimental results are shown in Table 2.

[0022] Table 2 Filtrate Intrusion Amount As shown in Table 2, Examples 1-3 have good film-forming and sealing properties, which can effectively prevent filtrate from entering the core. Among them, Example 3 adds graphene oxide, which is a nanoscale sealing material and can further improve the sealing performance.

[0023] The above description is not intended to limit the present invention in any way. Although the present invention has been disclosed through the above embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall fall within the scope of the present invention.

Claims

1. A high-temperature resistant, sealed solution for core extraction, characterized in that, The components include the following parts by weight: High-temperature resistant vegetable oil, 50-70 parts; Organic esters, 10-15 parts; Plasticizer, 8-12 parts; Emulsifier, 5-8 parts; Weighting agent, 1-5 parts.

2. The high-temperature resistant coring sealing liquid according to claim 1, characterized in that, The heat-resistant vegetable oil is avocado oil, rice bran oil, refined olive oil, rapeseed oil, tea oil, peanut oil, or corn oil.

3. The high-temperature resistant coring sealing liquid according to claim 1, characterized in that, The weighting agent is one of manganese ore powder, iron ore powder or barite powder, manganese tetroxide, barite or calcium carbonate.

4. The high-temperature resistant coring sealing liquid according to claim 1, characterized in that, The organic ester is diisodecyl phthalate or trioctyl trimellitate.

5. The high-temperature resistant coring sealing liquid according to claim 1, characterized in that, The plasticizer is one of the following: epoxidized soybean oil, triethyl citrate, acetylated triethyl citrate, acetylated tributyl citrate, tributyl citrate, and 2-octyl phthalate.

6. The high-temperature resistant coring sealing liquid according to claim 1, characterized in that, The emulsifier is alkylphenol polyoxyethylene ether or polyether-modified silicone oil.

7. The high-temperature resistant coring sealing liquid according to claim 1, characterized in that, It also includes 1-5 parts of nano-graphene.

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