A filling material for abandoned oil and gas pipelines, and a preparation method and filling process thereof

Abstract

The application relates to the field of petroleum chemical industry and discloses a filling material for waste oil and gas pipelines and a preparation method and a filling process thereof. The filling material comprises the following components and mass parts: fly ash 80-100 parts, cement 5-15 parts, water 120-150 parts, sodium metasilicate 0.1-1.5 parts, modified PVA glue liquid 0.5-10 parts, retarder 0.1-0.5 parts and expanding agent 5-15 parts. The filling material provided by the application only uses a very low mass part of cement, uses a large amount of fly ash, has better environmental friendliness, is lower in cost, has high fluidity, has long initial setting time, is particularly suitable for long-distance oil and gas pipelines, has good strength and solidity after solidification, can realize permanent solidification, has good stability, has a simple and easy-to-implement preparation method and is high in filling efficiency.

Description

Technical Field

[0001] This invention relates to the field of petrochemicals, specifically to a filling material for abandoned oil and gas pipelines, its preparation method, and filling process. Background Technology

[0002] Over the past 60 years of development of Shengli Oilfield, many of the early-built and put into operation oil and gas pipelines have entered a period of frequent pipeline accidents, experiencing numerous corrosion and deformation problems. During production, perforations have repeatedly caused serious environmental pollution and resulted in significant economic losses. Due to production adjustments, some pipelines are now either out of service or idle. Oil pipelines and other pipelines are laid in high-risk areas such as farmland, rivers, and residential areas. Furthermore, with the continuous expansion of cities, more and more buildings or factories are encroaching on or located close to underground pipelines, greatly increasing the difficulty of handling perforations and leaks, as well as the risks to environmental pollution and the safety of equipment, buildings, and personnel. With the ongoing optimization of the old oilfield's surface system, an even larger number of pipelines will be decommissioned and left idle.

[0003] Currently, environmental pollution caused by residual oil and gas in abandoned pipelines and their flow-conducting effects is a pressing issue that needs to be addressed. Without effective treatment, the potential for perforation and leakage of waste gas and liquid from abandoned pipelines, as well as the risks of land subsidence and explosions, pose insurmountable threats to the environment, property, and personal safety. In the event of an accident, it would cause incalculable economic losses to our production company and severely damage our corporate image.

[0004] The "Law of the People's Republic of China on the Protection of Oil and Gas Pipelines" stipulates that "when a pipeline is shut down, sealed, or scrapped, the pipeline company shall take necessary safety protection measures and report to the department in charge of pipeline protection of the local people's government at or above the county level for record-keeping." This law sets forth relevant requirements for the safe disposal of abandoned pipelines in principle. When an oil and gas pipeline reaches the end of its service life, or when the benefits of continuing to transport oil and gas are far lower than the transportation costs and the pipeline has no other potential uses, it needs to be scrapped.

[0005] Grouting, which involves filling abandoned pipelines with solid materials, can solve the problems of pipeline collapse and wastewater pollution, and is becoming a development trend in the field of on-site disposal of abandoned pipelines. Currently, pipeline filling materials used for grouting fall into two main categories: chemical grouts and cement-based grouts. Chemical grouts, also known as synthetic resin grouts, are made primarily from artificially synthesized resins and rapidly form a solid with a certain strength under the action of a curing agent. Synthetic resin grouts come in various types depending on the type of resin, such as urea-formaldehyde resin grout, cyanide grout, and unsaturated resin grout. Urea-formaldehyde resin is the most widely used. Chemical grouts have advantages such as good stability, good fluidity, strong injectability, low viscosity, and easy control of gel time, but they also have lower strength, poorer durability, higher price, and higher costs, and may even pollute the surrounding environment. Therefore, they are rarely used in grouting reinforcement projects. Cement-based grouts are based on cement and mixed with water to form a cement paste. Cement-based grouts have advantages such as high curing strength, but they have disadvantages such as difficulty in adjusting the gelation time and poor stability, making them unsuitable for long-distance grouting. Of course, various chemical additives can also be used to improve the properties of cementitious grout. For example, patent CN104631462A, "A Grouting and Filling Device and Method for Waste Oil and Gas Pipelines," provides a grouting and filling device for waste oil and gas pipelines. The device includes: a grouting machine connected to a grouting port at one end of the pipeline, used to inject grout from the grouting port into the pipeline and propel the grout forward in the pipeline; a sedimentation separator, one end of which is connected to a grout outlet at the upper end of the other end of the pipeline via a conduit, used to ensure that the pipeline is filled with grout; and a vacuum pump connected to the other end of the sedimentation separator, used to provide a vacuum environment for the pipeline during grouting, reducing the resistance caused by the elevation difference of the pipeline. In the above scheme, the device further includes: a first valve, the first valve being disposed between the grouting ports of the grouting machine, used to control the opening and closing state of the grouting ports. In the above scheme, the grouting port is parallel to the axis of the pipeline, used to convert the pressure of the grouting machine into power; the sedimentation separator is parallel to the highest point of the pipeline. In the above scheme, the device further includes: an observation hole, located at the highest point of the pipeline, used to observe the filling state of the grout in the pipeline; and a second valve, one end of which is connected to the observation hole, used to control the airtightness of the pipeline. In the above scheme, the device further includes: a third valve, located between the grout outlet and the sedimentation separator, used to control the on / off state of the vacuum environment. In the above scheme, the device further includes: foam balls, used to fill the pipeline when the elevation difference is no greater than 1m, assisting the grout to advance forward. In the above scheme, the device further includes: a cover plate, located at one end of the pipeline, used to seal one end of the pipeline.This invention also provides a grouting and filling method for waste gas and oil pipelines. The method includes: injecting grout from a grouting port into the pipeline using a grouting machine to propel the grout forward within the pipeline; providing a vacuum environment for the pipeline using a vacuum pump to reduce resistance caused by the elevation difference of the pipeline during grouting; and using a sedimentation separator to ensure the pipeline is filled with the grout. In the above scheme, the grouting port is parallel to the axis of the pipeline, used to convert the pressure of the grouting machine into power. In the above scheme, when the elevation difference of the pipeline is no greater than 1m, foam balls are used to fill the pipeline to assist the grout in advancing forward. This invention, due to improvements in the grouting and filling device and method, ensures advantages such as long grouting and filling distance and high grouting and filling rate for long-distance, large-diameter waste gas and oil pipelines. However, because cement grout is used, with cement as the sole main material, the material cost is relatively high. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention provides a filling material for abandoned oil and gas pipelines, its preparation method, and filling process, the technical solution of which is as follows:

[0007] A filling material for abandoned oil and gas pipelines, comprising the following components and their parts by weight: 80-100 parts fly ash, 5-15 parts cement, 120-150 parts water, 0.1-1.5 parts sodium hexametasilicate, 0.5-10 parts modified PVA adhesive, 0.1-0.5 parts retarder, and 5-15 parts expanding agent.

[0008] The fly ash is grade III fly ash from a power plant, with a fineness of ≤45% residue on a 45μm square-hole sieve.

[0009] The cement is silicate cement with a strength grade ≥42.5.

[0010] The modification method of the modified PVA adhesive is as follows: after dissolving low molecular weight PVA in water, 4-chlorobutyraldehyde is first added to it for polymerization to block some hydroxyl groups; then polyacrylamide is added to it to obtain a polymer containing hydroxyl and amine groups.

[0011] The mass ratio of PVA to 4-chlorobutyraldehyde is (100:28) to (100:32).

[0012] The mass ratio of 4-chlorobutyraldehyde to polyacrylamide is (100:2.1) to (100:2.5).

[0013] The retarder is one or more of lignin sulfonate, sodium carboxymethyl cellulose, and ferrous sulfate.

[0014] The expanding agent is UEA expanding agent.

[0015] According to the above-described method for preparing a filling material for abandoned oil and gas pipelines, the operation steps are as follows: according to the mass proportions of each component in the filling material, fly ash, cement, sodium hexametasilicate, modified PVA adhesive, retarder and expansion agent are placed in water and stirred evenly to obtain the filling material for abandoned oil and gas pipelines.

[0016] A filling process for abandoned oil and gas pipelines involves filling the pipelines with a filling material prepared using the aforementioned method. At the start of the filling operation, a mixer is connected to a filling pump, and a high-pressure filling hose connects the filling pump to a pre-drilled hole in the pipeline. The filling pump is then turned on, and the mixer ensures its conveying capacity, with the filling capacity controlled between 40 and 80 m³. 3 / h.

[0017] Compared with the prior art, the present invention has the following main advantages:

[0018] 1. The filler material provided by this invention uses only a very low mass fraction of cement and a large amount of fly ash, which has better environmental friendliness and lower cost.

[0019] 2. The filling material provided by the present invention has the advantages of high fluidity and long initial setting time, which can meet the requirements of long-distance grouting and is particularly suitable for long-distance oil and gas pipelines.

[0020] 3. The filler material provided by the present invention has good strength and solidity after curing, and can achieve permanent curing and good stability.

[0021] 4. The preparation method of the filler material provided by the present invention is simple and easy to implement.

[0022] 5. The filling process provided by this invention is highly operable and has high filling efficiency. Detailed Implementation

[0023] To make the technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below through embodiments, but the present invention is not limited to these embodiments.

[0024] In this embodiment, the fluidity and time-dependent loss of the filler slurry were determined according to the fluidity of cement paste in GB / T8077-2012 "Test Method for Homogeneity of Concrete Admixtures". The fluidity of the fly ash slurry was tested by changing the type and dosage of the admixture. The compressive strength of the fly ash slurry was tested using a detachable triple mold with an inner cavity size of 40mm × 40mm × 160mm. All test blocks were cured using standard methods.

[0025] Example 1: 85 kg of fly ash, 15 kg of cement, 120 kg of water, 0.5 kg of sodium hexametasilicate, 3 kg of modified PVA adhesive, 0.1 kg of lignin sulfonate retarder, and 5 kg of UEA expansion agent were mixed evenly to obtain a filler. The fluidity was measured to be 412 mm after 3 hours, 350 mm after 12 hours, with a stone-setting rate of 98.5% and a compressive strength of 3.80 MPa after 28 days.

[0026] Fly ash refers to the fine ash collected from the flue gas after coal combustion. It is a major solid waste discharged from coal-fired power plants, and its main components are SiO2 and Al2O3, with small amounts of Fe2O3 and CaO. In this embodiment, the fly ash used is grade III fly ash from a power plant, with a fineness of ≤45% residue on a 45μm square-hole sieve.

[0027] The main mineral components of silicate cement are tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite. Its strength grades are divided into six levels: 42.5, 42.5R, 52.5, 52.5R, 62.5, and 62.5R. In this embodiment, silicate cement with a strength grade ≥42.5 is used; in practice, a strength grade of 42.5 is sufficient to meet the requirements.

[0028] PVA is another name for polyvinyl alcohol, with the chemical formula [C2H4O]. n An organic compound. In this embodiment, the modification method of the modified PVA adhesive is as follows: after dissolving low molecular weight PVA in water, 4-chlorobutyraldehyde is first added to it for polymerization to block some hydroxyl groups; then polyacrylamide is added to it to obtain a polymer containing hydroxyl and amine groups. The mass ratio of PVA to 4-chlorobutyraldehyde is 100:30, and the mass ratio of 4-chlorobutyraldehyde to polyacrylamide is 1:2.3.

[0029] This embodiment provides a method for preparing a filling material for abandoned oil and gas pipelines. The operation steps are as follows: according to the mass parts of each component in the filling material, fly ash, cement, sodium hexametasilicate, modified PVA adhesive, retarder and expansion agent are placed in water and stirred evenly to obtain a filling material for abandoned oil and gas pipelines.

[0030] This embodiment provides a filling process for abandoned oil and gas pipelines, which uses filling material prepared by the above method to fill the abandoned oil and gas pipelines. At the start of the filling operation, a mixer is connected to a filling pump, and a special high-pressure filling pipe connects the filling pump to the pre-drilled hole in the pipeline. The filling pump is turned on, and the mixer ensures the pump's conveying capacity, with the filling capacity controlled at 40-80m³. 3 / h.

[0031] Example 2: 90 kg of fly ash, 10 kg of cement, 120 kg of water, 0.5 kg of sodium hexametasilicate, 5 kg of modified PVA adhesive, 0.1 kg of lignin sulfonate retarder, and 5 kg of UEA expansion agent were mixed evenly to obtain a filler. The fluidity was measured to be 430 mm after 3 hours, 385 mm after 12 hours, with a stone-setting rate of 97.3% and a compressive strength of 3.30 MPa after 28 days.

[0032] Fly ash refers to the fine ash collected from the flue gas after coal combustion. It is a major solid waste discharged from coal-fired power plants, and its main components are SiO2 and Al2O3, with small amounts of Fe2O3 and CaO. In this embodiment, the fly ash used is grade III fly ash from a power plant, with a fineness of ≤45% residue on a 45μm square-hole sieve.

[0033] The main mineral components of silicate cement are tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite. Its strength grades are divided into six levels: 42.5, 42.5R, 52.5, 52.5R, 62.5, and 62.5R. In this embodiment, silicate cement with a strength grade ≥42.5 is used; in practice, a strength grade of 42.5 is sufficient to meet the requirements.

[0034] PVA is another name for polyvinyl alcohol, with the chemical formula [C2H4O]. n An organic compound. In this embodiment, the modification method of the modified PVA adhesive is as follows: after dissolving low molecular weight PVA in water, 4-chlorobutyraldehyde is first added to it for polymerization to block some hydroxyl groups; then polyacrylamide is added to it to obtain a polymer containing hydroxyl and amine groups. The mass ratio of PVA to 4-chlorobutyraldehyde is 100:30, and the mass ratio of 4-chlorobutyraldehyde to polyacrylamide is 1:2.3.

[0035] This embodiment provides a method for preparing a filling material for abandoned oil and gas pipelines. The operation steps are as follows: according to the mass parts of each component in the filling material, fly ash, cement, sodium hexametasilicate, modified PVA adhesive, retarder and expansion agent are placed in water and stirred evenly to obtain a filling material for abandoned oil and gas pipelines.

[0036] This embodiment provides a filling process for abandoned oil and gas pipelines, which uses filling material prepared by the above method to fill the abandoned oil and gas pipelines. At the start of the filling operation, a mixer is connected to a filling pump, and a special high-pressure filling pipe connects the filling pump to the pre-drilled hole in the pipeline. The filling pump is turned on, and the mixer ensures the pump's conveying capacity, with the filling capacity controlled at 40-80m³. 3 / h.

[0037] Example 3: 100 kg of fly ash, 5 kg of cement, 150 kg of water, 0.5 kg of sodium hexametasilicate, 10 kg of modified PVA adhesive, 0.2 kg of lignin sulfonate retarder, and 15 kg of UEA expansion agent were mixed evenly to obtain a filler. The fluidity was measured to be 330 mm after 3 hours, 282 mm after 12 hours, with a stone-forming rate of 96.7% and a compressive strength of 2.11 MPa after 28 days.

[0038] Fly ash refers to the fine ash collected from the flue gas after coal combustion. It is a major solid waste discharged from coal-fired power plants, and its main components are SiO2 and Al2O3, with small amounts of Fe2O3 and CaO. In this embodiment, the fly ash used is grade III fly ash from a power plant, with a fineness of ≤45% residue on a 45μm square-hole sieve.

[0039] The main mineral components of silicate cement are tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite. Its strength grades are divided into six levels: 42.5, 42.5R, 52.5, 52.5R, 62.5, and 62.5R. In this embodiment, silicate cement with a strength grade ≥42.5 is used; in practice, a strength grade of 42.5 is sufficient to meet the requirements.

[0040] PVA is another name for polyvinyl alcohol, with the chemical formula [C2H4O]. n An organic compound. In this embodiment, the modification method of the modified PVA adhesive is as follows: after dissolving low molecular weight PVA in water, 4-chlorobutyraldehyde is first added to it for polymerization to block some hydroxyl groups; then polyacrylamide is added to it to obtain a polymer containing hydroxyl and amine groups. The mass ratio of PVA to 4-chlorobutyraldehyde is 100:30, and the mass ratio of 4-chlorobutyraldehyde to polyacrylamide is 1:2.3.

[0041] This embodiment provides a method for preparing a filling material for abandoned oil and gas pipelines. The operation steps are as follows: according to the mass parts of each component in the filling material, fly ash, cement, sodium hexametasilicate, modified PVA adhesive, retarder and expansion agent are placed in water and stirred evenly to obtain a filling material for abandoned oil and gas pipelines.

[0042] This embodiment provides a filling process for abandoned oil and gas pipelines, which uses filling material prepared by the above method to fill the abandoned oil and gas pipelines. At the start of the filling operation, a mixer is connected to a filling pump, and a special high-pressure filling pipe connects the filling pump to the pre-drilled hole in the pipeline. The filling pump is turned on, and the mixer ensures the pump's conveying capacity, with the filling capacity controlled at 40-80m³. 3 / h.

[0043] Application Example 1

[0044] The filler material obtained in Example 1 was used for filling an abandoned pipeline in an oil production plant of Shengli Oilfield. This abandoned pipeline was a discontinued external transmission pipeline, consisting of a Ф219×7.1 spiral submerged arc welded steel pipe with a length of 13.8 km. The filler material was stirred and mixed thoroughly. The mixer was connected to the filling pump, and a special high-pressure filling pipe was used to connect the filling pump to the pre-drilled hole in the pipeline. The filling pump was started, and the mixer was used to ensure the pump's conveying capacity, with the filling capacity controlled at 40–80 m³ / s. 3 / h, one construction can fill 3000km; after 28 days of testing, the filling meets the requirements of the Q / SH1020 2769—2020 standard of China Petrochemical Corporation Shengli Oilfield Administration Co., Ltd.

Claims

1. A filling process for abandoned oil and gas pipelines, characterized in that: The abandoned oil and gas pipeline is filled with filling material. At the start of the filling operation, the mixer is connected to the filling pump, and a special high-pressure filling hose is used to connect the filling pump to the pre-drilled hole in the pipeline. The filling pump is then turned on, and the mixer ensures the pump's conveying capacity, with the filling capacity controlled between 40 and 80 m³. 3 / h; The filler material includes the following components and their weight parts: 80-100 parts fly ash, 5-15 parts cement, 120-150 parts water, 0.1-1.5 parts sodium hexametasilicate, 0.5-10 parts modified PVA adhesive, 0.1-0.5 parts retarder, and 5-15 parts expansion agent. The fly ash is grade III fly ash from power plants, with a fineness of ≤45% residue on a 45μm square-hole sieve. The cement is silicate cement with a strength grade ≥42.5; The modification method of the modified PVA adhesive is as follows: after dissolving low molecular weight PVA in water, 4-chlorobutyraldehyde is first added to it for polymerization to block some hydroxyl groups; then polyacrylamide is added to it to obtain a polymer containing hydroxyl and amine groups. The mass ratio of PVA to 4-chlorobutyraldehyde is (100:28) to (100:32). The preparation steps of the filler material are as follows: according to the mass parts of each component in the filler material, fly ash, cement, sodium hexametasilicate, modified PVA adhesive, retarder and expansion agent are placed in water and stirred evenly to obtain a filler material for abandoned oil and gas pipelines.

2. The filling process for a waste oil and gas pipeline according to claim 1, characterized in that: The retarder is one or more of lignin sulfonate, sodium carboxymethyl cellulose, and ferrous sulfate.

3. The filling process for a waste oil and gas pipeline according to claim 1, characterized in that: The expanding agent is UEA expanding agent.