Novel method for removing oil blockage of shaft of gas well

Abstract

The invention relates to a novel method for removing oil blockage of a gas well shaft. The method comprises the steps that firstly, mixed liquid is injected into an annular space of the oil jacket, the temperature of the mixed liquid ranges from 270 DEG C to 300 DEG C, the specific gravity of the mixed liquid is 0.3, and the mixed liquid is composed of methyl alcohol, gasoline, xylene and CO2; (2) the adding amount of the mixed liquid is 5 cubic meters of the mixed liquid per 500 meters of shaft; (3) controlling the injection flow of the mixed liquid, wherein the injection flow is not less than 20 cubic meters per hour, and the injection time is not more than 15 minutes; and (4) the injection pressure depends on the wellhead pressure of the gas well and is not lower than 10 MPa, and the injection temperature is not lower than 270 DEG C. A certain amount of mixed liquid is injected through the oil sleeve space, and the technical problem of shaft blockage is solved.

Description

Technical Field

[0001] The invention relates to the technical field of improving the output and recovery rate of oil and gas production wells, and in particular to a new method for removing oil blockage in a gas wellbore. Background Art

[0002] As oil-bearing natural gas migrates from the bottom of a well to the wellhead, the temperature of the wellbore continues to drop, causing some of the crude oil dissolved in the natural gas to precipitate. These small droplets adhere to the inner wall of the tubing, creating a throttling effect. The lower temperature near the wellhead, combined with this throttling effect, accelerates the precipitation and solidification of the crude oil, causing blockage in the upper wellbore, impacting normal production, and ultimately causing the well to stop flowing.

[0003] Conventional gas wellbore oil blockage treatment method: high-temperature hot water is pumped into the wellbore through the casing, and the temperature difference is used to dissolve the solidified crude oil. The dissolved crude oil is then carried out of the wellbore with the airflow, and the normal production of the gas well is restored. This treatment method has the following problems: First, water hot washing is used to remove the oil blockage in the gas wellbore. Since the specific gravity of water (about 1) is much greater than the specific gravity of high-pressure natural gas in the wellbore (about 0.25), a large amount of hot water will quickly fall to the bottom of the well and cannot maintain long-term contact with the solidified crude oil, and the efficiency of hot washing is low; second, the water that falls to the bottom of the well will be converted into bottom-well liquid, reducing the gas production of the gas well. In severe cases, it will cause the gas well to stop blowing; third, the water added to the wellbore will be carried out of the wellbore with the airflow. Due to the high pressure, low temperature of the gas well and the presence of liquid water, the gas well will be converted from oil blockage to hydrate freeze-blockage. This will again lead to blockage of the gas wellbore, affecting the normal production of the gas well; fourthly, when hot washing is used to deblock in winter, once there is residual water in the transmission components or the blowing is not thorough, it will cause freezing, causing the boosting equipment to be pressurized, posing a safety hazard. Generally, water hot washing deblocking operations are not performed in winter, and oil blockage in the gas wellbore is more likely to occur during the winter production period. There is currently no effective oil deblocking technology; fifthly, hot washing will produce a large amount of liquid water falling into the bottom of the artificial well. Since most reservoirs are water-wet, a large amount of liquid will enter the gas well formation, causing water-sensitive damage, polluting the reservoir, and reducing the gas well production. Summary of the Invention

[0004] In order to solve the technical problems existing in the background technology, the present invention provides a new method for removing oil blockage in a gas well bore, which solves the technical problem of well bore blockage by injecting a certain amount of mixed liquid into the oil casing space.

[0005] The technical solution provided by the present invention is: a new method for removing oil blockage in a gas wellbore comprises the following steps:

[0006] (1) First, a mixed liquid is injected into the annular space of the oil casing. The temperature of the mixed liquid is 270℃-300℃, the specific gravity of the mixed liquid is 0.3, and the mixed liquid consists of methanol, gasoline, xylene and CO2;

[0007] (2) The amount of mixed liquid added: 5 cubic meters of mixed liquid is added for every 500 meters of wellbore;

[0008] (3) Injection flow rate of mixed liquid: injection flow rate shall not be less than 20 cubic meters per hour, and injection time shall not exceed 15 minutes;

[0009] (4) The injection pressure depends on the wellhead pressure of the gas well, which shall not be less than 10 MPa, and the injection temperature shall not be less than 270°C.

[0010] The mixed liquid is composed of 70% methanol, 15% gasoline, 5% xylene and 10% CO2 in percentage by mass.

[0011] The beneficial effects of the present invention are as follows: the methanol and carbon dioxide mixture in the mixed liquid of the present application has a low specific gravity under high temperature conditions, which can reduce the specific gravity of the entire mixed liquid to about 0.3, thereby reducing the falling speed of the mixed liquid in the casing, thereby fully exchanging heat with the wax-covered parts in the oil pipe to remove blockages and improve the removal efficiency. When the mixed liquid falls to the bottom of the well, it turns into small droplets and fully mixes with the natural gas in the wellbore. Methanol can prevent hydrate blockage, xylene is mainly used to dissolve wax, and gasoline is mainly used to dissolve heavy hydrocarbons, thereby preventing secondary blockage of natural gas in the oil pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Attachment Figure 1 It is a mixed liquid injection diagram of the present invention. DETAILED DESCRIPTION

[0013] The present invention is further described below with reference to the accompanying drawings and examples:

[0014] Example 1

[0015] like Figure 1 As shown: Taking the XS67 well as an example, the new method for removing oil blockage in the gas wellbore includes the following steps:

[0016] (1) First, a mixed liquid is injected into the annular space of the casing. Before injection, the normal temperature mixed liquid needs to be sealed and heated, and then injected into the casing wellbore. The following goals can be achieved: First, the mixed liquid is heated to 270℃. The specific gravity of the mixed liquid is 0.3, which is close to the specific gravity of high-pressure natural gas of 0.25. In this way, the mixed liquid is not easy to fall to the bottom of the well, and can be in contact with the solidified crude oil for a long time, eliminating the wax deposition problem and improving the plugging efficiency. The above-mentioned mixed liquid consists of methanol, gasoline, xylene and CO2; the mixed liquid is proportioned by mass as follows: 70% methanol, 15% gasoline, 5% xylene and 10% CO2.

[0017] (2) The amount of mixed liquid added: the amount added for every 500 meters of wellbore is 5 cubic meters of mixed liquid; first of all, the unblocking operation is changed from adding 20 cubic meters of hot water (10 cubic meters of hot water is needed for 1000 meters of wellbore, and the depth of the gas well is 2000 meters) to adding 5 cubic meters of mixed liquid (adding 500 meters of wellbore) to meet the treatment needs; in addition, since the amount of mixed liquid added is small and the fall back time is long, after falling to the bottom of the well, it will be mixed with the natural gas and can be taken out of the bottom of the well in time to avoid excessive liquid accumulation and affect the production capacity; in addition, the mixed liquid added to the bottom of the well dissolves in the high-pressure natural gas in the form of small particles, which can effectively prevent the formation of hydrates and avoid hydrate freezing and blocking the wellbore;

[0018] (3) Injection flow rate of mixed liquid: injection flow rate shall not be less than 20 cubic meters / h, and injection time shall not exceed 15 minutes;

[0019] (4) The injection pressure depends on the wellhead pressure of the gas well, which should not be less than 10MPa, and the injection temperature should not be less than 270℃. The mixed liquid can withstand low temperatures down to -60℃, and can normally handle wellbore oil blockage problems during winter production. Since no liquid water is introduced during the entire treatment operation, water-sensitive damage is avoided and the reservoir is protected.

[0020] (5) When injecting high-temperature mixed liquid, always pay attention to the changes in wellhead oil pressure. When the wellhead oil pressure rises and the gas production shows an instantaneous upward trend, it can be judged that the oil blockage is dissolving. When the wellhead oil pressure is equal to the casing pressure before injection and the gas production instantly returns to the gas flow rate before oil blockage, the oil blockage problem is eliminated.

[0021] (6) After the oil blockage is eliminated, the crude oil in the oil pipe will be gradually carried out of the wellbore, and the separator drainage needs to be increased to prevent the separation and drainage system from being blocked;

[0022] (7) In order to improve the efficiency of oil blockage removal, when the gas well flow rate recovers to the instantaneous gas flow rate before oil blockage, the entire gas volume is increased by 1 times, relying on the dual effects of large instantaneous flow and high temperature to quickly remove the blockage. The large instantaneous flow rate is maintained for 1 hour, and then the flow rate is adjusted to the flow rate value before oil blockage.

[0023] Previously, treating oil blockages in gas wells required one high-pressure pump truck, one hot water tanker, and four operators. The well had to be opened and closed six times, and the pump started and stopped more than ten times, with a processing cycle of at least two days. When treating oil blockages in winter, when the wellhead process freezes and pressure builds up, a high-temperature steam truck and two operators were required. High-temperature steam heating was required for six hours before reinjection, making the entire process time-consuming and labor-intensive, with low processing efficiency. However, by injecting a new high-temperature mixed liquid, the time required to treat oil blockages has been reduced from two days to 0.5 hours, with a 100% success rate and continuous and stable gas production achieved, achieving excellent results in field applications.

Claims

1. A new method for removing oil blockage in a gas wellbore, the method comprising the following steps: (1) First, a mixed liquid is injected into the annular space of the oil casing. The temperature of the mixed liquid is 270℃-300℃, the specific gravity of the mixed liquid is 0.3, and the mixed liquid consists of methanol, gasoline, xylene and CO2; (2) The amount of mixed liquid added: 5 cubic meters of mixed liquid is added for every 500 meters of wellbore; (3) Injection flow rate of mixed liquid: injection flow rate shall not be less than 20 cubic meters per hour, and injection time shall not exceed 15 minutes; (4) The injection pressure depends on the wellhead pressure of the gas well, which shall not be less than 10 MPa, and the injection temperature shall not be less than 270°C.

2. The new method for removing oil blockage in a gas wellbore according to claim 1 is characterized in that: The mixed liquid is composed of the following proportions by mass: 70% methanol, 15% gasoline, 5% xylene and 10% CO2.

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