Method for injecting thin oil into heavy oil well of offshore platform

Abstract

The invention discloses a method for injecting thin oil into a heavy oil well of an offshore platform. The method comprises the steps that thin oil of an offshore platform is injected into a heavy oil well through a buffer tank, a screw pump and a plunger pump for well shaft thin oil blending and underground oil extraction; the thin oil is thin oil extracted by an oil extraction platform, thin oil extracted by other oil extraction platforms and conveyed to the oil extraction platform through a pipeline, or other available thin oil; the thin oil is injected into a chemical agent through a chemical agent metering pump; the thin oil is heated by a heater; the heavy oil well can be one heavy oil well or a plurality of heavy oil wells. According to the method, a thin oil injection mode combining a buffer tank, a low-pressure screw pump and a high-pressure plunger pump is adopted, and it is guaranteed that the thin oil injection process is continuous and stable; the buffer tank adopts a breather valve to control the pressure of gas released by thin oil volatilization, and adopts a gas injection valve to inject gas such as nitrogen or carbon dioxide to prevent the buffer tank from burning or exploding due to too high concentration of sucked air; the method can be applied to offshore platform heavy oil well shaft thinning and underground oil extraction.

Description

Technical Field

[0001] The present invention relates to a method for injecting thin oil into heavy oil wells on an offshore platform, belonging to the technical field of oil exploitation. Background Art

[0002] There has been extensive research and application in reducing the viscosity of heavy oil and improving the fluidity of heavy oil by mixing thin oil into the heavy oil in the wellbore and surface pipelines. At the same time, thin oil can also be injected into the formation of heavy oil wells for plugging removal and production increase. When injecting thin oil into heavy oil wells in onshore oilfields, generally, a piston pump is used at the gathering station to pressurize and pump the dehydrated and degassed thin oil into the injection pipeline, and then it is injected into the oil well through the injection pipeline. However, the space on the offshore oil production platform is limited and the dehydration and degassing treatment is not sufficient. There are a large number of dissolved gases in both the thin oil produced by the oil production platform itself and the thin oil passing through the oil pipeline. There is a risk of combustion and explosion when the dissolved gas precipitates or leaks. Moreover, the mismatch between the production rate of thin oil on the offshore platform or the flow rate of thin oil passing through the oil pipeline and the injection rate is likely to cause unstable injection of thin oil, and even problems such as pressure buildup, leakage, or the pump running idly and getting stuck. Therefore, for offshore platforms with high safety requirements, a safe and reliable thin oil injection process method is needed. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for injecting thin oil into heavy oil wells on an offshore platform, which injects the thin oil of the offshore platform into the heavy oil wells through a buffer tank, a screw pump, and a piston pump for wellbore thin oil mixing and underground oil production.

[0004] To achieve the above purpose, the present invention provides a method for injecting thin oil into heavy oil wells on an offshore platform, including the step of injecting the thin oil of the offshore platform into the heavy oil wells through a buffer tank, a screw pump, and a piston pump for wellbore thin oil mixing and underground oil production;

[0005] The thin oil is the thin oil produced by the oil production platform, the thin oil produced by other oil production platforms and transported to the present oil production platform through pipelines, or other available thin oil;

[0006] The thin oil is injected with chemicals through a chemical metering pump;

[0007] The thin oil is heated through a heater;

[0008] The heavy oil well can be a single heavy oil well or multiple heavy oil wells.

[0009] In the present invention, the function of the buffer tank is to adjust the stable and safe injection of thin oil. It can be a vertical storage tank, a horizontal storage tank, or other storage tanks. The buffer tank needs to be equipped with an inlet valve, an outlet valve, a liquid level monitor, a breather valve, and a gas injection valve.

[0010] Among them, the volume of the buffer tank is selected according to the injection rate of light oil into the heavy oil well. Preferably, the volume of the buffer tank should be 0.5 to 5 times (by volume) of the daily injection volume of the heavy oil well.

[0011] Among them, the gas injection valve is connected to a container or generator of a gas such as nitrogen or carbon dioxide, and continuously or intermittently injects a gas such as nitrogen or carbon dioxide into the buffer tank to prevent the buffer tank from burning or exploding due to too high an air inhalation concentration.

[0012] In the present invention, the screw pump pressurizes the gas-containing light oil or volatile light oil in the buffer tank to above the bubble point pressure of the light oil, ensuring that the light oil at the inlet of the piston pump is a single-phase light oil without free gas.

[0013] Preferably, the outlet pressure of the screw pump is 1 to 10 MPa, and the displacement is determined according to the injection rate of light oil into the heavy oil well. Preferably, the displacement of the screw pump is 1 to 90 m 3 / hour.

[0014] In the present invention, the piston pump is a high-pressure piston pump for injecting light oil into a heavy oil well.

[0015] Preferably, the outlet pressure of the piston pump is 10 to 30 MPa, and the displacement is determined according to the injection rate of light oil into the heavy oil well. Preferably, the displacement of the piston pump is 1 to 90 m 3 / hour.

[0016] Preferably, when injecting light oil into a heavy oil well for wellbore dilution, only the screw pump can be used without using the piston pump.

[0017] In the present invention, the heater is a high-pressure liquid heater. Preferably, the high-pressure liquid heater can be a heat-conducting oil electric heater. Preferably, the power of the heater is determined according to the light oil injection rate and the elevated temperature, that is, heater power = power coefficient × light oil injection rate × specific heat of light oil × elevated temperature of light oil.

[0018] The method for injecting light oil into a heavy oil well on an offshore platform of the present invention is not limited to the above range, and is applicable to all places or uses where the light oil injection method provided by the present invention can be adopted, including injecting light oil into onshore pipelines and subsea pipelines on an offshore platform for viscosity reduction and transportation of heavy oil.

[0019] The present invention has the following beneficial technical effects:

[0020] (1) The method for injecting light oil into a heavy oil well on an offshore platform provided by the present invention adopts a light oil injection method combining a buffer tank, a low-pressure screw pump and a high-pressure piston pump, ensuring the continuity and stability of the light oil injection process.

[0021] (2) When the buffer tank in the method for injecting light oil into heavy oil wells on an offshore platform provided by the present invention controls the pressure of the gas released by the evaporation of light oil using a breather valve, nitrogen, carbon dioxide or other gases are injected using a gas injection valve to prevent the buffer tank from burning or exploding due to excessive inhalation of air. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic diagram of the technological process for injecting light oil into heavy oil wells on an offshore platform of the present invention;

[0023] The specific meanings of the markings in the figure are as follows: 1: chemical agent pump, 2: chemical agent bottle, 3: centrifuge, 4: nitrogen cylinder, 5: horizontal buffer oil tank, 6: screw pump, 7: high-pressure plunger pump, 8: heating skid, 9: wellhead;

[0024] Figure 2 is a schematic diagram of the horizontal buffer oil tank in Embodiment 1 of the present invention;

[0025] The specific meanings of the markings in the figure are as follows: 51: manhole, 52: inlet valve, 53: sewage discharge valve, 54: leg support, 55: outlet valve, 56: gas injection valve I, 57: gas injection valve II, 58: heat exchange valve, 59: breather valve, 60: safety valve, 61: inspection valve;

[0026] Figure 3 is a schematic diagram of the vertical buffer tank in Embodiment 2 of the present invention;

[0027] The specific meanings of the markings in the figure are as follows: 10: platform, 11: gas injection valve, 12: ladder, 13: inlet valve, 14: sewage discharge valve, 15: manhole, 16: outlet valve, 17: breather valve, 18: safety valve, 19: inspection valve. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] Unless otherwise specified, the experimental methods used in the following embodiments are all conventional methods.

[0029] Unless otherwise specified, the materials, reagents, etc. used in the following embodiments can all be obtained from commercial channels.

[0030] Embodiment 1: Horizontal Buffer Oil Tank

[0031] In this embodiment, a horizontal buffer oil tank is selected as the key equipment for light oil storage and transfer.

[0032] To adapt to the working conditions of the offshore oil production platform, a horizontal buffer oil tank with an appropriate volume is selected according to the injection rate of light oil into the heavy oil well and the space conditions of the offshore platform. Generally speaking, its volume is preferably 0.5 to 5 times the daily injection volume of the heavy oil well.

[0033] In actual operation, first, the thin oil is transported through a pipeline to the horizontal buffer oil tank 5. The inlet valve in this process controls the flow rate of the thin oil to ensure that the speed of the thin oil flowing into the oil tank is not too fast. Once the thin oil enters the horizontal buffer oil tank 5, the outlet valve is connected to the low-pressure screw pump 6. Under the action of the screw pump 6, the thin oil in the horizontal buffer oil tank 5 is transported to the high-pressure plunger pump 7. Thereafter, under the push of the high-pressure plunger pump 7, the thin oil is injected into one or more heavy oil wells (wellhead 9) of the offshore oil production platform to achieve the goals of wellbore dilution, near-wellbore plug removal, or huff and puff oil production.

[0034] To ensure the operation safety of the horizontal buffer oil tank 5, a breather valve 59 is installed on it. The main function of the breather valve 59 is to control the gas pressure generated by the evaporation of the thin oil and avoid the oil tank bursting due to excessive pressure. At the same time, gas injection valves (gas injection valve I 56, gas injection valve II 57) are also set on the buffer oil tank. The gas injection valve I 56 (gas injection valve II 57) is connected to a nitrogen or carbon dioxide gas storage tank or generator, and can continuously or intermittently inject nitrogen or carbon dioxide into the buffer tank to prevent safety accidents caused by too high an inhaled air concentration. In addition, it should be noted that the horizontal buffer oil tank 5 should be regularly inspected and maintained to ensure its working efficiency and safety.

[0035] For the horizontal buffer oil tank, since it occupies a relatively large area on the plane, it is necessary to ensure that there is enough working space around it so that operators can work safely and effectively during daily maintenance or emergency operations. At the same time, considering the particularity of the offshore environment, the horizontal buffer oil tank needs to have good anti-corrosion and anti-erosion performance to prevent the erosion of seawater and sea breeze on the oil tank.

[0036] Embodiment 2: Vertical buffer oil tank

[0037] In this embodiment, a vertical buffer oil tank is selected as the equipment for injecting thin oil.

[0038] Compared with the horizontal buffer oil tank, the vertical buffer oil tank saves more space, enabling it to be efficiently utilized on a limited offshore platform.

[0039] The operation process is similar to that of the horizontal buffer oil tank. First, the thin oil flows through the inlet valve 13 through a pipeline and is injected into the vertical buffer oil tank. At this time, the importance of the inlet valve is reflected. It controls the amount of oil flowing into the tank to prevent problems caused by too fast oil flow. Then, the outlet valve 16 is connected to the low-pressure screw pump to pump the thin oil in the buffer tank into the high-pressure plunger pump. Thereafter, the high-pressure plunger pump sends the thin oil into the heavy oil wells of the offshore oil production platform to achieve wellbore dilution, near-wellbore plug removal, or huff and puff oil production.

[0040] Similarly, to ensure the safe operation of the vertical buffer oil tank, a breather valve 17 and a gas injection valve 11 are installed on this tank body. The breather valve 17 can control the gas pressure generated by the evaporation of the thin oil and prevent the tank body from being damaged due to excessive pressure. The gas injection valve 11 can continuously or intermittently inject nitrogen or carbon dioxide into the buffer tank, which is crucial for preventing combustion or explosion that may be caused by excessive intake of air.

[0041] Due to the characteristics of the vertical buffer oil tank, special attention needs to be paid to some details during its use. First of all, due to its structural characteristics, the vertical buffer oil tank is easier to control pressure and liquid level than the horizontal buffer oil tank. Therefore, the operator needs to regularly check the liquid level and pressure gauge to ensure its normal operation. Secondly, due to the relatively high height of the vertical buffer oil tank, attention should be paid to preventing high-altitude falling accidents during installation and maintenance. Also, when injecting gas, it is necessary to ensure the purity of the gas to avoid introducing impurity gases that may cause chemical reactions.

[0042] For the vertical buffer oil tank, attention needs to be paid to the installation positions of auxiliary equipment such as valves and pipelines, and high-altitude operations should be avoided as much as possible to reduce safety risks. At the same time, due to its relatively large height, the vertical buffer oil tank has higher requirements for the stability of the platform. Therefore, when choosing the installation position, the bearing capacity and balance of the platform need to be fully considered.

[0043] During the use of the buffer oil tank, it is necessary to regularly clean and internally inspect the oil tank to prevent the accumulation of sludge from affecting the use efficiency of the tank body. At the same time, since the thin oil in the oil tank may contain certain harmful gases such as hydrogen sulfide, when carrying out inspections and maintenance, the staff needs to wear appropriate protective equipment to ensure their own safety.

[0044] When designing and manufacturing the oil tank, the easy disassembly and reusability of the oil tank also need to be considered. It should be designed into a modular structure as much as possible, so that when the oil tank needs to be replaced or repaired, the workload can be reduced and the work efficiency can be improved.

[0045] It should be clear that both horizontal and vertical buffer oil tanks have their unique precautions during use. Generally speaking, whether it is a horizontal buffer oil tank or a vertical buffer oil tank, their design and implementation need to fully consider the actual needs and safety issues of the offshore oil production platform. The volume selection of the buffer oil tank, the design of the inlet and outlet valves, gas injection and pressure control, etc. all require careful layout and precise control. At the same time, regardless of the type of buffer oil tank, regular inspections and maintenance are required to ensure its continuous, stable and safe operation. Only in this way can we achieve effective offshore heavy oil exploitation, ensure the stable supply of energy, and at the same time provide a safe working environment for offshore workers.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for injecting thin oil into a heavy oil well on an offshore platform, comprising the steps of injecting thin oil from the offshore platform into the heavy oil well through a buffer tank, a screw pump and a plunger pump to dilute the wellbore and produce oil underground; The thin oil is the thin oil produced by the oil production platform, the thin oil produced by other oil production platforms and transported to the oil production platform through pipelines, or other available thin oil; The thin oil is injected into the chemical agent through a medicine metering pump; The thin oil is heated by a heater; The heavy oil well may be one heavy oil well or multiple heavy oil wells.

2. The method according to claim 1, characterized in that: The function of the buffer tank is to adjust the injection of thin oil to be smooth and safe, and it can be a vertical storage tank, a horizontal storage tank or other storage tank; The buffer tank needs to be equipped with an inlet valve, an outlet valve, a liquid level monitor, a breathing valve and a gas injection valve; The volume of the buffer tank is selected according to the rate at which the thin oil is injected into the heavy oil well.

3. The method according to claim 2, characterized in that: The volume of the buffer tank should be 0.5 to 5 times the daily injection volume of the heavy oil well.

4. The method according to claim 2 or 3, characterized in that: The gas injection valve is connected to a container or generator of a gas such as nitrogen or carbon dioxide, and continuously or intermittently injects a gas such as nitrogen or carbon dioxide into the buffer tank.

5. The method according to any one of claims 1 to 4, characterized in that: The screw pump pressurizes the gas-containing thin oil or volatile thin oil in the buffer tank to a pressure above the bubble point pressure of the thin oil, so as to ensure that the thin oil at the inlet of the plunger pump is a single-phase thin oil without free gas.

6. The method according to claim 5, characterized in that: The outlet pressure of the screw pump is 1-10 MPa, and the displacement of the screw pump is 1-90 m 3 / Hour.

7. The method according to any one of claims 1 to 6, characterized in that: The plunger pump is a high-pressure plunger pump for injecting thin oil into a heavy oil well; The outlet pressure of the plunger pump is 10-30 MPa, and the displacement of the plunger pump is 1-90 m 3 / Hour.

8. The method according to any one of claims 1 to 7, characterized in that: The heater is a high pressure liquid heater.

9. The method according to claim 8, characterized in that: The high-pressure liquid heater is a thermal oil electric heater.

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