Unmanned compact aging oil treatment system and method suitable for offshore oilfield production

Abstract

The invention discloses an unmanned compact aging oil treatment system and method suitable for offshore oilfield production. The system comprises an aging oil demulsification unit, a centrifugal separation unit and a medicament injection unit, the aging oil demulsification unit comprises an aging oil flowmeter, an aging oil regulating valve, an aging oil heater, a compact electrostatic coalescer and a stirring and blending tank which are sequentially communicated with a dirty oil bin for supplying aging oil through a pipeline; the centrifugal separation unit comprises a centrifugal machine supply pump and a centrifugal machine which are sequentially communicated through a pipeline; an inlet of the centrifugal machine supply pump is connected with an outlet of the stirring and blending tank; the agent injection unit comprises a demulsifying agent storage tank and a demulsifying agent injection pump which are communicated through a pipeline, and is used for injecting a demulsifying agent into the aged oil demulsification unit. According to the invention, the gravity settling time required by demulsification of the aged oil can be greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the field of offshore engineering, and relates to an unmanned compact aging oil treatment system and method suitable for offshore oilfield production. Background Art

[0002] The crude oil in the storage tank of a floating production storage and offloading unit (hereinafter referred to as "FPSO") in the sea is gradually emulsified under the action of surfactants, conductive ions, sewage, sediment, scale, etc., and a "three-high" aging oil layer with high strength of the oil-water interface film, high impurity content, and high conductivity is formed at the oil-water interface in the tank. The aging oil is in the form of a water-in-oil (W / O) emulsion, and with the increase of the storage and accumulation time, its density, viscosity, proportion of heavy components, and acidity increase, the strength and stability of the emulsification interface film increase, and the dehydration difficulty is greatly improved: directly entering the crude oil treatment system, the aging oil is likely to cause the breakdown of the electric field of the electro-dehydrator and the non-compliance of the exported crude oil, affecting the normal production of the oilfield. In the production of offshore oilfields, the aging oil gradually increases with time, reducing the actual oil production of the oilfield, occupying the effective tank volume of the FPSO, affecting the efficiency and stability of the development of offshore oilfields, and posing a severe challenge to the production of offshore oilfields. At present, there are certain studies and reports on the causes, agents, and treatment equipment of aging oil in onshore oilfields. The aging oil is mainly intensively treated by means of large tank settlement, circulating heating, distillation and other facilities in onshore oilfields, which is not suitable for the limited space and less attended situation of offshore FPSOs. With the increasing requirements for energy conservation, production increase, and unmanned operation in offshore oilfields, an efficient and compact aging oil treatment process must be key considered in the design of offshore oilfields to ensure the reuse of aging oil and the efficient production of oilfields, and to practice the requirements of energy conservation and emission reduction. Summary of the Invention

[0003] The purpose of the present invention is to provide an unmanned compact aging oil treatment system and method suitable for offshore oilfield production.

[0004] The present invention provides an unmanned compact aging oil treatment system suitable for offshore oilfield production, including an aging oil demulsification unit, a centrifugal separation unit, and a chemical injection unit;

[0005] The aging oil demulsification unit includes an aging oil flowmeter, an aging oil regulating valve, an aging oil heater, a compact electrostatic coalescer, and a stirring and modulation tank that are sequentially connected by pipelines from a dirty oil tank that supplies aging oil. The aging oil demulsification unit is used to regulate the flow rate of aging oil and achieve efficient demulsification of aging oil through high temperature, demulsifier, electrostatic coalescence, and stirring and modulation;

[0006] The centrifugal separation unit includes a centrifuge feed pump and a centrifuge that are sequentially connected by pipelines. The inlet of the centrifuge feed pump is connected to the outlet of the stirring and modulation tank. The centrifugal separation unit is used to achieve centrifugal separation of oil, water, and sand in the demulsified aging oil to meet the three-phase separation index;

[0007] The chemical injection unit includes a demulsifier storage tank and a demulsifier injection pump connected by a pipeline, which is used to inject demulsifier into the aged oil demulsification unit to ensure the demulsification effect of the aged oil.

[0008] In the above system, the centrifugal separation unit further includes a moisture content tester and a centrifugal process switch valve;

[0009] The moisture content tester and the centrifugal process switch valve are both arranged on the connecting pipeline between the centrifuge supply pump and the centrifuge,

[0010] The moisture content tester is connected to the centrifugal process switch valve to automatically control the operation of the centrifuge.

[0011] In the above system, the centrifugal separation unit further includes a bypass process switch valve;

[0012] The pipeline where the bypass process switch valve is set is connected to the pipeline that is connected between the moisture content tester and the centrifugal process switch valve; the outlet of the pipeline where the bypass process switch valve is set is connected to the dirty oil tank; when the moisture content tester measures that the moisture content of the aged oil is less than 60%, the centrifugal process switch valve is in the open state and the bypass process switch valve is in the closed state, and the aged oil enters the centrifuge for dehydration and desanding; when the moisture content tester measures that the moisture content of the aged oil is greater than 60%, which exceeds the effective working range of the centrifuge, the centrifugal process switch valve is closed and the bypass process switch valve is opened, and the aged oil returns to the dirty oil tank.

[0013] In the above system, the aged oil demulsification unit further includes a liquid level gauge, and the liquid level gauge is arranged in the stirring and modulation tank;

[0014] The liquid level gauge measures the liquid level signal in the stirring and modulation tank to control the rotation speed of the centrifuge supply pump and the opening degree of the aged oil regulating valve, control the flow rate of the aged oil entering the process, and automatically maintain the liquid level stability of the stirring and modulation tank.

[0015] In the above system, on the pipeline between the aged oil flowmeter and the aged oil regulating valve of the aged oil demulsification unit, it is connected to the demulsifier injection pump, which is used to inject the demulsifier stored in the demulsifier storage tank into the aged oil demulsification unit through the demulsifier injection pump. The aged oil flowmeter automatically controls the rotation speed of the demulsifier injection pump to regulate the demulsifier injection amount to ensure the demulsification effect of the aged oil.

[0016] The system of the present invention is compactly skid-mounted and double-layer arranged, which not only reduces the floor area of the system, but also meets the requirements of the net positive suction head of the supply pump, and adapts to the requirements of configuring aged oil treatment facilities in the limited space of offshore FPSO.

[0017] The present invention also provides an unmanned compact aged oil treatment method adapted to offshore oil field production using the above system, comprising the following steps:

[0018] The aged oil in the dirty oil tank is measured by the aged oil flowmeter and mixed with the demulsifier in the demulsifier storage tank input by the demulsifier injection pump. The flow is then regulated by the aged oil regulating valve, heated by the aged oil heater, and the compact electrostatic agglomerator is used to aggregate the emulsion before entering the stirring and conditioning tank. The aged oil and demulsifier in the stirring and conditioning tank are stirred and mixed evenly by the agitator to promote demulsification. The demulsified aged oil is pressurized and transported to the centrifuge by the centrifuge supply pump. After high-speed rotation, the three-phase separation of oil, water and sand is achieved. The separated crude oil enters the crude oil treatment system, the separated sewage enters the sewage tank, and the separated sludge enters the sludge tank.

[0019] In the above method, the liquid level signal in the stirring and modulation tank is measured by the liquid level meter to control the rotation speed of the centrifuge supply pump and the opening of the aged oil regulating valve, control the flow of aged oil entering the process, and automatically maintain the liquid level stability of the stirring and modulation tank.

[0020] In the above method, when the moisture content tester determines that the moisture content of the aged oil is less than 60%, the centrifugal process switch valve is in an open state, the bypass process switch valve is in a closed state, and the aged oil enters the centrifuge for dehydration and desanding; when the moisture content tester determines that the moisture content of the aged oil is greater than 60%, it exceeds the effective working range of the centrifuge, the centrifugal process switch valve is closed, the bypass process switch valve is opened, and the aged oil returns to the dirty oil tank.

[0021] The present invention has the following advantages due to the adoption of the above scheme:

[0022] 1. High efficiency: The aged oil treatment process of the present invention integrates high temperature, demulsifier and electrostatic agglomeration to achieve efficient demulsification. With the support of heat, electricity and medicine, the gravity sedimentation time required for demulsification of aged oil is greatly reduced. The aged oil demulsification can be completed in 50 minutes of residence time, which greatly reduces the area and weight of the aged oil demulsification facilities. At the same time, the centrifuge is rotated at high speed to achieve three-phase separation of demulsified aged oil, achieving separation indicators of less than 2% water content in the oil phase, less than 3000ppm oil content in the water phase, and less than 3% oil content in the mud and sand, fully realizing oil-water-sand separation and crude oil recovery.

[0023] 2. Automatic: The aged oil treatment process of the present invention controls the flow rate of the centrifuge supply pump and the opening of the aged oil regulating valve by the liquid level of the stirring and modulation tank, and automatically adjusts the aged oil flow supplied to the centrifuge and the aged oil flow of the supply process; this process links the centrifuge operation process and the bypass process through a water content tester to achieve automatic control and operation of the treatment process. Normal operation does not require human participation, which greatly reduces the workload of offshore operation and maintenance.

[0024] 3. Compactness: The aging oil treatment process of the present invention adopts an integral skid-mounted structure with a compact double-layer layout, which not only reduces the floor area of the system but also meets the net positive suction head (NPSH) requirements of the centrifuge feed pump. The footprint of the 10 t / h scale is only 53 m 2 (6.6 m × 8 m), and the dry weight is only 30 t, meeting the requirements of configuring aging oil treatment facilities in the limited space of offshore FPSOs. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the unmanned compact aging oil treatment process of this application.

[0026] Each mark in the figure is as follows:

[0027] 1. Aging oil flowmeter; 2. Aging oil regulating valve; 3. Aging oil heater; 4. Compact electrostatic coalescer; 5. Stirring and conditioning tank; 6-1, 6-2 Stirrers; 7. Liquid level gauge; 8. Centrifuge feed pump; 9-1 Water cut tester; 9-2 Centrifugation process switch valve; 9-3 Bypass process switch valve; 10. Centrifuge; 11. Demulsifier storage tank; 12. Demulsifier injection pump. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The present application will be described in detail below with reference to the drawings and embodiments.

[0029] Embodiment 1

[0030] As Figure 1 shown, the present application provides an unmanned compact aging oil treatment process suitable for offshore oilfield production, in which the aging oil demulsification unit, centrifugal separation unit, and demulsifier injection unit are connected in series in sequence.

[0031] In the above example, after the aging oil is mixed with the demulsifier, it is metered by the aging oil flowmeter (1), the flow rate is regulated by the aging oil regulating valve (2), heated by the aging oil heater (3), coalesced by the compact electrostatic coalescer (4) for the emulsion, and then enters the stirring and conditioning tank (5). In the stirring and conditioning tank (5), the aging oil and the demulsifier are stirred and mixed evenly by the stirrer (6) to promote demulsification. The demulsified aging oil is pressurized and transported to the centrifuge (10) by the centrifuge feed pump (8). After high-speed rotation, the three-phase separation of oil, water, and sand is achieved. The separated crude oil enters the crude oil treatment system, the separated sewage enters the sewage tank, and the separated sludge enters the sludge tank.

[0032] In the above example, the liquid level gauge (7) of the stirring and conditioning tank (5) automatically adjusts the rotation speed of the centrifuge feed pump (8) and the opening degree of the aging oil regulating valve (2) to keep the liquid level of the stirring and conditioning tank (5) stable.

[0033] In the above example, the demulsifier storage tank (11) stores the demulsifier, and the demulsifier is injected into the aged oil demulsification unit through the demulsifier injection pump (12). The aged oil flowmeter (1) automatically controls the rotation speed of the demulsifier injection pump (12) to regulate the demulsifier injection amount, ensuring the demulsification effect of the aged oil.

[0034] Example 2

[0035] The aged oil enters the aged oil demulsification unit after being pressurized by the dirty oil tank pump, is metered by the aged oil flowmeter (1), and then mixed with the demulsifier from the chemical agent injection unit. The liquid level signal of the stirring and modulation tank level gauge (7) controls the flow rate of the aged oil entering the process through the aged oil regulating valve (2). The aged oil is heated to 90 °C by the aged oil heater (3) and then enters the compact electrostatic coalescer (4). Under the action of the electric field, the emulsion coalesces and the strength of the oil-water interface is weakened. Subsequently, the aged oil enters the stirring and modulation tank (5) and is stirred by the stirrer (6) for 50 minutes to promote the full mixing of the demulsifier and the aged oil, further destroying the oil-water interface and realizing the demulsification of the aged oil. The level gauge (7) of the stirring and modulation tank (5) controls the rotation speed of the centrifuge supply pump (7) and the opening degree of the aged oil regulating valve (1) in a split range to automatically maintain the liquid level stability of the stirring and modulation tank (5).

[0036] After the aged oil is fully demulsified, it enters the centrifuge supply pump (8) to increase the pressure. A water content tester (9-1) is set after the pump to monitor the water content of the aged oil. The water content tester (9-1) is associated with the centrifugation process switch valve (9-2) and the bypass process switch valve (9-3). When the water content of the aged oil is less than 60%, the centrifugation process switch valve (9-2) is in the open state and the bypass process switch valve (9-3) is in the closed state, and the aged oil enters the centrifuge (10) for dehydration and desanding; when the oil content of the aged oil is greater than 60%, it exceeds the effective working range of the centrifuge (10), the centrifugation process switch valve (9-2) is closed and the bypass process switch valve (9-3) is opened, and the aged oil returns to the dirty oil tank. The aged oil entering the centrifuge (10) operates at a speed of 3000 rpm for 60 s. High-speed rotation realizes crude oil dehydration, sewage deoiling, and mud and sand deoiling. The crude oil with 2% water content at the oil phase outlet and the sewage with 3000 ppm oil content at the water phase outlet enter the crude oil and sewage treatment systems for further treatment respectively. The oil content of the oil-containing mud and sand at the sand outlet is less than 3%, and it is stored in the sludge tank and transported out at an appropriate time.

[0037] The chemical agent injection unit is equipped with a demulsifier storage tank (10) and a demulsifier injection pump (11). The demulsifier injection pump (11) adjusts the frequency and demulsifier injection amount according to the aged oil flowmeter (12) to meet the requirements of aged oil demulsification.

[0038] In the above Example 2, the aged oil demulsification can be completed in 50 minutes of residence time, greatly reducing the area and weight of the aged oil demulsification facilities; the land occupation for a scale of 10 t / h is only 53 m 2(6.6m × 8m), with a dry weight of only 30t, meeting the requirements of the aging oil treatment facility for the limited space configuration of offshore FPSO.

[0039] The same amount of aging oil in the above-mentioned Embodiment 2 is demulsified by a conventional method. The demulsification by gravity sedimentation takes at least 12 hours, and the area of the aging oil demulsification facility required is 99m 2 , with a dry weight of about 78t.

[0040] From the comparison of the above experimental data, it can be seen that the present invention can significantly reduce the gravity sedimentation time required for aging oil demulsification, and greatly reduce the area and weight of the aging oil demulsification facility.

[0041] The present invention is only illustrated by the above-mentioned embodiments, and the structures, installation positions and connections of each component can be changed. Based on the technical solution of this invention patent, any improvement or equivalent transformation made to individual components according to the principle of the invention patent should not be excluded from the protection scope of this invention patent.

Claims

1. An unmanned compact aged oil treatment system adapted to offshore oilfield production, comprising an aged oil demulsification unit, a centrifugal separation unit, and a chemical injection unit; The aged oil demulsification unit includes an aged oil flowmeter, an aged oil regulating valve, an aged oil heater, a compact electrostatic coalescer, and a stirring and modulation tank that are sequentially connected through pipelines from a dirty oil tank for supplying aged oil. The aged oil demulsification unit is used for efficient demulsification of aged oil; The centrifugal separation unit includes a centrifuge feed pump and a centrifuge that are sequentially connected through a pipeline. The inlet of the centrifuge feed pump is connected to the outlet of the stirring and modulation tank. The centrifugal separation unit is used to achieve centrifugal separation of oil, water, and sand in the demulsified aged oil to meet the three-phase separation index; The chemical injection unit includes a demulsifier storage tank and a demulsifier injection pump connected through a pipeline, and is used to inject a demulsifier into the aged oil demulsification unit to ensure the demulsification effect of aged oil.

2. The system according to claim 1, wherein The centrifugal separation unit further includes a water content tester and a centrifugal process switch valve; Both the water content tester and the centrifugal process switch valve are arranged on the connecting pipeline between the centrifuge feed pump and the centrifuge; The water content tester is connected to the centrifugal process switch valve to automatically control the operation of the centrifuge.

3. The system according to claim 2, wherein The centrifugal separation unit further includes a bypass process switch valve; The pipeline where the bypass process switch valve is arranged is connected to the pipeline between the water content tester and the centrifugal process switch valve; the outlet of the pipeline where the bypass process switch valve is arranged is connected to the dirty oil tank; when the water content tester measures that the water content of the aged oil is less than 60%, the centrifugal process switch valve is in the open state and the bypass process switch valve is in the closed state, and the aged oil enters the centrifuge for dehydration and desanding; when the water content tester measures that the water content of the aged oil is greater than 60%, exceeding the effective working range of the centrifuge, the centrifugal process switch valve is closed and the bypass process switch valve is opened, and the aged oil returns to the dirty oil tank.

4. The system according to claim 1, wherein The aged oil demulsification unit further includes a liquid level gauge, and the liquid level gauge is arranged in the stirring and modulation tank; The liquid level gauge measures the liquid level signal in the stirring and modulation tank to control the rotation speed of the centrifuge feed pump and the opening degree of the aged oil regulating valve, control the flow rate of the aged oil entering the process, and automatically maintain the liquid level stability of the stirring and modulation tank.

5. The system according to claim 1, characterized in that, The pipeline between the aged oil flowmeter and the aged oil regulating valve in the aged oil demulsification unit is connected to the demulsifier injection pump, and is used to inject the demulsifier stored in the demulsifier storage tank into the aged oil demulsification unit through the demulsifier injection pump. The aged oil flowmeter automatically controls the rotation speed of the demulsifier injection pump to regulate the demulsifier injection amount to ensure the demulsification effect of aged oil.

6. An unmanned compact aged oil treatment method adapted to offshore oilfield production using the system according to any one of claims 1-5, comprising the following steps: The aged oil in the dirty oil tank is input through the aging oil flowmeter and mixed with the demulsifier from the demulsifier storage tank input by the demulsifier injection pump. Then, the flow rate is regulated by the aging oil regulating valve, heated by the aging oil heater, coalesced by the compact electrostatic coalescer, and then enters the stirring and conditioning tank. In the stirring and conditioning tank, the aged oil and the demulsifier are stirred and mixed evenly by the stirrer to promote demulsification. The demulsified aged oil is pressurized and transported to the centrifuge by the centrifuge feed pump. After high-speed rotation, the three-phase separation of oil, water, and sand is achieved. The separated crude oil enters the crude oil treatment system, the separated sewage enters the sewage tank, and the separated sludge enters the sludge tank.

7. The method according to claim 6, characterized in that The liquid level signal in the stirring and conditioning tank is measured by the liquid level gauge to control the rotation speed of the centrifuge feed pump and the opening degree of the aging oil regulating valve, control the flow rate of the aging oil entering the process, and automatically maintain the liquid level stability of the stirring and conditioning tank.

8. The method according to claim 6 or 7, characterized in that When the moisture content tester measures that the moisture content of the aged oil is less than 60%, the centrifugal process switch valve is in the open state and the bypass process switch valve is in the closed state, and the aged oil enters the centrifuge for dehydration and desanding; when the moisture content tester measures that the moisture content of the aged oil is greater than 60%, exceeding the effective working range of the centrifuge, the centrifugal process switch valve is closed and the bypass process switch valve is opened, and the aged oil returns to the dirty oil tank.

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