Treatment device system and treatment method for drilling flowback fluid of offshore oil and gas drilling platform

Abstract

The invention relates to a treatment device system and a treatment method for drilling flowback fluid of an offshore oil and gas drilling platform. The treatment device system comprises a pretreatment reaction pry, a vibrating screen rock debris separation pry, a solid-liquid centrifugal separation pry and an oil-water-solid three-phase separation pry which are sequentially connected in the flowing direction of feed liquid. The adjacent prying parts are in material connection through a pipeline and a control valve and are in position connection through a detachable connecting device; the vibrating screen rock debris separation pry is provided with a communicating pipeline in parallel, an inlet of the communicating pipeline is connected with an outlet of the pretreatment reaction pry, and an outlet of the communicating pipeline is connected with an inlet of the solid-liquid centrifugal separation pry. According to the device system provided by the invention, continuous treatment and up-to-standard discharge of the well drilling flowback waste liquid can be realized, the operation efficiency of a wellhead of an offshore platform is improved, and the treatment requirements of different liquid qualities are met.

Description

Technical Field

[0001] The present invention relates to the technical field of drilling fluid return treatment, and particularly to a treatment device system and a treatment method for drilling fluid return of an offshore oil and gas drilling platform. Background Art

[0002] In recent years, with the development of oil and gas exploration and development, the number of multi-branch wells, horizontal wells and complex geological drilling has been increasing day by day, and the problem of wellbore stability has become more and more prominent. Oil-based mud drilling fluid has been widely used and developed due to its strong stability and lubrication ability, etc., but this has also led to an increasing amount of waste oil-based mud drilling waste liquid. At present, a considerable amount of waste oil-based mud drilling waste liquid is directly disposed of by landfill, reinjection into the formation or centralized incineration on land without treatment, which not only wastes a large amount of mineral oil resources, but also causes pollution of soil, surface and groundwater, and directly or indirectly causes great harm to the environment and human health. Therefore, it is necessary to carry out harmless or resource-based treatment on such waste oil-based mud drilling waste liquid.

[0003] In the completion and workover fluid return operation of an offshore platform, the completion and workover fluid return waste liquid from different wellheads has the characteristics of large difference in liquid volume, variable return operation time, complex return fluid composition, etc. A large amount of emulsifiers, stabilizers and other various additives are added to the oil-based mud drilling fluid, resulting in its complex chemical composition and stable properties, and it is extremely difficult to separate oil and water. In addition, the space on the offshore platform is narrow, and the on-site drilling and completion operations are restricted by the site, and it is impossible to store and centrally treat the drilling and completion fluid return waste liquid for a long time. At present, most of the existing processes use traditional oil-water separators, etc. for treatment, and the treated sewage cannot reach the discharge standard, and the treated sewage needs to be transported by ship to land for centralized treatment, resulting in low efficiency of the platform drilling and completion operations and high production operation costs.

[0004] At the same time, the existing oil-based mud drilling waste liquid treatment technology has poor adaptability to the water quality of the return waste liquid from different wellheads, and it is difficult for the treated waste liquid to meet the requirements of environmental protection and discharge standards, and the treatment efficiency is also difficult to meet the production progress requirements of the offshore platform, seriously affecting the operation efficiency. Most of the existing equipment is relatively traditional, and it is difficult to meet the treatment requirements of different liquid qualities. The treatment effect is not good and the equipment is complex, which is not conducive to the treatment of the actual return waste liquid on the offshore platform.

[0005] Therefore, providing a treatment device system and a treatment method for drilling fluid return of an offshore oil and gas drilling platform is a technical problem that needs to be solved in the current field. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a treatment device system and a treatment method for the drilling return fluid of an offshore oil and gas drilling platform. Compared with the existing technology, the device system provided by the present invention can realize the continuous treatment and up-to-standard discharge of the drilling return waste liquid, improve the operation efficiency of the wellhead on the offshore platform, and meet the treatment requirements for different liquid qualities.

[0007] To achieve the purpose of this invention, the following technical solutions are adopted:

[0008] In the first aspect, the present invention provides a treatment device system for the drilling return fluid of an offshore oil and gas drilling platform. The treatment device system includes a pretreatment reaction skid, a vibrating screen cuttings separation skid, a solid-liquid centrifugal separation skid, and an oil-water-solid three-phase separation skid, which are connected in sequence along the direction of the liquid flow.

[0009] The adjacent skids are connected by pipelines and control valves for material connection, and are connected in position by a detachable connection device.

[0010] The vibrating screen cuttings separation skid is arranged in parallel with a conducting pipeline. The inlet of the conducting pipeline is connected to the outlet of the pretreatment reaction skid, and the outlet of the conducting pipeline is connected to the inlet of the solid-liquid centrifugal separation skid.

[0011] In the present invention, by setting the pretreatment reaction skid, the vibrating screen cuttings separation skid, the solid-liquid centrifugal separation skid, and the oil-water-solid three-phase separation skid, it can meet the treatment of different liquid qualities. The material connection is carried out through pipelines and control valves, which improves the separation effect of the three phases of process oil, water, and solids, ensures that the water quality index is qualified, and the purified oil phase can be directly input into the offshore production process without blocking the production process channel due to solid phase problems. In the present invention, when the particle size of the solid phase particles in the return waste liquid is < 5 mm and the content is small, the vibrating screen cuttings separation skid can be selectively deactivated through the conducting pipeline. Whether the conducting pipeline is enabled can be controlled by a control valve, and only the combination of the pretreatment reaction skid, the solid-liquid centrifugal separation skid, and the oil-water-solid three-phase separation skid is used to complete the operation task, thereby meeting the treatment of different liquid qualities and improving the flexibility of waste liquid treatment. In the present invention, there are no special limitations on the pipelines used for material connection, and conventional settings in the art can be adopted, such as connecting by high-pressure rubber hoses for pumping.

[0012] In the present invention, each skid is small in volume and light in weight, which is convenient for transportation and hoisting. Each skid adopts an independent control system, and the skids are combined in position by a detachable connection device. It can be used in combination according to the water quality of the waste liquid, and the positions of the skids can be flexibly configured. How to assemble the skids can be selected according to the treatment space, so as to meet the requirements of the narrow space and load on the offshore, and control the equipment size within the minimum range, thereby efficiently realizing the separation and treatment of oil-based drilling return fluid.

[0013] In the present invention, there is no special limitation on the positional connection manner of the pretreatment reaction skid, the vibrating screen cuttings separation skid, the solid-liquid centrifugal separation skid, and the oil-water-solid three-phase separation skid. For example, they can be arranged horizontally in sequence through a connecting device or stacked longitudinally according to the site conditions. The present invention can flexibly configure the positions of each skid through the connecting device, so as to cope with different external environments and spaces.

[0014] Preferably, the detachable connecting device includes a positioning plug and a positioning groove for accommodating the positioning plug.

[0015] Preferably, the pretreatment reaction skid includes a pretreatment reaction device and a chemical dosing device, and the chemical dosing device is arranged at the top inlet of the pretreatment reaction device.

[0016] Preferably, the number of the pretreatment reaction devices is at least 2, for example, it can be 2, 3, or 4, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable. The pretreatment reaction devices are arranged in parallel, and the outlet of each pretreatment reaction device is connected to the outlet main pipe through a multi-way control valve.

[0017] Preferably, a temperature adjustment mechanism is arranged inside the pretreatment reaction device.

[0018] In the present invention, the manner of arranging the temperature adjustment mechanism inside the pretreatment reaction device can adopt the conventional manner in the art, and the temperature adjustment mechanism can adopt the conventional temperature adjustment mechanism in the art, such as an electric heating mechanism, a steam heating mechanism, or a heat transfer oil heating mechanism, etc.

[0019] Preferably, the chemical dosing device includes an outer casing, and the outer casing includes a cylindrical structure and an upper end face and a lower end face arranged at both ends of the cylindrical structure.

[0020] Preferably, the cylindrical structure includes an upper section, a middle section, and a lower section which are communicated with each other in sequence from top to bottom. Both the upper section and the lower section are columnar structures, and the diameters at both ends of the middle section are larger than the middle diameter, and the longitudinal section is a funnel shape with central symmetry.

[0021] Preferably, an air supply pipe and a chemical dosing pipe are concentrically arranged inside the outer casing from outside to inside in sequence, and both the air supply pipe and the chemical dosing pipe pass through the upper end face.

[0022] In the present invention, the inlet of the chemical dosing pipe is generally connected to an external chemical supply device, and the inlet of the air supply pipe is generally connected to an external air supply device. The connection manner can adopt the common sealing and rotating connection manners in the art.

[0023] Preferably, a first blocking wall is provided at the bottom of the gap formed by the air supply pipe and the chemical addition pipe. The first blocking wall, the inner side wall of the air supply pipe, and the outer side wall of the chemical addition pipe together form an air supply gap. The gas inlet of the air supply gap faces upward, and a first air supply hole is provided on the side wall of the air supply pipe.

[0024] Preferably, a second blocking wall is provided at the bottom of the gap formed by the inner side wall of the upper section, the outer side wall of the air supply pipe, and the upper end face. The second blocking wall, the outer side wall of the air supply pipe, the inner side wall of the upper section, and the upper end face together form an air supply chamber, and a second air supply hole is provided in the second blocking wall.

[0025] Preferably, the bottom outlet of the chemical addition pipe is located at the position with the smallest diameter in the middle section.

[0026] Preferably, aeration holes are provided on the middle section, the lower section, and the lower end face.

[0027] Preferably, the sum of the number of aeration holes on the lower section and the lower end face > the number of aeration holes on the middle section.

[0028] In the present invention, by specifically designing the structure of the outer sleeve, while being able to utilize the relatively large space in the upper section to arrange the chemical addition pipe and the air supply pipe, the space for the air supply chamber is reserved, improving the air supply storage capacity and the aeration effect; the outlet of the chemical addition pipe is arranged at the position with the smallest diameter in the middle of the middle section, so that the chemical agent at the bottom opening of the chemical addition pipe is directly at the optimal aeration pressure position, thereby improving the ability of the gas to jet and disperse the chemical agent, improving the chemical addition uniformity and the reaction effect, narrowing the local air flow channel, and increasing the aeration speed; the sum of the number of aeration holes on the lower part and the lower end face > the number of aeration holes on the middle section, which can avoid the accumulation of the chemical agent at the bottom. Increasing the number of aeration holes can accelerate the injection of the chemical agent at the bottom and improve the chemical addition speed.

[0029] Preferably, the chemical addition device further includes a driving mechanism and stirring blades. The driving mechanism is arranged on the upper end face of the outer sleeve. The power output end of the driving mechanism drives the outer sleeve to rotate, and stirring blades are arranged circumferentially on the middle section and the lower section of the outer sleeve.

[0030] In the present invention, the chemical addition device is an integrated structure of chemical addition and stirring, which can reduce the complexity of the pretreatment reaction device, avoid having too many components outside the pretreatment reaction device, affecting the equipment layout, and reducing the risk of liquid leakage caused by the complexity of the device. During the chemical addition process, chemical addition is carried out through the centrally arranged chemical addition pipe. The upper opening of the air supply pipe sleeved outside the chemical addition pipe is introduced with gas. The gas sequentially passes through the air supply gap, the first air supply hole, the air supply chamber, the second air supply hole, and the aeration hole and enters the device interior. The chemical agent is jetted into the pretreatment reaction device through gas aeration and is combined with the stirring of the stirring blades to further improve the chemical addition uniformity and the reaction efficiency.

[0031] In the present invention, the driving mechanism can adopt any conventional structure or device for driving in the art. For example, the driving mechanism includes a motor and a gear. The motor drives the gear to rotate, and the power output end of the gear drives the outer sleeve to rotate, further driving the stirring blade to rotate to achieve stirring.

[0032] Preferably, the vibrating screen cuttings separation skid includes a vibrating screening device, a sludge tank, a buffer water tank, and a lift pump. The solid phase outlet of the vibrating screening device is connected to the sludge tank, the liquid phase outlet of the vibrating screening device is connected to the buffer water tank, and the outlet of the buffer water tank is connected to the solid-liquid centrifugal separation skid through the lift pump.

[0033] Preferably, the solid-liquid centrifugal separation skid includes a centrifugal device, a sludge tank, a collection water tank, and a lift pump. The solid phase outlet of the centrifugal device is connected to the sludge tank, the liquid phase outlet of the centrifugal device is connected to the collection water tank, and the outlet of the collection water tank is connected to the oil-water-solid three-phase separation skid through the lift pump.

[0034] Preferably, the centrifugal device in the solid-liquid centrifugal separation skid includes a high-efficiency horizontal scroll centrifuge.

[0035] Preferably, the oil-water-solid three-phase separation skid includes a centrifugal device, a platform separation device, a production water tank, and a white oil tank. The solid phase outlet of the centrifugal device is connected to the platform separation device, the water phase outlet of the centrifugal device is connected to the production water tank, and the oil phase outlet of the centrifugal device is connected to the white oil tank.

[0036] Preferably, the centrifugal device in the oil-water-solid three-phase separation skid includes a high-speed disc centrifuge.

[0037] Preferably, the treatment device system further includes a platform mud pit, and the outlet of the platform mud pit is connected to the pretreatment reaction skid.

[0038] Preferably, an analysis and detection device is arranged in the platform mud pit.

[0039] In the present invention, by adopting a high-speed disc centrifuge, the solid matter in the liquid phase can be effectively separated, and the separated oil phase meets the recovery standard. The high-speed disc centrifuge is generally equipped with a spare drum and a flushing water tank. The flushing water tank is used to supply water to the high-speed disc centrifuge. When the centrifuge fails, the spare drum can be directly activated to achieve the rapid installation and commissioning of the drum.

[0040] In a second aspect, the present invention provides a method for treating drilling return fluid of an offshore oil and gas drilling platform. The treatment method adopts the treatment device system for drilling return fluid of an offshore oil and gas drilling platform as described in the first aspect of the present invention;

[0041] The method includes the following steps:

[0042] The drilling return fluid is added with a chemical agent for mixing reaction to obtain a pretreated liquid; then the pretreated liquid is separated to obtain produced water, an oil phase, and residues.

[0043] In the treatment method provided by the present invention, a chemical agent is added according to the liquid quality of the drilling return fluid for mixing reaction, and then separation is carried out, which can realize the treatment of different liquid qualities and meet the requirements of up-to-standard discharge, that is, the obtained produced water meets the qualified standard for discharge, the obtained oil phase meets the recovery standard, and the obtained solid residues are sent to the platform separation device for further treatment.

[0044] Preferably, the treatment method includes the following steps:

[0045] (1) The drilling return fluid in the platform mud pit is detected by an analysis and detection device to obtain return fluid parameters, including the particle size of solid particles in the drilling return waste fluid;

[0046] (2) The drilling return fluid in the platform mud pit in step (1) is transported to a pretreatment reaction device. According to the return fluid parameters obtained in step (1), the types and concentrations of the added chemical agents are set. The chemical agents are added to the pretreatment reaction device through a chemical agent adding device and mixed with the return waste fluid for reaction. While the chemical agent adding device is adding the chemical agent, stirring and aeration are carried out to obtain a pretreated liquid;

[0047] (3) If the particle size of solid particles in the drilling return waste fluid < 5 mm, the pretreated liquid obtained in step (2) is sent into a high-efficiency horizontal scroll centrifuge through a conduction pipeline for solid-liquid separation. The obtained solid particles are sent into a sludge tank, and the obtained liquid phase is sent into a collection water tank; the liquid phase in the collection water tank is sent into a high-speed disc centrifuge through a lift pump for oil-water-solid three-phase separation. The separated produced water is sent into a produced water tank, the obtained oil phase is sent into a white oil tank, and the obtained residues are sent to the platform separation device;

[0048] If the particle size of solid particles in the drilling return waste fluid ≥ 5 mm, the pretreated liquid obtained in step (2) is sent into a vibrating screening device for screening. The screened cuttings particles are collected in a sludge tank, and the obtained liquid phase is sent into a buffer water tank. The liquid phase in the buffer water tank is sent into a high-efficiency horizontal scroll centrifuge through a lift pump for solid-liquid separation. The obtained solid particles are sent into a sludge tank, and the obtained liquid phase is sent into a collection water tank; the liquid phase in the collection water tank is sent into a high-speed disc centrifuge through a lift pump for oil-water-solid three-phase separation. The separated produced water is sent into a produced water tank, the obtained oil phase is sent into a white oil tank, and the obtained residues are sent to the platform separation device.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] (1) The treatment device system provided by the present invention has compatibility with water quality and quantity and strong shock resistance. By adding special agents, effective separation of oil, water, and solids in the waste liquid can be achieved. Using a three-stage separation process such as a vibrating screen cuttings separation skid, a solid-liquid centrifugal separation skid, and an oil-water-solid three-phase separation skid, it can process according to the size of solid particles from large to small, and has strong applicability to solid particles of different particle sizes and concentrations. After the oil phase is purified, it can be directly input into the offshore production process without blocking the production process channel due to solid phase problems.

[0051] (2) In the treatment device system provided by the present invention, the volume of each skid is small and the weight is light, which is convenient for transportation and hoisting. Each skid adopts an independent control system, and a detachable connection device is used to combine the positions of each skid. It can be used in combination according to the water quality of the waste liquid, and the positions of each skid can be flexibly configured. How to assemble each skid can be selected according to the treatment space, so as to cope with the narrow space placement at sea, and thus efficiently realize the separation and treatment of oil-based drilling return fluid.

[0052] (3) The treatment device system provided by the present invention is also applicable to the treatment of oil-containing waste liquid returned from the wellhead of onshore oil and gas fields. Adopting a skid-mounted method, it can be applied to the sewage treatment at the wellhead under various different geographical environments and road conditions, and has the advantages of flexible movement, transportation, and on-site installation. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 is a schematic diagram of the position structure of the treatment device system provided in a specific embodiment of the present invention based on a horizontal arrangement;

[0054] Figure 2 is a schematic diagram of the position structure of the treatment device system provided in a specific embodiment of the present invention based on a vertical stacking arrangement;

[0055] Figure 3 is a schematic diagram of the structure of the treatment device system provided in Embodiment 1 of the present invention based on the material flow direction;

[0056] Figure 4 is a schematic diagram of the structure of the chemical addition device provided in Embodiment 1 of the present invention;

[0057] In the figure, 101 - pretreatment reaction skid; 201 - vibrating screen cuttings separation skid; 301 - solid-liquid centrifugal separation skid; 401 - oil-water-solid three-phase separation skid; 501 - conduction pipeline; 601 - control valve; 701 - connection pipeline; 801 - positioning groove; 901 - positioning plug; 110 - support and fixing structure; 210 - roller.

[0058] 1 - Platform mud pit; 2 - Analysis and detection device; 3 - Chemical supply device; 4 - Chemical dosing device; 5 - Multi-way control valve; 6 - Check valve; 7 - Vibration screening device; 8 - Sludge tank; 9 - Buffer water tank; 10 - Lift pump; 11 - High-efficiency horizontal scroll centrifuge; 12 - Collection water tank; 13 - High-speed disc centrifuge; 14 - Platform separation device; 15 - Product water tank; 16 - White oil tank; 17 - Pretreatment reaction device;

[0059] 411 - Upper section; 412 - Middle section; 413 - Lower section; 414 - Upper end face; 415 - Lower end face; 41 - Chemical dosing pipe; 42 - Gas supply pipe; 43 - First gas supply hole; 44 - Second gas supply hole; 45 - Aeration hole; 46 - Stirring blade; 47 - Driving mechanism; 48 - First blocking wall; 49 - Second blocking wall. Detailed implementation manner

[0060] It should be understood that in the description of the present invention, the orientation or positional relationships indicated by the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise stated, the meaning of "a plurality" is two or more.

[0061] It should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "set", "connected", "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific situations.

[0062] The technical solution of the present invention will be further described below with reference to the drawings and through specific implementation manners.

[0063] In a specific implementation manner, the present invention provides a treatment device system for the drilling return fluid of an offshore oil and gas drilling platform, as Figure 1 and Figure 2As shown, the processing device system includes a pretreatment reaction skid 101, a vibrating screen cuttings separation skid 201, a solid-liquid centrifugal separation skid 301, and an oil-water-solid three-phase separation skid 401 connected in sequence along the flow direction of the liquid material; the adjacent skids are connected for materials through pipelines and control valves 601, and are connected in position through a detachable connection device; the vibrating screen cuttings separation skid 201 is provided with a parallel conduction pipeline 501, the inlet of the conduction pipeline 501 is connected to the outlet of the pretreatment reaction skid 101, and the outlet of the conduction pipeline 501 is connected to the inlet of the solid-liquid centrifugal separation skid 301.

[0064] In the present invention, by setting the pretreatment reaction skid 101, the vibrating screen cuttings separation skid 201, the solid-liquid centrifugal separation skid 301, and the oil-water-solid three-phase separation skid 401, it is possible to meet the treatment of different liquid qualities. The materials are connected through pipelines and control valves 601 to improve the separation effect of the process oil, water, and solid phases, ensure that the water quality index of the effluent is qualified, and the purified oil phase can be directly input into the offshore production process without blocking the production process channel due to solid phase problems. In the present invention, when the particle size of the solid-phase particles in the backflow waste liquid is <5 mm and the content is small, the vibrating screen cuttings separation skid 201 can be selectively deactivated through the conduction pipeline 501, and only the combination of the pretreatment reaction skid 101, the solid-liquid centrifugal separation skid 301, and the oil-water-solid three-phase separation skid 401 is used to complete the operation task, thereby meeting the treatment of different liquid qualities and improving the flexibility of waste liquid treatment. In the present invention, there is no special limitation on the pipeline for material connection, and the conventional settings in the art can be adopted, such as connecting by high-pressure rubber hoses for pumping.

[0065] In the present invention, each skid is small in volume and light in weight, which is convenient for transportation and hoisting. Each skid adopts an independent control system, and a detachable and separable connection device is used to combine the positions of the skids. It can be used in combination according to the water quality of the waste liquid, the positions of the skids can be flexibly configured, and how to assemble the skids can be selected according to the treatment space, so as to meet the requirements of narrow offshore spaces and loads, control the equipment size within the minimum range, and thus efficiently realize the separation and treatment of oil-based drilling waste liquid.

[0066] In some embodiments, the detachable connection device includes a positioning plug 901 and a positioning slot 801 for accommodating the positioning plug 901.

[0067] In some embodiments, such as Figure 1As shown, the pretreatment reaction skid 101, the vibrating screen cuttings separation skid 201, the solid-liquid centrifugal separation skid 301, and the oil-water-solid three-phase separation skid 401 are arranged horizontally in sequence. Each skid is connected by a detachable connection device, namely a positioning plug 901 and a positioning groove 801 for accommodating the positioning plug 901. The vibrating screen cuttings separation skid 201 is provided with a parallel conduction pipeline 501. The inlet of the conduction pipeline 501 is connected to the outlet of the pretreatment reaction skid 101, and the outlet of the conduction pipeline 501 is connected to the inlet of the solid-liquid centrifugal separation skid 301. As Figure 2 shown, each skid is arranged longitudinally in a stacked manner. Among them, the pretreatment reaction skid 101 and the vibrating screen cuttings separation skid 201 are longitudinally stacked from top to bottom, and the solid-liquid centrifugal separation skid 301 and the oil-water-solid three-phase separation skid 401 are longitudinally stacked from top to bottom, and are connected by the positioning plug 901 and the positioning groove 801 in the connection device. The outlet of the pretreatment reaction skid 101 is connected to the inlet of the solid-liquid centrifugal separation skid 301 through the conduction pipeline 501. Whether the conduction pipeline 501 is enabled is controlled by a control valve ( Figure 2 not shown in the figure). The outlet of the vibrating screen cuttings separation skid 201 is connected to the inlet of the solid-liquid centrifugal separation skid 301 through a connecting pipeline 701. Each skid can be provided with multiple connection devices on the upper and lower surfaces or the sides as needed to meet the requirements of horizontal arrangement or longitudinal stacked arrangement.

[0068] In the present invention, a support and fixation structure 110 can be selectively provided at the bottom of each skid. The support and fixation structure 110 is provided with rollers 210, which is convenient for the movement, fixation and assembly of each skid. The overall device system can also be directly arranged on an offshore floating platform, having strong adaptability.

[0069] In some embodiments, as Figure 3 shown, the pretreatment reaction skid includes a pretreatment reaction device 17 and a chemical dosing device 4. The chemical dosing device 4 is arranged at the top inlet of the pretreatment reaction device 17.

[0070] In some embodiments, the number of the pretreatment reaction devices 17 is at least 2, for example, it can be 2, 3, or 4, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable. The pretreatment reaction devices 17 are arranged in parallel, and the outlet of each pretreatment reaction device 17 is connected to an outlet main pipe through a multi-way control valve 5.

[0071] In the present invention, a plurality of pretreatment reaction devices 17 can be provided, and the number of pretreatment reaction devices 17 passed through can be selected according to the amount of liquid to be treated and parameters, so as to avoid the situation of waiting for treatment due to the long treatment time of a single pretreatment reaction device 17. Furthermore, the waste liquid can be continuously treated without stopping the machine, thereby improving the waste liquid treatment efficiency and treatment capacity. In addition, according to the parameter changes of the waste liquid, the multi-way control valve 5 can be used to control the waste liquid to flow into different pretreatment reaction devices 17, and corresponding concentration or type of medicament can be selected to be added. Furthermore, the waste liquid can be continuously treated according to the parameter changes of the waste liquid without stopping the machine, so as to meet the waste liquid treatment effect and accuracy. In addition, a one-way valve 6 is also provided between the multi-way control valve 5 and the pretreatment reaction device 17 to control the flow direction of the waste liquid.

[0072] In some embodiments, a temperature adjustment mechanism is provided inside the pretreatment reaction device 17.

[0073] In the present invention, the temperature adjustment mechanism in the pretreatment reaction device 17 can be set in a conventional manner in the art. The temperature adjustment mechanism can adopt a conventional temperature adjustment mechanism in the art, such as an electric heating mechanism, a steam heating mechanism or a heat transfer oil heating mechanism, etc. Stirring and mixing are carried out simultaneously in the pretreatment reaction device 17 to make the liquid heated evenly. The temperature is generally controlled at 40-60°C. The temperature adjustment mechanism can adopt an automatic temperature control system to reduce manual operation and avoid the volatilization of combustible gases and toxic gases caused by too high temperature, thus causing environmental and human body harm.

[0074] In some embodiments, as Figure 4 shown, the chemical addition device 4 includes an outer casing, and the outer casing includes a cylindrical structure and an upper end face 414 and a lower end face 415 provided at both ends of the cylindrical structure.

[0075] In some embodiments, the cylindrical structure includes an upper section 411, a middle section 412 and a lower section 413 which are sequentially communicated from top to bottom. Both the upper section 411 and the lower section 413 are columnar structures, and the diameters at both ends of the middle section 412 are larger than the middle diameter and the longitudinal section is a funnel shape with central symmetry.

[0076] In some embodiments, an air supply pipe 42 and a chemical addition pipe 41 are concentrically arranged inside the outer casing from outside to inside in sequence, and both the air supply pipe 42 and the chemical addition pipe 41 pass through the upper end face 414.

[0077] In the present invention, the inlet of the chemical addition pipe 41 is generally connected to the external chemical supply device 3, and the inlet of the gas supply pipe 42 is generally connected to the external gas supply device. The connection method can adopt the commonly used sealing and rotating connection methods in the art. In the present invention, the chemical addition pipe 41 adds chemicals according to the liquid quality of the waste liquid. The chemicals generally include commonly used chemicals in the art such as gel breakers, coagulants, demulsifiers, and flocculants, etc., to improve the subsequent separation effect of oil, water, and solids and ensure that the effluent water quality meets the standards. The demulsifier generally includes two types: liquid and solid. The chemical dosing concentration is generally between 0.5% and 5%, and the specific concentration needs to be set according to the water quality situation.

[0078] In some embodiments, a first blocking wall 48 is provided at the bottom of the gap formed between the gas supply pipe 42 and the chemical addition pipe 41. The first blocking wall 48, the inner side wall of the gas supply pipe 42, and the outer side wall of the chemical addition pipe 41 together form a gas supply gap. The gas inlet of the gas supply gap faces upward, and a first gas supply hole 43 is provided on the side wall of the gas supply pipe 42.

[0079] In some embodiments, a second blocking wall 49 is provided at the bottom of the gap formed between the inner side wall of the upper section 411, the outer side wall of the gas supply pipe 42, and the upper end face 414. The second blocking wall 49, the outer side wall of the gas supply pipe 42, the inner side wall of the upper section 411, and the upper end face 414 together form a gas supply chamber. The second blocking wall 49 is provided with a second gas supply hole 44.

[0080] In some embodiments, the bottom outlet of the chemical addition pipe 41 is located at the position where the diameter of the middle section 412 is the smallest.

[0081] In some embodiments, aeration holes 45 are provided on the middle section 412, the lower section 413, and the lower end face 415.

[0082] In some embodiments, the sum of the number of aeration holes 45 on the lower section 413 and the lower end face 415 > the number of aeration holes 45 on the middle section 412.

[0083] In the present invention, through the specific design of the structure of the outer sleeve, while being able to utilize the relatively large space of the upper section 411 to arrange the chemical addition pipe 41 and the gas supply pipe 42, the space for the gas supply chamber is reserved, improving the gas supply storage capacity and the aeration effect; the outlet of the chemical addition pipe 41 is provided at the position where the middle diameter of the middle section 412 is the smallest, so that the chemicals at the bottom opening of the chemical addition pipe 41 are directly in the optimal aeration pressure position, thereby improving the gas jet dispersion ability of the chemicals, improving the chemical addition uniformity and reaction effect, narrowing the local air flow channel, and increasing the aeration speed; the sum of the number of aeration holes 45 on the lower part and the lower end face 415 > the number of aeration holes 45 on the middle section 412, which can avoid the accumulation of chemicals at the bottom. Increasing the number of aeration holes 45 can accelerate the spraying of chemicals at the bottom and improve the chemical addition speed.

[0084] In some of these embodiments, the chemical dosing device 4 further includes a driving mechanism 47 and stirring blades 46. The driving mechanism 47 is disposed on the upper end face 414 of the outer casing. The power output end of the driving mechanism 47 drives the outer casing to rotate, and the middle section 412 and the lower section 413 of the outer casing are both provided with stirring blades 46 along the circumferential direction.

[0085] In the present invention, the chemical dosing device 4 is an integrated structure of chemical dosing and stirring, which can reduce the complexity of the pretreatment reaction device 17, avoid excessive components outside the pretreatment reaction device 17, affect the equipment layout, and reduce the risk of liquid leakage caused by the complexity of the device. During the chemical dosing process, chemical dosing is carried out through the centrally arranged chemical dosing pipe 41. The upper opening of the gas supply pipe 42 sleeved outside the chemical dosing pipe 41 is introduced with gas. The gas sequentially passes through the gas supply gap, the first gas supply hole 43, the gas supply chamber, the second gas supply hole 44 and the gas diffusion hole 45 and enters the device interior. Through gas aeration, the chemical agent is sprayed into the pretreatment reaction device 17 from the gas diffusion hole 45, and combined with the stirring of the stirring blades 46, the uniformity of chemical dosing and the reaction efficiency are further improved.

[0086] In the present invention, the driving mechanism 47 can adopt any conventional structure or device for driving in the art. For example, the driving mechanism 47 includes a motor and a gear. The motor drives the gear to rotate, and the power output end of the gear drives the outer casing to rotate, further driving the stirring blades 46 to rotate to achieve stirring.

[0087] In some of these embodiments, as Figure 3 shown, the vibrating screen cuttings separation skid includes a vibrating screening device 7, a sludge tank 8, a buffer water tank 9 and a lift pump 10. The solid phase outlet of the vibrating screening device 7 is connected to the sludge tank 8, the liquid phase outlet of the vibrating screening device 7 is connected to the buffer water tank 9, and the outlet of the buffer water tank 9 is connected to the solid-liquid centrifugal separation skid through the lift pump 10.

[0088] In some of these embodiments, as Figure 3 shown, the solid-liquid centrifugal separation skid includes a centrifugal device, a sludge tank 8, a collection water tank 12 and a lift pump 10. The solid phase outlet of the centrifugal device is connected to the sludge tank 8, the liquid phase outlet of the centrifugal device is connected to the collection water tank 12, and the outlet of the collection water tank 12 is connected to the oil-water-solid three-phase separation skid through the lift pump 10.

[0089] In some of these embodiments, the centrifugal device in the solid-liquid centrifugal separation skid includes a high-efficiency horizontal scroll centrifuge 11.

[0090] In some of these embodiments, as Figure 3As shown, the oil-water-solid three-phase separation skid includes a centrifugal device, a platform separation device 14, a production water tank 15, and a white oil tank 16. The solid phase outlet of the centrifugal device is connected to the platform separation device 14, the water phase outlet of the centrifugal device is connected to the production water tank 15, and the oil phase outlet of the centrifugal device is connected to the white oil tank 16.

[0091] In some embodiments, the centrifugal device in the oil-water-solid three-phase separation skid includes a high-speed disc centrifuge 13.

[0092] In the present invention, by using the high-speed disc centrifuge 13, the solids in the liquid phase can be effectively separated, and the separated oil phase can meet the recovery standard. The high-speed disc centrifuge 13 is generally equipped with a spare drum and a flushing water tank. The flushing water tank is used to supply water to the high-speed disc centrifuge 13. When the centrifuge fails, the spare drum can be directly enabled to achieve rapid installation and commissioning of the drum. In addition, continuous processing for 24 hours can be achieved through the spare drum, meeting the production requirements when the maximum liquid discharge volume of the offshore platform wellhead is reached.

[0093] In some embodiments, as Figure 3 shown, the treatment device system further includes a platform mud pit 1, and the outlet of the platform mud pit 1 is connected to the pretreatment reaction skid.

[0094] In some embodiments, an analysis and detection device 2 is provided in the platform mud pit 1.

[0095] In the present invention, in order to facilitate the detection of waste liquid parameters, multiple analysis and detection devices 2 can be selected to be provided on the platform mud pit 1 for detecting the liquid quality parameters of the waste liquid, such as pH, solid particle size, etc., so as to control the types and concentrations of the chemicals added later.

[0096] In another specific embodiment, the present invention provides a method for treating drilling return fluid of an offshore oil and gas drilling platform. The treatment method uses the treatment device system for drilling return fluid of an offshore oil and gas drilling platform provided by a specific embodiment of the present invention;

[0097] The method includes the following steps:

[0098] Adding chemicals to the drilling return fluid for mixing reaction to obtain a pretreated liquid; then separating the pretreated liquid to obtain produced water, an oil phase, and residues.

[0099] In the treatment method provided by the present invention, adding chemicals for mixing reaction according to the liquid quality of the drilling return fluid and then separating can achieve the treatment of different liquid qualities, meet the requirements of up-to-standard discharge, that is, the produced water obtained meets the qualified standard for discharge, the oil phase obtained meets the recovery standard, and the solid phase residues are sent to the platform separation device 14 for further treatment.

[0100] In some of these embodiments, the processing method includes the following steps:

[0101] (1) Detect the drilling return fluid in the platform mud pit 1 through the analysis and detection device 2 to obtain return fluid parameters, including the particle size of solid particles in the drilling return waste liquid;

[0102] (2) Transport the drilling return fluid in the platform mud pit 1 described in step (1) to the pretreatment reaction device 17. Set the types and concentrations of the added chemicals according to the return fluid parameters obtained in step (1). Add the chemicals into the pretreatment reaction device 17 through the chemical addition device 4 and mix and react with the return waste liquid. While the chemical addition device 4 is adding chemicals, stirring and aeration are carried out to obtain the pretreated liquid;

[0103] (3) If the particle size of solid particles in the drilling return waste liquid < 5 mm, send the pretreated liquid obtained in step (2) into the high-efficiency horizontal scroll centrifuge 11 through the conduction pipeline for solid-liquid separation. The obtained solid particles are sent to the sludge tank 8, and the obtained liquid phase is sent to the collection water tank 12; Send the liquid phase in the collection water tank 12 into the high-speed disc centrifuge 13 through the lift pump 10 for oil-water-solid three-phase separation. The separated produced water is sent to the produced water tank 15, the obtained oil phase is sent to the white oil tank 16, and the obtained residue is sent to the platform separation device 14;

[0104] If the particle size of solid particles in the drilling return waste liquid ≥ 5 mm, send the pretreated liquid obtained in step (2) into the vibrating screen device 7 for screening. The screened cuttings particles are collected in the sludge tank 8, and the obtained liquid phase is sent to the buffer water tank 9. The liquid phase in the buffer water tank 9 is sent into the high-efficiency horizontal scroll centrifuge 11 through the lift pump 10 for solid-liquid separation. The obtained solid particles are sent to the sludge tank 8, and the obtained liquid phase is sent to the collection water tank 12; Send the liquid phase in the collection water tank 12 into the high-speed disc centrifuge 13 through the lift pump 10 for oil-water-solid three-phase separation. The separated produced water is sent to the produced water tank 15, the obtained oil phase is sent to the white oil tank 16, and the obtained residue is sent to the platform separation device 14.

[0105] Example 1

[0106] This example provides a treatment device system for drilling return fluid of an offshore oil and gas drilling platform, as Figure 3 shown. The treatment device system includes a pretreatment reaction skid, a vibrating screen cuttings separation skid, a solid-liquid centrifugal separation skid, and an oil-water-solid three-phase separation skid connected in sequence along the direction of material liquid flow. It also includes a platform mud pit 1, and an analysis and detection device 2 is arranged in the platform mud pit 1;

[0107] The pre-treatment reaction skid includes a pre-treatment reaction device 17 and a chemical dosing device 4. The inlet of the chemical dosing device 4 is connected to an external chemical supply device 3. The chemical dosing device 4 is arranged on the top inlet of the pre-treatment reaction device 17. The number of the pre-treatment reaction devices 17 is 3, and the pre-treatment reaction devices 17 are arranged in parallel. The outlet of each pre-treatment reaction device 17 is connected to an outlet main pipe through a multi-way control valve 5. The outlet of the outlet main pipe is connected to a vibrating screening device 7. The platform mud pit 1 is connected to an inlet main pipe through a multi-way control valve 5. The outlet of the inlet main pipe is respectively connected to the pre-treatment reaction device 17. A check valve 6 is arranged between the multi-way control valve 5 and the pre-treatment reaction device 17. A temperature regulating mechanism is arranged inside the pre-treatment reaction device 17;

[0108] Among them, as Figure 4 shown, the chemical dosing device 4 includes an outer jacket. The outer jacket includes a cylindrical structure and an upper end face 414 and a lower end face 415 arranged at both ends of the cylindrical structure. The cylindrical structure includes an upper section 411, a middle section 412 and a lower section 413 which are sequentially communicated from top to bottom. Both the upper section 411 and the lower section 413 are columnar structures. The diameters of both ends of the middle section 412 are larger than the middle diameter and the longitudinal section is a funnel shape with central symmetry. Inside the outer jacket, a gas supply pipe 42 and a chemical dosing pipe 41 are concentrically arranged from outside to inside in sequence, and both the gas supply pipe 42 and the chemical dosing pipe 41 pass through the upper end face 414. A first blocking wall 48 is arranged at the bottom of the gap formed by the gas supply pipe 42 and the chemical dosing pipe 41. The first blocking wall 48, the inner side wall of the gas supply pipe 42 and the outer side wall of the chemical dosing pipe 41 together form a gas supply gap. The gas inlet of the gas supply gap faces upward. A first gas supply hole 43 is opened on the side wall of the gas supply pipe 42. A second blocking wall 49 is arranged at the bottom of the gap formed by the inner side wall of the upper section 411, the outer side wall of the gas supply pipe 42 and the upper end face 414. The second blocking wall 49, the outer side wall of the gas supply pipe 42, the inner side wall of the upper section 411 and the upper end face 414 together form a gas supply chamber. A second gas supply hole 44 is opened on the second blocking wall 49. The bottom outlet of the chemical dosing pipe 41 is located at the smallest diameter of the middle section 412. The middle section 412, the lower section 413 and the lower end face 415 are all provided with air holes 45. The sum of the number of air holes 45 in the lower section 413 and the lower end face 415 > the number of air holes 45 in the middle section 412. The chemical dosing device 4 further includes a driving mechanism 47 and a stirring blade 46. The driving mechanism 47 is arranged on the upper end face 414 of the outer jacket. The power output end of the driving mechanism 47 drives the outer jacket to rotate. Stirring blades 46 are arranged along the circumferential direction on both the middle section 412 and the lower section 413 of the outer jacket;

[0109] The shale shaker separation skid includes a vibrating screening device 7, a sludge tank 8, a buffer water tank 9, and a lift pump 10. The inlet of the vibrating screening device 7 is connected to the outlet of the multi-way control valve 5. The solid phase outlet of the vibrating screening device 7 is connected to the sludge tank 8. The liquid phase outlet of the vibrating screening device 7 is connected to the buffer water tank 9. The outlet of the buffer water tank 9 is connected to the high-efficiency horizontal scroll centrifuge 11 of the solid-liquid centrifugal separation skid through the lift pump 10;

[0110] The solid-liquid centrifugal separation skid includes a high-efficiency horizontal scroll centrifuge 11, a sludge tank 8, a collection water tank 12, and a lift pump 10. The solid phase outlet of the high-efficiency horizontal scroll centrifuge 11 is connected to the sludge tank 8. The liquid phase outlet of the high-efficiency horizontal scroll centrifuge 11 is connected to the collection water tank 12. The outlet of the collection water tank 12 is connected to the high-speed disc centrifuge 13 of the oil-water-solid three-phase separation skid through the lift pump 10;

[0111] The oil-water-solid three-phase separation skid includes a high-speed disc centrifuge 13, a platform separation device 14, a production water tank 15, and a white oil tank 16. The solid phase outlet of the high-speed disc centrifuge 13 is connected to the platform separation device 14. The water phase outlet of the high-speed disc centrifuge 13 is connected to the production water tank 15. The oil phase outlet of the high-speed disc centrifuge 13 is connected to the white oil tank 16.

[0112] In this embodiment, the maximum processing capacity of the treatment device system is 5m 3 / h. All the motors and electrical control cabinets used in the treatment device system are explosion-proof designed. The explosion-proof grade is EX dII BT4. The motors and electrical control cabinets adopt a protection grade of IP65 and above, meeting the explosion-proof and open-air operation requirements of oilfield operations. All material inlets and outlets adopt the union connection method. The pipelines adopt high-pressure rubber hoses, and the pipeline connection ports adopt the union connection method; The maximum skid-mounted size of each skid is: L≤4100mm, W≤2500mm, H≤3000mm, which is suitable for the compact space of offshore platforms and can be reasonably placed according to the space position of the offshore platform.

[0113] In summary, the device system provided by the present invention can realize the continuous treatment and up-to-standard discharge of drilling return waste liquid, and improve the operation efficiency of the wellhead on the offshore platform, meeting the treatment requirements for different liquid qualities.

[0114] The applicant declares that the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and public scope of the present invention.

Claims

1. A processing device system for drilling return fluid of an offshore oil and gas drilling platform, characterized in that: The processing device system comprises a pretreatment reaction skid, a vibrating screen cuttings separation skid, a solid-liquid centrifugal separation skid and an oil-water-solid three-phase separation skid which are sequentially connected along the flow direction of the feed liquid; Adjacent skids are connected for materials through pipelines and control valves, and for positions through detachable connection devices; The vibrating screen rock cuttings separation skid is provided with a conducting pipeline in parallel, the inlet of the conducting pipeline is connected to the outlet of the pretreatment reaction skid, and the outlet of the conducting pipeline is connected to the inlet of the solid-liquid centrifugal separation skid.

2. The processing device system according to claim 1, characterized in that: The detachable connection device comprises a positioning rod and a positioning groove for accommodating the positioning rod.

3. The processing device system according to claim 1 or 2, characterized in that: The pretreatment reaction skid comprises a pretreatment reaction device and a dosing device, wherein the dosing device is arranged on the top inlet of the pretreatment reaction device; Preferably, the number of the pretreatment reaction devices is at least 2, the pretreatment reaction devices are arranged in parallel, and the outlet of each pretreatment reaction device is connected to the outlet main pipe through a multi-way control valve; Preferably, a temperature regulating mechanism is provided inside the pretreatment reaction device.

4. The processing device system according to claim 3, characterized in that: The dosing device comprises a jacket, and the jacket comprises a cylindrical structure and an upper end surface and a lower end surface arranged at both ends of the cylindrical structure; Preferably, the cylindrical structure comprises an upper section, a middle section and a lower section which are connected in sequence from top to bottom, the upper section and the lower section are both columnar structures, the diameters of both ends of the middle section are larger than the middle diameter and the longitudinal cross section is a centrally symmetrical funnel shape; Preferably, the air supply pipe and the drug adding pipe are concentrically arranged in sequence from the outside to the inside of the outer casing, and both the air supply pipe and the drug adding pipe pass through the upper end surface; Preferably, a first blocking wall is provided at the bottom of the gap formed by the air supply pipe and the dosing pipe, the first blocking wall, the inner wall of the air supply pipe and the outer wall of the dosing pipe together constitute the air supply gap, the gas inlet of the air supply gap faces upward, and the side wall of the air supply pipe is provided with a first air supply hole; Preferably, a second blocking wall is provided at the bottom of the gap formed by the inner wall of the upper section, the outer wall of the air supply pipe and the upper end surface, the second blocking wall, the outer wall of the air supply pipe, the inner wall of the upper section and the upper end surface together constitute an air supply chamber, and the second blocking wall is provided with a second air supply hole; Preferably, the bottom outlet of the dosing tube is located at the smallest diameter of the middle section; Preferably, the middle section, the lower section and the lower end surface are all provided with aeration holes; Preferably, the sum of the number of aeration holes in the lower section and the lower end surface is greater than the number of aeration holes in the middle section; Preferably, the dosing device further comprises a driving mechanism and stirring blades, wherein the driving mechanism is arranged on the upper end surface of the outer sleeve, the power output end of the driving mechanism drives the outer sleeve to rotate, and the stirring blades are circumferentially arranged on the middle section and the lower section of the outer sleeve.

5. The processing device system according to any one of claims 1 to 4, characterized in that: The vibrating screen cuttings separation skid comprises a vibrating screening device, a sludge tank, a buffer water tank and a lifting pump. The solid phase outlet of the vibrating screening device is connected to the sludge tank, the liquid phase outlet of the vibrating screening device is connected to the buffer water tank, and the outlet of the buffer water tank is connected to the solid-liquid centrifugal separation skid through the lifting pump.

6. The processing device system according to claims 1-5, characterized in that: The solid-liquid centrifugal separation skid comprises a centrifugal device, a sludge tank, a collecting water tank and a lifting pump, wherein the solid phase outlet of the centrifugal device is connected to the sludge tank, the liquid phase outlet of the centrifugal device is connected to the collecting water tank, and the outlet of the collecting water tank is connected to the oil-water-solid three-phase separation skid via the lifting pump; Preferably, the centrifugal device in the solid-liquid centrifugal separation skid comprises a high-efficiency horizontal screw centrifuge.

7. The processing device system according to claims 1-6, characterized in that: The oil-water-solid three-phase separation skid comprises a centrifugal device, a platform separation device, a water production tank and a white oil tank. The solid phase outlet of the centrifugal device is connected to the platform separation device, the water phase outlet of the centrifugal device is connected to the water production tank, and the oil phase outlet of the centrifugal device is connected to the white oil tank. Preferably, the centrifugal device in the oil-water-solid three-phase separation skid comprises a high-speed disc centrifuge.

8. The processing device system according to any one of claims 1 to 7, characterized in that: The treatment device system also includes a platform mud pool, and the outlet of the platform mud pool is connected to the pretreatment reaction skid; Preferably, an analysis and detection device is provided in the platform mud pool.

9. A method for treating drilling flowback fluid from an offshore oil and gas drilling platform, characterized in that: The treatment method adopts the treatment device system of the drilling flowback fluid of the offshore oil and gas drilling platform as claimed in any one of claims 1 to 8; The method comprises the following steps: The drilling return fluid is added with a reagent for mixed reaction to obtain a pretreated liquid; and then the pretreated liquid is separated to obtain produced water, an oil phase and a residue.

10. The processing method according to claim 9, characterized in that: The processing method comprises the following steps: (1) Detecting the drilling return fluid in the platform mud pool by means of an analytical detection device to obtain the return fluid parameters, including the particle size of solid particles in the drilling return waste fluid; (2) transporting the drilling return fluid in the platform mud pool of step (1) to a pretreatment reaction device, setting the type and concentration of the added reagent according to the return fluid parameters obtained in step (1), adding the reagent to the pretreatment reaction device through a dosing device and mixing it with the return waste liquid for reaction, and stirring and aerating the dosing device while performing the dosing process to obtain a pretreated liquid; (3) If the particle size of the solid particles in the drilling return waste liquid is less than 5 mm, the pre-treated liquid obtained in step (2) is sent to a high-efficiency horizontal screw centrifuge through a conducting pipeline for solid-liquid separation, the obtained solid particles are sent to a sludge tank, and the obtained liquid phase is sent to a collection water tank; the liquid phase in the collection water tank is sent to a high-speed disc centrifuge through a lifting pump for oil-water-solid three-phase separation, the separated produced water is sent to a produced water tank, the obtained oil phase is sent to a white oil tank, and the obtained residue is sent to a platform separation device; If the particle size of the solid particles in the drilling return waste liquid is ≥5mm, the pretreated liquid obtained in step (2) is sent to a vibrating screening device for screening, the rock cuttings particles obtained by screening are sent to a sludge tank for collection, and the obtained liquid phase is sent to a buffer water tank. The liquid phase in the buffer water tank is sent to a high-efficiency horizontal screw centrifuge through a lifting pump for solid-liquid separation, the obtained solid particles are sent to a sludge tank, and the obtained liquid phase is sent to a collecting water tank; the liquid phase in the collecting water tank is sent to a high-speed disc centrifuge through a lifting pump for oil-water-solid three-phase separation, the separated produced water is sent to a produced water tank, the obtained oil phase is sent to a white oil tank, and the obtained residue is sent to a platform separation device.

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