Internal dehydrating flow field stabilization method for heavy viscous oil electric dehydrator

Abstract

A kind of heavy viscous crude oil is with the steady-state method of internal dehydration flow field of electric dehydrator, belong to oilfield high water cut viscous crude oil closed dehydration processing device technical field, closed electric dehydrator includes lower layer butterfly wing type step-by-step shunt liquid inlet device, lower layer water outlet device, upper layer suspension type oil collection device and middle electric dehydrating area, lower layer butterfly wing type step-by-step shunt liquid inlet device is uniformly distributed along pipe length certain angle liquid distribution hole, liquid distribution hole diameter is reduced from middle to both sides casting;Upper layer of equipment cylinder is provided with upper layer suspension type oil collection device, and vertical downward oil collection hole is arranged on upper layer suspension type oil collection device;Lower layer water outlet device is provided with vertical upward water outlet hole;The present application can effectively improve the separation effect of water-containing viscous oil, simplify the device inner part, reduce the size, and then reduce the engineering investment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of oilfield high water cut heavy oil crude oil closed dehydration treatment device, and particularly relates to a method for stabilizing internal dehydration flow field of an electric dehydrator for heavy oil. BACKGROUND

[0002] 70% of the global remaining oil resources are heavy oil resources, which are important substitutes for world oil resources. Heavy oil resources are widely distributed in China, and more than 70 heavy oil fields have been found in 12 basins. At present, four heavy oil production areas including Liaohe, Xinjiang, Shengli and Henan have been built, with an annual oil production of 10 million tons.

[0003] Dehydration treatment of water-containing crude oil is a key link in crude oil production. Foreign heavy oil dehydration generally adopts closed dehydration process with additional diluent (in oil field dehydration production, the additional diluent used is generally light crude oil produced by itself or distillate oil such as unrefined diesel oil from nearby refineries. The purpose is to adjust the density and viscosity of the crude oil, so as to facilitate the dehydration production and pipeline transportation of the crude oil). Some oil fields in China adopt closed dehydration process of thermal chemical sedimentation + electrochemical dehydration with additional diluent, and some oil fields adopt thermal chemical sedimentation two-stage dehydration process technology. Closed dehydration refers to whether the process is closed or not during the dehydration production of crude oil, which is divided into open dehydration process and closed dehydration process. The large tank thermal chemical sedimentation process is a typical open process, and the three-phase separator dehydration and electric dehydration process are representatives of closed dehydration.

[0004] At present, the main heavy oil blocks in China have entered the middle and late stages of development. In order to improve the production situation of the oil fields with the development mode conversion, scale expansion, increasingly complex produced liquid properties, difficult treatment and high cost, and to meet the external environmental requirements of the increasingly improved environmental protection standards, it is a trend to explore and research the closed dehydration process of heavy and viscous oil.

[0005] Heavy and viscous oil refers to crude oil with a viscosity of > 400 mPa·s at 50℃ when the density is 0.916 g / cm 3 and the density is ≤ 0.996 g / cm 3 . The main technical direction is to realize closed and efficient oil-water separation of heavy and viscous oil, and the new electric dehydration process technology. In the electric dehydration process, the most important core is the electric dehydrator, and the key to ensure the efficient operation of the electric dehydrator and improve the dehydration effect of heavy oil is the stability of the internal flow field. Therefore, the method for improving the flow field stability of the electric dehydrator for heavy oil has very important significance. SUMMARY

[0006] In order to solve the above-mentioned problems, the present application provides: a heavy viscous oil electric dehydrator internal dehydration flow field steady method, which realizes internal dehydration flow field steady through a closed electric dehydration device, the closed electric dehydration device comprises a lower butterfly wing type step-by-step shunt liquid inlet device, a lower water outlet device, an upper suspension type butterfly wing type oil collection device and an intermediate sedimentation electric de-doping area, the lower layer butterfly wing type step-by-step shunt liquid inlet device and the lower water outlet device are arranged at the lower position in the equipment cylinder, the intermediate sedimentation electric de-doping area is arranged at the middle position in the equipment cylinder, the lower layer butterfly wing type step-by-step shunt liquid inlet device inputs the mixed liquid into the equipment cylinder, the intermediate sedimentation electric de-doping area settles the mixed liquid in the equipment cylinder, the upper suspension type butterfly wing type oil collection device collects the oil in the mixed liquid, the lower water outlet device discharges the water of the mixed liquid in the equipment cylinder, the lower layer butterfly wing type step-by-step shunt liquid inlet device is a liquid distribution hole with a certain downward angle uniformly distributed along the pipe length, and the hole diameter gradually increases from the center to both sides; the upper suspension type butterfly wing type oil collection device is arranged at the upper position in the equipment cylinder, the upper suspension type butterfly wing type oil collection device is provided with a vertical downward oil collection hole, the hole diameter gradually increases from the center to both sides, and the lower water outlet device is provided with a vertical upward water outlet hole.

[0007] The present application has the following beneficial effects:

[0008] Firstly, the dehydration effect of viscous oil is improved.

[0009] The reasonable design enhances the effect of washing free water, directly separates large-diameter water droplets, and provides a stable flow state environment for the intermediate electric field and the gravity field area of the sedimentation section, which is beneficial to oil-water gravity separation and electric field effect;

[0010] Secondly, the oil-water separation time is reduced.

[0011] The liquid inlet, water collection and oil collection are arranged on the upper and lower sides of the device to avoid the generation of vortex, realize the purpose of quasi-static sedimentation, and shorten the sedimentation separation time.

[0012] Thirdly, the buffer pre-separation bin is cancelled, and the overall equipment size is reduced.

[0013] Through experimental verification, it is shown that the method is suitable for viscous oil dehydration, when the temperature is 20 DEG C, the water content of the water-containing viscous oil with a density of 0.916 g / cm 3 Density ≤ 0.996 g / cm 3 When the temperature is 50 DEG C and the viscosity is greater than 400 mPa·s, the water content of the water-containing viscous oil is less than 30%, under the action of the multi-field coupling electric field, the water content after treatment is as low as 1.5%, the dehydration effect is improved by more than 10%, which is better than the treatment effect of the existing electric dehydrator, and the overall size is reduced by more than 10%, the overall project investment is reduced, the treatment cost per ton of liquid of the water-containing viscous oil is reduced from 3.42 yuan to 2.9 yuan, and the treatment cost per ton of liquid is reduced by 15%.

[0014] The present application can effectively improve the separation effect of water-containing thick oil, simplify the inner part of the device, reduce the size, and further reduce the engineering investment. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 Structure schematic view of the inner part arrangement of the closed electric dehydrator of the present application;

[0016] Figure 2 Structure schematic view of the liquid inlet device of the present application;

[0017] Figure 3 Structure schematic view of the water outlet device of the present application;

[0018] Figure 4 Structure schematic view of the oil outlet device of the present application;

[0019] Figure 5 Structure of the butterfly wing type liquid inlet device and liquid distribution hole of the present application;

[0020] Figure 6 Detailed view of the suspension type oil outlet device and oil collection hole of the present application;

[0021] Figure 7 Detailed view of the water outlet device and water collection hole of the present application;

[0022] Figure 8 Velocity distribution nephogram of the bottom liquid inlet device of the present application;

[0023] Figure 9 Velocity distribution nephogram of the suspension type oil outlet device of the present application;

[0024] Figure 10 Pressure distribution nephogram of the bottom liquid inlet device of the present application;

[0025] Figure 11 Pressure distribution nephogram of the suspension type oil outlet device of the present application;

[0026] Figure 12 Pressure distribution nephogram of the liquid distribution pipe of the present application;

[0027] Figure 13 Structure schematic view of the internal arrangement of the existing electric dehydrator;

[0028] Figure 14 Structure schematic view of the internal arrangement of the existing electric dehydrator.

[0029] Among them, the reference signs are: 1, lower layer butterfly wing type step-by-step shunt liquid inlet device, 2, lower layer water outlet device, 3, upper layer suspension type butterfly wing type oil collection device, 4, middle settlement electric dehydrating zone, 11, pre-division bin, 22, buffer weir plate, 33, oil-water separation bin, 44, oil collection bin, 55, water collection bin. DETAILED DESCRIPTION

[0030] Crude oil is produced from wellhead, generally containing moisture, before being transported to the refinery, generally by the oil production enterprise oil field processing to meet the requirements of the export of crude oil. Among them, the crude oil dehydration is an important link, the equipment and system used are generally called "crude oil dehydration treatment equipment", the present application adopts a new type of internal part design and arrangement, a method for stabilizing the internal flow field of the treatment device.

[0031] A kind of internal dehydration flow field stabilization method for heavy viscous oil electric dehydrator, as shown in Figures 1-4 The internal dehydration flow field stabilization is realized by a closed electric dehydrator, and the closed electric dehydrator comprises a lower butterfly wing type step-by-step shunt liquid inlet device 1, a lower water outlet device 2, an upper suspension type butterfly wing type oil collection device 3 and an intermediate sedimentation electric dehydrating zone 4,

[0032] As shown in Figure 5 The lower butterfly wing type step-by-step shunt liquid inlet device 1 is uniformly distributed along the pipe length with a certain angle of liquid distribution hole, and the diameter of the liquid distribution hole decreases from the middle to the two sides of the casting;

[0033] In this way, the flow state and flow rate of each liquid outlet can be close to uniform, thereby inhibiting the turbulence degree of the liquid inlet, stabilizing the flow field in the electric dehydrator, reducing the sedimentation time, improving the oil-water separation effect, and providing the best water washing effect through the design of the angle, diameter and distribution of the liquid distribution hole, and removing most of the free water;

[0034] As shown in Figure 6 The upper suspension type butterfly wing type oil collection device 3 is arranged on the upper layer of the equipment cylinder, and the upper suspension type butterfly wing type oil collection device 3 is provided with a vertical downward oil collection hole;

[0035] As shown in Figure 7 The lower water outlet device 2 is provided with a vertical upward water outlet hole;

[0036] This arrangement reduces the disturbance to the middle oil-water interface and emulsion layer, and is beneficial to the gravity sedimentation separation of oil and water. Another advantage of this design concept is that the middle layer of the electric dehydrator is not provided with any other structure except the electrode assembly, thereby providing a stable flow state environment for the middle electric field, which is beneficial to the oscillation and coalescence separation of charged particles. The structure of the oil outlet device and the water outlet device is shown in the following figure.

[0037] In addition, compared with the existing commercial electric dehydrator, the existing commercial electric dehydrator is shown in Figures 13-14 , wherein 11 is a pre-division bin, 22 is a buffer weir plate, 33 is an oil-water separation bin, 44 is an oil collection bin, and 55 is a water collection bin. This arrangement is complicated, has a large pressure drop, greatly disturbs the stability of the fluid, is not conducive to sedimentation and separation, and therefore has poor application effect in the application of thick oil closed dehydration.

[0038] The internal structure is optimized, and the pre-separation bin and separation baffle are cancelled, so that compared with the existing commercial electric dehydrator, the method can reduce the equipment size and cost. The method can be applied to the closed dehydration process of thick oil with a density of 0.916 g / cm 3 ≤0.996 g / cm 3 and a viscosity of >400 mPa·s at 50℃, and provides guidance for the manufacture of new equipment and the modification of old equipment.

[0039] The specific solution of the equation is obtained by using the finite volume method of computer simulation, and the inner part arrangement mode, oil and water collection, opening size and distribution of the liquid inlet pipe are calculated. The Navier-Stokes equation with viscosity is used to list the continuity equation, momentum equation and energy equation as follows:

[0040] Continuity equation:

[0041] Momentum equation: X direction:

[0042] Y direction:

[0043] Z direction:

[0044] Energy equation:

[0045]

[0046] Wherein, ρ is the density, kg / m 3 ; t is the time, s; is the gradient operator; V is the velocity vector field, V=ui+vj+wk; u, v and w are the velocities in x, y and z directions, respectively, m / s; p is the static pressure, MPa; T is the temperature, ℃; τ xx , τ xz , τ yz , τ zx , τ zy , τ zz are the shear stresses in the respective directions, MPa; f is the volume force acting on a unit volume of microelement in a certain direction, N; q is the volumetric heating rate per unit mass, J / (kg·℃); e is the internal energy, J; k is the thermal conductivity, W·m -1 ·℃ -1 .

[0047] By using the method of the patent, a relatively stable flow state can be obtained, which is described in detail in Figures 8-12The velocity cloud chart can show the distribution of the fluid velocity in the tank, the fluid velocity in the tank is very uniform, and the fluid velocity gradient is very small, so a stable flow field is obtained, which provides a good electrophoresis and shock coalescence dehydration environment for the middle electric separation space. The butterfly wing type liquid inlet device used in this method makes the liquid in the tank uniformly distributed, stabilizes the flow field, and the liquid collection speed of the oil outlet pipe and the water collection pipe is uniform, and the liquid collection state is good. In addition, it can be seen from the figure that the pressure distribution in the tank is uniform, and no back mixing phenomenon occurs, and the effect is good. The pressure in the liquid distribution pipe gradually decreases, which is conducive to the flow of liquid, and the pressure at the outlet is high in the middle and low on both sides, and the distribution is uniform. The middle pressure of the oil collection pipe is high and the two sides are low, which is conducive to the flow and discharge of the oil phase.

[0048] The lower butterfly wing type step-by-step shunt liquid inlet device 1 is arranged at the lower part of the electric dehydrator, and the oil-water mixture enters the sealed electric dehydrator and uniformly escapes at the liquid distribution holes of the lower butterfly wing type step-by-step shunt liquid inlet device 1 after passing through the lower butterfly wing type step-by-step shunt liquid inlet device 1.

[0049] The angle range of the punching and the horizontal plane is 30°-60° through theoretical calculation and experimental analysis, and the punching angle is 45° when the liquid inlet quantity is 1000 Ncmd, the water content is ≤30%, the heavy oil physical property is 20℃-50℃, 0.916g / cm 3 3 , the viscosity is >400mPa·s.

[0050] The hole diameter of the lower butterfly wing type step-by-step shunt liquid inlet device 1 is 30mm within the axial midpoint distance of 2.7m, and the hole spacing is 50mm.

[0051] The hole diameter of the lower butterfly wing type step-by-step shunt liquid inlet device 1 is 20mm within the axial midpoint distance of 2.7m-5.4m, and the hole spacing is 50mm.

[0052] The hole diameter of the lower butterfly wing type step-by-step shunt liquid inlet device 1 is 15mm within the axial midpoint distance of 5.4m-8.1m, and the hole spacing is 50mm.

[0053] The hole diameter of the lower butterfly wing type step-by-step shunt liquid inlet device 1 is 20mm within the axial midpoint distance of 8.1m-12m, and the hole spacing is 50mm.

[0054] The oil-water mixture after preliminary separation is subjected to gravity sedimentation and oil-water separation under the action of an electric field in the middle sedimentation electric separation zone 4, and a 1.8m high cavity area is reserved in the middle sedimentation electric separation zone 4, so that the mixed liquid in the W / O state of oil wrapping water droplets realizes the separation state of electrophoresis+shock.

[0055] ​Wherein, after separation, the upper layer suspension butterfly oil collecting device 3 uses the pressure difference between the internal pressure of the electric dehydrator and the external pipeline connected with the upper layer suspension butterfly oil collecting device 3 to collect the floating oil layer, and the oil collecting hole of the upper layer suspension butterfly oil collecting device 3 is arranged in a vertical downward arrangement, and the lower layer water outlet device 2 is provided with a vertical upward water collecting hole.

[0056] First step: the oil-water mixture enters the electric dehydrator, the liquid inlet device is arranged at the lower part of the electric dehydrator, and after passing through the double-layer butterfly distribution liquid inlet device of the lower layer butterfly gradual flow liquid inlet device 1, it is uniformly discharged at the liquid distribution hole of the lower layer butterfly gradual flow liquid inlet device 1. Through theoretical calculation and experimental analysis, the punching angle with the horizontal plane is a certain angle (30°-60°), which is helpful for the flow and floating of large-diameter water particles in the oil-water mixture, and plays a role in demulsification and sinking of small-diameter distributed water droplets, and promotes the completion of preliminary settling. Through calculation and simulation comparison analysis, when the liquid inlet quantity is 1000 Ncmd, the water content is ≤30%, the thick oil physical property is 20℃-50℃, 0.916g / cm 3 < Density ≤0.996g / cm 3 , viscosity > 400 mPa·s, the punching angle is 45°, the hole diameter of the lower layer butterfly gradual flow liquid inlet device 1 is 30mm within the axial midpoint distance of 2.7m, the hole spacing is 50mm; the hole diameter is 20mm within the range of 2.7m-5.4m, the hole spacing is 50mm; the hole diameter is 15mm within the range of 5.4m-8.1m, the hole spacing is 50mm; the hole diameter is 20mm within the range of 8.1m-12m, the hole spacing is 50mm; the calculation and simulation results prove that under the premise of not affecting the stability of the flow field, this method speeds up the fusion and floating of large-particle water droplets, and the flow field of the liquid inlet is stable, and the liquid outlet flow rate of each liquid distribution hole is basically consistent.

[0057] Second step: the oil-water mixture after preliminary separation is subjected to gravity settling and oil-water separation under the action of electric field in the middle settling electric dehydrating zone 4. Since the mixture is in the state of oil wrapping water droplets (W / O state), an electrophoresis + oscillation separation effect needs to be provided between the electrodes, so if there are excess inner parts in the middle settling electric dehydrating zone 4, the separation effect will be affected. The electric dehydrator of the case retains a 1.8m high cavity area in the middle settling electric dehydrating zone 4, and there are no excess inner parts in the area, which provides a better environment for separation.

[0058] Third step: after separation, the upper suspension butterfly oil collection device 3 uses the pressure difference between the internal pressure of the electric dehydrator and the external pipeline connected to the oil collection device to collect the floating oil layer. Considering the need for a stable environment for the flow field at this time, the oil collection hole of the upper suspension butterfly oil collection device 3 is designed to be arranged vertically downward, which will only have an absorption effect on the vertical direction fluid and no effect on the two sides of the vertical line. Similarly, the lower water collection device 2 is also provided with a vertically upward water collection hole. Simulation calculations can prove that the oil collection device and water collection device designed in this way only perform liquid collection in the vertical direction, and have much less interference with the overall flow field than other hole angle designs. After a few hours of stable operation, the oil collection device finally obtains purified crude oil with a water content of ≤1.5%, and the operation effect is good.

[0059] The heavy viscous oil electric dehydrator internal dehydration flow field steady method of the patent application provides a stable flow field environment for the electric dehydrator interior by designing a new type of internal part arrangement method, optimizes the oil-water separation effect, and makes the water content of the purified crude oil obtained after the water-containing viscous oil with a temperature of 20-50℃, a density of ≤0.996 g / cm 3 <Density ≤0.996 g / cm 3 , viscosity > 400 mPa·s, and water content ≤30% is treated by airtight dehydration method ≤1.5%. The method improves the stability and dehydration effect of dehydration, and provides guidance for the upgrading of the land-based viscous oil dehydration system from an open type to a closed type.

[0060] The above is only the preferred specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can make equivalent replacements or changes to the technical solution and concept of the present application within the scope of the disclosed technology, which should be covered within the protection scope of the present application.

Claims

1. A method for stabilizing the steady state of the internal dehydration flow field of an electric dehydrator for heavy viscous oil, characterized by, The internal dehydration flow field is stabilized by a closed electric dehydration device, which comprises a lower butterfly wing type step-by-step shunt liquid inlet device (1), a lower water outlet device (2), an upper suspension type butterfly wing type oil collection device (3) and an intermediate sedimentation electric dehydration zone (4). The lower butterfly wing type step-by-step shunt liquid inlet device (1) and the lower water outlet device (2) are arranged at the lower position in the equipment cylinder. The intermediate sedimentation electric dehydration zone (4) is arranged at the middle position in the equipment cylinder. The lower butterfly wing type step-by-step shunt liquid inlet device (1) inputs the mixed liquid into the equipment cylinder. The intermediate sedimentation electric dehydration zone (4) settles the mixed liquid in the equipment cylinder. The upper suspension type butterfly wing type oil collection device (3) collects the oil in the mixed liquid. The lower water outlet device (2) discharges the water of the mixed liquid in the equipment cylinder. The lower butterfly wing type step-by-step shunt liquid inlet device (1) is a liquid distribution hole with a certain downward angle uniformly distributed along the pipe length, and the hole diameter gradually increases from the center to both sides. The upper suspension type butterfly wing type oil collection device (3) is arranged at the upper position in the equipment cylinder. The upper suspension type butterfly wing type oil collection device (3) is provided with a vertical downward oil collection hole with a hole diameter gradually increasing from the center to both sides. The lower water outlet device (2) is provided with a vertical upward water outlet hole.

2. The method for internal dehydrating flow field stabilization of the heavy oil electric dehydrator according to claim 1, characterized in that, The specific solution of the equation adopts the finite volume method of computer simulation mode to calculate the inner part arrangement mode, the opening size and distribution of the oil collection, water collection and liquid inlet pipe. The Navier-Stokes equation with viscosity is used to list the continuity equation, momentum equation and energy equation respectively as follows: Continuity equation: Momentum equation: X direction: Y direction: Z-direction: Energy equation: where p is density, kg / m 3 ; t is time, s; is the gradient operator; V is the velocity vector field, V = ui + vj + wk; u, v, w are the velocities in x, y, z directions, m / s; p is the static pressure, MPa; T is the temperature, °C; τ xx , τ xz , τ yz , τ zx , τ zy , τ zz are the shear stresses in the directions, MPa; f is the body force acting on a unit volume of an infinitesimal, N; q is the volumetric heating rate per unit mass, J / (kg·°C); e is the internal energy, J; k is the thermal conductivity, W·m -1 ·°C -1 .

3. The method for internal dehydrating flow field stabilization of the heavy oil electric dehydrator according to claim 1, characterized in that, The lower butterfly wing type step-by-step shunt liquid inlet device (1) is arranged at the lower part of the electric dehydrator. The oil-water mixture enters the closed electric dehydration device and uniformly escapes at the liquid distribution hole of the lower butterfly wing type step-by-step shunt liquid inlet device (1) after passing through the lower butterfly wing type step-by-step shunt liquid inlet device (1).

4. The method for internal dehydrating flow field stabilization of the heavy oil electric dehydrator according to claim 3, characterized in that, The angle range between the hole and the horizontal plane is 30°-60°.

5. The method for internal dehydrating flow field stabilization of the heavy oil electric dehydrator according to claim 4, characterized in that, The hole diameter is 30mm within the range of 2.7m from the axial midpoint of the lower butterfly wing type step-by-step shunt liquid inlet device (1), and the hole spacing is 50mm.

6. The method for internal dehydrating flow field stabilization of the heavy oil electric dehydrator according to claim 4, characterized in that, The hole diameter is 20mm within the range of 2.7m-5.4m from the axial midpoint of the lower butterfly wing type step-by-step shunt liquid inlet device (1), and the hole spacing is 50mm.

7. The method for internal dehydrating flow field stabilization of the heavy oil electric dehydrator according to claim 4, characterized in that, The hole diameter is 15mm within the range of 5.4m-8.1m from the axial midpoint of the lower butterfly wing type step-by-step shunt liquid inlet device (1), and the hole spacing is 50mm.

8. The method for internal dehydrating flow field stabilization of the heavy oil electric dehydrator according to claim 4, characterized in that, The hole diameter is 20mm within the range of 8.1m-12m from the axial midpoint of the lower butterfly wing type step-by-step shunt liquid inlet device (1), and the hole spacing is 50mm.

9. The method for internal dehydrating flow field stabilization of the heavy oil electric dehydrator according to claim 3, characterized in that, The oil-water mixture after preliminary separation is subjected to gravity settling and oil-water separation under the action of electric field in the intermediate sedimentation electric dehydration zone (4). A 1.8m high cavity area is reserved in the intermediate sedimentation electric dehydration zone (4) to make the mixed liquid between the electrodes present the oil-encapsulated water droplet state W / O state to realize the separation state of electrophoresis+oscillation.

10. The method for internal dehydrating flow field stabilization of an electric dehydrator for heavy viscous oil according to claim 9, characterized in that, After separation, the upper hanging butterfly wing oil collecting device (3) uses the pressure difference between the internal pressure of the electric dehydrator and the external pipeline connected with the upper hanging butterfly wing oil collecting device (3) to collect the floating oil layer, and the oil collecting hole of the upper hanging butterfly wing oil collecting device (3) is arranged in a vertically downward manner, and the lower water outlet device (2) is provided with a vertically upward water collecting hole.

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