RU2238403C2 - Method for oil preparation and means for realization of said method - Google Patents

Abstract

FIELD: oil extractive industry.

SUBSTANCE: method is based on preliminary vacuum treatment of flow of well product, during which multiple micro-explosions destroy armoring covers, instant reduction of emulsion phases occurs, limiting layers are not formed. Method is performed in common and three-phase separators, among which are those with preliminary phases separation and letting through of components through individual nozzles. Vacuum treatment is performed not for all emulsion, but for its most stable portion. Longitudinal magnetic field is used, and washing of vacuum-treated emulsion by layer water and fresh water. Slanting surface is used for intensifying phases separation. End separation is performed in three-phase separators, which includes addition of vacuum treated in a nozzle gas condensate.

EFFECT: higher efficiency.

3 cl, 6 dwg, 1 ex

Description

1. TECHNICAL FIELD

The invention relates to on-site preparation of oil well products, including its separation into oil, gas and water, followed by refinement of the components to marketable conditions (oil, gas) or to the requirements of on-site use (water, gas)

2. BACKGROUND

Intra-field preparation of oil includes its degassing, dehydration and desalination.

The problem of oil separation is considered in the parallel application “Method of oil separation at the end separation plants and means for its provision”.

The most common method for thermochemical oil dehydration, which includes the addition of a demulsifier, heating and subsequent separation in horizontal or inclined cylindrical apparatuses (see, for example, the book N. N. Baykov and others. Collection and field treatment of oil, gas and water - M .: Nedra, 1981, 105 pp. - prototype) due to the high cost of road demulsifiers, it requires large areas for the installation of oil and metal. In addition, he gave rise to the problem of boundary layers.

The design of the sumps is such that the dehydrated oil is taken from the upper (surface) layer, and the separated water from the bottom. On the border between water and oil, an undamaged emulsion gradually accumulates, fragments of destroyed armor shells, mechanical impurities, forming the so-called boundary layer. Accumulating and becoming obsolete, it can be captured by oil, sharply worsening the quality of its preparation, or by water discharged, causing the problem of its purification to the required conditions.

Returning trapped water to the process head exacerbates the problem. The discharge of boundary layers into separate reservoirs for trap emulsions creates a problem of their disposal. Due to the high water cut and severe pollution, they do not burn and cannot be pumped into the reservoirs, but attempts to destroy them (see, for example, RD 39001/10 - 002-89 “Technology for the integrated preparation of trap oils and discharged waters. - Ufa: VNIISPTneft , 40 pp.) Requires individual research and is often unsuccessful.

The output of boundary layers is known either from the terminal phase divider or directly from the sump (for example, AS No. 2042375) and their separate processing (for example, according to AS No. 1761187 - mechanical failure, AS No. 1044759 - thermochemical, AS No. 1047491 - acoustic), but there is no cardinal solution to the problem.

An intensive search is under way for the separation of persistent oil emulsions by:

- hydraulic effects (for example, the technique of creating a highly developed turbulent flow regime when the emulsion passes through a Laval nozzle (RF patent No. 2045982));

- pass the emulsion through the water layer (“flushing” of the emulsion - A.S. No. 189976, No. 528102);

- vibration effects with different frequencies (A.S. No. 957933 - 10-130 Hz, A.S. No. 1699494 - 500-1000 Hz, AC No. 1047491 - acoustic frequency, A.S. No. 700163, 749399 - high-frequency field, and in the dissertation of Khakimov BC “Development of the technology for the destruction of persistent oil emulsions by high-frequency electromagnetic fields in oil fields” - Ufa, BSU, 1984) - super-high-frequency (0.15-13 MHz);

- exposure to a magnetic field (AS No. 495040, RF patent No. 2095119);

- the addition of a diluent, for example, gas condensate (Oilfield business, 1978, No. 10, p. 22-23);

- exposure to an electric field (see, for example, the dissertation of Ph.D. Shvetsov “Intensification of the process of oil demulsification using electrocoalescenters with a perforated screen” - Ufa, 1985, as well as the work of Gershuni SM, Leibovsky MG Equipment for dehydration and desalting of oil in an electric field. OI “Chemical and oil refining engineering.” M.: TSNITI Himneftemash, 1983, 33 pp.)

However, there is no cardinal solution to the problem. Known methods are either unnecessarily expensive, or unreliable, or give rise to new problems (for example, in-pipe demulsification has caused brook corrosion of pipes). Without a clear preliminary definition of the boundaries of efficiency, most technologies are effective in some cases and not in others (for example, using venturi tubes, flushing emulsions, etc.).

Desalting of oil is carried out either by washing the emulsion with fresh water, or (since the carrier of salts is water) - by deepening the dehydration of oil. The effectiveness of the first method is closely related to the dispersion of the oil phase during washing. Therefore, it is not always effective and requires a large flow of fresh water. The second method involves multi-stage dehydration and therefore cumbersome and expensive.

Reducing the bulkiness of oil treatment plants can be achieved by combining different processes in one device. So, at the stage of preliminary dehydration and oil separation, three-phase separators appeared. Prior to the appearance of the latter, it was believed that the evolved gas interferes with the deposition of microdrops of water. Cases of deep dehydration in three-phase separators showed the fallacy of such ideas. So, at the central processing unit of the Severo-Orekhovskoye field (Sobol-Megion joint venture) three-phase separators ensure the quality of dehydration to a residual water content of less than 0.1%, while a residual oil content in the discharged water (5-6 mg / l) is enough even to discharge it into the sea without additional treatment (there is a test report). The experience of obtaining clean water directly during oil dehydration is described in an article by Zaitsev Yu.V. and others. "Combining the preparation of oil and water - the basis of field water treatment" - HX, 1972, No. 4, p.1.

To combine the processes of gas separation and purification, droplet separators built into the separator or remote (with the discharge of trapped oil into the separator) are widely used.

Dehydration and desalination combined with deep oil dehydration. We do not know how to combine the processes of dehydration, degassing and washing oil with fresh water.

3. SUMMARY OF THE INVENTION.

The processes of separation, dehydration of oil and purification of produced water could be carried out in one apparatus, if not for the threat of crushing of water droplets during the preliminary vacuum treatment. Because of this threat, in 1989, when VNIISPTneft developed a technology for deep oil separation at a semi-industrial stand, oil that was heavily watered (75-80% water) entering the stand from the oilfield pipeline was dehydrated beforehand under a pressure of 0.2-0.25 MPa. The accumulation of the required amount of dehydrated oil took 2.5-3 days. The course of sludge was estimated by a water-meter glass. But it was necessary to assess the deterioration of the subsequent oil sludge in commodity tanks, and in the spring of 1990 they decided to set the oil-field water-gas-oil mixture through a destabilizer (preliminary vacuum processing device) of the flow. Imagine our surprise when instead of a red emulsion black oil appeared in a water-measuring glass, followed by pure water. Subsequent analysis showed the acceleration and deepening of water separation more than 10 times. The boundary layer characteristic of control samples did not form after vacuum treatment. A special experiment on pumping the emulsion that has just been collected in the usual way from one tank to another through a destabilizer at the inlet with synchronous sampling for sediment at the inlet and outlet showed that the vacuum treatment efficiency is maintained over the entire water cut range: from 99% (bottom layer) to 1% (surface layer). The transition to a set of emulsions with the simultaneous discharge of separated water allowed us to reduce the time of the set of dehydrated oil to 4-5 hours, and in the subsequent operation of the stand (1990-1992), the set of dehydrated oil was made only in this way. The influence of vacuum treatment on the quality of the separated water was assessed during the operation of treatment facilities in Urai (UPC “Uraineftegaz”). The average daily oil content in the water discharged from the oil treatment unit was 6%, the instantaneous value reached 30%. And regardless of the initial oil content purification quality was in the range of 5-6 mg / l.

Model experiments at many DSPs in Bashkiria, the Komi Republic, Perm and Tyumen regions showed that preliminary vacuum treatment can destroy any emulsion, but the necessary pressure for vacuum processing is different: if fresh emulsions and low-viscosity oils at atmospheric outlet pressure have enough inlet pressure 0, 2-0.25 MPa, then the pressure of 0.5 MPa on the heavy oil of the Perm Region was insufficient, and it took a long time to destroy the long-standing boundary layers enriched with impurities at the central processing center in the Uraineftegaz TPP 1 MPa. If for the purpose of oil separation at KSU it is enough to provide a supercritical regime, then for the guaranteed destruction of the emulsion a new criterion is needed.

A feature of the work of destabilizers in oils and oil emulsions is the dependence of the recorded vacuum (hence, the degree of supersaturation of oil with gas) on the pressure at the inlet of the destabilizer. The degree of supersaturation of oil with gas very strongly (exponentially) affects the intensity of nucleation. Apparently, the restriction of the inlet pressure necessary for the destruction of emulsions is associated with the size of the minimum microdroplets of water and the distance between the two formed nuclei. For example, the last should be no more than the first. Then the destruction of the hardening shells on the smallest microdroplets of water will be ensured. The space in oil, not covered by gaps in a given period of time, under the influence of surface tension forces passes into a ball - i.e. a drop. In this case, the torn armor shell passes to the surface of the formed drop. Subsequent nuclei are formed already inside it and the droplet increases in size due to the released gas.

The nucleation rate also depends on the surface tension at the liquid-gas interface, decreasing with an increase in the latter also exponentially. Since the surface tension at the water-gas interface is approximately two times greater than at the oil-gas interface, the nucleation rate in water is millions of times lower than in oil. Therefore, when vacuum processing the emulsion, oil, not water, boils, and when the water content of the emulsion is greater than when the balls are packed tightly (26.6%), it reverses: instead of the water-in-oil emulsion, an oil-in-water emulsion is formed. At the same time, being saturated with microbubbles of gas, microdroplets of oil with a cross-layer transferred to them quickly float. In the absence of a bottom discharge due to the accumulation of water, any volume into which the emulsion enters after vacuum treatment is filled with water, facilitating phase reversal.

At the same time, saturated with gas bubbles, with armor shells transferred to them, microdroplets of oil quickly float up, and boundary layers are not formed.

For a model experiment with a bottom entry of a vacuum-treated sample into a limited volume (with the static formation of the surface layer), two results are characteristic:

the residual water content of the formed oil layer is either less than 2%, or corresponds to a dense packing of balls - 26.6%. The latter is the result of the capture of water by the floating micro-droplets of oil during the reluctant coalescence of the latter. It indicates that even after a 12-hour sludge, the boundary layers do not pass into the water phase.

The proposed hypothesis allows us to explain all the available experimental facts, but it is difficult to create a reliable mathematical model, which is being worked on.

A variety of conditions determines the ambiguity of possible solutions. From here follows the multi-link claims.

The method of oilfield preparation of oil includes the supply of the initial oilfield mixture to a three-phase separator, possibly an end phase divider — KDF, removal of separation products. According to the invention, the emulsion fed either to the separator or to the KDF is passed through a preliminary vacuum treatment unit of the flow — a destabilizer — in the form of a Venturi pipe with an elongated neck in the mode:

P ₁ ≥ P ₂ + P _1-2 + Δ P ₁

P ₂ ≤ P _s1 -Δ P ₂ ,

where P ₁ and P ₂ - pressure at the inlet to the destabilizer and at the outlet of it;

Δ P _1-2 - pressure loss on the depulsator when operating in continuous mode;

P _s1 is the pressure of oil saturation with gas at the inlet to the destabilizer;

Δ P _1,2 - pressure costs for the destruction of the emulsion, determined, for example, experimentally.

This method is suitable when there are no problems with coalescence of pop-up microdrops. In particular, it is applicable for deepening and accelerating the dehydration of existing plants during their reconstruction.

The effectiveness of the method can be significantly increased if additional conditions are imposed on the phase extraction from the CDF.

For provide for the preliminary separation of the initial gas-liquid mixture in the terminal phase divider and their separate entry into the apparatus (s). In this case, the gas phase is passed through an adjustable Laval nozzle before entering the apparatus, the water phase through a self-flotation treatment destabilizer, and the oil phase through a destabilizer operating in the above mode. The passage of gas through the Laval nozzle guarantees the vacuum treatment of accidentally trapped oil, the passage of water through the destabilizer deepens its purification from oil droplets. Since the conditions necessary for the destruction of the emulsion are the most severe, the operation of the remaining nozzles is provided with a margin.

Moreover:

not the entire emulsion is subjected to vacuum treatment in the indicated mode, but its most stable part, taken either from the CDF or from the three-phase separator near the phase boundary, and then pumped through the destabilizer in the indicated mode with the vacuum-treated emulsion being returned either directly to the apparatus or via the remote a precamera for any effect intensifying phase separation;

a longitudinal - along the streamline - magnetic field is superimposed on the zone of intense flow inhibition in the destabilizer.

The deceleration of the flow reaches hundreds of g (where g is the acceleration of gravity). At the same time, microdroplets of water freed from the shells, like passengers in a sharply braked bus, will collide. The efficiency of the collision of polar water droplets can be increased many times by ordering the arrangement of charges of microdrops along streamlines. Then, in addition to the inertial approach, the force of electric attraction of different charges will be added. A method of magnetic and electromagnetic processing of emulsions is known. But in methods known to us, magnetic field lines are perpendicular to the flow. Here, it is assumed that magnetic field lines coincide with streamlines, for example, due to the winding of a destabilizer made of non-magnetic steel. The differences are in the location of the magnetic field.

Let us now consider the problem of coalescence of micro droplets of oil at high water contents of the initial emulsion. It is known that turbulence enhances the coalescence of microdrops, but at the same time leads to their fragmentation. It is believed that a certain level of oil droplets corresponds to a certain level of turbulence. The efficiency of coalescence also depends on the concentration of microdrops. Hence the need to collect microdrops, and then transport them in a limited turbulent mode. Such a method and device for its implementation is available - it is an inclined tube water separator, but here, unlike the prototype, the oil emulsion is destroyed by vacuum treatment; the other and the purpose is not water withdrawal, but the collection and coalescence of vacuum-treated oil microdroplets. Hence, the vacuum-treated emulsion is passed through a layer of settled formation water along an ascending inclined surface before entering the final separation surface.

The emulsion previously washed in the formation water is passed through a layer of fresh hot water.

When rising along an inclined surface, the oil component, initially having a foam structure, coalesces, forming gas shells. Therefore, the specific gas load per unit surface at the exit of the foam structure to the surface is higher than the drop by drop allowance. These drops must be precipitated. The best conditions for dropping are formed during the turbulent movement of gas above a free surface. In addition, optimization of the conditions is required for the deposition of relatively large drops of water captured by the gas-oil flow rising along the inclined surface. Therefore, the pre-washed emulsion is additionally subjected to dynamic thin-layer sedimentation when it flows to the surface of the final section along the inclined chute in the mode of pressureless movement with a surface turbulent associated gas flow, while the treated gas is completely or partially introduced above the decay surface during the formation of the pressureless flow.

All of the above techniques are accompanied by in-depth degassing of oil. Therefore, in the case where the possibility of gravity extraction of oil and water is resolved (for example, when lifting 3-phase separators to a sufficient height, or when collecting marketable oil and purified water in the horizontal tanks below, it becomes possible to ensure the preparation of oil and water in one unit, including its degassing to a normalized saturated vapor pressure.

The final phase separation is carried out under a pressure of 0.005 MPa.

The solution has the following drawback: a decrease in atmospheric separation pressure is associated with the loss of oil of a portion of the propane-butane fractions, which strongly affects the viscosity of the oil and, consequently, its dehydration. This disadvantage can be eliminated by a known method of diluting oil with gas condensate (see Zarinov A.G. et al. “A method of intensifying the process of destruction of oil-water emulsions. Oilfield business, No. 10, 8, 1978, p.22-23). The fears are all the more justified because the method of oil separation with preliminary vacuum treatment according to the results of acceptance tests doubles the amount of gas taken while increasing its density by about 10% - i.e. in-depth selection is due to a deeper extraction of gases through propane inclusive. The addition of condensate to the inlet of the destabilizer will reduce the permissible vacuum and may worsen the destruction of the emulsion during vacuum treatment. The addition to the vacuum-treated mixture is fraught with the risk of increasing the pressure of saturation of oil with gas above the allowable limit - it is known that gas condensate contains many dissolved gases, lighter than propane. The situation is correctable when gas condensate is introduced into the emulsion. In this case, before mixing with the vacuum-treated emulsion, the gas condensate is subjected to preliminary vacuum treatment in an individual destabilizer and introduced into the stream of the vacuum-treated emulsion in the form of a gas-liquid mixture.

These techniques will not only reduce the viscosity of the oil-water emulsion, but also adjust the gas sampling towards a deeper extraction of light gas components (see, for example, AS No. 1326605, 1544790). Gas condensate is obtained by compressing the gases of the last stage of degassing and cooling it. When starting the condensate technology may be small. In the future, it will accumulate during the recycling of propane-butane fractions until the amount stabilizes at some individual level for each oil (up to 5-6% of the oil volume. HX, 1990, No. 8), which is enough to reduce the viscosity by tens time. The high condensate content will allow in many cases to reduce the temperature of the necessary oil heating or even completely extinguish the furnace, at least in the warm season, and eliminating hydraulic losses on the furnace will create the necessary pressure reserve for vacuum processing.

The question of means of mixing a vacuum-treated emulsion with condensate is closely raised. The fact is that vacuum-treated oil is a structure saturated with gas bubbles. In case of excessive turbulization, for example, when a vacuum-treated sample enters a closed volume with an incident jet, a thousand-fold oil pollution of the water occurs compared to the bottom inlet, i.e. microdroplets of oil lose gas and float extremely slowly. We need to separate the water clean. Therefore, it is best to introduce additives (condensate, formation or fresh water, including heated water) directly into the destabilizer into the flow in the region of moderate velocities with velocities close to them. When surfacing and further moving along an inclined surface, everything mixes well enough. From here follows a destabilizer - possibly with a pre-chamber and an adjustment unit, which is a nozzle with a confuser having a taper angle of 60 to 120 ° and paired with a radius R = 0.2 Dr with a cylindrical neck with a diameter Dr, length L = (1.5-2 , 5) Dr and a diffuser with an effective opening angle that smoothly or stepwise varies from 6-10 ° to 15-20 °, and an output diameter that provides a speed of not more than 1 m / s. According to the invention, in the range of speeds of 3-5 m / s, a streamlined cross with a central streamlined body is also integrated into the diffuser, inside of which channels for supplying additives with a speed of not more than 5-7 m / s in the flow direction are made, and either an annular chamber is located outside with holes for supplying additives, or there are holes for supplying water surrounding the diffuser from the outside with the recessed installation of the latter.

An annular chamber is not needed when serving as an additive to the settled formation fluid during recessed mounting of the diffuser. Such a need may arise when washing low-water emulsions. At an emulsion flow rate of 3-5 m / s at the additive supply point, due to the further transfer of kinetic energy to potential, sufficient pressure is created for supplying and at the same time, turbulence caused by the flow around the input device is weak and does not lead to gas loss with microdroplets of oil. The limitation of the rate of supplementation is due to the same considerations.

Washing the emulsion along an inclined surface can be arranged inside a three-phase separator. From here follows an oil treatment unit, including preliminary gas sampling, possibly emulsion heating furnaces, a three-phase separator, divided by an oil overflow partition into two compartments - a sludge and oil drain, an end separation unit and water purifiers. According to the invention, the three-phase separator is equipped with a destabilizer at the inlet of the emulsion into the apparatus, the inlet pipe is transferred to the lower generating capacitance at a distance of 0.5-1 m from the partition, above the inlet of the emulsion into the apparatus at a height of 0.5-1 m it is also welded with the lower end to the partition and to the walls of the tank, an inclined trough facing upside down, the open side down, the lower end of which is welded to the oil-septum wall and, possibly, to the walls of the tank, the upper end of the trough along the upper generatrix does not reach the elliptical bottom of the tank a distance of 0.5-1 m at a height of 0.1-0.2 m higher than the height of the upper edge of the oil-septum for foamy oils or not higher than it for non-foamy, the oil sludge compartment of the three-phase separator in its upper part is equipped with two rows of partitions with a step of 1 5-2 m: one row with a lower edge at the level of the upper edge of the oil-septum septum, and the upper one at a level not exceeding half the clearance above the septum, and the second row, offset from the first by 0.3-0.5 steps, has the shape of a segment with a lower generatrix not lower than half the clearance above the septum; and when performing end separation in a three-phase separator, the oil-drain compartment is equipped with a spatial step tray, and the existing treatment facilities for cleaning the discharge of oil from the three-phase water separator have the ability to switch to the buffer tank or reserve mode.

Explain the limitations of the claims. The location of the entrance to the separator and the lower end of the trough should prevent the emulsion from leaving the tray: above this section is the outlet of dehydrated oil, and this exit can cause a breakdown in the quality of the oil preparation. Therefore, the input area is reliably isolated, the lower end of the gutter is welded. In this case, the circulation that occurs when the emulsion is introduced, draws in water from the bottom of the tank, blocking the possibility of breakthrough of non-standing water.

The restrictions imposed on the exit of gas and oil from the gutter are due to the following considerations. The release of gas shells creates disturbances at the oil-gas interface. They are useful for oil dehydration. But if oil is prone to pricing, then the gas, coming to the surface, will form a foam. After exiting, he rushes to the bottom of the tank, and will drive this foam onto the wall, contributing to its destruction.

The input of the upper partitions in the settling zone of the separator is multifunctional. First of all, it is an obstacle to the foam and a prerequisite for its destruction by the gas flow. Secondly, oil is forced to dive slightly under the partitions, and the effect of periodic shaking is created, which is very useful for oil dehydration. And finally, the gas is forced to constantly change the direction of movement with the creation of vortex regions and the magnitude of the speed due to the difference in the area of the partitions. This contributes to the deposition of fine droplets of oil suspended in the stream. The drops of oil captured during defoaming, occupying the lower part of the gas flow, will be deposited on the partition with a sharp rise in gas up. Limitations of the altitude of the plate edges excludes gas flow without turns (in a straight line).

Finally, about the changes in the drain compartment. In existing three-phase separators, settled oil, pouring over the edge of the septum, falls on the free surface of the oil, trapping gas. With further oil getting into the end separator, there is nothing wrong with this; most likely, the presence of gas bubbles is even useful. But the presence of free gas in commercial oil is unacceptable. The oil sump compartment is small in volume, therefore, a conventional tray guaranteeing gas-free oil drainage to a free surface is difficult to perform gas-free oil drainage to a free surface, especially with unavoidable level fluctuations. Changing the direction of flow in the proposed embodiment when oil is transferred from a longitudinal tray to a transverse one reduces the speed, and therefore gas capture, and a two-story descent of oil reduces the length of the tray, the opposite slope of the transverse trays facilitates the placement and operation of the level sensor that controls the drain.

The three-phase separator has a drawback - the inability to control the dynamic sedimentation of water by changing the angle of inclination of the surface due to more important conditions for entering and leaving the inclined section. In addition, it is practically impossible to combine oil dehydration and its washing with fresh water in one capacitive type apparatus, but in dynamic conditions, when the speed of diffusion mixing is less than the speed of the supplied water, it is possible. Exactly the same as with dissolved salts, the situation is with temperature. But before serving hot fresh water, it is necessary to withdraw as much salt formation water as possible. Therefore, the removal of produced water must be performed in countercurrent with rising oil, as is done in inclined pipe water separators during preliminary water discharge. Therefore, a three-phase separator of a capacitive type should be preceded by a section for raising the emulsion to it, such as a pipe inclined device for preliminary water discharge, only instead of a section for draining gas and oil, which generates pressure fluctuations due to the formation of gas shells, there will be an entrance to the tank. The need for partial dehydration of oil before mixing with fresh heated water requires the organization of associated drainage of produced formation water. In this case, the problem arises where to take it: for injection into the reservoir, a section of upstream sediment of a significant volume is required, that is, an increase in the length of the prechamber, which can multiply the area for the entire installation; supplying it for purification to a three-phase separator requires raising the end of the inclined section above the oil level in this separator to compensate for the light weight of the liquid column in the inclined part due to the presence of a gas-oil mixture and a section with lighter fresh water compared to practically pure produced water on the way to three phase separator. The descent of oil into the three-phase separator can be carried out through a system of two inclined trays, as proposed in the parallel application "Method for self-flotation treatment of produced water and means for its implementation."

In inclined water separators with the opposite direction of the water and gas-oil phase, the maximum rate of reverse water movement is observed in the area of input of well production into the pipe water separator, which poses a risk of capture of the introduced oil by water. It can be reduced by looping around the entry point, connecting it with the upper end on the lower generatrix of the inclined pipe, and the lower one on the upper. For the treatment of the water discharged through the looping, the latter is tilted in the same direction as the water separator. The capture of the introduced oil by the drained water can be further reduced by introducing the vacuum-treated emulsion through a vertical pipe entering the section of the water separator, inclined at an angle of about 45 ° to the horizon, and protruding into the introduction section above its axis of symmetry. The end of the pipe has an oblique cut parallel to the generatrix of the section.

Hence, the inclined portion of the movement of the introduced vacuum-treated emulsion is taken out of the three-phase separator and is made in the form of a pipe inclined water separator connected in its upper part to the separator through a system of two inclined trays, the product inlet to the three-phase separator is made in the upper part of the elliptical bottom through two large diameter pipes and the inclined water separator itself is made with an inlet section inclined at an angle to the horizon of about 45 ° and provided with looping around the input region; at the same time, the inclined water separator in its lower part is equipped with a water retention section with a slight slope to the horizon, and in the upper part, when preparing commercial oil, by supply of fresh heated water.

MODE FOR CARRYING OUT THE INVENTION

The first paragraph of the claims does not impose special requirements on the apparatus necessary for oil dehydration, and the described method can be implemented both at the entrance to the apparatuses adapted for withdrawing the separated water, and (with a residence time of less than 20 minutes) in cases when the equipment is located within reach of 0.5 hours (the time of guaranteed preservation of the effect). That is, the partially dehydrating effect of vacuum treatment will be preserved if there is a sump, for example, a tank, behind the separator, which is not intended for water outlet. The main thing at this point is the vacuum treatment mode.

To determine the maximum permissible pressure at the inlet and outlet of the destabilizer, three values must be determined.

For a given emulsion, these values can be found experimentally when testing the destabilizer model. A research program has been developed, consisting of three stages:

- checking the self-similarity of the mode and determining the value Δ P _1-2 ;

- checking the sufficiency of the locking mode and determining the value of Δ P ₂ ;

- determination of the amendment Δ P ₁ .

An experimental setup for model research has been developed. But this information is know-how and their publication is highly undesirable.

The second paragraph of the claims (in the presence of CDF) allows you to stabilize the pressure at the inlet to the destabilizers and fully use the advantages of self-flotation water treatment. The experimental fact is important here that breaking down the emulsion requires the highest inlet pressure. In this case, the gas nozzle, as a rule, operates in the mode of sound locking of the channel, ensuring independence of the inlet pressure from backpressure oscillations, and at the same time subjecting the captured oil to vacuum treatment. The pressure in the neck of the water nozzle will, as a rule, be greater than in the neck of the nozzle for breaking the emulsion, and this provides a finer cleaning of produced water, and, finally, the method will unload the emulsion nozzle and provide the ability to change the degree of water content of the emulsion. The implementation of this method will require the optimal input of the components of the original stream into the apparatus. Since the oil layer adjacent to the gas-oil interface in the CDF is practically dehydrated, it is best to inject gas at the site of formation of the free surface of the liquid to clean it from suspended oil droplets. The exception is the cases of an abnormally small amount of dissolved gas in oil (observed if the gas consists mainly of methane and ethane), when the conditions of preliminary dehydration when lifting to the apparatus may require partial gas injection at the oil lifting section to increase the speed, and, therefore, reduce layer thickness of rising oil. And finally, vacuum-treated water is best introduced at the beginning of the movement of separated water, and if this is not possible (for example, when the emulsion is fed under an inclined trough inside the container), then together with the vacuum-treated emulsion.

The third method, involving the vacuum treatment of the most stable part of the emulsion, when implemented, requires solving the issue of intermediate processing and the place of introduction of the vacuum-treated emulsion. The following options are possible here:

- the vacuum-treated emulsion is fed into the stream of raw materials supplied for dehydration, immediately before entering the apparatus;

- a vacuum-treated emulsion is fed directly to the apparatus into the water layer (for washing) in the area of the main part of the emulsion entering the apparatus;

- the vacuum-treated emulsion is mixed with a solvent (condensate) or heated water, washed when advancing to a prechamber located above a three-phase separator in the immediate vicinity of it, is divided into phases, and then (possibly through hydraulic locks) each phase is supplied in 3 phase separator. At the same time, a well-known variant of supplying the separated oil phase to the water layer and water to the oil layer is also possible.

- Oil, dehydrated in the removal chamber, is pumped, in whole or in part, in small doses into marketable oil to prevent the accumulation of boundary layers or into the incinerator.

The choice of option is individual and should be made in each case based on model tests.

The technical feasibility of magnetic processing (fourth point) is not in doubt. At present, a glass model of the destabilizer has been prepared and an annular magnet worn on the model has been found. It is supposed to evaluate the effect of the magnetic field on the strength of the emulsion and its dehydration as soon as possible. After studying the influence of a constant magnetic field, it is planned to wind a winding on the model and test the effect of the intensity of various magnetic fields on dehydration. Test results will be sent to you during the consideration of the application.

The fifth method is based on an experiment conducted from October 11 to October 19, 2000 at BPS No. 89 of the Ufaneft Oil and Gas Production Complex of Bashneft Oil and Gas Complex, which showed that vacuum treatment accelerates oil dehydration by about 1.5 times compared to throttling, and additional flushing accelerates dehydration by another 2-3 times.

The need for preliminary sufficiently deep dehydration of saline formation water requires stabilization of the formation water front in space, which, given the variability of the amount of released water, requires regulation of its flow. At the same time, a self-adjusting technology is practically excluded due to the dependence of the pressure at the place of water drainage from variable gas evolution. Therefore, regulation of water drainage is necessary. But then the problem arises of the source of the control signal. The produced water differs from the supplied fresh density and temperature. But the boundaries of their separation of properties cannot be clear due to diffusion. Moreover, due to the vortices accompanying the passage of gas shells, turbulent diffusion is also possible. To ensure the presence of an area occupied only by fresh water, in these conditions it is possible by ensuring the supply of fresh water at a speed not less than the speed of turbulent diffusion, but the outflow of fresh water into the salt water creates a threat of a breakthrough after it and oil, which is unacceptable: oil should leave the inclined plot on a substrate of fresh water. We are not aware of either a theoretical or experimental solution to this problem. At the same time, the problem of washing oil from crystalline salt in some fields confined to salt formations is very acute. Currently, negotiations are underway with the Institute of YuganskNIPIneft, which is interested in solving the problem, on the organization of such studies. In the meantime, it is planned to install three sets of density and temperature sensors: below the place of fresh water supply, above it and before the oil and water enter the inclined tray from the lift side to control the water drain.

Dynamic sedimentation of oil with descent along the tray was carried out during tests at the UPC “Uraineftegaz” CCC of the technology of self-flotation treatment of water directly discharged from oil treatment plants. Due to heavy contamination with mechanical impurities, oil collected from the entire region by many booster pumping stations is prepared only with a constant daily discharge of 6% of oil from sedimentation tanks with water. The instant oil content in the water reached 30%. To all modes, regardless of the initial contamination, the water after treatment remained clean (5-6 mg / l of residual oil products). The analysis of the selected oil for residual water content was not carried out.

The invention proposes the use of a three-phase separator as a KSU. There are no technical problems with such a translation, with the exception of two points that were previously reported:

- the problem of the delivery of separated oil and water is solved in small fields without problems by gravity dumping into buffer tanks, followed by pumping them directly to consumers or through ground tanks. In remote fields, it may be advisable to use the evolved gas as fuel for power plants. A slightly increased arrangement of three-phase separators is useful for the preliminary preparation of well products for separation when passing a pipe water separator on the way to the separator.

The problem of the deterioration of water separation due to the loss of propane-butane fractions is partially solved by going through the process of droplet enlargement with the joint movement of gas and oil along an inclined surface.

The invention involves the supply of condensate to a vacuum-treated emulsion with preliminary vacuum treatment in an individual destabilizer. The method enhances the action of the known methods of supplying condensate to improve the quality of separation (A.S. No. 1326605) and oil dehydration (Zaripov A.G. et al. Method for intensifying the process of destruction of oil-water emulsions. Oilfield business, No. 10, 1978, p.22- 23) by increasing the content of the necessary fractions during the recirculation process and by increasing the mass transfer surface with the introduction of boiling condensate.

The fact is that when equilibrium is reached, the amount of component remaining in the oil is proportional to the amount of component in the system. Artificial input of propane-butane fractions increases the amount of heavy gases in the system and, consequently, in the liquid phase. During recirculation, the system is enriched with the amount of circulating components while maintaining the overall balance.

The destabilizer for oil dehydration due to the high gas content of the liquid passing through it must have a diffuser divergence angle greater than for self-flotation water treatment, but (to reduce projectile formation) less, at least at the outlet, than the destabilizer for KSU. Since the energy losses due to vortex formation are proportional to the square of the velocity, it is highly desirable to introduce additives along the way and mix them, while preserving the gas micro droplets of oil saturation without increasing the flow rate. This requires, as the tightness of the passage area of the crosspiece diffuser with the central body increases, the corresponding expansion of the outer walls of the channel is required. The condition of continuous flow limits the angle of divergence of the walls. Therefore, the restriction of the flow should change quite smoothly. This can be achieved by performing the frontal part of the central body in the form of sharp peaks and arranging the edges of the crosspiece at an acute angle towards the oncoming flow. It is known that separation of the boundary layer in Venturi nozzles gives rise to oscillations and is accompanied by the formation of gas shells (see, for example, the book by V.V. Pilipenko, Cavitation self-sustained oscillations. - Kiev: ND, 1989, 316 pp.), Which is unacceptable in our case. Therefore, the profiling of the channel walls must be treated very responsibly. The presence of external tapering makes it possible to make a cross without an external rim, and then, inserting it into the appropriate nests, solder (scald) from the outside. After soldering the ribs, an annular chamber is welded from the outside.

An example of the design of a three-phase separator is shown in figures 1-3. In the cylindrical horizontal tank 1 there is a baffle 2, usual for three-phase separators, with a height corresponding to the maximum throughput of an unfilled pipeline. It divides the separator into two compartments - slop and drain. The settling compartment in its bottom part is equipped with two nozzles: a spillway near the spherical bottom and a vacuum-treated emulsion near the partition. Above the receiving branch pipe there is an inclined open bottom channel 3 with a length of the entire length of the settling section. Its profile is visible on the arrow A. In the upper part of the settling section there are two rows of partitions: the upper row with partitions of the segment shape 4, and the lower 5, the profile of which is visible in sections.

The presence of an oil-septum partition guarantees constant level in the settling section, but poses a risk of the intermediate layer becoming stuck, therefore, a pipe with a sampling valve is provided for the possibility of control and removal of the old layer. The pipe communicates with the drainage tank by a line with two valves to enable removal of the area between them and the connection of a mobile pumping unit for vacuum processing of the boundary layer. A gas outlet pipe with a droplet separator is located on the upper generating capacitance near the partition.

If a three-phase separator in the process circuit is connected at the oil outlet to the control unit, then in the oil drain compartment, in addition to the oil level sensor and oil drain pipe, there is nothing. If a three-phase separator is used as a KSU (this option is shown in Fig. 1), in addition to them, to prevent the capture of free gas by a flowing jet, it is equipped with a system of three trays: longitudinal 6 and two transverse symmetrical to each other 7. The transverse trays with their upper edges are welded , i.e. they form a spatial angle with an edge inclined towards the horizon to meet the flow of oil flowing down from the longitudinal tray. The slope should completely inhibit the flow and prevent oil from falling from the outer edge of the tray. All trays in their lower part are made with support legs, between which there is a cutout for oil passage. The longitudinal tray with the lower edge rests on the transverse trays. The cutout in it is made so that the oil can spread under it. Cross trays with their paws rest on the side of the tank. In this case, the upper paw is located in the region of the horizontal diameter of the tank, the lower one is below it. A gap is cut between the paws, directing the flowing oil to the lower half of the tank wall, so that free fall on the surface of the oil is excluded at any level in the oil drainage compartment.

At the outlet of the destabilizer flooded with water, the vacuum-treated emulsion is either foam or microdroplets of oil saturated with gas bubbles. Since the washing efficiency is directly related to the dispersion of the oil being washed, to prevent the microdroplets of oil from becoming larger, the destabilizer should be located as close as possible to the inlet pipe, preferably on a valve installed directly on the tank outlet pipe, which must be raised to the appropriate value for installation and maintenance of the destabilizer. The torch of the vacuum-treated emulsion, pushing water in front of itself, deviates along an inclined surface, and, being much lighter than the surrounding water, presses against it and rushes up. Microdroplets of water falling into the water, stripped from the armor shells, immediately merge with the surrounding water. The water captured during lifting during the movement is enlarged and forced out. The foam structure is destroyed by friction forces, forming a continuous oil phase saturated with enlarging gas bubbles. Trapped in a stream of water, falling into the oil layer, is crushed into large drops, which quickly settle, filtering through a layer of oil.

When gas shells break through the free surface of the oil, relatively large droplets of oil are captured, which will rapidly settle when the gas moves between partitions with a variable speed. The resulting foam will be delayed by the first septum (and when breaking through the top, by the next), and is destroyed by the gas flow and sprinkling when large drops of oil fall. Each projectile breakthrough will be accompanied by wave formation on the surface, contributing to the rapid deposition of the remaining drops of water. During its movement to the oil-draining threshold, the upper layer of oil will be forced to dive under the partitions, cleaning itself of smaller droplets, until there is almost anhydrous oil on the surface, which will overflow through the threshold into the oil-draining compartment. When overflowing over the tray, the oil spreads in a relatively thin layer and will be freed from the microbubbles of free gas. Residual gas contamination with oil droplets will be eliminated by a droplet separator at the gas outlet from the tank.

When testing the technology of self-flotation purification, the water was contaminated by boundary layers. That is why it was necessary to apply measures against the convective capture of pollution by purified water. Here, it was originally in fresh oil and contaminated with it. The experience of two years of operating a semi-industrial stand at VNIISPTneft shows that despite the breakthroughs of gas shells, the water remained visually absolutely clean after the formation of the bottom layer of 15-20 cm. The experience of operating three-phase separators at the Severo-Orekhovsky field (CJSC JV Sobol) shows that water It remains completely clean (residual oil content at the level of 5-6 mg / l) at any level of inflow.

In an embodiment of the oil treatment unit with a remote pipe water separator and associated flushing of the emulsion with fresh water, it becomes possible to individually optimize the oil treatment unit for a particular field. The fact is that the thickness of the oil layer and the mode of its movement will depend on the slope of the section, the speed of the reverse movement of water - on the water cut of the oil and its diameter, the length of the section determines the time spent in this mode.

So, the section sludge water I (see figure 4-6) has an angle of inclination of the generatrix, eliminating the capture of settled oil by water and ensuring timely removal of oil when it emerges.

Section II (introductory) due to the large angle of inclination to the horizon and the high inlet nozzle allows avoiding clogging of treated water, both by creating conditions for its free passage along the bottom of the section and preventing the accumulation of introduced oil during its evacuation.

In addition, in its rear part, the oil flow creates a local pressure drop, which contributes to the entrainment and contamination introduced with bypassed water, the input of which is located slightly lower.

Section III - oil dehydration section. Since coalescence occurs during the advancement of oil droplets in this section, the length of this section should be reduced if possible. Bypass is connected by about half when oil is dehydrated, and its diameter is selected from the condition that the process of post-treatment of water is not overturned.

Section IV - section for washing the emulsion with fresh water. The ideal balance for this section is that half of the fresh water introduced goes down and mixes with the produced water, half goes with the released oil into a three-phase separator. This section ends with a cross member 8 - a transverse section of pipe with a diameter larger than the water separator. Symmetrically to the input at a minimum distance from it, two inclined trays 9 are welded into the crosspiece, smoothly passing into incomplete pipelines connected to the capacity of a three-phase separator. In the latter, the cross-members, the baffle and the system of trays of gas-free oil drainage, discussed in the previous paragraph, can be saved. The location of the pipes of the settling compartment is changed: instead of the pipe for the input of raw materials, a pipe of purified water is placed; input of the product is carried out through two large diameter pipes in the upper half of the spherical bottom. The part of the system inclined towards the separator is designed so that, with the exception of the flat-bottom section, the turbulence does not exceed the critical point of view of droplet crushing.

Since during the implementation of the invention, any microdroplet of oil boils, increasing in volume in proportion to its gas content without increasing weight, and produced water retains its density, the driving force of the process of separation of media is much greater than that of prototypes. This determines the intensification and improvement of the quality of separation. In addition, the transition of armor shells to pop-up oil microdroplets significantly reduces the likelihood of the formation of boundary layers or, at least, significantly slows down their growth rate. The simultaneous deepening of degassing creates the prerequisites for a significant reduction in the technological chain of oil treatment plants.

Claims (15)

1. The method of on-site oil preparation, comprising supplying the initial oil-field mixture to a three-phase separator or to a three-phase separator through an end phase divider - KDF, removal of separation products - the oil phase, gas phase and water phase, characterized in that it is supplied either to a three-phase separator, or in KDF, an emulsion or an emulsion or oil phase taken from a separator or KDF is passed through a vacuum processing device — a destabilizer in the form of a Venturi tube with an elongated neck in the mode P ₁ ≥ P ₂ + P _1-2 + Δ P ₁ , P ₂ ≤ P _s1 -Δ P ₂ , where P ₁ and P ₂ - pressure at the inlet to the destabilizer and at the outlet of it; P _1-2 - pressure loss on the destabilizer when operating in continuous mode; P _s1 is the pressure of oil saturation with gas at the inlet to the destabilizer; Δ P _1,2 - the pressure on the destruction of the emulsion or oil phase. 2. The method according to claim 1, characterized in that the gas phase is passed through an adjustable Laval nozzle, and the water phase is passed through a self-flotation cleaning destabilizer. 3. The method according to claim 1, characterized in that the emulsion from the CDF or three-phase separator is selected near the phase boundary, then the pump is passed through a destabilizer. 4. The method according to claim 1, characterized in that a longitudinal, along the streamline, magnetic field is imposed on the zone of intensive flow inhibition in the destabilizer. 5. The method according to claim 1, characterized in that the vacuum-treated emulsion is passed through a layer of settled formation water along an ascending inclined surface before entering the final separation surface. 6. The method according to claim 5, characterized in that the emulsion previously washed in the formation water is passed through a layer of fresh hot water. 7. The method according to claim 5 or 6, characterized in that the pre-washed emulsion is additionally subjected to dynamic thin-layer sedimentation when draining to the surface of the final section along an inclined tray in a pressure-free mode with a surface turbulent associated gas flow, while the gas is passed through an adjustable Laval nozzle and fully or partially introduced over the surface of the decline in the formation of a pressureless flow. 8. The method according to one of claims 1 to 6, characterized in that the final separation of the phases is carried out under a pressure of 0.005 MPa. 9. The method according to claim 1, characterized in that gas condensate is supplied to the emulsion treated with vacuum, while before mixing with the emulsion the gas condensate is subjected to preliminary vacuum treatment in an individual destabilizer and introduced into the emulsion stream in the form of a gas-liquid mixture. 10. A destabilizer, which is a nozzle with a confuser having a taper angle of 60 to 120 °, and mated with a radius R = 0.2Dr with a cylindrical neck with a diameter Dr, length L = (1.5-2.5) Dr, and a diffuser with effective opening angle, smoothly or stepwise varying from 6-10 ° to 15-20 °, and an output diameter that provides a speed of not more than 1 m / s, characterized in that a streamlined cross is built into the diffuser in the speed range 3-5 m / s with a central streamlined body, inside of which channels are made for the supply of additives with a speed of not more than 5-7 m / s in in the flow direction, and an annular chamber with openings for supplying additives is located outside. 11. The destabilizer according to claim 10, characterized in that it has a pre-chamber and an adjustment unit. 12. Oil treatment unit, including a gas pre-sampling unit, a three-phase separator, divided by an oil overflow partition into two compartments - a sludge and oil drain, an end separation unit and water purifiers, characterized in that the three-phase separator is equipped with a destabilizer at the emulsion inlet to the apparatus, the inlet pipe is transferred on the lower generatrix of the tank at a distance of 0.5-1 m from the partition, above the emulsion inlet to the apparatus at an altitude of 0.5-1 m, the inclined welded bottom end to the partition and the walls of the tank the forehead turned upside down, the open side down, the lower end of which is welded to the oil-septum septum, the upper end of the trough along the upper generatrix does not reach the elliptical bottom of the tank at a distance of 0.5-1 m in height, 0.1-0.2 m above the height of the upper edge of the oil-septum partition or not higher than it, the oil sump compartment of the three-phase separator in its upper part is equipped with two rows of partitions with a step of 1.5-2 m: one row with a lower edge at the level of the upper edge of the oil-septum, and the upper one at the level of above half clearance above the septum, and the second row, offset from the first by 0.3-0.5 steps, has the shape of a segment with a lower generatrix not lower than half the clearance above the septum. 13. Installation according to claim 12, characterized in that when performing the final separation in the three-phase separator, the oil drain compartment is equipped with a spatial step tray, and the existing treatment facilities for cleaning the oil and water discharged from the three-phase separator can be switched to buffer tanks or reserve mode. 14. Installation according to claim 12, characterized in that it has an emulsion heating furnace, and an inclined trough is welded with a lower end to the oil-septum partition and the walls of the tank. 15. Installation according to claim 12, characterized in that the inclined portion of the movement of the injected emulsion treated with vacuum is moved outside the three-phase separator and is made in the form of a pipe inclined water separator connected in its upper part to the separator through a system of two inclined trays, the product inlet a three-phase separator is made in the upper part of the elliptical bottom through two large diameter pipes, and the inclined water separator itself is made with an inlet section inclined at an angle to the horizon of about 45 ° and equipped with a looping DC input area, wherein the inclined dehydrator in its lower portion provided with a section dootstoya water with a small inclination to the horizontal, and the top - a supply of fresh preheated water.

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