EA003315B1 - System for producing de-watered oil from an underground formation - Google Patents

Abstract

1. System for producing de-watered oil from an underground formation to the surface, which system comprises -a production well extending downwardly from the surface and having an inlet below the surface; -a reception well penetrating the underground formation and capable of receiving well fluid therefrom, wherein the downstream part of the reception well comprises a substantially horizontal or inclined section for primary oil/water separation of the well fluid ; -a water discharge system having an upstream end that is capable of receiving during normal operation liquid from the lower region of the downstream part of the reception well; and -a secondary underground oil/water separator, characterised in that the secondary separator has an upstream end that is capable of receiving during normal operation liquid from the upper region of the downstream part of the reception well, the secondary separator having an outlet for de-watered oil that is in fluid communication with the inlet of the production well and an outlet for a water-enriched component that is in fluid communication with the water discharge system. 2. System according to claim 1, wherein the water discharge system comprises means to inject the liquid from the lower region and the water-enriched component into an underground formation. 3. System according to claim 1 or 2, further comprising a connection well, wherein the connection well has an inlet arranged to receive liquid from the lower region of the downstream part of the reception well, and an outlet in fluid communication with the water discharge system. 4. System according to claim 1 or 2, wherein the water discharge system comprises a water discharge well that is a branch of the reception well. 5. System according to claim 1 or 2, wherein the water discharge system comprises a water-discharge well of which the slope declines in the direction of fluid flow. 6. System according to any one of the claims 1-5, further comprising an additional reception well arranged to receive well fluid from the underground formation, wherein the downstream part of the additional reception well is in fluid communication with the downstream part of the reception well. 7. System according to any one of the claims 1-6, further comprising underground measurement equipment to measure a characteristic of a fluid at a certain position in the system. 8. System according to claim 7, wherein the characteristic is a concentration of a component in a fluid. 9. System according to claim 7, wherein the characteristic is the vertical level of an interface between layers of different components of the well fluid at a certain position in the system. 10. System according to any one of the claims 1-9, further comprising means to control the flow of a fluid at a certain position in the system. 11. System according to any one of the claims 7-9, wherein the system comprises means to control the flow of a fluid at a certain position in the system, and wherein data obtained from the underground measurement equipment is used as input for the means to control the flow of a fluid. 12. System according to any one of claims 1-11, wherein the secondary underground oil/water separator is selected from the group comprising a cyclone, a coalescer, or a static separator. 13. System according to claim 12, wherein the secondary separator is a static separator which is arranged in a separation chamber, and wherein the height of the separation chamber is larger than the thickness of the dispersion band that is formed therein under normal operation conditions. 14. System according to claim 13, wherein the static separator further comprises a flow distributor means, arranged to distribute at a predetermined vertical position the well fluid received through the separator's inlet over the cross-sectional area of the separation chamber. 15. System according to claim 13 or 14, wherein the static separator further comprises a level detector means and a flow control means in order to maintain during normal operation an interface between two liquid layers at a predetermined level. 16. System according to claim 13, wherein the static separator further comprises a stack of vertically spaced apart inclined plates, wherein between each pair of neighbouring plates a separation space is defined; -a substantially vertical inlet conduit communicating with the separator's upstream end, which inlet conduit traverses the stack of plates and is arranged to receive the well fluid at its lower end, and is provided with one or more outlets each of which opens into a separation space; -a substantially vertical oil collection channel having an oil outlet at its upper end communicating with the separator's outlet for de-watered oil, which oil collection channel has one or more oil inlets, each oil inlet being arranged to receive fluid from the uppermost region of a separation space, wherein at least the plate immediately below each oil inlet is provided with a vertically upward pointing baffle; and -a substantially vertical water collection channel having a water outlet at its lower end communicating with the separator's outlet for the water-enriched component, which oil collection channel has one or more water inlets, each water inlet being arranged to receive fluid from the lowermost region of a separation space, wherein at least the plate immediately above each water inlet is provided with a vertically downward pointing baffle. 17. System according to claim 16, wherein the inclined plates are substantially flat and arranged substantially parallel to each other, wherein each inclined plate is provided with a downward pointing baffle attached to the rim at the lower side of the inclined plate and an upward pointing baffle attached to the rim at the upper side of the inclined plate, wherein the remaining parts of the rim fit sealingly to the wall of the separation chamber, wherein the oil collection channel is formed by the space delimited by the upward pointing baffles and the wall, and wherein the water collection channel is formed by the space delimited by the downward pointing baffles and the wall. 18. System according to claim 16, wherein the inclined plates have substantially the form of funnels arranged substantially parallel to each other, wherein each funnel is provided with a central opening. 19. System according to any one of claims 13-18, wherein the separation chamber has a height/diameter ratio smaller than 6. 20. System according to any one of claims 1-19, wherein the secondary underground oil/water separator is arranged in an extended section of the production well.

Description

The present invention relates to a system for extracting dewatered oil from an underground field.

In the description and in the claims, the expression “borehole fluids” is used to refer to a fluid containing liquid petroleum products and water entering the system in accordance with the present invention from an underground field. Further liquid petroleum products will be called simply oil.

The present invention relates in particular to a system in which a well fluid can be divided underground in such a way that oil dehydrated beneath the surface of the earth enters the surface. It should be understood that the surface may also be the bottom of the sea.

International Patent Application Publication No. XVO 98/41304 discloses a system for extracting oil from an underground field in accordance with the preamble of claim 1, comprising a production well descending down from the surface of the earth and having an inlet below the surface of the earth, receiving a well passing into the underground a field capable of receiving from it a borehole current medium and having a lower part containing a substantially horizontal section and a water withdrawal system having an upstream horse Receiving the current environment of the lower region of the horizontal section, wherein the inlet of the production well adapted for passing fluid from the upper region of the horizontal section.

During normal operation of a known system, the flow of a well fluid is chosen such that the fluid is separated in the horizontal section. In the upper and lower regions of the horizontal section, fluid layers form, and an interface forms between the layers. At the lower end of the horizontal section, the fluid flowing in the lower region is a water-rich component, and the fluid flowing in the upper region is an oil-rich component of the well fluid. The oil-rich component is delivered to the surface, and the remaining water-enriched component is removed. The selectively water-rich phase is subjected to a further purification step.

The known system provides only a one-time removal of most of the water. To obtain essentially dehydrated oil with a concentration of water that is so low that it can be transported by pipeline, the known system additionally contains a separator for separating oil and water on the surface of the earth. In addition, the publication revealed that for such a one-time removal of most of the water, the level of the interface must be maintained within narrow limits.

The known system not only aims at a one-time removal of most of the water, but it also aims at achieving a low concentration of oil in the water-rich component, and if necessary, this is done at the price of a higher concentration of water produced by the oil.

The author of the application considers the behavior of a mixture of oil and water when they are separated using their own model. Calculations of the model, the results of which are discussed below with reference to figures 1, 2, reveal that under actual operating conditions in horizontal wells (including the flow rate of the well fluid, the length and diameter of the horizontal section), the concentration of water in the oil-rich component is significant. In practice, it is necessary to dewater the produced oil before it is transported from a profitably operated well, for example, through a pipeline.

From this it can be seen that to achieve the results shown in FIG. 2, 3 of the aforementioned publication of the international patent application, unrealistic operating conditions must be used.

UK Patent No. 2326895 A discloses a device for extracting a fluid containing hydrocarbons and water from an underground field using a single stage of underground separation to reduce separation equipment on the surface of the earth. The device comprises an inclined section of the well, where at least two separate paths for fluid flows are made, separated by barriers, pipes or the like. Fluid obtained from the hydrocarbon-rich part in this section of the well is directly pumped to the surface, and fluid obtained from the water-enriched part in this section of the well may be injected back into the field. At least one pump during operation is controlled by a detector, which is located close to the means of separation.

The aim of the present invention is to create a system for extracting oil from an underground field, in which oil can be dewatered before entering the surface, so that the water concentration in the produced oil is low enough, so that no further dehydration is required on the ground before transporting from a profitable well. .

Another objective of the present invention is to create a system for oil production, which can be used under actual operating conditions.

Another objective of the invention is to create a system for the underground separation of the well fluid, which is easy to operate, reliable and effective.

To this end, in accordance with the present invention, a system has been created for extracting dehydrated oil from an underground field, comprising a production well descending down from the surface of the earth and having an inlet below the surface of the earth, receiving a well passing into an underground field capable of receiving from it a borehole fluid and having a downstream part comprising a substantially horizontal or inclined section for the primary separation of well fluid into oil and water, and a system water withdrawal, having an upstream end, receiving well fluid from the lower region of the downstream part of the receiving well during normal operation, and a secondary underground separator for separating oil and water, characterized in that the secondary underground separator has an upstream end, capable of receiving fluid from the upper section of the downstream part of the receiving well during normal operation and having an outlet for dry oil communicated with the inlet the development of the production well, and the outlet for the water-enriched component communicated with the water withdrawal system.

The present invention is based on the understanding that the authors of the application have achieved using their own model that the well fluid flowing essentially in the horizontal or inclined section of the well is separated under actual operating conditions, so that near the downstream end of the horizontal or inclined section the water concentration (% by volume) in the upper, oil-rich component is significantly greater than the concentration of oil (% by volume) in the lower, water-rich component. In particular, it was found that the oil-rich component under actual operating conditions contains more than 10% by volume of water. The water-rich component may have an oil concentration of from 0.01 to 0.1% by volume. In the description and claims, the expression "upper region" and "lower region" is used in connection with the horizontal section and refers to the space above the horizontal plane separating the horizontal section, and these expressions also refer to the area of the same shape when used in relation to the inclined section . The expression “essentially horizontal section” is used to recognize the fact that directional drilling in practice can lead to a deviation from the intended horizontal direction. The inclined section is a section of a well that is not substantially horizontal, and may have a deviation angle from the horizontal plane of up to 80 °, with the well section deflected upward in its upstream part in which the well fluid flows.

The present invention is further described by more detailed consideration of examples with reference to the accompanying drawings, which depict the following:

FIG. 1 depicts the first calculation result of a well fluid separation model in a horizontal pipe;

FIG. 2 shows a second calculation result of a well fluid separation model in a horizontal pipe;

FIG. 3 schematically shows a first embodiment of the present invention;

FIG. 4 schematically shows a second embodiment of the present invention;

FIG. 5 schematically shows a third embodiment of the present invention;

FIG. 6 schematically shows a fourth embodiment of the present invention;

FIG. 7 schematically shows an embodiment representing a static separator suitable for use as a secondary separator in the present invention;

FIG. 8 schematically depicts a detail of the static separator shown in FIG. 7

FIG. 1 presents the results of the calculation performed using the model developed by the author of the application. FIG. 1 shows, for an oil / water mixture flowing in a horizontal pipe, the calculated water concentration (percent by volume) in the oil-rich component in the upper region at the end of the horizontal pipe (ordinate) as a function of the length of the horizontal pipe in meters (abscissa).

The calculations were carried out using our own model, which allows you to set the parameters that characterize the separation of the flow of an oil / water mixture in horizontal pipes into an upper, oil-rich component and a lower, water-rich component. The model incorporates a number of input parameters, including viscosity and flow rates of oil and water, pipe diameter, initial drop size. The model experimentally changed in field conditions in horizontal pipes.

For the application of the present invention, the input parameters for the calculations are chosen in such a way that they are typical and fall within the boundaries of actual operating conditions. Selected incoming parameters include oil density of 790 kg / m ³ , oil viscosity mPa / s, flow rate 2000 m ³ / day, pipe diameter 0.23 m, total water concentration in the mixture 50% by volume, initial water drop size 50 microns.

As is clear from FIG. 1, the concentration of water in the oil-rich component decreases with increasing length of the horizontal pipe. The model indicates that, with a length of 1000 m, the oil-rich component contains approximately 12% water by volume.

For other model calculation results, references are made to FIG. 2. FIG. 2 shows for the oil / water mixture flowing in a horizontal pipe the calculated concentration (% by volume) of the oil-rich component in the upper region at the end of a horizontal pipe having a length of 1000 m (ordinate) as a function of oil viscosity in mPa / s (abscissa) for flow rates of 1000 m ³ / day (curve 1), 1600 m ³ / day (curve 2) and 2000 m ³ / day (curve 3). Other input parameters are the same as those used to calculate FIG. one.

FIG. 3 shows a system 2 for extracting dewatered oil from an underground field 2, comprising a production well 3, descending from the surface of the earth and having an inlet 5 below the surface 4 and an outlet 6 equipped with a wellhead equipment 6a on the surface 4.

The system also contains a receiving well 7, passing into the underground field and capable of receiving well fluid through the means 8 of the inlet. The downstream part 9 of the receiving well 7 contains an essentially horizontal section 10, where during normal operation, the primary separation of the fluid by the well occurs. The receiving well 7 is connected at the intersection point 11 with the production well 3 above inlet 5.

In addition, the system 12 water excretion has an upstream end 13 adapted to receive during normal operation of the fluid from the upper region 14 of the downstream part of the receiving well 7.

Weirs, holes, dividers, packers and the like (not shown) to control and maintain separation of the flow of liquid components selectively positioned at or near the upstream end 13 and / or the intersection 11.

The water removal system 12 in this embodiment is positioned for the downward continuation of the production well 3 below the intersection point 11, where the continuation cross-section of the well may differ from the same production well 3. In addition, the water removal system 12 has an inlet 15 for receiving the water-rich component, and a pump 16 for removing fluid from the system 12 for removing water in section 17 of the well downstream of the pump 16. Section 17 of the well is designed to provide convenient removal of fluid from the system Water removal to an underground field (not shown) is available, and well section 17 is also provided with means to prevent backflow.

Additionally, a secondary underground separator 18 is used to separate oil and water, which has an inlet 19 at its upstream end, which receives during normal operation the fluid from the upper region 20 of the downstream part 9 of the receiving well 7. The separator 18 has an outlet 21 for dehydrated oil, communicated with the inlet 5 of the production well 3, and the outlet 22 for the water-enriched component, communicated via pipe 23 with the hole 15 in the system 12 water removal. The separator in this embodiment is installed in the section of the production well 3, located above the intersection point 11 in such a way that the separator may not intersect during normal operation. The section of the production well 3, in which the separator 18 is installed, may be a well bore, an extended drilling reamer.

During normal operation, the system 1 according to the embodiment shown in FIG. 3, the borehole fluid flowing through the inlet 8 of the receiving well 7 flows into the downstream part 9, including the horizontal section 10, and is divided. Fluid layers are formed in the upper and lower regions of the upstream part 9 of the receiving well 7, and an interface is formed between the layers (not shown). At the downstream end of the receiving well 7, the fluid flowing in the lower region 14 is a water-rich component, and the fluid flowing in the upper region 20 is an oil-rich component of the well fluid. The wellbore fluid stream is separated in this primary separator to such an extent that the water-rich component has a substantially low oil concentration.

The water-rich component enters the water discharge system 12 at the upper end 13 at the intersection point 11.

The oil-rich component enters secondary separator 18 through inlet 19 and is divided into dehydrated oil, usually containing less than 10% by volume of water, preferably less than 2% by volume, more preferably less than 0.5% by volume of water, and a water-enriched component which may contain from 0.01% by volume to 0.1% by volume of oil. The separation efficiency depends in part on the type of separator used.

The dehydrated oil leaves the separator 18 through the outlet 21 and flows through the inlet 5 into the production well 3 and further to the surface 4, where it is withdrawn from the system 1 through the wellhead equipment 6a at the outlet 6. The water-rich component leaves the separator through the outlet 22 and the pipe 23 and is mixed in the hole 15 with a water-rich component to form water without oil in the water removal system 12. During normal operation, the water removal system 12 is filled to a certain water level (not shown) with water without oil. Water without oil is discharged through section 17 by pump 16.

As is clear from the above description of the system shown in FIG. 3, the specific advantages of the present invention are that the well fluid is separated into oil without water and water without oil. In this case, water without oil is removed to the underground field, and the system in accordance with the invention delivers only dehydrated oil to the surface.

The curvature of the well section between the substantially horizontal section 10 and the intersection point 11 is designed so that the quality of the separation does not significantly deteriorate.

FIG. 4 schematically shows another embodiment of the present invention. Those parts that are similar to the parts described with reference to FIG. 3 are denoted by the same reference numbers. System 100 is an evolution of system 1 shown in FIG. 3, further comprising a connecting well 101. A connecting well 101 in this embodiment is connected to a receiving well 7 at an intersection point 102 near the downstream end 103 of a substantially horizontal section 10, and a water removal system 12 12 at an intersection point 106 below places 11 intersection. The inlet of the connecting well 101 is located at the intersection point 102 so as to receive fluid from the lower region 14, and the outlet of the connecting well 101 is located at the intersection point 106 and communicated with the water removal system.

US patent No. 4390067 discloses a system of wells, including at least two wells, descending down from the surface of the earth and connected by at least one horizontal well.

During normal system operation

The 100 water-rich component does not enter the water withdrawal system through the intersection point 11. At this end, a packer 108 may be selectively installed, located below the intersection point 11, which has a convenient opening for a pipe 23 connecting the outlet opening 22 with an opening 15.

FIG. 5 schematically shows a third embodiment of the present invention. Those parts that are similar to the parts described with reference to FIG. 3 are denoted by the same reference numbers. The system 200 shown in FIG. 5 differs from system 1 shown in FIG. 3, in that the water injection system 202 comprises a water extraction well 204, which is designed as a branch of the receiving well 7. The connection 206 of the wells 7 and 204 is located near the outlet of the substantially horizontal section 10 of the lower part 9 of the receiving well 7.

During normal operation, the well fluid undergoes a primary separation, essentially in the horizontal section 10, and enters, passing through the intersection 206 near the lower end of the horizontal section, into section 208, which has a lower region 209. The lower region 209 receives a water-rich component from the lower region 14 of the downstream part 9 of the receiving well 7.

During normal operation, the oil-rich component of the well fluid flows into the layer in the upper region 210 of section 208 and then through the upwardly bent section 212. From section 212 of the well it enters the secondary separator 18 to separate oil and water through inlet 19. In separator 18 the oil-rich component is divided into dehydrated oil and a water-rich component. The dehydrated oil leaves the separator 18 through the outlet 21, passes into the inlet 5 of the production well 3 and then to the surface 4, where it is withdrawn from the system 200 through the equipment 6a of the wellhead of the outlet 6. The water-rich component leaves the separator through the outlet 22 and flows through the pipe 23 into the hole 15 located in the upper region 209 of section 208. There, the water-enriched component is mixed with the water-rich component to form water without oil.

Through pipe 216, having an inlet 217, placed in the lower region 209, water without oil is received by the water removal system 202. With the help of pump 16, water without oil is pumped through the well 204 of water removal and output through outlet 218 to the underground field 220.

FIG. 6 schematically shows a fourth embodiment of the present invention. Those parts that are similar to the parts described with reference to FIG. 3 are denoted by the same reference numbers. The system 300 shown in FIG. 6 differs from the system shown in FIG. 3, on the construction of a secondary separator for the separation of oil and water and the water removal system.

The secondary separator 18 of the system 300 is installed in the extended borehole section of the lower end of the production well 3. The separator 18 is designed to receive fluid from the upper region 302 of the horizontal section 10 downstream part 9 of the receiving well 7 through the inlet 18. The separator 18 is located near the bottom the flow of the end 303 of the horizontal section 10. The separator 18, in addition, has an outlet 21 for dry oil, communicated with the inlet 5 of the production well 3, and the outlet 22 for bogaschennogo water component. The outlet 22 is connected via a pipe 23 with an opening 15, made in the lower region 304 of the horizontal section 10 near the downstream end 303 of the horizontal section 10.

The water removal system 305 in this embodiment comprises a water recovery well 306, which has a slope in the direction of fluid flow. The water outflow well 306 has an inlet 310 at its upper end connected to the downstream end 303 of the horizontal section 10. The slope of the water outflow 306 is chosen so that the incoming layering flow is not substantially disturbed.

In the downstream part of the well 306, the discharge of water at a position below the lowest level of the horizontal section 10, a pump 16 is installed to drain water without oil through the outlet 312 to the underground field 315, and in addition means are used to prevent backflow of water (not shown) .

During normal operation of the system 300, as shown in FIG. 6, the well fluid flowing through the inlet 8 of the receiving well 7 flows into the downstream part 9, including the horizontal section 10, which acts as the primary separator for the well fluid. Fluid layers are formed in the upper and lower regions of the horizontal section 10, and an interface forms between the layers (not shown). Near the downstream end 303 of the horizontal section 10, the fluid flowing to the lower region 304 is a water-rich component, and the fluid flowing in the upper region 302 is an oil-rich component. The wellbore fluid stream is divided to such an extent that the water-rich component has a substantially low oil concentration.

The oil-rich component passes to the second separator 18 through inlet 19 and is divided into dehydrated oil and a water-enriched component, where the dehydrated oil flows to surface 4, as described with reference to FIG. 3. The water-enriched component leaves the separator through the outlet 22 and the pipe 23 and mixes around the hole 15 in the lower region 304 with the water-rich component to form water without oil downstream of the hole 15.

Water without oil enters the well to drain water through the inlet 310. Below the lowest level of the essentially horizontal section, the well of water removal during normal operation is filled with water without oil. By means of the pump 16, the oil without oil is pumped through the well 306 of the water withdrawal and discharged through the outlet 312 to the underground field 315.

It may be desirable to obtain oil from many host wells using a single production well and a single separator for separating oil and water. In this case, the system in accordance with the invention includes one or more additional receiving wells that pass into an underground field at various locations and receive a fluid from there. The downstream part of the additional receiving wells communicated with the downstream part of the receiving well. Dividing a well's fluid into water-rich and oil-rich components can occur in many host wells, either alone or in a common lower part, after mixing all of the fluid in the well or partially in both ways.

International Patent Application Publication No. XVO 98/25005 discloses a subterranean well system comprising an essentially vertical well and one or more sections of a horizontal well extending from a main vertical well.

International Patent Application Publication No. νθ 98/50679 discloses a subsurface well system comprising a main well and one or more additional wells, with each well descending from the surface and containing a substantially horizontal section located in the reservoir. The horizontal sections of additional wells communicate with the horizontal section of the main well in the reservoir, but do not have a physical intersection with the main well.

An underground oil and water separator for use in the system according to the present invention may be of various kinds known in the art, such as, for example, a cyclone, mixed or static separator. Mainly used is a static separator installed in the separation chamber, the height of which is greater than the thickness of the oil / water dispersion layer formed under normal operating conditions. The separation chamber may preferably be located in the extended section of the production well.

It has been established that the underground separation chamber has an advantage in the physical conditions in the well, for example, elevated temperature and pressure, which influence the behavior of oil and water separation in such a way that effective separation of the fluid obtained from the upper region of the downstream part of the receiving well , relatively dry oil and relatively pure water can be achieved under practically and economically feasible conditions.

The fluid produced during normal operation by a static separator from the upper region of the downstream part of the receiving well is the oil-rich component of the well fluid in the form of an oil / water dispersion containing more than 10% by volume of water. The separation of such an oil / water dispersion in the separation chamber under the influence of gravity can be described using a model developed by the applicant. Such a so-called dispersion layer model was published in N.S. Royetshap e! A1., 8RE regreg # # 38816, 1997. The model can be used to describe the separation in the separation chamber. An important separation mechanism is based on mixing small droplets of water into the dispersion layer, which is drained into the lower layer as soon as the droplets reach a sufficiently large size. During normal operation, three layers of fluid are formed: the bottom layer of relatively pure water, the middle layer containing the dispersion of oil and water, and the top layer of relatively dry oil. The middle layer is also called the dispersion layer.

Conveniently, the inlet and outlet openings of the separator are designed so that the incoming and separated components flow vertically or almost vertically into or out of the separation chamber.

In the first embodiment of such a static separator, this separator further comprises flow distribution means designed to be distributed when the fluid is provided in a vertical arrangement over the cross-sectional area of the separation chamber. Preferably, the fluid passes into the separation chamber in a prescribed vertical position through one or more openings at a local flow rate below 1 m / s. The separation chamber provides separation of the fluid into the lower layer of the water-enriched component, the middle dispersion layer of the oil and water components, and the upper layer of the dehydrated oil component. Fluid from the upper and lower layers can be removed through the outlet openings for the dehydrated oil and the water-enriched component, respectively. The separator may additionally include a level detector for measuring the vertical position of the interface between the fluid layers and monitoring the flow, designed to maintain the separation between the fluid layers at a normal vertical level during normal operation.

In the second embodiment, the static separator for use as a secondary separator in the present invention further comprises a series of vertically separately arranged inclined plates having between the pair of adjacent plates there is a separation space, a substantially vertical inlet tube communicating with the upper end of the separator, intersecting the row of plates adapted to receive fluid from the upper region of the lower part of the receiving well at its lower end, and provided with one or several liquid outlets opening into the separation space, a substantially vertical oil collecting channel having an oil outlet at its upper end communicated with the outlet of the anhydrous oil separator and one or more openings intended to pass the fluid from the most the upper part of the separation space, and at least the plate directly below each oil outlet is provided with a vertical upward partition oh, and, essentially, a vertical channel for collecting water, having an upper outlet at its lower end, communicated with an outlet of a separator for the water-enriched component, and one or more inlets for water intended for passage of fluid from lower sections dividing space, and at least the plate directly above each water inlet is provided with a vertical downward partition.

FIG. 7 shows an embodiment of a static separator 410 installed in a separation chamber 406 in an expanded section of a production well (not shown). The separation chamber 406 has a substantially circular cross section. The vertical well 408 of the separation chamber 406 is formed by the surrounding structure 409, but it should be understood that the wall can also be created by a well pipe, such as a casing. The wall of the separation chamber also forms the wall of the separator. Static separator 410 includes a series of inclined, substantially flat plates 430, 431, 432, arranged substantially parallel with each other and vertically in space at the same distance from each other. The space bounded between two adjacent plates is a separation space. For example, plates 430, 431 form a separation space 435, plates 431, 432 form a separation space 436. Under the lowest plate 432 of a row of plates there is a parallel main plate 437. The outer edge of the main plate tightly adjoins the walls of the separation chamber 406. Between the plates 432 and the main plate 437 forms another separation space 438.

The row of plates intersects the inlet pipe 440, which runs vertically downward from the hole 442 through a row of plates in the center of the separation chamber 406. The passage for the inlet pipe through the plate, for example, passage 443 through the plate 431, is designed so that the wall of the inlet pipe 440 tightly adheres to the plate for example, plate 431, thus preventing communication between adjacent separation spaces, for example, separation spaces 435, 436, along the inlet pipe. In addition, the outlet pipe is provided with a circular outlet 444, 445, 446, which opens into the separation space 435, 436, 438, respectively. It becomes clear that additional outlets may open in different radial directions. The outlet openings are preferably located in the direction of the axis of the horizontal plate around which the plate bends, i.e. in FIG. 7 is an axis perpendicular to the plane of the sheet.

Further details regarding inclined plates are further discussed with reference to FIG. 8, where the plates 431, 432 of FIG. 7. The edge 447 of the plate 431 forms a right angle 449 on the upper side 448 of the plate 431, to which the upwardly directed partition 450 joins. On the lower part 452, the edge 447 forms a right angle 454, to which the downwardly directed partition 456 joins.

Referring again to FIG. 7, the other inclined plates of the row of plates are likewise provided with upward and downward-oriented partitions 458, 459, 460, 461 on their upper and lower sides, respectively. The remaining portions of the edge of each inclined plate to which the partitions are attached, tightly adjoin the wall 480.

The static separator 410 also includes an oil collecting port 465, which is formed by a spatial segment bounded by upwardly directed partitions 458, 450, 459 and a wall 408. The oil collecting port 465 contains oil inlets, for example, an oil inlet 470 environments from the uppermost area 472 of the separation space

436. An oil inlet is formed by an upper angle 449 of the plate 431 and a downwardly directed partition 459 of the plate 432 directly below the oil inlet 470. Channel 465 collection of oil additionally has an outlet 473, the message with the outlet 415 static separator 410.

Opposite the oil collection channel 465, the separator 410 has a water collection channel 475 formed by a spatial segment bounded by downwardly directed partitions 460, 456, 461 and a wall 408. The water collection channel 475 has water inlets, for example, an inlet 480, which is designed to produce fluid medium from the lower region 482 of the separation space 435. The inlet 480 is formed by the lower angle 454 of the plate 431 and the downward partition 430 directly above the water inlet 480. The oil collecting channel 465 is added tion comprises an outlet 483 in communication with the outlet 418 of the separator 410.

Plates 430, 431, 432 with attached partitions are designed so that the shortest horizontal distance between the upward-pointing partition and the wall 408 increases in the direction from the bottom to the top, and the shortest horizontal distance between the downward-directed partition and the wall 408 increases in the direction from the top to the bottom . Thus, the cross-sectional area of both the oil collection channel 465 and the water collection channel 475 increases in the direction of their outlet openings 473, 483, respectively. Since separator 410 does not contain parts that move during its normal operation, it is a static separator for separating oil and water.

During normal operation, the fluid passes into the static separator 410 at its upstream end 412, passes into the inlet 440 at the opening 442 and enters the spaces of the separator 435, 436, 437 through the outlet 444, 445 and 446. It was found that good separation results are achieved if all the holes have the same cross-sectional area. Good results are achieved if the diameter of the holes corresponds to the diameter of the inlet pipe, so that the pressure drop over the hole is small.

The separation process will be discussed further. For this, the separation space 436 is examined in detail by the plates 431, 432. In the separation space 436, three fluid layers are formed: an upper layer of dehydrated oil, a middle dispersion layer and a lower water-rich layer. A layer of dehydrated oil flows through the highest area 472 of the separation space 436, which it leaves, passing into the oil collection channel through the inlet 470. Water-enriched layer flows through the lowest area 485 of the separation area 436, from where it passes into the water collection channel through the inlet 486. The separation in spaces 435, 436 is similar. The oil recovery channel 465 receives the dehydrated oil component from all separation spaces, and since the cross section of the channel expands toward the outlet 473, the speed of the vertical upward flow of the dewatered oil in the channel 465 may remain substantially constant. From the outlet 473, the assembled component of the dried oil flows to the outlet 415 of the separator for the dried oil.

The water collection channel 475 collects the water-enriched component from all separation spaces, and since the cross-section of the channel expands from top to bottom in the direction of the outlet 408, the speed of the vertical downward flow of the water-enriched component in channel 475 can be maintained substantially constant. Through the outlet 483, the collected water enriched component flows to the outlet 418 of a separator for the water enriched component.

In yet another embodiment, the inclined plates may have substantially the shape of funnels arranged substantially parallel to each other, and each funnel is provided with a central hole.

By installing a series of separate vertically arranged inclined plates, the efficiency of the separation chamber can increase, that is, a lower height can provide the same specific performance as a smaller separation chamber with plates placed in it. In practice, a reduction in the required height of the separation chamber can often be achieved with a ratio in the range from 1.5 to 6. Sometimes the height of the separation chamber is not a factor limiting the well design, in which case a separator without a row of plates can be used.

The basic dimensions of the separation chamber are calculated using the dispersion layer model under the following assumptions: the total flow rate through the separator is 1000 m ³ / day of well fluid containing 50% by volume of water at a dry oil density of 0.001 Pa / s. In this case, a separating chamber with a diameter of 1 m and a height of 5 m is required. For comparison, we note that when installing a row of platinum in the separating chamber, the required height can be reduced to, for example, 2 m. where diameter means the diameter of a circle having the same cross-sectional area as the volume of the separation chamber divided by its height.

It is clear that in practice when applying the present invention, additional technical measurements that are well known in the technical field and which are owned by an expert can be used. As an example, some of these measurements will be briefly described below.

The wells of the system in accordance with the present invention, or sections thereof, may be provided with casing, packing, gaskets, flow controllers, measuring equipment, data lines, energy transfer lines to underground equipment, or other means known in the art to operate and monitor the well system. .

In the case when the well fluid besides oil and water also contains gas, a layer of gas can form in the downstream part of the receiving well over the layer in which the remaining fluid flows. Gas can reduce the separation efficiency of the separator. In this regard, it is preferable to design a gas outlet connected to the gas exhaust system in a convenient part of the system.

It may be desirable to make measurements using underground equipment. It may be convenient to control and monitor system operation.

For example, measuring equipment can be installed to monitor the content of oil, gas or water in a fluid in certain parts of the system. For example, with suitable equipment, it is possible to measure the content of water or oil in water without oil, in a water-rich component, in a water-enriched component, or in dehydrated oil.

In addition, although the exact vertical level of the interface between the layers of different components in a particular area of the system is usually not critical to the functioning of the system, and it can vary within certain limits, it may be desirable to measure this level with a detector.

The result of such measurements can, for example, be used to control the flow rate of a fluid in certain parts of the system. It is well known in the art how to control the flow rate in the system of the invention, for example, the flow rate of a flowing well fluid, fluid from the upper region or from the lower region of the downstream part of the receiving well, water without oil or dry oil. To this end, the system may contain controlled valves, pumps, stops, moving arms, additional openings or other suitable devices.

It may be desirable to accelerate the separation of fluid components by chemical or physical means, for example, by the introduction of chemicals known in the art.

In the case when the inclined section of the well is adapted for primary separation of the well fluid, it is convenient to install an essentially horizontal section on the lower stream end of the inclined section, in the upstream section and around the secondary separator, the length of which can reach, for example, 10 m .

It is understood that water without oil may be introduced into an underground field from which well fluid has been removed. Thus, the introduction of water without oil can serve as a means of maintaining pressure in an underground field.

Thus, the present invention creates a system for extracting oil from an underground field, in which oil can be dehydrated under the surface of the earth in such a way that the water concentration of the produced oil is so low that there is no need for additional dehydration of the oil on the surface before it is transported from the well in operation.

Claims (20)

CLAIM 1. A system for producing dehydrated oil from an underground field, comprising a production well that goes down from the surface of the earth and has an inlet below the surface of the earth, a well that passes into an underground field, capable of receiving downhole fluid from it, and having a downstream portion, comprising a substantially horizontal or inclined section for primary separation of the wellbore fluid into oil and water, a water withdrawal system having an upstream end, receiving fluid from the lower region of the downstream part of the receiving well during normal operation, and a secondary underground separator for separating oil and water, characterized in that the secondary underground separator has an upstream end capable of receiving fluid from the upper section during normal operation the downstream part of the receiving well, and an outlet for dehydrated oil, in communication with the inlet of the production well, and the outlet for water-enriched component communicated with the withdrawal system. 2. The system according to claim 1, characterized in that the water removal system comprises means for removing fluid from the lower region and the water-rich component to an underground source. 3. The system according to claim 1 or 2, characterized in that it further comprises a connecting well having an inlet for receiving fluid from the lower region of the downstream part of the receiving well, and an outlet in communication with the water removal system. 4. The system according to claim 1 or 2, characterized in that the water withdrawal system comprises a water withdrawal well, which is a branch of the receiving well. 5. The system according to claim 1 or 2, characterized in that the water removal system comprises a well for removing water, having a downward slope in the direction of fluid flow. 6. The system according to any one of claims 1 to 5, characterized in that it further comprises an additional receiving well, designed to receive downhole fluid from an underground field and having a downstream part in communication with the downstream part of the receiving well. 7. The system according to any one of claims 1 to 6, characterized in that it further includes equipment for underground measurement for measuring the characteristics of the fluid in certain parts of the system. 8. The system according to claim 7, characterized in that the characteristic is the concentration of the component in the fluid. 9. The system according to claim 7, characterized in that the characteristic is the vertical level of the interface between the layers of various components of the downhole fluid in certain parts of the system. 10. The system according to any one of claims 1 to 9, characterized in that it further comprises means for controlling the flow of fluid in certain parts of the system. 11. The system according to any one of claims 7 to 9, characterized in that it has means for controlling the flow of fluid in certain parts of the system, and the data obtained from the underground measuring equipment is used as input to control the flow of the fluid. 12. The system according to any one of claims 1 to 11, characterized in that the secondary underground separator for separating oil and water is selected from the group consisting of a cyclone, mixed or static separator. 13. The system according to item 12, wherein the secondary separator is a static separator installed in the separation chamber, and the height of the separation chamber is greater than the thickness of the dispersion layer formed under normal operating conditions. 14. The system according to item 13, wherein the static separator contains means for distributing the flow, intended for distribution with the provided vertical arrangement of the borehole fluid passing through the inlet of the separator over the cross-sectional area of the separation chamber. 15. The system according to item 13 or 14, characterized in that the static separator further comprises means for determining the level and control the flow to maintain during normal operation the interface between the two layers of fluid and the intended level. 16. The system of claim 13, wherein the static separator further comprises a series of vertically separate inclined plates having between each pair of adjacent plates a dividing space, a substantially vertical inlet pipe in communication with the upstream end of the separator intersecting the row of plates adapted to receive fluid from the upper region of the lower part of the receiving well at its lower end and provided with one or more outlets for the fluid opening in the separator the space, essentially a vertical oil-collecting channel having an oil outlet at its upper end, in communication with the outlet of the dehydrated oil separator, and one or more inlets intended for the passage of fluid from the uppermost region of the separation space, at least the plate immediately below each oil outlet is provided with a vertical upwardly baffle and, essentially, a vertical channel for collecting water, having an upper outlet at its lower end, in communication with the outlet of the separator for the water-enriched component, and one or more water inlets for the passage of fluid from the lowermost regions of the separation space, with at least a plate directly above each the water inlet is provided with a vertical downward-directed partition. 17. The system according to clause 16, wherein the inclined plates are essentially flat and mounted essentially parallel to each other, and each inclined plate is provided with a downwardly directed partition connected to the edge of the lower side of the inclined plate, and directed upward by a partition connected to the edge of the upper side of the inclined plate, while the rest of the edge is hermetically adjacent to the wall of the separation chamber, and the oil collection channel is formed as a space bounded upward the partitions and the wall, and the water collection channel is formed as a space bounded by downwardly directed partitions and the wall. 18. The system of clause 16, wherein the inclined plates are essentially the shape of funnels located essentially parallel to each other, and each funnel has a Central hole. 19. The system according to any one of paragraphs.13-18, characterized in that the separation chamber has a height to diameter ratio of less than 6. 20. The system according to any one of claims 1 to 19, characterized in that the secondary underground separator for separating oil and water is installed in the extended section of the production well.