steam injection valve

Abstract

The present application relates to a steam injection valve, comprising a main body with upper and lower ends for connecting with oil pipes, a valve core is seated in the central flow passage of the main body, two sealing structures are arranged between the valve core and the main body, a lateral hole is arranged on the valve core between the two sealing structures, a lateral opening is arranged on the main body between the two sealing structures, the lateral opening is communicated with the lateral hole, a bridge channel extending downward from the upper end is arranged on the main body, the lower end of the bridge channel is communicated with the central flow passage of the main body below the two sealing structures, the valve core is configured to be closed at the upper end and capable of flowing fluid from bottom to top to the lateral hole, and the flow passage area of the valve core can change with the change of the pressure difference of the steam on both sides, so that the amount of steam passing through it remains constant. The steam injection valve of the present application can keep the steam injection amount constant under the condition that the pressure difference of the float changes at both ends, so as to shield the influence of upstream and downstream pressure disturbance on steam flow.

Description

Technical Field

[0001] This invention belongs to the field of oilfield engineering technology, and specifically relates to a steam injection valve. Background Technology

[0002] Offshore oilfields are rich in heavy oil resources, and thermal recovery is an effective technology for heavy oil development. Currently, thermal recovery in offshore heavy oil blocks is mostly in the steam huff and puff stage, but the efficiency of thermal recovery gradually decreases with the increase of huff and puff cycles. To improve the efficiency of thermal recovery, steam drive can be used as a replacement, which can increase the recovery rate by 10%-20% compared to huff and puff wells. However, the demand for steam injection volume regulation is more urgent for steam drive than for steam huff and puff wells, especially for directional wells implementing steam drive in stratified sections. Due to the unique properties of steam and the influence of formation differences, steam tends to form dominant channels in high-permeability, high-yield sections, resulting in heat waste, while the impact on low-permeability sections is low.

[0003] Currently, offshore oilfields lack in-depth research on steam conditioning technology and mature steam conditioning tools. Furthermore, conditioning technologies used in onshore oilfields are not applicable to offshore oilfields. For example, selective steam injection can only switch between two layers, resulting in low production efficiency; while eccentric stratified steam injection is limited by tool size, resulting in a small injection volume per layer; moreover, eccentric stratified steam injection tools cannot guarantee stable steam injection volume and cannot perform frequent adjustments to ensure that each layer is injected with the appropriate amount of steam. Summary of the Invention

[0004] To address all or some of the aforementioned problems, the present invention aims to provide a steam injection valve that can maintain a constant steam injection volume despite changes in the pressure difference across the float, thereby shielding the steam flow rate from the effects of upstream and downstream pressure disturbances.

[0005] According to one aspect of the present invention, a steam injection valve is provided, comprising a main body with an upper end and a lower end respectively for connection to an oil pipe, a valve core being mounted in a central flow channel of the main body, two sealing structures being provided between the valve core and the main body, a lateral hole being provided on the valve core between the two sealing structures, a lateral opening being provided on the main body between the two sealing structures, the lateral opening communicating with the lateral hole, a bridge-type channel extending downward from the upper end being provided on the main body, the lower end of the bridge-type channel communicating with the central flow channel of the main body below the two sealing structures, the valve core being configured to be closed at the upper end and allowing fluid to flow upward to the lateral hole, and the flow channel area of ​​the valve core being variable with the pressure difference of the steam on both sides thereof.

[0006] Furthermore, the valve core includes a valve seat, the upper end of which is fixedly and sealed with a retrieval head, and the lower end of which sits within the central flow channel of the main body. Two sealing structures are disposed between the valve seat and the main body, and the lateral hole is disposed on the valve seat between the two sealing structures. A valve nozzle and a valve stem are fixedly disposed within the valve seat. The valve stem is located within the central flow channel of the valve nozzle. A spring and a float are sleeved on the valve stem. The lower end of the spring contacts the upper end of the float. Both the spring and the float are limited on the valve stem. The compression of the spring can change with the change of the steam pressure difference to drive the float to move up and down within the valve nozzle, thereby changing the flow channel area between the float and the valve nozzle.

[0007] Furthermore, the float is a conical block with an outer diameter that gradually increases from top to bottom; the spring, which is positioned on the valve stem, is configured to be in a compressed state, and at this time, the minimum outer diameter of the float corresponds to the minimum inner diameter of the valve nozzle.

[0008] Furthermore, a pressure cap is fixedly connected to the lower end of the valve seat, and the lower end of the pressure cap sits in the central flow channel of the main body; an enlarged groove extending upward from the lower end is opened in the central flow channel of the valve seat, and an enlarged groove extending downward from the upper end is opened in the central flow channel of the pressure cap; the valve nozzle is fixedly disposed in the groove formed by the two enlarged grooves.

[0009] Furthermore, a step is provided on the outer wall of the valve seat, and one of the sealing structures is fitted on the valve seat between the step and the pressure cap; the other sealing structure is fitted on the valve seat between the step and the retrieval head.

[0010] Furthermore, two pressure rings are fixedly connected to the valve stem, and the spring and the float are limited on the valve stem by the two pressure rings.

[0011] Furthermore, a centralizing ring is fixedly connected to the upper end of the valve seat, and the valve stem is fixedly connected to the centralizing ring.

[0012] Furthermore, the valve nozzle is a tapered tube with an inner diameter that gradually decreases from top to bottom.

[0013] Furthermore, the upper end of the main body is connected to an upper connector for connecting to the oil pipe above the main body, and the lower end of the main body is connected to a lower connector for connecting to the oil pipe below the main body.

[0014] Furthermore, an outer cylinder is threadedly connected to the outer wall of the main body.

[0015] As can be seen from the above technical solution, the steam injection valve provided by the present invention has the following beneficial effects:

[0016] The steam injection valve of the present invention can maintain a constant steam injection volume when the pressure difference at both ends of the float changes, thereby shielding the influence of upstream and downstream pressure disturbances on the steam flow rate; and the steam injection valve of the present invention can meet the allocation requirements of multiple steam injection sections by dropping and retrieving the float of the valve core; the steam injection valve of the present invention provides an effective measure for thermal recovery well layer change production and balanced steam injection. Attached Figure Description

[0017] Figure 1 This is a cross-sectional view of a steam injection valve according to an embodiment of the present invention;

[0018] Figure 2 This is a cross-sectional view of the valve core according to an embodiment of the present invention;

[0019] Figure 3 for Figure 2 Enlarged view of point A in the middle;

[0020] Figure 4 for Figure 2 Enlarged view of point C in the middle;

[0021] Figure 5 This is a cross-sectional view of the main body of an embodiment of the present invention;

[0022] Figure 6 This is a schematic diagram illustrating the working principle of a float.

[0023] The attached diagram is labeled as follows: upper connector 1, main body 2, side opening 201, bridge channel 202, valve core 3, outer cylinder 4, lower connector 5, retrieval head 301, straightening ring 302, valve seat 303, pressure cap 304, sealing structure 305, pressure ring 306, valve nozzle 307, spring 308, valve stem 309, float 310. Detailed Implementation

[0024] To better understand the purpose, structure, and function of this invention, a steam injection valve of this invention will be described in further detail below with reference to the accompanying drawings.

[0025] like Figure 1 , Figure 5As shown, this invention illustrates a steam injection valve, comprising a main body 2 with its upper and lower ends for connection to an oil pipe. A valve core 3 is mounted in the central flow channel of the main body 2. Two sealing structures 305 are provided between the valve core 3 and the main body 2. A lateral hole is provided on the valve core 3 between the two sealing structures 305. A lateral opening 201 is provided on the main body 2 between the two sealing structures 305, and the lateral opening 201 communicates with the lateral hole. A bridge-type channel 202 extending downward from the upper end is provided on the main body 2. The lower end of the bridge-type channel 202 communicates with the central flow channel of the main body 2 below the two sealing structures 305. The valve core 3 is configured to be closed at the upper end and to allow fluid to flow from bottom to top to the lateral opening. The flow channel area of ​​the valve core 3 can vary with the pressure difference of the steam on both sides to keep the amount of steam passing through it constant.

[0026] The steam injection valve in this embodiment includes a main body 2 and a valve core 3. The valve core 3, as a movable part, is mounted in the central flow channel of the main body 2. The valve core 3 and the main body 2 are also provided with a double sealing structure 305 to form a sealing fit. In a multi-stage steam injection well, the valve core 3 of each stage of the steam injection valve corresponds one-to-one with the main body 2, and the inner diameter of the main body 2 and the outer diameter of the valve core 3 decrease sequentially along the wellbore, thereby forming a multi-stage retrievable structure.

[0027] In practice, the upper and lower ends of the main body 2 are connected to the tubing respectively and are lowered into the wellbore through the tubing; the valve core 3 can be hung in the main body 2 before the tubing is lowered into the well, or it can be hung in the main body 2 using a wireline retrieval tool when injection adjustment is required later.

[0028] When steam is injected, because the upper end of valve core 3 is closed and a sealing structure 305 is provided between valve core 3 and valve seat 303, steam can only flow into the central flow channel of main body 2 below the two sealing structures 305 through the bridge channel 202 of main body 2. Part of the steam flowing into the central flow channel goes down into the bridge channel 202 of the lower steam injection valve of main body 2, and the other part moves from bottom to top along the flow channel of valve core 3 to the side hole of valve core 3. Since the injection pressure is higher than the formation pressure, this part of steam enters the annulus outside main body 2 through the side hole and side opening 201, and then enters the formation.

[0029] When production conditions change and the steam injection volume needs to be adjusted, the valve core 3 of each stage steam injection valve can be replaced using a wire-guided retrieval tool.

[0030] The pressure and steam dryness loss generated by the steam flowing through the bridge-type channel 202 of the main body 2, the side hole of the valve core 3 and the side opening 201 of the main body 2 are small. In addition, the side opening 201 and the side hole are designed to help the gas and liquid phases of wet steam to mix fully.

[0031] For valve core 3, such as Figure 2 , Figure 4 , Figure 5 As shown, it includes a valve seat 303, with a retrieval head 301 fixedly and sealed to the upper end of the valve seat 303. The lower end of the valve seat 303 sits in the central flow channel of the main body 2. Two sealing structures 305 are set between the valve seat 303 and the main body 2. A lateral hole is set on the valve seat 303 between the two sealing structures 305. A valve nozzle 307 and a valve stem 309 are fixedly set inside the valve seat 303. The valve stem 309 is located in the central flow channel of the valve nozzle 307. A spring 308 and a float 310 are sleeved on the valve stem 309. The lower end of the spring 308 contacts the upper end of the float 310. The spring 308 and the float 310 are both limited on the valve stem 309. The compression of the spring 308 can change with the change of the steam pressure difference to drive the float 310 to move up and down in the valve nozzle 307, so as to change the flow channel area between the float 310 and the valve nozzle 307.

[0032] Specifically, the valve seat 303 and the salvage head 301 are fixedly and sealed together, sealing the upper end of the valve core 3 and allowing steam to enter only the bridge-type channel 202 of the main body 2. In practice, the valve seat 303 and the salvage head 301 are fixedly connected by a threaded structure and sealed by a sealing ring. The salvage head 301 is designed for use with commonly used marine salvage tools, and its displacement control mechanism requires design calculations to select a suitable model.

[0033] The displacement control part of the valve core 3 is realized by the valve nozzle 307, spring 308, valve stem 309 and float 310. The valve nozzle 307, spring 308, valve stem 309 and float 310 are all placed in the valve seat 303. The upper end of the valve seat 303 is fixedly connected to the central ring 302, and the valve stem 309 passes through the central part of the central ring 302.

[0034] The valve nozzle 307 in this embodiment of the invention is a tapered tube with a certain profile, that is, a tapered tube whose inner diameter gradually decreases from top to bottom.

[0035] The float 310 is a conical block with an outer diameter that gradually increases from top to bottom. The float 310 is placed inside the valve nozzle 307. A spring 308 is positioned above the float 310. The spring 308 and the float 310 are collectively constrained by the valve stem 309, and the spring 308, constrained by the valve stem 309, is in a compressed state. At this time, the minimum outer diameter of the float 310 corresponds to the minimum inner diameter of the valve nozzle 307. When the pressure below the float 310 increases due to the presence of steam, the steam pushes the float 310 to compress the spring 308 and move it upwards. This increases the compression of the spring 308, increasing the diameter of the float 310 corresponding to the minimum inner diameter of the valve nozzle 307. The flow channel area between the float 310 and the valve nozzle 307 decreases, thus offsetting the displacement change caused by the pressure difference.

[0036] Regarding the float 310, the following explanation is provided: Two pressure rings 306 are fixedly connected to the valve stem 309. The spring 308 and the float 310 are limited on the valve stem 309 by the two pressure rings 306. The initial position of the float 310 is the position where it contacts the pressure ring 306 below. At this time, the spring 308 is in a compressed state, and the minimum outer diameter of the float 310 corresponds to the minimum inner diameter of the valve nozzle 307. This position can be set as the initial starting pressure difference for adaptive regulation. As the pressure difference continues to change, the float 310 and the spring 308 move upward accordingly, causing the steam flow area to change accordingly, thereby keeping the discharge constant.

[0037] When steam enters the steam injection valve's internal channel, it easily forms bubbly flow and slug flow due to the multiphase fluid properties. The bridge-type channel 202 of the main body 2 can break large bubbles into smaller bubbles, thus making the bubbles flow more uniformly towards the side holes. At this time, the steam flow rate can be considered as a mixed liquid, and the steam flow rate can be calculated based on the density of the mixed liquid. Specifically, the steam flow rate control equation is as follows:

[0038]

[0039] In Equation 1, Q m The flow rate of wet steam is expressed in kg / h; A represents the fluid flow area in mm². 2 ;α m ρ represents the flow coefficient; ε represents the expansion coefficient; m This indicates the density of the wet steam at the outlet, in kg / m³. 3 ΔP represents the pressure difference across float 310, in MPa. Equation 1 states that the wet steam flow rate is equal to the product of the square root of the first term and the second term, where the first term is equal to twice the product of the outlet wet steam density and the pressure difference across float 310, and the second term is equal to the product of the fluid flow area, the flow coefficient, and the expandability coefficient.

[0040] For Equation 1: As the float 310 moves, the flow coefficient will change slightly. To simplify the calculation, the flow coefficient is set to a constant; the expandability coefficient is obtained from steam experimental testing. The float 310 and valve stem 309 are made of high-gloss hard metal. The friction and viscosity between the float 310 and valve stem 309 are ignored in the calculation, and the density change of wet steam at the valve outlet during the mechanical regulation stage is ignored.

[0041] For Equation 1, when the float 310 is in its initial position (the minimum outer diameter of the float 310 corresponds to the minimum inner diameter of the valve nozzle 307), if... Figure 6 As shown, the pre-compression of spring 308 is x0, the radius of float 310 is y0, and the minimum diameter of valve nozzle 307 is set to D. Substituting into equation one, we can obtain equation two:

[0042]

[0043] According to Equation 2, Equation 3 regarding the radius of the float 310 can be obtained:

[0044]

[0045] Next, let the stiffness of spring 308 be k, the diameter of valve stem 309 be d, and the working pressure difference between the two ends of float 310 when it is in the initial position be ΔP0. The preload at this time is F0, which can be calculated by Equation 4:

[0046]

[0047] When the float 310 moves, the amount of movement is represented by dx. The compression of the spring 308 at this time is x0+dx. Let's assume that the float 310 moves to y0+dy, which corresponds to the minimum inner diameter of the valve nozzle 307. Let's set the spring force of the spring 308 at this time to F. x Let the pressure difference at this time be equal to ΔP. x Then the spring force of spring 308 at this time can be calculated by equation five:

[0048]

[0049] According to Equation 4, the expression for ΔP0 can be calculated. Substituting the expression for ΔP0 into ΔP in Equation 2, we obtain Equation 6 as follows; according to Equation 5, the expression for ΔP can be calculated. x The expression for ΔP x Substituting the expression for ΔP into Equation 2 yields Equation 7:

[0050]

[0051] Based on equations six and seven, the linear equation for float 310 can be obtained. When the pressure difference between the two ends of float 310 reaches a certain level, considering that spring 308 is in a compressed state, and considering that the ratio of inlet pressure to outlet pressure is greater than the critical pressure ratio, the steam is in a critical flow state to maintain a constant steam discharge. Based on this, the maximum outer diameter of float 310 when spring 308 is in a compressed state can be obtained, thus obtaining the outer diameter of the entire float 310.

[0052] In practical applications, the size of the adaptive steam injection valve core can be designed based on the reservoir injection volume and wellhead injection parameters of each well section.

[0053] Specifically, for valve seat 303: a pressure cap 304 is fixedly connected to the lower end of valve seat 303, and the lower end of pressure cap 304 sits in the central flow channel of main body 2; an expansion groove extending upward from the lower end is opened in the central flow channel of valve seat 303, and an expansion groove extending downward from the upper end is opened in the central flow channel of pressure cap 304; valve nozzle 307 is fixedly installed in the groove formed by the two expansion grooves.

[0054] In specific implementation, for example, the valve seat 303 and the pressure cap 304 are connected by threads; the expansion grooves on the valve seat 303 and the pressure cap 304 facilitate fixing the valve nozzle 307 in the groove formed by the two expansion grooves, thereby achieving the limiting of the valve nozzle 307.

[0055] Regarding the setting of the two sealing structures 305, such as Figure 3 As shown, a step is provided on the outer wall of the valve seat 303, and one sealing structure 305 is fitted on the valve seat 303 between the step and the pressure cap 304; another sealing structure 305 is fitted on the valve seat 303 between the step and the retrieval head 301.

[0056] In practice, an annular groove can be provided in the middle of the step as needed to accommodate fluid entering between the valve seat 303 and the body 2 through the lateral hole between the two sealing structures 305.

[0057] In the steam injection valve of this embodiment of the invention, the upper end of the main body 2 is connected to an upper connector 1, which is used to connect to the oil pipe above the main body 2. The lower end of the main body 2 is connected to a lower connector 5, which is used to connect to the oil pipe below the main body 2. An outer cylinder 4 is threadedly connected to the outer wall of the main body 2.

[0058] Specifically, the upper connector 1 is connected to the main body 2 by threads, and the outer cylinder 4 is connected to the thread at the maximum outer diameter of the main body 2; the lower connector 5 is connected to the lower part of the main body 2 by threads. Thus, the upper connector 1, the lower connector 5 and the main body 2 form the working cylinder of the steam injection valve.

[0059] The steam injection valve of the present invention can maintain a constant steam injection volume when the pressure difference across the float 310 changes, thereby shielding the influence of upstream and downstream pressure disturbances on the steam flow rate; and the steam injection valve of the present invention can meet the allocation requirements of multiple steam injection sections by replacing the float 310 of the valve core 3 by casting and retrieving; the steam injection valve of the present invention provides an effective measure for thermal recovery well layer replacement production and balanced steam injection.

[0060] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0061] Furthermore, the terms "a," "two," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly defined.

[0062] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A steam injection valve, characterized in that, The device includes a main body with upper and lower ends for connection to oil pipes. A valve core is mounted in the central flow channel of the main body. Two sealing structures are provided between the valve core and the main body. A lateral hole is opened on the valve core between the two sealing structures. A lateral opening is opened on the main body between the two sealing structures. The lateral opening communicates with the lateral hole. A bridge-type channel extending downward from the upper end is opened on the main body. The lower end of the bridge-type channel communicates with the central flow channel of the main body below the two sealing structures. The valve core is configured to be closed at the upper end and allow fluid to flow from bottom to top to the lateral hole. The flow channel area of ​​the valve core can change with the pressure difference of the steam on both sides.

2. The steam injection valve according to claim 1, characterized in that, The valve core includes a valve seat, with a retrieval head fixedly and sealed to the upper end of the valve seat. The lower end of the valve seat sits within the central flow channel of the main body. Two sealing structures are disposed between the valve seat and the main body. The lateral hole is disposed on the valve seat between the two sealing structures. A valve nozzle and a valve stem are fixedly disposed within the valve seat. The valve stem is located within the central flow channel of the valve nozzle. A spring and a float are sleeved on the valve stem. The lower end of the spring contacts the upper end of the float. Both the spring and the float are limited on the valve stem. The compression of the spring can change with the change of the steam pressure difference to drive the float to move up and down within the valve nozzle, thereby changing the flow channel area between the float and the valve nozzle.

3. The steam injection valve according to claim 2, characterized in that, The float is a conical block with an outer diameter that gradually increases from top to bottom; the spring that is limited on the valve stem is configured to be in a compressed state, and at this time the minimum outer diameter of the float corresponds to the minimum inner diameter of the valve nozzle.

4. The steam injection valve according to claim 2, characterized in that, A pressure cap is fixedly connected to the lower end of the valve seat, and the lower end of the pressure cap sits in the central flow channel of the main body; an expansion groove extending upward from the lower end is opened in the central flow channel of the valve seat, and an expansion groove extending downward from the upper end is opened in the central flow channel of the pressure cap; the valve nozzle is fixedly installed in the groove formed by the two expansion grooves.

5. The steam injection valve according to claim 4, characterized in that, The outer wall of the valve seat is provided with a step, and one of the sealing structures is fitted on the valve seat between the step and the pressure cap; the other sealing structure is fitted on the valve seat between the step and the retrieval head.

6. The steam injection valve according to claim 2, characterized in that, Two pressure rings are fixedly connected to the valve stem, and the spring and the float are limited on the valve stem by the two pressure rings.

7. The steam injection valve according to claim 2, characterized in that, A centralizing ring is fixedly connected to the upper end of the valve seat, and the valve stem is fixedly connected to the centralizing ring.

8. The steam injection valve according to claim 2, characterized in that, The valve nozzle is a tapered tube whose inner diameter gradually decreases from top to bottom.

9. The steam injection valve according to any one of claims 1-8, characterized in that, The upper end of the main body is connected to an upper connector, which is used to connect to the oil pipe above the main body. The lower end of the main body is connected to a lower connector, which is used to connect to the oil pipe below the main body.

10. The steam injection valve according to claim 9, characterized in that, An outer cylinder is threadedly connected to the outer wall of the main body.

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