Oilfield wellhead gas recovery CNG system

Abstract

The application discloses an oil field wellhead gas recovery CNG system, comprising a pry body, a gas-liquid separation unit, a compressor unit, a dehydration unit, a filling unit and a switching valve are installed on the pry body, the gas-liquid separation unit has two gas-liquid separation unit output pipelines, one of the gas-liquid separation unit output pipelines is communicated with a compressor input end, a compressor unit output pipeline and the other gas-liquid separation unit output pipeline are communicated with two input ends of the dehydration unit, the oil field wellhead gas is recovered through the integrated CNG system, the subsequent equipment is convenient to migrate, and based on the size of external pressure (tank truck internal pressure) and filling pressure, the wellhead gas is filled in the mode of not being treated by the compressor or being filled after being compressed by the compressor, the working length of the compressor and the abrasion of the compressor caused by natural gas impurities can be effectively reduced, the service life of the compressor is prolonged, and the maintenance interval is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of natural gas processing equipment, in particular to an oilfield wellhead gas recovery CNG system. BACKGROUND

[0002] The products on the market have not realized pry installation, that is, the CNG equipment for oilfield gas is placed independently, occupies a large space, and it is difficult for oilfield personnel to monitor and operate the equipment. In addition, if the oilfield wants to move the equipment to another wellhead, it will be very cumbersome to move each device and connect the pipeline, and the oilfield personnel need to put in a lot of effort. Therefore, an oilfield wellhead gas recovery CNG system is needed to be developed, which integrates scattered devices into a pry device. In addition, the existing CNG system directly outputs high-pressure natural gas, so the compressor needs to be kept in a working state. During the initial stage of the filling system, a higher filling pressure is not necessarily required, so it needs to be improved to reduce the working time of the compressor and prolong the service life. SUMMARY

[0003] The present application provides an oilfield wellhead gas recovery CNG system, which can at least solve one problem pointed out in the background.

[0004] An oilfield wellhead gas recovery CNG system includes a pry body, which is provided with a gas-liquid separation unit, a compressor unit, a dehydration unit, a filling unit, and a switching valve. The gas-liquid separation unit has two gas-liquid separation unit output pipelines, one of which is in communication with the compressor input end, and the other is in communication with the two input ends of the dehydration unit. The position of the dehydration unit input end in communication with the gas-liquid separation unit output pipeline is higher than that of the dehydration unit input end in communication with the compressor unit output pipeline. The natural gas output pipeline of the dehydration unit is in communication with the filling unit.

[0005] The switching valve is installed at the intersection of the two gas-liquid separation unit output pipelines. The switching valve is driven based on the output pressure of the filling unit and the pressure in the tank car, so that the gas-liquid separation unit is in communication with the compressor unit or the dehydration unit.

[0006] Preferably, the dehydration unit includes a dehydration pipeline, a regeneration pipeline, and two molecular sieve adsorption towers connected in parallel to the dehydration pipeline and the regeneration pipeline. The molecular sieve adsorption towers have high-pressure input ends and low-pressure input ends.

[0007] Preferably, the dehydration pipeline includes:

[0008] The dehydration unit low-input pipe is in communication with the compressor unit output pipeline, and the two ends of the dehydration unit low-input pipe are connected to the high-pressure input ends of the two molecular sieve adsorption towers, respectively.

[0009] a high portion input pipe of the dewatering unit, in communication with the gas-liquid separation unit output pipe, two ends of the high portion input pipe being connected with low pressure input ends of the two molecular sieve adsorption towers, respectively; and

[0010] a gas output pipe, in communication with the filling unit input pipe, two ends of the gas output pipe being in communication with output ends of the two molecular sieve adsorption towers, respectively;

[0011] Preferably, the dewatering unit low portion input pipe is provided with a low pressure input end valve one and a low pressure input end valve two; the dewatering unit high portion input pipe is provided with a high pressure input end valve one and a high pressure input end valve two; and the gas output pipe is provided with a gas output valve one and a gas output valve two.

[0012] Preferably, the regeneration pipeline comprises:

[0013] a temperature rising water removal pipeline, in communication with hot regeneration gas input ends of bottoms of the two molecular sieve adsorption towers, respectively;

[0014] a temperature lowering dehumidification pipeline, in communication with output ends of tops of the two molecular sieve adsorption towers, respectively;

[0015] a heating unit, connected to the temperature rising water removal pipeline;

[0016] a condensing unit, connected to the temperature lowering dehumidification pipeline;

[0017] a circulating pump, in communication with the temperature rising water removal pipeline and the temperature lowering dehumidification pipeline.

[0018] Preferably, the temperature rising water removal pipeline is provided with a regeneration gas input valve one and a regeneration gas input valve two at positions where the temperature rising water removal pipeline is connected with the hot regeneration gas input ends of the two molecular sieve adsorption towers, respectively.

[0019] The temperature lowering dehumidification pipeline is provided with a regeneration gas output valve one and a regeneration gas output valve two at positions where the temperature lowering dehumidification pipeline is connected with the output ends of the two molecular sieve adsorption towers, respectively.

[0020] Preferably, the molecular sieve adsorption tower comprises a tower body and a plurality of molecular sieve layers arranged in the tower body, and each of the molecular sieve layers is provided with a support layer on both upper and lower sides.

[0021] Preferably, the support layer is a porous alumina layer.

[0022] Preferably, the plurality of molecular sieve layers are divided into two groups, and a low pressure input end region is located between the two groups of molecular sieve layers.

[0023] A rotating layer is arranged in the low pressure input end region, the rotating layer is located on the upper side of the support layer, a plurality of accommodation grooves are arranged on the rotating layer and matched with the through holes of the support layer, an elastic member is arranged between the tower body and the rotating layer, and a baffle is hingedly connected in the tower body and located at the low pressure input end.

[0024] When the gas-liquid separation unit output pipeline is communicated with the low-pressure input end, the baffle is blown open, the baffle is abutted on the elastic member and the elastic member is compressed, so that the rotating layer is rotated by a certain angle, until the accommodation groove is distributed in dislocation with the through hole on the supporting layer.

[0025] Preferably, the elastic member comprises a protrusion arranged on the upper side of the rotating layer and a connecting rod arranged on the inner wall of the tower body, and the protrusion and the connecting rod are connected through a spring.

[0026] Compared with the prior art, the beneficial effects of the present application are: the present application realizes oilfield wellhead gas recovery through an integrated CNG system, facilitates the migration of subsequent equipment, and based on the size of external pressure (tanker internal pressure) and filling pressure, adaptively selects the mode of filling without compressor treatment or the mode of filling after compression and pressurization, which can effectively reduce the working length of the compressor and the wear of the compressor caused by impurities in natural gas, improve the service life of the compressor, and improve the maintenance interval. BRIEF DESCRIPTION OF DRAWINGS

[0027] Fig. 1 is a CNG system working flowchart for oilfield wellhead gas recovery;

[0028] Fig. 2 is a principle diagram of the dehydration unit;

[0029] Fig. 3 is a schematic diagram of the internal structure of the molecular sieve adsorption tower;

[0030] Fig. 4 is a schematic diagram of the rotating layer structure when the natural gas enters the tower body from the high-pressure input end;

[0031] Fig. 5 is a schematic diagram of the rotating layer structure when the natural gas enters the tower body from the low-pressure input end.

[0032] BRIEF DESCRIPTION OF DRAWINGS:

[0033] 1-Gas-liquid separation unit, 2-Compressor unit, 3-Dehydration unit, 4-Refilling unit, 5-Switching valve, 6-Tank truck, 7-Gas-liquid separation unit output pipe, 11-Molecular sieve adsorption tower, 12-High pressure input end, 13-Low pressure input end, 14-Dehydration unit lower input pipe, 15-Dehydration unit upper input pipe, 16-Gas output pipe, 17-Low pressure input valve one, 18-Low pressure input valve two, 19-High pressure input valve one, 20-High pressure input valve two 21-Gas output valve one, 22-Gas output valve two, 31-Heating and dehumidifying pipeline, 32-Heating unit, 33-Cooling and dehumidifying pipeline, 34-Condensing unit, 35-Circulating pump, 36-Regeneration gas input valve one, 37-Regeneration gas input valve two, 38-Regeneration gas output valve one, 39-Regeneration gas output valve two, 41-Molecular sieve layer, 42-Support layer, 43-Rotating layer, 44-Allowing groove, 45-Baffle, 46-Protrusion, 47-Connecting rod, 48-Spring. Detailed Implementation

[0034] The following detailed description of a specific embodiment of the present invention is provided in conjunction with the accompanying drawings. However, it should be understood that the scope of protection of the present invention is not limited to the specific embodiment.

[0035] like Figs. 1-2 As shown, an embodiment of the present invention provides an oilfield wellhead gas recovery CNG system, including a skid and a gas-liquid separation unit 1, a compressor unit 2, a dehydration unit 3, a filling unit 4, and a switching valve 5 installed on the housing;

[0036] The oilfield wellhead gas first enters the desander (wellhead gas filtration equipment) through the inlet shut-off valve. The desander separates the solid impurities in the natural gas. The separated natural gas enters the gas-liquid separation unit 1 of the CNG system after passing through the inlet anti-plunger flow separator. The natural gas exits from the top of the gas-liquid separation unit 1 and splits into two paths, which are then loaded into the tank truck 6.

[0037] One route involves natural gas directly entering the dehydration unit 3 for deep dehydration, resulting in a finished gas with an atmospheric dew point of -55°C. The clean compressed natural gas after dehydration is then injected into the tank truck 6 via the refueling unit 4. Once the pressure inside the tank truck 6 is balanced with the inlet pressure, the other route is switched, where natural gas directly enters the compressor unit 2. The natural gas is pressurized to 22 MPa in the compressor unit 2, then enters the dehydration unit 3, and finally is injected into the tank truck 6 via the refueling unit 4.

[0038] The specific plan for implementing the above natural gas processing is as follows:

[0039] The gas-liquid separation unit 1 has two gas-liquid separation unit output pipes 7, one of which is in communication with the input end of the compressor unit 2, the output pipe of the compressor unit 2 and the other gas-liquid separation unit output pipe 7 are in communication with the two input ends of the dehydration unit 3, and the gas output pipe 16 of the dehydration unit 3 is in communication with the filling unit 4;

[0040] The switching valve 5 is installed at the intersection of the two gas-liquid separation unit output pipes 7, and is driven by the output pressure of the filling unit 4 and the pressure in the tank truck 6, so that the gas-liquid separation unit 1 is in communication with the compressor unit 2 or the dehydration unit 3.

[0041] The dehydration unit 3 includes a dehydration pipeline, a regeneration pipeline, and two molecular sieve adsorption towers 11 connected in parallel to the dehydration pipeline and the regeneration pipeline, the molecular sieve adsorption towers 11 have a high-pressure input end 12 and a low-pressure input end 13, the input end of the dehydration unit 3 in communication with the gas-liquid separation unit 1 output pipe is the low-pressure input end 13, the input end of the dehydration unit 3 in communication with the compressor unit 2 output pipe is the high-pressure input end 12, and the position of the high-pressure input end 12 is lower than that of the low-pressure input end 13;

[0042] One of the two molecular sieve adsorption towers 11 is in a dehydration state, i.e. in contact with natural gas to remove water from the natural gas, and the other molecular sieve adsorption tower 11 is in a regeneration state, i.e. in contact with hot gas to remove water from the molecular sieve for subsequent recycling;

[0043] The dehydration pipeline includes a dehydration unit low-end input pipe 14, a dehydration unit high-end input pipe 15, and a gas output pipe 16;

[0044] The dehydration unit low-end input pipe 14 is in communication with the compressor unit 2 output pipe, and the two ends of the dehydration unit low-end input pipe 14 are connected with the high-pressure input end 12 of the two molecular sieve adsorption towers 11 respectively, and the dehydration unit low-end input pipe 14 is provided with a low-pressure input end valve one 17 and a low-pressure input end valve two 18, which respectively control the natural gas entering the low-pressure input end 13 of the two molecular sieve adsorption towers 11;

[0045] The dehydration unit high-end input pipe 15 is in communication with the gas-liquid separation unit output pipe 7, and the two ends of the dehydration unit high-end input pipe 15 are connected with the low-pressure input end 13 of the two molecular sieve adsorption towers 11 respectively, and the dehydration unit high-end input pipe 15 is provided with a high-pressure input end valve one 19 and a high-pressure input end valve two 20, which respectively control the natural gas entering the high-pressure input end 12 of the two molecular sieve adsorption towers 11;

[0046] The gas output pipeline 16 is in communication with the input pipeline of the filling unit 4, and the two ends of the gas output pipeline 16 are in communication with the output ends of the two molecular sieve adsorption towers 11 respectively; the gas output pipeline 16 is provided with a gas output valve one 21 and a gas output valve two 22, and the gas output valve one 21 and the gas output valve two 22 are used for controlling the output of the natural gas of the two molecular sieve adsorption towers 11 respectively.

[0047] Wherein, the regeneration pipeline comprises a temperature-rising water-removing pipeline 31, a temperature-lowering moisture-removing pipeline 33, a heating unit 32, a condensing unit 34 and a circulating pump 35;

[0048] The heating unit 32 can be heated by resistance wire, and the condensing unit 34 can separate water from natural gas by reducing temperature through cooling equipment;

[0049] The temperature-rising water-removing pipeline 31 is in communication with the hot regeneration gas input ends at the bottoms of the two molecular sieve adsorption towers 11 respectively, the heating unit 32 is connected into the temperature-rising water-removing pipeline 31, and the temperature-rising water-removing pipeline 31 is provided with a regeneration gas input valve one 36 and a regeneration gas input valve two 37 respectively at the connection positions of the two molecular sieve adsorption towers 11;

[0050] The temperature-lowering moisture-removing pipeline 33 is in communication with the output ends at the tops of the two molecular sieve adsorption towers 11 respectively, the condensing unit 34 is connected into the temperature-lowering moisture-removing pipeline 33, and the temperature-lowering moisture-removing pipeline 33 is provided with a regeneration gas output valve one 38 and a regeneration gas output valve two 39 respectively at the connection positions of the two molecular sieve adsorption towers 11;

[0051] The circulating pump 35 is used for connecting the temperature-rising water-removing pipeline 31 and the temperature-lowering moisture-removing pipeline 33.

[0052] The wellhead gas pressure is 3.0-20.0 Mpa, and the pressure will be attenuated during the wellhead gas recovery process, so that the compressor unit is not needed in the initial stage, and thus the natural gas can be directly introduced into the dehydration unit 3 through one of the gas-liquid separation unit output pipelines 7 for dehydration, when the wellhead gas pressure is attenuated or the gas pressure in the tank truck 6 is greater than the filling pressure, the switching valve 5 is switched to make the natural gas pass through the compressor unit 2 and then enter the dehydration unit 3, so that the use time of the compressor can be effectively reduced, the abrasion of the compressor caused by impurities can be reduced, and the service life of the compressor is prolonged.

[0053] Embodiment two

[0054] As shown in Figs. 3-5 the embodiment, the oilfield wellhead gas recovery CNG system is provided, and on the basis of the embodiment one, the molecular sieve adsorption tower 11 is designed as follows:

[0055] The molecular sieve adsorption tower 11 comprises a tower body and a plurality of molecular sieve layers 41 arranged in the tower body, and the upper and lower sides of any molecular sieve layer 41 are provided with support layers 42.

[0056] The support layer 42 of the embodiment is a porous alumina layer;

[0057] The plurality of molecular sieve layers 41 is divided into two groups, and the area where the low-pressure input end 13 is located is between the two groups of molecular sieve layers 41.

[0058] A rotating layer 43 is arranged in the area where the low-pressure input end 13 is located, the rotating layer 43 is located on the upper side of one of the support layers 42, a plurality of accommodation grooves 44 are arranged on the rotating layer 43 and matched with the through-hole structure on the support layer 42, the tower body and the rotating layer 43 are connected through an elastic member, and a baffle 45 located at the low-pressure input end 13 is hinged in the tower body.

[0059] The elastic member includes a protrusion 46 arranged on the upper side of the rotating layer 43 and a connecting rod 47 arranged on the inner wall of the tower body, and the protrusion 46 and the connecting rod 47 are connected through a spring 48.

[0060] When the gas-liquid separation unit output pipeline 7 is communicated with the low-pressure input end 13, the baffle 45 is compressed by the elastic member, i.e., the baffle 45 is in contact with the elastic member and the elastic member is compressed, so that the rotating layer 43 is rotated by a certain angle, until the accommodation grooves 44 are distributed in a staggered manner with the through-hole structure on the support layer 42, thereby preventing the natural gas from moving downward and reducing the pressure loss of the natural gas. When the switching valve 5 is switched, the gas pressure at the low-pressure input end 13 disappears, and the elastic member and the baffle 45 return to the initial position. At this time, the accommodation grooves 44 are opposite to the through-holes of the support layer 42, and the natural gas enters from the high-pressure input end 12, passes through the first group of molecular sieve layers 41, the rotating layer 43, and the second group of molecular sieve layers 41, and is finally discharged from the output end of the molecular sieve adsorption tower to the filling unit 4.

[0061] It is apparent to those skilled in the art that the present application is not limited to the details of the foregoing exemplary embodiments, and that the present application can be implemented in other particular forms without departing from the spirit and essential characteristics of the present application. Thus, the embodiments should be considered in all respects as illustrative and not restrictive, and the scope of the present application should be determined by the appended claims rather than the above description, and it is intended to encompass all changes falling within the meaning and scope of equivalents of the claims. Any reference signs in the claims should not be construed as limiting the claims to which the reference signs relate.

[0062] In addition, it should be understood that although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. An oilfield wellhead gas recovery CNG system comprising a sled body, characterized in that, The prying body is provided with a gas-liquid separation unit, a compressor unit, a dehydration unit, a filling unit and a switching valve; the gas-liquid separation unit has two gas-liquid separation unit output pipelines, one of which is communicated with the compressor input end, the compressor unit output pipeline and the other gas-liquid separation unit output pipeline are communicated with two input ends of the dehydration unit, and the position of the dehydration unit input end communicated with the gas-liquid separation unit output pipeline is higher than that of the dehydration unit input end communicated with the compressor unit output pipeline; the natural gas output pipeline of the dehydration unit is communicated with the filling unit; The switching valve is installed at the intersection of the two gas-liquid separation unit output pipelines, and is driven based on the filling unit output pressure and the tank pressure, so that the gas-liquid separation unit is communicated with the compressor unit or the dehydration unit; The dehydration unit comprises a dehydration pipeline, a regeneration pipeline and two molecular sieve adsorption towers connected in parallel to the dehydration pipeline and the regeneration pipeline; the molecular sieve adsorption tower has a high-pressure input end and a low-pressure input end; The molecular sieve adsorption tower comprises a tower body and a plurality of molecular sieve layers arranged in the tower body; the upper and lower sides of any molecular sieve layer are provided with support layers; The plurality of molecular sieve layers are divided into two groups, and the low-pressure input end is located between the two groups of molecular sieve layers; A rotating layer is arranged in the region of the low-pressure input end, and the rotating layer is located on the upper side of the support layer; a plurality of accommodation grooves are formed in the rotating layer and matched with the through holes in the support layer; the tower body and the rotating layer are connected through elastic members; and a baffle is hinged in the tower body and located at the low-pressure input end; When the gas-liquid separation unit output pipeline is communicated with the low-pressure input end, the baffle is blown open, the baffle abuts against the elastic member and compresses the elastic member, so that the rotating layer rotates by a certain angle until the accommodation grooves are distributed in a staggered manner with the through holes in the support layer.

2. An oilfield wellhead gas recovery CNG system as defined in claim 1, characterized in that, The dehydration pipeline comprises: a dehydration unit low-input pipeline communicated with the compressor unit output pipeline, two ends of the dehydration unit low-input pipeline are connected with the high-pressure input ends of the two molecular sieve adsorption towers, respectively; a dehydration unit high-input pipeline communicated with the gas-liquid separation unit output pipeline, two ends of the dehydration unit high-input pipeline are connected with the low-pressure input ends of the two molecular sieve adsorption towers, respectively; and a gas output pipeline communicated with the filling unit input pipeline, two ends of the gas output pipeline are communicated with the output ends of the two molecular sieve adsorption towers, respectively.

3. An oilfield wellhead gas recovery CNG system as defined in claim 2, wherein, The dehydration unit low-input pipeline is provided with a low-pressure input end valve one and a low-pressure input end valve two; The dehydration unit high-input pipeline is provided with a high-pressure input end valve one and a high-pressure input end valve two; The gas output pipeline is provided with a gas output valve one and a gas output valve two.

4. The oilfield wellhead gas recovery CNG system of claim 1, wherein, The regeneration pipeline comprises: a temperature rising water removal pipeline communicated with the hot regeneration gas input ends at the bottoms of the two molecular sieve adsorption towers, respectively; a temperature lowering dehumidification pipeline communicated with the output ends at the tops of the two molecular sieve adsorption towers, respectively; a heating unit connected to the temperature rising water removal pipeline; a condensing unit connected to the temperature lowering dehumidification pipeline; a circulating pump communicated with the temperature rising water removal pipeline and the temperature lowering dehumidification pipeline.

5. An oilfield wellhead gas recovery CNG system as claimed in claim 4, characterised in that, The heating and water-removing pipeline is connected with the input ends of the two molecular sieve adsorption towers, and the input valve one and the input valve two are respectively arranged at the connection positions. The cooling and dehumidifying pipeline is connected with the output ends of the two molecular sieve adsorption towers, and the output valve one and the output valve two are respectively arranged at the connection positions.

6. An oilfield wellhead gas recovery CNG system as defined in claim 1, wherein, The support layer is a porous alumina layer.

7. An oilfield wellhead gas recovery CNG system as defined in claim 1, wherein, The elastic member comprises a protrusion arranged on the upper side of the rotating layer and a connecting rod arranged on the inner wall of the tower body, and the protrusion and the connecting rod are connected through a spring.

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