Pressure-switching pressure reduction system

Abstract

A pressure-reduction system includes inlets for receiving high-pressure gas, a piping network connected with the inlets, pressure-reduction stages connected with the piping network and operable to reduce pressure of the high-pressure gas to low-pressure gas, and a heater configured to heat the gas after at least one of the pressure-reduction stages. The piping network is configured to switch between the inlets and, upon switching, buffer a pressure differential in order to avoid a pressure shock.

Description

PRESSURE-SWITCHING PRESSURE REDUCTION SYSTEM BackgroundIn a hydraulic fracturing operation, pumps are used to inject fracking fluid down a wellbore in order to assist with fracturing of rock formations. The pumps have traditionally been diesel fuel powered, but more recently pumping has been conducted with electrically powered pumps. Turbine generators at the site combust natural gas to generate the necessary electrical power to run the pumps. Compressed natural gas is delivered to the site in large tanks, which allows maximum amounts of the natural gas to be delivered. The initial pressure of the compressed natural gas, however, is much higher than the desired input pressure into the turbine generators. The natural gas from the delivery tanks is therefore run through a pressure reduction system to reduce the pressure and produce “treated” compressed natural gas that is at the desired input pressure (and temperature) for the turbine generators. SUMMARYA pressure-reduction system according to an example of the present disclosure includes inlets for receiving high-pressure gas, a piping network connected with the inlets, pressure-reduction stages connected with the piping network and operable to reduce pressure of the high-pressure gas to low-pressure gas, and a heater configured to heat the gas after at least one of the pressure-reduction stages. The piping network is configured to switch between the inlets and, upon switching, buffer a pressure differential in order to avoid a pressure shock.The present disclosure may include any one or more of the individual features disclosed above and / or below alone or in any combination thereof. BRIEF DESCRIPTION OF THE DRAWINGSThe various features and advantages of the present disclosure will become apparent to those skilled in the art from the following detailed description. In this disclosure, like reference numerals designate like elements where appropriate and reference numerals with the addition of one-hundred or multiples thereof designate modified elements that are understood to incorporate the same features and benefits of the corresponding elements. The drawings that accompany the detailed description can be briefly described as follows.Figure 1 illustrates a compressed natural gas system.Figure 2 illustrates a pressure-reduction system of the compressed natural gas system.DETAILED DESCRIPTIONFigure 1 schematically illustrates an example of a compressed natural gas system 150. For example, the system 150 is configured to deliver treated natural gas to equipment on a gas / oil well site, such as turbine generators at a hydraulic fracturing operation. As used herein, “treated natural gas” refers to natural gas that has undergone a controlled pressure reduction from an initial relatively high pressure to a lower, target pressure and temperature for input into the downstream equipment. In one example, the system 150 is mobile and thus does not include any permanent structures, such as buildings that stand permanently in one place.In the example shown, the system 150 involves a pressurized natural gas source 152, a gas distributer 154, and multiple pieces of equipment 156 to which compressed natural gas is to be delivered. It is to be appreciated that the equipment 156 is shown in order to demonstrate an example configuration and operation of the system 150, and the equipment 156 may or may not be considered to be a part of the system 150. The pressurized natural gas source 152 is any source of natural gas that has a pressure and temperature that meets pressure and temperature targets for input into the equipment 156. In one example, the pressurized natural gas source 152 includes a pressure reduction system.152a. As will be discussed in further detail below, the pressure reduction system 152a includes multiple stages of controlled, progressive pressure reductions and temperature manipulations in order to take high pressure input natural gas and provide an output of natural gas that is controlled to a pressure and temperature that that meets pressure and temperature targets for input into the equipment 156. In the illustrated example, the treated compressed natural gas from the pressure reduction system 152a is output through one or more gas feed lines 158 to the gas distributer 154. In another embodiment, the distributer 154 is excluded and the treated compressed natural gas is fed directly into the equipment 156.The gas distributer 154, if present, serves to supply the compressed natural gas through gas supply lines 160 to the multiple pieces of equipment 156, e.g., turbine generators. In one example, the lines 158 / 160 are hoses that are rated for transferring natural gas and rated for the applicable pressures that the gas will be at in the system 150. The hoses may also have additional properties to be better suited to a given implementation of the system 150, such as but not limited to, flexibility, temperature durability, and chemical resistance. The hoses, distributer 154, and other components of the system 150 should also meet any applicable codes and / or site regulations for handling and / or delivering compressed natural gas, which a person of ordinary skill in the art will be aware of.Figure 2 schematically illustrates a pressure reduction system ("PRS") 10 that can be used at 152a. As indicated above, the PRS 10 is situated between the turbine generators 156 and a natural gas supply and serves to reduce the initial pressure to the desired input pressure and temperature into the turbine generators 156.

[0001] Referring to Figure 2, the PRS 10 includes a plurality of inlets 12 (also colloquially "lanes") for receiving high pressure natural gas, e.g., from the delivery tank(s). For example, each of the inlets 12 includes a connector that is configured to securely connect to a hose that runs from the delivery tank(s). It is to be understood that any connectors or connections, either shown or described, is a fluid connection. The inlets 12 lead into a piping network 14. The piping network 14 includes a manifold 16 that receives the incoming natural gas and delivers it through outlet pipe 18 to a first stage pressure-reduction 19a of pressure-reduction section 20. The reduction in pressure results in a reduction in temperature of the natural gas. Thus, after the first stage pressure-reduction 19a, the gas flows through a heating coil in a heater 22, which serves to increase the temperature of the gas. The gas then flows to a second stage pressure-reduction 19b, where the pressure of the gas is again reduced, before flowing through another heating coil in the heater 22. The gas then flows to a final, third stage pressure-reduction 19c, where the pressure of the gas is again reduced, before flowing through outlet 24 of the PRS 10 and then to the distributer 154 or directly to the turbine generators 156.

[0002] As the natural gas from the delivery tank is consumed, the pressure of the gas provided at the inlet 12 decreases. In order to continually supply the natural gas to the turbine generators 156, a second delivery tank is connected to another of the inlets 12 so that when the first delivery tank is exhausted, the PRS 10 can switch to the second delivery tank. The term "exhausted" may mean that the delivery tank is completely empty but more typically refers to a minimum desired input pressure into the PRS 10. For example, once the delivery pressure diminishes to a low threshold level, there may not be enough natural gas throughput to meet the demand of the downstream turbine generators 156. As a result, when the delivery pressure reaches the low threshold level, the PRS 10 switches to the second delivery tank. This switch can be conducted manually or in an automated manner via a controller 162 that is in communication with pressure sensors / transmitters 26 and valves 28 / 29 associated with each inlet 12. As an example, the valves 28 / 29 are electrically-actuated valves that are in electrical communication with controller 162. For instance, when the pressure of the gas from the delivery tank 1 reaches the low threshold level, valves 28 / 29 associated with the inlet 12 from that tank are selectively closed, and valves 28 / 29 associated with the inlet 12 of LANE 2 that is connected to delivery tank 2 are opened.

[0003] The piping network 14 includes a manifold 16 that receives the incoming natural gas and delivers it through outlet pipe 18 to the first stage pressure-reduction 19a of pressure-reduction section 20. Each inlet 12 is connected with an inlet line 12a that leads directly into the manifold 16. The valves 28 is disposed in the inlet line 12a. Each inlet line 12a also has a bypass line 30 that bypasses the respective inlet line valve 28. Each bypass line has a bypass line valve 29.

[0004] The pressure at the low threshold level may be substantially different than the initial pressure of the second, "fresh" delivery tank. In that regard, an instantaneous switch to delivery tank 2 could result in a large, sudden pressure increase (pressure shock), which in turn may damage sensitive components in the PRS 10 (or at least reduce the life of the components). In this regard, the piping network 14 is configured to buffer the pressure differential in order to avoid a pressure shock. The following example demonstrates buffering of the pressure differential in order to avoid a pressure shock pressure. For instance, gas input is switched from the LANE 1 inlet 12 to the LANE 2 inlet 12. The sensors / transmitters 26 communicate inlet pressures to an on-board controller system 162 (e.g., Scadacore) in the PRS 10. As the natural gas from the supply delivery tank 1 is consumed through LANE 1, the gas pressure at the LANE 1 inlet 12 depletes from 4000 psi initially to a low pressure level that is typically less than 1000 psi, such as 300 psi. The low pressure level may be preset in the controller 162 as the low threshold level to trigger the switch to LANE 2. When the inlet pressure at LANE 1 diminishes to the low threshold level, the controller responsively switches to LANE 2 for supply delivery tank 2 and closes LANE 1. The delivery tank 2 (at 4000 psi) is connected to LANE 2. When the input pressure for LANE 1 reaches the 300 psi threshold (e.g., less than 1000 psi), the valve 28a closes (all valves 28 are now in a closed state). The bypass valve 29b then opens and stays open until inlet pressure is equalized from inlet 12 of LANE 2 through the piping network 14 (including manifold 16), valve 28b then opens and valve 29a closes. Thus, the bypass lines 30 does not serve merely to bypass the inlet line valves 28, but rather to add volume and permit the gas to diffuse and thus reduce pressure in the piping network 14 to equalize before the equalized gas is then provided into the first pressure-reduction 19a. This reduces or eliminates any pressure shock in the system 150, and thus facilitates enhanced durability of the system 150. This system also protects the internal pressure of the PRS 10 from diminishing below the low threshold level.Although a combination of features is shown in the illustrated examples, not all of them need to be combined to realize the benefits of various embodiments of this disclosure. In other words, a system designed according to an embodiment of this disclosure will not necessarily include all of the features shown in any one of the Figures or all of the portions schematically shown in the Figures. Moreover, selected features of one example embodiment may be combined with selected features of other example embodiments.The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from this disclosure. The scope of legal protection given to this disclosure can only be determined by studying the following claims.

Claims

What is claimed is:

1. A pressure reduction system comprising:a plurality of inlets for receiving high-pressure gas;a piping network connected with the inlets;a plurality of pressure-reduction stages connected with the piping network and operable to reduce pressure of the high-pressure gas to low-pressure gas; anda heater configured to heat the gas after at least one of the pressure-reduction stages, wherein the piping network is configured to switch between the inlets and, upon switching, buffer a pressure differential in order to avoid a pressure shock.

2. The system as recited in claim 1, wherein the piping network includes electrically-actuated valves.

3. The system as recited in claim 2, wherein the piping network includes a plurality of inlet lines connected to receive the high-pressure gas from the inlets, the electrically-actuated valves include a plurality of inlet line valves disposed in the inlet lines, and a manifold connected to each of the inlet lines.

4. The system as recited in claim 3, wherein the piping network includes a plurality of bypass lines, each of the bypass lines bypassing one of the inlet line valves, and the electrically-actuated valves include a plurality of bypass valves disposed in the bypass lines .

5. The system as recited in claim 4, further comprising a controller electrically connected with each of the electrically-actuated valves.

6. The system as recited in claim 5, wherein, responsive to the switching, the controller is configured to open at least one of the bypass valves and close all of the inlet line valves.

7. The system as recited in claim 6, wherein the controller is configured to trigger the switching in response to a low-pressure threshold of gas received to one of the inlets.

8. The system as recited in claim 8, wherein the low-pressure threshold is less than 1000 psi.

9. The system as recited in claim 1, further comprising a heater configured to increase a temperature of the gas after each of the pressure-reduction stages.

10. The system as recited in claim 1, further comprising a gas distributer connected with an outlet located downstream of the pressure-reduction stages.

11. The system as recited in claim 1, further comprising a plurality of turbine generators connected with an outlet located downstream of the pressure-reduction stages.

12. The system as recited in claim 1, wherein the piping network includes a plurality of inlet lines connected to receive the high-pressure gas from the inlets, a plurality of inlet line valves disposed in the inlet lines, and a manifold connected to each of the inlet lines.

13. The system as recited in claim 12, wherein the piping network includes a plurality of bypass lines, each of the bypass lines bypassing one of the inlet line valves, and a plurality of bypass valves disposed in the bypass lines.

14. The system as recited in claim 13, further comprising a controller electrically connected with each of the inlet line valves and the bypass line valves.

15. The system as recited in claim 14, wherein, responsive to the switching, the controller is configured to open at least one of the bypass valves and close all of the inlet line valves.

16. The system as recited in claim 15, wherein the controller is configured to trigger the switching in response to a low-pressure threshold of gas received to one of the inlets.

17. The system as recited in claim 16, wherein the low-pressure threshold is less than 1000 psi.

18. The system as recited in claim 17, further comprising a heater configured to increase a temperature of the gas after each of the pressure-reduction stages.

19. The system as recited in claim 18, further comprising a gas distributer connected with an outlet located downstream of the pressure-reduction stages. 

Images