High-pressure hybrid vessel for low-power hydrocarbon vapor recovery

Abstract

A hybrid production and storage vessel includes a liquid hydrocarbon outlet, a produced water outlet and a vent, wherein a weir separates the liquid hydrocarbon outlet and the produced water outlet. A vapor recovery unit includes one or more compressors and one or more motors connected to said compressors. A vent line connects the vent to the compressors and a valve controls flow through the vent line. A sensor is positioned to provide an indication of a level of pressure within the hybrid production and storage vessel. A controller is connected to the one or more motors, the valve and the sensor, wherein upon a level of pressure reaching a selected threshold, the controller operates to open the valve and drive the one or more motors.

Description

HIGH-PRESSURE HYBRID VESSELFOR LOW-POWER HYDROCARBON VAPOR RECOVERYBACKGROUND

[0001] Current designs for hydrocarbon production facilities (i.e. oil and gas wells) tend to leak and / or flare a substantial amount of methane and other hydrocarbon vapors, and suffer various inefficiencies due to product quality challenges and unreliable grid power or insufficient on-site generation for continuous vapor recovery unit (VRU) operation. The significant impact and scope of emissions is such that global and national agencies across the world have targeted this wasted energy source and atmospheric pollution nexus for immediate reduction. Examples include the U.S. Environmental Protection Agency (EP A) and the International Energy Agency (IEA).

[0002] To reduce emissions, liquid hydrocarbon production facilities employ various equipment, including low pressure separators, storage tanks, and VRUs to capture gas vapors that would otherwise leak to atmosphere. Current liquid hydrocarbon production facilities use VRUs driven by electric motors and thus require a reliable power source to operate. When a liquid hydrocarbon and gas source (e.g., a well) produce fluids at low pressure, the reliability, efficiency, and effectiveness of VRUs is diminished. Thus, many VRUs are installed at the beginning of a facility production cycle but fall into disuse or disrepair. When this situation happens, gas and vapor is vented, flared, or not captured. Similar emissions issues occur due to inefficiencies or issues with capture of product at: (i) natural gas wells, and (ii) plugged and abandoned wells (commonly known as ‘zombie wells’); which often continue to emit hydrocarbon vapors despite containment efforts.

[0003] There is significant pressure in the current market to uncover new ways to reduce vented, flared, or otherwise lost product resulting in atmospheric pollution. Avenues to improve energy efficiency, capture rogue emissions, and reduce flaring are sought by companies, governments, and agencies.SUMMARY

[0004] Concepts described herein relate to a vapor recovery system in a hydrocarbon production facility. The facility includes one or more hybrid production and storage vessels including a liquid hydrocarbon outlet, a produced water outlet and a vent. The vessels may include multiple National Pipe Taper (NPT) ports for optional chemical injection to enhance demulsification. An internal weir separates the liquid hydrocarbon outlet and the produced water outlet to facilitate phase separation. The system includes a vapor recovery unit (VRU) having one or more compressors and one or more motors connected to said compressors. A vent line connects the vent to a compressor and a valve controls flow through the vent line. A sensor provides an indication of a level of pressure within each hybrid production and storage vessel and a controller is connected to the motors, the valve, and the sensor. In one embodiment, upon a level of pressure reaching a selected threshold greater than 25 pounds per square inch (psi), the controller operates to open the valve and drive the motors.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. l is a schematic flow diagram of a hydrocarbon production facility.

[0006] FIG. 2 is a front isometric view of a vapor recovery system.

[0007] FIG. 3 is a rear isometric view of the vapor recovery system of FIG 2.

[0008] FIG. 4 is a plan view of the vapor recovery system of FIG. 2.

[0009] FIG. 5 is a left side view of the vapor recovery system of FIG. 2.

[0010] FIG. 6 is a right side view of the vapor recovery system of FIG. 2.

[0011] FIG. 7 is a section view of the vapor recovery system of FIG. 2.DESCRIPTION

[0012] The designs and concepts described herein relate to a multi-use vapor recovery system, which improves overall operations while capturing methane. The designs and concepts serve to reduce emissions, enhance product output, and / or lower power requirements to operate in various applications and types of hydrocarbon production facilities.

[0013] The concepts can be applied with slight variations depending on the facility or well type, but provide benefits to each with regard to lower power, lower emissions, and / or improved product.

[0014] In a plugged and abandoned well application, the concepts provide a unique approach to capture vapor emissions that would have escaped to atmosphere, improving current mitigation approaches of either putting a flare on the site, or ‘re-plugging’ the well, which very often still emits vapors after additional containment efforts.

[0015] In a gas well application, the concepts provide a unique approach to separate natural gas from contaminants, increasing product quality and preventing gas from being flared (i.e. methane emissions). In certain gas well locations, the concepts may replace or remove other equipment requirements while improving overall operations.

[0016] In a liquid hydrocarbon facility, the application provides for reduced electrical power requirements, reduced emissions, prevention of venting events, and higher product quality. The design optimizes higher pressure in the hybrid production and storage vessels to minimize power requirements for vapor recovery units.

[0017] FIG. 1 is a schematic flow diagram of a low power hydrocarbon processing and storage method or process 100 in a hydrocarbon processing facility. Inlet fluids into the process 100 are provided through an initial flow line 102 (e.g., from a well or processing equipment) optionally through a heater treater 103 for thermal demulsification, then to one or more hybrid production and storage vessels 104, wherein the one or more hybrid production and storage vessels 104 may be connected in sequence for staged separation or in parallel for increased capacity.

[0018] As illustrated herein, one or more hybrid production and storage vessels 104 are multifunction three-phase separators that separate fluids from flow line 102 into low-pressure (LP) gas, liquid hydrocarbons (e.g., oil, natural gas liquids), and produced water. In addition to separation, vessels 104 can serve as a storage location for fluids from flow line 102. LP gas is vented from hybrid production and storage vessels 104 through a vent line 120. Hybrid production and storage vessels 104 are further useful in creating a consistent volume of flash gas with high residence time for liquid-vapor separation and substantial flash surface with complete gas capture. As a result, a volume of gas venting or flaring from a hydrocarbon processing facility is reduced, while product quality and quantity are increased. In one embodiment, flow of gas remains in a laminar state throughout process 100, minimizing turbulence in the hybrid production and storage vessels.

[0019] Produced water from hybrid production and storage vessels 104 is sent along line 126, whereas liquid hydrocarbons from hybrid production and storage vessels 104 are sent or supplied along line 128. Meters (e.g., meters 144 and 146 schematically illustrated) can be connected to each of the lines 126 and 128, respectively, to provide an indication of volume of fluid sent from each hybrid production and storage vessels 104. Line 126 can lead to one or more produced water vessels 106. Water from vessel 106 can be pumped through line 132 into a disposal line, a truck, or stored. Line 128 can lead to one or more liquid hydrocarbon vessels 108. Liquid hydrocarbons from vessel 108 can be pumped through line 134 into a sales line, a truck, or otherwise stored.

[0020] Hybrid production and storage vessels 104 and storage vessels 106 and 108, in one embodiment, are oriented horizontally (i.e., having a major axis extending along a length of the vessel and a minor axis extending along a height of the vessel, a maximum dimension of the vessel along the major axis being greater than the maximum dimension of the vessel along the minor axis). One or more vapor recovery units (VRUs) 110 are fluidly coupled with hybrid production and storage vessels 104 through vent line 120. Additionally, a vent line 122 fluidly connects vessels 106 and 108 to the one or more vapor recovery units 110. In a further embodiment, storage vessels 106 and 108 may be oriented vertically or at a non-horizontal angle.

[0021] In one embodiment, VRU 110 is positioned to receive vapor from more than one vessel. Lines 120 and 122, in one embodiment, can connect to VRU 110 at different positions based on different pressure within lines 120 and 122. In one example, VRU 110 can include one or morestages that will provide compression of gas at different pressures to produce LP gas along a line 130. In one embodiment, each stage can include a separate motor and compressor for each stage can be included in VRU 110. In instances where pressure along 120 or 122 exceeds a threshold pressure controlled by a regulating valve 150 to VRU 110, gas can be sent to the flare through a flare line 124 and measured with meter 142. Flaring may be required in certain circumstances, such as equipment failure or gas sales lines being shut down.

[0022] Enclosure of hybrid production and storage vessels 104 and vessels 106 and 108 using vent lines 120 and 122 creates an enclosed, pressurized volume that limits oxygen from entering. In one embodiment, pressure within vessel 104 can be maintained at a similar level to that of an LP line 130. When using similar pressure for vessel 104 and line 130, duty cycle, required horsepower, and overall energy consumption of VRU 110 can be minimized. By limiting or preventing oxygen from entering the volume, there is a lower likelihood of an emission event because of gas rejection at a delivery point due to a gas composition specification, a lower likelihood of creating an explosive gas mixture, and a lower likelihood of creating a corrosive environment. Additionally, a need for a separate vapor recovery tower is eliminated. Meters (e.g., meter 140 schematically illustrated) can be connected to each of the lines 120, 122 to provide an indication of volume of gas produced from each of the vessels 104, 106, 108.

[0023] Water from hybrid production and storage vessels 104 is sent through a dump line 126 to water storage vessel 106, controlled by dump valve 152. Meter 144 can be connected to the dump line 126 to provide an indication of volume of water produced from hybrid production and storage vessel(s) 104. Liquid hydrocarbons from hybrid production and storage vessels 104 is sent through a dump line 128 to liquid hydrocarbons storage vessel 108, controlled by dump valve 154. Meter 146 can be connected to the dump line 128 to provide an indication of volume of liquid hydrocarbons produced from hybrid production and storage vessels 104.

[0024] One or more back pressure valves 156 can be positioned onto line 122 to regulate pressure along line 122 and to VRU 110. Control valves 158 operable by a controller 160 is configured to control gas flow from vessel 104 to VRU 110, and from 106 and 108 to VRU 110. In addition, controller 160 can be communicatively coupled to VRU 110 to drive one or more motors of the VRU 110, as well as other components (e.g., sensors) to implement process 100 within the facility.In one embodiment, controller 160 determines if pressure within vessel 104 has reached a selected threshold. If pressure reaches the selected threshold, controller 160 opens valve 158 along line 120, closes valve 158 along line 122, and drives the one or more motors of the VRU 110 to produce gas along LP line 130. In one embodiment, controller 160 determines if pressure within either vessel 106 or 108 has reached a selected threshold. If pressure reaches the selected threshold, controller 160 opens valve 158 along line 122, closes valve 158 along line 120, closes a corresponding valve (either 152 or 154, respectively) of the vessel with pressure detected (either 106 or 108, respectively), and drives the one or more motors of the VRU 110 to produce gas along LP line 130. As such, controller 160 can be utilized to reduce power consumption of VRU 110, as VRU 110 can be selected to operate when pressure reaches the selected threshold. After pressure drops below the selected threshold, controller 160 can operate to close valve 158 along line 120 and cease driving the one or more motors of VRU 110. As a result, residence time of gas within vessel 104 can be greater than 1 hour. This amount of time is achieved through high-pressure operation and threshold-controlled venting by the controller.

[0025] FIGS. 2-7 illustrate several views of a low power hybrid production and storage vessel assembly 200, including a hybrid production and storage vessel 202 mounted to a skid or frame 204. Assembly 200 can be incorporated into process 100 as discussed above with respect to FIG.1. Hybrid production and storage vessel 202 is constructed to allow for a high operating pressure (e g., at a target of greater than 25 pounds per square inch (psi), greater than 50 psi, greater than 100 psi, greater than 150 psi, between 200 and 300 psi, and up to 1,000 psi). In the method and facility, the vessels operate at greater than 25 psi with NPT ports for demulsification. In one embodiment, vessel 202 is formed of carbon steel that is approximately 3 / 8” thick. In another embodiment, vessel 202 is formed of carbon steel that is approximately ’A” to 1” thick, or 1” to 1.5” thick. In other embodiments, vessel 202 can be formed of stainless steel. In the illustrated embodiment, the vessel 202 is formed of a cylindrical body having two end caps on either end of the cylindrical body. A length of the vessel 202 (i.e., along a major axis of the body) is greater than a diameter of the cylindrical body. A ratio of length to diameter of the cylindrical body can be selected as desired. In various embodiments, the ratio can be 1.5:1, 2: 1, 3:1, 4: 1, 5:1 or greater than 5: 1, or any ratio in between. In an alternative embodiment, vessel 202 can be a spherical vessel to optimize pressure distribution and reduce material thickness requirements, while maintaining the same internal components such as the weir, NPT ports, and diverter plate. Forexample, a spherical vessel with a diameter equivalent to the cylindrical length (e.g., 240 inches) could be used for high-pressure applications up to 1,000 psi. In one specific embodiment, the length of the cylindrical body is 240 inches and the diameter of the cylindrical body is 96 inches, which equals a length to diameter ratio of 2.5 : 1.

[0026] A plurality of vertical supports 206 extends from frame 204 to support either side of vessel 202. Fluid (e.g., liquid hydrocarbons, produced water) is provided to vessel 202 through an inlet 208 connected to a piping assembly 210. Connected to vessel 202 include a pressure relief valve 212, side cleanout 214, level sensor 216 (e.g., a guided wave radar sensor), optionally including an emulsion layer detection sensor 290 connected to the controller for automated dosing of demulsifiers through the NPT ports to efficiently split and separate phases, temperature indicator transmitter 218, a pressure indicator transmitter 220, a pressure indicating gauge 222, and a temperature indicating gauge 224, and multiple NPT ports 280-286 for optional chemical injection to acidify or demulsify the fluid mixture, facilitating easier separation of components. Optionally, NPT ports can be used for chemical injection, emulsion layer sensors, coalescing media, electrostatic coalescer, and ultrasonic devices. A level safety switch 226 can be utilized for prevention of overfilling the vessel 202. A control valve 228 controls flow of gas from vent 232 to compressor 264. A wiring interconnect junction box including a controller 250 can be utilized to locate and electrically connect various components of assembly 200, including level sensor 216, temperature indicator transmitter 218 and pressure indicator transmitter 220 and control valve 228.

[0027] Vessel 202 further includes a vent 232 connected to a gas outlet pipe assembly 234, a liquid hydrocarbons outlet 236 connected to a liquid hydrocarbons outlet pipe assembly 238, and a produced water outlet 240 connected to a produced water outlet pipe assembly 242. A liquid hydrocarbon side drain 244 is further provided within vessel 202.

[0028] A VRU 260 is directly coupled to (e.g., mounted to, connected to, secured to) frame 204 as shown in FIGS. 2-6. Pipe assembly 234 extends and is connected with the VRU 260 to transfer gas from vent 232 to VRU 260. VRU 260 includes one or more electric motors 262 and one or more compressors 264. During operation, VRU 260 displaces gas contained within vessel 202 by operating one or more motors to rotate input shafts of one or more compressors 264. In one embodiment, an electric motor 262 is a brushless direct current motor. While gas is beingdisplaced, the temperature of the gas rises. A gas cooler 266 is positioned to cool gas exiting compressor 264. Gas exits VRU 260 through a piping assembly 268.

[0029] Controller 250 is configured to operate one or more motors 262 when conditions within vessel 202 are present. For example, controller 250 can be connected to pressure indicator transmitter 220. When a pressure indicated by pressure indicator transmitter 220 reaches a selected threshold, controller 250 opens valve 228 and operates one or more motors 262. In one embodiment, an amount of torque delivered by one or more motors 262 is selected based on the pressure indicated by transmitter 220. In addition, an amount of torque delivered to one or more motors 262 can vary based on real-time pressure feedback from the pressure indicator transmitter 220.

[0030] With reference to FIG. 7, a section view of hybrid production and storage vessel 202 illustrates an inlet diverter plate 270 that operates to direct high velocity fluids received from inlet 208, and multiple NPT ports 280-286 positioned along the vessel for injecting chemicals such as mild acids (e.g., acetic acid or citric acid) to slightly acidify the mixture, promoting breakout of emulsions and improving separation efficiency. Diverter plate 270 provides an initial stage of separation, causing methane-containing gas to collect within an upper portion of the vessel 202 as liquid falls to a bottom portion of the vessel 202. A wave baffle 272 reduces turbulence of liquid in vessel 202 and assists in gravitational separation of liquid in vessel 202. As gravitational separation occurs, liquid hydrocarbons float on top of more dense liquids, referred to as produced water. Liquid hydrocarbons float over a weir plate 274 and collect at a right-hand portion of the vessel 202. The hybrid production and storage vessel may optionally include an emulsion layer detection sensor 290 connected to the controller for automated dosing of demulsifiers through the NPT ports 280-286, coalescing media or packing materials 292 positioned downstream of the baffle 272 to promote emulsion breaking, an electrostatic coalescer 294 integrated near the weir plate 274 to apply electric fields for demulsifying emulsions, and an ultrasonic module 296 mounted to the vessel to apply vibrations for demulsifying the fluid mixture.

[0031] Ultimately, gas exits vessel 202 through vent 232, which can include a mist extractor 276. Mist extractor 276 provides surface area within the flowing gas stream that liquids entrained in thegas collect onto, and fall back into the liquid space via gravity. Accordingly, liquids within the gas are removed from the flowing gas stream through vent 232.

[0032] A connection to a power grid, thermoelectric generator, solar, battery, or other supplemental generator can be included to operate the electric components.

[0033] When applied across hundreds or thousands of hydrocarbon facilities, concepts presented herein can reduce methane and rogue vapor emissions and dramatically reduce power requirements.

[0034] Various embodiments of the invention have been described above for purposes of illustrating the details thereof and to enable one of ordinary skill in the art to make and use the invention. The details and features of the disclosed embodiments] are not intended to be limiting, as many variations and modifications will be readily apparent to those of skill in the art. Accordingly, the scope of the present disclosure is intended to be interpreted broadly and to include all variations and modifications coming within the scope and spirit of the appended claims and their legal equivalents.

Claims

CLAIMS1. A vapor recovery assembly in a hydrocarbon production facility, comprising: one or more hybrid production and storage vessels, each vessel including a liquid hydrocarbon outlet, a produced water outlet, a vent, a weir separating the liquid hydrocarbon outlet and the produced water outlet, and multiple National Pipe Taper (NPT) ports for optional chemical injection to enhance demulsification; a vapor recovery unit including one or more compressors and one or more motors connected thereto; a vent line connecting the vent to the compressors; a valve controlling flow through the vent line; a sensor providing an indication of level of pressure within the vessels; and a controller connected to the one or more motors, the valve, and the sensor, wherein upon level of pressure reaching a selected threshold greater than 25 pounds per square inch, the controller operates to open the valve and drive the one or more motors.

2. The vapor recovery assembly of claim 1, wherein the one or more hybrid production and storage vessels are connectable in sequence or in parallel.

3. The vapor recovery assembly of claim 1, wherein the vent includes a mist extractor.

4. The vapor recovery assembly of claim 1, wherein the controller is configured to control a variable torque by the one or more motors to the one or more compressors proportionally based on the indication of the level of pressure.

5. The vapor recovery assembly of claim 4, wherein the controller is configured to vary the torque delivered by the one or more motors while the valve is open.

6. The vapor recovery assembly of claim 1, wherein a motor is a brushless direct current motor.

7. The vapor recovery assembly of claim 1 , further comprising a frame supporting the vessel and the vapor recovery unit.

8. The vapor recovery assembly of claim 1, further comprising a heater treater positioned upstream of the vessels to heat incoming fluids and aid in emulsion breaking.

9. The vapor recovery assembly of claim 1, wherein the vessels further include coalescing media for enhanced demulsification.

10. The vapor recovery assembly of claim 1, wherein the vessels include an electrostatic coalescer positioned near the weir to apply electric fields for demulsifying emulsions, thereby improving separation efficiency and product quality.

11. The vapor recovery assembly of claim 1, further comprising an optional ultrasonic device mounted to the vessels for demulsifying the fluid mixture.

12. The vapor recovery assembly of claim 1, further comprising an emulsion layer sensor connected to the controller for automated chemical injection through the multiple NPT ports to enhance demulsification.

13. The vapor recovery assembly of claim 1, wherein at least one of the one or more hybrid production and storage vessels is spherical.

14. A method of operating a hydrocarbon production facility, comprising: receiving fluid into one or more hybrid production and storage vessels including a produced water outlet, a liquid hydrocarbon outlet, a vent, and a weir separating the produced water outlet and the liquid hydrocarbon outlet with multiple NPT ports for optional injection of chemical treatments to acidify or demulsify the fluid mixture, the vessels configured for operation at pressures greater than 25 pounds per square inch (psi); detecting a level of pressure within the vessels;upon the level of pressure reaching a selected threshold greater than 25 psi, operating a control valve to transfer gas within the vessels to a vapor recovery unit having one or more motors and one or more compressors; and delivering torque from one or more motors to operate said compressors.

15. The method of claim 14, wherein the vent includes a mist extractor for removing liquid droplets from gas in the vessels.

16. The method of claim 14, further comprising delivering torque from the one or more motors to the one or more compressors based on the level of pressure.

17. The method of claim 16, further comprising varying the torque delivered by the one or more motors to the one or more compressors.

18. The method of claim 14, wherein a motor is a brushless direct current motor.

19. The method of claim 14, wherein a residence time of gas in the vessel is at least 1 hour.

20. A hydrocarbon production facility, comprising: one or more hybrid production and storage vessels including a liquid hydrocarbon outlet, a produced water outlet, a first gas vent, liquid hydrocarbon outlet and produced water outlet separated by a weir, and multiple NPT ports for optional injection of chemical treatments to acidify or demulsify the fluid mixture, the vessels configured for operation at pressures greater than 25 pounds per square inch (psi); a liquid hydrocarbon storage vessel connected to the liquid hydrocarbon outlet and including a second gas vent; a produced water storage vessel connected to the produced water outlet and including a third gas vent; a vapor recovery assembly comprising: a vapor recovery unit including one or more motors and one or more compressors;a valve controlling flow from the first gas vent to the one or more compressors; a sensor providing an indication of level of pressure within the vessels; and a controller connected to the valve, the one or more motors, and the sensor, wherein upon the indication of the level of pressure reaching a selected threshold greater than 25 psi, the controller operates to open the valve and drive the one or more motors.

21. The hydrocarbon production facility of claim 20, wherein the vent includes a mist extractor configured to remove liquid droplets from gas in the vessels.

22. The hydrocarbon production facility of claim 20, wherein the controller delivers torque from the one or more motors to the compressors based on the indication of the level of pressure.

23. The hydrocarbon production facility of claim 22, wherein the controller is configured to vary the torque delivered by the one or more motors to the one or more compressors.

24. The hydrocarbon production facility of claim 20, wherein a motor is a brushless direct current motor.

25. The hydrocarbon production facility of claim 20, wherein a residence time of gas in the vessel is greater than 1 hour.

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