Patent Application
20220325188
The embodiments disclosed herein relate to crude oil stabilization separation systems and processes. More particularly, the embodiments disclosed herein provide improved low carbon foot print stabilization systems and processing of crude oils including shale oil or tight oil, resulting in fewer separation stages and lowering of hydrocarbon dewpoint of vapors to the vapor recovery unit.
It is common commercial practice to produce a stabilized crude oil for storage in a stock oil storage tank at the wellhead by treating a mixed stream of crude oil and natural gas to obtain a stabilized liquid hydrocarbon stream and a gaseous stream. This stabilization is typically carried out in a stabilization unit. The treating step is also referred to as a stabilization process.
The stabilization process helps to make the crude liquid hydrocarbons more suitable for further processing or handling, such as safe storage and/or for shipment in tankers. The stabilization process is commonly a multistage gas-liquid separation process, designed to separate lighter hydrocarbons, and thereby reducing vapor pressure to meet a desired specification such as a Reid Vapor Pressure (RVP) which is commonly used to ensure that the crude oil from the stabilization unit is acceptable for storage and/or transportation by a sea-going vessel such as an oil tanker and usually is less than 10 psi (68.9 kPag). The stabilization process often takes place in areas where available space may be limited, the site may be remote and/or skilled labor may not be available for construction.
Exemplary prior art of separation systems for stabilizing conventional crude oils is shown in
In other systems, such as those described in U.S. Patent Publication No. 2020/0165528, which is incorporated by reference in its entirety, crude oil stabilization is achieved in two stages compared to three or more separator stages in previously known art. In this system, well fluid is first subjected to a High Pressure (HP) separation in which bulk of the water and gas is removed. The oil, still containing gas, light hydrocarbons and some water, after pressure letdown is directed to a heated Low Pressure (LP) separator. The heated LP separator operates at a pressure in the range 3-10 psig and use heat to facilitate the separation of water and light end hydrocarbons from oil to result in stabilized oil product which is sent through LACT unit to customers. Hydrocarbon vapor from heated LP separator are typically recovered in Vapor Recovery units (VRU).
Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for more efficient and lower cost stabilization processes for crude oil including shale or tight oil. There also remains a need in the art for a stabilization system with a smaller footprint that is easier to be modularized for better feasibility at remote locations. Additional objects of the present invention will become apparent from the following summary and detailed discussion of preferred embodiments of this invention.
A system for stabilizing a hydrocarbon feedstock includes a High Pressure Separation (HPS) unit in fluid communication with a feedstock inlet. The HPS unit includes an oil outlet. The system includes a heated Low Pressure (LP) Separator unit downstream from and in fluid communication with the oil outlet of the HPS unit. The heated LP separator unit includes an oil outlet. The system includes a heat exchanger positioned between the HPS unit and the heated LP separator unit.
In some embodiments, the heat exchanger includes a vapor outlet. The vapor outlet can be routed to at least one of a gas outlet line from the HPS unit or the heated LP separator unit. A vapor recovery unit (VRU) can be downstream from and in fluid communication with a gas product outlet of the heated LP separator unit to recover hydrocarbon vapor therefrom. A gas injection input can be between the gas product outlet of the heated LP separator unit and the VRU. The gas injection input can be in fluid communication with a gas outlet of the HPS unit.
In some embodiments, the heat exchanger operates at a pressure ranging from 3-10 psig. The heat exchanger can include a first heat exchanger circuit having an upstream side in fluid communication with the oil outlet of the heated LP separator unit and a downstream side in fluid communication with a Lease Automatic Custody Transfer (LACT) unit inlet. The heat exchanger can include a second heat exchanger circuit in thermal communication with the first heat exchanger circuit. The second heat exchanger circuit can include an upstream side in fluid communication with the oil outlet of the HPS unit and a downstream side in fluid communication with a heated LP separator inlet.
The heated LP separator unit can be configured to operate at a pressure less than 20 psig. The heated LP separator unit can be configured to operate at a pressure from 3 psig to 10 psig. The heated LP separator unit can be configured to operate at a temperature above 110° F. The heated LP separator unit can be configured to operate at a temperature ranging from 110° F. to 160° F. The oil outlet of the heated LP separator unit can be configured to discharge stabilized oil having a Reid Vapor Pressure (RVP) of less than 10 psi. The system can be a two-stage separation system. The HPS unit can be configured to operate at a pressure ranging from 75 psig to 250 psig.
In accordance with another aspect, a process for stabilizing a hydrocarbon feedstock includes delivering the hydrocarbon feedstock to a feedstock inlet of a High Pressure Separation (HPS) unit. The process includes pressurizing the hydrocarbon feedstock in the HPS unit to separate at least one of a gas product or a water product from the hydrocarbon feedstock to generate an un-stabilized oil portion of the hydrocarbon feedstock. The process includes discharging the un-stabilized oil portion of the hydrocarbon feedstock from an oil outlet of the HPS unit. The process includes delivering the un-stabilized oil portion of the hydrocarbon feedstock to a heat exchanger to generate a pre-heated un-stabilized oil portion of the hydrocarbon feedstock. The process includes delivering the pre-heated un-stabilized oil portion of the hydrocarbon feedstock to a heated Low Pressure (LP) separator unit downstream from the heat exchanger. The process includes heating the pre-heated un-stabilized oil portion of the hydrocarbon feedstock in the heated LP separator unit to separate at least one of a second gas product or a second water product from the pre-heated un-stabilized oil portion of the hydrocarbon feedstock to generate a stabilized oil portion of the hydrocarbon feedstock. The process includes discharging the stabilized oil portion of the hydrocarbon feedstock from an oil outlet of the heated LP separator unit.
The process can be limited to two stages of separation. In some embodiments, the process includes delivering hydrocarbon vapor from a vapor outlet of the heat exchanger to at least one of a gas outlet line from the HPS unit or the heated LP separator unit. The process can include delivering a fraction of the gas product from the HPS unit to an inlet line of a vapor recovery unit (VRU) downstream from and in fluid communication with a gas product outlet of the heated LP separator unit. The process can include transferring the stabilized oil portion of the hydrocarbon feedstock from an oil outlet of the heated LP separator unit through a first heat exchanger circuit and to a Lease Automatic Custody Transfer (LACT) unit inlet. The process can include delivering the un-stabilized oil portion of the hydrocarbon feedstock to a heat exchanger includes delivering the un-stabilized oil portion of the hydrocarbon feedstock through a second heat exchanger circuit of the heat exchanger in thermal communication with the first heat exchanger circuit. The second heat exchanger circuit can have an upstream side in fluid communication with the oil outlet of the HPS unit and a downstream side in fluid communication with a heated LP separator inlet.
The heated LP separator can operate at a pressure less than 20 psig. The heated LP separator unit can operate s at a pressure ranging from 3 psig to 10 psig. The heated LP separator unit can operate at a temperature above 110° F. The heated LP separator unit can operate at a temperature ranging from 110° F. to 160° F. The HPS can operate at a pressure ranging from 75 psig to 250 psig. The process can include discharging stabilized oil having a Reid Vapor Pressure (RVP) of less than 10 psi from the oil outlet of the heated LP separator.
These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction with the drawings.
So that those skilled in the art to which the subject invention appertains will readily understand how to make and use the devices and methods of the subject invention without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein:
Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject invention. For purposes of explanation and illustration, and not limitation, a schematic representation of an exemplary embodiment of a stabilization system in accordance with the invention is shown in
As shown in
A heated Low Pressure (LP) Separator unit 104, e.g., the second stage, is a heated three-phase separator and is downstream from un-stabilized oil outlet 119 of HPS unit 102. The heated LP separator unit 104 includes an inlet 114, a heating input 111, a gas product outlet 152 (gas phase), a water product outlet 117 (aqueous phase), and an oil outlet 116, e.g., a stabilized oil outlet 116 (hydrocarbon phase). A gas stream 118 associated with the gas product outlet 152 is indicated schematically by the arrow 118 extending from heated LP separator unit 104. Water product outlet and the water product stream associated therewith are both indicated schematically by the arrow 117 extending from heated LP separator unit 104. Stabilized oil outlet and the stabilized oil stream associated therewith are both indicated schematically by the arrow 116 extending from heated LP separator unit 104. Inlet 114 is configured to receive the un-stabilized oil portion of the hydrocarbon feedstock that is discharged from HPS unit 102 via un-stabilized oil outlet 119. The heated LP separator unit 104 includes an internal weir plate 124 that segregates water and oil.
With continued reference to
Heat is applied by way of heating input 111 to separate the un-stabilized oil stream 112 from the HPS unit 102 into the stabilized oil stream 116, the water stream 117 and the vapor stream 118. Because of the heat duty reduction described above, system 100 allows for the potential to reduce cost and size of crude oil heater, e.g. heating input 111, and the associated equipment, including the size of the heated LP separator 104. Depending on the composition and characteristics of the un-stabilized oil in stream 112, the operating pressure and temperature in the heated LP separator unit 104 is controlled to boil off the lighter hydrocarbons from the un-stabilized oil in stream 112 to result in the stabilized oil of oil stream 116. A typical Heater Treater, e.g., heater treater 4, is provided by flue gases from a fired heater flowing directly through internal fire tubes. While heating in the heated LP separator 104 an internal heat exchanger using external heating medium. Lower heat energy is needed by use of internal heater because flashed gas and separated water portion is not heated in this scheme.
Heated LP separator unit 104 is configured to operate at a pressure less than 20 psig (137.9 kPag), for example, in some embodiments heated LP separator unit 104 operates at a pressure ranging from 3 to 10 psig (21 to 69 kPag). This is different from Heater Treater 4 (of
Stabilized oil outlet 116 of heated LP separator unit 104 is configured to discharge stabilized oil that meets the desired specifications, e.g., in embodiments of the present disclosure, having a Reid Vapor Pressure (RVP) of less than 10 psi (68.9 kPa). RVP is a common measure of the volatility of crude oil and other petroleum products. It is defined as the absolute vapor pressure exerted by a liquid at 100° F. (37.8° C.) and is determined by the test method ASTM Standard D-323 or equivalent. The term “stabilized oil” or “stabilized oil portion” as used throughout this description means crude oil with a vapor pressure low enough to comply with transport and storage requirements, which is indicated by Reid Vapor Pressure (RVP) of less than 10 psi at 100° F. (37.78° C.). It will be readily appreciated by those skilled in the art that the requirements for stabilization may vary or can be based on other parameters.
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A process for stabilizing a hydrocarbon feedstock includes delivering the hydrocarbon feedstock into a feedstock inlet, e.g., feedstock inlet 110 or 210, of a HPS unit, e.g., HPS unit 102 or 202, separating gas and water products from the hydrocarbon feedstock in the HPS unit to generate an un-stabilized oil portion of the hydrocarbon feedstock. Processing the hydrocarbon feedstock in the HPS unit includes maintaining a pressure ranging from 75 to 250 psig (517 to 1723 kPag) in the HPS unit. In some embodiments, this includes maintaining a pressure ranging from 125 to 200 psig (862 to 1379 kPag). The process includes discharging the un-stabilized oil portion of the hydrocarbon feedstock from an outlet, e.g., un-stabilized oil outlet 119 or 219, of the HPS unit. The process includes delivering the un-stabilized oil portion of the hydrocarbon feedstock to a heat exchanger, e.g., heat exchanger 128 or 228, to generate a pre-heated un-stabilized oil portion of the hydrocarbon feedstock.
The process includes delivering the pre-heated un-stabilized oil portion of the hydrocarbon feedstock into a heated LP separator unit, e.g., heated LP separator unit 104 or 204, downstream from the un-stabilized oil outlet of the HPS unit, heating the un-stabilized oil portion of the hydrocarbon feedstock in the heated LP separator unit to separate a second gas product, e.g., that indicated schematically by gas product outlet 118 or 218, and a second water product, e.g., that indicated schematically by second water product outlet 117 or 217, from the un-stabilized oil portion of the hydrocarbon feedstock to generate a stabilized portion of the hydrocarbon feedstock, and discharging the stabilized portion of the hydrocarbon feedstock from a stabilized oil outlet, e.g., stabilized oil outlet 116 or 216, of the heated LP separator unit. The process can include delivering a fraction, e.g. fraction 134 or 234, of the gas product from the HPS unit to an inlet line, e.g. inlet line 121 or 221, of a vapor recovery unit (VRU) downstream from and in fluid communication with a gas product outlet of the heated LP separator unit. In some embodiments, e.g., as shown in
The process includes pressurizing the un-stabilized oil portion of the hydrocarbon feedstock in the heated LP separator unit by operating the heated LP separator unit at a pressure less than 20 psig (137.9 kPag). Some embodiments include pressurizing the un-stabilized oil portion of the hydrocarbon feedstock in the heated LP separator unit by maintaining a pressure ranging from 3 psig to 10 psig (21 to 69 kPag) in the heated LP separator unit.
The stabilized oil portion of the hydrocarbon feedstock that is discharged from the stabilized oil outlet of the heated LP separator unit has a Reid Vapor Pressure (RVP) of less than 10 psi (68.9 kPa). The process includes transferring the stabilized oil portion of the hydrocarbon feedstock from the stabilized oil outlet of the heated LP separator unit through a first heat exchanger circuit, e.g. first heat exchanger circuit 136 or 236, and to a Lease Automatic Custody Transfer (LACT) unit, e.g., LACT unit 108 or 208, downstream from and in fluid communication with the stabilized oil outlet. Delivering the un-stabilized oil portion of the hydrocarbon feedstock to a heat exchanger includes delivering the un-stabilized oil portion of the hydrocarbon feedstock through a second heat exchanger circuit, e.g. second heat exchanger circuit 144 or 244, of the heat exchanger. The second heat exchanger circuit is in thermal communication with the first heat exchanger circuit. The process includes discharging the gas product through a gas product outlet, e.g., gas product outlet 115 or 215, of the HPS unit, discharging the second gas product from a gas product outlet, e.g., gas product outlet 118 or gas product outlet 218, of the heated LP separator unit, and/or recovering the second gas product with a vapor recovery unit (VRU) downstream, e.g., VRU unit 106 or 206, from and in fluid communication with the gas product outlet of the heated LP separator unit. While the described system and process are described in the context of light feedstocks, e.g., shale oil or tight oil, the claimed process and system can process other suitable types of feedstocks as well.
Embodiments of the present disclosure provide for stabilization systems, methods and processes that have reduced heat duty, reduced downtime, and reduced GHG emissions as compared with other systems having two separation stages. The processes, methods and systems of the embodiments of the present disclosure, as described above and shown in the drawings, provide for stabilization systems with increased efficiency, reduced cost and smaller size. While the system, processes and methods of the subject invention have been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the spirit and scope of the subject invention. The above description and examples are merely illustrative of the invention and should not be construed as limiting the scope of the invention. Various modifications will become apparent to the skilled artisan in view of the foregoing disclosure. It is intended that all such modifications coming within the scope and spirit of the appended claims should be embraced thereby.
