Patent Application
20250075133
The present disclosure relates to efficiencies in operating a gas-oil separation plant (GOSP), and more specifically, to heat exchangers positioned upstream of a three-phase separator to enhance an oil and water separation process within the three-phase separator.
Crude oil produced from a subterranean wellbore often contains hydrocarbons mixed with impurities such as water and suspended solids. The crude oil may be separated into its constituent components at a gas-oil separation plant (GOSP) facility near the wellbore such that the unwanted components do not need to be transported further. The hydrocarbons (oil and associated gasses) may be separated from the water, and the resulting fluid streams may be directed to individual locations for further processing. Typically, the separated oil in a GOSP is directed through two or three dehydrator and desalting stages before the oil has a basic sediment and water (BS&W) content suitable for export to a refinery. Each of the desalting stages may include the injection of chemicals and wash water into the oil to maintain a desired BS&W specifications.
Conventional GOSP facilities may suffer from deficiencies including low product yield, inefficient use of available heat sources, e.g., discharge streams of compressors, many separate units being used to meet a desired BS&W specification, high operating costs due to heating requirements, a large spatial footprint and high capital costs. One particular inefficiency may include the repeated injection of chemicals and wash water in the desalting stages and subsequent dehydration of the oil stream. Minimizing the chemicals and wash water consumed in the desalting units may allow for a GOSP facility to increase production at an increased efficiency.
Various details of the present disclosure are hereinafter summarized to provide a basic understanding. This summary is not an extensive overview of the disclosure and is neither intended to identify certain elements of the disclosure, nor to delineate the scope thereof. Rather, the primary purpose of this summary is to present some concepts of the disclosure in a simplified form prior to the more detailed description that is presented hereinafter.
According to an embodiment consistent with the present disclosure, a gas-oil separation plant (GOSP) system includes a crude inlet line extending from a source of an inlet fluid stream and to an upstream heat exchanger. The upstream heat exchanger includes an outer shell fluidly coupled to the crude inlet line and a bundle of tubes extending through the outer shell and fluidly coupled to a source of a heated fluid. The bundle of tubes is defined between a lower tube height and an upper tube height that are defined above a lower end of the outer shell. A first exchanger discharge extends above the lower end of the outer shell and is operable to discharge an oil component of the inlet fluid stream from the upstream heat exchanger as a heated oil stream. At least one level controller is operable to control a flow of at least one of the inlet fluid stream into the outer shell or the heated oil stream from the outer shell to maintain a lower level of the oil component in the outer shell at or below the first tube height and an upper level of the oil component at or above the second tube height. A separation vessel is fluidly coupled to the first exchanger discharge downstream of the upstream heat exchanger. The separation vessel is operable to separate the heated oil stream into gas, oil and water components.
According to other embodiments of the present disclosure, a method for operating a GOSP system includes (a) flowing an inlet fluid stream into an outer shell of an upstream heat exchanger, (b) passing a heated fluid through a bundle of tubes extending through the outer shell of the upstream heat exchanger to heat the inlet fluid stream and permit a water component of the inlet fluid stream to accumulate at a lower end of the outer shell and an oil component of the inlet fluid stream to accumulate on the water component (c) discharging a heated oil stream of the oil component from the outer shell of the upstream heat exchanger through a first exchanger discharge, (d) adjusting a flow of at least one of the inlet fluid stream or the heated oil stream to maintain a lower level of the oil component in the outer shell at or below a first tube height and an upper level of the oil component at or above the second tube height; a pressure of the inlet fluid stream with an inlet pressure control valve coupled within the crude inlet line, and (c) flowing the heated oil stream to a separation vessel downstream of the upstream heat exchanger and separating the heated oil stream into gas, oil and water components within the separation vessel.
Any combinations of the various embodiments and implementations disclosed herein can be used in a further embodiment, consistent with the disclosure. These and other aspects and features can be appreciated from the following description of certain embodiments presented herein in accordance with the disclosure and the accompanying drawings and claims.
Embodiments of the present disclosure will now be described in detail with reference to the accompanying Figures. Like elements in the various figures may be denoted by like reference numerals for consistency. Further, in the following detailed description of embodiments of the present disclosure, numerous specific details are set forth in order to provide a more thorough understanding of the claimed subject matter. However, it will be apparent to one of ordinary skill in the art that the embodiments disclosed herein may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description. Additionally, it will be apparent to one of ordinary skill in the art that the scale of the elements presented in the accompanying Figures may vary without departing from the scope of the present disclosure.
Embodiments in accordance with the present disclosure generally relate to a gas-oil separation plant (GOSP) facility having an upstream heat exchanger disposed upstream of a three-phase separator such that an oil stream may pass through the upstream heat exchanger before entering the three-phase separation unit. The upstream heat exchanger may include a shell and tube structure disposed within an oil component of the crude oil stream such that the oil component may be heated without wasting heat on a free standing water component of the oil stream. Level control sensors within the upstream heat exchanger facilitate maintaining appropriate levels of the oil and water components within the upstream heat exchanger for efficient heating of the oil component. The upstream heat exchanger may be fed by a dedicated hot fluid source, or by hot oil exiting a stabilization column of the GOSP facility. The heat imparted to the oil component by the upstream heat exchanger may excite the water molecules in the oil stream, which will make the oil water separation process within the three-phase separator more effective and reliable. The effective water separation will reduce the amount of chemicals and wash water consumed in dehydration and desalting stages downstream of the three-phase separator.
The inlet fluid stream “I” passes through a motor operated valve (MOV) 106 in the crude inlet line 102. The MOV 106 may be operated based on observed conditions of the inlet fluid stream “I” such as temperature and pressure upstream of the MOV 106 to provide desired conditions for the fluid stream “I” to enter the upstream heat exchanger 104. In many embodiments, a set point for the MOV 106 is determined at the design stage of the GOSP system 100 and remains fixed throughout the operational life of the GOSP system 100. In other embodiments, the MOV 106 may be manipulated to alter the set points indicative of desired conditions for the fluid stream “I” to enter the upstream heat exchanger 104.
As described in greater detail below, the upstream heat exchanger 104 may extract heat from a hot fluid stream “H” to provide heat to the inlet fluid stream “I”. Heating of crude oil in the inlet fluid stream “I” improves oil/water separation downstream by allowing the coalescence of water droplets and settling out of water in the liquid phase. Heating also encourages degassing of crude oil to stabilize the crude. The hot fluid stream “H” may enter the upstream heat exchanger 104 through an inlet conduit 108 and exit through an outlet conduit 110. In some embodiments, the outlet conduit 110 may be fluidly coupled to the inlet conduit 108 through a heater (not shown) such that the hot fluid stream “H” may be recirculated through the GOSP system 100 in a closed loop. In other embodiments the hot fluid stream “H” may be provided from any available heat source.
The upstream heat exchanger 104 receives the inlet fluid stream “I” through the crude inlet line 102 and discharges both a heated oil stream “O” through a first exchanger discharge 112 and a water stream “W” through a second exchanger discharge 114. The water stream “W” may be carried out of the GOSP system 100 for disposal or, in some embodiments, may be carried to a water/oil separation plant (WOSEP) (not shown). The heated oil stream “O” is directed into a separation vessel, such as a three-phase separator 118, through a pressure control valve (PCV) 120.
Similar to the MOV 106, the PCV 120 may be operated based on observed conditions of the oil stream “O” upstream of the PCV 120 to provide desired conditions for the oil stream “O” to enter the three-phase separator 118. In many embodiments, a set point for the PCV 120 is determined at the design stage of the GOSP system 100 and remains fixed throughout the operational life of the GOSP system 100, and in other embodiments, the PCV 120 may be manipulated to alter the set points indicative of desired conditions for the fluid stream “O” to enter the three-phase separator 118.
In the illustrated embodiment, the three-phase separator 118 is a horizontal separation vessel, which generally uses gravity to separate the incoming oil stream “O” into a gas component, an oil component and a water component. In some embodiments, the separation vessel 104 may alternatively or additionally employ various other methods of separating the incoming oil stream “O” into components including impingement, changing a flow direction and/or velocity of the fluid stream and/or application of a centrifugal force. The gas component exits the three-phase separator 118 through a gas line 122 as gas stream “G.” The gas stream “G” may be carried out of the GOSP system 100 for disposal, e.g., flaring, or, in some embodiments the gas stream “G” may be exported to other facilities (not show) for further processing. The water component exits the three-phase separator 118 through a water line 124 and joins the water stream “W.” The oil component continues as oil stream “O” from the three-phase separator 118 through oil line 126.
The oil line 126 carries the oil stream “O” to a low pressure degassing tank (LPDT) 130. The LPDT 130 may include a cyclonic separator or other mechanisms for further separating entrained gas from the oil stream “O.” The gas separated in the LPDT 130 may pass through a gas line 132 to join the gas stream “G.” Any water separated in the LPDT 130 may pass through a water line 134 to join the water stream “W,” and the oil stream “O” may exit the LPDT through oil line 136, which carries the oil stream “O” to a downstream heat exchanger 140.
The downstream heat exchanger 140 may include first and second exit lines 142, 144. The first exit line 142 may carry dry oil with a suitable BS&W content for export to a refinery or other processing facility. A second exit line 144 may carry oil containing salts and other sediments to one or more dehydrators and/or de-salters 146. The oil stream “O” entering the downstream heat exchanger 140 through the oil line 136 may be heated within the downstream heat exchanger 140 and discharged through the second exit line 144, and the second exit line 144 then carries the oil stream “O” to the one or more dehydrators and/or de-salters 146.
The one or more dehydrators and/or de-salters 146 may include a dehydrator upstream of first and second stage de-salters in one or more embodiments. The dehydrators and/or de-salters 146 may also include skimmers or other mechanisms for removing salts and other sediments from the oil stream “O.” Any water separated from the oil stream “O” in the dehydrators and/or de-salters 146 may pass through a water line 148 to join the water stream “W.”
Upstream of the dehydrators and/or de-salter 146, a chemical stream “C” is injected into the oil stream “O” through a chemical injection line 150. The chemical stream “C” may include demulsifiers to separate oil-in-water emulsions. Within the dehydrators and/or de-salters 146, a wash water stream “WW” is injected into the oil stream “O” through a wash water injection line 152. The wash water stream “WW” may include water with low salinity to maintain the oil stream “O” within BS&W specifications. The dehydrated and de-salted oil stream “O” exits the dehydrator and/or de-salters 146 through oil line 156 extending to a stabilization column 160.
The stabilization column 160 allows for the removal of volatile hydrocarbon compounds from the oil stream “O.” In some embodiments, the stabilization column 160 may include one or more reboilers (not shown) that heat the oil stream “O” to promote off-gassing of volatile compounds. The oil stream “O” exits the stabilization column 160 through oil line 162 returning to the downstream heat exchanger 140. The oil stream “O” entering the downstream heat exchanger 140 through the oil line 162 may provide heat to the oil stream “O” passing through the downstream heat exchanger 140 between the oil line 136 and the second exit line 144 as described above. The oil stream “O” entering the downstream heat exchanger 140 through the oil line 162 may then pass to the first exit line 142 for export and/or further processing.
The upstream heat exchanger 104 may reduce the viscosity and surface tension of the water droplets within the oil stream “O” entering the three-phase separator 118. The separation of water from the oil stream “O” in the three-phase separator 118 is promoted, which may, in turn, facilitate the dehydration and de-salting of the oil stream “O” through the dehydrator and de-salter 146 before the oil stream may be exported through the first exit line 142. By facilitating the dehydration and de-salting of the oil stream “O” through the dehydrator and/or de-salters 146, the costs associated with the injection of the chemical stream “C” and the wash water stream “WW” may also be reduced.
Referring now to
In the GOSP system 200, however, the upstream heat exchanger 104 is fed by heat from the oil stream “O” exiting the stabilization column 160. As described above, the oil stream “O” may be heated within the stabilization column 160 to promote separation of volatile compounds from the oil stream, and this heat may be carried to the upstream heat exchanger 104 within an inlet conduit 208. Within the upstream heat exchanger 104, the heat may be imparted to the inlet fluid stream “I”, and the dry oil stream “O” may be discharged through an outlet conduit 210 to be exported to a refinery or other processing facility. In this manner, the GOSP system 200 does not require a separate hot fluid stream “H” to drive the upstream heat exchanger 104, but may use the available heat in the oil stream “O” before exporting the oil stream “O.”
Referring now to
The one or more tubes 304 are generally bundled and extend vertically between a lower tube height H1 and an upper tube height H2 defined from a lower end of the outer shell 302. The upper and lower heights H1, H2 are defined between the first and second levels L1, L2 such that the one or more tubes 304 extend through the oil component 314. Thus, the oil component 314 may readily be heated by a fluid flowing through the tubes 304. Specifically, the oil component 314 may be heated by the hot fluid stream “H” (
Referring now to
The inlet fluid stream “I” enters the outer shell 302 of the upstream heat exchanger 104 through the crude inlet line 102, while the oil stream “O” and water stream “W” are discharged through the first exchanger discharge 112 and the second exchanger discharge 114 as described above. The first exchanger discharge 112 extends above a lower end of the outer shell 302 and above the first level L1 such that the oil component 314 may be drawn therethrough. The second exchanger discharge 114 may extend from the bottom of the outer shell such that the water component 316 may be drawn therethrough. The first and second exchanger discharges 112, 114 each include a draw-off valve 322, 324 coupled therein for regulating the respective fluid streams “O” and “W” flowing through the exchanger discharges 112, 114 from the outer shell 302. Each of the draw-off valves 322, 324 is operably coupled to a respective level controller 326, 328. The level controllers 326, 328 may each include or otherwise be communicatively coupled to one or more level sensors 342, 344 within the outer shell 302. In one or more embodiments, the level sensors 342, 344 may detect a density, pressure, moisture content or any other fluid parameter indicative of the lower and upper levels L1, L2.
The one or more level sensors 342 may detect the level L2 of the oil component 314 (
The level controllers 326, 328 are operable calculate an adjustment position for the draw-off valves 322, 324, and instruct an actuator 346, 348 of the respective the draw-off valve 322, 324 to adjust the position of the draw-off valve 322, 324 appropriately. For example, the level controller 326 may instruct the actuator 346 of the draw-off valve 322 to move toward a closed position if the one or more level control sensors 342 detect the second level L2 has fallen to a predetermined upper threshold greater than the second height H2 of the bundle of tubes 304 (
In this manner, the level controllers 326, 328 are operable to maintain the water component 316 (
Referring now to
At step 404, a first level L1 of the water component 316 and a second level L2 of the oil component 314 of the inlet fluid steam “I” within the upstream heat exchanger 104 is detected. The levels L1 and L2 may represent any predetermined parameters representative of the upper (L2) and lower (L1) limits of the oil component 314, and may be measured by the level sensors 342, 344. The procedure 400 then proceeds to decision 406 where the level controllers 326, 328 may determine whether the detected levels L1 and L2 are within predetermined ranges. For example, the level controller 326 may compare the detected level L2 to an upper threshold. In some embodiments, the upper threshold may be equal to or greater than the second height H2, or the upper end of the tubes 304. In this manner, the level controller 326 may determine whether the oil component 314 completely covers the upper end of the tubes 304. Similarly, the level controller 328 may compare the detected level L1 to a lower threshold, which in some embodiments is equal to or less than the first height H1, or the lower end of the tubes 304. The level controller 328 may thus determine whether a lower end of the tubes 304 are covered by the oil component 314.
If at decision 406, the level controllers 326, 328 determine that the oil component is not completely covering the tubes 304, e.g., the levels L1, L2 are not in the predetermined range, the procedure 400 proceeds to step 408. At step 408, one or both of the of the draw-off valves 322, 324 may be adjusted. The draw-off valve 322 may be moved toward a closed position to permit the oil component 314 to accumulate, thereby allowing the second level L2 to reach the upper threshold, and/or the draw off valve 324 may be moved toward an open position to remove excess portions of the water component 316, thereby allowing the first level L1 to fall to the lower threshold. The level controllers 326, 328 may similarly instruct any valve or pump in the GOSP system 100, 200 to adjust an operational parameter affecting the levels L1, L2 to maintain the oil component 314 in a predetermined range about the tubes 304 in the upstream heat exchanger 104.
If at decision 406, the level controllers 326, 328 determine that the oil component 314 is within a predetermined range, e.g., completely covering the tubes 304, the procedure 400 may skip over step 408 and proceed directly to step 410. At step 410 the heated oil stream “O” is drawn out of the upstream heat exchanger 104 and flows to three-phase separator 118, where the oil stream “O” is further separated into gas, oil and water components. The heat applied to the oil stream “O” in the upstream heat exchanger 104 facilitates the oil-water separation process within the three-phase separator 118.
With the water separated, at step 412, the oil stream “O” flows to the dehydrator and/or de-salters 146. In some embodiments, the oil stream “O” flows through the degassing tank 130 and/or downstream heat exchanger 140 between the three-phase separator 118 and the dehydrator and/or de-salter 146. At or near the de-salters 146, chemical stream “C’ and/or wash water stream “WW” is injected into the oil stream to ensure the oil stream “O” is complies with a predetermined BS&W specification. Because of the enhanced separation of water from the oil stream “O,” the consumption of chemicals and wash water in the chemical “C’ and wash water “WW” streams may be reduced. The procedure 400 then proceeds to step 414 where the oil stream flows either back to the downstream heat exchanger 140 to provide heat to the oil stream “O” or back to the upstream heat exchanger 104 to provide heat to the incoming inlet fluid stream “I.” The oil stream “O” may be directed through stabilization column 160 before reaching the dehydrator 140 or the upstream heat exchanger 104. The oil stream may be heated within the stabilization column 160, and the heat may be delivered to the downstream heat exchanger 140 or the upstream heat exchanger 104. The dry oil stream “O” may then be exported at step 416 with desired BS&W specifications. The oil stream “O” may be exported for further processing or consumption.
It should be appreciated that the steps of procedure 400 may be conducted in alternate orders, and many or all of the steps may be conducted concurrently. Also not every step may be performed in every procedure for operating the GOSP system 100, 200.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, for example, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “contains”, “containing”, “includes”. “including.” “comprises”, and/or “comprising.” and variations thereof, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Terms of orientation are used herein merely for purposes of convention and referencing and are not to be construed as limiting. However, it is recognized these terms could be used with reference to an operator or user. Accordingly, no limitations are implied or to be inferred. In addition, the use of ordinal numbers (e.g., first, second, third, etc.) is for distinction and not counting. For example, the use of “third” does not imply there must be a corresponding “first” or “second.” Also, if used herein, the terms “coupled” or “coupled to” or “connected” or “connected to” or “attached” or “attached to” may indicate establishing either a direct or indirect connection, and is not limited to either unless expressly referenced as such.
While the disclosure has described several exemplary embodiments, it will be understood by those skilled in the art that various changes can be made, and equivalents can be substituted for elements thereof, without departing from the spirit and scope of the invention. In addition, many modifications will be appreciated by those skilled in the art to adapt a particular instrument, situation, or material to embodiments of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, or to the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Moreover, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, or component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative.
