WO2024155902A1

WO2024155902A1 - Hydrocarbon removal from recovered water using direct co 2 extraction

Info

Publication number: WO2024155902A1
Application number: PCT/US2024/012182
Authority: WO
Inventors: Albert OKHRIMENKO; Reda Karoum; Benjamin Holton; Richard Bingham
Original assignee: Schlumberger Technology Corporation; Schlumberger Canada Limited; Services Petroliers Schlumberger; Schlumberger Technology B.V.
Priority date: 2023-01-20
Filing date: 2024-01-19
Publication date: 2024-07-25

Abstract

A method of removing organic materials from recovered water comprises providing recovered water to a vessel, providing extractive CO₂ to the vessel, physically contacting the recovered water with the extractive CO₂ within the vessel in a counter-flow arrangement, and extracting organic chemicals from the recovered water directly into the extractive CO₂.

Description

HYDROCARBON REMOVAL FROM RECOVERED WATER USING DIRECT CO₂ EXTRACTION

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent application claims benefit of United States Provisional Patent Application Serial No. 63/480,858 filed January 20, 2023, which is entirely incorporated herein by reference.

FIELD

[0002] This patent application relates to apparatus and methods for separating hydrocarbons and other chemicals from recovered water at manufacturing, processing, constructing, or other similar types of facilities or industrial sites. Specifically, extractive CO2 is used in direct contact with recovered water to remove unwanted chemicals from the water.

BACKGROUND

[0003] Treatment of recovered water at manufacturing facilities is a common endeavor. Rainwater, and other water, enters a manufacturing facility and, while contacting equipment of the manufacturing facility, may acquire trace chemicals from the equipment, ground, or other surfaces. Some of the chemicals may need to be removed before the water can be released to the environment, so the water is recovered and treated to remove such materials.

[0004] In a hydrocarbon processing environment, or any environment where hydrocarbon chemicals can be contacted by environmental water, removal of hydrocarbon materials from the water before releasing the water to the environment is useful, and in some cases required. Efficient and effective means of separating hydrocarbon materials, and other unwanted materials, from recovered water is always needed.

SUMMARY

[0005] Embodiments described herein provide a method of removing organic materials from recovered water, the method comprising providing recovered water to a vessel; providing extractive CO2 to the vessel; physically contacting the recovered water with the extractive CO2 within the vessel in a counter-flow arrangement; and extracting organic chemicals from the recovered water directly into the extractive CO2.

[0006] Other embodiments described herein provide a method of treating environmental water collected at a hydrocarbon production facility, the method comprising routing recovered water obtained from environmental water to a vessel; providing extractive CO2 to the vessel; physically contacting the recovered water with the extractive CO2 within the vessel in a counter-flow arrangement; and extracting organic chemicals from the recovered water directly into the extractive CO2.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Fig. 1 is a flow diagram summarizing a process for removing organic materials from recovered water according to one embodiment.

[0008] Fig. 2 is a flow diagram summarizing a process of treating a collected waste stream according to one embodiment.

[0009] Fig. 3 is a graph of solubility of several oils in CO2 at 60°C and 150 bar (15 MPa).

[0010] Fig. 4 is a graph of solubility of the oils of Fig. 3 in CO2 at 60°C and 250 bar (25 MPa).

DETAILED DESCRIPTION

[0011] Apparatus and methods are described herein for efficient and effective separation of organic materials from recovered water using extractive CO2 (“eCO2”). Supercritical CO2 (“sCO2“), which is a specific case of eCO2,is known to dissolve a wide range of organic molecules, including many hydrocarbon molecules, molecules containing hydrocarbon portions and hetero atoms, surfactant molecules such as fluorinated and oxygenated surfactants (for example alcohol alkoxylates), along with hydrocarbon based surfactants and amphiphilic molecules. Some polymers are also dissolved by SCO2.

[0012] It has been discovered that eCO2 can be used in direct fluid extraction to remove unwanted chemicals from water recovered at manufacturing facilities. In one case, waste streams collected at hydrocarbon drilling rigs can be subjected to solids removal and then to direct physical contact with eC02 to remove hydrocarbons and surfactants, among other species, from the water before returning the water to the environment.

[0013] Extractive CO2 is CO2 that has been brought to a thermodynamic state that is near-critical, sub-critical, or super-critical such that the extractive function of the CO2 is enhanced or maximized. CO2 at a pressure of 35-350 bar and temperature of 5-85°C is generally useful as eCO2. Supercritical CO2 is obtained at temperatures and pressures above the critical point of CO2, which is at 31 °C and 73.8 bar. CO2 at temperatures and pressures within these ranges, including SCO2 and sub-critical CO2 (SUCO2), is useful for dissolving and/or extracting a wide range of materials, and can be used as an extraction medium.

[0014] Extractive CO2 has advantages as an extraction medium for oily materials. Besides being able, in some cases, to dissolve up to 70% oil by mass in the eCO2, solubility of a given substance in the eC02 can be tailored or adjusted by adjusting temperature and/or pressure of the eCCh Such capability enables a differential solubility capability that can give selectivity for target substances.

[0015] Fig. 1 is a process diagram summarizing a process 100 for removing organic materials from recovered water. Recovered water 102 is provided to a vessel 104 for direct physical contact with an eCO2 stream 106. The recovered water 102 is provided to the vessel 104 at a first end 108 thereof, while the eC02 stream 106 is provided to the vessel 104 at a second end 110 thereof, opposite from the first end 108. The vessel can be any container capable of providing a space for contacting the recovered water 102 with the eCO2 106, and in some cases may be an elongated structure, such as a tower or elongated drum, that can provide a counter-flow environment for contacting the recovered water with the eCO2. The vessel 104 may contain flow structures or mixing structures, such as baffles, screens, trays, valves, packing materials, and the like for enhancing mixing and increasing surface area of contact between the recovered water and the eC02.

[0016] The recovered water and eCO2 are immiscible and form a two-phase mixture, which may be like an emulsion in some cases, especially depending on species in the recovered water. Organic chemicals in the water move to the interface between the water phase and the eCO2 phase arising from the direct physical contact between the two materials, and cross the interface into the eC02. The direct f luid-to- fluid transport between the two materials allows the interface to be managed for optimal transport between the phases. Enhanced mixing, for example, can reduce the transport path length for chemicals to move from the water phase to the extractive phase, which can allow increased throughput of recovered water in the process 100.

[0017] Operating condition of the vessel 104 is maintained to prevent vaporization of CO2 in the vessel 104. Temperature and/or pressure of the eCO2 input to the vessel 104 at the second end 110 can be adjusted based on a sensed temperature of the recovered water input to the vessel 104 at the first end 108 to ensure CO2 remains extractive in the vessel 104.

[0018] The vessel 104 is configured to allow separation of eCO2 at the first end 108 in the interior of the vessel 104, and to allow separation of a water effluent 122 at the second end 110 in the interior of the vessel 104. An eCO2 effluent 112, carrying extracted chemicals, is withdrawn at the first end 108 and routed to a separator 114 to vaporize CO2 to separate the CO2 from the extracted chemicals. A small settling vessel can optionally be provided at each of the first and second ends 108 and 110 to allow separation of any materials carried over or under at the ends of the vessel 104. An overhead settler 116 can allow any water that carries over at the first end 108 of the vessel 104 to be separated by gravitational separation and returned, in a water return line 118, to the recovered water 102 for reprocessing in the vessel 104. Likewise, a bottoms settler 120 can allow any eC02 that carries under at the second end 110 of the vessel 104 to be separated and returned, in an eCO2 return line 121 to the eC02 stream 106 for re-entry to the vessel 104.

[0019] Chemicals miscible with eCO2, such as organic chemicals including hydrocarbons, surfactants, emulsifiers, viscosifiers, de-emulsifiers, and the like, move from the water phase to the eCCh phase within the vessel 104. As the recovered water 102 and the eCO2 106 flow through the vessel 104 in opposite directions, the recovered water 102 and the eCO2 106 mix intimately within the vessel 104 to allow transport of chemicals from the water phase to the eC02 phase, removing or reducing the chemicals from the recovered water 102 such that the water effluent 122 has little or none of the chemicals to be removed or reduced.

[0020] A clean water stream 124 is withdrawn from the bottoms settler 120. A composition sensor 126 can be coupled to the clean water stream 124 to determine presence, or concentration, of any chemicals intended to be removed by contact with the eCO2. To the extent conditions within the vessel 104 do not allow such chemicals to be removed to the desired extent, all or a portion of the clean water stream 124 can be returned to the recovered water 102 in a water recycle 128. A flow controller 130 can be coupled to the water recycle 128, and can be controlled by signals from the composition sensor 126, as shown here, or by a controller (not shown) operatively coupled to the composition sensor 126 and the flow controller 130, to route all or a portion of the clean water stream 124 into the water recycle 128. Any or all of the clean water stream 124 that is not routed to the water recycle 128 can be returned to the environment as a water return 132.

[0021] The composition sensor 126 can be any convenient type of sensor. In one embodiment, the composition sensor 126 is a total petroleum hydrocarbons sensor, which can be a spectroscopic or microscopic sensor. Spectroscopic sensors that can be used include infrared sensors, ionization sensors, fluorescence sensors, and the like. An optical microscopy sensor can also be used to detect and quantify organic materials in the clean water stream 124.

[0022] Operation of the extraction process in the vessel 104 can also be controlled based on measurements taken using the composition sensor 126. For example, flow rate of eCO2 to the vessel 104 can be adjusted based on the measurements. For example, where composition of any chemical to be removed is below a threshold, flow rate of eCO2 can be reduced to conserve energy, and where composition of any such chemical rises above a threshold, flow rate of eCC>2 can be increased. Thermodynamic state of the eCO2 can also be adjusted based on the measurements taken using the composition sensor 126. For example, temperature and pressure of the eCO2 can be adjusted to increase or decrease solubility of selected chemicals in the eCO2, and thus extraction of those chemicals. As described below, thermodynamic state of the eCO2 affects solubility of different chemicals differently, so adjusting the thermodynamic state of the eC02 can affect selectivity of the extraction process within the vessel. Thus, the composition sensor 126 can be used to compare composition of two chemicals in the clean water stream 124, and thermodynamic state of the eC02 can be adjusted based on the comparison.

[0023] CO2 is withdrawn from the overhead settler 116 as overhead CO2 134 and routed to the separator 114. The separator 114 can be a vessel, or a series of vessels, to reduce pressure of the overhead CO2 134. CO2 vaporizes and is withdrawn from the separator 114 as CO2 gas 136. Removed chemicals 138 separate from the CO2 and are separately withdrawn from the separator 114. The removed chemicals 138 can be reused in any suitable process or routed to disposal. As noted above, the overhead settler 116 and the bottoms settler 120 are optional. Where the overhead settler 116 is not used, the overhead CO2 134 will be the same as the eCO2 effluent 112. Where the bottoms settler 120 is not used, the clean water stream 124 will be the same as the water effluent 122.

[0024] CO2 gas 136 is recycled into extractive condition for reuse. The CO2 is pressurized in a pressurizer 140 to increase pressure of the CO2 to a pressure representing an extractive condition of CO2. The pressure may be near, at, or above the pressure of the critical point of CO2, which is known to be about 7.4 MPa. The CO2 may be cooled prior to pressurizing, using a cooler 142. Thus, the CO2 gas, and/or a cooler effluent, can form a pressurizer feed 146 that is routed to the pressurizer 140 to form a pressurized CO2. Temperature of the pressurized CO2 can be adjusted in a heater 148 to yield the eCO2 106. In cases where the heater 148 is used, the heater 148 is operated to ensure the CO2 effluent is at a desired temperature representing an extractive condition of the CO2. As noted above, the eCO2 may be superheated, i.e. heated to a temperature above that required to render SCO2, to ensure CO2 remains in a supercritical state for the entire circuit through the vessel 104 and the overhead settler 116 to the separator 114. In general, the eCO2 may be brought to a temperature using the heater 148, and pressure using the pressurizer 140 that ensures the CO2 remains extractive despite any heat loss during extraction processing. Pressure adjustment is done to keep CO2 in its extractive state as temperature changes. Operation of the heater 148 and/or the pressurizer 140 may be adjusted based on a temperature of the recovered water 102 being charged to the vessel 104 sensed by a temperature sensor 150. The heater 1 8 and/or pressurizer 140 may be operatively coupled to the temperature sensor 150, so that signals from the temperature sensor 150 control operation of the heater 148 and/or pressurizer 140, or both the heater 148 and the temperature sensor 150, and optionally the pressurizer 140, can be operatively coupled to a controller (not shown) configured to control the process based on signals from the temperature sensor 150.

[0025] Flow rate of eCO2 is provided to the vessel 104 in the eCO2 106 at a first mass flow rate. Flow rate of the recovered water 102 is provided to the vessel 104 at a second mass flow rate. A ratio of the first mass flow rate to the second mass flow rate may be from about 4: 1 to about 10:1 in some embodiments. In one embodiment, the ratio of the first mass flow rate to the second mass flow rate is about 10:1. Where additional CO2 is needed to maintain the flow ratio of eCO2 to recovered water, makeup CO2 can be added at any convenient location in the CO2 circulation. Here, a makeup CO2 stream 152 is added to the CO2 gas 136 upstream of the optional cooler 142 and the pressurizer 140. Quantity of make-up CO2 can be ascertained by monitoring flow rate of eCO2 106 to the vessel 104. In one embodiment, a flow controlled 54 may be coupled to the eCO2 106 to control flow of eCO2 to the vessel 104. The flow controller 154 may be controlled using signals from a flow sensor 156 coupled to the recovered water 102, or using signals from a controller (not shown) operatively coupled to both the flow sensor 156 and the flow controller 154. Operative coupling of the flow controller 154 to the flow sensor 156 is not shown to simplify the figure.

[0026] If CO2 is lost from the CO2 circulation, for example through fugitive emissions and other mechanisms, the volume of eCO2 106 available to flow to the vessel 104 is reduced. In order to maintain a suitable flow rate of the eCO2 106, the flow controller 154 will open to increase flow. As the flow controller 154 approaches maximum flow capacity, it may be surmised that additional CO2 will soon be needed in the CO2 circulation. Flow of make-up CO2 into the CO2 circulation, for example at the CO2 gas 136, can be controlled, for example, using the position of the flow controller 154. A target for the position of the flow controller 154, for example 50% of the flow capacity of the controller, or a maximum of the position of the flow controller 154, for example 90% of the flow capacity of the controller, can be used to begin flowing the make-up CO2 152, or to increase flow rate of the make-up CO2 152. An inventory (not shown) of CO2 can be included in the CO2 circulation, for example before or after the pressurizer 140, to decouple flow rates in the CO2 circulation, if desired.

[0027] To increase mixing, the eCO2 106 and the recovered water 102 can be provided to the vessel 104 in a manner that induces rotation of fluid within the vessel 104, in addition to counter-flow of the two fluids. One or both fluids can be injected into the vessel 104 tangentially to add angular momentum to the fluid within the vessel 104. If only one fluid is injected tangentially, the fluid within the vessel 104 will have angular momentum in one direction, which is the same direction as the angular momentum of the injected fluid. If both fluids are injected tangentially, the fluids can be injected with opposite-direction angular momentum to increase mixing. If the flow rate of the eCO2 is large enough, compared with the flow rate of the recovered water 102, portions of the fluid within the vessel 104 may have angular momentum in opposite directions, resulting in a zone of angular momentum within the vessel 104 near zero. Mixing within the vessel 104 will be enhanced along the entirety of the vessel 104 by differential angular momentum of the fluid. Flow structures within the vessel 104 may also be configured to maximum the mixing enhancement afforded by fluid angular momentum within the vessel 104.

[0028] Packing materials of any suitable kind can be used in the vessel 104, often with enhanced extractive effect. In one case, %” stainless steel Raschig rings provided improved operation. In general, packing materials can be disposed within the vessel 104 in any suitable manner. For example, packing materials may be disposed between two distribution members, one at each of the first end 108 and the second end 110 of the vessel 104, such that the vessel 104 is substantially filled with packing materials. In other cases, one or more portions of the interior of the vessel, such as a portion of the space between the first end 108 and the second end 110, can be filled with packing materials. Supports for the packing materials can be attached, or otherwise disposed, at any desired location in the interior of the vessel 104 to contain a volume of packing materials. In some cases, more than one discrete volume of packing materials can be disposed in the interior of the vessel 104.

[0029] Fig. 2 is a process diagram summarizing a process 200 of treating a collected waste stream according to one embodiment. The process 200 is an example of a manufacturing process that can use the process 100 to treat water recovered from the process. In this case, the manufacturing process is a hydrocarbon exploration and/or production process that has a water collection tank 202 to collect environmental water that contacts surfaces and equipment of the hydrocarbon exploration and/or production process. A similar implementation can be envisioned for other manufacturing, production, exploration, and construction processes, or other similar types of facilities or industrial sites.

[0030] The collected water is routed to a solids removal unit 204, which can be a hydrocyclone, centrifuge, filtration unit, or other suitable solids removal unit, or a combination of such units. For example, in one embodiment, the solids removal unit 204 comprises a centrifuge facility and a filtration facility, with a water effluent of the centrifuge facility routed to the filtration facility for fine solids removal. The solids removal unit 204 produces recovered water 206, which may serve as the recovered water 102 of the process 100. Here, the process 100 is shown as the treatment facility for the recovered water 206. Solids from the solids removal unit can be routed to an appropriate use or disposal as removed solids 208. The removed solids 208 can be used to prepare drilling fluids, such as drilling mud, or other suitable use.

[0031] Fig. 3 is a graph of oil solubility in eCO2 solvent at 60°C and 150 bar (15 MPa) versus mass ratio of solvent to oil. Results are plotted for five different oils, all of which are hydrocarbon-based oils. Each oil was contacted with varying amounts of eCO?, and the mass percentage of oil dissolved by the eCC was recorded. Percent oil dissolved by the eCO2 is plotted on the vertical axis and mass ratio of solvent (eCC>2) to feed (oil) is plotted on the horizontal axis. In Fig. 3, solubility ranged from about 20% to about 70% at a solvent to feed ratio near 2, and increased to 55- 90% as solvent to feed ratio approached 10:1. The graph of Fig. 3 shows that different oils have different solubility in eCO2 at a given processing condition, and that the solubility can be manipulated by adjusting mass ratio of eCO2 to oil. [0032] Fig. 4 is a graph of oil solubility in CO2 at 60°C and 250 bar (25 MPa), similar to the graph of Fig. 3. The same oils are plotted as in Fig. 3. In Fig. 4, solubilities approaching 60% were observed near solvent to feed ratio of 1. Solubilities at that ratio ranged from about 25% to about 60%. Comparing the results of Figs. 3 and 4, it can be observed that oil uptake increased with increasing mass of eCO2, and that oil solubility in eCO2 increased with higher pressure. In Fig. 3, solubilities observed at a solvent to feed ratio of 2 ranged from about 10% to about 35%, while in Fig. 4 solubilities at that ratio ranged from about 30% to about 75%, indicating that using eC02 at higher pressure generally dissolved more oil. Solubility of each oil increased at the higher pressure, and the rank order of solubility among the oils did not change. The results in Fig. 4 show that solubility of oil in CO2 is different at different processing conditions, and that selectivity of CO2 for different oils also changes with processing conditions.

[0033] The results of Figs. 3 and 4 show that processing conditions can be varied to affect how eCO2 extracts hydrocarbon from a liquid mixture. Temperature and pressure can be varied to optimize extraction of hydrocarbons using eCO2, and it is thought that such methods can extend to extraction of other species using eC02. For example, it is believed that varying processing conditions can affect selectivity of eCO2 for polar versus non-polar molecules.

[0034] The preceding description has been presented with reference to present embodiments. Persons skilled in the art and technology to which this disclosure pertains will appreciate that alterations and changes in the described structures and methods of operation can be practiced without meaningfully departing from the principle, and scope of this present disclosure. Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope.

Claims

1. A method of removing organic materials from recovered water, the method comprising: providing recovered water to a vessel; providing extractive CO2 to the vessel; physically contacting the recovered water with the extractive CO2 within the vessel in a counter-flow arrangement; and extracting organic chemicals from the recovered water directly into the extractive CO2.

2. A method of treating environmental water collected at a hydrocarbon production facility, the method comprising: routing recovered water obtained from environmental water to a vessel; providing extractive CO2 to the vessel; physically contacting the recovered water with the extractive CO2 within the vessel in a counter-flow arrangement; and extracting organic chemicals from the recovered water directly into the extractive CO2.

3. A method of treating environmental water collected at a hydrocarbon production facility, the method comprising: routing recovered water obtained from environmental water to a vessel; measuring a temperature of the recovered water; providing extractive CO2 to the vessel at a temperature and pressure selected based on the temperature of the recovered water; physically contacting the recovered water with the extractive CO2 within the vessel in a counter-flow arrangement; and extracting organic chemicals from the recovered water directly into the extractive CO2.

4. The method of any of claims 1 to 3, wherein physically contacting the recovered water with the extractive CO2 within the vessel in a counter-flow arrangement comprises disposing a packing material within an interior of the vessel and flowing the recovered water and the extractive CO2 through the packing material.

5. The method of any of claims 1 -4, further comprising recovering a water effluent from the vessel and measuring a composition of the water effluent.

6. The method of claim 5, further comprising routing a portion of the water effluent to the vessel with the recovered water.

7. The method of any of claims 1 -6, further comprising recovering extractive CO2, containing a chemical extracted from the recovered water, from the vessel and vaporizing CO2 from the extractive CO2 containing the chemical to separate CO2 vapor from the chemical.

8. The method of claim 7, further comprising forming extractive CO2 from the CO2 vapor and returning the extractive CO2 to the vessel.

9. The method of any of claims 1-8, wherein the recovered water is collected in a tank at a manufacturing site.

10. The method of any of claims 1 -9, further comprising maintaining an operating condition within the vessel to prevent vaporization of CO2 within the vessel.

11. The method of any of claims 5-10, further comprising separating extractive CO2 from the water effluent and returning the separated extractive CO2 to the vessel.

12. The method of any of claims 7-11 , further comprising separating water from the recovered extractive CO2, prior to vaporizing CO2, and returning the separated water to the vessel.

13. The method of any of claims 5-12, further comprising adjusting operation of the extraction process performed in the vessel based on the composition of the water effluent.

14. The method of any of claims 7-13, further comprising adding make-up CO2 to the CO2 vapor.

15. The method of claim 14, wherein adding make-up CO2 is based on position of a flow controller controlling flow rate of eC02 provided to the vessel.