Patent ID: 12257607

DESCRIPTION OF THE INVENTION

As set forth above, drill cuttings and brine impacted soil may contain a significant amount of salt which can impact ground water and vegetation growth if left in subsurface locations at high concentrations without proper treatment or containment. It is now recognized that there is a need for a solution that can remove salts from media using minimum resources (e.g., water), with simple devices, and operate at a relatively low cost to effectively manage salt issues associated with drill cuttings and brine impacted soil. These and other technical problems are addressed by the embodiments of this disclosure, which relate to the use of one or more vessels (e.g., mixing tanks) filled with water to extract salts from salt-containing media (SCM) (e.g., drill cuttings or brine impacted soil). For example, embodiments of the invention may utilize a series of mixing tanks (e.g., two or more tanks, such as between 2 and 10 tanks) filled with water to extract salts out from SCM. Other embodiments of the invention may utilize one or more vessels to mix water with SCM in a manner that extracts salts out from the SCM.

In general, present embodiments include washing SCM with water before discharging the media into a disposal location (e.g., reserve pit). The washing process may involve the use of multiple mixing tanks in series, where water and the SCM enter and exit the system in opposing locations and flow counter to one another. An example system10for salt removal from SCM (e.g., drill cuttings) is depicted inFIG.1.

In the illustrated embodiment ofFIG.1, the system10includes a hydrocarbon production system11including a drilling system12that produces SCM, in particular drill cuttings14, during operation. While some of the remaining discussion references drill cuttings14as SCM, it should be noted that the features and operations described herein may be applicable to other salt-containing media as well, such as brine-impacted soil. The system10may, in some embodiments, include a media conveyance system including, for example, an auger or other conveyor positioned downstream of the drilling system12. In the illustrated embodiment, the system10includes a shale shaker15and centrifuge16configured to receive drilling material from the drilling system12and provide the drill cuttings14to a wash system18. In other embodiments, the wash system18may receive SCM (drill cuttings14) directly from the drilling system12(e.g., with no shale shaker15and/or centrifuge16). The wash system18is configured to wash the drill cuttings14to reduce their salinity. In embodiments where the system10is configured to treat brine-impacted soil, certain elements such as the drilling system12, shale shaker15, and the centrifuge16may not be present and instead a media conveyance system may simply supply soil to the wash system18.

The wash system18includes a plurality of mixing tanks20—depicted in this embodiment as including a first mixing tank20a, a second mixing tank20bdownstream of the first mixing tank20a, and a third mixing tank20cdownstream of the second mixing tank20b. Here, “upstream” and “downstream” are relative to the movement of drill cuttings14(SCM) through the system10. While the mixing tanks20are shown as being in series, in some embodiments, at least some of the mixing tanks20may be placed and/or operated in parallel. The wash system18also includes at least one mixing device (e.g., agitator22) configured to mix (e.g., agitate) the SCM (drill cuttings14) with water. In the illustrated embodiment ofFIG.1, the wash system18includes at least one agitator22for each of the mixing tanks20.

The system10may also include one or more sensors24configured to monitor parameters of the washing process conducted by the wash system18. The one or more sensors24may include level sensors configured to monitor the level of fluid in the mixing tanks20, salinity testers, conductivity sensors that allow determination of salinity, or any combination thereof. In one embodiment, the system10may include a level sensor in each of the mixing tanks20but only one sensor for determining the salinity in the first tank20a, which as arranged is configured to have the highest salinity discharge as discussed in further detail below. In other embodiments, each of the mixing tanks20may have a corresponding sensor24for determining salinity (also referred to as a “salinity sensor” herein).

Each of the mixing tanks20may also be equipped with appropriate equipment for selective discharge of solids and liquids. By way of example, each of the mixing tanks20may include an inlet, an outlet, valves, conduits, and so forth that allow water (e.g., feed water, saline water) to be introduced into and discharged out of the mixing tanks20. Each of the mixing tanks20may also include features such as an inlet, an outlet, augers, strainers, and so forth to convey the drill cuttings14(or other SCM) through the wash system18—eventually as washed SCM25(e.g., washed drill cuttings having a lower salinity compared to the drill cuttings initially introduced into the wash system18) into a discharge location such as a reserve pit26. The reserve pit26may include, by way of non-limiting example, a fresh water compartment26aand a brine compartment26b. The washed SCM25generated by the wash system18may, in some embodiments, be provided to the fresh water compartment26awhile brine (saline water) generated by the wash system18may be, in some embodiments, stored in the brine compartment26b.

As described in more detail with respect toFIG.2, in some embodiments, each of the mixing tanks20may be equipped with a solid/liquid separating system to separate out the solids and a solid conveying device to send solids to a downstream tank. The solid/liquid separating system and conveyance system may have various forms and can include integrated equipment that has both functions (e.g., equipment that performs both separation and transport). A liquid transfer device, such as a pump, may be positioned in between the mixing tanks20to transport the liquid to the upstream mixing tank.

As shown inFIG.1one or more pumps28or other liquid conveyance devices may be utilized to motivate water (fresh and/or saline) through the wash system18. For example, the one or more pumps28may be placed upstream or downstream of any one or a combination of the mixing tanks20. In the illustrated embodiment, the system10includes a pump28that introduces feed water30(e.g., fresh water) into the third mixing tank20c. Other pumps may be used to move the water out of the third mixing tank20cand into the second mixing tank20b. After the water has been motivated through the wash system18, the one or more pumps28may finally motivate the resulting brine water32out of the first tank20afor further use or disposal. As may be appreciated with reference to the movement of water through the wash system18, the feed water30thus flows in an opposite direction relative to the SCM, i.e., in a countercurrent flow. By way of non-limiting example, the feed water30may be sourced from the fresh water compartment26aof the reserve pit26or another fresh water source.

The system10may also include a control system34having one or more processors36and one or more memory devices38configured to monitor parameters of the system10and control the operation of the system10to produce the brine32and reduced salinity drill cuttings. The control system34may include a distributed control system or any other control system configuration and is described in further detail below. In particular, the one or more processors36may execute machine-readable instructions to perform various monitoring and control functions. The one or more memory devices38store machine-readable information such as executable code, data, and so forth, relating to the system10and the operation thereof. The control system34may also include associated interface devices (not shown) such as a display and user input devices (e.g., a keyboard, keypad, mouse, touchscreen) to allow interaction and to provide alerts to an operator where appropriate.

The control system34, as noted, may control many aspects of the operation of the system10including feed rates of the drill cuttings14and the feed water30, mixing rates, rates of material transfer between the mixing tanks20, residence time of the water and drill cuttings within each mixing tank20, and so forth. As an example process, the SCM is conveyed into the first mixing tank20ain the series, where it is submerged and washed with water. The washed SCM is then conveyed to subsequent tanks in a sequential manner, where it is washed with water repeatedly as it moves to each tank. Feed water30, in contrast, is supplied into the last tank in the series (the third mixing tank20c, in the illustrated embodiment) and conveyed in the opposite direction of the SCM toward the first mixing tank20a. By generating such counter-flow, the SCM will always be washed (e.g., mixed) with the lowest salinity water before leaving the wash system18resulting in low salt content, whereas the water will carry the extracted salts towards the first mixing tank20ain the series.

The water in the first mixing tank20amay be controlled by the control system34such that it will not exit the system18until it reaches a target salinity. Thus, only a stream of high salinity water, which the salinity can be adjusted as desired, will be generated during such a process. Depending on the situation, the generated high salinity water may be reused directly or after treatment for other purposes such as drilling.

In some of the systems described herein, for all mixing tanks20except for the first and last, the SCM will be conveyed from the previous tank in the series while water is conveyed from the subsequent tank. After sufficient mixing of SCM and water in the tanks20, the SCM will be transferred to the next tank while water is pumped to the previous tank in the series. For the first mixing tank20a, SCM may be supplied from the hydrocarbon production system11and exiting water (e.g., the high salinity brine32) may be sent to a location for storage or further use. By way of non-limiting example, as noted above, the brine32may be stored in the brine compartment26bof the reserve pit26. In other embodiments, the brine32may be stored in a storage vessel (e.g., frac tanks). For the last tank in the series (the third mixing tank20cinFIG.1), the SCM may be conveyed to a staging area, temporary storage vessel, or final disposal location (e.g., the freshwater compartment26aof the reserve pit26), while the feed water30may be fed from a feeding system (e.g., fresh water compartment26a, a water tank, tap).

The control system34may utilize readings from conductivity sensors to measure the salt concentration of water, and may utilize readings from level sensors to detect the water level in the mixing tanks20. The conductivity sensors will be used in the first mixing tank20ain the series to determine when the high salinity brine32would be discharged. The control system34may further utilize readings from conductivity sensors installed in the last tank in the series to initiate feed water inflow when the salinity in the last mixing tank (third mixing tank20cinFIG.1) exceeds a set value. The control system34may use readings from level sensors installed in all the mixing tanks20and will either initiate in-flow of water when the water level drops below a set point or start discharging of water if water level exceeds a set point.

Present embodiments address a number of technical issues. For example, using the disclosed system and process, salts can be removed from SCM and transferred to a high salinity brine. This may significantly reduce potential environmental impacts that may be attributable to salt contents of SCM when disposed in the subsurface. Since salts are concentrated into highly saline brine the volume of wastewater generated from the process and the water required for the salt extraction could be minimized.

Embodiments of this invention may be used on all onshore drilling sites where the drill cuttings and drilling fluid contains high level of salts. The disclosed system and method removes salts from drill cuttings before it is discharged into reserve pits or containers, and can also be used to clean drill cuttings that have already been discharged, or reserve pits that have been closed. Present embodiments can potentially reduce the cost of pit closure, pit draining, fresh water purchase, and brine purchase for drilling.

As previously noted, the disclosed system and method may be used to remediate brine impacted soil, and is particularly effective for sites where the salt concentrations in soil are high. For low salt level soils, adding a desalination process to further concentrate the generated brine may maximize the benefit.

In reference to the control system34ofFIG.1, in some implementations, some or all of the functionalities attributed herein to the control system34may be provided by external resources not illustrated as being in the system10. External resources may include hosts/sources of information, computing, and/or processing and/or other providers of information, computing, and/or processing outside of the system10.

Any communication medium may be used to facilitate interaction between any components of the system10and the control system34. One or more components of the system10may communicate with each other and/or the control system34through hard-wired communication, wireless communication, or both. For example, one or more components of the system10may communicate with each other through a network. For example, the processor36may wirelessly communicate with the memory38. By way of non-limiting example, wireless communication may include one or more of radio communication, Bluetooth communication, Wi-Fi communication, cellular communication, infrared communication, or other wireless communication. Other types of communications are contemplated by the present disclosure.

Although the control system34, the processor36, and the memory38are shown inFIG.1as single entities, this is for illustrative purposes only. One or more of the components of the control system34may be contained within a single device or across multiple devices. For instance, the processor36may comprise a plurality of processing units. These processing units may be physically located within the same device, or the processor36may represent processing functionality of a plurality of devices operating in coordination. The processor36may be separate from and/or be part of one or more components of the system10. The processor36may be configured to execute one or more functions by software; hardware; firmware; some combination of software, hardware, and/or firmware; and/or other mechanisms for configuring processing capabilities on the processor36. The control system34may be implemented in a single computing device, across multiple computing devices, in a client-server environment, in a cloud environment, and/or in other devices/configuration of devices. The control system34may be implemented using a computer, a desktop, a laptop, a phone, a tablet, a mobile device, a server, and/or other computing devices.

While certain processes are described herein as being implemented via processor36through machine-readable instructions, this is merely for ease of reference and is not meant to be limiting. In some implementations, one or more functions of computer program components described herein may be implemented via hardware (e.g., dedicated chip, field-programmable gate array) rather than software. One or more functions of components of the system10described herein may be software-implemented, hardware-implemented, or software and hardware-implemented.

The description of the functionality provided by the control system34herein is for illustrative purposes, and is not intended to be limiting. For example, one or more functionalities, interfaces, and so forth, may be eliminated, and some or all of its functionality may be provided by other computer program components.

The electronic storage media of the memory38may be provided integrally (i.e., substantially non-removable) with one or more components of the control system34and/or as removable storage that is connectable to one or more components of the control system34via, for example, a port (e.g., a USB port, a Firewire port, etc.) or a drive (e.g., a disk drive, etc.). The memory38may include one or more of optically readable storage media (e.g., optical disks, etc.), magnetically readable storage media (e.g., magnetic tape, magnetic hard drive, floppy drive, etc.), electrical charge-based storage media (e.g., EPROM, EEPROM, RAM, etc.), solid-state storage media (e.g., flash drive, etc.), and/or other electronically readable storage media. The memory38may be a separate component within the system10, or the memory38may be provided integrally with one or more other components of the system10(e.g., the processor36). Although the memory38is shown inFIG.1as a single entity, this is for illustrative purposes only. In some implementations, the memory38may comprise a plurality of storage units. These storage units may be physically located within the same device, or the memory38may represent storage functionality of a plurality of devices operating in coordination.

FIG.2depicts an example of a more particular arrangement of features associated with the mixing tank20that allows for the mixing and countercurrent flow between the SCM and the feed water30. Generally, the mixing tank20, which may be representative of one or more of the mixing tanks20ofFIGS.1and3-5, is configured to receive SCM (e.g., cuttings14) from an SCM source50, such as the hydrocarbon production system11. A solids conveyance system52, for example, may transport the SCM from the hydrocarbon production system11and into the mixing tank20via an SCM inlet54of the mixing tank20. The solids conveyance system52may include, by way of example, one or more devices configured to transport solids into, out of, and between mixing tanks20(i.e., into, through, and out of the wash system18). The one or more devices may include one or more conveyor belts, augers, hoppers, troughs, or the like. In one embodiment, the SCM may be fluidized using one or more fluids to facilitate transfer. For instance, a relatively small amount of water (e.g., relative to what is mixed with the SCM in the mixing tank20) may be added to the solids to move the solids in a more fluidized manner compared to dry solids.

The control system34as illustrated is communicatively coupled to the solids conveyance system52. In some embodiments, the control system34may be configured to control operation of the solids conveyance system52in response to various inputs. In some embodiments, for instance, the control system34may be configured receive a signal indicative of the salinity level of liquids within the mixing tank20from the sensor24and may control operation of the solids conveyance system52in response to at least this input. In this way, the solids conveyance system52may operate (e.g., in response to control signals from the control system34) to introduce SCM into the mixing tank20via the SCM inlet54and may operate to move washed SCM25out of the mixing tank20via a washed SCM outlet56. The washed SCM may be provided to a washed SCM recipient58, which may be another mixing tank20(e.g., for further washing of the SCM) or the reserve pit26noted with respect toFIG.1.

With respect to the flow of water through the mixing tank20, as illustrated in the example ofFIG.2, the mixing tank20includes a water inlet60and a brine outlet62which allow for the inflow of feedwater30and the outflow of brine32, respectively. The control system34may control flow of the feedwater30into the mixing tank20by sending control signals to one or more flow control devices such as the pump28a, which has its outlet fluidly connected to the water inlet60. Similarly, the control system34may control flow of the brine32out of the mixing tank20by sending control signals to one or more flow control devices such as the pump28b, which has its inlet fluidly coupled to the brine outlet62and its outlet fluidly connected to a brine recipient64. Thus, the pump28bmay be used to provide the brine32to, for instance, another mixing tank20, the hydrocarbon production system11, the brine compartment26bof the reserve pit26, or another destination.

In some embodiments, for instance, the control system34may be configured receive one or more signals indicative of the water level and/or salinity level of liquids within the mixing tank20from the one or more sensors24and may control operation of the pump28a(configured to pump the feed water30into the mixing tank20) and/or the pump28b(configured to pump the brine32out of the mixing tank20) in response to at least this input.

As shown in the example, the water inlet60and the SCM inlet54are on opposing sides of the mixing tank20and the washed SCM outlet56and the brine outlet62are on opposing sides of the mixing tank20. These relative positions may encourage countercurrent flow of water and SCM within the mixing tank20, although this relative positioning is not necessarily required. Such positioning may also encourage turbulence within the mixing tank20, which may facilitate mixing.

To further encourage mixing, the mixing tank20may also include the mixing device22as described above. The control system34in some embodiments may control the mixing device22based on any one or a combination of factors including inputs received from the one or more sensors24. The mixing device22, as noted, may be an agitator such as an impeller device, a sonication device, etc.

A solid-liquid separator66, which may be a part of the solids conveyance system52or separate from the solids conveyance system52, is configured to separate the washed SCM25from water in the mixing tank20. The solid-liquid separator66may include, by way of non-limiting example, a filter, a strainer, a centrifuge, a hydrocyclone, a belt press, a membrane plate and frame, a screw press, or the like. The solid-liquid separator66may be moved into and out of the mixing tank20or may be installed in the mixing tank20in a fixed manner.

It should be noted that the embodiments set forth above may be used in any appropriate combination, and that elements of the system10may have alternative arrangements that fall within the scope of this disclosure. Indeed, alternative arrangements to the system10depicted inFIG.1are shown inFIGS.3-5. Further, it should be noted that arrangements depicted inFIGS.1-5may be used alone, or in any appropriate combination. Particular elements, such as pumps, the control system34, and associated features described herein with respect toFIGS.1and2are not shown inFIGS.3-5for clarity. However, the systems shown inFIGS.3-5may incorporate any or all of the features described with respect toFIGS.1and2.

FIG.3depicts an embodiment of the system10capable of treating the SCM in a batchwise manner. All or a combination of this configuration may be used alone or in combination with other approaches described herein. In the embodiment ofFIG.3, only water is transferred between the mixing tanks20, and thus the SCM (cuttings14) do not move between the mixing tanks20. As noted with respect toFIG.1, the cuttings14are eventually disposed in the reserve pit26(e.g., in the fresh water compartment26a).

In the configuration ofFIG.3, water (e.g., brine32) discharged from one of the mixing tanks20is transferred to the next mixing tank20(e.g., from mixing tank20cto mixing tank20b). Alternatively, if target salinity for the brine32is reached, the brine32may be transferred from the mixing tank20at which the target salinity is reached to a separate brine storage such as the brine storage compartment26bof the reserve pit26. Thus, the brine32can be generated from all mixing tanks20and not just the first tank20a. In some embodiments, the brine32may be recycled to the hydrocarbon production system11for further use.

In addition, each of the mixing tanks20will repeat the cycle of water injection—mixing with the SCM (cuttings14)—water discharge until the salinity level of the water in the mixing tank20or the salinity level of the SCM (cuttings14) drop to a certain level. Once the salinity drops to a threshold (e.g., desired) level, the mixing tank20is no longer processed. For instance, the control system34, in response to receiving an indication (e.g., signal from the one or more sensors24) that the threshold level has been reached, may halt the inflow of SCM and water into the particular mixing tank20from which the signal was generated. This process will continue with other remaining mixing tanks20only. By way of non-limiting example, flow may be closed off at the particular mixing tank20at which the threshold level of salinity was reached.

When flow is cut off to a particular mixing tank20the feed water injection will start from either an upstream or a downstream mixing tank20, depending on which mixing tanks20have water and cuttings that have reached the targeted salinity level. As set forth inFIG.2, each tank may be equipped with the mixing device22, a water conveying device such as the pumps28aand28b, the solid-liquid separator66, and a device that can convey cuttings to a final discharge point (e.g., the fresh water compartment26aof the reserve pit26). In some embodiments, solid/liquid separation may be done by pausing mixing to allow gravity separation, instead of using a specific device. Further, because each mixing tank20in the embodiment ofFIG.3will be processed individually, each mixing tank20includes the one or more sensors24(seeFIG.2) to measure water level and salinity. As may be appreciated, in the embodiment ofFIG.3, the terms “upstream” and “downstream” will be defined relative to the movement of water not the SCM/cuttings.

FIG.4depicts an embodiment of the system10in which a single mixing tank20includes a plurality of compartments70(depicted as compartments70a,70b, and70c). In this embodiment, the compartments70may act as separate mixing tanks20and may, in some embodiments, have features that allow for the movement of the feed water30and/or the SCM (e.g., cuttings14) across the compartments70. As depicted, for example, the mixing tank20may have a single outer housing72but may include partitions74a,74bthat fully or partially isolate the compartments70from one another. The partitions74a,74bmay be retractable or have a retractable portion, or may only partition a portion of the compartments70from one another, so as to allow for at least some fluid communication between the compartments70.

Optionally, as illustrated, in some embodiments the mixing tank20may have a solids conveyance device76that passes through all the compartments70instead of multiple individual conveyance devices for each compartment70. This may allow the SCM to be washed with water having decreasing levels of salinity as it is moved through the compartments70, while also allowing the water in each compartment to be individually monitored and processed.

In addition and as another option, water spray devices78(e.g., nozzles78a,78b,78c) may spray water on the cuttings14as they move on the conveyance device rather than or in addition to having a mixing device; water will be circulated within each compartment70until target salinity is reached in the first compartment70cand water from subsequent compartments is conveyed to the upstream compartments70band70a.

As shown inFIG.5, in some embodiments a static tank (e.g., plug flow tank90) may be used in addition to or in lieu of the mixing tanks20disclosed herein. In addition, while a single plug flow tank90is depicted inFIG.5, in some embodiments multiple such tanks may be utilized, and they may be connected in series or in parallel in the manner shown inFIGS.1,3, and4. Further, while the plug flow tank90does not include a mixing device, it may include all the other features shown inFIG.2, such as inlets, outlets, sensors, and so forth.

In the embodiment shown inFIG.5, in certain configurations the cuttings14are not moved. In this way, if multiple tanks are used, only water is conveyed from one tank to another.

As illustrated, the feed water30enters the tank90from its bottom and exits from the top of the tank90, creating an upward flow (with respect to gravity). Optionally, a device (e.g., a distribution plate) may encourage equal distribution of the inflowing water throughout the bottom of the tank90.

In situations where the effluent water salinity exceeds a threshold level, it may be provided to the brine compartment27bor other brine storage. If the salinity is under a threshold, the brine32then can be either stored for next batch or disposed. If salinity drops to a predetermined level, the washing process is considered complete.

Optionally, in accordance with the embodiments described herein, certain chemicals (e.g., potassium, magnesium, calcium, aluminum, ferric salts, polyamines, coagulants) can be added to the feed water30to increase process efficiency by altering cuttings properties.

In the embodiment ofFIG.5, the washing process can start operation either as the tank90gets filled or after the tank90is filled with the cuttings14. Further, devices to fluidize the cuttings14(e.g., jet pump, agitator) can be used to facilitate easier discharge of cuttings after process is complete. Optionally, a liquid/solid separation device may be positioned at the outlet of the tank90.

It will be understood that various modifications may be made to the embodiments disclosed herein. Therefore, the above description should not be construed as limiting, but merely as exemplifications of example embodiments. For example, the functions described above and implemented as the best mode for operating the present invention are for illustration purposes only. Other arrangements and methods may be implemented by those skilled in the art without departing from the scope and spirit of this invention. Moreover, those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.