Patent Description:
Drilling for oil and gas produces drill cuttings which are brought to ground surface in the circulating drilling fluid. The drill cuttings may be substantially separated from the drilling fluid using various combinations of shale shakers, centrifuges and mud tanks. However, some liquid or moisture remains associated with the solid "cuttings" as a surface layer and, in some cases, internally thereof. In cases where the drilling fluid is hydrocarbon-based, the cuttings usually are associated with oil, water and drilling fluid chemical additives.

Disposal of the wet cuttings is often problematic, as the associated liquids are of environmental concern. These liquids also present problems in handling and treatment. There is a well-known propensity of these cuttings to cake or form unwanted agglomerations when heated and due to mechanical handling and transport operations. This tendency is affected by the amount of liquid present and the nature of the solids and liquids, which can be quite variable.

Current methods for disposing of cuttings contaminated with drilling fluid include: hauling the cuttings to a land fill and burying them; composting; bio-remediation; thermal desorption; and combustion. The current methods focus on how to clean up the mess once drilling is terminated, rather than on how to prevent its occurrence in the first place. With most currently used methods, little, if any, of the liquids are recovered, resulting in a loss of drilling fluid. The lost fluid results in increased costs to the drilling operator, including increased disposal costs.

Thermal desorption processes are appealing for use in cleaning up cuttings associated with hydrocarbon-based drilling fluids because they can theoretically achieve a zero-residual hydrocarbon level. The thermal desorption processes currently used focus on removal of the liquids after drilling is terminated, and usually involve indirect heat. It is commonly believed that using indirect heat to dry the cuttings will reduce the risk of an uncontrolled exothermic reaction between the heated air and the drilling fluids, and that direct heating would require using a heating gas supply that does not support combustion (i.e., a non-combustible heating gas supply). As a result, in processes that use direct heat, friction, rather than heated air, is typically used to generate heat for drying the cuttings (e.g., via hammermill). In addition, current processes that use direct heat are not intended to recover drilling fluid since they usually involve direct heat in conjunction with combustion of the produced drilling fluid vapour. <CIT> relates to a system for recovering drilling fluid from drill cuttings being produced by a drilling rig and recycling the recovered fluid to the rig drilling storage and circulating system.

For a better understanding of the various implementations described herein and to show more clearly how they may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which:.

Herein described are systems and methods for removing drilling fluid from wet drill cuttings. The systems and methods provide practical and efficient means for the drying of drill cuttings generated in the drilling of oil and gas. The wet drill cuttings are directly heated using a low oxygen, generally inert gas mixture at a temperature such that at least a portion of the drilling fluid is evaporated therefrom and at least some solid, dry drill cuttings remaining. The low oxygen, generally inert gas is a mixture of non-condensable inert gases and nitrogen. The nitrogen gas is provided, at least in part, by a nitrogen generator. The non-condensable inert gas may be recycled from outputs from the oil and gas drilling process and/or outputs of system components described herein.

Utilizing a low oxygen, generally inert gas mixture helps reduce the potential for unwanted reactions, including uncontrolled, exothermic reactions. This gas mixture is provided to the wet drilling cuttings so as to contact and directly heat them and is also referred to herein as the "process gas". The low oxygen content of the process gas usually allows the process gas to be provided to the wet drill cuttings at higher temperatures with a lower explosion risk of the drilling fluid than many known systems, particularly known systems that utilize a lean drying gas. The hotter combustion process usually requires less excess oxygen and does not usually increase the carbon monoxide content of the heating gas. In addition, the described methods are performed at a pressure above atmospheric pressure, rather than in a vacuum, to help prevent air from entering the system (which may introduce excess oxygen). According to some embodiments, the drying of the drill cuttings is continuous. According to some embodiments, the drying of the drill cuttings is performed as a batch process.

In terms of process efficiency, it has been found that lower oxygen levels usually result in less inert gas being heated as there will be less excess nitrogen. Generally, lower excess oxygen levels tend to result in less heat being absorbed by the heating of extra inert nitrogen which, in turn, tends to result in a higher combustion exhaust temperature. This helps achieve a higher process gas temperature, which can improve heat transfer and help minimize the overall process gas flow, subsequently reducing solids entrainment and carryover.

The described systems and methods also provide for the recovery of drilling fluids and dried solid drill cuttings. At least a portion of the evaporated drilling fluid may be condensed such that condensed drilling fluid can be separately recovered from dried solid drill cuttings.

As described further below, the described systems and methods may further comprise additional means to measure and fine tune the oxygen, nitrogen and/or carbon monoxide levels of the gas flow at various stages of the processes.

For the purposes of this application, "wet drill cuttings" include rock and biomass particles, and drilling fluid retrieved from a well drilling operation. The exact composition of the wet drill cuttings will vary from one operation to another and during an operation due to changing rock/biomass composition and drilling fluid composition. However, the wet drill cuttings can comprise, without limitation, hydrocarbons, water, shales, clays, sandstone, carbonates, drilling fluids and combinations thereof.

The terms "rich" and "lean" are also used herein. For clarity, "rich" and "lean" is used herein to denote the level of oxygen in an air-fuel mixture. A "rich air-fuel mixture" or "rich exhaust" is an air-fuel mixture having lower oxygen levels below stoichiometric. In contrast, a "lean air-fuel mixture" or "lean exhaust" is an air-fuel mixture having an excess of oxygen (oxygen level above stoichiometric). As would then be understood, "rich combustion" denotes combustion of a rich air-fuel mixture and "lean combustion" denotes combustion of a lean air-fuel mixture.

It will be appreciated that for simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the exemplary aspects of the present application described herein. However, it will be understood by those of ordinary skill in the art that the exemplary aspects described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the exemplary aspects described herein. Also, the description is not to be considered as limiting the scope of the exemplary aspects described herein. Any systems, method steps, method blocks, components, parts of components, and the like described herein in the singular are to be interpreted as also including a description of such systems, method steps or tasks, components, parts of components, and the like in the plural, and vice versa.

Attention is directed to <FIG>, which depicts an example system <NUM> for removing drilling fluid from wet drill cuttings, according to non-limiting embodiments. System <NUM> operates at a pressure above atmospheric pressure, which helps prevent air from the surrounding environment from entering the system (air which will usually contain excess oxygen). System <NUM> comprises a nitrogen generator <NUM>, combustion chamber <NUM>, a heat transfer device <NUM>, a processor <NUM> having a processing chamber <NUM> and at least one condensing device <NUM>.

Nitrogen generator <NUM> is configured to receive air, such as air <NUM>, via at least one air inlet <NUM>, and to separate the received air <NUM> into constituent nitrogen and oxygen gases, such as nitrogen gas <NUM> and oxygen gas <NUM>. The nitrogen generator <NUM> comprises at least one nitrogen outlet <NUM> and at least one oxygen outlet <NUM>. Any suitable nitrogen generating device, or combination of devices, is contemplated. For example, according to some embodiments, the nitrogen generator may be a membrane or pressure swing adsorption (PSA) type, of sufficient size to provide a make-up stream of nitrogen to offset any process losses, with the bulk of the inert process gas stream being recycled non-condensable process gases. Any available source of ostensibly inert gas may be utilized.

The combustion chamber <NUM> is configured to heat a first mixture comprising the constituent oxygen gas <NUM>, air, such as combustion air <NUM>, and a hydrocarbon-based fuel to a combustion temperature, Tc, thereby producing a first combustion exhaust <NUM>. The combustion chamber <NUM> comprises one or more burners to heat the first mixture. For example, according to some embodiments, the combustion chamber <NUM> comprises at least one high efficiency, low excess oxygen burner. The constituent oxygen gas <NUM> is provided, directly or indirectly, to the combustion chamber <NUM> via at least one oxygen inlet <NUM>. The air is provided, directly or indirectly, to the combustion chamber <NUM> via at least one air inlet <NUM> and the hydrocarbon-based fuel is provided to the combustion chamber <NUM>, directly or indirectly, via at least one fuel inlet <NUM>. The hydrocarbon-based fuel is provided from any suitable fuel source, such as natural gas fuel source <NUM> or flue gas. The combustion air <NUM> may be supplied in any suitable manner, such as by a centrifugal or positive displacement blower (not shown). The first combustion exhaust <NUM> is provided from the combustion chamber <NUM> via at least one combustion exhaust outlet, such as exhaust outlet <NUM>.

The constituent nitrogen gas <NUM> is mixed with non-condensable inert gas <NUM> to create a second mixture <NUM>. The non-condensable inert gas is preferably recycled non-condensable gas residual from condensing process vapors out of the process gas stream but could be from any other reliable source such as engine exhaust if available in suitable quantities.

The first combustion exhaust <NUM> and the second mixture <NUM> are provided to the heat transfer device <NUM>, directly or indirectly, via inlets <NUM> and <NUM>, respectively. The heat transfer device <NUM> is configured to heat the second mixture <NUM> to a first temperature, T<NUM>, by transferring heat from the first combustion exhaust <NUM> to the second mixture <NUM>. The heat transfer device <NUM> comprises any device or combination of devices suitable for transferring heat from the first combustion exhaust <NUM> to the second air-fuel mixture <NUM>. For example, according to some embodiments, the heat transfer device <NUM> is a heat exchanger. The heated second mixture <NUM> exits the heat transfer device <NUM> via at least one outlet, such as outlet <NUM>, for receipt by the processing chamber <NUM>. After at least a portion of the heat has been transferred therefrom, the cooler, first combustion exhaust is released from the heat transfer device <NUM> via at least one outlet, such as outlet <NUM>. According to some embodiments, the released first combustion exhaust is released as flue gas <NUM>.

The processing chamber <NUM> comprises a cuttings inlet <NUM>, through which wet drill cuttings <NUM> are received into the processing chamber <NUM>, a dry solids outlet <NUM>, an evaporated drilling fluids outlet <NUM> and a second mixture inlet <NUM> configured to receive the heated second mixture <NUM> directly or indirectly from the heat transfer device <NUM>. In particular, the second mixture inlet <NUM> is in fluid communication with the outlet <NUM> of the heat transfer device <NUM>.

Processor <NUM> may be any mechanical device or combination of mechanical devices configured to distribute hot gases into drill cuttings received by the processing chamber <NUM>. The components of the processor <NUM>, including those of the processing chamber <NUM>, are selected to operate reliably at temperatures sufficient to vaporize the drilling fluids contaminating the wet drill cuttings <NUM>. According to some embodiments, selection of the components of the processor <NUM> takes into consideration an additional safety margin to give a maximum failure temperature above a pre-determined operating temperature, as discussed further below.

The processor <NUM> is configured to provide the heated second mixture <NUM> to the processing chamber <NUM>, directly or indirectly (such as via the second mixture inlet <NUM>), to contact and directly heat the received wet drill cuttings <NUM> by convection so that at least a portion of the drilling fluid is evaporated therefrom and at least some dry solid cuttings remain. According to some embodiments, the processor <NUM> operates at a temperature above the saturation temperature of the evaporated drilling fluids <NUM>. According to some embodiments, the processor <NUM> is configured to agitate or mechanically mix the wet drill cuttings <NUM> received into the processing chamber <NUM> while the heated second mixture <NUM> is being provided thereto. The agitation or mechanical mixing helps facilitate the heating and drying of the wet cuttings by conduction, and to transfer heat from drier drill cuttings to less dry drill cuttings. Any suitable device or combination of devices or components to agitate or mechanically mix the drill cuttings is contemplated.

Attention is directed to <FIG>, which depicts example processing chamber 110B according to non-limiting embodiments and in which like or similar elements are denoted by like or similar numbers in <FIG>. For simplicity and ease of understanding, discussion of the systems and devices depicted in <FIG> will focus on certain similarities and differences from those depicted in <FIG>. Processing chamber 110B comprises fixed stage <NUM> and agitator stage <NUM>. Fixed stage <NUM> is in fluid communication with second mixture inlet <NUM> and configured to receive processing gas (e.g., the heated second mixture <NUM>). Fixed stage <NUM> comprises fixed bed <NUM>, which comprises at least one fluidly permeable interface operatively connected to second mixture inlet <NUM>. Agitator stage <NUM> is in fluid communication with fixed bed <NUM> and configured to receive processing gas therefrom. As shown in <FIG>, agitator stage <NUM> may be upstream fixed stage <NUM>. Agitator stage <NUM> is also operatively connected to cuttings inlet <NUM> to receive wet drill cuttings <NUM> therefrom. In addition, agitator stage <NUM> comprises at least one mixing device, such as mixing device <NUM>, configured to agitate wet drill cuttings <NUM> received via cuttings inlet <NUM>. According to some embodiments, mixing device <NUM> is a mechanical mixing device.

According to some embodiments, processing chamber 110B further comprises a purging device <NUM> downstream fixed stage <NUM> and configured to compel at least a portion of the dry solid drill cuttings <NUM> for receipt by the dry solids outlet <NUM>. According to some embodiments, purging device <NUM> comprises a screw conveyor configured to remove at least a portion of the processed cuttings from the bottom of fixed stage <NUM>.

According to some embodiments, fixed stage <NUM> comprises a heat distribution system <NUM> configured to distribute the processing gas across at least one heat distribution plane of agitator stage <NUM>, such as heat distribution plane H-H (which may be parallel to an axial plane of mixing device <NUM>).

In operation, process gas (e.g., the heated second mixture <NUM>) received from second mixture inlet <NUM> is distributed into fixed bed <NUM>. According to some embodiments, the process gas is distributed across a plane parallel to the axial plane of mixing device <NUM>, for example, (which may be a mechanical tumbling device), and downstream the area agitated by mixing device <NUM>, forming a fixed, heated bed downstream the agitator stage <NUM>.

Introducing process gas to wet drill cuttings <NUM> in stages (a fixed stage and an agitator stage) may provide for uniform distribution of the process gas to wet drill cuttings <NUM>, which may provide for more uniform and efficient heat transfer while also providing more of the process gas to the interior of the processing chamber 110B than externally (for better thermal efficiency). In addition, combining a fixed stage and an agitator stage may also provide for increased residence time for agglomerates to dry. As the agglomerates dry, fine particles that are released usually tend to migrate up to the agitator stage while heavier particles may remain. A purging device may be used to assist in the downstream migration of the heavier particles and agglomerates into the fixed stage.

As shown in <FIG>, for example, the processor <NUM> is further configured to provide the evaporated drilling fluid <NUM> to the evaporated drilling fluids outlet <NUM> for recovery therefrom and to provide the dry solid drill cuttings <NUM> to the dry solids outlet <NUM> for recovery therefrom.

The at least one condensing device <NUM> comprises a condenser inlet <NUM> in fluid communication with the evaporated drilling fluids outlet <NUM>. The at least one condensing device <NUM> is configured to condense at least a portion of the evaporated drilling fluids <NUM> received directly or indirectly from the evaporated drilling fluids outlet <NUM> (such as via the condenser inlet <NUM>), and to provide condensed drilling fluid <NUM> to a condenser outlet <NUM> for recovery therefrom. Any suitable device or combination of devices for condensing at least a portion of the evaporated drilling fluids <NUM> are contemplated.

As discussed above, a feature of the described systems and methods is using a very hot process gas stream to directly heat and dry the wet drill cuttings. The oxygen level of the post-combustion process gas is in a range low enough to allow the process gas to reach an elevated temperature sufficient for thermal desorption of the drilling fluids and to achieve a lower risk of explosion than process gas having excess oxygen (lean mixture). For example, <CIT>) recommends maintaining an oxygen level below <NUM>% on a mole fraction basis to prevent explosion of the drilling fluid vapor. According to some embodiments, the oxygen level in the process gas stream is about <NUM>% or less. According to some embodiments, the oxygen level in the process gas stream is about <NUM>%. According to some embodiments, the oxygen level in the process gas stream is in the range of about <NUM>% to about <NUM>% or in the range of about <NUM>% to about <NUM>%. The elevated temperature of the second mixture <NUM> air in conjunction with the expected, slightly elevated combustion pressures will help force the process gas through the drill cutting solids, after which the pressure in the vapor space will only be slightly above atmospheric. The low oxygen level of the process gas stream provides for minimum excess gas to heat, higher process gas temperatures and, in combination with the high degree of nitrogen dilution, minimizes potential for any unwanted chemical reactions. The exact oxygen level realized in operation may be determined by the degree of second mixture <NUM> is heated prior to receipt by the processing chamber <NUM> and the back pressure in the combustion chamber <NUM>.

According to some embodiments, the temperature of the hot process gas stream is in a range of about <NUM> to about <NUM>, or a range of about <NUM> to about <NUM>, or a range of about <NUM> to about <NUM>. According to some embodiments, the temperature of the hot process gas stream is about <NUM>. According to some embodiments, the temperature of the hot process gas stream is in the range of about <NUM> to about <NUM>. It is understood that the inlet temperature of the processing chamber second mixture inlet <NUM>, and associated ducts/nozzles, may be higher, and material selection may take these higher temperatures into account. For example, the temperature profile of the processor <NUM>, including the processing chamber <NUM>, after the process gas enters the processing chamber <NUM> is such that the process gas gives up its heat typically within a few inches to asymptotically approach the process gas temperatures described above.

According to some embodiments, the described systems and methods include components to further assist in heating the second mixture <NUM>. Attention is directed to <FIG>, which depicts example system <NUM> for removing drill fluid from wet drill cuttings, according to non-limiting embodiments, and in which like or similar elements are denoted by like or similar numbers in <FIG> or <FIG>. For simplicity and ease of understanding, discussion of the systems and devices depicted in <FIG> will focus on certain similarities and differences from those depicted in <FIG> or <FIG>.

Similarly to example system <NUM>, example system <NUM> comprises the nitrogen gas generator <NUM>, the combustion chamber <NUM>, the heat transfer device <NUM>, the processor <NUM> and the at least one condensing device <NUM>. In addition, example system <NUM> comprises a natural gas powered generator <NUM> or other suitable natural gas powered device (e.g., an engine) that is configured to produce natural gas exhaust <NUM>. The natural gas exhaust <NUM> provides additional heat to be transferred to the second mixture <NUM>, which may improve overall thermal efficiency. For example, according to some embodiments, at least a portion of the natural gas exhaust <NUM> is combined with the first combustion exhaust <NUM> (as combined exhaust <NUM>) prior to receipt by the heat transfer device <NUM>, as shown in <FIG>. However, according to some embodiments, the natural gas exhaust <NUM> is provided separately to the heat transfer device <NUM> from the first combustion exhaust <NUM>, and then combined with the first combustion exhaust <NUM> therein. The second mixture <NUM> is heated by transferring heat from the combined exhaust <NUM> or separately from the natural gas exhaust <NUM> and the first combustion exhaust <NUM>. According to some embodiments, the natural gas-powered generator <NUM> is configured to provide the natural gas exhaust <NUM> to combine with the second mixture <NUM> to supplement the heated, inert process gas. According to some embodiments, the natural gas exhaust <NUM> is provided to the processing chamber <NUM> separately from the second mixture <NUM> and then combined with the second mixture <NUM> therein.

According to some embodiments, the natural gas-powered generator <NUM> provides motive force and/or electricity to the processor <NUM> and/or other system components. For example, the natural gas-powered generator <NUM> may provide at least some shaft power <NUM> to the processor <NUM>. As another example, the natural gas-powered generator <NUM> may provide at least some electricity to other system components.

According to some embodiments, example system <NUM> comprises a heating device <NUM> to further heat the second mixture <NUM> prior to receipt by the processing chamber <NUM>. Any suitable device or combination of devices for heating the second mixture <NUM> is contemplated. According to some embodiments, the heating device <NUM> is an electric heating device. According to some embodiments, the natural gas-powered generator <NUM> is configured to provide at least some electricity and/or motive force to the heating device <NUM> (such as motive force and/or electricity <NUM>).

According to some embodiments, the described systems and methods comprise features to facilitate the recovery of solids and/or fluids, and to reduce waste constituents. Attention is directed to <FIG>, which depicts example system <NUM> for removing drilling fluid from wet drill cuttings, according to non-limiting embodiments, and in which like or similar elements are denoted by like or similar numbers in <FIG>. For simplicity and ease of understanding, discussion of the systems and devices depicted in <FIG> will focus on certain similarities and differences from those depicted in <FIG>.

As shown in <FIG>, example system <NUM> further comprises a fine filter <NUM> in fluid communication with the evaporated drilling fluids outlet <NUM> and configured to separate fine solid drill cuttings <NUM> from the evaporated drilling fluids <NUM>. For example, the fine filter <NUM> comprises at least one filter inlet <NUM> in fluid communication with the evaporated drilling fluids outlet <NUM> and at least one filter outlet, such as filter outlets <NUM> and <NUM>. The filtered evaporated drilling fluids <NUM> are provided to filter outlet <NUM> for delivery to the condensing device <NUM>, directly or indirectly, therefrom. According to some embodiments, the fine solid drill cuttings <NUM> are recovered from the filter outlet <NUM>, separately from the dry solid drill cuttings <NUM>. According to some embodiments, the fine solid drill cuttings <NUM> are recovered with the dry solid drill cuttings <NUM> (as shown in <FIG>).

According to some embodiments, example system <NUM> comprises a solids cooling device <NUM> configured to receive the dry solid drill cuttings <NUM>, directly or indirectly, from the dry solids outlet <NUM>. The solids cooling device <NUM> comprises at least one dry solids inlet <NUM> for receiving the dry solid drill cuttings <NUM> and/or fine solid drill cuttings <NUM> and at least one cooled dry solids outlet <NUM> for recovery of cooled dry solids <NUM>, directly or indirectly, therefrom.

According to some embodiments, example system <NUM> comprises a second heat transfer device <NUM> in fluid communication with the evaporated drilling fluids outlet <NUM> and the air inlet <NUM> of the combustion chamber <NUM>. The second heat transfer device <NUM> is configured to receive the evaporated drilling fluids <NUM>, directly or indirectly, from the evaporated drilling fluids outlet <NUM>, and the air (such as combustion air <NUM>) for the first mixture from which the first combustion exhaust <NUM> is produced. The second heat transfer device <NUM> is further configured to transfer heat from the evaporated drilling fluids <NUM> (or filtered evaporated drilling fluids <NUM>) to the received air (such as combustion air <NUM> to produce heated combustion air <NUM>). This heat transfer will generally pre-heat the air prior to mixing with the hydrocarbon-based fuel (such as natural gas) for combustion by the combustion chamber <NUM> and, usually, at least partially condense the received evaporated drilling fluids <NUM> (or filtered evaporated drilling fluids <NUM>). The at least partially condensed evaporated drilling fluids <NUM> are provided to heat transfer device outlet <NUM> for receipt by the condensing device <NUM>. According to some embodiments, the second heat transfer device <NUM> is a heat exchanger; however, any suitable heat transfer device or combination of suitable heat transfer devices is contemplated.

According to some embodiments, the solids cooling device <NUM> is configured to receive water for cooling the received dry solid drill cuttings <NUM>. For example, according to some embodiments, the solids cooling device <NUM> is configured to receive water from a reservoir or other suitable source. According to some embodiments, waste water and/or water recycled from components of the systems described herein is provided to the solids cooling device <NUM>. Using waste water may results in a side benefit of reducing the volume of wastewater sent to disposal wells as it cools by evaporation. For example, according to some embodiments, the second heat transfer device <NUM> and/or the condensing device <NUM> is configured to separate at least some water <NUM> from the condensed drilling fluid <NUM> and to provide the recovered water <NUM> to the solids cooling device <NUM>. According to some embodiments, as depicted in <FIG>, the solids cooling device <NUM> comprises at least one water inlet <NUM> that is in fluid communication with condensing device outlet <NUM> and/or the heat transfer device outlet <NUM>.

According to some embodiments, a portion of the condensed drilling fluid <NUM> or of the at least partially condensed evaporated drilling fluids <NUM> comprises non-condensable inert gas <NUM>. According to some embodiments, the system <NUM> comprises a flare stack <NUM> configured to receive and purge at least a portion of the non-condensable inert gas <NUM>. According to some embodiments, at least a portion of the non-condensable inert gas <NUM> is recycled to be provided as part of the non-condensable inert gas <NUM>.

According to some embodiments, the systems and methods described herein may comprise additional devices and features to help monitor and/or modify characteristics of the fluid flow, such as the oxygen level, carbon monoxide level and flow rate, to help improve thermal efficiency, reduce waste products and/or conserve fuel. For example, according to some embodiments, the described systems, such as example system <NUM>, further comprises at least one sensor, such as sensor <NUM>, configured to determine an oxygen level and/or a carbon monoxide level of the process gas being provided to the processing chamber <NUM> (such as the process gas comprised of the second mixture <NUM> and/or the natural gas exhaust <NUM>). Any suitable sensing device or combination of sensing devices is contemplated.

According to some embodiments, the systems comprise at least one controller <NUM> operatively connected to the at least one sensor. The at least one controller <NUM> is configured to monitor the determined oxygen and/or carbon monoxide level(s) and to perform at least one safety action based on a predetermined threshold. For example, according to some embodiments, when the determined oxygen and/or carbon monoxide level(s) exceed or fall below a predetermined threshold, the at least one controller <NUM> is configured to trigger an audible and/or visible alarm and/or shutdown operation of the system.

Attention is now directed to <FIG>, which depict a flowchart of a method <NUM> for removing drilling fluid from wet drill cuttings. In order to assist with the explanation of method <NUM>, it will be assumed that the method id performed using example systems <NUM> to <NUM>, as indicated. Furthermore, the following discussion of method <NUM> will lead to a further understanding of systems <NUM> to <NUM>, and the various components of those systems. However, it is to be understood that systems <NUM> to <NUM> and/or method <NUM> can be varied and need not work exactly as discussed herein in conjunction with each other, and that such variations are within the scope of the present embodiments. It is to be emphasized, however, that method <NUM> need not be performed in the exact sequence as shown, unless otherwise indicated; and likewise various blocks may be performed in parallel rather than in sequence. Hence, the elements of method <NUM> are referred to herein as "blocks" rather than "steps". It is also to be understood, however, that method <NUM> can be implemented on variations of systems <NUM> to <NUM> as well.

As discussed above, the described methods, including method <NUM>, are performed at a pressure above atmospheric pressure. At block <NUM>, air is separated into constituent nitrogen and oxygen gases. For example, according to some embodiments, a nitrogen generator (such as nitrogen generator <NUM>) is used to perform block <NUM>; however, any suitable device or combination of devices is contemplated. At block <NUM>, a first mixture comprising the constituent oxygen gas with a mixture of air and natural gas is heated to a combustion temperature, Tc, thereby producing a first combustion exhaust (such as first combustion exhaust <NUM>). At block <NUM>, heat is transferred from the first combustion exhaust to a second mixture that comprises the constituent nitrogen gas and non-condensable inert gas, thereby heating the second mixture to a first temperature, T<NUM>. For example, according to some embodiments, a heat transfer device, such as heat transfer device <NUM>, is utilized to transfer to heat the second mixture. At block <NUM>, the heated second mixture is provided to the wet drill cuttings to contact and directly heat the wet drill cuttings by convection so that at least a portion of the drilling fluid is evaporated therefrom and at least some dry solid drill cuttings remain. At block <NUM>, at least a portion of the evaporated drilling fluid to produce condensed drilling fluid. At block <NUM>, the condensed drilling fluid and the dry solid drill cuttings are separately recovered.

As discussed above, the methods and systems described herein may be varied to improve thermal efficiency. For example, according to some embodiments, the air of the first mixture is pre-heated prior to heating the first mixture to Tc (block <NUM>). According to some embodiments, this pre-heating comprises transferring at least a portion of heat from the evaporated drilling fluids to the air of the first mixture. At block <NUM>, the first combustion exhaust may be heated by adding natural gas exhaust prior to simultaneously with block <NUM> (which may be provided by natural gas-powered generator <NUM> or other suitable natural gas-powered device). At block <NUM>, the second mixture (the "process gas") is further heated to a second temperature, T<NUM>, higher than the first temperature, T<NUM>, prior to being provided to the wet drill cuttings at block <NUM>.

As discussed above, the methods and systems described herein utilize a heated process gas of ostensibly inert gas(es) to contact and directly heat wet drill cuttings by convection so that at least a portion of the drilling fluid is evaporated therefrom and at least some dry solid drill cuttings remain. In systems <NUM> to <NUM> and method <NUM>, a nitrogen generator is utilized to help produce the process gas (e.g., the second mixture <NUM> of constituent nitrogen gas <NUM> output from nitrogen generator <NUM> and non-condensable inert gas <NUM>). However, according to some embodiments, the ostensibly inert process gas is produced without the assistance of a nitrogen generator.

Attention is directed to <FIG>, which depicts example system <NUM> for removing drilling fluid from wet drill cuttings, according to non-limiting embodiments, and in which like or similar elements are denoted by like or similar numbers in <FIG>. For simplicity and ease of understanding, discussion of the systems and devices depicted in <FIG> will focus on certain similarities and differences from those depicted in <FIG>. As shown, example system <NUM> comprises a combustion chamber <NUM>, the heat transfer device <NUM>, the processor <NUM> (and processing chamber <NUM>) and the at least one condensing device <NUM>. The combustion chamber <NUM> comprises the air inlet <NUM>, fuel inlet <NUM> and combustion exhaust outlet <NUM>. The combustion chamber <NUM> is configured to receive air, such as combustion air <NUM>, via air inlet <NUM> and hydrocarbon based fuel via fuel inlet <NUM> (provided from any suitable fuel source, such as natural gas fuel source <NUM> or flue gas), and to heat a first mixture of the received air and fuel to a combustion temperature, Tc, to thereby produce the combustion exhaust <NUM>. As in example systems <NUM> to <NUM>, the combustion exhaust <NUM> is provided to the heat transfer device <NUM>, which transfers heat therefrom to another fluid. In particular, the heat transfer device <NUM> is configured to transfer heat from the received combustion exhaust <NUM> to non-condensable inert gas <NUM> (received via inlet <NUM>), thereby heating the non-condensable inert gas <NUM> to a first temperature (to produce heated non-condensable inert gas <NUM>).

Similarly to example system <NUM>, example system <NUM> also comprises the natural gas powered generator <NUM> or other suitable natural gas powered device (e.g., an engine) configured to produce natural gas exhaust <NUM> (also referred to herein as a natural gas exhaust generating device). However, in example system <NUM>, the natural gas powered generator <NUM> is configured to provide at least a portion of the ostensibly inert gas (process gas) and, according to some embodiments, provide additional heat to the heated non-condensable inert gas <NUM>. For example, according to some embodiments, at least a portion of the natural gas exhaust <NUM> is combined with the non-condensable inert gas <NUM> (to produce gas mixture <NUM>) for delivery to the processing chamber <NUM> (via inlet <NUM>, also referred to herein as process gas inlet <NUM>). By way of another example, according to some embodiments, the natural gas exhaust <NUM> is provided separately to the processing chamber <NUM> from the non-condensable inert gas <NUM> and then combined therein (e.g., the processing chamber <NUM> may be configured to receive the natural gas exhaust <NUM> via an inlet separate from the inlet through which the heated non-condensable inert gas <NUM> is received into the processing chamber <NUM>).

According to some embodiments, example system <NUM> further comprises heating device <NUM> configured to receive and further heat at least one of the heated non-condensable inert gas <NUM> and the natural gas exhaust <NUM> to a second temperature higher than the first temperature prior to receipt by the processing chamber <NUM> (via the process gas inlet <NUM> or any other suitable inlet of the processing chamber <NUM>). Similarly to example system <NUM>, the heating device <NUM> comprises any suitable device or combination of devices for heating the heated non-condensable inert gas <NUM> and/or the natural gas exhaust <NUM> is contemplated (e.g., suitable for heating the gas mixture <NUM>). According to some embodiments, the heating device <NUM> is an electric heating device.

Persons skilled in the art will appreciate that, for simplicity, some components that may facilitate safe, reliable operation of the system have been omitted. Such components include, but are not limited to, various sensors, valves, pumps, blowers, material handling equipment, pressure controls, backflow preventer devices and air locks. Additional means of improving thermal and energy efficiency may be incorporated in the described methods and systems. For example, additional heat recovery equipment may be included to minimize net heat loss. Such equipment may be sized to provide the desired heat input for expected or desired flow rates and liquid content, according to known teachings. The equipment may also be sized such that it has extra capacity and ability to modulate the described operations with varying input parameters.

Persons skilled in the art will appreciate that there are yet more alternative implementations and modifications possible, and that the above examples are only illustrations of one or more implementations. The scope, therefore, is only to be limited by the claims appended hereto.

It will also be understood that for the purposes of this application, "at least one of X, Y, and Z" or "one or more of X, Y, and Z" language can be construed as X only, Y only, Z only, or any combination of two or more items X, Y, and Z (e.g., XYZ, XYY, YZ, ZZ).

In the present application, components may be described as "configured to" or "enabled to" perform one or more functions. Generally, it is understood that a component that is configured to or enabled to perform a function is configured to or enabled to perform the function, or is suitable for performing the function, or is adapted to perform the function, or is operable to perform the function, or is otherwise capable of performing the function.

Additionally, components in the present application may be described as "operatively connected to", "operatively coupled to", and the like, to other components. It is understood that such components are connected or coupled to each other in a manner to perform a certain function. It is also understood that "connections", "coupling" and the like, as recited in the present application include direct and indirect connections between components.

References in the application to "one embodiment", "an embodiment", "an implementation", "a variant", etc., indicate that the embodiment, implementation or variant described may include a particular aspect, feature, structure, or characteristic, but not every embodiment, implementation or variant necessarily includes that aspect, feature, structure, or characteristic. Moreover, such phrases may, but do not necessarily, refer to the same embodiment referred to in other portions of the specification. Further, when a particular aspect, feature, structure, or characteristic is described in connection with an embodiment, it is within the knowledge of one skilled in the art to affect or connect such module, aspect, feature, structure, or characteristic with other embodiments, whether or not explicitly described. In other words, any module, element or feature may be combined with any other element or feature in different embodiments, unless there is an obvious or inherent incompatibility, or it is specifically excluded.

As such, this statement is intended to serve as antecedent basis for the use of exclusive terminology, such as "solely", "only", and the like, in connection with the recitation of claim elements or use of a "negative" limitation. The terms "preferably", "preferred", "prefer", "optionally", "may", and similar terms are used to indicate that an item, condition or step being referred to is an optional (not required) feature of the invention.

The singular forms "a", "an", and "the" include the plural reference unless the context clearly dictates otherwise. The term "and/or" means any one of the items, any combination of the items, or all of the items with which this term is associated. The phrase "one or more" is readily understood by one of skill in the art, particularly when read in context of its usage.

The term "about" can refer to a variation of ± <NUM>%, ± <NUM>%, ± <NUM>%, or ± <NUM>% of the value specified. For example, "about <NUM>" percent can in some embodiments carry a variation from <NUM> to <NUM> percent. For integer ranges, the term "about" can include one or two integers greater than and/or less than a recited integer at each end of the range. Unless indicated otherwise herein, the term "about" is intended to include values and ranges proximate to the recited range that are equivalent in terms of the functionality of the composition, or the embodiment.

As will be understood by one skilled in the art, for any and all purposes, particularly in terms of providing a written description, all ranges recited herein also encompass any and all possible sub-ranges and combinations of sub-ranges thereof, as well as the individual values making up the range, particularly integer values. A recited range includes each specific value, integer, decimal, or identity within the range. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, or tenths. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc..

Claim 1:
A method for removing drilling fluid from wet drill cuttings (<NUM>), comprising:
at a pressure above atmospheric pressure:
separating air (<NUM>) into constituent nitrogen gas (<NUM>) and constituent oxygen gas (<NUM>);
heating a first mixture comprising the constituent oxygen gas (<NUM>) with a mixture of air and natural gas to a combustion temperature to produce a first combustion exhaust (<NUM>);
transferring heat from the first combustion exhaust (<NUM>) to a second mixture (<NUM>) comprising the constituent nitrogen gas (<NUM>) and non-condensable inert gas (<NUM>), thereby providing a heated second mixture (<NUM>) at a first temperature;
providing the heated second mixture (<NUM>) to the wet drill cuttings (<NUM>) to contact and directly heat the wet drill cuttings (<NUM>) by convection so that at least a portion of drilling fluid is evaporated therefrom and at least some dry solid drill cuttings (<NUM>) remain;
condensing at least a portion of the evaporated drilling fluid (<NUM>) to produce condensed drilling fluid (<NUM>); and
separately recovering the condensed drilling fluid (<NUM>) and the dry solid drill cuttings (<NUM>).