Apparatus and method for drilling fluid density separator utilizing rotating disks

FIELD OF THE INVENTION

The present invention relates generally to material separators, and specifically to a density separator for drilling fluid.

BACKGROUND OF THE INVENTION

Drilling mud has been utilized in hydrocarbon reservoirs for many years. The mud is used to establish a proper rate of penetration of the drill bit into the hole. Many variables, such as the desired hole depth, are considered when determining the necessary properties of the mud, and what materials are required to achieve the required consistency. The mud may include minerals called barite or hematite, both of which are very, dense. Other components in the mud may include a clay mineral that is intended to seal and lubricate the outside wall of the hole and create a specific rheology in the drilling mud.

As the hole is drilled, drilling mud is constantly pumped down to the drill bit in order to clean the cuttings away from the bit. The mud then returns to the surface, carrying the drill cuttings with it. The spent drilling mud comprises a variety of materials, such as sand, clay, barite, hematite and/or drill cuttings, for example. The barite and hematite are added to the mud in order to increase the fluid density, and these minerals are very expensive. As such, there are a variety of conventional techniques to remove these minerals from the drilling fluid.

One of the conventional separation techniques utilizes a screen, which separates the mud based on particle size. However, the disadvantage to such a method occurs when the sizes of the cuttings are substantially the same size as the barite or hematite. As such, the screen is ineffective in isolating the barite or hematite. A second common separation technique is the centrifuge. This machine uses high acceleration forces in order to pin dense particles to the wall of a spinning chamber where they are removed and recovered. However, the disadvantage to this method is that coarser undesirable drill cuttings also become pinned to the wall together with the dense minerals. Therefore they are also recovered, even though it is more desirable to discard these particles.

In view of the foregoing, there is a need in the art for a separator to overcome or alleviate the before mentioned shortcomings of the prior art.

SUMMARY OF THE INVENTION

The present invention provides systems and methods to separate minerals based primarily on density, with only a minimal interference from the effect of particle size. In an exemplary embodiment, a separator creates and maintains slurry with a controllable density, which can be targeted between 3.0 and 3.9 kilograms per liter for separating barite from drill cuttings. The invention consists of a primary separation chamber containing the dense slurry, and a multiple number of secondary separation chambers used to separate cuttings from the drilling fluid. The invention also contains inlet hardware allowing the mixed mineral suspension (such as spent drilling fluid, etc.) to enter the first separation chamber, and hardware allowing the three outlet (separated) streams to exit the device. One of the three outlet streams carries the minerals that have a density greater than the user selectable density set point, together with an added mineral, the second outlet carries the minerals that have a density less than the density set point, and the third outlet carries cleaned drilling fluid.

The slurry density in the primary separator is maintained and controlled without using toxic or expensive chemicals, but does involve an additional inert mineral, some of which may exit together with the desired heavy minerals. The heavy mineral outlet stream is then directed to a third separator device that separates the added mineral from the barite, and returns the added mineral back to the feed stream that is pumped into the first separation chamber.

The present invention works by maintaining a controllable magnetic field within a specifically designed separation chamber. Finely ground magnetite or ferrosilicon is added to the feed slurry (spent drilling fluid) to create the separating slurry. The density of the resultant slurry depends on the strength of the magnetic field, which is provided by electric coils that surround the exterior of the separation chamber and interact with permanent magnets located in the interior of the separation chamber.

This invention is further designed to recover barite or other weighting agents from spent drilling fluid. Alternative applications exist in the mineral processing industry, to concentrate any mineral with a density that is substantially greater than the density of the surrounding gangue rock, and which already requires some size reduction to achieve liberation. These potential applications include: barite mining, galena (lead), titanium, gold, iron ore, and coal mining applications.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a three-dimensional view of a density separator according to an exemplary embodiment of the present invention;

FIG. 1A is a break-away view of the primary chamber, secondary chamber and coil illustrated in FIG. 1;

FIGS. 1B-1D illustrate exploded views of the density separator as illustrated in FIG. 1;

FIG. 2 is a diagram of a density separator according to an exemplary embodiment of the present invention;

FIG. 2A is a sectional view of an electrode array according to an exemplary embodiment of the present invention;

FIG. 3 is a diagram of a density separator according to an exemplary embodiment of the present invention;

FIG. 3A is an exploded view of a disk as illustrated in FIG. 3;

FIG. 3B is a sectional view of an electrode array according to an exemplary embodiment of the present invention;

FIG. 3C is an isometric view of a disk as illustrated in FIG. 3;

FIG. 3D is a section view of the disk as illustrated in FIG. 3C;

FIG. 4 is a diagram of a density separator according to an exemplary embodiment of the present invention; and

FIG. 4A is a top view of the density separator illustrated in FIG. 4.

While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Illustrative embodiments of the invention are described below as they might be employed to separate and recover expensive drilling fluid additives. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. Further aspects and advantages of the various embodiments of the invention will become apparent from consideration of the following description and drawings.

FIG. 1 illustrates an exemplary embodiment of a density separator 20 in accordance with the present invention. Density separator 20 includes a primary separation chamber 22 surrounded by a hollow coil 24 which may be, for example, a copper wire. FIG. 1A illustrates an exemplary break away view of density separator 20 and the associated components. FIG. 1A illustrates a series of five images of increasing complexity, arranged like an Assembly Procedure, from left to right. In reference to FIGS. 1 and 1A, primary separation chamber 22 extends all the way down to the bottom of the coil 24 and a little bit beyond the bottom of the coil 24, as shown in FIG. 1B.

A conical core 26 is located inside primary chamber 22, having a plurality of permanent magnets 28 (FIG. 1A) located inside. Core 26 is hollow and sealed at the bottom. Although not illustrated, core 26 will have bearings on either end of it to facilitate spinning. Magnets 28 are stationary with respect to core 26 and are attached to the inner wall of core 26. Although described as a plurality of magnets, those ordinarily skilled in the art having the benefit of this disclosure realized there may be only one magnet if desired. Magnets 28 are treated in this embodiment as permanent magnets, however those ordinarily skilled in the art having the benefit of this disclosure realize electromagnets may also be utilized.

A pump impeller 30 is attached to the top of core 26. Impeller 30 rotates on a vertical axis instead of the more commonly used horizontal axis. A cylindrical portion 32 and plate 34 are located just below impeller 30 forming the suction pipe and suction side wall of the centrifugal pump casing. A hole extends all the way through the plate 34 and cylindrical potion 32 which is a bit larger in diameter than pump impeller 30. As such, plate 34 and cylindrical portion 32 are attached by sliding each on from above impeller 30. Cylindrical portion 32 does not contact the core 26 because, at the bottom of cylindrical portion 32, there is a gap between the inside wall of cylindrical portion 32 and the outside wall of core 26, as shown in FIGS. 1B and 1C. The gap is created when plate 34 is attached atop primary separation chamber 22 where it rests. Accordingly fluid from inside primary chamber 22 will be pressurized and sucked upwardly through the gap and into cylindrical section 32, up through plate 34 via the gap between plate 34 and impeller 30, where the fluid is then pumped outwardly by impeller 30.

Referring to FIG. 1D, chamber 22 is slightly larger in diameter then lowermost end of core 26. As such, there is a gap in between the two at the very bottom of the device. An inlet 36 is coupled to upper end of primary chamber 22, which is where the pumped fluid enters chamber 22 via an opening (not shown) into chamber 22. Once fluid enters it begins swirling around the inside of chamber 22. Since the fluid is being pumped, there is some pressure on the fluid as it enters the inlet 36. The coil 24 and feed pump work together to generate the circular motion because, as the feed pump pumps fluid into primary chamber 22, the fluid will already be spinning to some degree and then the core 26 is also spinning because of the interaction with coil 24.

As previously described, there is a gap between the lowermost end of core 26 and primary chamber 22, which allows material to fall out the bottom of chamber 22. As the fluid entering chamber 22 spins, the heavy materials in the fluid are pinned to the outer wall of chamber 22 and eventually fall out of the bottom of chamber 22 through the circular gap. Accordingly, the dense material is removed from the fluid while the lighter material exits chamber 22 up through the gap between cylindrical section 32 and core 26, where the light material is then hit by the blades of impeller 30 and pumped outwardly.

As the fluid is pumped outwardly by impeller 30, the fluid enters a secondary separation chamber 38, which consist of two hydrocyclones 40. Cyclones 40 also have inlets 42 which are in fluid communication with central chamber 44 covering impeller 30. Central chamber 44 is a sealed chamber which fits atop impeller 30. Accordingly, since fluid exits chamber 22, and is pumped into inlets 42 by impeller 30, through the attached curved channels, and into cyclones 40, then these parts working together essentially a centrifugal pump. Although this exemplary embodiment only utilizes two cyclones, those ordinarily skilled in the art having the benefit of this disclosure realize more or less cyclones may be employed as desired.

The fluid exiting the top of chamber has two components to it. It has a liquid component and the lower density drill cuttings, resulting in a solid material/liquid mixture. As the fluid mixture exits the top of chamber 22, it is being supercharged by the impeller 30, and then is sent at a relatively higher pressure into the two other hydrocyclones 40. Accordingly, a second separation occurs here in addition to the first separation occurring in chamber 22. However, unlike chamber/hydrocyclone 22, hydrocyclone 40 does not have a magnetic core; rather, only the centripetal acceleration due to the fluid velocity is used to separate the drill cuttings and fluid. Therefore, the fluid exits the top of cyclone 40 while the more dense material (e.g., drill cuttings) exits the bottom of cyclone 40 via a hole 41 (FIGS. 1B & 1C) and will flow into a hose or some other transferring means attached to cyclone 40 (also not shown). In the alternative, the material may be dumped into some container and carried away periodically. Simultaneously, the less dense fluid comes out at the top of cyclone 40 via an opening at the top and enters hoses 46.

In further reference to FIGS. 1 and 1A, electric coil 24 is coupled around chamber 22. The fluid which is fed into separator 20 also contains magnetite, ferrosilicon, or any other permanently magnetic material of a suitable particle size distribution. Magnetite is a mineral that is naturally magnetic. In the present invention, a concentration of magnetite powder is fed into the chamber 22 as it is part of the spent drilling mud, resulting in a dense slurry having a bulk specific gravity ideally between 3.1 and 3.5. Flow line mud also forms part of the fluid feed.

The interaction of the electric field in between the permanent magnets 28 in the core 26 and the electric coil 24 creates a magnetic field gradient which essentially holds the magnetite particles within the slurry in that part of the chamber. The magnetite mineral as a pure mineral has a specific gravity around 5 and water is of course around 1. Therefore a slurry that has a volume percent of at least 25% will double the density of the fluid inside chamber 22. The magnetic field, which can be controlled by regulating the current through coil 24 as understood in the art, provides control over the density of the fluid that is inside the chamber 22.

In operation, the dense fluid inside chamber 22 is forced to the bottom of chamber 22 because of the high density of the magnetite slurry. This density of this slurry allows higher density particles to fall into, through, and then below it, while lower density particles float above it. If a particle of a light density enters the section of the chamber 22 that has a high density, it will effectively float on top, which facilitates the less dense material being sucked into cylinder 32. Accordingly, the magnetite slurry concentration is used as a density gauge to distinguish what is considered to be a more dense material from a less dense material. By varying the amperage power supply to coil 24, the density of the magnetite slurry can be controlled which, in turn, controls the densities necessary to float one mineral above, and a different mineral below the magnetite slurry adjacent the coil 24. As such, greater current in the coil creates a greater magnetic field strength in the chamber 22, which then, because of the magnetite, creates a much higher density fluid. The fluid entering chamber 22 will also have weighting agents from spent drilling fluid, such as, for example, barite.

Referring to FIG. 1, an exemplary embodiment of the present invention also includes a catcher 48 below coil 24 which may be necessary due to the relative sizes of the machinery. Catcher 48 collects the material coming out of the gap between the lower end of chamber 22 and core 26. Once collected by catcher 48, the material falls into a magnetic separator 50 coupled to the bottom of catcher 48. Inside of the magnetic separator 50 is a permanent magnet 52 held at a angle inside of a rotating non-magnetic cylinder which carries the magnetite up and over the discharge lip 54 and into tank 56, as known in the art. Magnetite powder is added to tank 56 in order to get the process started. After a sufficient amount of magnetite is added to make the slurry dense enough, most of it should be recycled using the magnetic separator. Also, note some magnetite will need to be added continuously in order to replace the magnetite that is lost due to random inefficiencies that occur in the process.

In operation, fluid is fed into chamber 22 via inlet 36. The fluid contains a mixture of fluid, drill cuttings, magnetite and barite, for example. The magnetic field created by the interaction between coil 24 and core 26 forces the magnetite to suspend within the field. As such, the less dense drill cuttings in the fluid are forced to the top of chamber 22 above the magnetite, while the more dense barite falls through the suspended magnate to the bottom of chamber 22. As such, the material coming out of the bottom of the chamber 22 consists of both the magnetite particles that escape the field as well as the barite particles and some liquid. After the cuttings and fluid are pumped through secondary separator 38, hoses or pipes 46 carry clean liquid from hydrocyclone separators 40 into separator 50 while, simultaneously, the drill cuttings fall out the bottom of hydrocyclones 40.

The clean fluid flowing through hoses 46 are then collected in separator 50, along with the more dense material falling from chamber 22. As such, the collected mixture includes magnetite, barite, and liquid. Because of the magnetic properties of the magnetite, magnet 52 separates the magnetite from the barite, where the magnetite then falls over the overflow lip 54 into another tank 56 where it may be re-used. A pump 58 is coupled to tank 56 in order to pump the magnetite from tank 56, through hose or pipe 60 and back into chamber 22. The liquid and barite remaining in separator 50 then flows out of the bottom of the separator 50 via an opening (not shown) where the barite may be reused. As desired by the final operator, hoses or pipes 46 may also be directed to additional separations further downstream, such as to the inlet of a centrifuge. In that case, the volume of liquid required to operate separator 50 properly would need to be provided by the cleaned fluid exiting the centrifuge, or via the addition of other liquid mud additives that are normally available on the rig, and would be added anyway to maintain other mud properties.

Referring to FIG. 2, an alternative exemplary embodiment of the present invention is disclosed. This embodiment comprises a single column vessel, which itself includes several distinct zones, as illustrated in FIG. 2. The uppermost zone is the LGS/LCM discharge zone, and consists of a two concentric internal launders. The outside internal launder collects LGS minerals, and the inside internal launder collects LCM materials. LGS is a low gravity solids (i.e., light density material or low specific gravity material such as clay, drill cuttings, shale, etc.). LCM is lost circulation material which is a specialty material having even lighter density.

The middle zone is the feed separation zone, consisting of an array of mild steel powder coated electrodes 64, charged with either DC or AC current. The wire coils may be located external to the separation zone, given that the mild steel structures will transmit the magnetic field into the desired location and the desired shape. The coils may also be incorporated into the internal structure in order to minimize transmission losses of the magnetic fields. In this exemplary embodiment, the array 64 should not have any two elements approach each other by a distance of about ¼ inch. This feature prevents tramp oversize particles from clogging the device.

The electrode array 64 will be designed to maximize the field gradient. Magnetic force is a product of the field strength and the field gradient. Therefore, maximizing the gradient (by mechanical means) also maximizes the magnetic force for any given field strength. Geometrically, the array 64 will consist of a large number of points and arcs, as illustrated in FIG. 2A. DC current creates a stationary magnetic field between the electrode pairs, which will hold a concentration of magnetite powders within the fluid, depending upon the current.

An AC current will create a similarly shaped field, however, when the magnetite particles are sized smaller than their own magnetic field domain, the particles rotate in place with an rpm value equal to the frequency of the AC current. The individual particle rotations may be very advantageous for enhancing the bulk flow of the non-magnetic particles within the fluid. Needless to say, the frequency, amperage, and the overall combination of DC current and AC current are all subject to optimization. The feed tube will discharge within the middle zone, such that the magnetite slurry surrounds the incoming feed. As an option, the feed tube may enter the side of the vessel just above the high density zone. The flow through the column 62 will depend on the incoming feed rate, in such a way that the level is held constant by the level control float and the control valve at the bottom. A non-contact level detector mounted above the float will sense the float position (not shown in FIG. 2). The sensor could be any one of a variety of styles available for this purpose.

In operation, fluid, having both dense and less dense material as previously described, is fed in on the left side and enters a chamber 62 that has suspended magnetite that is held in place by an electrode array 64. Inside chamber 62, heavy materials fall through the suspended magnetite slurry and fall out the bottom, while the lighter weight materials will drift up and out the top of the suspended magnetite section. The lighter weight materials create overflow 66 at the top of chamber 62. The LCM out and the LGS/Fluid and Clay out are two different level control pipes to catch minerals that are floating on top of the cylinder 62. Those ordinarily skilled in the art having the benefit of this disclosure realize a modified flotation column may be used for this purpose. In an alternative embodiment, a “Wash Water” tank can be added above the column to rinse the LCM materials of all LGS material, and the control of column flow “bias” may not need to be controlled.

As in the previous embodiment, the alternate embodiment of FIG. 2 creates a magnetite slurry that has a high density. The feed is pumped into the middle of this fluid providing enough turbulence in chamber 62 to cause the barite or other heavy minerals to fall through the suspended magnetite down to the bottom. The density of the suspended magnetite is so great that the lighter material will be lifted out and above it. Control valve 68 at the bottom of this column can be adjusted so that the bulk of the liquid goes up. Between the feed in and overflow there is an upward velocity of fluid such that the fluid is dragging lighter particles upwardly out of the suspended magnetite; however, the barite will fall through the suspended magnetite due to its density. In this embodiment, the flow in and flow out will be controlled by some control means in order to make the separation work properly. Such control means are known in the art.

Referring to FIG. 3, another exemplary embodiment of the present invention is illustrated. This embodiment comprises is a modular design consisting of multiple circular separation disks 70 stacked in a single device. FIG. 3A illustrates an exploded view of a single disk 70. However, unlike the previous embodiments, the assembly of stacked separation disks will be mounted on hardware enabling them to rotate. Each disk 70 will contain a positive and negative electrode array similar to the embodiment of FIG. 2. FIG. 3B illustrates an exemplary arrangement for electrode array, and FIG. 3C shows a cross-section of one separation disk.

In operation, a stationary feed pipe discharges into the feed chamber at the center of the stack of separating disks 70. Each disk 70 has a short pipe section allowing a limited amount of feed to travel from the central chamber into each disk. The feed travels along the lower surface of each disk, until it reaches the magnetite slurry. There, the heavy minerals flow through the magnetite, while the light minerals flow upward and over the magnetite slurry. The heavies continue traveling outward until they reach an internal rotating wall, which directs them downward through the machine. Eventually, the heavies are collected in a non-rotating chamber (FIG. 3) that collects them and discharges them out the bottom of the machine as indicated by the downward arrow on the left of FIG. 3. The lights travel outwardly in a similar way until they reach a channel that carries them through the wall that retains the heavies. Once through the first rotating wall, they are collected within the non-rotating outside wall of the device, and fall to the bottom of the separator where they exit as shown by the downward arrow on the right of FIG. 3.

In this embodiment, when the rotation speed is fast enough, the gravity force pulling straight down is inconsequential compared to the centripetal acceleration force that pushes material toward the outside wall of the cylinder. As the feed enters the center of the device, the centripetal force pulls the fluid to the right and left. The circular dotted line 72 in FIG. 3A indicates a region of suspended magnetite held in place by the magnetic field established between the two sloped electrode walls. The region of suspended magnetite also exists on the right hand side, but is not shown for clarity. One sloped electrode wall is charged in one way, and the other wall is charged in the opposite way, so that a voltage applied between the two walls creates a magnetic field that holds the magnetite in place. The two sloped electrode walls are indicated by arrows on the right hand side of FIG. 3A, but the walls also exist on the left.

As previously described, the amount of suspended magnetite can be controlled by the voltage supplied through the electrode array 74, which may be either DC or AC voltage. Accordingly, the light material floats above this high density separation zone and the heavy material travels straight through it. As such, the magnetite remains in place but the barite will be pressed through the rotating, mixing chamber of high density magnetite slurry in order to get out of the machine. With reference to FIGS. 3C and 3D, the light materials will travel through a set of dedicated trapezoidal shaped chutes 71 that direct them through the wall that contains the heavy materials 73. With reference to FIG. 3D, the cross section plane traverses the outwardly directed lights chute in the far upper left hand side of the image, while the cross section plane traverses the downwardly directed heavies passageway along the far right hand side wall (Note that the wall of the entire container is not shown in this image).

Referring to FIG. 4, another alternative exemplary embodiment of the present invention is illustrated. This embodiment is very similar to the design and operation of the embodiment of FIG. 1, with a few exceptions. In this embodiment, a conical chamber 76 is utilized along with a mating coil 80 to provide the electric field. Instead of a conical shaped core, core 78 is a pipe instead of a magnetic core. In operation, the new feed enters a feed box 82 sitting above a pump 84. The fluid feed is then pumped into the primary hydrocyclone 76 and it swirls around the inside of chamber 76 until is reaches coil 80. Here, as previously described, the magnetite is held in place. Thereafter, the heavier barite in the fluid and some magnetite will fall below the suspended magnetite and into the magnetic separator 86, while the lighter fluid and drill cuttings move up to the top of chamber 76 where it is eventually separated in secondary hydrocyclones 90 as previously described in relation to FIG. 1. In this embodiment, three secondary hydrocyclones 90 are illustrated as shown in FIG. 4A, and there is no centrifugal pump impeller.

Once the heavy material is collected in magnetic separator 86, the magnetite is discharged up and over lip 88 into box 82 where it is again mixed with the new feed fluid. The lighter materials forced up to the top of chamber 76 flows into secondary hydrocyclones 90 following the horizontal feed passageway 91. Heavier drill cuttings fall out of the bottom of secondary hydrocyclones 90. At the same time, the clean fluid is circulated up and out of the cyclones via pipes 92, where it recombines at pipe 78 and is discharged into magnetic separator 86. After the magnetite has been removed, only the fluid and barite remain. As previously described, it exits out of opening 94 for further use as desired.

The present invention has applicable in a wide range of industries, all of which require high processing volumes per installation, and would likely generate a high demand for a successful separating device. Such industries include, but are not limited to, drilling, mining of base, semi-precious and fossil fuels, as well as water treatment. The present invention may be applied to a variety of minerals requiring separation such as minerals with high specific gravity including, for example, barite, hematite, clay, shale, sand, hematite (Fe), magnetite (Fe), scheelite (W), wolframite (W), Ilmenite (Ti), galena (Pb), chalcopyrite (Cu), sphalerite (Zn), pyrite, ash forming minerals, fly ash, and specifically designed surface active absorbent minerals. Low specific gravity minerals include, for example, clay, shale, sand, lost circulation materials, quartz, coal, and clean water.

Although various embodiments have been shown and described, the invention is not limited to such embodiments and will be understood to include all modifications and variations as would be apparent to one skilled in the art.

Apparatus and method for drilling fluid density separator utilizing rotating disks

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