Separating solids from liquids in a drilling fluid

A drilling fluid shaker screen system includes a screen assembly that includes a screen including a plurality of screen sections. A first screen section includes a first screen mesh size and a second screen section includes a second screen mesh size different than the first screen mesh size. The drilling fluid shaker screen system further includes a rotation assembly mounted to the screen assembly. The rotation assembly includes one or more rollers moveable to rotate the screen assembly about an axis of rotation. The drilling fluid shaker screen system further includes a motor assembly coupled to the screen assembly and configured to vibrate the screen assembly. A housing includes a cuttings outlet that is fluidly coupled to a cuttings inlet formed in the screen and a liquid outlet separate from the cuttings outlet that is fluidly coupled to the plurality of screen sections.

TECHNICAL FIELD

This disclosure relates to separating solids from liquids in a drilling fluid.

BACKGROUND

In drilling and workover operations, drilling fluid (often called “drilling mud”) is used to keep a hydrostatic pressure within a wellbore while drilling or while work over by circulating the drilling fluid into the wellbore. For example, the drilling fluid may be circulated through a tubular work string or drill pipe and through one or more nozzles formed in the drill bit and out into the wellbore. The drilling fluid helps with well control, as well as carries cuttings removed from a subterranean formation by the drill bit during drilling the wellbore back to the surface. These cuttings can be separated from the drilling fluid to maintain an initial set of properties (for example, viscosity, density, gel strength) of the drilling fluid.

SUMMARY

This disclosure describes implementations of a shaker screen system that may be used to separate formation cuttings from a liquid in a drilling fluid that has been used and recovered from a wellbore drilling or workover operation. In some aspects, the shaker screen system includes a screen assembly that includes multiple screen sections attached or coupled together (for example, within a circular screen). In some aspects, one or more of the multiple screen sections are formed of screens with varying mesh sizes, thereby allowing cuttings of different sizes to pass through the one or more screen sections.

In an example implementation, a drilling fluid shaker screen system includes a screen assembly that includes a screen mounted to a funnel, the screen including a plurality of screen sections. A first screen section of the plurality of screen sections includes a first screen mesh size and a second screen section of the plurality of screen sections includes a second screen mesh size different than the first screen mesh size. The first and second screen mesh sizes are based at least in part on a size of one or more cuttings entrained in a drilling fluid used in a drilling or workover operation. The drilling fluid shaker screen system further includes a rotation assembly mounted to the screen assembly. The rotation assembly includes one or more rollers moveable to rotate the screen assembly about an axis of rotation. The drilling fluid shaker screen system further includes a motor assembly coupled to the screen assembly and configured to vibrate the screen assembly; and a housing coupled to the screen assembly and the rotation assembly. The housing includes a cuttings outlet that is fluidly coupled to a cuttings inlet formed in the screen and a liquid outlet separate from the cuttings outlet that is fluidly coupled to the plurality of screen sections.

In an aspect combinable with the example implementation, the screen includes a circular screen area, and each of the plurality of screen sections includes a co-equal portion of the circular screen area.

In another aspect combinable with any of the previous aspects, the plurality of screen sections include four screen sections that include the first and second screen sections, each of the four screen sections including a quarter of the circular screen area.

In another aspect combinable with any of the previous aspects, the four screen sections further include a third screen section that includes a third screen mesh size and a fourth screen section that includes a fourth screen mesh size.

In another aspect combinable with any of the previous aspects, each of the first, second, third, and fourth screen mesh sizes is different.

In another aspect combinable with any of the previous aspects, the screen is mounted to the funnel at an angle that slopes downward from a perimeter of the screen toward the cuttings inlet.

In another aspect combinable with any of the previous aspects, the rotation assembly includes at least one rail mounted to at least one of the screen assembly or the rotation assembly and adjacent a perimeter of the screen assembly.

In another aspect combinable with any of the previous aspects, the rail is configured to receive at least a portion of the one or more rollers.

Another aspect combinable with any of the previous aspects further includes a vibration assembly mounted to the housing and including one or more springs configured to oscillate the screen assembly based at least in part on operation of the motor assembly.

In another aspect combinable with any of the previous aspects, the vibration assembly is mounted to a bottom portion of the rotation assembly, and the rotation assembly is mounted to a bottom portion of the funnel.

Another aspect combinable with any of the previous aspects further includes a locking assembly that includes a first member attached to the screen assembly; a second member attached to the rotation assembly; a bore formed through each of the first and second members; and a pin insertable through the bore to fixedly lock the screen assembly to the rotation assembly.

In another aspect combinable with any of the previous aspects, the first screen mesh size is configured to allow a first cutting to pass there through, and the second screen mesh size is configured to allow a second cutting larger than the first cutting to pass there through.

In another aspect combinable with any of the previous aspects, the cuttings inlet includes a hole in the screen centered at a center of the screen assembly.

In another aspect combinable with any of the previous aspects, the housing defines an interior volume fluidly coupled to the liquid outlet.

In another example implementation, a method for separating cuttings from liquid in a drilling fluid includes circulating a drilling fluid that includes a liquid and a plurality of formation cuttings to a screen assembly that includes a screen, the screen including a plurality of screen sections; vibrating the screen assembly during circulation of the drilling fluid to the screen assembly; while vibrating the screen assembly, separating, with the screen assembly, the liquid from the plurality of formation cuttings; while vibrating the screen assembly, separating a first portion of the plurality of formation cuttings of a first size from the drilling fluid with a first screen section that includes a first screen mesh size; rotating the screen assembly; subsequent to rotating the screen assembly and while vibrating the screen assembly, separating a second portion of the plurality of formation cuttings of a second size different than the first size from the drilling fluid with a second screen section that includes a second screen mesh size different than the first screen mesh size; directing the separated liquid through the screen assembly to a liquid outlet; and directing at least one of the first or second portions of the plurality of formation cuttings to a cuttings outlet formed in the screen.

In an aspect combinable with the example implementation, the screen includes a circular screen area, and each of the plurality of screen sections includes a co-equal portion of the circular screen area.

Another aspect combinable with any of the previous aspects further includes further rotating the screen assembly; while vibrating the screen assembly, separating a third portion of the plurality of formation cuttings of a third size different from the first and second sizes from the drilling fluid with a third screen section that includes a third screen mesh size different than the first and second screen mesh sizes; further rotating the screen assembly; and while vibrating the screen assembly, separating a fourth portion of the plurality of formation cuttings of a fourth size different from the first, second, and third sizes from the drilling fluid with a fourth screen section that includes a fourth screen mesh size different than the first, second, and third screen mesh sizes.

Another aspect combinable with any of the previous aspects further includes directing at least one of the third or fourth portions of the plurality of formation cuttings through the screen assembly with the separated liquid to the liquid outlet; and directing the other of the at least one of the third or fourth portions of the plurality of formation cuttings to the cuttings outlet formed in the screen.

Another aspect combinable with any of the previous aspects further includes directing the at least one of the first or second portions of the plurality of formation cuttings at a downward angle toward the cuttings inlet and away from a perimeter of the screen.

In another aspect combinable with any of the previous aspects, vibrating the screen assembly includes operating a motor to drive a gear or wheel coupled with the screen assembly; based on driving the gear or wheel, oscillating the screen assembly with a plurality of springs coupled to the screen assembly.

In another aspect combinable with any of the previous aspects, rotating the screen assembly includes moving at least one roller coupled with the screen assembly on a rail; and based on moving the at least one roller, rotating the screen assembly about an axis of rotation.

In another aspect combinable with any of the previous aspects, the first screen section that includes the first screen mesh size is positioned to receive the drilling fluid that includes the liquid and the plurality of formation cuttings during separating the first portion of the plurality of formation cuttings of the first size from the drilling fluid with the first screen section.

In another aspect combinable with any of the previous aspects, rotating the screen assembly includes rotating the screen assembly to position the second screen section that includes the second screen mesh size to receive the drilling fluid that includes the liquid and the plurality of formation cuttings.

Another aspect combinable with any of the previous aspects further includes prior to rotating the screen assembly, unlocking the screen assembly against rotation.

In another aspect combinable with any of the previous aspects, directing the at least one of the first or second portions of the plurality of formation cuttings to the cuttings outlet formed in the screen includes directing the at least one of the first or second portions of the plurality of formation cuttings to the cuttings outlet that is centered at a center of the screen assembly.

Another aspect combinable with any of the previous aspects further includes directing at least a portion of the separated liquid through the screen assembly through the liquid outlet and to an enclosed portion of a housing that is coupled to the screen assembly.

Implementations of a shaker screen system according to the present disclosure may include one or more of the following features. For example, the shaker screen system may provide for multiple, different screens that each have a different screen mesh size in a single assembly. As another example, the shaker screen system may more efficiently remove unwanted fine particles as compared to conventional shaker screens, which can save cost and rig time during a drilling or workover operation. As another example, the shaker screen system may allow for switching from one screen mesh size to another without the conventional requirement of stopping operations to remove and install screens of different mesh size in the shaker screen system. As yet another example, the shaker screen system may require less time (for example, by an operator) to change to a desired screen mesh size.

DETAILED DESCRIPTION

The present disclosure describes a shaker screen system that may be used to separate formation cuttings from a liquid of a drilling fluid that is recovered to a terranean surface from a wellbore in a drilling or workover operation. In some aspects, the shaker screen system includes a rotating screen, which allows multiple size mesh to be installed in one screen to remove different size cuttings from a flow of the drilling fluid. Thus, in some aspects, the example implementations of the shaker screen system may scale efficiently and be used to separate cuttings from liquid in many different types of drilling fluid (for example, according to viscosity, density, or otherwise) as well as many different types of subterranean formations (for example, shale, sandstone, or otherwise).

FIG. 1is a schematic diagram of wellbore drilling or workover process10(“drilling process10”) that includes a shaker screen system24according to the present disclosure. Generally, the drilling process10represents a process in which a wellbore14is formed from a terranean surface17and through one or more subterranean formations18by a drilling rig12. The drilling process10, in this example, includes a drill bit16coupled to a downhole conveyance (for example, a tubular drill string, such as conventional or coiled tubing) that forms the wellbore14with a drilling fluid20. The drilling fluid20is provided to the drill bit16by, for example, the downhole conveyance, and circulates through the drill bit16during drilling of the wellbore14in order to, for example, cool the drill bit16and removing cuttings from the subterranean formation18back to the surface17. Thus, return drilling fluid22includes the drilling fluid20(for example, a water or foam and chemical mixture) as well as cuttings (for example, bits of rock cut from the formation18by the drill bit16). Return drilling fluid22, therefore, includes liquid28and cuttings26from the formation18, which may be removed.

As shown inFIG. 1, the return drilling fluid22is circulated out of the wellbore14to the shaker screen system24. As described in more detail in this disclosure, the shaker screen system24separates the liquid28from the cuttings26of the return drilling fluid22with a screen that includes multiple screen sections. At least one of the screen sections has a particular screen mesh size (for example, a size of the holes in the screen section) that is different than another particular screen mesh size of another screen section of the screen. Thus, different sized cuttings26may be filtered by the shaker screen system24. Some cuttings26may be small enough to remain entrained in the liquid28. Other cuttings26may be large enough to be separated from the liquid28by the shaker screen system24.

As shown in the example implementation ofFIG. 1, the liquid28(which may include some cuttings26of a size small enough to remain entrained in the liquid28through the shaker screen system24) and the cuttings26are separated into two separate streams. The liquid28is circulated from the shaker screen system24in a fluid pathway32and into a mud tank36. Generally, the mud tank36is used to hold the separated liquid28and provide the separated liquid28as a source of liquid for additional drilling fluid20(in other words, to recycle back into the drilling process10as drilling fluid20). The cuttings26are circulated into a cuttings pathway30and into one or more waste pits34. Generally, the waste pits34are pits or other enclosures that store the cuttings26for proper disposal.

FIG. 2is a schematic diagram of an example implementation of a shaker screen system200according to the present disclosure. The shaker screen system200, in this example, may be used as the shaker screen system24shown in the drilling process10inFIG. 1.FIG. 3is an exploded view of the example implementation of the shaker screen system200. As shown in this implementation, the shaker screen system200includes a housing212that forms a partial enclosure with an open top. A screen assembly202is mounted to the open top of the housing212by legs236that insert into holes252. The screen assembly202, in this example, includes a screen204(for example, circular) that is comprised of multiple screen sections206. In this example, there are four screen sections206that combine to form the screen204in equal portions (here, quarter portions). Other implementations may include more or fewer screen sections206.

Each of the multiple screen sections206may have a screen mesh size that is different than a screen mesh size of the other screen sections206. For example, as shown inFIGS. 2-3, each of the four screen sections206may have a screen mesh size different than the screen mesh size of the other screen sections206. Thus, as the screen204rotates during operation of the shaker screen system200, a particular screen section206of a particular screen mesh size will remove specific cuttings26of a specific particle size, and as the screen204continues to rotate, the next screen section206of a different screen mesh size will remove, for example, even finer particles of cuttings26. During a full rotation of the screen204(for example, 360° about the axis248), the return drilling fluid22may be restored to the same or similar properties (for example, viscosity, density) as the drilling fluid20.

In this example, there are four different screen mesh sizes, which allow for four differently-sized cuttings from a return drilling fluid to be separated from the liquid in the return drilling fluid. In other examples, two of the four screen sections206may have a particular screen mesh size and two of the four screen sections206may have another particular screen mesh size. In other examples, one of the four screen sections206may have a particular screen mesh size and three of the four screen sections206may have another particular screen mesh size. Other examples of different combinations of screen sections206and screen mesh sizes are also contemplated by the present disclosure.

Turning briefly toFIG. 6, the screen204is positioned at a top of a funnel234that includes the legs236that can be inserted into a rotation assembly208that is mounted to the housing212below the screen assembly202. The funnel234and screen204include a cuttings inlet226formed with a center that coincides with a centerline axis248of the shaker screen system200. Springs238are positioned about the legs236in order for the screen assembly202to “float” on the rotation assembly208.

Turning briefly toFIG. 8, this figure shows a detail of the screen assembly202. In this example implementation, the funnel234may be angled (for example, downward) at a particular angle. In this example, the angle is at or about 20°, but other angles are contemplated by the present disclosure. The screen204may also be angled from a perimeter227of the screen204toward the cuttings inlet226. In this example the screen204may also be angled downward at or about 20°.

Turning briefly toFIG. 5, a detail of the connection between the screen assembly202and the rotation assembly208is shown. As illustrated in this figure, the leg236is inserted into the hole252of an upper plate250of the rotation assembly208. The spring238buffets contact between the screen assembly202and the rotation assembly209. Once the leg236is positioned through the hole252, a cotter pin264may be positioned to secure the screen assembly202to the rotation assembly209, as shown.

Turning back toFIGS. 2 and 3, the rotation assembly208operates to provide rotation246to the screen assembly202, for example during operation of the shaker screen system200or between operation times of the shaker screen system200. In this example, the rotation assembly208includes one or more rails242(in this example, two, an upper rail242and a lower rail242) that circumscribe an inside perimeter of the rotation assembly208. One or more rollers244are mounted to the rails242and are moved (for example, rotated) to rotate the rotation assembly208and the screen assembly202.

Turning briefly toFIGS. 4A-4B, these figures illustrate portions of the rotation assembly208. For example, as shown, in this example, the rails242are attached to the upper plate250and a lower plate258of the rotation assembly208. The rails242are aligned along the perimeters of the lower and upper plates258and250, respectively. A roller244is connected, in this example, to the upper plate250through a leg254to receive and ride on the rails242as shown. In operation, the rotation assembly208may be rotated in order to rotate the shaker screen assembly202into a position such that a particular screen section206(with a particular screen mesh size) is positioned to receive the return drilling fluid22. As described with reference toFIG. 7, for instance, once positioned appropriately, the shaker screen assembly202may be locked or otherwise held in place. If a different screen section206(with different screen mesh size) is desired, the shaker screen assembly202may be unlocked and rotated (on the rotation assembly208) so that a different screen section206is positioned to receive the return drilling fluid22.

The example implementation of the shaker screen system200includes a vibration assembly210mounted to or in the housing212below a rotation assembly208. As shown in this example, the vibration assembly210include multiple springs214that facilitate oscillation of the rotation assembly208(for example, vertical oscillation), which in turn is translated to the screen assembly202during operation of the shaker screen system200. In this example implementation, a motor assembly216may be operated (for example, by the controller999) to provide vibratory movement to initiate (and also, maintain, in some aspects) oscillation of the rotation assembly208(for example, vertical oscillation), which in turn is translated to the screen assembly202during operation of the shaker screen system200.

As shown, the motor assembly216includes an electric motor232coupled to a motor gear218, that in turn is coupled to a drive gear222through a belt or chain220. A control system (or controller)999is communicably coupled to the motor assembly216to control operations of the motor assembly216. In example implementations, the controller999may be a microprocessor-based, electro-mechanical, pneumatic, or hydraulic controller that may control the motor assembly216based on operator input and/or based on a sensed operation of the motor assembly216, and more generally, the shaker screen system200.

As shown in the example implementation of the shaker screen system200, a cuttings pathway224extends vertically through the shaker screen system200, with the cuttings inlet226forming an inlet to the pathway224and the pathway224having a cuttings outlet228formed opposite the cuttings inlet226. As explained in more detail later, cuttings26from the return drilling fluid22that are not small enough to be entrained with the liquid28are separated from the return drilling fluid22and move (for example, through vibration) to the cuttings inlet226and then through the cuttings pathway224for removal from the outlet228(for example, to one or more mud pits). In some examples, the cuttings pathway224is formed of a tubular that extends between the cuttings inlet226and the cuttings outlet228. Thus, once in the pathway224, cuttings26may not escape into a liquid pathway230of the housing212.

As further shown in this example, the liquid pathway230extends vertically through the shaker screen system200in an annulus between the cuttings pathway224and the housing212. The liquid pathway230includes an inlet231located under the screen204in order to receive the separated liquid28from the return drilling fluid22. In this example, the liquid pathway230include an outlet240to direct the liquid28to, for example, one or more mud tanks36. As explained in more detail later, liquid28(and small cuttings26entrained in the liquid28) from the return drilling fluid22is separated from the return drilling fluid22and falls through the screen204into the liquid pathway230. In some examples, the liquid pathway230is formed of a tubular that extends between the inlet231and a bottom of the housing212. Thus, once in the pathway230, liquid28may not escape into an inner volume of the housing212or into the cuttings pathway224.

Turning toFIGS. 4B and 7, these figures illustrate an example implementation of a locking assembly268of the shaker screen system200. For example, during non-operation of the shaker screen system200or, for example, to lock a particular screen section206(with a desired screen mesh size) at a desired location, the rotation assembly208may be locked against rotational movement, thereby also locking the screen assembly202against rotational movement. As shown in this example, the locking assembly268includes a plate260attached to the upper plate250and a plate260attached to the lower plate258. Each of the plates260includes a bore262there through. When the plates260are aligned, the bores262of the plates260are aligned to accept a locking pin266through the bores262. The locking pin266, once inserted through both bores262, locks the upper and lower plates250and258against rotational movement, thereby preventing rotational movement of the rotation assembly208.

FIG. 9is a flowchart that describes an example method900for separating formation cuttings26from a liquid28in a return drilling fluid22. The example method900is described with reference to the shaker screen system200shown in the figures. Method900may begin at step902, which includes circulating a drilling fluid of liquid and formation cuttings to a screen assembly that includes a screen of multiple screen sections. For example, return drilling fluid22may be circulated to the screen assembly202of the shaker screen system200shown in the figures. The return drilling fluid22is comprised of liquid28and cuttings26. As shown inFIGS. 2-3, the screen assembly202includes multiple screen sections206of the screen204. In some aspects, the screen sections206have differing screen mesh sizes to allow for different sizes of the particles in the cuttings26to fall through the mesh.

Method900may continue at step904, which includes vibrating the screen assembly during circulation of the drilling fluid to the screen assembly. For example, as shown inFIGS. 2-3, the motor assembly216(for example, with electric motor232or other prime mover) may be started (and controlled by the controller999) to vibrate the shaker assembly200. The motor232drives the motor gear218, which in turn drives the gear222through belt or chain220. As the gear222rotates, the shaker screen assembly202vibrates. For example, oscillation of the rotation assembly208(and likewise the screen assembly202) may occur based on the operation of the motor assembly216to initiate vibration and also the springs214mounted below the rotation assembly208. In some aspects, initial operation of the motor assembly216may be sufficient to begin (and maintain) oscillation of the assemblies208and202by the springs214. In some aspects, continual operation of the motor assembly216may be needed to begin (and maintain) oscillation of the assemblies208and202by the springs214. In some aspects, the oscillation may be eccentric.

Method900may continue at step906, which includes which includes separating, with the screen assembly, the liquid from the formation cuttings. For example, as the return drilling fluid22is circulated to the screen204, the liquid28may be separated by failing through the screen sections206. The separated liquid28falls into the liquid pathway230and exits the housing212of the shaker screen system200at the outlet240(for example, to the mud tank36). In some aspects, a portion of the cuttings26may also be entrained in the liquid28and fall through the screen sections206into the liquid pathway230. For example, one or more particular screen sections206may be selected based on or include a screen mesh size that allows certain size particles to stay entrained with the liquid28. As the screen assembly202rotates and the particular screen sections206receive the circulated return drilling fluid22, such smaller particles may pass through these screen sections206.

Method900may continue at step908, which includes separating a first portion of the formation cuttings of a first size from the drilling fluid with a first screen section of a first screen mesh size. For example, particles larger than those entrained with the liquid28may remain in the return drilling fluid22on the screen204until such particles are moved (for example, by vibration) to a first screen section206with a mesh size that allows the particles of the cuttings26to fall there through (to the cuttings pathway224). Other, larger particles of the cuttings26may remain on the screen204as they do not fall through the first screen section206.

Method900may continue at step910, which includes directing the separated liquid through the screen assembly to a liquid outlet. For example, the separated liquid28falls into the liquid pathway230and exits the housing212of the shaker screen system200at the outlet240(for example, to the mud tank36). In some aspects, of course, steps908and910may be performed simultaneously or substantially simultaneously.

Method900may continue at step912, which includes rotating the screen assembly. For example, in some aspects, the first screen section of the first screen mesh size may be desired to separate the formation cuttings of the first size from the liquid. But as the return drilling fluid may change consistency (for example, with different sized formation cuttings due to, for instance, a different rock formation). Thus, in some aspects, another screen mesh size (in a second screen section) may be desired at some point during method200. In some aspects, rotating the screen assembly includes unlocking the rotation assembly208to allow rotation of the rotation assembly208, and thus the shaker screen assembly202, to move the desired shaker screen section206to receive the return drilling fluid22. Once rotated, the shaker screen assembly202may be re-locked into position, for instance, by re-locking the rotation assembly208.

Method900may continue at step914, which includes separating a second portion of the formation cuttings of a second size different than the first size from the drilling fluid with a second screen section of a second screen mesh size that is different than the first screen mesh size. For example, the larger particles that do not fall through the first screen section206of step908may nonetheless be moved (for example, through vibration) to a second screen section206with a larger mesh size (in other words, larger holes in the screen section) relative to the first screen section206of step908. Once the larger particles of the cuttings26are moved to the second screen section206, such particles may then fall through the second screen section206to the cuttings pathway224. In additional aspects of method900, steps912and914may be repeated for each different screen mesh size of the different screen sections206of the screen204.

Method900may continue at step916, which includes directing the separated liquid through the screen assembly (the second screen section) to the liquid outlet. For example, the separated liquid28falls into the liquid pathway230and exits the housing212of the shaker screen system200at the outlet240(for example, to the mud tank36). In some aspects, of course, steps914and916may be performed simultaneously or substantially simultaneously.

Method900may continue at step918, which includes directing at least one of the first or second portions of the formation cuttings to a cuttings inlet formed in the screen. For example, once the particles of the cuttings26fall through one of the first or second screen sections206, such particles may then enter the cuttings pathway224and exit the housing212to the waste pits34.