Integrated multi-stage sand separation system

A separator system includes a separator including an inlet configured to receive a mixed fluid, a first outlet, and a second outlet. The separator system includes a pressure tank physically coupled to the separator, and including a partition wall defining a collection chamber and a separation chamber in the pressure tank, a first inlet communicating with the collection chamber and coupled to the separator to receive at least some of the solids component from the separator, and a second inlet communicating with the separation chamber and in communication with the separator. The second inlet is configured to receive at least some of the liquid component and the gaseous component from the separator. The pressure tank also includes a first drain in communication with the collection chamber, and a first liquid outlet in communication with the separation chamber. The pressure tank includes a gas outlet in communication with the separation chamber.

BACKGROUND

Hydraulic fracturing is a well-treatment process in which preferential flowpaths for hydrocarbons are established in a subterranean rock formation by pumping a fluid at high pressures into a well to initiate fractures in the rock formation. The fluid is predominately water, but may also include solids, such as sand or ceramic proppants, which at least partially fill the fractures and maintain the preferential flowpaths.

When oil or other fluids are produced/recovered from the well, it may be desirable to remove sand or other solids from the produced fluid. A separator system is employed to perform this function. One type of separator system used for this application is a cyclone separator. The cyclone separator operates at steady state by imparting a generally helical flowpath in a fluid. In such a flow, the denser particulate matter drops out into a hopper, because of its greater density, while the less-dense liquids and gases flow inward and up through an outlet.

Other separator systems include sedimentation tanks. In sedimentation tanks, the produced fluid may be fed to the tank, where the solids may settle out, and immiscible liquids/gases may likewise stratify based on density. Weirs may be employed in such tanks to separate the various phases from one another.

Cyclone separators and sedimentation tanks are sometimes used in series. For example, the cyclone separator may be positioned upstream of the sedimentation tank. As such, the cyclone separators remove the solids, while the sedimentation tanks allow the different phases of fluid (e.g., gas, water, and oil) to separate. However, this can result in a relatively large footprint for the separator system and, in some cases, the space at the wellsite may be limited.

SUMMARY

A separator system is disclosed. The separator system includes a separator including an inlet configured to receive a mixed fluid, a first outlet, and a second outlet, the separator being configured to at least partially separate a solids component of the mixed fluid from a liquid component and a gaseous component of the mixed fluid, and to direct the separated solids component to the first outlet and at least some of the liquid and gaseous components to the second outlet. The separator system also includes a pressure tank physically coupled to the separator, the pressure tank including a partition wall defining a collection chamber and a separation chamber in the pressure tank, a first inlet communicating with the collection chamber and coupled to the first outlet of the separator, the first inlet being configured to receive at least some of the solids component from the first outlet and provide the solids component to the collection chamber, and a second inlet communicating with the separation chamber and in communication with the second outlet of the separator. The second inlet is configured to receive at least some of the liquid component and the gaseous component from the second outlet. The pressure tank also includes a first drain in communication with the collection chamber, and a first liquid outlet in communication with the separation chamber. The first liquid outlet is configured to allow at least a portion of the liquid component that is received into the separation chamber to be removed therefrom. The pressure tank also includes a gas outlet in communication with the separation chamber. The gas outlet is configured to allow at least a portion of a gaseous component that is received into the separation chamber to be removed therefrom.

A method for separating is disclosed. The method includes receiving a mixed flow into a separator. The mixed flow includes a fluid component and a solid component. The method also includes separating the fluid component from the solid component in the separator, receiving at least some of the solid component from the separator into a collection chamber of a pressure tank, and receiving at least some of the fluid component from the separator into a separation chamber of the pressure tank. The collection chamber and the separation chamber are separated by a partition wall in the pressure tank. The method further includes separating the fluid component into a gas and one or more liquids in the separation chamber.

A pressure tank is also disclosed. The pressure tank includes a partition wall between a collection chamber and a separation chamber defined in the pressure tank, and a first inlet communicating with the collection chamber and configured to be physically coupled to a first outlet of a separator. The first inlet is configured to receive a solids component from the first outlet and provide the solids component to the collection chamber. The pressure tank further includes a second inlet communicating with the separation chamber and in communication with a second outlet of the separator. The second inlet is configured to receive a liquid component and a gaseous component from the second outlet of the separator. The pressure tank further includes a first drain in communication with the collection chamber, and a first liquid outlet in communication with the separation chamber. The first liquid outlet is configured to allow at least a portion of the liquid component that is received into the separation chamber to be removed therefrom. The pressure tank includes a gas outlet in communication with the separation chamber. The gas outlet is configured to allow at least a portion of a gaseous component that is received into the separation chamber to be removed therefrom.

The foregoing summary is intended merely to introduce some aspects of the following disclosure and is thus not intended to be exhaustive, identify key features, or in any way limit the disclosure or the appended claims.

DETAILED DESCRIPTION

The following disclosure describes several embodiments for implementing different features, structures, or functions of the invention. Embodiments of components, arrangements, and configurations are described below to simplify the present disclosure; however, these embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, the present disclosure may repeat reference characters (e.g., numerals) and/or letters in the various embodiments and across the Figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed in the Figures. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. Finally, the embodiments presented below may be combined in any combination of ways, e.g., any element from one exemplary embodiment may be used in any other exemplary embodiment, without departing from the scope of the disclosure.

Additionally, certain terms are used throughout the following description and claims to refer to particular components. As one skilled in the art will appreciate, various entities may refer to the same component by different names, and as such, the naming convention for the elements described herein is not intended to limit the scope of the invention, unless otherwise specifically defined herein. Further, the naming convention used herein is not intended to distinguish between components that differ in name but not function. Additionally, in the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to.” All numerical values in this disclosure may be exact or approximate values unless otherwise specifically stated. Accordingly, various embodiments of the disclosure may deviate from the numbers, values, and ranges disclosed herein without departing from the intended scope. In addition, unless otherwise provided herein, “or” statements are intended to be non-exclusive; for example, the statement “A or B” should be considered to mean “A, B, or both A and B.”

FIG. 1illustrates a side view of an integrated, multi-stage separation system100, according to an embodiment. The system100includes a separator102, which may be a cyclone separator, and may be configured to separate solids from liquids and gases, but may also be configured to separate any matter based on density (e.g., two fluids of different densities). The system100further includes a pressure tank104. The pressure tank104may be in a horizontal configuration, e.g., having a central longitudinal axis that extends parallel to the ground. The pressure tank104may be internally partitioned into a solids collection chamber and a separation chamber, as will be explained in greater detail below. The pressure tank104may be a single piece or may be two half-cylinders that are connected together, axial-end-to-end.

The system100may include a mixed-fluid inlet110, which may be connected to an inlet112of the separator102. The separator102may be physically connected to the pressure tank104via a close-coupled (e.g., no external piping or tubing therebetween) flange connection114, and a first outlet116of the separator102may extend through the flange connection114. The separator102and the pressure tank104may thus both be supported by a base118(e.g., two or more legs) connected to the pressure tank104. The pressure tank104may be generally cylindrical, with convex ends and a central axis that extends horizontally, but in other embodiments, may be any other suitable shape. As shown, the separator102may be vertically above the pressure tank104, e.g., supported thereby via the flange connection114. The pressure tank104may include a first inlet119, which may communicate with the first outlet116of the separator102.

The separator102may further include a second outlet120. A crossover line122may extend from the second outlet120to a second inlet124of the pressure tank104. The crossover line122may communicate the second outlet120to the interior of the pressure tank104.

The pressure tank104may include a first liquid outlet126, a second liquid outlet128, and a gas outlet129. The outlets126,128,129may be positioned to receive fluids from within the separator region of the pressure tank104, as will be described in greater detail below. As shown, however, the gas outlet129is coupled to the top of the pressure tank104, while the liquid outlets126,128are positioned at the bottom thereof. The outlets126,128,129may be each be coupled to suitable pipes or hoses for removal of gases, liquids, and/or solids received therethrough.

The pressure tank104may include a first drain130and a second drain132, also positioned at the bottom of the pressure tank104. The drains130,132may be configured to allow drainage of solids and/or liquids from within the pressure tank104, e.g., as part of a blowdown procedure to empty the bottom of the pressure tank104of solids. For example, the first drain130may be configured to communicate with the collection chamber, and the second drain132may be configured to communicate with the separation chamber, as will be described in greater detail below. The pressure tank104may further include one or more washout connections140. Hoses may be connected to the washout connection140, e.g., to circulate water through the pressure tank104, e.g., as part of the blowdown procedure or another washout procedure.

FIG. 2illustrates a side, cross-sectional view of the separation system100, according to an embodiment. As mentioned above, the system100generally includes the separator102and the tank104, the internal components of which are now visible. Specifically, in an embodiment, the separator102may include a hollow, generally cylindrical housing200, in which a conical structure202and an outlet tube204are positioned, with the conical structure202surrounding the outlet tube204. The inlet112to the separator102may be tangentially oriented, so as to induce a vortex flow therein that pushes relatively dense solids to the outside. The relatively dense matter (e.g., solids) may contact the wall of the conical structure202and drop out of the flow, while relatively light matter (e.g., gases and liquids) are received through the outlet tube204. From the outlet tube204, such liquids and gases may proceed through the second outlet120through the crossover line122, and into the pressure tank104via the second inlet124.

As mentioned above, the pressure tank104may be partitioned. For example, the pressure tank104may include an interior partition wall220, which may divide the pressure tank104into a collection chamber222and a separation chamber224on opposite axial (e.g., horizontal) sides of the wall220, such that the chambers222,224are horizontally-adjacent, as shown. The partition wall220may prevent communication between the chambers222,224.

The collection chamber222may be in communication with the first outlet116of the separator102. As such, the collection chamber222may receive separated liquids and solids from the separator102, e.g., elements that may not proceed into the second outlet120. The collection chamber222may allow such elements to reside in the tank104, e.g., without further separation processes, other than time and gravity, applied thereto. During a start-up phase, liquids and solids may flow into the collection chamber222. Once the (mostly) liquid phase fills the collection chamber222, further liquids may proceed out of the second outlet120, while solids may continue to fall by gravity into the collection chamber222and sink toward the bottom. The solids (and some of the liquids) may be removed from the collection chamber222intermittently via the blowdown drain130.

A washout apparatus or “sparge ring”230may be included in the collection chamber222. Because of the geometry of the pressure tank104, some solids may tend to remain in the collection chamber222during blowdown operations. Accordingly, the sparge ring230may receive a flow of water (or another liquid) via the washout connection140(FIG. 1), and direct the water to the walls of the interior of the collection chamber222. This may wash such solids into the blowdown drain130and thus promote evacuation of solids from within the collection chamber222.

Turning now to the separation chamber224, the separation chamber224may include structures that promote separation of fluids based on density. For example, the separation chamber224may include a weir240, which may extend upwards from a bottom of the separation chamber224, but not all the way to the top thereof. The weir240may be positioned between the second inlet124and the outlets128,129. Accordingly, the weir240and the partition wall220may define a first liquid collection region242therebetween, which is aligned with the second inlet124, so as to receive fluid directly therefrom. Further, the weir240may be positioned such that the outlet126and the drain132are positioned between the weir240and the partition wall220, and are thus in communication with the first liquid collection region242.

A second liquid (or “oil”) collection region244may be defined by the weir240and an end246of the pressure tank104. The outlet128may communicate directly with the second liquid collection region244, and may allow for evacuation of liquid hydrocarbons (e.g., oil) through the outlet128.

A gas collection region248may extend along the length of the separation chamber224, above the water and second liquid collection regions242,244. The outlet129, in the top of the pressure tank104, may communicate directly with the gas collection region248, and may allow for evacuation thereof.

FIG. 3illustrates a side, cross-sectional view of the system100during steady-state operation, according to an embodiment. As mentioned above, there may be a start-up operation stage, during which the inlet fluids are directed to the collection chamber222, until the collection chamber222fills up and the liquid level reaches the bottom of the conical structure202. After this point, as illustrated, the steady-state operation begins, in which the separator102acts to at least partially remove solids from the liquids/gases, and the liquids/gases proceed through the second outlet120.

Accordingly, during (e.g., steady-state) operation, a multi-phase or “mixed” fluid may be received via the inlet110into the separator system100. The mixed fluid may include one or more immiscible liquids (e.g., water and oil), solids (e.g., sand), and/or gases (e.g., gaseous mixtures including methane). The mixed fluid may then be received into the (e.g., cyclone) separator102, where it may be swirled into a vortex flow in the conical structure202. In the conical structure202, the vortex flow causes the solid components to separate from the liquids/gases. The solids then drop, by gravity, from the conical structure202into the collection chamber222of the pressure tank104via the first outlet116of the separator102and the first inlet119of the pressure tank104. The collection chamber222thus serves to receive the separated solids, and in some embodiments, may not serve any other purpose.

The collection chamber222may include a down-flow system that may serve to initiate a small downward flow within the collection chamber222. This may assist in flowing the solids (entrained in the liquid) downward in the collection chamber.

In the separator102, the liquids and gases may flow inwards and upwards from within the conical structure202, through the outlet tube204. The liquids and gases may then flow through the second outlet120, the crossover line122, and the second inlet124of the pressure tank104. As noted above, the second inlet124may open into the separation chamber224. In particular, the second inlet124may be aligned with the first liquid collection region242, between the partition wall220and the weir240. The fluids received via the second inlet124may thus fill the first liquid collection region242, with the immiscible liquids (e.g., water and oil) separating in the first liquid collection region242and stratifying based on density.

The less-dense liquids (e.g., oil) at the top of the first liquid collection region242may thus eventually spill over the weir240. The less-dense liquids that spill over the weir240may be received into the second liquid collection region244. The gaseous components of the mixed fluid received via the inlet124may also separate out, and may generally migrate upwards in the separation chamber224to the gas collection region248.

The contents of the separation chamber224may be evacuated (allowed to leave the pressure tank104), e.g., intermittently, so as to give the liquids and gases sufficient time to separate. Accordingly, the first liquid outlet126may be employed to drain the relatively denser liquid (e.g., water) from the bottom of the first liquid collection region242. The second liquid outlet128may be employed to drain the relatively lighter liquid (e.g., oil) from the bottom of the second liquid collection region244. The gas outlet129may be employed to evacuate gas from the top of the gas collection region248.

In some embodiments, a pressure-relief valve300may optionally extend across the partition wall220. This may serve to protect the partition wall220from excessive pressure-differentials between the separation chamber224and the collection chamber222. Such a pressure-relief valve may include any suitable type of one-way (e.g., check) valve or a bi-directional valve, and may be configured to allow liquids or gases to flow between the collection chamber222and the separation chamber224so as to reduce a pressure differential therebetween.

FIG. 4illustrates a flowchart of a method400for separating, e.g., by operating the separation system100, according to an embodiment. It will be appreciated that although the method400is described in the context of the separation system100, this is merely for convenience, and various embodiments of the method400may be employed with other separation systems100.

The method400may begin by receiving a mixed flow of liquids, solids, and gas through a separator inlet112of a separator102, as at402. The separator102is close-coupled and supported on a horizontally-oriented pressure tank104. The separator102may serve to separate the solids from the fluids (e.g., liquids and/or gases) in the mixed flow, as at404. The separated solids (and potentially some of the fluid) may be received through a first inlet119of the pressure tank104and into a collection chamber222that makes up a portion of the interior volume of the pressure tank104, as at406.

At least some of the fluid may be received from a second outlet120of the separator102, through a crossover line122, and into a second inlet124of the pressure tank104and into a separation chamber224, as at408. In some embodiments, at least during a transient start-up stage, at least some fluid may proceed through the first inlet119into the collection chamber222, then back through the inlet119, through the separator102, and into the crossover line122. During and after the transient, start-up phase, fluid in the crossover line122, having at least some of the solids separated therefrom, may then proceed into the separation chamber224.

In some embodiments, the separation chamber224is also part of the interior volume of the pressure tank104, but is partitioned from the collection chamber222. For example, the separation chamber224may be prevented from communication with the collection chamber222. In other examples, a pressure-relief, check, or another type of valve may optionally be employed to provide for controlled pressure equalization between the two chambers222,224.

The fluid that flows through the second inlet124may be received into a first liquid collection region242of the separation chamber224of the pressure tank104, as at410. A weir240may be positioned in the separation chamber224, defining an axial end of the first liquid collection region242, while the partition wall220between the separation chamber224and the collection chamber222defines the other axial end thereof.

In the first liquid collection region242, the fluid may separate into its component phases, e.g., water, liquid hydrocarbon (e.g., oil), and gas, as at412. The gas may occupy the upper portion of the pressure tank104, and may be evacuated, e.g., periodically, through an outlet129formed in the top of the tank104, as at414. The liquid hydrocarbon (e.g., oil) may float on the denser water, forming a top layer of the liquid in the first liquid collection region242. Thus, upon reaching the top of the weir240, the liquid hydrocarbon may flow over the weir240and into the second liquid (or “oil”) collection region244, while the water remains in the first liquid collection region242, as at416. Periodically, the water and liquid hydrocarbon may be evacuated via outlets126,128, respectively, formed in the bottom of the tank104in the first and second liquid collection regions242,244, respectively, as at418and420.

Further, the solids and/or liquids in the collection chamber222may periodically be removed (blown-down) therefrom via a blowdown drain130, as at422.

Accordingly, it will be appreciated that the separation system100disclosed herein may provide an integrated, multi-stage separator function. The first stage may be a cyclone separator, and the second stage may be a gravity-based separator. The two stages may be coupled physically together, so as to minimize a footprint of the system100. More particularly, the collection chamber222and the separation chamber224, components of two different types of separators, may be contained within a single pressure tank104.

As used herein, the terms “inner” and “outer”; “up” and “down”; “upper” and “lower”; “upward” and “downward”; “above” and “below”; “inward” and “outward”; “uphole” and “downhole”; and other like terms as used herein refer to relative positions to one another and are not intended to denote a particular direction or spatial orientation. The terms “couple,” “coupled,” “connect,” “connection,” “connected,” “in connection with,” and “connecting” refer to “in direct connection with” or “in connection with via one or more intermediate elements or members.”