Patent Description:
Various tools are utilized in subterranean operations, such as hydrocarbon exploration, drilling and completion operations, to increase or maximize production efficiency. Sand control devices such as sand screens are utilized to control the ingress of particulate contaminants into production fluid and to aid in stabilizing production formations. Examples of sand control devices include screen assemblies having conformable sleeves or components that are expanded downhole. In some cases, high temperature conditions experienced downhole can affect the performance such sand control devices. The document <CIT> relates to an apparatus and method for use in a wellbore, wherein the composition may include a shape-conforming material and nanoparticles sufficient to absorb energy to heat the shape-conforming material to near or above a glass transition temperature. The document <CIT> relates to a well completion method comprising covering a substrate tube with a porous compliant material, expanding and accommodating the material toward the wellbore wall, and filtering fluid through the compliant material into the base pipe. The document <CIT> relates to a sand screen apparatus for use in a well comprising a composite having a compressed state and an expanded state, the composite comprising a base polymer and one or a plurality of reactive fillers.

In a first aspect of the invention, there is provided a fluid control device according to claim <NUM>.

In a second aspect of the invention, there is provided a fluid control method according to claim <NUM>.

Devices, systems and methods for controlling sand and other undesirable material in a downhole environment are described herein. An embodiment of a fluid control device or tool includes a screen assembly having a porous medium made from a high temperature thermoplastic polymer. The thermoplastic polymer is formed as a foam or other porous medium and acts to filter fluid entering the fluid control device, e.g., production fluid including formation fluids such as oil and hydrocarbon gas. The porosity of the thermoplastic polymer imparts a shape memory characteristic to the porous medium, which allows the porous medium to be compressed into a run-in shape and size, and expanded downhole to conform to a borehole or otherwise expand so that sand, particulates and other undesirable material is filtered from production fluid.

In one embodiment, the porous medium is formed as an open cell foam that at least partially surrounds a base pipe or other support structure. Fluid entering a borehole from a subterranean region into an annulus flows through the porous medium and into a fluid conduit in fluid communication with the surface, while sand and other particulates, as well as larger solids, are prevented from entering the fluid conduit. The screen assembly may include one or more layers of the porous medium, either alone or in combination with one or more additional filtration layers or devices, such as perforated sleeves, wire mesh, bead screens and/or others.

Embodiments described herein present a number of advantages. The filtration assemblies and screen assemblies described herein can be used in higher temperature environments than conventional screens and conventional shape memory devices. The assemblies can withstand such higher temperatures without significantly degrading, and can be configured to expand at various selected temperatures, thereby providing a robust and effective tool that can be used in a variety of environments encountered downhole.

<FIG> depicts an example of a system <NUM> configured to perform a subterranean operation, and illustrates an example of a screen assembly including a conformable and expandable porous thermoplastic medium. The system <NUM> in this example is a resource or energy production system <NUM> that includes a borehole string <NUM> disposed in a borehole <NUM> extending into a subterranean region or a resource bearing formation, such as an earth formation <NUM>. It is noted that the porous medium is not limited to this example, and can be incorporated into any suitable downhole device or component.

The borehole string <NUM> includes a completion string having a production assembly <NUM>. The production assembly <NUM> includes a screen assembly <NUM>, and may also include a flow control device such as an inflow control device (ICD). The production assembly <NUM> may include additional components, such as one or more packer assemblies <NUM> configured to isolate components and/or zones in the borehole <NUM>.

The system <NUM> also includes surface equipment <NUM> such as a drill rig, rotary table, top drive, blowout preventer and/or others to facilitate deploying the borehole string <NUM>, operating various downhole components, monitoring downhole conditions and controlling fluid circulation through the borehole <NUM> and the borehole string <NUM>. For example, the surface equipment <NUM> may include a fluid control system <NUM> including one or more pumps in fluid communication with a fluid tank <NUM> or other fluid source. The fluid control system <NUM> facilitates injection of fluids, drilling fluid (e.g., drilling mud), stimulation fluid (e.g., a hydraulic fracturing fluid), gravel slurries, proppant, and others. The fluid control system <NUM> or other suitable system may be used to inject a fluid (referred to as an activation fluid) to trigger shape memory recovery as discussed in more detail below.

One or more components of the borehole string <NUM> may be configured to communicate with a surface location (e.g., the surface equipment <NUM>). The communication may be wired or wireless. A processing device such as a surface processing unit <NUM> and/or a subsurface processing unit <NUM> and/or <NUM>, which may be disposed in the borehole <NUM> and connected to one or more downhole components. The processing device may be configured to perform functions such as controlling downhole components, transmitting and receiving data, processing measurement data and/or monitoring operations. The processing device may also control aspects of fluid circulation and injection, such as controlling injection of a triggering fluid.

The screen assembly <NUM> in this embodiment includes a base pipe <NUM> and an expandable porous medium <NUM> made from a thermoplastic material. The medium is manufactured to have properties that result in shape memory functionality. In one embodiment, the thermoplastic material is configured to form a foam or other porous medium having a selected porosity, which has been found to impart shape memory behavior. This behavior allows the medium to be compressed or compacted into a compacted or run-in shape, and expanded due to downhole temperatures to an expanded shape. In the embodiment of <FIG>, the medium <NUM> is configured to expand to a size or diameter sufficient to contact and conform to an annular region of the borehole <NUM>. In one embodiment, the porosity is selected, designed and/or formed to have a porosity of greater than or equal to about <NUM>%.

The base pipe <NUM> defines an inner fluid conduit <NUM> that can be connected to a borehole string or otherwise in fluid communication with a selected location such as a surface location. For example, the inner fluid <NUM> is in fluid communication with a production conduit <NUM> connected to the surface. A plurality of holes or other fluid passages <NUM> provide fluid paths for fluid entering through the porous medium <NUM> to flow through the base pipe <NUM> and into the inner fluid conduit <NUM>.

As noted above, the porous medium is made from a thermoplastic polymer. A thermoplastic polymer is a plastic polymer that becomes moldable or pliable at temperatures exceeding some threshold temperature, and returns to a solidified state after the temperature is reduced. Examples of thermoplastic polymers that may be used to make the porous medium <NUM> include acrylates, nylon, polypropylene, polyesters, epoxies and others.

The porosity of the thermoplastic porous medium <NUM> provides for a shape memory effect, in which the medium <NUM> can be compacted from an initial shape, and later activated by heating the medium <NUM> to a temperature above a glass transition temperature (Tg), to partially or fully recover the initial shape. For example, the medium <NUM> is compacted at a temperature above the glass transition temperature, and subsequently cooled to retain the compact shape (run-in shape). The screen assembly <NUM> can then be deployed in the borehole <NUM>. When the screen assembly <NUM> reaches a temperature greater than the Tg, the porous medium <NUM> expands to recover all or some of the initial shape.

The porous medium <NUM>, in one embodiment is made from a thermoplastic polymer (alone or in combination with other materials) that can be deployed in high downhole temperature environments, e.g., up to at least about <NUM> degrees C or <NUM> degrees F. In one embodiment, a "high temperature" is a temperature that is at or above a downhole or subterranean temperature. In one embodiment, the temperature is at least about <NUM> degrees C. For example, the high temperature thermoplastic is a material selected or configured to withstand temperatures of at least about <NUM> degrees F or <NUM> degrees C. The high temperature resistance of the polymer, combined with shape memory properties due to (at least) the porosity, results in a medium that can be used in higher temperature environments as compared to conventional screens and conventional shape memory polymers.

The porous medium <NUM> can be a single layer or multiple layers. In addition, the porous medium can be made from one type of thermoplastic (e.g., polytetrafluoroethylene) or multiple types (e.g., polytetrafluoroethylene and polyether ether ketone).

The porous medium <NUM> may be part of a screen device or assembly that includes additional layers or filtration components. For example, the screen assembly <NUM> may be made from one or more layers of the porous medium <NUM>, in combination with one or more additional filtration elements or layers, such as metal screens, wire mesh, polymeric screens, mesh wool, bead screens, perforated sleeves and/or others.

In one embodiment, the porous medium is made from a porous polytetrafluoroethylene (PTFE) material. PTFE is a synthetic fluoropolymer of tetrafluoroethylene, which is a versatile material due to its excellent chemical inertness, outstanding weathering, high temperature resistance, excellent electrical insulation, low coefficient of friction and hydrophobic properties. These unique properties allow PTFE to be used in diverse range of domestic and industrial applications. PTFE also exhibits resistance to high temperatures, having a melting point of about <NUM> degrees C or <NUM> degrees F.

PEEK is a robust thermoplastics material that has excellent mechanical and chemical resistance properties that are retained even at high temperatures. PEEK melts at about <NUM> degrees C or <NUM> degrees F, and porous PEEK has a glass transition temperature of around <NUM> degrees C or <NUM> degrees F). PEEK is highly resistant to thermal degradation, as well as to attack by both organic and aqueous environments. PEEK material thermal and mechanical properties can be further enhanced by crosslinking to allow its use in even higher temperatures.

In one embodiment, the thermoplastic polymer is a cross-linked polymer. Cross-linked polymers can provide additional mechanical strength and/or resistance to higher temperatures, which can provide for effective shape memory properties at higher temperatures and/or greater expansion. Cross-linked thermoplastic polymers, such as cross-linked PTFE, have been found to improve both strength and shape rebound. Other types of thermoplastic polymers that can be used include chemically modified polymers (e.g., chemically modified PTFE and/or chemically modified PEEK), other cross-linked polymers (e.g., cross-linked PEEK), and polymers having a filler incorporated therein (e.g., carbon fiber and/or carbon nanotubes).

In one embodiment, the porous thermoplastic medium <NUM> is configured to be expanded via an activation fluid. The activation fluid acts to reduce the glass transition temperature of the medium to a temperature that is at or below the temperature of a downhole environment. For example, the activation fluid is configured to reduce the glass transition temperature to below about <NUM>-<NUM> degrees C or <NUM>-<NUM> degrees F, or other temperature level or range encountered downhole. The activation fluid is selected based on considerations including downhole temperature and desired transition temperature.

The ability to lower the transition temperature downhole allows for the porous medium to be compacted at higher temperatures, which may allow for more compaction. A suitable activation fluid can reduce glass transition temperature so that the more compaction on the surface can be done at higher temperature while achieving expansion at lower glass transition temperature downhole.

The activation fluid may be a water based fluid, such as a brine or water based drilling mud, or an oil based fluid. The fluid is configured to activate the medium <NUM> and expand it by lowering the Tg temporarily so that downhole temperature causes expansion. The activation fluid may also trigger and/or facilitate expansion due to the activation fluid seeping into pores in the compacted foam and forcing expansion from within the pores. Various chemical additives may be included to control aspects of activation, including activation temperature and the rate of expansion.

Although embodiments are discussed in the context of sand control and as part of the system <NUM>, it is to be understood that the embodiments are not so limited. The medium <NUM> may be configured for any desired downhole application (or surface application) and thus have any suitable shape, size, material composition and chemical composition.

<FIG> depict an example of a porous medium <NUM> made from a thermoplastic polymer. In this example, the porous medium <NUM> is an open cell foam made from PTFE, and is formed as a cylinder. It is noted that the porous medium <NUM> may take any form that provides fluid paths that allow fluid to enter a production conduit or other location. Examples of such forms include closed cell foam, foam having both open and closed cells, a lattice, interweaved fibers or other elongated members, perforated plates or sleeves, and others.

<FIG> show the porous medium <NUM> in various states. As shown in <FIG>, the porous medium was initially manufactured as a foam having a porosity of about <NUM>-<NUM>%. At this point, the porous medium is in an initial state and has an initial width of about <NUM> to about <NUM> inches (<NUM> inch = <NUM>) Referring to <FIG>, the foam is compacted under a temperature that is greater than the transition temperature Tg, and allowed to cool. In this example, the temperature during the compaction phase is greater than about <NUM> degrees C. The foam is now in a compacted state, and has a width of about <NUM> to about <NUM> inches.

The foam was then deployed in an environment having crude oil and a temperature above the transition temperature (e.g., <NUM> degrees C). At this temperature, the foam expanded to a width of about <NUM> to about <NUM> inches, which represents good shape memory recovery of about <NUM>-<NUM>%. The shape recovery can be improved further by optimizing the porosity of the material and/or by improving the properties of the PTFE material by way of crosslinking, adding fillers and/or chemically modifying the PTFE.

The porous medium <NUM> can be manufactured in a number of ways. One example is a sacrificial method in which the thermoplastic material (e.g., PTFE) is processed to create a selected porosity by mixing or blending the thermoplastic material with a sacrificial filler. Porosity is created by subsequently dissolving or otherwise removing the filler to create pores. Another example involves heating the material to a liquid or pliable state and blowing air or other gases to create bubbles or voids. In yet another example, glass spheres or other hollow bodies are blended with the thermoplastic material, followed by solidification and application of a compressive force to break the hollow bodies.

<FIG> depicts an embodiment of a method <NUM> of manufacturing a porous thermoplastic medium, such as the porous medium <NUM> and/or <NUM>. The method <NUM> includes one or more stages <NUM>-<NUM>. In one embodiment, the method <NUM> includes the execution of all of stages <NUM>-<NUM> in the order described. However, certain stages may be omitted, stages may be added, or the order of the stages changed.

At stage <NUM>, powdered thermoplastic material (e.g., PTFE) or beads of the thermoplastic material are mixed with a dissolvable substance such as a salt. The salt may be in a particulate form, and the size of the particles may be selected based on the desired pore size or porosity. In addition, the ratio between the amount of the thermoplastic material and the amount of salt can be selected based on the desired porosity. For example, powdered PTFE and powdered salt are mixed with a proportion of about <NUM>% salt (e.g., <NUM>) and about <NUM>% PTFE (e.g., <NUM>).

At stage <NUM>, the mixture is preformed to a desired shape, such as a hollow cylindrical shape configured to be disposed on a base pipe. At stage <NUM>, the mixture is fused and sintered together at a suitably high temperature to create an integrated body.

At stage <NUM>, the salts are then extracted from the integrated body. For example, the salt is extracted and dissolved by use of water at elevated temperature under pressure, leaving a porous thermoplastic medium. Additional quality control and inspection tests may be performed at stage <NUM>. The resulting porous medium has a porosity of about <NUM> to about <NUM>%.

Figure <NUM> illustrates a method <NUM> of controlling particulates such as produced sand in a borehole. The method is performed in conjunction with a fluid control device or tool such as the screen assembly <NUM>. The method <NUM> includes one or more stages <NUM>-<NUM>. In one embodiment, the method <NUM> includes the execution of all of stages <NUM>-<NUM> in the order described. However, certain stages may be omitted, stages may be added, or the order of the stages changed. Although the method <NUM> is described in conjunction with the screen assembly <NUM>, the method can be utilized in conjunction with any suitable fluid control device or system.

In the first stage <NUM>, at fluid control device or apparatus, such as the screen assembly <NUM> is prepared for deployment. A porous thermoplastic medium as described herein (e.g., the medium or conformable sleeve <NUM>) is disposed on a support structure, and is compacted from an initial shape to a smaller diameter shape (a compacted or run-in shape) at a temperature above the Tg of the medium.

In the second stage <NUM>, the device is deployed to a subterranean environment via a borehole. For example, the screen assembly <NUM> in the compacted state is deployed in the borehole <NUM> to a selected location, such as a production zone. At this stage, the Tg of the porous medium is above the temperature at the selected subterranean location.

In the third stage <NUM>, the porous medium is activated to cause the medium to expand into an expanded state, in which some or all of the initial or run-in shape is recovered. For example, the screen assembly <NUM> and the medium <NUM> is activated by injecting an activation fluid, such as a water-brine or oil-based liquid, to lower the Tg. The activation fluid causes the Tg of the medium <NUM> to fall below the downhole temperature, which causes the medium <NUM> to expand and conform to a surface of the borehole <NUM>.

In the fourth stage <NUM>, production is commenced, and fluid from the subterranean region is drawn through the porous medium. For example, fluid from the formation <NUM> is drawn through the medium <NUM> to filter out sand and other undesirable material. In the fifth stage <NUM>, production fluid including fluid from the formation is produced at the surface.

Embodiments described herein provide an effective means to control sand and prevent undesired materials from entering a production string or being produced. The devices described herein can be configured to operate effectively at a wide range of temperatures, including temperatures higher than those at which conventional sand control devices operate. The various porous configurations of the thermoplastic polymers provides for a shape memory effect that allows for compaction and expansion at such high temperatures. These configurations allow for the use of the thermoplastic polymers described herein, which can have more robust properties and resistance to high temperatures than traditional or conventional shape memory polymers (SMP).

Claim 1:
A fluid control device (<NUM>) comprising:
a support structure configured to be deployed in a borehole (<NUM>);
a filtration component disposed at the support structure, the filtration component including a porous medium (<NUM>) made from a thermoplastic polymer material, the porous medium (<NUM>) including an open cell foam, the porous medium (<NUM>) having a porosity selected to cause the porous medium (<NUM>) to exhibit shape memory behavior, the porous medium (<NUM>) configured to be compacted from an initial shape to a compacted shape, deployed in the borehole (<NUM>), and subsequently expanded due to a downhole temperature to conform to a surface of the borehole (<NUM>),
characterized in that the porosity of the porous medium is at least about <NUM> percent.