MX2007013052A - Particle control screen with depth filtration - Google Patents

Abstract

A particle control screen includes a support layer. A first filter layer is disposed around the support layer. A second filter layer is disposed around the first filter layer. A third filter layer is disposed around the second filter layer. Each of the filter layers has a pore size. The pore size of the third filter layer is greater than the pore size of the second filter layer. The pore size of the second filter layer is greater than the pore size of the first filter layer.

Description

COLATOR FOR CONTROL OF PARTICLES WITH DEPTH FILTRATION RELATED REQUESTS This application claims the benefit of the provisional patent application of E.U.A. No. 60 / 797,897, filed May 4, 2006, the complete description of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION The present invention relates to a strainer for particle control for depth filtration, particularly for use in a well. Liquids and gases in oil and gas wells usually include particulate materials that need to be filtered, including sand, clay, and other unconsolidated particulate matter. The presence of sand and other fine particles in the production fluid and well equipment often leads to the rapid wear of the well machinery and expensive hardware. Underground filters, also known as sand strainers or well strainers, have been used in the oil industry to remove particulate materials from production fluids. Well strainers are generally tubular in shape and include a perforated base tube, a porous filter layer wrapped around and secured to the tube, and an outer cover. Well strainers are used when the fluid enters a production line so that the production fluid must pass through the filter layer and into the perforated tube before entering the production line and being pumped to the surface . In the context of filtration at the bottom of the borehole, the woven wire mesh is considered surface filtration, which means that the mesh prevents the particles of the desired size in microns and larger ones from passing through the mesh and all the particles are trapped in the upper surface of the mesh. The wrap yarn is also a common type of surface filtration. The wrapping yarn is a generally triangular thread wrapped around a base tube, with a determined space between threads to achieve a classification of microns. One difficulty with surface filtration is that as the larger particles are captured in the filter layer, the open spaces become smaller and smaller, thus capturing smaller and smaller particles. Finally, the particles that are captured are so fine that the filter becomes clogged, severely reducing or stopping the flow of formation fluids through the strainer to the base tube. Large reserves of thick, viscous hydrocarbons exist in locations such as the Orinoco belt in Venezuela and the oil sands of Alberta, as well as fields in Sumatra, China, Brazil, the North Sea and Kazakhstan. Different names are used to describe the material, such as heavy oil, extra heavy oil, oil sands or bitumen. Heavy oil is a viscous, asphaltic, and dense oil (ie, low API gravity) that is chemically characterized by the presence of asphaltenes, which are very large molecules that incorporate most of the sulfur and metals in the oil. Heavy oil generally has a gravity of less than 22 degrees API gravity and a viscosity of more than 100 centipoise. The extra heavy oil is heavy oil that has an API gravity of less than 10 degrees. Natural bitumen, also called tar sands or oil sands, generally has a viscosity greater than 10,000 centipoise. Oil sands can include as little as 10% bitumen and 85% or more of clay, sand, and stones. Heavy oil is more difficult to remove from formation and also includes more particulate matter than conventional oil fields. In this way, heavy oil is also generally more difficult to filter than conventional oil fields. Accordingly, there is a need for a filter assembly at the bottom of the bore with improved filtration performance, and especially for use with heavy oil.

BRIEF DESCRIPTION OF THE INVENTION In various aspects, the present invention utilizes depth filtration to trap particles of different sizes in different locations throughout the thickness of the filtration means. Larger particles are trapped in the outer layer of the mesh with the subsequent layers trapping smaller and smaller particles until the desired final classification of microns is reached. This prevents particulate formation from becoming so thin that plugging occurs and increases the filter particle holding capacity, which gives the filter a longer life. In one aspect, a strainer for particle control includes a support layer. A first filter layer is disposed around the support layer. A second filter layer is disposed around the first filter layer. A third filter layer is disposed around the second filter layer. Each of the filter layers has a pore size. The pore size of the third filter layer is larger than the pore size of the second filter layer. The pore size of the second filter layer is greater than the pore size of the first filter layer. In another aspect, a method for filtering a fluid in a formation at the bottom of the bore includes providing an assembly that includes a base tube and a strainer assembly for particle control. The strainer assembly for particle control includes a layer of support, a first filter layer arranged around the support layer, and a second filter layer disposed around the first filter layer. Each of the filter layers has a pore size. The pore size of the second filter layer is greater than the pore size of the first filter layer. At least one first end of the strainer assembly for particle control is circumferentially welded with the base tube. The assembly is disposed in a formation at the bottom of the perforation comprising a fluid comprising heavy oil. The fluid is taken from the formation through the strainer assembly for the control of particles and towards the base tube. The strainer assembly for particle control filters the fluid.

BRIEF DESCRIPTION OF THE DBBUJQS Figure 1 is a fragmentary perspective view of an embodiment of an assembly at the bottom of the perforation; Figure 2A is a fragmentary side view of the assembly at the bottom of the perforation of Figure 1; Figure 2B is a fragmentary side view of another embodiment of an assembly at the bottom of the perforation; Figure 3A is a partial cross-sectional view of the assembly at the bottom of the perforation of Figure 1; Figure 3B is a partial cross-sectional view of another embodiment of an assembly at the bottom of the perforation; Figure 4 is an end view of the assembly at the bottom of the perforation of Figure 1; Figure 5 is a fragmentary perspective view of an embodiment of an assembly at the bottom of the perforation; Figure 6 is a graph showing pressure decrease as a function of time for tests involving various colander assemblies; Figure 7 is a graph showing the amount of particles held as a function of time for tests involving various colander assemblies; Figure 8 is a graph showing the pressure decrease as a function of time for tests involving various colander assemblies; and Figure 9 is a graph showing the amount of particles held as a function of time for tests involving various colander assemblies.

DETAILED DESCRIPTION OF THE iNVENCSON The invention is described with reference to the drawings in which similar elements are referred to by similar numbers. The relationship and operation of the various elements of this invention are better understood by means of the following description. Each aspect thus defined may be combined with another aspect or aspects unless clearly indicated otherwise. The modalities as described below are only presented by way of example, and the invention is not limited to the embodiments illustrated in the drawings. In conventional surface filtration methods, the particles are captured in the filter layer, resulting in an effective classification of microns that is significantly less than the micron classification of the original filtration mesh up to the point where the sieve plug occurs. The present invention utilizes depth filtration to trap particles of different sizes in different locations throughout the thickness of filtration media. The larger particles are trapped in the filter layer that is further out with the inner layers trapping smaller and smaller particles until the desired final classification of microns is reached. The depth filtration prevents the formation of particles decreases the classification of filter micras and increases the retention capacity of filter particles, giving the filter a longer life.

The present invention is particularly useful for filtering heavy oil. As used herein, the term "heavy oil" includes heavy oil, extra heavy oil, oil sands, tar sands and bitumen. Due to its high viscosity, heavy oil does not flow easily in conventional wells. Heavy oil can be extracted using several methods including, but not limited to, steam flooding, steam assisted gravity drainage (SAGD), and cold production. In the steam flooding method, injection wells pump steam into the heavy oil reservoir. The steam pressure pushes the heated heavy oil into adjacent production wells. In SAGD, two horizontal wells are drilled in the oil sands, one at the bottom of the formation and another on the same. Steam is injected into the upper well where the heat melts the bitumen. The bitumen flows into the lower well, where it is pumped to the surface. In cold production, the oil is simply pumped out of the formation, often using specialized pumps called progressive cavity pumps. This only works well in areas where the oil is fluid enough to pump. Each of these methods generally results in production fluids with a higher content of particulate material than conventional oil fields. Referring to FIGS. 1 and 2A, a first embodiment of a strainer assembly for particle control 10 is illustrated as being incorporated in a sand or particle filter system. The assembly of The particle control strainer 10 is mounted on a base tube 20 which may be arranged, for example, in an open well. A strainer assembly for particle control 10 is arranged around the base tube 20, and a wrapper or mantle 30 is arranged around the strainer assembly for particle control 10. The wrapper 30 is generally perforated, slotted, wrapped with thread. A portion of the base tube 10 is perforated with holes 22 to allow oil, natural gas, or heavy oil to flow from the open well. To prevent sand and other particles from being carried to the base tube 20 through said holes 22, the perforated portion of the base tube 20 is covered with the strainer assembly for particle control 10. Although Figure 1 shows the various fragmented layers for visualization purposes, in actual use, the layers generally run substantially the entire length of the base tube 20. The strainer assembly for particle control 10 is usually cylindrical in shape to coincide with the base tube 20. As shown in FIG. shown in Figure 2A, the strainer for particle control includes at least one support layer 12 and at least two filter layers 14, 16 around the support layer 12. To create a depth filtration effect, the The pore size of the outer filter layer 16 is greater than the pore size of the inner filter layer 14. In one embodiment, the strainer for particle control includes three filter layers 14, 16, 18, in which e the pore size of the outer filter layer 18 is larger than the size of pore of the second filter layer 16, and the pore size of the second filter layer 16 is larger than the pore size of the inner filter layer 14. The number of filter layers may vary depending on the desired application. For example, in another embodiment, the strainer for particle control may include a fourth filter layer (not shown) disposed between the support layer 12 and the inner filter layer 14. In other embodiments, the strainer for particle control may Include five, six, or more filter layers. The support layer 12 provides structural support for the strainer assembly 10 and can also act as a drainage layer. The support layer 12 can be woven wire mesh, of welded wire, of wrapping yarn, or any other structure which supports the filtration layers and provides a flow path for the drainage of the forming fluid between the filter media and the base tube. A second embodiment of the particle control colander 15, shown in Figure 2B, includes a second support layer 13 disposed around the inner support layer 12. The second support layer 13 provides additional structural support and drainage capacity. The filter layers 14, 16, 18 can be wire mesh. However, other materials are also possible. The filter layers 14, 16, 18 can be diffusion-bonded, sintered, or non-sintered. A variety of fabric types can be used, including square (including both plain and twill) and Dutch (including plain, twill, inverted or twill) inverted). The filter layers 14, 16, 18 preferably use square mesh to form the depth filtration means. However, the filter layers 14, 16, 18 can also use off-aspect or "off-count" fabrics, which are woven fabrics in plain with the warp and transverse yarns of the same diameter with different yarn counts. . It should be noted that the filter layers 14, 16, 18 can be formed using all types of mesh and mesh counts and yarn diameters. As shown in Figures 3A and 3B, the support layer 12 and filter layers 14, 16, 18 are generally in direct contact with each other. Depending on the application, a cylindrical metal structure 40 can also be used. The metal structure 40 provides a "safe edge" that protects the strainer assembly 10 at its end, and can be welded to other structures (such as the tube base 20) or can be welded as desired without worrying about burning the colander strands of the mesh layers. The filter layers 14, 16, 18 can also overlap part of the material of the metal structure 40 and be welded thereto. A circumferential metal weld 42 connects the strainer assembly 10 and the cylindrical metal structure 40. In one embodiment shown in Figure 3B, a particulate strainer assembly 17 includes a support layer 12 and two filter layers 14 and 16. As shown in Figures 3A, 3B and 4, the support layer 12 and mesh layers 14, 16, 18 are preferably in direct contact with each other without noticeable space between the layers. However, it is possible have spaces between some or all layers. In addition, it is possible to have spacers or other materials, such as additional mesh layers, between the mesh layers. These additional spacers or mesh layers can be especially useful for applications using sintered or diffusion-bonded mesh layers. In addition, the strainer for particle control 10 can also be used in expandable strainer applications. As best seen in Figure 1, the particle control strainer 10 desirably includes a longitudinal weld seam 32 running along the strainer assembly for particle control 10. The weld seam 32 seals an edge 34 of the filter layer with the other edge 36. The welding seam 32 can also connect the support layer 12 and filter layers 14, 16, 18. As described below, the filter layers may also be spirally wrapped around the base tube 20. To provide a sufficient filtration of sand and particulate material, the filter layers 14, 16, 18 have pore sizes to selectively avoid the flow of certain particle sizes through the base tube 20. The first or innermost filter layer 14, preferably has a pore size of between 75 and 300 microns. The second filter layer or intermediate layer 16, preferably has a pore size of between 150 and 400 microns. The third filter layer or external layer 18, preferably has a pore size between 200 and 1200 microns. An additional filter layer (not shown) may be disposed around the support layer 12 as an innermost layer with a pore size between 75 microns and 150 microns.

Different conditions at the bottom of the perforation may involve fluids with different particle size distributions. In this way, the particle size distribution of the fluid can influence the selection of the pore sizes of the mesh layers in the strainer assembly for particle control. In various embodiments, the first filter layer 14 can have a pore size of between 100 and 200 microns or between 200 and 300 microns. The second filter layer 16 can have a pore size between 150 and 300 microns, between 250 and 350 microns, or between 300 and 450 microns. The third filter layer 18 can have a pore size between 500 and 1200 microns, between 200 and 400 microns, between 500 and 600 microns or between 600 and 800 microns. The support or drainage layer 12 (and 13, if present) is usually much thicker than the filter layers. Typical sizes for support layer 12 include 16x16x0.023"(41x41x0.058cm), 20x20x0.016" (51 x51x0.040cm) and 10x10x0.035"(25.4x25.4x0.088cm) .The layer or layers of support 12 and / or 13 can also be a much thicker layer (such as 8x8x0.032"- 20.32x20.32x0.081 cm)), which however, would be difficult to weld integrally with the other meshes in the seam. In the event that a thicker support / drainage layer or layers are required, the support / drainage layers will generally not be attached to the seam weld. The support and / or filter layers may also include wrapping yarn.

At least one end 24 of the strainer assembly for particle control 10 (and / or metal structure 40) is generally circumferentially welded to the base tube 20 by welding 26. A wrap 30 is disposed around the strainer for control of particles and also preferably welded thereto. This arrangement provides a seal between the base tube 20 and the well formation, so that the fluid in the formation can not enter the base tube 20 without being filtered by the strainer assembly for particle control 10. The assembly operation for Particle control 10 is as follows. The strainer assembly for particle control 10 is arranged in a subsurface formation or at the bottom of the perforation. A fluid comprising a hydrocarbon, such as heavy oil or crude oil, flows through the assembly 10 to the surface. The fluid may also include other components such as natural gas, steam and / or water. The fluid flows either when being pumped through it, or due to the pressure that exists in the sounding. During the flow through the assembly 10, the fluid first passes through the outer envelope 30. The outermost filter layer 18 removes relatively large particles of the fluid. The next filter layer 16 removes medium size particles from the fluid. The inner filter layer 14 removes smaller particles from the fluid. The fluid subsequently passes through the holes 22 of the base tube 20 and can subsequently be brought to the surface. This multi-layer filtration provides a more efficient removal of particles than a single-layer filter.

Each filter layer generally has a thickness between 0.012 cm and 0.152 cm. The strainer for particle control 10 usually has a transverse thickness of between about 0.050 cm and about 0.0762 cm, preferably between about 0.127 cm and about 0.381 cm, and particularly between about 0.177 cm and 0.228 cm. In well applications, the strainer assembly for particle control 10 usually has an axial length of between about 0.915 meters and about 12.2 meters. It will be appreciated that the actual size scales may vary depending on the actual requirements of the well. Referring now to a method for forming the strainer assembly for particle control 10, the support layer 12 and filter layers 14, 16, 18 can be diffusion-bonded, sintered, or non-sintered. For non-sintered filter layers, two or more filter layers are stacked, and the mesh sizes depend on the desired filtration qualities. The filter layers are placed one with respect to the other to form a multi-layer non-sintered strainer. The filter layers can be bonded together to hold them in place for subsequent manufacturing steps. During adhesion, the filter layers can be pressed flat through a plate to prevent ripples from forming. Metal strips 40 (shown in Figures 3A and 3B) can be attached to opposite ends of the multi-layer non-sintered strainer. The metal strips 40 are welded to the multi-layer non-sintered strainer.

The strainer is subsequently configured in a generally cylindrical shape. If the longitudinal edges of the layers are not aligned, they can be trimmed so that the longitudinal edges of each layer are generally coterminal. A plasma cutting machine can be used to trim the longitudinal edges. To do this, the generally cylindrical shape is placed on the plasma cutting machine and secured on a mandrel. The mandrel is used to securely hold the generally cylindrical shape and also provides a guide for the plasma cutting machine to cut the longitudinal edges. The mandrel includes a groove milled along its length. The plasma torch travels along the mandrel and trims the longitudinal edges of each layer. The trimming process makes possible the formation of a longitudinal weld of non-synthesized / non-diffused mesh layers. The longitudinal edges of the mesh layers are subsequently joined by welding. A longitudinal seam weld 32 is made along the entire length of the pipe, as shown in Figure 1. In an alternate form of construction, the filter layers are deposited around the base tube 20 or support layer 12 by spiral wrapping, as shown in Figure 5. A long strip is provided. layer mesh that includes several filter layers. The filter layers 14, 16, 18 are wrapped around the base tube 20 or another support layer so that the edges of filter layers overlap in the spiral seam 38. The seam 38 spirals axially along the tube base 20 or other support since the filter layers are wound around the base tube 20 or other support. In another alternate method of construction, the filter layers are formed in a generally cylindrical configuration and the longitudinal edges in the filter layers overlap and are welded. The complete filter assembly is subsequently slipped into an assembly shell towards a base tube. The ends of the strainer are attached to the base tube using standard assembly methods, including, but not limited to, narrowing, stamping or stamping and welding. If the filter layers will be sintered or diffusion bonded, two or more filter layers are stacked, and the mesh sizes depend on the desired filtration qualities. The filter layers are placed one with respect to the other to form a multi-layer strainer. The filter layers are subsequently sintered or joined by diffusion for subsequent manufacturing steps. The support layer or layers may or may not be incorporated in the diffusion-bonded laminate depending on the application requirements. After the addition of the metal structure 40 (if desired) to each end of the laminate sheet, the strainer is subsequently formed in a generally cylindrical configuration. The longitudinal edges of the mesh layers are then joined by welding. A longitudinal seam weld 32 is made along the entire length of the tube. The welding in each phase of the assembly can be done through any known method, which includes arc welding of gas tungsten (GTAW), tungsten welding with inert gas (TIG), plasma welding, metal with inert gas (MIG), and laser welding. The material of each weld is conventional and is selected to be compatible with the metal of the support tube (which in one embodiment is stainless steel) and the mesh layers (which in one embodiment are stainless steel). The strainer assembly for particle control can be made from 315 L, Carpenter 20Cb3, Inconel 825, and other types of stainless steel filter media to withstand production environments. The particle strainer assembly 10 can be disposed on a base tube 20 with any number of wrapping configurations, making circumferential welds at each end of the particle strainer assembly 10 to form a complete well strainer. The particle strainer assembly 10 can be assembled along the extension of the base tube 10 in sections of a determined length, for example, in sections of 1.22 meters, 2745 meters, or 12.81 meters, through which each section it is subsequently secured to the base tube 10, as for example by welding them thereto. Typical lengths for a base tube are 6.10, 9.15 or 12.2 meters, although shorter or longer lengths are certainly possible. In one embodiment, the strainer assemblies for multi-particle control 10 are connected together with an assembly tube for particle control. Because the strainer assembly for particle control 10 uses depth filtration, it has a longer service life Prolonged that control strainers that use surface filtration. It also has an improved flow rate, a reduced risk of wear in the strainer, and reduces the frequency and cost of backwash of the well when the speed of production decreases.

EXAMPLES The following examples of the invention and comparative examples are provided by way of explanation and illustration. The strainer assemblies for particle control are prepared using one of the techniques described above.

EXAMPLE 1 A colander assembly with a desired classification of microns for 125 micron filtration is prepared. The strainer assembly includes two support layers and four filter layers, as shown in Table 1 below.

TABLE 1 EXAMPLE 2 A colander assembly is prepared with a desired classification of microns for 180 micron filtration. The strainer assembly includes two support layers and three filter layers, as shown in Table 2 below.

TABLE 2 EXAMPLE 3 A strainer assembly with a desired classification of microns for 250 micron filtration is prepared. The strainer assembly includes a support layer and three filter layers, as shown in Table 3 below.

TABLE 3 EXAMPLE 4 A colander assembly is prepared with a desired classification of microns for 425 micron filtration. The strainer assembly includes a support layer and two filter layers, as shown in Table 4 below.

TABLE 4 EXAMPLE 5 A colander assembly with a desired classification of microns for 125 micron filtration is prepared. The strainer assembly includes two support layers and five filter layers, as shown in Table 5 below.

TABLE 5 EXAMPLE 8 A colander assembly is prepared with a desired classification of microns for filtration of 150 microns. The strainer assembly includes one wrapping yarn and four other filter layers, as shown in Table 6 below.

TABLE 6 EXAMPLE 7 A colander assembly is prepared with a desired classification of microns for filtration of 150 microns. The strainer assembly includes one wrapping yarn and four other filter layers, as shown in Table 7 below.

TABLE 7 EXAMPLE 8 A colander assembly is prepared with a desired classification of microns for 140 micron filtration. The strainer assembly includes two support layers and five filter layers, as shown in Table 8 below. The filter layers are square woven.

TABLE 8 EXAMPLE 9 A colander assembly with a desired classification of microns for 125 micron filtration is prepared. The strainer assembly includes two support layers and six filter layers, as shown in Table 9 below. The interior filter layer is plain Dutch fabric.

TABLE 9 EXAMPLE 10 A colander assembly is prepared with a desired classification of microns for filtration of 150 microns. The strainer assembly includes a support layer and five filter layers, as shown continued in table 10. The inner filtration layer is plain Dutch twill weave.

TABLE 10 EXAMPLE 11 A colander assembly is prepared with a desired classification of microns for 180 micron filtration. The strainer assembly includes two support layers and four filter layers, as shown in Table 11 below. The inner filtration layer is a square fabric in twill.

TABLE 11 EXAMPLE 12 A colander assembly is prepared with a desired classification of microns for 180 micron filtration. The strainer assembly includes two support layers and three filter layers, as shown in Table 12 below. The inner filtration layer is a smooth square fabric.

TABLE 12 EXAMPL013 A colander assembly is prepared with a desired classification of microns for 140 micron filtration. The strainer assembly includes two support layers and four filter layers, as shown in Table 13 below. The inner filtration layer is a smooth square fabric.

TABLE 13 EXAMPLE 1- A colander assembly is prepared with a desired classification of microns for 140 micron filtration. The strainer assembly includes two support layers and five filter layers, as shown in Table 14 below. The interior filtration layer is a smooth square fabric.

TABLE 14 EXAMPLE 15 A colander assembly is prepared with a desired classification of microns for 140 micron filtration. The strainer assembly includes two support layers and six filter layers as shown in Table 15 below. The inner filtration layer is a smooth square fabric.

TABLE 15 COMPARATIVE EXAMPLE A By way of comparison, a Poromax® product, a prior art colander assembly, has a desired classification of microns for 125 micron filtration. The strainer assembly includes two support layers and a filter layer, as shown in Table 16 below.

TABLE 18 COMPARATIVE EXAMPLE B A colander assembly is prepared with a desired classification of microns for filtration of 150 microns. The strainer assembly includes a commercially available wrap yarn strainer. The wrap yarn strainer consisted of 0.090 wedge yarn with 0.015 cm spaces between yarns, and support yarns with 0.317 cm diameter in a separation of 1587 cm.

COMPARATIVE EXAMPLE C A colander assembly is prepared with a classification of microns for filtration, which requires 150 microns. The strainer assembly includes two support layers and a filter layer, as shown in Table 17 below.

TABLE 17 The tests were performed to evaluate the relative effectiveness of various strainer configurations. Discs were prepared using the designs of Examples 9-15 and Comparative Examples A-C. The discs had diameters of 4,787 cm and were sealed in an apparatus to provide a flow diameter of 3,937 cm. The tests were carried out using two types of test fluid with viscosities and particulate matter modeled under typical conditions of the bottom of the borehole. The first fluid was modeled on a fluid typical of South America and the second fluid on a typical Asian fluid. The supply tank was filled with the desired test fluid. The test fluid was pumped through an absolute cleaning filter of 2 μ? T? for 2 hours. Added particulate material for obtain a concentration of 0.10 grams / L. A sample of the test fluid was analyzed to confirm the level of particulate material in the fluid. A disc incorporating a strainer configuration was placed in a housing. The test fluid was circulated through the disk at a flow rate of 200 ml / min. The pressure decrease across the disc was measured during the course of the test. Fluid samples were collected downstream from the disk to determine the amount of particles retained by the disk. The results of the South American fluid are shown in Figures 6 and 7. Figure 6 shows the decrease in pressure as a function of time for samples prepared from the strainer configurations of Examples 9 and 10 and comparative examples AC . The moment when the pressure drop rises rapidly coincides with the filter clogging, and in this way provides a useful estimate of filter life. It can be seen that the colander configurations of Examples 9 and 10 provide a much longer service life, and therefore a superior performance, than the colander configurations of the comparative examples. Figure 7 is a graph showing the amount of particles retained as a time function for samples prepared from the strainer configurations of examples 9 and 10 and comparative examples A-C. It can be seen that the inventive strainers removed acceptable quantities of particles, and withdrew a larger amount of particles during the life of the filter that the colanders of the comparative examples. Figure 8 shows the decrease in pressure as a function of time for samples prepared from the strainer configurations of examples 8, 9 and 11 -15 comparative examples A and B. It can be seen that the strainer configurations of the examples 8, 9 and 11 -15 provide a longer service life (up to an order of magnitude greater) than the colander configurations of the comparative examples. Fig. 9 is a graph showing the amount of particles retained as a function of time for samples prepared from the strainer configurations of examples 8, 9 and 11-15 and comparative examples A and B. It can be seen that the inventive strainers removed acceptable quantities of particles, and removed a larger quantity of particles during the life of the filter than the strainers of the comparative examples. In this way, it can be seen that the particle control strainers of the present invention reduce the seal in the filter assemblies and increase the particle retention capacity of the filters, thereby giving a longer life to the filters. Although the present invention has been described with reference to referred modalities, those skilled in the art will recognize that changes can be made and formed in detail without departing from the spirit and scope of the invention. Therefore, it is intended that the above detailed description be considered as illustrative rather than limiting, and that it be understood that they are the following claims, including all equivalents, which are intended to define the scope of this invention.

Claims (23)

1. NOVELTY OF THE INVENTION CLAIMS 1. - A strainer for particle control, comprising: a support layer; a first filter layer disposed around the support layer; a second filter layer disposed around the first filter layer; and a third filter layer disposed around the second filter layer, wherein each of the filter layers has a pore size, and the pore size of the third filter layer is greater than the pore size of the filter layer. second filter layer, and the pore size of the second filter layer is larger than the pore size of the first filter layer. 2. - The colander for particle control according to claim 1, further characterized in that the support layer comprises a first support layer, further comprising a second support layer disposed around the first support layer. 3. The strainer for particle control according to claim 1, further characterized in that it additionally comprises a fourth filter layer disposed between the support layer and the first filter layer. 4. - The strainer for particle control according to claim 1, further characterized in that at least one of the filter layers is wire mesh. 5. - The strainer for particles conrol according to claim 1, further characterized in that it additionally comprises a weld seam running along the strainer assembly for particle control and connecting each of the filter layers. 6. The strainer for particle control according to claim 1, further characterized in that the first filter layer has a pore size of between 75 and 300 microns, the second filter layer has a pore size of between 150 and 300 microns. 400 microns, and the third filter layer has a pore size of between 500 and 1200 microns. 7. The strainer for particle control according to claim 1, further characterized in that the first filter layer has a pore size of between 75 and 300 microns, the second filter layer has a pore size of between 150 and 300 microns. 400 microns and the third filter layer has a pore size between 200 and 500 microns. 8. The strainer for particle control according to claim 1, further characterized in that the first filter layer has a pore size of between 200 and 300 microns, the second filter layer has a pore size of between 300 and 300 microns. 450 microns, and the third filter layer has a pore size between 600 and 800 microns. 9. The strainer for particle control according to claim 1, further characterized in that the first filter layer has a pore size of between 100 and 200 microns, the second filter layer has a pore size of between 250 and 350 microns, and the third filter layer has a pore size of between 500 and 600 microns. 10. - The strainer for particle control according to claim 3, further characterized in that the fourth filter layer has a pore size between 75 microns and 150 microns. 11. - An assembly at the bottom of the perforation, comprising: a perforated base tube; and a strainer assembly for particle control arranged around the base tube, comprising: a support layer; a first filter layer arranged around the support layer and having a pore size of between 75 and 300 microns; a second filter layer disposed around the first filter layer and having a pore size of between 150 and 400 microns; and a third filter layer disposed around the second filter layer and having a pore size of between 200 and 1200 microns; wherein at least a first end of the strainer assembly for particle control is circumferentially welded to the base tube. The assembly at the bottom of the perforation according to claim 11, further characterized in that the support layer comprises a first support layer, further comprising a second support layer disposed around the first support layer. 13. The assembly at the bottom of the perforation according to claim 1 1, further characterized in that it additionally comprises a fourth filter layer disposed between the support layer and the first filter layer. 14. - The assembly at the bottom of the perforation according to claim 11, further characterized in that at least one of the filter layers is wire mesh. 15. The assembly at the bottom of the perforation according to claim 11, further characterized in that it additionally comprises a welding seam running along the strainer assembly for particle control and connecting each of the filter layers . 16. The assembly at the bottom of the perforation according to claim 11, further characterized in that the filter layers are wrapped in a spiral around the base tube. 17. - The assembly at the bottom of the perforation according to claim 1, further characterized in that the first filter layer has a pore size of between 200 and 300 microns, the second filter layer has a pore size of between 300 and 400 microns, and the third filter layer has a pore size of between 600 and 800 microns. 18. - The assembly at the bottom of the perforation according to claim 11, further characterized in that the first filter layer has a pore size of between 100 and 200 microns, the second filter layer has a pore size of between 250 and 350 microns and the third filter layer has a pore size between 500 and 600 microns. 19. - A method for filtering a fluid in a formation at the bottom of the perforation, comprising: providing an assembly comprising: a base tube; and a strainer assembly for particle control, comprising: a support layer; a first filter layer disposed around the support layer and a second filter layer disposed around the first filter layer, wherein each of the filter layers has a pore size, and wherein the pore size of the filter the second filter layer is larger than the pore size of the first filter layer, and wherein at least a first end of the strainer assembly for particle control is circumferentially welded to the base tube; arranging the assembly in a formation at the bottom of the perforation comprising a fluid comprising heavy oil; bring the fluid from the formation through the strainer assembly for particle control and to the base tube, where the strainer assembly for particle control filters the fluid. 20. - The method according to claim 19, further characterized in that the support layer comprises a first support layer further comprising a second support layer disposed around the first support layer. 21. - The method according to claim 19, further characterized in that it additionally comprises a third filter layer disposed around the second filter layer, wherein the pore size of the third filter layer is greater than the pore size Second filter layer. 22. - The method according to claim 19, further characterized in that it additionally comprises a seam of Welding that runs along the strainer assembly for particle control and connects the filter layers. 23. The method according to claim 21, further characterized in that the first filter layer has a pore size of between 100 and 300 microns, the second filter layer has a pore size of between 200 and 400 microns, and The third filter layer has a pore size between 500 and 800 microns.