RU2499130C1 - Well strainer - Google Patents

Abstract

FIELD: oil-and-gas industry.

SUBSTANCE: device comprises filtration sections, each comprising filtration jacket provided with lengthwise rods with end rings rigidly secured at base element composed of perforated tube. Filtration jacket is composed of lengthwise round rods and ring-like stiffness ribs. Said lengthwise rods are rigidly and coaxially secured at edges of stiffness ribs and end rings. Stiffness ribs are arranged between end rings with allowance for filtration section length. Note here every filtration section is mounted at separate base element. Metal gauzes are rigidly fitted in tube every hole with mesh size increasing from tube outside to its inside. Minimum mesh size is larger than clearance between lengthwise rods.

EFFECT: simplified assembly, higher reliability.

3 dwg

Description

The invention relates to the oil and gas industry and is intended for filtering fluid in an injection well.

A well-known well filter (patent RU No. 2074313, IPC 8 E21B 43/08) containing a base element in the form of a pipe with holes and filter sections concentrically mounted on it, each of which includes longitudinal spacers and a filter jacket made of spirally wound thereon wire and welded at the contact points and end rings parallel to each other and connected by welding with cushioning links, moreover, for curved wells, the filter jacket is two-level.

The disadvantages of this downhole filter are:

firstly, the possibility of damage during the descent and the difficulty of welding the turns of wire to the spacer links and to control its quality, since the place of welding is under the turns of the wire with a very small gap (0.1-0.3 mm);

secondly, high cost, and for curved wells, the cost of manufacturing a two-level filter increases.

The closest in technical essence is the downhole filter and method of its manufacture (patent RU No. 2147676, IPC 8 E21B 43/08, published in Bulletin No. 11 of 04/20/2000), containing filter sections, each of which includes a filter jacket provided with end rings at the ends, while the filtering jacket is made of transverse fastening strips and longitudinal rods rigidly connected to the end rings.

The disadvantages of this downhole filter are:

- firstly, the complexity of the assembly associated with the bending of the fastening strips into rings with strips inward using a special machine and their fastening;

- secondly, during bending, the fixing strips are deformed, and their inner cavity contracts, while the outer one is stretched, and therefore cracks are formed between the longitudinal rods, the width of which may differ from each other around the perimeter of the filtering jacket. In addition, without seats for attaching longitudinal rods, it is practically impossible to achieve a small slit width (0.5-0.7 mm) between the longitudinal rods along their length due to misalignment between them. In this connection, the width of the slots between the longitudinal rods will not be constant already during the assembly process, which reduces the efficiency (filtration quality) of the downhole filter during subsequent operation;

thirdly, longitudinal rods of elliptical section trap sand and mechanical impurities in the annular gap between the longitudinal rods and the base elements, which causes a quick clogging of the well filter, and this also reduces its efficiency.

An object of the invention is to simplify the assembly of the downhole filter, as well as increasing the efficiency of its operation during its subsequent operation in the well.

The stated technical problem is solved by a downhole filter containing filter sections, each of which includes a filter jacket equipped with longitudinal rods with end rings at the ends, rigidly fixed to the base element, made in the form of a pipe with holes.

What is new is that the filtering jacket is made of longitudinal rods of circular cross section and stiffeners in the form of rings, while the longitudinal rods are rigidly and coaxially with a gap between themselves fixed on the periphery of the stiffeners and end rings, while the stiffeners are installed between the end rings based on the length each filter section, and each filter section is mounted on a separate base element, and metal grids are rigidly installed in each hole in the pipe, the mesh sizes of which increase externally in the inside of the pipe, and the minimum mesh size is larger than the gap between the longitudinal rods.

Figure 1 schematically shows a plot of the proposed downhole filter for an injection well.

Figure 2 shows a section of a downhole filter along section A-A.

Figure 3 shows a top view - B of the hole with the grid.

Figure 4 shows an enlarged view - C hole of the pipe with nets placed in it.

The downhole filter consists of a base element 1 (see figure 1), made in the form of a pipe with holes 2 and a filter section 3 mounted on it.

Each filter section 3 contains a filter jacket 4 with end rings 5.

The filtering jacket 4 includes stiffening ribs 6 (see figure 2), made in the form of rings and longitudinal rods 7 of circular cross section.

The longitudinal rods 7 are rigidly and coaxially with the required clearance-S fixed (for example, by welding) on the periphery of the stiffeners 6 and end rings 5.

Stiffeners 6 are installed between the end rings 5, and their number is determined empirically, based on the length of each filter section 3, and each filter section 3 is mounted on a separate base element 1.

In each hole 2 in the pipe (base element 1), for example, metal grids 8, 8 ', 8'', ... 8 ⁿ (see FIG. 4) are soldered rigidly installed (see FIG. 4) whose cell sizes decrease from inside 9 to outside 10 (see 1) pipes (base element 1), i.e. the cell sizes S ₈ > S ₈ '> S ₈ "> S ₈ '" of the corresponding metal grids 8, 8 ', 8'', ... 8 ⁿ (see Fig. 4) decrease when the fluid flows from inside 9 to outside 10 of the pipe (base item 1).

The mesh sizes of the metal grids 8, 8 ', 8'', ... 8 ⁿ (see Figs. 3 and 4) in the hole 2, as well as the width of the slots between the longitudinal rods 7 (see Figs. 1 and 2) of circular cross section are selected based on granulometric analysis of the filtrate based on the expected operating conditions of the well filter, for example in an injection well, by selecting the filtrate and determining the fractional composition of the particles in the injected fluid.

For example, based on particle size analysis, it was found that the fractional composition of particles (filtrate) has sizes from 0.5 to 2.0 mm, therefore, four metal grids 8, 8 are installed in each hole 2 (see figures 1 and 3, 4) ', 8' 'and 8' '' with a mesh size of 2.0 × 2.0; 1.7 x 1.7; 1.3 x 1.3; 1.0 × 1.0, respectively, and the width of the slots between the longitudinal rods 7, that is, the gap S (see figure 2) take 0.7 mm

The number of metal grids 8, 8 ', 8'', ... 8 ⁿ (see Fig. 4) installed in openings 2 is determined empirically based on the preferred size of the filtrate in the injected liquid.

Well filter works as follows.

For example, a pipe string (not shown in FIGS. 1 and 2) descends into an injection well having a curved shaft, incorporating the proposed well filter, consisting of separate filter sections 3 (see FIG. 1), interconnected by basic elements 1, made in the form of pipes with holes 2.

After installing the filter in the well, a pipe string (not shown in FIGS. 1, 2, 3, 4) is pumped into the well by means of a pump (of any known design) (for example, waste water)

The liquid from the inside 9 (see Figs. 1, 2, 3, 4) of the pipe (base element 1) through metal grids 8, 8 ', 8'', ... 8 ⁿ , installed in the hole of the hole 2, flows out 10 of the pipe (base element 1), while filtering the largest particles of the filtrate with a size of 1.0 to 2.0 mm, settling on the grids 8, 8 ', 8''and8'''.

Further, a fluid having a filtrate filtered on metal grids 8, 8 ', 8' 'and 8' '' with a particle size of less than 1.0 mm passes through slots with a gap - S between the longitudinal rods 7 of circular cross section is cleaned of the filtrate (sand, mechanical impurities suspended in liquid particles, etc.), the size of which is from 0.7 to 1.0 mm. Then the filtered injected fluid enters the reservoir (not shown in Figs. 1, 2, 3, 4)

During operation of the downhole filter, the annular gap - b between the filter jacket 4 and the base element 1 (see figures 1, 2 and 3, 4) will not become clogged with sand and mechanical impurities due to:

- firstly, cleaning the bulk of the filter on 8, 8 ', 8' 'and 8' '' metal grids (large and medium filtrate fractions, in this example from 1.0 mm to 2.0 mm).

- secondly, the circular cross section of the longitudinal rods 7 of the filter jacket 4. If necessary, the design of the proposed downhole filter allows you to rinse it without removing from the well.

The proposed downhole filter is easily assembled without deformation of structural elements and without the use of a special bending machine, in addition, it is quite effective during operation, since the presence of several metal grids with different mesh sizes, decreasing from the inside out, allows filtering a significant part of the filtrate (large and medium), and longitudinal rods filter out the finer filtrate, and their execution in the form of a circular cross section virtually eliminates clogging of the downhole filter during bots.

Claims (1)

A downhole filter containing filter sections, each of which includes a filter jacket, equipped with longitudinal rods with end rings at the ends, rigidly fixed to the base element, made in the form of a pipe with holes, characterized in that the filter jacket is made of longitudinal rods of circular cross section and ribs stiffness in the form of rings, while the longitudinal rods are rigidly and coaxially with a gap between each other fixed on the periphery of the stiffeners and end rings, while the stiffeners are installed between the ends Vym rings, from the length of each filter section, each filter section is mounted on a separate base member, and each aperture in the tube rigidly mounted metal grid, mesh sizes which increase from outside to inside the tube, the minimum mesh size larger gap between the longitudinal rods.

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