FIELD OF THE INVENTION

The present invention relates to the field of petroleum exploitation, and more particularly to an expandable sand screen.

BACKGROUND OF THE INVENTION

Currently, sand screens used in the field of petroleum exploitation are all

conventional sand screens. Such conventional sand screens have a small drainage area, large oil flow resistance, and low structural rigidity, and are subject to collapse and damage. In addition, the quality of well cementing cannot be ensured. Because there is an excessively large space between the surface of the sand screen and the inner wall of the casing, gravel packing is required, which is a high-cost process for which quality cannot be guaranteed. The expandable sand screen technology is a new merging sand control technology, in which a sand control screen expands its diameter during downhole construction. This technology was first applied to the Oman Thayfut5 well. After it is put into production, the sand control effect was proved. Although this technology has been spread to all over the world, for example, has been applied to oil fields in the North Sea, Southeast Asia, and China's Bohai Sea, the filtering gap cannot be controlled during expansion of the sand screen. Generally, the gap will be expanded several times, which may make it impossible to achieve the expected sand control effect.

SUMMARY OF THE INVENTION

The present invention provides an expandable sand screen that can control the gap and achieve a satisfactory sand removal effect.

The present invention uses the following technical solution: An expandable sand screen includes an inner pipe, an intermediate pipe fixedly sleeved on the inner pipe, and an outer pipe fixedly sleeved on the intermediate pipe, where a plurality of slots is distributed on a wall of the inner pipe, the intermediate pipe is formed by a wire-like object that is wound spirally, and a plurality of holes is distributed on a wall of the outer pipe.

l Preferably, the slots on the inner pipe have a length of 20 to 100 mm and a width of 1 to 10 mm, and are evenly distributed on the wall.

Preferably, the intermediate pipe is formed by a stainless steel wire that is wound continuously and spirally.

Preferably, the holes on the wall of the outer pipe are round holes having a diameter of 5 to 20 mm, elongated holes having a length of 5 to 30 mm and a width of 1 to 10 mm, or elliptical holes, and are evenly distributed on the wall.

Preferably, a distance between two ends of the inner pipe is longer than the

intermediate pipe (2) and the outer pipe (3), one end being provided with an external thread and the other end being provided with an internal thread.

Preferably, two ends of the slot are rounded to provide a smooth transition.

The present invention has the following advantages and benefits:

1 . The size of sand particles to be filtered can be precisely controlled.

2. The expanded diameter increases the drainage area and reduces the oil flow resistance, increasing the daily crude oil production per well by 30-50%.

3. Because the pressure is directly applied on the pipe wall during expansion, the maximum sealing pressure of the casing is sealed to withstand a pressure of 50 MPa, so as to ensure the quality of well cementing. For use in open-hole sections, an anchor may be provided to fix the hanger at the bottom. A liquid adhesive is provided for the expandable hanger at the top so as to ensure the reliability of circumferential sealing.

4. The outer surface of the expandable sand screen of this solution is close to the inner wall of the casing, so that gravel packing is unnecessary, thereby greatly lowering the project cost.

5. The expansion resistance is balanced between the porous section and the connection section of the sand screen, and the circumferentially continuous layer of the sand screen forms a statically determinate arch structure, which has a high overall structural rigidity and is stable and durable and not subject to deformation and damage. 6. After downhole expansion, the gap in the stainless steel wire that forms the intermediate pipe can be controlled.

BRIEF DESCRIPTION OF THE DRAWINGS

To clearly describe the technical solution of the embodiments of the present invention or the prior art, the accompanying drawings required for describing the embodiments or the prior art are briefly described below. Apparently, the accompanying drawings in the following description are merely embodiments of the present invention.

Persons of ordinary skill in the art can further obtain other drawings according to these accompanying drawings without creative efforts.

FIG. 1 is a schematic structural view of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The technical solution in the embodiments of the present invention is hereinafter described clearly and completely with reference to the accompanying drawings. Apparently, the described embodiments are merely a part rather than all of the embodiments of the present invention. All the other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

Many details are provided in the following description to make the present invention more comprehensible. However, the present invention may also be implemented in other manners that are different from that described herein, and persons skilled in the art can make similar variations without departing from the spirit of the present invention. Therefore, the present invention is not limited to specific embodiments disclosed below.

Moreover, the present invention is described in detail with reference to the schematic view. In the detailed description of the present invention, the cross-sectional view illustrating the structure of device components is not drawn to scale but is partially enlarged, and the schematic view is merely exemplary and is not intended to limit the protection scope of the present invention. Furthermore, three-dimensional dimensions including length, width and height should be presented in practice.

As shown in FIG. 1 , the present invention includes an inner pipe 1 , an intermediate pipe 2 fixedly sleeved on the inner pipe 1 , and an outer pipe 3 fixedly sleeved on the intermediate pipe 2, where a plurality of slots is distributed on a wall of the inner pipe 1 , the intermediate pipe 2 is formed by a wire-like object that is wound spirally, and a plurality of holes is distributed on a wall of the outer pipe 3.

The slots on the inner pipe 1 have a length of 60 mm and a width of 5 mm, and are evenly distributed on the wall. Two ends of the slot are rounded to provide a smooth transition.

The intermediate pipe 2 is formed by a stainless steel wire that is wound continuously and spirally.

The holes on the wall of the outer pipe 3 are round holes having a diameter of 10 mm, elongated holes having a length of 20 mm and a width of 5 mm, or elliptical holes, and are evenly distributed on the wall.

A distance between two ends of the inner pipe 1 is longer than the intermediate pipe 2 and the outer pipe 3, one end being provided with an external thread and the other end being provided with an internal thread, so that a plurality of inner pipes 1 can be connected to each other.

In use, the construction process is simple and convenient. The present invention is placed in a preset casing, and the casing is placed in a drilling well. An expansion head and an anchoring apparatus are sequentially disposed at the bottom of the present invention. When the casing encloses the perforated interval, a drill pipe is used downhole to provide a water pressure, so as to pressurize a launching chamber above the anchoring apparatus at the bottom, so that the expansion head in the middle is pushed to move upwards and enters the inner pipe 1 to expand the diameter of the inner pipe 1 . Then, the expansion head is directly pulled up by using a mechanical force, so that the sand screen at the top continues expanding. After the whole sand screen expands, the expansion head is removed. Thus, the

expansion ends.

This solution is not only applicable to drilling of petroleum wells, but also is applicable to drilling of other wells and geothermal wells as required.

One embodiment of the present invention has been described in detail above, but the described content is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the present invention. Any equivalent variations and improvements made without departing from the claimed scope of the present invention shall fall within the protection scope of the present invention.