RU2199651C2 - Method protecting operating string of injection well against attack of pumped chemically corrosive water - Google Patents

Abstract

FIELD: oil and gas industry. SUBSTANCE: method protecting operating string of injection well against attack of pumped chemically corrosive water includes setting of tubing string in well at needed depth, filling of tubular annulus with sealing compound. Glass reinforced plastic pipes are employed in the capacity of tubing string. Walls of operating well are examined for chemical and physical wear prior to sinking of tubing string. Cement mortar is used as substance with sealing property. Tubular annulus is filled with corrosion inhibitor before injection of cement mortar. If wear of operating string exceeds permissible level string of glass reinforced plastic pipes of maximum possible diameter is sunk and cemented to wellhead. EFFECT: protection of operating string against corrosion, diminished technical effect on environment. 1 cl, 2 dwg

Description

 The invention relates to the oil and gas industry and will find application in protecting production casing in injection wells from the action of injected chemically aggressive water.

 A known method of sealing the annular space of the well with the sealing elements of the packer [1], comprising a housing mounted between the housing nodes of the pipe with a seal located on it in the form of an elastic shell and expanding the cone associated with the drive.

 The disadvantage of this method is that for its implementation requires a complex and metal-intensive design or additional tripping operations.

 The closest in technical essence and the achieved result to the proposed invention is a method of protecting the production casing of the injection well from the action of chemically aggressive water being injected, which includes lowering the tubing string into the well - tubing to the required depth, filling the annulus with a substance with a sealing property [2] .

 The aim of the invention is to protect the production casing from corrosion, reducing the industrial load on the environment.

 The technical problem to be solved consists in the fact that in the method of protecting the production casing of the injection well from the action of chemically aggressive water being pumped, including the descent of the tubing string into the borehole to the required depth, filling the annulus with a substance with a sealing property, use fiberglass pipes, before lowering the tubing string, the walls of the production string are examined for chemical and physical deterioration, and as a substance with a sealing property using cement slurry, wherein before injection tube space is filled with a liquid corrosion inhibitor, and in case of deterioration of the production tubing string above the permissible GRP pipe is lowered from the maximum possible diameter, and its cemented to the wellhead.

 In the proposed method, a device made of easily drilled materials is lowered onto a fiberglass tubing, preventing cement from falling into the interval of the well or liquid filter with a corrosion inhibitor in the formation.

 Preliminary studies on patent and scientific literature on the fund of the TatNIPIneft Institute showed that the above set of essential features of the proposal is new and has not been previously used in practice, which allows us to conclude that the technical solution meets the criterion of "novelty", and its We consider industrial applicability to be appropriate, which follows from its full description.

 The above drawings explain the essence of the invention, in which Fig. 1 shows a tubing string lowered into a well from fiberglass pipes with the device in its initial position to prevent cement from falling into the interval of the filter, or mixing and leaving the reservoir in the annulus with corrosion inhibitor, in partial longitudinal section. In Fig.2 - the same as in Fig.1, when the annular space in the well is filled in the sealing interval with a hardening sealing material - cement mortar, before cutting the pins by the force of the squeeze plug, in partial longitudinal section.

 A device for implementing the method includes a tubular body 1 with cementing holes 2, overlapped by the tail portion 3 of the seat 4 of the valve 5, placed in the cavity of the body. Cementing holes 2 on the outside are blocked by a self-sealing cuff 6, made in the form of a V-shaped cross-section and placed in the casing 7. The latter, with the help of shear pins 8, passed through the slots 9 of the housing 1, is connected to the valve seat 4. All elements of the device are made of easily drilled materials, for example, of duralumin or fiberglass, except for the sealing sleeve.

 The method is carried out in the following sequence.

 Before starting work, the walls of the production casing are examined for chemical and physical deterioration, because from prolonged use (20-30 years) it is subjected to strong corrosion and physical impact during repeated tripping and lifting operations. As a result, the pipe string loses its tightness and becomes unsuitable for further operation.

 As a means for mechanical cleaning can be used descent on conventional tubing under the name "Device for cleaning the inner surface of the casing" [3]. It is simple in design and has increased efficiency (Development of the TatNIPIneft Institute). It contains a housing, inside of which pistons are installed, equipped with cutting elements - scrapers, with the possibility of radial movement.

 After finishing work on cleaning the casing wall of the production casing and lifting conventional tubing, a device to prevent cement from entering the interval of the filter is connected to the bottom of the tubing from fiberglass pipes and lowered into the well to the required depth, as shown in Fig. 1. Other devices known in the arsenal of technology can also be used as such a device. Further, a liquid with a corrosion inhibitor is pumped through a fiberglass tubing string to fill the annulus of the well. It, exerting pressure on the movable valve, moves it down until the pins 8 abut against the bottom of the slots 9, while opening the cementing holes 2 (see Fig. 2) and simultaneously releasing the self-sealing sleeve 6 from the casing 7 and, therefore, overlapping ( isolation) of the annulus. In this case, the liquid through the open cementing holes 2, bending the petals of the self-sealing cuff 6, enters the annulus. After the calculated volume is injected, a substance with sealing and fastening properties, for example, cement mortar, is pumped after this liquid. At the end of the injection of the required volume, it is pressed through with a cork plug made of rubber material or plastic, which sits on the seat 4 of the valve 5, which is recorded by a pressure gauge at the wellhead with an increase in pressure. When the pressure reaches the calculated value, the pins 8 are cut off, and the valve assembly together with the squeeze plug fall into the bottom, thereby freeing the cavity of the housing 1 for pumping the working agent into the reservoir 10, while at the same time the cementing holes 2 are blocked by the petal of the sealing collar 6. Then the well leave to wait for the hardening of cement OZZ, after which the injection of fluid into the reservoir resume.

 If it is necessary to remove the pipe string from the well, it is disconnected from the cemented part using a downhole pipe cutter or by rotating the column from a left-hand thread sub with which the cementless last pipe is supplied, and the remaining cemented part is drilled, since all the main parts of the device are made of easily drilled material.

 If the wear of the production string is higher than the permissible, then the string of fiberglass pipes of the maximum possible diameter is lowered to the required depth and cemented to the wellhead. In this case, the string of fiberglass pipes is lowered to the required depth by attaching the above-described device to the lower part, which prevents the mixing of chemically aggressive fluids injected into the formation with a corrosion inhibitor in the annulus or its penetration into the formation during prolonged shutdowns of the well, in which it is possible to reduce the formation pressure. Then a fluid with a corrosion inhibitor is pumped into the well, which also fills the annulus through the cementing holes. At the same time, after the calculated volume has been pumped, similarly to the above-described technologies, the valve seat pins are cut off with the help of a squeeze plug, which are then fed to the bottom, freeing the passage section of the device body. Next, the well is put into operation under injection of fluid into the reservoir.

 In wells with low permeability formations, the device used is additionally equipped with an anchoring element in order to protect the self-sealing cuff from abrasion during oscillatory movements of the pipe string during the operation of the well.

Sources of information
1. A.S. 1726730, E 21 V 33/12, publ. in B.I. 14, 1992

 2. MIRONOV E.A. Commercial wastewater injection into productive and absorbing horizons, Moscow, Nedra, 1971, pp. 164-165 - prototype.

 3. Patent R.F. 2042792, Е 21 В 37/02, B.I. 24, 1995

Claims (2)

 1. The method of protecting the production casing of the injection well from the action of injected chemically aggressive waters, including the descent of the tubing string into the borehole to the required depth, filling the annulus with a substance with a sealing property, characterized in that fiberglass pipes are used as the tubing, before lowering the tubing string, the walls of the production string are examined for chemical and physical deterioration, and cement is used as a substance with a sealing property creature, and before it is injected, the annulus is filled with a liquid with a corrosion inhibitor.  2. The method according to claim 1, characterized in that in case of wear of the production string above the permissible string of fiberglass pipes lower the maximum possible diameter and cement it to the wellhead.

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