RU2219329C1 - Method fixing oil and gas wells - Google Patents

Abstract

FIELD: oil and gas production, stabilization of wells with corrosive and active stratal water, gas and gas-water-oil fluid. SUBSTANCE: according to invention casing string is cemented in well. At least one length of casing string located in zone of possible exposure to corrosive media is implemented in the form of one or several corrosion-resistant casings. After injection of calculated volume of cement mortar intervals of possible action of corrosive media and productive pools are limited with the help of separators with formation of reinforced cement stone in zone of location of the latter. Tubes made of steel brand 09 ГСΦ or of stainless steel are used in the capacity of corrosion-resistive tubes. Outer surfaces of tubes bordering on corrosion- resistive tubes are treated with anticorrosive coat before sinking of casing string. EFFECT: increased reliability of well fixing with provision for long service life of casings located in interval of action of corrosive media, protection of adjacent casings bordering on these casings against corrosive action of corrosive media, increased time between well overhauls and reduced scope of repair and insulation operations. 1 cl, 3 dwg

Description

The invention relates to the oil and gas industry and may find application in the fastening of wells with aggressive and active formation waters, gases, and also oil-water fluid.

A known method of reducing the permeability of formations by colmatization using a device for wedging and mudding the walls of the well [1] before attaching it, comprising a housing with a central channel, a sleeve concentrically mounted relative to the housing, and nozzles.

The method provides claying and clogging of the wall of the well, which leads to an increase in the quality of attachment, i.e. raising cement mortar to a design height. However, colmatants mainly from clay particles, penetrating to a shallow depth in formations with aggressive and active waters, are destroyed over time, thereby opening access to aggressive media to the cement stone through cracks and further to the casing pipes.

These disadvantages are partially eliminated in the method [2], which provides for the overlapping of complicated zones of formations with the help of profile overlappers by installing them in a previously expanded interval of the formation.

This method is implemented by a device containing a repair pipe-overlap, in the cavity of which a flare is installed with an emphasis in the lower part, a shoe is installed in the lower part of the overlap cavity in the form of a screw with a stop interconnected by a thread, cams, O-rings and. etc.

The installation of the shutoff in a pre-expanded interval of the formation limits its scope, since the main volume of drilling is carried out in directional wells, in which, when the interval of the formation is expanded, a one-sided increase in the barrel occurs, which does not allow the coaxial installation of the shutoff, and this leads to a decrease in the diameter of the well, therefore high-quality isolation of the reservoir will not occur. In addition, the manufacture of the shutter itself requires expensive equipment and time.

There is also known a method of fastening a well [3] under the name “Method of sealing oil and gas wells", according to which at least one section of the casing located in the zone of possible exposure to a liquid or gaseous medium is made in the form of one or more corrosion-connected in series Resistant casing pipes. In this case, the execution of casing pipes is corrosion-resistant by the method of thermal spraying, for example, using a standard electric arc apparatus, metal The stainless steel coating is 0.3-0.5 mm thick and has a roughness of 40-80 microns to increase the mechanical characteristics of the adhesion of cement stone to the pipe body and ensure durability.

This technical solution is closer to the proposed one and can be taken as a prototype.

Its disadvantage is that when using it, durability is not achieved, since in difficult well conditions when lowering the casing string to a greater depth, the stainless steel coating is of relatively small thickness, only 0.3-0.5 mm, in contact with hard abrasive rock wells, partially peeled off, allowing access of aggressive liquid or gas to the body of the exposed parts of the pipe. Therefore, this does not provide reliable protection of casing pipes from aggressive media, negating efforts to improve environmental safety and durability.

In addition, the danger of the spread of active water and gases through micro-gaps to neighboring unprotected casing pipes adjacent to the pipes with a protective coating is not excluded.

The objective of the present invention is to increase the reliability of the fastening of the well with ensuring the durability of the casing, opposite the strata with aggressive and active waters, gases, and gas-oil fluid.

The problem is solved by attaching an oil and gas well with aggressive media by cementing a casing in it, at least one section of which, located in the zone of possible exposure to aggressive media, is performed in the form of one or more corrosion-resistant casing pipes connected in series. According to the invention, after the calculated volume of cement mortar is injected, the intervals of possible exposure to aggressive environments, as well as productive formations with gas-oil liquid, are limited by disconnectors and in the areas where the disconnectors are located, they form a reinforced cement stone, while pipes made of steel of GSF grade 09 are used as corrosion-resistant pipes. or stainless steel.

Another difference of the method is that before the casing string is lowered into the well at intervals of exposure to aggressive media with a thickness of more than 50 m, the outer surface pipes adjacent to the corrosion-resistant pipes are coated with an anti-corrosion coating.

Patent studies on the novelty of the essential features of the proposal were carried out according to the patent fund of the TatNIPIneft Institute with a retrospectiveness of 20 years. The results of patent research showed that the objects characterized by such a combination of essential features were not found, therefore, we can assume that the claimed object has novelty and, in our opinion, meets the criterion of “inventive step”.

The drawings illustrate the essence of the invention, in which Fig. 1 shows a well with cemented casing and formations with aggressive media, opposite which are installed casing pipes with corrosion-resistant properties and limited by disconnectors, in partial section.

Figure 2 is a view of I figure 1 is one of the design options used disconnector when implementing the method, a General view in partial section.

In Fig.3 - the same as in Fig.2 - in the working position.

The disconnector includes a self-sealing cuff 1, placed in a cone-shaped stop 2 with petals 3 made in the expanded part of the cone, which are simultaneously centering elements. The lower part of the cone ends with an elongated shank 4 with scrapers 5. The latter play the role of a turbulator for cement mortar, and subsequently as reinforcing cement stone elements.

By agreement with the geological and geophysical services of the drilling enterprise, the intervals of formations 6, 7 and 8 with aggressive media are determined, depending on their thickness, casing pipes 9, 10 and 11, which are opposite these formations, are made of steel with increased corrosion resistance, for example, steel grade 09 GSF, strength class K 52 or stainless steel, manufactured by the Chelyabinsk Tube Rolling Plant (ChTPZ), according to the technical specifications TU-14-158-105-97, which have increased corrosion resistance. Moreover, if the thickness of such layers is a significant thickness, for example, exceeds 50-70 m, then the casing pipes 12 adjacent to the corrosion-resistant pipes 10 are pre-coated with an anti-corrosion coating.

Before the descent into the well 13, the end sections of one or more corrosion-resistant casing pipes 9, 10, 11 connected in series are equipped with disconnectors 14, which are available in the arsenal of equipment, for example, the construction described above, to limit the intervals of the layers 6, 7 and 8 from the above and below layers. Disconnectors of this design favorably differ from the known ones in that they are multifunctional, perform the function of a centralizer, clean the walls of the well from clay peel, and the cleaning scrapers subsequently act as a swirl of cement, removing it from the caverns, and then the elements reinforcing the cement stone, thereby increasing the quality of cementing, in addition, its sealing elements protect the underlying layers from hydraulic fracturing.

After the casing is lowered into the well, it is cemented by positioning the casing pipes 9, 10 and 11, which have increased corrosion resistance, opposite the intervals of the formations 6, 7 and 8, as shown in figure 1.

In the cementing process, the injected cement slurry, getting from the pipe space through the shoe of the column into the annular one and reaching the scrapers 5, which protrude beyond the maximum outer diameter of the stop 2, passing between them and the partitions 15, receives turbulent movement, which leads to more complete replacement of the drilling grouting, reducing the likelihood of inclusion in the cement ring of the drilling fluid, thereby increasing the reliability of separation of formations. At the same time, scrapers play an important role in ensuring the quality of fastening of the well; when the casing is lowered into the well, the clay crust partially peels off the walls of the well, loosening it, creates favorable conditions for its subsequent washing with buffer fluid, which is pumped into the well before the cement mortar is injected, and the process of waiting for the hardening of cement form a reinforced cement stone. Next, the cement slurry, passing through the gaps of the petals and the annular gap formed between the self-sealing cuff 1 and the wall of the borehole 13, rises up, filling the annulus above the device. After pumping the grouting mortar of the calculated volume, the pump is stopped, the column of grouting mortar behind the column exerts hydrostatic pressure on the sealing collar, the latter, self-sealing from the action of this pressure, blocks the wellbore, thereby ensuring separation of the underlying reservoirs from the upper ones and protecting the underlying reservoirs from hydraulic fracturing.

Thus, such an integrated approach to the fastening of wells by the proposed method will not only increase the reliability and durability of casing pipes that are in the range of exposure to aggressive media, but also protect adjacent casing adjacent to these pipes from the damaging effect of aggressive media due to their possible propagation. All this, ultimately, will lead to a multiple increase in the overhaul period of the well and, consequently, to a sharp reduction in the cost of repair and insulation work associated with shutdowns of working wells, the involvement of teams for overhaul of equipment wells, with the cost of time and materials.

Sources of information

1. A.S. No. 1051236, E 21 V 37/00, publ. in BI No. 40, 83.

2. Pat. RF № 1782079, 6 Е 21 В 29/10, 33/13, publ. in BI No. 2, 95.

3. Pat. RF № 2156350, 7 Е 21 В 33/14, publ. in BI No. 26, 2000 (prototype).

Claims (2)

1. The method of fastening an oil and gas well with aggressive media by cementing a casing in it, at least one portion of which, located in the zone of possible exposure to aggressive media, is performed in the form of one or more corrosion-resistant casing pipes connected in series, characterized in that after injection of the estimated volume of cement mortar, the intervals of possible exposure to aggressive environments, as well as productive formations with gas-oil fluid are limited by disconnectors in the zones the locations of the disconnectors form a reinforced cement stone, while pipes made of 09 GSF steel or stainless steel are used as corrosion-resistant pipes. 2. The method according to claim 1, characterized in that before the casing string is lowered into the well at intervals of exposure to aggressive media with a thickness of more than 50 m, the outer surface pipes adjacent to the corrosion-resistant pipes are coated with an anti-corrosion coating.

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