RU2542014C1 - Procedure for elimination of behind- casing flows - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method includes expansion of a casing string in each interval of behind-the-casing flows outside limits of elastic deformation until gaps between the string and the cement as well as between the cement and the rock are eliminated. Expansion is performed by a device equipped with rollers used as working members; the device is run in at the drill string to the upper mark of the interval of required expansion above the existing or preliminary made perforation interval, thereupon by rotation of the device with simultaneous downfeed and injection of fluid, under the action of the above fluid the rollers are set to the operating position; by an impact on the inner surface of the casing string it is expanded by rolling out within the whole interval of the behind-the-casing flow or at several individual areas. At rolling-out excessive stress is generated on the walls of the casing string in order to reinforce the behind-the-casing cement by its thickening, at that the diameter of the rolling out device in the operating position is selected by 4-8.5% more than the inner diameter of the casing string before expansion.

EFFECT: speeding-up of the repair process, reducing the number of operations.

3 dwg

Description

The invention relates to the oil and gas industry, and in particular to methods for overhaul wells.

A known method of sealing annular flows, carried out by a device for sealing annular flows (patent RU No. 2287664, IPC E21B 33/13, published in bulletin No. 32 of 11/20/2006), including installing the device in the expansion interval, creating excess pressure in the hydraulic cylinders drive with the withdrawal of a wedge cone, expanding smooth or with transverse protrusions dies, pressing on the walls of the well, with their expansion beyond the plastic deformation and elimination of annular flows.

The disadvantage of this method is that when using dies with transverse protrusions with loads exceeding the force of plastic deformation, unauthorized opening of the casing and the occurrence of downhole fluid flows are possible with a probability of 50% (every second installation), that is, an emergency.

The closest in technical essence is the method of elimination of annular flows (patent SU No. 1813873, IPC E21B 33/13, published in Bulletin No. 17 of 05/07/1993), including sealing of the channels of the flows, while in order to simplify the technology of work, the casing in the overflow interval or in individual sections extend beyond the limits of elastic deformations.

The disadvantage of this method is that the hydraulic anchor in this application does not create a full annular expansion, which leads to low sealing efficiency of annular flows.

Also the disadvantages of both methods are:

- the need for a large number of installation cycles of movement, rotation of the device and local subsequent expansion in an extended and continuous interval to eliminate annular flows, which leads to an increase in repair time and, as a consequence, to high material costs;

- the need to increase pressure to very high values (up to 100 MPa), which requires the use of special equipment and tools, and this is associated with a significant increase in the cost of applying the method;

- the inability to expand pipes over 4% (in diameter) to eliminate annular cross-flows that occur directly along the cement, since the liquid in the cracks and pores of the cement is practically incompressible.

The technical objectives of the proposal are the guaranteed exclusion of annular flows due to compaction of annular cement with an expansion of 4-8.5% in inner diameter, reduction of material costs when expanding the casing string due to the use of rolling and, as a result, the use of lower pressures and quantities expandable item settings.

Technical problems are solved by the method of elimination of annular flows, including the expansion of the casing in each flow interval beyond the elastic deformations to eliminate gaps between the casing and cement, as well as between cement and rock.

New is that the extension of the casing is carried out by a device equipped with rollers as working elements, which is lowered on the drill pipe string to the upper mark of the interval of necessary expansion above the existing or pre-made perforation interval, after which the device is rotated with simultaneous flow down and pumping of fluid, under the action of which the rollers reach the working position, acting on the inner surface of the casing string, expand it by flaring on the sun m flow interval or in several separate sections, and during flaring create excessive stress on the walls of the casing for additional hardening of the annular cement by sealing it in thickness, while the diameter of the flare in the working position is chosen 4-8.5% larger than the inner diameter of the casing to its expansion.

Figure 1 shows the crossflow between the cement ring and the rock of the well; figure 2 - crossflow between the casing and the cement ring, figure 3 is the expansion of the casing flare to eliminate overflows.

The method is carried out in the following sequence.

Before carrying out repair work in the well 1 (Fig. 1), geophysical studies are performed to establish the interval of flows 2 between the cement ring 3 and the rock 4 and / or between the casing 5 (Fig. 2) and the cement ring 3, as well as the density of the annular cement (cement density is 1.6-1.8 kg / cm ³ , and the density of the reservoir fluid in the pores and cracks of cement is 0.88-1.2 kg / cm ³ ) in the cement ring 3 and the location and presence of areas of disturbances and perforations in the casing 5 (figure 2). In the course of the research, it is also determined which expansion relative to the inner diameter of the casing string 5 to adjust the device 6 (Fig. 3) from 4 to 8.5%. The lower the density of cement in the cement ring 3 (Fig. 1), the greater the device 6 is tuned for expansion. Practical studies have shown that expansion by more than 4% leads to compaction of annular cement, and by 8.5% it is guaranteed to exclude annular flows as between the cement ring 3 and the rock 4 and / or between the casing 5 (figure 2) and the cement ring 3, and directly on the cement even with the lowest possible low density of cement in the cement ring 3 (figure 1). Having determined the intervals of annular flows, perforation 7 (Fig. 3) of the casing 5 is made in the lower part of the expansion interval in the absence of existing perforation intervals 7. The device 6, equipped with rollers 8 as working elements, is lowered on the drill pipe string 9 to the upper mark 10 the interval of the necessary expansion 11 is higher than the interval 7. Rotating the device 6 with the simultaneous supply of drill pipes 9 downward and pumping fluid (at a pressure of not more than 3 MPa) through them, under the action of which the rollers 8 enter the working position and acting on the inner surface of the casing 5, expand it by flaring beyond the elastic deformations by 4-8.5% relative to the inner diameter of the casing 5 over the entire flow interval 2 or in several separate sections until the gaps between the casing 5 and the cement ring are eliminated 3 (FIG. 2), between the cement ring 3 and the rock 4 (FIG. 1), and also due to the compaction of cement in the cement ring 3 (FIG. 2) in thickness, eliminating pores and cracks in it. At the same time, the liquid from the annulus and from the pores and cracks of the cement in the cement ring 3 is expelled at intervals 7 (Fig. 3) into the casing 5 (Fig. 1) or into the water layer below (in Fig. Not shown), without interfering the expansion of the casing 5 by the required value of 4-8.5%. Studies have shown that after such an expansion, annular flows were almost completely excluded.

For further operation of the well 1 (Fig. 1), the intervals 7 (Fig. 3) of perforation or disturbances in the casing 5 are overlapped, if necessary, with patches (for example, expandable nozzles, corrugated pipes or through packers) when using productive formations below the expansion interval (s) 11 or cut off (for example, deaf packers or plug packers) when using productive formations above the expansion interval (s) 11.

The proposed method allows to eliminate annulus flows, including annular cement, by expanding the casing by 4-8.5% relative to the inner diameter, as well as reduce material costs and accelerate the process of repairing the well due to lower loads and pressures, as well as the number of operations - one for each expansion interval.

Claims (1)

A method for eliminating casing flows, including expanding the casing in each flow interval beyond elastic deformations to eliminate gaps between the casing and cement, and between cement and rock, characterized in that the casing is expanded with a device equipped with rollers as working elements, which is lowered on the drill pipe string to the upper mark of the interval of necessary expansion above the existing or pre-completed perforation interval, after which by rotating the device with a simultaneous downward flow and injection of fluid, under which the rollers enter the working position, acting on the inner surface of the casing string, expand it by flaring over the entire flow interval or in several separate sections, and during expansion create excessive stress on the casing wall for additional hardening of annular cement by compaction by thickness, while the diameter of the flare in the working position is chosen 4-8.5% more than the internal the diameter of the casing string before it expands.

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