RU2312972C2 - Method and device for fluid-containing reservoir isolation - Google Patents

Abstract

FIELD: oil and gas industry, particularly methods or devices for cementing, for plugging holes, crevices, or the like.

SUBSTANCE: method involves creating disc cavern in rock; filling the cavern with plugging composition; creating technological window within reservoir cap, wherein technological window height and width are calculated from equation; fully crushing casing pipe body; washing-out rock and creating at least 2-3 disc caverns within technological window interval; filling well bore and disc caverns with light-weight salt or aqueous solution; repeatedly filling total well bore volume and disc caverns with plugging solution; filling opened well bore and disc caverns with plugging solution at decreased flow rate of 0.5-3.0 l/sec along with upper casing pipe part shoe sealing and increasing pressure. Device comprises pump, guiding jet nozzles and valve ball. Guiding jet nozzles extend in radial direction and are uniformly distributed along total body circle in upper, central and lower horizontal planes of section thereof so that 3-6 nozzles are located at each plane. Device also has bypass channels communicating device interior with guiding jet nozzles. Jet nozzles are united in 2 alternately acting groups. Nozzles installed in central horizontal plane are directed in horizontal plane. Nozzles located in upper and lower horizontal planes spaced apart 0.15-0.5 m are inclined at 7-30° to horizontal plane. Device also has slide with additional valve ball installed in upper part thereof.

EFFECT: increased efficiency.

2 cl, 6 dwg, 2 ex

Description

The invention relates to the oil and gas industry, in particular to overhaul carried out in the process of exploitation of fields and liquidation of wells. The greatest application will be found in the isolation of fluid-containing formations with abnormally high reservoir pressure (AAP), the operation and liquidation of wells in multilevel deposits, as well as in the burial of toxic and radioactive waste.

A known method of isolating an overlapped production stratum according to the patent of the Russian Federation No. 2154150 (IPC ЕВВ 33/13), including the installation of cement bridges in the production string of the well, where one of the cement bridges is installed in the cover of the productive stratum of the well, for which the well bore is previously released installing a cement bridge from the production casing and cement ring by milling the production casing and drilling a cement ring, and the wellbore is expanded by 10-15 mm per st Ron from the original size of the barrel. At the same time, when installing the bridge, non-shrinking, or corrosion-resistant, or expanding materials are used.

The disadvantages of this method are:

- low efficiency of insulation work, especially when isolating formations with AVPD. This is due to the fact that the insulating work is carried out in the wellbore, expanded only 10-15 mm to the side of the original size, while it is known that during drilling in rock at a distance of up to 3-5 well radii due to vibromechanical stresses both horizontal and vertical microcracks, which then serve as filtration paths for reservoir fluids (gas, oil, water). It is not possible to block these filtration paths (microcracks) by selling grouting material under pressure with this method, since the method is carried out in impermeable rocks-tires. And this does not allow to create a high-quality fluid-resistant screen.

The closest in technical essence to the proposed method is a method of isolating plantar water in an oil well, according to ed. St. SU No. 1206431, publ. 01/23/86, bull. No. 3, including the creation of a disk-shaped cavity in the water-oil contact zone oriented in the horizontal plane, injection of the working agent under a pressure sufficient for hydraulic fracturing, and the subsequent filling of the disk-shaped cavity and the resulting cracks with grouting mortar, in which to increase the insulation reliability by increasing the length of the cracks, before injection of the working agent, the surface of the disk-shaped cavity is treated with a fixing solution.

The disadvantages of this method are:

- low efficiency of insulating work, due to the hydraulic fracturing method, in which, as is known from domestic and foreign practice, horizontal and vertical micro- and subcracks of long length reaching several tens of meters are formed in isotropic and anisotropic formations, which leads to a sharp increase permeability in the borehole zone of the reservoir. Therefore, it is impossible to create a high-quality fluid-resistant screen after hydraulic fracturing, even when grouting material is injected under pressure into the reservoir (in practice, hydraulic fracturing is used to increase the production of formation fluids (gas, oil and water) and injectivity of injection wells by creating a message as to the thickness of the formation , and remote zones of the reservoir with a borehole zone);

- insufficient (mechanical) strength reliability of the grouting screen, especially when isolating formations with high pressure flow, due to the small thickness (0.2-0.5 m) of the disk-shaped cavity and the large axial load (from bottom to top) of extrusion, always occurring with a difference in reservoir pressure in the sole and the roof of the screen and depending on the diameter of the wellbore and pressure drop up to 100-900 tons or more.

Known devices are waterjet perforators, such as: OP-4, AP-6M, devices according to ed. St. USSR No. 1027372, 1170125, according to the patents of the Russian Federation No. 2038466, 2042796, 2185497 (IPC Е21В 43/114), intended for opening casing strings in wells and erosion of caverns in rock.

These devices have the following disadvantages:

- low efficiency of insulating work is caused by the fact that in the process of erosion of the rock cavities are formed not disk-shaped, but wheel-shaped. In such caverns, it is not possible to completely replace the working fluid (solution, water) with grouting material due to their configuration, which does not allow qualitatively blocking the filtration paths (micro- and macrocracks) of formation fluids in the borehole zone. The formation of wheel-shaped rather than disk-shaped cavities in the rock is facilitated by the fact that in known devices the axes of the hydraulic nozzles are located strictly horizontally;

- low technology and high complexity of the erosion of circular caverns. This is due to the lack of backup nozzles and a rotation unit in the design of devices. Therefore, it is necessary to rotate the entire pressure column from the mouth with the rotor and perform additional tripping operations to replace the nozzles, and this leads to abrasion (wear) of the coupling joints of the pressure column and the inner surface of the casing.

The closest in technical essence is a sandblast perforator, St. for utility model of the Russian Federation No. 17942, IPC ЕВВ 43/114, priority dated 06/14/2000, comprising a housing, guiding jet nozzles placed in the housing at an angle to its longitudinal axis, a valve and a shank, nozzles are unpaired in height along the perimeter of the housing at an angle of 60 ° to the longitudinal axis of the punch.

The disadvantages of this device are:

- low technology, long duration, complexity and cost of the erosion process of disk-shaped caverns in the rock. This is due to the presence in the device design of only one nozzle in horizontal planes, due to their unpaired height distribution, the absence of reserve nozzles and an autonomous rotation unit. Therefore, to create disk-shaped cavities in the rock, it is necessary to rotate the entire pressure column with a wellhead rotor, which leads to a quick abrasion (wear) of the coupling joints of the pressure column and the inner surface of the casing, especially in wells that have a large deviation from the vertical (vertically inclined, inclined) . This can lead to an emergency and the well to exit the production fund. In addition, when using this device, it will be necessary to perform additional tripping operations to replace the nozzles, since the erosion of the disk-shaped cavities by two nozzles in the rock can last several hours, while the resource of known nozzles made of VK alloy on an abrasive does not exceed 1-1.2 hours .

The technical result of the alleged invention is the creation of a high-quality fluid-resistant screen.

This technical result is achieved by solving a technical problem aimed at reducing permeability in the near-wellbore zone of the formation with a simultaneous increase in the strength of the grouting screen.

The stated technical problem is solved due to the fact that in the method of isolating a fluid-containing screen, including the creation of a disk-shaped cavity in the rock, injection of the working agent and the subsequent filling of the disk-shaped cavity with cement slurry, in the interval of the rocks of the tires lying over the formation, in close proximity to it, create technological window, the height of which is determined depending on the vertical axial load on the installed fluid-resistant screen, the adhesion of the cement stone with the mining th rock and extended borehole diameter according to the formula

where K is the safety factor;

H - the height of the installed screen;

where P ₁ , P ₂ - pressure acting on the sole and roof of the screen, kg / cm ² ;

F _cp - averaged cross-sectional area of the well, cm ²

where R _cp is the average radius of the well, see

Axial shear load is determined from the expression

where δ is the amount of adhesion of the screen material to the rock, kg / cm ² ;

D _cp is the average diameter of the cross section of the well, see

Taking the safety factor K = 1.5 and taking P _sd = 1.5Р ₀ , transforming the expression (3), the height of the installed screen with a 1.5-fold safety factor is calculated by the formula (1), while completely destroying the casing string , the diameter of the wellbore in this interval is less than the diameter of the formation zone during the drilling of horizontal and vertical macro- and microcracks, after thorough washing from metal chips, the rock is eroded and at least 2-3 caverns with a diameter of 1.5 are created in the interval of the technological window -5.0 times b longer than the zone of formation of macro- and microcracks, after 1.0-5.0 meters in height of the technological window, the wellbore and disk-shaped cavities are filled with a working agent in the form of a lightened saline or aqueous solution, then the entire volume of the wellbore and disk-shaped cavities are filled under the influence of gravity cement slurry, while the cement slurry has a density greater than water and lightweight mortar, lower the pressure column and with a low flow rate of 0.5-3.0 l / s fill the open wellbore and disk-shaped caverns tampon with an important solution with overlapping the shoe of the upper part of the casing string by less than 10-20 m and increase the pressure, not exceeding 0.8 of the hydraulic fracturing, to implement a method of isolating a fluid-containing formation in a device including a housing, guiding jet nozzles and a valve ball, housing rigidly fixed to the hollow shaft of the rotor of the downhole motor, which is attached to the pressure pipe string, the guiding jet nozzles are located radially and evenly around the entire circumference of the casing in the upper, middle and lower horizontal planes its cross sections of 3-6 nozzles for each plane, the device is equipped with bypass channels connecting the internal cavity of the device with the guiding jet nozzles, while the jet nozzles are combined into two groups of alternating action, one of the groups is connected to one of the bypass channels, the second to the other bypass channel, nozzles located in the middle horizontal plane are oriented in a strictly horizontal plane, nozzles located in the upper and lower horizontal planes, spaced from each other by 0.15-0.5 m, getting 7-30 ° angle to the horizontal plane, the device is also provided with a slide valve mounted in an upper portion of the valve ball.

The essence of the invention is that:

- to increase the efficiency of insulation work, at least 2 disk-shaped caverns are created;

- grouting material, when creating a fluid-resistant screen, is pumped under a pressure not exceeding 0.8 of the hydraulic fracturing;

- the height of the fluid-resistant screen is determined by the calculation formula;

- to create disk-shaped caverns, an appropriate device is used;

- when creating a fluidproof insulating screen, grouting mixtures based on salt and clay are used, because they have the greatest fluid impermeability of known materials.

Figure 1 shows the state of the well before erosion of disk-shaped caverns.

Figure 2 - the location of the disk-shaped caverns.

Figure 3 - state of the well after isolation of the fluid-containing formation.

Figure 4 and 5 is a device for implementing the method.

The method is as follows.

In the well bore, which opened the fluid-containing productive formation 1 and cased-hole column 2 according to the "Instructions on the procedure for liquidation, conservation of wells and equipment of their mouths and shafts" RD 08-492-02, 2002, install a cement bridge 3 in the interval of occurrence of formation 1 and 50-100 meters above it. Then, in the interval of rocks-tires 4 (clay, mudstones, etc.), lying above the reservoir 1 in close proximity to it using known milling devices, to ensure direct contact of the grouting material with the rock create a technological window 5 with a height of 10-50 m, with the complete destruction of the body of the casing string 2, while the diameter of the wellbore in this interval is always less than the diameter of the formation zone during the drilling of horizontal and vertical macro- and microcracks 6.

After thorough washing from metal shavings, the proposed rock erosion device (URGP) is lowered into the well (FIGS. 4, 5) and at least 2-3 disk-shaped caverns 7 are created in the interval of the technological window, the diameter of which is 1.5-5.0 times the zone of formation of macro- and microcracks 6 through 1.0-5.0 meters in height.

Then the well is washed from mud of eroded rock, its trunk and disk-shaped caverns are filled with a lightweight solution (usually saline) or water. Transferring a well to a lightweight fluid allows you to completely (most fully) fill the entire volume of the barrel and eroded disk-shaped cavities with grouting material due to the forces of gravity, since the grouting mixture is prepared with a density higher than that of water and lightweight mortar. After that, the pressure column is lowered and, in a known manner, with a reduced flow rate of 0.5-3.0 l / s, the open wellbore and disk-shaped caverns 7 are filled with grouting material 8, taking into account the overlap of the shoe of the upper part of the casing 2 by at least 10-20 m. Raise the pressure column 100-150 m above the head of the cement slurry and raise the pressure at the wellhead, taking into account the technical condition of the casing, but not higher than 0.8 hydraulic fracturing pressure, in which caverns were eroded (created). The well is kept under pressure for the time necessary to set the grouting material (usually 2-3 days), after which the wellhead pressure is removed.

After that, an additional cement bridge 9 with a height of 50-100 meters is installed in the casing according to RD 08-492-02, which provides direct contact with the roof of the fluidproof insulating screen made of grouting material.

The sale of grouting material into disk-shaped caverns under pressure, taking into account the technical condition of the casing, but not exceeding 0.8 of the hydraulic fracturing, prevents the formation of macro- and microcracks in it, which improves the quality of the created fluid-proof insulating screen.

Achieving the diameter of the disk-shaped caverns 7 is 1.5-5.0 times larger than the diameter of the zone of formation of macro- and microcracks 6 that occur in rocks during drilling due to vibromechanical stresses, it is necessary for their high-quality isolation by the created fluid-resistant screen from grouting material. At the same time, a decrease in the ratio of the diameter of caverns 7 to the diameter of zone 6 by less than 1.5 times will lead to a deterioration in the reliability (quality) of insulation works, and an increase of more than 5 times is impractical due to an increase in the consumption of grouting material and an increase in the cost of producing caverns. The creation of at least 2-3 disk-shaped caverns 7 and their location in height after 1-5 meters is necessary to increase the reliability of the created fluid-resistant screen, which helps to withstand the protruding axial load, especially when isolating the reservoirs with AVPD. At the same time, their location at a distance of less than 1.0 meters can lead to collapse of the rock, which will accordingly sharply reduce the quality of insulation work, and an increase in the distance of more than 5.0 m is unacceptable in low-pressure formations and in wells that hit into the crushing zone of tectonic disturbances.

Cutting of technological windows 5 with complete destruction of the body of the casing string 2 is a rather laborious and expensive process, therefore, knowledge of the required minimum height of the fluid-proof insulating screen, providing long-term high-quality and reliable insulation of the fluid-containing formation 1 at various thermobaric and vertical axial loads, will allow you to correctly plan the insulation work with minimal on them costs.

Example 1. The coefficient of anomalies of the fluid-containing formation is 1.3, the hydrodynamic drop on the fluid-resistant screen at a depth of 3500 m is 12.0 MPa, the average radius of the horizontal section of the well is 0.5 m, the axial vertical shear load on the screen is 942000 kg, δ - the adhesion of the clay material to the rock is 8.0 kg / cm ² .

By the formula (1), we determine that the required height of the installed screen and, accordingly, the technological window in the casing is 5.625 m.

Example 2. The coefficient of abnormality of the fluid-containing formation is 2.1, the hydrodynamic drop is 44.0 MPa, the average radius of the well is 1.0 m, the axial vertical load is 13816000 kg, δ is the adhesion of the salt material with the rock - 12.5 kg / cm ² .

Also using formula (1), we determine the required height of the screen and the technological window in the casing, which will be 52.80 m.

A device for implementing the method of isolating a fluid-containing formation during erosion of rocks (FIGS. 4, 5 and 6) comprises a hollow body 10, rigidly fixed to the hollow shaft of the rotor 11 of the downhole motor 12, which in turn is attached to the pressure pipe string.

In the housing 10 there are jet nozzles 13, 14 and 15 of alternating action, combined in two groups and radially evenly spaced around the entire circumference of the housing on three different horizontal planes of its section, valve balls 16 and 17, a spool made in the form of a sleeve 18 with seals 19 and locking pins 20, as well as bypass channels 21 and 22.

The jet nozzles 14 located in the middle horizontal plane between the nozzles 13 and 15 are oriented in a strictly horizontal plane. The jet nozzles 13 and 15 located in the upper and lower horizontal planes, spaced from each other by 0.15-0.5 m, are installed at an angle to the horizontal plane α = 7 ÷ 30 °.

The location of the jet nozzles 13 and 15 at an angle to the horizontal plane is necessary to give the eroded cavity in the rock a disk-like shape. In this case, the installation of jet nozzles at an angle of less than 7 ° is unacceptable, since cylindrical cavities will form due to the always existing opening (spraying) angle of the waterjet, and when the angle α is more than 30 °, the diameter of the disk-shaped cavity will sharply decrease, which may not overlap the diameter zone caverns 6 (see figure 1, 2, 3).

The number of jet nozzles (13, 14, 15) for each plane of their location is from 3 to 6 in each group. The presence of less than 3 nozzles will sharply increase the duration and laboriousness of the erosion process of disk-shaped cavities, and more than 6 will narrow the scope due to the design difficulties of their placement with small diameters of the device and require the use of additional expensive pumping equipment.

If the distance between the planes of the jet nozzles 13 and 15 is less than 0.15 m, caverns of a cylindrical shape will be formed, and not disk-shaped due to the influence of the nozzle jets of the middle plane 14 oriented in a strictly horizontal direction, an increase of more than 0.5 m is impractical due to the formation of caverns of large volume, which will require a large consumption of grouting material.

The presence of vertical bypass channels 21 in the housing 10 provides a hydroabrasive medium with jet nozzles of the second group 13-II, 14-II and 15-II when moving the spool 18 down to the stop, and horizontal channels 22 communicate the inside of the housing 10 with nozzles of the first group 13 -I, 14-I, 15-I.

The housing 10 is made in the form of a figured cup with a seating seat under the ball valve 16 in its lower part and with a flushing cylindrical hole.

The spool 18 is made in the form of a sleeve with a seating seat under the ball valve 17 in its upper part. The pins 20 hold it in its original position, and the seals 19 provide a seal between it and the housing 10, preventing the premature entry of the hydroabrasive medium into the vertical channels 21, and then into the nozzles of the second group.

The downhole motor provides axial rotation of the housing 10 with jet nozzles when pumping hydroabrasive fluid through it.

The inclusion in the device node downhole motor 12 will avoid rotation of the entire pressure pipe string.

A device for implementing the method of isolating a fluid-containing formation during erosion of the rock works as follows.

The device, which is rigidly fixed to the pressure column of pipes, is lowered into the well to a predetermined depth to create a disk-shaped cavity, and the ball valve 16 is thrown into the pipes. Then, hydroabrasive mixture (water with sand, a solution with an abrasive, etc.) is supplied through pressure pumps by ground pumps or just a working fluid without abrasive in less hard and easily eroded rocks under a pressure of 25-30 MPa. The ball valve 16 lowers down and closes the lower flushing cylindrical hole in the lower part of the housing 10. In this case, the waterjet mixture enters through the channels 22 into the jet nozzles of the first group 13-I, 14-I and 15-I, and the housing 10, driven by a motor 12 rotates around its axis. Hydroabrasive mixture, flowing out from jet nozzles at a speed of 200-210 m / s, destroys and erodes the rock, forming in this case disk-shaped caverns. After the estimated time has elapsed, the ground-based pumping units are stopped, the device is lifted to the next interval of work, and the feed of the waterjet mixture is again repeated to wash the next disk-shaped cavity. As the first group of jet nozzles (13-I, 14-I and 15-I) break down during several operations, as judged by the pressure drop on the ground pumps at the same flow rate of the waterjet, the erosion process is stopped and the ball valve is dumped into pressure pipes 17, the diameter of which is larger than the diameter of the ball valve 16. When the ball valve 17 is inserted into the seat seat of the spool 18, the pressure in the pressure pipes smoothly increases to 5.0-8.0 MPa, the pins 20 holding the spool 18 in the initial position are cut, and the spool is moved 18 down to the stop. At the same time, the intake of the hydroabrasive mixture into the worked nozzles of the first group is blocked, and access to the nozzles of the second group that had not worked before is opened (13-II, 14-II and 15-II). The process of switching to other nozzles is fixed by a sharp drop in pressure to 0 MPa at the pump units. Then, the hydroabrasive mixture is again fed and the working pressure at the nozzles is raised to 25-30 MPa. In this case, the waterjet mixture through the vertical channels 21 enters only the jet nozzles of the second group, and the erosion of disk-shaped caverns in the rock continues. After erosion of the required number of disk-shaped cavities in the working interval, the flow of the hydroabrasive mixture is stopped and the device, together with the column of pressure pipes, is removed to the surface.

Using the proposed method for isolating a fluid-containing formation and a device for its implementation will allow:

- to increase the efficiency and reliability of the fluid-proof insulating screen, especially when isolating formations with AVPD. This is due to the fact that the height of the fluid-proof insulating screen is preliminarily calculated according to the formula for each particular case, taking into account the axial buoyancy load of the underlying fluid-containing formations, the actual diameter of the well, and the physical and strength characteristics of the grouting materials. In this case, fluid-tight grouting mixtures based on clay and salt are used. The pressure of the grouting material into disk-shaped cavities does not exceed 0.8 hydraulic fracturing. Fluid-proof insulating screen includes at least 2 disk-shaped cavities;

- to ensure the manufacturability of the erosion process of disk-shaped caverns while reducing the complexity and cost. This is due to the fact that there is no need to rotate the entire pressure column with the wellhead rotor and in additional tripping operations to replace the used jet nozzles. In addition, in the absence of rotation of the entire column of pressure pipes, the possibility of its abrasion and the casing is excluded.

The estimated economic effect of using the proposed method for isolating a fluid-containing formation and a device for its implementation, depending on the depth of the work, their volume and the mechanical and strength characteristics of the rocks-tires, will be from 2 to 10 million rubles.

Claims (2)

1. A method of isolating a fluid-containing formation, including the creation of a disk-shaped cavity in the rock and the subsequent filling of the disk-shaped cavity with cement slurry, characterized in that in the interval of the rocks of the tires lying over the formation in close proximity to it, create a technological window, the height of which is determined depending on the vertical axial load of Po on the installed fluid-resistant screen, the adhesion of the cement stone to the rock and the extended diameter of the well according to the formula

where K is the safety factor; H - the height of the technological window and the installed screen;

where P ₁ , P ₂ - pressure acting on the sole and roof of the screen, kg / cm; F _cp is the average cross-sectional area of the well, cm ² ;

where R _cp is the average radius of the well, cm, from the expression the axial shear load is determined

where δ is the amount of adhesion of the screen material to the rock, kg / cm ² ; D _cp is the average diameter of the cross section of the well, cm, the height of the installed screen is calculated by the formula (1), while completely destroying the body of the casing when the diameter of the wellbore in this interval is less than the diameter of the formation zone during drilling of horizontal and vertical macro- and microcracks, erode the rock and do not create in the interval of the technological window less than 2-3 caverns, the diameter of which is 1.5-5.0 times larger than the zone of macro- and microcrack formation through 1.0-5.0 m in height of the technological window, fill the wellbore and disk-shaped caverns with a working agent in the form of lightweight saline or aqueous solution, then the entire volume of the wellbore and disk-shaped caverns under the influence of gravity are filled with grouting mortar, while grouting mortar has a density greater than water and lightweight mortar, lower the pressure column and with a reduced flow rate of 0.5-3.0 l / s fill the open wellbore and disk-shaped caverns with cement slurry with overlapping the shoe of the upper part of the casing string by less than 10-20 m and increase the pressure without exceeding 0.8 of the hydraulic fracturing. 2. The device for implementing the method according to claim 1, comprising a housing, guiding jet nozzles and a valve ball, characterized in that the housing is rigidly fixed to the hollow shaft of the rotor of the downhole motor attached to the pressure pipe string, the guiding jet nozzles are located radially and evenly throughout the circumference of the housing in the upper, middle and lower horizontal planes of its cross section of 3-6 nozzles for each plane; the device is equipped with bypass channels connecting the internal cavity of the device with the guiding jet nozzles, while the jet nozzles are combined into two groups of alternating action, one of the groups is connected to one of the bypass channels, the second to the other bypass channel, nozzles located in the middle horizontal plane, oriented in a strictly horizontal plane, nozzles located in the upper and lower horizontal planes, spaced from each other by 0.15-0.5 m, are installed at an angle of 7-30 ° to the horizontal oskosti, the device is provided with a slide valve also provided in its upper part an additional ball valve.

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