RU2736429C1 - Cementing method of well - Google Patents

Abstract

FIELD: soil or rock drilling.

SUBSTANCE: invention relates to drilling, namely to improving quality of cementing of casing strings, equipment and technology of completion and operation of wells. Cementing method involves well preparation, lowering of casing string, tying of well head with cementing head, flushing of well, injection of grouting mortar. A pulse-wave action device is connected to the cementing head. It includes drill hose with installed on it gate valve, emitter of power waves, hydraulic hammer, pipelines for supply and discharge of oil and air, compressor, pump station and control device. Control device provides change of pulse-wave action mode taking into account rheological conditions of cementing process. Valve is opened immediately after grouting fluid is poured into casing pipes. Control device, pump station and compressor are started. Cement mortar is subjected to pulse-wave action. After completion of grouting mortar pouring and achievement of preset level in annular space, additional pulse-wave action is applied to backfill solution in casing string and borehole space. After the pulse-wave action is completed, further work is performed according to the cementing program.

EFFECT: higher efficiency of cementing due to improved structure and homogeneity of cement mortar, which improve quality of cementing of wells at simultaneous simplification of technical implementation of completion and operation of wells.

1 cl, 1 dwg

Description

The invention relates to the field of drilling, namely to improve the quality of cementing of casing strings, equipment and technology of completion and operation of wells.

The main reason for the decline in the quality of work during the completion and operation of wells is the active hydraulic connection of the fluid-saturated formations exposed by drilling with the wellbore. Therefore, the development of technologies and technical means that ensure effective isolation of permeable formations from the wellbore is an urgent problem.

Cementing is one of the most effective methods for completing and operating wells.

The quality of cementing is determined by the adhesion of the cement stone to the casing and the borehole walls, ensuring the homogeneity of the grouting slurry composition, the absence of volumetric defects and microcracks in the cement stone.

In this case, the condition for the absence of interstratal crossflows is reliable sealing of the contact of the cement stone with the wellbore, which is ensured by the properties of the cement (grouting) slurry, the methods of its supply to the annulus, as well as the features of the devices used for this.

Known hydrodynamic vibrator (RU No. 1764345), including a hollow cylindrical body with bypass ports, a working chamber with inlet and outlet openings, a spool, spring-loaded relative to the body and installed with the ability to overlap the bypass housing windows, and a rotor with an axis installed inside the working chamber, which differs the fact that, in order to increase the efficiency of work by reducing the starting and operating pressures and changing the amplitude of oscillations of the generated pressure, it is equipped with an eccentric cam-pusher, a rotor axis lock and a throttle with an adjustable hole, while the body is made with diametrically opposite recesses in which the rotor axis lock, the rotor in the form of a turbine, the blades of which are curved towards the fluid flow, and the spool - with side oval holes against the housing recesses, the eccentric cam follower is rigidly connected to the rotor axis, and the inlet and outlet openings of the working chamber are offset relative to the axis of the housing sa. Installation of a hydrodynamic vibrator in the lower part of the casing string between the check valve and the shoe requires additional tripping operations for its installation. The circulation of the solution through the device leads to its rapid wear and tear and rapid failure. In addition, the vibrator operates only when pumping fluid and is impossible after pumping the cement slurry, the vibrator operation is regulated by changing the cementing mode, and it is impossible to change the vibration frequency during operation.

Known wellhead mechanical vibrator (RU No. 2250982) containing a housing with inlet and outlet channels, a rotor with an impeller, resting on a bearing, characterized in that a valve is installed in the housing, made with slotted slots and a bottom with holes in its middle part, installed in the housing on a thread with the possibility of axial movement, a rotor with an impeller and holes in the bottom is mounted on a bearing in the axial channel of the spool, the slotted slots of which are made below the place of the rotor installation, for supplying fluid to the well, bypassing the spool, and above the location of the rotor, with the possibility of supplying fluid to the spool on the rotor impeller after its axial movement, while the axial channel of the spool is covered with a cover with a rod that can be inserted into the axial channel of the rotor, and the spool stroke in the housing is limited from below by an adapter. In this device, the frequency of the generated pulses is determined by the flow rate and rheological parameters of the pumped liquid, and a change in the frequency of the generated hydraulic pulse oscillations is possible only by changing the flow rate.

A well-known downhole electromechanical vibrator (RU No. 169384) contains a housing connected to a load-carrying geophysical cable, the electrical supply conductors of which are connected to an electric motor, the rotor shaft of which, mounted in a bearing, through a cam clutch, a spindle in a bearing, an elastic coupling and a runner is connected to the core unbalance, supported by a bearing, characterized in that the vibrator additionally contains a torque limiting clutch located at the spindle break, and upper and lower centralizers designed to interact with the borehole walls. The need to use a geophysical cable to place the vibrator in the well requires additional running equipment and reduces the reliability of the electromechanical vibrator.

The above disadvantages lead to an increase in the complexity of using known vibration devices, a decrease in the processability and quality of well cementing.

Known (SU 1523653) a method of cementing a casing in boreholes by supplying cement slurry to the annulus and impacting the fluid with hydropercussion pulses with a frequency of 20-150 Hz generated by synchronized wellhead and bottomhole sources. The disadvantages of this method are the use of two hydraulic vibrators and the need to synchronize their frequency, as well as the dependence of the frequency of hydraulic shock pulses on the flow rate of the cement slurry.

There is a known method and device for exciting lateral vibrations of a pipe string in a well (RU # 2157446), which includes placing a striker on a flexible suspension in the pipe string with liquid and exciting its radial periodic vibrations with transmission of transverse impacts to the string and a device for exciting transverse vibrations of the pipe string in a well, including a pipe string, partially or completely filled with liquid, a striker placed in the string, and an axial displacement limiter for the striker made in the form of a flexible suspension, one end of which is connected to the striker, and the other end of the flexible suspension is fixed to the wellhead. The disadvantages of the above method and device include the need to carry out tripping operations to place a striker or strikers on a flexible suspension into the pipe string with liquid and the use of additional auxiliary equipment for these purposes. In addition, to regulate the force of impacts, it is necessary and the frequency of oscillations to be poured into the string with a liquid with a different viscosity to change the placement of the load below the striker on a flexible suspension and the gap between the string and the striker.

The prototype of the claimed invention is a method for cementing oil and gas wells, characterized in that the casing is vibrated at a frequency equal to or multiples of the resonant frequency of the casing, at the stages of removing drilling fluid from the annulus and replacing it with a buffer fluid, filling the wellbore with grouting fluid with its subsequent pushing into the annulus and at the stage of setting the cement slurry and a device for implementing the specified method, containing a vibration exciter mounted on the aboveground part of the casing string, consisting of two unbalanced electromechanical vibrators made with parallel shafts with the possibility of opposite rotation, mounted on the aboveground part of the casing string directly under the cementing head using vertically positioned base plates covering the casing and a master oscillator to control the frequency converter for feeding vibration exciter (RU No. 2291948). In this method of cementing, the vibration exciter acts not on the cement slurry, but on the walls of the casing with the formation of resonant vibrations in it. At the same time, the structure and homogeneity of the cement slurry do not change significantly, which reduces the quality of the cementing process.

The objective and the technical result of the proposed invention is to create a method for the treatment of cement slurry that improves its structure and homogeneity and provides an increase in the quality of well cementing while simplifying the technical implementation of the completion and operation of wells. The claimed technical result is achieved by the fact that a cementing method is proposed, including preparation of the well, lowering the casing into it, piping the wellhead with a cementing head, flushing the well, pumping cement slurry, characterized in that a pulse-wave device is attached to the cementing head, including a drill sleeve, a power transmitter waves, a hydraulic hammer, pipelines for supplying and discharging oil and air, a compressor, a pumping station and a control device that provides a change in the pulse-wave action mode, taking into account the rheological conditions of the cementing process, immediately after the start of pumping cement slurry into the casing pipes, the valve opens, the control device starts the pumping station and the compressor and grouting slurry are subjected to a pulse-wave effect, and after the completion of pumping the grouting slurry and reaching a given level in the annulus, additional impulse-wave action on the cement slurry located in the casing and the annulus, and after the end of the impulse-wave action, further work is performed according to the cementing program.

The essence of the invention is illustrated by a drawing.

FIG. 1 - layout of equipment when performing work, where

1 - cementing head,

2 - drilling sleeve,

3 - valve,

4 - emitter of force waves,

5 - hydraulic hammer,

6, 7 - pipelines for supply and discharge of oil and air,

8 - compressor,

9 - pumping station,

10, 11, 12 - valves for supplying the working agent from the cementing unit.

13 - the place of connection of the pulse-wave action device for additional action on the cement slurry.

The proposed method of cementing is carried out as follows.

Through the valves supplying the working agent 10, 11, 12 of the cementing head 1, the cement slurry (working agent) enters the well. Immediately after the start of the pumping of the cement slurry through the valve 10, the control device (not shown) opens the valve 3 on the drilling sleeve 2, turns on the pumping station 9 and the compressor 8 and generates powerful pressure pulses, which are transmitted through the pipelines 6 and 7 to the hydraulic hammer 5 and the emitter 4 of force waves ... The grouting slurry in the zone of the impulse starts to move, since the elements of the grouting slurry microstructure are of the same order of magnitude as the pressure impulses. The force wave, moving along the formation together with the grouting slurry, peels the pollution products from the bottomhole zone and from the inner surface of the casing string. The impacts of the hydraulic hammer 5 also cause elastic deformation of the casing, which transforms into its damped vibrations. The control device allows you to change the mode of impulse - wave action taking into account the rheological conditions of the well cementing process. After the completion of the pumping of the cement slurry and reaching a predetermined level in the annular space, the valve 3 closes, the pulse-wave action device is connected to 13 and an additional effect on the cement slurry is carried out. After the end of the pulse-wave action, further work is carried out according to the cementing program.

Mechanical stirring at the stage of cement slurry preparation does not ensure complete homogeneity of the mixture. Residual heterogeneity develops further and often becomes the cause of various negative consequences observed in practice, for example, the formation of conglomerates of cement particles (coagulation) with a high local density, which leads to the destruction of the structure of the solution through the sedimentation of these conglomerates of particles. Another dangerous consequence of the initial heterogeneity of the solution is contraction - the appearance of large fragments of bound water, which further leads to the appearance of filtration channels in the cement stone.

With pulse-wave processing, these phenomena are excluded, since the vortex acoustic flows arising during the passage of pulses activate the processes of mass transfer in the cement slurry at the micro level, which leads to a more uniform distribution of the dispersed phase and mixing liquid in the bulk of the solution. During the processing period (≈20 min), about 6000 elementary acts of impulse-wave action take place at each point of the annular space. Casing vibrations create an additional acoustic field in the cement slurry. Additional acoustic pressure inside the casing in the working agent is ≈ 0.1 MPa, in the annular space in the cement slurry ≈ 0.045 MPa.

Longitudinal pressure pulses, which are generated with a period of ≈ 2 s, propagate in the working agent inside the casing and transfer energy to its wall, forming transverse vibration pulses. It should be noted that the elements of the technological equipment of the column are not influenced by pressure impulses due to their short duration and locality (short length). Large objects of the rig are "transparent" for them. On the other hand, the characteristic elements of the microstructure of the cement slurry have dimensions of the same order of magnitude as the pressure pulses, therefore, the cement slurry in the zone of the impulse also starts to move.

Solvate shells of cement particles under pulse-wave action are deformed in such a way that in the zone of contact with the metal it becomes thinner, which provides acceleration and increases the frequency of elementary acts of the formation of chemical bonds. The formation of a strong homogeneous intermediate layer at the metal-solution interface, in which the particles of the solution and the walls of the casing are chemically bonded, increases the strength and tightness of the contact zone of the cement stone, reduces the risk of vertical displacements of the column under its own weight during the operation of the well, which is an important indicator of the quality of the support ...

Reliable sealing of the cement stone contact with the wellbore is also ensured by the absence of interstratal crossflows.

The proposed pulse-wave method of cement slurry treatment can significantly reduce the risk of annular pressures due to more complete displacement of the drilling fluid and drilling fluid from the near-wellbore zone of increased conductivity.

The vibrations of the solution under the action of pressure impulses lead to the destruction of the mud cake, and the additional pressure displaces the remnants of the process fluids deep into the rock with the replacement of the freed pores, cracks and caverns with cement slurry, improving clogging.

The control device allows, without additional technological operations, to change the parameters of the pulse-wave action to ensure the optimal treatment mode, taking into account the composition, viscosity, cement slurry feed rate and other rheological conditions of well cementing, which significantly increases the manufacturability of the completion and operation of the well.

Thus, the proposed method of cementing, which includes a pulse-wave effect on the cement slurry, taking into account the rheological conditions of the well cementing, provides a set of physicomechanical and physicochemical processes in the volume of the cement slurry, as well as at the boundaries with the walls of the column and the wellbore, which reduce the setting time of the grouting slurry, improve the structure, strength and operational characteristics of the cement stone, and ultimately increase the manufacturability and quality of the cementing process.

Claims (1)

A method for cementing a well, including preparing a well, lowering a casing into it, tying a wellhead with a cement head, flushing a well, pumping a cement slurry, characterized in that a pulse-wave device is attached to the cementing head, including a drilling sleeve with a valve installed on it, a power wave emitter, a hydraulic hammer, pipelines for supplying and discharging oil and air, a compressor, a pumping station and a control device, with which they provide a change in the pulse-wave action mode, taking into account the rheological conditions of the cementing process, are opened immediately after the start of pumping the cement slurry into the casing pipes valve, with the help of the control device, the pumping station and the compressor are started, and the cement slurry is subjected to a pulse-wave effect, and after the completion of the pumping of the cement slurry and reaching a predetermined level in the annulus, an additional impulse-wave action on the cement slurry located in the casing and the annulus, and after the end of the impulse-wave action, further work is performed according to the cementing program.

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