RU2576253C1 - Method for multistage well cementing and set of equipment therefor - Google Patents

Abstract

FIELD: oil industry.

SUBSTANCE: invention relates to oil industry and can be used in cementing of casing strings in oil and gas wells during multistage cementing. Method is characterised by that casing string is equipped with first and second cementing couplings mounted at a distance from each other corresponding to distance between abnormal zones of well. Casing string is lowered to specified depth with intermediate washing. Design volume of cement grout of first stage of cementing is pumped. Bottom plug is pressed to fit in stop-pipe casing. First plug-bomb adapted for free fall to fit into lower seat of first cementing of coupling is lowered. In tube space is created excess pressure to specified value to open cementing window of first cementing of coupling. Excess cement grout first stage is cut off and a pause is held in expectation of setting of cement solution of first stage. Design volume of cement grout of second stage of cementing is pumped. Cement plug is lowered, press-fit in upper seat of first cementing coupling. In tube space is created excess pressure to specified value for cementing windows of first cementing coupling. Second plug-bomb to lowered to fit into lower seat of second cementing coupling. In tube space is created excess pressure to specified value to open cementing windows of second cementing coupling. Excess cement grout of second stage is cut off and pause is made in expectation setting of cement grout of second stage. Design volume of cement grout of third stage is then pumped. Upper plug is lowered and its squeezed to fit in upper seat of second cementing coupling. In tube space is created excess pressure to specified value for cementing windows of second cementing coupling and pause is held in expectation of setting of cement grout of third stage.

EFFECT: technical result is improved reliability of preventing behind-casing gas, oil and water showings of weak layers.

5 cl, 10 dwg

Description

The invention relates to the oil industry and can be used for cementing casing strings in oil and gas wells in three or more stages.

A known method of two-stage cementing of wells, including lowering the casing string to a predetermined depth, injecting cement slurry of the first cementing stage, starting the separation plug, stage-by-stage pumping of portions of the squeezing fluid (drilling mud), dumping the self-immersing plug-bomb into the casing to open circulation holes and restore circulation liquid behind the column above the circulation openings, washing out of the well cement slurry raised above the circulation openings cement rations (see USSR author's certificate No. 1578314, IPC E21B 33/14, published on July 15, 1990).

The known method does not exclude the possibility of annular gas and oil occurrences during thickening and setting of grouting grout, since as the column increases the volume and height of the column of process water during the flushing of grout from the well, the hydrostatic pressure of this column on the reservoir decreases in the interval of the first cementing stage. In this case, if the reservoir pressure exceeds the threshold pressure in the column of the grout, the flow of formation fluids into the well begins with the formation and development of transfer channels in the column of grout. In addition, during the subsequent transition from process water to the drilling fluid (in order to prevent a further decrease in hydrostatic pressure on the cement slurry column of the first stage), the begun processes of flow of formation fluids into the well continue, because of the formation of an impermeable bridge between the columns of the drilling and grouting mud and hanging of the latter on the walls of the well and casing, the increase in hydrostatic pressure is not transmitted from top to bottom along the column beginning to thicken and set grouting mortar.

The closest in technical essence to the proposed method is a method of stepwise cementing of wells, including pumping cement slurry of the first stage into the casing and forcing it into the well through the shoe of the column, opening the side cementing holes in the column and washing out an excess portion of the grout from the well and pumping it into the annulus through the side cementing holes, first of technical water in a volume greater than half the volume of its mixture with grouting, and then drilling mud, cementing the second stage and closing the side cement holes, and after pumping technical water into the annulus, the fluid flow at the outlet of the well is throttled, and after the excess portion of the grout is washed out, an additional portion of technical water is pumped into the annulus through the side cement holes a volume exceeding half the volume of its mixture with drilling fluid in the annulus, while at the beginning of the injection of additional pores With process water, the throttling of the fluid flow at the wellhead is temporarily stopped until the pressure at the wellhead completely drops, and after the additional portion of process water has been pumped, the annulus at the wellhead is sealed, excessive pressure is created in the column by pumping it from the wellhead and maintain this pressure until the end of the cementing a solution of the first stage (RF patent No. 2038462, IPC E21B 33/13, publ. June 27, 1995).

The known method provides for the prevention of annular gas and oil manifestations during the thickening and setting of the cement slurry of the first stage. The disadvantage of the method (regardless of the number of stages) is the need to maintain excess pressure until the end of the setting period of the cement slurry of the first stage, which negatively affects the quality of the cement stone and its contact with the casing. In addition, if this pressure exceeds the hydraulic fracturing pressure, there is a high probability of destruction of the integrity of the productive formation, its absorption of part of the cement slurry from the annulus and thereby the deterioration of the reservoir properties of the formation itself. The description of the known method does not mention the closing of the side cementing windows and cementing of the second stage. Thus, everything described there applies only to the first stage, and the possibility of using the invention in the second, third, etc. cementing steps not disclosed.

A device for stepwise cementing of a well is known, comprising a housing with lateral cementing holes, a housing located outside the housing and forming a cavity with the latter, a valve assembly including a seat with a tapered abutment surface, and a locking element, upper and lower cork plugs, including a shaft and an elastic sleeve (RF patent No. 2029066, IPC E21B 33/13, publ. July 15, 1995).

The disadvantages of the device are:

- large dimensions, due to the fact that the valve assembly is located inside the cavity between the housing and the casing;

- small conditional passage for cement mortar through the device;

- the device consists of several sections, and the failure of one of them will lead to the failure of the entire device;

- the locking element of the valve assembly is made of an elastically deformable material, which leads to difficulties in controlling it, a large dependence on the temperature in the installation zone of the device and does not provide proper sealing of the device after pumping the cement mortar of the second stage.

A device for stepwise cementing of a well is known, comprising a casing with lateral cemented openings, a casing located outside the casing and forming a cavity with the latter, a valve assembly including a saddle with a conical abutment surface and a locking element, upper and lower cork plugs, including a rod and an elastic sleeve, moreover, the cavity between the housing and the casing is formed around their entire perimeter, and the locking element of the valve assembly is made in the form of a sleeve telescopically interconnected with the housing to those located around the perimeter of the body and resting against the upper ends in the springs, and the latter at an emphasis mounted rigidly on the body, the lower ends of the bushings are made conical under the saddle, while the device is equipped with an additional valve in the form of an annular sleeve located between the casing and the housing, and a movable sleeve mounted inside the housing, said valve and sleeve being located above the cementing holes and connected to the housing by shear elements (RF patent No. 2223389, IPC E21B 33/14, publ. 02/10/2004).

The proposed device provides high throughput during the injection of cement mortar of the second stage and high reliability due to the use of a valve assembly with a double spring-loaded annular locking element. This achieves a very high degree of sealing of the device. The disadvantage of the device in its complexity of manufacture and increased in comparison with analogues dimensions in diameter (wall thickness). A double degree of protection requires space to accommodate parts. If you reduce the inner diameter of the product, then the technical characteristics deteriorate during operation. If you increase the outer diameter, the technical characteristics deteriorate during the descent into the well and cementing.

The closest in technical essence to the proposed tool kit is a tool for two-stage cementing of a well using inert fluids and solutions, containing a cementing sleeve with a set of plugs for it, consisting of lower and upper plugs and a bomb plug (see USSR author's certificate No. 1578314, IPC E21B 33/14, published July 15, 1990 - prototype).

A disadvantage of the known equipment is the difficulty of using inert fluids and solutions for cementing only two stages in oil and gas wells, which is insufficient in practical cases to prevent annular gas and oil occurrences of weak formations.

The technical result of the invention of the method consists in three-stage cementing with simple and quick prevention of casing gas and oil manifestations of weak formations.

The technical result of the invention of the tool kit is high operational reliability and ensuring guaranteed success of the cement grout injection operation at three cementing stages to prevent annular gas and oil manifestations.

The technical result of the invention of the method is achieved by the fact that in the method of multi-stage cementing of wells, performed using a tool kit having a first cementing sleeve and a set of plugs to it, including the lower and dividing plugs and the stopper-bomb, and including lowering the casing to a predetermined depth with intermediate flushing, pumping the estimated volume of cement mortar of the first cementing stage, starting the bottom plug, pushing the bottom plug before landing in the “Stop pipe” of the casing , launching the first stopper-bomb, made with the possibility of free fall, before landing in the lower saddle of the lower cement clutch, creating excess pressure in the pipe space to a predetermined value to open the technological windows of the lower cement clutch, cutting off excess cement mortar of the first stage and pausing while setting cement mortar of the first stage, injection of the estimated volume of cement mortar of the second cementing stage, starting the separation plug, pushing the separation plug before landing in the upper seat of the first cementing sleeve, creating excess pressure in the pipe space to a predetermined value to close the cementing windows of the first cementing sleeve, the third cementing stage has been introduced, for which the tool kit has been supplemented with an upper cementing sleeve and a set of plugs for it, including a second bomb bomb for landing in the lower saddle of the specified clutch and the upper plug, while after closing the cementing windows of the first cementing clutch, the second plug-bomb is launched to e landing in the lower saddle of the second cementing sleeve, create excess pressure in the pipe space to a predetermined value to open the cementing windows of the second cementing sleeve, cut off excess cement of the second stage and pause while setting cement for the second stage, then pump the calculated volume of cement of the third stage, the upper plug is launched and squeezed before landing in the upper saddle of the second cementing sleeve, create in the tube space There is excess pressure to a predetermined value to close the cementing windows of the second cementing clutch and pause while waiting for the cement of the third stage to set.

Preferably, the second cementing sleeve is formed with a channel allowing free fall of the lower tube, the first bomb tube and the separation tube in it.

It is advisable to install the first and second cementing couplings in the casing at a distance corresponding to the distance between the anomalous zones identified before cementing in the formation.

The technical result of the invention of the tool kit is achieved by the fact that the tool kit for multi-stage cementing of wells, comprising a first cementing sleeve with a set of plugs to it, consisting of a bottom plug, a first bomb plug and a separation plug, made with the possibility of cementing the casing in the well at the first and the second steps, an additional cementing sleeve has been introduced with a set of plugs to it, consisting of a second bomb plug and an upper plug made with cement casing in the well in the third stage, and the second cementing sleeve has a channel for free fall in it of the lower tube, the first bomb tube and the separation tube.

It is advisable to make the diameter of the passage channel of the second cementing sleeve larger than the diameter of the passage channel of the first cementing sleeve.

It is advisable to perform the maximum outer diameter of the first tube-bomb is less than the maximum outer diameter of the second tube-bomb.

When conducting patent research, no solutions were found that are identical to the declared one, therefore, the proposed solution meets the criterion of "novelty." The invention does not follow explicitly from the known solutions, therefore, the proposed invention meets the criterion of "inventive step".

In FIG. 1 shows a casing with the first and second cementing sleeves (in the initial position).

In FIG. 2 shows the casing after completion of cementing of the first stage (lower plug in the saddle of the stop pipe).

In FIG. Figure 3 shows the casing after landing the first cork bomb and opening the cementing windows of the first coupling.

In FIG. 4 shows the casing after completion of cementing of the second stage and closing of the cementing windows of the first (lower) cementing sleeve.

In FIG. 5 shows the casing after landing the second cork bomb and opening the cementing windows of the second coupling.

In FIG. 6 shows the casing after completion of cementing of the third stage and closing of the cementing windows of the second (upper) cementing sleeve.

In FIG. 7 shows a first (lower) cementing sleeve.

In FIG. 8 shows the first cork bomb.

In FIG. 9 shows a second (upper) cementing sleeve.

In FIG. 10 shows a second cork bomb.

In FIG. 1-6 the following notation is accepted:

1 - first (lower) cementing sleeve;

2 - second (upper) cementing sleeve;

3 - bottom plug;

4 - the first tube bomb;

5 - a separating stopper;

6 - second cork bomb;

7 - upper tube;

8 - cementing windows in the first cementing sleeve 1;

9 - cementing windows in the second cementing sleeve 1;

10 - casing string;

11 - shoe;

12 - valve reverse action (TsKOD);

13 - stop pipe;

14 - drilling fluid (flushing fluid);

15 - cement mortar;

16 - annulus;

D ₁ - the diameter of the passage channel of the first cementing sleeve;

D ₂ - the diameter of the passage channel of the second cementing coupling;

d ₁ - the maximum outer diameter of the first tube-bomb;

d ₂ - the maximum outer diameter of the second tube-bomb.

To implement the proposed method of multi-stage cementing of wells, a tool kit is used, including the first and second cementing couplings 1, 2 (Fig. 1) with the corresponding sets of plugs to them. The set of plugs of the first cementing sleeve 1 consists of a bottom plug 3, a first plug bomb 4 and a separation plug 5 (Fig. 4), which are capable of cementing the casing in the well in the first and second stages. The set of plugs of the second cementing sleeve 2 consists of a second plug-bomb 6 and the upper plug 7 (Fig. 6), made with the possibility of cementing the casing in the well in the third stage. The second cementing sleeve 2 has a channel for free fall in it of the lower plug 3, the first bomb plug 4 and the separation plug 5. In this case, the diameter D _{2 of the} passage channel of the second cement coupling 2 is larger than the diameter D _{1 of the} passage channel of the first cement coupling 1, and the maximum outer the diameter d _{1 of the} first tube-bomb 4 is less than the maximum outer diameter of the second tube-bomb 6. The first and second cementing couplings 1, 2 are made with the corresponding cementing holes 8, 9.

The method of multi-stage cementing of a well, for example in three stages, is as follows. On the shoe 11 is mounted a valve 12 reverse action (for example, CKOD) with a stop pipe 13, the first (lower) and second (upper) cementing couplings 1, 2 (Fig. 1). Depending on the geological conditions, between the stop pipe 13 and the first (lower) cementing sleeve 1, between the first (lower) and second (upper) cementing sleeves 1, 2, as well as above the second (upper) cementing sleeve 2, one or more casing is mounted pipes (if necessary). The images in FIG. 2-6 illustrate a three-stage casing cementing scheme.

At the first stage of cementing, the following actions are performed:

- make the descent of the assembly according to standard technology to a predetermined depth with intermediate washes (Fig. 1);

- pump the estimated volume of cement (grouting) mortar of the first stage and start the lower plug 2 (Fig. 2) from the tool kit and push it before landing in the stop pipe 13;

- start the first tube-bomb 3, which under its own weight falls before landing in the lower saddle of the first cementing sleeve 1 (Fig. 3);

- create excess pressure in the pipe space to a predetermined value, while opening the technological windows 8 of the first cementing sleeve 1 and cutting off the excess cement mortar of the first stage;

- make a pause in anticipation of setting the cement mortar of the first stage.

At the second stage of cementing, the following actions are performed:

- inject the estimated volume of cement (grouting) mortar of the second stage and start the separation plug 5 from the set of the first cementing sleeve 1 and pushing it before landing in the upper saddle of the first cementing sleeve 1;

- create in the pipe space excess pressure to a predetermined value, while closing the technological windows 8 of the first cementing sleeve 1 (Fig. 4);

- start the second plug-bomb 6 from the set of plugs of the second cementing sleeve 2, which under its own weight falls before landing in the lower saddle of the second cementing sleeve 2;

- create excess pressure in the pipe space to a predetermined value, at which the cementing windows 9 of the second cementing sleeve 2 open, and cut off the excess cement mortar of the second stage (Fig. 5);

- pause while waiting for the setting of the cement of the second stage.

At the third stage of cementing, the following actions are performed;

- pumping the estimated volume of cement (grouting) mortar of the third stage and start the upper plug 7 from the set of plugs of the second cementing sleeve 2 and pushing it before landing in the upper saddle of the second cementing sleeve 2;

- create in the pipe space an excess pressure to a predetermined value at which the cementing windows 9 of the second cementing sleeve 2 are closed (Fig. 6);

- pause while waiting for the setting of the cement mortar of the third stage.

The proposed tool kit has a small range of the same type of couplings and plugs, different only in the dimensions of the passage channels of these couplings and the maximum outer diameters of the first and second bomb plugs. The three-stage cementing method and tooling kit are simple for operational cementing of complex wells.

Claims (5)

1. A method of multi-stage cementing of wells, characterized in that the casing is equipped with the first and second cementing couplings, which are installed from each other at a distance corresponding to the distance between the anomalous zones of the well, the casing is lowered to a predetermined depth with intermediate flushing, the calculated volume is pumped cement mortar of the first stage of cementing, start the lower tube, push the lower tube until it fits into the stop pipe of the casing, start The first stopper-bomb, made with the possibility of free fall before landing in the lower saddle of the first cementing sleeve, creates excess pressure in the tube space to a predetermined value to open the cementing windows of the first cementing sleeve, cut off the excess cement mortar of the first stage and hold for a while waiting for the cement mortar to set the first stage, the calculated volume of the cement mortar of the second cementing stage is pumped in, the separation tube is launched, the separation tube is forced through about landing in the upper seat of the first cementing sleeve, create overpressure in the pipe space to a predetermined value to close the cementing windows of the first cementing sleeve, launch a second bomb tube until it fits into the lower seat of the second cementing sleeve, create overpressure in the pipe space up to a predetermined value to open the cementing windows of the second cementing sleeve, cut off the excess cement mortar of the second stage and pause while waiting for the cement mortar to set in of the second stage, then the calculated volume of the cement mortar of the third stage is injected, the upper plug is launched and squeezed to fit the second cement sleeve into the upper seat, create excess pressure in the pipe space to a predetermined value to close the cement windows of the second cement sleeve and pause while waiting setting the cement of the third stage. 2. The method according to p. 1, characterized in that the second cementing sleeve is performed with a channel that allows free fall of the lower tube, the first bomb tube and the separation tube in it. 3. A tool kit for multi-stage cementing of wells, including a casing stop pipe, a lower stop pipe for a stop pipe, a first cementing sleeve with lower and upper saddles, with a set of corks for it, consisting of a first bomb cork and a separation cork made with the possibility of cementing the casing in the well at the first and second stages with closing the cementing windows of the first cementing sleeve, the second cementing sleeve with lower and upper saddles, made with a channel to ensure the possibility of free fall in it of the lower plug, the first bomb plug and the separation plug and having a set of plugs from the second bomb plug and the upper plug, made with the possibility of cementing the casing in the well in the third stage with closing the cementing windows of the second cementing sleeve, the first and second cement couplings are installed from each other at a distance corresponding to the distance between the anomalous zones of the well.  4. The kit according to claim 3, characterized in that the diameter of the passage channel of the second cementing sleeve is larger than the diameter of the passage channel of the first cementing coupling. 5. The kit according to p. 3, characterized in that the maximum outer diameter of the first tube-bomb is less than the maximum outer diameter of the second tube-bomb.

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