CN114109297A

CN114109297A - Stage cementing method

Info

Publication number: CN114109297A
Application number: CN202010860357.2A
Authority: CN
Inventors: 秦金立; 郭朝辉; 陈武君; 刘阳; 刘明; 秦德威; 杨德锴; 梁晓阳; 刘奔; 敖竹青
Original assignee: China Petroleum and Chemical Corp; Sinopec Research Institute of Petroleum Engineering
Current assignee: China Petroleum and Chemical Corp; Sinopec Research Institute of Petroleum Engineering
Priority date: 2020-08-25
Filing date: 2020-08-25
Publication date: 2022-03-01
Anticipated expiration: 2040-08-25
Also published as: CN114109297B

Abstract

A staged cementing method, comprising: a step of running a pipe column, wherein the pipe column comprises a pipe string, a packing type stage cementing device, a first-stage bumping short section, a float collar and a float shoe; a first stage of cementing step, wherein first cement slurry is injected, a flexible plug is put in, first drilling fluid is injected, then a displacement type opening plug is put in, and expansion fluid and second drilling fluid are injected, so that the expansion fluid enters a rubber cylinder of the packing type stage cementing device to cause the rubber cylinder to expand; a second stage cementing step to finish stage cementing; and an accessory drilling step.

Description

Stage cementing method

Technical Field

The invention relates to a petroleum well cementation technology, in particular to a graded cementing method.

Background

The well cementation technology is an important technical link in the well drilling and completion process. The quality of well cementation directly affects the subsequent oil and gas exploitation operation.

The stage cementing process is a common process in well cementing technology. With the continuous deepening of exploration and development, the number of ultra-deep wells is increased, and a part of wells have serious leakage in the drilling process. In order to reduce the loss in the well cementation process and improve the well cementation quality, more and more ultra-deep lost wells adopt a packing and grading cementing method. Generally, a gravity type opening plug is put in immediately after completion of first-stage cementing. After a period of time (typically 60-100 minutes), the gravity-type opening plug activates the priming channel of the packing unit. At the moment, the drilling fluid is injected and flows into the packing rubber cylinder through the fluid injection channel, so that the expansion sealing of the packing type stage cementing device is realized.

However, in this method, a leak-off condition in the annulus cannot be avoided during the period of time not short for waiting for the gravity-type opening plug to be in place. In addition, the expanding sealing fluid of the packing type stage cementing device usually adopts non-strength drilling fluid, which causes the drilling fluid in the packing type stage cementing device rubber barrel to be in a squeezing state all the time due to non-strength. Therefore, there is a problem that the drilling fluid leaks or bursts the packing element to cause the sealing failure.

Therefore, the current staged cementing and cementing process is difficult to meet the requirements of modern cementing.

Disclosure of Invention

In order to solve the problems, the invention provides a graded cementing method.

According to a first aspect of the present invention, a staged cementing method is provided. The stage cementing method according to the invention comprises the following steps:

a step of running a pipe column, wherein the pipe column comprises a casing string, a packing type stage cementing device, a first-stage impact pressure short section, a float collar and a float shoe; a first stage of cementing step, wherein first cement slurry is injected, a flexible plug is put in, first drilling fluid is injected, then a displacement type opening plug is put in, and expansion fluid and second drilling fluid are injected, so that the expansion fluid enters a rubber cylinder of the packing type stage cementing device to cause the rubber cylinder to expand; a second stage cementing step to finish stage cementing; and an accessory drilling step.

In one embodiment, the volume of the first cement slurry is the volume from the packer stage grouter to the float shoe in the annulus.

In one embodiment, the volume of the first drilling fluid is selected to be slightly less than the volume within the string from the packer stage cementing to a primary bump-in sub.

In one embodiment, the rubber cylinder is filled with an accelerator, and the accelerator can be mixed with the expansion liquid to be solidified.

In one embodiment, the amount of inflation fluid is 2-3 times the amount required to inflate the cartridge.

In one embodiment, the volume of the second drilling fluid is equal to the volume from the encapsulated stage cementing to the wellhead within the tubular string.

In one embodiment, in the primary cementing step, the construction displacement is reduced as the flexible plug and the displacement type opening plug pass through the respective plug seats.

In one embodiment, in the secondary cementing step, a second cement slurry is injected, a shutoff plug is placed, and then a third drilling fluid is injected.

In one embodiment, the volume of the second cement slurry is the volume from the encapsulated stage injector to the wellhead within the annulus.

In one embodiment, between the primary cementing step and the secondary cementing step, a secondary injection passage is opened to establish communication with the annulus to circulate excess expansion fluid.

In one embodiment, the first, second, and third drilling fluids are the same drilling fluid.

The staged cementing method is suitable for both wells needing primary cementing and horizontal wells without primary cementing. For a well needing primary cementing, after a pipe column is put in place and internal and external circulation of the pipe column is established, certain drilling fluid with volume less than that of a packing grading lower casing is injected, a displacement type opening plug is put in, and expansion fluid and the drilling fluid are injected, so that a primary injection channel of the packing grading cementing device is activated while primary slurry replacing operation is completed, and the expansion fluid enters a rubber barrel of the packing grading cementing device through the primary injection channel to cause expansion sealing of the packing grading cementing device. Therefore, the staged cementing method has the advantage of quick time effect, avoids the problem of annular leakage in the process of waiting for the falling of the gravity type opening plug, improves the purity of the expansion liquid in the rubber cylinder, and ensures the curing strength of the liquid in the rubber cylinder. And for a horizontal well without primary cementing, the problem that a gravity type opening plug cannot be in place is avoided. After the pipe column is in place, the displacement type opening plug can be directly put into the pipe column, and expansion liquid and drilling fluid are injected into the pipe column, so that the inflation of the sealed type grading cementing device is realized, and the working efficiency and the curing strength of the inflation sealing liquid in the rubber sleeve are improved.

Drawings

The invention will be explained in more detail below with reference to the drawings and by means of exemplary embodiments which are schematic. In the figure:

FIG. 1 shows the overall structure of a staged cementing string for use in the method according to the present invention;

FIG. 2 shows a state diagram of a primary cementing operation according to the method of the present invention;

FIG. 3 shows a state diagram of a secondary cementing operation according to the method of the present invention;

FIG. 4 shows a flexible plug for use in the method according to the invention;

figure 5 shows a displacement type opening plug for use in the method according to the invention; and

fig. 6 shows a closing plug for use in the method according to the invention.

In the drawings, like parts are provided with like reference numerals. The figures are not drawn to scale.

Detailed Description

The invention will be further described with reference to the accompanying drawings. In the following, directional terms "lower," "downstream," "downward," etc. refer to a direction away from the wellhead, while "upper," "upstream," "upward," etc. refer to a direction toward the wellhead.

Fig. 1 shows a schematic construction of a stage cementing string 100 for use in the stage cementing method according to the present invention. The staged cementing string 100 is a packing staged cementing string in which a swelling sealer is curable, and is in an initial state after being run into a well. As shown in fig. 1, the pipe string 100 includes a casing string 10, a packing stage cementing unit 20, a primary bump sub 70, a float collar 80, and a float shoe 90, which are connected to each other by threads. The tubing string 100 is run into the design location in the well. After circulation is established between the inside and outside of the pipe string 100, a first stage cementing operation can be started. The encapsulated stage cementing injector 20 includes a cement cartridge (not shown) that may be expanded after the injection of a fluid to act as an annulus seal. The construction of such a packer stage cementing apparatus is well known in the art.

In addition, the casing string 10, the primary stabbing nipple 70, the float collar 80 and the float shoe 90 used herein are common components in the art, and establishing circulation between the inside and outside of the pipe string 100 is also well known in the art, so detailed description thereof will be omitted herein.

As shown in fig. 2, in the step of the primary cementing operation, a first cement slurry 30 is first injected. In one embodiment, the amount of the first cement slurry 30 may be selected as the volume of the portion of the annulus from the packer stage grouter 20 to the float shoe 90. Thereafter, a flexible plug 62 for primary slurry replacement is placed and the first drilling fluid 32 is injected. After the first drilling fluid 32 is injected, a displacement type opening plug 65 is plunged, the expansion fluid 35 is injected, and then the second drilling fluid 38 is injected. The flexible plug 62 and the displacement type opening plug 65 are shown in detail in fig. 4 and 5, respectively, and their structure and function are well known in the art.

The applicant has found in tests that it should be ensured that the displacement type opening plug 65 is in place before the flexible plug 62 is in place and is in compression during the steps of the primary cementing operation. This is because the displacement type opening plug 65 may not be in place if the flexible plug 62 is first bumped. Thus, the injection volume of the first drilling fluid 32 should be selected to be slightly less than the volume within the pipe string 100 from the stage cementing unit 20 to the primary bump-in sub 70. In the context of the present invention, the term "slightly smaller" is to be understood as being 0.1-0.5 square smaller, preferably 0.2 square smaller. By selecting the amount of first drilling fluid 32 to be slightly less than the volume from the packing cementing stage 20 to the primary bump-on nipple 70 within the pipe string 100, a first-in-place bump-on of the displacement type opening plug 65 can be assured.

After the displacement opening plug 65 is in place, a packer injection passage (not shown) within the packing stage cementing unit 20 is opened so that inflation fluid 35 can enter the cement barrel of the packing stage cementing unit 20 through the packer injection passage.

The expansion liquid 35 is used for injecting into the rubber cylinder of the packing type stage cementing device 20, so that the rubber cylinder is expanded to realize annular expansion seal. The expansion liquid is, for example, a part of the displacement liquid, and is preferably a liquid epoxy resin. As a preferred embodiment, an accelerator (not shown) is pre-filled in the rubber cylinder of the packing stage cementing unit 20 according to the present invention. The accelerator is a liquid that can be uniformly mixed with the expansion fluid and cured. In this way, the accelerator contained in the rubber sleeve is uniformly and rapidly diffused into the expansion liquid in the process of inflating the rubber sleeve of the sealed stage cementing unit 20 with the expansion liquid 35. Under the action of the accelerator, the liquid in the rubber cylinder can be solidified within 4-8 hours, and the liquid is slightly expanded and does not shrink after being solidified. Thereby, a good packing effect of the packing type stage cementing unit 20 is achieved.

In a preferred embodiment, the packer stage cementing apparatus 20 may be a packer as described in the applicant's prior Chinese patent application CN202010596606.1 (entitled "stage cementing apparatus" filed on even 6/28/2020). The entire contents of this application are incorporated herein by reference.

In a preferred embodiment, the amount of expansion fluid 35 is 2-3 times the amount of fluid required to inflate the packeted stage cementing unit 20. By selecting the amount of the expansion liquid 35 in this way, it is possible to ensure that there is sufficient uniform mixing of the expansion liquid 35 with the pre-set accelerator, so that curing takes place and micro-expansion is achieved.

In accordance with the present invention, the expansion fluid 35 is isolated from other fluids downhole by first using the flexible plug 62 and injecting the first drilling fluid 32, and then using the displacement type opening plug 65 and injecting the expansion fluid 35. In this case, the expansion fluid 35 does not mix with other fluids downhole, and thus can enter the cement barrel at a very high purity, mix with the accelerator in the cement barrel, and cure. Through the mode, the purity of the expansion liquid in the rubber cylinder is improved, the curing strength of the liquid in the rubber cylinder is ensured, and a good sealing effect is realized.

In addition, according to the present invention, the displacement type opening plug 65 is used instead of the gravity type opening plug of the related art, thereby avoiding the problem of annulus loss while waiting for the gravity type opening plug to fall. At the same time, the problems associated with the inability of gravity-type opening plugs to be properly positioned are naturally eliminated.

In accordance with the present invention, the amount of the second drilling fluid 38 may be selected as the volume within the tubular string 100 from the packer stage cementing 20 to the wellhead.

According to the method of the present invention, in the step of the primary cementing operation, the flexible plug 62 and the displacement type opening plug 65 reduce the construction displacement while passing through the plug seat or the like where the diameter is reduced. By this arrangement, it is ensured that both the flexible plug 62 and the displacement type opening plug 65 smoothly pass through the plug seat and smoothly collide and press. Specifically, in the process of replacing cement paste at the first stage, the recommended construction displacement is 1.5-2 m³And/min. The flexible plug 62 to be replaced is injected in a sealed and separated modeThe discharge capacity is reduced to 0.5 to 1m, for example, in the case of the cement machine 20³And/min. The displacement is reduced again, for example to 0.1-0.2 m, until the displacement type opening plug 65 reaches the packing type stage cementing device 12³And/min. At this time, the pressure change is observed, and a pressure fluctuation exists at the position of 6-8MPa, which indicates that the packer liquid injection channel of the packing type graded cementing device is opened. Thereafter, the thickness is 0.1 to 0.2m³The displacement of/min is pumped into the expansion fluid, so that the expansion fluid flows into a rubber barrel of the packing type stage cementing device 20 through a packer fluid injection channel. At the moment, the pressure of a well head is not more than 10MPa, and the pressure is stabilized for 5-10min, so that the expansion liquid fully expands the rubber cylinder of the sealed type stage cementing device, the rubber cylinder is attached to the well wall, and the annular space is isolated from top to bottom. By the mode, the static liquid column pressure of the upper liquid column to the leakage well can be cut off, and the leakage of the primary cement slurry is reduced.

After the step of primary cementing, the pressure build-up is continued, e.g. to 12-16MPa, thereby opening a secondary injection channel (not shown). After the secondary injection passage is opened, communication is established between the interior of the tubular string and the annulus. This allows excess expansion liquid 35 to be circulated. It will be readily appreciated that the construction of the secondary liquid injection channel and the manner of opening it may be performed by means well known to those skilled in the art.

And then performing secondary cementing operation. As shown in fig. 3, in the step of the secondary cementing operation, a second cement slurry 40 is first injected. The amount of this second cement slurry 40 is, for example, the volume in the annulus from the packer stage grouter 20 to the wellhead. Thereafter, a shutoff plug 68 (shown in fig. 6) is inserted to isolate the second cement slurry 40 from the drilling fluid to be injected thereafter. A third drilling fluid 42 is then injected. The discharge capacity is reduced to 0.1-0.2 m before the slurry is replaced and the closing plug 68 reaches the sealed stage cementing device 12³And/min. Observing the pressure change of the wellhead, adding 6-10MPa and stabilizing the pressure for 3-5min on the basis of later slurry replacement, returning water, and observing the water returning condition. If no backwater exists, the secondary liquid injection channel is closed. If backwater exists, the liquid injection and pressurization can be continued, the pressure is stabilized for 5-10min, and the secondary liquid injection channel is ensured to be closed. And then waiting to set, and finishing the graded well cementation operation. The secondary cementing operation isAs is well known to those skilled in the art, it will not be described in detail herein.

In one embodiment, the first, second, and

third drilling fluids

32, 38, 42 may be the same drilling fluid.

In the secondary cementing operation, the expansion liquid is continuously mixed and solidified with the accelerator in the rubber cylinder and finally integrated with the rubber cylinder. Through this kind of mode, strengthened packing ability, reduced packing rubber barrel's extrusion deformation, avoided the outer problem that leaks of inflation liquid.

After the secondary cementing operation, an attachment drilling operation may be performed. In this context, accessories refer to the flexible plug 62, the displacement type opening plug 65, the closing plug 68, and the associated plug seat, among others. In the accessory drilling and removing operation, after the graded cementing, when the annular cement joint strength meets the requirement, a roller bit or a PDC bit is put in so as to drill and remove the accessory. The above-described accessory drilling operation is well known to those skilled in the art and will not be described in detail herein.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In particular, the features mentioned in the embodiments can be combined in any way, without structural conflict. It is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A staged cementing method, comprising:

a step of running a pipe column, wherein the pipe column comprises a casing string, a packing type stage cementing device, a first-stage impact pressure short section, a floating hoop and a floating shoe;

a first stage of cementing step, wherein first cement slurry is injected, a flexible plug is put in, first drilling fluid is injected, then a displacement type opening plug is put in, and expansion fluid and second drilling fluid are injected, so that the expansion fluid enters a rubber cylinder of the packing type stage cementing device to cause the rubber cylinder to expand;

a second stage cementing step to finish stage cementing; and

and (5) drilling and removing the accessory.

2. The stage cementing method according to claim 1, wherein the volume of the first cement slurry is the volume from the packeted stage cementing device to the float shoe within the annulus.

3. The stage cementing method of claim 2, wherein the volume of the first drilling fluid is selected to be slightly less than the volume within the string from the encapsulated stage cementing unit to a primary bump-in sub.

4. The stage cementing method according to any one of claims 1 to 3, wherein an accelerator is filled in the rubber cylinder, and the accelerator can be mixed with the expansion fluid to be cured.

5. The stage cementing method according to claim 4, characterized in that the amount of the expansion fluid is 2-3 times the amount required to inflate the cement mortar.

6. The stage cementing method according to any one of claims 1 to 5, characterized in that the volume of the second drilling fluid is equal to the volume inside the string from the packer stage cementing device to the wellhead.

7. The stage cementing method according to any one of claims 1 to 6, wherein, in the primary cementing step, construction displacement is reduced as the flexible plug and the displacement-type opening plug pass through the respective plug seats.

8. The stage cementing method according to any one of claims 1 to 7, characterized in that, in the secondary cementing step, a second cement slurry is injected, a closing plug is thrown in, and then a third drilling fluid is injected.

9. The stage cementing method according to any one of claims 1 to 8, characterized in that the volume of the second cement slurry is the volume from the packeted stage cementing device to the wellhead within the annulus.

10. The stage cementing method according to any one of claims 1 to 9, wherein between the primary cementing step and the secondary cementing step, a secondary injection passage is opened to establish communication with the annulus, thereby circulating excess expansion fluid.