CN109138906B - Testing device and method for simulating comprehensive performance of underground well cementing cement sheath - Google Patents

Abstract

The invention provides a testing device and a method for simulating comprehensive performance of an underground well cementing cement sheath, wherein the testing device comprises the following components: the inner tube is provided with a closed inner cavity, two ends of the inner tube are connected in a sealing way through connecting plates, and the closed inner cavity is filled with pressure medium; the outer tube is sleeved outside the inner tube, an annular cavity is formed between the outer tube and the inner tube, two ends of the outer tube can be respectively connected with a first outer blind plug and a second outer blind plug, and a pressure testing connector capable of injecting pressure liquid into the outer tube is connected to the first outer blind plug; wherein, the annular cavity is filled with a well cementation cement ring. The invention can test the cementing capacity of cement rings in different cement slurry systems and different annular gaps, and can conveniently and accurately measure the cementing performance of the cementing cement slurry of the oil-gas well.

Description

Testing device and method for simulating the comprehensive performance of underground cement sheath

Technical field

The invention relates to the field of oil and gas well drilling and completion, and in particular to a testing device and method for simulating the comprehensive performance of downhole cement sheaths.

Background technique

With the continuous discovery and development of oil and gas resources, the current oil and gas exploration and development areas have gradually shifted from land to shallow seas and deep seas, from conventional wells with normal temperature and pressure conditions to high-temperature and high-pressure wells and even ultra-high-temperature and ultra-high-pressure wells. For offshore drilling with extremely high daily operating costs and high-temperature and high-pressure wells with extremely high difficulty, technical requirements, and operating costs, especially offshore high-temperature and high-pressure wells, every aspect of the operation will affect the operation timeliness, success or failure of the entire well. Whether or not it has a very critical impact. For high-temperature and high-pressure wells, since the temperature and pressure conditions of the formation are very harsh, high-quality cementing slurry can ensure qualified well cementing effects and ensure that the cement sheath will not be damaged due to harsh temperature and pressure conditions and lose its ability to downhole. Because of the supporting role of casing and formation, drilling sites, especially high-temperature and high-pressure drilling and completion operations, have extremely stringent requirements for the comprehensive performance of cement slurry. Therefore, it is extremely necessary to develop an economical, convenient and efficient device for testing the cementing properties of different cement slurries under different wellbore conditions. It can also quickly and efficiently screen out cement cement that meets the needs of the site. Pulp.

Contents of the invention

The purpose of the present invention is to provide a testing device and method for simulating the comprehensive performance of underground well cementing cement sheaths. The testing device is simple and intuitive, and can test the cementing ability of cement sheaths in different cement slurry systems and different annulus gaps. The present invention can be very Conveniently and accurately measure the cementing properties of oil and gas well cement slurries.

The above objects of the present invention can be achieved by adopting the following technical solutions:

The invention provides a testing device for simulating the comprehensive performance of underground cement sheaths, including:

The inner tube has a sealed inner cavity, the two ends of the inner tube are sealingly connected through the connecting plate, and the sealed inner cavity is filled with pressure medium;

The outer tube is sleeved on the outside of the inner tube. An annular cavity is formed between the outer tube and the inner tube. The two ends of the outer tube can be connected to a first outer blind plug and a second outer blind plug respectively. Blind plug, the first outer blind plug is connected with a pressure test joint capable of injecting pressure liquid into the outer pipe;

Wherein, the annular cavity is filled with a cement ring.

In an embodiment of the present invention, the first outer blind plug includes a first bottom wall and a first cylinder wall connected to the periphery of the first bottom wall, and the first cylinder wall has a first internal thread section, so The first external blind plug is threadedly connected to one end of the outer pipe through the first internal thread section, and the pressure test joint is provided on the first bottom wall.

In an embodiment of the present invention, a first quick connector is connected to the first cylinder wall, and a first pressure gauge can be connected to the first quick connector.

In an embodiment of the present invention, the second outer blind plug includes a second bottom wall and a second cylinder wall connected to the periphery of the second bottom wall, and the second cylinder wall has a second internal thread section, so The second outer blind plug is threadedly connected to the other end of the outer tube through the second internal thread section.

In an embodiment of the present invention, a second quick connector is connected to the second cylinder wall, and a second pressure gauge can be connected to the second quick connector.

In an embodiment of the present invention, the cement sheath is formed in the annular cavity through an inner blind plug, and the inner blind plug includes:

A stopper, one end of which is provided with a plurality of axial insertion holes along the circumferential direction, and the stopper is located in the first outer blind plug;

A first baffle with a plurality of connecting rods connected in the circumferential direction, the plurality of connecting rods can be inserted into the plurality of axial insertion holes, and the first baffle is located in the annular cavity;

The second baffle is located in the annular cavity, and the cement sheath is sandwiched between the first baffle and the second baffle.

In an embodiment of the present invention, there are four axial insertion holes, and the four axial insertion holes are arranged at one end of the stopper at equal intervals along the circumferential direction of the stopper.

In an embodiment of the present invention, the first baffle and the second baffle have first and second central holes for the inner tube to pass through.

In an embodiment of the present invention, the first central hole is an eccentric hole, and the second central hole is an eccentric hole.

The present invention also provides a testing method for simulating the comprehensive performance of underground well cementing cement sheaths, which adopts the above-mentioned testing device for simulating the comprehensive performance of underground well cementing cement sheaths. The testing method for simulating the comprehensive performance of underground well cementing cement sheaths includes Follow these steps:

Step S1: Measure the distances between the two ends of the cement ring and the two ends of the inner pipe, and mark the initial positions of the two ends of the cement ring on the outer pipe;

Step S2: Inject liquid medium into the outer tube through the pressure test joint on the first outer blind plug;

Step S3: After the pressure test is completed, measure the distance between the two ends of the cement ring and the two ends of the inner pipe again, and mark the two ends of the cement ring after the pressure test is completed on the outer pipe. The actual position of the end, and observe the change of the actual position marked on the outer tube relative to the initial position.

The characteristics and advantages of the testing device and method for simulating the comprehensive performance of underground cement sheaths of the present invention are:

(1) This device can carry out repeated simulation experiments many times, and is convenient for subsequent disassembly, repair and modification;

(2) This device has high testing accuracy and can quickly and accurately screen out cement slurry that meets the requirements on site;

(3) This device has a simple structure, low cost and is easy to use;

(4) This method can simulate different wellbore gaps based on actual site conditions to measure the cementing performance of the cement sheath;

(5) This device can combine the actual conditions on site to simulate the cement bonding performance under the condition of casing eccentricity.

Description of the drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without exerting creative efforts.

Figure 1 is a schematic structural diagram of a testing device for simulating the comprehensive performance of downhole cement sheaths of the present invention.

Figure 2 is a schematic structural diagram of the inner tube of the present invention.

Figure 3 is a schematic structural diagram of the outer tube of the present invention.

Figure 4 is a schematic structural diagram of the cement sheath formed in the annular cavity of the present invention.

Figure 5 is a schematic diagram of the connection structure between the stopper of the inner blind plug and the first baffle according to the present invention.

Figure 6 is a schematic structural diagram of the connection structure between the stopper and the first baffle according to the present invention and the inner tube.

Figure 7 is a schematic structural diagram of the device in Figure 6 cooperating with the outer tube and the first outer blind plug.

Figure 8 is a schematic diagram of the structure of the cement sheath formation and the annular cavity between the outer tube and the inner tube.

Explanation of reference numbers: 1. Inner tube; 11. Closed inner cavity; 12. Connecting plate; 2. Outer tube; 21. Annular cavity; 22. External thread section; 23. External thread section; 3. First external blind Blockage; 31. Pressure test joint; 32. First bottom wall; 33. First cylinder wall; 331. First internal thread section; 34. First quick connector; 35. First pressure gauge; 36. Closed annulus; 4. The second external blind plug; 41. The second bottom wall; 42. The second cylinder wall; 421. The second internal thread section; 43. The second quick connector; 44. The second pressure gauge; 5. Cement ring ; 6. Inner blind plug; 61. Stopper; 611. Axial insertion hole; 62. First baffle; 621. First center hole; 622. Threaded hole; 63. Second baffle; 631. Second center Hole; 64, connecting rod.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

Embodiment 1

As shown in Figure 1, in order to solve the problem of high temperature and high pressure drilling, especially offshore high temperature and high pressure drilling, which requires high cement slurry bonding performance and unclear cement slurry bonding performance, the present invention provides a method for simulating downhole cementing. A testing device for the comprehensive performance of well cement sheaths. The testing device includes an inner tube 1 and an outer tube 2. The inner tube 1 has a sealed inner cavity 11. The two ends of the inner tube 1 are sealingly connected through a connecting plate 12. The sealed The inner cavity 11 is filled with pressure medium; the outer tube 2 is sleeved on the outside of the inner tube 1, and an annular cavity 21 is formed between the outer tube 2 and the inner tube 1. Both sides of the outer tube 2 The ends can be connected to a first outer blind plug 3 and a second outer blind plug 4 respectively, and the first outer blind plug 3 is connected to a pressure test joint 31 that can inject pressure liquid into the outer tube 2; wherein, in The annular cavity 21 is filled with cement sheath 5 .

Specifically, as shown in Figure 2, the inner pipe 1 is a cylindrical steel pipe with a smooth outer wall. Its materials and dimensions are selected with reference to the casing sizes and materials commonly used in actual field operations. Both end faces of the inner pipe 1 are made of the same material. The connecting plate 12 made of the same steel pipe material is closed. In this embodiment, the connecting plate 12 is a circular plate, so that the inner tube 1 forms a cylinder with a sealed inner cavity 11 inside. In the present invention, the sealed inner cavity 11 of the inner tube 1 is filled with a pressure medium of a certain pressure. The pressure medium can be water, for example. Of course, other safe and non-polluting fluids such as air can also be used to ensure that the subsequent During the pressure test operation, the inner tube 1 will not be deformed under the action of external force, which will affect the test results and lead to inaccurate test data.

As shown in Figure 3, the outer tube 2 is made of the same material as the inner tube 1. It is in the shape of a cylindrical tube with both ends open. Both ends of the outer tube 2 are machined with external thread sections 22 and 23. The outer tube 2 It is sleeved on the outside of the inner tube 1, and an annular cavity 21 is formed between them. In the present invention, the wall thickness of the outer tube 2 can be selected according to experimental needs. By replacing the outer tube 2 with a thicker wall thickness and the same outer diameter, the annular cavity 21 formed between the outer tube 2 and the inner tube 1 can be made The volume is smaller, and accordingly, the thickness of the cement ring 5 filled between the outer pipe 2 and the inner pipe 1 is also smaller, so that the cement slurry to be tested can be simulated under the gap conditions of different annular cavities 21 cementing properties.

The two ends of the outer tube 2 are respectively connected to the first outer blind plug 3 and the second outer blind plug 4. The outer diameter of the outer tube 2 is slightly smaller than the outer diameters of the first outer blind plug 3 and the second outer blind plug 4. In the present invention, please refer to FIG. 1 . The first outer blind plug 3 includes a first bottom wall 32 and a first cylinder wall 33 connected to the periphery of the first bottom wall 32 . The first cylinder wall 33 has a third An internal thread section 331. The first external blind plug 3 is threadedly connected to one end of the outer pipe 2 through the first internal thread section 331. For example, the first external blind plug 3 is threadedly connected to one end of the outer pipe 2 through the first internal thread section 331. On the external thread section 22; the pressure test joint 31 is provided on the first bottom wall 32. In this embodiment, the height of the pressure test joint 31 is the same as the thickness of the first bottom wall 32. Further, a first quick connector 34 is connected to the first cylinder wall 33. The first quick connector 34 is provided on the first cylinder wall 33 between the end of the first internal thread section 331 and the first bottom wall 32. The first quick connector 34 is interconnected with the inside of the first outer blind plug 3 , and the first pressure gauge 35 can be connected to the first quick connector 34 so that the first pressure gauge 35 can monitor pressure changes in the corresponding sealed area.

In the present invention, the second outer blind plug 4 includes a second bottom wall 41 and a second cylinder wall 42 connected to the periphery of the second bottom wall 41. The second cylinder wall 42 has a second internal thread section 421. The second external blind plug 4 is threadedly connected to the other end of the outer tube 2 through the second internal thread section 421. For example, the second external blind plug 4 is threadedly connected to the external thread section 23 of the outer tube 2 through the second internal thread section 421. Further, a second quick connector 43 is connected to the second cylinder wall 42, and the second quick connector 43 is provided on the second cylinder wall 42 between the end of the second internal thread section 421 and the second bottom wall 41, The second quick connector 43 is interconnected with the inside of the second outer blind plug 4, and the second pressure gauge 44 can be connected to the second quick connector 43, so that the second pressure gauge 44 can monitor the pressure change in the corresponding sealed area.

In the embodiment of the present invention, as shown in Figure 4, the cement sheath 5 located in the annular cavity 21 between the inner pipe 1 and the outer pipe 2 is formed in the annular cavity 21 by an inner blind plug 6 of. Specifically, the inner blind plug 6 includes a stopper 61, a first stopper 62 and a second stopper 63. One end of the stopper 61 has a plurality of axial insertion holes 611 along the circumferential direction. The stopper 61 is located at Inside the first outer blind plug 3; the first baffle 62 is connected with a plurality of connecting rods 64 along the circumferential direction. The multiple connecting rods 64 can be inserted into a plurality of axial insertion holes 611. The first baffle 62 is located in the annular cavity. 21; the second baffle 63 is located in the annular cavity 21, and the cement ring 5 is sandwiched between the first baffle 62 and the second baffle 63.

Specifically, please refer to Figure 5. The stopper 61 is a solid cylinder or cuboid, which can be made of metal or other materials with higher strength. One end surface of the stopper 61 is spaced apart along the circumferential direction. There are a plurality of axial insertion holes 611. The axial insertion holes 611 may be small circular holes. The depth h of the axial insertion holes 611 may be 1 cm to 1.5 cm. In this embodiment, four axial insertion holes 611 are evenly spaced on one end surface of the stopper 61 .

Both the first baffle 62 and the second baffle 63 are annular baffles, and their outer diameters are slightly smaller than the inner diameter of the first cylinder wall 33 of the first outer blind plug 3 and the inner diameter of the second outer blind plug 4 . The inner diameter of the second cylinder wall 42 is provided with a first central hole 621 and a second central hole 631 on the first baffle 62 and the second baffle 63 respectively, so as to be sleeved on the outside of the inner tube 1 . In this embodiment, the first central hole 621 and the second central hole 631 are not limited to being opened at the center positions of the first baffle 62 and the second baffle 63. The first baffle 62 can be opened according to the needs of the experiment. The first central hole 621 and the second central hole 631 of the second baffle 63 are designed with various eccentric distances, that is, the center point of the first central hole 621 does not coincide with the center point of the outer circumference of the first baffle 62. And the center point of the second central hole 631 does not coincide with the center point of the outer circumference of the second baffle 63 . In the present invention, the diameter of the first central hole 621 of the first baffle 62 and the diameter of the second central hole 631 of the second baffle 63 are both similar to the outer diameter of the inner tube 1 and slightly larger than the outer diameter of the inner tube 1 . The outer diameters of the first baffle 62 and the second baffle 63 are slightly larger than the outer diameter of the stopper 61 and smaller than the inner diameter of the outer tube 2 . In the present invention, a plurality of threaded holes 622 are formed on one end surface of the first baffle 62 along the circumferential direction. In this embodiment, four threaded holes 622 are formed on one end surface of the first baffle 62 and are evenly spaced along the circumferential direction. The relative positions of the four threaded holes 622 on the first baffle 62 and the four axial insertion holes 611 on the block 61 are consistent and symmetrically distributed.

One end of the connecting rod 64 is machined with an externally threaded section for threaded connection with the threaded hole 622 on the first baffle 62; the other end of the connecting rod 64 is a smooth metal round rod, the diameter of which is the same as the stopper. The diameter of the axial insertion hole 611 on the stopper 61 is similar to ensure that the other end of the connecting rod 64 can be inserted into the axial insertion hole on the stopper 61 without free movement. Under the action of external force, the stopper 61 can be connected to the The rods 64 are separated.

As shown in Figure 5, after the four connecting rods 64, the stopper 61, and the first baffle 62 are connected in the above manner, relative movement or rotation will not occur, and at the same time, it can be ensured that the stopper 61 is placed vertically. state, the first baffle 62 can remain horizontal in a free state or under the action of an external force in the vertical direction. By replacing the first baffle 62 with the first central hole 621 with different eccentric distances and the first baffle 62 with different eccentric distances. With the second baffle 63 of the second center hole 631, the test device of the present invention can truly simulate the situation where the casing is not centered that may exist on site, so that the inner pipe 1 and the outer pipe 2 in the test device of the present invention are not in the same position. On the axis, a situation is formed where one side has a large space and the other side has a small space. For the side with a larger space, the volume of the cement slurry is larger, and the thickness of the cement ring 5 is thicker, while the side with a smaller space has a larger volume. The thickness of the side cement ring 5 is relatively small, resulting in uneven cement rings 5 on both sides of the inner pipe 1 and the outer pipe 2, so that the cement slurry to be tested can be tested when the pipe string is eccentric to different degrees. cementing ability.

The working steps of this testing device that simulates the comprehensive performance of underground cement sheath are as follows:

1. Weld the two ends of the prepared inner tube 1 to the connecting plates 12, and deburr both ends to ensure a uniform outer diameter, as shown in Figure 2;

2. Connect the threaded ends of the four connecting rods 64 to the first baffle 62 through threads, and ensure that the first baffle 62 is level;

3. Pass the inner tube 1 through the first center hole 621 of the first baffle 62 until one end surface of the inner tube 1 contacts the stopper 61, as shown in Figures 5 and 6;

4. Connect the first outer blind plug 3 and the outer pipe 2 together through threads, and connect the inner pipe 1, the first baffle 62, and the stopper 61 connected in step 3 along the outer pipe 2. The other end is installed into the outer tube 2 until the bottom end surface of the stopper 61 contacts the inner end surface of the first outer blind plug 3, as shown in Figure 7;

5. Place the device connected in step 4 upright. At this time, the first outer blind plug 3 is located on the lower side. Then fill the annular cavity 21 of the inner pipe 1 and the outer pipe 2 with the cement slurry to be tested. , the upper end surface filled with cement slurry is lower than the upper end surface of the annular cavity 21 between the inner pipe 1 and the outer pipe 2, as shown in Figure 4;

6. Use the second baffle 63 to compact the upper end surface of the filled cement slurry;

7. Keep the current state for the designed time period T, then place the entire device horizontally, and remove the first outer blind plug 3 at the lower end and the first baffle 62 and the second baffle 63 at both ends, as shown in Figure 8;

8. Measure the distance between the two end faces of the cement ring 5 at this time and the two end faces of the inner pipe 1, and mark the initial positions of both ends of the cement ring 5 on the outer pipe 2, and then plug the first outer blind 3 and the second outer blind plug 4 are respectively connected to both ends of the outer tube 2 in step 7, as shown in Figure 1;

9. Fill the closed annulus 36 formed by the outer pipe 2, the inner pipe 1 and the cement sheath 5 with liquid medium through the pressure test joint 31, and connect the first pressure gauge 35 and the second pressure gauge 44 to the corresponding On the first quick connector 34 and the second quick connector 43, record the current reading of the first pressure gauge 35 or zero-set the first pressure gauge 35; because the pressure in the corresponding sealed area monitored by the second pressure gauge 44 The variation may be small, so the accuracy required for the second pressure gauge 44 is higher than that of the first pressure gauge 35 , and the range of the second pressure gauge 44 may be smaller than that of the first pressure gauge 35 .

10. Connect the pressure test pipeline to the pressure test joint 31, and perform pressure work on this end. The pressure values are 2MPa, 5MPa, 8MPa, 10MPa, 15MPa and 20MPa respectively. After each group of pressure is completed, the pressure state is maintained for 15 minutes. During the pressure and During the entire process of maintaining pressure, record the pressure data of the first pressure gauge 35 and the second pressure gauge 44 in detail, focusing on recording whether there is any change in the second pressure gauge 44 during this process;

11. After the pressure test is completed, disassemble it, measure the distance between the two ends of the cement ring 5 and the two ends of the inner pipe 1 again, and mark the actual positions of the two ends of the cement ring 5 after the pressure test is completed on the outer pipe 2. Observe the change of the actual position of the mark on outer tube 2 relative to the initial position.

In the present invention, the first baffle 62 and the second baffle 63 with different eccentric distances are replaced, and the test is continued according to steps 1 to 11, thereby simulating the cementation performance of the cement slurry to be tested when the on-site casing is not centered.

In the present invention, outer pipes 2 with different inner diameters are replaced and the test is continued according to steps 1 to 11, thereby simulating the cementation performance of the cement slurry to be tested under the condition of different sizes of annulus gaps between the on-site casing and the formation.

Finally, after analyzing each set of data results, during the entire process of pressing and maintaining pressure, if there is no pressure change on the second pressure gauge 44, it can be considered that the cementing effect of this cementing cement slurry is better. Under the current experimental conditions Its bonding strength meets the requirements.

The beneficial effects of the present invention are as follows:

(1) This test device can carry out repeated simulation experiments many times and facilitates subsequent disassembly, repair and modification;

(2) This testing device has high testing accuracy and can quickly and accurately screen out the cement slurry that meets the requirements on site;

(3) This test device has a simple structure, low cost and is easy to use;

(4) This test device can combine the actual conditions on site to simulate the cementing performance of cement slurry under the condition of casing eccentricity.

Embodiment 2

As shown in Figures 1 to 8, the present invention also provides a testing method for simulating the comprehensive performance of underground cement sheaths, which uses the above-mentioned testing device for simulating the comprehensive performance of underground cement sheaths. The testing method for the comprehensive performance of the cement sheath includes the following steps:

Step S1: Measure the distances between the two ends of the cement ring 5 and the two ends of the inner pipe 1, and mark the initial positions of the two ends of the cement ring 5 on the outer pipe 2;

Step S2: Inject liquid medium into the outer tube 2 through the pressure test joint 31 on the first outer blind plug 3;

Step S3: After the pressure test is completed, measure the distance between the two ends of the cement ring 5 and the two ends of the inner pipe 1 again, and mark the cementing after the pressure test is completed on the outer pipe 2 Check the actual positions of both ends of the cement ring 5 and observe the changes in the actual positions marked on the outer pipe 2 relative to the initial position.

The specific experimental steps described in this embodiment have been specifically described in Embodiment 1 and will not be repeated here.

The present invention's testing method for simulating the comprehensive performance of downhole cement sheaths can test the bonding strength of cement sheaths under different cement slurry systems, different annulus gaps, and pipe string eccentricity, and can be very convenient and accurate for measuring oil and gas wells. The cementing properties of cement slurry provide theoretical guidance for on-site cementing operations.

The above are only a few embodiments of the present invention. Those skilled in the art can make various changes or modifications to the embodiments of the present invention based on the disclosure of the application documents without departing from the spirit and scope of the present invention.

Claims (9)

1. The utility model provides a testing arrangement of simulation well cementation cement sheath comprehensive properties in pit, its characterized in that includes:

the inner tube is provided with a closed inner cavity, two ends of the inner tube are connected in a sealing way through connecting plates, and the closed inner cavity is filled with pressure medium;

the outer tube is sleeved outside the inner tube, an annular cavity is formed between the outer tube and the inner tube, two ends of the outer tube can be respectively connected with a first outer blind plug and a second outer blind plug, the first outer blind plug is connected with a pressure test connector capable of injecting pressure liquid into the outer tube and a first pressure gauge, and the second outer blind plug is connected with a second pressure gauge;

the annular cavity is filled with a well cementation cement ring, the well cementation cement ring is formed in the annular cavity through an inner blind plug, and the inner blind plug comprises: one end of the stop block is provided with a plurality of axial insertion holes along the circumferential direction, and the stop block is positioned in the first outer blind plug; a first baffle plate, on which a plurality of connecting rods are connected in the circumferential direction, the connecting rods being insertable into the plurality of axial insertion holes, the first baffle plate being located in the annular cavity; the second baffle is positioned in the annular cavity, the well cementation cement ring is clamped between the first baffle and the second baffle, and the well cementation cement ring is positioned between the first outer blind plug and the second outer blind plug.

2. The device for testing the comprehensive performance of the simulated downhole cementing cement sheath according to claim 1, wherein the first external blind plug comprises a first bottom wall and a first cylinder wall connected to the periphery of the first bottom wall, the first cylinder wall is provided with a first internal thread section, the first external blind plug is in threaded connection with one end of the outer pipe through the first internal thread section, and the pressure testing joint is arranged on the first bottom wall.

3. The device for testing the comprehensive performance of the simulated downhole cementing ring according to claim 2, wherein a first quick connector is connected to the first cylinder wall, and the first pressure gauge can be connected to the first quick connector.

4. A device for simulating the overall performance of a well cementing cement sheath in a well according to any one of claims 1 to 3, wherein the second blind plug comprises a second bottom wall and a second cylinder wall connected to the periphery of the second bottom wall, the second cylinder wall is provided with a second internal thread section, and the second blind plug is in threaded connection with the other end of the outer pipe through the second internal thread section.

5. The device for testing the comprehensive performance of the simulated downhole cementing ring as claimed in claim 4, wherein a second quick connector is connected to said second wall, and said second pressure gauge is connectable to said second quick connector.

6. The device for testing the comprehensive performance of the underground well cementing cement sheath by simulation according to claim 1, wherein the number of the axial insertion holes is four, and the four axial insertion holes are arranged at one end of the stop block at equal intervals along the circumferential direction of the stop block.

7. The apparatus for testing the comprehensive performance of a simulated downhole cementing cement sheath as in claim 1, wherein said first baffle and said second baffle have a first central aperture and a second central aperture through which said inner pipe is threaded.

8. The apparatus for testing the comprehensive performance of a simulated downhole cementing cement sheath as claimed in claim 7, wherein said first central bore is an eccentric bore and said second central bore is an eccentric bore.

9. A method for testing the comprehensive performance of a simulated underground well cementation cement sheath, which is characterized in that the device for testing the comprehensive performance of the simulated underground well cementation cement sheath according to any one of claims 1 to 8 is adopted, and the method for testing the comprehensive performance of the simulated underground well cementation cement sheath comprises the following steps:

step S1: measuring the distance between the two ends of the well cementation cement sheath and the two ends of the inner tube respectively, and marking the initial positions of the two ends of the well cementation cement sheath on the outer tube;

step S2: injecting a liquid medium into the outer tube through the pressure test joint on the first outer blind plug;

step S3: and after the pressure test is finished, measuring the distances between the two ends of the well cementation cement sheath and the two ends of the inner pipe again, marking the actual positions of the two ends of the well cementation cement sheath after the pressure test is finished on the outer pipe, and observing the change condition of the actual positions marked on the outer pipe relative to the initial position.