CN111911087A - Well body structure penetrating through high-pressure layer and basalt collapsed layer and construction method of well body structure - Google Patents

Abstract

The present invention provides a wellbore structure passing through a high-pressure layer and a basalt collapsed layer and a construction method thereof. The construction method includes: step S10, running the casing string for the first opening, and cementing the well; step S20, running the first casing string The second opening of the casing string is cemented; in step S30, the third opening of the well section is drilled to the upper part of the high pressure layer, the third opening of the casing string is run, and the well is cemented; step S40, the fourth opening of the well section is drilled through the high pressure stratum, and drill to the upper part of the basalt collapsed layer, run the fourth opening casing string, and cement the well; step S50, the fifth opening well section drills through the basalt collapsed layer, and drills to the upper part of the oil and gas target layer, and runs into the first In step S60, the well section of the sixth opening is drilled to the oil and gas target layer, and the liner string is run in the sixth opening, and the well is cemented. Through the invention, accidents and complicated technical problems such as overflow, lost circulation, wellbore collapse, stuck pipe and the like are easy to occur when drilling under the geological conditions with high pressure layer and basalt collapsed layer.

Description

Wellbore Structure and Construction Method Through High Pressure Layer and Basalt Collapse Layer

technical field

The invention relates to the technical field of oil and natural gas exploration and development, in particular to a wellbore structure passing through a high-pressure layer and a basalt collapsed layer and a construction method thereof.

Background technique

In oil and gas exploration and development, it is necessary to establish an oil and gas channel between the surface and underground oil and gas layers, that is, an oil and gas well. During the construction of oil and gas wells, the formation is sealed with casing, and the outer wall of the casing is fixed with the formation with cement, thereby forming a combination of casing and cement. The combination of the casing and the cement is the wellbore structure. As one of the key contents of oil and gas exploration, the wellbore structure needs to fully consider the particularity of the pore pressure and geological conditions of the stratum to be drilled. Different casings can isolate different pressures and complex strata, and eliminate or reduce possible accidents and complications during drilling. risks of.

At present, in the exploration and development of oil and gas resources in deep strata, the depth of oil and gas ultra-deep wells is generally 6000m-9000m, and now it has exceeded 8000m. Due to the complex and changeable geological conditions in ultra-deep well drilling, complex formation pore pressure systems are often encountered, formation lithology is changeable, high-pressure layers, leakage layers and collapsed layers appear alternately, the geological conditions are relatively complex, and the construction of wellbore structure is relatively challenging big.

Ultra-deep wells in the Sichuan Basin often encounter complex formations such as high-pressure brine, mudstone formations and basalt formations in deep formations. When conventional wellbore structures are used, accidents and complications such as overflow, lost circulation, collapse, and sticking often occur during drilling. These accidents and complications will bring huge economic losses to oil and gas drilling, and even eventually cannot continue to drill to the oil and gas target layer, resulting in the scrapping of the wellbore.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a wellbore structure passing through the high pressure layer and the basalt collapse layer and its construction method, so as to alleviate the occurrence of overflow, lost circulation, Accidents and complex technical problems such as well wall collapse and stuck drill.

Above-mentioned purpose of the present invention can adopt following technical scheme to realize:

The present invention provides a method for constructing a wellbore structure passing through a high-pressure layer and a basalt collapsed layer, comprising:

Step S10, drilling the first opening well section, running the first opening casing string, and cementing the well;

Step S20, drilling the second opening well section, running the second opening casing string, and cementing the well;

Step S30, drilling the third opening well section, the third opening well section is drilled to the upper part of the high pressure layer, running the third opening casing string, and cementing;

Step S40, drilling the fourth opening well section, the fourth opening well section is drilled through the high pressure layer, and is drilled to the upper part of the basalt collapse layer, the fourth opening casing string is run, and the well is cemented;

Step S50, drilling the fifth opening well section, the fifth opening well section is drilled through the basalt collapse layer, and drilled to the upper part of the oil and gas target layer, the fifth opening casing string is run, and the well is cemented;

In step S60, the sixth opening well section is drilled, the sixth opening well section is drilled to the oil and gas target layer, the sixth opening liner string is run, and the well is cemented.

In a preferred embodiment, the running of the fourth open casing string includes: the fourth open casing string is suspended from the inner wall of the third open casing string.

In a preferred embodiment, the fifth opening casing string includes a fifth opening liner string, and the fifth opening liner string is suspended.

In a preferred embodiment, the fifth opening liner string is suspended from the inner wall of the third opening casing string.

In a preferred embodiment, the construction method includes a step S70 arranged after the step S60, and the step S70 includes: running a fifth opening tie back casing to the top of the fifth opening tail pipe string , cementing.

In a preferred embodiment, the running into the sixth opening liner string includes: the sixth opening liner string is suspended from the inner wall of the fifth opening casing string.

In a preferred embodiment, the first well section is drilled through the surface loose layer and the leak-prone formation, and the second well section is drilled through the upper shallow gas layer and the low-pressure leakage layer.

In a preferred embodiment, the high pressure formation comprises a high pressure brine formation.

The present invention provides a wellbore structure passing through a high pressure layer and a basalt collapsed layer, comprising:

Open casing string for the first time;

a second open casing string arranged in the first open casing string;

The third open casing string, the third open casing string is run down to the top of the high-voltage layer;

the fourth opening casing string; the fourth opening casing string penetrates the high pressure layer and goes down to the upper part of the basalt collapsed layer, and the fourth opening casing string isolates the high pressure layer;

a fifth open casing string, the fifth open casing string penetrates the basalt collapse layer, and runs down to the upper part of the oil and gas target layer, and the fifth open casing string isolates the basalt collapse layer;

The sixth opening liner string, the sixth opening liner string is lowered into the oil and gas target layer.

In a preferred embodiment, the fourth opening casing string is suspended from the inner wall of the third opening casing string by a four opening liner hanger.

In a preferred embodiment, the fifth opening casing string includes a fifth opening liner string, and the fifth opening liner string is suspended.

In a preferred embodiment, the fifth opening liner string is suspended from the inner wall of the third opening casing string through a five opening liner hanger.

In a preferred embodiment, the wellbore structure includes a fifth opening tieback casing, and the fifth opening tieback casing is run down to the top of the fifth opening liner string.

In a preferred embodiment, the sixth opening liner string is suspended from the inner wall of the fifth opening casing string through a six opening liner hanger.

In a preferred embodiment, the first opening casing string penetrates the surface loose layer and the leak-prone formation, and the second opening casing string penetrates the upper shallow gas layer and the low-pressure leakage layer.

The features and advantages of the present invention are:

The present invention provides a method for constructing a wellbore structure passing through a high-pressure layer and a basalt collapsed layer. The first opening of the casing string seals the upper loose, unstable and easy-to-leak well section to provide support for the next wellhead installation. The second opening of casing strings seals shallow gas and low-pressure formations that are easy to leak.

The third opening of the casing string goes down to the upper part of the high pressure layer to isolate the stratum with relatively low pore pressure in the upper part, so as to avoid the occurrence of the stratum with relatively low pore pressure in the upper part due to the increase of drilling fluid density when the high pressure layer is encountered in the next opening time. well leakage.

After drilling through the high pressure layer in the fourth opening section, run the fourth opening casing string to seal the formation, instead of drilling to the lower basalt collapse layer and then running the casing to seal the stratum, the fourth opening casing string The isolation requires high-density drilling fluid to maintain a stable high-pressure layer on the wellbore, which can effectively avoid accidents such as overflow of the upper high-pressure brine layer and wellbore collapse caused by reducing the density of the drilling fluid when drilling to the basalt collapsed layer. Fourth The casing string is opened for the next time to seal the upper high-pressure layer suitable for drilling with high-density drilling fluid, creating conditions for drilling with lower drilling fluid density in the next opening.

The fifth opening of the casing string seals the basalt collapse layer that is easy to collapse, creating conditions for the next opening to protect the reservoir and further reduce the drilling fluid density. The sixth opening of the liner string seals the oil and gas target layer.

Through the construction method of the wellbore structure, the conditions for drilling to the target oil and gas layer can be established, and the overflow, lost circulation, wellbore collapse, pipe sticking, etc. are prone to occur when drilling in geological conditions with high pressure layers and basalt collapse layers. Accidents and complex technical problems.

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings used in the description of the embodiments. Obviously, the accompanying 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 from these drawings without creative effort.

1 is a structural schematic diagram of a wellbore structure passing through a high-pressure layer and a basalt collapse layer provided by the present invention;

Figure 2a is a schematic diagram of the wellbore structure passing through the high pressure layer and the basalt collapse layer provided by the present invention and each structural layer in the formation;

Figure 2b is a diagram showing the relationship between each structural layer in the formation and the formation pore pressure;

Fig. 3 is a schematic diagram of the construction method of the wellbore structure passing through the high pressure layer and the basalt collapse layer provided by the present invention.

Description of reference numbers:

100. Cementing cement ring;

10. The first opening of the casing string; 101. The first opening of the well section;

20. The second opening of the casing string; 201. The second opening of the well section;

30. The third opening of the casing string; 301. The third opening of the well section;

40. Casing string for the fourth opening; 401. The well section for the fourth opening; 402. The liner hanger for the fourth opening;

50. The fifth opening of the casing string; 51, the fifth opening of the liner string; 52, the fifth opening of the tieback casing; 501, the fifth opening of the well section; 502, the fifth opening of the liner hanger;

60. The sixth opening liner string; 601, the sixth opening well section; 602, the sixth opening liner hanger;

71, high pressure layer; 711, high pressure brine layer; 712, high pressure mudstone layer; 72, basalt collapse layer; 73, oil and gas target layer;

80. Formation; 81. Formation pore pressure profile.

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 a part of the embodiments of the present invention, but not all of 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 shall fall within the protection scope of the present invention.

Faced with complex formations with high pressure layer 71 and basalt collapsed layer 72, due to the unreasonable wellbore structure and the limitation of casing layers, in the conventional wellbore structure, there will be multiple formation pore pressure systems in the same well section and complex formations of different natures. The pore pressure and collapse pressure of the high-pressure brine layer 711 and the mudstone formation are relatively high. In order to avoid overflow and wellbore collapse accidents, high-density drilling fluid should be used for drilling; while the basalt collapsed layer 72 has lower leakage pressure and formation fracture pressure, which are To avoid lost circulation and wellbore collapse accidents, it is necessary to use low-density drilling fluid for drilling. If the upper high-pressure brine layer 711, the mudstone formation in the middle, and the lower basalt collapsed layer 72 are drilled, casing is run for isolation, and after drilling to the basalt collapsed layer 72, the drilling fluid in the well section cannot meet the high-pressure brine layer at the same time. The high density of 711 and high-pressure mudstone formation 712, as well as the low density requirement of basalt collapsed layer 72, easily lead to accidents such as overflow of high-pressure salt water layer 711, collapse of mudstone formation, lost circulation and stuck drill of basalt collapsed layer 72.

Example 1

The present invention provides a method for constructing a wellbore structure with a basalt collapsed layer 72 under geological conditions, as shown in Fig. 2a and Fig. 3 , the constructing method includes: step S10, drilling the first well section 101, the next Enter the casing string 10 for the first opening, and cement the well; step S20, drill the well section 201 for the second opening, run the casing string 20 for the second opening, and cement the well; step S30, drill the well section 301 for the third opening , the third opening section 301 is drilled to the upper part of the high pressure layer 71, the third opening casing string 30 is run, and the well is cemented; step S40, the fourth opening section 401 is drilled, and the fourth opening section 401 is drilled through The high pressure layer 71 is drilled to the upper part of the basalt collapse layer 72, the fourth opening casing string 40 is run, and the well is cemented; step S50, the fifth opening well section 501 is drilled, and the fifth opening well section 501 is drilled through the basalt Collapse the layer 72, and drill to the upper part of the oil and gas target layer 73, run the casing string 50 for the fifth opening, and cement the well; step S60, drill the sixth opening well section 601, and drill the sixth opening well section 601 to the oil and gas In the target layer 73, the sixth opening liner string 60 is run for cementing.

In this construction method, the casing string 10 for the first opening seals the upper part of the loose, unstable and easy-to-leak well section to provide support for the next wellhead installation. The second opening casing string 20 seals the shallow gas and the low-pressure leakage-prone formation.

The third opening casing string 30 is lowered to the upper part of the high pressure layer 71 to isolate the formation with relatively low pore pressure in the upper part, so as to avoid the relatively low pore pressure in the upper part due to the increase of drilling fluid density when the lower opening encounters the high pressure layer 71 lost circulation in the formation.

After the fourth opening section 401 is drilled through the high pressure layer 71, the fourth opening casing string 40 is run to seal the formation, instead of drilling to the lower basalt collapse layer 72 and then running casing to seal the stratum. The secondary casing string 40 isolates the high-pressure layer 71 that requires high-density drilling fluid to maintain the wellbore stability, which can effectively prevent the upper high-pressure brine layer 711 from overflowing due to reducing the density of the drilling fluid when drilling to the basalt collapsed layer 72. In the event of wellbore collapse and other accidents, the casing string 40 in the fourth operation seals the upper high-pressure layer 71 suitable for drilling with high-density drilling fluid, creating conditions for lowering the density of the drilling fluid in the next operation.

The fifth opening casing string 50 seals the basalt collapse layer 72 that is easy to collapse, creating conditions for the next opening to protect the reservoir and further reduce the density of the drilling fluid for drilling. The sixth opening liner string 60 seals the oil and gas target layer 73 .

The construction method of the wellbore structure can be applied to ultra-deep wells. Through the construction method of the wellbore structure, the conditions for drilling the ultra-deep oil and gas target layer 73 can be established, and drilling under the geological conditions with high pressure layers and basalt collapsed layers 72 can be eased. Accidents and complex technical problems such as overflow, lost circulation, well wall collapse, and stuck pipe are prone to occur.

The high pressure layer 71 is a high pore pressure formation, and the pore pressure coefficient is greater than 1.6. For example, the high pressure layer 71 includes a high pressure brine layer 711, a high pressure mudstone formation 712 or a high pressure carbonate rock layer. 2a and 2b, the high pressure layer 71 shown in FIG. 2b includes a high pressure brine layer 711 and a high pressure mudstone formation 712, and the high pressure salt water layer 711 and the high pressure mudstone formation 712 can be sequentially distributed from top to bottom. In some cases, the applicable geological conditions of the wellbore structure also include a non-high pressure mudstone stratum, the high pressure layer 71 and the non-high pressure mudstone stratum are distributed up and down, and the non-high pressure mudstone stratum is located between the high pressure layer 71 and the basalt collapsed layer 72 . Referring to the formation pore pressure profile 81 in FIG. 2 b , the formation pore pressures at various depths of the formation 80 vary greatly with the appearance of the high pressure brine layer 711 , the high pressure mudstone formation 712 and the basalt collapsed layer 72 .

In step S10, a φ660.4mm roller cone bit can be used to drill through the loose layer on the surface and the stratum that is easy to leak, then the drill bit is pulled out, the first casing string 10 of φ508mm is run in, and the first casing string 10 of φ508mm is opened. 10. Inject cement into the annulus of the formation, seal the upper part of the loose, unstable and easy to lose well section, and provide support for the next wellhead installation. Specifically, using a φ660.4mm roller cone bit, after drilling to a well depth of 200m, the large displacement is fully circulated to clean up the cuttings in the well, so as to ensure the smooth running of the casing string 10 for the first opening; 10 Use a casing string with a diameter of φ508mm, a wall thickness of 11.13mm, and a partial ladder buckle. The drill bit is pulled out, and the first opening casing string 10 is run. In the annulus between the first opening casing string 10 and the formation, positive injection and reverse injection are used. The well is cemented by grouting, the cement is returned to the wellhead, and the injected cement slurry solidifies to form a cement sheath 100 .

In step S20, a φ444.5mm roller cone bit or a PDC bit can be used to drill through the upper shallow gas and low-pressure leakage layer, then pull out the drill bit, run the second opening casing string 20 with a diameter of φ365.13mm, and insert the The second opening of the casing string 20 is cemented with the annulus of the formation and the upper casing, so as to seal the shallow gas and the formation with low pressure and easy to leak. Specifically, use a φ444.5mm roller cone bit or a PDC bit, and after drilling to a well depth of 1500m, pull out the bit, replace it with a drilling tool assembly, and conduct sufficient drilling to ensure the smooth running of the casing string 20 for the second opening; The second opening casing string 20 is made of φ365.13mm, wall thickness 13.88mm, and stepped-buckle casing string. The second opening casing string 20 is run, and the interpolation method is used to connect the casing to the formation and the upper layer. Cement is injected into the annulus of the casing, and the cement is returned to the wellhead.

In step S30, the φ333.4mm PDC bit can be used to drill to the top of the high-pressure layer 71, then the drill bit is pulled out, and the third opening casing string 30 of φ273.05mm is run, and the third opening casing string 30 is connected to the formation and the stratum. The annulus with the upper casing is injected with cement to seal the formation with relatively low pore pressure in the upper part. Specifically, a φ333.4mm PDC bit was used to drill to a well depth of 4,500m, and after reaching the top of the high-pressure layer 71, the bit was pulled out, replaced with a drilling tool assembly for well drilling, and the well was fully drilled to ensure the smooth running of the casing string 30 for the third opening. The third opening casing string 30 adopts φ273.05mm, wall thickness 13.84mm, air-tight buckle casing string, and the third opening casing string 30 adopts double rubber plug and double density cement slurry system. The third opening of the casing string 30 and the annulus of the formation and the upper casing are injected with cement and cemented, and the cement is returned to the wellhead.

In an embodiment of the present invention, the fourth open casing string 40 is suspended from the inner wall of the third open casing string 30 . The use of liner suspension technology effectively reduces the one-time return height of casing annulus cementing, and avoids the complicated loss of circulation in basalt formations caused by excessive ground pump pressure during casing annulus cementing.

The φ241.3mm PDC bit can be used to drill the fourth opening section 401. After drilling through the upper high-pressure layer 71, the drill bit is pulled out, and the fourth opening casing string 40 of φ219.08mm is run to the bottom of the hole. The top of the pipe string 40 is connected to the fourth-opening liner hanger 402, the fourth-opening casing string 40 is suspended on the inner wall of the third-opening casing string 30, and the fourth-opening casing string 40 is connected to the formation and the The annulus of the upper casing is injected with cement and cemented to seal the formation that requires high-density drilling fluid to be drilled, so as to avoid accidents and complications such as overflow, collapse, lost circulation and stuck pipe due to the reduction of drilling fluid density. Specifically, the φ241.3mm PDC bit was used to drill the fourth opening section 401 to a well depth of 6400m, and after drilling through the upper high pressure layer 71, the bit was pulled out and replaced with a drilling tool assembly for well drilling to fully penetrate the well to ensure drilling. The fourth opening of the well section 401 can be run smoothly; the fourth opening of the casing string 40 can use φ219.08mm, wall thickness 12.7mm, direct-coupled liner string, run the fourth opening of the casing string 40 to the well depth 6398m, the top of the fourth opening casing string 40 is connected to the four opening liner hanger 402, and the fourth opening casing string 40 is suspended on the inner wall of the third opening casing string 30 at a well depth of 4300m; high-density In the salt-resistant cement slurry system, cement cementing is injected into the annulus between the casing string 40 of the fourth opening and the formation and the casing of the layer, and the cement is returned to the position of the liner hanger 402 of the fourth opening, and the upper part of the sealing is suitable for high-density drilling fluid The high-pressure brine formation 711 and the high-pressure mudstone formation 712 drilled create conditions for lowering the drilling fluid density in the next opening. In this construction method, the casing string 40 for the fourth opening is not reconnected to the casing, which can reduce the amount of casing and save the cost of drilling.

The fifth opening casing string 50 may be installed at the wellhead, or may be installed in a suspended manner. In the case where the fifth opening casing string 50 is installed at the wellhead, the fifth opening casing string 50 may be a casing extending from the bottom hole of the fifth opening well section 501 to the wellhead. In the case where the fifth opening casing string 50 is arranged in a suspended manner, the fifth opening casing string 50 includes the fifth opening liner string 51, and the fifth opening liner string 51 can be suspended from the third opening. The inner wall of the secondary casing string 30 .

The fifth opening casing string 50 is preferably arranged in a suspended manner. As shown in FIG. 2a , the fifth opening casing string 50 includes a fifth opening liner string 51 , and the fifth opening liner string 51 is suspended. . The fifth opening tail pipe string 51 can be suspended from the third opening casing string 30 , and can also be suspended from the fourth opening casing string 40 . More preferably, the fifth opening tail pipe string 51 is suspended from the inner wall of the third opening casing string 30 . In drilling the fifth opening section 501, after drilling through the basalt strata, the liner suspension technology is adopted, which effectively reduces the one-time return height of the annular cement injection of the fifth opening liner string 51, and avoids the fifth opening tailing. When the annulus of the pipe string 51 is cemented, the ground pump pressure is too high, resulting in lost circulation in the basalt collapsed layer 72. At the same time, the use of liner suspension can reduce the weight of the casing and increase the depth of the well into which the casing is run, thereby sealing off deeper holes. complex strata.

The PDC bit of φ190.5mm can be used to drill through the basalt collapse layer 72, then pull out the bit, run the fifth opening casing string 50 of φ168.28mm to the bottom of the well, and connect the fifth opening casing string 50 to the top of the hole. A liner hanger 502 is opened to hang the fifth open casing string 50 on the inner wall of the third open casing string 30, and inject into the annulus between the fifth open casing string 50 and the formation and upper casing Cementing wells. Specifically, a φ190.5mm PDC bit was used to drill to a well depth of 7000m, and after the basalt collapsed layer 72 was drilled, the bit was pulled out, replaced with a drilling tool assembly for well drilling, and the well was fully drilled to ensure the fifth opening of the casing string 50 smoothly. Running; the fifth opening casing string 50 adopts φ168.28mm, wall thickness 12.07mm, and direct-coupled liner string, and the fifth opening casing string 50 is run to the well depth of 6998m; the fifth opening casing string 50 The top is connected with a fifth-opening liner hanger 502, and the fifth-opening casing string 50 is suspended on the inner wall of the third-opening casing string 30 at a well depth of 4000 m. Cement cementing is injected into the annulus of the fifth opening casing string 50 and the stratum and upper casing, and the cement returns to the position of the fifth opening liner hanger 502 to seal the basalt collapse layer 72 that is easy to collapse. To protect the reservoir and further reduce the density of drilling fluid to create conditions for drilling.

Further, in the case where the fifth opening casing string 50 is set in a suspended manner, the construction method includes a step S70 after step S60, and the step S70 includes: lowering the fifth opening and connecting the casing 52 to the first The top of the liner string 51 is cemented five times. Run the fifth opening tieback casing 52, the fifth opening tieback casing 52 is run to the position of the fifth opening liner hanger 502, and the fifth opening tieback casing 52 and the third opening casing are connected The annulus of string 30 is cemented with injection cement. A 168.28mm casing string can be used for the fifth opening tieback sleeve 52. Specifically, the fifth opening tieback sleeve 52 is run into the fifth opening tieback sleeve 52 to a depth of the fifth opening liner hanger 502. position, and inject cement into the annulus of the fifth opening of the tieback casing 52 and the third opening of the casing string 30 . After the casing tie-back operation is completed, the sixth liner string 60 perforation completion operation will be started.

After the fifth opening of the liner string 51 is suspended and cemented, the casing tie-back is not carried out. After the sixth opening of the liner string 60 is suspended and cemented, the fifth opening of the tie-back casing 52 is performed, which can increase the When drilling the sixth well section 601, the drilling tool assembly is located in the annulus above the fifth-run liner hanger 502, which reduces the drilling fluid circulation equivalent density when drilling the sixth well section 601, thereby reducing the The risk of lost circulation in the target layer is complex.

The sixth opening liner string 60 can be installed at the wellhead, or can be installed in a suspended manner. Preferably, the sixth opening tail pipe string 60 is suspended from the inner wall of the fifth opening casing string 50 . In step S60, a φ139.7mm PDC drill bit can be used to drill to the target layer, take out the drill bit, and run down the sixth opening liner string 60 of φ114.3mm, and the top of the sixth opening liner string 60 is connected to the sixth opening The liner hanger 602 hangs the sixth liner string 60 on the inner wall of the fifth liner 51, and injects cement into the annular space between the sixth liner 60 and the formation and upper casing. Well, the oil and gas target layer 73 is sealed. Specifically, the φ139.7mm PDC bit was used to drill to the oil and gas target layer 73. After the footage reached 200m, the drill bit was pulled out and replaced with a drilling tool assembly for drilling the well to ensure the smooth running of the casing. The liner string 60 can be made of φ114.3mm, wall thickness 8.56mm, and long round buckle liner string. The sixth liner string 60 can be run down to the well depth of 7500m; the top of the sixth liner string 60 is connected to the sixth liner. The hanger 602 is used to hang the sixth opening liner string 60 on the inner wall of the fifth opening liner string, at a well depth of 6800m, and inject cement into the annulus between the sixth opening liner string 60 and the formation and upper casing. Well, the cement returns to the position of the six-opening liner hanger 602 to seal the oil and gas target layer 73 .

The sixth opening of the liner string 60 adopts the liner suspension cementing technology, and the casing is not connected back, which reduces the one-time return height of the casing annulus cementing, and avoids the high ground pump pressure when the casing annulus is cemented. The loss of circulation in the target layer is complicated, and at the same time, the amount of casing is reduced and the cost is saved.

Embodiment 2

The present invention provides a wellbore structure with a basalt collapse layer 72 under geological conditions, as shown in Figures 1 and 2a, the wellbore structure includes: a first opening casing string 10, a second opening casing String 20, third opening casing string 30, fourth opening casing string 40, fifth opening casing string 50 and sixth opening tail pipe string 60; Enter the second opening casing string 20; the third opening casing string 30 is run down to the top of the high pressure layer 71; the fourth opening casing string 40 penetrates the high pressure layer 71, and goes down to the upper part of the basalt collapse layer 72, The fourth casing string seals off the high pressure layer; the fifth casing string 50 penetrates the basalt collapsed layer 72 and runs down to the upper part of the oil and gas target layer 73; the fifth casing string seals off the basalt collapsed layer; The secondary liner string 60 is run into the oil and gas target layer 73 .

In this construction method, the casing string 10 for the first opening seals the upper part of the loose, unstable and easy-to-leak well section to provide support for the next wellhead installation. The second opening casing string 20 seals the shallow gas and the low-pressure leakage-prone formation.

The third opening casing string 30 is lowered to the upper part of the high pressure layer 71 to isolate the formation with relatively low pore pressure in the upper part, so as to avoid the relatively low pore pressure in the upper part due to the increase of drilling fluid density when the lower opening encounters the high pressure layer 71 lost circulation in the formation.

After the fourth opening section 401 is drilled through the high pressure layer 71, the fourth opening casing string 40 is run to seal the formation, instead of drilling to the lower basalt collapse layer 72 and then running casing to seal the stratum. The secondary casing string 40 isolates the high-pressure layer 71 that requires high-density drilling fluid to maintain the wellbore stability, which can effectively prevent the upper high-pressure brine layer 711 from overflowing due to reducing the density of the drilling fluid when drilling to the basalt collapsed layer 72. In the event of wellbore collapse and other accidents, the casing string 40 in the fourth operation seals the upper high-pressure layer 71 suitable for drilling with high-density drilling fluid, creating conditions for lowering the density of the drilling fluid in the next operation.

The fifth opening casing string 50 seals the basalt collapse layer 72 that is easy to collapse, creating conditions for the next opening to protect the reservoir and further reduce the density of the drilling fluid for drilling. The sixth opening liner string 60 seals the oil and gas target layer 73 .

This wellbore structure can be applied to ultra-deep wells. With this wellbore structure, conditions for drilling the ultra-deep oil and gas target layer 73 can be established, and it is easy to cause overflow when drilling under geological conditions with high pressure layers 71 and basalt collapse layers 72 . flow, lost circulation, wall collapse, stuck pipe and other accidents and complex technical problems.

Specifically, the wellbore structure further includes the first opening casing string 10 , the second opening casing string 20 , the third opening casing string 30 , the fourth opening casing string 40 , and the fifth opening casing string 40 . The casing string 50 and the sixth opening liner string 60 perform the cementing cement sheath 100 for cementing.

In an embodiment of the present invention, the fourth open casing string 40 is suspended from the inner wall of the third open casing string 30 through the four open end pipe hanger 402 .

In an embodiment of the present invention, the fifth opening casing string 50 includes a fifth opening liner string, and the fifth opening liner string is suspended.

In an embodiment of the present invention, the fifth opening liner string is suspended from the inner wall of the third opening casing string 30 through the fifth opening liner hanger 502 .

In an embodiment of the present invention, the wellbore structure includes a fifth opening tieback casing, and the fifth opening tieback casing is run down to the top of the fifth opening liner string.

In an embodiment of the present invention, the sixth opening liner string 60 is suspended from the inner wall of the fifth opening casing string 50 through the six opening liner hanger 602 .

In an embodiment of the present invention, the first opening casing string 10 penetrates the surface loose layer and the leak-prone formation, and the second opening casing string 20 penetrates the upper shallow gas and low pressure leakage layer.

The above are only a few embodiments of the present invention, and those skilled in the art can make various changes or modifications to the embodiments of the present invention according to the contents disclosed in the application documents without departing from the spirit and scope of the present invention.

Claims (15)

1. A method for constructing a shaft structure passing through a high-pressure layer and a basalt collapsed layer is characterized by comprising the following steps:

step S10, drilling a first open-time well section, putting a first open-time casing string, and cementing a well;

step S20, drilling a second open-time well section, putting a second open-time casing string, and cementing a well;

step S30, drilling a third open-time well section, wherein the third open-time well section is drilled at the upper part of the high-pressure layer, and a third open-time casing string is put into the well to be well-fixed;

step S40, drilling a fourth secondary well section, drilling the fourth secondary well section through the high-pressure layer and the basalt collapsed layer, descending a fourth secondary casing string, and cementing wells;

step S50, drilling a fifth open-time well section, wherein the fifth open-time well section is drilled through the basalt collapsed layer and is drilled to the upper part of an oil-gas target layer, and a fifth open-time casing string is put in for well cementation;

and step S60, drilling a sixth-opening-time well section, drilling the sixth-opening-time well section to the oil-gas target layer, putting a sixth-opening-time tail pipe string, and cementing the well.

2. The method of constructing a wellbore structure through a high-pressure zone and a basalt collapsed zone of claim 1, wherein the running fourth sub casing string comprises: and the fourth opening secondary casing string is hung on the inner wall of the third opening secondary casing string.

3. The method of constructing a wellbore structure traversing high pressure and basalt collapsed layers of claim 2, wherein the fifth open liner string comprises a fifth open liner string, the fifth open liner string being suspended.

4. The method of constructing a wellbore structure through a high pressure zone and a basalt collapsed zone of claim 3, wherein the fifth open sub tailpipe string is suspended from an inner wall of the third open sub casing string.

5. The method for constructing a wellbore structure penetrating a high-pressure zone and a basalt collapsed zone according to claim 3, wherein the constructing method comprises a step S70 provided after the step S60, and the step S70 comprises: and (5) running a fifth primary return sleeve to the top end of the fifth primary tail pipe string, and cementing.

6. The method of constructing a wellbore structure through a high-pressure zone and a basalt collapsed zone of claim 1, wherein the running a sixth open-ended liner string comprises: and the sixth starting secondary tail pipe string is suspended on the inner wall of the fifth starting secondary casing string.

7. The method of constructing a wellbore structure through a high pressure zone and a basalt collapsed zone of claim 1, wherein the first open sub is drilled through a surface unconsolidated formation and a lost circulation formation, and the second open sub is drilled through an upper shallow gas and low pressure lost circulation zone.

8. The method of constructing a wellbore structure through a high pressure zone and a basalt collapsed zone of claim 1, wherein the high pressure zone comprises a high pressure brine layer, a high pressure mudstone formation, or a high pressure carbonate formation.

9. A well bore structure passing through a high pressure zone and a basalt collapsed zone, comprising:

a first open-time casing string;

a second open-time casing string arranged in the first open-time casing string;

a third open-time casing string, wherein the third open-time casing string is arranged at the top of the high-pressure layer;

a fourth secondary casing string; the fourth secondary casing string penetrates through the high-voltage layer and is lowered to the upper part of the basalt collapsed layer, and the high-voltage layer is sealed by the fourth secondary casing string;

a fifth open-time casing string, wherein the fifth open-time casing string penetrates through the basalt collapsed layer and is lowered to the upper part of an oil-gas target layer, and the basalt collapsed layer is sealed by the fifth open-time casing string;

and the sixth opening tail pipe string is arranged in the oil and gas target layer.

10. The wellbore structure traversing high-pressure and basalt collapsed layers of claim 9, wherein the fourth slotted casing string is suspended from an inner wall of the third slotted casing string by a fourth slotted liner hanger.

11. The wellbore structure traversing high pressure and basalt collapsed layers of claim 10, wherein the fifth open liner string comprises a fifth open liner string, the fifth open liner string being suspended.

12. The wellbore structure traversing high pressure and basalt collapsed layers of claim 11, wherein the fifth primary string is suspended from an inner wall of the third primary string by a fifth primary string hanger.

13. The wellbore structure through a high pressure zone and a basalt collapsed zone of claim 11, comprising a fifth open sub casing run into a top end of the fifth open sub liner string.

14. The wellbore structure traversing high pressure and basalt collapsed layers of claim 9, wherein the sixth open liner string is suspended from an inner wall of the fifth open liner string by a sixth open liner hanger.

15. The wellbore structure traversing high pressure and basalt collapsed layers of claim 9, wherein the first open casing string penetrates an earth surface unconsolidated layer and a leaky formation, and the second open casing string penetrates an upper shallow gas and low pressure thief layer.

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