Horizontal well volume fracturing three-dimensional development method suitable for unconventional multilayer gas reservoir

Abstract

The present application relates to the technical field of horizontal well drilling and fracturing, and is a three-dimensional development method for volume fracturing of horizontal wells in unconventional multi-layer gas reservoirs, which comprises the following steps: a first well structure suitable for a first horizontal well with a horizontal section less than 1200m: step 1: drilling a well using a φ331.2mm drill bit to form a surface φ331.2mm borehole (11) with a surface well depth (14); step 2: lowering a φ244.5mm surface casing (12) into the φ331.2mm borehole (11). According to the method, after the first well is depleted, a φ152.4mm casing can be lowered into a φ177.8mm technical casing or completion casing after sidetracking, a φ114.3mm completion casing can be lowered to meet the volume fracturing requirements, an electric submersible pump, a screw pump or other external power tools can be lowered into the reserved φ177.8mm technical casing during gas recovery, the recovery efficiency is improved, and the old well site, ground pipeline and upper casing are all reused, thereby reducing the investment cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of horizontal well drilling and fracturing, and is a three-dimensional development method for volume fracturing of a horizontal well suitable for unconventional multi-layer gas reservoirs. BACKGROUND

[0002] A dense oil and gas field and a coalbed methane in the same block develop multiple sets of reservoirs vertically, and the use of horizontal well volume fracturing can greatly improve production and recovery. However, a horizontal well can generally only develop a single reservoir, and if multiple sets of reservoirs develop vertically, a new horizontal well (such as Figure 1 , 1 is a drilling rig 1, 2 is a horizontal well bore 2, 3 is a drilling rig 3, 4 is a horizontal well bore 4, 5 is a non-gas reservoir formation 5, 6 is an unconventional gas reservoir 6, 7 is a non-gas reservoir formation 7, 8 is an unconventional gas reservoir 8, and 9 is a non-gas reservoir formation 9) must be drilled, and the surface casing and technical casing of the first horizontal well cannot be reused, which greatly increases investment; a new well structure needs to be innovated, which can sidetrack a horizontal well in the first well after the first well develops a single set of reservoirs and is exhausted, so as to achieve the same efficient development effect as the first well. For example, horizontal well development, volume fracturing, and drainage gas recovery.

[0003] Currently, a single well structure is generally used for a horizontal well, such as a single φ139.7mm / φ127mm / φ114.3mm completion casing from the wellhead to the bottom of the well. After the first well is exhausted, if sidetracking is performed, a φ89mm tubing completion casing can only be run in, and because of the small diameter, volume fracturing cannot be performed, and efficient development cannot be achieved. SUMMARY

[0004] The present application provides a three-dimensional development method for volume fracturing of a horizontal well suitable for unconventional multi-layer gas reservoirs, which overcomes the deficiencies of the prior art and effectively solves the problem of increased costs due to the inability to reuse the surface casing and technical casing of the first horizontal well.

[0005] The technical solution of the present application is achieved by the following measures: a three-dimensional development method for volume fracturing of a horizontal well suitable for unconventional multi-layer gas reservoirs, which is performed according to the following steps:

[0006] A first well structure suitable for a first horizontal well with a horizontal section of less than 1200m:

[0007] Step 1: drilling with a φ331.2mm drill bit to form a surface φ331.2mm borehole (11) with a surface well depth of (14);

[0008] Step 2: running in a φ244.5mm surface casing (12) in the φ331.2mm borehole (11);

[0009] Step 3: Inject surface casing cement (13) between the φ331.2mm borehole (11) and the φ244.5mm casing (12);

[0010] Step 4: Drill a well using a φ222.3mm drill bit to form a φ222.3mm borehole (21), and the total drilling depth is (24);

[0011] Step 5: Lower a φ177.8mm completion casing (221) and a φ139.7mm completion casing (222) into the φ222.3mm borehole (21), and inject completion casing cement (23) between the φ222.3mm borehole (21) and the φ177.8mm completion casing (221) and the φ139.7mm completion casing (222);

[0012] Step 6: Perform a horizontal well volume fracturing operation in the φ177.8mm completion casing (221) and the φ139.7mm completion casing (222);

[0013] Second well structure suitable for the first horizontal well with a horizontal section greater than 1200m:

[0014] Step 1: Drill a well using a φ331.2mm drill bit to form a surface φ331.2mm borehole (11), and the surface drilling depth is (14);

[0015] Step 2: Lower a φ244.5mm surface casing (12) into the φ331.2mm borehole (11);

[0016] Step 3: Inject surface casing cement (13) between the φ331.2mm borehole (11) and the φ244.5mm casing (12);

[0017] Step 4: Drill a well using a φ222.3mm drill bit to form a φ222.3mm borehole (21), and the total drilling depth is (35);

[0018] Step 5: Lower a φ177.8mm technical casing (22) into the φ222.3mm borehole (21);

[0019] Step 6: Inject technical casing cement (23) between the φ222.3mm borehole (21) and the φ177.8mm technical casing (22);

[0020] Step 7: Drill a well using a φ152.4mm drill bit to form a φ152.4mm borehole (31), and the total drilling depth is (34);

[0021] Step 8: running in φ177.8mm technical casing (22) and φ152.4mm borehole (31), φ114.3mm completion casing (32), injecting completion cement (33) between φ177.8mm technical casing (22), φ152.4mm borehole (31) and φ114.3mm completion casing (32), and taking out running-in drill pipe (46);

[0022] Step 9: running in φ114.3mm tie-back casing (37);

[0023] Step 10: carrying out horizontal well volume fracturing operation in φ114.3mm tie-back casing (37), hanger (36) and φ114.3mm completion casing (32);

[0024] Step 11: after fracturing, taking out φ114.3mm tie-back casing (37), φ177.8mm technical casing (22) has large diameter and can be used for sidetracking;

[0025] Sidetracking of first well structure and second well structure:

[0026] Step 1: selecting sidetracking point (45);

[0027] Step 2: backfilling cement (40) below sidetracking point (45) to block unconventional gas reservoir (8);

[0028] Step 3: using φ152.4mm whipstock to sidetrack from φ177.8mm completion casing (221) or φ177.8mm technical casing (22) at sidetracking point (45), using φ152.4mm drill bit to drill a well, and forming φ152.4mm borehole (41) in unconventional gas reservoir (6), and completing drilling with well depth (44);

[0029] Step 4: running in running-in drill pipe (46), hanger (47) and φ114.3mm completion casing (42) in φ177.8mm completion casing (221) or φ177.8mm technical casing (22) and sidetracked φ152.4mm borehole (41), injecting cement (43) between hanger (47) and sidetracked φ152.4mm borehole (41) in φ177.8mm completion casing (221) or φ177.8mm technical casing (22), injecting cement (43) between φ114.3mm completion casing (42) and sidetracked φ152.4mm borehole (41), and taking out running-in drill pipe (46);

[0030] Step 5: running in φ114.3mm tie-back casing (48), and connecting φ114.3mm tie-back casing (48) with φ114.3mm completion casing (42) through hanger (47);

[0031] Step 6: Perform the horizontal well volume fracturing operation in the φ114.3mm tieback casing (48), hanger (47), and φ114.3mm completion casing (42);

[0032] Step 7: After fracturing, the tieback casing (48) is removed, and the hanger (47) is above the φ177.8mm completion casing (221) or φ177.8mm technical casing (22), which has a large diameter and can also be used for sidetracking.

[0033] The following is a further optimization or / and improvement of the above technical solutions of the application:

[0034] In the above first well structure, the lower end of the φ177.8mm completion casing (221) in step 5 is connected to the φ139.7mm completion casing (222) through the φ177.8mm casing box and the φ139.7mm casing pin short section (25).

[0035] In the above second well structure, in step 9, the φ114.3mm tieback casing (37) is connected to the φ114.3mm completion casing (32) through the hanger (36).

[0036] In the above first well structure and second well structure, in step 1 of sidetracking, the sidetracking point selection method is to select the well section with good quality cement (23) of the φ177.8mm completion casing (221) or φ177.8mm technical casing (22) outside the completion casing, and the dogleg severity of the build-up section of the sidetracked well is ≤5.5° / 30m.

[0037] The method described in the application can be used to lower the φ152.4mm casing for sidetracking in the φ177.8mm technical casing or completion casing after the first well is depleted, and then lower the φ114.3mm completion casing to meet the volume fracturing requirements. The φ177.8mm technical casing reserved during the gas production process can also be used to lower the electric submersible pump, screw pump and other external power tools to improve the recovery rate. At the same time, the old well site, ground pipeline and upper casing are all reused, reducing the investment cost. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 is a schematic diagram of the background technology structure. Figure 1 Figure 2 is a schematic diagram of the unconventional multilayer gas reservoir horizontal well three-dimensional development structure of the application.

[0039] Figure 3 is a schematic diagram of the composite casing two-opening well structure reservoir above φ177.8mm casing structure. Figure 2 Figure 4 is a schematic diagram of the unconventional multilayer gas reservoir horizontal well three-dimensional development structure of the application.

[0040] Figure 5 is a schematic diagram of the composite casing two-opening well structure reservoir above φ177.8mm casing structure. Figure 3 Figure 6 is a schematic diagram of the composite casing two-opening well structure reservoir above φ177.8mm casing structure.

[0041] Figure 4 ​The schematic diagram of the structure of the φ114.3mm completion casing sent by the drill pipe for the composite casing two-opening well structure after the sidetracking.

[0042] The schematic diagram of the structure of the φ114.3mm completion casing sent by the drill pipe for the composite casing two-opening well structure after the sidetracking. Figure 5 The schematic diagram of the structure of the φ114.3mm completion casing sent by the drill pipe for the composite casing two-opening well structure after the sidetracking.

[0043] The schematic diagram of the structure of the φ114.3mm completion casing sent by the drill pipe for the composite casing two-opening well structure after the sidetracking. Figure 6 The schematic diagram of the structure of the φ114.3mm completion casing sent by the drill pipe for the composite casing two-opening well structure after the sidetracking.

[0044] The schematic diagram of the structure of the φ114.3mm completion casing sent by the drill pipe for the composite casing two-opening well structure after the sidetracking. Figure 7 The schematic diagram of the structure of the φ114.3mm completion casing sent by the drill pipe for the composite casing two-opening well structure after the sidetracking.

[0045] The schematic diagram of the structure of the φ114.3mm completion casing sent by the drill pipe for the composite casing two-opening well structure after the sidetracking. Figure 8 The schematic diagram of the structure of the φ114.3mm completion casing sent by the drill pipe for the composite casing two-opening well structure after the sidetracking. The schematic diagram of the structure of the φ114.3mm completion casing sent by the drill pipe for the composite casing two-opening well structure after the sidetracking.

[0046] The schematic diagram of the structure of the φ114.3mm completion casing sent by the drill pipe for the composite casing two-opening well structure after the sidetracking. Figure 9 The schematic diagram of the structure of the φ114.3mm completion casing sent by the drill pipe for the composite casing two-opening well structure after the sidetracking. The schematic diagram of the structure of the φ114.3mm completion casing sent by the drill pipe for the composite casing two-opening well structure after the sidetracking.

[0047] The schematic diagram of the structure of the φ114.3mm completion casing sent by the drill pipe for the composite casing two-opening well structure after the sidetracking. Figure 10 The schematic diagram of the structure of the φ114.3mm completion casing sent by the drill pipe for the composite casing two-opening well structure after the sidetracking. The schematic diagram of the structure of the φ114.3mm completion casing sent by the drill pipe for the composite casing two-opening well structure after the sidetracking.

[0048] The schematic diagram of the structure of the φ114.3mm completion casing sent by the drill pipe for the composite casing two-opening well structure after the sidetracking. Figure 11 The schematic diagram of the structure of the φ114.3mm completion casing sent by the drill pipe for the composite casing two-opening well structure after the sidetracking. The schematic diagram of the structure of the φ114.3mm completion casing sent by the drill pipe for the composite casing two-opening well structure after the sidetracking.

[0049] The schematic diagram of the structure of the φ114.3mm completion casing sent by the drill pipe for the composite casing two-opening well structure after the sidetracking. Figure 12 The schematic diagram of the structure of the φ114.3mm completion casing sent by the drill pipe for the composite casing two-opening well structure after the sidetracking. DETAILED DESCRIPTION

[0050] The present application is not limited to the following examples, and the specific implementation can be determined according to the technical solution of the present application and the actual situation.

[0051] In the present application, in order to facilitate the description, the relative position relationship of each component is described according to the layout mode of the drawings attached to the specification, such as: the position relationship of front, back, up, down, left, right and the like is determined according to the layout direction of the drawings attached to the specification. Figure 1

[0052] The present application will be further described below in combination with examples and drawings:

[0053] Example 1: as shown in the drawings Figures 2 to 12As shown, the method for the horizontal well volume fracturing of unconventional multilayer gas reservoirs is performed according to the following steps:

[0054] The first well structure for the first horizontal well with a horizontal section less than 1200m:

[0055] Step 1: drilling with a φ331.2mm drill bit to form a surface φ331.2mm borehole (11) with a surface well depth of (14);

[0056] Step 2: running a φ244.5mm surface casing (12) in the φ331.2mm borehole (11);

[0057] Step 3: injecting surface casing cement (13) between the φ331.2mm borehole (11) and the φ244.5mm casing (12);

[0058] Step 4: drilling with a φ222.3mm drill bit to form a φ222.3mm borehole (21) with a total drilling depth of (24);

[0059] Step 5: running a φ177.8mm completion casing (221) and a φ139.7mm completion casing (222) in the φ222.3mm borehole (21) and injecting completion casing cement (23) between the φ222.3mm borehole (21) and the φ177.8mm completion casing (221) and the φ139.7mm completion casing (222);

[0060] Step 6: performing horizontal well volume fracturing in the φ177.8mm completion casing (221) and the φ139.7mm completion casing (222);

[0061] The second well structure for the first horizontal well with a horizontal section greater than 1200m:

[0062] Step 1: drilling with a φ331.2mm drill bit to form a surface φ331.2mm borehole (11) with a surface well depth of (14);

[0063] Step 2: running a φ244.5mm surface casing (12) in the φ331.2mm borehole (11);

[0064] Step 3: injecting surface casing cement (13) between the φ331.2mm borehole (11) and the φ244.5mm casing (12);

[0065] Step 4: drilling with a φ222.3mm drill bit to form a φ222.3mm borehole (21) with a total drilling depth of (35);

[0066] Step 5: φ177.8mm technical casing (22) is run in φ222.3mm borehole (21);

[0067] Step 6: φ177.8mm technical casing cement (23) is injected between φ222.3mm borehole (21) and φ177.8mm technical casing (22);

[0068] Step 7: φ152.4mm drill bit is used to drill well, φ152.4mm borehole (31) is formed, and the drilled well depth is (34);

[0069] Step 8: φ114.3mm completion casing (32) is run in φ177.8mm technical casing (22) and φ152.4mm borehole (31), completion cement (33) is injected between φ177.8mm technical casing (22), φ152.4mm borehole (31) and φ114.3mm completion casing (32), and the running-in drill pipe (46) is pulled out;

[0070] Step 9: φ114.3mm tie-back casing (37) is run in;

[0071] Step 10: horizontal well volume fracturing operation is carried out in φ114.3mm tie-back casing (37), hanger (36) and φ114.3mm completion casing (32);

[0072] Step 11: after fracturing, φ114.3mm tie-back casing (37) is pulled out, and φ177.8mm technical casing (22) has large diameter and can be used for sidetracking;

[0073] First wellbore structure and second wellbore structure sidetracking:

[0074] Step 1: sidetracking point (45) is selected;

[0075] Step 2: backfill cement (40) is filled below sidetracking point (45) to block unconventional gas reservoir (8);

[0076] Step 3: φ152.4mm whipstock is used to sidetrack from φ177.8mm completion casing (221) or φ177.8mm technical casing (22) at sidetracking point (45), φ152.4mm drill bit is used to drill well, φ152.4mm borehole (41) is formed in unconventional gas reservoir (6) by sidetracking, and the drilled well depth is (44);

[0077] Step 4: running in running drill pipe (46), hanger (47), φ114.3mm completion casing (42) in φ177.8mm completion casing (221) or φ177.8mm technical casing (22), sidetracked φ152.4mm borehole (41), cementing (43) between φ177.8mm completion casing (221) or φ177.8mm technical casing (22) and sidetracked φ152.4mm borehole (41) below hanger (47), cementing (43) between φ114.3mm completion casing (42) and sidetracked φ152.4mm borehole (41), and pulling out running drill pipe (46);

[0078] Step 5: running in φ114.3mm tieback casing (48), which is connected with φ114.3mm completion casing (42) through hanger (47);

[0079] Step 6: performing horizontal well volume fracturing operation in φ114.3mm tieback casing (48), hanger (47) and φ114.3mm completion casing (42);

[0080] Step 7: after fracturing, pulling out tieback casing (48), and φ177.8mm completion casing (221) or φ177.8mm technical casing (22) above hanger (47), which has large diameter and can be used for sidetracking.

[0081] The new well structure needs to meet the requirements that φ60.3mm or 48.3mm production pipe string can be run in after fracturing, and external power drainage gas recovery tool can be run in during the later stage of gas recovery; after the first well is depleted, horizontal well sidetracking can be performed in the original borehole, the diameter of the horizontal well completion casing after sidetracking is ≥114.3mm, and the fracturing discharge capacity is ≥8m³ / min. Therefore, φ177.8mm technical casing or completion casing needs to be reserved in the vertical section.

[0082] The present application provides the first horizontal well to develop a reservoir, to carry out horizontal well drilling, fracturing, gas production, and to reserve a φ177.8mm completion casing or a technical casing above the reservoir, to close the first reservoir from the sidetracking point when the first well is exhausted, to sidetrack from the reserved φ177.8mm completion casing or technical casing to develop the second reservoir, to lower a completion string meeting the horizontal well volume fracturing to carry out fracturing, gas production and other processes. If there is a third reservoir, it can be developed in turn to realize the three-dimensional development of the horizontal well volume fracturing of the unconventional multi-layer gas reservoir. Since the horizontal well volume fracturing can be realized each time, the single well fracturing reconstruction procedure can be maximized, and the ultimate goal of improving production and single well cumulative production can be achieved. The well site, surface pipeline and upper casing of the old well can be used to maximize the reduction of investment. The φ177.8mm technical casing or completion casing is reserved each time, which is beneficial to the lowering of electric submersible pumps, screw pumps and other external power tools in the gas production process, and improves the recovery efficiency.

[0083] Compared with the prior art, the present application has the following advantages:

[0084] 1. Starting from gas production and fracturing, the optimized wellbore structure is suitable for the development of different reservoirs of unconventional multi-layer gas reservoirs and is suitable for the full life cycle of unconventional multi-layer gas reservoirs.

[0085] 2. The same wellbore of the unconventional multi-layer gas reservoir can be developed in different periods, and each layer can use horizontal well volume fracturing to maximize the fracturing reconstruction of the reservoir and obtain the maximum production and recovery efficiency.

[0086] 3. The φ177.8mm technical casing or completion casing is reserved during the gas production process, and when the reservoir is exhausted, another reservoir can be developed by sidetracking at the sidetracking point to form a horizontal well with volume fracturing capacity.

[0087] 4. The φ114.3mm casing can be reused, which greatly saves the production and construction investment.

[0088] 5. One well site, surface casing, technical casing or completion casing and surface pipeline can be used multiple times, which greatly saves investment.

[0089] 6. When a reservoir is developed and exhausted, the second and third reservoirs can be developed by sidetracking to realize the replacement of production.

[0090] The above method suitable for the three-dimensional development of the horizontal well volume fracturing of the unconventional multi-layer gas reservoir can be further optimized or / and improved according to actual needs:

[0091] Example 2: as shown in the attached Figure 3As shown, in the first wellbore structure, in step 5, the lower end of the φ177.8mm completion casing (221) is connected to the φ139.7mm completion casing (222) through the φ177.8mm casing female buckle and the φ139.7mm casing male buckle short section (25).

[0092] Example 3: As shown in the attached Figure 7 、 8 As shown in FIG9 , the second wellbore structure, in step 9, the φ114.3 mm tieback casing (37) is connected to the φ114.3 mm completion casing (32) via a hanger (36).

[0093] Example 4: As shown in the attached Figure 4 、 5 As shown in Figures 6, 10, 11, and 12, in step 1 of side drilling of the first wellbore structure and the second wellbore structure, the side drilling point selection method is that the well section with good quality of φ177.8mm completion casing (221) or φ177.8mm technical casing (22) and outer completion casing cementing cement (23), and the dogleg degree of the side drilling well deflection section is ≤5.5° / 30m.

[0094] Example 5: Using a composite casing two-wellbore structure, with a φ177.8mm casing reserved above the reservoir

[0095] It is suitable for the first horizontal well with a horizontal section of less than 1200m. Its advantages are short drilling cycle and large fracturing displacement.

[0096] Step 1 Figure 3 ): Drilling was carried out using a φ331.2mm drill bit to form a surface φ331.2mm wellbore 11 with a surface well depth of 14;

[0097] Step 2 Figure 3 ) : A φ244.5 mm surface casing 12 is run into a φ331.2 mm wellbore 11;

[0098] Step 3 Figure 3 ) : Inject surface casing cement 13 between the φ331.2mm wellbore 11 and the φ244.5mm casing 12;

[0099] Step 4 Figure 3 ): A φ222.3 mm drill bit was used to drill a wellbore 21 with a diameter of 222.3 mm in an unconventional gas reservoir 8, and the well was completed to a secondary completion depth of 24;

[0100] Step 5 Figure 3): running φ177.8mm completion casing 221 + φ139.7mm completion casing 222 in φ222.3mm borehole 21, and connecting φ177.8mm completion casing 221 and φ139.7mm completion casing 222 with φ177.8mm casing box φ139.7mm casing pin nipple 25;

[0101] Step 6 Figure 3 ) : injecting completion casing cement 23 between φ222.3mm borehole 21 and φ177.8mm completion casing 221 + φ139.7mm completion casing 222;

[0102] Step 7 Figure 3 ) : performing horizontal well volume fracturing operation in φ177.8mm completion casing 221 + φ139.7mm completion casing;

[0103] Step 8: φ177.8mm completion casing 221 has a large diameter and can be used for sidetracking.

[0104] Composite casing two-opening wellbore structure sidetracking realizes multi-layer reservoir horizontal well volume fracturing three-dimensional development

[0105] Unconventional natural gas wells generally adopt depletion type exploitation, and when the natural gas in unconventional gas reservoir 8 is depleted, old well casing can be used for sidetracking.

[0106] Step 1 Figure 4 ) : selecting a sidetracking point: a well section with good quality of φ177.8mm completion casing 221 outer completion casing cement 23; the dogleg of the build-up section of the sidetracking well is ≤5.5° / 30m, and the sidetracking point 45 is selected;

[0107] Step 2 Figure 4 ) : backfilling cement 40 below the sidetracking point 45 to block unconventional gas reservoir 8;

[0108] Step Figure 4 ) 3: using φ152.4mm whipstock to sidetrack from the sidetracking point 45, using φ152.4mm drill bit to drill a well, and forming φ152.4mm borehole 41 in unconventional gas reservoir 6, and the drilled well depth is 44;

[0109] Step 4 Figure 4 ) : running φ114.3mm completion casing 42 in φ177.8mm completion casing 221 + φ152.4mm borehole 41, injecting cement 43 between φ177.8mm completion casing 221 + φ152.4mm borehole 41 below the suspender 47 and φ114.3mm completion casing 42, and removing the running drill pipe 46;

[0110] Step 5Figure 5 ): Run the φ114.3mm tieback casing 48;

[0111] Step 6 Figure 5 ), performing horizontal well volume fracturing operations in a φ114.3 mm tieback casing 48 + hanger 47 + φ114.3 mm completion casing 42;

[0112] Step 7 Figure 6 ): After fracturing, the tieback casing 48 is brought out, and above the hanger 47 is a φ177.8mm completion casing and a φ177.8mm technical casing 5, which has a large diameter and can also be used for side drilling.

[0113] Example 6: Using a suspended cementing three-well structure, with a φ177.8mm casing reserved above the reservoir

[0114] It is suitable for the first horizontal well with a horizontal section greater than 1200m. Its advantage is the long horizontal section. It can be used in stable reservoirs or barrier areas to increase the controlled reserves of a single well.

[0115] Step 1 Figure 7 ): Drilling was carried out using a φ331.2mm drill bit to form a surface φ331.2mm wellbore 11 with a surface well depth of 14;

[0116] Step 2 Figure 7 ) : A φ244.5 mm surface casing 12 is run into a φ331.2 mm wellbore 11;

[0117] Step 3 Figure 7 ) : Inject surface casing cement 13 between the φ331.2mm wellbore 11 and the φ244.5mm casing 12;

[0118] Step 4 Figure 7 ) : A φ222.3mm drill bit was used to drill a φ222.3mm wellbore 21, with an intermediate completion depth of 35m. A φ177.8mm technical casing 22 was run into the φ222.3mm wellbore 21;

[0119] Step 5 Figure 7 ): injecting intermediate cement 23 between the φ222.3mm wellbore 21 and the φ177.8mm technical casing 22;

[0120] Step 6 Figure 7 ): Drilling with a φ152.4 mm drill bit to form a φ152.4 mm wellbore 31 in the unconventional gas reservoir 8;

[0121] Step 7 Figure 7) : running in φ177.8mm technical casing 22 + φ152.4mm borehole 31 + running in drill pipe 46 + hanger 47 + φ114.3mm completion casing 32, injecting completion cement 33 between φ177.8mm technical casing 22 + φ152.4mm borehole 31 and φ114.3mm completion casing 32, and pulling out drill pipe 46;

[0122] Step 8 Figure 8 ) : running in φ114.3mm tieback casing 37;

[0123] Step 9 Figure 8 ), performing horizontal well volume fracturing operation in φ114.3mm tieback casing 37 + hanger 47 + φ114.3mm completion casing 32;

[0124] Step 10 Figure 9 ) : after fracturing, pulling out tieback casing 37, and φ177.8mm completion casing above hanger 47, φ177.8mm technical casing 5, which has large diameter, can be used for sidetracking.

[0125] Sidetracking of suspension cementing three-opening well structure realizes multi-layer system reservoir horizontal well volume fracturing three-dimensional development Figure 10 、 Figure 11 、 Figure 12 )

[0126] When natural gas in unconventional gas reservoir 8 is depleted, old well φ177.8mm technical casing can be used for sidetracking.

[0127] Step 1 Figure 10 ) : selecting sidetracking point: well section with good quality of φ177.8mm technical casing 22 outer completion casing cement 23; dogleg of build-up section of sidetracking well is ≤5.5° / 30m, and sidetracking point 45 is selected;

[0128] Step 2 Figure 10 ) : backfilling cement 40 below sidetracking point 45, and blocking unconventional gas reservoir 8;

[0129] Step 3 Figure 10 ) : using φ152.4mm whipstock to sidetrack from sidetracking point 45, using φ152.4mm drill bit to drill well, and forming φ152.4mm borehole 41 in unconventional gas reservoir 6, and completing drilling well depth of 44;

[0130] Step 4 Figure 10): running in φ177.8mm technical casing 22 + sidetracking φ152.4mm borehole 41 + running in drill pipe 46 + hanger 47 + φ114.3mm completion casing 42, injecting cement 43 between hanger 47 and φ114.3mm completion casing 42 in φ177.8mm technical casing 22 + sidetracking φ152.4mm borehole 41, and pulling out drill pipe 46;

[0131] Step 5 Figure 11 ) : running in φ114.3mm tieback casing 48;

[0132] Step 6 Figure 12 ), performing horizontal well volume fracturing operation in φ114.3mm tieback casing 48 + hanger 47 + φ114.3mm completion casing 42;

[0133] Step 7 Figure 12 ) : after fracturing, pulling out tieback casing 48, φ177.8mm completion casing above hanger 47, φ177.8mm technical casing 5, which has large drift diameter and can also be used for sidetracking.

[0134] Example 7: Surface casing, technical casing and completion casing types

[0135] (1) Composite casing two-opening wellbore structure casing optimization

[0136]

[0137] (2) Hanger cementing three-opening wellbore structure

[0138]

[0139] Example 8: Horizontal well volume fracturing method and construction parameters

[0140] In this wellbore structure, segmented fracturing technologies such as pumping bridge plug, coiled tubing drag, and cementing sliding sleeve can be matched to realize horizontal well volume fracturing.

[0141] The volume fracturing parameters are as follows:

[0142]

[0143] As can be seen from the above table, both completion strings can meet the needs of volume fracturing of more than 8m³ / min before sidetracking, so both completion strings can meet the needs of fracturing discharge of ≥8m³ / min after sidetracking.

[0144] Example 9: Matching unconventional gas reservoir drainage gas recovery method

[0145] The unconventional natural gas well generally has the characteristics of low pressure, low permeability, containing water and fast decline, and drainage gas recovery is the key to improve production and recovery, and the following table is the minimum liquid carrying flow rate of gas well with different API tubing specifications.

[0146]

[0147] (1) In order to reduce the critical liquid carrying flow rate of the gas well and take into account the gas recovery friction, generally, a φ60.3mm or φ48.3 production pipe string is selected;

[0148] (2) When the natural gas well production is reduced to 110% of the critical liquid carrying flow rate, the drainage gas recovery measures are taken in advance to reduce the pressure loss and prolong the stable production period. For example, foam drainage, plunger and other measures;

[0149] (3) When the foam drainage, plunger and other measures are invalid, the production pipe string and the annulus between the production pipe string and the completion casing are all liquid filled, and normal production cannot be achieved. Because the upper part is reserved with a φ177.8mm casing, the drift diameter is large, the electric submersible pump, screw pump tool and other tools can be lowered, the external power forced drainage is adopted, and the cumulative production and recovery of the gas well are improved.

[0150] The above technical features constitute the embodiments of the present application, have strong adaptability and implementation effect, and can increase or reduce unnecessary technical features according to actual needs to meet the needs of different situations.

Claims

1. A method for three-dimensional development of horizontal well volume fracturing for unconventional multilayer gas reservoirs, characterized in that Comprising the following steps: The first well structure suitable for the first horizontal well with the horizontal section less than 1200m: Step 1: drilling with a φ331.2mm drill bit to form a φ331.2mm surface hole (11), the surface hole depth being the first well depth (14); Step 2: running a φ244.5mm surface casing (12) in the φ331.2mm hole (11); Step 3: injecting surface casing cement (13) between the φ331.2mm hole (11) and the φ244.5mm casing (12); Step 4: drilling with a φ222.3mm drill bit to form a φ222.3mm hole (21), the total depth being the second well depth (24); Step 5: running a φ177.8mm completion casing (221) and a φ139.7mm completion casing (222) in the φ222.3mm hole (21), and injecting completion casing cement (23) between the φ222.3mm hole (21) and the φ177.8mm completion casing (221) and the φ139.7mm completion casing (222); Step 6: performing volume fracturing operation in the φ177.8mm completion casing (221) and the φ139.7mm completion casing (222); The second well structure suitable for the first horizontal well with the horizontal section greater than 1200m: Step 1: drilling with a φ331.2mm drill bit to form a φ331.2mm surface hole (11), the surface hole depth being the first well depth (14); Step 2: running a φ244.5mm surface casing (12) in the φ331.2mm hole (11); Step 3: injecting surface casing cement (13) between the φ331.2mm hole (11) and the φ244.5mm casing (12); Step 4: drilling with a φ222.3mm drill bit to form a φ222.3mm hole (21), the total depth being the third well depth (35); Step 5: running a φ177.8mm technical casing (22) in the φ222.3mm hole (21); Step 6: injecting technical casing cement (23) between the φ222.3mm hole (21) and the φ177.8mm technical casing (22); Step 7: drilling with a φ152.4mm drill bit to form a φ152.4mm hole (31), the total depth being the fourth well depth (34); Step 8: running a running-in drill pipe (46), a hanger (36) and a φ114.3mm completion casing (32) in the φ177.8mm technical casing (22) and the φ152.4mm hole (31), injecting completion cement (33) between the φ177.8mm technical casing (22), the φ152.4mm hole (31) and the φ114.3mm completion casing (32), and pulling out the running-in drill pipe (46); Step 9: running a φ114.3mm back-connection casing (37); Step 10: Perform the horizontal well volume fracturing operation in the φ114.3mm back-connection casing (37), hanger (36), φ114.3mm completion casing (32); Step 11: After fracturing, the φ114.3mm back-connection casing (37) is removed, and the φ177.8mm technical casing (22) has a large diameter and can be used for sidetracking; Sidetracking of the first well structure and the second well structure: Step 1: Select a sidetracking point (45); Step 2: Backfill cement (40) below the sidetracking point (45) to block the unconventional gas reservoir (8); Step 3: Use a φ152.4mm whipstock to sidetrack from the φ177.8mm completion casing (221) or the φ177.8mm technical casing (22) at the sidetracking point (45), use a φ152.4mm drill bit to drill a well, and form a φ152.4mm borehole (41) in the unconventional gas reservoir (6) to complete the drilling to a fifth well depth (44); Step 4: Lower a running drill pipe (46), a hanger (47), and a φ114.3mm completion casing (42) into the φ177.8mm completion casing (221) or the φ177.8mm technical casing (22) and the sidetracked φ152.4mm borehole (41), inject cement (43) between the φ177.8mm completion casing (221) or the φ177.8mm technical casing (22) and the sidetracked φ152.4mm borehole (41) below the hanger (47), inject cement (43) between the φ114.3mm completion casing (42) and the sidetracked φ152.4mm borehole (41), and remove the running drill pipe (46); Step 5: Lower a φ114.3mm back-connection casing (48), which is connected to the φ114.3mm completion casing (42) through the hanger (47); Step 6: Perform the horizontal well volume fracturing operation in the φ114.3mm back-connection casing (48), hanger (47), φ114.3mm completion casing (42); Step 7: After fracturing, remove the back-connection casing (48), and the section above the hanger (47) is the φ177.8mm completion casing (221) or the φ177.8mm technical casing (22), which has a large diameter and can be used for sidetracking.

2. The method for horizontal well volumetric fracturing stereoscopic development of unconventional multi-layer gas reservoirs according to claim 1, characterized in that In the first well structure, the lower end of the φ177.8mm completion casing (221) is connected to the φ139.7mm completion casing (222) through the φ177.8mm casing box and the φ139.7mm casing pin.

3. The method according to claim 1, characterized in that In the second well structure, the φ114.3mm back-connection casing (37) is connected to the φ114.3mm completion casing (32) through the hanger (36).

4. The method for horizontal well volumetric fracturing stereoscopic development of unconventional multi-layer gas reservoirs according to claim 1 or 2 or 3, characterized in that In the sidetracking of the first well structure and the second well structure, the sidetracking point is selected as follows: the well section with good quality cement (23) outside the φ177.8mm completion casing (221) or the φ177.8mm technical casing (22) and the dogleg severity of the build-up section of the sidetracked well is ≤5.5° / 30m.

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