Fracturing string for reducing nitrogen foam fracturing friction and protecting casing head

Abstract

The utility model discloses a fracturing string for reducing nitrogen foam fracturing friction and protecting a casing head, which comprises a casing, a safety joint, a hydraulic anchor and a packer are arranged in the casing, the safety joint, the hydraulic anchor and the packer are sequentially connected through a tool string, one end, far away from the hydraulic anchor, of the packer is connected with a horn mouth through a tool string, and the other end of the packer is connected with the hydraulic anchor. A sleeve head is arranged at the end opening, close to the safety connector, of the sleeve, and the other end of the tool string penetrates through the sleeve head. The fracturing pipe column for reducing the nitrogen foam fracturing friction resistance and protecting the casing head solves the problems that in the prior art, in the fracturing process, the friction resistance is large, and the pressure borne by the casing head is insufficient.

Description

Technical Field

[0001] The utility model belongs to the technical field of tight gas exploitation, and particularly relates to a fracturing string for reducing nitrogen foam fracturing friction and protecting a casing head. Background Art

[0002] In addition to the characteristics of "low permeability, low pressure, and low abundance" of tight gas reservoirs, the complex pore throat structure, small pore throat radius, and large pore throat ratio of the reservoirs have caused serious reservoir pore water lock problems. At the same time, the ability to flow back by relying on the reservoir's own energy is poor and slow, and the fracturing fluid retained in the formation causes great damage to the formation; due to geographical reasons, this block is dry and water-scarce. The use of nitrogen foam fracturing to improve the flowback capacity of the fracturing fluid is an effective solution to the problems of fracturing fluid loss and damage caused by retained formations in the transformation of low-pressure and low-permeability oil and gas reservoirs. Combined with the previous conversion or repeated transformation of old wells, due to the problem of insufficient pressure bearing capacity of the casing head of the old well production casing, the friction resistance of nitrogen foam fracturing construction is large, the wellhead pressure is high, the scale of fracturing is restricted, and the fracturing transformation effect is affected. Utility Model Content

[0003] The utility model aims to provide a fracturing string for reducing friction resistance of nitrogen foam fracturing and protecting casing heads, thereby solving the problems of large friction resistance and insufficient pressure bearing of casing heads in the fracturing process in the prior art.

[0004] The technical solution adopted by the utility model is a fracturing string for reducing friction resistance of nitrogen foam fracturing and protecting casing heads, comprising a casing, wherein a safety joint, a hydraulic anchor and a packer are arranged inside the casing, the safety joint, the hydraulic anchor and the packer are connected in sequence through a tool string, the end of the packer away from the hydraulic anchor is connected to a bell mouth through the tool string, a casing head is provided at the end of the casing near the safety joint, and the other end of the tool string passes through the casing head.

[0005] The utility model is also characterized in that:

[0006] The tubing string includes multiple tubings, one end of each of which passes through the casing head. The safety joint, hydraulic anchor and packer are connected in sequence through the multiple tubings, and the multiple tubings are commonly connected to the bellmouth.

[0007] The number of oil pipes is 4 or 5, the length of the multiple oil pipes is 40-50m, and the diameters of the multiple oil pipes are 73mm or 89mm.

[0008] A number of reservoir perforations are opened on the casing wall near the bell mouth.

[0009] Compared with the prior art, the beneficial effects of the present invention are:

[0010] (1) The utility model provides a fracturing string for reducing friction and protecting the casing head during nitrogen foam fracturing. It is suitable for depleted or underpressure wells, water-sensitive formations, and low-permeability gas wells. Nitrogen foam fracturing technology is used to increase reservoir energy. The injection method is a combined tubing + casing method, and a 40-50m tubing is used for injection at the wellhead. The fluid flows through the bell mouth and is then injected into the casing. This fracturing method can increase the displacement, reduce the amount of fluid entering the well, reduce reservoir damage, increase the return rate, and increase gas production.

[0011] (2) The fracturing string used in the present invention for reducing frictional resistance during nitrogen foam fracturing and protecting the casing head effectively reduces frictional resistance during fracturing construction by 20-30 MPa. Compared with nitrogen foam fracturing construction using 73mm oil pipe, the pump pressure is reduced by 20%-28%. Safety risks during fracturing construction are also reduced.

[0012] (3) The fracturing string of the utility model for reducing friction resistance of nitrogen foam fracturing and protecting casing head has a foam quality of sand-carrying liquid of 65-80%. At the same time, the amount of sand added is increased by 3.2% compared with the nitrogen foam fracturing of oil pipe, and the maximum sand ratio is increased from 69.8% to 84%.

[0013] (4) The fracturing string used in this utility model for reducing friction resistance of nitrogen foam fracturing and protecting casing head has high liquid efficiency, less liquid volume entering the ground, and the liquid volume used for single cubic meter of sand is 10m3 / s compared with conventional fracturing. 3 Reduced to 4m 3 , minimizing reservoir damage. The liquid nitrogen ratio reaches 105%, far exceeding the 7.6% used in conventional hydraulic fracturing. This increases reservoir energy and boosts the flowback rate to over 90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The utility model is a structural schematic diagram of a fracturing string for reducing friction resistance of nitrogen foam fracturing and protecting a casing head.

[0015] In the figure, 1. tool string, 2. casing head, 3. safety joint, 4. hydraulic anchor, 5. packer, 6. bell mouth, 7. casing, 8. reservoir perforation, 9. artificial bottom hole. DETAILED DESCRIPTION

[0016] The present invention will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0017] The utility model provides a fracturing string for reducing nitrogen foam fracturing friction and protecting casing heads, such as Figure 1As shown, it includes a casing 7, in which a safety joint 3, a hydraulic anchor 4 and a packer 5 are provided. The safety joint 3, the hydraulic anchor 4 and the packer 5 are connected in sequence through a tool string 1. The end of the packer 5 away from the hydraulic anchor 4 is connected to a bell mouth 6 through the tool string 1. A casing head 2 is provided at the end of the casing 7 near the safety joint 3, and the other end of the tool string 1 passes through the casing head 2; the tool string 1 includes multiple oil pipes, one end of each of the multiple oil pipes passes through the casing head 2, the safety joint 3, the hydraulic anchor 4 and the packer 5 are connected in sequence through multiple oil pipes, and the multiple oil pipes are commonly connected to the bell mouth 6; the number of oil pipes is 4-5, the length of the multiple oil pipes is 40-50m, and the diameter of the multiple oil pipes is 73mm or 89mm; a number of reservoir perforations 8 are opened on the wall of the casing 7 near the bell mouth 6, and the bottom of the casing 7 is an artificial well bottom 9.

[0018] Among them, the hydraulic anchor 4 is used to fix the oil pipe and the packer 5 during fracturing construction. During fracturing construction, the packer 5 can isolate the pressure transmission and protect the old well casing from the condition where the fracturing casing head cannot meet the construction requirements. At the same time, after the packer 5 is sealed and pressurized, its rubber expands to form a sealing state with the inner wall of the casing 7.

[0019] The working principle of the fracturing string provided by the utility model for reducing nitrogen foam fracturing friction and protecting the casing head is:

[0020] First, the fracturing fluid is injected into the oil pipe by pressure, using a combined injection method of oil pipe + casing 7. The fracturing fluid flows through the oil pipe in sequence through the hydraulic anchor 4, the packer 5 and the bell mouth 6, and finally flows out into the casing 7 through the bell mouth 6. The fracturing fluid enters the reservoir perforation 8 through the casing 7 and enters the reservoir through the reservoir perforation 8 to complete the fracturing.

[0021] During the construction process, the fracturing fluid flows from the oil pipe into the casing 7, and the inner diameter becomes larger. This combined injection method achieves a significant reduction in friction resistance.

[0022] When the pressure exceeds 35 MPa, the balance pressure is increased to control the pressure difference between the tubing and the casing 7 to be no more than 45 MPa, and the increased balance pressure is no more than 25 MPa, while ensuring that the pressure resistance of the packer 5 is no less than 70 MPa.

[0023] Example 1

[0024] This embodiment provides a fracturing string for reducing nitrogen foam fracturing friction and protecting the casing head, such as Figure 1As shown, it includes a casing 7, in which a safety joint 3, a hydraulic anchor 4 and a packer 5 are provided. The safety joint 3, the hydraulic anchor 4 and the packer 5 are connected in sequence through a tool string 1. The pressure resistance of the packer is not less than 70 MPa. The end of the packer 5 away from the hydraulic anchor 4 is connected to a bell mouth 6 through the tool string 1. A casing head 2 is provided at the end of the casing 7 near the safety joint 3, and the other end of the tool string 1 passes through the casing head 2; the tool string 1 includes four oil pipes with a length of 50 m and a diameter of 73 mm. One end of the four oil pipes passes through the casing head 2, the safety joint 3, the hydraulic anchor 4 and the packer 5 are connected in sequence through four oil pipes, and the four oil pipes are connected to the bell mouth 6 in common. A number of reservoir perforations 8 are opened on the pipe wall of the casing 7 near the bell mouth 6, and the bottom of the casing 7 is an artificial well bottom 9.

[0025] Example 2

[0026] This embodiment provides a fracturing string for reducing nitrogen foam fracturing friction and protecting the casing head, such as Figure 1 As shown, it includes a casing 7, in which a safety joint 3, a hydraulic anchor 4 and a packer 5 are provided. The safety joint 3, the hydraulic anchor 4 and the packer 5 are connected in sequence through a tool string 1. The pressure resistance of the packer is not less than 70 MPa. The end of the packer 5 away from the hydraulic anchor 4 is connected to a bell mouth 6 through the tool string 1. A casing head 2 is provided at the end of the casing 7 near the safety joint 3, and the other end of the tool string 1 passes through the casing head 2; the tool string 1 includes four oil pipes with a length of 50 m and a diameter of 89 mm. One end of the four oil pipes passes through the casing head 2, the safety joint 3, the hydraulic anchor 4 and the packer 5 are connected in sequence through four oil pipes, and the four oil pipes are connected to the bell mouth 6 in common. A number of reservoir perforations 8 are opened on the pipe wall of the casing 7 near the bell mouth 6, and the bottom of the casing 7 is an artificial well bottom 9.

[0027] Example 3

[0028] This embodiment provides a fracturing string for reducing nitrogen foam fracturing friction and protecting the casing head, such as Figure 1 As shown, it includes a casing 7, in which a safety joint 3, a hydraulic anchor 4 and a packer 5 are provided. The safety joint 3, the hydraulic anchor 4 and the packer 5 are connected in sequence through a tool string 1. The pressure resistance of the packer is not less than 70 MPa. The end of the packer 5 away from the hydraulic anchor 4 is connected to a bell mouth 6 through a tool string 1. A casing head 2 is provided at the end of the casing 7 near the safety joint 3, and the other end of the tool string 1 passes through the casing head 2; the tool string 1 includes 5 oil pipes with a length of 50 m, and the diameter of the 5 oil pipes is 73 mm. One end of the 5 oil pipes passes through the casing head 2, the safety joint 3, the hydraulic anchor 4 and the packer 5 are connected in sequence through 5 oil pipes, and the 5 oil pipes are connected to the bell mouth 6 in common. A number of reservoir perforations 8 are opened on the pipe wall of the casing 7 near the bell mouth 6, and the bottom of the casing 7 is an artificial well bottom 9.

[0029] Example 4

[0030] This embodiment provides a fracturing string for reducing nitrogen foam fracturing friction and protecting the casing head, such as Figure 1 As shown, it includes a casing 7, in which a safety joint 3, a hydraulic anchor 4 and a packer 5 are provided. The safety joint 3, the hydraulic anchor 4 and the packer 5 are connected in sequence through a tool string 1. The pressure resistance of the packer is not less than 70 MPa. The end of the packer 5 away from the hydraulic anchor 4 is connected to a bell mouth 6 through the tool string 1. A casing head 2 is provided at the end of the casing 7 near the safety joint 3, and the other end of the tool string 1 passes through the casing head 2; the tool string 1 includes 5 oil pipes with a length of 50 m, and the diameter of the 5 oil pipes is 89 mm. One end of the 5 oil pipes passes through the casing head 2, the safety joint 3, the hydraulic anchor 4 and the packer 5 are connected in sequence through 5 oil pipes, and the 5 oil pipes are connected to the bell mouth 6 in common. A number of reservoir perforations 8 are opened on the pipe wall of the casing 7 near the bell mouth 6, and the bottom of the casing 7 is an artificial well bottom 9.

[0031] Example 5

[0032] This embodiment provides a fracturing string for reducing nitrogen foam fracturing friction and protecting the casing head, such as Figure 1 As shown, it includes a casing 7, in which a safety joint 3, a hydraulic anchor 4 and a packer 5 are provided. The safety joint 3, the hydraulic anchor 4 and the packer 5 are connected in sequence through a tool string 1. The pressure resistance of the packer is not less than 70 MPa. The end of the packer 5 away from the hydraulic anchor 4 is connected to a bell mouth 6 through the tool string 1. A casing head 2 is provided at the end of the casing 7 near the safety joint 3, and the other end of the tool string 1 passes through the casing head 2; the tool string 1 includes four oil pipes with a length of 40 m and a diameter of 73 mm. One end of the four oil pipes passes through the casing head 2, the safety joint 3, the hydraulic anchor 4 and the packer 5 are connected in sequence through four oil pipes, and the four oil pipes are connected to the bell mouth 6 in common. A number of reservoir perforations 8 are opened on the pipe wall of the casing 7 near the bell mouth 6, and the bottom of the casing 7 is an artificial well bottom 9.

[0033] Example 6

[0034] This embodiment provides a fracturing string for reducing nitrogen foam fracturing friction and protecting the casing head, such as Figure 1As shown, it includes a casing 7, in which a safety joint 3, a hydraulic anchor 4 and a packer 5 are provided. The safety joint 3, the hydraulic anchor 4 and the packer 5 are connected in sequence through a tool string 1. The pressure resistance of the packer is not less than 70 MPa. The end of the packer 5 away from the hydraulic anchor 4 is connected to a bell mouth 6 through the tool string 1. A casing head 2 is provided at the end of the casing 7 near the safety joint 3, and the other end of the tool string 1 passes through the casing head 2; the tool string 1 includes four oil pipes with a length of 40 m and a diameter of 89 mm. One end of the four oil pipes passes through the casing head 2, the safety joint 3, the hydraulic anchor 4 and the packer 5 are connected in sequence through four oil pipes, and the four oil pipes are connected to the bell mouth 6 in common. A number of reservoir perforations 8 are opened on the pipe wall of the casing 7 near the bell mouth 6, and the bottom of the casing 7 is an artificial well bottom 9.

[0035] Example 7

[0036] This embodiment provides a fracturing string for reducing nitrogen foam fracturing friction and protecting the casing head, such as Figure 1 As shown, it includes a casing 7, in which a safety joint 3, a hydraulic anchor 4 and a packer 5 are provided. The safety joint 3, the hydraulic anchor 4 and the packer 5 are connected in sequence through a tool string 1. The pressure resistance of the packer is not less than 70 MPa. The end of the packer 5 away from the hydraulic anchor 4 is connected to a bell mouth 6 through the tool string 1. A casing head 2 is provided at the end of the casing 7 near the safety joint 3, and the other end of the tool string 1 passes through the casing head 2; the tool string 1 includes 5 oil pipes with a length of 40 m, and the diameter of the 5 oil pipes is 73 mm. One end of the 5 oil pipes passes through the casing head 2, the safety joint 3, the hydraulic anchor 4 and the packer 5 are connected in sequence through 5 oil pipes, and the 5 oil pipes are connected to the bell mouth 6 in common. A number of reservoir perforations 8 are opened on the pipe wall of the casing 7 near the bell mouth 6, and the bottom of the casing 7 is an artificial well bottom 9.

[0037] Example 8

[0038] This embodiment provides a fracturing string for reducing nitrogen foam fracturing friction and protecting the casing head, such as Figure 1 As shown, it includes a casing 7, in which a safety joint 3, a hydraulic anchor 4 and a packer 5 are provided. The safety joint 3, the hydraulic anchor 4 and the packer 5 are connected in sequence through a tool string 1. The pressure resistance of the packer is not less than 70 MPa. The end of the packer 5 away from the hydraulic anchor 4 is connected to a bell mouth 6 through the tool string 1. A casing head 2 is provided at the end of the casing 7 near the safety joint 3, and the other end of the tool string 1 passes through the casing head 2; the tool string 1 includes 5 oil pipes with a length of 40 m, and the diameter of the 5 oil pipes is 89 mm. One end of the 5 oil pipes passes through the casing head 2, the safety joint 3, the hydraulic anchor 4 and the packer 5 are connected in sequence through 5 oil pipes, and the 5 oil pipes are connected to the bell mouth 6 in common. A number of reservoir perforations 8 are opened on the pipe wall of the casing 7 near the bell mouth 6, and the bottom of the casing 7 is an artificial well bottom 9.

[0039] Example 9

[0040] Select an old well to transfer the layer and apply nitrogen foam fracturing, the layer is Shanxi Group 2 3 The corresponding depth of the reservoir perforation is 3172m. Five 50m oil pipes with an outer diameter of 73mm are used. The injection method of 50m oil pipe + casing 10 is used. At the beginning of the construction, the packer 5 is first sealed and the fracturing fluid with a foam mass of 70% is added, which is equivalent to a bottom hole displacement of about 5.0m 3 / min. During the sand adding stage, the ground sand concentration is 12.0 PPA, and the liquid volume per cubic meter of sand is 4m 3 / min, the proportion of liquid nitrogen reaches 105%, the construction pressure is stable during sand adding, the sand adding amount is completed according to the design requirements, and the construction pressure is 37.7-47.0MPa.

[0041] After the gas test as required, the flowback rate was 93%, the static pressure was 23.27MPa, and under the conditions of wellhead oil pressure of 11.3MPa and φ20.9mm orifice plate, the stable gas production in 12 hours was measured to be 4.5×104m3. 3 / d, the calculated unimpeded flow rate is 8.7×104m 3 / d.

[0042] Comparative Example 1

[0043] Select an old well to transfer the layer and apply nitrogen foam fracturing, the layer is Shanxi Group 2 3 The perforation section corresponds to a depth of 3210m. The outer diameter of the applied tubing is 89mm. 3210m tubing is used for injection. The surface sand concentration is 2.9PPA, which is equivalent to a bottom hole displacement of about 3m 3 / min, construction pressure 57-68MPa, construction displacement is relatively low, and construction pressure is relatively high.

[0044] Select a gas well and apply conventional clean fracturing fluid, located in Shanxi Group 2 3 The perforation section corresponds to a depth of 2973m. Fracturing is carried out by injecting 73mm tubing with a displacement of 3m 3 / min, construction pressure 57-70MPa, liquid volume per cubic meter of sand 10m 3 / min, liquid nitrogen ratio 7.6%.

[0045] This demonstrates that the fracturing string provided by the present invention for reducing friction in nitrogen foam fracturing and protecting the casing head can effectively reduce string friction and achieve high gas production. Comparison reveals that the fracturing string provided by the present invention significantly reduces friction, reduces pump pressure during operation by 20%-28%, increases displacement, and provides more effective reservoir stimulation while reducing operational safety risks.

[0046] This utility model provides a fracturing string for reducing friction in nitrogen foam fracturing and protecting the casing head. It is primarily suitable for stratum rotation or re-fracturing in older wells. Current technologies use tubing injection or direct casing injection for fracturing, while casing injection of sand-carrying fluid can create longer fractures in the formation. This utility model addresses the problem of older well casing heads failing to meet specified pressure requirements by employing a combination of multiple tubing and casing injection methods to protect the casing head and increase the fracturing pumping capacity.

Claims

1. A fracturing string for reducing friction in nitrogen foam fracturing and protecting casing heads, characterized in that: The invention comprises a casing (7), wherein a safety joint (3), a hydraulic anchor (4) and a packer (5) are provided in the casing (7), wherein the safety joint (3), the hydraulic anchor (4) and the packer (5) are connected in sequence through a tool string (1), wherein the end of the packer (5) away from the hydraulic anchor (4) is connected to a bell mouth (6) through the tool string (1), and a casing head (2) is provided at the end of the casing (7) close to the safety joint (3), and the other end of the tool string (1) passes through the casing head (2); the tool string (1) comprises Multiple oil pipes, one end of each of the multiple oil pipes passes through the casing head (2), the safety joint (3), the hydraulic anchor (4) and the packer (5) are connected in sequence through the multiple oil pipes, and the multiple oil pipes are commonly connected to the bell mouth (6); the number of the oil pipes is 4 or 5, the length of the multiple oil pipes is 40-50m, and the diameter of the multiple oil pipes is 73mm or 89mm; the pressure resistance of the packer is not less than 70Mpa; a plurality of reservoir perforations (8) are opened on the wall of the casing (7) near the bell mouth (6).

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