A combined pipe string for foam drainage in horizontal wells and a method of using the same

Abstract

The present application relates to the field of foam drainage gas recovery, and discloses a combined pipe column for horizontal well foam drainage, which is composed of a small-diameter pipe, a coiled tubing, a rupture disc, a guide head and a medicament injection head, wherein the small-diameter pipe is located in the coiled tubing. A method for using the combined pipe column for horizontal well foam drainage is also disclosed, which comprises the following steps: lowering the combined pipe column for horizontal well foam drainage into a designated position in a horizontal well, installing a well head of the coiled tubing, breaking the rupture disc at the bottom end of the coiled tubing, lowering the small-diameter pipe out of the coiled tubing by a certain length, and finally installing a well head of the small-diameter pipe. The present application can solve the problem that the small-diameter pipe in a long horizontal section well is not easy to be lowered into a designated position.

Description

Technical Field

[0001] This invention relates to the field of foam drainage gas production, specifically to a combined tubing string for foam drainage in horizontal wells and its application method. Background Technology

[0002] In the production of water-bearing gas wells (conventional wells, shale gas wells, and tight gas wells), gas production decreases and the ability to carry away fluids is reduced, meaning the well itself cannot carry away the fluids from the formation in a timely manner. Currently, foam drainage gas production technology is commonly used to assist in fluid carrying.

[0003] Foam drainage gas production involves injecting a foaming agent into the bottom of a gas well. Under the agitation of the gas flow, foam is formed, which reduces density, reduces slippage, and improves the efficiency of liquid carry-over in the gas flow. The accumulated liquid is carried out of the wellbore in the form of foam. Foam drainage gas production is the most widely used and most economical and effective drainage and production stabilization technology for water-bearing gas reservoirs.

[0004] In recent years, conventional gas, shale gas, and tight gas have mostly adopted horizontal well development methods, and the length of the horizontal section has gradually increased to over 3000m. In such long horizontal gas wells, how to remove the accumulated fluid as much as possible is a major challenge for stable gas well production. In horizontal wells, oilfields run tubing and casing inside the casing; the annular space between them is called the casing annulus. Due to the long deviated and horizontal sections, a large amount of fluid accumulates in the casing annulus when fluid accumulates at the bottom of the well. Therefore, foaming agents injected into the casing annulus are unlikely to spread to the entire casing annulus and enter the tubing to assist in foaming and fluid carrying. In this situation, a small-diameter pipe can be run inside the tubing, and the foaming agent can be injected directly near the tubing shoe through the small-diameter pipe, or the foaming agent can be injected through the tubing via a small-diameter pipe, thereby improving the speed and effectiveness of the foaming agent's fluid-carrying effect.

[0005] There are many domestic patents related to small-diameter pipes. CN201057026Y "Skid-mounted small-diameter pipe drainage and gas production device", CN 110410022A "A direct-connection small-diameter tubing string for oil and gas well production and its processing method", and CN 204920926U "Gas wellhead suspended small-diameter pipe chemical injection system" all involve improvements to small-diameter pipes. However, none of them solve the problem that small-diameter pipes are not easy to run into horizontal wells. Due to the irregular curvature of the original well tubing, there is a risk that small-diameter pipes will not be easy to run into the designated position and may be bent and broken inside the tubing. Summary of the Invention

[0006] The present invention aims to provide a combined tubing string for foam drainage in horizontal wells and its usage method, in order to solve the problem that small-diameter pipes in long horizontal well sections are not easy to be lowered to the designated position.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a combined tubing string for foam drainage in horizontal wells, comprising a coiled tubing, a rupture disc installed at the bottom of the coiled tubing, the rupture disc having a through hole along its axial direction, and a small-diameter pipe located inside the coiled tubing, the small-diameter pipe communicating with the through hole of the rupture disc.

[0008] The principle and advantages of this scheme are as follows: In the existing technology, when a small-diameter pipe is run into a horizontal well alone, the strength of the small-diameter pipe is insufficient, and the original well tubing itself has an irregular curve, so the running depth cannot reach the horizontal section. However, in the actual application of this scheme, a combination string of coiled tubing and small-diameter pipe can be manufactured at the same time and then run into the horizontal well. The running capacity of the coiled tubing will carry the small-diameter pipe down, so that the small-diameter pipe can be successfully run into the designed position.

[0009] In addition, in practical applications, this scheme can first lower the coiled tubing to the designated position, and then lower the small-diameter pipe from inside the coiled tubing to the bottom of the coiled tubing. This can utilize the integrity, smoothness, and guiding properties of the inner wall of the coiled tubing to smoothly lower the small-diameter pipe to the designated position, avoiding the risk of the small-diameter pipe being difficult to lower to the designated position and easily bending and breaking inside the tubing in the well due to the complexity of the tubing inside the horizontal well and the irregular bending of the tubing trajectory itself.

[0010] This solution utilizes a combined tubing string structure formed by a small-diameter pipe and coiled tubing to allow the small-diameter pipe to be lowered into a designated horizontal section of a well. This facilitates the injection of foaming agent used for foam drainage into the vicinity of the tubing shoe through the small-diameter pipe, or allows the foaming agent to be injected through the tubing via the small-diameter pipe. This enhances the auxiliary liquid-carrying effect of the foaming agent, effectively removing accumulated liquid from the horizontal section of a long horizontal gas well and achieving stable production of the gas well.

[0011] Preferably, as an improvement, the small-diameter tube is concentrically arranged with the continuous tubing, and there is a gap between the inner walls of the small-diameter tube and the continuous tubing.

[0012] This setup makes it easier for small-diameter pipes to be smoothly lowered into the designated position, avoiding frictional resistance between the small-diameter pipe and the continuous tubing.

[0013] Preferably, as an improvement, it also includes a guide head, which includes a connecting rod and a guide end, one end of the connecting rod being connected to the guide end and the other end of the connecting rod being connected to a small-diameter pipe, and multiple sets of universal joints being connected to the guide end.

[0014] This solution also includes a guide head, in which a connecting rod connects to a small-diameter pipe. Multiple sets of universal joints on the guide head can roll freely, guiding the small-diameter pipe during its lowering process and making the lowering process smoother.

[0015] Preferably, as an improvement, each universal joint consists of a connecting post and a ball. One end of the connecting post is connected to the guide end, and the other end of the connecting post is provided with a groove. The ball is located in the groove and can roll freely in the groove.

[0016] The universal joint in this design consists of a connecting post and a ball. The ball can roll freely within the groove of the connecting post, forming a ball-joint structure. The free rolling of the ball can guide the insertion of small-diameter pipes and allow them to pass through the bends in the oil pipe, thus facilitating the smooth insertion of small-diameter pipes.

[0017] Preferably, as an improvement, the guide end is spherical, and multiple sets of universal joints are evenly distributed along the circumference of the guide end.

[0018] This design ensures that the universal joints on the guide end are evenly distributed, resulting in better guiding effect for small-diameter pipes.

[0019] Preferably, as an improvement, it further includes a guide shorting, the guide shorting comprising a first shorting post and a second shorting post, the first shorting post and the second shorting post being ball-jointed, one end of the guide shorting being connected to a guide head, and the other end of the guide shorting being connected to a drug injection head.

[0020] The guide short connector set in this scheme can work together with the guide head to guide the lowering of small-diameter pipes, and the guide short connector helps to reduce the frictional resistance generated by the guide head.

[0021] Preferably, as an improvement, it also includes a drug injection head, one end of which is connected to a small-diameter pipe and the other end of which is connected to a guide head. The drug injection head includes a drug flow valve and a drug injection short circuit. The drug flow valve can control the fluid to flow only from the inside of the small-diameter pipe to the outside. The drug injection short circuit has multiple injection holes distributed on it.

[0022] In this scheme, chemicals can be injected into the well through the chemical injection head. The chemical flow valve on the chemical injection head can prevent external fluids from entering the small-diameter pipe and affecting the normal injection of chemicals.

[0023] A method for using a combination tubing string for foam drainage in a horizontal well involves lowering the combination tubing string into the designed position within the horizontal well, then installing the coiled tubing wellhead, drilling through the rupture disc at the bottom of the coiled tubing to form a through hole, and finally installing the small-diameter tubing wellhead.

[0024] This solution provides a method for running a combined tubing string for foam drainage in horizontal wells. This method enables small-diameter tubing to be smoothly run into the designated position in the well. The combined running method for foam drainage in horizontal wells in this solution can be used for small-diameter tubing foam drainage gas production in conventional gas, shale gas, and tight gas horizontal wells.

[0025] Preferably, as an improvement, the coiled tubing and the small-diameter tubing are simultaneously run into the horizontal well. The specific steps are as follows: the coiled tubing and the small-diameter tubing are simultaneously manufactured into a concentric combined tubing string; then a rupture disc is installed on the coiled tubing at the bottom of the combined tubing string; and then the concentric combined tubing string is run into the horizontal well at the designed position.

[0026] Currently, coiled tubing has good performance, can adapt to harsh environments, and has strong downhole running capability. In this scheme, coiled tubing and small-diameter tubing are integrated and then run into the horizontal well simultaneously. Compared with directly running the small-diameter tubing, which is prone to being obstructed by the inner wall of the tubing and thus unable to reach the designated position, this scheme can rely on the running capability of the coiled tubing to bring the small-diameter tubing to the designated position, making the running process easier.

[0027] Preferably, as an improvement, the coiled tubing and the small-diameter tubing are run into the horizontal well in sequence. The specific steps are as follows: First, the coiled tubing is run into the designed position in the well and the coiled tubing wellhead is installed; before the coiled tubing rupture plate is opened, the small-diameter tubing is run from inside the coiled tubing to the bottom of the coiled tubing.

[0028] In this scheme, the coiled tubing is sequentially lowered to the designated position before the small-diameter tubing is lowered. The coiled tubing has a smooth and intact interior, which provides good guidance for the small-diameter tubing during its lowering process. This effectively avoids the impact of complex conditions and structures inside the tubing on the lowering of the small-diameter tubing.

[0029] An application of a combined tubing string for foam drainage in horizontal wells, applicable to small-diameter tubing foam drainage gas production in horizontal wells of conventional gas, shale gas, or tight gas.

[0030] The combined tubing string for horizontal well foam drainage in this scheme has a wide range of applications and strong applicability. Attached Figure Description

[0031] Figure 1 This is a partial schematic diagram of a first embodiment of a combined tubing string for foam drainage in a horizontal well according to the present invention.

[0032] Figure 2 This is a schematic diagram of the guide head in an embodiment of a combined tubing string for foam drainage in a horizontal well according to the present invention.

[0033] Figure 3This is a schematic diagram of the guide short connection in Embodiment 1 of the combined tubing string for foam drainage in a horizontal well according to the present invention.

[0034] Figure 4 This is a schematic diagram of the agent injection head in Embodiment 1 of a combined tubing string for foam drainage in a horizontal well according to the present invention.

[0035] Figure 5 This is a schematic diagram of the guide end and universal joint in Embodiment 3 of a combined tubing string for foam drainage in a horizontal well according to the present invention. Detailed Implementation

[0036] The following detailed description illustrates the specific implementation method:

[0037] The reference numerals in the accompanying drawings include: continuous tubing 1, small diameter pipe 2, guide end 3, connecting rod 4, connecting post 5, ball 6, first shorting post 7, second shorting post 8, reagent check valve 10, reagent injection shorting post 11, and injection hole 12.

[0038] Example 1

[0039] The basic implementation examples are as follows: Figure 1 As shown: A combined tubing string for foam drainage in horizontal wells includes coiled tubing 1, small-diameter pipe 2, a rupture disc, a guide head, and a reagent injection head. The rupture disc is installed at the bottom of the coiled tubing 1, and the small-diameter pipe 2 is located inside the coiled tubing 1. The rupture disc has a through hole along its axial direction, and the internal space of the small-diameter pipe 2 communicates with the through hole of the rupture disc. In this embodiment, the rupture disc is opened to establish a natural gas production channel inside the coiled tubing 1, and also to provide a channel for the small-diameter pipe 2 to extend out of the coiled tubing 1 later.

[0040] In this embodiment, the small-diameter pipe 2 and the continuous oil pipe 1 are arranged concentrically, and there is a gap between the inner wall of the small-diameter pipe 2 and the continuous oil pipe 1. This can reduce the frictional resistance between the small-diameter pipe 2 and the continuous oil pipe 1, thereby improving the lowering capability of the small-diameter pipe 2.

[0041] The dimensions of the small-diameter pipe 2 and the coiled tubing 1 are determined based on the well depth, casing, or original tubing dimensions of the gas well. These dimensions are determined through calculations of compressive strength and stiffness. In this embodiment, the small-diameter pipe 2 has an outer diameter of Φ6.35mm, 9.525mm, 12.7mm, or 19.05mm and a wall thickness of 0.87-1.65mm. The coiled tubing 1 has an outer diameter of Φ38.1mm, Φ50.8mm, Φ60.3mm, Φ66.7mm, or Φ73.0mm and a wall thickness of 2.21-6.35mm.

[0042] like Figure 2As shown, the guide head includes a connecting rod 4 and a guide end 3. One end of the connecting rod 4 is connected to the guide end 3. The connection between the connecting rod 4 and the guide end 3 can be achieved by welding or by a detachable connection. The other end of the connecting rod 4 is connected to the small-diameter tube 2 via a guide connector and a reagent injection head. Specifically, in this embodiment, the end of the connecting rod 4 furthest from the guide end 3 is machined with an internal or external thread to connect with the external or internal thread of the guide connector. Furthermore, in this embodiment, the connecting rod 4 is a solid cylinder.

[0043] Multiple sets of universal joints are connected to the guide end 3. In actual use, 4-8 sets of universal joints are used. This embodiment uses 8 sets of universal joints as an example. Each universal joint consists of a connecting post 5 and a ball 6. One end of the connecting post 5 is connected to the guide end 3. In this embodiment, the connecting post 5 and the guide end 3 can be fixed by welding or by detachable connection. The other end of the connecting post 5 is provided with a groove, and the balls 6 are all located in the groove and can roll freely in the groove. That is, the balls 6 and the grooves that contain the balls 6 correspond to each other in sequence. The connection between the balls 6 and the grooves is similar to the ball hinge structure in the prior art. The balls 6 are confined in the groove and can roll freely in the groove without easily falling off. In this embodiment, the diameter of the balls 6 is 4-10mm.

[0044] In this embodiment, the guide end 3 is spherical, and eight sets of universal joints are evenly distributed along the circumference of the guide end 3. In this embodiment, the total length of the guide head is 150-500mm. This range of total guide head length can better adapt to the wellbore trajectory and facilitate installation and operation. The diameter of the connecting rod 4 is the same as or 2-10mm smaller than the diameter of the small diameter pipe 2, and the diameter of the spherical guide end 3 is 2-10mm larger than the diameter of the small diameter pipe 2.

[0045] like Figure 3 As shown, the guide short connector includes a first short connector post 7 and a second short connector post 8. The first short connector post 7 and the second short connector post 8 are connected by a ball joint. Both the first short connector post 7 and the second short connector post 8 are solid cylindrical structures. In this embodiment, one end of the first short connector post 7 is machined into a convex spherical shape, and one end of the second short connector post 8 is machined into a concave spherical shape. The convex and concave spherical shapes on the first and second short connector posts 7 and 8 are matched and connected to each other, making them less prone to detachment and allowing for free bending of 5-30°. In this embodiment, the first short connector post 7 and the second short connector post 8 can be of equal or unequal length.

[0046] One end of the guide short is connected to the guide head, and the other end is connected to the drug injection head. Specifically, in this embodiment, one end of the guide short is processed into an external thread, and the other end is processed into an internal thread so that multiple guide shorts can be interconnected or so that the ends of the guide shorts can be connected to the guide head and the drug injection head.

[0047] In this embodiment, each guide short is 150-500mm long, and 2-6 guide shorts can be used simultaneously depending on actual needs. The length range of 150-500mm for each guide short is suitable for horizontal wellbore trajectories. If it's too long, the guide short may need to bend to pass through wellbore sections with varying inclinations; if it's too short, processing becomes inconvenient. Furthermore, this solution allows for the use of 2-6 guide shorts simultaneously, adapting to complex horizontal wellbore trajectories, and the appropriate number of shorts helps reduce frictional resistance caused by the front guide.

[0048] like Figure 4 As shown, one end of the drug injection head is connected to the small-diameter pipe 2, and the other end is connected to the guide head via a guide short connector. The drug injection head includes a drug flow valve 10 and a drug injection short connector 11. The drug flow valve 10 controls the fluid to flow only from inside the small-diameter pipe 2 to the outside. In this embodiment, the drug flow valve 10 is existing technology, controlling the fluid to enter only from the inlet and preventing backflow. Multiple injection holes 12 are distributed on the drug injection short connector 11. In this embodiment, the injection holes 12 are arranged in two rows, with 4-8 injection holes 12 in each row, and the diameter of the injection holes 12 is 1-4 mm. The drug flow valve 10 and the drug injection short connector 11 are threaded together. The ends of the drug flow valve 10 and the drug injection short connector 11 that are far apart from each other are machined with internal or external threads for connection with the external or internal threads of the small-diameter pipe 2 and the guide short connector.

[0049] Furthermore, the reagent injection short connector 11 in this scheme is 150-500mm long and has the same diameter as the small diameter pipe 2, which can avoid the increase of frictional resistance.

[0050] This embodiment also discloses a method for using a combination tubing string for foam drainage in horizontal wells. The combination tubing string for foam drainage in horizontal wells is lowered into the designed position in the horizontal well, then the wellhead of the coiled tubing 1 is installed, then the rupture plate at the bottom end of the coiled tubing 1 is opened, then the small diameter pipe 2 is lowered out of the coiled tubing 1 for a certain length, and finally the wellhead of the small diameter pipe 2 is installed.

[0051] In this embodiment, coiled tubing 1 and small-diameter tubing 2 are simultaneously run into a horizontal well. The specific steps are as follows: Coiled tubing 1 and small-diameter tubing 2 are manufactured simultaneously into concentric coiled tubing 1 and small-diameter tubing 2 combination strings according to specifications and dimensions; a chemical injection head, a guide short connector, and a guide head are sequentially installed on the small-diameter tubing 2 at the bottom of the combination string; then, a coiled tubing 1 fracture disc is installed on the coiled tubing 1 at the bottom of the combination string; the concentric combination string is then run into the horizontal well at the designed position, and the wellhead of coiled tubing 1 is installed; after the fracture disc of coiled tubing 1 is drilled to form a through hole, the small-diameter tubing 2 can be run out of coiled tubing 1 for a certain length, such as 0-50m, as needed, and finally the wellhead of small-diameter tubing 2 is installed.

[0052] The method of combining the small-diameter tubing 2 and the coiled tubing 1 in this embodiment can be used for small-diameter tubing foam drainage gas production in conventional gas, shale gas, and tight gas horizontal wells.

[0053] Example 2

[0054] The difference between this embodiment and Embodiment 1 is that the coiled tubing 1 and the small-diameter pipe 2 are run into the horizontal well in sequence. The specific steps are as follows: First, the coiled tubing 1 is run into the designed position in the well and the wellhead of the coiled tubing 1 is installed; then, before the rupture disc of the coiled tubing 1 is opened, the small-diameter pipe 2 with a guide head at the lower end is run from inside the coiled tubing 1 to the end of the coiled tubing 1; then the rupture disc of the coiled tubing 1 is opened, and the small-diameter pipe 2 can be run out of the coiled tubing 1 for a certain length as needed, such as 0-50m; finally, the wellhead of the small-diameter pipe 2 is installed.

[0055] Example 3

[0056] like Figure 5 As shown, a combined tubing string for foam drainage in a horizontal well differs from Embodiment 1 in that: this embodiment uses four sets of universal joints. The four sets of universal joints are evenly distributed along the circumference of the guide end 3.

[0057] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A combined tubing string for foam drainage in horizontal wells, comprising coiled tubing, wherein a rupture disc is installed at the bottom of the coiled tubing, and the rupture disc has a through hole along its axial direction, characterized in that: It also includes a small-diameter tube located inside the continuous tubing and communicating with the through hole of the rupture disc; it also includes a guide head, which includes a connecting rod and a guide end, one end of the connecting rod being connected to the guide end and the other end of the connecting rod being connected to the small-diameter tube, and multiple sets of universal joints being connected to the guide end; It also includes a drug injection head, one end of which is connected to a small-diameter pipe and the other end of which is connected to a guide head. The drug injection head includes a drug flow valve and a drug injection short circuit. The drug flow valve can control the fluid to flow only from the inside of the small-diameter pipe to the outside. The drug injection short circuit has multiple injection holes distributed on it.

2. The combined tubing string for foam drainage in a horizontal well according to claim 1, characterized in that: The small-diameter tube is concentrically arranged with the continuous tubing, and there is a gap between the inner wall of the small-diameter tube and the continuous tubing.

3. The combined tubing string for foam drainage in a horizontal well according to claim 1, characterized in that: Each universal joint consists of a connecting post and a ball. One end of the connecting post is connected to the guide end, and the other end of the connecting post is provided with a groove. The ball is located in the groove and can roll freely in the groove.

4. The combined tubing string for foam drainage in a horizontal well according to claim 1, characterized in that: The guide end is spherical, and multiple sets of universal joints are evenly distributed along the circumference of the guide end.

5. A combined tubing string for foam drainage in a horizontal well according to claim 1, characterized in that: It also includes a guide short connector, which includes a first short connector post and a second short connector post, and the first short connector post and the second short connector post are ball-jointed. One end of the guide short connector is connected to the guide head, and the other end of the guide short connector is connected to the drug injection head.

6. A method for using a combined tubing string for foam drainage in a horizontal well, characterized in that: The combined tubing string for foam drainage in a horizontal well, as described in any one of claims 1-5, is lowered into the designed position in the horizontal well. Then, a coiled tubing wellhead is installed, and a through hole is formed by drilling the rupture disc at the bottom of the coiled tubing. Finally, a small-diameter tubing wellhead is installed.

7. The method of using a combined tubing string for foam drainage in a horizontal well according to claim 6, characterized in that: The coiled tubing and small-diameter tubing are simultaneously run into a horizontal well. The specific steps are as follows: the coiled tubing and small-diameter tubing are produced into a concentric combination string at the same time; then a rupture disc is installed on the coiled tubing at the bottom of the combination string; and then the concentric combination string is run into the horizontal well at the designed position.

8. The method of using a combined tubing string for foam drainage in a horizontal well according to claim 6, characterized in that: The coiled tubing and the small-diameter tubing are run into the horizontal well in sequence. The specific steps are as follows: First, run the coiled tubing into the designed position in the well and install the coiled tubing wellhead; before breaking through the coiled tubing rupture plate, run the small-diameter tubing from inside the coiled tubing to the bottom of the coiled tubing.

9. An application of a combined tubing string for foam drainage in a horizontal well according to any one of claims 1-5, characterized in that: Small-diameter pipe foam drainage gas production is applied to horizontal wells of conventional gas, shale gas, or tight gas.

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