A tubular string and method of completing a gas storage reservoir with low pressure reservoir protection

Abstract

This invention belongs to the technical field of horizontal well completion methods for gas storage facilities. It discloses a gas storage well completion method for tubing and low-pressure reservoir protection. The tubing string includes coiled tubing, with a tailpipe connected to the end of the coiled tubing. The tailpipe is a horizontal pipe and includes a screen pipe base. The tail end of the screen pipe base has a fluid outlet hole. Multiple flow passages are formed on the wall of the screen pipe base, including end through holes and fillable through holes. The end through holes are located at the end of the screen pipe base, and the fillable through holes are located between the end through holes and the end of the coiled tubing. The fillable through holes are filled with a soluble filler. This invention removes near-wellbore contamination by using low-pressure reservoir leakage prevention drilling technology, cleaning completion fluid, and acidizing with a soluble screen pipe process. This reduces reservoir contamination and improves single-well injection and production capacity.

Description

Technical Field

[0001] This invention belongs to the technical field of horizontal well completion methods for gas storage facilities, specifically relating to a gas storage well completion method that includes tubing string and low-pressure reservoir protection. Background Technology

[0002] Underground gas storage facilities are one of the main methods of natural gas storage, playing a vital role in ensuring natural gas supply and stabilizing the energy market. However, due to the typically low reservoir pressure coefficient, drilling mud is prone to leakage during injection and production well drilling, contaminating the reservoir. Simultaneously, the presence of solid particles in the drilling fluid can lead to filter cake formation or even intrusion into the formation during prolonged immersion, reducing the reservoir's conductivity. Furthermore, during acidizing treatment, limitations in the acid system and construction techniques prevent the complete removal of the drilling fluid's impact on the reservoir.

[0003] Chinese patent publication number CN108252703A, entitled "Completion Method for Layered Monitoring," describes the following steps: drilling; running a workover tubing into the well, the workover tubing being connected to a perforating gun; perforating the two main gas layers through the perforating gun at locations directly opposite the two main gas layers, thus connecting the two main gas layers to the well; removing the workover tubing and the perforating gun; running a completion tubing into the well, the completion tubing being connected to two working sleeves and two packers, the outer walls of the two working sleeves being equipped with two sets of parameter measuring devices corresponding to the two main gas layers respectively; one packer being located between the two main gas layers, and the other packer being located above the upper main gas layer; simultaneously sealing the two packers between the inner wall of the well casing and the outer wall of the completion tubing. While this patent application can perform well completion operations, it cannot reduce reservoir contamination during the completion process and cannot achieve a uniform acidizing process. Summary of the Invention

[0004] To overcome the problems existing in the prior art, the present invention aims to provide a gas storage well completion method with tubing and low-pressure reservoir protection. This method involves creating an end-hole in the tailpipe wall and filling through-holes in the remaining portion of the tailpipe wall. These filling through-holes contain soluble filler, ensuring smooth drilling fluid outflow and achieving a gradual dissolution effect from the end to the front when dissolving the soluble filler, resulting in more thorough acidizing. This low-pressure reservoir protection method reduces reservoir contamination and improves single-well injection and production capacity.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a tubing string comprising a continuous tubing, the end of which is connected to a tailpipe, the tailpipe being a horizontal pipe, the tailpipe including a screen tube base tube, the tail end of which has a liquid outlet hole, and the wall of the screen tube base tube having a plurality of flow passage holes, the flow passage holes including an end through hole and a fillable through hole; the end through hole is located at the end of the screen tube base tube, and the fillable through hole is located between the end through hole and the end of the continuous tubing; the fillable through hole is filled with a soluble filler.

[0006] Optionally, the soluble filler may be made of a soluble alloy, a soluble ceramic, or a biodegradable plastic.

[0007] Optionally, the ends of the soluble filler and the walls of the fillable through-hole are both threaded.

[0008] Secondly, this invention provides a method for completing a gas storage well with low-pressure reservoir protection, based on the aforementioned tubing string, comprising the following steps: Add solid plugging particles to the drilling fluid and perform leak-proof drilling in low-pressure reservoirs; After drilling is completed and before the tailpipe is set, use clean completion fluid to remove the drilling fluid. Acid is injected and discharged through the end through-hole. The acidification process is completed by gradually dissolving the soluble filler in each fillable through-hole from the end to the front.

[0009] Optionally, the solid-phase plugging particles are supramolecular gels.

[0010] Optionally, after gradually dissolving the soluble filler in each fillable through-hole from the end to the front, the tail tube is pulled outward and acid is continuously injected.

[0011] Optionally, after drilling is completed, impurities, suspended solids and sediments in the completion fluid are removed by high-speed agitation and filtration, and then the drilling fluid is replaced with clean completion fluid.

[0012] Optionally, before drilling to prevent leakage in low-pressure reservoirs, the density of the drilling fluid can be adjusted to 1.15–1.30 g / cm³ using additional additives. 3 The viscosity was adjusted to 10–30 mPa·s.

[0013] Optionally, the additional additives include: dispersants, suspending agents, or loss inhibitors.

[0014] Optionally, the acid solution is a hydrochloric acid solution with a mass concentration of 5% to 30%.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a tubing string in which the tail tube is a horizontal tube. The liquid outlet at the end of the tube is not easy to allow the liquid inside the tube to flow out from the side and is easily blocked. Through the end through hole, the drilling fluid can be ensured to flow out smoothly, and when dissolving soluble filler, the dissolution effect can be achieved from the end to the front, making the acidizing effect more thorough.

[0016] Furthermore, during the outward dragging of the tailpipe, due to inertia, the acid is not easily sprayed in all directions of the borehole. By opening multiple flow holes on the wall of the screen pipe base, the uniformity of spraying can be ensured.

[0017] This invention removes near-wellbore contamination from reservoirs through low-pressure reservoir leakage prevention drilling technology, clean completion fluid, and acidizing using soluble screen tubes. This reduces reservoir contamination and improves single-well injection and production capacity.

[0018] This invention has high practicality in reducing mud loss, mitigating reservoir damage, and improving near-wellbore permeability. It also enables low-pressure reservoir protection during drilling and completion, contributing to improved single-well injection and production capacity, and possesses significant practical value. When applying this invention's low-pressure reservoir protection method for gas storage completion, the unobstructed flow rates during testing of three horizontal wells in the gas storage facility reached 2.96 million, 3.001 million, and 2.861 million cubic meters per day, respectively. Attached Figure Description

[0019] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely schematic to aid in understanding the invention and do not specifically limit the shapes and proportions of the components. In the drawings: Figure 1 This is a three-dimensional schematic diagram of the overall structure of the tubular column of the present invention; Figure 2 This is a side view of the tubular column of the present invention; Figure 3 This is a schematic diagram of the flow passage of the tubing column of the present invention; Among them, 1. Tail tube; 2. Continuous tubing; 3. Liquid outlet hole; 10. Screen tube base tube; 11. Through-flow hole; 12. Soluble filler; 1101. End through-hole; 1102. Fillable through-hole. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0021] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0022] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed during use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0023] When an element is referred to as being "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only embodiments. The use of the term "horizontal" does not imply that the component is required to be absolutely horizontal, but rather that it may be slightly tilted. "Horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but rather that it may be slightly tilted.

[0024] It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of this invention, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or collections thereof.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification and appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0026] The present invention will now be described in detail with reference to the accompanying drawings.

[0027] A tubing string of the present invention includes a continuous tubing 2, the end of which is connected to a tailpipe 1. The tailpipe 1 is a horizontal pipe and includes a screen tube base pipe 10. The tail end of the screen tube base pipe 10 has a liquid outlet hole 3. The wall of the screen tube base pipe 10 is provided with a plurality of flow passage holes 11. Each flow passage hole 11 includes an end through hole 1101 and a fillable through hole 1102. The end through hole 1101 is located at the end of the screen tube base pipe 10, and the fillable through hole 1102 is located between the end through hole 1101 and the end of the continuous tubing 2. The fillable through hole 1102 is filled with a soluble filler 12. The tailpipe 1 of the present invention is a horizontal pipe. The liquid outlet 3 at its end is not easy to allow the liquid inside the pipe to flow out from the side and is easy to be blocked. Through the end through hole 1101, the drilling fluid can be ensured to flow out smoothly, and when dissolving the soluble filler 12, the effect of dissolving from the end to the front can be achieved, making the acidification effect more thorough.

[0028] A method for completing a gas storage well for low-pressure reservoir protection according to the present invention, using the aforementioned tubing string, includes the following steps: Add solid plugging particles to the drilling fluid and perform leak-proof drilling in low-pressure reservoirs; After drilling is completed, before the tailpipe 1 is suspended and set, the drilling fluid is replaced with clean completion fluid. Acid is injected and discharged through the end through-hole 1101. The soluble filler 12 in each fillable through-hole 1102 is gradually dissolved from the end to the front end, and the acidification modification is completed.

[0029] This invention removes near-wellbore contamination from reservoirs by employing low-pressure reservoir leak-proof drilling, cleaning completion fluids, and acidizing with soluble screen tubes. This reduces reservoir contamination and improves single-well injection and production capacity.

[0030] This invention is highly practical in reducing mud loss, mitigating reservoir damage, and improving near-wellbore permeability. Furthermore, it enables low-pressure reservoir protection during drilling and completion, contributing to improved single-well injection and production capabilities, and thus possesses significant practical value.

[0031] Example 1 like Figure 1 As shown, a tubing string of this embodiment includes a continuous tubing 2, the end of which is connected to a tailpipe 1, which is a horizontal pipe.

[0032] The tail tube 1 includes a screen tube base tube 10, the tail end of which has a liquid outlet hole 3, and the wall of the screen tube base tube 10 is provided with a plurality of flow passage holes 11. The plurality of flow passage holes are evenly distributed circumferentially along the screen tube base tube 10.

[0033] The through-hole 11 includes an end through-hole 1101 and a fillable through-hole 1102; the end through-hole 1101 is opened at the end of the screen tube base tube 10, and the fillable through-hole 1102 is opened between the end through-hole 1101 and the end of the continuous tubing 2.

[0034] The fillable through-hole 1102 is filled with soluble filler 12.

[0035] Optionally, the soluble filler 12 is made of a soluble alloy. Specifically, the soluble alloy is a soluble magnesium alloy or an aluminum alloy. This allows for the generation of magnesium chloride and aluminum chloride after acid injection.

[0036] Optionally, the soluble filler 12 is made of biodegradable plastic, specifically, polylactic acid (PLA) or polycaprolactone (PCL).

[0037] Optionally, the soluble filler 12 is made of a soluble alloy; specifically, the soluble ceramic is a soluble alumina ceramic.

[0038] Optionally, both the end of the soluble filler 12 and the wall of the fillable through hole 1102 are threaded. Further, since the soluble filler 12 does not need to be installed in the end through hole 1101, the wall of the end through hole 1101 is smooth and not threaded.

[0039] Since the tailpipe 1 of this invention is a horizontal pipe, the liquid outlet 3 at its end is not easy to allow the liquid inside the pipe to flow out from the side, and it is easy to get blocked when stationary. Through the end through hole 1101, the drilling fluid can be ensured to flow out smoothly, and when dissolving the soluble filler 12, the dissolution effect can be achieved from the end to the front, making the acidification effect more thorough. Furthermore, during the dragging process, due to inertia, the acid is not easy to spray in all directions of the drilling hole. By opening multiple through holes 11 on the pipe wall of the screen pipe base pipe 10, the uniformity of spraying can be ensured.

[0040] Horizontal well drilling in gas storage is a directional drilling method used in oil and gas field development to increase the contact area with the reservoir and improve oil and gas production. It is mainly used in the development of fractured carbonate reservoirs, reservoirs with gas caps or bottom water, thin-layer reservoirs, low-permeability reservoirs, heavy oil reservoirs, and high-water-cut reservoirs with artificial water injection. It increases the oil and gas production capacity of low-porosity, relatively tight reservoirs by increasing the contact area between the wellbore and the formation and by penetrating zones with better permeability.

[0041] The implementation process of a gas storage well completion method for low-pressure reservoir protection according to the present invention is as follows: After the horizontal section of the gas storage well is drilled, a soluble filler 12 with threads at its end is installed in a threaded fillable through-hole 1102, ensuring that the fillable through-hole 1102 is filled with the soluble filler 12. A suspended tailpipe 1 is then lowered, and clean completion fluid is used to replace the drilling mud, reducing the drilling fluid immersion time in the wellbore and minimizing reservoir damage.

[0042] During drilling, to protect low-pressure reservoirs, a low-pressure reservoir leakage prevention drilling process is employed. Solid plugging particles are added to the drilling fluid to increase its viscosity and suspension capacity, reducing erosion and contamination of the reservoir. The plugging material added to the drilling fluid should be easily acid-soluble, capable of completely removing the temporary plugging function through subsequent acidizing, thereby improving wellbore permeability.

[0043] Optionally, low-pressure reservoir leakage prevention drilling can be performed by adding additional additives to adjust the density and viscosity of the drilling fluid, controlling the density to be between 1.15 and 1.30 g / cm³. 3 With a viscosity of 10–30 mPa·s, it ensures the fluidity of drilling fluid while reducing the risk of mud leakage.

[0044] The additional additives include dispersants, suspending agents, or loss-inhibiting agents. Preferably, the additional additives are bentonite or polymers. These components can be selected and adjusted according to specific reservoir conditions and drilling requirements, including pressure coefficient, permeability, and pore throat radius. The drilling fluid density is adjusted according to reservoir conditions to reduce formation loss while ensuring that the reservoir section does not collapse or become stuck.

[0045] Solid plugging particles can seal cracks and pores to prevent fluid leakage. After drilling, impurities, suspended solids, and sediments in the completion fluid are removed through high-speed agitation and filtration.

[0046] Subsequently, after drilling is completed, before the tailpipe 1 is suspended and set, clean completion fluid is used to replace the drilling fluid, reducing the time the drilling fluid soaks in the wellbore and reducing the thickness of the mud filter cake.

[0047] Optionally, the solid-phase plugging particles are supramolecular gels. Supramolecular gels form gel particles with a certain strength and elasticity through non-covalent interactions. These gel particles can adapt to different formation conditions, form at specific temperatures, and penetrate formation pores or fractures to achieve plugging.

[0048] Subsequently, acid is injected and discharged through the end through-hole 1101, gradually dissolving the soluble filler 12 in each fillable through-hole 1102 from the end to the front.

[0049] After the soluble packing material 12 has completely dissolved, the tailpipe 1 is pulled outwards and acid is continuously injected to ensure acidification of multiple areas. This completes the acidification process and removes filter cake and near-wellbore contamination.

[0050] Specifically, the clean completion fluid is an active water or solid-free completion fluid system.

[0051] When the soluble filler 12 comes into contact with acid, it can dissolve rapidly and has certain mechanical strength and chemical stability to meet the pressure and temperature changes of the formation.

[0052] Optionally, the acid system is a hydrochloric acid solution with a mass concentration of 5% to 30%, used to dissolve the screen tube orifice filler and remove near-wellbore contamination, thereby improving reservoir permeability.

[0053] Preferably, the acidification method of the soluble screen tube process can be selected according to the reservoir pressure, temperature and other conditions, with the main acid being an acid system containing 15% hydrochloric acid. After the acid is injected into the screen tube, it reacts with the soluble filling material, and under the formation temperature and pressure, soluble compounds are rapidly generated to achieve efficient dissolution of the screen tube.

[0054] The low-pressure reservoir protection gas storage well completion method of the present invention can be widely applied to different reservoir conditions and characteristics to achieve low-pressure reservoir protection during drilling and completion.

[0055] Example 2 In this embodiment, the target formation of Well A is the Majiagou Formation of the Paleozoic Era, with a formation pressure of 20-25 MPa, a bottom layer temperature of 95°C, a completed vertical depth of 3130 meters, and a horizontal section length of 1500 meters.

[0056] In this embodiment, a plurality of flow holes 11 are provided on the upper surface, lower surface, left side and right side of the wall of the screen tube base tube 10. The flow holes 11 are evenly distributed on the wall of the screen tube base tube 10 along the circumferential and radial directions of the screen tube base tube 10.

[0057] In this embodiment, the tailpipe 1 is a horizontal pipe and the continuous oil pipe 2 is connected to the front end of the tailpipe 1 through a bend at one end.

[0058] In this embodiment, there are multiple end through holes 1101, and the multiple end through holes 1101 are formed in different radial directions and different circumferential directions on the wall of the screen tube base tube 10. This can prevent a single end through hole 1101 from becoming blocked.

[0059] In this embodiment, the soluble filler 12 is made of a soluble alloy.

[0060] This embodiment of a gas storage well completion method for low-pressure reservoir protection includes the following steps: Solid plugging particles are added to the drilling fluid, and low-pressure reservoir leakage prevention drilling is performed. The drilling fluid design adopts a soil-free, low-damage acid-soluble temporary plugging drilling (completion) fluid system with a density of 1.02–1.20 g / cm³. 3 Viscosity 10-30 mPa·s.

[0061] After drilling is completed, before the tailpipe 1 is suspended and set, the drilling fluid is replaced with clean completion fluid. Acid is injected and discharged through the end through-hole 1101. The soluble filler 12 in each fillable through-hole 1102 is gradually dissolved from the end to the front. The tail tube 1 is then pulled outward and acid is continuously injected. During the pulling process, the tail tube 1 is pulled at a constant speed to complete the acidification modification.

[0062] In this embodiment, reservoir stimulation is performed using a 50.8mm continuous tubing 2 to drive the acid production line. The main acid is 20% hydrochloric acid, and the acid consumption is 660m³. 3 .

[0063] After implementation, the well produced 2.96 million cubic meters per day without obstruction, a significant increase compared to wells implemented previously.

[0064] Unless otherwise specified, the equipment components involved in the above embodiments are all conventional equipment components, and the structural settings, working methods or control methods involved are all conventional settings, working methods or control methods in the art unless otherwise specified.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A tubular string, characterized in that, The system includes a continuous tubing (2), the end of which is connected to a tailpipe (1). The tailpipe (1) is a horizontal pipe and includes a screen tube base pipe (10). The tail end of the screen tube base pipe (10) has a liquid outlet hole (3). The wall of the screen tube base pipe (10) is provided with multiple flow holes (11). The flow holes (11) include an end through hole (1101) and a fillable through hole (1102). The end through hole (1101) is located at the end of the screen tube base pipe (10), and the fillable through hole (1102) is located between the end through hole (1101) and the end of the continuous tubing (2). The fillable through hole (1102) is filled with a soluble filler (12).

2. The tubular string according to claim 1, characterized in that, The soluble filler (12) is made of soluble alloy, soluble ceramic or biodegradable plastic.

3. The tubular string according to claim 1, characterized in that, The ends of the soluble filler (12) and the walls of the fillable through hole (1102) are both threaded.

4. A method for completing a gas storage well for low-pressure reservoir protection, characterized in that, A tubular column according to any one of claims 1 to 3 includes the following steps: Add solid plugging particles to the drilling fluid and perform leak-proof drilling in low-pressure reservoirs; After drilling is completed, before the tailpipe (1) is suspended and set, the drilling fluid is replaced with clean completion fluid; Acid solution is injected and discharged through the end through hole (1101). The soluble filler (12) in each fillable through hole (1102) is gradually dissolved from the end to the front end, and the acidification modification is completed.

5. The well completion method for a gas storage facility with low-pressure reservoir protection according to claim 4, characterized in that, The solid-phase plugging particles are supramolecular gels.

6. The well completion method for a gas storage facility with low-pressure reservoir protection according to claim 4, characterized in that, After gradually dissolving the soluble filler (12) in each fillable through hole (1102) from end to front, pull the tail tube (1) outward and continuously inject acid.

7. The well completion method for a gas storage facility with low-pressure reservoir protection according to claim 4, characterized in that, After drilling is completed, impurities, suspended solids and sediments in the completion fluid are removed by high-speed agitation and filtration, and then the drilling fluid is replaced with clean completion fluid.

8. The method for completing a gas storage tank for low-pressure reservoir protection according to claim 4, characterized in that, Before drilling to prevent leakage in low-pressure reservoirs, the density of the drilling fluid is adjusted to 1.15–1.30 g / cm³ using additional additives. 3 The viscosity was adjusted to 10–30 mPa·s.

9. A method for completing a gas storage tank for low-pressure reservoir protection according to claim 8, characterized in that, The additional additives include: dispersants, suspending agents, or loss inhibitors.

10. A method for completing a gas storage tank for low-pressure reservoir protection according to claim 4, characterized in that, The acid solution used is a hydrochloric acid solution with a mass concentration of 5% to 30%.

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