A parallel multi-main and branch horizontal well system

Abstract

The present invention relates to the field of coalbed methane mining, and specifically to a parallel multi-main and branch horizontal well system, which mainly comprises: an upper straight section, which is a longitudinal channel extending vertically downward through a wellhead; a directional section, which is an arc-shaped channel, and the head end of the directional section is connected to the bottom end of the upper straight section, and the tail end of the directional section horizontally cuts into the target formation through a landing point; a horizontal extension section, which is composed of multiple main and branch channels arranged in the target formation, and each of the main and branch channels is connected to the tail end of the directional section through a change-of-direction channel, and extends horizontally in its own direction.

Description

Technical Field

[0001] The invention relates to the field of coalbed methane mining, and in particular to a parallel multi-main and branch horizontal well system. Background Art

[0002] Existing coalbed methane development methods include: direct development using conventional oil and gas wells, clustered or clustered conventional oil and gas wells, coalbed methane multi-branch horizontal wells, coalbed methane hydraulic fracturing wells, etc.

[0003] However, the various coalbed methane development wells that have been used so far all have their own characteristics and disadvantages. For example, the direct use of conventional oil and gas wells for development has low production, high cost, and poor technical and economic performance. In addition, the well type and drilling and completion technology of conventional oil and gas wells are for free high-pressure reservoirs and cannot be directly applied to low-pressure coalbed methane reservoirs dominated by adsorption. The development of coalbed methane by clustering or clustering conventional oil and gas wells can reduce the operation and maintenance cost, but the cost of a single well or the whole is high and the technical and economic performance is poor. In addition, the well type and drilling and completion technology of conventional oil and gas wells are also for free high-pressure reservoirs. Although the wellhead is clustered to increase the gas production of the platform, the technical and economic performance of each single well is not fundamentally different from the first process idea, so the technical and economic performance of the platform is poor. In addition, the use of coalbed methane multi-branch horizontal wells increases the reservoir discharge pressure area through branch footage to adapt to low-pressure reservoirs and can achieve high production in a short period of time. However, due to the easy collapse of coal rock, the long-term drainage process (pump inspection, interruption, pressure The artificial collapse and natural collapse caused by the out-of-control (out-of-control) cause the open-hole branch footage to be invalid, and only the main branch contributes to the production, which is manifested as a cliff drop in production that can never be recovered; there is also coalbed methane hydraulic fracturing technology, which also has many defects, such as: the massive generation and migration of coal powder and particles in coal rock fracturing, which causes the failure of proppants, blockage and destruction of natural fractures, and easy formation of permanent closed edges and stress concentration. The effective control area of ​​resources is limited, and the scope and effect of fracturing may be very small due to the weak surfaces of complex three-dimensional network natural fractures in coal rock. Complex fracture system, low formation pressure, large amount of filtration and leakage, no pressure, no cracking, ineffective fracturing, low-pressure coalbed methane reservoir, and the efficiency of the drainage pressure channel at the fracturing point is very limited. The horizontal well hydraulic fracturing process leaves metal casing in the coal seam, which poses a major safety hazard to coal mining, and the abuse of conventional oil and gas drilling fluids and organic polymer chemical additives, permanent blockage and adsorption of low-pressure coal reservoir natural fracture systems, no output, and wells are scrapped. Summary of the invention

[0004] The purpose of the present invention is to provide a parallel multi-main and branch horizontal well system to solve the problems of low production, high cost and poor technical and economic performance of previous coalbed methane development wells in the above-mentioned background technology.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a parallel multi-main-branch horizontal well system, characterized in that it includes: an upper straight section, which is a longitudinal channel extending vertically downward through the wellhead; a directional section, which is an arc-shaped channel, and the head end of the directional section is connected to the bottom end of the upper straight section, and the tail end of the directional section horizontally cuts into the target formation through a landing point; a horizontal extension section, which is composed of multiple main-branch channels arranged in the target formation, and each main-branch channel is connected to the tail end of the directional section through a change-of-direction channel.

[0006] Preferably, the main branch channel includes a first channel and a second channel; the first channel and the second channel are arranged parallel to each other; the first channel and the second channel are arranged symmetrically with the tail end of the directional section as the axis; the first channel and the second channel extend in the direction indicated by the tail end of the directional section.

[0007] Preferably, the main branch channel includes a main channel; the main channel is coaxially set with the tail end of the directional section and extends horizontally in a direction away from the directional section.

[0008] Preferably, the main branch channel also includes a fourth channel and a fifth channel; the fourth channel and the fifth channel are respectively arranged in parallel on both sides of the first channel and the second channel; the fourth channel and the fifth channel respectively extend in the direction indicated by the tail end of the directional section.

[0009] Preferably, the main branch channel also includes a sixth channel and a seventh channel; the sixth channel and the seventh channel are respectively arranged in parallel on both sides of the fourth channel and the fifth channel; the sixth channel and the seventh channel respectively extend in the direction indicated by the tail end of the directional section.

[0010] Preferably, the main and branch channels are arranged parallel to each other, and the distances between the main and branch channels remain consistent.

[0011] Preferably, a parallel multi-main and branch horizontal well construction method mainly comprises the following steps:

[0012] S1, drilling a horizontal main branch channel from the landing point;

[0013] S2, after cyclic cleaning of the main branch channel, the screen tube is lowered to the end of the main branch channel;

[0014] S3, the screen is dropped and the well is drilled;

[0015] S4, drilling down to the sidetracking point in the branch area to conduct sidetracking construction;

[0016] S5: Repeat S2 and S3 until the construction of all main and branch channels is completed.

[0017] Preferably, the dogleg degree of the trajectory plane in S1 is controlled within a range of 4 degrees / 30M to 6 degrees / 30M.

[0018] Preferably, the screen tube is made of non-metallic material; the screen tube is controlled to be less than 50 meters away from the end of the main branch channel, and the top of the screen tube is less than 5 meters away from the side drilling point of the next main branch channel.

[0019] Preferably, the top end of the last screen tube remains in the last opening casing for the dropping operation, and the remaining length of the screen tube is not less than 20M.

[0020] Preferably, a screen tube is provided in the horizontal extension section; the screen tube is mainly composed of an upper connecting port and a locking mechanism, and the locking mechanism includes a sliding sleeve, a spring, an outer sleeve, a steel ball, a switch seat, and a track-changing cylinder; the upper end of the outer sleeve is connected to the upper connecting port, the sliding sleeve, the spring and the steel ball are installed in the outer sleeve, the switch seat is connected to the outer sleeve upward and to the screen tube downward, and the track-changing cylinder is installed in the switch seat, and its upper part is axially plug-matched with the sliding sleeve; a sliding sleeve key block is provided on the upper end face of the sliding sleeve, a sliding sleeve boss is provided at the lower end, and a ball seat matching with the steel ball is provided in the middle; the inner wall of the outer sleeve is provided with two annular protrusions, and the part above the upper protrusion is provided with a protrusion matching with the sliding sleeve The sleeve key block is axially slidably matched with the sleeve groove, and the spring is arranged between the upper annular protrusion in the sleeve groove and the sleeve key block. A sleeve annulus is arranged between the two protrusions to slide with the steel ball, and a sleeve deep cavity is arranged near the lower annular protrusion in the sleeve annulus; the lower part of the switch seat is provided with an inner shoulder, and the inner shoulder is provided with several switch seat through holes; the track-changing cylinder is arranged between the lower protrusion of the sleeve and the inner shoulder of the switch seat, and the upper part of its inner wall is evenly distributed with tracks, and the tracks and the sleeve protrusions form axial plug-in and circumferential transposition matching; the middle section of the sleeve is provided with a threaded hole, the diameter of the threaded hole is larger than the outer diameter of the steel ball, and the threaded hole is blocked by a steel ball plug.

[0021] Preferably, the screen tube includes an inner chamber, a sand filter net and an outer sheath, the sand filter net is wrapped around the outside of the inner chamber, the outer sheath covers the outside of the sand filter net, a lower connecting port is provided at the lower end of the inner chamber, the upper end is connected to the lower end of the inner boss of the switch seat, and the upper and lower ends of the outer sheath are respectively connected to the external thread of the switch seat and the external thread of the lower connecting port.

[0022] Preferably, a reed pipe is wound around the outer wall of the inner chamber, and the sand filter is wound around the outer wall of the inner chamber through the reed pipe.

[0023] The beneficial effects of the present invention are as follows: the parallel multi-main-branch horizontal well system uses underbalanced or clean water drilling to drill the well, and completes the well with a non-metallic screen pipe in the horizontal section.

[0024] Reservoir protection is adapted to the characteristics of coalbed methane reservoirs; the screen covers ≥90% of the horizontal section, and the long-term support wellbore is adapted to the long-term production of coalbed methane, effectively overcoming the easy collapse of coal seams.

[0025] The largest resource area is controlled with the least and most effective footage, and the optimized geometric and equidistant wellbore layout can efficiently cover the controlled resource area. At the same time, the mutual interference between drainage and production and pressure reduction is minimal, which can easily form an overall pressure reduction in the area and surface, quickly build and increase production, improve economic benefits and increase the speed of capital recovery.

[0026] Direct production from horizontal wells improves technical and economic efficiency: wellbore trajectory is controlled along the updip direction of the formation; vertical well construction and site requisition are not required; automatic, efficient and durable submersible screw pumps are used for direct production from horizontal wells; land occupation is reduced; and terrain and landform restrictions such as protected areas and buildings are avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the cross-section projection of parallel multi-main and branch horizontal wells;

[0028] Figure 2 It is a schematic diagram of the plane projection of parallel multi-branch horizontal wells - two main branches;

[0029] Figure 3 It is a schematic diagram of the plane projection of parallel multi-branch horizontal wells-three main branches;

[0030] Figure 4 It is a schematic diagram of the plane projection of parallel multi-branch horizontal wells - four main branches;

[0031] Figure 5 It is a schematic diagram of parallel multi-branch horizontal wells-five main branches plane projection;

[0032] Figure 6 It is a schematic diagram of the plane projection of parallel multi-branch horizontal wells-six main branches;

[0033] Figure 7 This is a cross-sectional view of the screen of a parallel multi-branch horizontal well. DETAILED DESCRIPTION

[0034] The following is a detailed description with reference to the accompanying drawings in the embodiments of the present invention.

[0035] See also Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 A parallel multi-main-branch horizontal well system, characterized in that it includes: an upper straight section 2, which is a longitudinal channel extending vertically downward through a wellhead 1; a directional section 3, which is an arc-shaped channel, and the head end of the directional section 3 is connected to the bottom end of the upper straight section 2, and the tail end of the directional section 3 horizontally cuts into the target formation 7 through a landing point 5; a horizontal extension section, which is composed of multiple main branch channels 4 arranged in the target formation 7, and each main branch channel 4 is connected to the tail end of the directional section 3 through a change-of-direction channel 6.

[0036] As a preferred embodiment 1, the main branch channel 4 includes a first channel 11 and a second channel 12; the first channel 11 and the second channel 12 are arranged parallel to each other; the first channel 11 and the second channel 12 are arranged symmetrically with the tail end of the directional section 3 as the axis: the first channel 11 and the second channel 12 extend in the direction indicated by the tail end of the directional section 3.

[0037] As a second preferred embodiment, the main branch channel 4 includes a main channel 13 ; the main channel 13 is coaxially set with the tail end of the directional section 3 and extends horizontally in a direction away from the directional section 3 .

[0038] As a preferred embodiment three, the main branch channel 4 also includes a fourth channel 14 and a fifth channel 15; the fourth channel 14 and the fifth channel 15 are respectively arranged in parallel on both sides of the first channel 11 and the second channel 12; the fourth channel 14 and the fifth channel 15 respectively extend in the direction indicated by the tail end of the directional section 3.

[0039] As a preferred embodiment four, the main branch channel 4 also includes a sixth channel 16 and a seventh channel 17; the sixth channel 16 and the seventh channel 17 are respectively arranged in parallel on both sides of the fourth channel 14 and the fifth channel 15; the sixth channel 16 and the seventh channel 17 extend in the direction indicated by the tail end of the directional section 3 respectively.

[0040] In the above embodiment, the main and branch channels 4 are set parallel to each other, and the spacing between the main and branch channels 4 remains consistent, which expands the mining area, improves the well productivity, reduces the economic risk in heterogeneous formations, reduces the unit technical cost, and improves the recovery rate of dense sandstone.

[0041] Furthermore, since the parallel multi-branch horizontal well system can be used in thin and ultra-thin layers, low and ultra-low permeability, edge and bottom water, reservoirs that require optimized pressure control and improved sweep efficiency, multiple groups of natural fractures, and reservoirs that will be added in the future, it saves completion costs and time, and is therefore a milestone in the development of multi-branch horizontal wells in conventional oil and gas.

[0042] The parallel multi-main and branch horizontal well construction method mainly includes the following steps:

[0043] S1, drilling a horizontal main branch channel 4 from the landing point 5;

[0044] S2, after cyclic cleaning of the main branch channel 4, the screen tube is lowered to the end of the main branch channel 4;

[0045] S3, the screen is dropped and the well is drilled;

[0046] S4, drilling down to the sidetracking point in the branch area to conduct sidetracking construction;

[0047] S5, repeat S2 and S3 until the construction of all main and branch channels 4 is completed.

[0048] As a preferred embodiment, the dogleg degree of the trajectory plane in S1 is controlled within a range of 4 degrees / 30M to 6 degrees / 30M.

[0049] As a preferred embodiment, the screen pipe is made of non-metallic material; the screen pipe is controlled to be less than 50M from the end of the main branch channel 4, and the top of the screen pipe is less than 5M from the side drilling point of the next main branch channel 4.

[0050] As a preferred embodiment, the top end of the last screen tube remains in the last opened casing for the dropping operation, and the remaining length of the screen tube is not less than 20M.

[0051] Through underbalanced or clean water drilling, the horizontal section of the whole well is completed with non-metallic screen pipes: the reservoir protection meets the characteristics of the coalbed methane reservoir; the screen pipe covers ≥90% of the horizontal section, and the long-term support wellbore is suitable for the long-term production of coalbed methane, effectively overcoming the easy collapse of the coal seam;

[0052] Through reasonable calculation and analysis, the main and branch channels 4 can generally be set to 2 to 6, and the parallel spacing can be set to 150M to 200M, so as to control the largest resource area with the least and most effective footage.

[0053] according to Figure 7As a preferred embodiment, the screen tube is mainly composed of an upper connection port 21 and a locking mechanism, and the locking mechanism includes a sleeve 23, a spring 24, a jacket, a steel ball 26, a switch seat, and a track change cylinder 28. The upper end of the jacket is connected to the upper connection port 21, and the sleeve 23, the spring 24, and the steel ball 26 are installed in the jacket. The switch seat is connected to the jacket upward and to the screen tube downward. The track change cylinder 28 is installed in the switch seat, and its upper part is axially plugged with the sleeve 23; the upper end face of the sleeve 23 is provided with a sleeve 23 key block, the lower end is provided with a sleeve 23 boss, and a ball seat that cooperates with the steel ball 26 is provided in the middle; the inner wall of the jacket is provided with two annular protrusions, and the part above the upper protrusion is provided with a sleeve groove that axially slides with the sleeve 23 key block. The spring 24 is arranged between the upper annular protrusion in the sleeve groove and the sleeve 23 key block, and a sleeve annulus that slides with the steel ball 26 is provided between the two protrusions. A deep cavity of the outer sleeve is provided near the lower annular protrusion; an inner convex shoulder is provided at the lower part of the switch seat, and a plurality of switch seat through holes are provided on the inner convex shoulder; the track change cylinder 28 is arranged between the lower protrusion of the outer sleeve and the inner convex shoulder of the switch seat, and a track 29 is evenly distributed on the upper part of its inner wall, and the track 29 and the convex column of the sliding sleeve 23 form an axial plug-in and circumferential transposition fit; a threaded hole is provided in the outer sleeve annular space section of the outer sleeve, and the diameter of the threaded hole is larger than the outer diameter of the steel ball 26, and the threaded hole is plugged by a steel ball thread Blocking; the screen tube includes an inner bore 30, a sand filter and an outer sheath 32, the sand filter is wound around the outside of the inner bore 30, the outer sheath 32 covers the outside of the sand filter, a lower connecting port 33 is provided at the lower end of the inner bore 30, the upper end is connected to the lower end of the inner boss of the switch seat, the upper and lower ends of the outer sheath 32 are respectively connected to the external thread of the switch seat and the external thread of the lower connecting port 33; a reed tube 34 is wound around the outer wall of the inner bore 30, and the sand filter is wound around the outside of the inner bore 30 through the reed tube 34.

[0054] Through the above arrangement, the screen is placed in the production section of the horizontal well. Under normal production conditions, the through hole of the switch seat with the screen is coaxially connected with the through hole of the track change cylinder 28, the locking mechanism is in an open state, and the sand-containing fluid in the formation enters the sand filter through the through hole of the outer sheath 32, and the filtered fluid enters the annulus between the filter and the inner bore 30. The fluid flows along the spiral flow channel of the reed tube 34 and enters the wellbore through the through hole of the switch seat and the through hole of the track change cylinder 28.

[0055] When the specified screen needs to be closed during the production process, a matching special control tool, i.e., the screen locking mechanism operator, is lowered into the wellbore. When the front movable block of the screen locking mechanism operator presses against the protrusion of the steel ball 26, the sleeve 23 is forced to overcome the elastic force of the spring 24 and move downward. During the movement, the boss of the sleeve 23 moves down from the position to the inclined rail and pushes the inclined rail. Due to the action of the inclined rail, the track change cylinder 28 rotates a certain angle. When the boss reaches the track 29, the sleeve 23 reaches the bottom dead point position, and the steel ball 26 is pushed into the deep cavity of the outer sleeve by the movable block of the locking mechanism operator. At this time, the self-locking process of the locking mechanism components is completed. The locking mechanism operator passes the switch and continues to move downward. At this time, the sleeve 23 is reset under the action of the spring 24. During the reset process, the boss moves up to the position of the track 29 to complete a switch action. During the movement, the boss forces the track change cylinder 28 to rotate a certain angle again under the action of the inclined rail. In this case, the movement of the protruding column from one place to another place on the track 29 is one action cycle, and the total rotation angle is 90 degrees. When the through hole of the track change cylinder 28 is offset by 90 degrees from the through hole of the switch seat, the locking mechanism is closed. After the action is completed, when the locking mechanism operator returns, its movable shift block encounters the protrusion of the steel ball 26 and shrinks and slips to exit smoothly. Conversely, if the locking mechanism is to be opened, the locking mechanism operator is lowered again, causing the track change cylinder 28 to rotate 90 degrees again. When the through hole of the track change cylinder 28 is coaxial with the through hole of the switch seat, the locking mechanism is opened. Since the switch has a self-locking function, the state can be kept stable during each action.

[0056] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A parallel multi-main and branch horizontal well system, characterized in that: include: An upper straight section, wherein the upper straight section is a longitudinal passage extending vertically downward from the wellhead; A directional section, wherein the directional section is an arc-shaped channel, and the head end of the directional section is connected to the bottom end of the upper straight section, and the tail end of the directional section horizontally cuts into the target stratum through the landing point; A horizontal extension section, wherein the horizontal extension section is composed of a plurality of main and branch channels arranged in the target stratum, and each of the main and branch channels is connected to the tail end of the directional section via a change-of-direction channel; A screen tube is provided in the horizontal extension section; the screen tube includes an upper connection port and a locking mechanism, the locking mechanism includes a sleeve, a spring, an outer sleeve, a steel ball, a switch seat, and a track change cylinder; the upper end of the outer sleeve is connected to the upper connection port, the sleeve, the spring, and the steel ball are installed in the outer sleeve, the switch seat is connected to the outer sleeve upward and to the screen tube downward, the track change cylinder is installed in the switch seat, and its upper part is axially plugged with the sleeve; a sleeve key block is provided on the upper end face of the sleeve, a sleeve boss is provided at the lower end, and a ball seat that cooperates with the steel ball is provided in the middle; the inner wall of the outer sleeve is provided with two annular protrusions, and the part above the upper protrusion is provided with a protrusion that axially engages with the sleeve key block The spring is arranged between the upper annular protrusion in the groove of the outer sleeve and the key block of the sliding sleeve, and an outer sleeve annulus is arranged between the two protrusions to slide with the steel ball, and a deep outer sleeve cavity is arranged near the lower annular protrusion of the outer sleeve annulus; the lower part of the switch seat is provided with an inner convex shoulder, and the inner convex shoulder is provided with a plurality of switch seat through holes; the track change cylinder is arranged between the lower protrusion of the outer sleeve and the inner convex shoulder of the switch seat, and the upper part of the inner wall thereof is evenly distributed with tracks, and the tracks and the convex column of the sliding sleeve form an axial plug-in and circumferential transposition fit; the middle section of the outer sleeve is provided with a threaded hole, the diameter of the threaded hole is larger than the outer diameter of the steel ball, and the threaded hole is blocked by a steel ball plug; The screen tube also includes an inner chamber, a sand filter and an outer sheath, the sand filter is wound around the outside of the inner chamber, the outer sheath is wrapped around the outside of the sand filter, a lower connection port is provided at the lower end of the inner chamber, the upper end is connected to the lower end of the inner shoulder of the switch seat, and the upper and lower ends of the outer sheath are respectively connected to the external threads of the switch seat and the external threads of the lower connection port; A reed pipe is wound around the outer wall of the inner chamber, and the sand filter is wound around the outside of the inner chamber through the reed pipe.

2. A parallel multi-main and branch horizontal well system according to claim 1, characterized in that: The main branch channel includes a first channel and a second channel; the first channel and the second channel are arranged parallel to each other; the first channel and the second channel are arranged symmetrically with the tail end of the directional section as the axis: the first channel and the second channel extend in the direction indicated by the tail end of the directional section.

3. A parallel multi-main and branch horizontal well system according to claim 2, characterized in that: The main branch channel includes a main channel; the main channel is coaxially connected to the tail end of the directional section and extends horizontally in a direction away from the directional section.

4. A parallel multi-main and branch horizontal well system according to claim 2, characterized in that: The main branch channel also includes a fourth channel and a fifth channel; the fourth channel and the fifth channel are respectively arranged in parallel on both sides of the first channel and the second channel; the fourth channel and the fifth channel respectively extend in the direction indicated by the tail end of the directional section.

5. A parallel multi-main and multi-branch horizontal well system according to claim 4, characterized in that: The main branch channel also includes a sixth channel and a seventh channel; the sixth channel and the seventh channel are respectively arranged in parallel on both sides of the fourth channel and the fifth channel; the sixth channel and the seventh channel respectively extend in the direction indicated by the tail end of the directional section.

6. A parallel multi-main and multi-branch horizontal well system according to claim 1, characterized in that: The main and branch channels are arranged parallel to each other, and the distances between the main and branch channels are kept consistent.

7. A construction method for a parallel multi-main and multi-branch horizontal well system as claimed in any one of claims 1 to 6, characterized in that: The following steps are involved: S1, drilling a horizontal main branch channel from the landing point; S2, after cyclic cleaning of the main branch channel, the screen tube is lowered to the end of the main branch channel; S3, the screen is dropped and the drill is started; S4, drilling down to the side drilling point in the direction-changing channel area to carry out side drilling construction; S5: Repeat S2 and S3 until the construction of all main and branch channels is completed.

8. The construction method according to claim 7, characterized in that: The dogleg degree of the trajectory plane in S1 is controlled within a range of 4 degrees / 30M to 6 degrees / 30M.

9. The construction method according to claim 7, characterized in that: The screen pipe is made of non-metallic material; the screen pipe is less than 50 meters away from the end of the main branch channel, and the top of the screen pipe is less than 5 meters away from the side drilling point of the next main branch channel.

10. The construction method according to claim 7, characterized in that: The top of the last screen tube remains in the last opening casing for the dropping operation, and the remaining length of the screen tube is not less than 20M.

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