A horizontal well precision steam injection string

Abstract

A fine steam injection tubing string for horizontal wells belongs to the field of oil production engineering technology. Technical solution: A heat-insulating pipe, a chamfered heat-insulating pipe, a flat chamfered pipe, a primary distributor, a first centralizer, a horizontal well thermal recovery packer A, a second centralizer, a secondary distributor, a third centralizer, a horizontal well thermal recovery packer B, a fourth centralizer, steam injection valve A, and steam injection valve B are connected sequentially. Beneficial effects: This invention features a compensating packer, solving the problem of sealing failure caused by tubing creep during steam injection; the packer has a double-seal structure design and uses a high-friction fixing body to improve sealing reliability; a forced release device and a safety joint are provided to ensure the safety and reliability of the tubing string; the steam injection volume of each unit is determined according to the physical properties, formation pressure, and steam injection parameters of the corresponding well section, and the flow area of ​​the steam injection valve is adjusted to achieve fine steam injection in horizontal wells, meeting the actual production needs of horizontal wells and having broad application value.

Description

Technical Field

[0001] This invention belongs to the field of oil production engineering technology, and specifically relates to a steam injection string for horizontal wells addressing uneven utilization of the horizontal section in heavy oil wells. Background Technology

[0002] Currently, with the continuous development of horizontal wells, the uneven utilization of reservoirs in horizontal sections has become a prominent issue, severely impacting production capacity. In recent years, to address this uneven utilization problem, research and application of steam injection strings such as dual-tube steam injection, multi-point steam injection, and segmented steam injection have been conducted. However, certain limitations still exist in field applications, mainly manifested in: ① The segmented horizontal well strings lack compensators, causing string creep during steam injection and leading to barrier seal failure; ② The strings lack anchoring devices, and the barrier seals use single-sleeve seals, resulting in limited sealing strength; ③ Errors exist in the steam injection volume across different horizontal sections during multi-point steam injection, affecting the injection effect. Therefore, there is an urgent need to research fine steam injection strings for horizontal wells to further alleviate the uneven utilization of reservoirs in horizontal sections. Summary of the Invention

[0003] To address the problems in the existing technology and meet the aforementioned needs, this invention provides a fine steam injection string for horizontal wells. This string utilizes a novel horizontal well thermal recovery packer with built-in compensation function, a double-sealing structure design, a high-friction fixing body, and forced unsealing for safe and reliable unsealing. A multi-stage distributor is also developed to accommodate different permeabilities and operating conditions in the horizontal section. Furthermore, the string design is optimized for horizontal wells with long sections and significant temperature variations, achieving fine steam injection in horizontal wells and meeting field requirements.

[0004] The technical solution is as follows:

[0005] A horizontal well precision steam injection string includes: a heat insulation pipe, a chamfered heat insulation pipe, a flat chamfered pipe, a primary distributor, a first centralizer, a horizontal well thermal recovery packer A, a second centralizer, a secondary distributor, a third centralizer, a horizontal well thermal recovery packer B, a fourth centralizer, a steam injection valve A, a steam injection valve B, and a hollow steel ball for sealing the passage.

[0006] The heat insulation pipe, chamfered heat insulation pipe, flat chamfered pipe, primary distributor, first centralizer, horizontal well thermal recovery packer A, second centralizer, secondary distributor, third centralizer, horizontal well thermal recovery packer B, fourth centralizer, steam injection valve A, and steam injection valve B are connected in sequence.

[0007] Furthermore, both the primary distributor and the secondary distributor include:

[0008] The dispenser body has a sliding sleeve and a shear pin inside;

[0009] A sealing ring is provided on the sliding sleeve.

[0010] Furthermore, both the horizontal well thermal recovery packer A and the horizontal well thermal recovery packer B include:

[0011] The upper connector, high-friction sealing rubber sleeve A, cone A, high-friction sealing rubber sleeve B, cone B, and lower connector are connected in sequence to form the main body of the packer;

[0012] The separator body has a built-in central tube;

[0013] An unsealing device is provided between the high-friction sealing tube A and the central tube;

[0014] The unsealing device extends to the position of the upper connector and the cone A;

[0015] A thermal expansion body is provided between the lower connector and the central tube.

[0016] Furthermore, a sealing ring is provided between the high-friction sealing sleeve A and the cone A.

[0017] Furthermore, a sealing ring is provided between the central tube and the lower connector.

[0018] Furthermore, both the high-friction sealing sleeve A and the high-friction sealing sleeve B include a slotted sleeve and a packer high-friction sleeve, with the packer high-friction sleeve being built into the slotted sleeve.

[0019] Furthermore, the hollow steel ball includes a first hollow steel ball for being dispensed into the primary distributor and a second hollow steel ball for being dispensed into the secondary distributor, wherein the diameter of the first hollow steel ball is larger than the diameter of the second hollow steel ball.

[0020] Furthermore, the diameter of the first hollow steel ball is 45mm, and the diameter of the second hollow steel ball is 35mm.

[0021] Furthermore, the diameter of the heat insulation tube is 114 mm, the diameter of the chamfered heat insulation tube is 89 mm, and the diameter of the flat chamfered tube is 89 mm.

[0022] Furthermore, the unsealing device is equipped with a limiting pin and a shearing pin to restrict the movement of cone A.

[0023] The beneficial effects of this invention are:

[0024] The horizontal well precision steam injection string described in this invention has the following beneficial effects:

[0025] 1. Design a packer with compensation function to solve the problem of seal failure caused by tubing creep during steam injection;

[0026] 2. The packer features a double-seal structure design and employs a high-friction fixing body to improve sealing reliability;

[0027] 3. It is equipped with a forced release device and a safety connector to ensure the safety and reliability of the tubing string;

[0028] 4. Determine the steam injection volume of each unit based on the physical properties, formation pressure, and steam injection parameters of the corresponding well section, and adjust the flow area of ​​the steam injection valve to achieve fine steam injection in horizontal wells.

[0029] The precision steam injection string for horizontal wells described in this invention solves the technical problem of uneven utilization in the horizontal section of horizontal wells, meets the actual production needs of horizontal wells, and has wide application value. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and detailed embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0031] Figure 1 This is a schematic diagram of the horizontal well precision steam injection tubing structure of the present invention;

[0032] Figure 2 This is a schematic diagram of the horizontal well thermal recovery packer structure of the present invention;

[0033] Figure 3 This is a schematic diagram of the unsealing device of the present invention;

[0034] Figure 4 This is an exploded view of the high-friction sealing rubber sleeve structure of the present invention;

[0035] Figure 5 This is a diagram showing the state of the rubber sleeve and the cut seam of the sleeve after the packer of the present invention has been sealed;

[0036] Figure 6 This is a schematic diagram of the distributor structure of the present invention;

[0037] Figure 7 This is a schematic diagram of the temperature curve of well Du212-XingH225 of the present invention;

[0038] The attached diagram is labeled as follows: 1-Insulation pipe, 2-Chamfered insulation pipe, 3-Flat chamfered pipe, 4-First-stage distributor, 5-First centralizer, 6-Horizontal well thermal recovery packer A, 7-Second-stage centralizer, 8-Second-stage distributor, 9-Third centralizer, 10-Horizontal well thermal recovery packer B, 11-Fourth centralizer, 12-Steam injection valve A, 13-Steam injection valve B; 41-Distributor body, 42-Sealing ring, 43-Sliding sleeve, 44 - Shear pin, 45- Hollow steel ball; 61- Upper connector, 62- Central tube, 63- Unsealing device, 64- High friction sealing sleeve A, 65- Limiting pin, 66- Shear pin, 67- Sealing ring, 68- Cone A, 69- High friction sealing sleeve B, 610- Cone B, 611- Sealing ring, 612- Lower connector, 613- Thermal expansion body; 641- Slit sleeve, 642- Packer high friction sleeve. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The following description, in conjunction with the accompanying drawings... Figure 1-7 Further explanation of the fine steam injection string for horizontal wells.

[0040] Example 1

[0041] A horizontal well precision steam injection string includes: a heat insulation pipe 1, a chamfered heat insulation pipe 2, a flat chamfered pipe 3, a primary distributor 4, a first centralizer 5, a horizontal well thermal recovery packer A6, a second centralizer 7, a secondary distributor 8, a third centralizer 9, a horizontal well thermal recovery packer B10, a fourth centralizer 11, a steam injection valve A12, a steam injection valve B13, and a hollow steel ball 45 for sealing the passage; the heat insulation pipe 1, the chamfered heat insulation pipe 2, the flat chamfered pipe 3, the primary distributor 4, the first centralizer 5, the horizontal well thermal recovery packer A6, the second centralizer 7, the secondary distributor 8, the third centralizer 9, the horizontal well thermal recovery packer B10, the fourth centralizer 11, the steam injection valve A12, and the steam injection valve B13 are connected in sequence.

[0042] Both the primary distributor 4 and the secondary distributor 8 include: a distributor body 41, which has a sliding sleeve 43 and a shearing pin 44 inside; a sealing ring 42 is provided on the sliding sleeve 43.

[0043] Both the horizontal well thermal recovery packer A6 and the horizontal well thermal recovery packer B10 include: an upper connector 61, a high-friction sealing sleeve A64, a cone A68, a high-friction sealing sleeve B69, a cone B610, and a lower connector 612 connected in sequence to form the packer body; the packer body has a built-in central tube 62; an unsealing device 63 is provided between the high-friction sealing sleeve A64 and the central tube 62; the unsealing device 63 extends to the position of the upper connector 61 and the cone A68; a thermal expansion body 613 is provided between the lower connector 612 and the central tube 62.

[0044] A sealing ring 67 is provided between the high-friction sealing sleeve A64 and the cone A68. A sealing ring 611 is provided between the central tube 62 and the lower connector 612. Both the high-friction sealing sleeve A64 and the high-friction sealing sleeve B69 include a slotted sleeve 641 and a packer high-friction sleeve 642, with the packer high-friction sleeve 642 being built into the slotted sleeve 641.

[0045] Limiting pin 65 and shearing pin 66 are the limiting pin for cone A68 and the shearing pin for the positioning block of unsealing device 63, respectively. The upper connector 61 is threadedly connected to the unsealing device 63, and the unsealing device 63 is fixedly connected to the central tube 62 with shearing pins. In its initial state, the limiting pins 65 / 66 restrict the movement of cone A68 and the positioning block of unsealing device 63. When the packer is lowered into the well for steam injection, the pressure increases, pushing cone 68 to move. When the steam injection pressure exceeds the shearing force of the limiting pin 68, the pin shears off, causing the cone to compress the sealing rubber sleeve and expand, sealing the space within the ring. After steam injection, the tubing is pulled up, and the two-stage sealing rubber sleeves elastically retract and lose their sealing effect under friction, completing the packer unsealing. However, due to the high temperature inside the well, insufficient retraction of the rubber sleeve, incomplete unsealing, or excessive friction of the casing, the tubing string is continuously pulled up. The upper connector 61 is connected to the central tube 62 via the unsealing device 63 using shear pins. When the shear pins are broken, the central tube 62 and the upper connector 61 are stretched. The stretching process is the process in which the upper connector 61 drives the rubber sleeve step by step, forcibly separating it from the cone A68 and the central tube 62. After the central tube 62 and the upper connector 61 are stretched to a position sufficient for unsealing, they hook together. The tubing string is then pulled up again, and the rubber sleeve is forcibly retracted by its elasticity and the force of the tubing string being pulled up, thus successfully unsealing the casing.

[0046] The hollow steel ball 45 includes a first hollow steel ball for being dispensed into the primary distributor 4 and a second hollow steel ball for being dispensed into the secondary distributor 8, wherein the diameter of the first hollow steel ball is larger than the diameter of the second hollow steel ball.

[0047] The horizontal well thermal recovery packer A6 and horizontal well thermal recovery packer B10 are mainly composed of a central telescopic pipe (central pipe 62), a sealer body (high friction sealing rubber sleeve 64), a thermal expansion body 613, an inner sealing element (sealing ring 67), a high friction fixing body (high friction sealing rubber sleeve A and high friction sealing rubber sleeve B), and an unsealing device 63.

[0048] During operation, the thermally expandable body 613 inside the packer, under high temperature, pushes the cone-shaped sealing element to expand, sealing the annular space of the oil sleeve and forming an initial seal. Simultaneously, the self-sealing pressure generated as the injection steam pressure increases achieves a secondary seal. The high-friction fixed body presses against the inner wall of the casing, improving the packer's sealing performance. The central telescopic tube can slide freely within the packer, compensating for changes in the expansion and contraction of the injection tubing. During unsealing, the tubing is lifted to forcibly release the packer.

[0049] By developing injection valves with different inner diameters of sliding sleeves, the injection valves are opened step by step by throwing a ball to quantitatively inject steam into the horizontal section, achieving a precise purpose.

[0050] Example 2

[0051] This is either a new embodiment or a supplement to Embodiment 1.

[0052] In recent years, in response to the problem of uneven utilization of horizontal wells, research and application of steam injection tubing such as dual-tube steam injection, multi-point steam injection, and segmented steam injection have been carried out. However, the contradiction of uneven utilization of horizontal wells remains prominent.

[0053] This invention addresses the uneven utilization of the horizontal section of heavy oil horizontal wells and the limitations of existing technologies by proposing a fine steam injection string for horizontal wells to alleviate the contradiction of uneven reservoir utilization in the horizontal section of horizontal wells.

[0054] As attached Figure 1 As shown, component 1 is a Φ114mm heat insulation pipe; component 2 is a Φ89mm chamfered heat insulation pipe; component 3 is a Φ89mm flat chamfered pipe; component 4 is a primary distributor; components 5 / 7 / 9 / 11 are centralizers; components 6 / 10 are horizontal well thermal recovery packers; component 8 is a secondary distributor; and components 12 / 13 are steam injection valves.

[0055] Based on the horizontal well temperature test curve and the operational status of the horizontal section, tools such as the steam injection valve, centralizer, and packer are sequentially lowered. After steam injection, the thermal recovery packer is set. The toe section is injected first. When the steam injection volume at the toe section reaches the design requirement, a 38mm hollow steel ball is dropped into the wellhead. Under the steam injection pressure, the steel ball moves to the position of the secondary distributor sliding sleeve, sits on the sleeve, and blocks the passage. When the pressure exceeds 2MPa, the sliding sleeve pin shears off, the sleeve moves to the right, and the lateral steam outlet is exposed, allowing steam injection to begin on the intermediate section. When the steam injection volume in the intermediate section reaches the design requirement, a 45mm hollow steel ball is dropped into the wellhead. Under the steam injection pressure, the steel ball moves to the position of the primary distributor sliding sleeve. Similarly, the pin shears off, and the lateral steam outlet is exposed, allowing steam injection to begin on the heel section. This process continues until steam injection is complete. By using a two-stage distributor to quantitatively inject steam into each horizontal section, precise steam injection in the horizontal well is achieved, improving the operational status of the horizontal section.

[0056] As attached Figure 2 As shown, part 61 is the upper connector; part 62 is the central tube; part 63 is the unsealing device; part 64 is the high-friction sealing rubber sleeve; part 67 is the sealing ring; part 68 is the cone; part 69 is the high-friction sealing rubber sleeve; part 610 is the cone; part 611 is the sealing rubber ring; part 612 is the lower connector; and part 613 is the thermal expansion body.

[0057] During operation, the horizontal well thermal expansion packer is connected to the steam injection string and lowered into the well according to design requirements. When high-temperature steam flows through the packer, the expander inside the packer expands outward upon encountering the high temperature, pushing the outer sealing element to expand and seal the annular space of the casing. At this point, the seal is only an initial seal between the packer and the casing. The packer's ability to seal at higher pressures mainly comes from the self-sealing pressure generated by the steam injection pressure itself. The central telescopic tube can slide freely within the packer, with a telescopic distance of 0.4 meters, to compensate for the length changes of the steam injection string caused by temperature variations.

[0058] As attached Figure 3 As shown, a forced unsealing device is provided. After the tool is sealed, the positioning block of the unsealing protection device is released. At this time, the central tube and the upper connector are connected by shear pins. If the unsealing is incomplete or the friction of the sleeve is too large when the tool is unsealed, the shear pins will be broken, and the central tube and the upper connector will be elongated. The elongation process is the process in which the upper connector drives the rubber sleeve and the protective ring to be forcibly separated from the cone and the central tube in stages. After the central tube and the upper connector are elongated to a position sufficient for unsealing, they hook together. Continue to lift the tubing. The rubber sleeve and the protective ring are forcibly retracted by the elasticity and the component force of the lifting tubing, and the auxiliary tool is successfully unsealed.

[0059] Currently, most heavy oil horizontal wells in the Liaohe Oilfield adopt the screen casing completion method, with staggered slots on each casing, each slot being 45mm long, 0.3mm wide, and spaced 30mm apart. (See attached image) Figure 4As shown, conventional thermal recovery packer sleeves are designed with smooth, round surfaces, providing good sealing performance against the casing wall in perforated completions. However, the irregular surface of slotted casings makes the sleeve prone to deformation after expansion and sealing, affecting the sealing effect. Furthermore, horizontal wells have long sections and large steam injection volumes, typically around 4000-8000 tons. Prolonged steam injection causes creep in the injection tubing under pressure, making conventional thermal recovery packers prone to failure. For the special slotted casing in screen-completed wells, a high-friction fixing element is used in the packer sleeve design. This involves designing a 20mm long and 0.5mm wide rubber strip on the sleeve surface based on the shape and dimensions of the casing slots (slot length, width, etc.). Using a casting method, the packer sleeve expands and is squeezed into the casing slots, providing excellent anchoring. The high-friction sealing sleeve can fix the packer to the casing at high temperatures, preventing movement and maintaining a good seal.

[0060] As attached Figure 6 As shown, part 41 is a distributor; part 42 is a sealing ring; part 43 is a sliding sleeve; part 44 is a shear pin; and part 45 is a hollow steel ball.

[0061] The distributor mainly consists of a body, a sliding sleeve, and a shear pin. The hollow steel ball design ensures the horizontal well tubing remains horizontal. Solid steel balls, due to their higher density, are less easily pushed to the distributor position by steam injection, while the hollow steel ball, with its lower density, can be pushed to the distributor position by the airflow. After the ball is dropped, it sits on the sliding sleeve 43. When the steam injection pressure reaches 2 MPa, the pin shears off, the sliding sleeve moves to the right, and the ball blocks the radial channel on its seat, exposing the side outlet, completing the layer-by-layer steam injection. The inner diameters of the sliding sleeves 43 are 33 mm and 38 mm, and the diameters of the hollow steel balls are 35 mm and 45 mm. Dropping a smaller ball opens the secondary distributor, and dropping a larger ball opens the primary distributor. After steam injection is complete, the ball detaches, forming a channel to meet blowout prevention requirements.

[0062] Based on the above technical requirements and combined with actual field production conditions, the horizontal well precision steam injection string described in this invention has the following characteristics:

[0063] Invention Point 1: Development of a new type of horizontal well thermal recovery packer

[0064] Technical features:

[0065] ① The packer has a built-in compensation function;

[0066] ②Double-seal structure design;

[0067] ③Use a high-friction fixing body;

[0068] ④ Forced unsealing, unsealing is safe and reliable.

[0069] Invention Point 2: Development of a multi-stage distributor

[0070] The currently used multi-point simultaneous injection technology mainly employs orifice-type steam injection valves, utilizing valves with different orifice diameters and numbers to simultaneously inject steam into each injection chamber. However, due to factors such as differences in well section operation, injection speed, well section length, and friction, there is a certain error compared to the designed steam injection volume.

[0071] A multi-stage distributor was developed by taking into account the different permeability and usage conditions of the horizontal section.

[0072] Invention Point 3: Refined Steam Injection String Design

[0073] For horizontal wells with long sections and significant temperature variations, the tubing string design is optimized to achieve precise steam injection and meet on-site requirements.

[0074] Example 3

[0075] Implementation results:

[0076] Du 212-Xing H225, this well has entered the 16th cycle of steam injection and purge, the horizontal section is 373.2m long, the well temperature test shows that the well temperature difference is large (the well temperature of the horizontal section reflects the operation of the horizontal section, the higher the well temperature, the better the operation). The average temperature of the well section is 87.4℃, the maximum temperature difference is 74.1℃, and the contradiction of uneven operation is prominent.

[0077] like Figure 7 As shown in the table, based on the well temperature curve before the intervention, this round divided the well section into three steam injection units, and each unit was injected with steam according to the design requirements to improve the utilization of the horizontal section. The table shows that the steam injection pressure differs in each section, indicating that the packer's sealing effect is good, achieving the purpose of steam injection into the isolated well section. After the intervention, the well temperature changed significantly, and the production effect was also improved, maximizing the oil production contribution rate of the horizontal well section.

[0078]

[0079] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A precision steam injection string for horizontal wells, characterized in that, include: Insulation pipe (1), chamfered insulation pipe (2), flat chamfered pipe (3), primary distributor (4), first centralizer (5), horizontal well thermal recovery packer A (6), second centralizer (7), secondary distributor (8), third centralizer (9), horizontal well thermal recovery packer B (10), fourth centralizer (11), steam injection valve A (12), steam injection valve B (13), hollow steel ball for sealing the passage (45); The heat insulation pipe (1), the chamfered heat insulation pipe (2), the flat chamfered pipe (3), the primary distributor (4), the first centralizer (5), the horizontal well thermal recovery packer A (6), the second centralizer (7), the secondary distributor (8), the third centralizer (9), the horizontal well thermal recovery packer B (10), the fourth centralizer (11), the steam injection valve A (12), and the steam injection valve B (13) are connected in sequence; Both the primary distributor (4) and the secondary distributor (8) include: The dispenser body (41) has a sliding sleeve (43) and a shear pin (44) inside. A sealing ring (42) is provided on the sliding sleeve (43); Both the horizontal well thermal recovery packer A (6) and the horizontal well thermal recovery packer B (10) include: The upper connector (61), high friction sealing rubber sleeve A (64), cone A (68), high friction sealing rubber sleeve B (69), cone B (610), and lower connector (612) are connected in sequence to form the main body of the packer; The main body of the separator has a built-in central tube (62). An unsealing device (63) is provided between the high-friction sealing tube A (64) and the central tube (62). The unsealing device (63) extends to the position of the upper connector (61) and the cone A (68); A thermal expansion body (613) is provided between the lower connector (612) and the central tube (62). Both the high-friction sealing sleeve A (64) and the high-friction sealing sleeve B (69) include a slotted sleeve (641) and a packer high-friction sleeve (642), wherein the packer high-friction sleeve (642) is built into the slotted sleeve (641); The hollow steel ball (45) includes a first hollow steel ball for being dispensed into the primary distributor (4) and a second hollow steel ball for being dispensed into the secondary distributor (8), wherein the diameter of the first hollow steel ball is larger than the diameter of the second hollow steel ball.

2. The horizontal well precision steam injection string as described in claim 1, characterized in that, A sealing ring (67) is provided between the high-friction sealing sleeve A (64) and the cone A (68).

3. The horizontal well precision steam injection string as described in claim 1, characterized in that, A sealing ring (611) is provided between the central tube (62) and the lower connector (612).

4. The horizontal well precision steam injection string as described in claim 1, characterized in that, The diameter of the first hollow steel ball is 45mm, and the diameter of the second hollow steel ball is 35mm or 38mm.

5. The horizontal well precision steam injection string as described in claim 1, characterized in that, The diameter of the heat insulation pipe (1) is 114 mm, the diameter of the chamfered heat insulation pipe (2) is 89 mm, and the diameter of the flat chamfered pipe (3) is 89 mm.

6. The horizontal well precision steam injection string as described in claim 1, characterized in that, The unsealing device (63) is provided with a limiting pin (65) and a shearing pin (66) for restricting the movement of cone A (68).

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