Well completion fracturing method for multilateral well

Abstract

The embodiment of the invention provides a multi-branch well completion fracturing method, a multi-branch well comprises a main well and a plurality of branch well holes, and the multi-branch well completion fracturing method comprises the steps that well completion fracturing operation is conducted on all the branch well holes in sequence; the method for conducting well completion fracturing operation on the single branch well hole comprises the steps that a flexible screen pipe comprising a first flexible pipe column and a second flexible pipe column is put into a multi-branch well, so that the first flexible pipe column extends into the branch well hole, and the second flexible pipe column is arranged along a main well; a flexible fracturing pipe column is put into the branch well hole through the flexible screen pipe; fracturing is conducted on the branch well holes through the flexible fracturing pipe column; the flexible fracturing pipe column is taken out; and the first flexible pipe column and the second flexible pipe column are separated, and the second flexible pipe column is taken out of the main well. According to the well completion fracturing method for the multi-branch well, when the flexible fracturing pipe column carries out fracturing operation, the first flexible pipe column of the flexible screen pipe can provide support for the corresponding branch well hole, and collapse of the branch well hole can be avoided compared with open hole fracturing.

Description

Technical Field

[0001] This application relates to the field of oil and gas drilling technology, and in particular to a method for completing and fracturing multi-branch wells. Background Technology

[0002] In the development of complex oil and gas reservoirs, especially in space-constrained, steeply structured, fault-block, or low-permeability reservoirs, multi-branch well technology is widely used to increase reservoir contact area and single-well productivity. Multi-branch wells extend branch wells in multiple directions from a main well to penetrate multi-layered or highly heterogeneous reservoirs. Understandably, a multi-branch well includes a main well and multiple branch wells.

[0003] In related technologies, in order to successfully insert flexible fracturing tubing into the branch wellbore, fracturing operations are performed on the branch wellbore while it is in an open-hole state.

[0004] However, the fracturing effect of related technologies on branch wells is limited and they are prone to causing the branch wells to collapse. Summary of the Invention

[0005] This application provides a multi-branch well completion fracturing method that facilitates the smooth insertion of flexible fracturing tubing into the branch wellbore while solving the problems of limited fracturing effect and easy collapse of the branch wellbore.

[0006] This application provides a method for completing and fracturing a multi-branch well, wherein the multi-branch well includes a main well and multiple branch wellbores. The method includes: sequentially performing completion and fracturing operations on each of the branch wellbores; and performing completion and fracturing operations on a single branch wellbore, including: running a flexible screen pipe comprising a first flexible tubing string and a second flexible tubing string into the multi-branch well, such that the first flexible tubing string extends into the branch wellbore and the second flexible tubing string is positioned along the main well; running a flexible fracturing tubing string into the branch wellbore through the flexible screen pipe; fracturing the branch wellbore through the flexible fracturing tubing string; removing the flexible fracturing tubing string; separating the first flexible tubing string and the second flexible tubing string, and removing the second flexible tubing string from the main well.

[0007] In some embodiments, the multi-branch well completion and fracturing method includes: the branch well located at a higher position is subjected to completion and fracturing operations before the branch well located at a lower position.

[0008] In some embodiments, the flexible screen tube includes a plurality of tube units, with adjacent tube units hinged together.

[0009] In some implementations, the first flexible tubing and the second flexible tubing are detachably connected by a drop tool.

[0010] In some embodiments, the branch wellbore has a build-up section for connecting the main well, the radius of curvature of the build-up section being no greater than 8m.

[0011] In some embodiments, the method for performing well completion fracturing operations on a single branch well further includes: after running a flexible screen pipe comprising a first flexible tubing string and a second flexible tubing string into the multi-branch well, suspending the second flexible tubing string in the main well.

[0012] In some embodiments, the first flexible tubing string includes a first centralizer; after the flexible screen pipe including the first flexible tubing string and the second flexible tubing string is run into the multi-branch well, the first flexible tubing string is supported in the branch wellbore by the first centralizer.

[0013] In some embodiments, the method further includes: when running a flexible screen pipe comprising a first flexible tubing string and a second flexible tubing string into the multi-branch well, running a hanger into the multi-branch well along with the flexible screen pipe, and fixing the upper end of the second flexible tubing string in the multi-branch well through the hanger; when running a flexible fracturing tubing string through the flexible screen pipe into the branch wellbore, the flexible fracturing tubing string is adapted to pass through the guide hole of the hanger; and when removing the second flexible tubing string from the main well, removing the hanger together with it.

[0014] In some embodiments, the multi-branch well completion fracturing method further includes, after running a flexible fracturing string through the main well and the flexible screen into the branch wellbore, setting the main well and the flexible fracturing string.

[0015] In some embodiments, the multi-branch well completion and fracturing method further includes, after completing and fracturing operations on each of the branch wellbores: shutting in the main well to allow the fracturing fluid to be fully filtered out and to promote the settling of the proppant; and opening the main well to perform blowout and backflow to remove the residual fracturing fluid from each of the branch wellbores.

[0016] The multi-branch well completion and fracturing method provided in this application involves running a flexible screen pipe, including a first flexible tubing string and a second flexible tubing string, into the multi-branch well. The first flexible tubing string extends into the branch wellbore, while the second flexible tubing string is positioned along the main well. This provides guidance for subsequent running of the flexible fracturing tubing string into the branch wellbore, facilitating its smooth entry into the corresponding branch wellbore along the extension direction of the flexible screen pipe. During fracturing operations, the first flexible tubing string of the flexible screen pipe provides support for the corresponding branch wellbore, preventing branch wellbore collapse compared to open-hole fracturing.

[0017] The multi-branch well completion and fracturing method provided in this application restores the internal space of the main well by separating the first and second flexible tubing strings and removing the second flexible tubing string from the main well after fracturing one branch wellbore and removing it from the corresponding branch wellbore. This eliminates interference from the flexible screen pipe on the main well, or facilitates the continued installation of flexible screen pipes and flexible fracturing tubing strings in other branch wellbores, enabling continuous completion and fracturing operations for each branch wellbore; or it facilitates the removal of relevant tools left in the main well during drilling. Simultaneously, the first flexible tubing string left in the corresponding branch wellbore continues to provide support for the branch wellbore during subsequent oil and gas production, promoting long-term, stable, and safe operations. Attached Figure Description

[0018] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0019] Figure 1 A schematic diagram of a multi-branch well completion and fracturing method provided in an embodiment of this application;

[0020] Figure 2 A schematic diagram illustrating a method for performing well completion fracturing operations on a single branch wellbore, as provided in an embodiment of this application;

[0021] Figure 3 A schematic diagram of a flexible fracturing string provided for the implementation of this application for well completion fracturing operations on an upper branch wellbore;

[0022] Figure 4 A schematic diagram of a flexible fracturing string provided for the implementation of this application for well completion fracturing operations in a branch well located below;

[0023] Figure 5 This is a schematic diagram of the structure of a flexible screen tube provided in some embodiments of this application;

[0024] Figure 6 This is a schematic diagram of the structure of the spray gun pipe section provided in the embodiments of this application;

[0025] Figure 7 This is a schematic diagram of the structure of the second centralizer provided in the embodiments of this application;

[0026] Figure 8 This is a partial structural schematic diagram of a flexible screen tube provided in some embodiments of this application.

[0027] Explanation of reference numerals in the attached figures:

[0028] 10 - Multi-branch well; 11 - Main well; 11a - Casing; 11b - Window; 12 - Branch wellbore; 12a - Angled section;

[0029] 20 - Hanger; 21 - Guide hole;

[0030] 30-Package;

[0031] 100-Flexible sieve tube; 110-First flexible tube column; 111-First guide shoe; 112-Sieve hole; 113-First stabilizer; 1131-Loop ring; 1132-Spring plate; 120-Second flexible tube column; 130-Tube unit; 131-Ball head; 132-Ball hinge seat; 133-Annular protrusion; 140-Discarding tool;

[0032] 200 - Flexible fracturing tubing; 201 - Feed tubing; 210 - Second guide shoe; 220 - Perforated tubing section; 230 - First flexible connector; 240 - Check valve; 250 - Second flexible connector; 260 - Spray gun tubing section; 261 - Nozzle; 270 - Second centralizer; 271 - Centralizer tubing section; 272 - Centralizer ring; 280 - Third flexible connector; 290 - Connecting tubing section;

[0033] 300 - Incliner; 310 - First Incliner; 320 - Second Incliner.

[0034] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0035] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0036] In the development of complex oil and gas reservoirs, especially in space-constrained, steeply structured, fault-block, or low-permeability reservoirs, multi-branch well technology is widely used to increase reservoir contact area and single-well productivity. Multi-branch wells extend branch wells in multiple directions from a main well to penetrate multi-layered or highly heterogeneous reservoirs. Understandably, a multi-branch well includes a main well and multiple branch wells.

[0037] In related technologies, in order to successfully run flexible fracturing tubing into branch wells, fracturing operations are performed on the branch wells while they are in an open-hole state. It should be noted that the branch well being in an open-hole state means that the branch well is not supported and reinforced by running a screen pipe (which may be flexible).

[0038] For example, after a screen pipe is run into a branch well, at least a portion of the screen pipe extends into the main well and is inclined toward the main well. On the one hand, when a flexible fracturing string is run into the branch well, the lower end of the flexible fracturing string is difficult to align with the upper end of the screen pipe, making it difficult for the flexible fracturing string to smoothly enter the inner cavity of the screen pipe, thereby hindering the flexible fracturing string from extending into the branch well.

[0039] Furthermore, during subsequent construction work on other branch wells, it will affect the retrieval and placement of related tools below them. For example, after a screen pipe is installed in an upper branch well, when another screen pipe is installed in a lower branch well, the upper end of the screen pipe in the upper branch well will obstruct the installation of the second screen pipe.

[0040] However, in related technologies, the fracturing effect on branch wells is limited and they are prone to collapse. Understandably, because the corresponding branch wells are not supported and reinforced, the pressure-bearing capacity of the surrounding reservoir is limited, making the branch wells prone to collapse.

[0041] The multi-branch well completion and fracturing method provided in this application involves running a flexible screen pipe, including a first flexible tubing string and a second flexible tubing string, into the multi-branch well. The first flexible tubing string extends into the branch wellbore, while the second flexible tubing string is positioned along the main well. This provides guidance for subsequent running of the flexible fracturing tubing string into the branch wellbore, facilitating its smooth entry into the corresponding branch wellbore along the extension direction of the flexible screen pipe. During fracturing operations, the first flexible tubing string of the flexible screen pipe provides support for the corresponding branch wellbore, preventing branch wellbore collapse compared to open-hole fracturing.

[0042] The multi-branch well completion and fracturing method provided in this application restores the internal space of the main well by separating the first and second flexible tubing strings and removing the second flexible tubing string from the main well after fracturing one branch wellbore and removing it from the corresponding branch wellbore. This eliminates interference from the flexible screen pipe on the main well, or facilitates the continued installation of flexible screen pipes and flexible fracturing tubing strings in other branch wellbores, enabling continuous completion and fracturing operations for each branch wellbore; or it facilitates the removal of relevant tools left in the main well during drilling. Simultaneously, the first flexible tubing string left in the corresponding branch wellbore continues to provide support for the branch wellbore during subsequent oil and gas production, promoting long-term, stable, and safe operations.

[0043] Reference Figures 1 to 7 As shown, it should be noted that in the description of this application, "upper" and "lower" refer to the order in which the corresponding objects enter the multi-branch well 10 when they are run into the multi-branch well 10, wherein the "lower" part is run into the main well 11 or the branch wellbore 12 before the "upper" part.

[0044] The following is combined Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 A detailed explanation will be provided.

[0045] The multi-branch well completion and fracturing method provided in this application embodiment targets a multi-branch well 10 including a main well 11 and multiple branch wellbores 12. Exemplarily, the number of branch wellbores 12 can be 2, 3, 4, 5, 6, or even more; this application does not limit this. This embodiment mainly describes the method in detail with two branch wellbores 12. The main well 11 may have a casing 11a, which is used to support the main well 11. The sidewall of the casing 11a has windows 11b for connecting the corresponding branch wellbores 12. It should be noted that the casing 11a has no screen holes.

[0046] Reference Figures 1 to 7 As shown, the multi-branch well completion and fracturing method provided in this application includes S100, in which well completion and fracturing operations are performed sequentially on each branch wellbore 12. Taking a wellbore with two branch wellbores 12 as an example, well completion and fracturing operations are first performed on one branch wellbore 12; then well completion and fracturing operations are performed on the other branch wellbore 12.

[0047] For example, in some possible embodiments, the main well 11 may be in an open-hole state before the completion and fracturing operations are performed on each branch wellbore 12. In this case, the main well 11 can be supported after the completion and fracturing operations are performed on each branch wellbore 12, for example by supporting the main well 11 by running a screen pipe.

[0048] The method for performing well completion fracturing operations on a single branch wellbore 12 includes the following steps S101 to S105.

[0049] S101, a flexible screen pipe 100, including a first flexible tubing string 110 and a second flexible tubing string 120, is lowered into the multi-branch well 10, so that the first flexible tubing string 110 extends into the branch wellbore 12, and the second flexible tubing string 120 is positioned along the main well 11. It should be noted that the flexible screen pipe 100 has a certain degree of flexibility, so that it can bend and extend from the main well 11 into the corresponding branch wellbore 12.

[0050] It should be noted that during drilling operations in multi-branch wells (work prior to well completion and fracturing), a directional drilling rig 300 is installed in the main well 11 to allow the flexible drilling tool (used for drilling into branch wellbore 12) to turn from the main well 11 (via the aforementioned window 11b) to the preset direction of the corresponding branch wellbore 12. After the drilling operation in the multi-branch well is completed, the directional drilling rig 300 can be temporarily stored in the multi-branch well 10. When the flexible screen pipe 100 is run into the multi-branch well 10, the directional drilling rig 300 can provide guidance for the turning of the flexible screen pipe 100.

[0051] For example, the lower end of the first flexible tubing string 110 is provided with a first guide shoe 111. When the flexible screen pipe 100 is run into the multi-branch well 10, the first guide shoe 111 can be used to pull the first flexible tubing string 110 to move in the corresponding branch wellbore 12.

[0052] For example, the circumferential wall of the first flexible tubing string 110 has a plurality of screen holes 112, which are used to connect the reservoir and the inner cavity of the first flexible tubing string 110 so that oil and gas can flow from the reservoir into the first flexible tubing string 110 through the screen holes 112 after well completion.

[0053] It should be noted that whether or not to provide corresponding sieve holes on the side wall of the second flexible tube column 120 can be flexibly selected according to requirements.

[0054] For example, after this step is completed, the second flexible tubing string 120 is approximately parallel to the main well 11, or even coaxial with the main well 11; the upper end of the second flexible tubing string 120 is oriented toward the wellhead of the main well 11.

[0055] For example, the first flexible tube column 110 and the second flexible tube column 120 are connected by a detachable structure, such as a drop tool 140.

[0056] S102, the flexible fracturing string 200 is run into the branch wellbore 12 through the flexible screen pipe 100. Understandably, during this process, the flexible screen pipe 100 can provide turning guidance for the running of the flexible fracturing string 200, so that the flexible fracturing string 200 enters the corresponding branch wellbore 12 along the first flexible string 110.

[0057] It should be noted that the flexible fracturing string 200 is at least partially flexible to be suitable for passing through the directional fracturing section 12a.

[0058] For example, the flexible fracturing string 200 may include, from bottom to top, a second guide shoe 210, a porous pipe section 220, a first flexible joint 230, a one-way valve 240, a second flexible joint 250, a spray gun pipe section 260, a second centralizer 270, a third flexible joint 280, and a connecting pipe section 290.

[0059] For example, the flexible fracturing string 200 may also include a delivery string 201 adapted to extend in the main well 11. For example, tubing may be used as the delivery string 201.

[0060] The second guide shoe 210 is used to pull the flexible fracturing string 200 to travel in the first flexible string 110 of the flexible screen tube 100.

[0061] The first flexible joint 230, the second flexible joint 250, and the third flexible joint 280 are flexibly connected at their respective positions and communicate with the internal flow channels of the flexible fracturing string 200, so that the flexible fracturing string 200 has the ability to bend at the respective positions, so that the flexible fracturing string 200 can be turned from the first flexible string 110 of the flexible screen tube 100 to the second flexible string 120 of the flexible screen tube 100.

[0062] For example, the spray gun section 260 has a plurality of nozzles 261 through which fluid can be sprayed outward, and the spray gun section 260 is used to connect the second flexible joint 250 and the second stabilizer 270.

[0063] For example, the second stabilizer 270 has a stabilizer section 271 and a stabilizer ring 272 located on the outer wall of the stabilizer section 271. The stabilizer section 271 is in communication with the spray gun section 260. The stabilizer ring 272 is adapted to support the stabilizer section 271 in the first flexible column 110 of the flexible screen tube 100.

[0064] The one-way valve 240 is used for unidirectional flow of liquid from the spray gun section 260 toward the porous section 220.

[0065] S103, the branch wellbore 12 is fracturing using the flexible fracturing tubing string 200.

[0066] For example, perforation fluid is pumped into the nozzle section 260 via a flexible fracturing string 200, and a high-speed abrasive jet (jet velocity of approximately 200 m / s) is formed using nozzle 261 to perform sand-blasting perforation in the reservoir near the branch wellbore 12. The parameters for sand-blasting perforation can be controlled as follows: sand quantity of 1.0–1.5 m³, sand ratio of 7%–8%, using quartz sand with a particle size of 0.43–0.85 mm, to ensure that the perforation depth meets the requirements for subsequent fracturing initiation.

[0067] It should be noted that during the perforation stage described above, the perforating fluid can penetrate the wall of the first flexible tubing 110. The first flexible tubing 110 can be made of steel.

[0068] For example, well washing can be performed through the porous pipe section 220 before the perforation work described above. It should be noted that the porous pipe section 220 has several outlet holes through which the well washing fluid flows out of the porous pipe section 220.

[0069] After perforation, pre-flush fluid, proppant-carrying fluid, and displacement fluid are sequentially pumped in through the flexible fracturing string 200. The pre-flush fluid, proppant-carrying fluid, or displacement fluid flows into the corresponding reservoir through the nozzle 261 and the perforated portion of the first flexible string 110. The pre-flush fluid is used to create fractures and connect the perforation to the natural fractures; the proppant-carrying fluid delivers proppant into the fractures to maintain conductivity; and the displacement fluid propels the remaining proppant into the fractures. During fracturing, the flow rate is controlled between 1.24 m³ / min and 1.4 m³ / min, and the injection pressure can be dynamically adjusted according to the reservoir fracture pressure. During fracturing, the fracturing curve, friction, total injection volume, and pressure recovery value after pump shutdown are continuously monitored to determine fracture network connectivity and the establishment of effective conductivity.

[0070] It should be noted that during the above process, the fracturing fluids such as pre-fracturing fluid, proppant-carrying fluid, and displacement fluid flow out of the flexible fracturing string 200 through the nozzle section 260.

[0071] S104, remove the flexible fracturing string 200.

[0072] S105, the first flexible tubing string 110 and the second flexible tubing string 120 are separated, and the second flexible tubing string 120 is taken out from the main well 11.

[0073] For example, when the first flexible tube 110 and the second flexible tube 120 are connected by a release tool 140, the two parts can be separated by manipulating the release tool 140.

[0074] For example, the connection point of the first flexible tubing string 110 and the second flexible tubing string 120 can be located in the branch wellbore 12. In this way, after the second flexible tubing string 120 is removed, the first flexible tubing string 110 will not interfere with the main wellbore 11 at all, so that the main wellbore 11 can be smoothly run down again, or the tools located in the main wellbore 11 below the window 11b corresponding to the first flexible tubing string 110 can be smoothly removed.

[0075] For example, in some operational scenarios, after drilling and running casing 11a into the main well 11, cement is injected around the outside of casing 11a to form a cement sheath to reinforce the main well 11. In this case, the connection point between the first flexible tubing string 110 and the second flexible tubing string 120 can be located within the portion of window 11b formed in the cement sheath. Thus, after the second flexible tubing string 120 is removed, the end of the first flexible tubing string 110 is located within the portion of window 11b formed in the cement sheath, thereby supporting the upper end of the first flexible tubing string 110 through the cement sheath.

[0076] Understandably, well completion and fracturing operations can be performed sequentially on each branch wellbore 12 using the methods described in S101 to S105 above. It should be noted that when well completion and fracturing operations are completed on all branch wellbores 12, a corresponding first flexible tubing string 110 is left in each branch wellbore 12 to reinforce the corresponding branch wellbore 12.

[0077] The multi-branch well completion and fracturing method provided in this application involves running a flexible screen pipe 100, including a first flexible tubing string 110 and a second flexible tubing string 120, into the multi-branch well 10. The first flexible tubing string 110 extends into the branch wellbore 12, while the second flexible tubing string 120 is positioned along the main well 11. This provides guidance for the subsequent running of the flexible fracturing tubing string 200 into the branch wellbore 12, facilitating its smooth entry into the corresponding branch wellbore 12 along the extension direction of the flexible screen pipe 100. During fracturing operations, the first flexible tubing string 110 of the flexible screen pipe 100 provides support to the corresponding branch wellbore 12, preventing collapse of the branch wellbore 12 compared to open-hole fracturing.

[0078] The multi-branch well completion and fracturing method provided in this application, after fracturing a branch wellbore 12 and removing the flexible fracturing string 200 from the corresponding branch wellbore 12, restores the internal space of the main wellbore 11 by separating the first flexible string 110 and the second flexible string 120 and removing the second flexible string 120 from the main wellbore 11. This eliminates the interference of the flexible screen pipe 100 on the main wellbore 11, or facilitates the continued implementation of the work of running flexible screen pipes 100 and flexible fracturing strings 200 in other branch wellbores 12, enabling continuous completion and fracturing operations for each branch wellbore 12; or facilitating the removal of relevant tools left in the main wellbore 11 during drilling. Simultaneously, the first flexible string 110 remaining in the corresponding branch wellbore 12 will continue to provide support for the branch wellbore 12 during subsequent oil and gas production, facilitating long-term, stable, and safe operation.

[0079] In some embodiments, the multi-branch well completion and fracturing method may further include: the branch well 12 located at the higher position is subjected to completion and fracturing operations before the branch well 12 located at the lower position.

[0080] It should be noted that during the drilling operation (work before well completion and fracturing) of a multi-branch well, the lower branch wellbore 12 is drilled first, followed by the upper branch wellbore 12. During the drilling operation of each branch wellbore 12, a directional drilling tool 300 is used as a flexible drill string for guidance. Taking a multi-branch well 10 comprising two branch wellbores 12 as an example, for ease of distinction, the two directional drilling tools 300 are referred to as the first directional drilling tool 310 and the second directional drilling tool 320, respectively.

[0081] When drilling the lower branch wellbore 12, the first directional guide 310 is used to guide the flexible drill string. When drilling the upper branch wellbore 12, a second directional guide 320 is superimposed on top of the first directional guide 310 and used to guide the flexible drill string. After drilling the two branch wellbores 12, the first directional guide 310 and the second directional guide 320 can be temporarily left in the multi-branch well 10.

[0082] The multi-branch well completion and fracturing method involves performing completion and fracturing operations on the higher branch wellbore 12 before the lower branch wellbore 12. After the higher branch wellbore 12 is completed and fracturing, the upper second directional guide 320 can be removed (i.e., the "removal of relevant tools left in the main well during drilling" mentioned earlier). Then, the lower first directional guide 310 is used to guide and support the flexible screen pipe 100 that is run into the lower branch wellbore 12. This optimizes the operation process, improves efficiency, and during the running of the flexible fracturing string 200 through the corresponding flexible screen pipe 100, the corresponding directional guide 300 provides support and lifting for the flexible screen pipe 100. After the fracturing operation is completed in the branch well 12 located below, the first directional device 310 is taken out from the multi-branch well 10. It is understandable that the first directional device 310 and the second directional device 320 will not be interfered with by the flexible screen pipe 100 when they are taken out from the multi-branch well 10.

[0083] In some embodiments, the flexible screen 100 includes a plurality of tube units 130, with adjacent tube units 130 hinged together. This facilitates bending of the flexible screen 100 so that it can bend and extend from the main well 11 into the branch wellbore 12.

[0084] For example, in two adjacent tube units 130, a ball joint 131 can be provided at the lower end of the previous tube unit 130, and a ball joint seat 132 can be provided at the upper end of the next tube unit 130. The two tube units 130 are hinged by the rotational connection of the ball joint 131 and the ball joint seat 132. For example, the ball joint 131 and the ball joint seat 132 can be made of steel. The tube unit 130 can be made entirely of steel.

[0085] In some embodiments, the first flexible tubing string 110 and the second flexible tubing string 120 are detachably connected by a release tool 140. It is understood that in this embodiment, the release tool 140 facilitates separation between the first flexible tubing string 110 and the second flexible tubing string 120, thereby improving the efficiency of fracturing operations in multi-branch wells.

[0086] It should be noted that the core function of the release tool 140 is to reliably connect the first flexible tube column 110 and the second flexible tube column 120 when needed; and to safely and reliably detach the first flexible tube column 110 and the second flexible tube column 120 through ground commands when required for operation, so as to separate them.

[0087] For example, the dropping tool 140 may be a hydraulic dropping tool.

[0088] For example, the hydraulic release tool is used to achieve reliable connection and remote unlocking between the first flexible tube 110 and the second flexible tube 120. The hydraulic release tool mainly consists of an upper connector, a main body shell, an inner sliding sleeve (release mandrel), a locking mechanism (locking block or spring claw), a hydraulic drive assembly (piston and shear pin), and a lower connector.

[0089] During the connection phase, the upper connector is connected to the second flexible tube column 120 by threads, and the lower connector is connected to the first flexible tube column 110. At this time, the inner sliding sleeve is in the initial locked position, and its outer diameter support surface forces the locking mechanism (such as a locking block or spring claw) to be tightly supported in the inner locking groove of the lower connector, so that the upper and lower connectors form a rigid connection in the axial direction, which can transmit tension and pressure.

[0090] When the operation enters the release phase, hydraulic load is transmitted through the main body shell to the internal hydraulic piston via ground pressurization. When the pressure reaches the preset shear value, the shear pin breaks, and the piston drives the inner sleeve to generate axial displacement. As the inner sleeve moves, the clearance groove designed on its surface aligns with the locking mechanism, causing it to lose radial support and retract towards the center, thereby releasing the axial restriction on the lower joint.

[0091] In some embodiments, the branch wellbore 12 has a build-up section 12a for connecting to the main well 11. The radius of curvature of the build-up section 12a is no greater than 8m, for example, 8m, 7.62m (25 feet), 7m, 6m, 5m, or even smaller. It is understood that the build-up radius of the corresponding flexible screen 100 and flexible fracturing string 200 is suitable for the corresponding build-up section 12a. In this case, the build-up radius of the branch wellbore 12 can be considered as an ultra-short radius case, and the multi-branch well completion fracturing method provided in this application embodiment is well applicable to this ultra-short radius case.

[0092] In some embodiments, the multi-branch well completion fracturing method, wherein the method for performing completion fracturing operation on a single branch wellbore 12 further includes: after running a flexible screen pipe 100 including a first flexible tubing string 110 and a second flexible tubing string 120 into the multi-branch well 10, suspending the second flexible tubing string 120 in the main well 11.

[0093] This helps to improve the stability of the orientation of the upper opening of the flexible screen tube 100, and facilitates the alignment of the flexible fracturing string 200 with the inner cavity of the flexible screen tube 100 during the subsequent insertion of the flexible fracturing string 200.

[0094] In some embodiments, the first flexible tubing string 110 includes a first centralizer 113. After a flexible screen 100 including the first flexible tubing string 110 and the second flexible tubing string 120 is run into the multi-branch well 10, the first flexible tubing string 110 is supported in the branch wellbore 12 by the first centralizer 113.

[0095] Thus, the first flexible tubing string 110 is supported on the branch wellbore 12 by the first centralizer 113, so that the first flexible tubing string 110 can be centered relative to the branch wellbore 12 at least in the support position.

[0096] For example, the branch wellbore 12 includes a horizontal section, and multiple (e.g., two or more) first centralizers 113 may be provided on the portion of the first flexible tubing 110 located in the horizontal section so that the corresponding portion of the first flexible tubing 110 is centered overall relative to the horizontal section.

[0097] For example, the first centralizer 113 may be formed as a locking anchor; or, the first centralizer 113 may be formed as an annular protrusion surrounding the first flexible tubing string 110, the annular protrusion being adapted to abut against the inner wall of the branch wellbore 12.

[0098] For example, the first centralizer 113 includes two collars 1131 and a plurality of spring plates 1132, the collars 1131 being adapted to be fitted onto the first flexible tubing string 110. One end of the spring plate 1132 is connected to one of the collars 1131, and the other end of the spring plate 1132 is connected to the other collar 1131, the spring plate 1132 being adapted to be supported in the branch wellbore 12. The first centralizer 113 also facilitates improving the smoothness of running the first flexible tubing string 110 into the branch wellbore 12.

[0099] For example, the collar 1131 and the first flexible tube 110 are detachably connected.

[0100] Reference Figure 8As shown, in some embodiments, in two adjacent tube units 130, one tube unit 130 has ball heads 131 at both ends, and the other tube unit has ball joint seats 132 at both ends. The two adjacent tube units 130 are hinged together by a set of ball heads 131 and ball joint seats 132. The tube unit is provided with annular protrusions 133, and the flexible screen tube 100 can be straightened by the annular protrusions 133.

[0101] In some embodiments, when a flexible screen pipe 100, including a first flexible tubing string 110 and a second flexible tubing string 120, is run into the multi-branch well 10, a hanger 20 is run into the multi-branch well 10 along with the flexible screen pipe 100 (i.e., the hanger 20 is already connected to the flexible screen pipe 100 before it is run into the multi-branch well 10), and the upper end of the second flexible tubing string 120 is fixed in the multi-branch well 10 by the hanger 20. When a flexible fracturing tubing string 200 is run into the branch wellbore 12 through the flexible screen pipe 100, the flexible fracturing tubing string 200 is adapted to pass through the guide hole 21 of the hanger 20. When the second flexible tubing string 120 is removed from the main well 11, the hanger 20 is also removed.

[0102] For example, the hanger 20 has an external thread, and the upper end of the flexible screen tube 100 has an internal thread that mates with the external thread. The hanger 20 and the upper end of the flexible screen tube 100 are connected by the mating of the external thread and the internal thread.

[0103] For example, the hanger 20 has an anchoring device for engaging with the inner wall of the main well 11, through which the hanger 20 can be fixed in the main well 11.

[0104] In this way, on the one hand, the upper end of the flexible screen pipe 100 lowered into the multi-branch well 10 can be fixed by the hanger 20, thereby enhancing the reliability of the subsequent flexible screen pipe 100 guiding the flexible fracturing string 200. On the other hand, when the second flexible string 120 is taken out from the main well 11, the hanger 20 is taken out together, so that the hanger 20 will not hinder the lowering of another flexible screen pipe 100 into the multi-branch well 10.

[0105] In some embodiments, the multi-branch well completion fracturing method, after the flexible fracturing string 200 is run into the branch wellbore 12 through the main well 11 and the flexible screen pipe 100, further includes setting the main well 11 and the flexible fracturing string 200. This helps maintain the pressure in the branch wellbore 12 during fracturing.

[0106] For example, in this process, a packer 30 can be used to seal the main well 11 and the flexible fracturing string 200. The specific type of packer 30 can be flexibly selected and set according to requirements. For example, the packer 30 can be a hydraulically set packer, the principle of which is to perform a sealing action by pressurizing the pipeline. The packer 30 can be configured as a section of the flexible fracturing string 200; the outer ring of the packer 30 abuts against the inner wall of the main well 11 and forms a seal between the packer 30 and the inner wall of the main well 11. In this way, the packer 30 forms an axial seal on the main well 11, so that the main well 11 can be pressurized during fracturing.

[0107] It should be noted that when a directional device 300 is placed in the multi-branch well 10, a seal is formed between the directional device 300 and the sidewall of the main well 11 to seal the main well 11 at the location of the directional device 300, so as to prevent the pressure applied during the fracturing process from leaking along the axis of the main well 11 towards the area below the directional device 300, thereby maintaining the fracturing pressure in the branch wellbore 12.

[0108] In some embodiments, the multi-branch well completion fracturing method may further include, after completing and fracturing operations on each branch wellbore 12: shutting in the main well 11 to allow the fracturing fluid to be fully filtered out and to promote the settling of the proppant; and opening the main well 11 to perform blowout and backflow to remove the residual fracturing fluid from each branch wellbore 12.

[0109] It should be noted that the wellhead of the main well 11 is equipped with a well control device, which can be used to shut down and open the main well 11.

[0110] In this embodiment, residual fracturing fluid in the wellbore can be discharged in this way, which helps to reduce the damage of residual fluid to the reservoir.

[0111] For example, kill fluid can be pumped in to balance formation pressure when needed, and residual proppant and fracturing fluid residue can be removed by reverse circulation well washing.

[0112] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for completing and fracturing multi-branch wells, characterized in that, The multi-branch well (10) includes a main well (11) and multiple branch wellbores (12). The multi-branch well completion and fracturing method includes: S100, performing completion and fracturing operations on each of the branch wellbores (12) in sequence; The method for performing well completion fracturing operations on a single branch wellbore (12) includes: S101, a flexible screen pipe (100) including a first flexible tubing string (110) and a second flexible tubing string (120) is lowered into the multi-branch well (10) so that the first flexible tubing string (110) extends into the branch wellbore (12) and the second flexible tubing string (120) is set along the main well (11); S102, a flexible fracturing string (200) is lowered into the branch wellbore (12) through the flexible screen pipe (100). S103, the branch wellbore (12) is fracturing using the flexible fracturing string (200); S104, Remove the flexible fracturing string (200). S105, the first flexible tubing string (110) and the second flexible tubing string (120) are separated, and the second flexible tubing string (120) is removed from the main well (11).

2. The multi-branch well completion and fracturing method according to claim 1, characterized in that, include: The branch well (12) located at the higher position is subjected to well completion and fracturing operations before the branch well (12) located at the lower position.

3. The multi-branch well completion and fracturing method according to claim 1, characterized in that, The flexible screen tube (100) includes multiple tube units (130), with adjacent tube units (130) hinged together.

4. The multi-branch well completion and fracturing method according to any one of claims 1 to 3, characterized in that, The first flexible tubing (110) and the second flexible tubing (120) are detachably connected by a drop tool (140).

5. The multi-branch well completion and fracturing method according to claim 1, characterized in that, The branch wellbore (12) has a build-up section (12a) for connecting the main well (11), the radius of curvature of the build-up section (12a) being no greater than 8m.

6. The multi-branch well completion and fracturing method according to claim 1, characterized in that, The method for performing well completion fracturing operations on a single branch wellbore (12) further includes: After the flexible screen pipe (100) including the first flexible string (110) and the second flexible string (120) is run into the multi-branch well (10), the second flexible string (120) is mounted on the main well (11).

7. The multi-branch well completion and fracturing method according to claim 6, characterized in that, The first flexible tubular string (110) includes a first centralizer (113). After the flexible screen pipe (100) including the first flexible string (110) and the second flexible string (120) is run into the multi-branch well (10), the first flexible string (110) is supported in the branch wellbore (12) by the first centralizer (113).

8. The multi-branch well completion and fracturing method according to claim 1 or 6, characterized in that, Also includes: When the flexible screen pipe (100) including the first flexible pipe string (110) and the second flexible pipe string (120) is lowered into the multi-branch well (10), the hanger (20) is lowered into the multi-branch well (10) together with the flexible screen pipe (100), and the upper end of the second flexible pipe string (120) is fixed in the multi-branch well (10) by the hanger (20); When the flexible fracturing string (200) is lowered into the branch wellbore (12) through the flexible screen pipe (100), the flexible fracturing string (200) is adapted to pass through the guide hole (21) of the hanger (20). When the second flexible tubing string (120) is removed from the main well (11), the hanger (20) is also removed.

9. The multi-branch well completion and fracturing method according to claim 1, characterized in that, After the flexible fracturing string (200) is run into the branch wellbore (12) through the main well (11) and the flexible screen pipe (100), the method further includes setting the main well (11) and the flexible fracturing string (200).

10. The multi-branch well completion and fracturing method according to claim 1, characterized in that, After completing and fracturing the various branch wells (12), the process also includes: The main well (11) is shut in to allow the fracturing fluid to be fully filtered out and to promote the settling of the proppant; The main well (11) is opened and the blowout is vented back to drain the residual fracturing fluid from each of the branch wellbores (12).

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