A cement isolation and segmented water control and sand prevention completion string and method for open hole horizontal wells

Abstract

The present invention discloses a segmented water control and sand prevention completion string and method for cementing and isolating open-hole horizontal wells, comprising an outer string and an inner string. The outer string is provided with casing, a cementing device, a sand filter, an external packer, a blind pipe, an external packer, a sand filter, and a well flushing valve in order from top to bottom, and the inner string is provided with a first packer, a cementing external blind pipe, a second packer, a cementing external blind pipe, an upper switch, a first protective packer, a lower switch, a second protective packer, and a plug in order from top to bottom. The invention adopts a double-tube structure, with the string provided with a cement injection port and a cement return port, to achieve cyclic injection of cement slurry and improve the quality of cementing. After cementing is completed, the inner injection port and the cement return channel are provided with an automatic closing mechanism, which automatically closes after the cementing pump is stopped to prevent the injected cement slurry from being spitted back.

Description

Technical Field

[0001] The present invention relates to a segmented sand control completion string and method for an open hole horizontal well of an oil production well, in particular to a segmented water control and sand control completion string and method for an open hole horizontal well with cement isolation. Background Art

[0002] Currently, the main completion methods for horizontal wells in unconsolidated sandstone reservoirs are openhole screen completion and cementing and perforating completion. Compared with cementing and perforating completion, openhole screen completion has become the primary completion method for horizontal wells in unconsolidated sandstone reservoirs due to its low cost, large drainage area, high production rate, and minimal reservoir damage. After a period of production, as the water cut continues to rise in the well, bottom water or edge water coning is prone to occur. Because there is no cementing between the sand control section and the wellbore of the horizontal well, and no cement sheath between the wellbore and the oil layer, the breakthrough of water will cause the water cut of the oil well to rise sharply, leading to flooding of the entire well section. Currently, there is a lack of effective management methods for water detection and water blocking in openhole sand control horizontal wells, which ultimately leads to the shutdown of the oil well due to high water cut. To slow the coning of bottom or edge water and allow for later control, the current process involves running open-hole packers during the completion phase to provide staged isolation. While this process can slow the coning of bottom water to a certain extent, relying solely on the packer's 2-meter-long rubber sleeve cannot truly isolate the oil layer, and water breakthrough can still occur. Especially in heavy oil reservoirs, the open-hole packer's rubber sleeve is prone to damage after steam injection, leading to staged failure.

[0003] In the prior art, CN101532372B discloses a segmented screen completion string, including casing, drill pipe, impact seat, double-layer expansion sealing tool, screen, casing external packer, and cementing assembly. The casing is installed in the wellbore, and the casing external packer is connected to it. The drill pipe is installed in the casing, and the impact seat, double-layer expansion sealing tool, screen, and cementing assembly are connected to it in sequence. This invention uses a leather cup packer, and the leather cup is facing upward, which is easy to accumulate sand in the leather cup. The double-layer expansion sealing tool seal is a leather cup, and the outer diameter of the leather cup is large, which is easily damaged during the downhole process. This string can only expand the external packer and cannot achieve cement sealing.

[0004] CN111535777A discloses a fixed-point squeeze injection string for sand and water control and its application method. The string comprises a guide shoe, a screen, a reverse check valve, several squeeze layers, an oil bleeder, and a safety joint. The squeeze layer includes an expansion packer and a constant pressure valve, which are fixedly connected to the constant pressure valve via tubing. The guide shoe is fixedly connected to one end of the screen, the other end of the screen fixedly connected to the inlet of the reverse check valve, and the outlet of the reverse check valve is fixedly connected to the expansion packer of the squeeze layer via tubing. Several squeeze layers are sequentially connected, and adjacent squeeze layers are fixedly connected via tubing. The constant pressure valve at the end of the squeeze layer is fixedly connected to the expansion packer via tubing, and the other end of the oil bleeder is fixedly connected to the safety joint. This string is used to squeeze sand and water control agents during screen completion and production in horizontal wells, and to achieve expansion sealing of open-hole packers in the screen completion string. Chemicals are pumped into the string for water control, but their performance is unstable under high temperature conditions, making them unsuitable for thermal recovery horizontal wells.

[0005] CN112664148B discloses a horizontal well sand control completion string and a method for rapid horizontal well sand control completion using the horizontal well sand control completion string. The horizontal well sand control completion string includes a wellbore string and a service string. The temperature-sensitive expansion screen in the wellbore string is activated by temperature or activator induction. After entering the well, expansion completion can be achieved by simply circulating hot fluid or activator. Activating the temperature-sensitive expansion screen effectively saves circulation and washing time. Compared with conventional gravel pack sand control, this method saves ground pumping equipment and sand injection processes, saving a considerable amount of operation time.

[0006] CN113250647A discloses a suspended well completion integrated packer and completion string. The suspended well completion integrated packer includes a coaxially connected setting mechanism, a tieback tube, a release mechanism, and a setting mechanism. The setting mechanism includes a setting center pipe, a setting assembly, a first setting cylinder sleeve, and a first annular setting piston. The setting mechanism includes a setting center pipe, a thrust sleeve, a start-up shear fixture, and a setting seal assembly. The release mechanism includes a release spring lock tube, a release lock head, a release shear fixture, and a release assembly. The suspended well completion integrated packer may also include a tieback mechanism, which includes a tieback lock sleeve and a tieback spigot assembly. The disclosed suspended packer setting mechanism can achieve independent setting, so that the functions of other tools in the open hole segmented completion string are not affected. The release mechanism has high compressive strength and can be released after setting.

[0007] However, the above completion strings cannot be applied to general open hole horizontal wells, and their structures are relatively complex and the operation steps are numerous, so they cannot be promoted and applied on a large scale. Summary of the Invention

[0008] The purpose of the present invention is to provide a segmented water control and sand prevention completion string and method for open hole horizontal wells. The invention can realize segmented water control and sand prevention completion of open hole horizontal wells, perform cement isolation between the layers between the upper and lower oil layers, and achieve effective external isolation after the occurrence of edge and bottom water coning during the production process of the horizontal well. It can also be used under the conditions of thermal recovery and steam injection, delay the coning of bottom water and edge water, and extend the high-yield and stable production period of the oil well.

[0009] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: the open hole horizontal well cement isolation segmented water control and sand prevention completion string includes an outer string and an inner string. The outer string is connected to the casing, the drill-free graded cementing device, the sand filter pipe, the outer pipe packer, the upper cementing device, the blind pipe, the lower cementing device, the outer pipe packer, the sand filter pipe, and the well washing valve in sequence from top to bottom. The inner string is connected to the expandable packer, the cementing outer blind pipe, the expandable packer, the upper switch, the expandable packer, the expandable packer, the backwash mechanism, the inner injection port, the lower switch, the expandable packer, and the wire plug in sequence from top to bottom. The string can realize cement isolation between the upper and lower oil layers when the open hole horizontal well is segmented for sand prevention, and can achieve effective outer pipe isolation after the edge and bottom water coning occurs during the horizontal well production process. It can also be used under the conditions of thermal recovery steam injection, delaying the coning of bottom water and edge water, and extending the high-yield and stable production period of the oil well.

[0010] The invention adopts a double-tube structure, and the pipe column is provided with a cement injection port and a cement return port to realize the cyclic injection of cement slurry and improve the quality of cement cementing. After the cementing construction is completed, the internal injection port and the cement injection return liquid channel are provided with an automatic closing mechanism, which automatically closes after the cementing pump is stopped to prevent the injected cement slurry from spitting back. The safety of cementing construction is improved. The cementing process adopts rubber plug replacement, which is convenient for measurement operation. After the cementing is completed, the well can be immediately reversely circulated for washing. The reverse circulation well washing channel adopts a separate liquid inlet channel to improve construction safety. The invention designs packers for protection in both the upper and lower oil layers, and cooperates with the double-tube structure of the process pipe column. , ensuring that the cement slurry will not pollute the oil layer, all levels of packers use expansion packers, there are no slips, and the construction process is safe and reliable; after the construction is completed, a cement cementing section is formed between the two sections of screen pipes, and the first interface is established with the casing through cement cementing, and the second interface is established with the formation, realizing cement sealing of the oil layer. The length of the cement section can be adjusted according to the physical properties of the oil layer, which provides effective guarantee for the later water plugging. In the later period, if the water content rises, if the water content of the upper section is higher, a mechanical sealing string is lowered to seal the upper section and produce the lower section. If the water content of the lower section is higher, the lower section is sealed and the upper section is produced, thereby extending the overall high-yield and stable production period of the open hole horizontal well. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Attachment Figure 1 Schematic diagram of the completion string for cement isolation and segmented water and sand control in an open hole horizontal well

[0012] Attachment Figure 2Open hole horizontal well cement isolation staged water control and sand control completion Open hole sand control completion status

[0013] Attachment Figure 3 The status of the tubing string inside the segmented cementing string for cement isolation and water control and sand control completion of open hole horizontal well

[0014] Attachment Figure 4 Cementing construction status for open hole horizontal well cement isolation staged water control and sand control completion

[0015] Attachment Figure 5 Cement replacement construction status for open hole horizontal well cement isolation staged water control and sand control completion

[0016] Attachment Figure 6 Construction status of backwash well for open hole horizontal well cement isolation staged water control and sand prevention completion

[0017] Attachment Figure 7 The well status after the cement isolation and segmented water control and sand prevention completion of the open hole horizontal well DETAILED DESCRIPTION

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0019] Example 1:

[0020] A certain oil field carried out cement isolation of an open hole horizontal well, using the completion string according to the present invention.

[0021] See attached Figure 1-2 The completion string includes an expandable packer 1, a cementing external blind pipe 2, a sand filter pipe 3, an external packer 4, an expandable packer 5, a pressure transmission channel 6, an internal and external conversion mechanism 7, a cementing return channel 8, an upper switch 9, an upper cementer 10, a blind pipe 11, an expandable packer 12, an internal injection port 13, a lower switch 14, a lower cementer 15, an external packer 16, a sand filter pipe 17, an internal and external conversion mechanism 18, a rubber plug limit ring 19, a backwash mechanism 20, a rubber plug 21, a cementing inner pipe 22, an expandable packer 23, and a wire plug 24.

[0022] The openhole horizontal well cement isolation and staged water control and sand prevention completion string consists of an outer string and an inner string. The outer string is connected, from top to bottom, to the casing, a non-drilling staged cementer, a sand filter 3, an external packer 4, an upper cementer 10, a blind leg 11, a lower cementer 15, an external packer, a sand filter, and a well flushing valve. The inner string is connected, from top to bottom, to the expandable packer 1, a cementing external blind leg 2, an expandable packer, a cementing external blind leg, an upper switch 9, an expandable packer, an expandable packer 12, a lower switch 14, an expandable packer 23, and a screw plug 24.

[0023] The inner tubing string for cement isolation and staged water control and sand prevention completion in an openhole horizontal well is connected, from top to bottom, to two sets of expandable packers, which are then threaded onto an upper switch 9. The upper portion of the upper switch 9 features radially distributed return holes and a stepped claw at the bottom. The lower portion of the upper switch is in turn threaded onto the two expandable packers, which in turn are threaded onto a lower switch 14. The upper portion of the lower switch 14 features a mechanism 18 for switching between internal and external flow channels, and a stepped claw at the bottom. A backwash mechanism 20 isolates the annulus between the cementing outer blind leg 2 and the cementing inner pipe 22. Forward cement extrusion prevents flow, while reverse well washing removes excess cement slurry. The inner tubing string is threaded onto the lower switch 14, expandable packers 23, and screw plugs 24. The inner tubing string is a double-layered structure consisting of the cementing outer blind leg 2 and the cementing inner pipe 22.

[0024] Example 2:

[0025] The completion string described above has a complete set of operating methods that match it, as follows:

[0026] Openhole Sand Control Completion: During the openhole sand control completion process, the outer string is connected, from top to bottom, to the casing, the non-drilling staged cementer, the sand filter 3, the external packer 4, the upper cementer 10, the blind leg 11, the lower cementer 15, the external packer, the sand filter, and the well flushing valve. The string is lowered to the designed depth for openhole completion cementing and the non-drilling staged cementer fishing operation.

[0027] Run the inner string of the segmented cementing string: see the attached Figure 3 The inner tubing string for cement-insulated, staged water and sand control completions in openhole horizontal wells is connected sequentially from top to bottom to the drill pipe, two sets of expansion packers, and an upper switch 9, which has radially distributed return holes on its upper portion and a stepped claw on its lower portion. The lower portion of the upper switch is in turn threaded with two expansion packers, which in turn are threaded with a lower switch 14. The upper portion of the lower switch 14 features a conversion mechanism 18 for internal and external flow channels, and a stepped claw on its lower portion. A backwash mechanism 20 isolates the annulus between the cementing outer blind pipe 2 and the cementing inner pipe 22. Forward cement extrusion prevents flow, while reverse well washing flushes excess cement slurry. The inner tubing string is threaded with the expansion packer and a threaded plug in sequence to the lower switch 12. The inner tubing string is a double-layered structure consisting of the cementing outer blind pipe 2 and the cementing inner pipe 22.

[0028] Cementing construction: see attached Figure 4 After the inner string of the open hole horizontal well cement isolation segmented water control and sand prevention completion string is lowered to the designed depth, the claw of the upper switch 9 contacts the sliding sleeve of the upper cementing device 10, and the claw of the lower switch 14 contacts the sliding sleeve of the lower cementing device 15. Slowly pressurize to shear the self-locking pins of the upper cementing device 10 and the lower cementing device 15, open the channel of the upper cementing device 10 and the lower cementing device 15, first perform positive circulation well washing, test the channel flow condition, prepare for cementing, and then cycle After the annulus is normal, circulation cementing begins. The cement slurry reaches the cementing inner tube 22 through the drill pipe. After reaching the cementing inner tube 22, the self-closing device of the inner injection port 13 is opened by pressure, and enters the formation through the liquid outlet of the lower cementing device 15. The cement slurry passes through the blind pipe 11 and the annulus of the formation to reach the liquid inlet of the upper cementing device 10, opens the self-closing channel of the cementing return channel 8, enters the annulus between the cementing outer blind pipe 2 and the cementing inner tube 22, and finally returns to the annulus of the drill pipe and casing.

[0029] Replacement cement construction: see attached Figure 5 A rubber plug 21 is inserted into the drill pipe. After the plug is inserted, a cement truck is used to displace the cement slurry into the formation annulus, and finally, the impact pressure is applied. When the rubber plug 21 reaches the stopper ring 19, the displacement is complete. After the pump is stopped, the cement return channel 8 and the internal injection port 13 are automatically closed by the closing device to prevent the backflow of cement slurry.

[0030] Backwash well construction: see attached Figure 6 , reverse circulation well washing, the liquid enters the annulus of the cementing outer blind pipe 2 and the cementing inner pipe 22 through the drill pipe and casing annulus, reaches the backwashing mechanism 20, the liquid pushes open the backwashing mechanism 20 and enters the cementing inner pipe 22, and the excess cement slurry in the annulus of the drill pipe and casing, the annulus of the cementing outer blind pipe 2 and the cementing inner pipe 22, and the cementing inner pipe 22 is backwashed out.

[0031] Pull out the inner string: The closing mechanism of the upper cementing device 10 and the lower cementing device 15 is forced to close under the action of the upper switch 9 and the lower switch 14, and is self-locked to finally complete the open hole horizontal well cement isolation staged water control and sand control completion construction, see the attached Figure 7 .

[0032] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A segmented water and sand control completion string for cement isolation of open hole horizontal wells, characterized by: It includes an outer pipe string and an inner pipe string, wherein the inner pipe string is a double-layer pipe structure of a cementing outer blind pipe and a cementing inner pipe; The outer pipe string is provided with casing, upper cementing device, sand filter, external pipe packer, blind pipe, lower cementing device, external pipe packer, sand filter, and well flushing valve in sequence from top to bottom; The inner pipe string is provided with an expansion packer, a cementing outer blind pipe, an expansion packer, a cementing outer blind pipe, an upper switch, an expansion packer, a lower switch, an expansion packer, and a plug in sequence from top to bottom; The upper switch is provided with radially evenly distributed liquid return holes; the lower switch is provided with a conversion mechanism for the inner and outer flow channels; The backwash mechanism is further included, wherein the backwash mechanism seals the annulus between the outer blind pipe of cement injection and the inner pipe of cement injection, prevents cement from flowing in the forward direction, and washes out excess cement slurry in the reverse direction of well washing; After the inner string is lowered to the designed depth, the upper switch contacts the sliding sleeve of the upper cementing device to open the channel of the upper cementing device, and the lower switch contacts the sliding sleeve of the lower cementing device to open the channel of the lower cementing device; During positive circulation well washing, cement slurry reaches the cementing inner pipe through the drill pipe. After reaching the cementing inner pipe, the self-closing device of the inner injection port is pushed open by pressure, and enters the formation through the liquid outlet of the lower cementing device. The cement slurry reaches the liquid inlet of the upper cementing device through the blind pipe and the annulus of the formation, opens the self-closing channel of the cementing return channel, enters the annulus of the outer blind pipe and the cementing inner pipe, and finally returns to the annulus of the drill pipe and casing.

2. The method for using the open hole horizontal well cement isolation segmented water control and sand control completion string according to claim 1, characterized in that: The following steps are involved: Open hole sand control completion: The open hole horizontal well cement isolation staged water control and sand control completion string is lowered to the designed depth, and open hole completion cementing and drilling-free staged cementing device fishing operations are carried out; The inner string of the segmented cementing string is lowered: the inner string of the segmented water control and sand prevention completion string for open hole horizontal well cement isolation is connected to the drill pipe, two sets of expansion packers, and the upper switch in sequence from top to bottom. The upper part of the upper switch has radially uniform return holes, and the lower part has a claw with a step; the lower part of the upper switch is sequentially threaded to connect the two sets of expansion packers and the lower switch. The upper part of the lower switch is a conversion mechanism for the internal and external flow channels, and the lower part has a claw with a step. The backwash mechanism isolates the annulus between the cementing outer blind pipe and the cementing inner pipe. Forward squeezing does not allow cement to circulate, and reverse well washing washes out excess cement slurry. It is sequentially threaded to connect the expansion packer and the plug with the lower switch; the inner string is a double-layer pipe structure of the cementing outer blind pipe and the cementing inner pipe; Cementing construction: After the inner string of the open hole horizontal well cement isolation segmented water control and sand prevention completion string is lowered to the designed depth, the claw of the upper switch contacts the sliding sleeve of the upper cementing device, and the claw of the lower switch contacts the sliding sleeve of the lower cementing device. The self-locking pins of the upper cementing device and the lower cementing device are slowly sheared off by pressure, and the channels of the upper cementing device and the lower cementing device are opened. The positive circulation well is first washed to test the flow of the channel in preparation for cementing. After the circulation is normal, the circulation cementing is started. The cement slurry passes through the drill pipe to the cementing inner pipe. After reaching the cementing inner pipe, the self-closing device of the inner injection port is opened by pressure, and enters the formation through the liquid outlet of the lower cementing device. The cement slurry passes through the blind pipe and the annulus of the formation to reach the liquid inlet of the upper cementing device, and the self-closing channel of the cementing return channel is opened to enter the annulus of the cementing outer blind pipe and the cementing inner pipe, and finally returns to the annulus of the drill pipe and casing; Cement displacement construction: insert a rubber plug into the drill pipe, and then use a cement truck to displace the cement slurry into the formation annulus, and finally perform impact pressure construction; the displacement is completed when the rubber plug reaches the rubber plug limit ring; after stopping the pump, the cement return channel and the internal injection port are automatically closed by the closing device to prevent cement slurry from spitting back; Backwash well construction: Reverse circulation well washing, the liquid enters the annulus of the cementing outer blind pipe and the cementing inner pipe through the drill pipe and casing annulus, reaches the backwash mechanism, and the liquid pushes the backwash mechanism open and enters the cementing inner pipe, and the excess cement slurry in the drill pipe and casing annulus, the cementing outer blind pipe and the cementing inner pipe annulus, and the cementing inner pipe is backwashed out; Pulling out the inner tubing string: The closing mechanisms of the upper and lower cementing devices are forced to close under the action of the upper and lower switches, and then self-lock to finally complete the cement isolation and segmented water control and sand prevention completion construction of the open hole horizontal well.

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