Grading well cementation device and method suitable for double-layer simultaneous production well and having reservoir protection function

Abstract

The invention relates to a graded well cementation device suitable for a double-layer simultaneous production well and having a reservoir protection function, and relates to the field of well cementation technology.The graded well cementation device comprises a casing string, the casing string penetrates through a first reservoir and a separation layer, and a cementing device is fixedly connected to the outer side of the casing string and located above the first reservoir; a plugging assembly is arranged between the cementing device and the first reservoir, and the plugging assembly separates the cementing device from the first reservoir. The method has the advantages that the first reservoir is prevented from being polluted by the cement paste, the requirements of the first reservoir and the second reservoir are met, and the requirement for safe drilling in the later period can be met.

Description

Technical Field

[0001] This application relates to the field of cementing technology, and in particular to a graded cementing apparatus and method applicable to wells with both dual-layer co-production and reservoir protection functions. Background Technology

[0002] Conventional cementing processes generally include: single-stage backfill cementing (single-density single-coagulation), single-stage backfill cementing (double-density double-coagulation), and staged cementing.

[0003] The conventional single-stage cementing process (single-density, single-coagulation) involves injecting a certain amount of cement slurry into the casing string from the wellhead during cementing (the amount of cement slurry is slightly larger than the volume of the annulus between the casing string and the well wall in the cemented section). The cement slurry density is maintained at a relatively consistent level (usually 1.85-1.90 g / cm³). 3 After the cement slurry is injected, a rubber plug is inserted into the casing string. Then, drilling fluid or water is used to push the rubber plug, displacing the cement slurry from the casing string into the annulus. After injection, pressure is applied and the cementing is completed.

[0004] One type of single-stage backfill cementing process (double-density, double-coagulation): The cementing process is the same as the conventional single-stage backfill cementing process (single-density, single-coagulation), except that the structure of the cement slurry column is adjusted. During construction, a certain amount of high-density cement slurry is first injected into the well (the volume of the cement slurry must be sufficient to seal the reservoir up to 300m above the surface; the density of the cement slurry is typically 1.85-1.90 g / cm³). 3 Then, a certain amount of low-density cement slurry is injected (the volume of cement slurry should be sufficient to seal the annulus from the ground to 300m above the reservoir). The specific volume of high-density and low-density cement slurry depends on the specific circumstances.

[0005] The staged cementing process involves the following steps: During casing string installation, a stage collar (with circulation holes and an internal sliding sleeve to allow for opening and closing of the circulation holes) is inserted at a designated position on the casing string. The cementing process is divided into two stages. The first stage cements the formation below the stage collar. During the first stage, the circulation holes of the stage collar are closed. Once the cement slurry returns to the stage collar position, the circulation holes are opened to establish circulation in the annulus above the stage collar. Afterward, pressure is applied and allowed to solidify for 4-6 hours. After solidification, the second stage cementing begins, following the same procedure as conventional cementing. After cementing, the circulation holes of the stage collar are closed, pressure is applied again, and the cementing is completed.

[0006] However, in some regions, the strata are arranged from top to bottom as the first reservoir, the separator, and the second reservoir, with the first and second reservoirs separated by the separator located in the middle. For example, in the Ordovician, Cambrian, and Jixian Wumishan Formation, geothermal resources are mainly concentrated in the Ordovician and Wumishan Formations.

[0007] Because the Wumishan Formation has low pressure bearing capacity and is prone to well leakage, casing must be run and cemented after drilling 2-3 meters into the Wumishan Formation to seal the upper well section. However, this cement slurry will contaminate the Ordovician formation, affecting water testing in the Ordovician. If water testing is conducted midway through drilling into the Ordovician, the acid used will significantly reduce the formation's pressure bearing capacity, making subsequent drilling impossible. Summary of the Invention

[0008] In order to prevent cement slurry from contaminating the first reservoir and meet the requirements of simultaneous production of the first and second reservoirs, while also meeting the requirements of safe drilling in the later stages, this application provides a staged cementing device and method suitable for wells with simultaneous production of two reservoirs and reservoir protection function.

[0009] The staged cementing device for dual-layer co-production wells with reservoir protection function provided in this application adopts the following technical solution:

[0010] A staged cementing device suitable for dual-layer co-production wells with reservoir protection function includes a casing string that penetrates the first reservoir and the separator layer. A cement injector is fixedly connected to the outside of the casing string and is located above the first reservoir. A sealing assembly is provided between the cement injector and the first reservoir to separate the cement injector from the first reservoir.

[0011] Optionally, the plugging assembly includes a packer, which is fixedly connected to the casing string. After the packer is seated, it divides and seals the annular space, dividing the annular space into a first cementing space below the packer and a second cementing space above the packer.

[0012] By adopting the above technical solution, the packer seals the annular space between the casing string and the outside after the packer is seated, and divides the annular space into a first cement injection space located below the packer and a second cement injection space located above the packer. The first cement injection space and the second cement injection space are independent spaces, reducing the impact of injecting cement into the first cement injection space on the interior of the second cement injection space.

[0013] Optionally, the cement injector and the packer are an integrated packer cement injector, which is sleeved on the outside of the casing and fixedly connected to the casing.

[0014] By adopting the above technical solution, the packer setting and the cement injection nozzle opening require the insertion of an opening plug (gravity plug) to open, effectively avoiding the problem of premature packer setting during tubing string insertion, well circulation flushing, and the first cement injection operation.

[0015] Optionally, the integrated sealing cement injector includes an integrated body, with a sealing part at the bottom of the integrated body. The sealing part expands to seal the annular space. A cement injection part is provided above the sealing part. An opening plug seat is provided inside the cement injection part. A bypass valve is provided below the opening plug seat. The bypass valve connects the interior of the cement injection part with the external annular space. When the opening plug is inserted, the opening plug seat supports the opening plug.

[0016] By adopting the above technical solution, the annular space can be effectively sealed through the expansion of the sealing section. A cement injection section is provided for convenient cement injection, and the internal open plug seat controls the cement flow, ensuring the accuracy and stability of cement injection. A bypass valve is located below the open plug seat, connecting the interior of the cement injection section to the external annular space. This allows cement to be discharged or the device to be cleaned when needed, facilitating maintenance and cleaning.

[0017] Optionally, a hanger is provided at the top of the casing column, the hanger is sleeved on the outside of the casing column, and the hanger is fixedly connected to the casing column.

[0018] By adopting the above technical solution, the hanger suspends the casing string at a fixed position in the well section, enabling the casing string to withstand the influence of external forces and the environment such as well depth, well pressure, and well temperature. It transfers the load on the casing string, such as well depth, well pressure, well temperature, and production dynamic load, to the wellhead equipment or downhole equipment, thereby ensuring the safe operation of the wellhead and downhole equipment, facilitating the running-in and lifting operations, and replacing and repairing the casing string.

[0019] Optionally, the suspension may be a slip-type suspension.

[0020] By adopting the above technical solution, the slip-type hanger is used for well completion, which can realize both suspension and cement injection construction.

[0021] Optionally, the outside of the suspension is provided with a top sealing structure, which seals the annular space after expansion.

[0022] By adopting the above technical solution, a top sealing structure is provided on the outside of the hanger to improve the sealing effect of the cement injection annulus.

[0023] Optionally, a cement-type float shoe is coaxially provided at the bottom end of the casing column, and the cement-type float shoe is fixedly connected to the casing column.

[0024] By adopting the above technical solution, the casing string can withstand its weight and be supported inside the wellbore, ensuring its vertical position and stability. An anti-backflow device is installed inside to prevent downhole fluid from flowing back into the casing string, ensuring that cement slurry can be smoothly injected downhole during cementing. There are multiple small holes or grooves at the bottom to guide the cement slurry out from the bottom of the float shoe, allowing it to rise along the outer wall of the casing string and form an annulus between the casing string and the wellbore, thereby controlling the cementing quality.

[0025] Optionally, a cement-type float hoop is provided above the cement-type float shoe on the casing column, and the cement-type float hoop is fixedly connected to the casing column.

[0026] By adopting the above technical solution, the casing string can be kept in the center of the wellbore, ensuring its vertical position and stability within the wellbore. This improves the flowability of cement slurry between the casing string and the wellbore, reduces side leakage, and enhances cementing quality. It helps the cement slurry distribute evenly within the annulus between the casing string and the wellbore, reducing voids and the possibility of uneven solidification. Through centered and uniform cementing of the casing string, cement-type float collars can improve the integrity and strength of the wellbore, reducing the risk of wellbore deformation and damage.

[0027] Optionally, a movable ball seat is provided above the cement-type floating hoop of the casing string.

[0028] By adopting the above technical solution, the flow of fluid in the casing string can be controlled. By opening or closing the opening on the ball seat, the fluid channel and flow rate can be adjusted for staged fracturing, selective production, and adjustment of the fluid flow direction in the wellbore.

[0029] This application also discloses a staged cementing method suitable for dual-layer co-production wells with reservoir protection function, applied to the aforementioned staged cementing device suitable for dual-layer co-production wells with reservoir protection function, the method comprising:

[0030] S01: Lower the casing string and confirm that the hanger and cement injector are in place;

[0031] S02: Throw the ball, hang the suspension device, and then remove it after inverting it;

[0032] S03: Inject cement into the interior of the first cement injection space and allow it to set;

[0033] S04: Deploy the opening plug to expand the packer, filling the first cement space and the second water space.

[0034] The mud space is divided, and cement is injected into the interior of the second cement space;

[0035] S05: When the rubber plug inside the casing string is pushed to the back pressure valve by the drilling fluid, a collision occurs.

[0036] Close the cement injector;

[0037] S06: Circulating well washing, after the drill bit has drilled out of the lower part of the wellbore, the drill bit is pulled out.

[0038] By adopting the above technical solution, in order to meet the water testing requirements of the first reservoir, the "slip-type hanger + integrated packer cement injector + detachable ball seat" process is used to achieve staged cementing. The main completion construction procedures are: three-stage drilling, preparation before completion construction, running the three-stage casing string, dropping the ball, setting the hanger, backing, detaching, first cementing, waiting for it to set, dropping the gravity plug, expansion sealing, opening the staged hoop circulation hole, second cementing, pressing, closing the cement injector, circulating well washing, drilling plug, and four-stage drilling.

[0039] Optionally, in S03, cement is injected into the interior of the first cement space, and the cement is quantitatively replaced according to the volume of the annulus of the target layer.

[0040] By adopting the above technical solution, cement slurry is not introduced into the first reservoir, thus achieving zero pollution of the Ordovician system by cement slurry.

[0041] Optionally, in S04, after the opening plug is inserted, the first pressure is applied to open the pressure transmission hole of the packer and seal the packer; the second pressure is applied to settle the packer; the third pressure is applied to open the flow hole of the cement injector and establish circulation.

[0042] Optionally, in S05, after closing the cement injector, the drill pipe is raised 2m, and 100KN is applied downward to seal the top and bottom structures. The drill pipe is then raised 5-10m, moved up and down, to perform high-volume well flushing. Finally, the drill pipe is pulled out 100m and allowed to set.

[0043] Optionally, the first pressure < the second pressure < the third pressure.

[0044] In summary, this application includes at least one of the following beneficial technical effects:

[0045] 1. By injecting cement in two relatively independent steps, the cement slurry can be prevented from contaminating the first reservoir, thus meeting the requirements for simultaneous production of the first and second reservoirs, while also meeting the requirements for safe drilling in the later stages. This process can achieve selective formation sealing and ensure cementing quality.

[0046] 2. Testing is conducted simultaneously after drilling is completed. Testing will not affect drilling operations and improves the safety of drilling operations. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the overall structure of a staged cementing device applicable to dual-layer co-production wells and with reservoir protection function in the embodiments of this application.

[0048] Figure 2 This is a structural schematic diagram of the primary and secondary cementing processes of a graded cementing device applicable to dual-layer co-production wells with reservoir protection functions in this application embodiment.

[0049] Figure 3 This is a schematic diagram of the drill plug and four-stage drilling structure of a staged cementing device applicable to dual-layer co-production wells with reservoir protection function in the embodiments of this application.

[0050] Explanation of reference numerals in the attached drawings: 1. Drill pipe; 2. Casing string; 21. Cement float shoe; 22. Cement float collar; 23. Movable ball seat; 3. Hanger; 4. Integrated packer cement injector; 41. Cement injection section; 42. Packer section; 5. First cement injection space; 6. Second cement injection space; 7. First reservoir; 8. Separator layer; 9. Second reservoir. Detailed Implementation

[0051] Conventional cementing processes generally include: single-stage backfill cementing (single-density single-coagulation), single-stage backfill cementing (double-density double-coagulation), and staged cementing.

[0052] The conventional single-stage cementing process (single-density, single-coagulation) involves injecting a certain amount of cement slurry into the casing string from the wellhead during cementing (the amount of cement slurry is slightly larger than the volume of the annulus between the casing string and the well wall in the cemented section). The cement slurry density is maintained at a relatively consistent level (usually 1.85-1.90 g / cm³). 3 After the cement slurry is injected, a rubber plug is inserted into the casing string. Then, drilling fluid or water is used to push the rubber plug, displacing the cement slurry from the casing string into the annulus. After injection, pressure is applied and the cementing is completed.

[0053] However, the above-mentioned process usually involves cement slurry with a density much greater than that of drilling fluid in the well. The hydrostatic pressure generated by the cement slurry column is also greater than that of the drilling fluid column. When the cemented section is too long or the formation has low pressure bearing capacity, well leakage is likely to occur, affecting the cementing quality. Cementing is a continuous operation and cannot selectively seal the formation. It is not suitable for formations with low pressure bearing capacity.

[0054] One type of single-stage backfill cementing process (double-density, double-coagulation): The cementing process is the same as the conventional single-stage backfill cementing process (single-density, single-coagulation), except that the structure of the cement slurry column is adjusted. During construction, a certain amount of high-density cement slurry is first injected into the well (the volume of the cement slurry must be sufficient to seal the reservoir up to 300m above the surface; the density of the cement slurry is typically 1.85-1.90 g / cm³). 3 Then, a certain amount of low-density cement slurry is injected (the volume of cement slurry should be sufficient to seal the annulus from the ground to 300m above the reservoir). The specific volume of high-density and low-density cement slurry depends on the specific circumstances.

[0055] However, the cost of the above process is slightly higher than that of the conventional single-pass cementing process (single-cementing and single-coagulation); although it reduces well leakage during cementing to some extent, it still cannot meet the construction requirements for some formations with very low pressure bearing capacity; cementing is a continuous operation and cannot achieve selective sealing of the formation.

[0056] The staged cementing process involves the following steps: During casing string installation, a stage collar (with circulation holes and an internal sliding sleeve to allow for opening and closing of the circulation holes) is inserted at a designated position on the casing string. The cementing process is divided into two stages. The first stage cements the formation below the stage collar. During the first stage, the circulation holes of the stage collar are closed. Once the cement slurry returns to the stage collar position, the circulation holes are opened to establish circulation in the annulus above the stage collar. Afterward, pressure is applied and allowed to solidify for 4-6 hours. After solidification, the second stage cementing begins, following the same procedure as conventional cementing. After cementing, the circulation holes of the stage collar are closed, pressure is applied again, and the cementing is completed.

[0057] However, the above-mentioned process is more expensive than the previous two processes, and the construction period is increased by 0.5-1 day; it cannot achieve selective sealing of the strata.

[0058] However, in some regions, the strata are arranged from top to bottom as the first reservoir, the separator, and the second reservoir, with the first and second reservoirs separated by the separator located in the middle. For example, in the Ordovician, Cambrian, and Jixian Wumishan Formation, geothermal resources are mainly concentrated in the Ordovician and Wumishan Formations.

[0059] Because the Wumishan Formation has low pressure bearing capacity and is prone to well leakage, casing must be run and cemented after drilling 2-3 meters into the Wumishan Formation to seal the upper well section. However, this cement slurry will contaminate the Ordovician formation, affecting water testing in the Ordovician. If water testing is conducted midway through drilling into the Ordovician, the acid used will significantly reduce the formation's pressure bearing capacity, making subsequent drilling impossible.

[0060] In order to prevent cement slurry from contaminating the first reservoir and meet the requirements of simultaneous production of the first and second reservoirs, while also meeting the requirements of safe drilling in the later stages, this application provides a staged cementing device and method suitable for wells with simultaneous production of two reservoirs and reservoir protection function.

[0061] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0062] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0063] The following is in conjunction with the appendix Figure 1-3 This application will be described in further detail.

[0064] This application discloses a staged cementing device applicable to dual-layer co-production wells that also provide reservoir protection. (Refer to...) Figure 1 , Figure 2 A staged cementing device suitable for dual-layer simultaneous production wells with reservoir protection functions includes a vertically installed casing string 2. The casing string 2 extends into the interior of the formation, which, from top to bottom, consists of a first reservoir 7, a separator layer 8, and a second reservoir 9. The separator layer 8 completely separates the first reservoir 7 and the second reservoir 9. In some embodiments, the first reservoir 7 is an Ordovician formation, the separator layer 8 is a Cambrian formation, and the second reservoir 9 is a Wumishan Formation. The bottom end of the casing extends to the position where the bottom end of the separator layer 8 connects with the second reservoir 9, and the top end of the casing string 2 is located above the first reservoir 7. The casing string 2 extends from top to bottom through the first reservoir 7, the separator layer 8, and into the second reservoir 9.

[0065] In some embodiments, a drill pipe 1 is provided above the casing string 2, and a hanger 3 is provided at the top of the casing string 2. The hanger 3 is coaxially arranged with the casing string, and the hanger 3 is relatively fixedly connected to the casing string 2. In some embodiments, the hanger 3 can be selected as an XG Y type Φ244.5×Φ177.8 (95 / 8"×7") tailpipe hanger 3, which is hydraulic. The tailpipe hanger 3 includes a single hydraulic cylinder, a single cone, a single row of slips, and a hydraulic seat-mounted hanger 3. It can realize suspension and cement injection construction; it has a top sealing structure to improve the sealing effect of the cement injection annulus.

[0066] The suspension device 3 mainly comprises a suspension device 3 body assembly, a feeding tool assembly, a sealing assembly, a return sleeve, a rubber plug, and a ball seat assembly. The suspension device 3 body assembly includes a cone, a hydraulic cylinder, a piston, and slips.

[0067] Place the return sleeve in front of the hanger, with the threaded end facing the hanger. Loosen the fixing pin on the plug cap of the lifting short connector, and pass the lifting short connector through the return sleeve, i.e., put the return sleeve on the lifting short connector, with the flared end of the return sleeve facing the plug cap. Remove the protective thread of the lifting short connector and check the sealing ring.

[0068] After connecting the lifting short connector to the upper connector of the reverse-clamp assembly, ensure that the pin holes are aligned when the two ends of the lifting short connector and the upper connector of the reverse-clamp assembly are in contact. Tighten the pins with an Allen wrench. Clean the threads of the sealing assembly housing and apply sealant to the sleeve column. Connect the reconnector sleeve to the threads of the sealing assembly housing. Push the plug cap into the flared end of the reconnector sleeve and tighten the fixing screw with an Allen wrench.

[0069] The feed tool assembly includes: a plug, a lifting sub, an undercut assembly, and a center tube.

[0070] The sealing assembly includes a sealing housing and a sealing core.

[0071] The rubber plugs include a drill pipe rubber plug and a special tailpipe rubber plug.

[0072] When the ball is dropped and seated, pressure is applied. The pressure is transmitted to the hydraulic cylinder through the pressure transmission hole on the main body of the hanger 3. The pressure pushes the piston upward, shearing the hydraulic cylinder shear pin, then pushing the push rod support sleeve, and causing the slips to move upward. The slips expand along the conical surface and wed into the annular gap between the cone of the hanger 3 and the upper casing string 2. When the drill string is lowered, the weight of the tailpipe is supported on the upper casing string 2. Pressure is continued to be applied to open the ball seat and establish normal circulation. Below the hanger 3, the casing string 2 is also equipped with a cement injector. Below the cement injector is a packer. After expansion, the packer, located on the outside of the separator, can press against the inside of the well wall. The packer divides the interior of the well into a first cement injection space 5 below the packer and a second cement injection space 6 above the packer. The first cement injection space 5 and the second cement injection space 6 are not connected.

[0073] After the hanger 3 is installed, the upper surface of the cement injected into the second cement injection space 6 is opposite to the position of the hanger 3. In some embodiments, the cement can be lowered without the hanger 3, in which case the upper surface of the cement injected into the second cement injection space 6 is flush with the wellhead position.

[0074] In some embodiments, the packer and the cementing device can be selected as an integrated packer cementing device 4 with an integral structure. The packer is seated and the cementing device opening is opened by inserting an opening plug, which effectively avoids the problem of the packer being prematurely seated during tubing string insertion, well flushing, and the first cementing operation.

[0075] The annular space is divided by a packer, which can receive the bottom of the upper second cement injection space 6. Since the density of the medium in the first cement injection space 6 opposite to the first reservoir 7 is less than the density of the cement slurry, the packer prevents the cement slurry in the second cement injection space 6 and the medium in the first cement injection space opposite to the first reservoir 7 from mixing.

[0076] The integrated sealing cement injector 4 includes an integrated body, and a cement injection section 41 is provided on the top of the integrated body. An opening plug seat is provided inside the cement injection section 41, and a bypass valve is provided on one side of the opening plug seat. The bypass valve connects the interior of the cement injection section 41 with the annular space inside the first cement injection section 41 to the outside.

[0077] A packer 42 is located below the cement injection section 41. After the packer 42 expands, it can seal the annular space. A gravity-type opening plug is inserted into the wellhead. When the opening plug sits into the opening plug seat by free fall, the pump is turned on to pressurize and open the liquid inlet of the packer 42 to expand and seal the packer. When the packer rubber sleeve filling pressure reaches the design value, the packer pressure relief valve is closed. The wellhead continues to pressurize and shears the pin on the opening sleeve. The opening sleeve moves upward and opens the circulation hole to establish circulation.

[0078] When in use, the tailpipe hanger 3, tailpipe, integrated packer cement injector 4, and matching accessories are lowered into the well to the designed depth using a dedicated delivery tool.

[0079] When the ball is thrown and the pressure is applied, the pressure is transmitted to the hydraulic cylinder through the pressure transmission hole on the main body of the hanger 3. The pressure pushes the piston upward, shears the hydraulic cylinder shear pin, and then pushes the push rod support sleeve, which in turn drives the slip upward. The slip expands along the conical surface and weds into the annular gap between the cone of the hanger 3 and the upper casing string 2. When the drill string is lowered, the weight of the tailpipe is supported on the upper casing string 2.

[0080] Continue pressurizing to clear the ball seat and establish normal circulation. Then proceed with reverse clamping, quantitative cementing, and allow it to set.

[0081] Before the setting and reverse connection steps, a trial setting operation should be performed. Due to the limitations of downhole conditions, sometimes the circulating pressure is too high and the hydraulic cylinder shear pin may be cut off before the ball is dropped. In this case, if there is no rotating cement head or no ball dropping hole on the cement head, the setting can be performed directly.

[0082] If the drill string is not successfully mounted, drop the ball and pump it at a small displacement. Closely monitor the pump pressure changes. When the ball reaches the ball seat, pressurize it to 11-12 MPa and stabilize the pressure for 2 minutes. Slowly lower the drill string. When the total suspended weight drops to equal the total weight of the drill string plus the weight of the traveling block (at this point, the retraction distance of the drill string is equal to or close to the calculated value), the mounting is successful.

[0083] Continue to press down by 10-15t to check the reliability of the seat.

[0084] After successfully hanging the ball, continue to pressurize to about 18 MPa to open the ball seat and establish normal circulation.

[0085] In case of an abnormality, stop the pump, loosen the rotary table, and set the drill pipe slips to ensure the load support sleeve bears a pressure of 5-8 tons. Then, rotate the rotary table forward to perform reverse turning, accumulating at least 20 effective reverse turns. Under normal circumstances, when using the rotary table for reverse turning, after rotating it forward several times, release the rotary table; the rotary table should hardly rotate back. If there is significant rotation, it may be that the load support sleeve is not under pressure or is under too much pressure, in which case adjustment is necessary.

[0086] Slowly raise the drill string to the neutral point and then raise it another 1.2 to 1.5 meters. If the suspended weight is always equal to the weight of the upper drill string plus the traveling block, it indicates that the connection has been reversed.

[0087] After the inverted connection is successful, the drill string is returned to its original position, causing the hanger to depress down by 5-8 tons. The well is then cemented after the cycle is completed according to the fixed requirements.

[0088] The annular space is divided into a first cementing space 5, which is opposite to the separator layer 8 and the first reservoir 7, and a second cementing space 6, which is located above the first reservoir 7, by an integrated packer cementing injector 4.

[0089] First, cement is injected into the interior of the first cement injection space 5 through the first cement injection step, and the cement slurry is quantitatively replaced according to the annular volume of the target layer.

[0090] By quantitatively displacing the annular volume of the target stratum, cement located within the target stratum will not rise into the interior of the upper stratum. In a specific embodiment, cement located within the separator (Cambrian strata) will solidify within the separator, and the upper surface of the cement within the separator will not be higher than the upper surface of the separator, thus preventing it from entering the interior of the first reservoir (Ordovician strata). This reduces cement slurry contamination of the Ordovician strata, meets the requirements for co-mining of the Ordovician and Wumishan Formations, and plays a role in reservoir protection.

[0091] Then, cement is injected into the interior of the second cementing space 6 through the second cementing step to perform the second cementing, and then the drill plug is installed to continue drilling into the interior of the second reservoir 9.

[0092] Since the first cement injection space 5 and the second cement injection space 6 are separated by the integrated cement injection device 4, they form two relatively independent spaces that are not connected. Cement is first injected into the interior of the first cement injection space 5 to quantitatively replace the cement slurry, thereby reducing the impact of the cement inside the first cement injection space 5 on other strata, and the cement is applied separately to the interior of the first cement injection space 5.

[0093] Cement is then injected into the interior of the second cement injection space 6 to reduce the impact of the cement inside the second cement injection space 6 on other strata, thus allowing the cement to act solely on the interior of the second cement injection space 6.

[0094] A cement-type float shoe 21 is provided at the bottom end of the casing column 2. The cement-type float shoe 21 is coaxially arranged with the casing column 2 and is fixedly connected to it.

[0095] A length is reserved at the bottom of the casing string 2, and then the cement-type float shoe 21 is installed at the end of the casing string 2. The cement-type float shoe 21 is usually made of metal and has strength and pressure resistance.

[0096] The cement float shoe 21 is equipped with an anti-backflow device, which is usually a ball or cone valve, to prevent downhole fluid from flowing back into the casing string 2 and to ensure that cement slurry can be smoothly injected downhole during the cementing process.

[0097] Above the cement float 21, cement grout is injected through the inside of the casing string 2. The cement grout enters the annulus between the casing string 2 and the well wall through small holes or grooves at the bottom of the cement float 21. After forming an annulus between the casing string 2 and the well wall, the cement grout rises along the wellbore, fills the annulus, and solidifies. The solidification process of the cement grout firmly connects the casing string 2 and the well wall together, forming a support and leakage barrier for the well wall.

[0098] Above the cement float shoe 21, the casing string 2 is coaxially equipped with a cement float collar 22, which is fixedly connected to the casing string 2. This ensures that the casing string 2 is kept in the center of the wellbore, guaranteeing its vertical position and stability within the wellbore.

[0099] Above the cement floating shoe 21, the casing column 2 is also provided with a movable ball seat 23, which is coaxially arranged with the casing column 2 and relatively fixedly connected.

[0100] The movable ball seat 23 can control the flow of fluid within the casing string 2. By opening or closing the orifice on the ball seat, the fluid passage and flow rate can be adjusted. It can be used for staged fracturing, selective production, and adjusting the flow direction of fluid within the wellbore.

[0101] Reference Figures 1-3 This application also provides a staged cementing method suitable for dual-layer co-production wells with reservoir protection function, applied to the aforementioned staged cementing device suitable for dual-layer co-production wells with reservoir protection function.

[0102] A staged cementing method suitable for wells with both dual-layer co-production and reservoir protection functions includes:

[0103] S01: First, carry out the preparatory work before the third drilling and well completion. Run the casing string 2 and accessories in sequence, and apply sufficient torque according to the standard. Fill the casing string with mud at least once every 20 casing strings. After connecting the cement float shoe 21 and cement float collar 22, connect the square drill pipe and start the pump or check the unobstructed flow and back pressure prevention of the cement float shoe 21 and cement float collar 22 through other means.

[0104] Run the casing string 2, confirm that the hanger 3 and cement injector are in place, and with the help of a special delivery tool, run the tailpipe hanger 3, tailpipe, packer-type staged cement injector and matching accessories into the well to the designed depth according to the design.

[0105] Control the lowering speed of casing string 2 (referring to the speed at which the casing string is lowered into the well after it is connected). Before the tool enters the well, calculate at 0.2 m / s. After the staged clamp enters the well, execute at 0.15 m / s. If there is serious leakage in the well, lower it into the well at a speed of 0.1 m / s. At the same time, the lowering process should be smooth and uniform. Sudden lowering and sudden braking are strictly prohibited.

[0106] S02: When the ball is thrown and sits down, the pressure is transmitted to the hydraulic cylinder through the pressure transmission hole on the main body of the suspension device 3. The pressure pushes the piston upward, shears the hydraulic cylinder shear pin, and then pushes the push rod support sleeve, which in turn drives the slip upward. The slip expands along the conical surface and weds into the annular gap between the cone of the suspension device 3 and the upper sleeve column 2.

[0107] As the drill string is lowered, the weight of the tailpipe is supported on the upper casing string 2. Continue pressurizing to clear the ball seat and establish normal circulation;

[0108] S03: Inject cement into the interior of the first cement injection space 5. The injected cement is quantitatively replaced according to the annular volume of the target layer, and then solidifies.

[0109] S04: Deploy the opening plug. After the gravity plug sits in the opening plug seat by free fall, start the pump to pressurize and pressurize to the first pressure. In some embodiments, the first pressure is set to 5-7 MPa. Open the pressure transmission hole of the packer and expand the packer to seal it.

[0110] When the pressure continues to rise to the second pressure, which in some embodiments is set at 16 MPa, the packer is secured.

[0111] Continue to increase the pressure to the third pressure, which in some embodiments is set to 18 MPa, open the flow hole of the cement injector, open the circulation hole to establish circulation, and expand the packer;

[0112] Separate the first cement injection space 5 and the second cement injection space 6, inject cement into the interior of the second cement injection space 6, press the drill pipe 1 plug to replace it, and combine the drill pipe 1 plug with the hollow plug of the hanger 3 to establish circulation and prepare for the second cementing.

[0113] S05: When the upper rubber plug inside casing string 2 is pushed to the back pressure valve by drilling fluid, causing a collision, the cement injector is shut off;

[0114] S06: Raise drill pipe 12m, press down 100KN, seal seat and top seal;

[0115] Raise the drill pipe 15-10m, move it up and down, and begin high-volume well flushing;

[0116] Pull out 100m of drill pipe, then wait for the water to settle.

[0117] Lower the 6-inch drill bit, drill to the cement float shoe 21 position, continue drilling, drill out the lower wellbore, and pull out the drill string.

[0118] The implementation principle of this application embodiment is as follows: In order to meet the water testing requirements of the first reservoir, the "slip-type hanger + integrated packer cement injector + detachable ball seat" process is adopted to achieve staged cementing.

[0119] Main well completion construction procedures: three-stage drilling, preparation before well completion construction, running the three-stage casing string, dropping the ball, setting the hanger, reverse threading, and detaching, first-stage cementing, waiting for it to set, dropping the gravity plug, expansion sealing, opening the stage hoop circulation hole, second-stage cementing, pressing and closing the cementing device, circulating well washing, drilling plug, and fourth-stage drilling.

[0120] Hanger selection: A slip-type hanger is used for suspended well completion. This hanger enables both suspension and cementing operations; it features a top sealing structure to improve the sealing effect of the cementing annulus.

[0121] Cement injector selection: Integrated sealing cement injector (the sealing cylinder adopts a compression type).

[0122] The packer setting and the cementing nozzle opening require the insertion of an opening plug (gravity plug) to open, effectively avoiding the problem of premature packer setting during tubing string insertion, well circulation flushing, and primary cementing operations.

[0123] The first-stage cement injection method uses a fixed amount of cement to replace the target layer, which is an annular volume. The cement slurry is not injected into the first reservoir, thus achieving zero pollution of the Ordovician system by the cement slurry.

[0124] Secondary cementing preparation (packer setting and opening of cement injector flow orifice). ① Insert the opening plug (gravity plug); ② Pressurize to 5-7 MPa, the packer pressure transmission orifice opens, and packer setting begins; ③ Continue to increase the pressure to 16 MPa to firmly set the packer; ④ Continue to increase the pressure to 18 MPa and open the cement injector flow orifice; ⑤ Establish circulation and prepare for secondary cementing.

[0125] Secondary cementing. ① Pump in secondary cement; ② Press the drill pipe plug to displace it; ③ Combine the drill pipe plug with the hollow plug of the hanger, shear the pin, and continue displacing; ④ Press down and close the cement injector; ⑤ Raise the drill pipe about 2m, press down 100kN, and seal the top and bottom; ⑥ Raise the drill pipe 5-10 meters, move it up and down, and flush the well with a large flow rate; ⑦ Pull out about 100 meters of drill pipe and wait for it to set.

[0126] Drill plug, drill in four directions.

[0127] Taking a specific example well as an example, the strata from top to bottom are Quaternary, Upper Tertiary, Lower Tertiary, Ordovician (first reservoir 7), Cambrian (separator 8), and Jixian Wumishan Formation (second reservoir 9). The main reservoirs are located in the Ordovician (first reservoir 7) and Jixian Wumishan Formation (second reservoir 9).

[0128] The well adopts a four-section wellbore structure. The second section is run with casing down to the top of the Ordovician (first reservoir 7); the third section is drilled together with the Cambrian (separator layer 8) in the Ordovician (first reservoir 7) section, and the third section is drilled to the top of the Wumishan Formation (second reservoir 9). The casing of the third section is suspended and the overlap section with the casing of the second section is no less than 300m; the fourth section is dedicated to drilling the Wumishan Formation (second reservoir 9) and is completed with screen pipe (screen pipe completion means that the screen pipe is run after drilling is completed and cementing is not required).

[0129] The purpose of this construction plan is to meet the requirements of simultaneous mining of both the Ordovician (first reservoir 7) and the Wumishan Formation of the Jixian System (second reservoir 9), while effectively protecting the Ordovician strata (first reservoir 7) from contamination by cement slurry.

[0130] The well was drilled to the top of the Wumishan Formation (Second Reservoir 9) in its third stage, with the packer positioned approximately 20 meters above the cement float 21. The Ordovician (First Reservoir 7) is the main reservoir, but the formation has poor pressure bearing capacity and is prone to leakage. To protect the reservoir from contamination as much as possible, the first-stage cementing was carried out to the top of the Cambrian (Separator 8), and then the packer was used to seal the two cementing spaces. A second-stage cementing was then performed. This method allows for the simultaneous production of the Ordovician (First Reservoir 7) and the Wumishan Formation (Second Reservoir 9) while effectively protecting the Ordovician formation (First Reservoir 7).

[0131] In summary, the casing string 2 extends through into the interior of the first reservoir 7 and the separator layer 8, and a sealing component is installed at the junction of the first reservoir 7 and the upper formation. The sealing component seals the junction between the casing string and the outer annulus space, forming an independent space above the sealing component and an independent space below the sealing component. The independent space above the sealing component and the independent space below the sealing component are relatively unconnected, so that independent operations can be carried out in the two independent spaces, reducing the mutual interference caused by the operations in the two independent spaces.

[0132] Thus, by performing the first cement injection into the independent space located below the plugging component, the cement is injected into the location of the partition layer 8 inside the first cement injection space 5 through a quantitative displacement method. The first cement injection will not affect the first reservoir 7 above the plugging component. Subsequently, a second cement injection is performed into the independent space located above the plugging component and the formation located above the first reservoir 7 to reduce the impact on the first reservoir 7.

[0133] By injecting cement into two relatively independent spaces, the cement slurry can be prevented from contaminating the first reservoir 7, thus meeting the needs of both the first reservoir 7 and the second reservoir 9, while also meeting the requirements for safe drilling in the later stages. This process can achieve selective formation sealing, and the cementing quality can be guaranteed.

[0134] In this invention, the term "multiple" refers to at least two or more, unless otherwise explicitly defined. The terms "install," "connect," "link," and "fix" should be interpreted broadly. For example, "connect" can be a fixed connection, a detachable connection, or an integral connection; "link" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0135] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

Claims

1. A staged cementing device suitable for dual-layer simultaneous production wells with reservoir protection function, characterized in that: It includes a casing string (2) that penetrates the first reservoir (7) and the separator (8). The casing string (2) is fixedly connected to a cement injector located above the first reservoir (7). A sealing assembly is provided between the cement injector and the first reservoir (7) to separate the cement injector from the first reservoir (7).

2. The staged cementing device for dual-layer co-production wells with reservoir protection function as described in claim 1, characterized in that: The sealing assembly includes a packer, which is fixedly connected to the casing string (2). After the packer is seated, it divides and seals the annular space. The packer divides the annular space into a first cementing space (5) located below the packer and a second cementing space (6) located above the packer.

3. The staged cementing device for dual-layer co-production wells with reservoir protection function as described in claim 2, characterized in that: The cement injector and the packer are an integrated packer cement injector (4). The integrated packer cement injector (4) is sleeved on the outside of the casing column (2) and is fixedly connected to the casing column (2).

4. The staged cementing device for dual-layer co-production wells with reservoir protection function as described in claim 3, characterized in that: The integrated sealing cement injector (4) includes an integrated body. A sealing part (42) is provided at the bottom of the integrated body. After the sealing part (42) expands, it seals the annular space. A cement injection part (41) is provided above the sealing part (42). An opening plug seat is provided inside the cement injection part (41). A bypass valve is provided on one side of the opening plug seat. The bypass valve connects the inside of the cement injection part (41) with the external annular space. When the opening plug is inserted, the opening plug seat supports the opening plug.

5. The staged cementing device for dual-layer co-production wells with reservoir protection function as described in claim 1, characterized in that: The top end of the casing column (2) is provided with a hanger (3), which is sleeved on the outside of the casing column (2) and is fixedly connected to the casing column (2).

6. The staged cementing device for dual-layer co-production wells with reservoir protection function as described in claim 4, characterized in that: The suspension device (3) is a slip-type suspension device (3).

7. The staged cementing device for dual-layer co-production wells with reservoir protection function as described in claim 6, characterized in that: The outside of the hanger (3) is provided with a top sealing structure, which seals the annular space after expansion.

8. The staged cementing device for dual-layer co-production wells with reservoir protection function as described in claim 1, characterized in that: A cement-type float shoe (21) is coaxially provided at the bottom end of the casing column (2), and the cement-type float shoe (21) is fixedly connected to the casing column (2).

9. The staged cementing device for dual-layer co-production wells with reservoir protection function as described in claim 8, characterized in that: The casing column (2) is located above the cement floating shoe (21) and is provided with a cement floating hoop (22), which is fixedly connected to the casing column (2).

10. The staged cementing device for dual-layer co-production wells with reservoir protection function as described in claim 9, characterized in that: The casing column (2) is located above the cement-type floating hoop (22) and is equipped with a movable ball seat (23).

11. A staged cementing method suitable for wells with dual-layer co-production and reservoir protection functions, characterized in that, The method, applied to the staged cementing apparatus described in any one of claims 1-10, which is suitable for dual-layer co-production wells and also has reservoir protection functions, comprises: S01: Lower the casing string (2), and confirm that the hanger (3) and cement injector are in place; S02: Throw the ball, hang it on the suspension device (3), and then remove it after inverting it; S03: Inject cement into the interior of the first cement space (5) and allow it to set; S04: Deploy the opening plug to expand the packer, separate the first cement space (5) and the second cement space (6), and inject cement into the interior of the second cement space (6); S05: When the upper rubber plug inside the casing string (2) is pushed to the back pressure valve by the drilling fluid, a collision pressure is generated, and the cement injector is shut off; S06: Circulating well washing, after the drill bit has drilled out of the lower part of the wellbore, the drill bit is pulled out.

12. The staged cementing method for dual-layer co-production wells with reservoir protection function according to claim 11, characterized in that: In S03, cement is injected into the interior of the first cement space (5), and the cement is quantitatively replaced according to the volume of the annulus of the target layer.

13. The staged cementing method for dual-layer co-production wells with reservoir protection function according to claim 11, characterized in that: In S04, after the opening plug is inserted, the first pressure is applied to open the pressure transmission hole of the packer and seal the packer; the second pressure is applied to settle the packer, and the third pressure is applied to open the flow hole of the cement injector and establish circulation.

14. The staged cementing method for dual-layer co-production wells with reservoir protection function according to claim 11, characterized in that: In S05, after closing the cement injector, the drill pipe (1) is raised by 2m, and 100KN is applied downward to seal the top and bottom structures. The drill pipe (1) is raised by 5-10m, and the pipe moves up and down to perform high-volume well washing. The drill pipe (1) is pulled out by 100m to allow the cement to set.

15. The staged cementing method for dual-layer co-production wells with reservoir protection function according to claim 13, characterized in that: The first pressure < the second pressure < the third pressure.

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