A cementing control system and method for narrow density window formations

Abstract

The present invention provides a narrow density window formation cementing control system, which includes: an automatic controller that generates a pressure adjustment instruction when overflow or leakage occurs during the cementing process; a throttle manifold connected to the automatic controller and executes the pressure adjustment instruction to ensure that the bottomhole pressure during the cementing process is within the narrow density window formation pressure range; a booster pump connected to the throttle manifold through a three-way connector and applies back pressure according to the wellhead back pressure value during the waiting process to ensure that the bottomhole pressure during the waiting process is within the narrow density window formation pressure range. The present invention applies a closed-loop concept to the entire cementing process, and through targeted design and precise control of parameters such as density, displacement, and back pressure in the narrow density window formation, effectively ensures that the bottomhole pressure during the cementing and waiting process is within the narrow density window formation pressure range, thereby achieving safe and quality cementing in the narrow density window formation. The present invention has the characteristics of simple operation and strong practicality, and is suitable for on-site promotion and application.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field cementing engineering, in particular to a narrow density window formation cementing control system and method. Background Art

[0002] With the rapid growth of the national economy, my country's demand for oil is increasing day by day. Oil extraction is gradually shifting to deeper and more complex blocks. The geological conditions of oil and gas reservoirs are also becoming more and more complex. The narrow density window problem in the drilling and completion process remains a global problem. Due to the narrow pressure window of the drilled formation and the uncertainty of the formation, various complex situations such as blowouts, leaks, collapses, and sticking are prone to occur during the drilling process. If not handled properly, it is very easy to cause safety accidents such as blowouts. The narrow density window encountered in drilling also greatly affects the design and construction of cementing. Since the cementing process has a long open hole section and multiple pressure systems, and cementing is a hidden project with a short duration and high cost, and it requires success in one go, once a problem occurs, it is generally difficult to remedy. Therefore, the design of cementing fluids for narrow density window formations and the control of the construction process are extremely important during the cementing process.

[0003] Conventional cementing methods used in existing technologies for formations with narrow density windows face challenges in achieving both stable pressure and leak prevention during the cementing process. Currently, the most common method for drilling in formations with narrow density windows is managed pressure drilling (MPD). This method utilizes a closed-loop system to precisely control the annular pressure profile, ensuring that bottomhole pressure remains within the safe density window. While the drilling process can be controlled, existing technologies lack a robust solution to the narrow density window problem during cementing.

[0004] In view of the problems of the prior art, the present invention provides a narrow density window formation cementing control system and method. Summary of the Invention

[0005] In order to solve the cementing operation problem of narrow density window formation in the above-mentioned prior art, the present invention provides a narrow density window formation cementing control system, characterized in that the system comprises:

[0006] An automatic controller for generating pressure regulation instructions when overflow or loss occurs during cementing;

[0007] a choke manifold connected to the automatic controller and configured to execute the pressure regulation instruction to ensure that the bottom hole pressure during cementing is within a narrow density window formation pressure range;

[0008] A booster pump is connected to the throttle manifold via a three-way connector and is used to apply back pressure according to the wellhead back pressure value during the waiting solidification process to ensure that the bottom hole pressure is within the narrow density window formation pressure range during the waiting solidification process.

[0009] According to one embodiment of the present invention, the system comprises:

[0010] a vibrating screen connected to the throttling manifold and used for filtering the solid phase in the mud;

[0011] A circulation tank connected to the vibrating screen for storing drilling fluid to meet circulation needs;

[0012] A drilling pump connected to the circulation tank is used to provide the necessary energy for the circulation of the drilling fluid, and to deliver the drilling fluid into the drill tool at a certain pressure and flow rate to complete the entire circulation process;

[0013] A cement head, which is connected to the drilling pump and is a special tool for injecting cement slurry and releasing the rubber plug. It is installed on the top of the casing during cementing;

[0014] A cementing pump connected to the cement head for providing power for cementing operations;

[0015] a water tank connected to the cementing pump;

[0016] A blowout preventer, connected to the cement head, is a well control device used to prevent blowouts and ensure construction safety;

[0017] A casing head, which is connected to the blowout preventer through a four-way connector and is used to support the gravity of the technical casing and the oil layer casing;

[0018] The casing is connected to the casing head and provides a passage for fluid to flow from the producing layer to the surface.

[0019] According to one embodiment of the present invention, when a radish head is installed at the cementing site, the annulus is sealed by the radish head, and the three ends of the three-way connector are respectively connected to the throttling manifold, the pressure-boosting pump, and the casing head.

[0020] According to one embodiment of the present invention, when a rotary control head is not installed at the cementing site, a rotary control head is installed above the blowout preventer to isolate the annulus.

[0021] According to one embodiment of the present invention, the system comprises:

[0022] a first flat valve connected between the pressure-compensating pump and the three-way connector;

[0023] A second flat valve is connected between the throttle manifold and the three-way connector.

[0024] According to one embodiment of the present invention, the system comprises:

[0025] The invention discloses a cement slurry density determining device, which is used to determine the cement slurry density in the cementing process according to the actual drilling pressure window in the drilling process.

[0026] According to one embodiment of the present invention, the system comprises:

[0027] The waiting-for-setting process control device is used to calculate the wellhead back pressure value during the waiting-for-setting process and generate a pressure compensation instruction according to the wellhead back pressure value to control the pressure compensation pump to apply back pressure.

[0028] According to another aspect of the present invention, there is provided a method for controlling cementing in a narrow density window formation, which is performed by a system as described above, and the method comprises:

[0029] When overflow occurs during cementing, the automatic controller generates a pressure adjustment instruction;

[0030] Executing the pressure regulation command through the choke manifold to ensure that the bottom hole pressure is within the narrow density window formation pressure range during cementing;

[0031] When leakage occurs during cementing, the automatic controller generates a pressure adjustment command to reduce the displacement or increase the throttle valve opening so that the wellhead back pressure gradually drops to 0. If the leakage is greater than the critical value, a wellhead back-squeeze cement operation is required after the cementing is completed.

[0032] During the waiting-for-setting process, the booster pump applies back pressure according to the wellhead back pressure value to ensure that the bottom hole pressure is within the narrow density window formation pressure range during the waiting-for-setting process.

[0033] According to one embodiment of the present invention, the method comprises:

[0034] The wellhead back pressure value during the waiting-for-setting process is calculated, and a pressure compensation instruction is generated according to the wellhead back pressure value to control the pressure compensation pump to apply back pressure.

[0035] According to another aspect of the present invention, a storage medium is provided, which contains a series of instructions for executing the method steps described above.

[0036] Compared with conventional cementing, the narrow density window formation cementing control system and method provided by the present invention applies the closed-loop concept to the entire cementing process. Through the targeted design and precise control of parameters such as density, displacement, and back pressure in the narrow density window formation, it can effectively ensure that the bottom hole pressure is within the narrow density window formation pressure range during cementing and waiting for setting, thereby achieving safe and high-quality cementing in the narrow density window formation. It has the characteristics of simple operation and strong practicality, and is suitable for on-site promotion and application.

[0037] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0039] Figure 1 Shows a structural block diagram of a narrow density window formation cementing control system according to one embodiment of the present invention;

[0040] Figure 2 A structural block diagram showing a case where a radish head is installed at a cementing site according to an embodiment of the present invention is shown; and

[0041] Figure 3 A structural block diagram is shown when no radish head is installed at the cementing site according to an embodiment of the present invention.

[0042] The markings in the accompanying drawings are as follows: 1. Water tank; 2. Cementing pump; 3. Drilling pump; 4. Blowout preventer; 5. Four-way connector; 6. Casing head; 7. First flat valve; 8. Second flat valve; 9. Booster pump; 10. Choke manifold; 11. Automatic controller; 12. Vibrating screen; 13. Circulation tank; 14. Cement head; 15. Drill pipe (casing); 16. Formation; 17. Annulus; 18. Rotating control head; 19. Three-way connector. DETAILED DESCRIPTION

[0043] To make the objectives, technical solutions and advantages of the present invention more clear, embodiments of the present invention are described in further detail below with reference to the accompanying drawings.

[0044] Figure 1 A structural block diagram of a narrow density window formation cementing control system according to an embodiment of the present invention is shown.

[0045] like Figure 1 As shown, a narrow density window formation cementing control system 100 includes an automatic controller 11, a choke manifold 10, and a booster pump 9.

[0046] Specifically, the automatic controller 11 is used to generate a pressure adjustment instruction when overflow or leakage occurs during the cementing process; the throttle manifold 10 is connected to the automatic controller 11 and is used to execute the pressure adjustment instruction to ensure that the bottom hole pressure is within the narrow density window formation pressure range during the cementing process; the pressure boosting pump 9 is connected to the throttle manifold 10 through a three-way connector 19 and is used to apply back pressure according to the wellhead back pressure value during the waiting process to ensure that the bottom hole pressure is within the narrow density window formation pressure range during the waiting process.

[0047] In one embodiment, a narrow density window formation cementing control system 100 includes a cement slurry density determination device for determining the cement slurry density during cementing and cementing according to an actual drilling pressure window during drilling.

[0048] Specifically, the cement slurry density determination device needs to collect the formation pore pressure p through geological logging data and adjacent well data. p , collapse pressure p b , formation fracture pressure p f , calculate the corresponding equivalent density respectively, that is, the equivalent density of formation pore pressure is ρ p , the collapse pressure equivalent density is ρ b , the equivalent density of the formation fracture pressure is ρ f .

[0049] The cement slurry density determination device needs to calculate the friction pressure drop p during the cementing process. L :

[0050]

[0051] Among them, ρ 钻 is the drilling fluid density, g / cm 3 ; f is the friction coefficient; v is the annulus return velocity, m / s; H is the well depth, m; D is the annulus outer diameter, m; d is the annulus inner diameter, m;

[0052] The cement slurry density determination device needs to determine the cement slurry density based on the actual drilling pressure window during the drilling process. Specifically:

[0053] If p f -Max(p p ,p b )>p L +Δp, the cement slurry density is designed according to conventional cementing design.

[0054] If p f -Max(p p ,p b )<p L+Δp, it is impossible to add a certain safety pressure coefficient Δp according to the conventional design. Δp is calculated from the safety additional value of drilling fluid density (0.05-0.1g / cm3 for oil wells and 0.07-0.15g / cm3 for gas wells). Δp=0.00981gh. Since there are many kinds of fluids in the annulus during cementing: flushing fluid, spacer fluid, cement slurry, plugging fluid, etc., the static equivalent density of the annulus during cementing is ρ ESD Pick:

[0055] ρ ESD =Max(ρ p ,ρ b )

[0056] The calculation of cement slurry density meets the following requirements:

[0057] ρ ESD gh=ρ 钻 gh1+ρ 冲 gh2+ρ 隔 gh3+ρ 领 gh4+ρ 尾 gh5

[0058] Among them, ρ 钻 is the drilling fluid density, g / cm 3 ρ 冲 is the density of the flushing fluid, g / cm 3 ρ 隔 is the density of the isolation fluid, g / cm 3 ρ 领 is the density of cement slurry, g / cm 3 ρ 尾 is the density of cement slurry tailings, g / cm 3 ρ ESD is the static equivalent density of the annulus during cementing, g / cm 3 ; h is the well depth, m; h1 is the length of the annular drilling fluid after cementing is completed, m; h2 is the length of the annular flushing fluid after cementing is completed, m; h3 is the length of the annular spacer fluid after cementing is completed, m; h4 is the length of the annular cement slurry lead after cementing is completed, m; h5 is the length of the annular cement slurry tail after cementing is completed, m.

[0059] Furthermore, the density and length requirements of the flushing and isolation fluids involved must meet the following specifications:

[0060] (1) The density of the flushing fluid is generally 1.0-1.03 g / cm 3 ;

[0061] (2) The density of the isolation fluid is generally less than the density of the cement slurry, 0.06-0.12 g / cm 3 ;

[0062] (3) The length of the flushing fluid and the spacer fluid in the annulus. When the flushing fluid or the spacer fluid is used alone, the length of the replacement in the annulus shall not exceed 250m. When used together, the design dosage shall be based on a 2:1 ratio, and the total length shall not exceed 300m. When the well depth exceeds 3000m, the total dosage of the spacer fluid and the flushing fluid shall be increased by 0.2-0.3m for every additional 300m. 3 ;

[0063] Furthermore, the density and length requirements of the lead and tail slurries of cement slurry must meet the following requirements:

[0064] (1) Return the slurry to the designed elevation;

[0065] (2) The tailings slurry returns to the main sealing well section more than 50-150m.

[0066] (3) The density of the lead pulp is recommended to be 0.01-0.02g / cm2 lower than that of the tail pulp. 3 .

[0067] According to the cement slurry density calculated by the cement slurry density determination device, Figure 1 or Figure 2 or Figure 3 The system shown in the figure is circulated. If leakage occurs during cementing, multiple grouting methods or wellhead reinjection should be used to reduce the annular space pressure and reduce the leakage. If overflow occurs during cementing, the pressure of the flow manifold 10 should be adjusted by the automatic controller 11. The adjustment of the throttle manifold 10 should meet the requirement of constant vertical pressure value during low pump speed test. The back pressure value at this time is the required back pressure value, which reduces the impact of overflow on cementing quality.

[0068] In one embodiment, a narrow density window formation cementing control system 100 includes a leakage control device, which is used to generate a pressure adjustment instruction through an automatic controller when leakage occurs during the cementing process, reduce the displacement or increase the throttle valve opening, so that the wellhead back pressure gradually decreases to 0, thereby reducing the annular space pressure and reducing the leakage; if the leakage is greater than a critical value, a wellhead back-squeeze cement operation is required after the cementing is completed.

[0069] The overflow control device calculates the bottom hole pressure p during cementing according to the density of various fluids in the selected annulus. d :

[0070] p d =ρ 钻 gh 1i +ρ 冲 gh 2i +ρ 隔 gh 3i +ρ 领 gh 4i +ρ 尾 gh 5i +∑pfi +p a

[0071]

[0072] Among them, h 1i is the length of drilling fluid in the annulus during cementing, m; h 2i is the length of the annular flushing fluid during cementing, m; h 3i is the length of the annular spacer fluid during cementing, m; h 4i h is the annular cement slurry collar length during cementing, m; 5i is the length of the annular cement slurry tail during cementing, m; p d is the bottom hole pressure during cementing, MPa; p fi is the friction pressure drop of each slurry column during cementing, MPa; v is the annular flow velocity, m / s; D is the annular outer diameter, m; d is the annular inner diameter, m; p a is the wellhead back pressure, MPa.

[0073] During cementing, the casing pressure should be kept as low as possible to zero, and the operation should be carried out without pressure. The bottomhole pressure should also meet the formation pressure range within the narrow density window, as follows:

[0074] Max(p p ,p b )<p d <p f

[0075] If the bottom hole pressure is not within the narrow density window formation pressure range, increase or decrease the cement slurry density or adjust the displacement according to the actual situation until it meets the requirements.

[0076] During the pump shutdown process, the bottom hole pressure is composed of the hydrostatic column pressure and the wellhead back pressure:

[0077] p' d =ρ 钻 gh 1i +ρ 冲 gh 2i +ρ 隔 gh 3i +ρ 领 gh 4i +ρ 尾 gh 5i +p a

[0078] As the frictional resistance disappears, a certain amount of back pressure needs to be added to keep the bottom hole pressure constant. At this time, p a =∑p fi .

[0079] In one embodiment, a narrow density window formation cementing control system 100 includes a waiting-for-setting process control device, which is used to calculate the wellhead backpressure value during the waiting-for-setting process and generate a pressure boosting instruction based on the wellhead backpressure value to control the pressure boosting pump to apply backpressure.

[0080] During the waiting process, the annular pressure will decrease due to the hydration of cement slurry, and a well kick may occur. Therefore, it is necessary to apply wellhead back pressure during the waiting process. The wellhead back pressure value p a Calculated by the following formula:

[0081]

[0082] Where τ is the static gel strength, Pa; z is the depth of cement slurry, m.

[0083] Specifically, the waiting and setting process control device calculates the back pressure value according to the above formula, and applies back pressure according to the calculated back pressure value through the pressure compensation pump 9.

[0084] This invention, based on the fundamental principles of managed pressure drilling, applies a closed-loop approach to the cementing process. By designing cementing fluid parameters such as density and displacement, and using an automatic choke manifold to adjust the throttle valve opening, bottomhole pressure is controlled within the formation pore-fracture pressure window (the narrow density window formation pressure range), achieving safe and high-quality cementing. This simple operation and high practicality make it suitable for cementing operations in formations with a narrow density window.

[0085] Figure 2 A structural block diagram is shown when a radish head is installed at a cementing site according to an embodiment of the present invention.

[0086] like Figure 2 As shown, when a radish head is installed at the cementing site, the radish head seals the annulus, and the three ends of the three-way connector 19 are respectively connected to the choke manifold 10, the pressure pump 9, and the casing head 6. The first flat valve 7 is connected between the pressure pump 9 and the three-way connector 19, and the second flat valve 8 is connected between the choke manifold 10 and the three-way connector 19.

[0087] Figure 2The system connection process shown is as follows: Connect the cementing pump 2, drilling pump 3 and throttle manifold 10; use a high-pressure hose to connect the throttle manifold 10 to the casing head 6, and open the second flat valve 8. Connect the pressure-boosting pump 9 to the throttle manifold 10; connect the pressure-boosting pump 9 to the throttle manifold 10 through a high-pressure hose, and close the first flat valve 7. Determine the equivalent density ECD of the narrow density window annulus and calculate the required density of the cementing cement slurry. After the cementing is completed, open the first flat valve 7, close the second flat valve 8, and the throttle manifold 10 can be cleaned or removed. Among them, ECD, or equivalent circulating density, refers to the density converted from the sum of the static liquid column pressure and the circulating friction during the circulation process, that is, the bottomhole pressure during the circulation process is converted into density according to the well depth, ECD = pd / (gh).

[0088] Before cementing, first disconnect the well killing manifold from the well crew and establish Figure 2 If a radish head is installed on site, the radish head can seal the annulus and form a closed loop system. Figure 2 The first circulation process shown is as follows: cementing pump 2 and water tank 1 are connected to cement head 14. Cementing fluid (flushing fluid, spacer fluid, cement slurry, plugging fluid, etc.) is pumped into drill pipe (casing) 15 via cementing pump 2. A conventional drilling pump 3 is connected to circulation tank 13 and then to cement head 14. Displacement fluid is pumped into drill pipe (casing) 15 by drilling pump 3. The fluid in annulus 17 enters choke manifold 10 through casing head 6 and then returns to circulation tank 13 via vibrating screen 12. To reduce the impact of cement slurry weight loss during the waiting period, a feed pump 9 is installed before choke manifold 10 to replenish annulus pressure during the waiting period.

[0089] like Figure 2 As shown, after the casing head 6 is connected to the four-way connector 5, it is connected to the automatic controller 11. The back pressure is adjusted by adjusting the opening of the choke manifold 10, so that the bottom hole pressure is controlled within the narrow density window formation pressure range; a three-way connector 19 is connected between the choke manifold 10 and the casing head 6, and the supply pump 9 is connected to the three-way connector 19 to replenish the pressure loss caused by the weight loss of cement slurry during the cementing and setting process.

[0090] Figure 3 A structural block diagram is shown when no radish head is installed at the cementing site according to an embodiment of the present invention.

[0091] like Figure 3 As shown, when a rotary control head is not installed at the cementing site, a rotary control head 18 is installed above the blowout preventer 14 to isolate the annulus. The first flat plate valve 7 is connected between the pressure pump 9 and the three-way connector 19, and the second flat plate valve 8 is connected between the choke manifold 10 and the three-way connector 19.

[0092] Figure 3The system connection process shown is as follows: Connect the cementing pump 2, the drilling pump 3 and the throttle manifold 10; use a high-pressure hose to connect the throttle manifold 10 to the rotary control head 18, and open the second flat valve 8. Connect the pressure-boosting pump 9 to the throttle manifold 10; connect the pressure-boosting pump 9 to the throttle manifold 10 through a high-pressure hose, and close the first flat valve 7. Determine the narrow density window annulus equivalent density ECD and calculate the required density of the cementing cement slurry. After the cementing is completed, open the first flat valve 7, close the second flat valve 8, and the throttle manifold 10 can be cleaned or removed. Among them, ECD, that is, equivalent circulating density, refers to the density converted from the sum of the static liquid column pressure and the circulating friction during the circulation process, that is: the bottomhole pressure during the circulation process is converted into density according to the well depth, ECD = pd / (gh).

[0093] Before cementing, first disconnect the well killing manifold from the well crew and establish Figure 3 If there is no rotary head on site, a rotating control head (RCD) 18 can be installed above the blowout preventer 4 to isolate the annulus and form a closed loop system. Therefore, the second circulation process ( Figure 3 ) is as follows: A cementing pump 2 and a water tank 1 are connected to a cement head 14. The cementing fluid (flushing fluid, spacer fluid, cement slurry, plugging fluid, etc.) is pumped into the drill pipe (casing) 15 via the cementing pump 2. A conventional drilling pump 3 is connected to a circulation tank 13 and then to the cement head 14. Displacement fluid is pumped into the drill pipe (casing) 15 by the drilling pump 3. The fluid in the annulus 17 enters the choke manifold 10 via a rotary control head (RCD) 18 and then returns to the circulation tank 13 via a vibrating screen 12. To reduce the effects of cement slurry weight loss during the waiting period, a make-up pump 9 is installed before the choke manifold 10 to replenish the annulus pressure during the waiting period.

[0094] like Figure 3 As shown, a rotary control head (RCD) 18 is installed above the wellhead blowout preventer group 14 to close the annulus and form a closed-loop system; after the choke manifold 10 is connected to the rotary control head (RCD) 18, it is connected to the automatic controller 11, and the back pressure is adjusted by adjusting the opening of the choke manifold 10, so as to control the bottom hole pressure within the narrow density window formation pressure range; a three-way connector 19 is connected between the choke manifold 10 and the rotary control head (RCD) 18, and a supply pump 9 is connected to the three-way connector 19 to replenish the pressure loss caused by the weight loss of cement slurry during the cementing process.

[0095] The present invention discloses a narrow density window formation cementing control system. The system includes two parts, "soft" and "hard", and through the combination of "soft" and "hard", the bottom hole pressure is controlled within the narrow density window formation pressure range. The optimization design of the relevant parameters such as the density, displacement, and back pressure of the narrow density window cementing fluid ensures that back pressure is applied as little as possible during the grouting process to reduce the possibility of leakage; during the pump stop process, back pressure is applied according to the design value to maintain a constant bottom hole pressure; during the waiting setting process, back pressure is applied according to the pressure change law during the cement slurry weight loss process to compensate for the pressure loss during the weight loss process; in the event of sudden leakage, multiple grouting methods or wellhead reinjection are adopted; in the event of sudden overflow, back pressure is applied through the automatic throttling manifold to reduce the impact of overflow on cementing quality.

[0096] The present invention controls the bottom hole pressure within a safe density window during cementing processes such as cementing and waiting for setting through detailed "soft" design of cementing fluid density, displacement, back pressure, etc., combined with the advantage of a hardware system (automatic throttle manifold) that can adjust back pressure in real time as needed. The invention has the characteristics of simple operation, strong practicality, and easy promotion, and is suitable for cementing construction in formations with narrow density windows.

[0097] The present invention also provides a narrow density window formation cementing control method, by Figure 1 or as Figure 2 or as Figure 3 The system shown performs, specifically:

[0098] S1. When overflow occurs during cementing, a pressure adjustment command is generated by the automatic controller.

[0099] S2. Execute pressure regulation instructions through the choke manifold to ensure that the bottom hole pressure is within the narrow density window formation pressure range during cementing.

[0100] S3. When leakage occurs during cementing, the automatic controller generates a pressure adjustment command to reduce the displacement or increase the throttle valve opening so that the wellhead back pressure gradually drops to 0; if the leakage is greater than the critical value, a wellhead back-squeezing cement operation is required after the cementing is completed.

[0101] S4. During the waiting-for-setting process, back pressure is applied by a booster pump according to the wellhead back pressure value to ensure that the bottom hole pressure is within the narrow density window formation pressure range during the waiting-for-setting process.

[0102] In one embodiment, the wellhead back pressure value during the waiting-for-setting process is calculated, and a pressure compensation instruction is generated according to the wellhead back pressure value to control the pressure compensation pump to apply back pressure.

[0103] The narrow density window formation cementing control system and method provided by the present invention may also be used in conjunction with a computer-readable storage medium storing a computer program, which is executed to implement the narrow density window formation cementing control method. The computer program is capable of executing computer instructions, which include computer program code. The computer program code may be in source code form, object code form, executable file, or some intermediate form.

[0104] Computer-readable storage media may include: any entity or device that can carry computer program code, recording media, USB flash drives, mobile hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc.

[0105] It should be noted that the content contained in computer-readable storage media can be appropriately increased or decreased according to the requirements of legislation and patent practices in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practices, computer-readable storage media do not include electrical carrier signals and telecommunications signals.

[0106] In summary, compared with conventional cementing, the narrow density window formation cementing control system and method provided by the present invention applies the closed-loop concept to the entire cementing process. Through the targeted design and precise control of parameters such as density, displacement, and back pressure in the narrow density window formation, it can effectively ensure that the bottom hole pressure during cementing and waiting for setting is within the narrow density window formation pressure range, realizing safe and high-quality cementing in the narrow density window formation. It has the characteristics of simple operation and strong practicality, and is suitable for on-site promotion and application.

[0107] It should be understood that the embodiments disclosed herein are not limited to the specific structures, processing steps, or materials disclosed herein, but should extend to equivalent substitutions of these features understood by those skilled in the relevant art. It should also be understood that the terminology used herein is for the purpose of describing specific embodiments only and is not intended to be limiting.

[0108] In the description of the present invention, unless otherwise specified, "plurality" means two or more; terms such as "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," and "tail" indicate positions or relationships based on those shown in the accompanying drawings. These terms are intended solely to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting the present invention. Furthermore, terms such as "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0109] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integral connection; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0110] References in this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Therefore, appearances of the phrases "one embodiment" or "an embodiment" in various places throughout this specification do not necessarily refer to the same embodiment.

[0111] The embodiments of the present invention are presented for purposes of illustration and description and are not intended to be exhaustive or to limit the invention to the disclosed forms. Many modifications and variations will be apparent to those skilled in the art. The embodiments are chosen and described in order to better illustrate the principles of the invention and its practical application and to enable those skilled in the art to understand the invention and design various embodiments with various modifications as suited for specific applications.

[0112] Although the embodiments disclosed herein are as described above, the contents described herein are merely embodiments for facilitating understanding of the present invention and are not intended to limit the present invention. Any person skilled in the art of the present invention may make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed herein. However, the scope of patent protection of the present invention shall still be subject to the scope defined by the appended claims.

Claims

1. A narrow density window formation cementing control system, characterized in that: The system comprises: An automatic controller for generating pressure regulation instructions when overflow or loss occurs during cementing; a choke manifold connected to the automatic controller and configured to execute the pressure regulation instruction to ensure that the bottom hole pressure during cementing is within a narrow density window formation pressure range; a booster pump connected to the throttle manifold via a tee connector, for applying back pressure according to the wellhead back pressure value during the waiting-for-setting process to ensure that the bottomhole pressure is within the narrow density window formation pressure range during the waiting-for-setting process; a vibrating screen connected to the throttling manifold and used for filtering the solid phase in the mud; A circulation tank connected to the vibrating screen for storing drilling fluid to meet circulation needs; A drilling pump connected to the circulation tank is used to provide the necessary energy for the circulation of the drilling fluid, and to deliver the drilling fluid into the drill tool at a certain pressure and flow rate to complete the entire circulation process; A cement head, which is connected to the drilling pump and is a special tool for injecting cement slurry and releasing the rubber plug. It is installed on the top of the casing during cementing; A cementing pump connected to the cement head for providing power for cementing operations; a water tank connected to the cementing pump; A blowout preventer, connected to the cement head, is a well control device used to prevent blowouts and ensure construction safety; A casing head, which is connected to the blowout preventer through a four-way connector and is used to support the gravity of the technical casing and the oil layer casing; a casing connected to the casing head to provide a passage for flow from the producing layer to the surface; A cement slurry density determination device, which is used to determine the cement slurry density during cementing and cementing according to the actual drilling pressure window during the drilling process; When a radish head is installed at the cementing site, the annulus is sealed by the radish head, and the three ends of the three-way connector are respectively connected to the throttling manifold, the pressure-boosting pump, and the casing head.

2. A narrow density window formation cementing control system according to claim 1, characterized in that: When a rotary control head is not installed at the cementing site, a rotary control head is installed above the blowout preventer to isolate the annulus.

3. A narrow density window formation cementing control system according to claim 1, characterized in that: The system comprises: a first flat valve connected between the pressure-compensating pump and the three-way connector; A second flat valve is connected between the throttle manifold and the three-way connector.

4. A narrow density window formation cementing control system according to claim 1, characterized in that: The system comprises: The waiting-for-setting process control device is used to calculate the wellhead back pressure value during the waiting-for-setting process and generate a pressure compensation instruction according to the wellhead back pressure value to control the pressure compensation pump to apply back pressure.

5. A method for controlling cementing in a narrow density window formation, characterized in that: Executed by the system according to any one of claims 1 to 4, the method comprises: When overflow occurs during cementing, the automatic controller generates a pressure adjustment instruction; Executing the pressure regulation command through the choke manifold to ensure that the bottom hole pressure is within the narrow density window formation pressure range during cementing; When leakage occurs during cementing, the automatic controller generates a pressure adjustment command to reduce the displacement or increase the throttle valve opening so that the wellhead back pressure gradually drops to 0. If the leakage is greater than the critical value, a wellhead back-squeeze cement operation is required after the cementing is completed. During the waiting-for-setting process, the booster pump applies back pressure according to the wellhead back pressure value to ensure that the bottom hole pressure is within the narrow density window formation pressure range during the waiting-for-setting process.

6. A narrow density window formation cementing control method according to claim 5, characterized in that: The method comprises: The wellhead back pressure value during the waiting-for-setting process is calculated, and a pressure compensation instruction is generated according to the wellhead back pressure value to control the pressure compensation pump to apply back pressure.

7. A storage medium, characterized in that: It contains a series of instructions for executing the method steps as claimed in any one of claims 5-6.

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