Offshore pump down pressure control cementing system and method

Abstract

The application belongs to the technical field of pressure control cementing, and discloses a high-precision, fast-response and dynamic pressure control offshore cementing system and method which can realize the whole process of offshore cementing without stopping the pump. The offshore cementing system without stopping the pump comprises a stepless variable speed cementing pump sled, an automatic plug cementing head, a manual throttle valve, a mud pump, a parameter acquisition device and a real-time analysis software for pressure control cementing. The stepless variable speed cementing pump sled is used for adjusting the injection displacement according to real-time control instructions to dynamically control the bottom hole pressure. The automatic plug cementing head is connected with the stepless variable speed cementing pump sled and is used for automatically releasing the rubber plug during the cementing process without stopping the pump. The manual throttle valve is arranged at the wellhead annulus outlet and is used for adjusting the wellhead back pressure. The mud pump forms a small circulation loop with the manual throttle valve and is used for compensating the wellhead pressure when the pump is unexpectedly stopped. The parameter acquisition device is used for collecting the wellhead pressure, displacement and fluid density data in real time. The real-time analysis software for pressure control cementing is used for calculating the equivalent circulating density at the bottom hole in real time based on the data of the parameter acquisition device and dynamically controlling the displacement of the stepless variable speed cementing pump sled and the start and stop of the mud pump.

Description

Technical Field

[0001] This invention relates to the field of controlled pressure cementing technology, specifically to a marine controlled pressure cementing system and method that does not require pump interruption. Background Technology

[0002] Controlled pressure cementing technology controls back pressure by implementing throttling measures at the wellhead annulus outlet. Existing controlled pressure cementing technologies rely on two core components: wellhead throttling devices and back pressure pumps, which have the following drawbacks:

[0003] 1) Pump shutdown pressure imbalance: During cementing, operations such as changing the injection fluid or running the casing require stopping the pump, which causes a sudden drop in bottom hole pressure, exceeding the safe range of the narrow density window, which can easily lead to well leakage or blowout.

[0004] 2) Equipment redundancy: Existing pressure-controlled cementing technology requires additional backpressure compensation systems, such as high-pressure air tanks and independent mud circulation pipelines, which occupy a large amount of platform space and have a low degree of automation.

[0005] 3) Response lag: In existing pressure controlled cementing technology, the throttle valve has a limited adjustment range, resulting in large pressure fluctuations at low flow rates and insufficient compensation accuracy. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention proposes a marine non-stop pump pressure controlled cementing system and method that can achieve high precision, rapid response, and dynamic pressure control throughout the entire marine cementing process.

[0007] The offshore non-stop pump controlled pressure cementing system according to the present invention includes: a continuously variable speed cementing pump skid: used to adjust the injection flow rate according to real-time control commands to dynamically control the bottom hole pressure; an automatic plugging cement head: connected to the continuously variable speed cementing pump skid, used to automatically release the plug during cementing without stopping the pump; a manual choke valve: installed at the wellhead annulus outlet, used to adjust the wellhead back pressure; a mud pump: forming a small circulation loop with the manual choke valve, used to compensate for the wellhead pressure in case of unexpected pump stoppage; a parameter acquisition device: used to acquire wellhead pressure, flow rate, and fluid density data in real time; and controlled pressure cementing real-time analysis software: based on the data from the parameter acquisition device, calculates the equivalent circulation density at the bottom hole in real time, and dynamically controls the flow rate of the continuously variable speed cementing pump skid and the start and stop of the mud pump.

[0008] Furthermore, the automatic cement dispensing head includes a hydraulically driven rubber stopper release mechanism, which is used to release the rubber stopper by triggering a pressure signal without stopping the pump.

[0009] Furthermore, the manual throttle valve has a single valve structure and does not require parallel automatic throttle valve assembly.

[0010] Furthermore, the mud pump and the manual throttle valve are directly connected via a high-pressure pipeline, forming a small circulation loop independent of the main cementing circulation.

[0011] Furthermore, the pressure-controlled cementing real-time analysis software includes: a wellbore pressure distribution calculation module, used to update the equivalent circulation density at the bottom of the well in real time based on the collected data; and a small circulation friction pressure loss calculation module, used to accurately compensate for pressure loss during pump shutdown.

[0012] Furthermore, the displacement adjustment accuracy of the continuously variable cementing pump skid is ±0.01m. 3 / min, response time ≤0.5 seconds.

[0013] According to the offshore non-stop pump controlled pressure cementing method of the present invention, the offshore non-stop pump controlled pressure cementing system includes the following steps: Step 1: Before cementing, the blowout preventer is shut off, and the wellbore fluid is backflushed to the platform mud pit through the kill manifold; Step 2: The continuously variable speed cementing pump skid is started, and the pre-flush fluid is injected according to the instructions of the controlled pressure cementing real-time analysis software, and the discharge rate is adjusted in real time to control the equivalent circulation density at the bottom of the well; Step 3: The rubber plug is released by the automatic cement head, without stopping the pump throughout the process; Step 4: If the pump stops unexpectedly, the mud pump is immediately started and a small circulation is formed with the manual choke valve to compensate for the wellhead pressure; Step 5: After cementing is completed, the controlled pressure cementing real-time analysis software continuously verifies the bottom hole pressure stability.

[0014] Furthermore, the trigger condition for displacement adjustment in step two is that the equivalent circulating density at the bottom of the well deviates from the design value by ±0.02 g / cm³. 3 .

[0015] Furthermore, in step four, the flow rate of the small circulation is dynamically calculated by the pressure-controlled cementing real-time analysis software based on the wellbore static pressure loss.

[0016] Furthermore, the offshore non-stop pump controlled pressure cementing method is applicable to both onshore and offshore platforms, and does not require additional high-pressure air packs or backpressure compensation devices.

[0017] Compared to the existing redundant architecture of "back pressure pump + automatic choke valve group + high pressure air tank", the offshore non-stop pump controlled pressure cementing system and method of the present invention simplifies the pressure control logic to "stepless speed cementing pump displacement direct adjustment + single manual choke valve small circulation compensation". While completely eliminating the risk of bottom hole pressure runaway during pump shutdown, it also abandons the traditional reliance on large back pressure pumps and automatic choke valve groups, realizing full-process non-stop pump automated operation. It significantly improves the safety and efficiency of offshore cementing in narrow density window formations, making the offshore non-stop pump controlled pressure cementing system of the present invention comprehensively superior in seven indicators: number of equipment, platform footprint, investment cost, response speed, pressure control accuracy, operation timeliness and automation level. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the offshore non-stop pump controlled pressure cementing system according to an embodiment of the present invention;

[0019] Figure 2 This is a schematic flowchart of a marine non-stop pump controlled pressure cementing method according to an embodiment of the present invention. Detailed Implementation

[0020] To better understand the purpose, structure, and function of this invention, the invention will be described in further detail below with reference to the accompanying drawings.

[0021] Figure 1 The structure of a marine non-stop pump controlled pressure cementing system 100 according to an embodiment of the present invention is shown. For example... Figure 1 As shown, the offshore non-stop pump controlled pressure cementing system 100 may include: a continuously variable speed cementing pump skid 1: used to adjust the injection flow rate according to real-time control commands to dynamically control the bottom hole pressure; an automatic plugging cement head 2: connected to the continuously variable speed cementing pump skid 1, used to automatically release the plug during cementing without stopping the pump; a manual choke valve 3: installed at the wellhead annulus outlet, used to adjust the wellhead back pressure; a mud pump: forming a small circulation loop with the manual choke valve 3, used to compensate for wellhead pressure in case of unexpected pump stoppage; a parameter acquisition device: used to collect wellhead pressure, flow rate, and fluid density data in real time; and controlled pressure cementing real-time analysis software: based on the data from the parameter acquisition device, calculates the equivalent circulation density at the bottom hole in real time, and dynamically controls the flow rate of the continuously variable speed cementing pump skid and the start and stop of the mud pump.

[0022] In the offshore non-stop pump controlled pressure cementing system 100 of this invention, the continuously variable speed cementing pump skid 1 is connected to the automatic plugging cement head 2 via a high-pressure pipeline, and the casing string is connected below the cement head; the manual choke valve 3 is installed at the wellhead annulus outlet, forming a closed-loop small circulation with the mud pump via a pipeline; the parameter acquisition device may include a pressure sensor and a flow meter, and the data is transmitted in real time to the controlled pressure cementing real-time analysis software. During the normal cementing stage: the continuously variable speed cementing pump skid 1 injects cement slurry at the designed displacement, and the parameter acquisition device provides real-time feedback on the wellhead pressure; the controlled pressure cementing real-time analysis software dynamically adjusts the pump speed according to the bottom hole equivalent circulation density (ECD) calculation results (if the ECD increases, the displacement is reduced, and vice versa). During the plugging stage: the automatic plugging cement head 2 releases the plug automatically, and the pump speed remains unchanged when the plug descends in the casing string to avoid pressure fluctuations. During the pump shutdown compensation phase: If the pump stops due to a fault, the pressure-controlled cementing real-time analysis software will immediately start the mud pump, and the opening of the manual throttle valve 3 can be automatically adjusted according to the friction calculation value of the small circulation loop to maintain stable wellhead pressure.

[0023] The offshore non-stop pump controlled pressure cementing system 100 of this invention transforms bottom hole pressure control from the traditional "throttle valve back pressure adjustment" to "automatic adjustment of continuously variable speed cementing pump displacement". It uses real-time algorithms of controlled pressure cementing real-time analysis software as the brain, continuously variable speed cementing pump as the actuator, and small circulation as safety redundancy to form a closed-loop pressure control system of "non-stop pumping - fast response - high precision - minimal equipment", which fundamentally solves the problems of pump stoppage pressure loss and equipment redundancy in narrow density window formation cementing.

[0024] In a preferred embodiment, the automatic cementing head 2 may include a hydraulically driven rubber plug release mechanism for releasing the rubber plug via a pressure signal without stopping the pump. This embodiment uses a hydraulic automatic cementing head, which can complete the rubber plug release within 3 seconds. The entire cementing process does not require stopping the pump, saving 2-4 hours of operation time per well and directly reducing daily operating costs.

[0025] In a preferred embodiment, the manual throttle valve 3 is a single valve structure, eliminating the need for a parallel automatic throttle valve assembly. A single manual throttle valve can meet back pressure regulation requirements, eliminating the need for a multi-valve parallel structure, shortening pipeline length, and reducing weight, making it particularly suitable for space-constrained offshore platforms.

[0026] In a preferred embodiment, the mud pump and the manual throttle valve 3 can be directly connected via a high-pressure pipeline to form a small circulation loop independent of the main cementing circulation. The small circulation loop is completely independent of the main cementing circulation and can establish local circulation within 10 seconds. In the event of an accidental pump stoppage, the wellhead pressure fluctuation is less than ±0.5MPa, thus avoiding downhole accidents.

[0027] According to a preferred embodiment of the present invention, the real-time analysis software for pressure-controlled cementing may include: a wellbore pressure distribution calculation module for updating the equivalent circulation density at the bottom of the well in real time based on acquired data; and a small circulation friction pressure loss calculation module for accurately compensating for pressure loss during pump shutdown. The compensation accuracy of the small circulation friction pressure loss calculation module is several times higher than that of the traditional manual chart lookup method, eliminating human estimation errors. This embodiment, through the coordinated operation of the wellbore pressure distribution calculation module and the small circulation friction pressure loss calculation module, can achieve precise closed-loop control of bottom-hole pressure throughout the entire cementing process (including pump shutdown), upgrading the traditional passive compensation relying on manual experience to active predictive control based on physical models, and breaking through the core pain points of pressure compensation lag and low accuracy in narrow density window cementing.

[0028] Furthermore, the displacement adjustment accuracy of the continuously variable cementing pump skid 1 can be ±0.01m. 3 / min, with a response time ≤0.5 seconds. This technical specification enables bottom hole pressure control accuracy to break through to the ±0.05MPa level, which is equivalent to 10 times the accuracy of traditional cementing pumps. It fundamentally solves the fracturing / well leakage risk of formations with narrow density windows, while providing core hardware support for continuous pump operation throughout the entire process.

[0029] Figure 2 This invention illustrates a method for offshore continuous pump control pressure cementing according to an embodiment of the present invention. Using the aforementioned offshore continuous pump control pressure cementing system 100, the method may include the following steps: Step 1 S1: Before cementing, the blowout preventer is shut off, and the wellbore fluid is backflushed to the platform mud pit via the kill manifold. Step 1 S1 is used to quickly remove impurities from the wellbore and establish a stable initial pressure baseline, laying a zero-error starting point for subsequent precise pressure control. Step 2 S2: The continuously variable speed cementing pump skid 1 is started, and pre-fluid is injected according to the instructions of the pressure control cementing real-time analysis software, with the discharge rate adjusted in real time to control the equivalent circulation density at the bottom of the well. Step 3 S3: The rubber plug is released through the automatic plugging cement head 2, without stopping the pump throughout the process. Step 3 S3 can complete the rubber plug placement while maintaining a constant pump speed, simplifying the complex process of traditional pump shutdown-plug placement-pump restart, while avoiding well leakage / blowout caused by sudden pressure drops. Step 4 (S4): In case of unexpected pump stoppage, immediately start the mud pump and manually throttle valve 3 to form a small circulation and compensate for the wellhead pressure. Step 5 (S5): After cementing is completed, verify the bottom hole pressure stability using controlled-pressure cementing real-time analysis software. Step 5 (S5) is used to continuously verify the bottom hole pressure stability after cementing by the controlled-pressure cementing real-time analysis software. It can detect and compensate for potential pressure loss risks in the early stages of cementing, avoiding annular air channeling or cement bonding failure. Simultaneously, it automatically records pressure data throughout the process, eliminating the need for manual pressure testing and secondary verification, helping to shorten the well completion cycle and reduce subsequent operational risks and costs.

[0030] In a preferred embodiment, the specific working process of the offshore non-stop pump controlled pressure cementing method system of the present invention can be as follows:

[0031] 1) System initialization: The blowout preventer is turned off, and the wellbore fluid establishes an initial circulation path through the kill manifold, manual choke valve, and platform mud pit.

[0032] 2) Design issuance: The pressure-controlled cementing real-time analysis software reads the engineering design scheme, parses it into four-dimensional construction parameters of "fluid type-displacement-density-volume", and issues them to the continuously variable speed cementing pump skid.

[0033] 3) Continuous injection and displacement: The continuously variable speed cementing pump skid 1 injects pre-filled fluid, cement slurry, and displacement fluid according to the set curve; the parameter acquisition device collects the wellhead inlet and outlet pressure, displacement, and density in real time; the pressure-controlled cementing real-time analysis software calculates the current bottom hole ECD at a frequency of 1Hz and compares it with the design value: if the ECD is too high, the pump displacement is reduced; if the ECD is too low, the pump displacement is increased; the adjustment command is sent to the pump skid servo system via the CAN bus within 5 seconds, and the closed-loop control ensures that the bottom hole pressure is always at the center of the safety window.

[0034] 4) Automatic plug release: When the displacement fluid reaches the set volume, the pressure controlled cementing real-time analysis software triggers the hydraulic mechanism of the automatic plug release cement head 2, and the rubber plug is released within 3 seconds. The pump speed remains unchanged, with no pump stoppage or pressure fluctuation.

[0035] 5) Pump stoppage compensation: In the event of a power outage, equipment failure, or other reasons that cause the main pump to stop injecting, the software immediately starts the mud pump and opens the manual throttle valve 3 to the calculated opening degree, forming a local small circulation of the mud pump, manual throttle valve, wellhead annulus, and mud pump. The pressure-controlled cementing real-time analysis software corrects the valve position in real time according to the small circulation friction and pressure loss model, so that the wellhead pressure recovers to the set value within 10 seconds, and the bottom hole pressure drop does not exceed 0.5MPa.

[0036] 6) End of verification: After cementing is completed, the pressure-controlled cementing real-time analysis software continuously monitors the wellhead pressure for 30 minutes. After confirming that there is no abnormal drop, the system exits the pressure-controlled mode and enters the waiting stage for cementing.

[0037] According to a preferred embodiment of the present invention, the triggering condition for displacement adjustment in step S2 can be a deviation of the equivalent circulation density at the bottom of the well from the design value by ±0.02 g / cm³. 3 This example uses an ECD deviation of ±0.02 g / cm. 3 As a trigger threshold, the bottom hole pressure is always kept in the center of the safety window, reducing the risk of well leakage / well kick by 90%.

[0038] In a preferred embodiment, the flow rate of the small circulation in step four is dynamically calculated by the pressure-controlled cementing real-time analysis software based on the wellbore static pressure loss. This dynamic calculation of the small circulation flow rate avoids overcompensation or undercompensation, saving mud and reducing waste liquid discharge per mud replacement cycle.

[0039] Furthermore, the offshore non-stop pump controlled pressure cementing method of this invention is applicable to both land and offshore platforms, and does not require additional high-pressure air packs or backpressure compensation devices. It is highly versatile and can be replicated and promoted to all high-pressure / narrow-window wells.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A non-stop pump controlled pressure cementing system for offshore operations, characterized in that, include: Continuously variable speed cementing pump skid: used to adjust the injection flow rate according to real-time control commands in order to dynamically control the bottom hole pressure; Automatic plugging cement head: connected to the continuously variable speed cementing pump skid, used to automatically release the rubber plug during the cementing process without stopping the pump; Manual throttle valve: installed at the wellhead annulus outlet, used to regulate wellhead back pressure; Mud pump: forms a small circulation loop with the manual throttle valve to compensate wellhead pressure in case of unexpected pump stoppage; Parameter acquisition device: used for real-time acquisition of wellhead pressure, flow rate, and fluid density data; and Controlled-pressure cementing real-time analysis software: Based on the data from the parameter acquisition device, it calculates the equivalent circulation density at the bottom of the well in real time and dynamically controls the discharge rate of the continuously variable cementing pump skid and the start and stop of the mud pump.

2. The offshore non-stop pump controlled pressure cementing system according to claim 1, characterized in that, The automatic cement dispensing head includes a hydraulically driven rubber stopper release mechanism, which is used to release the rubber stopper by triggering a pressure signal without stopping the pump.

3. The offshore non-stop pump controlled pressure cementing system according to claim 1 or 2, characterized in that, The manual throttle valve is a single valve structure and does not require parallel automatic throttle valve assembly.

4. The offshore non-stop pump controlled pressure cementing system according to claim 1 or 2, characterized in that, The mud pump and the manual throttle valve are directly connected via a high-pressure pipeline, forming a small circulation loop independent of the main cementing circulation.

5. The offshore non-stop pump controlled pressure cementing system according to claim 1 or 2, characterized in that, The controlled-pressure cementing real-time analysis software includes: a wellbore pressure distribution calculation module, used to update the equivalent circulation density at the bottom of the well in real time based on the collected data; and a small circulation friction pressure loss calculation module, used to accurately compensate for pressure loss during pump shutdown.

6. The offshore non-stop pump controlled pressure cementing system according to claim 1 or 2, characterized in that, The displacement adjustment accuracy of the continuously variable speed cementing pump skid is ±0.01m. 3 / min, response time ≤0.5 seconds.

7. A method for offshore continuous pump control pressure cementing, employing an offshore continuous pump control pressure cementing system according to any one of claims 1 to 6, characterized in that, Includes the following steps: Step 1: Before cementing, shut off the blowout preventer and backflow the wellbore fluid to the platform mud pit through the kill manifold; Step 2: Start the continuously variable speed cementing pump skid, inject the pre-flush fluid according to the instructions of the pressure-controlled cementing real-time analysis software, and adjust the discharge rate in real time to control the equivalent circulation density at the bottom of the well; Step 3: Release the rubber stopper through the automatic cement dispensing head; the pump does not need to be stopped throughout the process. Step 4: If an unexpected pump stop occurs, immediately start the mud pump and the manual throttle valve to form a small circulation to compensate for the wellhead pressure; Step 5: After cementing is completed, the controlled-pressure cementing real-time analysis software continuously verifies the bottom hole pressure stability.

8. The offshore non-stop pump controlled pressure cementing method according to claim 7, characterized in that, The trigger condition for displacement adjustment in step two is that the equivalent circulating density at the bottom of the well deviates from the design value by ±0.02 g / cm³. 3 .

9. The offshore non-stop pump controlled pressure cementing method according to claim 7, characterized in that, In step four, the flow rate of the small circulation is dynamically calculated by the pressure-controlled cementing real-time analysis software based on the wellbore static pressure loss.

10. The offshore non-stop pump controlled pressure cementing method according to claim 7, characterized in that, The offshore non-stop pump controlled pressure cementing method is applicable to both onshore and offshore platforms and does not require additional high-pressure air packs or backpressure compensation devices.

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