A multi-source information fusion cementing cement sheath sealing monitoring system and method

Abstract

The application discloses a multi-source information fusion cementing cement sheath sealing monitoring system and method, and mainly relates to the technical field of cementing cement sheath sealing, and aims to solve the problem that the existing scheme relies on downhole tools, is limited by casing metal shielding effect, and can only provide static data at discrete moments. The system comprises the following: a distributed sensing optical fiber arranged at a casing-cement sheath interface; a transmission optical fiber connected with the distributed sensing optical fiber in a fusion manner; a distributed optical fiber sensing instrument arranged on the ground and connected with the transmission optical fiber; an optical fiber matching analysis server connected with the distributed optical fiber sensing instrument; a plurality of multiplexing modules which are distributed along the casing axial direction at intervals and are connected in series through a composite cable; a resistivity sensing instrument arranged on the ground and connected with the composite cable; a resistance matching analysis server connected with the resistivity sensing instrument; and the optical fiber matching analysis server and the resistance matching analysis server are connected with a preset central server respectively.

Description

Technical Field

[0001] This application relates to the field of cement sheath sealing technology, and in particular to a cement sheath sealing monitoring system and method with multi-source information fusion. Background Technology

[0002] In deep and unconventional oil and gas wells under high temperature, high pressure, and alternating load conditions, cement sheaths are highly susceptible to residual tensile stress at the casing-cement sheath interface due to irreversible plastic deformation during cement solidification shrinkage and fracturing unloading. This stress induces the continuous initiation and expansion of micro-annulus gaps, forming hidden interface sealing failure channels. This process is characterized by nonlinearity, gradualism, and localization, making it difficult for traditional static assessment methods to capture its dynamic evolution trajectory, thus becoming the primary cause of wellbore integrity failure.

[0003] Current cementing quality monitoring technologies rely on downhole tools, which, limited by the casing metal shielding effect, can only provide static data at discrete moments. Acoustic amplitude logging and acoustic variable density logging have insufficient resolution and cannot identify micron-level interface debonding. Although ultrasonic pulse echo and behind-casing imaging technologies improve spatial resolution, they still cannot achieve real-time, continuous, and axially distributed synchronous perception of strain and resistivity changes in the cement sheath during load cycles. This leaves the dynamic damage process in a "black box" state, unable to support accurate early warning and intervention decisions. Summary of the Invention

[0004] This application provides a cement sheath sealing performance monitoring system and method based on multi-source information fusion, in order to solve the problem that existing solutions rely on downhole tools and are limited by the casing metal shielding effect, thus only providing static data at discrete moments.

[0005] Firstly, this application provides a multi-source information fusion-based cement sheath sealing performance monitoring system, the system comprising: Distributed sensing optical fiber deployed at the sleeve-cement ring interface; transmission optical fiber connected to the distributed sensing optical fiber by fusion splicing; distributed optical fiber sensor installed on the ground and connected to the transmission optical fiber; optical fiber matching analysis server connected to the distributed optical fiber sensor. Multiplexing modules are distributed at intervals along the axial direction of the sleeve and cascaded in series via composite cables, and measurement nodes are set on the multiplexing modules; wherein, the multiplexing modules are connected to the electrodes in the measurement nodes, and the measurement nodes contain a set of electrodes arranged according to the AC four-electrode measurement method; a resistivity sensor set on the ground is connected to the composite cable, and a resistance matching analysis server is connected to the resistivity sensor. The fiber optic analysis server and the resistor analysis server are respectively connected to a preset central server.

[0006] In one implementation of this application, the distributed sensing optical fiber is deployed in a spiral winding arrangement along the axial direction of the sleeve-cement ring interface.

[0007] In one implementation of this application, the end of the distributed sensing optical fiber is connected to the transmission optical fiber via fusion splicing. The transmission optical fiber extends upwards along the cementing casing string to the wellhead and connects to the optical signal port of the ground-based distributed optical fiber sensor.

[0008] In one implementation of this application, the multiplexing module is customized in the resistivity sub-section of the cementing, and / or the multiplexing module is fixed to the outer wall of the casing of the cementing by clamps; wherein the resistivity sub-section is threaded to the casing string.

[0009] In one implementation of this application, each measurement node includes a set of electrodes arranged according to the AC four-electrode measurement method, and the leads of the four electrodes are respectively connected to the corresponding interfaces of the same multiplexing module.

[0010] In one implementation of this application, the multiplexing modules are spaced apart along the bushing axis; The multiplexing module is equipped with a current and voltage mainline interface and a control mainline interface; The composite cable integrates a pair of current and voltage main lines and a control main line; The multiplexing module is connected to the corresponding main line of the composite cable through the current and voltage main line interface and the control main line interface, so that the composite cable can be cascaded with the multiplexing module in series.

[0011] Secondly, this application provides a multi-source information fusion method for monitoring the sealing performance of cement sheaths in wells, applied to a multi-source information fusion system for monitoring the sealing performance of cement sheaths in wells. The method includes: The optical signal is emitted by the distributed optical fiber sensor, enters the distributed sensing optical fiber through the transmission optical fiber, and the backscattered signal generated at various positions of the sensing optical fiber is received by the distributed optical fiber sensor. The temperature and strain distribution along the optical fiber path is obtained by the optical fiber matching analysis server. The measurement node to be measured is determined based on the address code of the multiplexing module corresponding to the measurement node; the resistance matching analysis server sends an addressing command with address code through the control main line in the composite cable, the internal switch of the selected multiplexing module is closed, and the local electrode is connected to the current measurement loop; the resistivity sensor supplies power to the electrode through the current and voltage main line and collects the voltage signal to calculate the resistivity of the cement ring at the measurement node. By acquiring temperature and strain distribution, measuring the resistivity of the cement sheath at the node, and the corresponding fiber optic monitoring and resistivity discrimination conditions for the current cementing stage through a preset central server, the state of the cement sheath in the current cementing stage can be identified.

[0012] In one implementation of this application, the state of the cement sheath at the current cementing stage is identified by acquiring temperature and strain distribution, resistivity of the cement sheath at the measurement node, and fiber optic monitoring and resistivity discrimination conditions corresponding to the current cementing stage through a preset central server. Specifically, this includes: When the well cementing is in the solidification and ring-forming stage, if the temperature rises by a preset first temperature range, the cementing quality is determined to be good; otherwise, the cementing quality is determined to be poor. When the resistivity increases by a magnitude greater than the preset first resistance, the cementing quality is determined to be good. When the resistivity increases or decreases by a factor less than the preset second resistance magnitude, the cementing quality is determined to be poor; the preset second resistance magnitude is less than the preset first resistance magnitude; otherwise, the cementing quality is determined to be medium. When the cementing quality corresponding to temperature is inconsistent with the cementing quality corresponding to resistivity, the worst cementing quality result is taken as the cement sheath state.

[0013] If all conditions are met, the current cementing quality is determined to be good; otherwise, the cementing quality is poor.

[0014] In one implementation of this application, the state of the cement sheath at the current cementing stage is identified by acquiring temperature and strain distribution, resistivity of the cement sheath at the measurement node, and fiber optic monitoring and resistivity discrimination conditions corresponding to the current cementing stage through a preset central server. Specifically, this includes: When the construction disturbance stage is underway, after each internal pressure unloading, if any strain distribution obtained shows a sudden increase or the temperature fluctuation is greater than the preset fluctuation range, the cement sheath state is determined to be a cement sheath state seal failure. When the resistivity undergoes a step change, the cement sheath state is determined to be a cement sheath state seal failure. Otherwise, the cement sheath condition is confirmed to be a cement sheath condition and the seal has not failed.

[0015] In one implementation of this application, the state of the cement sheath at the current cementing stage is identified by acquiring temperature and strain distribution, resistivity of the cement sheath at the measurement node, and fiber optic monitoring and resistivity discrimination conditions corresponding to the current cementing stage through a preset central server. Specifically, this includes: When the well cement sheath is in long-term service, if the strain distribution shows a trend of increasing or decreasing within the preset monitoring time period, or if the strain distribution is not in the preset normal distribution range, the well cement sheath condition is determined to be cement sheath sealing failure. When the resistivity shows a trend of increasing or decreasing within a preset monitoring period, or when the resistivity is not within a preset normal value range, the cement sheath condition is determined to be a cement sheath seal failure. Otherwise, the cement sheath condition is confirmed to be a cement sheath condition and the seal has not failed.

[0016] As can be seen from the above technical solutions, this application has the following advantages: By deploying distributed sensing optical fibers at the casing-cement sheath interface and connecting the transmission fibers via fusion splicing, in conjunction with a ground-based distributed optical fiber sensor, real-time sensing of the axial continuous and high spatial resolution strain distribution of the cement sheath under high temperature, high pressure, and alternating load environments was achieved. This structure overcomes the bottleneck of traditional downhole tools limited by casing metal shielding, eliminates the problem of dynamic evolution information loss caused by discrete sampling, and enables full-length, continuous axial monitoring of the initiation and expansion process of micro-annulus for the first time, providing a directly observable technical path for the progressive evolution of interface damage.

[0017] By integrating electrodes arranged according to the AC four-electrode measurement method onto a multiplexed module spaced along the casing axis, and cascading them in series via composite cables, along with a surface resistivity sensor and a resistance analysis server, synchronous, continuous, and axially distributed monitoring of the resistivity changes at the cement sheath interface is achieved. This design avoids the shortcomings of traditional sonic logging, such as insufficient resolution and inability to identify micron-level debonding. It allows for the precise capture of localized conductivity degradation caused by plastic deformation of the cement sheath during fracturing and unloading, and establishes an electrical parametric response mechanism that complements strain sensing, thereby improving the early identification capability of concealed sealing failure channels.

[0018] By connecting the fiber optic analysis server and the resistance analysis server to a pre-set central server, the unified aggregation, collaborative analysis, and structured output of heterogeneous sensor data of strain and resistivity were achieved. This architecture breaks through the limitations of monitoring a single physical quantity, enabling the mechanical and electrical responses during the cement sheath damage process to form a closed-loop feedback system that integrates multi-source information. This solves the decision-making blind spot in the "black box" state of the dynamic damage process, and provides traceable, locatable, and correlateable system-level data support for the formulation of wellbore integrity early warning and intervention strategies. Attached Figure Description

[0019] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the internal structure of a cement sheath sealing performance monitoring system based on multi-source information fusion provided in this application embodiment.

[0021] Figure 2This is a flowchart of a method for monitoring the sealing performance of cement sheaths in wells using multi-source information fusion, provided in an embodiment of this application.

[0022] Figure 3 This is a graph showing the change in cement ring resistivity over time starting from the setting period, as provided in an embodiment of this application.

[0023] Explanation of main figure symbols 1. Distributed sensing fiber optic cable; 2. Transmission fiber optic cable; 3. Distributed fiber optic sensor; 4. Fiber optic supporting analysis server; 5. Composite cable; 6. Multiplexing module; 7. Measurement node; 8. Resistivity sensor; 9. Resistance analysis server; 10. Preset central server; 11. Clamp; 12. Resistivity section. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Those skilled in the art should understand that the embodiments described below are merely preferred embodiments of this disclosure and do not imply that this disclosure can only be implemented through these preferred embodiments. These preferred embodiments are merely used to explain the technical principles of this disclosure and are not intended to limit the scope of protection of this disclosure. Based on the preferred embodiments provided by this disclosure, all other embodiments obtained by those skilled in the art without creative effort should still fall within the scope of protection of this disclosure.

[0026] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0027] The technical solutions proposed in the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0028] This application Figure 1 This application provides a multi-source information fusion-based cement sheath sealing performance monitoring system. For example... Figure 1As shown in the embodiments of this application, the system mainly includes: Distributed sensing optical fiber 1 is arranged at the sleeve-cement ring interface.

[0029] It should be noted that the distributed sensing fiber 1 is deployed in a spiral winding arrangement along the axial direction of the sleeve-cement ring interface.

[0030] Transmission fiber 2 is connected to the distributed sensing fiber 1 by fusion splicing.

[0031] It should be further noted that the end of the distributed sensing fiber 1 is connected to the transmission fiber 2 via fusion splicing; the transmission fiber 2 extends upward along the cementing casing string to the wellhead and connects to the optical signal port of the surface distributed fiber optic sensor 3. The transmission fiber 2 is used to connect the surface distributed fiber optic sensor 3 and the downhole distributed sensing fiber 1 to transmit optical signals. It has high temperature resistance, tensile strength, and compressive strength to adapt to the complex downhole environment.

[0032] A distributed optical fiber sensor 3 is installed on the ground and connected to the transmission optical fiber 2.

[0033] The fiber optic analysis server 4 is connected to the distributed fiber optic sensor 3.

[0034] It should be further explained that the distributed optical fiber sensor 3 is based on the principle of optical time-domain reflection or optical frequency-domain reflection. It can use distributed temperature sensing and distributed strain sensing technology to monitor the temperature and strain changes along the arrangement path of the distributed sensing optical fiber 1, so as to realize continuous and high spatial resolution sensing along the optical fiber path. The optical fiber matching analysis server 4 is used to adjust the working parameters of the distributed optical fiber sensor 3 (including spatial resolution, sampling frequency, pulse width, etc.) and store the monitoring results. It also has the functions of real-time data display and preliminary analysis.

[0035] Multiplexing modules 6 are distributed at intervals along the axial direction of the sleeve and cascaded in series via composite cables 5, and measurement nodes 7 are set on the multiplexing modules 6; Among them, the multiplexing module 6 is connected to the electrodes in the measurement node 7, and the measurement node 7 contains a set of electrodes arranged according to the AC four-electrode measurement method (it should be added that the electrodes are arranged downhole according to the AC four-electrode measurement method, consisting of a pair of current excitation electrodes and a pair of voltage measurement electrodes. The electrode materials are selected from corrosion-resistant and highly conductive metals or composite materials to ensure measurement stability under long-term contact with cement sheath). It should be further explained that the multiplexing module 6 is customized within the resistivity sub 12 of the cementing system (the resistivity sub 12 is a customized casing sub with the multiplexing module 6 embedded within it, which can be threaded onto the casing string, forming two parallel installation schemes with the clamp 11 for fixing the multiplexing module 6, suitable for applications with higher requirements for installation accuracy and protection level), and / or the multiplexing module 6 is fixed to the outer wall of the cementing casing via the clamp 11 (the clamp 11 is used to fix the multiplexing module 6 to the outer wall of the casing, forming two parallel installation schemes with the multiplexing module 6 embedded in the resistivity sub 12, which can be flexibly selected according to the site conditions); wherein, the resistivity sub 12 is threaded onto the casing string. Each measurement node 7 contains a set of electrodes arranged according to the AC four-electrode measurement method, and the leads of the four electrodes are respectively connected to the corresponding interface of the same multiplexing module 6. Furthermore, the multiplexing module 6 is installed on the outer wall of the bushing or embedded in the resistivity stub 12, and is used to control whether the electrode at the current position is connected to the current and voltage main line. Each multiplexing module 6 has a unique address command. When it receives an address command from the control main line that matches its own address, its internal switch closes, connecting the four local electrodes to the current and voltage main line, so that the resistivity sensor 8 can measure the resistivity of the cement ring at that location.

[0036] In a specific embodiment, the multiplexing modules 6 are spaced apart along the axial direction of the bushing.

[0037] The multiplexing module 6 is equipped with a current and voltage mainline interface and a control mainline interface.

[0038] Composite cable 5 integrates a pair of current and voltage main lines and one control main line. It should be noted that composite cable 5 is used to connect the resistivity sensor 8 on the ground and the measuring electrode downhole. It is composed of current and voltage main lines (a pair of current lines and a pair of voltage lines) and control main line, and the outer layer is equipped with a high-temperature resistant insulating sheath and armor layer to ensure the electrical reliability of long-term downhole operation.

[0039] The multiplexing module 6 is connected to the main line of the composite cable 5 through the current and voltage main line interface and the control main line interface, so that the composite cable 5 can be cascaded with the multiplexing module 6 in series.

[0040] A resistivity sensor 8 installed on the ground is connected to the composite cable 5, and a resistance analysis server 9 is connected to the resistivity sensor 8. The fiber optic analysis server 4 and the resistance analysis server 9 are respectively connected to the preset central server 10.

[0041] Based on the above description, this application discloses a multi-source information fusion cement sheath sealing monitoring system. Distributed sensing optical fiber 1 is laid at the casing-cement sheath interface, with the laying path either axial or spirally wound to form a continuous temperature and strain sensing link along the casing string. The end of the sensing optical fiber is connected to the transmission optical fiber 2 via fusion splicing, and the splice point is waterproofed and sealed. The transmission optical fiber 2 extends upwards along the casing string to the wellhead, ultimately connecting to the optical signal port of the ground-based distributed optical fiber sensor 3. The distributed optical fiber sensor 3 and the optical fiber-compatible analysis server 4 are connected via data cables to form a complete optical sensing link. The optical signal is emitted from the distributed optical fiber sensor 3, enters the distributed sensing optical fiber 1 via the transmission optical fiber 2, and the backscattered signals generated at various locations on the sensing optical fiber return along the original path. These signals are received and demodulated by the distributed optical fiber sensor 3 to obtain the temperature and strain distribution along the optical fiber path.

[0042] The multiplexing module 6 and electrodes can be customized into a dedicated resistivity short section 12, or directly fixed to the outer wall of the casing using clamps 11. The modules are spaced apart along the casing axis, forming multiple resistivity measurement nodes 7. Each measurement node 7 contains a set of electrodes arranged according to the AC four-electrode measurement method: a pair of current excitation electrodes and a pair of voltage measurement electrodes. The leads of the four electrodes are respectively connected to the corresponding interface of the same multiplexing module 6. When using the resistivity short section 12, the short section is threaded onto the casing string; when using clamps 11, the multiplexing module 6 is fixed to the outer wall of the casing using insulating clamps 11, and the electrodes are directly installed on the casing surface and connected to the module's leads. The multiplexing modules 6 are cascaded in series via composite cables 5. The composite cable 5 integrates a pair of current and voltage main lines and a control main line. Each time a multiplexing module 6 is connected, its current and voltage main line interface and control main line interface are connected to the corresponding main line on the downhole lead, thus achieving cascading of the modules. The uppermost end of the composite cable 5 is laid along the conduit post to the ground and connected to the resistivity sensor 8. The resistivity sensor 8 is connected to the resistance analysis server 9. The resistance analysis server 9 sends an addressing command with address code through the control main line. The internal switch of the selected multiplexer module 6 closes, connecting the local electrode to the measurement circuit. The resistivity sensor 8 supplies power to the electrode through the current and voltage main lines and collects the voltage signal, thereby calculating and measuring the resistivity of the cement ring at that location.

[0043] The fiber optic analysis server 4 and the resistance analysis server 9 are respectively connected to the preset central server 10 for joint analysis.

[0044] In addition, the embodiments provide a method for monitoring the sealing performance of cement sheaths through multi-source information fusion, such as... Figure 2 As shown in the embodiments of this application, the method mainly includes the following steps: Step 210: The optical signal is emitted by the distributed optical fiber sensor, enters the distributed sensing optical fiber through the transmission optical fiber, and the backscattered signals generated at various positions in the sensing optical fiber are received by the distributed optical fiber sensor. The temperature and strain distribution along the optical fiber path are obtained by the optical fiber matching analysis server.

[0045] In some embodiments, the distributed fiber optic sensor uses a narrow-linewidth laser with a pulse width of 10 ns to emit a probe light signal, which is coupled to a distributed sensing fiber pre-embedded in the cementing interface via a single-mode transmission fiber. The Rayleigh backscattered signal generated at each location is collected, and photoelectric conversion is completed by a built-in high-speed photodetector. The signal is then transmitted to a matching analysis server, and after spatial positioning calculation, continuous temperature and strain distribution data with meter-level spatial resolution along the fiber path are obtained.

[0046] Step 220: Determine the measurement node to be measured based on the address code of the multiplexing module corresponding to the measurement node; the resistance matching analysis server sends an addressing command with address code through the control main line in the composite cable, the internal switch of the selected multiplexing module closes, and the local electrode is connected to the current measurement loop; the resistivity sensor supplies power to the electrode through the current and voltage main line and collects the voltage signal to calculate the resistivity of the cement ring at the measurement node.

[0047] In some embodiments, the measurement node to be measured is first determined based on the isolation segment position of the cementing section. The unique address code of the multiplexing module corresponding to the measurement node is retrieved. The resistance matching analysis server sends an addressing command with the address code through the control main line in the composite cable. Only the internal relay switch of the multiplexing module selected by the addressing is closed, and the locally embedded ring electrode is connected to the current measurement circuit. The resistivity sensor outputs a constant current to the electrode through the current and voltage main line and collects the voltage signal to obtain the resistivity value of the cement sheath at the measurement node.

[0048] Step 230: Obtain temperature and strain distribution, resistivity of cement sheath at measurement nodes, and fiber optic monitoring and resistivity discrimination conditions corresponding to the current cementing stage through a preset central server, and identify the cement sheath status of the current cementing stage.

[0049] In some embodiments, when the well is in the waiting stage of solidification and ring formation, if the temperature increases by a preset first temperature range, the cementing quality is determined to be good; otherwise, the cementing quality is determined to be poor. When the resistivity increases by a magnitude greater than the preset first resistance, the cementing quality is determined to be good. When the resistivity increases or decreases by a factor less than the preset second resistance magnitude, the cementing quality is determined to be poor; the preset second resistance magnitude is less than the preset first resistance magnitude; otherwise, the cementing quality is determined to be medium. When the cementing quality corresponding to temperature is inconsistent with the cementing quality corresponding to resistivity, the worst cementing quality result is taken as the cement sheath state.

[0050] If all conditions are met, the current cementing quality is determined to be good; otherwise, the cementing quality is poor.

[0051] In some embodiments, when in the construction disturbance stage, after each internal pressure unloading, if any strain distribution obtained shows a sudden increase or temperature fluctuation is greater than a preset fluctuation range, the cement sheath state is determined to be a cement sheath state sealing failure. When the resistivity undergoes a step change, the cement sheath state is determined to be a cement sheath state seal failure. Otherwise, the cement sheath condition is confirmed to be a cement sheath condition and the seal has not failed.

[0052] In some embodiments, when the well cement sheath is in a long-term service phase, if the strain distribution shows a trend of increasing or decreasing within a preset monitoring time period, or if the strain distribution is not within a preset normal distribution range, the well cement sheath state is determined to be a cement sheath state sealing failure. When the resistivity shows a trend of increasing or decreasing within a preset monitoring period, or when the resistivity is not within a preset normal value range, the cement sheath condition is determined to be a cement sheath seal failure. Otherwise, the cement sheath condition is confirmed to be a cement sheath condition and the seal has not failed.

[0053] It should be noted that the preset central server accesses the temperature and strain distribution data output by the fiber optic analysis server and the cement sheath resistivity data of each measurement node output by the resistivity sensor through the local data interface. It retrieves the fiber optic monitoring discrimination conditions and resistivity discrimination conditions bound to the current cementing stage and compares them one by one according to the corresponding rules of the three preset stages of waiting for the sheath to solidify, construction disturbance, and long-term service. When the two types of monitoring results are inconsistent, the result with lower priority is taken, and finally the cement sheath status identification result corresponding to the current cementing stage is output.

[0054] As a specific example: Distributed sensing optical fibers were wound and fixed to the outer wall of the casing at a 20° helical angle. Simultaneously, measuring electrodes were integrated and installed at the mid-span of the casing to ensure good electrical contact with the cement sheath. Subsequently, a resistivity-sensing cement slurry was prepared and injected into the annulus. The basic formula for the cement slurry was: 800g of Grade G cement + 2% G33S water loss reducer + 4% SCFP-H elastic material + 42% water. 3% carbon fiber was uniformly incorporated into this formula as a conductive material. After the cement slurry had set and formed a complete cement sheath, circulating internal pressure was applied inside the casing to simulate formation fluid flow conditions. During this period, continuous monitoring was conducted using a distributed optical fiber monitoring system and a resistivity monitoring system. The results of this case are as follows: (1) The distributed optical fiber monitoring system monitored the temperature change during the cement solidification process and identified the cementing quality.

[0055] (2) The distributed optical fiber monitoring system realizes high-precision continuous monitoring of the strain at the sleeve-cement ring interface.

[0056] (3) The resistivity monitoring system detected the change in cement sheath resistivity over time from the start of the setting period, and can accurately identify crossflow events. When the formation is invaded by undersaturated brine, the resistivity drops sharply; when the formation is invaded by crude oil, the resistivity rises sharply. (See Appendix) Figure 3 .

[0057] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A multi-source information fusion system for monitoring the sealing performance of cement sheaths in well cementing, characterized in that, The system includes: Distributed sensing optical fiber deployed at the sleeve-cement ring interface; transmission optical fiber connected to the distributed sensing optical fiber by fusion splicing; distributed optical fiber sensor installed on the ground and connected to the transmission optical fiber; optical fiber matching analysis server connected to the distributed optical fiber sensor. Multiplexing modules are distributed at intervals along the axial direction of the sleeve and cascaded in series via composite cables, and measurement nodes are set on the multiplexing modules; wherein, the multiplexing modules are connected to the electrodes in the measurement nodes, and the measurement nodes contain a set of electrodes arranged according to the AC four-electrode measurement method; a resistivity sensor set on the ground is connected to the composite cable, and a resistance matching analysis server is connected to the resistivity sensor. The fiber optic analysis server and the resistor analysis server are respectively connected to a preset central server.

2. The cement sheath sealing performance monitoring system based on multi-source information fusion according to claim 1, characterized in that, The distributed sensing fiber optic cable is deployed in a spiral winding arrangement along the axial direction of the sleeve-cement ring interface.

3. The cement sheath sealing performance monitoring system based on multi-source information fusion according to claim 1, characterized in that, The distributed sensing fiber optic cable ends are connected to the transmission fiber optic cable via fusion splicing. The transmission optical fiber extends upwards along the cementing casing string to the wellhead and connects to the optical signal port of the ground-based distributed optical fiber sensor.

4. The cement sheath sealing performance monitoring system based on multi-source information fusion according to claim 1, characterized in that, The multiplexing module is customized into the resistivity sub-section of the cementing system, and / or the multiplexing module is fixed to the outer wall of the cementing casing by clamps; wherein the resistivity sub-section is threaded to the casing string.

5. The cement sheath sealing performance monitoring system based on multi-source information fusion according to claim 1, characterized in that, Each measurement node contains a set of electrodes arranged according to the AC four-electrode measurement method, and the leads of the four electrodes are respectively connected to the corresponding interface of the same multiplexing module.

6. The cement sheath sealing performance monitoring system based on multi-source information fusion according to claim 1, characterized in that, The multiplexing modules are spaced apart along the axial direction of the bushing. The multiplexing module is equipped with a current and voltage mainline interface and a control mainline interface; The composite cable integrates a pair of current and voltage main lines and a control main line; The multiplexing module is connected to the corresponding main line of the composite cable through the current and voltage main line interface and the control main line interface, so that the composite cable can be cascaded with the multiplexing module in series.

7. A method for monitoring the sealing performance of cement sheaths using multi-source information fusion, applied to the multi-source information fusion cement sheath sealing monitoring system described in claim 1, characterized in that, The method includes: The optical signal is emitted by the distributed optical fiber sensor, enters the distributed sensing optical fiber through the transmission optical fiber, and the backscattered signal generated at various positions of the sensing optical fiber is received by the distributed optical fiber sensor. The temperature and strain distribution along the optical fiber path is obtained by the optical fiber matching analysis server. The measurement node to be measured is determined based on the address code of the multiplexing module corresponding to the measurement node; the resistance matching analysis server sends an addressing command with address code through the control main line in the composite cable, the internal switch of the selected multiplexing module is closed, and the local electrode is connected to the current measurement loop; the resistivity sensor supplies power to the electrode through the current and voltage main line and collects the voltage signal to calculate the resistivity of the cement ring at the measurement node. By acquiring temperature and strain distribution, measuring the resistivity of cement sheath at the cementing node, and the corresponding fiber optic monitoring and resistivity discrimination conditions for the current cementing stage through a preset central server, the state of the cementing cement sheath in the current cementing stage can be identified.

8. The method for monitoring the sealing performance of cement sheaths by multi-source information fusion according to claim 7, characterized in that, By acquiring temperature and strain distribution data, measuring the resistivity of the cement sheath at the cementing node, and using a pre-set central server, along with the corresponding fiber optic monitoring and resistivity discrimination conditions for the current cementing stage, the state of the cement sheath at the current cementing stage is identified. Specifically, this includes: When the well cementing is in the solidification and ring-forming stage, if the temperature rises by a preset first temperature range, the cementing quality is determined to be good; otherwise, the cementing quality is determined to be poor. When the resistivity increases by a magnitude greater than the preset first resistance, the cementing quality is determined to be good. When the resistivity increases or decreases by a factor less than the preset second resistance magnitude, the cementing quality is determined to be poor; the preset second resistance magnitude is less than the preset first resistance magnitude; otherwise, the cementing quality is determined to be medium. When the cementing quality corresponding to temperature is inconsistent with the cementing quality corresponding to resistivity, the worst cementing quality result shall be taken as the state of the cement sheath. If all conditions are met, the current cementing quality is determined to be good; otherwise, the cementing quality is poor.

9. The method for monitoring the sealing performance of cement sheaths by multi-source information fusion according to claim 7, characterized in that, By acquiring temperature and strain distribution data, measuring the resistivity of the cement sheath at the cementing node, and using a pre-set central server, along with the corresponding fiber optic monitoring and resistivity discrimination conditions for the current cementing stage, the state of the cement sheath at the current cementing stage is identified. Specifically, this includes: During the construction disturbance phase, after each internal pressure unloading, if any strain distribution obtained shows a sudden increase or temperature fluctuation exceeds the preset fluctuation range, the cement sheath state is determined to be a cement sheath state seal failure. When the resistivity undergoes a step change, the cement sheath state is determined to be a cement sheath state seal failure. Otherwise, the cement sheath condition is confirmed to be a cement sheath condition and the seal has not failed.

10. The method for monitoring the sealing performance of cement sheaths by multi-source information fusion according to claim 7, characterized in that, By acquiring temperature and strain distribution data, measuring the resistivity of the cement sheath at the cementing node, and using a pre-set central server, along with the corresponding fiber optic monitoring and resistivity discrimination conditions for the current cementing stage, the state of the cement sheath at the current cementing stage is identified. Specifically, this includes: When the well cement sheath is in long-term service, if the strain distribution shows a trend of increasing or decreasing within the preset monitoring time period, or if the strain distribution is not in the preset normal distribution range, the well cement sheath condition is determined to be cement sheath sealing failure. When the resistivity shows a trend of increasing or decreasing within a preset monitoring period, or when the resistivity is not within a preset normal value range, the cement sheath condition is determined to be a cement sheath seal failure. Otherwise, the cement sheath condition is confirmed to be a cement sheath condition and the seal has not failed.

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