Well cementation cement sheath detection device and method

Abstract

The embodiment of the invention provides a well cementation cement sheath detection device and method. Relates to the technical field of oil-gas exploitation. The well cementation cement sheath detection device comprises a kettle body, a simulation surrounding rock, a sleeve, a sound wave detection assembly, a stress detection assembly, a pore pressure detection assembly and an axial displacement detection assembly. The sleeve is arranged in the simulated surrounding rock, a cement cavity is formed between the sleeve and the simulated surrounding rock, and the cement cavity is used for being filled with cement paste to form a cement sheath; the sound wave detection assembly is used for emitting sound waves towards the cement sheath so as to detect the internal solid-liquid proportion and settlement density change of the cement sheath in the solidification stage; the stress detection assembly is used for detecting internal stress of the cement sheath; the pore pressure detection assembly is used for detecting the pore pressure of the cement sheath in the solidification stage; the axial displacement detection assembly applies pressure to the cement sheath and detects the axial displacement of the cement sheath. The device is used for more comprehensively detecting the state of the well cementation cement sheath.

Description

Technical Field

[0001] This application relates to the field of oil and gas extraction technology, and in particular to a cement sheath detection device and method. Background Technology

[0002] In the process of oil and gas resource extraction, cementing is a core step in ensuring the integrity and sealing of the wellbore during well construction. As a critical barrier medium between the casing and the formation, the cement sheath must continuously withstand the combined effects of complex formation stress, drastic temperature and pressure fluctuations, and long-term erosion by formation fluids throughout the entire service life of the wellbore.

[0003] In related technologies, the main monitoring methods for initial stress in cement sheaths include cement bond logging and variable density logging. Cement bond logging evaluates the bonding quality of the first interface by measuring the amplitude of the casing wave; a lower amplitude indicates better bonding. Variable density logging and cement bond logging simultaneously record the entire wave train, and the relative energy of the casing wave and formation wave is used to further determine the bonding condition of the second interface.

[0004] However, existing detection methods are too simplistic, resulting in limited detection capabilities for cement sheaths in well cementing. Summary of the Invention

[0005] This application provides a cement sheath detection device and method to solve the problem of limited detection capabilities for cement sheaths.

[0006] In a first aspect, embodiments of this application provide a cement sheath testing device, comprising: a vessel body,

[0007] Simulated surrounding rock is provided inside the vessel body, and a confining pressure cavity is formed between the simulated surrounding rock and the vessel body;

[0008] A casing is disposed within the simulated surrounding rock, and a cement cavity is formed between the casing and the simulated surrounding rock. The cement cavity is filled with cement slurry to form a cement ring.

[0009] An acoustic wave detection component is disposed inside the reactor body. The acoustic wave detection component is used to emit acoustic waves toward the cement ring to detect changes in the solid-liquid ratio and settling density inside the cement ring during the solidification stage.

[0010] A stress detection component is disposed inside the cement ring and is used to detect the internal stress of the cement ring.

[0011] A pore pressure detection component is disposed inside the cement ring and is used to detect the pore pressure during the solidification stage of the cement ring.

[0012] An axial displacement detection component is connected to the cement ring, the axial displacement detection component applies pressure toward the cement ring, and detects the axial displacement of the cement ring.

[0013] In one possible implementation, the acoustic detection assembly includes an acoustic transmitter and an acoustic receiver. The acoustic transmitter is disposed inside the sleeve and emits acoustic waves toward the cement ring. The acoustic receiver is sleeved on the simulated surrounding rock and is used to receive the acoustic waves emitted by the acoustic transmitter.

[0014] In one possible implementation, the stress detection assembly includes a detection plate and a plurality of first monitoring optical fibers. The detection plate is sleeved on the outer wall of the sleeve, and the first monitoring optical fibers are disposed inside the cement ring for detecting stress within the cement ring.

[0015] In one possible implementation, the first monitoring optical fiber extends along the axial direction of the cement ring, and the included angle between adjacent first monitoring optical fibers on the same circumference is greater than or equal to 30° and less than or equal to 60°.

[0016] In one possible implementation, the pore pressure detection assembly includes a filter tube and a second monitoring optical fiber. The filter tube is disposed inside the cement ring and is used to filter the liquid in the cement slurry during the initial stage of cement ring casting. The second monitoring optical fiber is disposed inside the filter tube to detect the pore pressure of the cement ring.

[0017] In one possible implementation, the axial displacement detection assembly includes a press and a pressure block, the pressure block abutting against the top of the cement ring, the pressure block having a clearance opening, the sleeve being located within the clearance opening, and the press being connected to the pressure block to provide circumferential pressure to the cement ring.

[0018] In one possible implementation, the vessel body includes a vessel cylinder, an upper vessel cover, a lower vessel cover, and a pressure member. The upper vessel cover covers the top of the vessel cylinder, the lower vessel cover covers the bottom of the vessel cylinder, and the pressure member is connected to the lower vessel cover. The pressure member provides preset pressure to the confining pressure cavity and the interior of the sleeve, respectively.

[0019] In one possible implementation, the cement sheath detection device further includes a temperature control component, which includes a temperature detector and a heating element. Both the heating element and the temperature detector are disposed within the confining pressure chamber to simulate formation temperature. The temperature detector is used to detect the temperature within the confining pressure chamber.

[0020] In one possible implementation, the cement sheath detection device further includes a data acquisition component, which is communicatively connected to the acoustic wave detection component, the stress detection component, the pore pressure detection component, and the axial displacement detection component.

[0021] Secondly, embodiments of this application provide a method for detecting the initial stress of cement sheath in well cementing, using the aforementioned well cement sheath detection device, the method comprising:

[0022] First, the casing and simulated surrounding rock are installed in the reactor body, forming a cement cavity between the casing and the simulated surrounding rock. Then, the acoustic wave detection component is installed in the reactor body, and the pore pressure detection component and stress detection component are both set in the cement cavity.

[0023] Cement slurry is injected into the cement cavity to form a cement ring. After the cement slurry injection is completed, the axial displacement detection component is installed on the top of the vessel body and abuts against the cement ring, and the vessel body is sealed.

[0024] The cement ring is subjected to hydrostatic pressure by an axial displacement detection component, and the cement slurry is cured for a specified time until the cement ring is formed. During the curing period, the axial displacement of the axial displacement detection component is monitored in real time. The stress, strain and pore pressure of the cement ring during the solidification stage are monitored by the stress detection component and the pore pressure detection component. The solid-liquid ratio and density change inside the cement ring during the solidification stage are monitored in real time by the acoustic wave detection component.

[0025] This application provides a cement sheath testing device and method. A confining pressure cavity is formed by an apparatus and simulated surrounding rock, and a cement cavity is formed by a casing and simulated surrounding rock. An acoustic detection component is installed inside the apparatus to detect changes in the solid-liquid ratio and settling density within the cement sheath during its solidification stage. Stress and pore pressure detection components are installed within the cement sheath to detect internal stress and pore pressure during solidification. An axial displacement detection component applies axial pressure towards the cement sheath to detect its axial displacement. Through quantitative inversion of acoustic velocity, attenuation, and dispersion characteristics, the solid-liquid ratio and settling density distribution of the cement slurry during its transition from a suspended to a solid state are dynamically analyzed. A hydraulic press simultaneously applies an axial load and records the displacement curve in real time, directly mapping the displacement to the axial shrinkage of the cement sheath, thus comprehensively depicting its morphological changes throughout the solidification process. This allows for a more comprehensive detection of the cement sheath's condition, improving the accuracy and completeness of the data. Attached Figure Description

[0026] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0027] Figure 1 A schematic diagram of the cement sheath detection device provided in this application;

[0028] Figure 2 for Figure 1 A top view of the simulated surrounding rock.

[0029] Explanation of reference numerals in the attached figures:

[0030] 100. Vessel body; 110. Vessel cylinder; 120. Upper vessel cover; 130. Lower vessel cover; 140. Pressure component; 141. Gas cylinder; 142. First air inlet pipe; 143. First pressure gauge; 144. First regulating valve; 145. Second air inlet pipe; 146. Second pressure gauge; 147. Second regulating valve; 150. Insulation sleeve; 160. Sealing component;

[0031] 200. Simulated surrounding rock; 210. Confining pressure cavity;

[0032] 300, sleeve; 310, cement cavity; 320, cement ring;

[0033] 400. Acoustic wave detection component; 410. Acoustic wave transmitter; 420. Acoustic wave receiver;

[0034] 500. Stress detection assembly; 510. Detection plate; 520. First monitoring optical fiber;

[0035] 600. Pore pressure detection assembly; 610. Filter tube; 620. Second monitoring optical fiber;

[0036] 700. Axial displacement detection assembly; 710. Press; 720. Pressure block;

[0037] 800. Temperature control component; 810. Temperature detector; 820. Heating element;

[0038] 900. Data acquisition components.

[0039] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0040] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0041] Definition: Interface 1: The contact interface between the cement ring and the outer wall of the casing.

[0042] Second interface: The contact interface between the cement sheath and the surrounding rock of the formation (or well wall).

[0043] In the extraction of oil and gas resources, cementing operations are a crucial step in ensuring the integrity and sealing of the wellbore. As a vital medium between the casing and the formation, the cement sheath must withstand complex stresses from the formation and resist the effects of temperature, pressure variations, and fluid erosion. Its integrity directly impacts the long-term safe and stable production of oil and gas wells. Failure of the cement sheath can lead to serious problems such as oil and gas leaks, annular pressure buildup, and casing damage. This can result in decreased oil and gas production, increased extraction costs, and potential environmental pollution, causing significant economic losses and safety hazards.

[0044] Current monitoring methods for initial stress in cement sheaths have several shortcomings. Regarding stress-strain monitoring, most existing methods only focus on the first and second interfaces of the cement sheath, neglecting the internal stress-strain state during the setting period. The stress-strain conditions within the cement sheath during setting are complex and significantly impact its final performance; the lack of internal monitoring prevents a comprehensive understanding of the cement sheath's formation process and potential defects. Regarding solid-liquid ratio monitoring, existing methods lack coverage of this ratio during the setting period. The solid-liquid ratio changes continuously during setting, closely related to the initial stress and directly affecting the mechanical properties and integrity of the cement sheath. Without monitoring the solid-liquid ratio, it's difficult to delve into its intrinsic relationship with initial stress, hindering the development of a strong basis for cement sheath performance optimization. Finally, regarding the influence of cement sheath density, existing methods do not adequately consider the settling effect during setting. During setting, particle settling and other factors lead to uneven cement sheath density, significantly impacting its integrity; ignoring this settling effect... The uneven density leads to discrepancies between the assessment of initial stress in the cement sheath and the actual situation. Regarding the impact of cement sheath morphology changes, related technologies lack consideration of axial shrinkage during cement sheath solidification. Axial shrinkage occurs during cement sheath solidification, altering the interaction between the cement sheath and the casing and formation, thus affecting the distribution of initial stress. The lack of research on axial shrinkage makes it impossible to accurately grasp the changes in the mechanical behavior of the cement sheath throughout the solidification process. In terms of pore pressure monitoring, related technologies do not address pore pressure monitoring during the cement slurry solidification stage. Pore pressure changes continuously during cement slurry solidification, significantly influencing the strength development and initial stress formation of the cement sheath. Without pore pressure monitoring, it is impossible to fully understand the formation mechanism of initial stress in the cement sheath, making it difficult to formulate targeted measures to improve the quality and stability of the cement sheath.

[0045] This application provides a cement sheath testing device and method. A confining pressure cavity is formed by an apparatus and simulated surrounding rock, and a cement cavity is formed by a casing and simulated surrounding rock. An acoustic detection component is installed inside the apparatus to detect changes in the solid-liquid ratio and settling density within the cement sheath during its solidification stage. Stress and pore pressure detection components are installed within the cement sheath to detect internal stress and pore pressure during solidification. An axial displacement detection component applies axial pressure towards the cement sheath to detect its axial displacement. Through quantitative inversion of acoustic velocity, attenuation, and dispersion characteristics, the solid-liquid ratio and settling density distribution of the cement slurry during its transition from a suspended to a solid state are dynamically analyzed. A hydraulic press simultaneously applies an axial load and records the displacement curve in real time, directly mapping the displacement to the axial shrinkage of the cement sheath, thus comprehensively depicting its morphological changes throughout the solidification process. This allows for a more comprehensive detection of the cement sheath's condition, improving the accuracy and completeness of the data.

[0046] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0047] This application provides a cement sheath testing device for testing cement sheaths in a laboratory, thereby gaining a comprehensive understanding of parameters such as the initial stress and strain of the cement sheath, and providing experimental basis for the mixing ratio of cement sheaths and cement slurry.

[0048] This application provides a cement sheath detection device, referring to... Figure 1 The cement sheath testing device includes: a vessel body 100, a simulated surrounding rock 200, a casing 300, an acoustic detection component 400, a stress detection component 500, a pore pressure detection component 600, and an axial displacement detection component 700.

[0049] The simulated surrounding rock 200 is placed inside the vessel body 100, and a confining pressure cavity 210 is formed between the simulated surrounding rock 200 and the vessel body 100. The confining pressure cavity 210 is used to provide the pressure, temperature and other conditions inside the well to simulate the setting conditions of the cement sheath 320.

[0050] The casing 300 is set inside the simulated surrounding rock 200, and a cement cavity 310 is formed between the casing 300 and the simulated surrounding rock 200. The cement cavity 310 is filled with cement grout to form a cement ring 320.

[0051] The acoustic detection component 400 is installed inside the vessel body 100. The acoustic detection component 400 is used to emit acoustic waves toward the cement ring 320 to detect the changes in the solid-liquid ratio and sedimentation density inside the cement ring 320 during the solidification stage.

[0052] The stress detection component 500 is installed inside the cement ring 320 and is used to detect the internal stress of the cement ring 320.

[0053] A pore pressure detection component 600 is installed inside the cement ring 320. The pore pressure detection component 600 is used to detect the pore pressure during the solidification stage of the cement ring 320.

[0054] The axial displacement detection component 700 is connected to the cement ring 320. The axial displacement detection component 700 applies axial pressure toward the cement ring 320 and detects the axial displacement of the cement ring 320.

[0055] First, regarding stress-strain and pore pressure monitoring, a stress detection component 500 is placed inside the cement ring 320 to achieve real-time and continuous monitoring of the total internal stress during the setting stage of the cement ring 320. Second, regarding solid-liquid ratio and sedimentation effect monitoring, an acoustic wave detection component 400 is used to analyze the propagation speed and attenuation characteristics of acoustic waves inside the cement ring 320, enabling quantitative detection of changes in the solid-liquid ratio and sedimentation density during the setting stage of the cement ring 320. Third, regarding morphological changes in the cement ring 320, the axial displacement is monitored in real-time during pressurization using an axial displacement detection component 700. This displacement is used as the axial shrinkage during cement slurry solidification, thus accurately obtaining information on axial shrinkage during the cement ring 320's solidification process. Finally, regarding pore pressure monitoring, a pore pressure detection component 600 is installed inside the cement ring 320 to achieve precise measurement of the pore pressure during the cement ring 320's solidification stage.

[0056] For example, refer to Figure 1 The vessel body 100 includes a vessel cylinder 110, an upper vessel cover 120, a lower vessel cover 130, and a pressure member 140. The upper vessel cover 120 covers the top of the vessel cylinder 110, and the lower vessel cover 130 covers the bottom of the vessel cylinder 110. The pressure member 140 is connected to the lower vessel cover 130, and the pressure member 140 provides preset pressure to the confining pressure chamber 210 and the interior of the sleeve 300, respectively.

[0057] The vessel 110 is a cylindrical container with open ends. An upper lid 120 covers the top of the vessel 110, sealing the top opening, while a lower lid 130 covers the bottom, sealing the bottom opening. Simulated surrounding rock 200 is located inside the vessel 110 and coaxially aligned with it. A gap exists between the simulated surrounding rock 200 and the vessel 110, forming a confining pressure cavity 210. A sleeve 300 is fixed inside the simulated surrounding rock 200 and coaxially aligned with it, forming a cement cavity 310 between them. Cement grout is poured into the cement cavity 310 to obtain a cement ring 320.

[0058] Of course, in other examples, the vessel 110 can also be set to other shapes such as square.

[0059] The pressure component 140 may include a gas cylinder 141, a first air inlet pipe 142, a first pressure gauge 143, and a first regulating valve 144. The first air inlet pipe 142 extends through the lower cover 130 into the sleeve 300. The first pressure gauge 143 is installed on the first air inlet pipe 142 to detect the gas pressure inside the sleeve 300. The first air inlet pipe 142 is connected to the gas cylinder 141 to pressurize the sleeve 300, thereby simulating the pressure inside the sleeve 300. The first regulating valve 144 is installed on the first air inlet pipe 142 to regulate the pressure.

[0060] The first regulating valve 144 can be a pressure boosting or depressurizing valve.

[0061] For example, the pressure component 140 may further include a second air inlet pipe 145, a second pressure gauge 146, and a second regulating valve 147. The second air inlet pipe 145 is connected to the gas cylinder 141, and its other end extends through the lower cap 130 into the confining pressure chamber 210 to provide simulated wellbore pressure to the simulated surrounding rock 200. The second pressure gauge 146 is mounted on the second air inlet pipe 145 to detect the pressure within the confining pressure chamber 210, and the second regulating valve 147 is mounted on the second air inlet pipe 145 to regulate the pressure within the confining pressure chamber 210.

[0062] The second regulating valve 147 can be a pressure boosting or depressurizing valve.

[0063] For example, the pressure component 140 can also be communicatively connected to the data acquisition component 900. That is, the first regulating valve 144, the first pressure gauge 143, the second regulating valve 147, and the second pressure gauge 146 are all communicatively connected to the data acquisition component 900 so as to control the pressure in the confining pressure chamber 210 and the sleeve 300 through the data acquisition component 900.

[0064] For example, the lower vessel cover 130 is sealed to the vessel cylinder 110, the simulated surrounding rock 200, and the sleeve 300. A sealing element 160 is provided between the lower vessel cover 130 and the vessel cylinder 110, the simulated surrounding rock 200, and the sleeve 300 to improve the sealing effect. The sealing element 160 can be a rubber sealing ring.

[0065] For example, the upper vessel cover 120 is sealed to the vessel cylinder 110, the simulated surrounding rock 200, and the sleeve 300. A sealing element 160 is also provided between the upper vessel cover 120 and the vessel cylinder 110, the simulated surrounding rock 200, and the sleeve 300 to improve the sealing effect. The sealing element 160 can be a rubber sealing ring.

[0066] In one possible implementation, refer to Figure 1 The acoustic wave detection component 400 includes an acoustic wave transmitter 410 and an acoustic wave receiver 420. The acoustic wave transmitter 410 is disposed inside the sleeve 300 and emits acoustic waves toward the cement ring 320. The acoustic wave receiver 420 is sleeved on the simulated surrounding rock 200 and is used to receive the acoustic waves emitted by the acoustic wave transmitter 410.

[0067] The sound wave transmitter 410 is disposed inside the sleeve 300 and emits sound waves circumferentially along the sleeve 300, so that the sound waves cover the entire sleeve 300. The sound wave receiver 420 can be a wireless receiver. Multiple sound wave receivers 420 are configured and evenly distributed on the outer wall of the simulated surrounding rock 200 to receive the sound waves emitted by the sound wave transmitter 410.

[0068] By utilizing the propagation characteristics of sound waves in the solid-liquid two-phase medium during the setting stage of cement ring 320: the sound velocity increases with the increase of the solid skeleton, and the solid-liquid ratio can be directly inverted; the sound wave amplitude attenuation is sensitive to the density gradient and particle sedimentation, and can quantitatively characterize the uneven sedimentation; by continuously transmitting and receiving sound waves and analyzing the arrival time and amplitude changes of the first wave in real time, the evolution of the solid-liquid ratio and the sedimentation density distribution of cement ring 320 throughout the entire setting process can be obtained simultaneously.

[0069] In one possible implementation, refer to Figure 1 and Figure 2 The stress detection component 500 includes a detection piece 510 and a plurality of first monitoring optical fibers 520. The detection piece 510 is sleeved on the outer wall of the sleeve 300, and the first monitoring optical fibers 520 are disposed inside the cement ring 320. The first monitoring optical fibers 520 are used to detect the stress inside the cement ring 320.

[0070] For example, multiple strain gauges 510 are configured, and the strain gauges 510 are sleeved on the sleeve 300 to detect changes in stress and strain at the interface of the cement ring 320. The strain gauges 510 are wireless strain gauges. The wireless strain gauges are evenly distributed on the outer wall of the sleeve 300 to detect stress changes at the interface of the cement ring 320.

[0071] Among them, the wireless stress strain gauge attaches a resistance strain gauge to the surface of the object being measured. When the object is deformed under stress, the resistance changes according to ΔR / R=Kε. The voltage output by the Wheatstone bridge is digitized and then wirelessly uploaded via radio frequency or WiFi. The system uses σ=Eε to invert the stress in real time, realizing long-term monitoring without wiring.

[0072] Among them, the first monitoring fiber 520 is a stress-strain monitoring fiber used to detect changes in stress and strain inside the cement ring 320. The stress-strain monitoring fiber utilizes the principle of fiber grating (FBG) or distributed scattering (such as Brillouin or Rayleigh scattering): when the fiber deforms with the structure, its grating pitch or the spacing of its scattering points changes, causing the wavelength or phase of the reflected / scattered light to drift proportionally to the strain; the demodulator captures this spectral change in real time and directly converts it into the stress-strain distribution along the fiber according to the calibration coefficient, realizing continuous wireless monitoring with millimeter-level spatial resolution and kilometer-level range.

[0073] In one possible implementation, the first monitoring fiber 520 extends along the axial direction of the cement ring 320, and the included angle between adjacent first monitoring fibers 520 on the same circumference is greater than or equal to 30° and less than or equal to 60°.

[0074] The first monitoring optical fiber 520 is evenly distributed circumferentially along the cross-section of the cement ring 320, and multiple turns are arranged along the diameter of the cement ring 320, thereby forming a monitoring grid for more comprehensive detection of the initial stress change of the cement ring 320.

[0075] By arranging the first monitoring optical fiber 520 distributed at equal angles along the circumference inside the cement ring 320, a full circumferential detection structure is constructed to monitor the total internal stress and pore pressure of the cement ring 320 during the solidification stage from multiple directions. Specifically, this includes circumferential and radial stress and strain data and dynamic changes in pore pressure at different directions inside the cement ring 320.

[0076] For example, refer to Figure 2 The included angle α between adjacent first monitoring optical fibers 520 on the same circumference of the cement ring 320 can be 30°, 45°, or 60°.

[0077] In one possible implementation, refer to Figure 1 and Figure 2 The pore pressure detection component 600 includes a filter tube 610 and a second monitoring optical fiber 620. The filter tube 610 is disposed inside the cement ring 320 and is used to filter the liquid in the cement slurry during the initial stage of cement ring 320 pouring. The second monitoring optical fiber 620 is disposed inside the filter tube 610 to detect the pore pressure of the cement ring 320.

[0078] The filter tube 610 has pores on its surface to filter solids in the cement slurry. During the setting stage, the liquid in the cement slurry enters the filter tube 610 and comes into contact with the second monitoring optical fiber 620.

[0079] The filter tube 610 blocks solid particles from the cement slurry, allowing only pore liquid to enter. Inside the tube, a second monitoring optical fiber 620 (typically an FBG or distributed optical fiber) directly senses the pressure of this liquid, converting changes in grating wavelength or scattering phase into pore pressure values ​​in real time. This enables continuous, in-situ measurement of the pore pressure inside the cement ring 320 during the setting stage, achieving precise measurement of the pore pressure during the cement slurry's setting stage.

[0080] In one possible implementation, the axial displacement detection assembly 700 includes a press 710 and a pressure block 720. The pressure block 720 abuts against the top of the cement ring 320. The pressure block 720 is provided with a clearance opening, and the sleeve 300 is located in the clearance opening. The press 710 is connected to the pressure block 720 to provide circumferential pressure to the cement ring 320.

[0081] The upper cover has a mounting groove through which a pressure block 720 passes and abuts against the cement ring 320. The pressure block 720 is an annular block to provide axial pressure to the cement ring 320. By changing the pressure of the pressure block 720, the compression conditions of the cement ring 320 at different heights can be simulated. The pressure block 720 is connected to a press 710, which provides pressure to the pressure block 720 and records the displacement of the pressure block 720 as the axial shrinkage of the cement ring 320.

[0082] For example, the press 710 can be a hydraulic press. During the solidification process, the cement slurry undergoes axial shortening due to hydration shrinkage and the formation of a cement skeleton. In the experiment, the hydraulic press first applies a constant reference axial force to keep the press block 720 in contact with the top of the cement ring 320; as the cement slurry gradually solidifies and undergoes volume shrinkage, the top of the cement ring 320 will move slightly downward. The displacement sensor on the hydraulic press records this minute displacement in real time. Since the external load remains constant, the measured displacement corresponds exactly to the axial shrinkage of the cement slurry during solidification, thus allowing the axial deformation during the setting stage to be obtained in situ without additional unloading.

[0083] In one possible implementation, the cement sheath detection device further includes a temperature control component 800, which includes a temperature detector 810 and a heating element 820. Both the heating element 820 and the temperature detector 810 are disposed within the confining pressure chamber 210. The heating element 820 is used to heat the confining pressure chamber 210 to simulate the formation temperature, and the temperature detector 810 is used to detect the temperature within the confining pressure chamber 210.

[0084] For example, the heating element 820 and the temperature detector 810 are electrically connected to the data acquisition unit 900, and the data acquisition unit 900 controls the temperature inside the confining pressure chamber 210 through the heating element 820.

[0085] The temperature detector 810 can be a temperature sensor, which is located at the top of the confining pressure chamber 210. The heating element 820 can be an electric heating rod, which is located at the bottom of the confining pressure chamber 210. The heating element 820 heats the confining pressure chamber 210 to simulate the high-temperature environment downhole, thereby obtaining more accurate experimental data. The data acquisition unit 900 can be a controller, computer, etc., to control the temperature inside the confining pressure chamber 210.

[0086] For example, an insulation sleeve 150 is also fitted onto the outer wall of the vessel cylinder 110 to improve the insulation effect of the vessel cylinder 110. The insulation sleeve 150 can be a foam sleeve, a plastic sleeve, etc.

[0087] In one possible implementation, the cement sheath detection device further includes a data acquisition unit 900, which is communicatively connected to the acoustic wave detection component 400, the stress detection component 500, the pore pressure detection component 600, and the axial displacement detection component 700.

[0088] The data acquisition unit 900 can be a computer. The data acquisition unit 900 is connected to the first monitoring optical fiber 520, the second monitoring optical fiber 620, the press 710, the acoustic receiver 420, and the stress strain gauge to receive various detection information.

[0089] This application provides a method for detecting the initial stress of cement sheath in well cementing, using the aforementioned well cement sheath detection device. The method includes:

[0090] 1. First, install the casing 300 and simulated surrounding rock 200 inside the vessel body 100, forming a cement cavity 310 between the casing 300 and the simulated surrounding rock 200. Then, install the acoustic wave detection component 400 inside the vessel body 100, and set the pore pressure detection component 600 and the stress detection component 500 inside the cement cavity 310.

[0091] Specifically, according to the experimental requirements, the sleeve 300, filter tube 610, simulated surrounding rock 200 and vessel cylinder 110 are first installed on the lower vessel cover 130 after the sealing element 160 is placed on them. Then, wireless stress strain gauges are installed at equal intervals on the outer wall of the sleeve 300. Next, wireless acoustic receivers 420 are installed at equal intervals on the outer wall of the simulated surrounding rock 200. Then, the first monitoring optical fiber 520 is distributed at equal angles along the circumference. When arranged, the phase difference between adjacent first monitoring optical fibers 520 is 60°.

[0092] 2. Inject cement slurry into cement cavity 310 to form cement ring 320. After the cement slurry is injected, install axial displacement detection component 700 on top of vessel body 100 to abut against cement ring 320 and seal vessel body 100.

[0093] Specifically, the cement slurry is prepared according to the oil well cement test specifications. The cement slurry is then injected into the cement chamber 310. The amount of cement slurry injected is determined according to the experimental requirements. After the cement slurry is injected, the upper vessel cover 120 is installed on top of the vessel cylinder 110 after the sealing element 160 is placed on it. Then, the pressure block 720 of the press 710 is placed on top of the sealing element 160 and abuts against the cement ring 320 to provide pressure to the cement ring 320. Finally, the heat insulation sleeve 150 is installed on the outside of the vessel body 100.

[0094] 3. Apply hydrostatic pressure to the cement ring 320 using the axial displacement detection component 700, and cure the cement slurry for a specified time until the cement ring 320 is formed. During the curing period, monitor the axial displacement of the axial displacement detection component 700 in real time, and monitor the stress, strain and pore pressure of the cement ring 320 during the solidification stage using the stress detection component 500 and the pore pressure detection component 600. Also, monitor the solid-liquid ratio and density changes inside the cement ring 320 during the solidification stage in real time using the acoustic wave detection component 400.

[0095] Specifically, the electric heating rod is powered on and its temperature is adjusted to reach the temperature required for the experiment (i.e., the preset downhole temperature). After the temperature stabilizes, pressure is applied to the confining pressure chamber 210 through the second air inlet pipe 145. The second pressure gauge 146 is observed. When the confining pressure required for the experiment is reached, the second regulating valve 147 is closed, and pressure is applied to the inner cavity of the casing 300. The first pressure gauge 143 is observed. When the inner pressure of the casing 300 required for the experiment is reached, the first regulating valve 144 is closed. Then, according to the on-site working conditions, the hydrostatic column pressure is applied using the press 710.

[0096] The cement slurry is cured for the time specified in the standard until a cement ring 320 is formed. During the curing period, the axial displacement of the press 710 is monitored in real time. The stress, strain and pore pressure of the cement ring 320 during the solidification process are monitored in real time through the first monitoring optical fiber 520 and the data acquisition device 900. At the same time, the stress and strain of one interface of the cement ring 320 during the solidification process are monitored in real time through the wireless stress and strain gauge and the data acquisition device 900. The solid-liquid ratio and density change of the cement ring 320 during the solidification process are monitored in real time through the acoustic transmitter 410, the wireless acoustic receiver 420 and the data acquisition device 900.

[0097] After the experiment is completed, adjust the first regulating valve 144 and the second regulating valve 147 to release the internal pressure of the sleeve 300 and the internal pressure of the confining chamber 210, remove the upper cover 120, clean out the cement ring 320, clean the experimental equipment, and complete the experiment.

[0098] This application provides a method for detecting cement sheaths in well cementing. A confining pressure cavity 210 is formed by an apparatus 100 and simulated surrounding rock 200, and a cement cavity 310 is formed by a casing 300 and simulated surrounding rock 200. An acoustic detection component 400 is installed inside the apparatus 100 to detect changes in the solid-liquid ratio and settling density of the cement sheath 320 during its solidification stage. A stress detection component 500 and a pore pressure detection component 600 are installed inside the cement sheath 320 to detect the internal stress and pore pressure of the cement sheath 320 during its solidification stage. An axial displacement detection component 700 applies axial pressure towards the cement sheath 320 to detect its axial displacement. Through quantitative inversion of acoustic velocity, attenuation, and dispersion characteristics, the solid-liquid ratio and settling density distribution of the cement slurry during its transition from a suspended to a solid state are dynamically analyzed. The hydraulic press synchronously applies axial load and records displacement curves in real time, directly mapping the displacement to the axial shrinkage of cement ring 320, thus fully depicting the morphological changes throughout the solidification process. This allows for a more comprehensive detection of the state of cement ring 320, improving the accuracy and comprehensiveness of the data.

[0099] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A cement sheath detection device, characterized in that, include: The vessel body (100), Simulated surrounding rock (200) is disposed inside the vessel body (100), and a confining pressure cavity (210) is formed between the simulated surrounding rock (200) and the vessel body (100); A casing (300) is disposed within the simulated surrounding rock (200), and a cement cavity (310) is formed between the casing (300) and the simulated surrounding rock (200). The cement cavity (310) is filled with cement slurry to form a cement ring (320). An acoustic wave detection component (400) is disposed inside the vessel body (100). The acoustic wave detection component (400) is used to emit acoustic waves toward the cement ring (320) to detect the changes in the solid-liquid ratio and sedimentation density inside the cement ring (320) during the solidification stage. A stress detection component (500) is disposed inside the cement ring (320) and is used to detect the internal stress of the cement ring (320). A pore pressure detection component (600) is disposed inside the cement ring (320) and is used to detect the pore pressure of the cement ring (320) during the solidification stage. An axial displacement detection component (700) is connected to the cement ring (320). The axial displacement detection component (700) applies axial pressure toward the cement ring (320) and detects the axial displacement of the cement ring (320).

2. The cement sheath detection device according to claim 1, characterized in that, The acoustic wave detection component (400) includes an acoustic wave transmitter (410) and an acoustic wave receiver (420). The acoustic wave transmitter (410) is disposed inside the sleeve (300) and emits acoustic waves toward the cement ring (320). The acoustic wave receiver (420) is sleeved on the simulated surrounding rock (200) and is used to receive the acoustic waves emitted by the acoustic wave transmitter (410).

3. The cement sheath detection device according to claim 1, characterized in that, The stress detection assembly (500) includes a detection plate (510) and a plurality of first monitoring optical fibers (520). The detection plate (510) is sleeved on the outer wall of the sleeve (300), and the first monitoring optical fibers (520) are disposed inside the cement ring (320). The first monitoring optical fibers (520) are used to detect the stress inside the cement ring (320).

4. The cement sheath detection device according to claim 3, characterized in that, The first monitoring optical fiber (520) extends along the axial direction of the cement ring (320), and the included angle between adjacent first monitoring optical fibers (520) on the same circumference is greater than or equal to 30° and less than or equal to 60°.

5. The cement sheath detection device according to claim 1, characterized in that, The pore pressure detection component (600) includes a filter tube (610) and a second monitoring optical fiber (620). The filter tube (610) is disposed inside the cement ring (320) and is used to filter the liquid in the cement slurry during the initial stage of the cement ring (320) pouring. The second monitoring optical fiber (620) is disposed inside the filter tube (610) to detect the pore pressure of the cement ring (320).

6. The cement sheath detection device according to claim 1, characterized in that, The axial displacement detection assembly (700) includes a press (710) and a pressure block (720). The pressure block (720) abuts against the top of the cement ring (320). The pressure block (720) is provided with a clearance opening. The sleeve (300) is located inside the clearance opening. The press (710) is connected to the pressure block (720) to provide circumferential pressure to the cement ring (320).

7. The cement sheath testing device according to any one of claims 1-6, characterized in that, The vessel body (100) includes a vessel cylinder (110), an upper vessel cover (120), a lower vessel cover (130), and a pressure component (140). The upper vessel cover (120) covers the top of the vessel cylinder (110), and the lower vessel cover (130) covers the bottom of the vessel cylinder (110). The pressure component (140) is connected to the lower vessel cover (130), and the pressure component (140) provides preset pressure to the confining pressure cavity (210) and the inside of the sleeve (300), respectively.

8. The cement sheath testing device according to any one of claims 1-6, characterized in that, It also includes a temperature control component (800), which includes a temperature detector (810) and a heating element (820). The heating element (820) and the temperature detector (810) are both disposed in the confining pressure cavity (210) to simulate the formation temperature. The temperature detector (810) is used to detect the temperature in the confining pressure cavity (210).

9. The cement sheath testing device according to any one of claims 1-6, characterized in that, It also includes a data acquisition unit (900), which is communicatively connected to the acoustic wave detection component (400), the stress detection component (500), the pore pressure detection component (600), and the axial displacement detection component (700).

10. A method for detecting the initial stress of cement sheath in well cementing, characterized in that, Using the cement sheath testing device as described in any one of claims 1-9, the method comprises: First, the casing (300) and simulated surrounding rock (200) are installed inside the vessel body (100), forming a cement cavity (310) between the casing (300) and the simulated surrounding rock (200). Then, the acoustic wave detection component (400) is installed inside the vessel body (100), and the pore pressure detection component (600) and stress detection component (500) are both placed inside the cement cavity (310). Cement slurry is injected into the cement cavity (310) to form a cement ring (320). After the cement slurry is injected, the axial displacement detection component (700) is installed on the top of the vessel body (100) and abuts against the cement ring (320), and the vessel body (100) is sealed. The cement ring (320) is subjected to hydrostatic pressure by the axial displacement detection component (700), and the cement slurry is cured for a specified time until the cement ring (320) is formed. During the curing period, the axial displacement of the axial displacement detection component (700) is monitored in real time. The stress, strain and pore pressure of the cement ring (320) during the solidification stage are monitored by the stress detection component (500) and the pore pressure detection component (600). The solid-liquid ratio and density change inside the cement ring (320) during the solidification stage are monitored in real time by the acoustic wave detection component (400).

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