Method for determining initial setting time and final setting time of cement through multi-physical field combination

Abstract

The invention discloses a method for measuring initial setting time and final setting time of cement by multi-physical field combination, which comprises the following steps: stirring cement paste at a high speed according to a designed water-cement ratio, and recording the stirring completion time into a data acquisition and processing system; filling the stirred cement paste into a sample cavity of a clamping device; collecting monitoring data of the cement paste in the sample cavity, and calculating acoustic impedance and aspect ratio; calculating the volume resistivity after temperature correction according to the resistance value, and inverting the equivalent porosity; testing data to generate a T2 spectrum, and obtaining total hydrogen signal intensity; identifying and outputting initial setting time and final setting time in the combined change atlas through a data acquisition and processing system; multiple parameters are subjected to overlay analysis according to a unified time axis, and the initial setting time and the final setting time are cooperatively judged through the parameters.

Description

Technical Field

[0001] This invention relates to the field of cement solidification monitoring technology, and in particular to a method for determining the initial setting time and final setting time of cement using a multi-physical field combination. Background Technology

[0002] The hydration and hardening process of cementing from mixing to final setting directly affects the integrity of the wellbore and the sealing quality. The initial setting time and final setting time not only determine whether the cement slurry has the ability to support the casing, form itself, and resist fluid intrusion, but are also core parameters for determining the cement setting time on site and arranging key procedures such as well control and well opening.

[0003] Existing monitoring methods are mostly single-physics-field, decentralized observations. Among them, acoustic methods mainly rely on changes in longitudinal wave velocity, transverse wave velocity, and acoustic impedance to reflect the macroscopic stiffness of cement and the establishment of a rigid skeleton. Electrical methods, through resistivity and porosity inversion, are sensitive to changes in pore connectivity and pore liquid ion concentration. Low-field NMR, on the other hand, characterizes the occurrence state of pore fluid and the transformation process of free water to bound water through T2 spectrum and changes in total hydrogen signal intensity M0. Because the above three types of methods are often deployed and tested independently, not only are the time axes asynchronous and the data difficult to correspond under the same cement age, but any single parameter can only reflect one aspect of the solidification process. This can easily lead to misjudgments of the initial and final setting times due to noise or local anomalies. Especially in the field or under high temperature and high pressure (HPHT) conditions, it is even more difficult to achieve continuous and synchronous observation of the entire process of cement from slurry to final setting, and it is impossible to provide a reliable key time window within the overall framework of rigid skeleton formation-pore structure reconstruction-fluid migration. Summary of the Invention

[0004] (a) Technical issues The purpose of this invention is to provide a method for determining the initial setting time and final setting time of cement using a multi-physics field approach. Under a unified temporal and spatial framework, the method systematically characterizes the coupling relationship between the rigid skeleton structure evolution, pore structure evolution, and pore fluid migration of cement, and achieves quantitative identification of key nodes in the initial and final setting stages.

[0005] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: A method for determining the initial setting time and final setting time of cement using a multi-physics field combined method includes: The cement slurry is mixed at high speed according to the designed water-cement ratio, and the mixing time is recorded. t 0 is recorded in the data acquisition and processing system; The mixed cement slurry is filled into the sample chamber of the HPHT holder, heated to the predetermined temperature, and pressurized to the predetermined pressure. Through the data acquisition and processing system at timet 0 +Δt n During this time, monitoring data was collected on the cement slurry in the sample chamber. The collected monitoring data included the longitudinal wave propagation time. t p (t) transverse wave propagation time t s (t) Resistance value R raw (t) and LF-NMR-CPMG test data; According to longitudinal wave propagation time t p (t) transverse wave propagation time t s (t) Calculate the time separately t 0 +Δt n Time longitudinal wave propagation speed transverse wave propagation speed And calculate the acoustic impedance. Z and aspect ratio / ; Based on resistance value R raw (t) Calculation time t 0 +Δt n Temperature-corrected volume resistivity R(t) The equivalent porosity was inverted using the Archie formula. φ e (t) ; Generated based on LF-NMR-CPMG test data T The total hydrogen signal intensity was obtained by analyzing the two spectra and combining them with the inversion model and peak fitting processing. M 0 (t) ; Generated by the data acquisition and processing system , , Z、 / , R(t), φ e (t), T 2 spectra and M 0 (t) Compared to t The joint change map; The initial solidification time in the combined variation map was identified using a data acquisition and processing system. t initial and final freezing timet final And output it.

[0006] Preferred initial setting time t initial The identification methods include: Identifying joint change maps T The main peak of the spectrum 2 is significantly shifted to the left and the total hydrogen signal intensity is... M 0 (t) The window of time during which the decline accelerates; Identify the volume resistivity in the joint variation spectrum R(t) The minimum value and shear wave velocity that changed from continuous decline to rise The window period during which detection is stable and significantly increased; acoustic impedance Z and aspect ratio / Project onto the aspect ratio-acoustic impedance chart and identify the time window during which the dots migrate from the liquid region to the solid region; The initial freezing time is identified as the point where the three window time periods overlap. t initial .

[0007] Preferred final setting time t final The identification methods include: Identify transverse wave propagation velocity in the joint variation spectrum The increase in acoustic impedance Z approaches zero, and the aspect ratio... / Stable, and the window of time during which the points on the aspect ratio-acoustic impedance chart cluster in the solid region; Identify the volume resistivity in the joint variation spectrum R(t) The rapid increase turned into a slow increase, and the equivalent porosity φ e (t) Gradually changing window time period; Identifying joint change maps T The adjacent waveforms of the two spectra overlap and the total hydrogen signal intensity M 0 (t) A window of time that tends to stabilize; The final freezing time is identified as the point where the three window time periods overlap. t final .

[0008] Preferably, the HPHT holder integrates an ultrasonic probe, a low-field nuclear magnetic resonance coil, and two resistivity electrodes. The ultrasonic probe is used to collect the propagation time of longitudinal and transverse waves in the cement slurry, the low-field nuclear magnetic resonance coil is used to perform LF-NMR-CPMG testing on the cement slurry, and the two resistivity electrodes are used to measure the resistance value of the cement slurry.

[0009] Preferably, acoustic impedance Z and aspect ratio / The calculation methods include: Calculate P-wave velocity ,

[0010] Calculate the shear wave velocity ,

[0011] Calculate acoustic impedance Z , Z= ρ·V p Calculate aspect ratio / , / = /

[0012] in, For longitudinal waves t 0 +Δt n The propagation time in the cement slurry at that time transverse waves t 0 +Δt n The propagation time in the cement slurry is given by ρ, where ρ is the bulk density of the cement slurry. For the zero-delay compensation time of the longitudinal wave, For zero-delay compensation time for shear waves, Δt n This refers to the monitoring interval.

[0013] Preferably, the longitudinal wave zero delay compensation time and shear wave zero delay compensation time The methods for obtaining it include: Measure the effective acoustic path length of the sample cavity; The sample chamber is filled with deionized water with known longitudinal wave reference velocities and transverse wave reference velocities. Multiple longitudinal and transverse waves are emitted toward the sample cavity, and the longitudinal wave test velocity and transverse wave test velocity are obtained respectively. The propagation time is calculated by using the effective sound path length in conjunction with the P-wave test velocity and the P-wave reference velocity to calculate the P-wave zero-delay compensation time. and shear wave zero delay compensation time .

[0014] Preferably, the volume resistivity R(t) and equivalent porosity φ e (t) The calculation methods include: Calculate volume resistivity R(t) ,

[0015] Calculate equivalent porosity φ e (t) ,

[0016] in, The electrode constant is... For temperature coefficient, for t 0 +Δt n The resistivity of the cement grout at that time R w for t The original resistivity of cement slurry at 0°C, empirical coefficient ≈1.0, cementation index m≈2.0, Δt n This refers to the monitoring interval.

[0017] Preferably, the blank resistance value when there is no sample in the sample chamber. Electrode constant K and temperature coefficient The methods for obtaining the blank resistance value include: measuring the resistance between two resistivity electrodes when the sample chamber is empty. The sample chamber is filled with deionized water, and the resistance between the two resistivity electrodes is measured and compared with the known resistance of deionized water to obtain the electrode constant. K and temperature coefficient .

[0018] Preferably, the original solution resistance value R w The method for obtaining the resistivity value includes: filling the sample cavity with the mixed cement slurry, defoaming the cement slurry, and measuring the resistance value between two resistivity electrodes as the original solution resistance value. R w 。

[0019] (III) Beneficial Effects Multi-physics joint monitoring organically integrates acoustic (stiffness / skeleton), electrical (porosity / connectivity) and nuclear magnetic (fluid) properties. It comprehensively utilizes complementary acoustic, electrical and nuclear information on a unified time base to quantitatively and jointly determine the initial and final setting times of cement, providing a scientific and traceable basis for cementing quality evaluation and construction parameter optimization. Simultaneously, the HPHT holder and data acquisition and processing system enable acoustic, electrical, and nuclear magnetic resonance observations of samples at the same scale, and allow for the overlay analysis of multiple parameters along a unified time axis, utilizing parameter synergy to determine the initial solidification time. t initial Final setting time t final This avoids the problem that single-parameter criteria are easily affected by noise or outliers; For the first time, the coupling relationship between the rigid skeleton structure evolution, pore structure evolution and pore fluid migration of cementing was systematically characterized within a unified temporal and spatial framework. This study achieved quantitative identification of key nodes in the initial and final setting stages, demonstrating significant theoretical value and promising engineering applications. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the method flow of the present invention; Figure 2 This is a flowchart of the process logic of the present invention; Figure 3 This is the aspect ratio-acoustic impedance diagram of the present invention. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0022] See Figure 1 - Figure 2As shown, this embodiment of the invention proposes a method for jointly determining the initial and final setting times of cement using multiple physics fields. Specifically, it is implemented through a system consisting of a data acquisition and processing system and an HPHT holder. The data acquisition and processing system is a software program installed on a computer or other device. The HPHT holder has high-temperature and high-pressure resistant structural strength, with an internal sample cavity for filling cement slurry. An ultrasonic probe, a low-field nuclear magnetic resonance coil, and two resistivity electrodes are integrated around the sample cavity. The ultrasonic probe is used to acquire the propagation time of longitudinal and transverse waves in the cement slurry. The low-field nuclear magnetic resonance coil is used to perform LF-NMR-CPMG testing on the cement slurry. The two resistivity electrodes are used to measure the resistance value of the cement slurry. The specific methods for monitoring these parameters and the components used are existing technologies. The key difference in this embodiment is the simultaneous integration around the sample cavity, enabling the simultaneous acquisition of monitoring parameters, which differs from the independent monitoring structures in existing technologies. The LF-NMR-CPMG sequence is a common nuclear magnetic resonance testing method used to acquire... T 2.

[0023] The initial and final setting times of cement are simultaneously measured using an integrated HPHT clamp and data acquisition and processing system, employing acoustic, electrical, and nuclear magnetic resonance (NMR) physical fields. Specific methods include: S100. Mix cement slurry at high speed according to the designed water-cement ratio, and record the mixing time. t 0 is recorded in the data acquisition and processing system; the water-cement ratio is the ratio actually used in cementing, the mixing time is greater than 2 minutes to ensure thorough mixing, and the start time is recorded when mixing is completed. t The data is entered into the data acquisition and processing system so that the subsequent data acquisition and processing system can automatically determine the interval time. Δt n ,and Δt n Let n be the interval time, where n = 1, 2, 3... until the end of the monitoring period. During the monitoring period, there are several identical interval times. (During the actual monitoring process, due to differences in the acoustic, electrical, and nuclear magnetic resonance reaction states, the specific interval times may vary, but all must be based on...) t 0 is used as the starting point for timing (to ensure that the reference times are on the same time axis), and these time intervals will form the horizontal axis of the joint change graph. Simultaneously, information such as the hydration agent, admixture ratio, and ambient temperature of the mixed cement slurry needs to be recorded.

[0024] S200. Fill the sample cavity of the HPHT holder with the mixed cement slurry, heat it to the predetermined temperature, pressurize it to the predetermined pressure, and fill the sample cavity to the predetermined position from top to bottom during the filling process. At the same time, defoaming treatment is performed. The predetermined temperature and pressure mentioned here are the corresponding temperature and pressure in the cementing environment to realize the solidification process of simulating the actual working conditions.

[0025] At the same time, the original liquid resistance value is measured after filling with cement grout. R w The measurement specifically involves defoaming the cement slurry and measuring the resistance between two resistivity electrodes as the original solution resistance value. R w 。 It can also measure the effective sound path length after cement grout filling. L .

[0026] S300, through the data acquisition and processing system, in time t 0 +Δt n Timing begins from the start of cement slurry mixing, and monitoring is performed at consistent intervals. Δt n It refers to a fixed time interval; as long as the intervals are the same, the specific time interval length is determined by the amount of data to be collected. Generally, the shorter the interval, the better, as it will result in more data being collected. Specifically, monitoring data is collected on the cement slurry in the sample chamber, including the longitudinal wave propagation time. t p (t) transverse wave propagation time t s (t) Resistance value R raw (t) The LF-NMR-CPMG test data and other monitoring data were obtained by acquiring data through the aforementioned ultrasonic probe, low-field nuclear magnetic resonance coil, and two resistivity electrodes, and then processed by the data acquisition and processing system.

[0027] S400, based on longitudinal wave propagation time t p (t) transverse wave propagation time t s (t) Calculate the time separately t 0 +Δt n Time longitudinal wave propagation speed transverse wave propagation speed And calculate the acoustic impedance. Z and aspect ratio / ; Among them, longitudinal wave propagation time t p (t) transverse wave propagation time t s (t) The longitudinal wave propagation speed is obtained directly through ultrasonic probe detection. transverse wave propagation speed Acoustic impedance Z and aspect ratio / The specific calculation method is as follows: Calculate P-wave velocity ,

[0028] Calculate the shear wave velocity ,

[0029] Calculate acoustic impedance Z , Z= ρ·V p Calculate aspect ratio / , / = /

[0030] in, For longitudinal waves t 0 +Δt n The propagation time in the cement slurry at that time transverse waves t 0 +Δt n The propagation time in the cement slurry is given by ρ, where ρ is the bulk density of the cement slurry. For the zero-delay compensation time of the longitudinal wave, For zero-delay compensation time for shear waves, Δt n This refers to the monitoring interval.

[0031] Among them, the longitudinal wave zero delay compensation time and shear wave zero delay compensation time The methods for obtaining it include: Measure the effective acoustic path length of the sample cavity; The sample chamber is filled with deionized water with known longitudinal wave reference velocities and transverse wave reference velocities. Multiple longitudinal and transverse waves are emitted toward the sample cavity, and the longitudinal wave test velocity and transverse wave test velocity are obtained respectively. The propagation time is calculated by using the effective sound path length in conjunction with the P-wave test velocity and the P-wave reference velocity to calculate the P-wave zero-delay compensation time. and shear wave zero delay compensation time .

[0032] Among them, the longitudinal wave test velocity and longitudinal wave reference velocity of deionized water are 1500 m / s, within the effective sound path. L Under certain conditions, the delay time caused by the system during the monitoring process can be obtained, which serves as compensation for the calculation time of the actual propagation speed of longitudinal and transverse waves in the cement slurry.

[0033] S500, based on resistance value R raw (t) Calculation time t 0 +Δt n Temperature-corrected volume resistivity R(t) The equivalent porosity was inverted using the Archie formula. φ e (t) ; Among them, resistance value R raw (t) It is obtained by direct measurement using two resistivity electrodes, while the volume resistivity... R(t) and equivalent porosity φ e (t) Based on resistance value R raw (t)、 Original liquid resistance value R w The calculations are performed, and the specific calculation methods include: Calculate volume resistivity R(t) ,

[0034] Calculate equivalent porosity φ e (t) ,

[0035] in, The electrode constant is... For temperature coefficient, for t 0 +Δt n The resistivity of the cement grout at that time R w fort The original resistivity of cement slurry at 0°C, empirical coefficient ≈1.0, cementation index m≈2.0, Δt n This refers to the monitoring interval.

[0036] Generally speaking, the empirical coefficient More accurate values ​​of a and m can be obtained by preparing a series of cement stone standard samples with known porosity and measuring the volume resistivity under uniform temperature and pore water resistivity conditions. However, in this embodiment, the above estimation is used for the calculation formula.

[0037] Among them, the blank resistance value when there is no sample in the sample chamber Electrode constant K and temperature coefficient The methods for obtaining it include: When the sample chamber is empty, the resistance value between the two resistivity electrodes is measured as the blank resistance value. ; through blank resistance value This method can eliminate system resistance errors, thus obtaining the true resistance value of the cement slurry. The sample chamber is filled with deionized water, and the resistance value between the two resistivity electrodes is measured and compared with the known resistance value of deionized water to obtain the electrode constant. K and temperature coefficient Since the resistance and resistivity of deionized water are known values, the results can be obtained by comparing the test results with the actual results. × K The result is the system's corresponding constant, and the resistivity can be converted by simply detecting the resistance value of the cement slurry.

[0038] S600, generated based on LF-NMR-CPMG test data T The total hydrogen signal intensity was obtained by analyzing the two spectra and combining them with the inversion model and peak fitting processing. M 0 (t) ; generated through test data T Before the spectral analysis begins, the data acquisition and processing system needs to be calibrated. Specifically, this is done by placing a standard sample with 20% porosity at the center of a low-field nuclear magnetic resonance coil and using a CPMG sequence to test the T2 relaxation curve. This determines the echo interval TE (ms), the number of echoes NE, and the repetition time TR (s), enabling the system to stably distinguish between long T2 (free water) and short T2 (bound water) components. This calibration process is a mature existing method that can be applied to the data acquisition and processing system.

[0039] By monitoring the data and calculating the corresponding parameter data according to empirical formulas, since the acoustic, electrical and nuclear magnetic parameters are monitored simultaneously, all parameters are associated with the same time t.

[0040] S700, generated through the data acquisition and processing system , , Z、 / , R(t), φ e (t), T 2 spectra and M 0 (t) Compared to t The joint change spectrum can be generated by marking or removing abnormal waveforms, discrete points, or obviously distorted T2 spectra during the process. This can be done automatically by the system or manually by the operator, using the observation and comparison method.

[0041] S800, identifies the initial setting time in the combined variation map through the data acquisition and processing system. t initial and final freezing time t final The resulting joint variation map allows viewers to see the changes in various parameter data on the same time axis, and identifies the initial setting time based on these changes. t initial and final freezing time t final And output, thus achieving spatial consistency in joint monitoring of three physical fields, enabling the... V p (t) , V s (t) , Z The reflected "rigid skeleton", composed of R(t) , φ e (t) The reflected pore structure and its composition T 2. Spectrum M 0 (t) The fluid migrations reflected are comparable and coupletable.

[0042] Multiple parameters are overlaid on the same time axis to determine the initial setting time using parameter synergy. t initial Final setting time t final This avoids the problem of single-parameter criteria being easily affected by noise or outliers. The final result... t initia l andt final It can be directly converted into a suggestion for cement setting time in engineering, providing a quantitative and traceable basis for on-site decision-making.

[0043] Specifically, initial setting time t initial The identification methods include: First, identify the joint change map. T The main peak of the spectrum 2 is significantly shifted to the left and the total hydrogen signal intensity is... M 0 (t) The window of time during which the decline accelerates.

[0044] Secondly, identify the volume resistivity in the joint variation spectrum. R(t) The minimum value and shear wave velocity that changed from continuous decline to rise The window period during which detection is stable and significantly increased.

[0045] Then, the acoustic impedance Z and aspect ratio / Projecting the data onto an aspect ratio-acoustic impedance chart and identifying the time window during which points migrate from the liquid to the solid state; specifically, projecting acoustic parameter points from different times onto the same plane to distinguish solidification stages such as slurry and rigid framework. This differs from simply viewing... V p or V s Compared to curves, such as Figure 3 The diagram illustrates the state changes of cement paste during solidification at different volume densities using an aspect ratio-acoustic impedance chart. This chart more intuitively reflects the establishment and density changes of the rigid cement skeleton structure and can be combined with resistivity and NMR parameters for chart-level joint determination. Points in the chart are positioned upwards... Z ,high V p / V s Regional migration, used to distinguish the solid-liquid phase transition of cement paste, is often accompanied by... φ e (t) First decrease then increase, resistivity R(t) The evolution of cement structure from low to high and the disappearance of the free water peak indicate a structural evolution process from paste to gel to rigid skeleton stages.

[0046] Finally, the point where the three window time periods overlap is identified as the initial freezing time. t initial .

[0047] And final freezing time t final The identification methods include: First, identify the transverse wave propagation velocity in the joint variation spectrum. The increase in acoustic impedance Z approaches zero, and the aspect ratio... / Stable, and the point traces on the aspect ratio-acoustic impedance chart are concentrated in the solid region during the window time period.

[0048] Secondly, identify the volume resistivity in the joint variation spectrum. R(t) The rapid increase turned into a slow increase, and the equivalent porosity φ e (t) A gradually changing window of time.

[0049] Then, identify the joint change map. T The adjacent waveforms of the two spectra overlap and the total hydrogen signal intensity M 0 (t) A window of time that tends to stabilize.

[0050] Finally, the point at which the three window time periods overlap is identified as the final freezing time. t final .

[0051] Therefore, acoustic, electrical, and nuclear magnetic resonance observations are performed on samples at the same scale, and multiple parameters are superimposed and analyzed along a unified time axis, allowing for the collaborative determination of initial solidification time using these parameters. t initial Final setting time t final This avoids the problem that single-parameter criteria are easily affected by noise or outliers; for the first time, it systematically characterizes the coupling relationship between the evolution of the rigid skeleton structure of cement, the evolution of pore structure and the migration of pore fluid under a unified time and space framework, and realizes the quantitative identification of key nodes of initial setting and final setting.

[0052] To facilitate understanding of the relevant parameters and units involved in the conversions in this embodiment, the following explanation is provided.

[0053] Sound path length L , Unit: m.

[0054] Longitudinal wave propagation speed V p (t) , Unit: m / s.

[0055] Transverse wave propagation speed V s (t) , Unit: m / s.

[0056] Longitudinal wave propagation time , Unit: s.

[0057] transverse wave propagation time , Unit: s.

[0058] Longitudinal wave zero delay compensation time , Unit: s.

[0059] Shear wave zero delay compensation time , Unit: s.

[0060] Acoustic impedance Z , Unit: Pa·s / m.

[0061] Sample bulk density ρ, unit: g / cm³.

[0062] blank resistor R 0, unit: Ω.

[0063] Original liquid resistance value R w , Unit: Ω.

[0064] Cement grout resistance value , Unit: Ω.

[0065] Volume resistivity R(t) , Unit: Ω·m.

[0066] Equivalent porosity φ e (t) , Unit: %.

[0067] Initial setting time t initial , Unit: h.

[0068] Final freezing time t final , Unit: h.

[0069] Monitoring time t= t 0 +Δt n Unit: s or h; where Δt n The same or different intervals can be formed based on acoustic, electrical, and nuclear magnetic resonance monitoring characteristics, but all are based on t The interval period is set with 0 as the starting point for timing, so as to form the same time axis.

[0070] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0071] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0072] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for jointly determining the initial and final setting times of cement by multi-physical fields, characterized in that, Comprising: The time of completion of mixing of the cement paste at high speed according to the designed water-cement ratio t 0is recorded into the data acquisition processing system; The stirring completed cement paste is filled into the sample chamber of the HPHT holder, heated to a predetermined temperature, and pressurized to a predetermined pressure; The monitoring data of the cement slurry in the sample chamber is collected by the data acquisition processing system at the time t 0 +Δt n The monitoring data collected includes longitudinal wave propagation time t p (t) , transverse wave propagation time t s (t) , resistance value R raw (t) and LF-NMR-CPMG test data According to the longitudinal wave propagation time t p (t) , the shear wave propagation time t s (t) Respective calculation times t 0 +Δt n Time longitudinal wave propagation speed , the shear wave propagation speed , and calculate the acoustic impedance Z and the aspect ratio / ; According to the resistance value R raw (t) Calculation time t 0 +Δt n Bulk resistivity after temperature correction R(t) , and the equivalent porosity is inverted by Archie formula φ e (t) ; Generating from LF-NMR-CPMG test data T 2 spectra, and combining inversion model and peak fitting process to obtain total hydrogen signal intensity M 0 (t) ; generated by the data acquisition processing system 、 、 Z、 / 、 R(t), φ e (t), T 2 profiles and M 0 (t) joint change profiles relative to t ; Identifying initial and final set times in a joint change pattern by a data acquisition and processing system t initial and final set times t final and outputting.

2. The method for jointly determining the initial and final setting times of cement according to claim 1, characterized in that, initial setting time t initial The identification method includes: Identifying joint change patterns in T 2 The main peak of the spectrum is shifted significantly to the left and the total hydrogen signal intensity M 0 (t) Window time period where the decrease is accelerated; Identifying joint change maps for resistivity R(t) Minimums that transition from a sustained decrease to an increase and shear wave velocity A window period of stable detection and significant increase projecting the acoustic impedance Z and aspect ratio / onto an aspect ratio-acoustic impedance chart and identifying a window time period of the liquid region to the solid region migration; The time point at which the three window time periods coincide is identified as the initial set time t initial .

3. The method for jointly determining the initial and final setting times of cement according to claim 2, characterized in that, final setting time t final The identification method includes: Identifying shear wave propagation velocities in a joint change map and the increase in acoustic wave impedance Z approaches zero, the aspect ratio / is stable and the aspect ratio - acoustic impedance plot point cluster is in the solid region window time period; Identifying joint change maps in bulk resistivity R(t) From fast rise to slow rise, and equivalent porosity φ e (t) A slow varying window time period; Identifying joint change patterns in T 2 adjacent waveforms of the profile coincide and the total hydrogen signal intensity M 0 (t) a window time period tending to stabilize; The time point at which the three window time periods coincide is identified as the final set time t final .

4. The method for jointly determining the initial and final setting times of cement according to claim 1, characterized in that, The HPHT holder is integrated with an ultrasonic probe, a low-field nuclear magnetic resonance coil, and two resistivity electrodes, the ultrasonic probe is used to collect the propagation time of longitudinal and transverse waves in the cement paste, the low-field nuclear magnetic resonance coil is used to perform LF-NMR-CPMG test on the cement paste, and the two resistivity electrodes are used to measure the resistance value of the cement paste.

5. The method for jointly determining the initial and final setting times of cement according to claim 4, characterized in that, Acoustic impedance Z And aspect ratio / The method of calculating comprises: Computing the P-wave velocity , Computing shear wave velocity , Computing acoustic wave impedance Z , Z= p V p Computing aspect ratios ,​ / = / wherein, is the propagation time of a longitudinal wave in the cement paste at t 0 +Δt n is the propagation time of a transverse wave in the cement paste at is the propagation time of a longitudinal wave in the cement paste at t 0 +Δt n is the propagation time of a transverse wave in the cement paste at is the zero-time compensation time for longitudinal waves, is the zero-time compensation time for transverse waves, Δt n is the monitoring interval.

6. The method for jointly determining the initial and final setting times of cement according to claim 5, characterized in that, Longitudinal wave zero delay compensation time and shear wave zero delay compensation time The acquisition method comprises: The effective sound path length of the sample chamber is measured; The sample chamber is filled with deionized water with known longitudinal wave reference speed and transverse wave reference speed; Multiple longitudinal and transverse waves are emitted towards the sample chamber, and longitudinal and transverse test speeds are obtained respectively; The propagation time is calculated by calculating the time of flight for the effective acoustic path length with the longitudinal wave test velocity and the longitudinal wave reference velocity, respectively and the shear wave zero time compensation time .

7. The method for jointly determining the initial and final setting times of cement according to claim 4, characterized in that, Bulk resistivity R(t) And equivalent porosity φ e (t) The method of calculation comprises: Computing bulk resistivity R(t) , Calculating equivalent porosity φ e (t) , wherein, is the electrode constant, is the temperature coefficient, is t 0 +Δt n the resistance value of the cement paste at the time, R w is t 0 the raw cement resistance value of the cement paste, the empirical coefficient ≈1.0, the cementation index m ≈ 2.0, Δt n is the monitoring interval time.

8. The method for jointly determining the initial and final setting times of cement according to claim 7, characterized in that, Blank resistance value of the sample chamber when there is no sample in the sample chamber , electrode constant K , and temperature coefficient The acquisition method comprises: The resistance value between the two resistivity electrodes is measured as a blank resistance value when the sample chamber is empty ; The sample chamber is filled with deionized water, the resistance between the two resistivity electrodes is measured and compared to the known resistance of deionized water to obtain the electrode constant K and the temperature coefficient .

9. The method for jointly determining the initial and final setting times of cement according to claim 7, characterized in that, The raw solution resistance value R w The acquisition method comprises: After the stirring of the cement paste is completed, the cement paste is filled into the sample chamber, defoaming treatment is performed on the cement paste, and the resistance value between the two resistivity electrodes is measured as the raw liquid resistance value R w 。

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