Method and device for monitoring temperature and pressure in a co2 injection well

Abstract

The application provides a CO2 injection well temperature and pressure monitoring method and device, which injects the same pulsed laser into a first optical fiber and a reference optical fiber, obtains intensity ratio values of back Raman scattering light anti-Stokes signals and Stokes signals in the first optical fiber and corresponding intensity ratio values in the reference optical fiber, calculates a first temperature distribution along the first optical fiber and a reference temperature distribution along the reference optical fiber according to the two intensity ratio values, injects narrow line width pulsed laser into a second optical fiber, obtains a Brillouin frequency shift distribution along the well axis based on back Brillouin scattering spectra at each spatial position along the second optical fiber, generates a continuous pressure distribution along the well axis based on the reference temperature distribution and the Brillouin frequency shift distribution, and determines the first temperature distribution and the continuous pressure distribution as the monitoring result of the temperature and pressure of the whole well section. The method realizes continuous and real-time distributed monitoring of the temperature and pressure of the whole well section of the CO2 injection well.

Description

Technical Field

[0001] This application relates to the field of carbon capture, utilization and storage (CCUS) technology, and more specifically, to a method and apparatus for monitoring temperature and pressure in a CO2 injection well. Background Technology

[0002] With the increasing severity of global warming, carbon capture, utilization, and storage (CCUS) technology has attracted much attention. Among its components, the core step in achieving long-term geological storage is to compress captured CO2 into deep saline aquifers or depleted oil and gas reservoirs via injection wellbore. During continuous CO2 injection, the temperature and pressure distribution within the wellbore directly affects injection efficiency, wellbore integrity, and storage safety. Micro-leakage or premature failure of wellbore integrity can lead to CO2 escaping into shallow aquifers or flowing back to the surface, causing environmental risks and storage failure. Therefore, real-time and continuous monitoring of temperature and pressure throughout the injection wellbore is of significant engineering importance.

[0003] Currently, industrial monitoring of CO2 injection wellbores primarily relies on electronic point sensors, such as quartz crystal manometers, thermocouples, or platinum resistance thermometers. These sensors are typically installed at intervals along the wellbore axis at specific measuring points (such as the wellhead or several depth nodes downhole), transmitting electrical signals to a surface data acquisition system via armored cables. During monitoring, the system collects pressure and temperature values ​​at each discrete measuring point at fixed time intervals, converting them from analog to digital to form a limited set of "point data" used to determine the thermodynamic state inside the wellbore. In some operations, a downhole packer is used to segment the wellbore, installing independent sensors in each segment to attempt to improve monitoring resolution.

[0004] However, in the monitoring of CO2 injection in wellbore using the aforementioned point sensor technology, the discrete arrangement of the sensors leads to spatial blind spots. There are no measurement points in the well section between adjacent sensors, which can be several meters to tens of meters apart. CO2 micro-leakage may happen in these blind spots. In particular, when CO2 undergoes a phase transition in the wellbore (such as the transition from supercritical state to gaseous state), localized minute temperature and pressure anomalies are difficult to be captured by sensors that are far apart. Summary of the Invention

[0005] The purpose of this application is to provide a method and apparatus for monitoring temperature and pressure in a CO2 injection well, which enables continuous, real-time, distributed monitoring of temperature and pressure throughout the entire CO2 injection wellbore. By using a reference fiber to compensate for the effective decoupling of the influence of temperature on Brillouin frequency shift, the accuracy of pressure measurement is significantly improved.

[0006] Firstly, a method for monitoring temperature and pressure within a CO2 injection well is provided, which may include: The same pulsed laser is injected into the first optical fiber and the reference optical fiber respectively. The intensity ratio of the anti-Stokes signal to the Stokes signal of the backscattered Raman light in the first optical fiber and the corresponding intensity ratio in the reference optical fiber are obtained. The first temperature distribution along the first optical fiber and the reference temperature distribution along the reference optical fiber are calculated based on the two intensity ratios respectively. Narrow-linewidth pulsed laser light is injected into the second optical fiber, and the Brillouin frequency shift distribution along the well axis is obtained based on the backscattering spectrum at each spatial position along the second optical fiber. Based on the reference temperature distribution and the Brillouin frequency shift distribution, combined with the pre-calibrated pressure-frequency shift conversion coefficient, a continuous pressure distribution along the well axis is generated; the first temperature distribution and the continuous pressure distribution are determined as the monitoring results of temperature and pressure throughout the well section.

[0007] In one possible implementation, the reference optical fiber is sealed within a protective tube filled with inert gas, which is arranged along the wellbore axis within the annulus and parallel to the wellbore axis, so that the reference optical fiber only measures the ambient temperature within the annulus and is completely isolated from the pressure of the external CO2 medium.

[0008] In one possible implementation, obtaining the Brillouin frequency shift distribution along the well axis includes: For each spatial location, the discrete intensity data of the collected backscattered Brillouin scattering spectrum are arranged at equal intervals according to frequency to form the original spectral line sequence; the original spectral line sequence is then smoothed using a sliding window. The smoothed spectral sequence is fitted using a piecewise Lorentz function; the peak frequency is extracted from the fitted piecewise Lorentz function, and the difference between the peak frequency and the center frequency of the narrow linewidth pulsed laser is determined as the Brillouin frequency shift value at that spatial location; the Brillouin frequency shift values ​​at each spatial location are arranged in depth order to generate the Brillouin frequency shift distribution.

[0009] In one possible implementation, based on the reference temperature distribution and the Brillouin frequency shift distribution, and combined with pre-calibrated pressure-frequency shift conversion coefficients, a continuous pressure distribution along the well axis is generated, including: A joint response equation is established between Brillouin frequency shift and temperature and pressure. The equation is: the change in Brillouin frequency shift is equal to the sum of the frequency shift component caused by temperature change and the frequency shift component caused by pressure change. Substitute the reference temperature distribution into the joint response equation as the baseline temperature quantity, calculate the frequency shift component caused by temperature at each spatial location, and subtract the frequency shift component caused by temperature from the Brillouin frequency shift distribution to obtain the net frequency shift distribution caused by CO2 pressure change; The product of each net frequency shift value in the net frequency shift distribution and a pre-calibrated pressure-frequency shift conversion coefficient is used to determine the pressure value at the corresponding location, thereby generating a continuous pressure distribution along the well axis.

[0010] In one possible implementation, the frequency shift component caused by temperature change in the joint response equation is determined in the following way: The second optical fiber is pre-calibrated at temperature, and the change in Brillouin frequency shift corresponding to a unit temperature change is obtained as the temperature-frequency shift coefficient. During real-time downhole measurements, the deviation of the reference temperature distribution from a preset reference temperature baseline is multiplied by the temperature-frequency shift coefficient to obtain the temperature-induced frequency shift component at each spatial location.

[0011] In one possible implementation, the first temperature distribution and the continuous pressure distribution are defined as the monitoring results of temperature and pressure throughout the well section, including: This first temperature distribution is taken as the true temperature distribution along the well line; The first temperature distribution is spatiotemporally synchronized with the continuous pressure distribution to generate a two-dimensional temperature-pressure matrix containing the dimensions of well depth and sampling time. The temperature-pressure two-dimensional matrix was used to determine the monitoring results of temperature and pressure throughout the well section.

[0012] In one possible implementation, the first temperature distribution is spatiotemporally synchronized with the continuous pressure distribution to generate a two-dimensional temperature-pressure matrix containing the dimensions of well depth and sampling time, including: By using the same depth sampling interval and the same time sampling frequency, a two-dimensional matrix is ​​constructed by mapping temperature values ​​to pressure values ​​one-to-one. The row index of this two-dimensional matrix corresponds to the well depth sequence, and the column index corresponds to the sampling time sequence. Each element in this matrix is ​​a tuple, storing the temperature and pressure values ​​at any depth and at any time.

[0013] Secondly, a monitoring device for temperature and pressure inside a CO2 injection well is provided, the device including: The acquisition unit is used to inject the same pulsed laser into the first optical fiber and the reference optical fiber respectively, and acquire the intensity ratio of the anti-Stokes signal to the Stokes signal of the backscattered Raman light in the first optical fiber, and the corresponding intensity ratio in the reference optical fiber. The calculation unit is used to calculate the first temperature distribution along the first optical fiber and the reference temperature distribution along the reference optical fiber based on two intensity ratios, respectively. The acquisition unit is also used to inject narrow-linewidth pulsed laser into the second optical fiber and acquire the Brillouin frequency shift distribution along the well axis based on the backscattering spectrum at each spatial position along the second optical fiber. The generation unit is used to generate a continuous pressure distribution along the well axis based on the reference temperature distribution and the Brillouin frequency shift distribution, combined with a pre-calibrated pressure-frequency shift conversion coefficient; The determination unit is used to determine the first temperature distribution and continuous pressure distribution as the monitoring results of temperature and pressure throughout the well section.

[0014] Thirdly, an electronic device is provided, which includes a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus; Memory, used to store computer programs; When a processor executes a program stored in memory, it implements any of the steps described in the first aspect above.

[0015] Fourthly, a computer-readable storage medium is provided, wherein a computer program is stored therein, and when executed by a processor, the computer program implements the steps of any of the methods described in the first aspect above.

[0016] This application provides a method and apparatus for monitoring temperature and pressure in a CO2 injection well. The method injects identical pulsed laser light into a first optical fiber and a reference optical fiber, respectively, to obtain the intensity ratio of the anti-Stokes signal to the Stokes signal in the backscattered Raman light of the first optical fiber, and the corresponding intensity ratio in the reference optical fiber. Based on these two intensity ratios, a first temperature distribution along the first optical fiber and a reference temperature distribution along the reference optical fiber are calculated. A narrow-linewidth pulsed laser light is injected into a second optical fiber, and based on the backscattered Brillouin scattering spectrum at various spatial locations along the second optical fiber, the Brillouin frequency shift distribution along the well axis is obtained. Based on this reference temperature distribution and the Brillouin frequency shift distribution, combined with a pre-calibrated pressure-frequency shift conversion coefficient, a continuous pressure distribution along the well axis is generated. This first temperature distribution and the continuous pressure distribution are then used as the monitoring results for the temperature and pressure throughout the entire well section. This method achieves continuous, real-time, distributed monitoring of temperature and pressure throughout the entire CO2 injection wellbore, and by compensating for the influence of temperature on the Brillouin frequency shift through the reference optical fiber, it significantly improves the accuracy of pressure measurement. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic flowchart illustrating a method for monitoring temperature and pressure inside a CO2 injection well, provided in an embodiment of this application; Figure 2A schematic diagram of a monitoring device for temperature and pressure inside a CO2 injection well, provided for an embodiment of this application; Figure 3 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application. Unless otherwise defined, the technical or scientific terms used in this application should have the ordinary meaning understood by those skilled in the art. The terms "first," "second," and similar terms used in this application do not indicate any order, quantity, or importance, but are only used to distinguish different components. The terms "comprising" or "including," etc., mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, but does not exclude other elements or objects. The terms "connection," "coupled," or "linked," etc., are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect.

[0020] The CO2 injection well temperature and pressure monitoring method provided in this application relies on a CO2 injection well temperature and pressure monitoring system, which is applied to the injection wellbore during CO2 geological storage or oil displacement processes. The injection wellbore is a vertical or inclined well, including casing, tubing, and the annulus space between the casing and tubing.

[0021] (1) Composite sensing optical cable assembly A composite sensing optical cable is axially laid along the outer wall of the CO2 injection wellbore. This composite sensing optical cable contains two optical fibers: a first fiber and a second fiber. The first fiber can be a graded-index multimode fiber, for example, with a core diameter of 50 micrometers and a numerical aperture of 0.20, used for temperature measurement via Raman scattering. The second fiber can be a single-mode fiber, for example, with a cutoff wavelength less than 1310 nanometers and a mode field diameter of 9 micrometers, used for pressure measurement via Brillouin scattering radio frequency shifting. The first and second fibers are encapsulated within the composite sensing optical cable, which is covered by a helical metal armor layer. The outer diameter of the armor layer is capable of withstanding the external pressure inside the CO2 injection well. This armor layer protects the optical fibers from mechanical damage and ensures the geometric stability of the cable under the high-pressure environment downhole, preventing micro-bending loss due to pressure fluctuations.

[0022] (2) Reference fiber optic assembly A reference optical fiber, sealed within an inert gas protective tube, is installed within the annulus of the wellbore along its axial direction. Specifically, the reference optical fiber is sealed within a protective tube filled with high-purity argon gas at standard atmospheric pressure. This protective tube is positioned parallel to the wellbore axis within the annulus to ensure that the reference optical fiber is sensitive to the ambient temperature within the annulus but insensitive to pressure changes in the external CO2 medium (achieving pressure isolation). The inner wall of the protective tube is coated with a light-absorbing coating to absorb stray light remaining within the tube. At least three spacer rings are evenly distributed axially between the protective tube and the reference optical fiber. The outer diameter of each spacer ring is equal to the inner diameter of the protective tube, while its inner diameter is larger than the diameter of the reference optical fiber, allowing the reference optical fiber to suspend at the center of the tube without contacting the inner wall. This structure ensures that the reference optical fiber, besides bearing the constant static strain caused by its own gravity, does not experience additional dynamic mechanical stress and is unaffected by CO2 pressure, responding only to temperature changes in the gas within the annulus.

[0023] (3) Ground demodulation and processing system The system comprises a ground-based pulsed laser source, an optical signal receiving and demodulation module, and a computer processing unit. The pulsed laser source is connected to the first, second, and reference optical fibers via optical switches or couplers. The optical receiving module includes a high-sensitivity photodetector, an amplifier, and an analog-to-digital converter, converting the backscattered light signal into a digital signal. The computer processing unit executes temperature and pressure calculation algorithms and outputs the monitoring results.

[0024] The preferred embodiments of this application are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit this application. Furthermore, the embodiments and features in the embodiments of this application can be combined with each other without conflict.

[0025] Figure 1 This is a schematic flowchart illustrating a method for monitoring temperature and pressure within a CO2 injection well, as provided in an embodiment of this application. Figure 1 As shown, the method may include: Step S110: Inject the same pulsed laser into the first optical fiber and the reference optical fiber respectively, and obtain the intensity ratio of the anti-Stokes signal to the Stokes signal of the backscattered Raman light in the first optical fiber, and the corresponding intensity ratio in the reference optical fiber; calculate the first temperature distribution along the first optical fiber and the reference temperature distribution along the reference optical fiber based on the two intensity ratios respectively.

[0026] First, a narrowband pulsed laser beam is emitted from a ground-based pulsed laser source and simultaneously injected into both the first optical fiber and the reference optical fiber via an optical splitter. For example, the injected laser parameters could be: wavelength 1550 nanometers, pulse width 10 nanoseconds, and repetition frequency 1 kilohertz. As the laser propagates through the optical fiber, it generates backscattered Raman light at each spatial location, which returns along the original path to the ground receiver.

[0027] For the first fiber (multimode fiber) and the reference fiber, the anti-Stokes signal and the Stokes signal in their backscattered Raman light are collected, respectively. The intensity of the anti-Stokes signal is temperature-sensitive, while the intensity of the Stokes signal is essentially insensitive to temperature. The two signals are separated by a wavelength division multiplexer and received by two photodetectors respectively. After amplification and analog-to-digital conversion, discrete intensity sequences are obtained.

[0028] Let the distance along the fiber from the laser incident end be... At point , the intensity of the anti-Stokes signal collected is The strength of the Stokes signal is First, calculate the strength ratio at that point:

[0029] in, The dimensionless Raman intensity ratio represents the distance between the fiber and the incident end. The ratio of anti-Stokes intensity to Stokes intensity is given at this point. This ratio eliminates the common-mode effects of laser power fluctuations and fiber loss.

[0030] Then, the temperature value at that point is calculated using a pre-calibrated temperature conversion formula. The formula is as follows:

[0031] In the formula, Distance from the incident end The temperature of the optical fiber at that location; For the fiber optic start end ( The known reference temperature at point ( ) was obtained by measuring a high-precision ground-based thermometer; Let be the Boltzmann constant, and take . ; Let be Planck's constant, and take . ; For quartz optical fiber, the Raman frequency shift is typically taken as... ; To be at the reference temperature The strength ratio obtained from the measurement.

[0032] For all discrete Performing the above calculations yields a temperature variation sequence with depth, denoted as the first temperature distribution. (corresponding to the first fiber) and reference temperature distribution (Corresponding to the reference fiber optic line). Since the reference fiber optic cable is sealed inside an inert gas protective tube and does not come into contact with the CO2 medium, the temperature distribution it measures is the pure ambient temperature distribution within the wellbore annulus, which is unaffected by pressure.

[0033] Step S120: Inject a narrow-linewidth pulsed laser into the second optical fiber, and obtain the Brillouin frequency shift distribution along the well axis based on the backscattering spectrum at each spatial position along the second optical fiber.

[0034] A narrow-linewidth pulsed laser is injected into the second optical fiber (single-mode fiber), with the laser parameters being the center frequency. (e.g., 193.5 terahertz, corresponding to a wavelength of 1550 nanometers), with a linewidth less than 1 megahertz and a pulse width of 20 nanoseconds. Brillouin optical time-domain reflectometry (BOTDR) is used to collect the backscattering spectrum at each spatial location along the second fiber. Narrow-linewidth pulsed lasers can possess characteristics such as ultra-narrow linewidth and tunable peak power to excite stimulated Brillouin scattering in the fiber, ensuring spectral resolution.

[0035] Specifically, after coherent or direct detection, the backscattered Brillouin light yields the distribution of spectral intensity as a function of frequency at each spatial location. For a given spatial location... The spectrum is a discrete sequence, with the horizontal axis representing the frequency shift. (relative to the incident laser frequency) The vertical axis represents the intensity of scattered light. Preferably, the frequency scanning range is typically 10 GHz to 12 GHz, with a step size of 1 MHz.

[0036] In one embodiment, the specific steps for obtaining the Brillouin frequency shift distribution include: S21: For each spatial location The discrete intensity data of the collected backscattering Brillouin spectroscopy are arranged at equal frequency intervals to form the original spectral line sequence. ,in relative to the incident laser frequency frequency shift, .

[0037] S22: Perform a sliding window smoothing process on the original spectral sequence. In one example, this embodiment can use a Gaussian weighted moving average with a width of 11 frequency points and a Gaussian kernel standard deviation. Based on the current spatial location and its three adjacent locations (e.g., spatial location) Centered neighborhood window to The median of the peak signal-to-noise ratio of the Brillouin gain spectrum at 7 consecutive spatial locations is dynamically adjusted.

[0038] When the median is below the first threshold (e.g., 5 dB), When the median exceeds the second threshold (e.g., 15 dB), Otherwise take The smoothed spectral line sequence is denoted as... .

[0039] S23: For the smoothed spectral sequence, nonlinear least-squares fitting is performed using a piecewise Lorentz function. The piecewise Lorentz function is defined as:

[0040] In the formula: The intensity of the Brillouin scattering spectrum obtained by fitting; This is the frequency offset; Peak amplitude; The peak frequency (where the target parameter is the fitted parameter); The left wing half-height full width represents the width at which the peak descends to half its height on the left side; It is half the height and full width of the right wing.

[0041] The left and right wings share the same peak frequency. However, they have different full widths and heights (FWHMs) to accommodate the asymmetric distortion of the actual Brillouin spectrum caused by pressure gradients or non-uniform strain. The fitting process employs nonlinear optimization based on a trust-region reflection algorithm, with the initial values ​​set as follows: Take the maximum value of the smoothed spectral line. Take the frequency corresponding to the maximum value. The initial value is twice the frequency span from the left side of the peak intensity to half the peak intensity. The initial values ​​are similar. The stopping condition for the fitting iteration is the sum of the values ​​of two consecutive iterations. The change value is less than 0.01 MHz.

[0042] S24: Extract the peak frequency from the piecewise Lorentz function obtained from the fitting. Calculate the peak frequency and the incident laser frequency. The difference is used to obtain the Brillouin frequency shift at that spatial location:

[0043] S25: Arrange the Brillouin frequency shift values ​​at each spatial location in depth order to generate the Brillouin frequency shift distribution. .

[0044] By employing adaptive smoothing and piecewise Lorentz fitting, the peak frequency of the asymmetric Brillouin gain spectrum can be accurately extracted. Especially when the pressure gradient caused by injection leads to spectral distortion, the fitting error is significantly lower than that of conventional single-peak Lorentz fitting, the frequency shift resolution is significantly improved, and the corresponding pressure resolution is also effectively enhanced.

[0045] Step S130: Based on the reference temperature distribution and the Brillouin frequency shift distribution, and combined with the pre-calibrated pressure-frequency shift conversion coefficient, a continuous pressure distribution along the well axis is generated.

[0046] The goal of this step is to utilize the reference temperature distribution. From Brillouin frequency shift distribution The contribution caused solely by pressure is separated from the wellbore and then converted into a continuous pressure distribution along the well axis.

[0047] First, a joint response equation is established between the Brillouin frequency shift and temperature and pressure. The change in the Brillouin frequency shift... This can be represented as a frequency shift component caused by temperature changes. Frequency shift component caused by pressure change sum: ; in, , The intrinsic Brillouin shift is given under reference conditions (standard atmospheric pressure, known temperature).

[0048] The frequency shift component caused by temperature change is determined as follows: the second optical fiber is pre-calibrated for temperature, and the Brillouin frequency shift corresponding to a unit temperature change is obtained as the temperature-frequency shift coefficient. (Units are megahertz / Kelvin). In this embodiment, the second optical fiber was placed in a constant temperature chamber in a laboratory environment, and different temperatures (e.g., 0°C to 80°C) were applied. The corresponding Brillouin frequency shift was measured, and the result was obtained through fitting. (For a wavelength of 1550 nanometers).

[0049] When taking real-time measurements downhole, the reference temperature distribution will be used. With a preset reference temperature baseline The deviation value multiplied by The temperature-induced frequency shift component at each spatial location is obtained:

[0050] In the formula, The Brillouin frequency shift component is caused solely by temperature changes; The temperature-frequency shift coefficient represents the change in Brillouin frequency shift caused by a unit change in Kelvin temperature. The pure temperature distribution in the annulus is measured using a reference optical fiber; It is a reference temperature profile that is pre-measured and stored using a reference optical fiber under the condition of no injection and static pressure balance in the wellbore.

[0051] Next, by subtracting the temperature-induced component from the measured Brillouin frequency shift, we obtain the net frequency shift distribution caused solely by changes in CO2 pressure: In the formula, The total Brillouin frequency shift measured in the second optical fiber The frequency shift component caused by a specific temperature; The net frequency shift component is caused by the pressure to be determined.

[0052] It should be noted that in the actual data alignment process, the sampling interval of the reference temperature distribution (determined by the spatial resolution of Raman scattering, typically 1 meter) and the sampling interval of the Brillouin shift distribution (determined by the spatial resolution of BOTDR, typically 0.5 meters) may differ. Therefore, the reference temperature distribution is first aligned along the well axis. Perform cubic spline interpolation to make the sampling interval of the interpolated temperature sequence completely consistent with the sampling interval of the Brillouin frequency shift distribution, and then perform the above subtraction operation.

[0053] Then, each net frequency shift value in the net frequency shift distribution is multiplied by a pre-calibrated pressure-frequency shift conversion coefficient. This yields the pressure value at the corresponding location. Pressure-frequency shift conversion coefficient. The Brillouin frequency shift was obtained through laboratory pressure calibration: the second optical fiber was placed in an autoclave, and different pressures (e.g., 0.1 MPa to 30 MPa) were applied under isothermal conditions. The Brillouin frequency shift was measured, and a linear relationship was obtained by fitting the data. (That is, approximately 3.8 megahertz per megapascal). Therefore: ; In the formula, For depth CO2 pressure at the location; The reference pressure profile is usually taken as the hydrostatic pressure in the wellbore or a known initial pressure distribution. This is the net frequency shift component caused by pressure; The pressure-frequency shift conversion factor represents the change in Brillouin frequency shift caused by a unit change in pressure. This ultimately yields the continuous pressure distribution along the well axis. .

[0054] Step S140: Determine the first temperature distribution and continuous pressure distribution as the monitoring results of temperature and pressure for the entire well section.

[0055] The obtained first temperature distribution As the actual temperature distribution along the wellbore, and the generated continuous pressure distribution Spatiotemporal synchronization matching is performed to generate a two-dimensional temperature-pressure matrix containing well depth and sampling time dimensions, and this matrix is ​​used to determine the monitoring results of temperature and pressure throughout the well section. Specifically: First, set the same depth sampling interval. To adapt to the thermodynamic variations in different sections of a CO2 injection well, a non-equidistant sampling strategy is employed. In a specific example, the sampling interval is 1 meter in the 0-200 meter range below the wellhead, 2 meters in the 200-1000 meter range, and 0.5 meters in the range below 1000 meters to the well bottom. This generates a depth sequence. ,in This represents the number of sampling points.

[0056] Simultaneously, a consistent sampling frequency of 1 Hz is set, meaning data is collected once per second. Each sampling moment is denoted as... ( At every moment Perform steps S110 to S130 to obtain the temperature-depth sequence at that moment. and pressure depth sequence .

[0057] Then, construct a two-dimensional matrix. Its row index corresponds to the well depth sequence The column index corresponds to the sampling time series. Each element in this matrix is ​​a pair:

[0058] That is, each element stores the depth... and time The temperature and pressure values ​​are displayed. The tuples are stored as floating-point arrays with accompanying data quality flags. This quality flag is dynamically assigned a value based on the ratio of the anti-Stokes signal strength to the noise floor at the corresponding moment: when the signal strength is greater than 20 times the noise floor, (High quality); when the ratio is between 10 and 20, (Usable but with caution); When the ratio is less than 10, (Invalid data, not included in subsequent analysis).

[0059] Finally, this dynamically updated two-dimensional matrix The results of continuous real-time monitoring of temperature and pressure throughout the well section are output to the surface monitoring system for display and storage.

[0060] By using non-uniformly spaced depth sampling, the sampling resolution is optimized in areas with small temperature gradients (shallow layers) and rapid pressure changes (deep layers), which not only ensures the monitoring accuracy of key well sections but also saves data storage and transmission bandwidth. The introduction of quality markers makes the reliability of the data readily apparent, making it easier for operators to identify faults or abnormal periods.

[0061] Corresponding to the above method, this application also provides a monitoring device for temperature and pressure inside a CO2 injection well, such as... Figure 2 As shown, the device includes: The acquisition unit 210 is used to inject the same pulsed laser into the first optical fiber and the reference optical fiber respectively, and acquire the intensity ratio of the anti-Stokes signal to the Stokes signal of the backscattered Raman light in the first optical fiber, and the corresponding intensity ratio in the reference optical fiber. The calculation unit 220 is used to calculate the first temperature distribution along the first optical fiber and the reference temperature distribution along the reference optical fiber based on the two intensity ratios, respectively. The acquisition unit 210 is also used to inject narrow-linewidth pulsed laser into the second optical fiber and acquire the Brillouin frequency shift distribution along the well axis based on the backscattering spectrum at each spatial position along the second optical fiber. The generation unit 230 is used to generate a continuous pressure distribution along the well axis based on the reference temperature distribution and the Brillouin frequency shift distribution, combined with a pre-calibrated pressure-frequency shift conversion coefficient. The determination unit 240 is used to determine the first temperature distribution and continuous pressure distribution as the monitoring results of temperature and pressure throughout the well section.

[0062] The functions of each unit of the CO2 injection well temperature and pressure monitoring device provided in the above embodiments of this application can be realized through the above methods and steps. Therefore, the specific working process and beneficial effects of each unit in the CO2 injection well temperature and pressure monitoring device provided in the embodiments of this application will not be repeated here.

[0063] This application also provides an electronic device, such as... Figure 3 As shown, it includes a processor 310, a communication interface 320, a memory 330, and a communication bus 340, wherein the processor 310, the communication interface 320, and the memory 330 communicate with each other through the communication bus 340.

[0064] Memory 330 is used to store computer programs; When the processor 310 executes the program stored in the memory 330, it performs the following steps: Identical pulsed lasers are injected into the first optical fiber and the reference optical fiber respectively. The intensity ratio of the anti-Stokes signal to the Stokes signal of the backscattered Raman light in the first optical fiber and the corresponding intensity ratio in the reference optical fiber are obtained. Based on the two intensity ratios, the first temperature distribution along the first optical fiber and the reference temperature distribution along the reference optical fiber are calculated respectively. Narrow-linewidth pulsed lasers are injected into the second optical fiber. Based on the backscattered Brillouin spectroscopy at each spatial position along the second optical fiber, the Brillouin frequency shift distribution along the well axis is obtained. Based on the reference temperature distribution and the Brillouin frequency shift distribution, combined with the pre-calibrated pressure-frequency shift conversion coefficient, a continuous pressure distribution along the well axis is generated. The first temperature distribution and the continuous pressure distribution are determined as the monitoring results of temperature and pressure throughout the well section.

[0065] The communication bus mentioned above can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. This communication bus can be divided into address bus, data bus, control bus, etc. For ease of illustration, only one thick line is used to represent it in the diagram, but this does not mean that there is only one bus or one type of bus.

[0066] The communication interface is used for communication between the aforementioned electronic devices and other devices.

[0067] The memory may include random access memory (RAM) or non-volatile memory (NVM), such as at least one disk storage device. Optionally, the memory may also be at least one storage device located remotely from the aforementioned processor.

[0068] The processors mentioned above can be general-purpose processors, including central processing units (CPUs), network processors (NPs), etc.; they can also be digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0069] The implementation methods and beneficial effects of the various components of the electronic device in the above embodiments for solving the problem can be found in [reference needed]. Figure 1The steps in the illustrated embodiments are used to implement the electronic device. Therefore, the specific working process and beneficial effects of the electronic device provided in this application will not be repeated here.

[0070] In another embodiment provided in this application, a computer-readable storage medium is also provided, which stores instructions that, when executed on a computer, cause the computer to perform the monitoring method for temperature and pressure inside the CO2 injection well as described in any of the above embodiments.

[0071] In another embodiment provided in this application, a computer program product containing instructions is also provided, which, when run on a computer, causes the computer to execute the method for monitoring temperature and pressure in CO2 injection wells as described in any of the above embodiments.

[0072] Those skilled in the art will understand that the embodiments in this application can be provided as methods, systems, or computer program products. Therefore, the embodiments in this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the embodiments in this application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0073] This application describes embodiments of methods, apparatus (systems), and computer program products according to embodiments of this application with reference to flowchart illustrations and / or block diagrams. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0074] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0075] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0076] Although preferred embodiments have been described in this application, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of this application.

[0077] Obviously, those skilled in the art can make various modifications and variations to the embodiments of this application without departing from the spirit and scope of the embodiments of this application. Therefore, if these modifications and variations to the embodiments of this application fall within the scope of the claims in this application and their equivalents, then this application also intends to include these modifications and variations.

Claims

1. A method for monitoring temperature and pressure in a CO2 injection well, characterized in that, The method includes: laying a first optical fiber for temperature measurement via Raman scattering and a second optical fiber for pressure measurement via Brillouin scattering radio frequency shift along the well axis; and laying a reference optical fiber within the annulus of the wellbore along the well axis. The same pulsed laser is injected into the first optical fiber and the reference optical fiber respectively. The intensity ratio of the anti-Stokes signal to the Stokes signal of the backscattered Raman light in the first optical fiber and the corresponding intensity ratio in the reference optical fiber are obtained. The first temperature distribution along the first optical fiber and the reference temperature distribution along the reference optical fiber are calculated based on the two intensity ratios respectively. Narrow-linewidth pulsed laser light is injected into the second optical fiber, and the Brillouin frequency shift distribution along the well axis is obtained based on the backscattering spectrum at each spatial position along the second optical fiber. Based on the reference temperature distribution and the Brillouin frequency shift distribution, combined with the pre-calibrated pressure-frequency shift conversion coefficient, a continuous pressure distribution along the well axis is generated; the first temperature distribution and the continuous pressure distribution are determined as the monitoring results of temperature and pressure throughout the well section.

2. The method as described in claim 1, characterized in that, The reference optical fiber is sealed in a protective tube filled with inert gas, which is arranged along the wellbore axis in the annulus and parallel to the wellbore axis.

3. The method as described in claim 1, characterized in that, Obtain the Brillouin frequency shift distribution along the well axis, including: For each spatial location, the discrete intensity data of the collected backscattered Brillouin scattering spectrum are arranged at equal intervals according to frequency to form the original spectral line sequence; the original spectral line sequence is then smoothed using a sliding window. The smoothed spectral sequence is fitted using a piecewise Lorentz function; the peak frequency is extracted from the fitted piecewise Lorentz function, and the difference between the peak frequency and the center frequency of the narrow linewidth pulsed laser is determined as the Brillouin frequency shift value at that spatial location; the Brillouin frequency shift values ​​at each spatial location are arranged in depth order to generate the Brillouin frequency shift distribution.

4. The method as described in claim 1, characterized in that, Based on the reference temperature distribution and the Brillouin frequency shift distribution, and combined with the pre-calibrated pressure-frequency shift conversion coefficient, a continuous pressure distribution along the well axis is generated, including: A joint response equation is established between Brillouin frequency shift and temperature and pressure. The equation is: the change in Brillouin frequency shift is equal to the sum of the frequency shift component caused by temperature change and the frequency shift component caused by pressure change. Substitute the reference temperature distribution into the joint response equation as the baseline temperature quantity, calculate the frequency shift component caused by temperature at each spatial location, and subtract the frequency shift component caused by temperature from the Brillouin frequency shift distribution to obtain the net frequency shift distribution caused by CO2 pressure change; The product of each net frequency shift value in the net frequency shift distribution and a pre-calibrated pressure-frequency shift conversion coefficient is used to determine the pressure value at the corresponding location, thereby generating a continuous pressure distribution along the well axis.

5. The method as described in claim 4, characterized in that, In the joint response equation, the frequency shift component caused by temperature change is determined in the following way: The second optical fiber is pre-calibrated at temperature, and the change in Brillouin frequency shift corresponding to a unit temperature change is obtained as the temperature-frequency shift coefficient. During real-time downhole measurements, the deviation of the reference temperature distribution from a preset reference temperature baseline is multiplied by the temperature-frequency shift coefficient to obtain the temperature-induced frequency shift component at each spatial location.

6. The method as described in claim 1, characterized in that, The first temperature distribution and the continuous pressure distribution are determined as the monitoring results of temperature and pressure throughout the well section, including: This first temperature distribution is taken as the true temperature distribution along the well line; The first temperature distribution is spatiotemporally synchronized with the continuous pressure distribution to generate a two-dimensional temperature-pressure matrix containing the dimensions of well depth and sampling time. The temperature-pressure two-dimensional matrix was used to determine the monitoring results of temperature and pressure throughout the well section.

7. The method as described in claim 6, characterized in that, The first temperature distribution is spatiotemporally synchronized with the continuous pressure distribution to generate a two-dimensional temperature-pressure matrix containing the dimensions of well depth and sampling time, including: By using the same depth sampling interval and the same time sampling frequency, a two-dimensional matrix is ​​constructed by mapping temperature values ​​to pressure values ​​one-to-one. The row index of this two-dimensional matrix corresponds to the well depth sequence, and the column index corresponds to the sampling time sequence. Each element in this matrix is ​​a tuple, storing the temperature and pressure values ​​at any depth and at any time.

8. A device for monitoring temperature and pressure in a CO2 injection well, characterized in that, The device comprises: a first optical fiber for measuring temperature via Raman scattering and a second optical fiber for measuring pressure via Brillouin scattering radio frequency shift; and a reference optical fiber laid within the annulus of the wellbore along the well axis. The acquisition unit is used to inject the same pulsed laser into the first optical fiber and the reference optical fiber respectively, and acquire the intensity ratio of the anti-Stokes signal to the Stokes signal of the backscattered Raman light in the first optical fiber, and the corresponding intensity ratio in the reference optical fiber. The calculation unit is used to calculate the first temperature distribution along the first optical fiber and the reference temperature distribution along the reference optical fiber based on two intensity ratios, respectively. The acquisition unit is also used to inject narrow-linewidth pulsed laser into the second optical fiber and acquire the Brillouin frequency shift distribution along the well axis based on the backscattering spectrum at each spatial position along the second optical fiber. The generation unit is used to generate a continuous pressure distribution along the well axis based on the reference temperature distribution and the Brillouin frequency shift distribution, combined with a pre-calibrated pressure-frequency shift conversion coefficient; The determination unit is used to determine the first temperature distribution and continuous pressure distribution as the monitoring results of temperature and pressure throughout the well section.

9. An electronic device, characterized in that, The electronic device includes a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus; Memory, used to store computer programs; A processor, when executing a program stored in memory, implements the method of any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the method described in any one of claims 1-7.

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