A mirror imaging method for gas-water two-phase holdup based on array fiber optic probes

Abstract

The present invention discloses a method for mirror imaging of gas-water two-phase holdup based on an array of optical fiber probes, and relates to the technical field of dynamic monitoring of gas wells. The method comprises: projecting six optical fiber probes of a flow imager FIT onto a wellbore cross section at the same height, gridding and normalizing the wellbore inner diameter and probe positions to obtain a cross-sectional grid, and determining the two-dimensional coordinates of each optical fiber probe in the cross-sectional grid and the local gas holdup at each optical fiber probe coordinate; based on the law that gas and water flow are radially symmetrical along the center of the wellbore, the six optical fiber probes are rotated counterclockwise along the cross section in the wellbore to obtain a plurality of radially symmetrical mirror probes and corresponding coordinates, and the gas holdup at the coordinates of each radially symmetrical mirror probe is predicted, and the predicted gas holdup is interpolated in the cross-sectional grid using an interpolation algorithm to obtain a reconstructed gas-water image of the wellbore cross section. The present invention can overcome the limitations of single-position measurement.

Description

Technical Field

[0001] The present invention relates to the technical field of gas well dynamic monitoring, and in particular to a gas-water two-phase holdup rate mirror imaging method based on an array optical fiber probe. Background Art

[0002] Natural gas is a clean energy source, and China's gas fields are increasing their efforts to develop natural gas year by year. Dynamic monitoring of gas well production conditions has important application value. Analysis of production profile logging data can determine the gas and water production locations, the fluid properties of each production layer, and the production information of each phase. Traditional vertical well gas-water two-phase production profiles typically use a seven-parameter combination (natural gamma, magnetic positioning, temperature, pressure, flow rate, density, and capacitance water holdup or gas holdup) to perform sampling measurements at a single location in the center of the production wellbore's cross section. This results in limited measurement locations and an inability to comprehensively reflect fluid information at different locations on the wellbore cross section. Summary of the Invention

[0003] The purpose of the present invention is to provide a gas-water two-phase holdup rate mirror imaging method based on an array optical fiber probe, which can overcome the limitation of single position measurement in the prior art.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] A method for imaging the gas-water two-phase holdup rate using an array optical fiber probe, comprising:

[0006] The six fiber optic probes of the flow imager (FIT) were projected onto a wellbore cross section at the same height. The wellbore inner diameter and probe positions were gridded and normalized to obtain a cross-sectional grid. The two-dimensional coordinates of each fiber optic probe in the cross-sectional grid and the local gas holdup at each fiber optic probe coordinate were determined.

[0007] Based on the radial symmetry along the center of the wellbore when gas and water flow, the six fiber optic probes are rotated counterclockwise along the inner diameter of the wellbore by n°. The final mirror probe position differs from the initial fiber optic probe position by (360°-n°). The total rotation is times, get A radially symmetric mirror probe and its corresponding coordinates;

[0008] Based on the two-dimensional coordinates of each fiber optic probe and the local gas holdup at each fiber optic probe, the gas holdup at each radially symmetric mirror probe coordinate is predicted, and the predicted gas holdup is interpolated in the cross-sectional grid using an interpolation algorithm to obtain a reconstructed gas-water image of the wellbore cross section.

[0009] Optionally, the projecting of six optical fiber probes of the flow imager FIT onto a wellbore cross section at the same height, performing gridding and normalization processing on the wellbore inner diameter and the probe positions to obtain a cross-sectional grid specifically includes:

[0010] The fiber optic probe in each flow imager FIT is projected onto the wellbore cross section to obtain multiple unevenly distributed projection positions. The line connecting the projection positions is used as the X-axis, the vertical direction of the X-axis is used as the Y-axis, and the center of the wellbore is used as the coordinate origin. The wellbore cross section is gridded and normalized to obtain a cross-sectional grid; the cross-sectional grid includes the coordinate data of each grid.

[0011] Optionally, the two-dimensional coordinate calculation formula of each optical fiber probe in the cross-sectional grid is:

[0012]

[0013] Among them, l i ′ is the distance from the projection point of the i-th optical fiber probe to the bottom of the instrument; l i is the length of the i-th fiber optic probe along the instrument arm to the bottom of the instrument; is the opening angle of the instrument; D is the inner diameter of the wellbore; d is the normalized inner diameter of the wellbore; x i is the normalized two-dimensional coordinate of the i-th fiber probe.

[0014] Optionally, the local gas holdup rate calculation formula at each optical fiber probe coordinate is:

[0015]

[0016] Among them, Y gi represents the local gas holding fraction at the coordinate of the ith fiber probe; M i represents the measured response value of the i-th optical fiber probe; M g Indicates the response value of the fiber optic probe in pure gas; M W Indicates the response value of the fiber optic probe in pure water.

[0017] Optionally, the calculation method of the radially symmetric mirror probe coordinates is:

[0018] The two-dimensional space coordinates of the cross-section grid are (x i ,y i Six fiber optic probes A) (i=1,2,...,6) i (i=1,2,...,6), rotate θ degrees counterclockwise around the origin, and combine the rotation matrix R(θ) with the coordinate vector of the point Multiply to determine the coordinate point after rotation (x i ' j ,yi ' j ), expressed as:

[0019]

[0020] Among them, θ j is the jth rotation angle, x i ' j and y i ' j are the coordinates of the i-th fiber probe after rotation at the j-th rotation angle.

[0021] Optionally, the calculation formula of the rotation matrix R(θ) is:

[0022]

[0023] Where θ is the rotation angle in radians.

[0024] Optionally, the calculation formula for the rotation angle is:

[0025]

[0026] Where n is the angle of each rotation, Z represents the set of integers; π is the ratio of the circumference of a circle to its circumference.

[0027] Optionally, the calculation process of the local gas holdup rate at each optical fiber probe coordinate is:

[0028] Based on the calibration values ​​in single-phase water and single-phase gas and combined with the volume model, the local gas holdup at each fiber probe coordinate is calculated according to the response value of each fiber probe.

[0029] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0030] The present invention discloses a method for mirror imaging of gas-water two-phase holdup based on an array of optical fiber probes. The method comprises projecting six optical fiber probes of a flow imager (FIT) onto a wellbore cross section at the same height, gridding and normalizing the wellbore inner diameter and probe positions to obtain a cross-sectional grid, and determining the two-dimensional coordinates of each optical fiber probe in the cross-sectional grid and the local gas holdup at each optical fiber probe coordinate. Based on the law that gas and water flow are radially symmetrical along the wellbore center, the six optical fiber probes are rotated counterclockwise along the cross section within the wellbore to obtain multiple radially symmetrical mirror probes and corresponding coordinates, predicting the gas holdup at each radially symmetrical mirror probe coordinate, and interpolating the predicted gas holdup in the cross-sectional grid using an interpolation algorithm to obtain a reconstructed gas-water image of the wellbore cross section. The present invention can overcome the limitations of single-position measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 This is the theoretical flow pattern diagram of the gas-water two-phase vertical well in this embodiment;

[0033] Figure 2 This is the flow pattern diagram of the vertical well gas-water two-phase experiment in this embodiment;

[0034] Figure 3 is a comparison diagram of the instruments in this embodiment; wherein, Figure 3 (a) is a schematic diagram of conventional seven-parameter single-probe centered single position measurement; Figure 3 (b) is a schematic diagram of information measured at six different positions by six fiber optic probes in FIT;

[0035] Figure 4 This is a flow diagram of the gas holdup imaging method in this embodiment;

[0036] Figure 5 This is a schematic diagram of the probe projection in this embodiment;

[0037] Figure 6 Schematic diagram of the gridding process of the optical fiber probe in this embodiment;

[0038] Figure 7 Schematic diagram of wellbore cross-sectional image reconstruction of six optical fiber probes in this embodiment;

[0039] Figure 8 Schematic diagram of one mirror image of six optical fiber probes in this embodiment; wherein, Figure 8 (a) is a schematic diagram of the gridding process of twelve probes; Figure 8 Middle (b) is the reconstruction of twelve probe images;

[0040] Figure 9 This is a schematic diagram showing that the probe rotates counterclockwise twice in this embodiment;

[0041] Figure 10 This is the image of the gas holdup rate after the mirror probe in this embodiment is reconstructed; wherein, Figure 10 (a) is the total flow of gas and water 400m 3 Schematic diagram of the mirror imaging effect when / d; Figure 10 (b) is the total gas and water flow rate of 550m 3 Schematic diagram of the mirror imaging effect when / d;

[0042] Figure 11 is a comparison chart of the gas holdup rate under different flow conditions and different mirroring times in this embodiment; wherein, Figure 11 (a) is the total flow of gas and water 400m 3 Statistical diagram of gas holdup rate at / d; Figure 11 (b) is the total gas and water flow rate of 550m 3 Statistical diagram of gas holdup rate at / d. DETAILED DESCRIPTION

[0043] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0044] The purpose of the present invention is to provide a gas-water two-phase holdup rate mirror imaging method based on an array optical fiber probe, which can overcome the limitation of single position measurement in the prior art.

[0045] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0046] In order to overcome the limitations of the above-mentioned single-position measurement, the present invention proposes a gas holdup mirror imaging method based on an array fiber optic probe based on the response information of the multi-position measurement and the flow characteristics of the vertical well gas-water two-phase under different flow conditions. The method is as follows: (1) In the flow simulation loop wellbore, using the flow imager FIT (Flow Imager Tool), simulation experiments were carried out under different total gas and water flow rates and different water contents in the vertical well. It was found that the experimental flow types mainly include bubbly flow, elastic flow, slug flow and foamy flow, and the gas and water phases are symmetrically distributed along the central axis of the vertical wellbore. (2) Based on the data collected by the six fiber optic probes in FIT, the information of the unmeasured points was predicted by the interpolation algorithm, and the image of the gas phase and the water phase along the cross section of the wellbore was reconstructed. (3) Combined with the symmetrical distribution characteristics of fluid flow, the mirror imaging technology was proposed for the first time. The six fiber optic probes were rotated continuously along the radial counterclockwise by n°. The final mirror probe position differed from the initial fiber optic probe position by (360°-n°), and the total rotation was The fiber optic probe plus the mirror probe was realized Gas holdup cross-section imaging of the probe.

[0047] This gas holdup mirror imaging method achieves comprehensive measurement of the wellbore cross-section with a smaller number of probes. It can more accurately calculate the gas holdup of the gas-water two-phase in the vertical wellbore cross-section, better reflect the fluid properties of each production layer in the wellbore, thereby improving the evaluation effect of the gas production profile and providing technical support for water plugging and gas enhancement.

[0048] Based on the above technical solution, Figures 1-11 Take the example to describe the specific processing procedures of the above steps in detail.

[0049] The geometric state of gas and water flowing upward along the pipe string can be divided into several basic types, namely flow patterns. Figure 1 As shown in the figure, from left to right, there are five typical flow patterns in the gas-water phase of a vertical well. It can be seen that as the gas volume (gas fraction) increases, the flow pattern changes from bubbly flow to slug flow, slug flow, foam flow, and mist flow. Under the combined effects of gravity, buoyancy, and pressure differential, the gas and water phases in the vertical wellbore are essentially distributed radially symmetrically along the central axis of the wellbore.

[0050] Referring to the production status of low-yield gas wells on land in China, based on the flow loop simulation experimental device and FIT (Flow Imager Tool), the present invention designed an experimental scheme as shown in Table 1 and carried out simulation measurements under different flow rates and different water cuts. Figure 2 As shown in the figure, four flow patterns were found in this experiment: bubbly flow, slug flow, slug flow and foamy flow.

[0051] Table 1 Experimental plan

[0052]

[0053] Gas holdup, also known as void fraction, cross-sectional gas content, or true gas content, refers to the ratio of the gas phase area to the entire wellbore cross-sectional area in two-phase flow. Flow patterns are primarily determined by wellbore inclination, flow rates of each phase, pipe diameter, fluid density, and viscosity. There is a direct correlation between gas holdup and flow pattern; the distribution and variation of gas holdup vary under different flow patterns.

[0054] like Figure 3 As shown in (a), when logging the gas production profile of vertical wells in various gas fields in China, the central, single-position sampling measurement (PLT) is generally adopted in the wellbore. Figure 3(b) is the flow imager FIT (Flow Imager Tool) used in the present invention, in which six fiber optic probes can measure the local gas holdup at six different positions. Obviously, on the cross section of the wellbore, compared with PLT, FIT can provide more fluid distribution information, but the measurement points are still insufficient. At the same time, if more measurement probes (12 or 16) are added to the cross section of the wellbore, it will also interfere with the normal flow state of the fluid. For this reason, the present invention proposes a method for mirror imaging based on six fiber optic probes based on the characteristic that the vertical gas-water two-phase flow state is radially symmetrical along the center of the wellbore.

[0055] The flow of the present invention is as follows Figure 4 As shown in the figure, (1) the measurement values ​​of the six fiber optic probes on the flow imager FIT are projected onto the wellbore cross section at the same height, the wellbore inner diameter D and the probe position are normalized, and the coordinate values ​​of the six probes are calculated on the two-dimensional coordinate system and the wellbore cross section; (2) based on the calibration values ​​in single-phase water and single-phase gas, combined with the volume model, the local gas holdup at each probe is calculated according to the response value of each fiber optic probe, and combined with the interpolation algorithm, the gas holdup of the unmeasured point on the wellbore cross section is predicted, thereby realizing the reconstruction of the gas-water image along the wellbore cross section under different flow and water content conditions; (3) based on the law that the gas and water phases in the vertical wellbore are symmetrical along the wellbore center when they flow steadily, the idea of ​​mirror probe imaging is proposed, that is, the six fiber optic probes are symmetrically virtually imaged along the wellbore center, which is equivalent to having the measurement values ​​of twelve fiber optic probes. By the above method, the local gas holdup at twelve different positions along the X-axis on the wellbore cross section can be obtained directly and indirectly; (4) Then, the six fiber optic probes are rotated continuously counterclockwise by n° along the inner diameter of the wellbore. The final mirror probe position differs from the initial fiber optic probe position by (360°-n°), and the total rotation is times, we get the radially symmetric position of the original six probes. The image of the entire wellbore is reconstructed by combining the mirrored coordinate points of the six optical fiber probes and the mirrored probes. (5) The image reconstruction results of the six optical fiber probes and the mirrored probes are compared and analyzed. The specific steps are as follows:

[0056] Step 1: Project the six fiber optic probes onto the wellbore cross section at the same height, normalize the wellbore inner diameter D and the probe positions, and calculate the two-dimensional coordinate values ​​of the six probes on the wellbore cross section;

[0057] Step 2: Calculate the local gas holdup at each probe, which is used to predict the gas holdup at unmeasured points based on the local gas holdup and reconstruct the gas-water image of the wellbore cross section;

[0058] Step 3: Based on the principle of symmetry of gas-water flow along the wellbore center, a mirror probe concept is proposed: six probes are extended symmetrically along the wellbore center to obtain local gas holdup at twelve locations. The wellbore cross-sectional image is then reconstructed by interpolation based on the local gas holdup at the twelve locations.

[0059] Step 4: Based on the radial symmetry along the center of the wellbore during gas and water flow, the six fiber optic probes are rotated counterclockwise by n° along the inner diameter of the wellbore. The final mirror probe position differs from the initial fiber optic probe position by (360°-n°). The total rotation is times, we get the radially symmetric position of the original six probes. A radially symmetric mirror probe is used to reconstruct the wellbore image;

[0060] Step 5: Compare and analyze the imaging results of the six probes and the mirror probe.

[0061] As a specific implementation method, the specific method of step 1 is as follows:

[0062] like Figure 5 As shown in the figure, the position of each fiber optic probe on the instrument arm is fixed. When the instrument is placed in a wellbore with different inner diameters D, the opening angles of the two instrument arms are The projection positions of each probe on the wellbore cross section also change. When each probe is vertically projected onto the same wellbore cross section, the projection positions of each fiber optic probe on the wellbore cross section are A1, A2, ..., A6 in sequence, and are unevenly distributed. Figure 6 As shown in the figure, the line connecting the projection positions of each probe is taken as the X-axis, its vertical direction is the Y-axis, and the center of the wellbore is the coordinate origin. The wellbore cross section is gridded and normalized to obtain the normalized coordinate value of each fiber optic probe (the inner diameter of the wellbore after normalization is d). The formula for obtaining the coordinate value is as follows:

[0063]

[0064] Among them, l′ i is the distance from the projection point of the i-th fiber probe to the bottom of the instrument, in mm; l i is the length of the i-th fiber optic probe from the instrument arm to the bottom of the instrument, in mm; is the opening angle of the instrument, in degrees; D is the inner diameter of the wellbore, in mm; d is the normalized inner diameter of the wellbore; x i is the normalized horizontal coordinate of the i-th fiber probe.

[0065] As a specific implementation method, the specific method of step 2 is as follows:

[0066] To obtain gas holdup imaging across the entire wellbore cross section, it is necessary to pre-process the fiber probe response values ​​at six different locations on the same wellbore cross section to obtain the local gas holdup values ​​near each probe, and then use the interpolation algorithm to predict the gas holdup at other unmeasured points. The local gas holdup is:

[0067]

[0068] Among them, Y gi represents the local gas holding fraction at the coordinate of the ith fiber probe; M i represents the measured response value of the i-th optical fiber probe; M g Indicates the response value of the fiber optic probe in pure gas; M W Indicates the response value of the fiber optic probe in pure water.

[0069] Figure 7 Figure 3 is a schematic diagram of the reconstructed gas-water image on a wellbore cross section after interpolation. The color scale transitions from black to white, representing the transition from the water phase to the gas phase. Assuming there is an interpolation point to be predicted in the wellbore, probes closer to the interpolation point contribute more to the interpolation result, while probes farther away contribute less. It can be seen that this interpolation point is closer to probe 6 (A6) and farther from probe 1 (A1). Probe 6 contributes more to this interpolation point, so the predicted value at this interpolation point is closer to the measured value of probe 6, indicating that it represents the gas phase. Clearly, the gas holdup image obtained using only six probes shows a gas phase on the left and a water phase on the right, which is inconsistent with actual flow.

[0070] As a specific implementation method, the specific method of step 3 is as follows:

[0071] like Figure 7 As shown in Figure 2, on the X-axis, the six fiber optic probes are unevenly distributed around the coordinate origin. Based on the law that gas and water are symmetrically distributed when flowing along the wellbore, the six fiber optic probes can be mirrored along the Y-axis (equivalent to rotating the six probes 180° counterclockwise) to obtain the coordinates of the six mirrored optical fibers A1′, A2′, ..., A6′ (as shown in Table 2) and the predicted values:

[0072] x i ′=-x i

[0073] Y g ' i =Y gi

[0074] Where x i ′ is the horizontal coordinate of the i-th mirror probe; x i is the horizontal coordinate of the i-th optical fiber probe; Y gi represents the local gas holding rate value of the i-th optical fiber probe; Yg ' i The local holdup value of the i-th mirror probe.

[0075] Table 2 Coordinates of the six fiber probes and six mirror probes after normalization (mirror symmetry along the y-axis)

[0076]

[0077]

[0078] The effect of using six fiber optic probes and six mirror probes to reconstruct the air-water image is as follows: Figure 8 As shown. Among them, Figure 8 (a) is a schematic diagram of the spatial distribution of twelve probes after mirror symmetry. Figure 8 (b) shows the reconstructed image of the twelve probes. Clearly, the image after mirroring along the Y axis is more consistent with the symmetry of gas-water flow in a vertical well, but the gas phase is present on both sides, which is inconsistent with reality.

[0079] As a specific implementation method, the specific method of step 4 is as follows:

[0080] like Figure 8 As shown in (b), although the imaging effect is improved after the mirror image is made, it is still inconsistent with the radial symmetry of the gas and water flow along the center of the wellbore. Therefore, the six fiber optic probes are rotated counterclockwise along the inner diameter of the wellbore by n degrees. The final mirror image probe position is different from the initial fiber optic probe position by (360°-n°), and the total rotation is The coordinate points and predicted values ​​of each mirror probe are obtained. The specific steps are as follows:

[0081] The rotation matrix is:

[0082]

[0083] Where θ is the rotation angle in radians.

[0084]

[0085] Where n is the angle of each rotation, Z represents the set of integers, with the unit being degrees; π is the circumference of a circle, which is approximately equal to 3.14159.

[0086] The coordinates in the two-dimensional space are (x i ,y i Six fiber optic probes A) (i=1,2,...,6) i (i=1,2,...,6), rotate θ degrees counterclockwise around the origin, using the rotation matrix R(θ) and the coordinate vector of the point Multiply to get the rotated coordinate point (x i ' j ,y i ' j ). This process can be expressed as:

[0087]

[0088] Among them, θ j is the jth rotation angle, x i ' j and y i ' j are the coordinates of the original point of the i-th optical fiber probe after rotation at the j-th rotation angle.

[0089] After the above continuous rotation and mirroring process, we get mirror probes, which is equivalent to a total of Based on the probe coordinates and the predicted values ​​of each probe, we can reconstruct the gas holdup rate image after a large number of mirrored probes. Figure 9 As shown in the figure, taking the six fiber optic probes rotated counterclockwise twice as an example, the "triangle star" in the figure is a mirror probe rotated 120° counterclockwise, and the "five-pointed star" is a mirror probe rotated 240° counterclockwise. After two rotations, 12 mirror probes are obtained. At this time, there are 18 fiber optic probes at different positions on the cross section of the wellbore. The gas holdup image reconstruction effect is shown as follows: Figure 10 shown.

[0090] As a specific implementation method, the specific method of step 5 is as follows:

[0091] Based on a total gas and water flow of 400m 3 / d and 550m 3 / d experimental data and the method of step 4, the optical fiber probe is rotated (180°, 120°, ..., 6°) respectively, and rotated (1, 2, ..., 59) times in total to obtain (354, 174, ..., 6) mirror probes. Figure 10 As shown, based on the rotated mirror probe and according to the method of step 2, the gas holdup images at different flow rates, different water contents and different mirror times are reconstructed.

[0092] By comparing and analyzing the experimental video data and the imaging results of the holdup rate after mirroring, we can conclude that:

[0093] (1) When the total gas and water flow rate remains unchanged, when the rotation angle decreases, the number of mirror probes increases, and the gas holdup image appears smoother overall. At this time, it is more consistent with the distribution law of symmetry around the central axis of the wellbore when the gas and water flow in the actual vertical well is symmetrical.

[0094] (2) For the same total gas-water flow rate, when the water content is low, the increase in water phase flow rate will aggravate the accumulation of bubbles; when the water content is high, the air mass gradually increases, and the fiber optic probe has difficulty detecting small bubbles, which affects the quality of gas holdup imaging. Specifically: ① The total gas-water flow rate is 400m 3 / d, the low water content area (such as 10% and 30%) is mainly slug flow, and the high water content area is mainly bubbly flow. The gas holdup imaging shows that at low water content, there are more white areas, which is consistent with the slug flow characteristics. At high water content, the water phase is continuous and the gas phase is dispersed, which is consistent with the bubbly flow type. ② The total gas and water flow rate is 550m 3 At 10% water content, the flow is mainly foamy, with a continuous gas phase and a dispersed water phase. At 30% water content, the flow is mainly slug flow, while at 50%, 70%, and 90% water content, the flow is mainly bubbly. The holdup rate imaging diagram is consistent with the experimental flow pattern.

[0095] like Figure 11 The total gas and water flow is 400m 3 / d and 550m 3 / d, the average gas holdup on the wellbore cross section was calculated after different water cuts and different mirror probe imaging times. By comparison, it was found that under the same total gas and water flow rate conditions, when the water cut changes from a low value to a high value, as the gas phase flow rate increases, the gas accumulation phenomenon becomes more detailed, and the average gas holdup in the wellbore also increases accordingly. This trend is consistent with the actual situation. At the same time, the total gas and water flow rate is 550m 3 The average gas holdup rate at / d is slightly higher than the total gas and water flow rate of 400m 3 The average gas holdup rate at d.

[0096] The fiber optic probe array used in this invention is suitable for downhole high-temperature, high-pressure environments and can be used directly for measurements, demonstrating its practical application. Compared to traditional single-probe techniques for single-location measurements and flow imaging instruments with 12 or more probes, this array probe can measure gas holdup at multiple locations across the wellbore cross section while minimizing the impact of probe arrays on fluid flow.

[0097] Based on a multiphase flow simulator and a flow imager (FIT), this method utilizes limited fiber optic probe measurement information, combined with the radial symmetry of gas and water around the wellbore center during stable flow. This method introduces a mirror probe method, predicting the mirror probe coordinates and values ​​of unmeasured points on the wellbore cross section. This method reconstructs gas holdup imaging, making the imaging results clearer, more intuitive, and more accurate. Furthermore, it optimizes and calculates the average gas holdup of the gas and water phases in a vertical wellbore across the wellbore cross section, more comprehensively reflecting the gas and water distribution in the wellbore and effectively revealing the fluid characteristics of each producing layer within the wellbore. This enhances the accuracy of gas production profile assessments and provides technical support for the implementation of water-blocking and gas-increasing strategies.

[0098] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0099] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A method for imaging the gas-water two-phase holdup rate based on an array optical fiber probe, characterized in that: include: The six fiber optic probes of the flow imager (FIT) were projected onto a wellbore cross section at the same height. The wellbore inner diameter and probe positions were gridded and normalized to obtain a cross-sectional grid. The two-dimensional coordinates of each fiber optic probe in the cross-sectional grid and the local gas holdup at each fiber optic probe coordinate were determined. Based on the radial symmetry along the center of the wellbore when gas and water flow, the six fiber optic probes are rotated counterclockwise along the inner diameter of the wellbore by n°. The final mirror probe position differs from the initial fiber optic probe position by (360°-n°). The total rotation is times, get A radially symmetric mirror probe and its corresponding coordinates; Based on the two-dimensional coordinates of each fiber optic probe and the local gas holdup at each fiber optic probe, the gas holdup at each radially symmetric mirror probe coordinate is predicted, and the predicted gas holdup is interpolated in the cross-sectional grid using an interpolation algorithm to obtain a reconstructed gas-water image of the wellbore cross section; The six fiber optic probes of the flow imager FIT are projected onto the wellbore cross section at the same height, and the wellbore inner diameter and probe positions are gridded and normalized to obtain the cross-sectional grid, specifically including: The fiber optic probe in each flow imager FIT is projected onto the wellbore cross section to obtain a plurality of unevenly distributed projection positions. The wellbore cross section is gridded and normalized using the line connecting the projection positions as the X-axis, the perpendicular direction of the X-axis as the Y-axis, and the wellbore center as the coordinate origin to obtain a cross-sectional grid; the cross-sectional grid includes the coordinate data of each grid; The calculation formula for the two-dimensional coordinates of each optical fiber probe in the cross-sectional grid is: Among them, l i ′ is the distance from the projection point of the i-th optical fiber probe to the bottom of the instrument; l i is the length of the i-th fiber optic probe along the instrument arm to the bottom of the instrument; is the opening angle of the instrument; D is the inner diameter of the wellbore; d is the normalized inner diameter of the wellbore; x i is the normalized two-dimensional coordinate of the i-th fiber probe.

2. The method for imaging the gas-water two-phase holdup rate based on an array optical fiber probe according to claim 1, characterized in that: The calculation formula for the local gas holdup rate at each optical fiber probe coordinate is: Among them, Y gi represents the local gas holding fraction at the coordinate of the ith fiber probe; M i represents the measured response value of the i-th optical fiber probe; M g Indicates the response value of the fiber optic probe in pure gas; M W Indicates the response value of the fiber optic probe in pure water.

3. The method for imaging the gas-water two-phase holdup rate based on an array optical fiber probe according to claim 1, characterized in that: The calculation method of the radially symmetric mirror probe coordinates is: The two-dimensional space coordinates of the cross-sectional grid are (x i ,y i Six fiber optic probes A) (i=1,2,...,6) i (i=1,2,...,6), rotate θ degrees counterclockwise around the origin, and combine the rotation matrix R(θ) with the coordinate vector of the point Multiply to determine the coordinate point after rotation (x′ ij ,y′ ij ), expressed as: Among them, θ j is the jth rotation angle, x′ ij and y′ ij are the coordinates of the i-th fiber probe after rotation at the j-th rotation angle.

4. The method for imaging the gas-water two-phase holdover rate based on an array optical fiber probe according to claim 3, characterized in that: The calculation formula of the rotation matrix R(θ) is: Where θ is the rotation angle in radians.

5. The method for imaging the gas-water two-phase holdup rate based on an array optical fiber probe according to claim 4, characterized in that: The calculation formula of the rotation angle is: Where n is the angle of each rotation, Z represents the set of integers; π is the ratio of the circumference of a circle to its circumference.

Images