Gas-water two-phase gas holdup mirror image imaging method based on array optical fiber probe

Abstract

The invention discloses a gas-water two-phase gas holdup mirror image imaging method based on an array optical fiber probe, and relates to the technical field of gas well dynamic monitoring. The method comprises the steps that six optical fiber probes of a flow imager FIT are projected to the cross section of a shaft at the same height, gridding and normalization processing is carried out on the inner diameter of the shaft and the positions of the probes, cross section grids are obtained, and the two-dimensional coordinates of all the optical fiber probes in the cross section grids and the local gas holdup at the coordinates of all the optical fiber probes are determined; based on the rule that gas and water are in radial symmetry along the center of a shaft when flowing, the six optical fiber probes are rotated anticlockwise along the cross section in the shaft to obtain a plurality of radially symmetric mirror probes and corresponding coordinates, and the gas holdup at the coordinates of the radially symmetric mirror probes is predicted; and performing interpolation processing on the predicted gas holdup in the cross section grid by using an interpolation algorithm to obtain a reconstructed wellbore cross section gas-water image. The limitation of single position measurement can be overcome.

Description

Technical Field

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

[0002] Natural gas is one of the clean energy sources. China's gas fields have been increasing their efforts to develop natural gas year by year. Dynamic monitoring of gas well output has important application value. Through the analysis of output profile logging data, the gas and water output location, the fluid properties of each output layer and the production information of each phase can be determined. Traditional vertical well gas-water two-phase output profile wells usually use a seven-parameter combination (natural gamma, magnetic positioning, temperature, pressure, flow rate, density, capacitive water holdup or gas holdup) to perform sampling measurements at a single position in the cross-section center of the production wellbore. There is a phenomenon that the measurement position is limited and the fluid information at different positions on the wellbore cross section cannot be reflected as a whole. 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 based on an array optical fiber probe, comprising:

[0006] The six fiber optic probes of the flow imager FIT are projected onto the wellbore cross section at the same height, the wellbore inner diameter and the probe position are gridded and normalized to obtain a cross-sectional grid, and the two-dimensional coordinates of each fiber optic probe in the cross-sectional grid and the local gas holdup rate at the coordinates of each fiber optic probe are 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 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, 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, gridding and normalizing 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 on the wellbore cross section to obtain multiple unevenly distributed projection positions, and 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 to grid and normalize the wellbore cross section 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 optical fiber probe from 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 optical 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 rate value at the coordinate of the ith optical fiber probe; M i represents the measured response value of the i-th optical fiber probe; M g Represents the response value of the optical fiber probe in pure gas; M W It represents 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-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 replace 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 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] Here, θ is the rotation angle in radians.

[0024] Optionally, the calculation formula of 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 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 gas-water two-phase holdup mirror imaging method based on an array fiber optic probe, the method comprising projecting six fiber optic probes of a flow imager FIT onto a wellbore cross section at the same height, gridding and normalizing the wellbore inner diameter and the probe position to obtain a cross-sectional grid, and determining 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; based on the law that gas and water flow are radially symmetrical along the wellbore center, the six fiber optic 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 each radially symmetrical 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 wellbore cross-sectional gas-water image. 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 drawings required for use in the embodiments will be briefly introduced below. 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 creative labor.

[0032] Figure 1 The vertical well gas-water two-phase theoretical flow pattern diagram 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 optical fiber probes in FIT;

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

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

[0037] Figure 6 This is a 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] Fig. 9 This is a schematic diagram of the probe rotating counterclockwise twice in this embodiment;

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

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

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work 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 array fiber optic probe measured at multiple positions, combined with the flow characteristics of the vertical well gas-water two-phase under different flow states. The method is specifically as follows: (1) In the flow simulation loop wellbore, using the flow imager FIT (Flow Imager Tool), simulation experiments were carried out at different total gas-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-water two-phase is 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 is predicted by the interpolation algorithm, and the image of the gas phase and the water phase is reconstructed along the cross section of the wellbore. (3) Combined with the symmetrical distribution characteristics of fluid flow, the mirror imaging technology is proposed for the first time. The six fiber optic probes are rotated continuously counterclockwise along the radial direction by n°. The final mirror probe position differs from the initial fiber optic probe position by (360°-n°), and the total rotation is The fiber optic probe plus the mirror probe was realized. Gas holdup cross-section imaging of the probe.

[0047] The gas holdup mirror imaging method can achieve comprehensive measurement of the wellbore cross section with a smaller number of probes, and can more accurately calculate the gas holdup of the gas-water two-phase in the vertical well on the wellbore cross section, better reflect the fluid properties of each production layer in the wellbore, and thus improve the evaluation effect of the gas production profile, providing technical support for water plugging and gas increase.

[0048] Based on the above technical solution, Figure 1-Figure 11 Take the above steps as an 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 vertical well gas-water two-phase. It can be seen that: with the increase of gas volume (gas content), the flow pattern changes from bubble flow to slug flow, slug flow, foam flow and mist flow in sequence. Under the combined effects of gravity, buoyancy and pressure difference, any flow pattern of gas and water phases in the vertical wellbore is basically 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 contents. 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 ratio, 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. The formation of flow pattern is mainly determined by well inclination, flow rate of each phase, pipe diameter, fluid density, and viscosity. There is a direct correspondence between gas holdup and flow pattern. Under different flow patterns, the distribution and change rules of gas holdup are different.

[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 for short) 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, the normal flow state of the fluid will also be disturbed. 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 rates and water content conditions; (3) based on the law that the gas and water phases in the vertical wellbore are symmetrical along the center of the wellbore when they flow stably, the idea of ​​mirror probe imaging is proposed, that is, the six fiber optic probes are symmetrically virtually imaged along the center of the wellbore, which is equivalent to having the measurement values ​​of twelve fiber optic probes. In this way, the local gas holdup rate at twelve different positions along the X-axis on the wellbore cross section can be obtained directly and indirectly; (4) Then, the six optical fiber probes are rotated counterclockwise along the inner diameter of the wellbore by n° continuously, and the final mirror probe position differs from the initial optical fiber probe position by (360°-n°), with a total rotation of times, we obtain a radially symmetrical The image of the entire wellbore is reconstructed by combining the mirrored probes with the mirrored coordinate points; (5) the image reconstruction results of the six fiber optic 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 position, and calculate the two-dimensional coordinate values ​​of the six probes on the wellbore cross section;

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

[0058] Step 3: Based on the law of symmetry along the center of the wellbore when gas and water flow, the idea of ​​mirror probe is proposed: the six probes are extended symmetrically along the center of the wellbore to obtain the local gas holding rates at twelve positions, and then the wellbore cross-sectional image is reconstructed based on the interpolation of the local gas holding rates at the twelve positions;

[0059] Step 4: Based on the radial symmetry of the gas and water flow along the center of the wellbore, 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°), and the total rotation is times, we obtain a radially symmetrical A radially symmetric mirror probe for reconstructing 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 they 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 taken as the coordinate origin. The wellbore cross section is gridded and normalized to obtain the normalized coordinate value of each optical fiber 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 ith optical fiber probe to the bottom of the instrument, in mm; l i is the length of the ith optical fiber 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] In order to obtain the gas holdup imaging on the entire wellbore cross section, it is necessary to pre-process the fiber probe response values ​​at six different positions on the same wellbore cross section to obtain the local gas holdup values ​​near each probe, and then combine 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 rate value at the coordinate of the ith optical fiber probe; M i represents the measured response value of the i-th optical fiber probe; M g Represents the response value of the optical fiber probe in pure gas; M W It represents the response value of the fiber optic probe in pure water.

[0069] Figure 7 It is a schematic diagram of the reconstruction of the gas-water image on the wellbore cross section after interpolation. The color scale from black to white is the transition from the water phase to the gas phase. Assuming that there is an interpolation point to be predicted in the wellbore, the closer the probe is to the interpolation point, the greater its contribution to the interpolation result, and the farther the distance is, the smaller its contribution is. It can be seen that: the interpolation point is closer to probe No. 6 (A6) and farther from probe No. 1 (A1). Probe No. 6 contributes more to the interpolation point. Therefore, the predicted value of the interpolation point is closer to the measured value of probe No. 6, that is, it is in the gas phase. Obviously, in the gas holdup imaging diagram obtained by using only six probes, the left side mainly shows the gas phase and the right side mainly shows the water phase, which is inconsistent with the actual flow phenomenon.

[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 probes are unevenly distributed around the origin of the coordinate system. Based on the law that gas and water are symmetrically distributed when flowing along the wellbore, the six fiber 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] In the formula, x i ′ is the horizontal coordinate of the i-th mirror probe; x i is the horizontal coordinate of the ith optical fiber probe; 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 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 shown in Figure 2. 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) is the image reconstruction of the twelve probes. Obviously, the image after mirror symmetry along the Y axis is more consistent with the symmetry law of gas and water flow in the vertical well, but the upper and lower sides are gas phase, which is inconsistent with the actual situation.

[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 law that the gas and water flow is radially symmetrical along the center of the wellbore. Therefore, the six fiber optic probes are rotated counterclockwise along the inner diameter of the wellbore by n°. The final mirror image probe position differs from the initial fiber optic probe position by (360°-n°), and the total rotation is The specific steps are as follows:

[0081] The rotation matrix is:

[0082]

[0083] Here, 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 degree; 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 i ' j are the rotated coordinates of the original point of the i-th optical fiber probe at the j-th rotation angle.

[0089] After the above continuous rotation and mirroring process, we get mirror probes, which is equivalent to having a total of Based on the probe coordinates and the predicted values ​​of each probe, a large number of mirrored probes can be used to reconstruct the gas holdup rate images. Fig. 9 As shown in the figure, taking the six optical fiber 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, it is equivalent to a total of 18 optical fiber probes at different positions on the cross section of the wellbore. The gas holdup image reconstruction effect is shown as follows Fig.10 shown.

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

[0091] Based on total gas and water flow of 400m 3 / d and 550m 3 / d experimental data and the method of step 4, the fiber probe is rotated (180°, 120°, ..., 6°) respectively, and rotated (1, 2, ..., 59) times in total to obtain (354, 174, ..., 6) mirror probes. Fig.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 mirroring times are reconstructed.

[0092] By comparing and analyzing the experimental video data and the imaging results of the gas holding rate after mirroring, it can be concluded that:

[0093] (1) When the total gas-water flow rate remains unchanged, as 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 intensify the aggregation of bubbles; when the water content is high, the air mass gradually increases, and the optical fiber probe is difficult to detect small bubbles, which affects the quality of gas holdup imaging. 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 there are more white areas at low water content, 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-water flow rate is 550m 3 / d, at 10% water content, it is mainly foamy flow, with continuous gas phase and dispersed water phase. At 30% water content, it is mainly slug flow, and at 50%, 70%, and 90% water content, it is mainly bubbly flow. The gas holdup imaging diagram is consistent with the experimental flow pattern.

[0095] like Fig.11 The total gas and water flow is shown as 400m 3 / d and 550m 3 / d, the average gas holding rate on the wellbore cross section was calculated after different water content and different mirror probe imaging times. By comparison, it was found that under the same total gas and water flow rate, when the water content changes from a low value to a high value, as the gas phase flow rate increases, the gas aggregation phenomenon becomes more detailed, and the average gas holding rate of the wellbore also increases accordingly. This trend of change 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 400m / d is slightly higher than the total gas-water flow rate. 3 The average gas holdup rate at 100 °C / d.

[0096] The array fiber optic probe used in the present invention is suitable for underground high temperature and high pressure environments, can be directly used for downhole measurements, and has good practical application value. Compared with the traditional single-probe technology for single-position measurement and flow imagers with more than 12 probes, it can meet the needs of measuring local gas holdup at multiple different positions on the wellbore cross section, and can reduce the disturbance effect of the array probe on the fluid flow.

[0097] The present invention is based on a multiphase flow simulation device and a flow imager FIT, using 6 limited fiber optic probe measurement information, combined with the radial symmetry of gas and water around the center of the wellbore when flowing in the stable section, and introduces a mirror probe method, thereby predicting the mirror probe coordinates and values ​​of unmeasured points on the wellbore cross section, and realizing the reconstruction of gas holdup imaging, making the imaging results clearer, more intuitive and accurate. The average gas holdup of gas and water phases in the vertical well on the wellbore cross section is then optimized and calculated, which can more comprehensively reflect the gas and water distribution state in the wellbore, and effectively reveal the fluid characteristics of each production layer in the wellbore, thereby enhancing the accuracy of gas production profile evaluation and providing technical support for the implementation of water plugging and gas increase 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 article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood 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 are projected onto the wellbore cross section at the same height, the wellbore inner diameter and the probe position are gridded and normalized to obtain a cross-sectional grid, and the two-dimensional coordinates of each fiber optic probe in the cross-sectional grid and the local gas holdup rate at the coordinates of each fiber optic probe are 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 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 get Radially symmetric mirror probes and 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.

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 six optical fiber probes of the flow imager FIT are projected onto the wellbore cross section at the same height, and the wellbore inner diameter and the probe position are gridded and normalized to obtain the cross-sectional grid, specifically including: The fiber optic probe in each flow imager FIT is projected on the wellbore cross section to obtain multiple unevenly distributed projection positions, and 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 to grid and normalize the wellbore cross section to obtain a cross-sectional grid; the cross-sectional grid includes the coordinate data of each grid.

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 two-dimensional coordinate calculation formula 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 optical fiber probe from 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 optical fiber probe.

4. 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 rate value at the coordinate of the ith optical fiber probe; M i represents the measured response value of the i-th optical fiber probe; M g Represents the response value of the optical fiber probe in pure gas; M W It represents the response value of the fiber optic probe in pure water.

5. 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 replace the rotation matrix R(θ) with the coordinate vector of the point Multiply to determine the coordinate point after rotation (x i ' j ,y i ' j ), expressed as: Among them, θ j is the jth rotation angle, x i ' j and i ' j are the coordinates of the i-th fiber probe after rotation at the j-th rotation angle.

6. The method for imaging the gas-water two-phase holdup rate based on an array optical fiber probe according to claim 5, characterized in that: The calculation formula of the rotation matrix R(θ) is: Here, θ is the rotation angle in radians.

7. The method for imaging the gas-water two-phase holdup rate based on an array optical fiber probe according to claim 6, 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 a circle to its circumference.

8. 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 process of the local gas holdup rate at each optical fiber probe coordinate is: 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.

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