Shale gas well tubing running opportunity determination method

Abstract

The invention discloses a method for determining the oil pipe lowering time of a shale gas well. The method comprises the steps that firstly, shaft pressure drops generated when a shale gas updip well and a shale gas downdip well are produced through a sleeve and an oil pipe are calculated respectively; 2, drawing an updip well three-dimensional curved surface drawing and a downdip well three-dimensional curved surface drawing which have the same coordinate system; thirdly, preliminary reference charts of the oil pipe lowering time of the updip well and the downdip well under any wellhead pressure are determined respectively; 4, determining a preliminary reference chart of the oil pipe descending time of the updip well and the downdip well under different wellhead pressures; fifthly, final reference charts of the oil pipe descending time of the updip well and the downdip well are obtained through combination; and 6, determining the oil pipe descending time according to the final reference chart of the oil pipe descending time. According to the method, the oil pipe descending time of any shale gas well can be determined, the technical problems that the oil pipe intervention time of the shale gas well is difficult to determine and a clear guidance method is lacked at present are solved, and important technical support can be provided for developers to accurately judge the oil pipe descending time of the gas well.

Description

Technical Field

[0001] The present invention relates to the technical field of shale gas development, and in particular to a method for determining the timing of oil pipe drilling in a shale gas well. Background Art

[0002] For shale gas reservoirs, due to the compactness of the reservoir and the adsorption of organic matter, it has a special seepage mechanism, and the gas well production cycle is as long as several decades. A shale gas well will mainly go through two production stages from the start of production: (1) The initial production is high, but it decreases rapidly. The main produced gas is free gas in the fracture system.

[0003] (2) The production gradually becomes stable, and the main produced gas is free gas and adsorbed gas in the matrix pores.

[0004] Due to the long-term non-steady-state flow stage, shale gas wells generally have a long decline period, especially in the early stage of production, when the output is high but the decline is fast. The gas production volume in this stage accounts for a high proportion of EUR, which is an important stage for shale gas wells to contribute to production. In this stage, due to the rapid attenuation of formation energy, the wellbore liquid carrying capacity gradually decreases, and it is necessary to further intervene in the oil pipe for production. On the one hand, it can improve the wellbore liquid carrying capacity, and on the other hand, it can provide a channel for the implementation of the next step of production increase measures. In other words, the pressure-carrying oil pipe is a must and the first choice for shale gas horizontal well production increase measures, which is crucial to the efficient production of shale gas wells.

[0005] At present, in actual production, whether to intervene in the tubing is often determined based on whether the gas well exhibits liquid accumulation characteristics or a certain fixed condition (such as wellhead pressure less than 10MPa). However, the production differences between gas wells are usually large, and a single condition is not sufficient to determine whether tubing intervention is necessary. The tubing is often lowered too early or not in time. Both of these situations do not give full play to the role of the tubing, resulting in the production increase effect after the tubing is lowered into the gas well is not obvious. In most cases, liquid has already accumulated in the wellbore, and it is necessary to lower the tubing and cooperate with other measures to drain the liquid for production.

[0006] Some methods for determining the timing of tubing in shale gas wells have also been proposed in the prior art. For example, Du Yang et al. proposed that the timing of tubing in deep shale gas wells should be determined based on the timing of flow pattern change. However, after research, it was found that the two-phase flow pattern of shale gas wellbore will only change in the early stage of well opening. However, due to the large gas-liquid flow rate at this time, it is not suitable for tubing. After that, it is slug flow and there is no flow pattern change. Wang Qingrong et al. calculated the critical liquid carrying flow of shale gas wells in the Changning block and proposed that tubing should be lowered as soon as possible before the casing pressure exceeds 10 MPa after production. However, due to the influence of geological conditions, transformation engineering differences and other factors on different gas wells, the production characteristics vary greatly. This method has a single condition and cannot accurately guide the determination of the timing of tubing intervention in shale gas wells.

[0007] Based on the above technical problems, a new method that can accurately determine the timing of lowering the oil pipeline is urgently needed. Summary of the invention

[0008] The purpose of the present invention is to overcome the above-mentioned problems existing in the prior art, and to provide a method for determining the timing of tubing installation in shale gas wells. The present invention innovatively determines the timing of tubing installation based on the dynamic characteristics of shale gas production and the theory of gas-liquid two-phase flow in the wellbore, and uses the critical pressure drop of casing production and tubing production as the basic condition to determine the timing of tubing installation, thereby solving the current technical problems such as the difficulty in determining the timing of tubing intervention in shale gas wells and the lack of clear guidance methods. In addition, the present invention has a wide range of applications and can determine the timing of tubing installation in any shale gas well (including up-dip wells and down-dip wells), which can provide important technical support for developers to accurately determine the timing of tubing installation in gas wells.

[0009] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A method for determining the timing of running a tubing in a shale gas well, characterized by comprising the following steps: Step 1: Calculate the wellbore pressure drop of the upward-inclined shale gas well when the casing is used for production at different wellhead pressures, different gas volumes and different water-gas ratios, and the wellbore pressure drop of the upward-inclined shale gas well when the tubing is used for production; calculate the wellbore pressure drop of the downward-inclined shale gas well when the casing is used for production at different wellhead pressures, different gas volumes and different water-gas ratios, and the wellbore pressure drop of the downward-inclined shale gas well when the tubing is used for production; Step 2: Draw a three-dimensional curved surface diagram of the up-dip well with the same coordinate system according to the gas volume, water-gas ratio, and wellbore pressure drop of the up-dip well when the casing is used for production at any wellhead pressure, and the gas volume, water-gas ratio, and wellbore pressure drop of the up-dip well when the oil pipe is used for production; draw a three-dimensional curved surface diagram of the down-dip well with the same coordinate system according to the gas volume, water-gas ratio, and wellbore pressure drop of the down-dip well when the casing is used for production at any wellhead pressure, and the gas volume, water-gas ratio, and wellbore pressure drop of the down-dip well when the oil pipe is used for production; Step 3: Project the intersection of the pressure drop curve during casing production and the pressure drop curve during tubing production in the three-dimensional surface diagram of the up-dip well onto the two-dimensional plane of gas volume-water-gas ratio to obtain a preliminary reference chart for the timing of tubing installation at the wellhead pressure of the up-dip well; project the intersection of the pressure drop curve during casing production and the pressure drop curve during tubing production in the three-dimensional surface diagram of the down-dip well onto the two-dimensional plane of gas volume-water-gas ratio to obtain a preliminary reference chart for the timing of tubing installation at the wellhead pressure of the down-dip well; Step 4, select other different wellhead pressures and repeat steps 2-3 respectively to obtain a preliminary reference chart of the timing of tubing lowering for up-dip wells at different wellhead pressures and a preliminary reference chart of the timing of tubing lowering for down-dip wells at different wellhead pressures; Step 5: merge the preliminary reference charts of the timing of tubing lowering for the up-dip wells at different wellhead pressures to obtain the final reference chart of the timing of tubing lowering for the up-dip wells; merge the preliminary reference charts of the timing of tubing lowering for the down-dip wells at different wellhead pressures to obtain the final reference chart of the timing of tubing lowering for the down-dip wells; Step 6: Determine whether the shale gas well is an up-dip well or a down-dip well, select the final reference chart for the timing of tubing lowering corresponding to the well type, and determine the timing of tubing lowering based on the final reference chart for the timing of tubing lowering.

[0010] The method for determining the timing of lowering the oil pipe according to the final reference plate for the timing of lowering the oil pipe is as follows: Step S1: Based on the current production conditions of the shale gas well, query whether the well is located in a favorable area for tubing production or a favorable area for casing production in the corresponding final reference chart for the timing of tubing lowering; If the current production condition of the gas well obtained by query is in the favorable area for tubing production, it is determined that the gas well has missed the appropriate time to lower the tubing, and the liquid carrying capacity is insufficient, and tubing production must be lowered immediately; If the current production condition of the gas well obtained by query is located in the casing production favorable area, it is determined that the gas well currently has sufficient liquid carrying capacity and it is not yet the right time to lower the oil pipe, and the process goes to step S2; Step S2, obtaining the early production history data of the gas well, filtering the abnormal change data, and then establishing the production dynamic curve; Step S3: Based on the production performance curve, use numerical simulation method or empirical method to predict the future production change trend of the gas well, and repeat step S1 according to the prediction result until the appropriate time to lower the oil pipe is obtained.

[0011] In step 1, an up-dip well refers to a horizontal well whose horizontal section well inclination angle is greater than 90°, and a down-dip well refers to a horizontal well whose horizontal section well inclination angle is less than 90°.

[0012] In step 1, the wellhead pressure ranges from 0 to 80 MPa.

[0013] In step 1, the gas volume range is 0.1~100×10 4 m 3 / d.

[0014] In step 1, the range of water-gas ratio is 0~80m 3 / 10 4 m 3 .

[0015] In step 4, the wellhead pressure selected each time increases or decreases regularly based on the pressure in the previous wellhead.

[0016] In step S1, the current production conditions of the shale gas well include wellhead pressure, gas production and water-gas ratio.

[0017] In step S2, the early production history data of the gas well includes wellhead pressure data, gas production data and water production data.

[0018] In step S2, filtering abnormal change data refers to removing data with a daily gas production of 0 or data with a daily gas production that is abnormally lower / higher than that before and after a corresponding time point.

[0019] The advantages of adopting the present invention are: 1. Step 1 of the present invention calculates the wellbore pressure drop when casing production and tubing production are adopted for up-dip wells and down-dip wells respectively under all shale gas well production conditions, thereby ensuring the systematicness of the data and the comprehensiveness of the final reference drawing; Step 2 intuitively presents the data obtained in Step 1 in the form of a three-dimensional surface, and clarifies the intersection lines of the critical wellbore pressure drop when casing production and tubing production are adopted respectively; Step 3 projects the intersection lines in the three-dimensional surface diagram onto the two-dimensional plane of gas volume-water-gas ratio, thereby ensuring the intuitiveness and operability of the final drawing.

[0020] 2. The present invention is innovatively based on the dynamic characteristics of shale gas production and the theory of gas-liquid two-phase flow in the wellbore, and uses the critical pressure drop of casing production and tubing production as the basic condition to determine the timing of tubing installation, which solves the current technical problems such as the difficulty in determining the timing of tubing intervention in shale gas wells and the lack of clear guidance methods. The present invention has a wide range of applications and can determine the timing of tubing installation in any shale gas well (including up-dip wells and down-dip wells), which can provide important technical support for developers to accurately determine the timing of tubing installation in gas wells. In addition, the method described in the present invention is simple, easy to understand, easy to use, and easy to operate, and can be effectively applied to the actual production dynamic analysis of shale gas wells, thereby ensuring the timeliness of tubing installation in each shale gas well, and providing important guarantees for delaying the decline in gas well production and improving the stable production capacity of gas wells. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a flowchart of the present invention; Figure 2 A three-dimensional surface diagram of a down-dip well established for the present invention; Figure 3 It is a projection diagram of the intersection of the pressure drop curve surface during casing production and the pressure drop curve surface during tubing production of the down-dip well projected onto the two-dimensional plane of gas volume-water-gas ratio; Figure 4 The final reference chart for the timing of tubing lowering in up-dip wells; Figure 5 The final reference plate for the timing of tubing lowering in down-dip wells; Figure 6 This is a comparison chart of the production curves before and after the A-1 well is downpipeed. DETAILED DESCRIPTION

[0022] Example 1 A method for determining the timing of running a tubing in a shale gas well, such as Figure 1 As shown, it includes the following steps: Step 1: Calculate the wellbore pressure drop of the upward-inclined shale gas well when the casing is used for production at different wellhead pressures, different gas volumes and different water-gas ratios, and the wellbore pressure drop of the upward-inclined shale gas well when the tubing is used for production; calculate the wellbore pressure drop of the downward-inclined shale gas well when the casing is used for production at different wellhead pressures, different gas volumes and different water-gas ratios, and the wellbore pressure drop of the downward-inclined shale gas well when the tubing is used for production.

[0023] The up-dip well in this step refers to a horizontal well with a horizontal section well inclination angle greater than 90°, and the down-dip well refers to a horizontal well with a horizontal section well inclination angle less than 90°. The wellhead pressure ranges from 0 to 80 MPa, and the gas volume ranges from 0.1 to 100×10 4 m 3 / d, the range of water-gas ratio is 0~80m 3 / 10 4 m 3 .

[0024] Step 2: Draw a three-dimensional surface diagram of the up-dip well with the same coordinate system based on the gas volume, water-gas ratio, and wellbore pressure drop of the up-dip well when producing with casing at any wellhead pressure, and the gas volume, water-gas ratio, and wellbore pressure drop of the up-dip well when producing with tubing; draw a three-dimensional surface diagram of the down-dip well with the same coordinate system based on the gas volume, water-gas ratio, and wellbore pressure drop of the down-dip well when producing with casing at any wellhead pressure, and the gas volume, water-gas ratio, and wellbore pressure drop of the down-dip well when producing with tubing.

[0025] Step three, project the intersection line of the pressure drop surface during casing production and the pressure drop surface during tubing production in the three-dimensional surface diagram of the up-dip well onto the two-dimensional plane of gas volume-water-gas ratio, and obtain a preliminary reference plate for the timing of tubing lowering for the up-dip well at the wellhead pressure; project the intersection line of the pressure drop surface during casing production and the pressure drop surface during tubing production in the three-dimensional surface diagram of the down-dip well onto the two-dimensional plane of gas volume-water-gas ratio, and obtain a preliminary reference plate for the timing of tubing lowering for the down-dip well at the wellhead pressure.

[0026] Step 4, select other different wellhead pressures. The wellhead pressure selected each time can be regularly increased or decreased based on the previous wellhead pressure, and then repeat steps 2-3 respectively to obtain preliminary reference charts for the timing of tubing lowering at different wellhead pressures for up-dip wells and preliminary reference charts for the timing of tubing lowering at different wellhead pressures for down-dip wells.

[0027] Step 5: Combine the preliminary reference charts of tubing running timing for up-dip wells at different wellhead pressures to obtain the final reference chart of tubing running timing for up-dip wells; combine the preliminary reference charts of tubing running timing for down-dip wells at different wellhead pressures to obtain the final reference chart of tubing running timing for down-dip wells.

[0028] It should be noted that the above-mentioned merging of the preliminary reference drawings for the timing of oil pipeline laying refers to extracting the curves in the drawings in the form of data, and then re-making them in a new drawing to complete the merging; or superimposing the preliminary reference drawings for the timing of oil pipeline laying, hiding the other irrelevant curves, and only retaining the intersection lines to complete the merging.

[0029] Step 6: Determine whether the shale gas well is an up-dip well or a down-dip well, select the final reference chart for the timing of tubing installation of the corresponding well type, and determine the timing of tubing installation based on the final reference chart for tubing installation. Specifically, if the shale gas well is an up-dip well, select the final reference chart for the timing of tubing installation of the up-dip well to determine the timing of tubing installation. If the shale gas well is a down-dip well, select the final reference chart for the timing of tubing installation of the down-dip well to determine the timing of tubing installation.

[0030] The following is an explanation using the final reference diagram of the timing of lowering the tubing in a down-dip well as an example.

[0031] Steps 1 and 2: Based on the calculated wellbore pressure drop data when casing is used for production and the wellbore pressure drop data when tubing is used for production under different wellhead pressures, different gas volumes, and different water-gas ratios, the gas volume, water-gas ratio, and wellbore pressure drop of the down-dip well when casing is used for production and the gas volume, water-gas ratio, and wellbore pressure drop of the down-dip well when tubing is used for production under a certain wellhead pressure (taking 15 MPa as an example) are plotted into a three-dimensional surface diagram of the down-dip well with the same coordinate system. The plotted three-dimensional surface diagram of the down-dip well is shown in FIG. Figure 2 shown.

[0032] Step 3: Figure 2 The intersection line in is projected onto the two-dimensional plane of gas volume-water ratio, as Figure 3 As shown, the series with a wellhead pressure of 15 MPa in the down-tilt downhole tubing timing determination chart is obtained.

[0033] Step 4: Select other different wellhead pressures and repeat the above steps to obtain a preliminary reference chart for the timing of tubing lowering at different wellhead pressures for up-dip wells and a preliminary reference chart for the timing of tubing lowering at different wellhead pressures for down-dip wells.

[0034] Step 5: Combine the preliminary reference charts of the timing of tubing lowering for up-dip wells at different wellhead pressures and the preliminary reference charts of the timing of tubing lowering for down-dip wells at different wellhead pressures obtained in step 4 to obtain the following: Figure 4 The final reference plate and the timing of tubing lowering in the up-dip well shown in the figure are Figure 5 Final reference plate for timing of tubing run in a down-dip well as shown.

[0035] The present invention can determine the timing of laying the oil pipe in any shale gas well based on the above-mentioned chart, and can provide important technical support for developers to accurately judge the timing of laying the oil pipe in the gas well. It can be effectively applied to the actual production dynamic analysis of shale gas wells, thereby ensuring the timeliness of laying the oil pipe in each shale gas well, and providing important guarantee for delaying the decline of gas well production and improving the stable production capacity of gas wells.

[0036] Example 2 This embodiment provides a method for determining the timing of running the oil pipe in a shale gas well based on the embodiment 1. Figure 1 As shown, it includes the following steps: Step 1: Calculate the wellbore pressure drop of the upward-inclined shale gas well when the casing is used for production at different wellhead pressures, different gas volumes and different water-gas ratios, and the wellbore pressure drop of the upward-inclined shale gas well when the tubing is used for production; calculate the wellbore pressure drop of the downward-inclined shale gas well when the casing is used for production at different wellhead pressures, different gas volumes and different water-gas ratios, and the wellbore pressure drop of the downward-inclined shale gas well when the tubing is used for production.

[0037] The up-dip well in this step refers to a horizontal well with a horizontal section well inclination angle greater than 90°, and the down-dip well refers to a horizontal well with a horizontal section well inclination angle less than 90°. The wellhead pressure ranges from 0 to 80 MPa, and the gas volume ranges from 0.1 to 100×10 4 m 3 / d, the range of water-gas ratio is 0~80m 3 / 10 4 m 3 .

[0038] Step 2: Draw a three-dimensional surface diagram of the up-dip well with the same coordinate system based on the gas volume, water-gas ratio, and wellbore pressure drop of the up-dip well when producing with casing at any wellhead pressure, and the gas volume, water-gas ratio, and wellbore pressure drop of the up-dip well when producing with tubing; draw a three-dimensional surface diagram of the down-dip well with the same coordinate system based on the gas volume, water-gas ratio, and wellbore pressure drop of the down-dip well when producing with casing at any wellhead pressure, and the gas volume, water-gas ratio, and wellbore pressure drop of the down-dip well when producing with tubing.

[0039] Step three, project the intersection line of the pressure drop surface during casing production and the pressure drop surface during tubing production in the three-dimensional surface diagram of the up-dip well onto the two-dimensional plane of gas volume-water-gas ratio, and obtain a preliminary reference plate for the timing of tubing lowering for the up-dip well at the wellhead pressure; project the intersection line of the pressure drop surface during casing production and the pressure drop surface during tubing production in the three-dimensional surface diagram of the down-dip well onto the two-dimensional plane of gas volume-water-gas ratio, and obtain a preliminary reference plate for the timing of tubing lowering for the down-dip well at the wellhead pressure.

[0040] Step 4, select other different wellhead pressures. The wellhead pressure selected each time can be regularly increased or decreased based on the previous wellhead pressure, and then repeat steps 2-3 respectively to obtain preliminary reference charts for the timing of tubing lowering at different wellhead pressures for up-dip wells and preliminary reference charts for the timing of tubing lowering at different wellhead pressures for down-dip wells.

[0041] Step 5: Combine the preliminary reference charts of tubing running timing for up-dip wells at different wellhead pressures to obtain the final reference chart of tubing running timing for up-dip wells; combine the preliminary reference charts of tubing running timing for down-dip wells at different wellhead pressures to obtain the final reference chart of tubing running timing for down-dip wells.

[0042] Step 6: Determine whether the shale gas well is an up-dip well or a down-dip well, select the final reference chart for the timing of tubing installation of the corresponding well type, and determine the timing of tubing installation based on the final reference chart for tubing installation. Specifically, if the shale gas well is an up-dip well, select the final reference chart for the timing of tubing installation of the up-dip well to determine the timing of tubing installation. If the shale gas well is a down-dip well, select the final reference chart for the timing of tubing installation of the down-dip well to determine the timing of tubing installation.

[0043] The method for determining the timing of lowering the oil pipe according to the final reference chart for the timing of lowering the oil pipe is as follows: Step S1, obtaining the current production parameters of the shale gas well, including wellhead pressure, gas production and water-gas ratio, and then querying the current production conditions of the gas well. Based on the current production conditions of the shale gas well, query whether it is located in the favorable area for tubing production or the favorable area for casing production in the final reference plate of the corresponding tubing lowering timing.

[0044] If the current production condition of the gas well obtained by query is located in the favorable area for tubing production, it is determined that the gas well has missed the appropriate time to lower the tubing, and the liquid carrying capacity is insufficient, and tubing production must be lowered immediately.

[0045] If the current production condition of the gas well obtained by query is located in the casing production favorable area, it is determined that the gas well currently has sufficient liquid carrying capacity and it is not yet the right time to lower the oil pipe, and the process goes to step S2.

[0046] Step S2: Acquire the early production history data of the gas well, filter the abnormal change data, and then establish the production dynamic curve.

[0047] Among them, the production history data of the gas well in the early stage includes wellhead pressure data, gas production data and water production data, and filtering abnormal change data refers to removing data with a daily gas production of 0 or data that is abnormally low / high compared with the daily gas production before and after the corresponding time point. This step is conducive to ensuring the continuity and smoothness of the production dynamic curve by filtering abnormal change data.

[0048] Step S3: Based on the production performance curve, use numerical simulation method or empirical method to predict the future production change trend of the gas well, and repeat step S1 according to the prediction result until the appropriate time to lower the oil pipe is obtained.

[0049] It should be noted that, in the actual implementation of this embodiment, the classification of up-inclined wells and down-inclined wells is based on the well inclination angle of the horizontal section. When the well inclination angle is greater than 90°, it is determined to be an up-inclined well, and when the well inclination angle is less than 90°, it is determined to be a down-inclined well. When the well inclination angle is equal to 90°, the final reference plate for the timing of lowering the oil pipe for the up-inclined well and the final reference plate for the timing of lowering the oil pipe for the down-inclined well can be referred to at the same time, and the plate closer to the favorable area for oil pipe production is preferentially selected as a reference.

[0050] Example 3 This example verifies the method of the present invention based on Example 2, as follows: Take Well A-1 in a shale gas field as an example. This well is a down-dip well.

[0051] According to step S1, the wellhead pressure before the downhole oil pipe is 5.2 MPa, and the gas production is 4×10 4 m 3 / d, water-gas ratio 1.1 is m 3 / 10 4 m 3 ,exist Figure 5 On this basis, by querying the final reference chart of the timing of down-dip downhole tubing, it can be known that the current production condition of the well is in the favorable area for tubing production, and tubing production must be started immediately.

[0052] Figure 6 The production curve comparison of A-1 well before and after the oil pipe is lowered is shown. Figure 6 It can be seen that the well was guided by the method of the present invention and the oil pipe operation was immediately carried out. After the oil pipe production was switched to oil pipe production, the gas production increased from 4×10 4 m 3 / d increased to 5.9×10 4 m 3 / d, the yield increase was 47.5%, indicating that the method of the present invention has high practicability and reliability.

[0053] The above description is only a specific implementation mode of the present invention. Any feature disclosed in this specification, unless otherwise stated, can be replaced by other alternative features that are equivalent or have similar purposes; all the disclosed features, or all the steps in the methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A method for determining the timing of running a tubing in a shale gas well, characterized in that The following steps are involved: Step 1: Calculate the wellbore pressure drop of the upward-inclined shale gas well when the casing is used for production at different wellhead pressures, different gas volumes and different water-gas ratios, and the wellbore pressure drop of the upward-inclined shale gas well when the tubing is used for production; calculate the wellbore pressure drop of the downward-inclined shale gas well when the casing is used for production at different wellhead pressures, different gas volumes and different water-gas ratios, and the wellbore pressure drop of the downward-inclined shale gas well when the tubing is used for production; Step 2: Draw a three-dimensional curved surface diagram of the up-dip well with the same coordinate system according to the gas volume, water-gas ratio, and wellbore pressure drop of the up-dip well when the casing is used for production at any wellhead pressure, and the gas volume, water-gas ratio, and wellbore pressure drop of the up-dip well when the oil pipe is used for production; draw a three-dimensional curved surface diagram of the down-dip well with the same coordinate system according to the gas volume, water-gas ratio, and wellbore pressure drop of the down-dip well when the casing is used for production at any wellhead pressure, and the gas volume, water-gas ratio, and wellbore pressure drop of the down-dip well when the oil pipe is used for production; Step 3: Project the intersection of the pressure drop curve during casing production and the pressure drop curve during tubing production in the three-dimensional surface diagram of the up-dip well onto the two-dimensional plane of gas volume-water-gas ratio to obtain a preliminary reference chart for the timing of tubing installation at the wellhead pressure of the up-dip well; project the intersection of the pressure drop curve during casing production and the pressure drop curve during tubing production in the three-dimensional surface diagram of the down-dip well onto the two-dimensional plane of gas volume-water-gas ratio to obtain a preliminary reference chart for the timing of tubing installation at the wellhead pressure of the down-dip well; Step 4, select other different wellhead pressures and repeat steps 2-3 respectively to obtain a preliminary reference chart of the timing of tubing lowering for up-dip wells at different wellhead pressures and a preliminary reference chart of the timing of tubing lowering for down-dip wells at different wellhead pressures; Step 5: merge the preliminary reference charts of the timing of tubing lowering for the up-dip well at different wellhead pressures to obtain the final reference chart of the timing of tubing lowering for the up-dip well; The preliminary reference charts of the timing of tubing lowering in the down-dip well at different wellhead pressures are combined to obtain the final reference chart of the timing of tubing lowering in the down-dip well; Step 6: Determine whether the shale gas well is an up-dip well or a down-dip well, select the final reference chart for the timing of tubing lowering corresponding to the well type, and determine the timing of tubing lowering based on the final reference chart for the timing of tubing lowering.

2. A method for determining the timing of running a tubing in a shale gas well according to claim 1, characterized in that: The method for determining the timing of lowering the oil pipe according to the final reference plate for the timing of lowering the oil pipe is as follows: Step S1, querying the current production condition of the gas well obtained based on the current production condition of the shale gas well, querying whether it is located in the favorable area for tubing production or the favorable area for casing production in the corresponding final reference plate for the timing of tubing lowering; If the current production condition of the gas well obtained by query is in the favorable area for tubing production, it is determined that the gas well has missed the appropriate time to lower the tubing, and the liquid carrying capacity is insufficient, and tubing production must be lowered immediately; If the current production condition of the gas well obtained by query is located in the casing production favorable area, it is determined that the gas well currently has sufficient liquid carrying capacity and it is not yet the right time to lower the oil pipe, and the process goes to step S2; Step S2, obtaining the early production history data of the gas well, filtering the abnormal change data, and then establishing the production dynamic curve; Step S3: Based on the production performance curve, use numerical simulation method or empirical method to predict the future production change trend of the gas well, and repeat step S1 according to the prediction result until the appropriate time to lower the oil pipe is obtained.

3. A method for determining the timing of running a tubing in a shale gas well according to claim 1 or 2, characterized in that: In step 1, an up-dip well refers to a horizontal well whose horizontal section well inclination angle is greater than 90°, and a down-dip well refers to a horizontal well whose horizontal section well inclination angle is less than 90°.

4. A method for determining the timing of running a tubing in a shale gas well according to claim 1 or 2, characterized in that: In step 1, the wellhead pressure ranges from 0 to 80 MPa.

5. A method for determining the timing of running oil pipe in a shale gas well according to claim 1 or 2, characterized in that: In step 1, the gas volume range is 0.1~100×10 4 m 3 / d.

6. A method for determining the timing of running a tubing in a shale gas well according to claim 1 or 2, characterized in that: In step 1, the range of water-gas ratio is 0~80m 3 / 10 4 m 3 .

7. A method for determining the timing of running a tubing in a shale gas well according to claim 1 or 2, characterized in that: In step 4, the wellhead pressure selected each time increases or decreases regularly based on the pressure in the previous wellhead.

8. A method for determining the timing of running a tubing in a shale gas well according to claim 1 or 2, characterized in that: In step S1, the current production conditions of the shale gas well include wellhead pressure, gas production and water-gas ratio.

9. A method for determining the timing of running oil pipe in a shale gas well according to claim 1 or 2, characterized in that: In step S2, the early production history data of the gas well includes wellhead pressure data, gas production data and water production data.

10. A method for determining the timing of running oil pipe in a shale gas well according to claim 1 or 2, characterized in that: In step S2, filtering abnormal change data refers to removing data with a daily gas production of 0 or data with a daily gas production that is abnormally lower / higher than that before and after a corresponding time point.

Images