Plunger gas lift replacement opportunity determining method and system
By calculating and predicting the sleeve pressure during the well opening and judging the gas-liquid ratio during the well closing repressure stage, the problem of insufficient accuracy of plunger gas lift replacement timing in the prior art is solved, and more accurate judgment of plunger gas lift replacement timing is achieved, and the stability of gas well production is improved.
Patent Information
- Application Number
- CN202411918677.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-24
- Publication Date
- 2025-03-14
AI Technical Summary
In the prior art, the timing accuracy of determining the replacement plunger gas lift is insufficient and lacks prediction, which affects the production efficiency of the gas well.
By calculating and predicting the sleeve pressure when opening the well based on gas well production materials during the shut-off and repressure stage, and comparing it with the minimum sleeve pressure value of the plunger gas lift, it is determined whether the plunger can operate normally to the wellhead based on the gas-liquid ratio.
It improves the accuracy of the plunger gas lift replacement timing, and can predict in advance whether the plunger can run normally to the wellhead, helping the gas well to produce stably.
Smart Images
Figure CN119616427A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of oil and gas field development, and in particular to a method and system for determining the timing of plunger gas lift replacement. Background Art
[0002] During the natural gas production process, some formation water flows into the well along with the gas. When the gas flow rate is high, the produced liquid will be carried to the wellhead by the natural gas for discharge. However, when the gas flow rate is insufficient and the liquid cannot be discharged, liquid will accumulate at the bottom of the well, affecting the gas well production. At this time, it is necessary to take drainage and gas production measures for the liquid-accumulated gas well. Common drainage and gas production processes include gas lift, optimal pipe string, plunger gas lift, foam drainage and gas production processes, etc.
[0003] In the process of exploitation of water-producing gas wells, a variety of drainage and gas production processes are often used in combination. As the gas well is exploited, its output, gas-liquid ratio, and formation pressure will change. Therefore, it is necessary to adjust the drainage and gas production method in time according to the changes in formation properties to ensure efficient production of the gas well. Plunger gas lift drainage and gas production technology is a drainage measure with simple process and high degree of ground automation. It is generally used in the middle stage of gas well exploitation. Self-flowing production cannot carry liquid. At this time, a plunger is lowered into the well to discharge the accumulated liquid by the operation of the plunger. However, the plunger gas lift process has high requirements for the well environment. When the required energy is insufficient, the plunger will not be able to run to the wellhead to drain the liquid, affecting the production of the gas well. Therefore, it is very important to judge the timing of using plunger gas lift. When the plunger cannot drain normally, the drainage and gas production measures need to be replaced in time.
[0004] At present, the timing of replacing plunger gas lift in China is mainly based on field data monitoring, by monitoring wellhead pressure, liquid level changes and other data, combined with historical production data to analyze the operation of the plunger. However, field data is affected by many factors, and this method is not accurate enough and lacks predictability. The present invention combines casing pressure and gas-liquid ratio to calculate whether the plunger is discharging normally. The process is simple and can predict in advance whether the plunger can operate normally to the wellhead during the well shut-in stage. Summary of the invention
[0005] The object of the present invention is to provide a method for determining the timing of replacing a plunger gas lift, so as to solve the problem that the method for determining the timing of replacing a plunger gas lift in the prior art is insufficiently accurate and lacks predictability.
[0006] In order to solve the above problems, the present invention proposes a method for determining the timing of plunger gas lift replacement, and the technical solution adopted is:
[0007] A method for determining the timing of plunger gas lift replacement comprises the following steps:
[0008] Step S1, based on the gas well production data, the casing pressure when the well is opened is predicted by calculating in the well shut-in and re-pressurization stage to obtain the predicted casing pressure value when the well is opened;
[0009] Step S2, calculating the minimum casing pressure to ensure normal liquid drainage and gas production by plunger gas lift of the gas well based on the plunger production parameters, and obtaining the minimum casing pressure value of plunger gas lift;
[0010] Step S3, judging whether the predicted casing pressure value of the well opening is greater than the minimum casing pressure value of the plunger gas lift,
[0011] If the predicted casing pressure value of the well opening is less than the minimum casing pressure value of the plunger gas lift, the plunger cannot run to the wellhead to discharge the fluid, and the lifting method needs to be changed; otherwise, proceed to steps S4-S6;
[0012] Step S4, based on the single-cycle discharge volumes at different production stages of the gas well and the wellhead pressure changes corresponding to the single-cycle discharge volumes, obtaining the minimum gas lift required at the single-cycle discharge volumes at different production stages of the gas well;
[0013] Step S5, drawing a relationship curve between each single cycle discharge volume and its corresponding minimum lifting gas volume in the same production stage, and determining the critical gas-liquid ratio of the plunger gas lift well under each single cycle discharge volume in different production stages according to the relationship curve;
[0014] Step S6, according to the single-cycle discharge volume of the production stage to be judged, the critical gas-liquid ratio of the production stage is obtained from the relationship curve; the critical gas-liquid ratio of the production stage is compared with the actual gas-liquid ratio measured on site: if the actual gas-liquid ratio is greater than or equal to the critical gas-liquid ratio, it means that the gas volume in the production stage is sufficient to lift the liquid, and the plunger can run to the wellhead to discharge the liquid; if the actual gas-liquid ratio is less than the critical gas-liquid ratio, it means that the gas volume in the production stage is insufficient, the plunger cannot run to the wellhead to discharge the liquid, and the lifting method needs to be changed.
[0015] Further, in step S1, the casing pressure when the well is opened is predicted by calculating based on the gas well production data in the well shut-in and re-pressurization stage to obtain the predicted casing pressure value when the well is opened, including:
[0016] The gas mass increment in the wellbore during the shut-in and re-pressurization stage is obtained based on the formation fluid production; the casing pressure increment during the shut-in period is obtained based on the gas mass increment in the wellbore during the shut-in period, and combined with the casing pressure before shut-in, the predicted casing pressure value is obtained.
[0017] Furthermore, obtaining the gas mass increment in the wellbore during the shut-in and re-pressurization stage based on the formation fluid production includes:
[0018] According to the daily liquid production of the formation, the gas mass increment in the wellbore during the shut-in period is calculated in the shut-in and re-pressure stage; wherein the gas mass increment in the wellbore during the shut-in period is shown in Formula 1:
[0019] δm g =(q lr ×GLR×ρ scg -qlr ×S gl ×ρ g )δt Formula 1
[0020] In formula 1, q lr is the daily liquid production, GLR is the gas-liquid ratio, S gl is the average solubility of the bottom hole liquid, ρ scg is the density of natural gas under standard conditions, ρ g is the natural gas density under formation conditions, and δt is the shut-in time.
[0021] Further, the casing pressure increment during the shut-in period is obtained according to the gas mass increment in the wellbore during the shut-in period, and combined with the casing pressure before shut-in, to obtain the predicted casing pressure value for the well opening, including:
[0022] According to the gas mass increment in the wellbore during the shut-in period, without considering gas leakage, the casing pressure increment during the shut-in period is calculated by the state equation; wherein the state equation is shown in Formula 2:
[0023]
[0024] In formula 2, δm g is the gas mass increment in the wellbore during the shut-in period, Δp c is the casing pressure increment during the shut-in period, Z is the average deviation coefficient, T is the average gas temperature, R is the gas constant under the conditions of Z and T, and M mol is the molar mass of natural gas, h o is the length of the oil pipe, A c is the cross-sectional area of the casing annulus;
[0025] The casing pressure before shutting in and the casing pressure increment during shutting in are added to obtain the predicted casing pressure value at the start of the well. The predicted casing pressure value at the start of the well is shown in Formula 3:
[0026] p cn =p cl +Δp c Formula 3
[0027] In formula 3, p cl is the casing pressure before shut-in, Δp c It is the casing pressure increment during the shut-in period.
[0028] Further, in step S2, the minimum casing pressure value of the plunger gas lift is as shown in Formula 4:
[0029]
[0030] In formula 4, m p is the plunger deadweight, p wh is the wellhead pressure, p LF is the pressure of the friction loss in the liquid section, pgt is the static air column pressure above the plunger, p gtf is the pressure of gas friction loss, At is the internal area of the oil pipe, p lh is the static pressure of the lifting liquid column, and g is the acceleration due to gravity.
[0031] Further, in step S4, the minimum lifting gas volume required for each single cycle discharge volume at different production stages of the gas well is obtained based on each single cycle discharge volume at different production stages of the gas well and the change in wellhead pressure corresponding to each single cycle discharge volume, including:
[0032] The single-cycle discharge volume at different production stages of the gas well is counted, the wellhead pressure change corresponding to each single-cycle discharge is recorded, the minimum and maximum casing pressure values of the plunger gas lift under each single-cycle discharge volume are determined, and the minimum lifting gas volume under each single-cycle discharge volume at different production stages of the gas well is calculated based on the maximum casing pressure value.
[0033] Further, in step S5, the relationship curve between each single cycle displacement in different production stages and its corresponding minimum lifting gas volume is drawn, and the critical gas-liquid ratio of the plunger gas lift well under each single cycle displacement in different production stages is determined according to the relationship curve, including:
[0034] Each single cycle displacement in different production stages and its corresponding minimum gas lift volume are plotted on the same coordinates as X variables and Y variables, respectively. The minimum gas lift volume curve corresponding to each single cycle displacement in different production stages is obtained by data fitting, and the slope at each point of the curve can be obtained by calculation; the slope at each point of the curve is the critical gas-liquid ratio of plunger gas lift under each single cycle displacement in different production stages of the gas well.
[0035] Furthermore, the minimum lifting volume is as shown in Formula 5:
[0036]
[0037] In formula 5, d ti is the inner diameter of the oil pipe, H c is the depth of the fixture, Z is the average deviation coefficient, T is the average temperature of the gas, P cmax is the maximum casing pressure value.
[0038] The present invention also provides a plunger gas lift replacement timing determination system, which is used to implement the above plunger gas lift replacement timing determination method, comprising:
[0039] A prediction module is used to calculate and predict the casing pressure when the well is opened based on the gas well production data during the well shut-in and re-pressurization stage to obtain a predicted casing pressure value when the well is opened;
[0040] The minimum casing pressure calculation module calculates the minimum casing pressure to ensure normal drainage and gas production by plunger gas lift in the gas well based on the plunger production parameters, and obtains the minimum casing pressure value of plunger gas lift;
[0041] The casing pressure comparison module is used to determine whether the predicted casing pressure value for well opening is greater than the minimum casing pressure value for plunger gas lift.
[0042] If the predicted casing pressure at well opening is less than the minimum casing pressure of plunger gas lift, the lifting method needs to be changed; otherwise, the gas-liquid ratio comparison is performed;
[0043] The minimum gas lift calculation module is used to obtain the minimum gas lift required under each single cycle discharge volume at different production stages of the gas well based on each single cycle discharge volume at different production stages of the gas well and the wellhead pressure change corresponding to each single cycle discharge volume;
[0044] The critical gas-liquid ratio calculation module is used to draw a relationship diagram between the single-cycle displacement and the minimum gas lift volume, and obtain the minimum gas lift volume curve corresponding to each single-cycle displacement at different production stages through data fitting. According to this curve, the critical gas-liquid ratio of the plunger gas lift well under each single-cycle displacement at different production stages is determined;
[0045] The gas-liquid ratio comparison module is used to obtain the critical gas-liquid ratio of the production stage from the curve according to the single-cycle discharge volume of the production stage to be judged; the critical gas-liquid ratio of the production stage is compared with the actual gas-liquid ratio measured on site: if the actual gas-liquid ratio is greater than or equal to the critical gas-liquid ratio, it means that the gas volume in the production stage is sufficient to lift the liquid, and the plunger can run to the wellhead to discharge the liquid; if the actual gas-liquid ratio is less than the critical gas-liquid ratio, it means that the gas volume in the production stage is insufficient, the plunger cannot run to the wellhead to discharge the liquid, and the lifting method needs to be changed.
[0046] Compared with the prior art, this application has the following beneficial effects:
[0047] The present invention is an improved invention, and the present invention provides a method for determining the timing of plunger gas lift replacement. For production wells using plunger gas lift, the predicted casing pressure value for opening the well is calculated in advance during the well shut-in stage, and the predicted casing pressure value for opening the well is compared with the minimum casing pressure value for plunger gas lift to predict whether the plunger can run to the wellhead to discharge the liquid, thereby inferring whether the lifting measures need to be replaced. The present invention can plan the production plan in advance based on the prediction results on site, and provide effective assistance for the stable production of gas wells. At the same time, on the basis of judging whether the predicted casing pressure value for opening the well is greater than the minimum casing pressure value for plunger gas lift, combined with the judgment method of the actual gas-liquid ratio and the critical gas-liquid ratio, it is judged whether the plunger can run normally to the wellhead to discharge the liquid, thereby inferring whether the lifting measures need to be replaced, thereby improving the accuracy of determining the timing of plunger gas lift replacement.
[0048] In step S1, the casing pressure when the well is opened is predicted by calculating based on the gas well production data in the well shut-in and re-pressurization stage to obtain the predicted casing pressure value when the well is opened, including:
[0049] The gas mass increment in the wellbore during the shut-in and re-pressurization stage is obtained based on the formation fluid production; the casing pressure increment during the shut-in period is obtained based on the gas mass increment in the wellbore during the shut-in period, and combined with the casing pressure before shut-in, the predicted casing pressure value for opening the well is obtained, thereby improving the accuracy of the predicted casing pressure value for opening the well.
[0050] In step S5, the relationship curve between each single cycle displacement and its corresponding minimum lifting gas volume in different production stages is drawn, and the critical gas-liquid ratio of the plunger gas lift well under each single cycle displacement in different production stages is determined according to the relationship curve, including:
[0051] The single-cycle displacement and its corresponding minimum gas lift volume in different production stages are plotted on the same coordinates as X variables and Y variables, and the minimum gas lift volume curve corresponding to each single-cycle displacement in different production stages is obtained by data fitting. The slope at each point of the curve can be calculated; the slope at each point of the curve is the critical gas-liquid ratio of plunger gas lift under each single-cycle displacement in different production stages of the gas well. Based on this method, the critical gas-liquid ratio of plunger gas lift under each single-cycle displacement in different production stages of the gas well can be accurately determined. BRIEF DESCRIPTION OF THE DRAWINGS
[0052] Figure 1 It is a flow chart of the method for determining the timing of plunger gas lift replacement of the present application. DETAILED DESCRIPTION
[0053] As cited in the background technology, the timing of replacing the plunger gas lift in the prior art lacks predictability. Therefore, the present invention provides a method for determining the timing of replacing the plunger gas lift, including the following steps: first, based on the gas well production data, the casing pressure when opening the well is predicted by calculation during the well closing and re-pressurization stage, to obtain the predicted casing pressure value for opening the well; secondly, based on the plunger production parameters, the minimum casing pressure to ensure the normal drainage and gas production of the gas well plunger gas lift is calculated to obtain the minimum casing pressure value for the plunger gas lift; then, determine whether the predicted casing pressure value for opening the well is greater than the minimum casing pressure value for the plunger gas lift. If the predicted casing pressure value for opening the well is less than the minimum casing pressure value for the plunger gas lift, the lifting method needs to be changed, and the judgment process ends; if the predicted casing pressure value for opening the well is greater than or equal to the minimum casing pressure value for the plunger gas lift, proceed to the next step; then, based on the single-cycle drainage volume in different production stages of the gas well and the wellhead pressure changes corresponding to each single-cycle drainage, the timing of the gas well opening is determined. The minimum lifting gas volume required under each single cycle displacement in the same production stage; then, draw the relationship curve between each single cycle displacement in different production stages and its corresponding minimum lifting gas volume, and determine the critical gas-liquid ratio of the plunger gas lift well under each single cycle displacement in different production stages according to the relationship curve; finally, according to the single cycle displacement of the production stage to be judged, the critical gas-liquid ratio of the production stage is obtained from the curve; the critical gas-liquid ratio of the production stage is compared with the actual gas-liquid ratio measured on site, wherein, if the actual gas-liquid ratio is greater than or equal to the critical gas-liquid ratio, it means that the gas volume in the production stage is sufficient to lift the liquid, and the plunger can run to the wellhead to discharge the liquid; if the actual gas-liquid ratio is less than the critical gas-liquid ratio, it means that the gas volume in the production stage is insufficient, the plunger cannot run to the wellhead to discharge the liquid, and the lifting method needs to be changed. The plunger gas lift replacement timing determination method of the present invention can plan the production plan in advance according to the prediction results on site, providing effective help for the stable production of gas wells.
[0054] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.
[0055] Please refer to Figure 1 , Figure 1 : is a flow chart of a method for determining the timing of plunger gas lift replacement provided by an embodiment of the present application. The method for determining the timing of plunger gas lift replacement includes:
[0056] Step S1, based on the gas well production data, the casing pressure when the well is opened is predicted by calculating in the well shut-in and re-pressurization stage to obtain the predicted casing pressure value when the well is opened;
[0057] Here, gas well production data include wellhead pressure, gas production, liquid discharge, etc.
[0058] During the plunger gas lift drainage and gas production process, the plunger needs to overcome the wellhead back pressure, plunger deadweight, hydrostatic column pressure of the lifting fluid section, and running friction during operation. The casing pressure when opening the well must be greater than the minimum casing pressure to ensure that the plunger runs to the wellhead to drain the fluid. Therefore, the feasibility of plunger gas lift can be predicted and judged based on the relationship between the opening casing pressure and the minimum casing pressure.
[0059] During the shut-in and re-pressurization stage of the circulation process, the change in casing pressure during the shut-in stage can be calculated and predicted based on the gas well productivity equation and the gas state equation. The casing pressure when the well is opened can be obtained by adding it to the casing pressure before shutting in. By comparing it with the minimum casing pressure, it can be predicted whether the plunger can be started normally after the well is opened, thereby judging whether it is necessary to change the lifting method or continue to shut in and increase the pressure.
[0060] Specifically, the casing pressure at the time of opening the well is predicted by calculation based on the gas well production data during the well shut-in and re-pressurization stage, and the predicted casing pressure value at the time of opening the well is obtained, including: obtaining the gas mass increment in the wellbore during the well shut-in period based on the formation fluid production during the well shut-in and re-pressurization stage; obtaining the casing pressure increment during the well shut-in period based on the gas mass increment in the wellbore during the well shut-in period, and combining it with the casing pressure before shut-in, and then obtaining the predicted casing pressure value at the time of opening the well. Among them, obtaining the gas mass increment in the wellbore during the well shut-in period based on the formation fluid production during the well shut-in and re-pressurization stage includes:
[0061] According to the daily liquid production of the formation, the gas mass increment in the wellbore during the shut-in period is calculated in the shut-in and re-pressure stage; here, the gas mass increment in the wellbore during the shut-in period is shown in Formula 1:
[0062] δm g =(q lr ×GLR×ρ scg -q lr ×S gl ×ρ g )δt Formula 1
[0063] In formula 1, q lr is the daily liquid production, GLR is the gas-liquid ratio, S gl is the average solubility of the bottom hole liquid, ρ scg is the density of natural gas under standard conditions, ρ g is the natural gas density under formation conditions, and δt is the shut-in time.
[0064] Here, the calculation formula for daily liquid production is shown in Formula 6:
[0065] q lr=ΔPJ Equation 6
[0066] In formula 6, J is the liquid production index, and ΔP is the production pressure difference.
[0067] The casing pressure increment during the shut-in period is obtained based on the gas mass increment in the wellbore during the shut-in period, and combined with the casing pressure before shut-in, the predicted casing pressure value before well opening is obtained, including:
[0068] According to the gas mass increment in the wellbore during the shut-in period, without considering gas leakage, the casing pressure increment during the shut-in period is calculated by the state equation. Here, the casing pressure increment during the shut-in period is the pressure increment provided by the formation gas produced during the shut-in period for the casing; wherein, the state equation is shown in Formula 2:
[0069]
[0070] In formula 2, δm g is the gas mass increment in the wellbore during the shut-in period, Δp c is the casing pressure increment during the shut-in period, Z is the average deviation coefficient, T is the average gas temperature, R is the gas constant under the conditions of Z and T, and M mol is the molar mass of natural gas, h o is the length of the oil pipe, A c is the cross-sectional area of the casing annulus;
[0071] The casing pressure before shutting in and the casing pressure increment during shutting in are added to obtain the predicted casing pressure value at the start of the well. The predicted casing pressure value at the start of the well is shown in Formula 3:
[0072] p cn =p cl +Δp c Formula 3
[0073] In formula 3, p cl is the casing pressure before shut-in, Δp c It is the casing pressure increment during the shut-in period.
[0074] Here, the predicted casing pressure at the start of the well is the casing pressure when the well is started for production after the well is shut in.
[0075] Step S2, calculating the minimum casing pressure to ensure normal liquid drainage and gas production by plunger gas lift of the gas well based on the plunger production parameters, and obtaining the minimum casing pressure value of plunger gas lift;
[0076] Specifically, the calculation formula for the minimum casing pressure value of plunger gas lift is shown in Formula 4:
[0077]
[0078] In formula 4, m p is the plunger deadweight, p wh is the wellhead pressure, p LFis the pressure of the friction loss in the liquid section, p gt is the static air column pressure above the plunger, p gtf is the pressure of gas friction loss, At is the internal area of the oil pipe, p lh is the static pressure of the lifting liquid column, and g is the acceleration due to gravity.
[0079] Step S3, judging whether the predicted casing pressure value of the well opening is greater than the minimum casing pressure value of the plunger gas lift,
[0080] Among them, if the predicted casing pressure value for opening the well is less than the minimum casing pressure value for plunger gas lift, it means that the plunger cannot run to the wellhead to discharge the fluid during the next cycle. At this time, you can consider changing the lifting method, and the judgment process ends; if the predicted casing pressure value for opening the well is greater than or equal to the minimum casing pressure value for plunger gas lift, enter the next step of judgment.
[0081] When determining the timing of plunger gas lift replacement, another important parameter that affects whether the plunger gas lift can operate normally is the gas-liquid ratio. If the gas-liquid ratio of the gas well is too low, it will not provide enough lifting gas, resulting in the plunger being unable to run to the wellhead. Therefore, the minimum gas-liquid ratio that ensures the normal operation of the plunger in each lifting cycle, that is, the critical gas-liquid ratio, can be calculated and compared with the actual gas-liquid ratio of the gas well to determine whether the plunger can run to the wellhead.
[0082] Therefore, in step S4, based on the single-cycle discharge volumes at different production stages of the gas well and the wellhead pressure changes corresponding to the single-cycle discharge volumes, the minimum lifting gas volume required at the single-cycle discharge volumes at different production stages of the gas well is obtained.
[0083] Specifically, based on the single-cycle discharge volume at different production stages of the gas well and the wellhead pressure change corresponding to each single-cycle discharge volume, the minimum lifting gas volume required under each single-cycle discharge volume at different production stages of the gas well is obtained, including:
[0084] The single-cycle discharge volume at different production stages of the gas well is counted, the wellhead pressure changes corresponding to each single-cycle discharge are recorded, the minimum and maximum casing pressure values of the plunger gas lift under each single-cycle discharge volume are determined, and the minimum lifting gas volume under each single-cycle discharge volume at different production stages of the gas well is calculated based on the maximum casing pressure value. Here, the calculation formula for the minimum casing pressure value of the plunger gas lift is shown in Formula 4; the maximum working casing pressure value is shown in Formula 7:
[0085]
[0086] In formula 7, A c A is the cross-sectional area of the casing annulus, t is the internal area of the oil pipe, P cmin It is the minimum casing pressure value of plunger gas lift;
[0087] For each single cycle discharge volume, the minimum lift volume can be calculated based on the maximum casing pressure value, where the minimum lift volume is shown in Formula 5:
[0088]
[0089] In formula 5, d ti is the inner diameter of the oil pipe, H c is the depth of the fixture, Z is the average deviation coefficient, T is the average temperature of the gas, P cmax is the maximum casing pressure value.
[0090] Step S5, plotting a relationship curve between each single cycle discharge volume in different production stages and its corresponding minimum lifting gas volume, and determining the critical gas-liquid ratio of the plunger gas lift well under each single cycle discharge volume in different production stages according to the relationship curve.
[0091] Specifically, a relationship curve between each single cycle discharge volume and its corresponding minimum lifting gas volume in different production stages is drawn, and the critical gas-liquid ratio of the plunger gas lift well under each single cycle discharge volume in different production stages is determined according to the relationship curve, including:
[0092] Each single cycle displacement in different production stages and its corresponding minimum gas lift volume are plotted on the same coordinates as X variables and Y variables, respectively. The minimum gas lift volume curve corresponding to each single cycle displacement in different production stages is obtained by data fitting, and the slope at each point of the curve can be obtained by calculation; the slope at each point of the curve is the critical gas-liquid ratio of plunger gas lift under each single cycle displacement in different production stages of the gas well.
[0093] For example, in the same coordinate system, the statistical single-cycle displacement is used as the X variable, and the minimum gas lift volume calculated under each single-cycle displacement is used as the Y variable. The relationship curve between the two is drawn to obtain a relationship curve diagram between each single-cycle displacement at different production stages of the gas well and its corresponding minimum gas lift volume, wherein a single single-cycle displacement corresponds to a single point on the relationship curve diagram, and the slope of each point on the curve on the relationship curve diagram is the critical gas-liquid ratio of the plunger gas lift under each single-cycle displacement at different production stages of the gas well, that is, the critical gas-liquid ratio required for the water-producing gas well to ensure operation to the wellhead under the single-cycle displacement corresponding to the plunger gas lift process, which is used for subsequent comparison.
[0094] Step S6, according to the single-cycle discharge volume of the production stage to be judged, the critical gas-liquid ratio of the production stage is obtained from the curve; the critical gas-liquid ratio of the production stage is compared with the actual gas-liquid ratio measured on site: if the actual gas-liquid ratio is greater than or equal to the critical gas-liquid ratio, it means that the gas volume in the production stage is sufficient to lift the liquid, and the plunger can run to the wellhead to discharge the liquid; if the actual gas-liquid ratio is less than the critical gas-liquid ratio, it means that the gas volume in the production stage is insufficient, the plunger cannot run to the wellhead to discharge the liquid, and the lifting method needs to be changed.
[0095] Here, the two important parameters of casing pressure and gas-liquid ratio are used to judge whether the plunger can run to the wellhead to drain the liquid, so as to infer whether the lifting measures need to be replaced, so as to accurately determine the timing of replacing the plunger gas lift with other lifting methods in gas field production.
[0096] The present application also provides a plunger gas lift replacement timing determination system, which is used to implement the above plunger gas lift replacement timing determination method, including:
[0097] A prediction module is used to calculate and predict the casing pressure when the well is opened based on the gas well production data during the well shut-in and re-pressurization stage to obtain a predicted casing pressure value when the well is opened;
[0098] The minimum casing pressure calculation module calculates the minimum casing pressure to ensure normal drainage and gas production by plunger gas lift in the gas well based on the plunger production parameters, and obtains the minimum casing pressure value of plunger gas lift;
[0099] The casing pressure comparison module is used to determine whether the predicted casing pressure value for well opening is greater than the minimum casing pressure value for plunger gas lift.
[0100] If the predicted casing pressure at well opening is less than the minimum casing pressure of plunger gas lift, the lifting method needs to be changed; otherwise, the gas-liquid ratio comparison is performed;
[0101] The minimum gas lift calculation module is used to obtain the minimum gas lift required under each single cycle discharge volume at different production stages of the gas well based on each single cycle discharge volume at different production stages of the gas well and the wellhead pressure change corresponding to each single cycle discharge volume;
[0102] The critical gas-liquid ratio calculation module is used to draw a relationship diagram between the single-cycle displacement and the minimum gas lift volume, and obtain the minimum gas lift volume curve corresponding to each single-cycle displacement at different production stages through data fitting. According to this curve, the critical gas-liquid ratio of the plunger gas lift well under each single-cycle displacement at different production stages is determined;
[0103] The gas-liquid ratio comparison module is used to obtain the critical gas-liquid ratio of the production stage from the curve according to the single-cycle discharge volume of the production stage to be judged; the critical gas-liquid ratio of the production stage is compared with the actual gas-liquid ratio measured on site: if the actual gas-liquid ratio is greater than or equal to the critical gas-liquid ratio, it means that the gas volume in the production stage is sufficient to lift the liquid, and the plunger can run to the wellhead to discharge the liquid; if the actual gas-liquid ratio is less than the critical gas-liquid ratio, it means that the gas volume in the production stage is insufficient, the plunger cannot run to the wellhead to discharge the liquid, and the lifting method needs to be changed.
[0104] Here, those skilled in the art will appreciate that the specific operations of each module in the above plunger gas lift replacement timing determination system have been described in detail above. Figure 1 The method for determining the timing of plunger gas lift replacement has been described in detail, so its repeated description will be omitted.
[0105] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. The patent protection scope of the present invention shall be based on the claims. All equivalent structural changes made using the contents of the description and drawings of the present invention should also be included in the protection scope of the present invention.
Claims
1. A method for determining the timing of plunger gas lift replacement, characterized in that: The following steps are involved: Step S1, based on the gas well production data, the casing pressure when the well is opened is predicted by calculating in the well shut-in and re-pressurization stage to obtain the predicted casing pressure value when the well is opened; Step S2, calculating the minimum casing pressure to ensure normal liquid drainage and gas production by plunger gas lift of the gas well based on the plunger production parameters, and obtaining the minimum casing pressure value of plunger gas lift; Step S3, judging whether the predicted casing pressure value of the well opening is greater than the minimum casing pressure value of the plunger gas lift, If the predicted casing pressure value of the well opening is less than the minimum casing pressure value of the plunger gas lift, the plunger cannot run to the wellhead to discharge the fluid, and the lifting method needs to be changed; otherwise, proceed to steps S4-S6; Step S4, based on the single-cycle discharge volumes at different production stages of the gas well and the wellhead pressure changes corresponding to the single-cycle discharge volumes, obtaining the minimum gas lift required at the single-cycle discharge volumes at different production stages of the gas well; Step S5, plotting a relationship curve between each single cycle discharge volume in different production stages and its corresponding minimum lifting gas volume, and determining the critical gas-liquid ratio of the plunger gas lift well under each single cycle discharge volume in different production stages according to the relationship curve; Step S6, according to the single-cycle discharge volume of the production stage to be judged, the critical gas-liquid ratio of the production stage is obtained from the relationship curve; the critical gas-liquid ratio of the production stage is compared with the actual gas-liquid ratio measured on site: if the actual gas-liquid ratio is greater than or equal to the critical gas-liquid ratio, it means that the gas volume in the production stage is sufficient to lift the liquid, and the plunger can run to the wellhead to discharge the liquid; if the actual gas-liquid ratio is less than the critical gas-liquid ratio, it means that the gas volume in the production stage is insufficient, the plunger cannot run to the wellhead to discharge the liquid, and the lifting method needs to be changed.
2. The method for determining the timing of plunger gas lift replacement according to claim 1, characterized in that: In step S1, the casing pressure when the well is opened is predicted by calculating based on the gas well production data in the well shut-in and re-pressurization stage to obtain the predicted casing pressure value when the well is opened, including: The gas mass increment in the wellbore during the shut-in and re-pressurization stage is obtained based on the formation fluid production; the casing pressure increment during the shut-in period is obtained based on the gas mass increment in the wellbore during the shut-in period, and combined with the casing pressure before shut-in, the predicted casing pressure value is obtained.
3. The method for determining the timing of plunger gas lift replacement according to claim 2, characterized in that: The method of obtaining the gas mass increment in the wellbore during the shut-in and re-pressurization stage based on the formation fluid production includes: According to the daily liquid production of the formation, the gas mass increment in the wellbore during the shut-in period is calculated in the shut-in and re-pressure stage; wherein the gas mass increment in the wellbore during the shut-in period is shown in Formula 1: δm g = (q lr × GLR × ρ scg - q lr × S gl × ρ g ) δt Equation 1 In formula 1, q lr is the daily liquid production, GLR is the gas-liquid ratio, S gl is the average solubility of the bottom hole liquid, ρ scg is the density of natural gas under standard conditions, ρ g is the natural gas density under formation conditions, and δt is the shut-in time.
4. The method for determining the timing of plunger gas lift replacement according to claim 2, characterized in that: The method of obtaining the casing pressure increment during the shut-in period according to the gas mass increment in the wellbore during the shut-in period and combining it with the casing pressure before shut-in to obtain the predicted casing pressure value for the well opening includes: According to the gas mass increment in the wellbore during the shut-in period, without considering gas leakage, the casing pressure increment during the shut-in period is calculated by the state equation; wherein the state equation is shown in Formula 2: In formula 2, δm g is the gas mass increment in the wellbore during the shut-in period, Δp c is the casing pressure increment during the shut-in period, Z is the average deviation coefficient, T is the average gas temperature, R is the gas constant under the conditions of Z and T, and M mol is the molar mass of natural gas, h o is the length of the oil pipe, A c is the cross-sectional area of the casing annulus; The casing pressure before shutting in and the casing pressure increment during shutting in are added to obtain the predicted casing pressure value at the start of the well. The predicted casing pressure value at the start of the well is shown in Formula 3: p cn =p cl +Δp c Formula 3 In formula 3, p cl is the casing pressure before shut-in, Δp c It is the casing pressure increment during the shut-in period.
5. The method for determining the timing of plunger gas lift replacement according to claim 1, characterized in that: In step S2, the minimum casing pressure value of the plunger gas lift is as shown in Formula 4: In formula 4, m p is the plunger deadweight, p wh is the wellhead pressure, p LF is the pressure of the friction loss in the liquid section, p gt is the static air column pressure above the plunger, p gtf is the pressure of gas friction loss, At is the internal area of the oil pipe, p lh is the static pressure of the lifting liquid column, and g is the acceleration due to gravity.
6. The method for determining the timing of plunger gas lift replacement according to claim 1, characterized in that: In step S4, the minimum lifting gas volume required for each single cycle discharge volume at different production stages of the gas well is obtained based on each single cycle discharge volume at different production stages of the gas well and the change in wellhead pressure corresponding to each single cycle discharge volume, including: The single-cycle discharge volume at different production stages of the gas well is counted, and the wellhead pressure change corresponding to each single-cycle discharge is recorded. The minimum casing pressure value and the maximum casing pressure value of the plunger gas lift under each single-cycle discharge volume are determined, and the minimum lifting gas volume under each single-cycle discharge volume at different production stages of the gas well is calculated according to the maximum casing pressure value; the minimum lifting gas volume is shown in Formula 5: In formula 5, d ti is the inner diameter of the oil pipe, H c is the depth of the fixture, Z is the average deviation coefficient, T is the average temperature of the gas, P cmax is the maximum casing pressure value.
7. The method for determining the timing of plunger gas lift replacement according to claim 1, characterized in that: In step S5, the relationship curve between each single cycle displacement and its corresponding minimum lifting gas volume in different production stages is drawn, and the critical gas-liquid ratio of the plunger gas lift well under each single cycle displacement in different production stages is determined according to the relationship curve, including: Each single cycle displacement in different production stages and its corresponding minimum gas lift volume are plotted on the same coordinates as X variables and Y variables, respectively. The minimum gas lift volume curve corresponding to each single cycle displacement in different production stages is obtained by data fitting, and the slope at each point of the curve can be obtained by calculation; the slope at each point of the curve is the critical gas-liquid ratio of plunger gas lift under each single cycle displacement in different production stages of the gas well.
8. A plunger gas lift replacement timing determination system, characterized in that: The method for determining the timing of plunger gas lift replacement according to any one of claims 1 to 7 comprises: A prediction module is used to calculate and predict the casing pressure when the well is opened based on the gas well production data during the well shut-in and re-pressurization stage to obtain a predicted casing pressure value when the well is opened; The minimum casing pressure calculation module calculates the minimum casing pressure to ensure normal drainage and gas production by plunger gas lift in the gas well based on the plunger production parameters, and obtains the minimum casing pressure value of plunger gas lift; The casing pressure comparison module is used to determine whether the predicted casing pressure value for well opening is greater than the minimum casing pressure value for plunger gas lift. If the predicted casing pressure at well opening is less than the minimum casing pressure of plunger gas lift, the lifting method needs to be changed; otherwise, the gas-liquid ratio comparison is performed; The minimum gas lift calculation module is used to obtain the minimum gas lift required under each single cycle discharge volume at different production stages of the gas well based on each single cycle discharge volume at different production stages of the gas well and the wellhead pressure change corresponding to each single cycle discharge volume; The critical gas-liquid ratio calculation module is used to draw a relationship diagram between the single-cycle displacement and the minimum gas lift volume, and obtain the minimum gas lift volume curve corresponding to each single-cycle displacement at different production stages through data fitting. According to this curve, the critical gas-liquid ratio of the plunger gas lift well under each single-cycle displacement at different production stages is determined; The gas-liquid ratio comparison module is used to obtain the critical gas-liquid ratio of the production stage from the curve according to the single-cycle discharge volume of the production stage to be judged; the critical gas-liquid ratio of the production stage is compared with the actual gas-liquid ratio measured on site: if the actual gas-liquid ratio is greater than or equal to the critical gas-liquid ratio, it means that the gas volume in the production stage is sufficient to lift the liquid, and the plunger can run to the wellhead to discharge the liquid; if the actual gas-liquid ratio is less than the critical gas-liquid ratio, it means that the gas volume in the production stage is insufficient, the plunger cannot run to the wellhead to discharge the liquid, and the lifting method needs to be changed.