Gas well working condition judgment method and system

Abstract

The invention provides a gas well working condition judgment method and system, and belongs to the technical field of gas well exploiting.The gas well working condition judgment method comprises the steps that a plunger gas lift period of a gas well is divided into a well closing period and a well opening period, and a gas well indicator diagram is drawn; wherein each period time starts from 0, the well shut-in period time increases progressively in the positive direction of the transverse axis, the well opening period time increases progressively in the negative direction of the transverse axis, and the longitudinal axis is the oil pipe pressure value of the corresponding time; when the well opening time is equal to the well closing time, calculating a closed graph area enclosed by the oil pipe pressure value curve as a first indicator diagram area; when the well opening time is shorter than the well closing time, the oil pipe pressure value curve is prolonged to define a closed graph, and the area of the closed graph serves as the area of a second indicator diagram; when the well opening time is longer than the well closing time, calculating a closed graph area enclosed by the oil pipe pressure values as a third indicator diagram area; and when the first indicator diagram area or the second indicator diagram area or the third indicator diagram area exceeds an area threshold, judging that the working condition of the gas well is abnormal. The method can accurately judge whether the condition of the gas well is abnormal or not.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas well exploitation, and particularly relates to a method and a system for judging the working conditions of a gas well. Background Art

[0002] During the process of natural gas exploitation, the changes in the gas well output and the formation liquid output may cause the bottom liquid in the wellbore to stay and form a liquid column. This liquid column increases the hydrostatic backpressure of the gas well and weakens the self-flowing ability of the gas well. The presence of liquid accumulation increases the backpressure on the gas reservoir, resulting in the gas flow rate in the downhole tubing being less than the critical liquid-carrying flow rate. As a result, the liquid accumulation in the tubing cannot be carried to the wellhead by the upward gas flow for discharge, but accumulates at the bottom of the well under the action of gravity. This will cause the gas produced by the formation to be blocked by the liquid accumulation, thereby preventing the normal discharge of gas. In severe cases, it may even lead to the shutdown of the gas well. The plunger gas lift process utilizes the energy of the formation gas to effectively lift the liquid accumulation in the gas wellbore, thus significantly extending the production cycle of the gas well. This process not only has low equipment cost, high drainage efficiency, and short installation cycle, but also can significantly reduce the gas well pressure and further increase the gas well output. The plunger gas lift process has been widely applied in gas well production.

[0003] In the production of plunger gas lift for liquid drainage and gas production, the currently more commonly used graphical method for judging its production status is the periodic drainage curve, which reflects the changes in the tubing pressure and the casing pressure over time during the periodic production process of the plunger. Usually, one cycle follows another, with a very long time axis, which is suitable for observing the changes in the plunger gas lift production situation over a long time. The plunger gas lift drainage curve provides information on the performance of the plunger lifting system, helping engineers and technicians to simply diagnose problems during the operation of the plunger gas lift through this graph and providing a graphical judgment basis for the production of the gas well, serving as an important tool for optimizing the production of the gas well. Its advantages are: (1) It can visually display the pressure changes in the system during production through the curve, helping engineers and technicians to deeply understand the production of the gas well, especially the periodic reciprocating production law of the plunger; (2) The situation of the plunger can be early shown through the pressure curve, so as to take corrective measures in a timely manner; (3) It can qualitatively judge the liquid drainage working conditions of the plunger, used to improve the production system of the plunger gas lift and enhance the production efficiency.

[0004] However, the plunger gas lift periodic drainage curve still has many drawbacks: (1) Analysis lag: Generating the plunger lift periodic drainage curve can be a time-consuming process, especially for gas wells with complex plunger lift systems. The horizontal axis of the graph uses long time units such as clock + calendar. It requires the plunger to run for multiple consecutive cycles to judge the operating conditions of the plunger and the production change trend. This means that the conditions for prediction and early warning are very limited, and the adoption of optimization measures will also lag. (2) Limited accuracy: The plunger drainage curve cannot quantitatively characterize the key parameters of a single cycle of a gas well, such as calculating the periodic drainage volume, gas volume (pressure) recovery rate, and periodic liquid inflow of the gas well. In addition, the accuracy of the curve will be affected by the accuracy of the sensor and measurement errors. (3) Difficult to judge: There is a lack of evaluation criteria for the quality of the plunger drainage curve working conditions, a lack of standard graph boards and the evaluation parameters represented by each node of the standard graph board, and the standard values represented by the characteristics of various abnormal working conditions, making it impossible to timely feedback abnormal working conditions.

[0005] In summary, using the plunger gas lift periodic drainage curve to analyze the working conditions will result in an inability to accurately and real-time judge the working conditions of the gas well. Summary of the Invention

[0006] In order to overcome the deficiencies of the above-mentioned prior art, the present invention provides a method for judging the working conditions of a gas well.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A method for judging the working conditions of a gas well, comprising:

[0009] Dividing the plunger gas lift period of the gas well into a shut-in period and a production period and drawing a dynamometer card of the gas well; where the time of each period starts from 0, the time of the shut-in period increases along the positive direction of the horizontal axis, and the time of the production period increases along the negative direction of the horizontal axis, and the vertical axis is the tubing pressure value corresponding to the time;

[0010] When the production time is equal to the shut-in time, calculate the area of the closed figure enclosed by the tubing pressure value curve as the first dynamometer card area;

[0011] When the production time is shorter than the shut-in time, extend the tubing pressure value curve to enclose a closed figure, and take the area of the closed figure as the second dynamometer card area;

[0012] When the production time is longer than the shut-in time, calculate the area of the closed figure enclosed by the tubing pressure value as the third dynamometer card area;

[0013] When the first dynamometer card area or the second dynamometer card area or the third dynamometer card area exceeds the area threshold, judge that the working conditions of the gas well are abnormal.

[0014] Further, obtain the load coefficients of the tubing and casing in the gas well, the supply-to-discharge ratio of the tubing and casing, and the liquid drainage volume of the gas well; jointly use the load coefficients of the tubing and casing in the gas well, the supply-to-discharge ratio of the tubing and casing, the liquid drainage volume of the gas well, and the dynamometer card area as the judgment indexes for judging abnormal gas well conditions;

[0015] When the load coefficient of the tubing and casing in the gas well is greater than 1, it indicates that the gas well condition is abnormal;

[0016] If the supply-to-discharge ratio of the tubing and casing is above 1.0, it indicates that the gas well condition is abnormal;

[0017] When the liquid drainage volume of the gas well exceeds ±20% of the reference value, it indicates that the gas well condition is abnormal. Further, the calculation formula for the load coefficient of the tubing and casing is

[0018] as follows:

[0019]

[0020]

[0021] where P casing is the pressure of the casing before opening the well; P tubing is the pressure of the tubing before opening the well; P line is the pressure of the pipeline.

[0022] Further, the calculation formula for the supply-to-discharge ratio is:

[0023]

[0024] where σ 供 is the liquid production rate, σ 排 is the pressure build-up rate, σ 供排比 is the supply-to-discharge ratio; ΔP o1 is the tubing-casing pressure difference during afterflow, ΔP o2 is the tubing-casing pressure difference before shutting in the well, P s2 is the tubing pressure when shutting in the well, P s1 is the tubing pressure when opening the well; Δt o is the duration of afterflow, Δt s is the duration of shutting in the well.

[0025] Further, the opening cycle includes: a rising cycle and an afterflow cycle.

[0026] Further, it also includes: calculating the annular gas phase mass and the bottom-hole liquid holdup. When the annular gas phase mass and the bottom-hole liquid holdup decrease, it is judged that the gas well condition changes from abnormal to good. The algorithm for calculating the bottom-hole liquid holdup is:

[0027] Calculate the maximum and minimum values of the liquid holdup height difference between the tubing and the annulus:

[0028] The liquid holdup height of the tubing higher than the annulus is dH​l-S Ut The maximum and minimum values of the liquid level difference between the tubing and casing are expressed as:

[0029]

[0030] dH l_min = 0

[0031] where V -w is the total liquid accumulation volume during the well shut-in period, that is, the sum of the liquid accumulation volumes in the annulus and the tubing, with the unit of m 3 ; A tube is the internal flow area of the tubing, with the unit of m 2 ;

[0032] The total liquid accumulation volume during the well shut-in period is:

[0033] V _w = A tube H l_tube + A hk H l_hk

[0034] where H l_tube is the liquid level height in the tubing, with the unit of m; H l_hk is the liquid level height in the annulus;

[0035] Set the total liquid accumulation volume during the well shut-in period, and based on the setting, find the maximum and minimum values of the liquid level difference between the tubing and casing;

[0036] Initialize the loop counter:

[0037] The counter is:

[0038] Num -epoc = 0

[0039] Define the difference term ΔdH l-diff and the liquid level difference dH_l in the current loop as:

[0040]

[0041] dH_l = dH l_min + ΔdH l_diff

[0042] Convert the wellhead pressure to the bottom-hole flowing pressure:

[0043]

[0044] where p t-tube is the bottom-hole flowing pressure, with the unit of MPa; y g is the relative density of natural gas, dimensionless, taking 0.56 for methane; T is the average temperature of the system, with the unit of K, taking the average of the wellhead temperature and the formation temperature; Z -is the system average deviation factor, dimensionless; p w is the density of water, with the unit of kg / m 3 ; g is the acceleration of gravity, with the unit of m / s 2 ; H g-tube is the gas phase height in the tubing string, specifically: H l-tube -(H l-hk +dH_l), with the unit of m; H l_tube is the liquid phase height in the tubing string, specifically: H l_hk +dH_l, with the unit of m;

[0045] Calculate the bottom-hole flowing pressure:

[0046]

[0047] where, p -c is the bottom-hole casing pressure, with the unit of MPa; H g-hk is the gas phase height in the annulus, with the unit of m; H l_hk is the liquid phase height in the annulus, with the unit of m;

[0048] Calculate the current bottom-hole flowing pressure error:

[0049]

[0050] If the shut-in bottom-hole flowing pressure error is less than 0.001, exit the loop; otherwise, continue the calculation;

[0051] If p wf-k >p wf-tube then the minimum value of the liquid level difference between the tubing and casing is equal to the current liquid level difference, i.e., dH l_min =dH_l; otherwise, the maximum value of the liquid level difference between the tubing and casing is equal to the current liquid level difference, i.e., dH l_max =dH_l;

[0052] Update the loop counter:

[0053] Calculate the liquid holdup in the annulus and tubing according to the following formula:

[0054]

[0055] where, A k is the internal flow area of the annulus 2 .

[0056] Furthermore, the calculation of the gas phase mass in the annulus includes:

[0057] Calculate the annulus system pressure:

[0058]

[0059] where, Hg is the height of the gas column, with the unit of m, and is taken as 0.5 times the height of the annulus gas column; calculate the gas volume in the annulus:

[0060] V g-k-S ut = A k (H tube - H l-k-S ut )

[0061] where H tube is the total length of the tubing, with the unit of m; H l-k-S ut is the height of the liquid phase in the annulus, with the unit of m. Calculate the mass of the gas in the annulus:

[0062]

[0063] where M g is the relative molecular mass of the gas, dimensionless; R is the molar gas constant, with the unit of Pa·m 3 / (mol·K), and is taken as 8.314; z gsys-k-s Ut is the compressibility factor, and is taken as 0.92.

[0064] Furthermore, it further includes: when the operating condition of the gas well is abnormal, adjust the operating condition of the gas well by adjusting the well opening and closing time to make it satisfy:

[0065] σ 供 × (τ 开 + Δτ 延长 ) ≤ σ 恢复 × (τ 关 - Δτ 缩短 )

[0066] where σ 供 is the liquid supply rate; σ 恢复 is the pressure recovery rate; τ 开 and T 关 are respectively the well opening time and the well closing time of the original periodic production; Δτ 缩短 and Δτ 延长 are respectively the shortened well closing time and the extended well opening time.

[0067] A judgment system for the operating condition of a gas well, characterized by including:

[0068] A gas well indicator diagram construction module, used to divide the plunger gas lift cycle of the gas well into a well closing cycle and a well opening cycle and draw the gas well indicator diagram; where the time of each cycle starts from 0, the time of the well closing cycle increases along the positive direction of the horizontal axis, and the time of the well opening cycle increases along the negative direction of the horizontal axis, and the vertical axis is the tubing pressure value corresponding to the time;

[0069] A calculation module, used to calculate the area of the closed figure enclosed by the tubing pressure value curve as the first indicator diagram area when the well opening time is equal to the well closing time;

[0070] When the open - well time is shorter than the shut - in time, extend the tubing pressure value curve to enclose a closed figure, and take the area of the closed figure as the second dynamometer card area;

[0071] When the open - well time is longer than the shut - in time, calculate the area of the closed figure enclosed by the tubing pressure values as the third dynamometer card area;

[0072] A judgment module, configured to judge that the gas - well working condition is abnormal when the area of the first dynamometer card or the area of the second dynamometer card or the area of the third dynamometer card exceeds the area threshold.

[0073] The method for judging the working condition of a gas well provided by the present invention has the following beneficial effects:

[0074] The present invention uses the gas - well dynamometer card as a standard to judge the working condition of the gas well; the gas - well dynamometer card couples the plunger gas - lift dynamometer card of the gas well and the variation of production parameters with the cycle, and can process a large amount of production data from different gas wells; since the gas - well dynamometer card can qualitatively and quantitatively reflect the production status of each cycle of the gas well in real - time and accurately, the shape of the gas - well dynamometer card can be used to qualitatively judge whether there are abnormal working conditions in the gas - well production; it solves the problem that in the prior art, analyzing the working condition by using the plunger gas - lift periodic liquid - drainage curve makes it impossible to accurately and real - time judge the working condition of the gas well.

[0075] mine. Brief Description of the Drawings

[0076] In order to more clearly illustrate the embodiments of the present invention and its design, the drawings required for this embodiment will be briefly introduced below. The drawings in the following description are only partial embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0077] Figure 1 is a standard chart generated according to the definition of plunger gas - lift;

[0078] Figure 2 is a standard dynamometer card for short open and long shut - in;

[0079] Figure 3 is a standard dynamometer card for long open and short shut - in;

[0080] Figure 4 is a schematic diagram of the single - cycle evaluation method;

[0081] Figure 5 is a schematic diagram of the calculation process of the bottom - hole liquid - accumulation optimization algorithm. Detailed Embodiments

[0082] To enable those skilled in the art to better understand the technical solution of the present invention and be able to implement it, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and cannot be used to limit the protection scope of the present invention.

[0083] Embodiment

[0084] The present invention provides a method for judging the working conditions of a gas well, specifically as Figures 1-5 shown, including:

[0085] Based on the plunger gas lift periodic liquid drainage curve, by dividing the period into three production stages: shut-in, rising, and afterflow, defining the start time of each period as 0, the shut-in stage time along the positive direction of the horizontal axis, and the non-shut-in stage (rising and afterflow) time along the negative direction of the horizontal axis, and the vertical axis records the tubing pressure value at the corresponding time.

[0086] The plunger gas lift production system is divided into three cases according to the length of the opening and closing well time: the opening well time is equal to the closing well time (equal opening and closing), the opening well time is shorter than the closing well time (short opening and long closing), and the opening well time is longer than the closing well time (long opening and short closing) three working systems.

[0087] Under the working system where the opening well time is equal to the closing well time (equal opening and closing), the opening and closing well durations are the same, and the starting point and the ending point of the graph generated by the periodic production are approximately the same point, a closed graph can be drawn, and the area of the graph can be calculated according to the graph, as Figure 1 .

[0088] Under the working system where the opening well time is shorter than the closing well time (short opening and long closing), since the opening well time is shorter than the closing well time, the graph cannot be closed. Add the situation of extending the opening well time to equal opening and closing to make the graph closed. Calculate the area actually enclosed and the area increased after adding the auxiliary line (the area not enclosed) respectively, as Figure 2 .

[0089] Under the working system where the opening well time is longer than the closing well time (long opening and short closing), since the opening well time is longer than the closing well time, the graph is approximately closed and then moves to the negative time axis, only calculate the area enclosed when the time is positive, as Figure 3 .

[0090] The present invention provides a method for establishing a plunger gas lift analysis and evaluation method, including the following steps:

[0091] In the described establishment method, the load coefficient is calculated by the pressure measured at the wellhead of the tubing and the casing at a specific moment, and is calculated according to the following formula:

[0092]

[0093] In the formula, P casingis the pressure of the casing before opening the well; P tubing is the pressure of the tubing before opening the well; P line is the pressure of the pipeline.

[0094] The described establishment method calculates the supply - drainage ratio through the pressures measured at the wellhead of the tubing and the casing at a specific moment, and is calculated according to the following formula:

[0095]

[0096] where, σ 供 is the liquid production rate, σ 排 is the pressure build - up rate, σ 供排比 is the supply - drainage ratio; ΔP o1 is the tubing - casing pressure difference during the after - flow, ΔP o2 is the tubing - casing pressure difference before shutting in the well, P s2 is the tubing pressure when shutting in the well, P s1 is the tubing pressure when opening the well; Δt o is the duration of the after - flow, Δt s is the duration of shutting in the well.

[0097] The described establishment method draws a plunger gas lift work diagram and calculates its area according to the image.

[0098] The described establishment method calculates the periodic liquid drainage volume through the pressures measured at the wellhead of the tubing and the casing at a specific moment, and judges the change trend of the periodic bottom - hole liquid accumulation during the long - term operation of the plunger gas lift according to the liquid drainage volume of each period, reflecting the production status of the plunger gas lift.

[0099] Analyze the liquid accumulation state at the moment of shutting in the well, and estimate the liquid accumulation volume in the annulus at the moment of opening the well. Use the bisection method to quantitatively describe the wellbore liquid accumulation condition at the critical moment of shutting in the well, and gradually determine three key unknown parameters: the liquid accumulation volume at shutting in the well, the liquid accumulation height in the annulus at shutting in the well, and the liquid accumulation height in the tubing at shutting in the well. Quantitatively analyze the bottom - hole liquid accumulation situation of each period.

[0100] The described establishment method combines the liquid drainage volume and the area enclosed by the work diagram to calculate the operating power, and is calculated according to the following formula:

[0101]

[0102] where, Q is the actual liquid drainage volume in this working cycle, with the unit of m 3 ; S 实际围成面积It is the area enclosed by the actual dynamometer card during this working cycle. Since there is a significant difference in the order of magnitude between the actual liquid production volume and the actual enclosed area, in order to magnify the influence of the actual liquid production volume, a coefficient of 1000 is multiplied. The liquid production volume in each cycle and the area enclosed by the actual dynamometer card are always fluctuating. Analyzing the liquid production volume and the area enclosed by the actual dynamometer card separately cannot well reflect the operating conditions. Therefore, the introduction of the operating power η is to more comprehensively understand the relationship between the liquid production volume and the area enclosed by the dynamometer card and effectively address the challenges brought about by the volatility of these parameters.

[0103] For the establishment method described above, the following gives the range of production parameters under normal operating conditions:

[0104] Load factor less than 0.5: When the load factor of a gas well is less than 0.5, it means that the operating state of the gas well is relatively stable. Conversely, when the load factor is greater than 1, it means that an excessive tubing-casing pressure difference is generated during well shut-in, which may lead to unstable operation or premature shutdown of the gas well. Therefore, in order to ensure the stable operation of the gas well, the load factor should be maintained below 0.5. If the load factor exceeds 0.5, the abnormal state of the gas well needs to be judged according to the degree of its excess.

[0105] Liquid supply-drainage ratio less than or equal to 1.0: The liquid supply-drainage ratio reflects the situation of liquid accumulation at the bottom of the well. Therefore, under normal operating conditions, the load factor should be less than or equal to 1.0. When the liquid supply-drainage ratio is lower than 1.0, the liquid drainage rate exceeds the liquid supply rate, which may lead to excessive liquid accumulation at the bottom of the well, thereby affecting production efficiency. Conversely, if the liquid supply-drainage ratio exceeds 1.0, it means that the liquid supply rate is faster than the liquid drainage rate, which may cause excessive compression of the liquid when the plunger descends, affecting the normal operation of the plunger. Therefore, the liquid supply-drainage ratio should be maintained at 1.0 or below. If the liquid supply-drainage ratio exceeds 1.0, the abnormal state of the gas well needs to be judged according to the degree of its excess.

[0106] Liquid production volume: The liquid production volume is calculated from the dynamometer card data and represents the total liquid production volume in one cycle. Under the standard working system, the liquid production volume of the gas well will fluctuate within ±20% of a reference value, and if it exceeds this fluctuation range, the gas well can be considered to be in an abnormal operating condition.

[0107] Dynamometer card area: The dynamometer card area can reflect the liquid supply capacity, liquid drainage capacity, and gas production capacity that can be exploited of the gas well. It is normal for the actual dynamometer card area to fluctuate within a certain range of the ideal dynamometer card area. If it exceeds this certain range, it can be marked as an abnormal operating condition.

[0108] Combining the above parameters, these four items are used as the evaluation criteria for the quality of the operating conditions. The evaluation process is shown in Figure 4 Each item has a certain weight in the final evaluation. The final result obtained by integrating all parameters can be used as the standard for whether the gas well is operating normally.

[0109] The adjusted switch well time shall satisfy the following formula:

[0110]

[0111] Wherein, σ 供 is the liquid supply rate; σ 恢复 is the pressure recovery rate; τ 开 and T 关 are respectively the open well time and the shut-in well time of the original periodic production; ΔT 缩短 and ΔT 延长 are respectively the shortened shut-in well time and the extended open well time. In order to ensure normal gas production in the gas well, the gas well must have sufficient energy to discharge the formation liquid supply.

[0112] The present invention provides a bottom-hole liquid accumulation estimation algorithm, including the following steps:

[0113] (1) Calculate the maximum and minimum values of the liquid accumulation height difference between the tubing and the annulus

[0114] The liquid accumulation height of the tubing higher than the annulus is dH l-shut . The maximum and minimum values of the liquid accumulation height difference between the tubing and the annulus can be expressed as:

[0115]

[0116] dH l_min = 0

[0117] Wherein, V -w is the total liquid accumulation volume during the shut-in well stage, that is, the sum of the liquid accumulation volumes in the annulus and the tubing, with the unit of m3; A tube is the internal flow area of the tubing, with the unit of m2.

[0118] The total liquid accumulation volume during the shut-in well stage can be obtained by the following formula:

[0119] V _w = A tube H l_tube + A hk H l _ hk

[0120] Wherein, H l-tube is the liquid accumulation height of the tubing, with the unit of m; H l-hk is the liquid accumulation height of the annulus, with the unit of m.

[0121] In this calculation strategy, a hypothesis is made on the total liquid accumulation volume during the shut-in well stage, and then based on this hypothesis, the maximum and minimum values of the liquid accumulation height difference between the tubing and the annulus are obtained.

[0122] (2) Initialize the loop counter

[0123] During the calculation process, we also need a loop counter to track the number of iterations. This project initializes this counter as follows:

[0124] Num _epoch = 0

[0125] (3) Define the differential term ΔdH l-diff and the liquid accumulation height difference dH_l of the current cycle as follows:

[0126]

[0127] dH_l = dH l_min + ΔdH l_diff

[0128] (4) Convert the oil pressure to the bottom-hole flowing pressure according to the following formula:

[0129]

[0130] where p t-tube is the bottom-hole flowing pressure, in MPa; γ g is the relative density of natural gas, dimensionless, taking 0.56 for methane; T- is the average system temperature, in K, taking the average of the wellhead temperature and the formation temperature; Z- is the average system deviation factor, dimensionless, which needs to be obtained by iteration; ρ w is the density of water, in kg / m3; g is the acceleration due to gravity, in m / s2; H g-tube is the gas phase height in the tubing, specifically: H l_tube -(H l_hk + dH_l), in m; H l-tube is the liquid phase height in the tubing, specifically: H l-hk + dH_l, in m;

[0131] (5) Calculate the bottom-hole flowing pressure according to the following formula:

[0132]

[0133] where p-c is the bottom-hole casing pressure, in MPa; H g-hk is the gas phase height in the annulus, in m; H l_hk is the liquid phase height in the annulus, in m;

[0134] (6) Calculate the current bottom-hole flowing pressure error:

[0135]

[0136] If the shut-in bottom-hole flowing pressure error is less than 0.001, exit the loop; otherwise, continue the calculation;

[0137] (7) If pwf_hk >p wf_tube Then the minimum value of the liquid accumulation height difference between the casing and tubing is equal to the current liquid accumulation height difference, i.e., dH l_min = dH_l; otherwise, the maximum value of the liquid accumulation height difference between the casing and tubing is equal to the current liquid accumulation height difference, i.e., dH l_max = dH_l;

[0138] (8) Update the loop counter

[0139] Num _epoch = Num _epoch + 1

[0140] (9) If the loop counter is less than 30, then execute steps (3) to (7); otherwise, exit the loop.

[0141] (10) Calculate the liquid accumulation volume in the annulus and tubing according to the following formula:

[0142]

[0143]

[0144] where A hk is the internal flow area of the annulus, with the unit of m2.

[0145] Based on this algorithm, the calculation steps of the gas phase mass in the annulus at the well shut - in moment are as follows:

[0146] (1) Calculate the annulus system pressure:

[0147]

[0148] where H g is the height of the gas column, with the unit of m, taking 0.5 times the height of the gas column in the annulus.

[0149] (2) Calculate the gas phase volume in the annulus:

[0150] V g_hk_shut = A hk (H tube - H l_hk_shut )

[0151] where H tube is the total length of the tubing, with the unit of m; H l-hk-shut is the height of the liquid phase in the annulus, with the unit of m.

[0152] (3) Calculate the gas phase mass in the annulus:

[0153]

[0154] where M gis the relative molecular mass of the gas, dimensionless; R is the molar gas constant, with the unit of Pa*m3 / (mol*K), taking 8.314; z gsys-hk-shut is the compressibility factor, taking 0.92.

[0155] Based on this algorithm, the steps for judging the liquid accumulation state are as follows:

[0156] When there is always liquid accumulation in the wellbore annulus during the critical period from shut-in to open well, the gas in the annulus will not flow into the tubing.

[0157] (1) Calculate the total mass of the annulus gas

[0158] Assume the casing pressure when just emptying the liquid in the annulus, then the total mass of the annulus gas can be calculated according to the following formula:

[0159] m g_hk_open_now = 1.05m g_hk_shut_final

[0160] If the mass of this part of the gas just empties the liquid in the annulus, the apparent system pressure of the annulus gas column at the critical moment of opening the well is:

[0161]

[0162] (2) If the calculated casing pressure is not lower than the true casing pressure, there is no liquid accumulation in the annulus when opening the well; otherwise, there is liquid accumulation in the annulus when opening the well. That is, P -pk-pd > p c open, then there is no liquid accumulation in the annulus.

[0163] Based on this algorithm, the calculation steps for the gas-phase mass in the annulus at the moment of opening the well are as follows:

[0164] (1) Calculate the annulus system pressure:

[0165]

[0166] Among them, H g is the gas column height, with the unit of m, taking 0.5 times of the annulus gas column height.

[0167] (2) Calculate the gas-phase volume in the annulus:

[0168] V g_hk_open = A hk (H tube - H l_hk_open )

[0169] Among them, H tube is the total length of the tubing, with the unit of m;

[0170] H l-hk-open is the annulus liquid-phase height, with the unit of m.

[0171] (3) Calculate the gas-phase mass in the annulus:

[0172]

[0173] Among them, M g is the relative molecular mass of the gas, dimensionless; R is the molar gas constant, with the unit of Pa*m3 / (mol*K), taking 8.314; z gsys-hk-open is the compressibility factor, taking 0.92.

[0174] Based on this algorithm, the steps to calculate the normalized error are as follows:

[0175] Taking the annular gas phase mass at the well opening moment greater than 120% of the annular gas phase mass at the well shut-in moment as error 1, that is, error1 = |m g_hk_open -1.2m g_hk_shut |

[0176] Taking the liquid holdup in the wellbore at the well opening moment and 80% of the liquid holdup in the wellbore at the well shut-in moment as error 2;

[0177] That is

[0178] Then the normalized error of error 1 is:

[0179] error_e1 = error1 / max(m g-hk-open , 1.2m g_hk_shut )

[0180] Among them, the denominator is m g-hk-open and 1.2m g_hk_shut the larger value between them. This means that, in order to normalize the error, error1 is divided by the maximum value between the annular gas mass at the well opening and 1.2 times the annular gas mass at the well shut-in.

[0181] The normalized error of error 2 is:

[0182]

[0183] Among them, the denominator is and the larger value between them. Divide error1 by the maximum value between the annular gas mass at the well opening and 1.2 times the annular gas mass at the well shut-in.

[0184] The total error is:

[0185] error_to = error_e1 + error_e2

[0186] Based on this algorithm, the total flowchart for calculating the liquid holdup is shown in the figure.

[0187] The present invention also provides a software for a plunger gas lift production evaluation system, including:

[0188] A data processing module is used to process the plunger gas lift minute production data in a specified data format. It divides the data into cycles according to the pressure change situation and adds a time column for the horizontal axis of the drawn indicator diagram, which are respectively saved in different worksheets. Then, with time as the horizontal axis and tubing pressure as the vertical axis, the plunger indicator diagram of each cycle is drawn.

[0189] A calculation parameter module processes the processed cycle data respectively, extracts the tubing pressure and casing pressure at key time points to calculate load coefficients, gas-liquid ratio, liquid production volume, the area enclosed by the gas well indicator diagram, liquid drainage power, liquid drainage pressure difference, the area not enclosed by the gas well indicator diagram, etc., and saves them in a file.

[0190] A data storage module. The software's built-in database can save the calculated production parameters into a database file. Each time the software starts, it can read the data in the database without having to process the data again, saving a lot of time.

[0191] The following are specific embodiments of the present invention:

[0192] The present invention couples the change of the plunger gas lift indicator diagram and production parameters with the cycle, can process a large amount of production data from different gas wells, generate clear and accurate plunger indicator diagrams therefrom, and propose optimization strategies for each cycle based on the analysis results. It provides a process parameter trend chart to help engineers and managers quickly understand the change trend of the gas well state, so as to better make optimization decisions. These optimization strategies are designed to ensure a suitable production regime during most production cycles and provide continuous support for the stable production capacity of the gas well.

[0193] The data processing unit requires the user to provide an excel format data file, which should contain the following data columns:

[0194] [Time]: This column should contain the time of each record, and should be in the date and time format. Example: 20xx-xx-xx 10:43:50.000.

[0195] [Casing pressure (MPa)]: This column should contain the casing pressure corresponding to the time, with the unit of MPa and should be a real number. Example: 8.297.

[0196] [Tubing pressure (MPa)]: This column should contain the tubing pressure corresponding to the time, with the unit of MPa and should be a real number. Example: 8.297.

[0197] [Status]: This column should contain the status of the plunger at the corresponding time, and should be one of shut-in, rising, and continuous flow.

[0198] In the data import area, click the "Select Working Folder" button to specify the working folder. This working folder stores two files generated after software processing. One file is a CSV file, which is used to process production parameters, parameter change diagrams, etc.; the other file is an Excel (grouped) file, which is used to generate standard diagrams and actual diagrams. Then click the "Import Data" button, select the data file to be analyzed in the pop-up file selection dialog box. Subsequently, the imported data will be displayed on the left side of the software, and then the software will immediately start calculations and read production parameters.

[0199] After the data is successfully imported and read, the software will directly generate the production parameters, parameter change diagrams, and monthly data change diagrams contained in the file.

[0200] For production parameters, you can choose to display periodic data and monthly average data. At the same time, the processed production parameters can also be exported to Excel for easy viewing and management. Among them, parameter changes include: supply-to-discharge ratio, load factor, etc.

[0201] At the same time, you can select the number of plunger gas lift diagrams you want to generate in the standard diagram area, and then the software will directly generate diagrams in the actual diagram area.

Claims

1. A method for judging the working conditions of a gas well, characterized in that Including: Dividing the plunger gas lift cycle of a gas well into a shut - in period and a flowing period and plotting the indicator diagram of the gas well; where the time of each period starts from 0, the time of the shut - in period increases along the positive direction of the horizontal axis, and the time of the flowing period increases along the negative direction of the horizontal axis, and the vertical axis is the tubing pressure value corresponding to the time; When the flowing time is equal to the shut - in time, calculating the area of the closed figure enclosed by the tubing pressure value curve as the first indicator diagram area; When the flowing time is shorter than the shut - in time, extending the tubing pressure value curve to enclose a closed figure, and taking the area of the closed figure as the second indicator diagram area; When the flowing time is longer than the shut - in time, calculating the area of the closed figure enclosed by the tubing pressure value as the third indicator diagram area; When the first indicator diagram area or the second indicator diagram area or the third indicator diagram area exceeds the area threshold, determining that the working condition of the gas well is abnormal; 2. The judgment method of a gas well working condition according to claim 1, wherein Obtaining the load coefficient between the tubing and the casing in the gas well, the supply - to - production ratio between the tubing and the casing, and the liquid production volume of the gas well; taking the load coefficient between the tubing and the casing in the gas well, the supply - to - production ratio between the tubing and the casing, the liquid production volume of the gas well and the indicator diagram area together as the judgment indexes for determining the abnormal working condition of the gas well; When the load coefficient between the tubing and the casing in the gas well is greater than 1, it indicates that the working condition of the gas well is abnormal; If the supply - to - production ratio between the tubing and the casing is above 1.0, it indicates that the working condition of the gas well is abnormal; When the liquid production volume of the gas well exceeds ±20% of the reference value, it indicates that the working condition of the gas well is abnormal.

3. The method for judging the working condition of a gas well according to claim 2, wherein The calculation formula for the load coefficient between the tubing and the casing is: Wherein, P casing is the pressure of the casing before opening the well; P tubing is the pressure of the tubing before opening the well; P line is the pressure of the pipeline.

4. The method for judging the working condition of a gas well according to claim 2, wherein The calculation formula for the supply - to - production ratio is: Among them, σ 供 is the fluid production rate, σ 排 is the pressure build-up rate, σ 供排比 is the injection-production ratio; ΔP o1 is the tubing-casing pressure difference during afterflow, ΔP o2 is the tubing-casing pressure difference before well shut-in, P s2 is the tubing pressure at well shut-in, P s1 is the tubing pressure at well opening; Δt o is the duration of afterflow, Δt s is the duration of well shut-in.

5. A method for judging the working condition of a gas well according to claim 1, characterized in that, The flowing period includes: a rising period and a continuation - flow period.

6. The method for judging the working condition of a gas well according to claim 1, characterized in that Also including: Calculating the annular gas phase mass and the bottom - hole liquid accumulation volume. When the annular gas phase mass and the bottom - hole liquid accumulation volume decrease, it is determined that the working condition of the gas well changes from abnormal to normal. The algorithm for calculating the bottom - hole liquid accumulation volume is: Calculating the maximum and minimum values of the liquid accumulation height difference between the tubing and the casing: The liquid accumulation height of the tubing above the annulus is dH l_sut . The maximum and minimum values of the liquid accumulation height difference between the tubing and the casing are expressed as: dH l_min = 0 Among them, V _w is the total liquid accumulation volume during the well shut-in period, that is, the sum of the liquid accumulation volumes in the annulus and the tubing, with the unit of m 3 ; A tube is the internal flow area of the tubing, with the unit of m 2 ; The total liquid accumulation volume in the shut - in stage is: V _w = A tube H l_tube + A hk H l_hk Among them, H l_tube is the liquid accumulation height in the tubing, with the unit of m; H l_hk is the liquid accumulation height in the annulus; Setting the total liquid accumulation volume in the shut - in stage, and obtaining the maximum and minimum values of the liquid accumulation height difference between the tubing and the casing based on the setting; Initializing the loop counter: The counter is: Num -epoc = 0 Define the difference term ΔdH l_diff and the liquid level difference dH_l of the current cycle as follows: dH_l = dH l_min +ΔdH l_diff Converting the tubing pressure to the bottom - hole flowing pressure: Among them, p t_tube is the bottom-hole flowing pressure, with the unit of MPa; γ g is the relative density of natural gas, dimensionless, taking 0.56 for methane; is the average temperature of the system, with the unit of K, taking the average of the wellhead temperature and the formation temperature; is the average deviation factor of the system, dimensionless; ρ w is the density of water, with the unit of kg / m 3 ; g is the acceleration of gravity, with the unit of m / s 2 ; H g_tube is the gas-phase height in the tubing, specifically: H l_tube -(H l_hk +dH_l), with the unit of m; H l_tube is the liquid-phase height in the tubing, specifically: H l_hk +dH_l, with the unit of m; Calculating the bottom - hole flowing pressure: where p _c is the bottom hole casing pressure, in MPa; H g_hk is the height of the annular gas phase, in m; H l_hk is the height of the annular liquid phase, in m; Calculating the current bottom - hole flowing pressure error: If the bottom - hole flowing pressure error in the shut - in period is less than 0.001, then exit the loop; otherwise, continue the calculation; If p wf_k > p wf_tube then the minimum value of the liquid level difference between the tubing and the casing is equal to the current liquid level difference, i.e., dH l_min = dH_l; otherwise, the maximum value of the liquid level difference between the tubing and the casing is equal to the current liquid level difference, i.e., dH l_max = dH_l; Updating the loop counter: Calculating the annular and tubing liquid accumulation volumes according to the following formula: H l_tube = H l_k + dH_l V w_s ut = H l_k × (A k + A tube ) + dH_l × A tube Among them, A k is the internal flow area of the annulus 2 .

7. The method for judging the working condition of a gas well according to claim 6, characterized in that, The calculation of the annular gas phase mass includes: Calculating the annular system pressure: Among them, H g is the height of the gas column, with the unit of m, which is 0.5 times the height of the annular gas column; Calculating the gas phase volume in the annulus: V g_ k_s ut = A k (H tube - H l_ k_s ut ) Among them, H tube is the total length of the tubing, in m; H l_ k_s ut is the height of the annular liquid phase, in m. Calculating the gas phase mass in the annulus: Among them, M g is the relative molecular mass of the gas, dimensionless; R is the molar gas constant, with the unit of Pa*m 3 / (mol*K), taking 8.314; z gsys_ k_s ut is the compression factor, taking 0.

92.

8. A method for judging the working conditions of a gas well according to claim 1, characterized in that, Also including: When the working condition of the gas well is abnormal, adjusting the working condition of the gas well by adjusting the shut - in and flowing times to make it meet: σ 供 ×(τ 开 +Δτ 延长 )≤σ 恢复 ×(τ 关 -Δτ 缩短 ) Among them, σ 供 is the liquid supply rate; σ 恢复 is the pressure recovery rate; τ 开 and τ 关 are the open well time and the shut-in well time of the original periodic production respectively; Δτ 缩短 and Δτ 延长 are the shortened shut-in well time and the extended open well time respectively.

9. A judging system for the working conditions of a gas well, characterized in that, Including: A gas well indicator diagram construction module, which is used to divide the plunger gas lift cycle of the gas well into a shut - in period and a flowing period and plot the indicator diagram of the gas well; where the time of each period starts from 0, the time of the shut - in period increases along the positive direction of the horizontal axis, and the time of the flowing period increases along the negative direction of the horizontal axis, and the vertical axis is the tubing pressure value corresponding to the time; A calculation module, which is used to calculate the area of the closed figure enclosed by the tubing pressure value curve as the first indicator diagram area when the flowing time is equal to the shut - in time; When the flowing time is shorter than the shut - in time, extending the tubing pressure value curve to enclose a closed figure, and taking the area of the closed figure as the second indicator diagram area; When the open - well time is longer than the shut - in time, calculate the enclosed area of the tubing pressure values as the area of the third dynamometer card. A judgment module is used to judge that the gas - well working condition is abnormal when the area of the first dynamometer card or the area of the second dynamometer card or the area of the third dynamometer card exceeds the area threshold.

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