Quantitative design method for gas well intermittent dosing parameters

Abstract

The invention discloses a quantitative design method for gas well intermittent dosing parameters, and relates to the technical field of gas well foam drainage gas recovery. According to the method, gas well basic parameters and produced liquid physical property parameters are collected, on the basis of a Lie Fujian critical liquid carrying model and a foam liquid carrying lower limit equation, a quantitative calculation formula of the critical liquid accumulation amount and the dosing period is deduced, the single-time dosing amount is calculated in combination with the standard dosing concentration, and quantitative design of intermittent dosing parameters is achieved. As only aiming at the liquid phase which cannot be taken away by the gas-phase liquid-carrying flow velocity, a quantitative calculation basis is provided for on-site dosing parameter optimization, and meanwhile, the dosage of the medicament is reasonably reduced.

Description

Technical Field

[0001] This invention belongs to the field of gas well foam drainage gas production technology, specifically involving a quantitative design method for intermittent chemical dosing parameters in gas wells, applicable to the optimization of foam drainage gas production process in low-pressure, low-production gas wells. Background Technology

[0002] During gas field development, as formation energy continues to deplete, the problem of fluid accumulation in wellbores becomes increasingly prominent, leading to decreased gas well production and even water flooding shutdowns. Foam drainage gas production technology, with its advantages of simple construction, low cost, and rapid onset of action, is widely used in various large gas fields, and intermittent chemical dosing is the most widely used foaming agent dosing method in the field. The rationality of the dosing cycle and dosage design directly determines the effectiveness of the process and its economic efficiency.

[0003] Currently, relevant patented technologies have been researched for gas well chemical dosing technology. For example, Chinese patent CN 105927195A discloses a smart chemical dosing method for gas wells based on oil-casing pressure difference, Chinese patent CN 104632156 A discloses a cluster gas well smart dosing method combined with fluid accumulation diagnosis, and Chinese patents CN 204082096 U and CN 103754815 A have respectively optimized the flow control and metering adjustment structure of gas well chemical dosing devices.

[0004] However, existing technologies mostly focus on the development of dosing device hardware and automated control systems, with insufficient research on quantitative design methods for core parameters of intermittent dosing. The formulation of on-site dosing parameters still heavily relies on engineering experience, failing to combine critical fluid carrying theory with the dynamic changes in wellbore fluid accumulation to establish a systematic quantitative calculation method for dosing parameters. This results in problems such as reagent waste, unstable fluid carrying effect, and poor adaptability to gas wells under different operating conditions. Therefore, this invention proposes a quantitative design method for intermittent dosing parameters in gas wells to address the aforementioned deficiencies in existing technologies. Summary of the Invention

[0005] The purpose of this invention is to provide a quantitative design method for intermittent chemical dosing parameters in gas wells. By integrating multiphase flow theory, foam liquid-carrying characteristics and field gas well parameters, quantitative formulas for critical liquid accumulation and dosing cycle are derived, realizing the quantitative calculation of core parameters for intermittent dosing of foaming agents and overcoming the blindness of traditional experience-based dosing.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: 1. Collect basic parameters of the target gas well Collect gas well production data: including tubing inner diameter (used to calculate wellbore cross-sectional area). A Daily gas production V g (unit: m) 3 / d), Daily liquid productionQ lin (unit: m) 3 / d), wellbore temperature T (Unit: °C) Wellbore pressure P (Unit: MPa) Test the physical properties of the produced fluid: The surface tension of the produced fluid without the addition of a foaming agent was measured using a surface tension meter. s (Unit: N / m) Surface tension of the collected liquid after adding foaming agent in (Unit: N / m), liquid phase density measured using a hydrometer. r l (Unit: kg / m³) 3 ); Calculate gas phase density r g (Unit: kg / m³) 3 ): The natural gas compressibility factor Z is calculated using the industry-standard Gopal method, based on wellbore temperature. T (Unit: K) and pressure P (Unit: MPa) Calculate relative pressure P r = P / P c Relative temperature T r = T / T c ,in, P c The critical pressure of natural gas is taken as 4.6 MPa; T c The critical temperature of natural gas is taken as 190.6 K; Under non-supercritical conditions, calculations are performed using the modified ideal gas law. r g : r g = ( P × M ) / ( Z × R × T ); where M is the molar mass of natural gas, taken as 0.01604 kg / mol; R is the universal gas constant, taken as 8.314 J / (mol·K). Under supercritical conditions, the critical density conversion formula is used for calculation. r g : r g = r c × ( P / P r ) × ( T r / T )( r c = 162.7 kg / m 3 ).

[0007] Actual liquid-carrying gas velocity in the wellbore v gr The formula is obtained by transforming the critical liquid-carrying capacity formula. v gr = ( V g × Z × T) / (2.5×10 8 × A × P) in, v gr This represents the actual liquid-carrying gas velocity, in m / s. V g Daily gas production, in m³ 3 / d; Z The compressibility factor is dimensionless. T This represents the absolute temperature of the wellbore, expressed in Kelvin (K). A This refers to the cross-sectional area of ​​the well shaft, in meters (m²). 2 ; P This refers to the wellbore pressure, in MPa; 2.5 × 10⁻⁶. 8 Convert comprehensive coefficients for engineering units.

[0008] 2. Determine the critical liquid-carrying gas velocity and the minimum foam liquid-carrying gas velocity of the gas well. Calculation of critical liquid-carrying gas velocity based on Li Min's critical liquid-carrying model v c (Unit: m / s), the calculation formula is:

[0009] in, g The acceleration due to gravity is taken as 9.81 m / s². 2 At this point, the fluid carrying capacity in the wellbore without adding a foaming agent. Q gr and Q lin The liquid holdup in the wellbore is equal, therefore, without the addition of a foaming agent... H L for, H L = Q lin / ( vc × A × 86400) Among them, 86400 is the time conversion factor between seconds and days.

[0010] Determine the minimum foam liquid-carrying gas velocity by combining the lower limit equation of foam liquid carrying capacity. v fc (Unit: m / s) and their corresponding liquid holdup H L ´ : When a foaming agent is added, the required gas velocity for drainage and gas collection is just right to prevent liquid accumulation. v f The gas velocity decreased to the lower limit of the foam drainage gas extraction velocity. v fc The transition boundary from bubbly flow to slug flow is defined as the lower limit of the gas velocity in foam drainage sampling. The expression for this gas velocity is:

[0011] in, v sl Let be the flow velocity of the liquid phase, expressed in m / s, and calculated using the following formula: v sl = Q lin / ( A × 86400) At this point, the foam-carrying fluid flow rate in the wellbore after adding the foaming agent... Q lf and Q lin If they are equal, then the liquid holdup in the wellbore after adding the foaming agent is... H L ´ for, H L ´ = Q lin / ( v fc × A × 86400) H L and H L ´ Both are dimensionless parameters.

[0012] Verification calculation conditions: actual liquid-carrying gas velocity v gr Must meet v fc < vgr < v c ;like v gr > v c If it is determined that the well does not require auxiliary fluid-carrying measures, this method will be terminated; if v gr ≤ v fc After adjusting the foaming agent type to suit the operating conditions, re-execute the test. v fc The calculation and condition verification satisfy the requirements. v fc < v gr < v c Subsequent calculations can only be carried out after the conditions are met.

[0013] 3. Derive the critical accumulation volume and dosing cycle. Calculate the fluid carrying capacity in the wellbore without adding a foaming agent. Q gr Fluid carrying capacity in the wellbore after adding foaming agent Q lf The calculation formula is: Q gr = H L × v gr × A × 86400 Q lf = H L ´ × v gr × A × 86400 in, Q gr This refers to the fluid carrying capacity in the wellbore without the addition of a foaming agent, expressed in meters (m³). 3 / d; Q lf The foam-carrying fluid flow rate in the wellbore after adding foaming agent is expressed in m³. 3 / d; Calculate the critical volume of liquid accumulation V crit (unit: m) 3 ): V crit = ( Q lf -Q lin )× t eff / 1440 in, V crit This refers to the critical fluid accumulation volume in the wellbore, in cubic meters (m³). 3 ; t eff Effective liquid-carrying time of the foaming agent refers to the duration of the foaming agent's effective liquid-carrying capacity after it comes into contact with the accumulated liquid in the wellbore, and the unit is h; t acc The time it takes for the accumulated fluid in the wellbore to reach the critical fluid volume, in hours; 1440 is the conversion factor between days and minutes. Calculate the time it takes for the wellbore fluid to accumulate to the critical fluid volume. t acc (Unit: h): t acc = V crit / ( Q lin - Q gr )×24 Calculate the dosing cycle t dose (Unit: h): t dose = t acc + t eff in, t dose The dosing cycle for intermittent dosing of the foaming agent for the target gas well is expressed in hours (h).

[0014] 4. Calculate the dosage for a single application. According to the on-site process requirements, the dosage concentration is set as follows: c (Unit: g / L); Single dose V (Unit: L / time) Calculation formula: V = V crit × c × 1000 / C 0 in, V This refers to the dosage per application, expressed in liters (L). c This refers to the concentration of the added drug, expressed in g / L. C0 The concentration of the foaming agent stock solution prepared on-site is expressed in g / L; 1000 is the volume conversion factor between cubic meters and liters.

[0015] Based on the calculated single dosage V and dosing cycle t dose Based on the actual production management needs on site, a dosing plan that can be directly applied on site is formulated. It should be noted that, to ensure liquid carrying effect, the single dosing volume of the on-site dosing plan can be slightly larger than the calculated single dosing volume, and the dosing cycle can be slightly shorter than the calculated dosing cycle.

[0016] The beneficial effects of this invention are: (1) Based on the critical liquid carrying theory of multiphase flow and the liquid carrying mechanism of foam, a complete quantitative design system was constructed, realizing the transformation of dosing parameters from empirical estimation to quantitative calculation, which greatly improved the scientificity and accuracy of dosing parameter design; (2) By controlling the accumulation of liquid through the critical accumulation volume, the chemical is only applied to the liquid phase that the gas phase in the wellbore cannot carry to the surface, which greatly reduces the amount of foaming agent added and reduces production costs; (3) It is easy to operate, requiring only conventional gas well production data and basic physical property parameters. No complex experimental equipment is needed, and the dosing parameters can be designed quickly, making it easy to promote and apply in the field. Attached Figure Description

[0017] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0018] To make the objectives, calculation process, and advantages of this invention clearer, the invention will be further described in detail below with reference to field data from well 1-73.

[0019] Example 1: 1. Collect basic parameters of well 1-73 Tubing inner diameter: 50mm, wellbore cross-sectional area A = π×(0.05 / 2) 2 = 0.00196m 2 ; Daily gas production V g = 2000m 3 / d, daily liquid production Q lin = 1.1m 3 / d, v sl =1.1 / 86400 / 0.00196=0.0065m / s; Wellhead temperature and pressure: T 1 = 13℃ (286.15K). P 1 = 0.81 MPa; Bottom hole temperature and pressure: T 2 = 103℃ (376.15K). P 2 = 11.3 MPa; Produced fluid properties: σ = 0.072 N / m σ' = 0.03 N / m r l = 1000kg / m 3 ; Gas phase density calculation: average pressure in the wellbore P = 2.75 MPa, average temperature T = 60℃ (333.15K), P r = 2.75 / 4.6 = 0.6, T r = 333.15 / 190.6 = 1.75, substituting into the Gopal compression factor calculation formula, yields... Z = 0.962, in the non-supercritical state, r g = (2.75×10 6 ×0.01604) / (0.962×8.314×333.15)=16.5kg / m 3 .

[0020] 2. Calculate the critical liquid-carrying gas velocity and the minimum foam liquid-carrying gas velocity of the gas well, and their corresponding liquid holdup. v c = [4×9.81×0.072×(1000-16.5) / 16.5 2 ] -0.25 = 0.559m / s H L = 1.1 / 86400 / (0.559×0.00196) = 0.0116 v fc= 0.429×0.0065+0.546×[9.81×0.03×(1000-16.5) / 1000 2 ] 0.25 = 0.074m / s H L ´ = 1.1 / 86400 / (0.074×0.00196) = 0.0877 Actual liquid-carrying gas velocity, v gr = 2000 / 2.5 / 10 8 ×0.962×333.15 / 0.00196 / 2.75 = 0.475m / s, which satisfies v fc < v gr < v c .

[0021] 3. Derive the critical accumulation volume and dosing cycle. Q gr = 0.475×0.00196×0.0116×86400 = 0.934m 3 / d Q lf = 0.475×0.00196×0.0877×86400 = 7.06m 3 / d The effective liquid carrying time of the foaming agent used was measured to be 20 minutes in the indoor liquid carrying experiment. V crit = (7.06-1.1)×20 / 1440 = 0.0828m 3 t acc = 0.0828 / (1.1-0.934)×24 = 11.95h t dose = 11.95 + 20 / 60= 12.3h 4. Calculate the dosage for a single application. Taking a gas production plant with a chemical concentration of 1‰ as an example, calculate the dosage. V , V = 0.0828×1‰×1000 = 0.0828L / time, average daily dosage = 0.0828×(24 / 12.3) = 0.162L / d 5. Determining Dosing Parameters The calculated single application rate was 0.0828L, and the application cycle was 12.3 hours. To facilitate on-site application management, the single application rate was set at 0.1L, and the application cycle at 12 hours. This represents a 96% reduction compared to the original on-site application rate of 5L / day, and a 50% reduction in workload compared to the on-site application frequency of 4 times / day.

[0022] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A quantitative design method for intermittent chemical dosing parameters in gas wells, characterized in that, The method is used to optimize the dosing cycle and dosage of the foaming agent in foam drainage gas extraction technology, and includes the following steps: Step 1: Collect basic parameters of the target gas well, including daily gas production, wellbore temperature, wellbore pressure, tubing inner diameter, and daily fluid production, and calculate the actual fluid-carrying gas velocity in the wellbore based on the basic parameters. v gr The calculation formula is: v gr = ( V g × Z × T) / (2.5×10 8 × A × P) in, v gr This represents the actual liquid-carrying gas velocity, in m / s. V g Daily gas production, in m³ 3 / d; Z The compressibility factor is dimensionless. T This represents the absolute temperature of the wellbore, expressed in Kelvin (K). A The cross-sectional area of ​​the wellbore is calculated from the inner diameter of the collected tubing, and the unit is meters (m). 2 ; P This refers to the wellbore pressure, in MPa; 2.5 × 10⁻⁶. 8 Calculate the comprehensive coefficient for engineering units; Step 2: Calculate the critical liquid-carrying gas velocity of the gas well based on Li Min's critical liquid-carrying model. v c Determine the minimum foam liquid-carrying gas velocity by combining the lower limit equation for foam liquid carrying capacity. v fc ;in, v c This represents the critical liquid-carrying gas velocity of a gas well, expressed in m / s. v fc The minimum foam-carrying liquid-gas velocity is expressed in m / s. Step 3: Verify calculation conditions: actual liquid-carrying gas velocity v gr Must meet v fc < v gr < v c ;like v gr > v c If it is determined that the well does not require auxiliary fluid-carrying measures, this method will be terminated; if v gr ≤ v fc After adjusting the foaming agent type to suit the operating conditions, repeat step 2. v fc The calculations and condition verification in this step satisfy the requirements. v fc < v gr < v c Subsequent calculations can only be carried out after the conditions are met; Step 4: Using the calculated results v c and v fc Calculate the liquid holdup in the wellbore without adding a foaming agent according to the liquid holdup calculation formula. H L Liquid holdup in the wellbore after adding foaming agent H L ´ Both are dimensionless parameters, and the calculation formula is: H L = Q lin / ( v c × A × 86400) H L ´ = Q lin / ( v fc × A × 86400) in, Q lin The target daily liquid production of the gas well is expressed in m³. 3 / d; H L The liquid holdup in the wellbore without the addition of a foaming agent is dimensionless. H L ´ The liquid holdup in the wellbore after adding foaming agent is dimensionless; 86400 is the time conversion factor between seconds and days. Step 5: Calculate the fluid carrying capacity in the wellbore without adding a foaming agent. Q gr Foam-carrying fluid flow rate in the wellbore after adding foaming agent Q lf The calculation formula is: Q gr = H L × v gr × A × 86400 Q lf = H L ´ × v gr × A × 86400 in, Q gr This refers to the fluid carrying capacity in the wellbore without the addition of a foaming agent, expressed in meters (m³). 3 / d; Q lf The foam-carrying fluid flow rate in the wellbore after adding foaming agent is expressed in m³. 3 / d; Step 6: Calculate the critical accumulation volume V crit The time it takes for the fluid in the wellbore to accumulate to the critical fluid volume. t acc The calculation formula is: V crit = （ Q lf - Q lin ）× t eff / 1440 t acc = V crit / ( Q lin - Q gr ) × 24 in, V crit This refers to the critical fluid accumulation volume in the wellbore, in cubic meters (m³). 3 ; t eff Effective liquid-carrying time of the foaming agent refers to the duration of the foaming agent's effective liquid-carrying capacity after it comes into contact with the accumulated liquid in the wellbore, and the unit is h; t acc The time it takes for the accumulated fluid in the wellbore to reach the critical fluid volume, in hours; 1440 is the conversion factor between days and minutes. Step 7, Dosing Cycle t dose for t acc and t eff The sum, calculated as follows: t dose = t acc + t eff in, t dose The dosing cycle for intermittent addition of frother to the target gas well, expressed in hours (h). Step 8: Calculate the critical accumulation volume based on the value obtained in Step 6. V crit and the set dosage concentration c Calculate the dosage for a single application. V The calculation formula is: V = V crit × c × 1000 / C 0 in, V This refers to the dosage per application, expressed in liters (L). c This refers to the concentration of the added drug, expressed in g / L. C 0 The concentration of the foaming agent stock solution prepared on-site is expressed in g / L; 1000 is the volume conversion factor between cubic meters and liters. Based on the above calculations, the dosing cycle is obtained. t dose Compared with single dosage V Determine the foaming agent dosing cycle and single dosing amount for the foam drainage gas production process of the target gas well.

2. The quantitative design method for intermittent chemical dosing parameters in gas wells according to claim 1, characterized in that, The effective liquid carrying time of the foaming agent t eff Measured through indoor liquid-carrying experiments or field tests.

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