Method for solving one-point method empirical formula based on exponential expression

Abstract

The invention discloses a one-point method empirical formula solving method based on an exponential expression, which comprises the following steps: substituting component data of a target gas reservoir into well test interpretation software, and drawing a change relation curve of mu Z along with p; according to the gas reservoir pressure of the target gas reservoir, the pressure interval where the target gas reservoir is located is judged; determining an expression form of a productivity equation according to the pressure interval where the gas reservoir is located; calculating an exponential productivity equation empirical coefficient of each productivity test well of the gas reservoir according to the seepage coefficient, the seepage index and the open flow capacity of each productivity test well of the gas reservoir; averaging the empirical coefficient and the seepage index of the exponential productivity equation of each productivity test well of the gas reservoir, and substituting the average value into the determined representation form of the productivity equation to obtain an exponential one-point method empirical formula of the target gas reservoir. According to the method, the problem that a traditional binomial one-point method productivity empirical formula based on a pressure square form is insufficient in precision in gas well exploration gas test productivity evaluation of medium and high pressure gas reservoirs is solved, and the application range of one-point method productivity well test gas well productivity evaluation is widened.

Description

Technical Field

[0001] The present invention relates to a method for obtaining an exponential one - point method empirical formula, belonging to the field of petroleum engineering. Background Technique

[0003] In the field of natural gas development, the effective evaluation of gas well productivity is an important basis for realizing reasonable gas production allocation and efficient development of gas wells. Accurate productivity evaluation can not only provide scientific guidance for gas reservoir development, but also optimize the gas well production plan, improve resource extraction efficiency, and reduce development costs. The first step in carrying out gas well productivity evaluation is to conduct gas well productivity well testing. Through well testing, dynamic parameters such as gas well production and pressure can be obtained, and the test data can be further analyzed and interpreted to obtain the actual productivity of the gas well, and judge its development potential and production capacity. At present, the gas well productivity well testing methods mainly include four types: back - pressure well testing, isochronal well testing, modified isochronal well testing, and one - point method well testing. Among them, the one - point method productivity well testing has become an important means for evaluating gas well productivity due to its simple operation and short time consumption. The accuracy of the one - point method well testing for evaluating gas well productivity depends on the applicability of the one - point method empirical formula. If the one - point method empirical formula adopted is not suitable for the target gas reservoir, there will be a large error between the calculated open - flow potential and the true open - flow potential of the gas well. For a specific gas reservoir, a one - point method open - flow potential empirical formula suitable for itself should be studied. Therefore, it is of great significance to study different forms of one - point method productivity formulas and enrich the applicable range of one - point method productivity formulas. The traditional one - point method productivity empirical formulas are all established by following the method of Chen Yuanqian's one - point method formula, and they are all binomial one - point method productivity empirical formulas based on the form of pressure squared. The structural forms of gas well productivity equations mainly include binomial and exponential forms. Both binomial productivity equations and exponential productivity equations are widely used in the calculation and evaluation of gas well productivity in various oil and gas reservoirs. However, at present, only relevant research results on binomial one - point method productivity empirical formulas are seen, and there are no relevant theoretical derivations and empirical formulas based on exponential one - point method productivity formulas, nor one - point method productivity empirical formulas based on pseudo - pressure and pressure forms. This seriously restricts the accurate evaluation of gas well productivity during well testing for gas exploration wells. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for obtaining an exponential one - point method empirical formula in view of the problems existing in the prior art. This method theoretically derives the structural form of the gas well exponential one - point method productivity formula for the first time, and at the same time derives one - point method productivity formulas based on pressure form, pressure squared form, and pseudo - pressure form, making up for the problem of insufficient accuracy of the traditional binomial one - point method productivity empirical formula based on pressure squared form in the productivity evaluation of gas exploration wells in medium - and high - pressure gas reservoirs, and enriching the applicable range of one - point method productivity well testing for evaluating gas well productivity.

[0005] The technical solution provided by the present invention to solve the above technical problems is: a method for obtaining an exponential one-point method empirical formula, including the following steps:

[0006] Step S10: Substitute the component data of the target gas reservoir into the well test interpretation software, calculate the natural gas viscosity μ and deviation factor Z under different pressures p, and plot the curve of the change of μZ with p;

[0007] Step S20: Divide the pressure range in the curve of the change of μZ with p into pressure interval I, pressure interval II, and pressure interval III, and determine the pressure interval where the target gas reservoir is located according to the gas reservoir pressure of the target gas reservoir;

[0008] Step S30: Determine the expression form of the productivity equation according to the pressure interval where the gas reservoir is located;

[0009] Step S40: Obtain the seepage coefficient C, seepage exponent n, and open flow potential q of each productivity well test well in the gas reservoir according to the productivity well test interpretation results of each productivity well test well in the gas reservoir AOF ;

[0010] Step S50: Calculate the exponential productivity equation empirical coefficient α of each productivity well test well in the gas reservoir according to the seepage coefficient C, seepage exponent n, and open flow potential q of each productivity well test well in the gas reservoir AOF ;

[0011] Step S60: Take the average value of the exponential productivity equation empirical coefficient α and seepage exponent n of each productivity well test well in the gas reservoir respectively, and then substitute them into the expression form of the productivity equation determined in Step S30 to obtain the exponential one-point method empirical formula of the target gas reservoir.

[0012] A further technical solution is that in Step S20, a first pressure point and a second pressure point are determined in the curve of the change of μZ with p; if the gas reservoir pressure of the target gas reservoir is less than the first pressure point, the pressure interval where the target gas reservoir is located is pressure interval I; if the gas reservoir pressure of the target gas reservoir is greater than or equal to the first pressure point and less than or equal to the second pressure point, the pressure interval where the target gas reservoir is located is pressure interval II; if the gas reservoir pressure of the target gas reservoir is greater than the second pressure point, the pressure interval where the target gas reservoir is located is pressure interval III.

[0013] A further technical solution is that the determination process of the first pressure point in Step S20 is: take the pressure value corresponding to 1.05 times the starting point μZ value in the curve of the change of μZ with p as the first pressure point value.

[0014] A further technical solution is that the determination process of the second pressure point in Step S20 is: fit the curve of the change of μZ with p to obtain a curve fitting formula; then take the derivative of the curve fitting formula and set the second derivative to 0, and calculate the obtained x value, then this x value is the second pressure point value.

[0015] A further technical solution is that in the step S30, if the gas reservoir pressure is in Region I, the productivity equation is suitable for being expressed in the form of pseudo-pressure and the form of pressure squared; if the gas reservoir pressure is in Region II, the productivity equation is only suitable for being expressed in the form of pseudo-pressure; if the gas reservoir pressure is in Region III, the productivity equation is suitable for being expressed in the form of pseudo-pressure and the form of pressure.

[0016] A further technical solution is that the exponential one-point method empirical formula in the form of pseudo-pressure in the step S30 is as follows:

[0017]

[0018] In the formula: ψ R is the pseudo-pressure of the gas reservoir, MPa 2 / (mPa·s); ψ wf is the bottom-hole pseudo-pressure of the gas well, MPa 2 / (mPa·s); q AOF is the absolute open flow potential; α is the empirical coefficient of the exponential productivity equation; q sc is the gas well production under standard conditions, 10 4 m 3 / d.

[0019] A further technical solution is that the exponential one-point method empirical formula in the form of pressure in the step S30 is as follows:

[0020]

[0021] In the formula: p R is the gas reservoir pressure, MPa; p wf is the bottom-hole flowing pressure of the gas well, MPa; q AOF is the absolute open flow potential; α is the empirical coefficient of the exponential productivity equation; q sc is the gas well production under standard conditions, 10 4 m 3 / d.

[0022] A further technical solution is that the exponential one-point method empirical formula in the form of pressure squared in the step S30 is as follows:

[0023]

[0024] In the formula: p R is the gas reservoir pressure, MPa; p wf is the bottom-hole flowing pressure of the gas well, MPa; q AOF is the absolute open flow potential; α is the empirical coefficient of the exponential productivity equation; q sc is the gas well production under standard conditions, 10 4 m 3 / d.

[0025] A further technical solution is that the calculation formula for the empirical coefficient α of the exponential productivity equation is as follows:

[0026]

[0027] In the formula: q AOF is the open flow potential; C is the seepage coefficient; n is the seepage exponent; α is the empirical coefficient of the exponential productivity equation.

[0028] The beneficial effects of the present invention: The present invention breaks through the limitations of the binomial single-point method productivity empirical formula in the traditional pressure square form in terms of the equation structure, and enriches the productivity evaluation method for exploration gas test wells. Description of the Drawings

[0029] Figure 1 is the relationship curve of μZ vs. p and the pressure zone schematic diagram;

[0030] Figure 2 is the relationship curve of μZ vs. p and the pressure zone schematic diagram of gas reservoir X. Specific Embodiments

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] A method for obtaining an empirical formula of a single-point method based on an exponential form provided by the present invention includes the following steps:

[0033] Step S10: Substitute the component data of the target gas reservoir into the well test interpretation software, calculate the natural gas viscosity μ and deviation factor Z under different pressure p conditions, and draw the change relationship curve of μZ with p (as Figure 1 shown);

[0034] Step S20: Divide the pressure range in the change relationship curve of μZ with p into pressure interval I, pressure interval II, and pressure interval III, and determine the pressure interval where the target gas reservoir is located according to the gas reservoir pressure of the target gas reservoir;

[0035] The pseudo-pressure of natural gas is defined as:

[0036]

[0037] In the formula: ψ is the pseudo-pressure function of natural gas, MPa 2 / (mPa·s); p is the natural gas pressure, in MPa. p0 is the reference pressure (usually taken as the atmospheric pressure), in MPa; μ is the natural gas viscosity, in mPa·s. Z - the natural gas deviation factor, dimensionless.

[0038] According to different pressure boundaries of the gas reservoir, the pressure is divided into three different pressure intervals: low, medium, and high, which are represented by regions Ⅰ, Ⅱ, and Ⅲ respectively, as Figure 1 shown;

[0039] Specifically, the first pressure point and the second pressure point are determined from the curve of the variation of μZ with p; if the gas reservoir pressure of the target gas reservoir is less than the first pressure point, the pressure interval where the target gas reservoir is located is pressure interval Ⅰ; if the gas reservoir pressure of the target gas reservoir is greater than or equal to the first pressure point and less than or equal to the second pressure point, the pressure interval where the target gas reservoir is located is pressure interval Ⅱ; if the gas reservoir pressure of the target gas reservoir is greater than the second pressure point, the pressure interval where the target gas reservoir is located is pressure interval Ⅲ.

[0040] It can be seen from Figure 1 that at the starting part of the curve, the curve is approximately a horizontal straight line, and μZ hardly changes with the change of p, and μZ is approximately a constant. The μZ value at the end of this part is approximately the same as the μZ value at the starting point. Therefore, this part of the region is defined as region Ⅰ, and the end point of region Ⅰ is 1.05 times the μZ value at the starting point. In this way, the increase in the μZ value is only 5%, and the curve in region Ⅰ can still be regarded as an approximately horizontal straight line. In region Ⅰ, the pseudo-pressure of natural gas can be simplified to the form of the square of pressure:

[0041]

[0042] In the formula: (μZ)c is the product of μ and Z as a constant, in mPa·s.

[0043] It can be seen from Figure 1 that at the end part of the curve, the curve is approximately a straight line with a certain slope, and μZ has a linear relationship with p, and p / (μZ) is a constant. Therefore, this part of the region is defined as region Ⅲ, and the starting point of region Ⅲ is the inflection point of the curve, that is, the point where the curvature is zero (the second derivative of the curve is calculated and set equal to 0, and the coordinates of the corresponding point are calculated in this way). In this way, the curve in region Ⅲ can be regarded as an approximately straight line with a certain slope. In region Ⅲ, the pseudo-pressure of natural gas can be simplified to the form of pressure:

[0044]

[0045] In the formula: (p / (μZ))c is p divided by μZ as a constant, in MPa / mPa·s.

[0046] Step S30: Determine the expression form of the productivity equation according to the pressure interval where the gas reservoir is located;

[0047] If the gas reservoir pressure is in Region I, the productivity equation is suitable for being expressed in the form of pseudo-pressure and the square of pressure;

[0048] If the gas reservoir pressure is in Region II, the productivity equation is only suitable for being expressed in the form of pseudo-pressure;

[0049] If the gas reservoir pressure is in Region III, the productivity equation is suitable for being expressed in the form of pseudo-pressure and pressure;

[0050] Derive the structural form of the exponential one-point method productivity formula for gas wells based on the exponential productivity equation. The derivation process is as follows:

[0051] The exponential productivity equation is:

[0052] q sc =C(ξ R -ξ wf ) n (4)

[0053] In the formula, ξ is a form variable related to pressure; ξ R is the form variable under the gas reservoir pressure condition; ξ wf is the form variable under the bottom-hole flowing pressure condition; q sc is the gas well production under standard conditions, 10 4 m 3 / d; C is the seepage coefficient; n is the seepage exponent.

[0054] For a low-pressure gas reservoir, ξ = p 2 ; for a high-pressure gas reservoir, ξ = p; for a gas reservoir in any pressure range, ξ = ψ.

[0055] When ξ wf =0, the production of the gas well is the absolute open flow rate, and Equation (4) becomes:

[0056] q AOF =C(ξ R ) n (5)

[0057] In the formula, q AOF is the absolute open flow rate of the gas well, 10 4 m 3 / d.

[0058] Multiply Equation (4) by Equation (5), we get;

[0059] q sc q AOF =C(ξ R -ξ wf ) n ·C(ξ R ) n (6)

[0060] By transforming Equation (6), we get:

[0061]

[0062] Define the empirical coefficient of the exponential productivity equation as:

[0063]

[0064] Substitute Equation (10) into Equation (9) to obtain the calculation formula for the absolute open flow rate of the exponential one-point method:

[0065]

[0066] For a low-pressure gas reservoir, Equation (11) can be written as:

[0067]

[0068] Where p R is the gas reservoir pressure, MPa; p wf is the flowing bottom-hole pressure of the gas well, MPa.

[0069] For a high-pressure gas reservoir, Equation (11) can be written as:

[0070]

[0071] For a gas reservoir in any pressure range, Equation (11) can be written as:

[0072]

[0073] Where: ψ R is the pseudo-pressure of the gas reservoir, MPa 2 / (mPa·s); ψ wf is the bottom-hole pseudo-pressure of the gas well, MPa 2 / (mPa·s).

[0074] Equations (12)–(14) are the productivity formulas of the exponential one-point method expressed in the form of pressure squared, pressure, and pseudo-pressure, respectively.

[0075] Step S40: Obtain the seepage coefficient C, seepage exponent n, and absolute open flow rate q of each productivity test well in the gas reservoir according to the productivity test interpretation results of each productivity test well in the gas reservoir AOF ;

[0076] Step S50: Calculate the empirical coefficient α of the exponential productivity equation of each productivity test well in the gas reservoir according to the seepage coefficient C, seepage exponent n, and absolute open flow rate q of each productivity test well in the gas reservoir AOF in the gas reservoir;

[0077] Step S60: Take the average values of the empirical coefficients α and the percolation exponents n of the exponential productivity equations for each deliverability well test in the gas reservoir, and then substitute them into the representation form of the productivity equation determined in Step S30 to obtain the exponential one-point method empirical formula for the target gas reservoir;

[0078] Step S70: Substitute the formation pressure, bottom-hole flowing pressure, and gas production data of the production wells in the gas reservoir (when applying the empirical formula in the form of pseudo-pressure, the formation pressure and bottom-hole flowing pressure need to be converted into pseudo-formation pressure and pseudo-bottom-hole flowing pressure) into the exponential one-point method empirical formula of this gas reservoir to obtain the absolute open flow potential of this well. Applying this formula can greatly accelerate the working speed of the gas reservoir deliverability well test and achieve efficient and reasonable gas well production allocation.

[0079] Embodiment

[0080] The following takes a deep high-pressure gas reservoir (referred to as gas reservoir X) in the Tarim Basin as an embodiment to further introduce the present invention in detail.

[0081] Step S10: The component data of gas reservoir X is shown in Table 1. Substitute the component data of gas reservoir X into the well test interpretation software to calculate the natural gas viscosity μ and deviation factor Z under different pressure p conditions;

[0082] Table 1 Natural gas component data table of gas reservoir X

[0083] Component Composition (%) Component Composition (%) <![CDATA[C1]]> 97.597 <![CDATA[nC5]]> 0.001 <![CDATA[C2]]> 0.669 <![CDATA[C6]]> 0.001 <![CDATA[C3]]> 0.024 <![CDATA[C 7+ > 0 <![CDATA[iC4]]> 0.002 <![CDATA[CO2]]> 0.88 <![CDATA[nC4]]> 0.004 <![CDATA[N2]]> 0.82 <![CDATA[iC5]]> 0.002 / /

[0084] Step S20: According to the previously calculated natural gas viscosity μ, deviation factor Z, and pressure p data, plot the curve of the variation of μZ with p, as Figure 2 shown;

[0085] Step S30: According to the different pressure boundaries of gas reservoir X, divide the pressure into 3 different pressure intervals: low, medium, and high, and represent them with regions Ⅰ, Ⅱ, and Ⅲ respectively;

[0086] Step S301: As Figure 2 shown, at the starting part of the curve, the curve is approximately a horizontal straight line, and μZ hardly changes with the change of p, and μZ is approximately a constant. The μZ value at the end of this part is approximately the same as the μZ value at the starting point. Therefore, this part of the region is defined as region Ⅰ. The μZ value at the starting point of region Ⅰ is 0.015090762, corresponding to a pressure of 0. The end point of region Ⅰ is 1.05 times the μZ value at the starting point, that is, the end point μZ value is 0.015090762 × 1.05 = 0.01584555, corresponding to a pressure of 10.88 MPa. In this way, the curve in region Ⅰ can still be regarded as an approximately horizontal straight line. In region Ⅰ, the pseudo-pressure of natural gas can be simplified to the form of pressure square;

[0087] Step S302: As Figure 2As shown, at the end part of the curve, the curve is approximately a straight line with a certain slope. μZ has a linear relationship with p, and p / (μZ) is a constant. Therefore, this part of the region is defined as Region III. The starting point of Region III is the inflection point of the curve, that is, the point where the curvature is zero. The fitted curve formula is:

[0088] y = -0.0000000207x 3 + 0.0000060078x 2 + 0.0001071919x + 0.0142204942 (15)

[0089] Taking the second derivative of Equation (15) gives:

[0090] y″ = -0.0000001242x + 0.0000120156 (16)

[0091] Let y″ = 0, and we get x = 96.74 MPa. Then the inflection point of the curve, that is, the starting point pressure of Region III, is 96.74 MPa. In this way, the curve of Region III can be regarded as an approximately straight line with a certain slope. In Region III, the pseudo-pressure of natural gas can be simplified to the pressure form;

[0092] Step S40: The average buried depth of Gas Reservoir X is 7132 m, the original reservoir pressure is 108.91 MPa, the reservoir temperature is 166.5 °C, and the reservoir pressure of 108.91 MPa is greater than 96.74 MPa. It is judged that the pressure interval where the gas reservoir is located is Region III. Therefore, the productivity equation of Gas Reservoir X is suitable for being expressed in both pseudo-pressure form and pressure form;

[0093] Step S50: Organize the productivity test interpretation results of each productivity test well in Gas Reservoir X, and determine the seepage coefficient C, seepage exponent n, and open flow potential q of each productivity test well in Gas Reservoir X in two pressure forms of pressure and pseudo-pressure AOF , and determine the empirical coefficient α of each productivity test well in two pressure forms of pressure and pseudo-pressure according to Equation (10). The results are shown in Table 2;

[0094] Table 2 Interpretation results table of 7 productivity test wells in Gas Reservoir X

[0095]

[0096]

[0097] Step S60: Take the average values of the empirical coefficient α and seepage exponent n of each productivity test well in Gas Reservoir X in two pressure forms of pressure and pseudo-pressure respectively, and substitute them into Equation (13) and Equation (14) respectively to obtain the exponential one-point method empirical formula of Gas Reservoir X based on pressure and pseudo-pressure forms;

[0098] The empirical formula of the exponential one-point method for Gas Reservoir X based on the pressure form is as follows:

[0099]

[0100] The empirical formula of the exponential one-point method for Gas Reservoir X based on the pseudo-pressure form is as follows:

[0101]

[0102] Step S70: Substitute the formation pressure, bottom-hole flowing pressure, and gas production data of each productivity test well in Gas Reservoir X (when applying the empirical formula in pseudo-pressure form, the formation pressure and bottom-hole flowing pressure need to be converted into pseudo-formation pressure and pseudo-bottom-hole flowing pressure) into Equations (17) and (18) for back-calculation. The errors between the calculation results of the empirical formula and the measured results for each well are shown in Table 3. The average back-calculation errors of the exponential one-point method productivity empirical formulas in pressure form and pseudo-pressure form are 2.84% and 3.04% respectively, proving that the empirical formula is accurate and reliable.

[0103] Table 3 Open-flow potential and error calculation results of different empirical formulas for 7 productivity test wells in Gas Reservoir X

[0104]

[0105]

[0106] Step S80: The formation pressure of production well A in Gas Reservoir X is 102.47 MPa, the bottom-hole flowing pressure is 89.21 MPa, the gas production is 598,400 m³ / day, the pseudo-formation pressure is 292,771.14 MPa 2 / (mPa·s), and the pseudo-bottom-hole flowing pressure is 254,885.46 MPa 2 / (mPa·s). Substitute these data into the exponential one-point method empirical formula of this gas reservoir. The open-flow potential calculated by the empirical formula of the exponential one-point method based on the pressure form for this well is 1,773,600 m³ / day, and the open-flow potential calculated by the empirical formula of the exponential one-point method based on the pseudo-pressure form is 1,810,100 m³ / day. Applying this formula can greatly accelerate the productivity test work speed of the gas reservoir and achieve efficient and reasonable gas well production allocation.

[0107] As mentioned above, it is not any form of limitation to the present invention. Although the present invention has been disclosed through the above embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments of equivalent changes by using the disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change, and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for obtaining an exponential one-point empirical formula, characterized in that: The following steps are involved: Step S10, substituting the component data of the target gas reservoir into the well test interpretation software, calculating the natural gas viscosity μ and the deviation factor Z under different pressures p, and drawing a curve of the relationship between μZ and p; Step S20, dividing the pressure range in the curve of the relationship between μZ and p into pressure interval I, pressure interval II, and pressure interval III, and determining the pressure interval where the target gas reservoir is located according to the gas reservoir pressure of the target gas reservoir; Step S30, determining the expression form of the production capacity equation according to the pressure range where the gas reservoir is located; Step S40: Obtain the permeability coefficient C, permeability index n and open flow rate q of each productivity test well in the gas reservoir according to the productivity test interpretation results of each productivity test well in the gas reservoir. AOF ; Step S50: according to the permeability coefficient C, permeability index n and open flow rate q of each gas reservoir production test well AOF Calculate the empirical coefficient α of the exponential productivity equation for each productivity test well in the gas reservoir; Step S60, taking the average values ​​of the empirical coefficient α and the permeability index n of the exponential productivity equation of each productivity test well in the gas reservoir, and substituting them into the expression form of the productivity equation determined in step S30 to obtain the exponential one-point empirical formula of the target gas reservoir.

2. The method for obtaining an exponential one-point empirical formula according to claim 1, characterized in that: In the step S20, the first pressure point and the second pressure point are determined in the curve of the relationship between μZ and p; if the reservoir pressure of the target gas reservoir is less than the first pressure point, the pressure interval where the target gas reservoir is located is pressure interval I; if the reservoir pressure of the target gas reservoir is greater than or equal to the first pressure point and less than or equal to the second pressure point, the pressure interval where the target gas reservoir is located is pressure interval II; if the reservoir pressure of the target gas reservoir is greater than the second pressure point, the pressure interval where the target gas reservoir is located is pressure interval III.

3. The method for obtaining an exponential one-point empirical formula according to claim 1, characterized in that: The process of determining the first pressure point in step S20 is as follows: in the curve of the relationship between μZ and p, the pressure value corresponding to 1.05 times the value of μZ at the starting point is taken as the value of the first pressure point.

4. The method for obtaining an exponential one-point empirical formula according to claim 1, characterized in that: The process of determining the second pressure point in step S20 is: fitting the curve of the relationship between μZ and p to obtain a curve fitting formula; then taking the derivative of the curve fitting formula and setting the second-order derivative to 0, calculating the x value, which is the second pressure point value.

5. The method for obtaining an exponential one-point empirical formula according to claim 1, characterized in that: In step S30, if the gas reservoir pressure is in region I, the production capacity equation is suitable for being expressed in pseudo-pressure form and pressure square form; if the gas reservoir pressure is in region II, the production capacity equation is only suitable for being expressed in pseudo-pressure form; if the gas reservoir pressure is in region III, the production capacity equation is suitable for being expressed in pseudo-pressure form and pressure form.

6. The method for obtaining an exponential one-point empirical formula according to claim 5, characterized in that: The exponential one-point empirical formula of the pseudo-pressure form in step S30 is: Where: R is the pseudo pressure of gas reservoir, MPa 2 / (mPa·s);ψ wf is the pseudo bottom hole pressure of the gas well, MPa 2 / (mPa·s);q AOF is the unimpeded flow rate; α is the empirical coefficient of the exponential capacity equation; q sc is the gas well production under standard conditions, 10 4 m 3 / d.

7. The method for obtaining an exponential one-point empirical formula according to claim 5, characterized in that: The exponential one-point empirical formula of the pressure form in step S30 is: Where: p R is the gas reservoir pressure, MPa; p wf is the bottom flow pressure of the gas well, MPa; q AOF is the unimpeded flow rate; α is the empirical coefficient of the exponential capacity equation; q sc is the gas well production under standard conditions, 10 4 m 3 / d.

8. The method for obtaining an exponential one-point empirical formula according to claim 5, characterized in that: The one-point empirical formula of the exponential form of the pressure squared in step S30 is: Where: p R is the gas reservoir pressure, MPa; p wf is the bottom flow pressure of the gas well, MPa; q AOF is the unimpeded flow rate; α is the empirical coefficient of the exponential capacity equation; q sc is the gas well production under standard conditions, 10 4 m 3 / d.

9. The method for obtaining an exponential one-point empirical formula according to claim 1, characterized in that: The calculation formula of the empirical coefficient α of the exponential capacity equation is: Where: q AOF is the unobstructed flow rate; C is the seepage coefficient; n is the seepage index; α is the empirical coefficient of the exponential capacity equation.

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