A method for correcting negative slope of binomial deliverability match curve

Abstract

The application discloses a method for correcting negative slope of binomial productivity fitting curve, comprising the following steps: 1, finding out the inverted peak shape and corresponding well testing work system according to the fitting curve with negative slope, and establishing the first relationship in the initial stage of opening well; 2, establishing the second relationship in the production period according to the production time; 3, establishing the third relationship about the pressure change of measuring point according to the first relationship and the second relationship, establishing the fourth relationship about the additional pressure increase according to the first relationship, the second relationship and the third relationship, and obtaining the additional pressure increase; 4, obtaining the corrected pressure of measuring point according to the additional pressure increase and the measured pressure of measuring point corresponding to the well testing work system, and realizing the correction of the negative slope of the fitting curve according to the corrected pressure of measuring point. The application can maximize the use of actual pressure measurement data, and effectively correct the fitting curve corresponding to the well testing work system when the inverted peak shape appears.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas exploration and development technology, and in particular relates to a method for correcting the negative slope of a binomial production capacity fitting curve. Background Technology

[0002] Gas well productivity assessment is a core component of gas field development. For a gas well that has already been put into production or is being planned for production, the most important factors are the initial single-well production value and the initial maximum production value, so as to guide the subsequent production allocation of the gas well.

[0003] Currently, production capacity equations are typically derived from field production testing to evaluate the production capacity of a single well. However, extensive field practice shows that this method is far from meeting actual production needs. Especially in deep, highly heterogeneous, low-permeability gas reservoirs, high-angle wells and horizontal wells are generally used to achieve increased production and obtain industrial oil and gas flow. For these types of reservoirs, modified isochronous well testing is often used to evaluate single-well production capacity. However, if fluid accumulates at the bottom of the well during testing, and the pressure gauge fails to reach below the fluid level due to well structure limitations, the fluid at the bottom of the well may be carried out during the test, resulting in a different fitted curve. Figure 4 The inverted peak shape shown not only causes anomalies in some data of the fitted curve, resulting in parameter B of the calculated production capacity equation being less than 0 and n being greater than 1, but also causes the binomial production capacity fitted curve to exhibit a negative slope. Consequently, the data obtained at great expense of human and material resources cannot be used to establish a usable production capacity equation.

[0004] To address the aforementioned technical issues, document CN110778306A, published on February 11, 2020, discloses a method for correcting anomalies in gas well productivity equations. This method includes the following steps: Step 1, acquiring gas well productivity test and pressure recovery test interpretation data; Step 2, calculating the available geological reserves within the test range under each test operating regime based on the cumulative gas production under each test operating regime, and calculating the average formation pressure within the available range at the end of each test operating regime using the material balance equation; Step 3, substituting the test production, bottomhole flowing pressure, and average formation pressure within the available range at the end of each test operating regime into the binomial productivity equation to construct a new productivity equation calculation model. This method can correct the anomaly of a negative slope in the gas well binomial productivity equation, significantly improving the accuracy of conventional gas well productivity analysis. However, actual analysis revealed that this method corrects the fitted curves under all regimes, and the correction is achieved by calculating the detection radius and cumulative gas production from utilized reserves for each regime to adjust the average formation pressure. This method is cumbersome, time-consuming, and lacks specificity. Furthermore, it fails to maximize the use of actual pressure measurement data, resulting in the ineffective application of data obtained at great expense. Summary of the Invention

[0005] The purpose of this invention is to overcome the aforementioned technical problems in the prior art and to provide a method for correcting the negative slope of the binomial production capacity fitting curve. This invention can maximize the use of actual pressure measurement data to effectively correct the fitting curve under the corresponding well test operation mode when an inverted peak shape appears, so as to establish a usable production capacity equation based on actual test data and achieve the purpose of reliably evaluating the production capacity of a single well.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for correcting the negative slope of a binomial capacity fitting curve, the technical solution of which includes the following steps:

[0008] Step 1: Identify the inverted peak shape and corresponding well test operation regime based on the fitted curve showing negative slope. Based on the logging data of the corresponding well test operation regime, establish the first relationship between the measuring point pressure, bottom hole flowing pressure and fluid accumulation height in the early stage of well opening.

[0009] Step 2: Based on the production time, establish a second relationship between the measuring point pressure, bottom hole flowing pressure, and fluid accumulation height during the production period;

[0010] Step 3: Based on the first and second relationships, establish the third relationship regarding the pressure change at the measuring point. Based on the first, second, and third relationships, establish the fourth relationship regarding the increase in additional pressure. Calculate the increase in additional pressure based on the fourth relationship.

[0011] Step 4: Based on the additional pressure increase and the measured pressure at the corresponding well test operating conditions, the corrected measuring point pressure is obtained, and the negative slope of the fitted curve is corrected based on the corrected measuring point pressure.

[0012] The method described above is used to correct the deviation in pressure measurement values ​​caused by changes in the fluid column in the wellbore during isochronous well testing.

[0013] In step 1, the first relation established is:

[0014] p cwf =p wf -ρ g gH-(ρ w -ρ g )gH w (1)

[0015] In equation (1), p cwf The pressure measured at the initial well opening point is in MPa; p wf The bottom hole flowing pressure during the initial stage of well opening is expressed in MPa; ρ g The density of natural gas under formation conditions, in kg / m³3 ;ρ w The density of water under formation conditions, in kg / m³ 3 H represents the distance between the pressure measurement point and the medium-depth reservoir, in meters. w The distance, in meters, is the initial fluid accumulation level between the wellbore and the middle depth of the reservoir.

[0016] In step 2, after setting the gas well production time Δt, some of the liquid accumulated at the bottom of the well is carried out of the wellbore along with the natural gas. At this time, the height of the liquid accumulated at the bottom of the well decreases by ΔH. Then, the second relationship is established as follows:

[0017] p′ cwf =p′ wf -ρ g gH-(ρ w -ρ g )g(H w -ΔH) (2)

[0018] In equation (2): p′ cwf The pressure measured at the point after a production time Δt, in MPa; p′ wf The bottom hole flowing pressure after production time Δt, in MPa; H w ΔH represents the distance between the initial fluid accumulation surface and the middle depth of the reservoir during the initial well opening phase, in meters; ΔH represents the change in fluid accumulation height, in meters.

[0019] In step 3, the third relationship regarding the pressure change at the measuring point is established as follows:

[0020] Δp cwf =p′ cwf -p cwf (3)

[0021] In equation (3), ΔP cwf The value is the change in pressure at the measuring point after a production time of Δt, in MPa.

[0022] In step 3, the fourth relationship regarding the increase in additional pressure is established as follows:

[0023] Δp cwf =(p′) wf -p wf )+Δp (4)

[0024] In equation (4), (p′ wf -p wf ) represents the pressure change caused by normal production at the gas well, and ΔP represents the additional pressure increase.

[0025] In step 4, the calculation method for the corrected measuring point pressure is as follows:

[0026] p′ cwf校正 =p′ cwf实测 -Δp (5)

[0027] In the formula: p′ cwf3 The corrected measuring point pressure is expressed in MPa; p cwf3 The measured pressure at the measuring point is in MPa.

[0028] In step 4, the specific process of correcting the negative slope of the fitted curve based on the corrected measuring point pressure is as follows:

[0029] First, the binomial productivity equation is derived based on the measured pressure after correction under the current well test operating system and the measured pressure of other well test operating systems and / or the measured pressure after correction under other well test operating systems. Then, the parameter B of the binomial productivity equation is calculated, and the negative slope of the fitted curve is corrected based on the parameter B.

[0030] The pressure at the measuring point is obtained by testing with a pressure gauge.

[0031] The pressure gauge is positioned above the liquid level.

[0032] The advantages of using this invention are:

[0033] 1. This invention maximizes the use of actual pressure measurement data to effectively correct the fitting curve under the corresponding well testing operating conditions when an inverted peak morphology occurs. This facilitates the establishment of a usable production capacity equation based on actual test data, achieving the goal of reliably evaluating single-well production capacity. Simultaneously, it avoids situations where data obtained at great expense of manpower and resources cannot be used effectively.

[0034] 2. This invention only corrects for deviations in pressure measurements caused by changes in the fluid column in the wellbore during isochronous well testing. Compared to the cited literature in the background art, it is more targeted and purposeful. Furthermore, this invention only corrects for well testing operating procedures corresponding to inverted peak morphology in the fitted curve, not all well testing operating procedures disclosed in the cited literature in the background art. Therefore, the correction time of this invention is shorter, and the correction process is simpler.

[0035] Furthermore, the method used in the cited literature to correct the average formation pressure under each well test regime by calculating the detection radius and cumulative gas production from utilized reserves requires recalculating the pressure. In contrast, this invention fully utilizes on-site pressure measurement data during calibration, correcting the pressure values ​​based on the actual changes in the measured pressure gauge readings. Therefore, this invention has wider applicability, is easier for on-site personnel to operate, and has a faster calculation speed.

[0036] 3. Compared with using various unstable well test modes or calculating the A and B values ​​in the binomial production capacity equation to establish the production capacity equation, the correction method of this invention is simple to operate, the calculation results are reliable, and it is convenient for field technicians to use. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the wellbore structure during the initial stage of well opening.

[0038] Figure 2 This is a schematic diagram of the wellbore structure after a production time of Δt.

[0039] Figure 3 An enlarged schematic diagram illustrating the inverted peak morphology segment of a gas well during the third well testing operation;

[0040] Figure 4 This is a diagram illustrating the fitting curve of a gas well during a corrected isochronous well test. Detailed Implementation

[0041] Example 1

[0042] This invention discloses a method for correcting the negative slope of a binomial productivity fitting curve. This method only corrects the deviation in pressure measurement values ​​caused by changes in the wellbore fluid column during isochronous well testing. Specifically, this method can make full use of field pressure measurement data to specifically correct the well testing operating conditions corresponding to the appearance of an inverted peak shape, and has the advantages of short correction time and simple correction process.

[0043] The present invention will now be described in detail using the third well testing operation system as an example. The technical solution of the present invention includes the following steps:

[0044] Step 1: First, locate the inverted peak shape based on the fitted curve showing a negative slope. Then, determine the corresponding well test operating regime based on the location of the inverted peak shape within the fitted curve. Finally, establish the first relationship between the measuring point pressure, bottom hole flowing pressure, and accumulated fluid height during the initial well opening phase based on the logging data from the corresponding well test operating regime. The measuring point pressure is obtained from a pressure gauge positioned above the accumulated fluid surface within the wellbore.

[0045] like Figure 1 As shown, in the initial stage of well drilling, H exists at the bottom of the well. w Liquid accumulation height, pressure at measuring point p cwf With bottom hole flowing pressure p wf If there is a correlation between them, then the first relational expression is:

[0046] p cwf =p wf -ρ g gH-(ρ w -ρ g )gH w (1)

[0047] In equation (1), p cwf The pressure measured at the initial well opening point is in MPa; p wf The bottom hole flowing pressure during the initial stage of well opening is expressed in MPa; ρg The density of natural gas under formation conditions, in kg / m³ 3 ;ρ w The density of water under formation conditions, in kg / m³ 3 H represents the distance between the pressure measurement point and the medium-depth reservoir, in meters. w The distance, in meters, is the initial fluid accumulation level between the reservoir and the middle depth.

[0048] Step 2: Based on the production time, establish a second relationship between the measuring point pressure, bottom hole flowing pressure, and liquid accumulation height during the production period.

[0049] like Figure 2 As shown, after a gas well production time Δt is set, some of the liquid at the bottom of the well is carried out of the wellbore along with the natural gas. At this time, the height of the liquid at the bottom of the well decreases by ΔH. The second relationship is then established as follows:

[0050] p′ cwf =p′ wf -ρ g gH-(ρ w -ρ g )g(H w -ΔH) (2)

[0051] In equation (2): p′ cwf The pressure measured at the point after a production time Δt is in MPa; p′ wf The bottom hole flowing pressure after production time Δt, in MPa; H w ΔH represents the distance between the initial fluid accumulation surface and the middle depth of the reservoir during the initial well opening phase, in meters; ΔH represents the change in fluid accumulation height, in meters.

[0052] Step 3: Establish a third relationship for the pressure change at the measuring point based on the first and second relationships. Establish a fourth relationship for the increase in additional pressure based on the first, second, and third relationships. Calculate the increase in additional pressure based on the fourth relationship.

[0053] The third relationship established regarding the pressure change at the measuring point is as follows:

[0054] Δp cwf =p′ cwf -p cwf (3)

[0055] In equation (3), ΔP cwf The value is the change in pressure at the measuring point after a production time of Δt, in MPa.

[0056] The fourth relationship established regarding the increase in additional pressure is as follows:

[0057] Δp cwf =(p′) wf -p wf)+Δp (4)

[0058] In equation (4), (p′ wf -p wf The pressure change is denoted as ΔP, which represents the pressure change caused by the removal of fluid from the wellbore during normal production. ΔP is the additional pressure rise due to the removal of fluid from the wellbore; this value is positive. Figure 3 As shown.

[0059] Step 4: Based on the additional pressure increase and the measured pressure at the corresponding well test operating conditions, derive the corrected measuring point pressure. Then, use the corrected measuring point pressure to correct the negative slope of the fitted curve. The specific process is as follows:

[0060] First, the binomial productivity equation is derived based on the measured pressure after correction under the current well test operating system and the measured pressure of other well test operating systems and / or the measured pressure after correction under other well test operating systems. Then, the parameter B of the binomial productivity equation is calculated, and the negative slope of the fitted curve is corrected based on the parameter B.

[0061] The calculation method for the corrected measuring point pressure is as follows:

[0062] p′ cwf校正 =p′ cwf实测 -Δp (5)

[0063] In the formula: p′ cwf3 The corrected measuring point pressure is expressed in MPa; p cwf3 The measured pressure at the measuring point is in MPa.

[0064] Similarly, if the fitted curves for other well testing operating conditions exhibit an inverted peak shape, the same method described above should be used to process them, thereby obtaining the corrected pressure gauge readings. Finally, based on the corrected readings, a binomial productivity equation can be established to accurately evaluate the productivity of a single well.

[0065] Example 2

[0066] The applicant further illustrates this invention using the GS001 well in the Dengying Formation gas reservoir of the Gaoshiti-Moxi block in Southwest Oil and Gas Field Company as an example. This gas reservoir is currently in its early development stage, characterized by low permeability and strong heterogeneity. Well GS001 is a highly deviated well. A modified isochronous test with a 4-system was conducted in April 2020. Due to wellbore limitations, the pressure gauge only reached 4700m, a depth of 319.75m from the reservoir's mid-depth. Using actual pressure measurement data to derive a binomial productivity equation, the B-value was -0.2566, and the fitted curve of the binomial productivity equation had a negative slope, making it impossible to establish a productivity equation. Figure 4As shown in the fitted curves, the third and fourth well test operating conditions exhibit a distinct inverted peak shape. Therefore, the additional pressure rise calculated using the method described in this invention is 0.94 MPa and 1.03 MPa, respectively. Subtracting the corresponding additional pressure rise from the measuring point pressures of the third and fourth well test operating conditions, the corrected measuring point pressures are 30.72 MPa and 29.96 MPa, respectively. Using the measuring point pressures of the first and second well test operating conditions and the corrected measuring point pressures, the production capacity equation is derived, yielding parameter B of 0.2727. The negative value B has been successfully corrected, and the final calculated unobstructed flow rate of the well is 60.58 × 10⁻⁶. 4 m 3 / d. The error between the results and those obtained by the one-point method and the steady-point capacity calculation method is within 5%, proving that the calculation results of this correction method are highly reliable. At the same time, it is simple and quick to operate, making it convenient for field technicians to use.

[0067] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All features or steps in the disclosed methods or processes may be combined in any way, except for mutually exclusive features and / or steps.

Claims

1. A method for correcting the negative slope of a binomial capacity fitting curve, characterized in that... Includes the following steps: Step 1: Identify the inverted peak shape and corresponding well test operation regime based on the fitted curve showing negative slope. Based on the logging data of the corresponding well test operation regime, establish the first relationship between the measuring point pressure, bottom hole flowing pressure and fluid accumulation height in the early stage of well opening. Step 2: Based on the production time, establish a second relationship between the measuring point pressure, bottom hole flowing pressure, and fluid accumulation height during the production period; Step 3: Based on the first and second relationships, establish the third relationship regarding the pressure change at the measuring point. Based on the first, second, and third relationships, establish the fourth relationship regarding the increase in additional pressure. Calculate the increase in additional pressure based on the fourth relationship. Step 4: Based on the additional pressure increase and the measured pressure at the corresponding well test operating conditions, the corrected measuring point pressure is obtained, and the negative slope of the fitted curve is corrected based on the corrected measuring point pressure. The method described is used to correct the deviation in pressure measurement values ​​caused by changes in the fluid column in the wellbore during isochronous well testing. In step 1, the first relation established is: （1） In equation (1), p cwf The pressure measured at the initial well opening point, in MPa; p wf The bottom hole flowing pressure during the initial stage of well opening, in MPa; ρ g The density of natural gas under formation conditions, in kg / m³ 3 ; ρ w The density of water under formation conditions, in kg / m³ 3 ; H The distance, in meters, is the distance between the pressure measurement point and the mid-depth reservoir. H w The distance between the initial fluid accumulation surface and the middle depth of the reservoir during the initial well opening phase, in meters; In step 2, gas well production is set. t After a period of time, some of the liquid accumulated at the bottom of the well is carried out of the wellbore along with the natural gas, at which point the height of the liquid at the bottom of the well decreases. H， The second relation established is: （2） In formula (2): p cwf For production t Pressure measured at the time point, in MPa; p wf For production t Bottom hole flowing pressure after time, MPa; H w The distance between the initial fluid accumulation surface and the middle depth of the reservoir during the initial well opening phase, in meters; H The value represents the change in liquid height, in meters (m). In step 3, the third relationship regarding the pressure change at the measuring point is established as follows: （3） In equation (3), P cwf For production t The change in pressure at the measuring point after a certain time, in MPa; In step 3, the fourth relationship regarding the increase in additional pressure is established as follows: （4） In equation (4), ( p wf - p wf The pressure changes resulting from normal gas well production. P This adds pressure to increase value.

2. The method for correcting the negative slope of a binomial capacity fitting curve according to claim 1, characterized in that: In step 4, the calculation method for the corrected measuring point pressure is as follows: （5） In the formula: p cwf3 The corrected pressure at the measuring point, in MPa; p cwf3 The measured pressure at the measuring point is in MPa.

3. The method for correcting the negative slope of a binomial capacity fitting curve according to claim 1, characterized in that: In step 4, the specific process of correcting the negative slope of the fitted curve based on the corrected measuring point pressure is as follows: First, the binomial productivity equation is derived based on the measured pressure after correction under the current well test operating system and the measured pressure of other well test operating systems and / or the measured pressure after correction under other well test operating systems. Then, the parameter B of the binomial productivity equation is calculated, and the negative slope of the fitted curve is corrected based on the parameter B.

4. The method for correcting the negative slope of a binomial capacity fitting curve according to claim 1, characterized in that: The pressure at the measuring point is obtained by testing with a pressure gauge.

5. The method for correcting the negative slope of a binomial capacity fitting curve according to claim 4, characterized in that: The pressure gauge is positioned above the liquid level.

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