A method for interpreting conventional well tests in complex reservoirs

Abstract

This invention provides a method for interpreting conventional well tests in complex reservoirs. The method includes considering permeability variations near the wellbore in a complex region, analyzing pressure recovery curves, calculating the flow coefficient based on shut-in time and bottom-hole pressure in each zone, analyzing the variation trend of reservoir properties around the well based on changes in the flow coefficient, calculating reservoir permeability at different time intervals, amplifying the time interval data to observe the relationship between reservoir properties and time intervals, and obtaining the wellbore reservoir coefficient based on the pressure recovery theory, considering the changes in bottom-hole pressure over time based on shut-in time and time. The method also calculates the pressure recovery rise value based on the wellbore reservoir coefficient and when the test data time intervals are the same. This invention is suitable for reservoirs with water injection, polymer injection, alternating gas and water injection, wellbore contamination, or improved permeability near the wellbore, and is also applicable to the interpretation of well test data from reservoirs with varying rock properties.

Description

Technical Field

[0001] This invention belongs to the field of reservoir interpretation technology, and particularly relates to a method for interpreting conventional well tests in complex reservoirs. Background Technology

[0002] As is well known, well testing is one of the important means to understand reservoir characteristics and conduct reservoir evaluation. In recent years, many theoretical models of well testing have been established, such as homogeneous models, dual-well models, and multi-well testing models. These models can solve the interpretation of most well test data. However, when the geological conditions of the oilfield are relatively complex, and production enhancement measures such as fracturing and acidizing are adopted, or when the oilfield is exploited by water injection, gas injection, or polymer injection, it becomes very difficult to interpret some well test data using the above models, and it is difficult to obtain satisfactory interpretation results. Therefore, reservoirs with bottomhole contamination, reservoirs with improved permeability around the well, and reservoirs that have undergone water injection, gas injection, or polymer injection are generally described as complex reservoirs. There are also reservoirs with fluctuating underground rock properties and varying permeability of the same oil layer, which can also be described as complex reservoirs. Therefore, well test interpretation can establish well test interpretation models for complex reservoirs with two or more zones. These models can only be interpreted using modern well testing from typical curve fitting, and cannot be interpreted using conventional well test interpretation methods. Summary of the Invention

[0003] The purpose of this invention is to overcome the deficiencies of the existing technology and provide a method for interpreting conventional well test data in complex reservoirs. This method can be appropriately used for reservoirs with water injection, polymer injection, alternating gas and water injection, or reservoirs with contamination or improved permeability near the bottom of the well. It is also applicable to the interpretation of well test data in reservoirs with different rock properties.

[0004] The present invention adopts the following technical solution:

[0005] A method for interpreting conventional well tests in complex reservoirs includes the following steps:

[0006] Step 1. Explanation of reservoir permeability

[0007] The permeability variation near the wellbore is considered using a composite region, and the analysis is performed using pressure recovery curves, based on the shut-in time. and The bottom-hole pressure in each zone was obtained, and the flow coefficient was calculated. The variation trend of reservoir properties around the well was analyzed based on the change in the flow coefficient, and reservoir permeability was calculated at different time intervals. The data from each time interval was magnified to observe the relationship between reservoir properties and time intervals.

[0008] Step 2. Interpretation of Wellbore Reservoir Coefficient

[0009] According to the pressure recovery theory, based on the shut-in time and The wellbore storage coefficient is obtained by measuring the change in bottom hole pressure over time. Based on the wellbore storage coefficient and the pressure recovery rise value when the time interval of the test data is the same, the pressure recovery rise value is calculated.

[0010] Furthermore, step 1 includes: S101. When the pressure recovers... If the well shut-in time is short and the pressure recovers to zone I, the bottomhole flowing pressure is:

[0011] (twenty four)

[0012] To restore pressure at the bottom of the well, MPa, q is the flowing pressure at the bottom of the well, in MPa, and q is the production flow rate before shut-in, in meters. 3 / ks, where B is the fluid volume coefficient, which is dimensionless. Let be the fluid viscosity in inner region I, in mPa·s. The penetration rate of inner zone I. , Let the reservoir thickness of inner region I be m. Let m be the outer boundary of the inner region I. Let m be the pressure conductivity coefficient of the inner region I. 2 / ks, where The shut-in time is ks.

[0013] S102. When the pressure is transmitted to Zone II, the bottom hole pressure is:

[0014] (25)

[0015] In the formula, —Penetration rate of outer zone II, , —Reservoir thickness in outer zone II, in meters. Let be the well radius, in meters. The production time before the oil well is shut down is ks.

[0016] S103. When the pressure is transmitted to Zone III, the bottom hole pressure is:

[0017] (26)

[0018] In the formula:

[0019] —Penetration rate in outer zone III, ;

[0020] —Reservoir thickness in outer zone III, in meters;

[0021] —The pressure conductivity coefficient of outer zone III, m2 / ks;

[0022] —The radius of the interface between outer zone II and outer zone III, in meters;

[0023] — Bottomwell pressure when shut in, MPa.

[0024] Furthermore, it also includes S104. When the pressure recovers... If the recovery time is short and the pressure recovers to zone I, the bottom hole pressure will be:

[0025] (27)

[0026] — Well shut-in time, ks;

[0027] S105. When the pressure is transmitted to Zone II, the bottom hole pressure is:

[0028] (28)

[0029] S106. When the pressure is transmitted to Zone III, the bottom hole pressure is:

[0030] (29)

[0031] Furthermore, it also includes S107. Assumption and The recovery time all occurs within the same region, meaning they all satisfy the same pressure recovery formula. In region I, we have:

[0032] (30)

[0033] S108. In Zone II:

[0034] (31)

[0035] S109. In Zone III:

[0036] (32)

[0037] —The boundary radius between outer zone II and outer zone III (30)-(32) simplifies to:

[0038] (33)

[0039] From equation (33), the magnitude of the pressure recovery value depends on the changes in reservoir properties and the length of the shut-in time interval. The change in the flow coefficient can be calculated from equation (33), i.e.:

[0040] (34)

[0041] In the formula: and It is the number of well shut-in time intervals. Number of pressure recovery data points; h—formation thickness, m; if All fall within the inner area Corresponding The flow coefficient of reaction zone I, if They all fall in Zone II, corresponding to Reflecting the flow coefficient of the outer region, when Cross-regional, Mutations can occur.

[0042] The variation trend of reservoir physical parameters around the well was analyzed by equation (34), and the reservoir permeability was calculated at different time intervals.

[0043] Furthermore, step 2 includes: the relationship between bottom hole pressure and time is as follows:

[0044] (35)

[0045] When recovering The bottom flow pressure is:

[0046] (36)

[0047] When recovering The bottom flow pressure is:

[0048] (37)

[0049] From equations (36) and (37), we get:

[0050] (38)

[0051] The change in the wellbore reservoir coefficient is obtained from equation (38) as follows:

[0052] (39)

[0053] From equation (39), we can see that the wellbore storage coefficient is not constant with time and gradually increases with time.

[0054] The beneficial effects of this invention are:

[0055] 1. Improved the accuracy of the explanation:

[0056] The method provided by this invention is simpler and more applicable than traditional analysis methods, and can avoid the difficulty of manually selecting straight line segments. By considering the change of the wellbore reservoir coefficient over time, the new method can more accurately reflect the actual changes in reservoir properties and improve the accuracy of well test interpretation.

[0057] 2. Wider range of applications:

[0058] It is particularly suitable for well testing in low-permeability or highly heterogeneous oil and gas reservoirs. For reservoirs with fluctuating rock properties, the new method can also provide accurate well test interpretation results.

[0059] 3. Guiding reservoir development:

[0060] By providing accurate well test interpretation results, the new method can help engineers better understand reservoir characteristics and develop more reasonable development plans.

[0061] 4. Through comparison of different calculations, the method of this invention is simpler and more applicable than traditional analysis methods. This method avoids the artificial selection of straight segments, especially in low-permeability or ultra-low-permeability reservoirs where straight segments do not appear, which is very difficult to analyze. This method is more suitable for well testing of oil and gas reservoirs with severe heterogeneity, and can better interpret the formation during well testing, providing better guidance for subsequent development. Attached Figure Description

[0062] Figure 1 This is the composite reservoir geological model of the present invention;

[0063] Figure 2 For well test analysis curves of composite reservoir pressure drop;

[0064] Figure 3 For the pressure recovery test analysis curve of the composite reservoir;

[0065] Figure 4 This is the well pressure recovery curve for a certain well;

[0066] Figure 5 To illustrate the effect of different time intervals on the interpretation of the recovery curve results;

[0067] Figure 6 A magnified diagram showing the effect of different time intervals on the interpretation of the recovery curve;

[0068] Figure 7 The reservoir coefficient analysis curve for a conventional wellbore is shown.

[0069] Figure 8 Calculate the wellbore reservoir coefficient variation curve using a new method for a certain well;

[0070] Figure 9 This is a flowchart of the steps of the present invention. Detailed Implementation

[0071] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0072] 1. Basic Principles of Well Test Interpretation in Composite Reservoirs

[0073] like Figure 1 As shown, the geological model of a composite reservoir, taking a three-zone model as an example, consists of three homogeneous annular regions, inner and outer. Inner zone I can be considered as the change in permeability caused by reservoir contamination near the well bottom. The boundary radius of inner zone I is... The unit is m, and the reservoir thickness of inner zone I is... The unit is m, and the outer boundary of the inner region I is... The unit is m, and the permeability of inner zone I is... ,unit The fluid viscosity in inner region I is The unit is mPa·s, and the reservoir thickness in outer zone II is... The unit is m, and the permeability of outer zone II is... ,unit The viscosity of fluid II in outer region II is The unit is mPa·s, and the reservoir thickness in outer zone III is... The unit is m, and the permeability of outer zone III is... ,unit The fluid viscosity in both region III and region II is ,unit .

[0074] 2. Pressure drop well test

[0075] During the drilling and completion of an oil well, the area near the well can be considered the inner zone, or the contaminated zone. The effect of the skin coefficient can be viewed as a change in permeability. Before the bottomhole pressure change propagates to the interface between Zone I and Zone II, the pressure at any point in the formation within Zone I is calculated as follows:

[0076] (1)

[0077] In the formula, q is the production flow rate before well shut-in, in meters. 3 / ks; B—fluid volume coefficient, dimensionless. —Formation pressure before well shut-in, MPa; r—Distance from any point in the formation to the well, m. t—Production time from the start of well opening, ks.

[0078] The bottom-hole flowing pressure at any given time is:

[0079] (2)

[0080] (3)

[0081] In the formula, —Well radius, m

[0082] Alternatively, equation (2) can be simplified to:

[0083] (4)

[0084] In the formula:

[0085] —The pressure conductivity coefficient of inner region I, m 2 / ks;

[0086] —Porosity of inner zone I;

[0087] —Total compressibility coefficient of inner zone I, 1 / MPa;

[0088] —Pressure at the formation r distance from the well at time t, in MPa;

[0089] —Flow pressure at the bottom of the well, MPa;

[0090] The pressure at any point in the inner strata can also be rewritten as:

[0091] (5)

[0092] In the formula: ;

[0093] Equation (5) can be approximated as:

[0094] (6)

[0095] From equation (6), we can see that at the boundary... The pressure is:

[0096] (7)

[0097] —Intersection The pressure, MPa.

[0098] The formation parameters of inner zone I are explained by equation (4). In practice, equation (4) is only applicable to new wells. It is not the original formation pressure, but the formation pressure before the pressure drop test. The volume coefficient is also a function of the formation pressure. For old wells, the formation pressure must be tested first before corresponding analysis can be carried out.

[0099] When the pressure wave travels to When outside, Assuming an effective wellbore diameter, the formation pressure in Zone II at this time is:

[0100] (8)

[0101] (9)

[0102] In the formula: —The pressure conductivity coefficient of outer zone II, m 2 / ks;

[0103] —Porosity of outer zone II;

[0104] —Total compressibility coefficient of outer zone II, 1 / MPa.

[0105] Combining equation (7) and equation (8), when the pressure wave reaches the interface between zone I and zone II, that is, at... When the formation pressures are equal, that is:

[0106] (10)

[0107] From equation (10), the bottom-hole flowing pressure when the pressure wave reaches zone II is:

[0108] (11)

[0109] Equation (11) explains the formation parameters of outer zone II. Combining equations (4) and (11) allows for the interpretation of reservoir properties in both inner and outer zones, such as... Figure 2 As shown, the first straight line segment reflects the pressure response characteristics of the inner zone I, and the second straight line segment reflects the pressure response characteristics of the outer zone II.

[0110] The slope of the first straight segment is:

[0111] (12)

[0112] The slope of the second straight segment is:

[0113] (13)

[0114] When the pressure reaches the boundary between Zone II and Zone III When it comes to this, Assuming it's the effective wellbore diameter, the formation pressure at the interface is:

[0115] (14)

[0116] In the formula:

[0117] —The pressure conductivity coefficient of outer zone III, m 2 / ks;

[0118] —Porosity of outer zone III;

[0119] —Total compressibility coefficient of outer zone III, 1 / MPa.

[0120] —Formation pressure at the boundary between Zone II and Zone III, MPa

[0121] Extrapolating from equation (7), at the boundary r2, the formation pressure is:

[0122] (16)

[0123] —Formation pressure in Zone II, MPa —Outer boundary of inner region I, m;

[0124] Substituting equation (7) into equation (16) yields:

[0125] (17)

[0126] In the formula, The meaning is the flowing pressure at the bottom of the well, in MPa;

[0127] From equations (14) and (17), we get:

[0128] (18)

[0129] The formation parameters of Zone III are explained by equation (18). The third straight line segment reflects the pressure response characteristics of Zone III, namely:

[0130] (19)

[0131] When the pressure wave reaches Zone III, the third straight segment appears. The method for interpreting its parameters is the same as before and will not be described again.

[0132] 3. Pressure recovery well test

[0133] Well production has been going on for a long time. According to the principle of pressure drop superposition, before the shut-in pressure wave reaches the interface between Zone I and Zone II, the bottom hole pressure change is as follows:

[0134] (20)

[0135] —Well bottom recovery pressure, MPa —Production time before well shutdown, ks — Well shut-in time, ks;

[0136] Equation (20) can be rewritten as: ;

[0137] The stratigraphic parameters of inner zone I are explained by equation (20).

[0138] After the shut-in pressure wave propagates to the outer interface of Zones I and II, the bottomhole pressure changes as follows:

[0139] (twenty two)

[0140] The stratigraphic parameters of outer zone II are explained by equation (22).

[0141] Combining equations (21) and (22) allows for the interpretation of reservoir properties in both inner and outer zones, such as... Figure 3 As shown, and The relationship is linear; the first straight line segment reflects the pressure response characteristics of inner zone I, and the second straight line segment reflects the pressure response characteristics of outer zone II.

[0142] Similarly, when the pressure returns to Zone III, the bottom hole flowing pressure becomes:

[0143] (twenty three)

[0144] Stress relief With well shut-in time The semi-logarithmic curve shows a linear relationship, and its slope is the same as that of the pressure drop curve. The parameter interpretation method is also the same, so it will not be described again.

[0145] Theoretically, for complex reservoirs, whether it's pressure drop testing or pressure recovery testing, semi-logarithmic analysis requires a linear segment to be valid; otherwise, reservoir properties cannot be interpreted. However, changes in reservoir properties may be gradual, treated as a continuous medium field. Therefore, actual curves rarely show obvious piecewise linear segments. Figure 4 As shown, it is difficult to find the corresponding straight line, so it is very difficult to perform conventional well test analysis using conventional analysis methods.

[0146] 4. A new method for well test analysis of complex reservoirs

[0147] 4.1 Explanation of Reservoir Permeability

[0148] like Figure 9As shown, by considering the permeability variation near the wellbore in a composite region, the influence of the skin coefficient can be ignored. Analysis is performed using the pressure recovery curve. When the pressure recovers... If the recovery time is short and the pressure recovers to zone I, the bottom hole flowing pressure is:

[0149] (twenty four)

[0150] To restore pressure at the bottom of the well, MPa, q is the flowing pressure at the bottom of the well, in MPa, and q is the production flow rate before shut-in, in meters. 3 / ks, where B is the fluid volume coefficient, which is dimensionless. Let be the fluid viscosity in inner region I, in mPa·s. The penetration rate of inner zone I. , Let the reservoir thickness of inner region I be m. Let m be the outer boundary of the inner region I. Let m be the pressure conductivity coefficient of the inner region I. 2 / ks, where The shut-in time is ks.

[0151] When the pressure is transmitted to Zone II, the bottom hole pressure is:

[0152] (25)

[0153] In the formula, —Penetration rate of outer zone II, , —Reservoir thickness in outer zone II, in meters. Let be the well radius, in meters. Let ks be the production time before well shut-in. When the pressure reaches Zone III, the bottomhole pressure is:

[0154] (26)

[0155] In the formula:

[0156] —Penetration rate in outer zone III, ;

[0157] —Reservoir thickness in outer zone III, in meters;

[0158] —The pressure conductivity coefficient of outer zone III, m 2 / ks;

[0159] —The radius of the interface between outer zone II and outer zone III, in meters;

[0160] — Bottomwell pressure when shut in, MPa.

[0161] When the pressure is restored If the recovery time is short and the pressure recovers to zone I, the bottom hole pressure will be:

[0162] (27)

[0163] — Well shut-in time, ks;

[0164] When the pressure is transmitted to Zone II, the bottom hole pressure is:

[0165] (28)

[0166] When the pressure is transmitted to Zone III, the bottom hole pressure is:

[0167] (29)

[0168] Assumption and The recovery time is all within the same region, meaning they all satisfy the same pressure recovery formula. Therefore, in region I, we have:

[0169] (30)

[0170] In Zone II:

[0171] (31)

[0172] In Zone III:

[0173] (32)

[0174] —Radius of the interface between outer zone II and outer zone III

[0175] Equations (30)-(32) can all be simplified to:

[0176] (33)

[0177] As can be seen from equation (33), the magnitude of the pressure recovery value depends on the changes in reservoir properties and the length of the shut-in time interval. The change in the flow coefficient can be calculated from equation (33), i.e.:

[0178] (34)

[0179] In the formula: and It is the number of well shut-in time intervals. Number of pressure recovery data points; h—formation thickness, m;

[0180] if All fall within the inner area Corresponding The flow coefficient of reaction zone I, if They all fall in Zone II, corresponding to Reflecting the flow coefficient of the outer region, when Cross-regional, Mutations can occur.

[0181] in conclusion

[0182] Through comparison of different calculations, the new method is simpler and more applicable than traditional analysis methods. This method avoids the artificial selection of straight segments, especially in low-permeability or low-permeability reservoirs where straight segments are not present, which is very difficult to analyze. This method is more suitable for well testing in oil and gas reservoirs with severe heterogeneity, and can better interpret the formation during well testing, providing better guidance for subsequent development.

[0183] Example

[0184] Table 1 shows the basic data of a certain production well. The stable production time before well shut-in was approximately 200 hours. A semi-logarithmic analysis curve was plotted according to equation (23), as shown below. Figure 4 As shown, no straight line segments appeared, making conventional well test analysis very difficult.

[0185]

[0186] Equation (34) first analyzes the changing trend of reservoir physical parameters around the well, such as Figure 5 As shown, reservoir permeability was calculated at different time intervals, representing a continuous change process from the inside to the outside of the reservoir. Regardless of the pressure recovery time interval, the trend of reservoir property changes was consistent. The time intervals ranged from 1 point, 2 points, 5 points, and 10 points. The larger the time interval, the easier it is to mask the drastic changes in reservoir properties. Figure 6 As shown, when the data is magnified, the reservoir properties change more significantly with decreasing time intervals. Larger changes in property parameters occur with longer time intervals, while changes in reservoir properties weaken, exhibiting homogeneity. Smaller time intervals more easily reflect the true changes in reservoir properties. Previous conventional well test interpretation methods struggled to describe the continuous process of reservoir property changes, or could only interpret simple areas using modern well test interpretation methods. After determining the changes in reservoir properties using this method, the early stages are significantly affected by wellbore reservoir effects, and the wellbore reservoir coefficient is determined based on early data.

[0187] 4.2 Interpretation of Wellbore Reservoir Coefficient

[0188] According to the pressure recovery theory, the relationship between bottom hole pressure and time is as follows:

[0189] (35)

[0190] When recovering The bottom flow pressure is:

[0191] (36)

[0192] When recovering The bottom flow pressure is:

[0193] (37)

[0194] From equations (36) and (37), we get:

[0195] (38)

[0196] The change in the wellbore reservoir coefficient is obtained from equation (38) as follows:

[0197] (39)

[0198] As can be seen from equation (39), —Wellbore reservoir coefficient, m 3 / MPa, when the test data time interval is the same, the pressure recovery rise value is not necessarily constant, due to... Figure 4 Early data, analyzed using conventional methods such as Figure 7 As shown, its wellbore storage coefficient is calculated to reach 107m. 3 / MPa, calculate its wellbore reservoir coefficient over time using the new method, as shown in the curve. Figure 8 As shown, the wellbore reservoir coefficient is not constant with time, but gradually increases over time. The results of conventional analysis are much larger than those of the new method.

[0199] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of composite reservoir conventional well test interpretation, characterized in that, Including the following steps: Step 1. Explanation of reservoir permeability The permeability variation near the wellbore is considered using a composite region, and the analysis is performed using pressure recovery curves, based on the shut-in time. and The bottom-hole pressure of each zone was obtained, the flow coefficient was calculated, and the trend of reservoir physical parameters around the well was analyzed based on the change of the flow coefficient. The reservoir permeability was calculated at different time intervals, and the data of the time intervals were magnified to observe the relationship between reservoir physical properties and time intervals. Step 2. Interpretation of Wellbore Reservoir Coefficient According to the pressure buildup theory, the wellbore storage coefficient is obtained from the change of the bottom hole pressure with time and The pressure buildup rise is calculated from the wellbore storage coefficient and the test data when the time interval is the same. Step 1 also includes: S107. Assume With Time is recovered in the same region, that is, all meet the same pressure recovery formula, in I region: (30); To restore pressure at the bottom of the well, MPa, q is the flowing pressure at the bottom of the well, in MPa, and q is the production flow rate before shut-in, in meters. 3 / ks, where B is the fluid volume coefficient, which is dimensionless. Let be the fluid viscosity in inner region I, in mPa·s. The penetration rate of inner zone I. , Let the reservoir thickness of inner region I be m. Let be the well radius, in meters. Let m be the pressure conductivity coefficient of the inner region I. 2 / ks, where For well shut-in time, ks; S108. In Zone II: (31); —Penetration rate of outer zone II, , —Reservoir thickness in outer zone II, in meters. —The pressure conductivity coefficient of outer zone II, m 2 / ks, Let m be the outer boundary of inner region I; S109. In Zone III: (32); —The radius of the interface between outer zone II and outer zone III, in meters; —Penetration rate in outer zone III, ; —Reservoir thickness in outer zone III, in meters; —The pressure conductivity coefficient of outer zone III, m 2 / ks; Equations (30)-(32) can be simplified to: (33); From equation (33), the magnitude of the pressure recovery value depends on the changes in reservoir properties and the length of the shut-in time interval. The change in the flow coefficient can be calculated from equation (33), i.e.: (34); In the formula: and It is the time interval sequence number. Number of pressure recovery data points; h—formation thickness, m; if All fall within the inner area Corresponding The flow coefficient of reaction zone I, if They all fall in Zone II, corresponding to Reflecting the flow coefficient of the outer region, when Cross-regional, Mutations will occur; The variation trend of reservoir physical parameters around the well was analyzed by equation (34), and the reservoir permeability was calculated at different time intervals.

2. The method according to claim 1, characterized in that, Step 1 includes: S101. When pressure recovers If the recovery time is short and the pressure recovers to zone I, the bottom hole flowing pressure is: (twenty four); To restore pressure at the bottom of the well, MPa, q is the flowing pressure at the bottom of the well, in MPa, and q is the production flow rate before shut-in, in meters. 3 / ks, where B is the fluid volume coefficient, which is dimensionless. Let be the fluid viscosity in inner region I, in mPa·s. The penetration rate of inner zone I. , Let the reservoir thickness of inner region I be m. Let m be the outer boundary of the inner region I. Let m be the pressure conductivity coefficient of the inner region I. 2 / ks, where For well shut-in time, ks; S102. When the pressure is transmitted to Zone II, the bottom hole pressure is: (25); In the formula, —Penetration rate of outer zone II, , —Reservoir thickness in outer zone II, in meters. Let be the well radius, in meters. The production time before the oil well is shut in, ks; S103. When the pressure is transmitted to Zone III, the bottom hole pressure is: (26); In the formula: —Penetration rate in outer zone III, ; —Reservoir thickness in outer zone III, in meters; —The pressure conductivity coefficient of outer zone III, m 2 / ks; —The radius of the interface between outer zone II and outer zone III, in meters; — Bottomwell pressure when shut in, MPa.

3. The method according to claim 2, characterized in that, Step 1 also includes: S104. When pressure recovers If the recovery time is short and the pressure recovers to zone I, the bottom hole pressure will be: (27); — Well shut-in time, ks; S105. When the pressure is transmitted to Zone II, the bottom hole pressure is: (28); S106. When the pressure is transmitted to Zone III, the bottom hole pressure is: (29).

4. The method according to claim 1, characterized in that, Step 2 includes: The relationship between bottom hole pressure and time is given by: C—wellbore reservoir coefficient, m 3 / MPa, q—Production flow rate before well shut-in, m 3 / ks; B—fluid volume coefficient, dimensionless. —Flow pressure at the bottom of the well, MPa —Well bottom recovery pressure, MPa For well shut-in time, ks: (35); When recovering The bottom flow pressure is: (36); When recovering The bottom pressure of the well is, — Well shut-in time, ks: (37); From equations (36) and (37), we get: (38); The change in the wellbore reservoir coefficient is obtained from equation (38) as follows: (39); From equation (39), we can see that the wellbore storage coefficient is not constant with time and gradually increases with time.

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