Comprehensive division method for elastic flooding stage and natural water flooding stage of fracture-vug type oil well

Abstract

The invention discloses a comprehensive division method for an elastic flooding stage and a natural water flooding stage of a fracture-vuggy oil well, and relates to the field of oil and gas reservoir engineering. According to the technical scheme, the production characteristic type of a single well is determined according to characteristics of a production dynamic curve or an energy indication curve; for a conventional oil well, determining a demarcation point of an elastic flooding stage and a natural water flooding stage through a production dynamic curve; aiming at the well with obvious water invasion, determining a demarcation point of an elastic flooding stage and a natural water flooding stage by utilizing a flowing substance balance method; and for unobvious wells in other stages, an oil well elastic flooding stage and a natural water flooding stage are comprehensively judged and divided by using a nozzle flow formula normalization method, an analogy stage boundary method and a unit or well group stage division method. The method is beneficial for solving the problem that different production stages of a fracture-vug type reservoir oil well are not clearly divided, and particularly solving the research problems that transition from an elastic flooding stage to a natural water flooding stage is not obvious, follow-up water invasion time, water invasion paths and the like related to remaining oil distribution are affected.

Description

Technical Field

[0001] The invention relates to the field of oil and gas reservoir engineering, and more specifically, to a comprehensive division method for elastic drive stage and natural water drive stage of a fracture-cavity oil well. Background Art

[0002] Fracture-cave oil and gas reservoirs refer to special types of oil reservoirs with large caves and fractures as the main storage space. They have the characteristics of low permeability and high porosity. It is impossible to extract crude oil by natural pressure. It needs a certain driving force to push the oil and gas to the wellhead for collection. The two important stages of the production process are the elastic drive stage and the natural water drive stage. In the elastic drive stage, the reservoir pressure increases due to the influence of external factors such as water injection, causing the crude oil in it to migrate toward the wellhead and gradually be produced. In the natural water drive stage, the colloids and surfactants in the reservoir are washed away by water, causing the crude oil to be replaced by water, which increases the water content in the produced crude oil. For this reason, it is necessary to divide the drive stage before the oil and gas reservoir is exploited, so as to adjust the production measures and production strategies according to different drive stages to ensure the steady development and efficient utilization of the oil and gas reservoir.

[0003] As for the division of driving stages, the commonly used method is recorded in the book "Development Technology of Carbonate Fracture-Vug Reservoirs in Tahe Oilfield" written by Dou Zhilin et al., which judges the driving stage through the curve of the relationship between static pressure and cumulative liquid production. When the slope of the curve shows an obvious inflection point (the straight line becomes a curve), it means that the driving mode has changed, or the edge and bottom water have fully played a role. If it tends to be stable, it means that the edge and bottom water is large; if the slope of the straight line decreases, it means that the edge and bottom water is limited; if the curve drops linearly, it means that there is no edge and bottom water or the energy of the edge and bottom water is weak, and the reservoir is in a purely elastic driving state. This method is simple and easy to use, and can quickly determine the driving stage of the oil well, and has been widely used in the actual development of oil fields.

[0004] However, in actual situations, the transition between the elastic drive stage and the natural water drive stage is not obvious. This is mainly because there are many complex factors in the oil recovery process, such as the geological characteristics, physical and chemical properties of the reservoir, as well as the oil recovery method and the characteristics of the injected liquid, which will affect the development status and evolution of the reservoir. Therefore, when the elastic drive stage transitions to the natural water drive stage, the process is a gradual process, and the transition speed and path of different reservoirs will also be different. If we cannot accurately judge the transition between the elastic drive stage and the natural water drive stage, it will have a certain impact on the subsequent oil and gas production. For example, if the natural water drive stage is entered too early, it may cause excessive water content in the reservoir, thereby reducing the quality of the produced crude oil; and if the natural water drive stage is entered too late, it may affect the improvement of the oil and gas reservoir recovery rate.

[0005] To this end, the present invention hopes to provide a comprehensive division method for the elastic drive stage and the natural water drive stage of a fracture-cavity oil well, so as to improve the accuracy of the drive stage division. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention aims to provide a comprehensive division method for the elastic drive stage and the natural water drive stage of a fracture-cavity oil well, which determines the production characteristic type of a single well by relying on the characteristics of a production performance curve and an energy indication curve; for conventional oil wells, the dividing point between the elastic drive stage and the natural water drive stage is determined by the production performance curve; for wells with obvious water invasion, the dividing point between the elastic drive stage and the natural water drive stage is determined by the flow material balance method; for wells with unclear stages, the elastic drive stage and the natural water drive stage of the oil well are divided by comprehensive judgment using the nozzle flow formula normalization method, the analogy stage boundary method, and the unit or well group stage division method.

[0007] To achieve the above object, the present invention provides the following technical solution: a method for dividing the elastic flooding stage and the natural water flooding stage of a fracture-cavity oil well, which comprises the following steps:

[0008] S1. Based on the production performance curve or energy indication curve, the fracture-cavity oil wells are divided into conventional oil wells and oil wells with inconspicuous driving stages. The wells with inconspicuous driving stages are further divided into wells with obvious water invasion and wells with other inconspicuous driving stages.

[0009] Production dynamic curve: The oil wells whose curves first present trapezoidal or triangular shapes and then present S-shaped or parabolic shapes are conventional oil wells; the oil wells whose overall slope of the curves presents a downward trend are wells with obvious water invasion; the other oil wells are wells with other unobvious driving stages;

[0010] Energy indication curve: The oil wells whose curve slope first decreases and then increases are conventional oil wells; the oil wells whose curve slope first decreases and then stabilizes are wells with obvious water invasion; the other oil wells are wells with insignificant other driving stages;

[0011] S2. For conventional oil wells, the elastic drive stage and the natural water drive stage are divided according to the production performance curve;

[0012] For wells with obvious water invasion, the flow material balance method is used to draw production indicator curves to divide the elastic drive stage and the natural water drive stage;

[0013] For other wells with unclear driving stages, production performance curves, production indicator curves and water content curves are drawn based on the law of nozzle flow changes to divide the wells into elastic drive stage and natural water drive stage.

[0014] The present invention is further configured as follows: the curve characteristic of the production performance curve of a conventional oil well is first linearly decreasing, and then the slope gradually decreases until the curve is flat; the slope change law of the conventional oil well production performance curve is obtained by fitting, and the intersection between the linear decreasing section and the slope decreasing section is used as the stage division point of the elastic drive stage and the natural water drive stage.

[0015] The present invention is further configured as follows: the abscissa of the production dynamic curve is the cumulative oil production, and the ordinate is the oil pressure, and the oil pressure is any one of the bottom hole flow pressure, the wellhead oil pressure, and the wellhead casing pressure.

[0016] The present invention is further configured as follows: the curve characteristic of the production indicator curve of the well with obvious water invasion is discontinuous, and the whole first decreases linearly, and then the slope gradually decreases in a step-like manner until the curve is flat; the slope change law of the production dynamic curve of the well with obvious water invasion is obtained by fitting, and the intersection point between the linear decreasing section and the slope decreasing section is used as the stage division point of the elastic drive stage and the natural water drive stage.

[0017] The present invention is further configured as follows: for wells with obvious water invasion, the horizontal coordinate of the production indicator curve is the normalized cumulative oil production N pn , the vertical axis is the normalized output q n , the formula is as follows:

[0018]

[0019] Where NPn is normalized cumulative oil production, unit is 104t; N P is the cumulative oil production corresponding to the total pressure drop, in units of 104t; B o is the crude oil volume coefficient corresponding to the total pressure drop, dimensionless; C t is the comprehensive compression coefficient, which is a given value in MPa-1; B oi is the volume coefficient of the original crude oil, dimensionless; ΔP is the total pressure drop, in MPa;

[0020]

[0021] In the formula, q n is the normalized yield, unit is t / d·MPa -1 ; q is the output, unit is t / d; ΔP is the total pressure drop, unit is MPa.

[0022] The present invention is further configured as follows: the comprehensive compression coefficient C t It is the sum of the rock compressibility coefficient and the crude oil compressibility coefficient, both of which are obtained through experiments.

[0023] The present invention is further configured to divide the elastic flooding stage and the natural water flooding stage based on the change law of the nozzle flow, specifically:

[0024] Normalize the nozzle output to obtain the normalized nozzle adjustment output q t The normalization process steps are: first, select the reference nozzle; second, give the formula coefficient of each nozzle; third, convert the output and pressure of each nozzle according to the corresponding formula coefficient to obtain the corresponding normalized nozzle adjustment output q t ;

[0025] Taking the accumulated oil production as the horizontal axis, in the same coordinate system, the oil pressure and the normalized oil nozzle are used to adjust the production q t and water content as the ordinate, construct three curves;

[0026] When the oil pressure is high and the water content is 0, q t The curve is divided into elastic flooding stage and natural water flooding stage in turn. t The stage where the curve amplitude is large and gradually decays is divided into the elastic drive stage. t The stage when the curve amplitude decreases and tends to be stable is divided into the natural water drive stage.

[0027] The present invention is further configured as follows: t The calculation formula is as follows:

[0028]

[0029] In the formula, q t is the normalized nozzle adjustment output, unit is t / d; c is the formula coefficient, which is a given value, unit is t / d·MPa-1·mm-2; Pt is the normalized nozzle adjustment pressure, which is a given value, unit is MPa; D0 is the nozzle diameter, unit is mm.

[0030] The present invention is further configured as follows: the formula coefficient c is the ratio between the output and pressure data of the nozzle in the stable production stage of the early production period obtained by linear fitting.

[0031] The present invention is further configured as follows: for oil wells that cannot be divided into elastic drive stage and natural water drive stage based on the nozzle flow variation law, the elastic drive stage and natural water drive stage are divided by recovery factor analogy method.

[0032] The present invention is further configured as follows: the recovery rate analogy method specifically comprises: for the relatively constant volume wells in the pure elastic drive stage in the well group, the maximum elastic drive stage recovery rate curves of these wells are counted; the pressure change of the relatively constant volume wells is small, and the wellhead flow is stable; the maximum elastic drive stage is the stage with the highest recovery rate achieved by the elastic drive mechanism; then, the maximum elastic drive stage of the wells with an unclear driving stage is determined by analogy based on the known maximum elastic drive stage recovery rate curve, the stage before the maximum elastic drive stage is the elastic drive stage of the wells with an unclear driving stage, and the stage after the maximum elastic drive stage is the natural water drive stage of the wells with an unclear driving stage.

[0033] The present invention is further configured as follows: when there is no relatively constant volume well in the pure elastic drive section in the well group where the well with an unclear driving stage is located, the driving stage of the well with an unclear driving stage is divided according to the energy indication curve of the well group, and the stage where the slope of the curve becomes smaller is divided into elastic drive, and the stage where the slope of the curve becomes larger is divided into natural water drive.

[0034] The present invention is further configured as follows: in S1, the fracture-cavity oil wells are divided into conventional oil wells, wells with obvious water invasion and wells with inconspicuous other driving stages according to the energy indication curve.

[0035] In summary, compared with the prior art, the present invention has the following beneficial effects: the present invention determines the production characteristic type of a single well by relying on the characteristics of the production dynamic curve and the energy indication curve; for conventional oil wells, the boundary point between the elastic drive stage and the natural water drive stage is determined by the production dynamic curve; for wells with obvious water invasion, the boundary point between the elastic drive stage and the natural water drive stage is determined by the flow material balance method; for wells with unclear stages, the elastic drive stage and the natural water drive stage of the oil well are divided by comprehensive judgment using the mouth flow formula normalization method, the analogy stage boundary method, and the unit or well group stage division method. The present invention helps to solve the problem of unclear division of different production stages of fracture-cavity oil wells, especially the unclear transition from the elastic drive stage to the natural water drive stage, which affects the subsequent water invasion time and water invasion path, and other research problems related to the distribution of residual oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A technical flow chart of an embodiment;

[0037] Figure 2 is the production performance curve of a conventional oil well in the embodiment;

[0038] Figure 3 is the production indicator curve of the well with severe water invasion in the embodiment;

[0039] Figure 4 It is a schematic diagram of the correlation curve of the normalization of the mouth flow in the embodiment;

[0040] Figure 5 This is the production dynamic curve of a certain well;

[0041] Figure 6 The production dynamic curve after the pressure of a well is adjusted by normalizing the oil nozzle;

[0042] Figure 7 This is the production dynamic curve of a well after the normalized oil nozzle is adjusted for production. DETAILED DESCRIPTION

[0043] The technical solution of the present invention will be clearly described below in conjunction with the accompanying drawings. Obviously, the described embodiments are not all embodiments of the present invention, and all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the invention.

[0044] Example

[0045] like Figure 1 As shown, it is a flow chart of a preferred embodiment of the present invention, a method for dividing the elastic flooding stage and the natural water flooding stage of a fracture-cavity oil well, which comprises the following steps:

[0046] S1. Based on the production performance curve or energy indication curve, fracture-cavity oil wells are divided into conventional oil wells and oil wells with unclear driving stage. Among them, wells with unclear driving stage are further divided into wells with obvious water invasion and wells with other unclear driving stages.

[0047] Production dynamic curve: The oil wells whose curves first present a trapezoidal or triangular shape and then an S-shaped or parabolic shape are conventional oil wells; the oil wells whose overall slope of the curve presents a downward trend are wells with obvious water invasion; the other oil wells are wells with other unobvious driving stages.

[0048] Energy indication curve: The oil wells whose curve slope first decreases and then increases are conventional oil wells; the oil wells whose curve slope first decreases and then stabilizes are wells with obvious water invasion; the other oil wells are wells with unobvious other driving stages.

[0049] In this embodiment, the energy indication curve is used as the first basis for classifying conventional oil wells, wells with obvious water invasion, and wells with unclear other driving stages.

[0050] S2. For conventional oil wells, the production performance curve method is used to divide the elastic drive stage and the natural water drive stage; Figure 2 As shown in the figure, the curve characteristics of the production performance curve of conventional oil wells are linear decrease first, and then the slope gradually decreases until the curve is flat; the slope change law of the production performance curve of conventional oil wells is obtained by fitting, and the intersection between the linear decrease section and the slope decrease section is used as the stage division point between the elastic drive stage and the natural water drive stage.

[0051] The horizontal axis of the production performance curve is the cumulative oil production, and the vertical axis is the oil pressure, and the oil pressure is any one of the bottom hole flow pressure, wellhead oil pressure, and wellhead casing pressure. The cumulative oil production unit is t, and the oil pressure unit is MPa.

[0052] For wells with obvious water invasion, the flow material balance method is used to draw the production indicator curve, which is divided into the elastic drive stage and the natural water drive stage. The curve characteristic of the production indicator curve of the well with obvious water invasion is discontinuity. The overall curve is linearly decreasing first, and then the slope gradually decreases in a step-like manner until the curve is flat; the slope change law of the production dynamic curve of the well with obvious water invasion is obtained by fitting, and the intersection between the linear decreasing section and the slope decreasing section is used as the stage division point between the elastic drive stage and the natural water drive stage. The horizontal coordinate of the production indicator curve is the normalized cumulative oil production N pn , the vertical axis is the normalized output q n , the formula is as follows:

[0053]

[0054] Where NPn is normalized cumulative oil production, unit is 104t; N P is the cumulative oil production corresponding to the total pressure drop, in units of 104t; B o is the crude oil volume coefficient corresponding to the total pressure drop, dimensionless; C t is the comprehensive compression coefficient, which is a given value in MPa-1; B oi is the volume coefficient of the original crude oil, dimensionless; ΔP is the total pressure drop, in MPa;

[0055]

[0056] In the formula, q n is the normalized yield, unit is t / d·MPa -1 ; q is the output, unit is t / d; ΔP is the total pressure drop, unit is MPa.

[0057] In this embodiment, the comprehensive compression coefficient C t It is the sum of the rock compressibility coefficient and the crude oil compressibility coefficient, both of which are obtained through experiments.

[0058] For other wells with unclear driving stages, production performance curves, production indicator curves and water content curves are drawn based on the change law of nozzle flow to divide the elastic drive stage and natural water drive stage. Specifically:

[0059] like Figure 4 As shown, the nozzle output is normalized to obtain the normalized nozzle adjustment output q t The normalization process steps are: first, select the reference nozzle; second, give the formula coefficient of each nozzle; third, convert the output and pressure of each nozzle according to the corresponding formula coefficient to obtain the corresponding normalized nozzle adjustment output q t ;q t The calculation formula is as follows:

[0060]

[0061] In the formula, q t is the normalized nozzle adjustment output, unit is t / d; c is the formula coefficient, which is a given value, unit is t / d·MPa-1·mm-2; Pt is the normalized nozzle adjustment pressure, which is a given value, unit is MPa; D0 is the nozzle diameter, unit is mm.

[0062] In this embodiment, the coefficient c of the formula is the ratio between the output and pressure data of the nozzle in the stable production stage of the early production period obtained by linear fitting.

[0063] Taking the accumulated oil production as the horizontal axis, in the same coordinate system, the oil pressure and the normalized oil nozzle are used to adjust the production q t and water content as the ordinate, construct three curves;

[0064] When the oil pressure is high and the water content is 0, q t The curve is divided into elastic flooding stage and natural water flooding stage in turn. t The stage where the curve amplitude is large and gradually decays is divided into the elastic drive stage. t The stage when the curve amplitude decreases and tends to be stable is divided into the natural water drive stage. As the exploitation progresses, the oil well will also experience typical characteristics of the natural water drive stage, such as a sharp drop in oil pressure, a sharp drop in normalized nozzle adjustment production, and an increase in water content.

[0065] Specifically, for oil wells that cannot be divided into the elastic drive stage and the natural water drive stage based on the law of mouth flow changes, the elastic drive stage and the natural water drive stage are divided by the recovery rate analogy method. The recovery rate analogy method specifically includes: for the relatively constant volume wells in the pure elastic drive stage in the well group, the maximum elastic drive stage recovery rate curves of these wells are counted; the pressure change of the relatively constant volume wells is small, and the wellhead flow is stable; the maximum elastic drive stage is the stage with the highest recovery rate achieved by the elastic drive mechanism; then, the maximum elastic drive stage of the well with an unclear driving stage is determined by analogy based on the known maximum elastic drive stage recovery rate curve, the stage before the maximum elastic drive stage is the elastic drive stage of the well with an unclear driving stage, and the stage after the maximum elastic drive stage is the natural water drive stage of the well with an unclear driving stage.

[0066] Specifically, when there is no relatively constant volume well in the pure elastic drive section in the well group where the well with an unclear driving stage is located, the driving stage of the well with an unclear driving stage is divided according to the energy indicator curve of the well group, and the stage where the slope of the curve becomes smaller is divided into elastic drive, and the stage where the slope of the curve becomes larger is divided into natural water drive.

[0067] like Figure 5-7As shown in the figure, a method for dividing the elastic drive stage and the natural water drive stage of a fracture-cavity oil well is applied in a well. The production system of the well is frequently adjusted. The pressure and production are adjusted by normalizing the nozzle. Analysis of the normalized pressure curve shows that the oil pressure has an obvious upward trend in the water zone stage under the same nozzle, and the production time point for dividing the elastic drive and water drive stages is determined to be 590 days; analysis of the normalized production curve shows that the production has an obvious upward trend in the water zone stage under the same nozzle, and the production time point for dividing the elastic drive and water drive stages is determined to be 625 days. The difference in the comprehensive stage division results is about 6%, and the overall difference is small. Since the pressure response speed is faster than the production, the pressure identification result is mainly 590 days.

[0068] In summary, this embodiment relies on the characteristics of the production performance curve and the energy indication curve to determine the production characteristic type of a single well; for conventional oil wells, the production performance curve is used to determine the boundary between the elastic drive stage and the natural water drive stage; for wells with obvious water invasion, the flow material balance method is used to determine the boundary between the elastic drive stage and the natural water drive stage; for wells with unclear stages, the elastic drive stage and the natural water drive stage of the oil well are divided by comprehensive judgment using the mouth flow formula normalization method, the analogy stage boundary method, and the unit or well group stage division method. This method helps to solve the problem of unclear division of different production stages of fracture-cavity oil wells, especially the unclear transition from the elastic drive stage to the natural water drive stage, which affects the subsequent water invasion time and water invasion path, and other research problems related to the distribution of residual oil.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A comprehensive division method for elastic flooding stage and natural water flooding stage of fracture-cavity oil wells, characterized by: S1. Based on the production performance curve or energy indication curve, the fracture-cavity oil wells are divided into conventional oil wells and oil wells with inconspicuous driving stages. The wells with inconspicuous driving stages are further divided into wells with obvious water invasion and wells with other inconspicuous driving stages. Production dynamic curve: The oil wells whose curves first present trapezoidal or triangular shapes and then present S-shaped or parabolic shapes are conventional oil wells; the oil wells whose overall slope of the curves presents a downward trend are wells with obvious water invasion; The other wells are all wells with insignificant other driving stages; Energy indication curve: The oil wells whose curve slope first decreases and then increases are conventional oil wells; the oil wells whose curve slope first decreases and then stabilizes are wells with obvious water invasion; The other wells are all wells with insignificant other driving stages; S2. For conventional oil wells, the elastic drive stage and the natural water drive stage are divided according to the production performance curve; For wells with obvious water invasion, the flow material balance method is used to draw the production indicator curve, which is divided into the elastic drive stage and the natural water drive stage. For wells with unclear drive stages, the production dynamic curve, production indicator curve and water content curve are drawn based on the mouth flow change law to divide the elastic drive stage and the natural water drive stage.

2. The comprehensive division method of elastic flooding stage and natural water flooding stage of a fracture-cavity oil well according to claim 1 is characterized by: The curve characteristics of the production performance curve of conventional oil wells are linear decrease first, then the slope gradually decreases until the curve is flat; the slope change law of the production performance curve of conventional oil wells is obtained by fitting, and the intersection between the linear decrease section and the slope decrease section is used as the stage division point between the elastic drive stage and the natural water drive stage.

3. The comprehensive division method of elastic flooding stage and natural water flooding stage of a fracture-cavity oil well according to claim 2 is characterized by: The horizontal coordinate of the production performance curve is the cumulative oil production, and the vertical coordinate is the oil pressure. The oil pressure is any one of the bottom hole flow pressure, the wellhead oil pressure, and the wellhead casing pressure.

4. The comprehensive division method of elastic flooding stage and natural water flooding stage of a fracture-cavity oil well according to claim 1 is characterized by: The production indicator curve of the well with obvious water invasion is characterized by discontinuity. It first decreases linearly as a whole, and then the slope gradually decreases in steps until the curve becomes flat. The slope change law of the production dynamic curve of the well with obvious water invasion is obtained by fitting, and the intersection between the linear decreasing section and the slope decreasing section is used as the stage division point between the elastic drive stage and the natural water drive stage.

5. The comprehensive division method of elastic flooding stage and natural water flooding stage of a fracture-cavity oil well according to claim 3 is characterized by: For wells with obvious water invasion, the horizontal axis of the production indicator curve is the normalized cumulative oil production N. pn , the vertical axis is the normalized output q n , the formula is as follows: Where N Pn is the normalized cumulative oil production, the unit is 10 4 t;N P is the cumulative oil production corresponding to the total pressure drop, in units of 10 4 t; B o is the volume coefficient of crude oil corresponding to the total pressure drop, dimensionless; C t is the comprehensive compression coefficient, a given value in MPa -1 ; B oi is the original crude oil volume coefficient, dimensionless; ΔP is the total pressure drop, in MPa; In the formula, q n is the normalized yield, unit is t / d·MPa -1 ; q is the output, unit is t / d; ΔP is the total pressure drop, unit is MPa.

6. A comprehensive division method for elastic flooding stage and natural water flooding stage of a fracture-cavity oil well according to claim 4, characterized in that: Comprehensive compression coefficient C t It is the sum of the rock compressibility coefficient and the crude oil compressibility coefficient, both of which are obtained through experiments.

7. The comprehensive division method of elastic flooding stage and natural water flooding stage of a fracture-cavity oil well according to claim 1 is characterized by: Based on the change law of mouth flow, the elastic flooding stage and natural water flooding stage are divided into: Normalize the nozzle output to obtain the normalized nozzle adjustment output q t ; The normalization process steps are: first, select the reference nozzle; Second, give the formula coefficients for each nozzle; Third, convert the output and pressure of each nozzle according to the corresponding formula coefficient to obtain the corresponding normalized nozzle adjustment output q t ; Taking the accumulated oil production as the horizontal axis, in the same coordinate system, the oil pressure and the normalized oil nozzle are used to adjust the production q t and water content as the ordinate, construct three curves; When the oil pressure is high and the water content is 0, q t The curve is divided into elastic flooding stage and natural water flooding stage in turn. t The stage where the curve amplitude is large and gradually decays is divided into the elastic drive stage. t The stage when the curve amplitude decreases and tends to be stable is divided into the natural water drive stage.

8. A comprehensive division method for elastic flooding stage and natural water flooding stage of a fracture-cavity oil well according to claim 7, characterized in that: q t The calculation formula is as follows: In the formula, q t is the normalized nozzle adjustment output, unit is t / d; c is the formula coefficient, which is a given value, unit is t / d·MPa -1 mm -2 ; Pt is the normalized nozzle adjustment pressure, which is a given value in MPa; D0 is the nozzle diameter in mm.

9. A comprehensive division method for elastic flooding stage and natural water flooding stage of a fracture-cavity oil well according to claim 8, characterized in that: The coefficient c of the formula is the ratio between the output and pressure data of the nozzle in the stable production stage of the early production period obtained by linear fitting.

10. The comprehensive division method of elastic flooding stage and natural water flooding stage of a fracture-cavity oil well according to claim 1, characterized in that: For oil wells that cannot be divided into elastic drive stage and natural water drive stage based on the mouth flow change law, the elastic drive stage and natural water drive stage are divided by recovery factor analogy method.

11. A comprehensive division method for elastic flooding stage and natural water flooding stage of a fracture-cavity oil well according to claim 10, characterized in that: The recovery rate analogy method specifically consists in that, for the relatively constant volume wells in the pure elastic drive stage in the well group, the maximum elastic drive stage recovery rate curves of these wells are counted; the pressure change of the relatively constant volume wells is small, and the wellhead flow is stable; the maximum elastic drive stage is the stage with the highest recovery rate achieved by the elastic drive mechanism; then, based on the known maximum elastic drive stage recovery rate curve, the maximum elastic drive stage of the wells with an unclear driving stage is determined by analogy, the stage before the maximum elastic drive stage is the elastic drive stage of the wells with an unclear driving stage, and the stage after the maximum elastic drive stage is the natural water drive stage of the wells with an unclear driving stage.

12. A comprehensive division method for elastic flooding stage and natural water flooding stage of a fracture-cavity oil well according to claim 11, characterized in that: When there is no relatively constant volume well in the pure elastic drive section in the well group where the well with unclear driving stage is located, the driving stage of the well with unclear driving stage is divided according to the energy indicator curve of the well group. The stage where the slope of the curve becomes smaller is divided into the elastic drive stage, and the stage where the slope of the curve becomes larger is divided into the natural water drive stage.

13. The comprehensive division method of elastic flooding stage and natural water flooding stage of a fracture-cavity oil well according to claim 1, characterized in that: In S1, the energy indicator curve is used to divide the fracture-cavity oil wells into conventional oil wells, wells with obvious water invasion, and wells with unclear other driving stages.

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