Method for calculating effective cleanout time in low permeability reservoir near wellbore region

Abstract

The present application relates to a low permeability reservoir near wellbore area effective cleanout time calculation method, and belongs to the technical field of oil and gas exploitation. The low permeability reservoir near wellbore area effective cleanout time calculation method disclosed by the present application comprises the following steps: obtaining the original formation pressure, formation volume density and permeability of a target formation; determining the minimum production pressure difference required to overcome the flow resistance of the near wellbore pollution zone based on the permeability; determining the maximum production pressure difference based on the positive correlation between the rock skeleton strength and the formation volume density; determining the reasonable production pressure difference of the oil well; keeping the gas well producing at a constant reasonable production pressure difference to obtain production data; drawing a relationship graph between the cumulative total liquid production and the production time and a two-dimensional right-angle Cartesian coordinate graph based on the production data; determining the cumulative liquid production required for effective well cleanout; and determining the effective cleanout time of the low permeability reservoir near wellbore area. The present application is more in line with the actual situation of the formation, and can provide theoretical support for determining the effective cleanout operation time of the reservoir.

Description

Technical Field

[0001] This invention relates to a method for calculating the effective well cleaning time in the near-wellbore area of ​​low-permeability oil reservoirs, belonging to the field of oil and gas extraction technology. Background Technology

[0002] In low-permeability reservoirs, the formation of near-wellbore mud cake, drilling and completion fluid intrusion, and solid particles during drilling and completion can cause severe formation damage. Well cleaning operations are crucial for mitigating near-wellbore damage and ensuring normal reservoir production by effectively removing contaminated fluids and mud cake that have invaded the formation. During well cleaning, the produced fluids, along with the drilling and completion fluids, exhibit highly unsteady flow characteristics, making transient fluid flow characterization difficult and hindering the determination of a suitable well cleaning operation regime. This significantly impacts the accuracy of subsequent testing data and production capacity.

[0003] Therefore, it is necessary to establish a method for calculating the effective well cleaning time in the near-well zone of low-permeability reservoirs, so as to provide a theoretical basis for the formulation of a reasonable well cleaning operation system for reservoirs. Summary of the Invention

[0004] To address the aforementioned problems, this invention primarily overcomes the shortcomings of existing technologies by proposing a method for calculating the effective well cleaning time in the near-wellbore area of ​​low-permeability reservoirs. This invention determines the effective well cleaning operation time by establishing a mathematical relationship between downhole pressure and flow rate. This method is well-founded, more consistent with actual formation conditions, and provides theoretical support for determining the effective well cleaning operation time in oil reservoirs.

[0005] The technical solution provided by this invention to solve the above-mentioned technical problems is: a method for calculating the effective well cleaning time in the near-wellbore area of ​​low-permeability oil reservoirs, comprising the following steps:

[0006] Obtain the original formation pressure, formation volume density, and permeability of the target formation;

[0007] Determine the minimum production pressure differential required to overcome the flow resistance of the near-wellbore contamination zone based on permeability;

[0008] The maximum production pressure differential is determined based on the positive correlation between the strength of the rock skeleton and the bulk density of the formation.

[0009] The reasonable production pressure difference of an oil well is determined by balancing the minimum and maximum production pressure difference.

[0010] Maintain gas well production under a constant and reasonable production pressure differential to obtain production data;

[0011] A graph showing the relationship between cumulative total liquid production and production time was drawn based on production data.

[0012] A two-dimensional Cartesian coordinate graph was plotted based on the production data, showing the square of the wellhead flow rate divided by the reasonable production pressure differential and the cumulative total fluid production.

[0013] The cumulative fluid production required for effective well cleaning is determined based on a two-dimensional Cartesian coordinate graph.

[0014] Based on the relationship between cumulative total fluid production and production time, and the cumulative fluid production required for effective well cleaning, the effective well cleaning time in the near-wellbore area of ​​low-permeability reservoirs is determined.

[0015] A further technical solution is that the original formation pressure is obtained by downhole pressure gauges, and the formation volume density and permeability are obtained by logging tools.

[0016] A further technical solution is that the formula for calculating the minimum production pressure difference is:

[0017]

[0018] In the formula: It is the minimum production pressure differential, in psi; k It refers to penetration rate, mD.

[0019] A further technical solution is that the formula for calculating the maximum production pressure difference is:

[0020]

[0021] In the formula: It is the maximum production pressure differential, in psi; It is the formation bulk density measured by radioactive logging curves, in g / m³. 3 .

[0022] A further technical solution is that the formula for calculating the reasonable production pressure difference is:

[0023]

[0024] In the formula: It is the maximum production pressure differential, in psi; It is the minimum production pressure differential, in psi; This is the safety factor, taken as 0.5, dimensionless; It is the reasonable production pressure differential, psi.

[0025] A further technical solution is that the production data includes the flow rate of wellhead fluid produced at different times and the cumulative total fluid production.

[0026] A further technical solution is that determining the cumulative fluid production required for effective well cleaning based on a two-dimensional Cartesian coordinate graph includes linearly fitting the descending segment of the two-dimensional Cartesian coordinate graph, extending the linear fitting line to the X-axis, and reading the coordinates of the intersection point of the fitting line and the X-axis. This coordinate value is the cumulative fluid production required for effective well cleaning.

[0027] A further technical solution is that determining the effective well cleaning time in the near-wellbore area of ​​a low-permeability reservoir based on the relationship between the cumulative total fluid production and production time, and the cumulative fluid production required for effective well cleaning, includes finding the production time corresponding to the cumulative fluid production required for effective well cleaning in the relationship between the cumulative total fluid production and production time, which is the effective well cleaning time in the near-wellbore area of ​​the low-permeability reservoir.

[0028] The beneficial effects of this invention are as follows: This invention utilizes well logging data and production monitoring data to obtain the fluid volume required for effective well cleaning in the near-wellbore area of ​​an oil well. The effective cleaning time is determined by referring to a graph showing the relationship between cumulative total fluid production and production time. Compared to traditional assessment methods, this method is reliable in principle, more convenient and faster, and can provide theoretical support for determining the well cleaning operation time in the near-wellbore area of ​​low-permeability reservoirs. Attached Figure Description

[0029] Figure 1 This is a two-dimensional rectangular Cartesian coordinate graph;

[0030] Figure 2 This is a graph showing the relationship between the cumulative total liquid production and production time. Detailed Implementation

[0031] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] The method for calculating the effective well cleaning time in the near-wellbore area of ​​low-permeability reservoirs provided by this invention includes the following steps:

[0033] I. Obtaining the original formation pressure using downhole pressure gauges during drilling =4600psi, formation volume density obtained using logging tools. =2.35g / m 3 and penetration rate k =50mD;

[0034] II. Based on the permeability of the target formation, calculate the minimum production pressure differential required to overcome the flow resistance of the near-wellbore contaminated zone. =282.00psi;

[0035]

[0036] In the formula: It is the minimum production pressure differential, in psi; k It refers to penetration rate, mD.

[0037] III. Calculate the maximum production pressure difference based on the positive correlation between the strength and density of the rock skeleton. =897.19psi;

[0038]

[0039] In the formula: It is the maximum production pressure differential, in psi; It is the formation bulk density measured by radioactive logging curves, in g / m³. 3 .

[0040] IV. Calculate the reasonable production pressure difference for the oil well by balancing the minimum and maximum production pressure difference. ;

[0041]

[0042] In the formula: This is the safety factor, taken as 0.5, dimensionless; It is the reasonable production pressure differential, psi.

[0043] V. Maintain a constant and reasonable production pressure differential at the gas well. Production was carried out, and the flow rate of the wellhead produced fluid at different times was recorded. Total cumulative liquid production Production data, etc.

[0044] VI. Calculate the cumulative total liquid production based on the production data. Relationship with production time (e.g.) Figure 2 (as shown)

[0045] 7. Draw a graph based on the production data, using the square of the wellhead flow rate divided by the reasonable production pressure differential. Total cumulative liquid production Two-dimensional Cartesian coordinate graph (e.g.) Figure 1 As shown in the figure, the vertical axis represents the square divided by the reasonable production pressure difference, and the horizontal axis represents the cumulative total liquid production.

[0046] 8. Linear fitting of the square of the flow rate divided by the reasonable production pressure difference Total cumulative liquid production In the descending segment of the two-dimensional Cartesian coordinate graph, extend the linear fitting line to the X-axis and read the coordinates of the intersection point of the fitting line and the X-axis. This coordinate value is the cumulative fluid production required for effective well cleaning. (1.7Mstb);

[0047] 9. In the cumulative total liquid production Find the cumulative fluid production required for effective well cleaning in the graph showing the relationship between production time and time. Corresponding production time tThis is the effective well cleaning time in the near-well area of ​​a low-permeability reservoir (2.1 days).

[0048] The above description is not intended to limit the present invention in any way. Although the present invention has been disclosed through the above embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall fall within the scope of the present invention.

Claims

1. A method for calculating the effective well cleaning time in the near-wellbore area of ​​a low-permeability oil reservoir, characterized in that, Includes the following steps: Obtain the original formation pressure, formation volume density, and permeability of the target formation; Determine the minimum production pressure differential required to overcome the flow resistance of the near-wellbore contamination zone based on permeability; The maximum production pressure differential is determined based on the positive correlation between the strength of the rock skeleton and the bulk density of the formation. The reasonable production pressure difference of an oil well is determined by balancing the minimum and maximum production pressure difference. Maintain gas well production under a constant and reasonable production pressure differential to obtain production data; A graph showing the relationship between cumulative total liquid production and production time was drawn based on production data. A two-dimensional Cartesian coordinate graph was plotted based on the production data, showing the square of the wellhead flow rate divided by the reasonable production pressure differential and the cumulative total fluid production. The cumulative fluid production required for effective well cleaning is determined based on a two-dimensional Cartesian coordinate graph. Based on the relationship between cumulative total fluid production and production time, and the cumulative fluid production required for effective well cleaning, the effective well cleaning time in the near-wellbore area of ​​low-permeability reservoirs is determined.

2. The method for calculating the effective well cleaning time in the near-wellbore area of ​​a low-permeability reservoir according to claim 1, characterized in that, The original formation pressure was obtained by downhole pressure gauges, and the formation volume density and permeability were obtained by logging tools.

3. The method for calculating the effective well cleaning time in the near-wellbore area of ​​a low-permeability reservoir according to claim 1, characterized in that, The formula for calculating the minimum production pressure difference is: In the formula: It is the minimum production pressure differential, in psi; k It refers to penetration rate, mD.

4. The method for calculating the effective well cleaning time in the near-wellbore area of ​​a low-permeability reservoir according to claim 1, characterized in that, The formula for calculating the maximum production pressure difference is: In the formula: It is the maximum production pressure differential, in psi; It is the formation bulk density measured by radioactive logging curves, in g / m³. 3 .

5. The method for calculating the effective well cleaning time in the near-wellbore area of ​​a low-permeability reservoir according to claim 1, characterized in that, The formula for calculating the reasonable production pressure difference is: In the formula: It is the maximum production pressure differential, in psi; It is the minimum production pressure differential, in psi; This is the safety factor, taken as 0.5, which is dimensionless. It is the reasonable production pressure differential, psi.

6. The method for calculating the effective well cleaning time in the near-wellbore area of ​​a low-permeability reservoir according to claim 1, characterized in that, The production data includes the flow rate of wellhead fluid at different times and the cumulative total fluid production.

7. The method for calculating the effective well cleaning time in the near-wellbore area of ​​a low-permeability reservoir according to claim 1, characterized in that, The determination of the cumulative fluid production required for effective well cleaning based on a two-dimensional Cartesian coordinate graph includes linearly fitting the descending segment of the two-dimensional Cartesian coordinate graph, extending the linear fitting line to the X-axis, and reading the coordinates of the intersection point of the fitting line and the X-axis. This coordinate value is the cumulative fluid production required for effective well cleaning.

8. The method for calculating the effective well cleaning time in the near-wellbore area of ​​a low-permeability reservoir according to claim 1, characterized in that, The determination of the effective well cleaning time in the near-wellbore area of ​​a low-permeability reservoir based on the relationship between the cumulative total fluid production and production time, and the cumulative fluid production required for effective well cleaning, includes finding the production time corresponding to the cumulative fluid production required for effective well cleaning in the relationship between the cumulative total fluid production and production time. This is the effective well cleaning time in the near-wellbore area of ​​the low-permeability reservoir.

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