A construction method for simultaneous injection and production of horizontal wells

Abstract

The present invention discloses a construction method for simultaneous injection and production of horizontal wells, which specifically includes: based on the development history, cumulative output, remaining oil, and formation energy of the horizontal well before it is put into production, the formation deficit volume is predicted according to the original formation pressure, the initial production, the current production, and the current formation pressure; the reservoir physical property parameters and the fracturing construction parameters are analyzed when the horizontal well is put into production to obtain the output of each layer section, and then the water injection layer section and the oil production layer section are determined; the original well downhole production string is pulled out, and the simultaneous injection and production integrated string is lowered; after water is injected into the integrated string, the oil production time is determined according to the current formation pressure change. The present invention realizes simultaneous oil production by water injection in the same layer section of the horizontal well, and improves the single well production while supplementing energy, that is, the average daily increase in liquid per well is increased from 4.0t to 7.0t, and the daily increase in oil production is increased from 0.3t to 0.6t.

Description

Technical Field

[0001] The invention relates to the technical field of energy and production enhancement of horizontal wells in petroleum geological development, and in particular to a simultaneous injection and production construction method for horizontal wells. Background Art

[0002] In the development process of most horizontal wells in China, the initial production capacity is high. As time goes by and there is no well water injection for energy replenishment, the production capacity decreases rapidly during the development process. During the stable production period, the remaining recoverable reserves are large, but the degree of exploitation is low. At present, in response to the above problems, the development is generally carried out by horizontal well energy storage or water well fracturing. In the short term, the single well production can be increased to a certain extent, but it has still decreased significantly for a long time, and the problem of increasing decrease caused by no energy replenishment has not been fundamentally solved.

[0003] By analyzing the development rules and characteristics of horizontal wells, it is found that the conventional development model still cannot fundamentally solve the problem. In order to solve the problem of accelerated decline due to lack of energy replenishment in horizontal wells, it is necessary to invent a horizontal well energy replenishment development technology to increase both formation energy and development effect. Summary of the invention

[0004] In order to solve the problem of energy replenishment after the horizontal well is put into production, the present invention provides a simultaneous injection and production construction method for horizontal wells, which performs water injection in layers with a lower production degree and oil production in layers with a higher production degree, thereby increasing the production of a single well.

[0005] To achieve the above objectives, the present application proposes a simultaneous injection and production construction method for a horizontal well, which specifically includes:

[0006] Based on the development history, cumulative output, remaining oil, and formation energy of the horizontal well before it is put into production, the formation deficit volume is predicted according to the original formation pressure, initial production, current production, and current formation pressure;

[0007] Analyze the reservoir physical property parameters and fracturing construction parameters when the horizontal well is put into production to obtain the output of each layer section, and then determine the water injection layer section and oil production layer section;

[0008] Pull out the original well's underground production string and put in an integrated injection and production string;

[0009] After water is injected into the integrated pipe string, the oil production time is determined according to the current formation pressure change.

[0010] Furthermore, the formation deficit volume is calculated as follows:

[0011] Q=Qo / ρ0*Bo+(Q cumulative production-Qo)*Bw-Q fracturing fluid*Bw

[0012] Among them, Q is the deficit (injection amount), the unit is m 3 ; Qo is the cumulative oil production, unit is t; ρ0 is the crude oil density, unit is g / cm 3 ; Bo is the volume coefficient of crude oil; Q cumulative production is the cumulative liquid production of a single well, in t; Bw is the volume coefficient of water, which can be taken as 1.001 (constant); Q fracturing fluid is the injection volume of fracturing fluid, in m 3 .

[0013] Furthermore, when the current formation pressure recovers to 60% of the initial formation pressure of exploitation, the integrated pipe string is used for oil production, and at the same time, the integrated pipe string is normally injected with water for energy replenishment.

[0014] Furthermore, the integrated tubing string adopts a down-injection and up-production type tubing string, which uses a packer to divide the horizontal section of the oil well into two sections, and implements water injection in the lower section and oil production in the upper section.

[0015] Furthermore, a check valve is provided at the tail of the horizontal section of the injection-down and production-up type pipe string, and a packer is provided between the check valve and the slag prevention tee, and oil in the upper section of the packer is produced through the slag prevention tee.

[0016] Furthermore, a centralizer is provided between the packer and the check pressure regulator.

[0017] Furthermore, a gravity anchor is provided at the turning point of the injection-down and production-up type pipe string, and a screw pump is provided above the gravity anchor.

[0018] Furthermore, when the check pressure regulator is pressurized to 21 MPa, the packer expands and opens. There is a spring ball in the check pressure regulator, which opens during water injection and closes during oil production, thereby achieving repeated alternation of water injection and oil production.

[0019] Furthermore, a check valve is used to ensure that the screw pump rotor is lowered without pressure relief, and if the formation pressure is low, water injection is continued to replenish energy.

[0020] Furthermore, the integrated pipe string adopts an injection-up and production-down type pipe string, which divides the horizontal oil layer into two sections, and implements water injection in the upper section and oil production in the lower section.

[0021] Furthermore, a pressure regulator is provided at the tail of the horizontal section of the injection-up and production-down type pipe string, and a centering packer is provided in front of the pressure regulator.

[0022] Furthermore, a gravity anchor is provided at the turning point of the injection-up and production-down type pipe string, and a screw pump is provided on the gravity anchor.

[0023] As a further step, after the packer with the righting seal is expanded, the pressure regulator is opened to inject water into the upper section of the horizontal well from the annulus of the casing, and oil is produced in the lower section at the same time.

[0024] As a further improvement, the injection-up and production-down type tubing string can realize water injection and oil production at the same time, and the water injection volume is dynamically adjusted according to the change of oil well production.

[0025] As a further step, the method for determining the formation pressure of the horizontal well is: taking the average daily liquid production during stable production at the initial stage of production as the base value, and then dividing the average daily liquid production during normal production before the integrated tubing string construction by the base value to obtain a percentage.

[0026] As a further step, the ratio of the dynamic liquid level corresponding to the initial production stage to the dynamic liquid level before the integrated tubing string construction is used to represent the current formation pressure. The base value is taken as the time when the current formation pressure recovers to 60% of the initial production formation pressure to calculate how many cubic meters of pressure need to be injected, and then the standard for water injection and energy replenishment is formulated. The oil production time is determined based on the daily water injection volume and the horizontal well formation pressure.

[0027] As a further step, the water injection layer section and the oil production layer section are determined as follows: first obtain the formation parameters of each perforation section of the horizontal well, and the calculation formula is: KiHi / μ, where Ki is the permeability of the i-th section; Hi is the thickness of the i-th oil layer; μ is the viscosity of the crude oil. Since the horizontal wells are developed in the same layer, the viscosity is calculated according to one value.

[0028] As a further step, after obtaining the value of each perforation section, the smallest one is taken as the base value, and the formation parameters of the remaining sections are divided by this value. If the ratio range is between 0-2, it is divided into the first section. If the ratio range is greater than 2 and less than 5, it is divided into the second section. The two sections are used for oil production or water injection respectively.

[0029] As a further step, reservoirs with formation parameters less than 2 have lower output, and perforation sections with formation parameters greater than 2 have a high degree of production and large deficits. The deficit sections are used as oil-producing sections due to their good reservoir properties and high oil saturation, and the sections with lower output are used as water injection sections for energy supplement.

[0030] Compared with the prior art, the above technical scheme adopted by the present invention has the following advantages: the present invention realizes simultaneous water injection and oil production in the same layer of a horizontal well by lowering an integrated injection and production pipe string into the well, injecting water through a layer with a lower production degree and producing oil through a layer with a higher production degree, thereby increasing the single well production while replenishing energy, that is, the average daily increase in liquid per well is increased from 4.0t to 7.0t, and the daily increase in oil is increased from 0.3t to 0.6t. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the structure of the injection-down and mining-up type pipe string;

[0032] Figure 2 This is a schematic diagram of the structure of the injection-up and mining-down type pipe string;

[0033] Explanation of the serial numbers in the figure: 1. Screw pump; 2. Gravity anchor; 3. Anti-slag tee; 4. Packer; 5. Centralizer; 6. Check valve; 7. Packer with centralizer; 8. Constant pressure device. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application, that is, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0035] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0036] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0037] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] Example 1

[0039] In view of the problems existing in the development of horizontal wells, under the current low international oil prices, in line with the principle of saving costs and improving efficiency, the technical means of simultaneous injection and simultaneous production are adopted, and the formation energy is supplemented by sewage reinjection. The process adopts the method of water injection at the front end of the horizontal section and oil production at the back end, or water injection at the back end of the horizontal section and oil production at the front end. It provides a construction method of simultaneous injection and simultaneous production for horizontal wells, which specifically includes:

[0040] Based on the development history, cumulative output, remaining oil, and formation energy of the horizontal well before it is put into production, the formation deficit volume is predicted according to the original formation pressure, initial production, current production, and current formation pressure;

[0041] Analyze the reservoir physical property parameters and fracturing construction parameters when the horizontal well is put into production to obtain the output of each layer section, and then determine the water injection layer section and oil production layer section;

[0042] Pull out the original well's underground production string and put in an integrated injection and production string;

[0043] After water is injected into the integrated pipe string, the oil production time is determined according to the current formation pressure change.

[0044] like Figure 1 As shown, when the integrated pipe string adopts the injection-down and production-up pipe string, the horizontal section of the oil well is divided into two sections by using a packer, and the lower section is injected with water and the upper section is produced with oil. The check valve 6 is pressurized to 21MPa, and the packer 4 is opened after expansion and sealing. There is a spring ball in the check valve that is opened when water is injected and closed when oil is produced. The check valve can be used to achieve no pressure relief when the rotor of the screw pump 1 is lowered. If the formation pressure is low, water injection can be continued to replenish energy. The anti-slag tee 3 is connected under the gravity anchor 2 to enable the production layer fluid to enter the screw pump. The pipe string can realize water injection and oil production alternately and repeatedly.

[0045] like Figure 2 As shown, when the integrated string adopts the injection-up and production-down type string, the horizontal oil layer is divided into two sections, and water is injected into the upper section and oil is produced in the lower section. After the packer 7 is sealed, the pressure regulator 8 is opened to inject water from the annulus of the casing into the upper section of the horizontal well, and oil is produced in the lower section at the same time. The string can realize water injection and oil production at the same time, and the water injection volume can be dynamically adjusted according to the change of oil well production.

[0046] Preferably, the formation deficit volume is calculated as follows:

[0047] Q=Qo / ρ0*Bo+(Q cumulative production-Qo)*Bw-Q fracturing fluid*Bw

[0048] Among them, Q is the deficit, the unit is m 3 ; Qo is the cumulative oil production, unit is t; ρ0 is the crude oil density, unit is g / cm 3 ; Bo is the volume coefficient of crude oil; Q cumulative production is the cumulative production of a single well, in t; Bw is the volume coefficient of water; Q fracturing fluid is the injection volume of fracturing fluid, in m 3 .

[0049] The method for determining the time of oil production and water injection is determined according to the formation pressure. The higher the formation pressure value, the stronger the liquid supply energy of the production layer section corresponding to the well. But the higher the better. The corresponding oil production capacity and the corresponding formation pressure value of each oil field are used as the judgment criteria. However, since the formation pressure test of horizontal wells is difficult, there is currently no better test method to determine the pressure values ​​of different sections in the same layer. Therefore, the concept of relative liquid volume ratio is introduced to replace the pressure change. The method for determining the formation pressure of horizontal wells is: the liquid production volume of the horizontal well is used as the benchmark for determination. The average daily liquid production volume during stable production at the initial stage of production is used as the base value, and then the average daily liquid production volume during normal production before the construction of the integrated pipe string is divided by the base value to obtain the percentage. The requirement is: under the condition that the working system has not changed. Or the ratio of the corresponding dynamic liquid level at the initial stage of production to the dynamic liquid level before the construction of the integrated pipe string is used to represent the current formation pressure level. Combined with the understanding of the overall production law in this area, under normal circumstances, when the current formation pressure is maintained at 60% or more of the formation pressure at the initial stage of production, the oil production level is good, so 60% is used as a reference value. The cumulative deficit is calculated according to the above formula, and the pressure recovery to 60% is used as the base value for estimation. It is then calculated how many cubic meters of water are needed to restore the formation pressure to 60%. The standard for water injection replenishment is then formulated, and the oil production time is determined based on the daily water injection volume and the formation pressure of the horizontal well.

[0050] Method for determining water injection layer section and oil production layer section: first obtain the formation parameters of each perforation section of the horizontal well, and the calculation formula is: KiHi / μ, where Ki is the permeability of the i-th section; Hi is the thickness of the i-th oil layer; μ is the viscosity of crude oil. Since the horizontal well is developed in the same layer, the viscosity is calculated according to one value. After obtaining the value of each perforation section, take the smallest one as the base value, and divide the formation parameters of the remaining sections by this value. If the ratio range is between 0-2, it is divided into the first section. If the ratio range is greater than 2 and less than 5, it is divided into the second section. The two sections are used for oil production or water injection respectively; the division of layers can be adjusted according to actual conditions. It is generally believed that the better the formation parameters, the better the reservoir development and the more output. Therefore, after the layer sections are divided, the output can be determined. The reservoir with formation parameters less than 2 has a lower output, and the perforation section with formation parameters greater than 2 has a higher degree of exploitation and a larger deficit. The deficit layer section is used as an oil production layer section because of its good reservoir physical properties and high oil saturation. The lower production layer is used as the water injection layer to supplement energy. Due to the pressure difference between the production layer and the water injection layer, water injection in the low production layer can easily displace the remaining oil into the depleted layer.

[0051] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A method for simultaneous injection and production of horizontal wells, characterized in that: Specifically include: Based on the development history, cumulative output, remaining oil, and formation energy of the horizontal well before it is put into production, the formation deficit volume is predicted according to the original formation pressure, initial production, current production, and current formation pressure; Analyze the reservoir physical property parameters and fracturing construction parameters when the horizontal well is put into production to obtain the output of each layer section, and then determine the water injection layer section and oil production layer section; Pull out the original well's underground production string and put in an integrated injection and production string; After injecting water into the integrated pipe string, the oil production time is determined according to the current formation pressure change; The integrated pipe string adopts a down-injection and up-production type pipe string, which uses a packer to divide the horizontal section of the oil well into two sections, and implements water injection in the lower section and oil production in the upper section; A check valve is provided at the tail of the horizontal section of the injection-down production-up type pipe string, and a packer is provided between the check valve and the slag prevention tee, and the oil in the upper section of the packer is produced through the slag prevention tee; when the check valve is pressurized to 21MPa, the packer expands and seals and opens, and a spring ball is provided in the check valve, which is opened during water injection and closed during oil production, so that water injection and oil production can be alternately and repeatedly implemented; The water injection layer section and the oil production layer section are determined as follows: first, the formation parameters of each perforation section of the horizontal well are obtained, and the calculation formula is: KiHi / μ, where Ki is the permeability of the i-th section; Hi is the thickness of the i-th oil layer; μ is the viscosity of the crude oil. Since the horizontal wells are developed in the same layer, the viscosity is calculated according to one value; After obtaining the value of each perforation section, take the smallest one as the base value, and divide the formation parameters of the remaining sections by this value. If the ratio range is between 0 and 2, it is divided into the first section. If the ratio range is greater than 2 and less than 5, it is divided into the second section. The two sections are used for oil production or water injection respectively. Reservoirs with formation parameters less than 2 have low output, and perforation sections with formation parameters greater than 2 have a high degree of production and large deficits. The deficit sections are used as oil-producing sections because of their good reservoir properties and high oil saturation, and the sections with lower output are used as water injection sections for energy supplement.

2. A method for simultaneous injection and production of horizontal wells according to claim 1, characterized in that: The calculation method of the formation deficit volume is: Q=Qo / ρ0*Bo+(Q cumulative production-Qo)*Bw-Q fracturing fluid*Bw Among them, Q is the deficit, the unit is m 3 ; Qo is the cumulative oil production, unit is t; ρ0 is the crude oil density, unit is g / cm 3 ; Bo is the volume coefficient of crude oil; Q cumulative production is the cumulative liquid production of a single well, in t; Bw is the volume coefficient of water; Q fracturing fluid is the injection volume of fracturing fluid, in m 3 .

3. A method for simultaneous injection and production of horizontal wells according to claim 1, characterized in that: When the current formation pressure recovers to 60% of the initial formation pressure of exploitation, the integrated pipe string is used for oil production, and at the same time, the integrated pipe string is normally injected with water for energy replenishment.

4. A method for simultaneous injection and production of horizontal wells according to claim 1, characterized in that: A centralizer is provided between the packer and the check pressure regulator.

5. A method for simultaneous injection and production of horizontal wells according to claim 1, characterized in that: A gravity anchor is arranged at the turning point of the injection-down and production-up type pipe string, and a screw pump is arranged above the gravity anchor.

6. A method for simultaneous injection and production of horizontal wells according to claim 1, characterized in that: The check valve is used to ensure that the screw pump rotor is lowered without pressure relief. If the formation pressure is low, water injection will continue to replenish energy.

7. A method for simultaneous injection and production of horizontal wells according to claim 1, characterized in that: The integrated pipe string adopts an injection-up and production-down type pipe string, which divides the horizontal oil layer into two sections, and implements water injection in the upper section and oil production in the lower section.

8. A method for simultaneous injection and production of horizontal wells according to claim 7, characterized in that: A pressure regulator is arranged at the tail of the horizontal section of the injection-up and production-down type pipe string, and a packer with a centralizing function is arranged in front of the pressure regulator.

9. A method for simultaneous injection and production of horizontal wells according to claim 7, characterized in that: A gravity anchor is arranged at the turning point of the injection-up and production-down type pipe string, and a screw pump is arranged on the gravity anchor.

10. A method for simultaneous injection and production of horizontal wells according to claim 8, characterized in that: After the packer with the righting seal is expanded, the pressure regulator is opened to realize water injection from the annulus of the oil casing to the upper section of the horizontal well, and oil is produced in the lower section at the same time.

11. A method for simultaneous injection and production of horizontal wells according to claim 7, characterized in that: The injection-up and production-down type pipe string can realize water injection and oil production at the same time, and the water injection volume is dynamically adjusted according to the change of oil well production.

12. A method for simultaneous injection and production of horizontal wells according to claim 1, characterized in that: The method for determining the current formation pressure is: taking the average daily liquid production during stable production at the initial stage of production as the base value, and then dividing the average daily liquid production during normal production before the construction of the integrated tubing string by the base value to obtain a percentage, and using the percentage to represent the current formation pressure; or, using the ratio of the corresponding dynamic liquid level at the initial stage of production to the dynamic liquid level before the construction of the integrated tubing string to represent the current formation pressure, and using the current formation pressure to recover to 60% of the initial formation pressure as the base value to calculate how many cubic meters of water need to be injected, and then formulate the standard for water injection and energy replenishment, and determine the oil production time in combination with the daily water injection volume and the formation pressure of the horizontal well.

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