Characterization method for energy utilization efficiency of water-flooding oil reservoir

Abstract

The invention provides a characterization method for the energy utilization efficiency of a water-flooding oil reservoir. The characterization method comprises the steps that S1, basic geological parameters and development parameters of a target oil reservoir are collected; s2, establishing a numerical simulation model of the oil-water two-phase flow; s3, calculating to obtain oil phase, water phase and total viscous resistance loss in the water drive development process; and S4, the energy utilization efficiency of the oil reservoir in the water injection development process is obtained. By calculating the water-flooding oil reservoir energy consumption and the energy utilization efficiency, the main control factors influencing the energy utilization efficiency in the water-flooding process and the change rule of the main control factors are obtained, the method has the advantages of being direct in calculation, high in flexibility and the like, and theoretical technical support is provided for efficient and green development of water-flooding oil reservoirs.

Description

Technical Field

[0001] This invention relates to the field of water-drive reservoir development technology, and in particular to a method for characterizing the energy utilization efficiency of water-injected reservoirs. Background Technology

[0002] Currently, most oilfields in China use water injection for extraction. This method involves injecting water into the formation to provide pressure, thereby increasing crude oil recovery and ensuring stable oil production. After years of research, it has been widely applied and has achieved good economic benefits. However, with the continuous development of water injection in oilfields, the water cut of the produced fluids is constantly increasing. On the one hand, the energy consumption of the entire development and production system is increasing daily; on the other hand, the proportion of energy consumption used for oil displacement is constantly decreasing, leading to a continuous decline in the energy utilization efficiency of the water drive process. How to reduce the total energy consumption of the water drive process and improve its energy utilization efficiency is an important goal and approach to achieving efficient and green development of water-driven oil reservoirs.

[0003] Water injection development systems comprise three subsystems: the water wellbore injection subsystem, the reservoir subsystem, and the oil wellbore lifting subsystem. Domestic and international research on energy consumption in injection-production systems primarily focuses on energy losses in the water injection and production wellbores, emphasizing energy losses at various nodes within the wellbores, condition assessments, influencing factor analyses, potential for improving system efficiency, and energy reduction technologies. Reservoir energy calculations mainly rely on approximate formation pressure assessments, without quantitative calculations or characterization of reservoir energy. Due to the complexity of underground seepage, research on the processes and mechanisms of energy consumption and utilization within reservoir subsystems is limited, resulting in relatively general analyses. Typically, calculations are performed to obtain the fluid energy extracted from the surface injection and production ends and the energy replenished by water injection over a certain period, calculating the underground energy utilization status of the water injection development reservoir and evaluating the energy utilization level during underground reservoir seepage. However, the distinction between oil displacement and water displacement energy consumption is not emphasized in energy consumption studies, and energy efficiency characterization is incomplete. Summary of the Invention

[0004] In view of the above problems, the present invention is proposed to provide a method for characterizing the energy utilization efficiency of water-injected reservoirs to overcome or at least partially solve the above problems.

[0005] According to one aspect of the present invention, a method for characterizing the energy utilization efficiency of water-injected reservoirs is provided, the characterization method comprising:

[0006] Step S1: Collect basic geological parameters and development parameters of the target reservoir;

[0007] Step S2: Establish a numerical simulation model of oil-water two-phase flow;

[0008] Step S3: Calculate the viscous resistance losses of the oil phase, water phase, and total viscous resistance during water drive development;

[0009] Step S4: Obtain the energy utilization efficiency of the reservoir during water injection development.

[0010] Optionally, the target reservoir can be developed using water injection.

[0011] Optionally, step S2: establishing a numerical simulation model of oil-water two-phase flow specifically includes:

[0012] Based on traditional reservoir numerical simulation methods, the numerical simulation model for oil-water two-phase flow is as follows:

[0013]

[0014] In the formula, A is the cross-sectional area of ​​the fluid seepage; ρ is the density of the fluid; k is the absolute permeability of the porous media in the reservoir; k r ρ is the relative permeability; μ is the fluid viscosity; p is the reservoir pressure; x is the length; g is the gravitational acceleration; D is the elevation, the vertical depth measured from a certain reference surface. q represents the average area; q represents the mass flow rate of the injected or extracted fluid per unit volume of rock under formation conditions; t represents time; s represents the saturation of the fluid in multiphase flow; subscript o represents the oil phase; subscript w represents the water phase.

[0015] Optionally, step S2: establishing a numerical simulation model of oil-water two-phase flow further includes:

[0016] The oil-water saturation relationship and the capillary pressure relationship are as follows:

[0017] s O +s w =1 (2)

[0018] p cow =p O -p w (3)

[0019] In the formula, p cow It represents the capillary pressure between the oil and water phases.

[0020] Optionally, step S3: calculating the viscous resistance losses of the oil phase, water phase, and total viscous resistance during water-drive development specifically includes:

[0021] Based on mechanical equilibrium analysis and capillary bundle theory, the expression form of viscous force in the water drive development process of reservoir system is clarified;

[0022] A mathematical model of viscous force resistance loss in the oil-water two-phase system was obtained.

[0023] Optionally, the mathematical model for obtaining the viscous force resistance loss of the oil-water two-phase system specifically includes:

[0024] An innovative mathematical model for single-phase flow energy conversion was established, and the single-phase flow energy conversion model was obtained.

[0025] Based on the single-phase flow energy conversion model, a mathematical model for viscous force resistance loss in oil-water two-phase flow is derived.

[0026] Optionally, the calculation method for the viscous force resistance loss of the oil-water two-phase system is as follows:

[0027]

[0028] In the formula, H o For the viscous resistance loss of the oil phase; H w denoted as viscous resistance loss of the aqueous phase; i represents x, y, and z, indicating three different directions of seepage; k is the permeability of the sandstone; k r denoted by , where is the relative permeability of the fluid; μ is the fluid viscosity; v is the fluid seepage velocity; L is the fluid flow distance; Q is the fluid seepage flow rate; t is the time for water injection development; V is the fluid volume; subscript o represents the oil phase; subscript w represents the water phase.

[0029] Optionally, the method for calculating the total viscous resistance loss in the reservoir is as follows:

[0030]

[0031] In the formula, H t The total viscous resistance loss of oil and water; i represents x, y, and z, indicating three different directions of seepage; l represents o and w, indicating the oil phase and water phase, respectively; k is the permeability of sandstone; k r denoted as the relative permeability of the fluid; μ as the fluid viscosity; v as the fluid seepage velocity; L as the fluid flow distance; Q as the fluid seepage flow rate; t as the water injection development time; and V as the fluid volume.

[0032] Optionally, step S4: obtaining the energy utilization efficiency of the reservoir during water injection development specifically includes: obtaining the energy utilization efficiency during water injection development based on the calculation method of total viscous resistance loss in the reservoir and viscous resistance loss of the oil phase and water phase.

[0033] Optionally, obtaining the energy utilization efficiency during the water injection development process specifically includes:

[0034]

[0035] In the formula, η o The energy utilization efficiency of the oil phase; η wE represents the energy utilization efficiency of the aqueous phase; α represents the weight of the loss rate; β represents the weight of the loss percentage; E i Energy injected into the reservoir; E p Energy extracted from an oil reservoir; H o For the viscous resistance loss of the oil phase; H w This refers to the viscous resistance loss in the aqueous phase.

[0036] This invention provides a method for characterizing the energy utilization efficiency of water-driven reservoirs. The method includes: step S1: collecting basic geological parameters and development parameters of the target reservoir; step S2: establishing a numerical simulation model of oil-water two-phase flow; step S3: calculating the viscous resistance losses of the oil phase, water phase, and total flow during water-drive development; and step S4: obtaining the energy utilization efficiency of the reservoir during water-drive development. By calculating the energy consumption and energy utilization efficiency of water-driven reservoirs, the main controlling factors affecting the energy utilization efficiency during water-drive development and their variation laws are obtained. This method features direct calculation and high flexibility, providing theoretical and technical support for the efficient and green development of water-drive reservoirs.

[0037] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 Provided for embodiments of the present invention;

[0040] Figure 2 Viscous resistance loss field diagram of a heterogeneous grid provided in an embodiment of the present invention;

[0041] Figure 3 The instantaneous viscous resistance loss curves of the oil phase with different injection volumes are provided in the embodiments of the present invention.

[0042] Figure 4 The energy utilization efficiency of different wells is calculated for the purposes of this invention. Detailed Implementation

[0043] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0044] The terms "comprising" and "having," and any variations thereof, in the specification, embodiments, claims, and drawings of this invention are intended to cover non-exclusive inclusion, such as including a series of steps or units.

[0045] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0046] Example 1

[0047] like Figure 1 As shown, a method for characterizing the energy utilization efficiency of water-injected reservoirs includes:

[0048] Step S1: Collect basic geological parameters and development parameters of the reservoir;

[0049] Step S2: Establish a numerical simulation model of oil-water two-phase flow;

[0050] Step S3: Calculate the viscous resistance losses of the oil phase, water phase, and total viscous resistance during water drive development;

[0051] Step S4: Obtain the energy utilization efficiency of the reservoir during water injection development.

[0052] In step S1, the target reservoir is developed using water injection.

[0053] In step S2, based on traditional reservoir numerical simulation methods, the numerical simulation model for oil-water two-phase flow is as follows:

[0054]

[0055] In the formula, A is the cross-sectional area of ​​the fluid seepage; ρ is the density of the fluid; k is the absolute permeability of the porous media in the reservoir; k r ρ is the relative permeability; μ is the fluid viscosity; p is the reservoir pressure; x is the length; g is the gravitational acceleration; D is the elevation, the vertical depth measured from a certain reference surface. q represents the average area; t represents the mass flow rate of the injected or extracted fluid per unit volume of rock under formation conditions; s represents time; s represents the saturation of the fluid in multiphase flow; subscript o represents the oil phase; subscript w represents the water phase.

[0056] The oil-water saturation relationship and the capillary pressure relationship are as follows:

[0057] s o +s w =1 (2)

[0058] p cow =p o -p w (3)

[0059] In the formula, p cow It represents the capillary pressure between the oil and water phases.

[0060] In step S3, based on mechanical equilibrium analysis and capillary bundle theory, the expression form of viscous force in the water drive development process of the reservoir system is clarified, a mathematical model of unidirectional flow energy conversion is innovatively established, and a mathematical model of viscous force loss in the oil-water two-phase system is derived from the single-phase flow energy conversion model.

[0061] The calculation method for viscous resistance loss between the oil phase and the water phase in an oil reservoir is as follows:

[0062]

[0063] In the formula, H o For the viscous resistance loss of the oil phase; H w denoted as viscous resistance loss of the aqueous phase; i represents x, y, and z, indicating three different directions of seepage; k is the permeability of the sandstone; k r denoted by , where μ is the relative permeability of the fluid; is the fluid viscosity; is the fluid seepage velocity; is the fluid flow distance; is the fluid seepage flow rate; is the water injection development time; is the fluid volume; is the subscript o for oil phase; and w for water phase.

[0064] The method for calculating the total viscous resistance loss in an oil reservoir is as follows:

[0065]

[0066] In the formula, H t The total viscous resistance loss of oil and water; i represents x, y, and z, indicating three different directions of seepage; l represents o and w, indicating the oil phase and water phase, respectively; k is the permeability of sandstone; k r denoted as the relative permeability of the fluid; μ as the fluid viscosity; v as the fluid seepage velocity; L as the fluid flow distance; Q as the fluid seepage flow rate; t as the water injection development time; and V as the fluid volume.

[0067] In step S4, based on the calculation methods for the total viscous resistance loss in the reservoir and the viscous resistance loss between the oil phase and the water phase, the calculation method for energy utilization efficiency during water injection development is obtained as follows:

[0068]

[0069] In the formula, η o The energy utilization efficiency of the oil phase; η w E represents the energy utilization efficiency of the aqueous phase; α represents the weight of the loss rate; β represents the weight of the loss percentage; E i Energy injected into the reservoir; E p Energy extracted from an oil reservoir; H o For the viscous resistance loss of the oil phase; H w This refers to the viscous resistance loss in the aqueous phase.

[0070] Example 2

[0071] A method for characterizing the energy utilization efficiency of water-injected reservoirs includes:

[0072] Step 1: Collect basic geological and development parameters of the reservoir. For a certain water-injection development reservoir, the reservoir depth is 1000-1010 m, the initial formation pressure is 10 MPa, the porosity is 0.28%, the crude oil viscosity is 20 mPa·s, and the reservoir fluid consists of crude oil and water. The initial oil saturation is 0.75%, the initial water saturation is 0.25%, and the rock compressibility coefficient is 3 × 10⁻⁶. - 3 1 MPa, development method is water injection development, injection well injection volume is 24 m³ 3 / d.

[0073] Step 2: Establish a numerical simulation model for oil-water two-phase flow:

[0074]

[0075] In the formula, A is the cross-sectional area of ​​the fluid seepage; ρ is the density of the fluid; k is the absolute permeability of the porous media in the reservoir; k r ρ is the relative permeability; μ is the fluid viscosity; p is the reservoir pressure; x is the length; g is the gravitational acceleration; D is the elevation, the vertical depth measured from a certain reference surface. q represents the average area; t represents the mass flow rate of the injected or extracted fluid per unit volume of rock under formation conditions; s represents time; s represents the saturation of the fluid in multiphase flow; subscript o represents the oil phase; subscript w represents the water phase.

[0076] Step 3, calculate the viscous resistance loss between the oil phase and the water phase in the reservoir:

[0077]

[0078] In the formula, H o For the viscous resistance loss of the oil phase; H w denoted as viscous resistance loss of the aqueous phase; i represents x, y, and z, indicating three different directions of seepage; k is the permeability of the sandstone; k rdenoted by , where μ is the relative permeability of the fluid; is the fluid viscosity; is the fluid seepage velocity; is the fluid flow distance; is the fluid seepage flow rate; is the water injection development time; is the fluid volume; is the subscript o for oil phase; and w for water phase.

[0079] And, the total viscous resistance loss in the reservoir:

[0080]

[0081] In the formula, H t The total viscous resistance loss of oil and water; i represents x, y, and z, indicating three different directions of seepage; l represents o and w, indicating the oil phase and water phase, respectively; k is the permeability of sandstone; k r denoted as the relative permeability of the fluid; μ as the fluid viscosity; v as the fluid seepage velocity; L as the fluid flow distance; Q as the fluid seepage flow rate; t as the water injection development time; and V as the fluid volume.

[0082] Figure 2 and Figure 3 These are, respectively, the viscous resistance loss field diagram and the instantaneous viscous resistance loss curve.

[0083] Step 4, calculate the energy utilization efficiency during the water injection development process:

[0084]

[0085] In the formula, η o The energy utilization efficiency of the oil phase; η w E represents the energy utilization efficiency of the aqueous phase; α represents the weight of the loss rate; β represents the weight of the loss percentage; E i Energy injected into the reservoir; E p Energy extracted from an oil reservoir; H o For the viscous resistance loss of the oil phase; H w This refers to the viscous resistance loss in the aqueous phase.

[0086] At the end of production, the cumulative viscous resistance loss in the oil phase was 9.608 × 10⁻⁶. 9 J. Then, the energy injected into the reservoir is obtained by multiplying the bottom-hole flowing pressure of the injection well by the injection rate, and the energy produced from the reservoir is obtained by multiplying the bottom-hole flowing pressure of the production well by the production rate. The overall oil phase energy utilization efficiency η during the water injection development process of this reservoir is then calculated. o =39.2%.

[0087] Figure 4 The energy utilization efficiency of each well.

[0088] Beneficial effects: Based on mechanical equilibrium analysis and the principle of energy conservation, a characterization method for energy utilization efficiency of water-injected reservoirs is obtained. Energy consumption and energy utilization efficiency of water-injected reservoirs are calculated, and a characterization model for viscous resistance loss is established. It has the advantages of clear physical meaning, direct calculation, and high flexibility.

[0089] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for characterizing the energy utilization efficiency of water-injected oil reservoirs, characterized in that, The characterization method includes: Step S1: Collect basic geological parameters and development parameters of the target reservoir; Step S2: Establish a numerical simulation model of oil-water two-phase flow; Step S3: Calculate the viscous resistance losses of the oil phase, water phase, and total viscous resistance during water drive development; Step S4: Obtain the energy utilization efficiency of the reservoir during water injection development.

2. The method for characterizing the energy utilization efficiency of water-injected oil reservoirs according to claim 1, characterized in that, The target reservoir is developed using water injection.

3. The method for characterizing the energy utilization efficiency of water-injected reservoirs according to claim 1, characterized in that, Step S2: Establishing a numerical simulation model for oil-water two-phase flow specifically includes: Based on traditional reservoir numerical simulation methods, the numerical simulation model for oil-water two-phase flow is as follows: In the formula, A is the cross-sectional area of ​​the fluid seepage; ρ is the density of the fluid; k is the absolute permeability of the porous media in the reservoir; k r ρ is the relative permeability; μ is the fluid viscosity; p is the reservoir pressure; x is the length; g is the gravitational acceleration; D is the elevation, the vertical depth measured from a certain reference surface. q represents the average area; q represents the mass flow rate of the injected or extracted fluid per unit volume of rock under formation conditions; t represents time; s represents the saturation of the fluid in multiphase flow; subscript o represents the oil phase; subscript w represents the water phase.

4. The method for characterizing the energy utilization efficiency of a water-injection oil reservoir according to claim 3, characterized in that, Step S2: Establishing a numerical simulation model for oil-water two-phase flow further includes: The oil-water saturation relationship and the capillary pressure relationship are as follows: s o +s w =1 (2) p cow =p o -p w (3) In the formula, p cow It represents the capillary pressure between the oil and water phases.

5. The method for characterizing the energy utilization efficiency of water-injected oil reservoirs according to claim 1, characterized in that, Step S3: Calculating the viscous resistance losses of the oil phase, water phase, and total viscous resistance during water-drive development specifically includes: Based on mechanical equilibrium analysis and capillary bundle theory, the expression form of viscous force in the water drive development process of reservoir system is clarified; A mathematical model of viscous force resistance loss in the oil-water two-phase system was obtained.

6. The method for characterizing the energy utilization efficiency of a water-injection oil reservoir according to claim 5, characterized in that, The mathematical model for obtaining the viscous force resistance loss of the oil-water two-phase system specifically includes: A mathematical model for single-phase flow energy conversion was innovatively established, and a single-phase flow energy conversion model was obtained. Based on the single-phase flow energy conversion model, a mathematical model for viscous force resistance loss in oil-water two-phase flow is derived.

7. The method for characterizing the energy utilization efficiency of a water-injection oil reservoir according to claim 6, characterized in that, The calculation method for the viscous force resistance loss of the oil-water two-phase system is as follows: In the formula, H o For the viscous resistance loss of the oil phase; H w denoted as viscous resistance loss of the aqueous phase; i represents x, y, and z, indicating three different directions of seepage; k is the permeability of the sandstone; k r denoted by , where is the relative permeability of the fluid; μ is the fluid viscosity; v is the fluid seepage velocity; L is the fluid flow distance; Q is the fluid seepage flow rate; t is the time for water injection development; V is the fluid volume; subscript o represents the oil phase; subscript w represents the water phase.

8. The method for characterizing the energy utilization efficiency of a water-injection oil reservoir according to claim 6, characterized in that, The method for calculating the total viscous resistance loss in the reservoir is as follows: In the formula, H t denoted as , where is the total viscous resistance loss between oil and water; i represents x, y, and z, indicating three different directions of seepage; l represents o and w, indicating the oil and water phases respectively; k is the permeability of the sandstone; k r denoted as the relative permeability of the fluid; μ as the fluid viscosity; v as the fluid seepage velocity; L as the fluid flow distance; Q as the fluid seepage flow rate; t as the water injection development time; and V as the fluid volume.

9. The method for characterizing the energy utilization efficiency of a water-injected reservoir according to claim 1, characterized in that, Step S4: Obtaining the energy utilization efficiency of the reservoir during water injection development specifically includes: obtaining the energy utilization efficiency during water injection development based on the calculation method of total viscous resistance loss in the reservoir and viscous resistance loss of the oil phase and water phase.

10. The method for characterizing the energy utilization efficiency of a water-injected reservoir according to claim 9, characterized in that, The energy utilization efficiency obtained during the water injection development process specifically includes: In the formula, η O The energy utilization efficiency of the oil phase; η w E represents the energy utilization efficiency of the aqueous phase; α represents the weight of the loss rate; β represents the weight of the loss percentage; E i Energy injected into the reservoir; E p Energy extracted from an oil reservoir; H o For the viscous resistance loss of the oil phase; H w This refers to the viscous resistance loss in the aqueous phase.

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