A method for optimizing the horizontal well drilling limit of offshore general heavy oil reservoir cold production development
By utilizing displacement experiments to obtain fluid characteristic parameters during the cold production development of horizontal wells in ordinary heavy oil reservoirs at sea, and establishing production capacity equations and IPR charts, the adaptability problem of well placement thickness limit research was solved, achieving high-precision well placement optimization and development decision support.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CNOOC TIANJIN BRANCH
- Filing Date
- 2026-05-12
- Publication Date
- 2026-06-09
AI Technical Summary
In existing technologies, the study of well thickness limits for cold production development of horizontal wells in offshore ordinary heavy oil reservoirs suffers from problems such as theoretical models not being compatible with fluid characteristics and high data dependence, which prevents its application in new blocks.
By conducting displacement experiments under different crude oil viscosities and permeabilities, we obtained the characteristic parameters of Bingham-type and power-law-type fluids, established horizontal well productivity equations that include the characteristics of Bingham and power-law fluids, drew IPR charts, and optimized well thickness limits.
It provides a high-precision and targeted method for optimizing well placement boundaries, offering an objective basis for heavy oil reservoir development decisions and improving the speed and convenience of development plans.
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Figure CN122174750A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of wellbore boundary technology for cold production development of horizontal wells, and in particular to a method for optimizing wellbore boundaries for cold production development of horizontal wells in ordinary heavy oil reservoirs at sea. Background Technology
[0002] China has relatively abundant offshore heavy oil resources, with proven geological reserves of approximately 42 × 10⁻⁶. 8 The resources are highly concentrated in the Bohai Sea region. However, offshore oilfield development is constrained by the special operating environment, with limitations on offshore equipment and platform carrying capacity. Furthermore, thermal recovery of heavy oil, such as steam injection and steam drive, requires significant investment in heating equipment, injection and production pipelines, and energy consumption, resulting in low economic feasibility.
[0003] Therefore, for underground crude oil with a viscosity of 150~1000 mPa.s For ordinary heavy oil, the industry has gradually explored and promoted the development model of directional wells with multi-layer water injection and horizontal wells with stratified cold production. By leveraging the long well section of horizontal wells to contact the reservoir, oil production efficiency is improved, while water injection from directional wells replenishes formation energy, balancing development effect and cost input.
[0004] However, the ordinary heavy oil reservoirs in the Bohai Sea exhibit significant unique fluid characteristics: the crude oil has a high content of gum and asphaltenes. During cold extraction and development, the underground crude oil exhibits dual non-Newtonian fluid characteristics, namely Bingham-type and power-law-type fluids. When the crude oil seepage pressure gradient is lower than the initiation pressure gradient, the crude oil behaves as a Bingham fluid, requiring the overcoming of yield stress to flow. When the pressure gradient exceeds the initiation pressure gradient, the crude oil's flow viscosity dynamically adjusts with the seepage velocity, transforming it into a power-law fluid. This complex rheological characteristic leads to a significant difference between the crude oil seepage law and that of conventional Newtonian fluids, such as light oils. This directly makes it difficult to adapt traditional methods for studying the thickness limits of horizontal well placement, becoming a core bottleneck restricting development decisions.
[0005] Currently, the most commonly used methods for studying the thickness limits of horizontal wells in the industry are reservoir engineering methods and numerical simulation methods. Reservoir engineering methods primarily target Newtonian fluids and do not consider the complex rheological characteristics of heavy oil reservoirs. Therefore, they have large errors for heavy oil reservoirs undergoing cold production development and are difficult to use to guide the deployment of development strategies for heavy oil fields. Numerical simulation methods require a large amount of static and dynamic data, making them less applicable to new blocks or oil fields and difficult to implement. In summary, current research on the thickness limits of horizontal wells for cold production development in ordinary heavy oil reservoirs in the Bohai Sea suffers from problems such as theoretical models not being suitable for fluid characteristics and high data dependence, making them unapplicable to new blocks.
[0006] Therefore, there is an urgent need for an optimization method for the well boundary of horizontal wells in the cold production and development of ordinary heavy oil reservoirs at sea to solve the above problems. Summary of the Invention
[0007] The purpose of this invention is to provide an optimization method for well placement boundaries in the cold production development of horizontal wells in offshore ordinary heavy oil reservoirs. This method addresses the technical problems in existing studies on well thickness boundaries for cold production development of horizontal wells in the Bohai Sea ordinary heavy oil reservoirs, where theoretical models are not adapted to fluid characteristics and data dependence is high, making the method unapplicable to new blocks. The various technical effects of the preferred solutions provided by this invention are detailed below.
[0008] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for optimizing well boundaries in the cold production and development of horizontal wells in offshore ordinary heavy oil reservoirs, comprising the following steps: S1: Based on the reservoir properties and viscosity variation range in the target area, conduct displacement experiments under different crude oil viscosities and permeabilities; S2: Obtain the characteristic parameters of the Bingham-type fluid in a typical heavy oil reservoir from the displacement experiment; S3: Obtain the power-law fluid characteristic parameters of ordinary heavy oil reservoirs from the displacement experiment; S4: Establish the productivity equation for horizontal wells in the cold production development of heavy oil reservoirs, including Bingham fluid characteristics and power-law fluid characteristics; S5: Draw IPR charts for cold production development of horizontal wells in ordinary heavy oil reservoirs; S6: Query the chart to obtain the well thickness limit for cold production development of horizontal wells.
[0009] Furthermore, in step S1, based on the reservoir properties and viscosity variation range of the target area, displacement experiments are conducted under different crude oil viscosities and permeabilities, including: Formation crude oil, simulated formation water, and sand-filled pipes were prepared, and displacement experiments were carried out under different permeabilities, crude oil viscosities, and seepage velocities using unsteady constant-rate displacement experiments.
[0010] Further, in step S2, the characteristic parameters of the Bingham type fluid in a typical heavy oil reservoir are obtained from the displacement experiment, including: Based on the displacement experiment data from step S1, a curve showing the change in starting pressure gradient versus crude oil mobility was plotted. The characteristic parameters of the Bingham-type fluid were obtained using a fitting formula, which is:
[0011] In the formula, To initiate the pressure gradient, 10 -3 MPa / m; Permeability, mD; The static viscosity of crude oil is given in mPa·s. Let be the crude oil flow rate, mD / (mPa·s); A and B are Bingham fluid characteristic parameters, respectively.
[0012] Further, in step S3, the power-law fluid characteristic parameters of a typical heavy oil reservoir are obtained from the displacement experiment, including: Based on the seepage velocity in step S1, the pressure difference across the sand-filled pipe, and the starting pressure gradient in step S2, the kinematic viscosity of the crude oil is calculated using the following formula:
[0013] in, Here, represents the kinematic viscosity of crude oil, in mPa·s; l ΔP is the length of the sand-filled pipe, in cm; ΔP is the measured pressure difference between the two ends of the sand-filled pipe, in MPa. The seepage velocity was set for the experiment, in cm / s.
[0014] Plot the relationship between the kinematic viscosity and the seepage velocity of crude oil to obtain the power-law fluid characteristic parameters of ordinary heavy oil reservoirs.
[0015] Furthermore, the plotting of the relationship between the kinematic viscosity and the seepage velocity of crude oil to obtain the power-law fluid characteristic parameters of ordinary heavy oil reservoirs includes: Plotting the seepage velocity as the X-axis and the kinematic viscosity of crude oil as the Y-axis, the relationship curves between the kinematic viscosity of crude oil and the seepage velocity for each set of experiments were obtained, yielding the power-law fluid characteristic parameters of ordinary heavy oil reservoirs.
[0016] In the formula, G is the pressure gradient, 10 -3 MPa / m; denoted as the kinematic viscosity of crude oil, in mPa·s; n and m are characteristic parameters of power-law fluids.
[0017] Furthermore, in step S4, the productivity equation for horizontal wells in the cold production development of heavy oil reservoirs is established, including Bingham fluid characteristics and power-law fluid characteristics, including: The three-dimensional elliptical flow in the horizontal well is decomposed into elliptical flow on the horizontal plane and radial flow on the vertical wellbore plane. The pseudo-seepage resistance is defined, and the total seepage resistance generated by the horizontal well is calculated as the sum of the pseudo-seepage resistance in the outer zone and the pseudo-seepage resistance in the inner zone. By combining the total seepage resistance generated by the horizontal well with the total production pressure difference generated by the horizontal well in the discharge region under stable seepage, a horizontal well productivity equation including Bingham and power-law fluid characteristics is obtained.
[0018] Furthermore, the pseudo-seepage resistance is defined, and the following is adopted:
[0019] in, Total production differential pressure, MPa; Q is horizontal well production, m³. 3 / d;n are the power-law fluid characteristic parameters obtained in step S3.
[0020] Furthermore, the total seepage resistance generated by the horizontal well is calculated, where: The apparent seepage resistance in the outer zone is expressed as:
[0021] The pseudo-seepage resistance in the inner zone can be expressed as:
[0022] The total seepage resistance generated by the horizontal well is:
[0023] in, This is the crude oil volume coefficient. m ; h For the effective thickness of the reservoir, m ; L This refers to the length of the horizontal section of a horizontal well in a mine. m ; The oil drain radius, m ; Where is the wellbore radius. m ; n, m These are the power-law fluid characteristic parameters obtained in step S3; For penetration rate, mD .
[0024] Furthermore, by combining the total seepage resistance generated by the horizontal well with the total production pressure differential generated by the horizontal well in the discharge region under stable seepage, a horizontal well productivity equation incorporating Bingham and power-law fluid characteristics is obtained, wherein: The total production pressure differential generated in the discharge zone of a horizontal well under steady flow is:
[0025] The production capacity equation for cold production development of heavy oil reservoirs using horizontal wells is obtained as follows:
[0026] in, Formation pressure, MPa; The bottom hole pressure is MPa.
[0027] Further, in step S5, an IPR (Independent Production Recovery) chart for horizontal well cold production development in ordinary heavy oil reservoirs is drawn, including: By combining the crude oil mobility and effective thickness range of a single sand body in ordinary heavy oil reservoirs at sea, and using the formulas from steps S2 to S4, IPR charts for horizontal well cold production development under different crude oil mobility and reservoir thicknesses are drawn.
[0028] This invention provides a method for optimizing well placement boundaries in the cold production development of horizontal wells in offshore heavy oil reservoirs. Based on the reservoir properties and viscosity variations in the target area, displacement experiments are designed under different crude oil viscosities and permeabilities. Based on numerous crude oil displacement experiments, Bingham-type and power-law-type fluid characteristic parameters of the target area are obtained. These complex non-Newtonian fluid characteristic parameters are transformed into functions related to reservoir and fluid properties. A productivity equation for horizontal wells in the cold production development of heavy oil reservoirs is established, including Bingham and power-law fluid characteristics, thus obtaining the well placement boundaries for cold production development. This method solves the problems of high difficulty and lack of theoretical support in optimizing well placement for cold production development in heavy oil reservoirs. It provides an objective evaluation for heavy oil reservoir development strategy decisions and has the advantages of high prediction accuracy and strong targeting. It provides a fast, convenient, and objective basis for decisions on cold production development of horizontal wells in heavy oil reservoirs and optimization of well placement boundaries, which is beneficial for the research of offshore heavy oil reservoir development schemes and the adjustment of production measures. Attached Figure Description
[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. 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.
[0030] Figure 1 A schematic flowchart illustrating the well boundary optimization method for horizontal well cold production development according to an embodiment of the present invention; Figure 2 A graph showing the relationship between crude oil flowability and starting pressure gradient established according to an embodiment of the present invention; Figure 3 A graph showing the relationship between the kinematic viscosity and seepage velocity of crude oil established according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the decomposition of the seepage field and resistance field in a horizontal well according to an embodiment of the present invention; Figure 5 The crude oil flow rate is 4 mD / (mPa·s) Cold production development of horizontal wells under different reservoir thicknesses IPR plate; Figure 6 The crude oil flow rate is 8 mD / (mPa·s) Cold production development of horizontal wells under different reservoir thicknesses IPR plate; Figure 7 The crude oil flow rate is 12 mD / (mPa·s) Cold production development of horizontal wells under different reservoir thicknesses IPR plate; Figure 8 This is a map showing the thickness limits for horizontal well layout in the Bohai A oilfield. Detailed Implementation
[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.
[0032] This invention provides a method for optimizing the wellbore boundaries in the cold production and development of horizontal wells in ordinary heavy oil reservoirs at sea, comprising the following steps: S1: Based on the reservoir properties and viscosity variation range in the target area, conduct displacement experiments under different crude oil viscosities and permeabilities; S2: Obtain the characteristic parameters of the Bingham-type fluid in a typical heavy oil reservoir from the displacement experiment; S3: Obtain the power-law fluid characteristic parameters of ordinary heavy oil reservoirs from the displacement experiment; S4: Establish the productivity equation for horizontal wells in the cold production development of heavy oil reservoirs, including Bingham fluid characteristics and power-law fluid characteristics; S5: Draw IPR charts for cold production development of horizontal wells in ordinary heavy oil reservoirs; S6: Query the chart to obtain the well thickness limit for cold production development of horizontal wells.
[0033] This method for optimizing well placement boundaries in horizontal wells for cold production development of ordinary heavy oil reservoirs at sea, based on the reservoir properties and viscosity variation range of the target area, designs displacement experiments under different crude oil viscosities and permeabilities. Based on numerous crude oil displacement experiments, it obtains Bingham-type and power-law-type fluid characteristic parameters of the target area's crude oil. The complex non-Newtonian fluid characteristic parameters are transformed into functions related to reservoir and fluid properties. A productivity equation for horizontal wells in cold production development of heavy oil reservoirs, including Bingham and power-law fluid characteristics, is established, yielding the well placement boundaries for horizontal wells in cold production development. This method solves the problems of high difficulty and lack of theoretical support in optimizing well placement for cold production development of heavy oil reservoirs, providing an objective evaluation for heavy oil reservoir development strategy decisions. Furthermore, this method has the advantages of high prediction accuracy and strong targeting, providing a rapid, convenient, and objective basis for decisions on horizontal well cold production development and well placement boundary optimization in heavy oil reservoirs. This is beneficial for the research of offshore heavy oil reservoir development schemes and the adjustment of production measures.
[0034] Specifically, in step S1, based on the reservoir properties and viscosity variation range of the target area, displacement experiments are carried out under different crude oil viscosities and permeabilities, including: preparing formation crude oil, simulating formation water and sand-filled pipes, and conducting displacement experiments under different permeabilities, different crude oil viscosities and different seepage velocities using unsteady constant-rate displacement experiments.
[0035] During the experiment, the formation crude oil was prepared according to the petroleum industry standard, the formation water was simulated by standard brine, and the formation sand was filled with natural formation sand particles. The sand filling pipe and sand sample ratio were determined according to the permeability distribution range of the target area.
[0036] The following is a specific embodiment: In this embodiment, a total of 8 groups of sand-filled pipe displacement experiments were designed. The sand used for the experimental sand-filled pipes was selected from natural formation sand. The specifications of the sand-filled pipes and the sand particle ratio are shown in Table 1. The viscosity of the crude oil used in the experiment was between 100 mPa·s and 700 mPa·s, the permeability was between 1510 and 3530 mD, and the corresponding mobility was between 2.2 and 35.3 mD / (mPa·s).
[0037] Table 1 Specifications of Sand Filling Pipes and Sand Sample Gradation Table
[0038] According to petroleum industry standards, crude oil samples were prepared by collecting degassed crude oil from the target area. The formation water samples used in the experiments employed standard brine to simulate formation water. The standard brine was prepared using 99.5% analytical grade sodium chloride, and the simulated formation water salinity was 10000 mg / L. The flow velocities for each displacement experiment were designed to be 0.0006 cm / s, 0.0014 cm / s, 0.0024 cm / s, 0.0034 cm / s, 0.0044 cm / s, and 0.0054 cm / s, respectively. The displacement experiment design is shown in Table 2.
[0039] Table 2 Displacement Experimental Design
[0040] In step S2, the characteristic parameters of the Bingham type fluid in a typical heavy oil reservoir are obtained from the displacement experiment, including: plotting the starting pressure gradient and crude oil mobility based on the displacement experiment data from step S1. The variation curve was used to obtain the characteristic parameters of the Bingham-type fluid through a fitting formula, which is:
[0041] In the formula, To initiate the pressure gradient, 10 -3 MPa / m; Permeability, mD; The static viscosity of crude oil is given in mPa·s. Let be the crude oil flow rate, mD / (mPa·s); A and B are Bingham fluid characteristic parameters, respectively.
[0042] Specifically, in this embodiment, the pressure gradient and seepage velocity data under each set of experiments are linearly fitted based on the displacement experiment to obtain the starting pressure gradient under that set of experiments. Plot the curve of starting pressure gradient versus crude oil mobility with crude oil mobility as the X-axis and starting pressure gradient as the Y-axis. Fit the curve to obtain the relationship between crude oil mobility and starting pressure gradient, and obtain the characteristic parameters of the Bingham type fluid: A = 19.588, B = -0.94. (See...) Figure 2 .
[0043] Formula (1) In step S3, the power-law fluid characteristic parameters of ordinary heavy oil reservoirs are obtained through displacement experiments, including: calculating the kinematic viscosity of crude oil based on the seepage velocity in step S1, the pressure difference across the sand-packed pipe, and the starting pressure gradient in step S2, using the following formula: Formula (2) in, Here, represents the kinematic viscosity of crude oil, in mPa·s; l The length of the sand-filled pipe refers to the length of the horizontal section under laboratory conditions. cm ΔP is the measured pressure difference between the two ends of the sand-filled pipe, MPa; v is the seepage velocity set in the experiment, cm / s.
[0044] Plot the relationship between crude oil kinematic viscosity and seepage velocity for each experimental group, with seepage velocity as the X-axis and crude oil kinematic viscosity as the Y-axis. (See figure) Figure 3 The power-law fluid characteristic parameters of ordinary heavy oil reservoirs were obtained. Formula (3) In the formula, G is the pressure gradient, 10 -3 MPa / m; ρ is the kinematic viscosity of crude oil, mPa·s; n and m are characteristic parameters of power-law fluids, see [reference needed]. Figure 3 And Table 3.
[0045] Table 3 Displacement Experimental Design
[0046] In step S4, the production capacity equation for horizontal wells in the cold production development of heavy oil reservoirs, including Bingham fluid characteristics and power-law fluid characteristics, is established. This includes: decomposing the three-dimensional elliptical flow of the horizontal well into elliptical flow on the horizontal plane and radial flow on the vertical wellbore plane; defining pseudo-seepage resistance and calculating the total seepage resistance generated by the horizontal well as the sum of the pseudo-seepage resistance in the outer zone and the pseudo-seepage resistance in the inner zone; and obtaining the horizontal well production capacity equation, including Bingham and power-law fluid characteristics, by combining the total seepage resistance generated by the horizontal well with the total production pressure difference generated by the horizontal well in the discharge area under stable seepage.
[0047] Among them, the pseudo-seepage resistance is defined by adopting
[0048] in, Total production differential pressure, MPa; Q is horizontal well production, m³. 3 / d;n are the power-law fluid characteristic parameters obtained in step S3.
[0049] Calculate the total seepage resistance generated by the horizontal well, where: The apparent seepage resistance in the outer zone is expressed as:
[0050] The pseudo-seepage resistance in the inner zone can be expressed as:
[0051] The total seepage resistance generated by the horizontal well is:
[0052] in, This is the crude oil volume coefficient. m ; h For the effective thickness of the reservoir, m ; L This refers to the length of the horizontal section of a horizontal well in a mine. m ; The oil drain radius, m ; r w Where is the wellbore radius. m ; n, m These are the power-law fluid characteristic parameters obtained in step S3; For penetration rate, mD .
[0053] By combining the total seepage resistance generated by the horizontal well with the total production pressure differential generated by the horizontal well in the discharge zone under steady flow, a horizontal well productivity equation incorporating Bingham and power-law fluid characteristics is obtained, where: The total production pressure differential generated in the discharge zone of a horizontal well under steady flow is:
[0054] The production capacity equation for cold production development of heavy oil reservoirs using horizontal wells is obtained as follows:
[0055] in, Formation pressure, MPa; The bottom hole pressure is MPa.
[0056] In this embodiment, the three-dimensional elliptical flow in the horizontal well is transformed into two interconnected two-dimensional flows: an elliptical flow on the outer horizontal plane and a radial flow on the inner vertical plane of the wellbore. (See...) Figure 4 .
[0057] The elliptical flow on the outer horizontal surface satisfies the following oil discharge zone requirements. Based on conformal transformation, the elliptical flow is mapped to a circular radial flow, and the outer radius of the circular radial flow is... inner radius = Pressure in the outer region of circular radial flow Internal pressure The elliptical flow rate on the outer horizontal plane can be expressed as: Formula (4) Combining the concept of seepage resistance, the pseudo-seepage resistance in the outer zone is obtained: Formula (5) The inner zone represents radial flow on the plane perpendicular to the horizontal wellbore. Using conformal mapping, this can be mapped to a flow radius with the horizontal wellbore as the axis. The inner region is a circular area, therefore the inner region output can be expressed as: Formula (6) The pseudo-seepage resistance in the inner zone can be expressed as: Formula (7) Based on the principle of hydroelectric similarity, the total seepage resistance generated by a horizontal well in the discharge zone under steady seepage is: Production meets By combining the formulas, the production capacity formula for cold production development of horizontal wells in heavy oil reservoirs can be obtained.
[0058] Formula (8) After considering formation anisotropy, the productivity formula for horizontal wells can be expressed as: Formula (9) Parameter: Permeability Anisotropy Coefficient The definition is as follows: Formula (10) in, Horizontal permeability, mD; denoted as vertical permeability, mD.
[0059] In step S5, draw the IPR chart for cold production development of horizontal wells in ordinary heavy oil reservoirs, including: combining the crude oil mobility and effective thickness range of a single sand body in ordinary heavy oil reservoirs at sea, and combining the formulas in steps S2 to S4 to draw the IPR chart for cold production development of horizontal wells under different crude oil mobility and different reservoir thicknesses.
[0060] Based on data such as target production and reasonable production pressure differential of horizontal wells in offshore heavy oil reservoirs, the effective thickness limit for cold production development of horizontal wells is obtained by querying the IPR chart of cold production development of horizontal wells in ordinary heavy oil reservoirs in step S5.
[0061] In this embodiment, it is known that the crude oil mobility of ordinary heavy oil reservoirs in the Bohai Oilfield is generally between 4 and 12 mD / (mPa·s), and the effective thickness of a single sand body is between 4 and 12 m. Using formulas (1), (3), and (9), a set of IPR curves for cold production development of horizontal wells under different crude oil mobility and different effective sand body thicknesses at sea was established. (See...) Figures 5-7 .
[0062] The Bohai A oilfield has an average permeability of 2000 mD, a crude oil viscosity of 501 mPa·s, and a crude oil mobility of 4.0 mD / (mPa·s). The target production per well for cold production development of horizontal wells in this oilfield is 40 m³ / s. 3 / d, the reasonable production pressure differential is 5.0MPa. Referring to the chart, the limit for well thickness under cold production conditions for horizontal wells is 10.4m. See Figure 8 .
[0063] This method for optimizing wellbore limits in the cold production development of horizontal wells in ordinary heavy oil reservoirs at sea, based on the reservoir properties and viscosity variations in the target area, designs displacement experiments under different crude oil viscosities and permeabilities to obtain Bingham-type and power-law-type fluid characteristic parameters of the crude oil in the target area. Utilizing the principle of hydroelectric similarity and the equivalent seepage resistance method, a formula for calculating the production capacity of horizontal wells in the cold production development of heavy oil considering dual non-Newtonian fluid characteristics is established. A set of wellbore thickness limit maps for cold production development of horizontal wells is obtained, solving the problems of high difficulty and low accuracy in predicting the production capacity of cold production development in this type of reservoir, and providing an objective basis for decision-making and deployment of heavy oil field development models.
[0064] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A method for optimizing well boundaries in the cold production development of horizontal wells in ordinary heavy oil reservoirs at sea, characterized in that, Includes the following steps: S1: Based on the reservoir properties and viscosity variation range in the target area, conduct displacement experiments under different crude oil viscosities and permeabilities; S2: Obtain the characteristic parameters of the Bingham-type fluid in a typical heavy oil reservoir from the displacement experiment; S3: Obtain the power-law fluid characteristic parameters of ordinary heavy oil reservoirs from the displacement experiment; S4: Establish productivity equations for horizontal wells in the cold production development of heavy oil reservoirs, including Bingham fluid characteristics and power-law fluid characteristics, including: The three-dimensional elliptical flow in the horizontal well is decomposed into elliptical flow on the horizontal plane and radial flow on the vertical wellbore plane. The pseudo-seepage resistance is defined, and the total seepage resistance generated by the horizontal well is calculated as the sum of the pseudo-seepage resistance in the outer zone and the pseudo-seepage resistance in the inner zone. By combining the total seepage resistance generated by the horizontal well with the total production pressure difference generated by the horizontal well in the discharge region under stable seepage, a horizontal well productivity equation including Bingham and power-law fluid characteristics is obtained. S5: Draw IPR charts for cold production development of horizontal wells in ordinary heavy oil reservoirs; S6: Query the chart to obtain the well thickness limit for cold production development of horizontal wells.
2. The method for optimizing well boundaries in the cold production development of horizontal wells in offshore ordinary heavy oil reservoirs according to claim 1, characterized in that, In step S1, based on the reservoir properties and viscosity variation range of the target area, displacement experiments are conducted under different crude oil viscosities and permeabilities, including: Formation crude oil, simulated formation water, and sand-filled pipes were prepared, and displacement experiments were carried out under different permeabilities, crude oil viscosities, and seepage velocities using unsteady constant-rate displacement experiments.
3. The method for optimizing well boundaries in the cold production development of horizontal wells in offshore ordinary heavy oil reservoirs according to claim 2, characterized in that, In step S2, the characteristic parameters of the Bingham-type fluid in a typical heavy oil reservoir are obtained from the displacement experiment, including: Based on the displacement experiment data from step S1, a curve showing the change in starting pressure gradient versus crude oil mobility was plotted. The characteristic parameters of the Bingham-type fluid were obtained using a fitting formula, which is: ， In the formula, To initiate the pressure gradient, 10 -3 MPa / m; Permeability, mD; The static viscosity of crude oil is given in mPa·s. Let be the crude oil flow rate, mD / (mPa·s); A and B are Bingham fluid characteristic parameters, respectively.
4. The method for optimizing well boundaries in the cold production development of horizontal wells in offshore ordinary heavy oil reservoirs according to claim 3, characterized in that, In step S3, the power-law fluid characteristic parameters of ordinary heavy oil reservoirs are obtained from the displacement experiment, including: Based on the seepage velocity in step S1, the pressure difference across the sand-filled pipe, and the starting pressure gradient in step S2, the kinematic viscosity of the crude oil is calculated using the following formula: ， in, Here, represents the kinematic viscosity of crude oil, in mPa·s; l ΔP is the length of the sand-filled pipe, in cm; ΔP is the measured pressure difference between the two ends of the sand-filled pipe, in MPa; v is the seepage velocity set in the experiment, in cm / s; Plot the relationship between the kinematic viscosity and the seepage velocity of crude oil to obtain the power-law fluid characteristic parameters of ordinary heavy oil reservoirs.
5. The method for optimizing well boundaries in the cold production development of horizontal wells in offshore ordinary heavy oil reservoirs according to claim 4, characterized in that, The plotting of the relationship between the kinematic viscosity and the seepage velocity of crude oil yields power-law fluid characteristic parameters for ordinary heavy oil reservoirs, including: Plotting the seepage velocity as the X-axis and the kinematic viscosity of crude oil as the Y-axis, the relationship curves between the kinematic viscosity of crude oil and the seepage velocity for each set of experiments were obtained, yielding the power-law fluid characteristic parameters of ordinary heavy oil reservoirs. ， In the formula, For pressure gradient, 10 -3 MPa / m; denoted as the kinematic viscosity of crude oil, in mPa·s; n and m are characteristic parameters of power-law fluids.
6. The method for optimizing well boundaries in the cold production development of horizontal wells in offshore ordinary heavy oil reservoirs according to claim 1, characterized in that, Define the pseudo-seepage resistance and adopt ， in, Total production pressure differential, MPa ; Q For horizontal well production, m³ / d ; n These are the power-law fluid characteristic parameters obtained in step S3.
7. The method for optimizing well boundaries in the cold production and development of horizontal wells in offshore ordinary heavy oil reservoirs according to claim 6, characterized in that, Calculate the total seepage resistance generated by the horizontal well, where: The apparent seepage resistance in the outer zone is expressed as: , The pseudo-seepage resistance in the inner zone can be expressed as: , The total seepage resistance generated by the horizontal well is: ， in, This is the crude oil volume coefficient. m ; h For the effective thickness of the reservoir, m ; L This refers to the length of the horizontal section of a horizontal well in a mine. m ; The oil drain radius, m ; r w Where is the wellbore radius. m ; n, m These are the power-law fluid characteristic parameters obtained in step S3; For penetration rate, mD .
8. The method for optimizing well boundaries in the cold production development of horizontal wells in offshore ordinary heavy oil reservoirs according to claim 7, characterized in that, By combining the total seepage resistance generated by the horizontal well with the total production pressure differential generated by the horizontal well in the discharge region under steady seepage conditions, a horizontal well productivity equation incorporating Bingham and power-law fluid characteristics is obtained, where: The total production pressure differential generated by the horizontal well in the discharge zone is: ， The production capacity equation for cold production development of heavy oil reservoirs using horizontal wells is obtained as follows: , in, For formation pressure, MPa ; For bottom hole flowing pressure, MPa.
9. The method for optimizing well boundaries in the cold production development of horizontal wells in offshore ordinary heavy oil reservoirs according to claim 8, characterized in that, In step S5, the development of horizontal wells for cold production in ordinary heavy oil reservoirs is mapped. IPR Plates, including: Combining the crude oil mobility and effective sand body thickness range of ordinary heavy oil reservoirs at sea, and using the formulas from steps S2 to S4, we plotted the cold production development of horizontal wells under different crude oil mobility and reservoir thicknesses. IPR plate.