Method for determining oil-water spatial distribution of heavy oil reservoir by using heavy oil fluid potential

Abstract

The application provides a method for determining oil-water space distribution of heavy oil reservoir by using heavy oil fluid potential, comprising the following steps: step 1, calculating the threshold pressure gradient of the heavy oil reservoir; step 2, calculating the heavy oil fluid potential considering the threshold pressure gradient; step 3, establishing a three-dimensional model of the heavy oil fluid potential; step 4, determining the heavy oil fluid potential value of the oil-water interface; and step 5, determining the oil-water space distribution of the heavy oil reservoir. The method for determining the oil-water space distribution of the heavy oil reservoir by using the heavy oil fluid potential considers the influence of the threshold pressure gradient on the fluid potential in the heavy oil reservoir and other non-Darcy seepage reservoirs, establishes a heavy oil reservoir fluid potential calculation method, solves the problems of the inclined oil-water interface and the complex oil-water space distribution of the heavy oil reservoir, and lays a foundation for the reasonable and effective development of the heavy oil reservoir, and has important guiding significance for the development practice of the heavy oil field.

Description

Technical Field

[0001] This invention relates to the field of petroleum development technology, and in particular to a method for determining the spatial distribution of oil and water in heavy oil reservoirs using the fluid potential of heavy oil. Background Technology

[0002] In conventional light oil reservoirs, due to the significant difference in density between crude oil and formation water, a "oil-above-water" distribution pattern is typically observed, with oil at higher structural elevations and water at lower structural elevations. The oil-water interface is approximately horizontal, resulting in a relatively simple oil-water distribution. However, in heavy oil reservoirs, the high viscosity of the formation crude oil and the smaller density difference between heavy oil and water create a highly complex oil-water relationship with a large fluid interface difference. This can even lead to a "water-high, oil-low" distribution pattern, with an extremely irregular oil-water interface. Precisely determining the spatial distribution of heavy oil and formation water makes it impossible to accurately determine the spatial distribution, resulting in production wells producing only water and no oil. This poses a significant challenge to oilfield development and severely restricts the economical and effective development of heavy oil fields. Therefore, an effective method is urgently needed to determine the spatial distribution of oil and water in heavy oil reservoirs, and subsequently, to formulate corresponding development strategies. This has important guiding significance for the economical and effective development of heavy oil reservoirs.

[0003] Current research on the oil-water distribution patterns in heavy oil reservoirs is limited to simple structural descriptions of the oil-water interface between drilled wells, failing to analyze the controlling factors of oil-water spatial distribution. Therefore, it is impossible to describe and predict the spatial distribution of heavy oil reservoirs based on this information. Furthermore, the reasons for the complex oil-water distribution in heavy oil reservoirs have only been qualitatively explained, lacking quantitative interpretation and prediction. This significantly impacts the prediction of favorable areas for heavy oil accumulation and drilling success rates, and severely restricts the economical and effective development of heavy oil reservoirs.

[0004] Chinese patent application CN201510223722.8 discloses a method and apparatus for characterizing residual oil based on a fluid potential field. The method includes: establishing a mathematical model of oil-water two-phase fluid seepage during the reservoir development stage; obtaining the values ​​of various parameters in the development fluid potential based on the mathematical model of oil-water two-phase fluid seepage; establishing a distribution model of the actual fluid potential field of the reservoir based on the values ​​of the various parameters in the development fluid potential; and analyzing the distribution of high-potential and low-potential regions of the fluid potential field based on the distribution model of the actual fluid potential field, so as to characterize the residual oil.

[0005] Chinese patent application CN201610709563.7 discloses a method and apparatus for identifying low-resistivity oil layers in multi-layered sandstone reservoirs. The method includes classifying reservoir types in a target exploration area using seismic data, identifying oil-water layers, and determining suspected low-resistivity oil layers; determining the reservoir type of the stratigraphic unit to which the suspected low-resistivity oil layer belongs based on trap formation; performing reservoir formation mechanism analysis on the reservoir type to determine whether it meets the reservoir formation conditions; if so, further subdividing all sand bodies within the stratigraphic unit containing the suspected low-resistivity oil layer into oil-water reservoir units; and within a single oil-water reservoir, reading the elevation of the suspected low-resistivity oil layer and the oil-water interface of the reservoir to identify the oil-bearing nature of the suspected low-resistivity oil layer.

[0006] Chinese patent application CN201310266117.X discloses a method for modeling irregular oil-water interfaces. The method includes: initially simulating the spatial distribution of the oil-water interface in an oil-bearing area; determining the fluctuation range of the oil-water interface based on the deepest and shallowest oil-water interface depths encountered in a single well, and using this as a constraint to control the results obtained in the previous step; for pure water areas, determining the water top interface based on the top surface structure of the water and sand; merging the oil-water interface of the oil-bearing area with the interface of the pure water area to finally obtain the irregular oil-water interface of the entire area.

[0007] The existing technologies described above differ significantly from this invention and fail to address the technical problems we aim to solve. To accurately determine the spatial distribution of oil and water in heavy oil reservoirs and predict favorable areas for heavy oil accumulation, it is necessary to change the traditional methods for studying the distribution patterns of heavy oil. Therefore, we have invented a method for determining the spatial distribution of oil and water in heavy oil reservoirs using the fluid potential of heavy oil, thus solving the aforementioned technical problems. Summary of the Invention

[0008] The purpose of this invention is to provide a method for determining the spatial distribution of oil and water in heavy oil reservoirs using the fluid potential of heavy oil, thereby solving the problem of the complex and unclear spatial distribution of oil and water in heavy oil reservoirs.

[0009] The objective of this invention can be achieved through the following technical measures: a method for determining the spatial distribution of oil and water in a heavy oil reservoir using the fluid potential of heavy oil, the method comprising:

[0010] Step 1: Calculate the starting pressure gradient of the heavy oil reservoir;

[0011] Step 2: Calculate the heavy oil fluid potential considering the initiation pressure gradient;

[0012] Step 3: Establish a three-dimensional model of the heavy oil fluid potential;

[0013] Step 4: Determine the heavy oil fluid potential at the oil-water interface;

[0014] Step 5: Determine the spatial distribution of oil and water in heavy oil reservoirs.

[0015] The objective of this invention can also be achieved through the following technical measures:

[0016] In step 1, in heavy oil reservoirs, which are non-Darcy flow reservoirs, there is a starting pressure gradient for crude oil flow; the starting pressure gradient of heavy oil is measured through laboratory reservoir starting pressure gradient experiments. Since the starting pressure gradient J of heavy oil is usually related to the viscosity μ of the heavy oil... o And it is closely related to the reservoir permeability K, therefore, the starting pressure gradient J and the viscosity μ of heavy oil can be established. o The relationship between the reservoir permeability K and the reservoir permeability K.

[0017] In step 1, the heavy oil starting pressure gradient J and heavy oil viscosity μ are established. o The relationship between the reservoir permeability K and the reservoir permeability K is:

[0018] lnJ=alnμ o +blnK+c (1)

[0019] Right now

[0020] J = e c μ o a K b (2)

[0021] Let constant e c =A

[0022] achievable

[0023] J = Aμ o a K b (3)

[0024] In the formula:

[0025] J—Heavy oil start-up pressure gradient, Pa / m;

[0026] μ o — Formation viscosity of heavy oil, mPa·s;

[0027] K—Permeability of the reservoir rock medium in heavy oil reservoirs, 10 -3 μm 2 ;

[0028] a, b, c, A — coefficients to be determined;

[0029] Therefore, the above formula (3) can be used to characterize the starting pressure gradient of heavy oil in different locations of different wells in heavy oil reservoirs.

[0030] In step 2, firstly, the potential energy Φ is calculated.z Pressure energy Φ p Kinetic energy Φ q and interface energy Φ r The traditional crude oil fluid potential Φ' is calculated; then, the heavy oil fluid potential considering the initiation pressure gradient is calculated based on this.

[0031] In step 2, the conventional crude oil fluid potential is expressed as:

[0032]

[0033] In the formula:

[0034] Φ'—Conventional crude oil fluid potential, J / m 3 ;

[0035] Φ z —Fluid potential energy, J / m 3 ;

[0036] Φ p —Fluorite pressure energy, J / m 3 ;

[0037] Φ q —Fluid kinetic energy, J / m 3 ;

[0038] Φ r —Fluid interface energy, J / m 3 ;

[0039] ρ o —Crude oil density, kg / m³ 3 ;

[0040] ρ w — Formation water density, kg / m³ 3 ;

[0041] g—acceleration due to gravity, m / s² 2 ;

[0042] z—elevation of the measuring point, in meters; sea level is taken as the reference surface, with values ​​above the reference surface being positive and values ​​below the reference surface being negative;

[0043] p—pressure at the measuring point, Pa;

[0044] q o —Flow velocity, m / s;

[0045] σ—fluid interfacial tension, N / m;

[0046] θ—Contact angle of multiphase fluid, °;

[0047] r—the radius of the pore throat in the rock medium, in meters;

[0048] In step 2, when calculating the fluid potential of heavy oil considering the initiation pressure gradient, in non-Darcy flow reservoirs such as heavy oil reservoirs, due to poor reservoir properties and high crude oil viscosity, the liquid-solid interface interaction force increases, resulting in poor crude oil fluidity. Crude oil cannot flow under normal conditions; it only begins to flow when the driving force exceeds the initiation pressure. At this point, the viscous force between the crude oil and the reservoir cannot be ignored. Therefore, the work done by the solid-liquid interface viscous force to overcome when a unit volume and unit length of fluid begins to flow at a certain point in the reservoir is defined as the fluid viscous energy Φ. J Its expression is:

[0049]

[0050] In the formula:

[0051] Φ J —Fluorescence energy, J / m 3 ;

[0052] J—Fluid initiation pressure gradient, Pa / m;

[0053] l—Length of the fluid column along the direction of the starting pressure gradient, in meters;

[0054] The expression for calculating the fluid potential of heavy oil considering the initiation pressure gradient is as follows:

[0055]

[0056] In the formula:

[0057] Φ—Heavy oil fluid potential considering the starting pressure gradient, J / m 3 ;

[0058] Oil and water are generally incompressible, and their kinetic energy can be neglected in still water or when the fluid flow is very slow. In this case, the potential energy of heavy oil can be simplified to:

[0059]

[0060] This allows for the calculation of the fluid potential of heavy oil considering the starting pressure gradient.

[0061] In step 3, firstly, based on the secondary interpretation results of the drilled well logging, a three-dimensional elevation depth model (z), a three-dimensional porosity model (Por), and a three-dimensional permeability model (Perm) of the target block reservoir are established using three-dimensional geological modeling software; secondly, based on mercury intrusion porosimetry data, the rock pore throat radius r and the porosity of the rock medium are established. The relationship between the fluid potential and the permeability K is determined; finally, the three-dimensional model of the heavy oil fluid potential, model(Φ), is calculated.

[0062] In step 3, the established rock pore throat radius r and rock medium porosity are... Relationship with penetration rate K:

[0063]

[0064] Right now

[0065]

[0066] Let constant e u =M

[0067] achievable

[0068]

[0069] In the formula:

[0070] —Porosity of rock medium, %;

[0071] K—Permeability of rock medium, 10 -3 μm 2 ;

[0072] m, n, u, M — coefficients to be determined;

[0073] Therefore, the fluid interface energy Φ is established. r 3D model model(Φ r ):

[0074]

[0075] In the formula, σ—fluid interfacial tension, N / m;

[0076] θ—Contact angle of multiphase fluid, °;

[0077] And based on the heavy oil starting pressure gradient J and heavy oil viscosity μ o The relationship between fluid viscous energy Φ and reservoir permeability K is established. J 3D model model(Φ J ).

[0078] model(Φ J )=Aμ o a [model(Perm)] b (12)

[0079] a, b, A — coefficients to be determined.

[0080] In step 3, the calculated three-dimensional model (Φ) of the heavy oil fluid potential is:

[0081]

[0082] This allows for the establishment of a three-dimensional model of the fluid potential of heavy oil.

[0083] In step 4, based on well logging data, the potential value of heavy oil fluid at the oil-water interface of the drilled wells is calculated and statistically analyzed. The potential value of heavy oil fluid at the oil-water interface is determined by comprehensive judgment of multiple wells.

[0084] In step 5, fluid potential is a description and characterization of the energy state of underground fluids, used to describe the energy changes and migration patterns of fluids. Fluids tend to flow from high potential areas to low potential areas; therefore, the level of heavy oil fluid potential determines the spatial distribution of underground heavy oil. Using the determined heavy oil fluid potential value at the oil-water interface, in the three-dimensional model, the space where the heavy oil fluid potential is lower than or equal to the heavy oil fluid potential value at the oil-water interface is the distribution space of heavy oil, and the space where the heavy oil fluid potential value is higher than the heavy oil fluid potential value at the oil-water interface is the distribution space of formation water.

[0085] The method for determining the spatial distribution of oil and water in heavy oil reservoirs using the fluid potential of heavy oil in this invention takes into account the influence of the starting pressure gradient on the fluid potential in non-Darcy flow reservoirs such as heavy oil reservoirs. It establishes a method for calculating the fluid potential of non-Darcy flow reservoirs such as heavy oil reservoirs, solves the problem of the inclined oil-water interface and complex spatial distribution of oil and water in heavy oil reservoirs, lays the foundation for the rational and effective development of heavy oil reservoirs, and has important guiding significance for the development practice of heavy oil fields. Attached Figure Description

[0086] Figure 1 This is a flowchart of a specific embodiment of a method for determining the spatial distribution of oil and water in a heavy oil reservoir using the fluid potential of heavy oil according to the present invention;

[0087] Figure 2 This is a three-dimensional model diagram of the heavy oil fluid potential in a specific embodiment of the present invention;

[0088] Figure 3 This is a structural diagram of a heavy oil reservoir in a specific embodiment of the present invention. Detailed Implementation

[0089] To make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings.

[0090] The method for determining the spatial distribution of oil and water in a heavy oil reservoir using the fluid potential of heavy oil of the present invention includes the following steps:

[0091] Step 1: Calculate the starting pressure gradient of the heavy oil reservoir block. In non-Darcy flow reservoirs such as heavy oil reservoirs, a starting pressure gradient exists for crude oil flow. The starting pressure gradient of heavy oil can be measured through laboratory reservoir starting pressure gradient experiments. Since the starting pressure gradient J of heavy oil is usually related to the viscosity μ of heavy oil... oAnd it is closely related to the reservoir permeability K, therefore, the starting pressure gradient J and the viscosity μ of heavy oil can be established. o Relationship with reservoir permeability K:

[0092] lnJ=alnμ o +blnK+c (1)

[0093] Right now

[0094] J = e c μ o a K b (2)

[0095] Let constant e c =A

[0096] achievable

[0097] J = Aμ o a K b (3)

[0098] In the formula:

[0099] J—Heavy oil start-up pressure gradient, Pa / m;

[0100] μ o — Formation viscosity of heavy oil, mPa·s;

[0101] K—Permeability of the reservoir rock medium in heavy oil reservoirs, 10 -3 μm 2 ;

[0102] a, b, c, A — coefficients to be determined.

[0103] Therefore, the above formula (3) can be used to characterize the starting pressure gradient of heavy oil in different locations of different wells in heavy oil reservoirs.

[0104] Step 2: Calculate the fluid potential of heavy oil considering the initiation pressure gradient.

[0105] First, the calculation includes the potential energy Φ z Pressure energy Φ p Kinetic energy Φ q and interface energy Φ r The traditional crude oil fluid potential Φ' is included. The traditional crude oil fluid potential can be expressed as:

[0106]

[0107] In the formula:

[0108] Φ'—Conventional crude oil fluid potential, J / m 3 ;

[0109] Φz —Fluid potential energy, J / m 3 ;

[0110] Φ p —Fluorite pressure energy, J / m 3 ;

[0111] Φ q —Fluid kinetic energy, J / m 3 ;

[0112] Φ r —Fluid interface energy, J / m 3 ;

[0113] ρ o —Crude oil density, kg / m³ 3 ;

[0114] ρ w — Formation water density, kg / m³ 3 ;

[0115] g—acceleration due to gravity, m / s² 2 ;

[0116] z—elevation of the measuring point, in meters (sea level is taken as the reference surface; above the reference surface is positive, and below the reference surface is negative).

[0117] p—pressure at the measuring point, Pa.

[0118] q o — Flow velocity, m / s.

[0119] σ—fluid interfacial tension, N / m;

[0120] θ—Contact angle of multiphase fluid, °;

[0121] r—the radius of the pore throat in the rock medium, in meters.

[0122] Then, based on this, the fluid potential of heavy oil considering the initiation pressure gradient is calculated. In non-Darcy flow reservoirs such as heavy oil reservoirs, due to poor reservoir properties and high crude oil viscosity, the liquid-solid interface interaction force increases, resulting in poor crude oil fluidity. Crude oil cannot flow under normal conditions; it only begins to flow when the driving force is greater than the initiation pressure. At this point, the viscous force between the crude oil and the reservoir cannot be ignored. Therefore, the work done by the solid-liquid interface viscous force to overcome when a unit volume and unit length of fluid begins to flow at a certain point in the reservoir is defined as the fluid viscous energy Φ. J Its expression is:

[0123]

[0124] In the formula:

[0125] ΦJ —Fluorescence energy, J / m 3 ;

[0126] J—Fluid initiation pressure gradient, Pa / m;

[0127] l — Length of the fluid column along the direction of the starting pressure gradient, in meters.

[0128] The expression for calculating the fluid potential of heavy oil considering the initiation pressure gradient is as follows:

[0129]

[0130] In the formula:

[0131] Φ—Heavy oil fluid potential considering the starting pressure gradient, J / m 3 ;

[0132] Oil and water are generally incompressible, and their kinetic energy can be neglected in still water or when the fluid flow is very slow. In this case, the potential energy of heavy oil can be simplified to:

[0133]

[0134] This allows for the calculation of the fluid potential of heavy oil considering the starting pressure gradient.

[0135] Step 3: Establish a three-dimensional model of the heavy oil fluid potential.

[0136] First, based on the secondary interpretation results of the drilled well logging, a three-dimensional elevation depth model (z), a three-dimensional porosity model (Por), and a three-dimensional permeability model (Perm) of the target block reservoir are established using three-dimensional geological modeling software.

[0137] Secondly, based on mercury intrusion porosimetry data, the relationship between the rock pore throat radius r and the rock medium porosity was established. Relationship with penetration rate K:

[0138]

[0139] Right now

[0140]

[0141] Let constant e u =M

[0142] achievable

[0143]

[0144] In the formula:

[0145] —Porosity of rock medium, %;

[0146] K—Permeability of rock medium, 10 -3 μm 2 ;

[0147] m, n, u, M — coefficients to be determined.

[0148] Therefore, the fluid interface energy Φ is established. r 3D model model(Φ r ).

[0149]

[0150] And based on the heavy oil starting pressure gradient J and heavy oil viscosity μ o The relationship between fluid viscous energy Φ and reservoir permeability K is established. J 3D model model(Φ J ).

[0151] model(Φ J )=Aμ o a [model(Perm)] b (12)

[0152] a, b, A — coefficients to be determined.

[0153] Finally, the three-dimensional model (Φ) of the heavy oil fluid potential is calculated.

[0154]

[0155] This allows for the establishment of a three-dimensional model of the fluid potential of heavy oil.

[0156] Step 4: Determine the heavy oil fluid potential at the oil-water interface. Based on well logging data, calculate and statistically analyze the heavy oil fluid potential at the oil-water interface of drilled wells, and make a comprehensive judgment from multiple wells to determine the heavy oil fluid potential at the oil-water interface.

[0157] Step 5: Determine the spatial distribution of oil and water in heavy oil reservoirs. Fluid potential is a description and characterization of the energy state of underground fluids, used to describe the energy changes and migration patterns of fluids. Fluids tend to flow from high-potential areas to low-potential areas. Therefore, the level of heavy oil fluid potential determines the spatial distribution of underground heavy oil. Using the determined heavy oil fluid potential value at the oil-water interface, in the three-dimensional model, the space where the heavy oil fluid potential is lower than or equal to the value at the oil-water interface represents the distribution space of heavy oil, while the space where the heavy oil fluid potential is higher than the value at the oil-water interface represents the distribution space of formation water.

[0158] In a specific embodiment 1 of the present invention, such as Figure 1 As shown, Figure 1This is a flowchart of the method for determining the spatial distribution of oil and water in a heavy oil reservoir using the fluid potential of heavy oil, according to the present invention.

[0159] In one embodiment, a reservoir in the Guantao Formation of Shengli Oilfield was selected for a study on determining the spatial distribution of oil and water in a heavy oil reservoir using heavy oil fluid potential. This reservoir is a structural-lithological heavy oil reservoir with edge and bottom water. The structural burial depth of the target layer is -1170 to -1230 m, the original formation pressure P is 11–12 MPa, the crude oil viscosity under formation conditions is 500 mPa·s, and there is a significant initiation pressure gradient when the crude oil begins to flow. The crude oil density under formation conditions is 959 kg / m³. 3 The formation water density is 1000 kg / m³ under formation conditions. 3 The interfacial tension σ between oil and water in this heavy oil reservoir is 25 × 10⁻⁶. -3 The oil density is N / m, the oil-water contact angle θ of the heavy oil is 35°, the porosity of the oil layer is generally 30-40%, and the permeability is generally 500-6000×10⁻⁶. -3 μm 2 It is a high-porosity, high-permeability heavy oil reservoir.

[0160] In step 101, the starting pressure gradient of the heavy oil reservoir block is calculated. In non-Darcy flow reservoirs such as heavy oil reservoirs, a starting pressure gradient exists for crude oil flow. The starting pressure gradient of heavy oil can be measured through laboratory reservoir starting pressure gradient experiments. Since the starting pressure gradient J of heavy oil is usually related to the viscosity μ of heavy oil... o And it is closely related to the reservoir permeability K, therefore, the starting pressure gradient J and the viscosity μ of heavy oil can be established. o Relationship with reservoir permeability K:

[0161] lnJ=alnμ o +blnK+c (1)

[0162] Right now

[0163] J = e c μ o a K b (2)

[0164] Let constant e c =A

[0165] achievable

[0166] J = Aμ o a K b (3)

[0167] In the formula:

[0168] J—Heavy oil start-up pressure gradient, Pa / m;

[0169] μo — Formation viscosity of heavy oil, mPa·s;

[0170] K—Permeability of the reservoir rock medium in heavy oil reservoirs, 10 -3 μm 2 ;

[0171] a, b, c, A — coefficients to be determined.

[0172] Based on the experimental results, the crude oil initiation pressure gradient J of this oil reservoir is related to the oil viscosity μ. o The relationship with reservoir permeability K is as follows:

[0173]

[0174] Therefore, the oil viscosity energy Φ of each well in this oil layer can be obtained. J .

[0175] The process proceeds to step 102.

[0176] In step 102, the heavy oil fluid potential considering the initiation pressure gradient is calculated. First, the potential energy Φ is calculated. z Pressure energy Φ p Kinetic energy Φ q and interface energy Φ r The traditional crude oil fluid potential Φ' is included. The traditional crude oil fluid potential can be expressed as:

[0177]

[0178] In the formula:

[0179] Φ'—Conventional crude oil fluid potential, J / m 3 ;

[0180] Φ z —Fluid potential energy, J / m 3 ;

[0181] Φ p —Fluorite pressure energy, J / m 3 ;

[0182] Φ q —Fluid kinetic energy, J / m 3 ;

[0183] Φ r —Fluid interface energy, J / m 3 ;

[0184] ρ o —Crude oil density, kg / m³ 3 ;

[0185] ρ w — Formation water density, kg / m³ 3;

[0186] g—acceleration due to gravity, m / s² 2 ;

[0187] z—elevation of the measuring point, in meters (sea level is taken as the reference surface; above the reference surface is positive, and below the reference surface is negative).

[0188] p—pressure at the measuring point, Pa.

[0189] q o — Flow velocity, m / s.

[0190] σ—fluid interfacial tension, N / m;

[0191] θ—Contact angle of multiphase fluid, °;

[0192] r—the radius of the pore throat in the rock medium, in meters.

[0193] Then, based on this, the fluid potential of heavy oil considering the initiation pressure gradient is calculated. In non-Darcy flow reservoirs such as heavy oil reservoirs, due to poor reservoir properties and high crude oil viscosity, the liquid-solid interface interaction force increases, resulting in poor crude oil fluidity. Crude oil cannot flow under normal conditions; it only begins to flow when the driving force is greater than the initiation pressure. At this point, the viscous force between the crude oil and the reservoir cannot be ignored. Therefore, the work done by the solid-liquid interface viscous force to overcome when a unit volume and unit length of fluid begins to flow at a certain point in the reservoir is defined as the fluid viscous energy Φ. J Its expression is:

[0194]

[0195] In the formula:

[0196] Φ J —Fluorescence energy, J / m 3 ;

[0197] J—Fluid initiation pressure gradient, Pa / m;

[0198] l — Length of the fluid column along the direction of the starting pressure gradient, in meters.

[0199] The expression for calculating the fluid potential of heavy oil considering the initiation pressure gradient is as follows:

[0200]

[0201] In the formula:

[0202] Φ—Heavy oil fluid potential considering the starting pressure gradient, J / m 3 ;

[0203] Oil and water are generally incompressible, and their kinetic energy can be neglected in still water or when the fluid flow is very slow. In this case, the potential energy of heavy oil can be simplified to:

[0204]

[0205] This allows for the calculation of the fluid potential of heavy oil considering the starting pressure gradient.

[0206] The process proceeds to step 103.

[0207] In step 103, a three-dimensional model of the heavy oil fluid potential is established. First, based on the secondary interpretation results of the drilled well logging, a three-dimensional elevation-depth model (model(z),) a three-dimensional porosity model (model(Por), and a three-dimensional permeability model (model(Perm)) of the target block reservoir are established using three-dimensional geological modeling software.

[0208] Secondly, based on mercury intrusion porosimetry data, the relationship between the rock pore throat radius r and the rock medium porosity was established. Relationship with penetration rate K:

[0209]

[0210] Right now

[0211]

[0212] Let constant e u =M

[0213] achievable

[0214]

[0215] In the formula:

[0216] —Porosity of rock medium, %;

[0217] K—Permeability of rock medium, 10 -3 μm 2 ;

[0218] m, n, u, M — coefficients to be determined.

[0219] Based on the experimental results, the pore throat radius r of the oil reservoir and the porosity of the rock medium The relationship with the penetration rate K is as follows:

[0220]

[0221] Therefore, the fluid interface energy Φ is established. r 3D model model(Φ r ).

[0222]

[0223] And based on the heavy oil starting pressure gradient J and heavy oil viscosity μ o The relationship between fluid viscous energy Φ and reservoir permeability K is established. J 3D model model(Φ J ).

[0224] model(Φ J )=Aμ o a [model(Perm)] b

[0225] =4900×μ o 0.0853 ×[model(Perm)] -0.0853 (14)

[0226] Finally, the three-dimensional model (Φ) of the heavy oil fluid potential is calculated.

[0227]

[0228] This allows for the establishment of a three-dimensional model of the fluid potential of heavy oil.

[0229] The process proceeds to step 104.

[0230] In step 104, the heavy oil fluid potential value at the oil-water interface is determined. Based on well logging data, the heavy oil fluid potential value at the oil-water interface of drilled wells is calculated and statistically analyzed. A comprehensive assessment of multiple wells determines the heavy oil fluid potential value at the oil-water interface to be 382 × 10⁻⁶. 3 Pa.

[0231] The process proceeds to step 105.

[0232] In step 105, the spatial distribution of oil and water in the heavy oil reservoir is determined. Fluid potential is a description and characterization of the energy state of underground fluids, used to describe the energy changes and migration patterns of fluids. Fluids tend to flow from high-potential areas to low-potential areas. Therefore, the level of heavy oil fluid potential determines the spatial distribution of underground heavy oil. Using the determined heavy oil fluid potential value at the oil-water interface, in the three-dimensional model, the space where the heavy oil fluid potential is lower than or equal to the value at the oil-water interface is the distribution space of heavy oil, and the space where the heavy oil fluid potential is higher than the value at the oil-water interface is the distribution space of formation water. That is, in the three-dimensional model of heavy oil fluid potential model(Φ), the heavy oil fluid potential value is less than or equal to 382 × 10⁻⁶. 3 The range of Pa refers to the distribution range of heavy oil, where the fluid potential of heavy oil is greater than 382 × 10⁻⁶. 3 The range of Pa represents the distribution range of formation water.

[0233] Based on the above steps, the spatial distribution of oil and water in heavy oil reservoirs can be determined using the fluid potential of heavy oil.

[0234] In a specific embodiment 2 of the present invention, a three-dimensional model of heavy oil fluid potential considering the initiation pressure gradient is thus established. Figure 2 As can be clearly seen from the figure, heavy oil is mainly distributed in the low potential region, and the predicted crude oil fluid potential contour line is 382×10. 3 The area below Pa represents the spatial distribution range of heavy oil. (See the top surface structure diagram of this oil layer.) Figure 3 Compared to previous methods, this approach accurately delineates two water-producing wells (Z185 and Z29-35) in the northwest, more precisely determining the distribution range of heavy oil and providing a solid foundation for the economical and effective development of heavy oil reservoirs. This method, utilizing the fluid potential of heavy oil to determine the spatial distribution of oil and water in heavy oil reservoirs, considers the influence of the starting pressure gradient on fluid potential in non-Darcy flow reservoirs such as heavy oil reservoirs. It establishes a method for calculating the fluid potential of non-Darcy flow reservoirs such as heavy oil reservoirs, solving the problems of inclined oil-water interfaces and complex spatial distribution of oil and water in heavy oil reservoirs. This lays the foundation for the rational and effective development of heavy oil reservoirs and has important guiding significance for the development practice of heavy oil fields.

[0235] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0236] Except for the technical features described in the specification, all other technologies are known to those skilled in the art.

Claims

1. A method for determining the spatial distribution of oil and water in a heavy oil reservoir using the fluid potential of heavy oil, characterized in that, The method for determining the spatial distribution of oil and water in heavy oil reservoirs using the fluid potential of heavy oil includes: Step 1: Calculate the starting pressure gradient of the heavy oil reservoir; Step 2: Calculate the heavy oil fluid potential considering the initiation pressure gradient; Step 3: Establish a three-dimensional model of the heavy oil fluid potential; Step 4: Determine the heavy oil fluid potential at the oil-water interface; Step 5: Determine the spatial distribution of oil and water in heavy oil reservoirs; In step 2, the conventional crude oil fluid potential is expressed as: （4） In the formula: Φ'—Conventional crude oil fluid potential, J / m 3 ; Φ z —Fluid potential energy, J / m 3 ; Φ p —Fluorite pressure energy, J / m 3 ; Φ q —Fluid kinetic energy, J / m 3 ; Φ r —Fluid interface energy, J / m 3 ; ρ o —Crude oil density, kg / m³ 3 ; ρ w — Formation water density, kg / m³ 3 ; g—acceleration due to gravity, m / s² 2 ; z—elevation of the measuring point, in meters; sea level is taken as the reference surface, with values ​​above the reference surface being positive and values ​​below the reference surface being negative; p—pressure at the measuring point, Pa; q o —Flow velocity, m / s; σ—fluid interfacial tension, N / m; θ—Contact angle of multiphase fluid, °; r—the radius of the pore throat in the rock medium, in meters; In step 2, when calculating the fluid potential of heavy oil considering the initiation pressure gradient, in non-Darcy flow heavy oil reservoirs, due to poor reservoir properties and high crude oil viscosity, the liquid-solid interface interaction force increases, resulting in poor crude oil flowability. Under normal conditions, crude oil cannot flow; it only begins to flow when the driving force exceeds the initiation pressure. At this point, the viscous force between the crude oil and the reservoir cannot be ignored. Therefore, the work done by the solid-liquid interface viscous force to overcome when a unit volume and unit length of fluid begins to flow at a certain point in the reservoir is defined as the fluid viscous energy Φ. J Its expression is: （5） In the formula: Φ J —Fluorescence energy, J / m 3 ; J—Fluid initiation pressure gradient, Pa / m; l—Length of the fluid column along the direction of the starting pressure gradient, in meters; The expression for calculating the fluid potential of heavy oil considering the initiation pressure gradient is as follows: （6） In the formula: Φ—Heavy oil fluid potential considering the starting pressure gradient, J / m 3 ; Oil and water are incompressible. When in a still water environment or when the fluid flow is very slow, kinetic energy can be ignored. In this case, the potential of heavy oil fluid simplifies to: （7） This enables the calculation of the fluid potential of heavy oil considering the starting pressure gradient.

2. The method for determining the spatial distribution of oil and water in a heavy oil reservoir using the fluid potential of heavy oil as described in claim 1, characterized in that, In step 1, in heavy oil reservoirs, which are non-Darcy flow reservoirs, there is a starting pressure gradient for crude oil flow; the starting pressure gradient of heavy oil is measured through laboratory reservoir starting pressure gradient experiments. Since the starting pressure gradient J of heavy oil is usually related to the viscosity μ of the heavy oil... o And it is closely related to the reservoir permeability K, therefore, the starting pressure gradient J and the viscosity μ of heavy oil are established. o The relationship between the reservoir permeability K and the reservoir permeability K.

3. The method for determining the spatial distribution of oil and water in a heavy oil reservoir using the fluid potential of heavy oil as described in claim 2, characterized in that, In step 1, the heavy oil starting pressure gradient J and heavy oil viscosity μ are established. o The relationship between the reservoir permeability K and the reservoir permeability K is: （1） Right now （2） Let constant have to （3） In the formula: J—Heavy oil start-up pressure gradient, Pa / m; μ o — Formation viscosity of heavy oil, mPa·s; K—Permeability of the reservoir rock medium in heavy oil reservoirs, 10 -3 μm 2 ; a, b, c, A — coefficients to be determined; Therefore, the above formula (3) is used to characterize the starting pressure gradient of heavy oil in different locations of different wells in heavy oil reservoirs.

4. The method for determining the spatial distribution of oil and water in a heavy oil reservoir using the fluid potential of heavy oil as described in claim 1, characterized in that, In step 2, firstly, the potential energy Φ is calculated. z Pressure energy Φ p Kinetic energy Φ q and interface energy Φ r The traditional crude oil fluid potential Φ' is calculated; then, the heavy oil fluid potential considering the initiation pressure gradient is calculated based on this.

5. The method for determining the spatial distribution of oil and water in a heavy oil reservoir using the fluid potential of heavy oil as described in claim 1, characterized in that, In step 3, firstly, based on the secondary interpretation results of the drilled well logging, a three-dimensional elevation depth model (z), a three-dimensional porosity model (Por), and a three-dimensional permeability model (Perm) of the target block reservoir are established using three-dimensional geological modeling software; secondly, the relationship between the rock pore throat radius r and the rock medium porosity φ and permeability K is established using mercury intrusion porosimetry test data; finally, a three-dimensional model (Φ) of the heavy oil fluid potential is calculated.

6. The method for determining the spatial distribution of oil and water in a heavy oil reservoir using the fluid potential of heavy oil as described in claim 5, characterized in that, In step 3, the relationship between the rock pore throat radius r and the rock medium porosity φ and permeability K is established: （8） Right now （9） Let constant have to （10） In the formula: φ—Porosity of rock medium, % K—Permeability of rock medium, 10 -3 μm 2 ; m, n, u, M — coefficients to be determined; Therefore, the fluid interface energy Φ is established. r 3D model (Φ) r ): （11） In the formula, σ—fluid interfacial tension, N / m; θ—Contact angle of multiphase fluid, °; And based on the heavy oil starting pressure gradient J and heavy oil viscosity μ o The relationship between fluid viscous energy Φ and reservoir permeability K is established. J 3D model (Φ) J ); （12） a, b, A — coefficients to be determined.

7. The method for determining the spatial distribution of oil and water in a heavy oil reservoir using the fluid potential of heavy oil as described in claim 6, characterized in that, In step 3, the calculated three-dimensional model (Φ) of the heavy oil fluid potential is: （13） Therefore, a three-dimensional model of the fluid potential of heavy oil was established.

8. The method for determining the spatial distribution of oil and water in a heavy oil reservoir using the fluid potential of heavy oil as described in claim 1, characterized in that, In step 4, based on well logging data, the potential value of heavy oil fluid at the oil-water interface of the drilled wells is calculated and statistically analyzed. The potential value of heavy oil fluid at the oil-water interface is determined by comprehensive judgment of multiple wells.

9. The method for determining the spatial distribution of oil and water in a heavy oil reservoir using the fluid potential of heavy oil as described in claim 1, characterized in that, In step 5, fluid potential is a description and characterization of the energy state of underground fluids, used to describe the energy changes and migration patterns of fluids. Fluids tend to flow from high potential areas to low potential areas; therefore, the level of heavy oil fluid potential determines the spatial distribution of underground heavy oil. Using the determined heavy oil fluid potential value at the oil-water interface, in the three-dimensional model, the space where the heavy oil fluid potential is lower than or equal to the heavy oil fluid potential value at the oil-water interface is the distribution space of heavy oil, and the space where the heavy oil fluid potential value is higher than the heavy oil fluid potential value at the oil-water interface is the distribution space of formation water.

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