Method for judging oil reservoir production degree

Abstract

The method comprises the following steps: establishing an original temperature field geologic model under a geological attribute background representing the distribution characteristics of a temperature field before an oil reservoir is put into development; based on the original temperature field geologic model, establishing a current temperature field geologic model representing the current temperature field of the oil reservoir; information of the current temperature field geologic model and the original temperature field geologic model is analyzed, compared and calculated, a temperature field change model is obtained, and the oil reservoir production degree is judged based on the temperature field change model. According to the method, the original temperature field geologic model and the current temperature field geologic model are established, and the current temperature field geologic model and the original temperature field geologic model are subjected to comparison operation to obtain the temperature field change model, so that the oil reservoir reserve utilization degree information is reflected, the remaining oil rich zone is displayed in a three-dimensional manner, the process operation is simple, and the efficiency is high. And the method has relatively high implementability.

Description

Technical Field

[0001] The present invention relates to the field of oilfield development, and in particular to a method for determining the degree of oil reservoir production. Background Art

[0002] Current research on reservoir production is generally qualitative, e.g., good reservoir properties generally indicate high production. However, there is no method to effectively characterize the relationship between reservoir properties and production. Some researchers have introduced the concept of the oil recovery efficiency coefficient, based on the relationship between recovery factor, sweep coefficient, and oil displacement efficiency, to describe the production status of multilayered heterogeneous reservoirs. They have established a relationship between the oil recovery efficiency coefficient and the recovery factor of individual layers in multilayered heterogeneous reservoirs. Combined with numerical simulation results, the oil recovery efficiency coefficient of each layer has been calculated. By analyzing the cumulative distribution curves of the oil recovery efficiency coefficient before and after structural adjustment measures such as fracturing, water plugging, and subdivided water injection, as well as the changes in the average and variability of the oil recovery efficiency coefficient, the authors reveal the differences in production levels between reservoirs. This provides a new method and theoretical basis for evaluating the production status of heterogeneous reservoirs during the extremely high water cut period. Some researchers, starting from the waterflood reserve utilization level, have proposed a method for waterflood reserve utilization based on oil well units. Based on the injection-production well pattern, basic development units are divided according to the streamline boundaries between oil and water wells, directional wells, and horizontal wells. Static well-controlled reserves calculations are then performed for each unit. The utilization level is then calculated using the static and dynamic data of each oil well unit and the Type B waterflood curve. This provides an important reference for further development optimization.

[0003] Overall, current literature review reveals few studies examining the relationship between reservoir temperature field changes and reservoir production. In actual development, porous media in reservoirs undergo non-isothermal flow, primarily due to the heterogeneity of the original reservoir's geothermal temperature and the difference between the injection temperature and the reservoir temperature. This heterogeneity is primarily caused by factors such as geothermal gradients, geothermal flow, reservoir depth, and reservoir basement structure. Even in horizontal oil layers, geothermal temperatures are heterogeneous due to the influence of geothermal gradients, resulting in non-isothermal fluid flow (fluids flow from high-temperature areas to low-temperature areas or vice versa). Secondary oil recovery in oil fields primarily relies on normal-temperature waterflooding. As waterflooding progresses, the difference between the injection temperature and the reservoir's geothermal temperature affects the reservoir temperature distribution and the fluid flow in the porous media. Due to the heterogeneity of geothermal temperature in oil reservoirs and the flow of fluids in porous media in oil reservoirs, the seepage of porous media is accompanied by heat transfer during oilfield development. The seepage process of porous media in oil reservoirs during oilfield development is the result of the interaction between mass transfer and energy transfer, that is, the coupled process of heat transfer and mass transfer in porous media. Therefore, in the simulation of reservoir temperature field, it is necessary to consider the changes in temperature field and its effect on the seepage of porous media based on geological properties. The purpose of temperature field research is to study the coupled process of heat transfer and seepage in porous media of oil reservoirs, establish a mathematical model of oil reservoirs with coupled seepage and heat transfer, simulate the coupled process of seepage and heat transfer in porous media of oil reservoirs more realistically, further improve the accuracy and reliability of reservoir temperature field simulation, and provide correct guidance for oilfield development and management.

[0004] Document CN 108266169 B discloses a method and apparatus for detecting the production level of a horizontal oil reservoir. The method determines a first temperature of the pipe wall of a production well at multiple preset nodes when the horizontal oil reservoir is not being used, detects a second temperature of the oil reservoir within the production well at multiple preset nodes, and compares the first and second temperatures to determine the detection results of the horizontal oil reservoir at the multiple preset nodes. The production level of the horizontal oil reservoir is then determined based on the detection results at the multiple preset nodes. By determining the production status of the horizontal oil reservoir at multiple preset nodes, the production level of the entire horizontal oil reservoir can be determined.

[0005] Based on this, there is room for improvement in characterizing the degree of reservoir production through simulation of reservoir temperature field changes. Summary of the Invention

[0006] In view of the lack of research on quantitatively characterizing the degree of reservoir production by simulating the reservoir temperature field, the purpose of the present invention is to provide a method for determining the degree of reservoir production and solve the technical problem of insufficient research on accurately locating the remaining oil sweet spot section.

[0007] In order to achieve the above object, the technical solution provided by the present invention is:

[0008] A method for determining the producing degree of an oil reservoir comprises:

[0009] Establishing an original temperature field geological model based on the geological attribute background that characterizes the distribution characteristics of the temperature field before the reservoir is put into development;

[0010] Based on the original temperature field geological model, a current temperature field geological model is established to characterize the current temperature field of the reservoir;

[0011] Analyze and compare the information of the current temperature field geological model and the original temperature field geological model, obtain the temperature field change model, and determine the degree of oil reservoir production based on the temperature field change model.

[0012] In some embodiments, the geological attributes include reservoir porosity, permeability, oil saturation, and temperature.

[0013] In some embodiments, an original temperature field geological model is established in the context of geological attributes, including: clarifying the sedimentary microfacies information of the target layer based on well logging information and three-dimensional seismic data; based on the sedimentary microfacies information, in the process of inter-well interpolation calculation, combining seismic attribute control to establish an original temperature field geological model of original physical property characteristics.

[0014] In some embodiments, the raw physical properties include reservoir porosity and permeability.

[0015] In some embodiments, establishing a geological model of the original temperature field in the context of geological attributes includes the following steps:

[0016] Step 1: Establish a structural model that meets the accuracy requirements based on seismic interpretation levels and fault information and single well geological stratification;

[0017] Step 2: Combine logging lithologic information with the control of regional sedimentary microfacies to establish a lithofacies model based on the structural model established in step 1;

[0018] Step 3: Based on the well logging interpretation of reservoir porosity, permeability, and oil saturation data, a reservoir attribute model is established based on the lithofacies model established in step 2 under the control of seismic attributes;

[0019] Step 4: Based on the original temperature information of the single well and combined with the geothermal gradient parameters of the reservoir, the original temperature field geological model is established based on the reservoir property model established in step 3 through truncated Gaussian interpolation.

[0020] In some embodiments, in step 1, the structural model is to establish the concept of the reservoir body, set the horizontal and vertical grids according to the well spacing, and divide the reservoir body into several structural grid bodies. In the subsequent process of establishing the lithofacies model and the reservoir property model, the structural grid bodies are used as calculation units for assignment.

[0021] In some embodiments, in step 2, the lithofacies model is fitted based on the structural model and the lithologic information of a single well, and the lithologic information is assigned to the structural grid.

[0022] In some embodiments, the lithology information includes rock thermal property parameter information, and the rock thermal property parameters include thermal conductivity, thermal resistivity and specific heat of the rock.

[0023] In some embodiments, in step 3, a reservoir property model is established, including: selecting a suitable interpolation method according to the reservoir characteristics, assigning values ​​to the structural grid under the background of the facies property constraints in step 2, and assigning values ​​to the structural grid includes assigning parameters of reservoir porosity, permeability and oil saturation.

[0024] In some embodiments, in step 4, constraints are performed based on step 3, a distribution attribute body of the original temperature field is fitted, and values ​​are assigned to the construction grid body, where the assignment to the construction grid body includes assigning the original temperature of the temperature field.

[0025] In some embodiments, in step 3, establishing a reservoir attribute model under the control of seismic attributes includes: extracting seismic attributes, calibrating seismic attributes in combination with the identification results of single well phases, establishing a sedimentary microfacies model under the control of seismic phases, and characterizing the distribution characteristics of the sedimentary microfacies belts in the reservoir to constrain the reservoir attribute model.

[0026] In some embodiments, the steps of establishing a reservoir attribute model under the control of seismic attributes include: converting the seismic data body from the time domain to the frequency domain; interpolating the seismic signals in the frequency domain to generate a seismic phase map; performing seismic phase analysis based on waveform classification, using the waveform characteristics of the seismic traces to compare the seismic data traces within a certain layer one by one, and classifying the seismic reflection waves representing the same type of sedimentary phase into one category, thereby obtaining the planar distribution law of the seismic anomaly body, and then revealing the distribution law of different sedimentary microfacies belts.

[0027] In some embodiments, establishing a present-day temperature field geological model includes: using the measured present-day temperature of a single well as an attribute parameter, using a single well point as a fitting point, introducing geothermal gradient and temperature transfer characteristics of the reservoir temperature in the rock skeleton and different media, and establishing a present-day temperature field geological model that characterizes the reservoir.

[0028] In some embodiments, the medium includes oil, gas, or water in a reservoir.

[0029] In some embodiments, establishing a current temperature field geological model includes: collecting and organizing temperature measurement data of single wells in the reservoir, and organizing production dynamic data of single wells in the reservoir for calculation; solving thermal property parameters of reservoir rocks, fitting the temperature field near the wellbore, and applying the Gaussian interpolation method based on the calculation results of the temperature field near the wellbore to calculate the temperature field between wells, and obtaining the current temperature field distribution in the reservoir.

[0030] In some embodiments, the production dynamic data of a single well in the reservoir includes the injection volume and the production and reserves of the single well in the reservoir, and collecting and organizing the temperature measurement data of a single well in the reservoir includes collecting the temperature measurement well section information and converting the temperature measurement well section information into temperature attributes and loading it into the current temperature field geological model.

[0031] In some embodiments, solving the reservoir rock thermal property parameters includes solving the reservoir rock thermal resistivity and rock specific heat.

[0032] In some embodiments, during the process of fitting the temperature field near the wellbore, a well treatment model is established, and the well is treated as an internal boundary condition in the temperature field control equation.

[0033] In some embodiments, when fitting the temperature field near the wellbore, the temperature field control equation in the three-dimensional axisymmetric cylindrical coordinate system is as follows:

[0034] Shaft:

[0035]

[0036] Surrounding rock:

[0037]

[0038] Among them, λ * =[λ o (1-F w )+λ w F w ], is the equivalent thermal conductivity in the well, unit is W / (m·℃); λ0 is the equivalent thermal conductivity of the rock skeleton, unit is W / (m·℃); λ w is the thermal conductivity of the formation fluid, unit is W / (m·℃); F w is the water content of the fluid in the well;

[0039] (ρc)*=[ρ o c o (1-F w )+ρ w c w F w ], c0 is the initial temperature of the rock skeleton, unit is ℃; c w is the initial temperature of the formation fluid, unit is °C; ρ0 is the rock skeleton density, unit is kg / m 3ρ w is the formation fluid density, unit is kg / m 3 ; F w is the water content of the fluid in the well;

[0040] v z =q lw / 2πr w , is the fluid velocity in the well, unit is m / s; q lw is the fluid flow rate in section l, unit is L / s; r w is the distance from point w around the wellbore, in meters; T is the temperature at point l from the wellbore, in degrees Celsius; r is the wellbore diameter, in meters; t is the temperature inside the wellbore, in degrees Celsius; z is the depth, in meters.

[0041] In some embodiments, the analysis and comparison of the information of the current temperature field geological model and the original temperature field geological model to obtain the temperature field change model is implemented by the petrel software module. The data bodies of the current temperature field geological model and the original temperature field geological model are compared to obtain the change amount and obtain the temperature field change data body.

[0042] In some embodiments, determining the oil reservoir production degree based on the temperature field change model includes: obtaining a temperature field change amplitude according to the temperature field change model, and determining the oil reservoir production degree according to the temperature field change amplitude.

[0043] The beneficial effects of the present invention are:

[0044] The method of the present invention for determining the degree of oil reservoir production establishes an original temperature field geological model and a current temperature field geological model, and performs comparative calculations on the current temperature field geological model and the original temperature field geological model to obtain a temperature field change model, which is used to reflect the degree of oil reservoir reserve production and realize a three-dimensional display of the remaining oil-rich zones. The process operation is simple and has strong feasibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 Schematic diagram showing the well treatment model when establishing the current temperature field geological model;

[0046] Figure 2 A flow chart showing a method for determining the extent of reservoir production;

[0047] Figure 3 A schematic diagram showing an injection-production well pattern when establishing a current temperature field geological model according to an embodiment of the present invention;

[0048] Figure 4 A schematic diagram showing remaining oil distribution prediction according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the embodiments and drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0050] The method of the present invention for determining the degree of oil reservoir production includes: establishing an original temperature field geological model under the background of geological attributes that characterizes the distribution characteristics of the temperature field of the oil reservoir before it is put into development; establishing a current temperature field geological model that characterizes the current temperature field of the oil reservoir based on the original temperature field geological model; analyzing and comparing information of the current temperature field geological model and the original temperature field geological model to obtain a temperature field change model, and determining the degree of oil reservoir production based on the temperature field change model.

[0051] Establishing the original temperature field geological model under the background of geological attributes is the basis of the method of determining the degree of oil reservoir production in the present invention, which includes: solving the original temperature field geological model under the control of geological attributes to characterize the natural temperature field state of the oil reservoir before it is put into development, and providing a reference standard for subsequent temperature field changes after the oil reservoir is put into development.

[0052] In some embodiments, the geological attributes include reservoir porosity, permeability, oil saturation, and temperature. In the process of fitting the temperature field, the oil saturation of the reservoir is used as a reference calculation basis.

[0053] In some embodiments, establishing an original temperature field geological model based on geological attributes includes: clarifying sedimentary microfacies information of the target interval based on well logging information and 3D seismic data; and establishing an original temperature field geological model of original physical properties based on the sedimentary microfacies information and incorporating seismic attribute control during interwell interpolation calculations. The original physical properties include reservoir porosity and permeability.

[0054] In some embodiments, establishing a geological model of the original temperature field in the context of geological attributes includes the following steps:

[0055] Step 1: Establish a structural model that meets the accuracy requirements based on seismic interpretation levels and fault information and single well geological stratification;

[0056] Step 2: Combine logging lithologic information with the control of regional sedimentary microfacies to establish a lithofacies model based on the structural model established in step 1. The lithologic information includes rock thermal property parameter information.

[0057] Step 3: Based on the well logging interpretation of reservoir porosity, permeability, and oil saturation data, and under the control of seismic attributes, a reservoir attribute model is established based on the lithofacies model established in step 2. The reservoir attribute model includes a porosity model, a permeability model, and an oil saturation model.

[0058] Step 4: Based on the original temperature information of the single well and combined with the geothermal gradient parameters of the reservoir, the original temperature field geological model is established based on the reservoir property model established in step 3 through truncated Gaussian interpolation.

[0059] In step 1, the structural model is used to establish the concept of the reservoir body. Horizontal and vertical grids are set according to the well spacing, and the reservoir body is divided into several structural grid bodies. In the subsequent process of establishing the lithofacies model and reservoir property model, the structural grid bodies are used as calculation units for assignment.

[0060] In step 2, the lithofacies model is fitted based on the structural model and the lithologic information of the individual wells, and the lithologic information is assigned to the structural grid. The prediction of inter-well lithologic properties is based on seismic facies.

[0061] In step 3, a reservoir property model is established, including selecting an appropriate interpolation method based on reservoir characteristics and assigning values ​​to the structural grid within the context of the lithofacies attribute constraints of step 2. In some embodiments, the appropriate interpolation method is conventionally truncated Gaussian interpolation. In some embodiments, assigning values ​​to the structural grid includes assigning parameters for reservoir porosity, permeability, and oil saturation.

[0062] In step 4, constraints need to be applied based on step 3 to fit the distribution attribute volume of the original temperature field and assign values ​​to the construction grid volume. In some embodiments, assigning values ​​to the construction grid volume includes assigning attribute values ​​of the temperature field. The attribute values ​​of the temperature field include the original temperature and the current temperature of the temperature field. In step 4 of establishing the geological model of the original temperature field in the context of geological attributes, assigning values ​​to the construction grid volume only includes assigning the original temperature of the temperature field.

[0063] In step 3, establishing a reservoir attribute model under seismic attribute control includes extracting seismic attributes, calibrating seismic attributes based on single-well facies identification results, establishing a sedimentary microfacies model under seismic facies control, and characterizing the distribution characteristics of the reservoir's sedimentary microfacies zones to constrain the reservoir attribute model. In some embodiments, seismic attribute extraction includes seismic data processing and cluster analysis of seismic waveforms. The distribution pattern of the sedimentary microfacies zones is a lithologic distribution pattern.

[0064] In some embodiments, the steps of establishing a reservoir attribute model under the control of seismic attributes include: converting the seismic data body from the time domain to the frequency domain; interpolating the seismic signals in the frequency domain to generate a seismic phase map; performing seismic phase analysis based on waveform classification, using the waveform characteristics of the seismic traces to compare the seismic data traces within a certain layer one by one, and classifying the seismic reflection waves representing the same type of sedimentary phase into one category, thereby obtaining the planar distribution law of the seismic anomaly body, and then revealing the distribution law of different sedimentary microfacies belts.

[0065] In some embodiments, establishing a reservoir attribute model under seismic attribute control includes: converting the seismic data in the target layer segment from the time domain to the frequency domain, then performing frequency domain unequal length seismic signal interpolation, then performing frequency domain waveform clustering and calibrating the clustering results according to the logging phase, then generating a seismic phase map based on the waveform classification results, and finally performing a comprehensive geological analysis to compile a sedimentary microfacies map.

[0066] In some embodiments, converting the seismic data volume from the time domain to the frequency domain is accomplished by equation (1):

[0067]

[0068] Among them, a(f) is the interpolation function value, a n is the frequency domain signal; n is the discrete point number; Δf is the frequency domain sampling interval; f is the frequency value at the point to be interpolated; i is the imaginary unit; π is a constant.

[0069] The function sinc(x) = sin(x) / x is called the sinc function, and equation (1) is also known as the frequency-domain sinc interpolation formula. Since sinc interpolation requires an infinitely long signal, and actual signals are truncated into discrete signals of finite length, accurate sinc interpolation is difficult to achieve in practice.

[0070] In some embodiments, the frequency domain sinc interpolation formula is further derived to obtain a discrete sincd interpolation function in the frequency domain of a finite-length discrete signal, as shown in equation (2):

[0071]

[0072] Among them, a(f) is the interpolation function value; a n is the frequency domain signal; n is the discrete point number; Δf is the frequency domain sampling interval; f is the frequency value at the point to be interpolated; i is the imaginary unit; π is a constant; N is the signal frequency, and d is the signal length, which is a finite-length discrete signal artificially truncated during the formula calculation process.

[0073] As can be seen, the discrete sincd interpolation function uses all points in the signal frequency domain, which reduces computational efficiency when N is large. Therefore, in practical applications, the sincd interpolation function can be truncated to select a few terms for interpolation.

[0074] Under original reservoir conditions, temperature increases with depth. This pattern of temperature variation with depth is called the geothermal profile, and the temperature values ​​on this profile are called geothermal temperatures. Under reservoir conditions, the viscosity and density of crude oil, the solubility of gas in oil, and the state and properties of free gas directly influence geothermal temperature. Thermal energy from deep within the Earth is continuously transferred toward the surface through thermal conduction in rocks, thermal convection in liquids, and tectonic movements. For shallow reservoirs, when no oil is injected or produced, heat transfer within the reservoir is primarily through rock conduction. Therefore, geothermal temperature in shallow reservoirs is primarily influenced by the thermal properties of the reservoir rock, as well as the refraction and redistribution of heat flow.

[0075] In some embodiments, in step 4, during the calculation process, the original temperature field is a relatively uniform and stable temperature field that changes with depth and different physical properties, and different media are in temperature field equilibrium. Physical properties include reservoir porosity and permeability, and media include fluids such as oil, gas, and water in the reservoir.

[0076] In some embodiments, establishing the original temperature field geological model in the context of geological attributes includes establishing the original temperature field model in the context of reservoir porosity, permeability, and oil-water two-phase fluid saturation.

[0077] Establishing a geological model of the current temperature field (also known as fitting the current temperature field information) involves studying the changes in the reservoir temperature field during reservoir development based on comprehensive consideration of injection temperature, original formation temperature (i.e., geothermal temperature), and geothermal gradient.

[0078] In some embodiments, establishing the current temperature field geological model includes studying the effect of temperature on oil saturation, water injection rate, and production well output during displacement, as well as the effect of pressure and permeability on the temperature field.

[0079] In some embodiments, establishing a current temperature field geological model includes: using the measured current temperature of a single well as an attribute parameter, using the single well point as a fitting point, introducing geothermal gradients and the temperature transfer characteristics of the reservoir temperature in the rock skeleton and different media, and establishing a current temperature field geological model representing the reservoir. The media include fluids such as oil, gas, and water in the reservoir.

[0080] The main purpose of studying reservoir temperature field simulation is to investigate changes in reservoir temperature fields during reservoir development using numerical simulation methods. The Earth is a large heat source, with heat flowing from the Earth's interior to the surface. Subsurface temperatures increase with depth. Before development, reservoirs are in thermal equilibrium. When development begins, the fluid seepage through the porous media disrupts the original thermal equilibrium, causing the reservoir temperature field to change as development progresses. Temperature logging in development logging can, to a certain extent, reflect changes in the reservoir temperature field. However, temperature logging is measured at specific points in the reservoir development process, and primarily measures wellbore temperature. Therefore, temperature logging cannot reflect changes in the entire reservoir temperature field.

[0081] In some embodiments, establishing a current temperature field geological model includes: utilizing current 3D geological modeling techniques to discretize single well point data into scientifically appropriate grid spaces within the reservoir to form a current temperature field geological model. This current temperature field geological model can be used to study not only changes in the temperature field of pay zones, but also changes in the temperature fields of production wells and injection wells as the reservoir develops.

[0082] In some embodiments, establishing a current temperature field geological model includes: collecting and organizing temperature measurement data from individual reservoir wells, and simultaneously organizing production performance data from individual reservoir wells for calculation; solving for thermal property parameters of reservoir rocks, fitting the temperature field near the wellbore, and applying Gaussian interpolation to calculate the interwell temperature field based on the calculated temperature field near the wellbore to determine the current temperature field distribution within the reservoir. The production performance data from individual reservoir wells includes the injection rate and production and reserves of the individual reservoir wells. Collecting and organizing temperature measurement data from individual reservoir wells includes collecting temperature measurement well section information and converting the temperature measurement well section information into temperature attributes for loading into the current temperature field geological model.

[0083] The thermal properties of reservoir rocks include thermal conductivity λ, thermal resistivity and specific heat c. The reciprocal of thermal conductivity λ is called thermal resistivity Solving the thermal properties of reservoir rocks includes solving the thermal resistivity of the reservoir rocks. and rock specific heat c. Rock thermal resistivity It is related to the rock density ρ, permeability and the properties of the fluid in the rock. Rock thermal resistivity The relationship with rock density ρ is shown in equation (3):

[0084]

[0085] Where ρ is the rock density, unit is kg / m 3 .

[0086] It can be seen that the denser the rock, the smaller the thermal resistivity. Water is a medium with good thermal conductivity, so the thermal resistivity of rock decreases with the increase of rock water saturation Sw. The relationship with rock water saturation Sw is shown in equation (4):

[0087]

[0088] in, is the thermal resistivity of the rock without water, unit is ℃ / W; Sw is the water saturation of the rock.

[0089] The thermal resistivity of oil and natural gas is higher than that of water, so when the water in the pores of the rock is replaced by oil and natural gas, the thermal resistivity value of the rock increases.

[0090] The specific heat of rock c refers to the amount of heat absorbed (or released) by a unit mass of rock when the temperature rises (or falls) by 1°C. The specific heat of rock c depends largely on the mineral composition of the rock and the water saturation Sw of the rock. The specific heat of rock c increases with the increase of the water saturation Sw of the rock.

[0091] In the process of establishing the current temperature field geological model, the relationship between the temperature field and the thermal property parameters of the reservoir rock is established through the relationship between the thermal property parameters of the reservoir rock and the rock density ρ and the fluid saturation in the rock.

[0092] Usually, the target research area of ​​the reservoir is very large, and the distance between wells is generally tens to hundreds of meters, while the radius of the oil well is only about 0.1 meters. Therefore, the grid cannot be used to approximate the boundary of the well; secondly, the depth of the oil reservoir pay layer is generally more than a kilometer, and it is impossible to grid approximate the entire formation, and it is also meaningless to simulate a large number of non-paying layers. Therefore, in the process of establishing the current temperature field geological model, the temperature field around the wells and wellbores in the pay layer is included. In some embodiments, if there is a well (production well or injection well) at a certain grid, fitting the temperature field near the wellbore includes establishing Figure 1 The well treatment model is shown. The well treatment model is used as a known point for interpolation calculations during the subsequent temperature field modeling process. In some embodiments, the well treatment model is placed in the reservoir as a defined known point, so that the well treatment model has a value in the structural grid of the corresponding well. That is, after processing the well corresponding to the well treatment model, the value of the known grid point corresponding to the well treatment model is added to the structural grid of the corresponding well as a defined known point, which is then used to interpolate the empty structural grid between the wells.

[0093] In the process of fitting the temperature field near the wellbore, the well is usually treated as an internal boundary condition in the temperature field control equation. The internal boundary conditions include: the bottom temperature of the injection well T i,j,k , unit ℃; fixed well production qlsc , unit m 3 / d (cubic meters / day); fixed bottom hole pressure p wf , unit is kPa.

[0094] The bottom hole temperature T of the injection well in the well grid block (i, j, k) in the well processing model i,j,k , can be used as a known internal boundary condition and introduced into the differential equation of the grid node (i, j, k). However, during the water injection process, the wellhead water injection temperature T r Affected by geothermal temperature, T i,j,k ≠T r , in the interpolation calculation process of establishing the current temperature field geological model, it is input into the model as a calculation reference formula.

[0095] When the initial temperature is T r When water flows through the wellbore, there is a temperature difference between the fluid and the formation, and in the longitudinal direction of the fluid. Therefore, there is heat transfer in the radial and longitudinal directions. According to the energy conservation equation, the temperature field control equations (5) and (6) in the three-dimensional axisymmetric cylindrical coordinate system can be written:

[0096] Shaft:

[0097]

[0098] Surrounding rock:

[0099]

[0100] Among them, λ * =[λ o (1-F w )+λ w F w ], is the equivalent thermal conductivity in the well, unit is W / (m·℃); λ0 is the equivalent thermal conductivity of the rock skeleton, unit is W / (m·℃); λ w is the thermal conductivity of the formation fluid, unit is W / (m·℃); F w is the water content of the fluid in the well;

[0101] (ρc) * =[ρ o c o (1-F w )+ρ w c w F w ], c0 is the initial temperature of the rock skeleton, unit is ℃; c w is the initial temperature of the formation fluid, unit is °C; ρ0 is the rock skeleton density, unit is kg / m 3 ρ w is the formation fluid density, unit is kg / m 3 ; Fw is the water content of the fluid in the well;

[0102] v z =q lw / 2πr w , is the fluid velocity in the well, unit is m / s; q lw is the fluid flow rate in section l, unit is L / s; r w is the distance from point w around the wellbore, in meters;

[0103] T is the temperature at point 1 away from the wellbore, unit: °C; r is the wellbore diameter, unit: m; t is the temperature inside the wellbore, unit: °C; z is the depth, unit: m.

[0104] Equations (5) and (6) include the following initial and boundary conditions:

[0105] The initial conditions are shown in equation (7):

[0106] T z | t＝0 =a+gz (7)

[0107] Where a is the geothermal temperature at z = 0, in °C; g is the geothermal gradient, in °C / 100m; z is the depth, in m; T z is the temperature at depth z, in °C; t is the initial value 0, in °C.

[0108] The boundary conditions of the wellbore surrounding rock formation are shown in equation (8):

[0109]

[0110] Where a is the geothermal temperature at z = 0, in °C; g is the geothermal gradient, in °C / 100m; z is the depth, in m; T z is the temperature at depth z, in °C; r b is the distance from point b near the wellbore, in meters.

[0111] The dynamic coupling boundary conditions of the wellbore and surrounding rock are shown in equation (9):

[0112]

[0113] Where h is the surface heat transfer coefficient between the wellbore and the formation, unit is W / (m 2 ℃); T l 、T b denote the temperature of the fluid and formation at the coupling boundary of the wellbore and surrounding rock, r w is the distance from point w around the wellbore, in meters; T is the temperature, in degrees Celsius; r is the wellbore diameter, in meters; λ r is the coefficient.

[0114] The Petrel software module analyzes and compares the current temperature field geological model with the original temperature field geological model to determine the temperature field change model. By comparing the data volumes of the current and original temperature field geological models, the change in value is determined, resulting in a temperature field change data volume. The temperature field change model refers to the 3D visualization of the temperature field change data volume.

[0115] A model is a three-dimensional representation of a data volume, or a three-dimensional demonstration. Building a model can be thought of as building a data volume, combining various data volumes and performing calculations to generate a new data volume. The model displays the number of wells drilled in the reservoir, their depths, the reservoir's length and width, the number of strata, and the locations of oil and water. The data volume is related to the aforementioned structural grids. An appropriate number of structural grids, such as one million, are created as needed to minimize the grids to approximate the real-world conditions. Each structural grid is populated with a specific amount of data. The reservoir is three-dimensional and corresponds to a data volume. The reservoir has planar data variations, namely its length and width, and multiple structural grids can be generated on each plane. Furthermore, the reservoir also has vertical structural grids. Each structural grid has parameters such as structural values, porosity, permeability, saturation, and temperature. The reservoir is represented on the screen through the model.

[0116] In some embodiments, the temperature field change is obtained by calculating the original temperature and the current temperature of the temperature field for each structural grid to obtain the change, and the changes of all structural grids are added together to form a change data body.

[0117] Determining the oil reservoir production degree based on the temperature field change model includes: obtaining the temperature field change amplitude according to the temperature field change model, and determining the oil reservoir production degree by the temperature field change amplitude. The area with a relatively small temperature field change amplitude is an area with a low oil reservoir production degree.

[0118] In some embodiments, the Petrel software module's computational process involves solving linear equations. This process involves applying differential approximation and linearization to the original and current temperature field geological models, generating four linear equations at each grid node. For a system of n grids, this results in a linear system of 4n equations. Each step of the linearization process involves solving a linear equation.

[0119] In some embodiments, the linear equations are solved by processing the sparse matrix A to minimize the storage space requirements of the calculation, reduce operations that have no practical significance, and improve the speed of solving large linear equations.

[0120] In some embodiments, solving the linear equation by processing the sparse matrix A includes: based on the characteristic that the sparse matrix A has symmetric positive definiteness, performing Cholesky decomposition on the sparse matrix A, as shown in equation (10).

[0121] A=LDL T (10)

[0122] Where L is a lower triangular matrix and D is a diagonal matrix, as shown below:

[0123]

[0124] L T To compare the elements at both ends, the elements at both ends include a i1 =l il d1, d1 = a 11 , l i1 =a il / d1(i=1,2,3,…n).

[0125] The calculation equations of matrices L and D can be obtained as follows (11):

[0126]

[0127] After the sparse matrix A is decomposed by Cholesky, the solution of the linear equation system Ax=d (A represents the sparse matrix, x is the unknown vector, and d represents the known vector) is equivalent to solving the equation system (12):

[0128]

[0129] The temperature field change data body representing the temperature field change is obtained by calculation, and the calculation results are assigned to the construction grid in the form of numerical values, and the change amplitude is represented by the different numerical sizes of the construction grid.

[0130] The method for determining the degree of oil reservoir production of the present invention also includes locating a sweet spot for remaining oil. In some embodiments, locating the sweet spot for remaining oil includes analyzing geological model information of the current temperature field, combining it with a reservoir reserve simulation, establishing a relationship between current temperature and reservoir reserves based on the current temperature field distribution, and determining the current distribution of remaining reserves in the reservoir, thereby accurately locating the sweet spot for remaining oil.

[0131] The method for determining the degree of oil reservoir production in the present invention first establishes a geological model based on the reservoir's original seismic data and well logging information. Based on the original well temperature data, the temperature field distribution is fitted to establish an original temperature field geological model within the geological model context. Based on the high-precision geothermal field fitting, a current temperature field geological model is established by measuring the wellbore temperature information of the current target layer. By comparing the original temperature field geological model with the current temperature field geological model, a temperature field change data volume is obtained to reflect the degree of reserve production and achieve a three-dimensional display of the remaining oil-rich zones. The process is simple to operate and highly feasible.

[0132] The process of applying the method for determining the oil reservoir producing degree of the present invention to a block of an oil reservoir in Mangystau Oblast of the Republic of Kazakhstan is as follows: Figure 2 As shown. This reservoir is a sandstone reservoir with a burial depth of 800-1500 meters and an original geothermal gradient of 2.8°C / 100 meters. It is a delta plain and frontal subfacies deposit, with microfacies such as river channels, swamps, and estuary bars. Positive tectonic development is currently in the middle to late stages of waterflood development. Wells are spaced 200 meters apart, and comprehensive 3D seismic and well temperature test data are available.

[0133] First, based on well temperature test data from the initial development phase within the study area, combined with relevant logging data and coring analysis and laboratory data, macroscopic core descriptions from nine cored wells and imaging logging data from two wells within the study area were used to observe and identify lithologic characteristics. Furthermore, based on the characteristics of the logging data, GR (natural gamma ray), PE (photoelectric absorption cross-section index), and DEN (density) were selected as the primary curves for logging facies analysis. These three curves are sensitive to lithologic information and relatively insensitive to fluids in rock pores, making them suitable for logging facies-lithofacies analysis and establishing relationships between logging facies and lithofacies. Based on well logging and seismic data, the sedimentary microfacies of the target interval are determined. Seismic facies analysis is performed by correlating existing wellpoint locations with individual well facies and seismic attribute characteristics. Waveform group reflection structure, continuity, amplitude, frequency, and geometry are analyzed on the seismic profile. Correspondence between waveform attributes and well logging curves is established, and cluster analysis is performed. This algorithm is then developed to identify and group channel microfacies that are important for interwell connectivity, further investigating the configuration and spatial distribution of various sedimentary systems. Based on sedimentary microfacies information, a geological model of the original physical properties is constructed, incorporating seismic attribute control during interwell interpolation calculations. The original reservoir temperature field is collected. Temperature field attributes are coupled to the geological attribute model. Based on the temperature transfer characteristics of geothermal gradients within the rock skeleton and various media, a mathematical model representing the initial reservoir temperature field is developed, representing the original temperature field within the geological attribute context.

[0134] Secondly, based on the comprehensive consideration of water injection temperature, geothermal temperature, and geothermal gradient, the changes in the reservoir temperature field during reservoir development are studied, namely the impact of temperature on oil saturation, water injection volume, and production well output during displacement, as well as the impact of pressure and permeability on the temperature field. The measured current temperature of a single well is used as an attribute parameter, and the single well point is used as a fitting point. The geothermal gradient and the temperature transfer characteristics of the reservoir temperature in the rock skeleton and different media are introduced, and the temperature field model is input to establish a geological model representing the current temperature field of the reservoir, such as Figure 3 shown.

[0135] Secondly, the current temperature field geological model and the original temperature field geological model are analyzed and compared to obtain the temperature field change model and the temperature field change data volume. The oil reservoir production degree is determined according to the grid node classification.

[0136] Finally, the current temperature field geological model information is analyzed, combined with the reservoir reserve simulation, and the relationship between current temperature and reservoir reserves is established according to the current temperature field distribution. The current remaining reserves distribution is obtained and the remaining oil sweet spot section is accurately located. The results are as follows: Figure 4 shown.

[0137] The proposed method for determining reservoir production has been initially implemented in a fault block of a reservoir in Mangystau Oblast, Kazakhstan, and has demonstrated effective calculations for determining reserve production. By processing single-well injection and production data and converting them into temperature field information, a relationship between temperature and reserves was established, enabling the current distribution of remaining reserves to be determined and the remaining oil sweet spots to be accurately located. The accuracy of the predictions was also verified by the productivity of newly drilled wells.

[0138] The method for determining the degree of oil reservoir production in the present invention is based on the principle of non-isothermal seepage. On the basis of a model that integrates sedimentary phases and reservoir physical property information, the changes in the reservoir temperature field are calculated by changing the temperature of a single well reservoir, thereby quantitatively characterizing the degree of reserve production.

[0139] The above embodiments merely illustrate the implementation methods of the present invention. Although the descriptions thereof are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art may make various modifications and improvements without departing from the scope of the present invention, and such modifications and improvements shall fall within the scope of protection of the present invention.

Claims

1. A method for determining the degree of production of an oil reservoir, characterized in that: include: Establishing the original temperature field geological model under the geological attribute background to characterize the distribution characteristics of the temperature field before the oil reservoir is put into development; Based on the original temperature field geological model, a current temperature field geological model is established to characterize the current temperature field of the reservoir; The information of the current temperature field geological model and the original temperature field geological model is analyzed and compared to obtain the temperature field change model, and the oil reservoir production degree is determined based on the temperature field change model.

2. The method for determining the degree of oil reservoir production according to claim 1, characterized in that: The geological attributes include reservoir porosity, permeability, oil saturation and temperature.

3. The method for determining the degree of oil reservoir production according to claim 1, characterized in that: Establishing the original temperature field geological model under the background of geological attributes includes: clarifying the sedimentary microfacies information of the target layer based on well logging information and three-dimensional seismic data; establishing the original temperature field geological model of the original physical property characteristics in combination with seismic attribute control during the inter-well interpolation calculation based on the sedimentary microfacies information.

4. The method for determining the degree of oil reservoir production according to claim 3, characterized in that: The original physical properties include reservoir porosity and permeability.

5. The method for determining the degree of oil reservoir production according to claim 1, characterized in that: Establishing the original temperature field geological model under the geological attribute background includes the following steps: Step 1: Establish a structural model that meets the accuracy requirements based on the seismic interpretation level and fault information and single well geological stratification; Step 2: Establishing a lithofacies model based on the structural model established in step 1 under the control of regional sedimentary microfacies in combination with logging lithology information; Step 3: Based on the well logging interpretation of reservoir porosity, permeability, and oil saturation data, a reservoir attribute model is established based on the lithofacies model established in step 2 under the control of seismic attributes; Step 4: Based on the original temperature information of the single well and in combination with the geothermal gradient parameters of the reservoir, an original temperature field geological model is established based on the reservoir attribute model established in step 3 by truncated Gaussian interpolation.

6. The method for determining the degree of oil reservoir production according to claim 5, characterized in that: In step 1, the structural model is to establish the concept of the reservoir body. The horizontal and vertical grids are set according to the well spacing, and the reservoir body is divided into several structural grid bodies. In the subsequent process of establishing the lithofacies model and the reservoir attribute model, the structural grid body is used as the calculation unit for assignment.

7. The method for determining the degree of oil reservoir production according to claim 6, characterized in that: In the step 2, the lithofacies model is fitted according to the lithology information of a single well on the basis of the structural model, and the lithology information is assigned to the structural grid.

8. The method for determining the degree of oil reservoir production according to claim 7, characterized in that: The lithology information includes rock thermal property parameter information, and the rock thermal property parameters include thermal conductivity, thermal resistivity and specific heat of the rock.

9. The method for determining the degree of oil reservoir production according to claim 7, characterized in that: In step 3, a reservoir property model is established, including: selecting a suitable interpolation method according to reservoir characteristics, assigning values ​​to the structural grid body under the background of lithofacies property constraints in step 2, and assigning values ​​to the structural grid body includes assigning parameters of reservoir porosity, permeability and oil saturation.

10. The method for determining the degree of oil reservoir production according to claim 9, characterized in that: In step 4, constraints are performed on the basis of step 3, the distribution attribute body of the original temperature field is fitted, and values ​​are assigned to the construction grid body, wherein the assignment to the construction grid body includes assigning the original temperature of the temperature field.

11. The method for determining the degree of oil reservoir production according to claim 5, characterized in that: In step 3, establishing a reservoir attribute model under the control of seismic attributes includes: extracting seismic attributes, calibrating seismic attributes in combination with the identification results of single well phases, establishing a sedimentary microfacies model under the control of seismic phases, characterizing the distribution characteristics of the reservoir sedimentary microfacies belts, and constraining the reservoir attribute model.

12. The method for determining the degree of oil reservoir production according to claim 5, characterized in that: The steps of establishing a reservoir attribute model under the control of seismic attributes include: converting the seismic data volume from the time domain to the frequency domain; interpolating the seismic signals in the frequency domain to generate a seismic phase map; seismic phase analysis based on waveform classification, using the waveform characteristics of the seismic traces to compare the seismic data traces in a certain layer one by one, and classifying the seismic reflection waves representing the same type of sedimentary phase into one category, thereby obtaining the planar distribution law of the seismic anomaly body, and then revealing the distribution law of different sedimentary microfacies belts.

13. The method for determining the degree of oil reservoir production according to claim 1, characterized in that: Establishing the present temperature field geological model includes: taking the present temperature measured in a single well as an attribute parameter, taking the single well point as the fitting point, introducing the geothermal gradient and the temperature transfer characteristics of the reservoir temperature in the rock skeleton and different media, and establishing the present temperature field geological model that characterizes the reservoir.

14. The method for determining the degree of oil reservoir production according to claim 13, characterized in that: The medium includes oil, gas and water in the reservoir.

15. The method for determining the degree of oil reservoir production according to claim 1, characterized in that: Establishing the current temperature field geological model includes: collecting and organizing the temperature measurement data of individual wells in the reservoir, and organizing the production dynamic data of individual wells in the reservoir for calculation; solving the thermal property parameters of the reservoir rock, fitting the temperature field near the wellbore, and applying the Gaussian interpolation method based on the calculation results of the temperature field near the wellbore to calculate the temperature field between wells, and obtain the current temperature field distribution in the reservoir.

16. The method for determining the degree of oil reservoir production according to claim 15, characterized in that: The production dynamic data of the single well in the oil reservoir includes the injection volume and the production and reserves of the single well in the oil reservoir. The collection and collation of the temperature measurement data of the single well in the oil reservoir includes collecting the temperature measurement well section information and converting the temperature measurement well section information into temperature attributes and loading it into the current temperature field geological model.

17. The method for determining the degree of oil reservoir production according to claim 15, characterized in that: Solving the thermal property parameters of reservoir rocks includes solving the thermal resistivity and specific heat of the rocks in the reservoir.

18. The method for determining the degree of oil reservoir production according to claim 15, characterized in that: In the process of fitting the temperature field near the wellbore, a well treatment model is established, and the well is treated as an internal boundary condition in the temperature field control equation.

19. The method for determining the degree of oil reservoir production according to claim 18, characterized in that: In the process of fitting the temperature field near the wellbore, the temperature field control equation in the three-dimensional axisymmetric cylindrical coordinate system is as follows: Shaft: Surrounding rock: Among them, λ * =[λ o (1-F w )+λ w F w ], is the equivalent thermal conductivity in the well, in W / (m·℃); λ0 is the equivalent thermal conductivity of the rock skeleton, in W / (m·℃); λ w is the thermal conductivity of the formation fluid, in W / (m·℃); F w is the water content of the fluid in the well; (ρc) * =[ρ o c o (1-F w )+ρ w c w F w ], c0 is the initial temperature of the rock skeleton, unit is °C; c w is the initial temperature of the formation fluid, in °C; ρ0 is the rock skeleton density, in kg / m 3 ρ w is the formation fluid density, unit: kg / m 3 ; F w is the water content of the fluid in the well; v z =q lw / 2πr w , is the fluid velocity in the well, unit is m / s; q lw is the fluid flow rate in segment l, in L / s; r w is the distance from point w around the wellbore, in meters; T is the temperature at point l in the wellbore, in degrees Celsius; r is the wellbore diameter, in meters; t is the temperature inside the wellbore, in degrees Celsius; z is the depth, in meters.

20. The method for determining the degree of oil reservoir production according to claim 1, characterized in that: The petrel software module is used to analyze and compare the information of the current temperature field geological model and the original temperature field geological model to obtain the temperature field change model. The data bodies of the current temperature field geological model and the original temperature field geological model are compared to obtain the change amount and obtain the temperature field change data body.

21. The method for determining the degree of oil reservoir production according to claim 20, characterized in that: Determining the oil reservoir production degree based on the temperature field change model includes: obtaining the temperature field change amplitude according to the temperature field change model, and determining the oil reservoir production degree according to the temperature field change amplitude.

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