Method and equipment for predicting geological reserve parameters of tight oil

Abstract

The embodiment of the invention provides a method for predicting tight oil geological reserve parameters, and belongs to the technical field of oil exploration and development. The method comprises the steps that by analyzing geological parameters of a target work area, numerical values corresponding to reservoir evaluation indexes corresponding to the target work area are determined, and the reservoir evaluation indexes comprise matrix reservoir parameters, fracture parameters and oiliness parameters; according to a preset reserve classification evaluation standard, in combination with the numerical value corresponding to the reservoir evaluation index corresponding to the target work area, determining a reserve category corresponding to the target work area, the preset reserve classification evaluation standard comprising a numerical value range of the reservoir evaluation indexes corresponding to different reserve categories; based on the reserve category corresponding to the target work area, determining a reserve parameter corresponding to the target work area; the reserve parameters comprise one or more of the following parameters: a single well initial yield limit, a single well economic recoverable reserve limit and reserve abundance.

Description

Technical Field

[0001] This invention relates to the field of petroleum exploration and development technology, and specifically to a method, equipment, and computer program product for predicting tight oil geological reserve parameters. Background Technology

[0002] Continental tight oil is an important unconventional oil and gas resource, mainly distributed in Mesozoic and Cenozoic continental oil and gas basins, coexisting or contacting with lacustrine source rocks to form large areas of tight sandstone oil or tight carbonate oil. However, due to the complex geological conditions, strong reservoir heterogeneity, poor physical properties, and significant differences in reserve quality, the exploration and development costs of such reservoirs are extremely high. For example, in the early stages of tight oil development on the southern margin of the Ordos Basin, the indiscriminate development using horizontal well fracturing technology resulted in a large number of low-yield and inefficient wells, and the development effect did not meet expectations. Summary of the Invention

[0003] The purpose of this invention is to provide a method, apparatus, and computer program product for predicting tight oil geological reserves. This method can solve or at least partially solve the above-mentioned defects of the prior art.

[0004] To achieve the above objectives, a first aspect of the present invention provides a method for predicting geological reserve parameters of tight oil, the method comprising:

[0005] By analyzing the geological parameters of the target work area, the values ​​of the reservoir evaluation indicators corresponding to the target work area are determined. The reservoir evaluation indicators include matrix reservoir parameters, fracture parameters, and oil-bearing parameters.

[0006] Based on a preset reserve classification and evaluation standard, and combined with the corresponding values ​​of reservoir evaluation indicators for the target work area, the reserve category corresponding to the target work area is determined. The preset reserve classification and evaluation standard includes the numerical range of reservoir evaluation indicators for different reserve categories.

[0007] Based on the reserve category corresponding to the target work area, the reserve parameters corresponding to the target work area are determined; the reserve parameters include one or more of the following: the initial production limit of a single well, the economically recoverable reserve limit of a single well, and the reserve abundance.

[0008] In some embodiments, the matrix reservoir parameters include: sedimentary characteristics, reservoir parameters, and permeability parameters; the fracture parameters include fault scale and fracture intensity; and the oil-bearing parameters include oil saturation.

[0009] In some embodiments, the sedimentary features include: sandstone thickness and sorting factor;

[0010] The storage parameters include: porosity;

[0011] The seepage parameters include: permeability and the radius of the main flow throat;

[0012] The fault dimensions include length and fault displacement.

[0013] In some embodiments, the preset reserve classification evaluation criteria are determined in the following ways:

[0014] Based on the preset rate of return corresponding to different reserve categories, calculate the initial production limit of a single well and the economically recoverable reserve limit of a single well corresponding to different reserve categories.

[0015] Analyze the production parameters of the wells already developed in the selected work area;

[0016] Based on the production parameters of the developed wells, the reserve category of the developed wells is determined, wherein the production parameters include the initial production limit for a single well and the economically recoverable reserve limit for a single well; and

[0017] Analyze the matrix reservoir parameters, fracture parameters, and oil-bearing parameters of the developed wells in the selected work area; and determine the numerical range of the matrix reservoir parameters, fracture parameters, and oil-bearing parameters corresponding to the reserve category of the developed wells.

[0018] In some embodiments, determining the matrix reservoir parameters corresponding to the reserve category of the developed well based on the reserve category of the developed well includes:

[0019] Analyze the relationship between core permeability and sand body thickness in developed wells; and

[0020] Based on the correlation between core permeability and sand body thickness of the developed wells, the numerical range of matrix reservoir parameters corresponding to the reserve categories of the developed wells is determined.

[0021] In some embodiments, determining the fracture parameters corresponding to the reserve category of the developed well based on the reserve category of the developed well includes:

[0022] This study analyzes the relationship between the fracture strength index (FFI) of a single well and the initial production limit of developed wells, as well as the relationship between the FFI and the economically recoverable reserves limit of developed wells.

[0023] Based on the relationship between the single-well fracture strength index (FFI) and the initial production limit of developed wells, and the relationship between the single-well fracture strength index (FFI) and the economically recoverable reserves limit of developed wells, the numerical range of fracture parameters corresponding to the reserve categories of the developed wells is determined.

[0024] In some embodiments, determining the numerical range of the oil-bearing parameter corresponding to the reserve category of the developed well, based on the reserve category of the developed well, includes:

[0025] Analyze the relationship between the initial production limit of a single well and the oil saturation of developed wells; and

[0026] Based on the relationship between the initial production limit of a single well and the oil saturation of the developed wells, the numerical range of the oil-bearing parameters corresponding to the reserve category of the developed wells is determined.

[0027] In some embodiments, calculating the initial production limits of a single well for different reserve categories based on the preset rate of return for different reserve categories includes:

[0028] The initial production limit for a single well is calculated using the following formula:

[0029]

[0030] Among them, Q c Indicates the initial production limit of a single well; P T The investment payback period is represented by t; the economic evaluation period is represented by P. t The price of crude oil is represented by n; the commodity rate is represented by r. c Indicates the ratio of taxes and surcharges to income; C ovt Indicates unit variable cost; η t I represents the coefficient of variation of dimensionless output; t Indicates the new construction investment for a single well; S oft This represents fixed operating costs.

[0031] In some embodiments, calculating the economically recoverable reserves limit for a single well corresponding to different reserve categories based on the preset rate of return for different reserve categories includes:

[0032] The economically recoverable reserves limit for a single well can be calculated using the following formula:

[0033] N=∑Q t

[0034] Where N represents the economically recoverable reserves limit for a single well; Q t This indicates the annual production of a single well.

[0035] A second aspect of the present invention provides an apparatus for predicting geological reserves of tight oil, the apparatus including a processor, a memory, and a program stored in the memory and executable on the processor, wherein the processor executes the program to run the method for predicting geological reserves of tight oil.

[0036] A third aspect of the present invention provides a computer program product, including a computer program, characterized in that the computer program, when executed by a processor, implements the method for predicting tight oil geological reserve parameters.

[0037] The method provided in this invention first analyzes the geological parameters of the target work area, then determines the reserve category corresponding to the target work area according to a preset reserve classification and evaluation standard, and finally determines the reserve parameters corresponding to the target work area based on the reserve category. On the one hand, it can determine the proportion and planar distribution characteristics of different types of reserves in the total reserves; on the other hand, it can establish a reserve utilization sequence and formulate oilfield development plans according to the principle of efficient development, such as prioritizing the utilization of Class I reserves while simultaneously preparing for the development of Class II reserves, thereby maximizing the efficient development of continental tight oil.

[0038] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0039] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0040] Figure 1 This is a flowchart illustrating the method for predicting tight oil geological reserve parameters provided in an embodiment of the present invention.

[0041] Figure 2 This is a schematic diagram illustrating the technical and economic boundaries of oilfield development;

[0042] Figure 3 This is a map showing the lower limit of the thickness of tight oil sand bodies in an oilfield on the southern edge of the Ordos Basin.

[0043] Figure 4 This is a graph showing the intersection of fracture intensity (FFI) and initial production of a single horizontal well in a tight oil field on the southern edge of the Ordos Basin.

[0044] Figure 5 This is a cross-plot of the fracture intensity (FFI) of tight oil in an oilfield on the southern edge of the Ordos Basin and the recoverable reserves of a single horizontal well.

[0045] Figure 6 This is a plot showing the intersection of tight oil porosity and oil saturation in an oilfield on the southern edge of the Ordos Basin.

[0046] Figure 7 A graph showing the intersection of initial production and oil saturation of a tight oil horizontal well in an oilfield on the southern edge of the Ordos Basin. Detailed Implementation

[0047] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present invention.

[0048] Figure 1 This is a flowchart illustrating the method for predicting tight oil geological reserve parameters provided in an embodiment of the present invention, as shown below. Figure 1 As shown in the figure, this embodiment of the invention provides a method for predicting geological reserve parameters of tight oil, the method comprising:

[0049] Step S101: By analyzing the geological parameters of the target work area, determine the values ​​of the reservoir evaluation indicators corresponding to the target work area.

[0050] The reservoir evaluation indicators include matrix reservoir parameters, fracture parameters, and oil-bearing parameters. Specifically, the inventors of this application discovered during their research that the geological factors determining the scale of reserves mainly include effective thickness, porosity, and oil saturation. Porosity is primarily controlled by the matrix reservoir, while oil saturation is controlled by both the matrix reservoir and fractures. Based on oil well production dynamics analysis, the geological factor affecting the quality of tight oil reserves is mainly fractures. Fractures not only control the heterogeneous distribution of oil content in the reservoir but are also a major factor in high well production. Therefore, reservoir evaluation indicators can be determined by analyzing the tight oil matrix reservoir, fractures, and oil-bearing properties.

[0051] In some embodiments, the matrix reservoir parameters include: sedimentary characteristics, reservoir parameters, and permeability parameters; the fracture parameters include fault scale and fracture intensity; and the oil-bearing parameters include oil saturation.

[0052] In some embodiments, the sedimentary features include: sandstone thickness and sorting factor; the reservoir parameters include: porosity; the seepage parameters include: permeability and mainstream throat radius; and the fault scale includes: length and fault displacement.

[0053] Sandstone thickness typically refers to the vertical or horizontal dimension of a sandstone layer.

[0054] Sorting factor is a concept in sedimentology used to measure the uniformity or homogeneity of sediment grain size. It is a dimensionless numerical value, typically used to describe the range of grain size distribution within sediments. The sorting factor is usually calculated based on a sediment grain size distribution curve, which can be obtained through sieving experiments or grain size analyzers. The grain size distribution curve shows the proportion of different sized grains in the sediment.

[0055] Permeability is a physical quantity that describes the ability of a fluid (such as water, oil, gas, etc.) to flow through a porous medium (such as rock, soil, etc.). It is a parameter that measures how easily a porous medium allows fluid to pass through.

[0056] The mainstream throat radius refers to the throat radius corresponding to a cumulative contribution of 95% to permeability, and is an important parameter characterizing the micropore structure of low-permeability reservoirs. The throat radius refers to the radius of the channel connecting pores. The throat radius has a significant impact on the conductivity and storage capacity of sandstone reservoirs. Generally, sandstone reservoirs with larger throat radii have better conductivity, while sandstone reservoirs with smaller throat radii have better storage capacity.

[0057] Fault length refers to the total length of a fault extending on or beneath the Earth's surface, while fault displacement refers to the distance the rocks on either side of a fault have moved relative to each other.

[0058] Step S102: Determine the reserve category corresponding to the target work area based on the preset reserve classification and evaluation standards and the corresponding values ​​of the reservoir evaluation indicators corresponding to the target work area.

[0059] The preset reserve classification and evaluation criteria include the numerical ranges of reservoir evaluation indicators corresponding to different reserve categories. Specifically, the preset reserve classification and evaluation criteria include the numerical ranges of matrix reservoir parameters, fracture parameters, and oil-bearing parameters corresponding to different reserve categories.

[0060] In some embodiments, the preset reserve classification evaluation criteria are determined through the following steps S201 to S205:

[0061] Step S201: Based on the preset rate of return corresponding to different reserve categories, calculate the initial production limit of a single well and the economically recoverable reserve limit of a single well corresponding to different reserve categories.

[0062] Figure 2 This is a schematic diagram of the technical and economic boundaries for oil field development, such as... Figure 2 As shown, the technical and economic limits for oilfield development mainly include: the initial production limit for a single well and the economically recoverable reserves limit for a single well. The technical and economic limits for oilfield development refer to the minimum production or recoverable reserves that a new well must achieve to recover the increased investment and operating costs of the new well and obtain the minimum rate of return under existing oilfield development technology and fiscal system.

[0063] In some embodiments, the initial production limit of a single well is determined by the cash inflow and outflow relationship of a single well during oilfield development. Further, the cash outflow of a single well is calculated using the following formula:

[0064] CO = I t +S oft +C ovt·Q t +T r

[0065] Where CO represents cash outflow from a single well; I t This indicates the new construction investment for a single well, expressed in ten thousand yuan; S oft This represents fixed operating costs, expressed in ten thousand yuan per year; C ovt This represents the unit variable cost, expressed in yuan / ton; Q t This indicates annual production, expressed in tons; T r This indicates taxes and surcharges, expressed in ten thousand yuan.

[0066] Specifically, cash outflows from a single well include: new construction investment, operating costs, and taxes.

[0067] New construction investment includes investment in single-well new development projects, including drilling investment, oil production engineering investment, and surface gathering and transportation engineering investment.

[0068] Operating costs include fixed costs and variable costs. Fixed costs include: production personnel wages, employee welfare expenses, material costs, power costs, well logging and testing costs, downhole operation costs, other mining costs, maintenance and repair costs, etc.

[0069] Taxes refer to items such as value-added tax, urban construction and maintenance fees, education surcharges, resource taxes, and income taxes, which are calculated in accordance with relevant national regulations, in accordance with the national fiscal and tax system and the regulations of the petrochemical industry.

[0070] Furthermore, the total output of a single well is calculated using the following formula:

[0071]

[0072] Where CI represents the total output of a single well; P t This indicates the price of crude oil, in yuan / ton; Q t represents annual output; n represents the commodity rate, which is a decimal.

[0073] Specifically, the output of a single well consists of the sales revenue of the main products and by-products, which is numerically equal to the product of sales volume, commodity rate, and sales price.

[0074] Furthermore, the initial production limit for a single well (newly drilled well) refers to the minimum initial production that should be achieved under certain development technologies and fiscal and tax systems, so that the revenue obtained from a single well (newly drilled well) can cover all investment and oil production operating costs and obtain the minimum rate of return. When the initial production of a single well exceeds this value, it is considered economically feasible, that is, it satisfies the following formula:

[0075] CI-CO≧0

[0076] Where CI represents the total output of a single well, and CO represents the cash outflow of a single well. Based on the above formula, the following formula can be further derived:

[0077]

[0078] Among them, Q c This indicates the initial production limit for a single well, in tons per day; P T The investment payback period is represented by t, which is represented by t, and the economic evaluation period is represented by t, which is represented by P. t This represents the price of crude oil, in yuan / ton; n represents the commodity rate; r c Indicates the ratio of taxes and surcharges to income; C ovt This represents the unit variable cost, expressed in yuan / ton; η t I represents the coefficient of variation of dimensionless output; t This indicates the new construction investment for a single well, expressed in ten thousand yuan; S oft This represents fixed operating costs, expressed in ten thousand yuan per year.

[0079] In some embodiments, the economically recoverable reserves limit for a single well is calculated using the following formula:

[0080] N=ΣQ t

[0081] Where N represents the economically recoverable reserves limit for a single well, in tons; Q t This indicates the annual production of a single well.

[0082] In some embodiments, the benchmark rate of return in the petroleum industry (currently, for a certain domestic petroleum company, it is an after-tax internal rate of return of 8%) and the interest rate of long-term loans with a term of five years or more from the People's Bank of China (the annual real interest rate calculated based on the nominal interest rate is 4.99%) are two important dividing points. When the economic evaluation internal rate of return of a single well is greater than the industry benchmark rate of return, it is considered a reserve that can be developed profitably and is defined as a Class I reserve (profitable reserve); when the economic evaluation internal rate of return of a single well is between 4.99% and 8%, it is considered a reserve that is not developed efficiently and is defined as a Class II reserve (inefficient reserve); when the economic evaluation internal rate of return of a single well is less than 4.99%, it is considered a reserve that is not developed efficiently and is defined as a Class III reserve (currently, there is no profitable reserve).

[0083] Furthermore, based on the preset rate of return corresponding to different reserve categories, the initial production limit of a single well and the economically recoverable reserve limit of a single well corresponding to different reserve categories are calculated as shown in the table below.

[0084]

[0085] Step S202: Analyze the production parameters of the wells already developed in the selected work area.

[0086] Step S203: Determine the reserve category of the developed well based on the production parameters of the developed well.

[0087] The production parameters include the initial production limit of a single well and the economically recoverable reserves limit of a single well.

[0088] Step S204: Analyze the matrix reservoir parameters, fracture parameters, and oil-bearing parameters of the wells already developed in the selected work area.

[0089] Step S205: Based on the reserve category of the developed well, determine the numerical range of matrix reservoir parameters, fracture parameters, and oil-bearing parameters corresponding to the reserve category of the developed well.

[0090] In some embodiments, determining the matrix reservoir parameters corresponding to the reserve category of the developed well based on the reserve category of the developed well includes:

[0091] Analyze the relationship between core permeability and sand body thickness in developed wells; and

[0092] Based on the correlation between core permeability and sand body thickness of the developed wells, the numerical range of matrix reservoir parameters corresponding to the reserve categories of the developed wells is determined.

[0093] Specifically, effective thickness and porosity are key parameters that determine the scale of reserves. Due to the influence of top compaction and bottom cementation, the thickness of sand bodies in tight oil reservoirs in oilfields is positively correlated with reservoir properties. The permeability of sand bodies below 7m is less than 0.1mD on average, and the matrix porosity is less than 7%, which are mainly Class IV matrix reservoirs with almost no oil and gas storage and permeability capacity and no effective thickness.

[0094] Furthermore, taking an oilfield on the southern edge of the Ordos Basin as an example, the process of determining the numerical range of matrix reservoir parameters corresponding to the reserve categories of the developed wells is explained in detail. Through statistical analysis of production data and geological parameters from over 200 horizontal wells in an oilfield on the southern edge of the Ordos Basin, wells with initial production of less than 3 tons / day and economically recoverable reserves of less than 3000 tons are mainly classified as Class III matrix reservoirs, with average permeability between 0.1-0.3 mD and average porosity between 7-9%. Figure 3 This is a map showing the lower limit of the thickness of tight oil sand bodies in an oilfield on the southern margin of the Ordos Basin, for reference. Figure 3 Based on the relationship between core permeability and sand body thickness, the sand body thickness is generally between 7-14m. According to the pre-calculated initial production limit of a single well and the economically recoverable reserve limit of a single well corresponding to different reserve categories, it can be seen that such oil wells are all distributed in the three types of reserve areas.

[0095] To meet the requirement of a benchmark rate of return greater than 5%, horizontal wells in Class II reservoir areas need an initial production of 3-10 tons / day and an economically recoverable reserve of 3000-6000 tons. Statistical analysis shows that these oil wells mainly develop Class I and Class II matrix reservoirs, with an average permeability greater than 0.3 mD and an average porosity greater than 9%. Based on the correlation between core permeability and sand body thickness, the sand body thickness needs to be greater than 14 m. Statistical analysis also shows that oil wells with a benchmark rate of return greater than 8%, i.e., horizontal wells that meet the requirements of an initial production of 10 tons / day and an economically recoverable reserve of greater than 6000 tons, have matrix reservoir parameters that are not significantly different from those of horizontal wells in Class II reservoir areas, mainly consisting of Class I matrix reservoirs, followed by Class II reservoirs.

[0096] The evaluation criteria for matrix reservoir quality categories are shown in the table below:

[0097]

[0098] In some embodiments, five parameters are preferred as further subdivision parameters of matrix reservoir parameters: sand body thickness, sorting coefficient, porosity, permeability, and mainstream throat radius. Based on the correspondence between core permeability and sand body thickness of a well in an oilfield on the southern margin of the Ordos Basin, the numerical range of matrix reservoir parameters corresponding to different reserve categories is determined.

[0099] The numerical ranges of matrix reservoir parameters corresponding to different reserve categories are shown in the table below:

[0100]

[0101] In some embodiments, determining the fracture parameters corresponding to the reserve category of the developed well based on the reserve category of the developed well includes:

[0102] This study analyzes the relationship between the fracture strength index (FFI) of a single well and the initial production limit of developed wells, as well as the relationship between the FFI and the economically recoverable reserves limit of developed wells.

[0103] Based on the relationship between the single-well fracture strength index (FFI) and the initial production limit of developed wells, and the relationship between the single-well fracture strength index (FFI) and the economically recoverable reserves limit of developed wells, the numerical range of fracture parameters corresponding to the reserve categories of the developed wells is determined.

[0104] Specifically, according to the requirement that a Class I reserve area meets the benchmark rate of return greater than 8%, the initial production of a horizontal well must reach 10 tons / day, and the economically recoverable reserves of a single well must be greater than 6,000 tons. Taking an oilfield on the southern margin of the Ordos Basin as an example, normalized cross-plots of the fracture strength index (FFI) and the initial production of a horizontal well are established (refer to...). Figure 4), Cross-plot of single-well fracture strength index (FFI) and horizontal well recoverable reserves (refer to) Figure 5 As shown in the two figures above, when the initial production of a horizontal well reaches 10 tons / day and the economically recoverable reserves of a single well are greater than 6,000 tons, the fracture strength index (FFI) needs to be greater than 0.4.

[0105] According to the requirement of a benchmark rate of return greater than 5% for Class II reserve areas, the initial production of a horizontal well needs to reach 3-10 tons / day, and the economically recoverable reserves of a single well should be between 3,000 and 6,000 tons. This is illustrated by the cross-plot of the normalized single-well fracture strength index (FFI) and the initial production of a horizontal well (refer to...). Figure 4 ), Cross-plot of single-well fracture strength index (FFI) and horizontal well recoverable reserves (refer to) Figure 5 It is understood that when the initial production of a horizontal well reaches 3 tons / day and the economically recoverable reserves of a single well are greater than 3,000 tons, the fracture strength index (FFI) needs to be greater than 0.2.

[0106] Therefore, by establishing a chart of fracture parameters and initial production and recoverable reserves of a single horizontal well, the fracture parameter limit requirements corresponding to the three types of reserves can be determined. That is, the fracture strength index of the first type of reserve area must be greater than 0.4, the fracture strength index of the second type of reserve area must be between 0.2 and 0.4, and the fracture strength index of the third type of reserve area must be less than 0.2.

[0107] The degree of fracture development in the study area is controlled by the scale of the fault zone and has a controlling effect on the distribution of oil-bearing properties in the reservoir. However, it is not necessarily true that the larger the scale of the fault zone and the more developed the fractures, the more favorable it is for oil and gas enrichment. Large-scale fracture zones associated with faults with a displacement >20m and a length >2.5km are unfavorable for oil and gas preservation, with poor oil-bearing properties in the reservoirs. The water cut of nearby horizontal wells is all above 50%, resulting in poor reserve quality. Medium-scale fracture zones controlled by faults with a displacement between 10-20m and a length between 1.0-2.5km are the main oil and gas enrichment areas, with good oil-bearing properties and high reserve quality. The oil-bearing properties and reserve quality near small-scale fracture zones are secondary.

[0108] In some embodiments, the normalized fracture strength (FFI) is used as the main fracture index. Combined with the classification standards for large, medium, and small-scale fracture zones, and considering the fracture length and displacement parameters, a classification and evaluation standard for tight oil reserves in an oilfield on the southern margin of the Ordos Basin is determined. Furthermore, the numerical ranges of fracture parameters corresponding to different reserve categories are determined. The numerical ranges of fracture parameters corresponding to different reserve categories are shown in the table below:

[0109]

[0110] In some embodiments, determining the numerical range of the oil-bearing parameter corresponding to the reserve category of the developed well, based on the reserve category of the developed well, includes:

[0111] Analyze the relationship between the initial production limit of a single well and the oil saturation of developed wells; and

[0112] Based on the relationship between the initial production limit of a single well and the oil saturation of the developed wells, the numerical range of the oil-bearing parameters corresponding to the reserve category of the developed wells is determined.

[0113] Specifically, the oil saturation of tight oil reservoirs is controlled by both fractures and reservoir quality. The oil content is highly heterogeneous, and the level of oil saturation directly affects the quality of reserves, making it one of the important parameters for reserve classification and evaluation.

[0114] Analysis of the oil testing and production results from thousands of vertical wells and hundreds of horizontal wells in an oilfield on the southern margin of the Ordos Basin revealed that the discovered tight oil edges and bottom water are not significant, with oil and water coexisting in the reservoir. This is because the tight oil reservoirs on the southern margin of the Ordos Basin are dense, with small pore throats and significant lateral variations in lithology and physical properties. In addition, the strata are relatively flat, making it difficult for oil and water to differentiate effectively. Instead, the reservoirs are dominated by coexisting oil and water-bearing oil layers, with fewer pure oil or pure water layers. This is significantly different from typical conventional sandstone oil reservoirs.

[0115] To maximize the assessment of tight oil reserves, this invention includes both oil-bearing layers and oil-water confluence layers in the reserve calculation, provided they meet the standards for industrial oil flow wells in the region. Therefore, the oil saturation of the oil-water confluence layer is used as the lower limit of reservoir saturation for reserve calculation. Due to limitations in oilfield data and actual production characteristics, the oil testing method is primarily used. The oil testing method mainly involves plotting cross-sectional diagrams of oil saturation and porosity of oil-bearing layers and oil-water confluence layers from multiple industrial oil flow wells in the study area (see reference). Figure 6 This is used to determine the minimum oil saturation and porosity required for industrial-grade oil flow wells, serving as the lower limit for reserve calculations. Figure 6 From this, we can derive that the lower limit of oil saturation for calculating tight oil reserves is 30%, which means that the lower limit of oil saturation for classified reserves is 30%.

[0116] According to the requirement of a benchmark rate of return greater than 8% for Class I reserve areas, the initial production of a horizontal well must reach 10 tons / day, and the economically recoverable reserves of a single well must be greater than 6000 tons. Since the cumulative production of an oil well is affected by many factors such as geological conditions, fracturing measures, and operating procedures, and the initial production reflects the geological conditions themselves more closely, it is more closely related to the reservoir's oil saturation. Therefore, a cross-plot of the initial production of a horizontal well and the oil saturation interpreted from logging is established (refer to...). Figure 7 ).Depend on Figure 7It is understood that for a horizontal well to achieve an initial production rate of 10 tons / day, the average oil saturation of the reservoir must be greater than 50%. Similarly, for Class II reservoir areas to meet the requirement of an internal rate of return greater than 5%, the initial production rate of a horizontal well must reach 3 tons / day, and the average oil saturation of the reservoir must be greater than 40%.

[0117] Based on the lower limit of 30% for oil saturation in the classified reserves, the different oil saturation thresholds for the three types of reserves can be determined: Type I reserves must have an oil saturation greater than 50%, Type II reserves must have an oil saturation between 40% and 50%, and Type III reserves must have an oil saturation between 30% and 40%, as detailed in the table below:

[0118]

[0119] Based on a detailed description of the three major heterogeneous geological characteristics of tight oil matrix reservoirs, fractures, and oil-bearing properties, this invention analyzes the geological factors affecting the scale and quality of tight oil reserves. Combining the economic and production capacity limits of different benchmark rates of return, it determines the configuration relationship of "matrix reservoir + fracture + oil-bearing properties" for different types of reserves. Based on the reserve calculation, it also determines the geological parameter limits and reserve abundance limits for different types of reserves.

[0120] It should be noted that reserve abundance is determined by reserves. In the field of oil exploration and development, reserve abundance refers to the size of reserves per unit area or unit volume. Reserve abundance helps to assess the potential of oil and gas fields, thereby guiding subsequent exploration and development work.

[0121] In some embodiments, the following formula is used to calculate reserve abundance: Reserve Abundance = Reserve / Area (or Volume)

[0122] In some embodiments, based on technical and economic limitations and combining the evaluation results of matrix reservoir heterogeneity, fracture heterogeneity, and oil-bearing heterogeneity, a classification and evaluation standard for tight oil reserves in the southern margin of the Ordos Basin was established. The numerical ranges of matrix reservoir parameters, fracture parameters, and oil-bearing parameters for different reserve categories are shown in the table below:

[0123]

[0124] It should be noted that in the table above, the reserve abundance is determined by the economically recoverable reserves limit of a single well. In the field of oil exploration and development, reserve abundance refers to the size of reserves per unit area or unit volume. Reserve abundance helps to assess the potential of oil and gas fields, thereby guiding subsequent exploration and development work.

[0125] Step S103: Determine the reserve parameters corresponding to the target work area based on the reserve category corresponding to the target work area.

[0126] The reserve parameters include one or more of the following: initial production limit of a single well, economically recoverable reserve limit of a single well, and reserve abundance.

[0127] In some embodiments, the preset reserve classification and evaluation standard is the tight oil reserve classification and evaluation standard of the southern margin of the Ordos Basin. The reserve category corresponding to the target work area is determined by applying the tight oil reserve classification and evaluation standard of the southern margin of the Ordos Basin, and the reserve parameters corresponding to the target work area are further determined.

[0128] Specifically, Category I reserves are those that are technically and economically recoverable under current conditions. They meet the following criteria: a benchmark rate of return greater than 8%, initial production of 10 tons / day per horizontal well, and economically recoverable reserves greater than 6000 tons per well. The geological characteristics include a Class I / II matrix reservoir, a medium-grade fracture zone, and good oil content (SO4 > 50%), with a reserve abundance greater than 50 × 10⁻⁶. 4 t / km 2 It belongs to the "sweet spot" of dense oil.

[0129] Category II reserves: These are reserves that can be utilized through technological breakthroughs or under certain economic conditions. They meet the following criteria: a benchmark rate of return greater than 5%, initial production of horizontal wells exceeding 3 tons / day, and economically recoverable reserves between 3000 and 6000 tons per well. The geological characteristics consist of a Category I / II matrix reservoir + a small-scale fracture zone + moderate oil content (40% < SO2 < 50%), with a reserve abundance of (30-50) × 10⁻⁶. 4 t / km 2 between;

[0130] Category III Reserves: Reserves that cannot be effectively utilized under current technical and economic conditions. Benchmark rate of return is less than 5%, initial production of a single horizontal well is less than 3 tons / day, and the economically recoverable reserves per well are less than 3000 tons. Geological characteristics include a Category II / III matrix reservoir zone + poorly developed fractures + poor reservoir oil content (30% < SO < 40%), and reserve abundance is less than 30 × 10⁻⁶ tons. 4 t / km 2 .

[0131] In some embodiments, the X well area, which is representative of an oilfield in the southern margin of the Ordos Basin, was selected as the target work area for reserve classification and evaluation. Based on a three-dimensional geological model, the geological reserves of the X well area were calculated. Combined with the tight oil reserve classification and evaluation standards of the southern margin of the Ordos Basin, a reserve classification and evaluation was carried out, clarifying the proportion of different types of reserves in the total reserves and their planar distribution characteristics in the well area.

[0132] Type I reserves account for 31.6% of the total reserves in Well X, representing only one-third of the area's total geological reserves. These are primarily oil-rich fracture zones formed by medium-scale faults, distributed in strip-like patterns across several medium-level fault zones in the northwest, southeast, north-central, and west of the well area. These reservoir areas are characterized by well-developed fractures and relatively high oil saturation (>50%), making them "sweet spots" for tight oil in the southern margin of the Ordos Basin. These "sweet spots" are scattered across 20 units, nine of which have an area less than 0.2 km². 2 The reserves are less than 100,000 tons and are characterized by being small and dispersed. Based on previous development experience, it is believed that these reserves can be effectively utilized under current economic conditions through horizontal well staged volumetric fracturing technology, making them a primary target for priority development and utilization of tight oil.

[0133] Category II reserves account for 48.7%, nearly half of the total geological reserves. These are areas where small-scale fracture zones overlap with Category I / II reservoirs, forming the main geological reserve composition of the X well area. They are primarily distributed in the main river channel from southwest to northeast and in the middle of the southeastern main river channel. The reservoir properties are slightly worse, they are located at a certain distance from the fracture zones, and exhibit some microfractures, showing an irregular, contiguous distribution along the fracture zones. Currently, the exploitation scope of this type of reserve is limited, but it is assessed that through technological breakthroughs and cost reduction, effective exploitation can be achieved in the future.

[0134] The third category of reserves accounts for 19.6%, a relatively small proportion, mainly distributed in tributaries and riverbanks, and irregularly contiguous along the second category of reserve areas. However, these reserves have low oil saturation and relatively poor reservoir properties. The assessment concludes that these reserves are currently difficult to exploit under economic and technological conditions.

[0135] The method provided in this invention first analyzes the geological parameters of the target work area, then determines the reserve category corresponding to the target work area according to a preset reserve classification and evaluation standard, and finally determines the reserve parameters corresponding to the target work area based on the reserve category. On the one hand, it can determine the proportion and planar distribution characteristics of different types of reserves in the total reserves; on the other hand, it can establish a reserve utilization sequence and formulate an oilfield development plan following the principle of efficient development. For example, it can prioritize the utilization of Class I reserves while simultaneously preparing for the development of Class II reserves, maximizing the efficient development of continental tight oil.

[0136] This invention also provides an apparatus for predicting tight oil geological reserve parameters. The apparatus includes a processor, a memory, and a program stored in the memory and executable on the processor. When the processor executes the program, it runs the method for predicting tight oil geological reserve parameters.

[0137] This invention also provides a computer program product, including a computer program, characterized in that the computer program, when executed by a processor, implements the method for predicting tight oil geological reserve parameters.

[0138] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method of predicting a tight oil geological reserve parameter, characterized in that, The method comprises: determining a value corresponding to a reservoir evaluation index of the target work area by analyzing a geological parameter of the target work area, wherein the reservoir evaluation index comprises a matrix reservoir parameter, a fracture parameter, and an oil-bearing property parameter; determining a reserve category corresponding to the target work area according to a preset reserve classification evaluation standard and in combination with the value corresponding to the reservoir evaluation index of the target work area, wherein the preset reserve classification evaluation standard comprises a numerical range of the reservoir evaluation index corresponding to different reserve categories; and determining a reserve parameter corresponding to the target work area based on the reserve category corresponding to the target work area, wherein the reserve parameter comprises one or more of a single-well initial production limit, a single-well economic recoverable reserve limit, and a reserve abundance.

2. The method of claim 1, wherein: the matrix reservoir parameter comprises a deposition feature, a reservoir parameter, and a percolation parameter; the fracture parameter comprises a fault scale and a fracture intensity; and the oil-bearing property parameter comprises an oil saturation.

3. The method of claim 2, wherein: the deposition feature comprises a sandstone thickness and a sorting coefficient; the reservoir parameter comprises a porosity; the percolation parameter comprises a permeability and a main flow throat radius; and the fault scale comprises a length and a fault separation. The preset reserve classification evaluation standard is determined by: calculating a single-well initial production limit and a single-well economic recoverable reserve limit corresponding to different reserve categories according to a preset rate of return corresponding to different reserve categories; analyzing production parameters of developed wells in the selected work area; 4. The method of claim 1, wherein: determining a reserve category of the developed wells according to the production parameters of the developed wells, wherein the production parameters comprise a single-well initial production limit and a single-well economic recoverable reserve limit; and analyzing a matrix reservoir parameter, a fracture parameter, and an oil-bearing property parameter of the developed wells in the selected work area, and determining a numerical range of the matrix reservoir parameter, the fracture parameter, and the oil-bearing property parameter corresponding to the reserve category of the developed wells according to the reserve category of the developed wells.

5. The method of claim 4, wherein: determining the matrix reservoir parameter corresponding to the reserve category of the developed wells according to the reserve category of the developed wells comprises: analyzing a core permeability-sand body thickness correspondence of the developed wells; and determining a numerical range of the matrix reservoir parameter corresponding to the reserve category of the developed wells based on the core permeability-sand body thickness correspondence of the developed wells. determining the fracture parameter corresponding to the reserve category of the developed wells according to the reserve category of the developed wells comprises: analyzing a relationship between a single-well fracture intensity index FFI and the single-well initial production limit of the developed wells, and a relationship between the single-well fracture intensity index FFI and the single-well economic recoverable reserve limit of the developed wells; and ​ 6. The method of claim 4, wherein, ​ ​ Based on the relationship between the single-well fracture intensity index FFI and the single-well initial production limit of the developed well, and the relationship between the single-well fracture intensity index FFI and the single-well economic recoverable reserve limit of the developed well, the value range of the fracture parameter corresponding to the reserve category of the developed well is determined.

7. The method of claim 4, wherein, The value range of the oil-bearing property parameter corresponding to the reserve category of the developed well is determined according to the reserve category of the developed well, which comprises: analyzing the relationship between the single-well initial production limit and the oil-bearing saturation of the developed well; and Based on the relationship between the single-well initial production limit and the oil-bearing saturation of the developed well, the value range of the oil-bearing property parameter corresponding to the reserve category of the developed well is determined.

8. The method of claim 4, wherein, The single-well initial production limit corresponding to different reserve categories is calculated according to the preset yield rate corresponding to different reserve categories, which comprises: The single-well initial production limit is calculated by the following formula: where Q c represents the initial production limit of a single well; P T represents the payback period of investment; t represents the economic evaluation period; P t represents the crude oil price; n represents the commodity rate; r c represents the ratio of tax and surcharges to income; C ovt represents the unit variable cost; η t represents the dimensionless production change coefficient; I t represents the new construction investment of a single well; S oft represents the fixed operating cost.

9. The method of claim 4, wherein, The single-well economic recoverable reserve limit corresponding to different reserve categories is calculated according to the preset yield rate corresponding to different reserve categories, which comprises: The single-well economic recoverable reserve limit is calculated by the following formula: N =∑Q t where N represents the economic recoverable reserves limit of a single well; Q t represents the annual production of a single well.

10. An apparatus for predicting tight oil geological reserve parameters, characterized by, The device comprises a processor, a memory, and a program stored on the memory and executable on the processor, and the processor executes the program to run the method for predicting the geological reserve parameter of the tight oil reservoir as claimed in any one of claims 1 to 9.

11. A computer program product comprising a computer program, characterized in that, The computer program, when executed by the processor, implements the method for predicting the geological reserve parameter of the tight oil reservoir as claimed in any one of claims 1 to 9.

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