Methods, systems, and computer programs for determining the lower limit of effective porosity in tight sandstone reservoirs

Abstract

This invention relates to the field of petroleum migration and accumulation mechanisms in tight reservoirs, and discloses a method, system, and computer program product for determining the lower limit of effective porosity in tight sandstone reservoirs. The method includes: determining the hydrocarbon expulsion intensity of the source rock using a preset hydrocarbon expulsion intensity determination model based on the values ​​of preset parameters; determining the gas charging force using a preset charging force determination model based on the values ​​of preset parameters and the hydrocarbon expulsion intensity; determining the critical pore throat radius for natural gas to exit the reservoir containing the source rock and enter the tight sandstone reservoir using a preset pore throat radius determination model based on the values ​​of various charging resistance parameters and preset parameters; determining the relationship between effective porosity and critical pore throat radius based on mercury intrusion porosimetry data of the tight sandstone reservoir; and then determining the lower limit of effective porosity of the tight sandstone reservoir based on this relationship. This method can effectively calculate the lower limit of porosity in tight sandstone reservoirs, providing a new approach for the evaluation of tight sandstone reservoirs.

Description

Technical Field

[0001] This disclosure relates to the mechanism of natural gas migration and accumulation in tight sandstone reservoirs, and particularly to a method, system, and computer program product for determining the lower limit of effective porosity in tight sandstone reservoirs. Background Technology

[0002] Deep tight sandstone gas is one of the most important unconventional natural gas resources. In the journal "Experimental Geology of Petroleum" (Vol. 28, No. 3, p. 211) in 2006, Jiang Zhenxue gave the definition of "pre-formed" tight sandstone gas reservoir by comparing the reservoir formation characteristics, conditions and formation mechanisms of tight gas reservoirs. That is, the reservoir compaction process occurs before the natural gas charging during the peak period of source rock hydrocarbon expulsion. This is called the reservoir pre-tightening deep basin gas reservoir type (abbreviated as "pre-formed" deep basin gas reservoir).

[0003] The lower limit of the physical properties of effective reservoirs in "pre-formed" tight sandstone is generally measured by the minimum porosity and minimum permeability that allow fluids to access and permeate. Among these, determining the lower limit of effective porosity is of great significance for formulating the next development plan for oil and gas fields, improving the tight oil accumulation mechanism, and increasing reserve geological reserves.

[0004] Among related technologies, the method of determining the lower limit of physical properties through empirical statistical methods has the advantages of simplicity and speed. However, due to the lack of sufficient theoretical support, it is difficult to determine whether it reflects the true situation of the reservoir. Experimental simulation mainly adopts core displacement experiments, the key of which is the determination of various parameters and the selection of samples. The experimental process and results are relatively ideal. Zheng Dingye, in "Petroleum and Natural Gas Geology" 2020, Vol. 41, No. 4, p. 749, determined the method for determining the lower limit of effective pore throat radius of three source-reservoir combination relationships in tight sandstone reservoirs from the perspective of dynamic mechanism. However, he did not clearly point out the criteria for judging the lower limit of effective porosity of "pre-formed" tight sandstone reservoirs.

[0005] While existing technologies offer some methods for calculating the lower limits of effective reservoir properties under constraints of hydrocarbon accumulation dynamics and pore structure—such as establishing functional relationships between oil-water interfacial tension and formation temperature, between the maximum connected pore throat radius and permeability, and between reservoir K / φ and K under pore throat structure type constraints—and calculating the lower limits of effective reservoir properties under different formation temperature conditions constrained by hydrocarbon accumulation dynamics and pore throat structure, these methods are not applicable to determining the lower limits of deep tight sandstone reservoirs. Summary of the Invention

[0006] The purpose of this invention is to provide at least one method, system, computer equipment, and computer program product for determining the lower limit of effective porosity in tight sandstone reservoirs. The method for determining the lower limit of effective porosity in tight sandstone reservoirs provided by this invention is simple to operate and can accurately and effectively calculate the lower limit of porosity in tight sandstone reservoirs, providing a new approach for the evaluation of tight sandstone reservoirs.

[0007] To address the aforementioned technical problems, at least one embodiment of this application provides a method for determining the lower limit of effective porosity in tight sandstone reservoirs, the method comprising:

[0008] Based on the values ​​of various preset parameters of the source rock, the hydrocarbon expulsion intensity of the source rock is determined by a preset hydrocarbon expulsion intensity determination model; wherein the source rock contains coal seams and mudstone, and the preset parameters include: porosity, hydrocarbon expulsion rate, organic matter abundance, mudstone thickness, coal seam thickness, and density of the source rock.

[0009] Based on the values ​​of each preset parameter and the hydrocarbon expulsion intensity, the gas charging power is determined by a preset charging power determination model; wherein, the charging power is the gas charging power when natural gas is discharged from the reservoir where the source rock is located and charged into the tight sandstone reservoir, and the tight sandstone reservoir is in contact with the reservoir where the source rock is located.

[0010] The values ​​of each charging resistance parameter of natural gas during the charging operation are determined, and the critical pore throat radius when natural gas is discharged from the reservoir where the source rock is located into the tight sandstone reservoir is determined by a preset pore throat radius determination model based on the values ​​of each charging resistance parameter and the preset parameter.

[0011] The relationship between effective porosity and critical pore throat radius is determined based on the mercury injection test data of the tight sandstone reservoir. Based on the critical pore throat radius, the lower limit of effective porosity of the tight sandstone reservoir is determined through the relationship between effective porosity and critical pore throat radius.

[0012] At least one embodiment of this application also provides a system for determining the lower limit of effective porosity in tight sandstone reservoirs, comprising:

[0013] The hydrocarbon expulsion intensity determination module is used to determine the hydrocarbon expulsion intensity of the source rock based on the values ​​of various preset parameters of the source rock through a preset hydrocarbon expulsion intensity determination model; wherein the source rock contains coal seams and mudstone, and the preset parameters include: porosity, hydrocarbon expulsion rate, organic matter abundance, mudstone thickness, coal seam thickness, and density of the source rock.

[0014] A gas charging power determination module is used to determine the gas charging power based on the values ​​of each preset parameter and the hydrocarbon expulsion intensity through a preset charging power determination model; wherein, the charging power is the gas charging power when natural gas is discharged from the reservoir where the source rock is located and charged into the tight sandstone reservoir, and the tight sandstone reservoir is in contact with the reservoir where the source rock is located.

[0015] The critical pore throat radius determination module is used to determine the values ​​of various charging resistance parameters of natural gas during the charging operation, and to determine the critical pore throat radius when natural gas is discharged from the reservoir where the source rock is located into the tight sandstone reservoir based on the values ​​of the charging resistance parameters and the preset parameters through the preset pore throat radius determination model.

[0016] The effective porosity lower limit determination module is used to determine the relationship between effective porosity and critical pore throat radius based on mercury injection test data of the tight sandstone reservoir, and to determine the effective porosity lower limit of the tight sandstone reservoir based on the relationship between the effective porosity and critical pore throat radius.

[0017] At least one embodiment of this application also provides a computer device, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the method described above.

[0018] At least one embodiment of this application also provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the fiber optic detection method as described above.

[0019] The method, system, medium, and computer program product for determining the lower limit of effective porosity in tight sandstone reservoirs provided in this application are simple to operate and can accurately and effectively calculate the lower limit of porosity in tight sandstone reservoirs, providing a new approach for the evaluation of tight sandstone reservoirs, compared with the prior art.

[0020] In some optional embodiments, the values ​​of each preset parameter are obtained through geophysical methods and experimental testing.

[0021] In some optional embodiments, the preset hydrocarbon expulsion intensity determination model includes:

[0022] E q =q e ×TOC×(h m +h c )×ρ s

[0023] Among them, E q q represents hydrocarbon expulsion intensity. eHydrocarbon emission rate, TOC organic matter abundance, h m h represents the thickness of the mudstone. c ρ is the thickness of the coal seam. s This represents the density of the source rock.

[0024] In some optional embodiments, determining the gas charging power based on the values ​​of each of the preset parameters and the hydrocarbon expulsion intensity using a preset charging power determination model includes:

[0025] The burial depth of the reservoir where the source rock is located is obtained from the well logging curve of the source rock;

[0026] The thermodynamic temperature is determined by using a preset thermodynamic temperature determination model based on the burial depth of the source rock in the reservoir.

[0027] Based on the values ​​of the preset parameters, the hydrocarbon expulsion intensity, the burial depth of the reservoir where the source rock is located, and the thermodynamic temperature, the gas injection power is determined by the preset injection power determination model.

[0028] In some optional embodiments, the preset injection kinetics determination model includes:

[0029]

[0030] Among them, P e The gas is charged using power, Z is the gas compressibility coefficient, and E is the gas compressibility coefficient. q For hydrocarbon expulsion intensity, ρ gl Let R be the gas density of natural gas, R be the molar gas constant, T be the thermodynamic temperature, and h be the temperature. m h represents the thickness of the mudstone. c Where φ is the coal seam thickness, φ is the porosity of the source rock, and M is a constant.

[0031] In some optional embodiments, the preset thermodynamic temperature determination model includes:

[0032]

[0033] Where T is the thermodynamic temperature, H D K1, K2, K3, and K4 are constants, representing the burial depth of the reservoir where the source rock is located.

[0034] In some optional embodiments, the relationship between the effective porosity and the critical throat radius includes:

[0035]

[0036] Where, φ 下限 K5 and K6 are both constants, representing the lower limit of effective porosity, and r is the critical pore throat radius.

[0037] In some optional embodiments, the preset throat radius determination model includes:

[0038]

[0039] Where r is the critical throat radius, Z is the gas compressibility coefficient, and q e R is the hydrocarbon expulsion rate, T is the molar gas constant, M is the thermodynamic temperature, and h is a constant. m h represents the thickness of the mudstone. c ρ is the thickness of the coal seam. w Where is the density of water, g is the acceleration due to gravity, H is the height of the water column, φ is the porosity of the source rock, σ is the gas-water interfacial tension, θ is the wetting angle, and K7 is a constant. Attached Figure Description

[0040] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0041] Figure 1 A flowchart illustrating a method for determining the lower limit of effective porosity in tight sandstone reservoirs, provided in this embodiment of the disclosure;

[0042] Figure 2 A flowchart illustrating another method for determining the lower limit of effective porosity in tight sandstone reservoirs provided in this disclosure embodiment;

[0043] Figure 3 A schematic diagram of a hydrocarbon source rock in the Ordos Basin provided in this embodiment of the present disclosure;

[0044] Figure 4 A schematic diagram of hydrocarbon expulsion intensity from the Benxi Formation source rocks in the Ordos Basin is provided as an embodiment of this disclosure.

[0045] Figure 5 This is a diagram showing the relationship between the throat radius and porosity in a mercury intrusion porosimetry experiment, provided as an embodiment of this disclosure. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been presented in the various embodiments of the present invention to enable the reader to better understand the present invention. However, the technical solutions claimed in the present invention can be implemented even without these technical details and various changes and modifications based on the following embodiments.

[0047] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method, system, medium, and computer program product for determining the lower limit of effective porosity in tight sandstone reservoirs. Compared to existing technologies, the method for determining the lower limit of effective porosity in tight sandstone reservoirs provided by this invention is simple to operate and can accurately and effectively calculate the lower limit of porosity in tight sandstone reservoirs, providing a new approach for the evaluation of tight sandstone reservoirs.

[0048] To improve the drilling success rate of deep, pre-formed tight sandstone reservoirs, avoid ineffective reservoir layers, and save production costs, a reasonable and feasible method for determining the lower limit of effective porosity in pre-formed tight sandstone reservoirs is needed. This invention discloses a method, system, medium, and computer program product for determining the lower limit of effective porosity in tight sandstone reservoirs, which can be used to determine the lower limit of effective porosity in deep, pre-formed tight sandstone reservoirs.

[0049] Example 1:

[0050] The embodiments of the present invention relate to a method for determining the lower limit of effective porosity in tight sandstone reservoirs, which can be used to determine the lower limit of effective porosity in deep "pre-formed" tight sandstone reservoirs.

[0051] Compared with the prior art, the method for determining the lower limit of effective porosity of tight sandstone reservoirs provided by the present invention is simple to operate and can accurately and effectively calculate the lower limit of porosity of tight sandstone reservoirs, providing a new approach for the evaluation of tight sandstone reservoirs.

[0052] The following is a detailed explanation of the implementation details of the method for determining the lower limit of effective porosity in tight sandstone reservoirs according to this embodiment. The following content is only for the convenience of understanding and is not necessary for implementing this solution.

[0053] The method for determining the lower limit of effective porosity in tight sandstone reservoirs in this embodiment can be applied to electronic devices with communication, computing, and data storage capabilities.

[0054] like Figure 1 As shown in this embodiment, the method for determining the lower limit of effective porosity in tight sandstone reservoirs includes the following steps:

[0055] Step 110: Determine the hydrocarbon expulsion intensity of the source rock by using a preset hydrocarbon expulsion intensity determination model based on the values ​​of each preset parameter of the source rock; wherein the source rock contains coal seams and mudstone, and the preset parameters include: porosity, hydrocarbon expulsion rate, organic matter abundance, mudstone thickness, coal seam thickness, and density of the source rock.

[0056] In this step, relevant preset parameters of the source rock strata (mudstone + coal seam) for injecting natural gas into deep "pre-formed" tight sandstone reservoirs are obtained, and then the hydrocarbon expulsion intensity of the source rock is determined based on each preset parameter.

[0057] Step 120: Determine the gas charging power using a preset charging power determination model based on the values ​​of each preset parameter and the hydrocarbon expulsion intensity; wherein, the charging power is the gas charging power when natural gas is discharged from the reservoir where the source rock is located and injected into the tight sandstone reservoir, and the tight sandstone reservoir is in contact with the reservoir where the source rock is located.

[0058] In this step, the charging power for natural gas to be injected into the "pre-formed" tight sandstone reservoir is determined based on the relevant preset parameters of the source rock strata and the hydrocarbon expulsion intensity determined in the previous steps.

[0059] Step 130: Determine the values ​​of each charging resistance parameter of natural gas during the charging operation, and determine the critical pore throat radius when natural gas is discharged from the reservoir where the source rock is located into the tight sandstone reservoir based on the values ​​of each charging resistance parameter and the preset parameters, using a preset pore throat radius determination model.

[0060] In this step, the parameters related to the natural gas charging resistance (static water column pressure + capillary force) include: ρ w (density of water), g (acceleration due to gravity), H (height of water column), σ (interfacial tension between air and water), and θ (wetting angle).

[0061] Where, ρ w The density of water and gravitational acceleration were obtained by consulting the NIST database, and the height of the water column H could be obtained from the altitude of the target layer. Other constants were constants, such as σ = 0.75 N / m and N = 145°.

[0062] Step 140: Determine the relationship between effective porosity and critical pore throat radius based on the mercury injection test data of the tight sandstone reservoir, and determine the lower limit of effective porosity of the tight sandstone reservoir based on the critical pore throat radius and the relationship between effective porosity and critical pore throat radius.

[0063] In this step, the relationship between effective porosity and critical pore throat radius can be determined by fitting the mercury intrusion porosimetry data of tight sandstone reservoirs.

[0064] The method for determining the lower limit of effective porosity in tight sandstone reservoirs provided in this embodiment is simple to operate and can accurately and effectively calculate the lower limit of porosity in tight sandstone reservoirs, providing a new approach for the evaluation of tight sandstone reservoirs.

[0065] Example 2:

[0066] Based on the above embodiments, this embodiment further explains and illustrates the method for determining the lower limit of effective porosity in tight sandstone reservoirs provided in the above embodiments.

[0067] In step 110: Based on the values ​​of various preset parameters of the source rock, the hydrocarbon expulsion intensity of the source rock is determined by a preset hydrocarbon expulsion intensity determination model; wherein the source rock contains coal seams and mudstone, and the preset parameters include: porosity, hydrocarbon expulsion rate, organic matter abundance, mudstone thickness, coal seam thickness, and density of the source rock.

[0068] In some embodiments, the values ​​of each preset parameter are obtained through geophysical methods and experimental testing.

[0069] In some embodiments, the preset hydrocarbon expulsion intensity determination model includes:

[0070] E q =q e ×TOC×(h m +h c )×ρ s

[0071] Among them, E q q represents hydrocarbon expulsion intensity. e Hydrocarbon emission rate, TOC organic matter abundance, h m h represents the thickness of the mudstone. c ρ is the thickness of the coal seam. s This represents the density of the source rock.

[0072] In this step, relevant preset parameters of the source rock strata (mudstone + coal seam) for injecting natural gas into deep "pre-formed" tight sandstone reservoirs are obtained, and then the hydrocarbon expulsion intensity of the source rock is determined based on each preset parameter.

[0073] In step 120: Based on the values ​​of each preset parameter and the hydrocarbon expulsion intensity, the gas charging power is determined by a preset charging power determination model; wherein, the charging power is the gas charging power when natural gas is discharged from the reservoir where the source rock is located and charged into the tight sandstone reservoir, and the tight sandstone reservoir is in contact with the reservoir where the source rock is located.

[0074] In some embodiments, determining the gas charging power using a preset charging power determination model based on the values ​​of each preset parameter and the hydrocarbon expulsion intensity includes:

[0075] The burial depth of the reservoir where the source rock is located is obtained from the well logging curve of the source rock;

[0076] The thermodynamic temperature is determined by using a preset thermodynamic temperature determination model based on the burial depth of the source rock in the reservoir.

[0077] Based on the values ​​of the preset parameters, the hydrocarbon expulsion intensity, the burial depth of the reservoir where the source rock is located, and the thermodynamic temperature, the gas injection power is determined by the preset injection power determination model.

[0078] In some embodiments, the preset injection kinetics determination model includes:

[0079]

[0080] Among them, P e The gas is charged using power, Z is the gas compressibility coefficient, and E is the gas compressibility coefficient. q For hydrocarbon expulsion intensity, ρ gl Let R be the gas density of natural gas, R be the molar gas constant, T be the thermodynamic temperature, and h be the temperature. m h represents the thickness of the mudstone. c Where φ is the coal seam thickness, φ is the porosity of the source rock, and M is a constant.

[0081] In some embodiments, the preset thermodynamic temperature determination model includes:

[0082]

[0083] Where T is the thermodynamic temperature, H D K1, K2, K3, and K4 are constants, representing the burial depth of the reservoir where the source rock is located.

[0084] Preferably, K1, K2, K3 and K4 are 14, 2.8, 100 and 273.15 respectively.

[0085] In this step, the charging power for natural gas to be injected into the "pre-formed" tight sandstone reservoir is determined based on the relevant preset parameters of the source rock strata and the hydrocarbon expulsion intensity determined in the previous steps.

[0086] In step 130: the values ​​of each charging resistance parameter of natural gas during the charging operation are determined, and the critical pore throat radius when natural gas is discharged from the reservoir where the source rock is located into the tight sandstone reservoir is determined by the preset pore throat radius determination model based on the values ​​of each charging resistance parameter and the preset parameters.

[0087] In some embodiments, the preset throat radius determination model includes:

[0088]

[0089] Where r is the critical throat radius, Z is the gas compressibility coefficient, and q e R is the hydrocarbon expulsion rate, T is the molar gas constant, M is the thermodynamic temperature, and h is a constant. m h represents the thickness of the mudstone. cρ is the thickness of the coal seam. w Where is the density of water, g is the acceleration due to gravity, H is the height of the water column, φ is the porosity of the source rock, σ is the gas-water interfacial tension, θ is the wetting angle, and K7 is a constant.

[0090] Preferably, the value of K7 is 2.

[0091] In this step, the parameters related to the natural gas charging resistance (static water column pressure + capillary force) include: ρ w (density of water), g (acceleration due to gravity), H (height of water column), σ (interfacial tension between air and water), and θ (wetting angle).

[0092] Where, ρ w The density of water and gravitational acceleration were obtained by consulting the NIST database, and the height of the water column H could be obtained from the altitude of the target layer. Other constants were constants, such as σ = 0.75 N / m and N = 145°.

[0093] In step 140: the relationship between effective porosity and critical pore throat radius is determined based on the mercury injection test data of the tight sandstone reservoir, and the lower limit of effective porosity of the tight sandstone reservoir is determined based on the critical pore throat radius through the relationship between effective porosity and critical pore throat radius.

[0094] In some embodiments, the relationship between the effective porosity and the critical throat radius includes:

[0095]

[0096] Where, φ 下限 K5 and K6 are both constants, representing the lower limit of effective porosity, and r is the critical pore throat radius.

[0097] Preferably, the values ​​of K5 and K6 are 3.2068 and 1.9163, respectively.

[0098] In this step, the relationship between effective porosity and critical pore throat radius can be determined by fitting the mercury intrusion porosimetry data of tight sandstone reservoirs.

[0099] In summary, this embodiment provides a numerical simulation method for determining the lower limit of porosity in "pre-formed" tight sandstone reservoirs, belonging to the research field of petroleum migration and accumulation mechanisms in tight reservoirs. In this embodiment, the balance relationship between dynamics (hydrocarbon expulsion intensity) and resistance (the sum of capillary force and hydrostatic pressure) under the critical conditions was designed and established; and the correlation between critical porosity and pore throat radius was fitted using high-pressure mercury injection experimental data, providing important theoretical support for studying the formation mechanism and distribution prediction of deep tight oil and gas reservoirs.

[0100] The method for determining the lower limit of effective porosity in tight sandstone reservoirs provided in this application is simple to operate and can accurately and effectively calculate the lower limit of porosity in tight sandstone reservoirs, providing a new approach for the evaluation of tight sandstone reservoirs, compared with the prior art.

[0101] Example 3:

[0102] Based on the above embodiments, this embodiment is a specific example.

[0103] In this embodiment, a method for determining the lower limit of effective porosity in tight sandstone reservoirs is provided, which may include steps (1) to (4), specifically:

[0104] (1) Obtain relevant parameters of the source rock strata (mudstone + coal seam) for injecting natural gas into deep “pre-formed” tight sandstone reservoirs;

[0105] (2) Based on the relevant parameters of the source rock strata obtained, determine the calculation method of the charging power when natural gas is charged into the "pre-formed" tight sandstone reservoir;

[0106] (3) Obtain relevant parameters of the “first-formed” tight sandstone reservoir and determine the calculation formula for the critical pore throat radius of natural gas injected into the reservoir after it is discharged from the source rock;

[0107] (4) Based on the critical pore throat radius calculation formula, a natural gas charging intensity force balance calculation model is established, and finally the lower limit of the effective porosity of the reservoir is determined. Wherein:

[0108] Step (1) specifically involves the following parameters of the source rock strata (mudstone + coal seam): hydrocarbon generation potential index, TOC, thickness of the source rock and density of the source rock. The parameters are obtained through geophysical methods and experimental testing.

[0109] Based on relevant parameters of the source rock (including hydrocarbon generation potential index, TOC, source rock thickness, and source rock density), the hydrocarbon expulsion intensity is determined using a pre-set hydrocarbon expulsion intensity determination model with coal seams and mudstone as common source rocks. The pre-set hydrocarbon expulsion intensity determination model can be expressed as follows:

[0110] E q =q e ×TOC×(h m +h c )×ρ s

[0111] Among them, E q Hydrocarbon emission intensity, in meters (m). 3 / km 2 ;q eHydrocarbon expulsion rate, i.e., the amount of hydrocarbons expelled per gram of organic carbon, expressed in mg / g; TOC, or organic matter abundance, expressed as a percentage; h m h represents the thickness of the mudstone, in meters (m). c ρ represents the coal seam thickness in meters (m). s This refers to the density of the source rock, expressed in kg / m³. 3 .

[0112] Step (2) specifically involves: First, the thermodynamic temperature of the target layer can be determined using a preset thermodynamic temperature determination model. The preset thermodynamic temperature determination model can be expressed as:

[0113]

[0114] Among them, H D The depth of the target layer is expressed in meters (m), and its value can be obtained from well logging curves.

[0115] Then, the driving force for hydrocarbon generation from the source rock is determined using a pre-set charging dynamics determination model. This pre-set charging dynamics determination model can be expressed as:

[0116]

[0117] Among them, P e The gas charging power is expressed in MPa; Z is the gas compressibility coefficient; E q Hydrocarbon emission intensity, in meters (m). 3 / km 2 ;ρ gl This refers to the density of a gas, expressed in kg / m³. 3 R is the molar gas constant; T is the thermodynamic temperature, K; φ is the source rock porosity, %; M is the molar mass, in kg / mol.

[0118] Finally, the obtained E q Substituting T into the charging dynamics calculation model, the charging dynamics of natural gas into the "pre-formed" tight sandstone reservoir are obtained. All other constants in the formula are constants, including: Z = 717, R = 8.31433, M = 0.016. Furthermore, the value of φ can be obtained experimentally; ρ gl It is related to temperature and pressure and can be found in the NIST database.

[0119] Step (3) specifically involves: first determining the parameters related to the natural gas injection resistance (static water column pressure + capillary force), including ρ. w (density of water), g (acceleration due to gravity), H (height of water column), σ (interfacial tension between air and water), and θ (wetting angle).

[0120] Where, ρ wThe density of water and gravitational acceleration were obtained by consulting the NIST database, and the height of the water column was obtained from the altitude of the target layer. All other constants were constants, including: σ = 0.75 N / m, N = 145°.

[0121] Next, the critical pore throat radius r when natural gas enters the reservoir is determined.

[0122] Optionally, based on the principle of force balance, namely the principle that natural gas enters the "first-formed" tight sandstone reservoir by breaking through the maximum pore throat radius of the reservoir, the critical pore throat radius relationship related to the charging power can be derived.

[0123] In some embodiments, the preset throat radius determination model includes:

[0124]

[0125] Where r is the critical throat radius, Z is the gas compressibility coefficient, and q e R is the hydrocarbon expulsion rate, T is the molar gas constant, M is the thermodynamic temperature, and h is a constant. m h represents the thickness of the mudstone. c ρ is the thickness of the coal seam. w ρ is the density of water, g is the acceleration due to gravity, H is the height of the water column, φ is the porosity of the source rock, σ is the gas-water interfacial tension, and θ is the wetting angle.

[0126] Step (4) specifically involves determining the correlation between the effective porosity and the critical pore throat radius of the "pre-formed" tight sandstone reservoir based on the mercury intrusion porosimetry results. The specific calculation formula is as follows:

[0127] φ=3.2068e 1.9163 r

[0128] in, , represents the lower limit of effective porosity of "pre-formed" tight sandstone reservoirs, in %; r is the critical pore throat radius corresponding to the effective porosity of the reservoir, in μm.

[0129] To improve the drilling success rate of deep "pre-formed" tight sandstone reservoirs, avoid ineffective reservoir layers, and save production costs, a reasonable and feasible method for determining the lower limit of effective porosity in "pre-formed" tight sandstone reservoirs is needed. The method for determining the lower limit of effective porosity in tight sandstone reservoirs disclosed in this embodiment can be used to determine the lower limit of effective porosity in deep "pre-formed" tight sandstone reservoirs.

[0130] Example 4:

[0131] Based on the above embodiments, this embodiment provides a specific application example.

[0132] In this embodiment, the calculation of the effective porosity lower limit of a "pre-formed" tight sandstone reservoir in a certain area of ​​the Ordos Basin is used as an example for illustration.

[0133] refer to Figure 2 The method for determining the lower limit of effective porosity in tight sandstone reservoirs provided in this embodiment includes the following steps:

[0134] Step 1: Obtain relevant parameters of the source rock strata (mudstone + coal seam) for injecting natural gas into the "pre-formed" tight sandstone reservoir;

[0135] 1) Determine the relevant parameters of the source rock strata (mudstone + coal seam), including obtaining the hydrocarbon generation potential index (i.e., hydrocarbon expulsion rate q) through geophysical methods and experimental testing. e ), TOC and the density parameters of source rocks, Figure 3 This is a plan view of the source rocks in the Ordos Basin, showing the total thickness of mudstone and coal seams.

[0136] 2) The hydrocarbon expulsion intensity of the Benxi Formation source rocks in the Ordos Basin was determined using a pre-set hydrocarbon expulsion intensity determination model. The pre-set hydrocarbon expulsion intensity determination model can be expressed as:

[0137] E q =q e ×TOC×(h m +h c )×ρ s

[0138] Among them, E q Hydrocarbon emission intensity, in meters (m). 3 / km 2 ;q e Hydrocarbon expulsion rate, i.e., the amount of hydrocarbons expelled per gram of organic carbon, mg / g; TOC, organic matter abundance, %; h m h represents the thickness of the mudstone, in meters (m). c ρ represents the coal seam thickness, in meters (thickness can be obtained from relevant logging data). s This refers to the density of the source rock, expressed in kg / m³. 3 .

[0139] refer to Figure 4 , Figure 4 This is a hydrocarbon expulsion intensity map of the Benxi Formation source rocks in the Ordos Basin. The map shows that the hydrocarbon expulsion intensity of the Benxi Formation ranges from 2 to 18 × 10⁻⁶. 8 m 3 / km 2 Between these, the hydrocarbon expulsion center is located in the southern part of the basin.

[0140] Step 2: Based on the relevant parameters of the source rock strata obtained, determine the calculation method for the charging power when natural gas is injected into the "pre-formed" tight sandstone reservoir;

[0141] 1) First, the thermodynamic temperature of the target layer is determined using a preset thermodynamic temperature determination model, which can be expressed as:

[0142]

[0143] Among them, H D The depth of the target layer is expressed in meters (m). The depth of the Benxi Formation can be determined from well logging curves to be between 2000 and 4000 meters.

[0144] 2) Then, the driving force for hydrocarbon generation from the source rock is determined by a preset charging power determination model, which can be expressed as:

[0145]

[0146] 3) Finally, the obtained E q By substituting T into the preset charging power determination model, the charging power of natural gas when charging into the "pre-formed" tight sandstone reservoir can be obtained.

[0147] Among them, P e The gas charging power is expressed in MPa; Z is the gas compressibility coefficient; E q Hydrocarbon emission intensity, in meters (m). 3 / km 2 ;ρ gl This refers to the gas density of natural gas, expressed in kg / m³. 3 R is the molar gas constant; T is the thermodynamic temperature, K; φ is the source rock porosity, %. φ can be obtained experimentally, ρ gl These parameters are related to temperature and pressure and can be obtained from the NIST database. Additionally, the default fixed parameters in the formula include: Z = 717, R = 8.31433, and M = 0.016.

[0148] Step 3: Obtain relevant parameters of the "pre-formed" tight sandstone reservoir and determine the calculation formula for the critical pore throat radius of natural gas injected into the reservoir after it is discharged from the source rock;

[0149] 1) First, determine the parameters related to the natural gas injection resistance (static water column pressure + capillary force), including ρ. w (density of water), g (acceleration due to gravity), H (height of water column), σ (interfacial tension between air and water), and θ (wetting angle).

[0150] Where, ρ w The density of water and gravitational acceleration were obtained by consulting the NIST database, and H was obtained from the altitude of the target layer. All other constants were constants, σ ​​= 0.75 N / m, θ = 145°.

[0151] 2) Next, determine the critical pore throat radius r when natural gas enters the reservoir.

[0152] Table 1 shows the critical pore throat radius under different charging intensities, hydrostatic pressures, and capillary forces. Table 2 shows the lower porosity limits corresponding to different pore throat radii in the Ordos Basin. The simulation results show that the greater the hydrocarbon expulsion intensity, the higher the corresponding charging power, and the lower the required lower porosity limit.

[0153] Table 1

[0154]

[0155] Table 2

[0156]

[0157] Step 4: Based on the critical pore throat radius calculation formula, establish a natural gas charging intensity force balance calculation model, and finally determine the lower limit of the effective porosity of the reservoir.

[0158] 1) The correlation between effective porosity and critical pore throat radius in "pre-formed" tight sandstone reservoirs was determined using mercury intrusion porosimetry: The relationship between effective porosity and critical pore throat radius can be expressed as:

[0159] φ=3.2068e 1.9163 r

[0160] Where φ is the lower limit of effective porosity of the "pre-formed" tight sandstone reservoir, in %; r is the critical pore throat radius corresponding to the effective porosity of the reservoir, in μm.

[0161] Figure 5 This is a graph showing the relationship between the throat radius and porosity in a mercury porosimetry experiment. The data points in the graph show a positive correlation between the throat radius and porosity; the larger the throat radius, the higher the porosity.

[0162] To improve the drilling success rate of deep "pre-formed" tight sandstone reservoirs, avoid ineffective reservoir layers, and save production costs, a reasonable and feasible method for determining the lower limit of effective porosity in "pre-formed" tight sandstone reservoirs is needed. The method for determining the lower limit of effective porosity in tight sandstone reservoirs disclosed in this embodiment can be used to determine the lower limit of effective porosity in deep "pre-formed" tight sandstone reservoirs.

[0163] Example 5:

[0164] Another embodiment of this application relates to a system for determining the lower limit of effective porosity in tight sandstone reservoirs.

[0165] The following is a detailed description of the implementation details of the tight sandstone reservoir effective porosity lower limit determination system in this embodiment. The following content is only for ease of understanding and is not necessary for implementing this solution. The tight sandstone reservoir effective porosity lower limit determination system provided in this embodiment includes:

[0166] The hydrocarbon expulsion intensity determination module is used to determine the hydrocarbon expulsion intensity of the source rock based on the values ​​of various preset parameters of the source rock through a preset hydrocarbon expulsion intensity determination model; wherein the source rock contains coal seams and mudstone, and the preset parameters include: porosity, hydrocarbon expulsion rate, organic matter abundance, mudstone thickness, coal seam thickness, and density of the source rock.

[0167] The gas charging power determination module is used to determine the gas charging power based on the values ​​of each preset parameter and the hydrocarbon expulsion intensity through a preset charging power determination model; wherein, the charging power is the gas charging power when natural gas is used to charge the reservoir where the source rock is located.

[0168] The critical pore throat radius determination module is used to determine the values ​​of various charging resistance parameters of natural gas during the charging operation, and to determine the critical pore throat radius when natural gas is discharged from the reservoir where the source rock is located into the tight sandstone reservoir based on the values ​​of the charging resistance parameters and the preset parameters through the preset pore throat radius determination model.

[0169] The effective porosity lower limit determination module is used to determine the relationship between effective porosity and critical pore throat radius based on mercury injection test data of the source rock, and to determine the effective porosity lower limit of the reservoir where the source rock is located based on the critical pore throat radius and the relationship between the effective porosity and the critical pore throat radius.

[0170] In the hydrocarbon expulsion intensity determination module: based on the values ​​of various preset parameters of the source rock, the hydrocarbon expulsion intensity of the source rock is determined by a preset hydrocarbon expulsion intensity determination model; wherein, the source rock contains coal seams and mudstone, and the preset parameters include: porosity, hydrocarbon expulsion rate, organic matter abundance, mudstone thickness, coal seam thickness, and density of the source rock.

[0171] In some embodiments, the values ​​of each preset parameter are obtained through geophysical methods and experimental testing.

[0172] In some embodiments, the preset hydrocarbon expulsion intensity determination model includes:

[0173] E q =q e ×TOC×(h m +h c )×ρ s

[0174] Among them, E qq represents hydrocarbon expulsion intensity. e Hydrocarbon emission rate, TOC organic matter abundance, h m h represents the thickness of the mudstone. c ρ is the thickness of the coal seam. s This represents the density of the source rock.

[0175] In this hydrocarbon expulsion intensity determination module, relevant preset parameters of the source rock strata (mudstone + coal seam) for injecting natural gas into deep "pre-formed" tight sandstone reservoirs are obtained, and then the hydrocarbon expulsion intensity of the source rock is determined based on each preset parameter.

[0176] In the gas charging power determination module: based on the values ​​of each preset parameter and the hydrocarbon expulsion intensity, the gas charging power is determined by a preset charging power determination model; wherein, the charging power is the gas charging power when natural gas is discharged from the reservoir where the source rock is located and charged into the tight sandstone reservoir, and the tight sandstone reservoir is in contact with the reservoir where the source rock is located.

[0177] In some embodiments, determining the gas charging power using a preset charging power determination model based on the values ​​of each preset parameter and the hydrocarbon expulsion intensity includes:

[0178] The burial depth of the reservoir where the source rock is located is obtained from the well logging curve of the source rock;

[0179] The thermodynamic temperature is determined by using a preset thermodynamic temperature determination model based on the burial depth of the source rock in the reservoir.

[0180] Based on the values ​​of the preset parameters, the hydrocarbon expulsion intensity, the burial depth of the reservoir where the source rock is located, and the thermodynamic temperature, the gas injection power is determined by the preset injection power determination model.

[0181] In some embodiments, the preset injection kinetics determination model includes:

[0182]

[0183] Among them, P e The gas is charged using power, Z is the gas compressibility coefficient, and E is the gas compressibility coefficient. q For hydrocarbon expulsion intensity, ρ gl Let R be the gas density of natural gas, R be the molar gas constant, T be the thermodynamic temperature, and h be the temperature. m h represents the thickness of the mudstone. c Where φ is the coal seam thickness, φ is the porosity of the source rock, and M is a constant.

[0184] In some embodiments, the preset thermodynamic temperature determination model includes:

[0185]

[0186] Where T is the thermodynamic temperature, H D K1, K2, K3, and K4 are constants, representing the burial depth of the reservoir where the source rock is located.

[0187] Preferably, K1, K2, K3 and K4 are 14, 2.8, 100 and 273.15 respectively.

[0188] In this gas charging power determination module, the charging power for natural gas to be charged into the "pre-formed" tight sandstone reservoir is determined based on the relevant preset parameters of the source rock strata and the hydrocarbon expulsion intensity determined in the aforementioned steps.

[0189] In the critical pore throat radius determination module: the values ​​of each charging resistance parameter of natural gas during the charging operation are determined, and based on the values ​​of each charging resistance parameter and the preset parameters, the critical pore throat radius when natural gas is discharged from the reservoir where the source rock is located into the tight sandstone reservoir is determined by the preset pore throat radius determination model.

[0190] In this critical orifice-throat radius determination module, the parameters related to natural gas injection resistance (hydrostatic pressure + capillary force) include: ρ w (density of water), g (acceleration due to gravity), H (height of water column), σ (interfacial tension between air and water), and θ (wetting angle).

[0191] Where, ρ w The density of water and gravitational acceleration were obtained by consulting the NIST database, and the height of the water column H could be obtained from the altitude of the target layer. Other constants were constants, such as σ = 0.75 N / m and N = 145°.

[0192] In the effective porosity lower limit determination module: the relationship between effective porosity and critical pore throat radius is determined based on the mercury injection test data of the tight sandstone reservoir, and the effective porosity lower limit of the tight sandstone reservoir is determined based on the critical pore throat radius through the relationship between the effective porosity and the critical pore throat radius.

[0193] In some embodiments, the relationship between the effective porosity and the critical throat radius includes:

[0194]

[0195] Where, φ 下限 K5 and K6 are both constants, representing the lower limit of effective porosity, and r is the critical pore throat radius.

[0196] Preferably, the values ​​of K5 and K6 are 3.2068 and 1.9163, respectively.

[0197] In this module for determining the lower limit of effective porosity, the relationship between effective porosity and critical pore throat radius can be determined by fitting the mercury intrusion porosimetry data of tight sandstone reservoirs.

[0198] It is worth mentioning that all modules involved in this embodiment are logical modules. In practical applications, a logical unit can be a physical unit, a part of a physical unit, or a combination of multiple physical units. Furthermore, to highlight the innovative aspects of this application, this embodiment does not introduce units that are not closely related to solving the technical problems proposed in this application; however, this does not mean that other units are absent in this embodiment.

[0199] Example 6:

[0200] Another embodiment of this application relates to an electronic device, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the method for determining the lower limit of effective porosity of tight sandstone reservoirs in the above embodiments, specifically:

[0201] Step 110: Determine the hydrocarbon expulsion intensity of the source rock by using a preset hydrocarbon expulsion intensity determination model based on the values ​​of each preset parameter of the source rock; wherein the source rock contains coal seams and mudstone, and the preset parameters include: porosity, hydrocarbon expulsion rate, organic matter abundance, mudstone thickness, coal seam thickness, and density of the source rock.

[0202] Step 120: Determine the gas charging power using a preset charging power determination model based on the values ​​of each preset parameter and the hydrocarbon expulsion intensity; wherein, the charging power is the gas charging power when natural gas is discharged from the reservoir where the source rock is located and injected into the tight sandstone reservoir, and the tight sandstone reservoir is in contact with the reservoir where the source rock is located.

[0203] Step 130: Determine the values ​​of each charging resistance parameter of natural gas during the charging operation, and determine the critical pore throat radius when natural gas is discharged from the reservoir where the source rock is located into the tight sandstone reservoir based on the values ​​of each charging resistance parameter and the preset parameters, using the preset pore throat radius determination model.

[0204] Step 140: Determine the relationship between effective porosity and critical pore throat radius based on the mercury injection test data of the tight sandstone reservoir, and determine the lower limit of effective porosity of the tight sandstone reservoir based on the critical pore throat radius and the relationship between effective porosity and critical pore throat radius.

[0205] In step 110: Based on the values ​​of various preset parameters of the source rock, the hydrocarbon expulsion intensity of the source rock is determined by a preset hydrocarbon expulsion intensity determination model; wherein the source rock contains coal seams and mudstone, and the preset parameters include: porosity, hydrocarbon expulsion rate, organic matter abundance, mudstone thickness, coal seam thickness, and density of the source rock.

[0206] In some embodiments, the values ​​of each preset parameter are obtained through geophysical methods and experimental testing.

[0207] In some embodiments, the preset hydrocarbon expulsion intensity determination model includes:

[0208] E q =q e ×TOC×(h m +h c )×ρ s

[0209] Among them, E q q represents hydrocarbon expulsion intensity. e Hydrocarbon emission rate, TOC organic matter abundance, h m h represents the thickness of the mudstone. c ρ is the thickness of the coal seam. s This represents the density of the source rock.

[0210] In this step, relevant preset parameters of the source rock strata (mudstone + coal seam) for injecting natural gas into deep "pre-formed" tight sandstone reservoirs are obtained, and then the hydrocarbon expulsion intensity of the source rock is determined based on each preset parameter.

[0211] In step 120: Based on the values ​​of each preset parameter and the hydrocarbon expulsion intensity, the gas charging power is determined by a preset charging power determination model; wherein, the charging power is the gas charging power when natural gas is discharged from the reservoir where the source rock is located and charged into the tight sandstone reservoir, and the tight sandstone reservoir is in contact with the reservoir where the source rock is located.

[0212] In some embodiments, determining the gas charging power using a preset charging power determination model based on the values ​​of each preset parameter and the hydrocarbon expulsion intensity includes:

[0213] The burial depth of the reservoir where the source rock is located is obtained from the well logging curve of the source rock;

[0214] The thermodynamic temperature is determined by using a preset thermodynamic temperature determination model based on the burial depth of the source rock in the reservoir.

[0215] Based on the values ​​of the preset parameters, the hydrocarbon expulsion intensity, the burial depth of the reservoir where the source rock is located, and the thermodynamic temperature, the gas injection power is determined by the preset injection power determination model.

[0216] In some embodiments, the preset injection kinetics determination model includes:

[0217]

[0218] Among them, P e The gas is charged using power, Z is the gas compressibility coefficient, and E is the gas compressibility coefficient. q For hydrocarbon expulsion intensity, ρ gl Let R be the gas density of natural gas, R be the molar gas constant, T be the thermodynamic temperature, and h be the temperature. m h represents the thickness of the mudstone. c Where φ is the coal seam thickness, φ is the porosity of the source rock, and M is a constant.

[0219] In some embodiments, the preset thermodynamic temperature determination model includes:

[0220]

[0221] Where T is the thermodynamic temperature, H D K1, K2, K3, and K4 are constants, representing the burial depth of the reservoir where the source rock is located.

[0222] Preferably, the values ​​of K1, K2, K3 and K4 are 14, 2.8, 100 and 273.15, respectively.

[0223] In this step, the charging power for natural gas to be injected into the "pre-formed" tight sandstone reservoir is determined based on the relevant preset parameters of the source rock strata and the hydrocarbon expulsion intensity determined in the previous steps.

[0224] In step 130: the values ​​of each charging resistance parameter of natural gas during the charging operation are determined, and the critical pore throat radius when natural gas is discharged from the reservoir where the source rock is located into the tight sandstone reservoir is determined by the preset pore throat radius determination model based on the values ​​of each charging resistance parameter and the preset parameters.

[0225] In this step, the parameters related to the natural gas charging resistance (static water column pressure + capillary force) include: ρ w (density of water), g (acceleration due to gravity), H (height of water column), σ (interfacial tension between air and water), and θ (wetting angle).

[0226] Where, ρ w The density of water and gravitational acceleration were obtained by consulting the NIST database, and the height of the water column H could be obtained from the altitude of the target layer. Other constants were constants, such as σ = 0.75 N / m and N = 145°.

[0227] In step 140: the relationship between effective porosity and critical pore throat radius is determined based on the mercury injection test data of the tight sandstone reservoir, and the lower limit of effective porosity of the tight sandstone reservoir is determined based on the critical pore throat radius through the relationship between effective porosity and critical pore throat radius.

[0228] In some embodiments, the relationship between the effective porosity and the critical throat radius includes:

[0229]

[0230] Where, φ 下限 K5 and K6 are both constants, representing the lower limit of effective porosity, and r is the critical pore throat radius.

[0231] Preferably, the values ​​of K5 and K6 are 3.2068 and 1.9163, respectively.

[0232] In this step, the relationship between effective porosity and critical pore throat radius can be determined by fitting the mercury intrusion porosimetry data of tight sandstone reservoirs.

[0233] To improve the drilling success rate of deep "pre-formed" tight sandstone reservoirs, avoid ineffective reservoir layers, and save production costs, a reasonable and feasible method for determining the lower limit of effective porosity in "pre-formed" tight sandstone reservoirs is needed. The method for determining the lower limit of effective porosity in tight sandstone reservoirs disclosed in this embodiment can be used to determine the lower limit of effective porosity in deep "pre-formed" tight sandstone reservoirs.

[0234] The memory and processor are connected via a bus, which can include any number of interconnecting buses and bridges, connecting various circuits of one or more processors and memories. The bus can also connect various other circuits, such as peripheral devices, voltage regulators, and power management circuits, which are well known in the art and will not be described further herein. The bus interface provides an interface between the bus and the transceiver. The transceiver can be a single element or multiple elements, such as multiple receivers and transmitters, providing a unit for communicating with various other devices over a transmission medium. Data processed by the processor is transmitted over the wireless medium via an antenna, which further receives data and transmits it to the processor.

[0235] The processor manages the bus and general processing, and also provides various functions, including timing, peripheral interfaces, voltage regulation, power management, and other control functions. Memory is used to store data used by the processor during operation.

[0236] Example 7:

[0237] Another embodiment of this application relates to a computer-readable storage medium storing a computer program. When executed by a processor, the computer program implements the method for determining the lower limit of effective porosity in tight sandstone reservoirs described in the above embodiments, specifically:

[0238] Step 110: Determine the hydrocarbon expulsion intensity of the source rock by using a preset hydrocarbon expulsion intensity determination model based on the values ​​of each preset parameter of the source rock; wherein the source rock contains coal seams and mudstone, and the preset parameters include: porosity, hydrocarbon expulsion rate, organic matter abundance, mudstone thickness, coal seam thickness, and density of the source rock.

[0239] Step 120: Determine the gas charging power using a preset charging power determination model based on the values ​​of each preset parameter and the hydrocarbon expulsion intensity; wherein, the charging power is the gas charging power when natural gas is discharged from the reservoir where the source rock is located and injected into the tight sandstone reservoir, and the tight sandstone reservoir is in contact with the reservoir where the source rock is located.

[0240] Step 130: Determine the values ​​of each charging resistance parameter of natural gas during the charging operation, and determine the critical pore throat radius when natural gas is discharged from the reservoir where the source rock is located into the tight sandstone reservoir based on the values ​​of each charging resistance parameter and the preset parameters, using the preset pore throat radius determination model.

[0241] Step 140: Determine the relationship between effective porosity and critical pore throat radius based on the mercury injection test data of the tight sandstone reservoir, and determine the lower limit of effective porosity of the tight sandstone reservoir based on the critical pore throat radius and the relationship between effective porosity and critical pore throat radius.

[0242] In step 110: Based on the values ​​of various preset parameters of the source rock, the hydrocarbon expulsion intensity of the source rock is determined by a preset hydrocarbon expulsion intensity determination model; wherein the source rock contains coal seams and mudstone, and the preset parameters include: porosity, hydrocarbon expulsion rate, organic matter abundance, mudstone thickness, coal seam thickness, and density of the source rock.

[0243] In some embodiments, the values ​​of each preset parameter are obtained through geophysical methods and experimental testing.

[0244] In some embodiments, the preset hydrocarbon expulsion intensity determination model includes:

[0245] E q =q e ×TOC×(h m +h c )×ρ s

[0246] Among them, E q q represents hydrocarbon expulsion intensity. eHydrocarbon emission rate, TOC organic matter abundance, h m h represents the thickness of the mudstone. c ρ is the thickness of the coal seam. s This represents the density of the source rock.

[0247] In this step, relevant preset parameters of the source rock strata (mudstone + coal seam) for injecting natural gas into deep "pre-formed" tight sandstone reservoirs are obtained, and then the hydrocarbon expulsion intensity of the source rock is determined based on each preset parameter.

[0248] In step 120: Based on the values ​​of each preset parameter and the hydrocarbon expulsion intensity, the gas charging power is determined by a preset charging power determination model; wherein, the charging power is the gas charging power when natural gas is discharged from the reservoir where the source rock is located and charged into the tight sandstone reservoir, and the tight sandstone reservoir is in contact with the reservoir where the source rock is located.

[0249] In some embodiments, determining the gas charging power using a preset charging power determination model based on the values ​​of each preset parameter and the hydrocarbon expulsion intensity includes:

[0250] The burial depth of the reservoir where the source rock is located is obtained from the well logging curve of the source rock;

[0251] The thermodynamic temperature is determined by using a preset thermodynamic temperature determination model based on the burial depth of the source rock in the reservoir.

[0252] Based on the values ​​of the preset parameters, the hydrocarbon expulsion intensity, the burial depth of the reservoir where the source rock is located, and the thermodynamic temperature, the gas injection power is determined by the preset injection power determination model.

[0253] In some embodiments, the preset injection kinetics determination model includes:

[0254]

[0255] Among them, P e The gas is charged using power, Z is the gas compressibility coefficient, and E is the gas compressibility coefficient. q For hydrocarbon expulsion intensity, ρ gl Let R be the gas density of natural gas, R be the molar gas constant, T be the thermodynamic temperature, and h be the temperature. m h represents the thickness of the mudstone. c Where φ is the coal seam thickness, φ is the porosity of the source rock, and M is a constant.

[0256] In some embodiments, the preset thermodynamic temperature determination model includes:

[0257]

[0258] Where T is the thermodynamic temperature, HD K1, K2, K3, and K4 are constants, representing the burial depth of the reservoir where the source rock is located.

[0259] Preferably, K1, K2, K3 and K4 are 14, 2.8, 100 and 273.15 respectively.

[0260] In this step, the charging power for natural gas to be injected into the "pre-formed" tight sandstone reservoir is determined based on the relevant preset parameters of the source rock strata and the hydrocarbon expulsion intensity determined in the previous steps.

[0261] In step 130: the values ​​of each charging resistance parameter of natural gas during the charging operation are determined, and the critical pore throat radius when natural gas is discharged from the reservoir where the source rock is located into the tight sandstone reservoir is determined by the preset pore throat radius determination model based on the values ​​of each charging resistance parameter and the preset parameters.

[0262] In this step, the parameters related to the natural gas charging resistance (static water column pressure + capillary force) include: ρ w (density of water), g (acceleration due to gravity), H (height of water column), σ (interfacial tension between air and water), and θ (wetting angle).

[0263] Where, ρ w The density of water and gravitational acceleration were obtained by consulting the NIST database, and the height of the water column H could be obtained from the altitude of the target layer. Other constants were constants, such as σ = 0.75 N / m and N = 145°.

[0264] In step 140: the relationship between effective porosity and critical pore throat radius is determined based on the mercury injection test data of the tight sandstone reservoir, and the lower limit of effective porosity of the tight sandstone reservoir is determined based on the critical pore throat radius through the relationship between effective porosity and critical pore throat radius.

[0265] In some embodiments, the relationship between the effective porosity and the critical throat radius includes:

[0266]

[0267] Where, φ 下限 K5 and K6 are both constants, representing the lower limit of effective porosity, and r is the critical pore throat radius.

[0268] Preferably, the values ​​of K5 and K6 are 3.2068 and 1.9163, respectively.

[0269] In this step, the relationship between effective porosity and critical pore throat radius can be determined by fitting the mercury intrusion porosimetry data of tight sandstone reservoirs.

[0270] To improve the drilling success rate of deep "pre-formed" tight sandstone reservoirs, avoid ineffective reservoir layers, and save production costs, a reasonable and feasible method for determining the lower limit of effective porosity in "pre-formed" tight sandstone reservoirs is needed. The method for determining the lower limit of effective porosity in tight sandstone reservoirs disclosed in this embodiment can be used to determine the lower limit of effective porosity in deep "pre-formed" tight sandstone reservoirs.

[0271] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. This program is stored in a storage medium and includes several instructions to cause a device (which may be a microcontroller, chip, etc.) or processor to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0272] In some embodiments of this application, a computer program product is also provided, including a computer program that, when executed by a processor, implements the steps of the methods described in the above embodiments.

[0273] Those skilled in the art will understand that the above embodiments are specific embodiments for implementing this application, and in practical applications, various changes can be made to them in form and detail without departing from the spirit and scope of this application.

Claims

1. A method for determining the lower limit of effective porosity in tight sandstone reservoirs, characterized in that, include: Based on the values ​​of various preset parameters of the source rock, the hydrocarbon expulsion intensity of the source rock is determined by a preset hydrocarbon expulsion intensity determination model; wherein the source rock contains coal seams and mudstone, and the preset parameters include: porosity, hydrocarbon expulsion rate, organic matter abundance, mudstone thickness, coal seam thickness, and density of the source rock. Based on the values ​​of each preset parameter and the hydrocarbon expulsion intensity, the gas charging power is determined by a preset charging power determination model; wherein, the charging power is the gas charging power when natural gas is discharged from the reservoir where the source rock is located and charged into the tight sandstone reservoir, and the tight sandstone reservoir is in contact with the reservoir where the source rock is located. The values ​​of each charging resistance parameter of natural gas during the charging operation are determined, and the critical pore throat radius when natural gas is discharged from the reservoir where the source rock is located into the tight sandstone reservoir is determined by a preset pore throat radius determination model based on the values ​​of each charging resistance parameter and the preset parameter. The relationship between effective porosity and critical pore throat radius is determined based on the mercury injection test data of the tight sandstone reservoir. Based on the critical pore throat radius, the lower limit of effective porosity of the tight sandstone reservoir is determined through the relationship between effective porosity and critical pore throat radius.

2. The method according to claim 1, characterized in that, The values ​​of each preset parameter are obtained through geophysical methods and experimental testing.

3. The method according to claim 1, characterized in that, The preset hydrocarbon expulsion intensity determination model includes: E q = q e × TOC × (h m + h c ) × p s where E q is the expulsion intensity, q e is the expulsion rate, TOC is the organic matter abundance, h m is the shale thickness, h c is the coal seam thickness, p s is the density of the source rock.

4. The method according to claim 1, characterized in that, The step of determining the gas injection power based on the values ​​of each preset parameter and the hydrocarbon expulsion intensity using a preset injection power determination model includes: The burial depth of the reservoir where the source rock is located is obtained from the well logging curve of the source rock; The thermodynamic temperature is determined by using a preset thermodynamic temperature determination model based on the burial depth of the source rock in the reservoir. Based on the values ​​of the preset parameters, the hydrocarbon expulsion intensity, the burial depth of the reservoir where the source rock is located, and the thermodynamic temperature, the gas injection power is determined by the preset injection power determination model.

5. The method according to claim 4, characterized in that, The preset injection kinetics determination model includes: where P e is the gas filling power, Z is the gas compressibility factor, E q is the hydrocarbon expulsion intensity, p gl is the gas density, R is the molar gas constant, T is the thermodynamic temperature, h m is the shale thickness, h c is the coal seam thickness, and φ is the porosity of the source rock, and M is a constant.

6. The method according to claim 4, characterized in that, The preset thermodynamic temperature determination model includes: where T is the thermodynamic temperature, H D is the burial depth of the source rock, and K1, K2, K3, and K4 are constants.

7. The method according to claim 1, characterized in that, The relationship between effective porosity and critical throat radius includes: where φ 下限 is the lower limit of effective porosity, K5 and K6 are constants, and r is the critical pore throat radius.

8. The method according to claim 1, characterized in that, The preset throat radius determination model includes: where r is the critical pore throat radius, Z is the gas compressibility factor, q e is the hydrocarbon expulsion rate, R is the molar gas constant, T is the thermodynamic temperature, M is a constant, h m is the shale thickness, h c is the coal seam thickness, p w is the water density, g is the gravitational acceleration, H is the water column height, f is the porosity of the source rock, s is the gas-water interfacial tension, q is the wetting angle, and K7 is a constant.

9. A system for determining the lower limit of effective porosity in tight sandstone reservoirs, characterized in that, include: The hydrocarbon expulsion intensity determination module is used to determine the hydrocarbon expulsion intensity of the source rock based on the values ​​of various preset parameters of the source rock through a preset hydrocarbon expulsion intensity determination model; wherein the source rock contains coal seams and mudstone, and the preset parameters include: porosity, hydrocarbon expulsion rate, organic matter abundance, mudstone thickness, coal seam thickness, and density of the source rock. A gas charging power determination module is used to determine the gas charging power based on the values ​​of each preset parameter and the hydrocarbon expulsion intensity through a preset charging power determination model; wherein, the charging power is the gas charging power when natural gas is discharged from the reservoir where the source rock is located and charged into the tight sandstone reservoir, and the tight sandstone reservoir is in contact with the reservoir where the source rock is located. The critical pore throat radius determination module is used to determine the values ​​of various charging resistance parameters of natural gas during the charging operation, and to determine the critical pore throat radius when natural gas is discharged from the reservoir where the source rock is located into the tight sandstone reservoir based on the values ​​of the charging resistance parameters and the preset parameters through the preset pore throat radius determination model. The effective porosity lower limit determination module is used to determine the relationship between effective porosity and critical pore throat radius based on mercury injection test data of the tight sandstone reservoir, and to determine the effective porosity lower limit of the tight sandstone reservoir based on the relationship between the effective porosity and critical pore throat radius.

10. A computer program product, comprising a computer program, characterized in that, When executed by a processor, the computer program implements the steps of the method according to any one of claims 1 to 8.

Images