Method and equipment for determining shale oil reservoir forming initial depth

Abstract

The invention discloses a method and equipment for determining the initial reservoir forming depth of shale oil, and the method comprises the steps: obtaining curves of oil-generating pressurization values of mudstone and carbonate rock along with time through an oil-generating pressurization experiment, then carrying out curve conversion, and calculating the initial reservoir forming depth of shale oil by calculating the capillary resistance of the carbonate rock. According to the method, the reservoir forming initial depth of the shale oil is determined according to the superposition curve and the capillary resistance, and due to the fact that the reservoir forming initial depth is determined through the superposition curve and the capillary resistance, the scheme does not need to emphasize on utilization of geological factors and is not affected by other factors, and the finally obtained result is more accurate. Moreover, the method provided by the invention considers the influence of mudstone and carbonate rock on the reservoir forming initial depth of shale oil at the same time, avoids the problem that only conventional oil and gas of single hydrocarbon source rock lithology are aimed in related technologies, and is suitable for determining the reservoir forming initial depth of unconventional oil and gas such as shale oil and the like.

Description

Technical Field

[0001] This application belongs to the field of unconventional shale oil exploration and development technology, and in particular relates to a method and equipment for determining the initial depth of shale oil accumulation. Background Technology

[0002] As my country's oil and gas exploration and development technologies become increasingly mature, unconventional oil and gas resources such as shale oil and gas are showing enormous development potential and are gradually becoming important strategic resources for my country's future development. Shale oil refers to petroleum stored in organic-rich shale formations. It is a type of unconventional oil and gas, and its accumulation mechanism is very different from that of conventional oil and gas.

[0003] In related technologies, basin simulation, mass balance calculations, and the dehydration threshold of clay minerals are mainly used to determine the initial depth of hydrocarbon accumulation. However, these methods rely heavily on geological factors, and some also use geochemical parameters. These methods are susceptible to various influences, leading to poor accuracy in the final results. Therefore, they have significant limitations in determining the initial depth of shale oil accumulation and poor applicability.

[0004] Therefore, determining the initial depth of shale oil accumulation is a problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The embodiments of this application provide a method and equipment for determining the initial depth of shale oil accumulation, thereby enabling accurate determination of the initial depth of shale oil accumulation.

[0006] Other features and advantages of this application will become apparent from the following detailed description, or may be learned in part from practice of this application.

[0007] According to a first aspect of the embodiments of this application, a method for determining the initial depth of shale oil accumulation is provided, including:

[0008] The curve of oil generation pressure value of mudstone changing with time was calculated using oil generation pressure test, and the second curve was obtained by calculating the curve of oil generation pressure value of carbonate rock changing with time using oil generation pressure test.

[0009] The first curve is converted into a third curve, which is used to characterize the oil generation pressure value of the mudstone as a function of burial depth. The second curve is converted into a fourth curve, which is used to characterize the oil generation pressure value of the carbonate rock as a function of burial depth.

[0010] Calculate the capillary resistance of the carbonate rock;

[0011] The third curve and the fourth curve are superimposed to form a superimposed curve. The initial depth of shale oil accumulation is determined based on the superimposed curve and the capillary resistance.

[0012] In some embodiments of this application, based on the foregoing scheme, the step of converting the first curve into a third curve includes:

[0013] Obtain the burial history data of the well where the shale oil is located, including the relationship between the burial depth of the well and the change over time;

[0014] Based on the relationship between burial depth and time, each time point on the horizontal axis of the first curve is converted into the corresponding burial depth, while the vertical axis remains unchanged. The curve is then redrawn to obtain the third curve.

[0015] In some embodiments of this application, based on the foregoing scheme, the step of converting the second curve into a fourth curve includes:

[0016] Obtain the burial history data of the well where the shale oil is located, including the relationship between the burial depth of the well and the change over time;

[0017] Based on the relationship between burial depth and time, each time point on the horizontal axis of the second curve is converted into the corresponding burial depth, while the vertical axis remains unchanged. The curve is then redrawn to obtain the fourth curve.

[0018] In some embodiments of this application, based on the foregoing scheme, the calculation of the capillary resistance of the carbonate rock includes:

[0019] The pore size distribution of the carbonate reservoir was determined by high-pressure mercury intrusion porosimetry.

[0020] The capillary pressure distribution is calculated based on the aforementioned aperture distribution.

[0021] The capillary resistance of the carbonate rock is determined using the capillary pressure distribution.

[0022] In some embodiments of this application, based on the foregoing scheme, the calculation of capillary pressure distribution based on the pore size distribution includes:

[0023] The orifice size value is converted into a capillary pressure value using the Young-Laplace equation, wherein the Young-Laplace equation includes:

[0024]

[0025] In the formula, P cσ is the capillary pressure encountered by oil and gas entering the reservoir; θ is the oil-water interfacial tension; θ is the wetting angle; r is the pore size of the tight reservoir.

[0026] Keeping the ordinate of the aperture distribution unchanged, the aperture values ​​are converted into capillary pressure values ​​and redrawn to obtain the capillary pressure distribution.

[0027] In some embodiments of this application, based on the foregoing scheme, determining the shale oil reservoir initiation depth according to the superposition curve and the capillary resistance includes:

[0028] In the superimposed curve, the depth of the abscissa corresponding to the point where the pressure increase of mudstone oil generation is greater than that of carbonate oil generation, and the difference between the pressure increase of mudstone oil generation and the pressure increase of carbonate oil generation is greater than the capillary resistance, is taken as the initial depth of hydrocarbon accumulation.

[0029] In some embodiments of this application, based on the foregoing scheme, the method for determining that the difference between the mudstone oil generation pressurization and the carbonate rock oil generation pressurization is greater than the capillary resistance includes:

[0030] The capillary pressure value at which the maximum percentage of capillary pressure distribution is obtained;

[0031] When the difference between the pressure increase of the mudstone oil generation and the pressure increase of the carbonate rock oil generation is greater than the capillary pressure value, it is determined that the difference between the pressure increase of the mudstone oil generation and the pressure increase of the carbonate rock oil generation is greater than the capillary resistance.

[0032] According to a second aspect of the embodiments of this application, an apparatus for determining the initial depth of shale oil reservoir formation is provided, comprising:

[0033] Curve plotting module: Used to calculate the curve of oil generation pressure value of mudstone changing with time using oil generation pressure test, to obtain the first curve; and used to calculate the curve of oil generation pressure value of carbonate rock changing with time using oil generation pressure test, to obtain the second curve;

[0034] The conversion module is used to convert the first curve into a third curve, which is used to characterize the oil generation pressure value of the mudstone as a function of burial depth. It is also used to convert the second curve into a fourth curve, which is used to characterize the oil generation pressure value of the carbonate rock as a function of burial depth.

[0035] A calculation module is used to calculate the capillary resistance of the carbonate rock;

[0036] The depth confirmation module is used to overlay the third curve and the fourth curve to form an overlay curve, and to determine the initial depth of shale oil accumulation based on the overlay curve and the capillary resistance.

[0037] According to a third aspect of the embodiments of this application, a device for determining the initial depth of shale oil reservoir formation is provided, including a processor and a memory, wherein the memory stores computer program instructions that can be executed by the processor, and when the processor executes the computer program instructions, it implements the steps of the method described in any of the first aspects above.

[0038] According to a fourth aspect of the embodiments of this application, a computer-readable storage medium is provided, wherein computer program instructions are stored therein, and when executed by a processor, the computer program instructions cause the processor to perform the steps of the method as described in any of the first aspects above.

[0039] In this application, a first curve is obtained by calculating the oil generation pressure value of mudstone over time using an oil generation pressure test; a second curve is obtained by calculating the oil generation pressure value of carbonate rock over time using the same test; the first curve is converted into a third curve, which characterizes the oil generation pressure value of the mudstone as a function of burial depth; the second curve is converted into a fourth curve, which characterizes the oil generation pressure value of the carbonate rock as a function of burial depth; the capillary resistance of the carbonate rock is calculated; the third curve and the fourth curve are superimposed to form a superimposed curve; and the initial depth of shale oil accumulation is determined based on the superimposed curve and the capillary resistance.

[0040] The method in this application considers the influence of both mudstone and carbonate rocks on the initial depth of shale oil accumulation, avoiding the problem of related technologies that only target conventional oil and gas from a single source rock lithology. This application is applicable to determining the initial depth of unconventional oil and gas accumulation, such as shale oil. This application uses oil generation and pressurization experiments to obtain curves showing the change of oil generation and pressurization values ​​of mudstone and carbonate rocks over time, then performs curve transformation. Furthermore, it calculates the capillary resistance of the carbonate rocks and determines the initial depth of shale oil accumulation based on the superimposed curve and the capillary resistance. Because the initial depth of accumulation in this application is determined through superimposed curves and capillary resistance, the scheme of this application does not rely heavily on geological factors and is not affected by other factors, resulting in more accurate final results.

[0041] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0042] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings:

[0043] Figure 1 A flowchart illustrating a method for determining the initial depth of shale oil accumulation in one embodiment is shown.

[0044] Figure 2 A detailed flowchart of a method for determining the initial depth of shale oil accumulation in one embodiment is shown;

[0045] Figure 3 The graph shows the relationship between the pressure increase of mudstone and carbonate rock source oil production and time in the application examples;

[0046] Figure 4 The graph shows the relationship between the pressure increase of mudstone and carbonate rock source oil production and depth in the application examples;

[0047] Figure 5 A pore size distribution diagram of a carbonate reservoir is shown in an application example;

[0048] Figure 6 The capillary pressure distribution of a carbonate reservoir is shown in an application example.

[0049] Figure 7 A schematic diagram of the superimposed curves in an application embodiment is shown;

[0050] Figure 8 A block diagram of a device for determining the initial depth of shale oil accumulation in an embodiment of this application is shown;

[0051] Figure 9 A schematic diagram of a device for determining the initial depth of shale oil accumulation is shown in one embodiment. Detailed Implementation

[0052] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0053] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this application. However, those skilled in the art will recognize that the technical solutions of this application can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this application.

[0054] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0055] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0056] It should also be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such uses of these terms can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described.

[0057] Determining the initial depth at which oil and gas reservoirs begin to form is of great significance for analyzing the source of oil and gas in a region, identifying effective source rocks, calculating resources, determining oil and gas accumulation models, and guiding oil and gas field exploration and development.

[0058] Oil generated from source rocks is discharged and migrates to conventional reservoirs to become conventional oil reservoirs, while oil that remains in the source rocks becomes shale oil. Shale oil refers to petroleum hosted in organic-rich shale formations. It refers to siltstone, fine sandstone, and carbonate rocks within the source rocks of organic-rich shale formations with a single layer thickness of no more than 5m, and a cumulative thickness accounting for less than 30% of the total thickness of the shale formation. These formations have no natural production capacity or are below the lower limit of industrial petroleum production, requiring special technological measures to achieve industrial petroleum production.

[0059] Shale oil is a type of unconventional oil and gas, with a significantly different accumulation mechanism compared to conventional oil and gas. In China, shale oil is primarily hosted in continental lacustrine shale formations, characterized by complex rock types and mineral compositions. This results in highly distinctive and diverse reservoir "sweet spots" within these lacustrine shale formations, providing favorable locations for both source-captured and in-situ retained hydrocarbons. Based on geological conditions and sedimentary characteristics, these reservoir "sweet spots" in China's continental shale formations can be broadly classified into three types: interbedded, mixed-sedimentary, and shale-type. The lithological types of "sweet spots" within mixed-sedimentary shale oil can vary, primarily consisting of carbonate rocks. This application focuses on this type of carbonate rock as the main lithological type of "sweet spot," with source rocks including both mudstone and carbonate rocks.

[0060] Studies on the initial depth of hydrocarbon accumulation employ various techniques, including basin simulation, mass balance calculations, and the dehydration threshold of clay minerals. These methods tend to rely heavily on geological factors. Other methods utilize geochemical parameters, such as source rock maturity parameters, hydrocarbon generation and expulsion thermal simulation experiments, hydrocarbon generation potential indices, and crude oil maturity parameters. Therefore, commonly used methods include source rock maturity parameters, hydrocarbon generation and expulsion experiments, and hydrocarbon generation potential indices.

[0061] The methods mentioned above are primarily applicable to conventional hydrocarbon accumulation, but not specifically to unconventional hydrocarbons. Since the accumulation mechanisms of conventional and unconventional hydrocarbons differ, the methods used for determination will inevitably differ. Furthermore, these methods target a single lithology such as mudstone or carbonate rock, failing to consider the impact of differences in hydrocarbon generation and expulsion between the two lithologies on hydrocarbon accumulation. Moreover, these methods rely heavily on geochemical experiments or numerical simulations, offering an indirect, geologically and geochemically oriented analysis that is susceptible to various factors, resulting in poor accuracy. Mixed-phase shale oil is a type of unconventional hydrocarbon, with source rocks comprising both mudstone and carbonate rocks. Therefore, the methods described in these techniques have significant limitations in determining the initial depth of accumulation for this type of shale oil and are not well-suited for it.

[0062] To address the aforementioned problems, this application discloses the following technical solution.

[0063] Figure 1 A flowchart illustrating a method for determining the initial depth of shale oil accumulation in one embodiment is shown. Figure 1 As shown, this application provides a method for determining the initial depth of shale oil accumulation, which may include the following steps 101 to 104.

[0064] In step 101, the curve of the oil generation pressure value of mudstone changing with time is calculated using the oil generation pressure test to obtain the first curve, and the curve of the oil generation pressure value of carbonate rock changing with time is calculated using the oil generation pressure test to obtain the second curve.

[0065] Oil generation and pressurization refers to the process by which, during the burial, compaction, and heating of source rocks, when the organic matter reaches a certain maturity, the high-density kerogen begins to decompose, generating low-density oil, causing the volume to expand. Because the rock is relatively dense, the generated oil is not easily discharged and is compressed, leading to an increase in pore fluid pressure; this process is called oil generation and pressurization.

[0066] This application can calculate the curve of oil generation pressure value of mudstone changing with time through oil generation pressure test, to obtain the first curve, and calculate the curve of oil generation pressure value of carbonate rock changing with time, to obtain the second curve.

[0067] In step 102, the first curve is converted into the third curve, which is used to characterize the change of oil generation pressure value of mudstone with burial depth. The second curve is converted into the fourth curve, which is used to characterize the change of oil generation pressure value of carbonate rock with burial depth.

[0068] In one embodiment of this application, the method for converting a first curve into a third curve includes:

[0069] Obtain historical data on the burial depth of shale oil wells, including the relationship between the burial depth and the time of the wells.

[0070] This application aims to determine the initial depth of shale oil reservoir formation. Therefore, it requires obtaining historical burial data for the wells where the shale oil was formed. This historical data includes the relationship between the burial depth of the wells and the changes over time. For example, databases or historical records may contain data on the changes in the burial depth of the wells at different times. For instance, in the historical burial data, the geological time of the well is 10 Ma, where Ma is a unit of geological time, 1 Ma = 10 to the power of 6 or millions of years, corresponding to a burial depth of 3000 meters.

[0071] Based on the relationship between burial depth and time, each time point on the horizontal axis of the first curve is converted into the corresponding burial depth, while the vertical axis remains unchanged. The curve is then redrawn to obtain the third curve.

[0072] Once the relationship between burial depth and time is determined, a one-to-one correspondence between burial depth and time can be established, meaning the corresponding time can be converted into the corresponding burial depth. For example, the time of 10 Ma on the horizontal axis of the first curve can be converted to 300 m, and all units on the horizontal axis can be converted to meters, while the vertical axis remains unchanged. The curve is then redrawn to obtain the third curve.

[0073] In one embodiment of this application, a method for converting a second curve into a fourth curve includes:

[0074] Obtain historical data on the burial depth of the shale oil wells, including the relationship between the burial depth and the time of the shale oil wells.

[0075] Based on the relationship between burial depth and time, each time point on the horizontal axis of the second curve is converted into the corresponding burial depth, while the vertical axis remains unchanged. The curve is then redrawn to obtain the fourth curve.

[0076] The transformation steps for the fourth curve are similar to those for the third curve, and will not be described in detail here.

[0077] After obtaining the third and fourth curves, proceed to step 103.

[0078] In step 103, the capillary resistance of the carbonate rock is calculated.

[0079] Figure 2 A detailed flowchart of a method for determining the initial depth of shale oil accumulation in one embodiment is shown; in some embodiments of this application, such as... Figure 2 As shown, the method for calculating the capillary resistance of carbonate rocks in step 103 of this application includes steps 201-203.

[0080] Step 201: Determine the pore size distribution of carbonate reservoirs using high-pressure mercury intrusion porosimetry.

[0081] High-pressure mercury intrusion spectroscopy (HS-MS) is a method for measuring the size and distribution of pores in materials by injecting molten mercury. Its principle is based on the surface tension and contact angle of mercury. When molten mercury is injected into the pores of a material, the contact angle between the mercury and the pore wall changes, thus altering the surface tension of the mercury. By measuring the pressure change of the mercury within the pore, the pore diameter can be calculated.

[0082] This application utilizes high-pressure mercury intrusion porosimetry to determine the pore size distribution of carbonate reservoirs. The pore size distribution reveals the pore component of different pore sizes within the carbonate reservoir. For example, the pore component with a pore size less than 0.01 μm is determined to be 0.1.

[0083] The pore size distribution of carbonate reservoirs can be accurately measured using the above method. Proceed to step 202.

[0084] Step 202: Calculate the capillary pressure distribution based on the pore size distribution.

[0085] After obtaining the pore size distribution, the capillary pressure distribution can be calculated from the pore size distribution.

[0086] In some embodiments of this application, the method for calculating capillary pressure distribution based on pore size distribution includes:

[0087] The orifice size value is converted into a capillary pressure value using the Young-Laplace equation, which includes:

[0088]

[0089] In the formula, P c σ is the capillary pressure experienced by oil and gas as they enter the reservoir; θ is the oil-water interfacial tension; θ is the wetting angle; and r is the pore size of the tight reservoir.

[0090] In the above formula, P c The unit is MPa, the oil-water interfacial tension is a constant, for example, 9 mN / m, the wetting angle can be a fixed angle, for example, 180°; the unit of tight reservoir pore size is nm.

[0091] For example, in step 201, if the pore component with a pore size less than 0.01 μm is 0.1, then substituting 0.01 μm as the tight reservoir pore size r into the Young-Laplace equation above will yield the capillary pressure P. c It is 0.8 MPa.

[0092] Keeping the ordinate of the aperture distribution unchanged, the aperture values ​​are converted into capillary pressure values ​​and redrawn to obtain the capillary pressure distribution.

[0093] Then, all the orifice values ​​are converted into capillary pressure values ​​using the above formula, and used as the horizontal axis again, while the vertical axis remains unchanged, so that the capillary pressure distribution can be redrawn.

[0094] Step 203: Determine the capillary resistance of carbonate rocks using capillary pressure distribution.

[0095] The capillary resistance of carbonate rocks can be determined by the capillary pressure distribution, where the unit of capillary resistance can also be MPa.

[0096] After determining the capillary resistance, proceed to step 104.

[0097] In step 104, the third and fourth curves are superimposed to form a superimposed curve. The starting depth of shale oil accumulation is determined based on the superimposed curve and capillary resistance.

[0098] In this application, the method for superimposing the third curve and the fourth curve is as follows: since the horizontal and vertical coordinates of the third curve and the fourth curve are the same, the third curve can be kept stationary, and the data points of the horizontal and vertical coordinates of the fourth curve can be copied one by one into the third curve to form a superimposed curve.

[0099] Once the superposition curve is formed, the initial depth of shale oil accumulation can be determined based on the superposition curve and capillary resistance. In some embodiments of this application, the method for determining the initial depth of shale oil accumulation based on the superposition curve and capillary resistance includes:

[0100] In the superimposed curve, the depth of the abscissa corresponding to the point where the pressure increase of mudstone oil generation is greater than that of carbonate oil generation, and the difference between the pressure increase of mudstone oil generation and carbonate oil generation is greater than the capillary resistance, is taken as the initial depth of hydrocarbon accumulation.

[0101] In determining the initial depth of shale oil accumulation, this application requires not only selecting the portion where the pressure boost from mudstone generation is greater than that from carbonate generation, but also considering the abscissa corresponding to the point where the difference between the pressure boost from mudstone and carbonate generation exceeds capillary resistance. The depth of the abscissa when both conditions are met is taken as the initial depth of oil accumulation. Here, the depth of the abscissa can be the minimum depth within the specified range.

[0102] In some embodiments of this application, based on the foregoing scheme, the method for determining that the difference between mudstone oil generation pressurization and carbonate rock oil generation pressurization is greater than capillary resistance includes:

[0103] The capillary pressure value at which the maximum percentage of capillary pressure distribution is obtained;

[0104] When the difference between the pressure boosting of mudstone oil generation and the pressure boosting of carbonate rock oil generation is greater than the capillary pressure value, it is determined that the difference between the pressure boosting of mudstone oil generation and the pressure boosting of carbonate rock oil generation is greater than the capillary resistance.

[0105] Since the capillary pressure distribution includes the proportion and value of each capillary pressure, for example, if more than 40% of the capillary pressure values ​​are less than 0.0008 MPa, then 40% is the maximum value of the capillary pressure proportion distribution. Therefore, the corresponding 0.0008 MPa is the capillary pressure value at this time. When the difference between the pressure boosting of mudstone oil generation and the pressure boosting of carbonate rock oil generation is greater than the capillary pressure value of 0.0008 MPa, it is determined that the difference between the pressure boosting of mudstone oil generation and the pressure boosting of carbonate rock oil generation is greater than the capillary resistance.

[0106] In summary, the proposed method in this application utilizes the relationship between the pressure difference generated during hydrocarbon generation in mudstone and carbonate source rocks in mixed-sedimentary shale oil and the capillary resistance of carbonate reservoirs to determine the initial depth of shale oil accumulation. It fully considers both mudstone and carbonate source rocks, thus making it applicable to unconventional oil and gas reservoirs, avoiding the problem of related technologies that only target conventional oil and gas reservoirs with a single source rock lithology. This application uses oil generation pressure tests to obtain curves showing the change in oil generation pressure values ​​of mudstone and carbonate rocks over time, then performs curve transformation. It also calculates the capillary resistance of carbonate rocks and determines the initial depth of shale oil accumulation based on the superimposed curve and the capillary resistance. Since the initial depth of accumulation in this application is determined through superimposed curves and capillary resistance, the proposed method does not rely heavily on geological factors and is unaffected by other factors, resulting in more accurate results.

[0107] The main research method of this application is to use the physical simulation experimental data of hydrocarbon generation and pressurization of source rocks to study from the perspective of dynamics and take into account the capillary force of carbonate rocks. This invention effectively solves the problem that previous methods mainly target conventional oil and gas in single source rock lithology, and realizes a method to accurately determine the initiation depth of unconventional oil reservoirs in two types of source rocks. It has stronger pertinence, accuracy and advancement than related technologies.

[0108] The method in this application also takes into account the characteristics of shale oil. Unlike conventional oil reservoirs, shale oil reservoirs typically have small pore throat radii in carbonate reservoirs. Therefore, when the source rock and tight reservoir are in direct contact, oil cannot form an effective oil column height, and buoyancy does not play a dominant role in shale oil accumulation. Thus, as long as the pressure difference from oil generation exceeds the capillary resistance, oil can enter the carbonate rock from the mudstone, becoming another source of shale oil besides the carbonate rock itself.

[0109] Therefore, this application primarily considers capillary resistance, further improving the accuracy of determining the initial depth of shale oil accumulation. It achieves a method for accurately determining the initial depth of unconventional oil reservoirs in two types of source rocks, demonstrating greater specificity, accuracy, and advancement compared to related technologies.

[0110] Moreover, this application has great practical significance. Since mixed-sediment shale oil is widely distributed in Liaohe Oilfield and even throughout the country, its implementation will be of great significance for the identification of effective source rocks, resource calculation and determination of favorable exploration zones for this type of shale oil, and its application prospects are very broad.

[0111] It should be noted that the method described in this application has a wide applicability, including shale oil with only one lithology. In this case, simply setting the carbonate rock data to zero is sufficient. When the carbonate rock hydrocarbon generation and pressurization data is zero, only the hydrocarbon generation and pressurization of mudstone and the capillary resistance of mudstone are compared. Therefore, our method is more advanced, applicable to both types of lithology, and also to one type, and is backward compatible.

[0112] The above describes one embodiment of this application. The following describes an application embodiment of this application.

[0113] This application uses a specific region as an example to determine the initial depth of shale oil accumulation. Specifically,

[0114] Taking the S area of ​​the L-depression as an example, this study determines the initial depth of carbonate shale oil accumulation. The tectonic activity during the Sha-4 period was relatively weak, resulting in a stable and gentle tectonic setting. The paleoclimate was a relatively hot and dry subtropical climate, situated in a closed lacustrine environment. The main source rocks were mudstone and shale, along with a set of lacustrine carbonate sediments. The area possessed large-area heterogeneous reservoirs in close contact with the source rocks, providing the basic geological conditions for shale oil formation.

[0115] To achieve the above objectives, the present invention employs the following technical solution, including the following steps:

[0116] Step 1: Calculate the relationship between the pressure increase of mudstone and carbonate rock oil generation and time.

[0117] An oil generation and pressurization calculation model was selected and parameters were collected. Oil generation and pressurization experiments were used to calculate the oil generation and pressurization values ​​at different evolution stages of mudstone and carbonate rocks in the S area of ​​the L-depression, i.e., the curves of oil generation and pressurization changing over time. Figure 3 As shown, Figure 3 The diagram illustrates the relationship between pressure build-up and time in mudstone and carbonate rock oil generation in an application example. The left graph shows the pressure build-up in mudstone oil generation over time, and the right graph shows the pressure build-up in carbonate rock oil generation over time. Figure 3 As shown in the left figure, the hydrocarbon generation pressure of mudstone is close to 0 at a geological time of 40 Ma, while that of carbonate rocks is only close to 0 at a geological time of 45 Ma. Figure 3 The relationship between the oil generation pressure of mudstone and carbonate rock and the change over time can be clearly obtained.

[0118] Step 2: Relationship between oil generation and pressurization in mudstone and carbonate rocks and depth

[0119] Based on the above-mentioned relationship between the oil generation and pressure increase of the two lithologies over time, and combined with the burial history of the well containing the sample (corresponding to the shale oil well), a graph showing the variation of the oil generation and pressure increase values ​​of the two lithologies with depth can be obtained. For example... Figure 4 As shown, Figure 4 The diagram illustrates the relationship between oil generation and pressurization in mudstone and carbonate rocks and depth in an application example. This application can be based on the well's burial history; for example, by finding that geological time 10 Ma corresponds to a burial depth of 3200 m and geological time 20 Ma corresponds to a burial depth of 2700 m, the corresponding depth can be determined. Figure 3 Transform the diagram in the middle into Figure 4 , among which, Figure 4 The left-hand graph represents the relationship between pressure enhancement and depth in mudstone oil generation, while the right-hand graph represents the relationship between pressure enhancement and depth in carbonate rock oil generation. According to... Figure 4 It can be seen that when mudstone is buried at a depth of 1000 meters, the corresponding hydrocarbon generation pressure is close to 0, while when carbonate rock is buried at a depth of 0 meters, the corresponding hydrocarbon generation pressure is close to 0.

[0120] Step 3: Determine the initial depth of shale oil accumulation.

[0121] First, calculate the capillary resistance of carbonate rocks.

[0122] The pore size distribution of carbonate reservoirs can be obtained by high-pressure mercury intrusion. Figure 5 A pore size distribution map of a carbonate reservoir in an application example is shown, such as... Figure 5 As shown, a pore size distribution map of a carbonate reservoir was obtained using high-pressure mercury intrusion porosimetry. The horizontal axis represents the pore size distribution, and the vertical axis represents the pore size components, which can be the proportion of each pore size. Figure 5 It can be seen that in the current carbonate rocks, the pore size component with a pore size less than 0.01 μm is 0.1, the pore size component with a pore size greater than 10 μm is 0.41, and the remaining pore size with a pore size between 0.01 μm and 10 μm accounts for 1 - 0.41 - 0.1 = 0.49.

[0123] After obtaining the orifice size distribution, the capillary pressure distribution map is then calculated. The capillary pressure calculation method is based on the Young-Laplace equation:

[0124]

[0125] In the formula, P c σ is the capillary pressure encountered by oil and gas entering the reservoir, in MPa; σ is the oil-water interfacial tension, in 9 mN / m; θ is the wetting angle, in 180°; and r is the pore size of the tight reservoir, in nm.

[0126] The capillary pressure distribution is calculated by inputting the orifice size distribution into the formula above. Figure 6 The capillary pressure distribution diagram of a carbonate reservoir in an application example is shown, such as... Figure 6 As shown, through and Figure 5The comparison shows that the portion with a pore size less than 0.01 μm is converted into a capillary pressure greater than 0.8 MPa; the portion with a pore size greater than 10 μm is converted into a capillary pressure less than 0.0008 MPa. Figure 6 In the diagram, the vertical axis represents the distribution of breakthrough pressure, which also corresponds to a sum of 1.

[0127] pass Figure 6 This allows you to determine the capillary resistance of the carbonate rock. Proceed to the next steps.

[0128] According to the overlay diagram of the oil generation and pressurization curves of mudstone and carbonate rocks as a function of depth, among which, such as Figure 7 As shown, Figure 7 A schematic diagram of the superimposed curves in an application embodiment is shown. (By...) Figure 7 The superimposed curves can be observed, allowing us to understand the changes in oil generation and pressurization with depth in mudstone and carbonate rocks. (Reference) Figure 4 As can be seen, the dotted line corresponds to the curve of mudstone oil generation pressure variation with depth, which is the curve where hydrocarbon generation pressure is zero at a burial depth of about 1000 meters. The other curve is the curve of carbonate rock oil generation pressure variation with depth, which means that the hydrocarbon generation pressure of carbonate rock only approaches zero at a burial depth of 0 meters.

[0129] pass Figure 7 It can be seen that when the burial depth exceeds 3000m, a positive oil generation pressure value is generated between mudstone and carbonate rock (i.e., mudstone oil generation pressure > carbonate rock oil generation pressure), and the pressure difference is much greater than the capillary resistance. Therefore, 3000m is the starting depth of mudstone accumulation in the Leijia area.

[0130] The pressure difference here is much greater than the capillary resistance, which can be used as a reference. Figure 6 , Figure 6 The portion of the capillary pressure less than 0.0008 MPa constitutes the largest proportion, while the pressure difference only needs to be much greater than this 0.0008 MPa. This is because, for the pressure difference, as long as it is greater than the vast majority of capillary pressures, this pressure difference is sufficient to force the capillary in.

[0131] In one embodiment of this application, reference is made to Figure 6 Alternatively, 0.008MPa or 0.08MPa can be selected as the capillary pressure value here, and this application does not impose any restrictions on this.

[0132] The above method can be used to determine the initial depth of shale oil accumulation.

[0133] Therefore, the method described in this application accurately determines the initial depth of unconventional oil reservoirs of two types of source rocks, exhibiting greater specificity, accuracy, and advancement than related technologies. Furthermore, it can be applied in practice to solve the problems of identifying effective source rocks and calculating resource quantities for shale oil.

[0134] The first aspect of this application has been described above; the other aspects will be described below.

[0135] Figure 8 A block diagram of a device for determining the initial depth of shale oil accumulation in an embodiment of this application is shown. Figure 8 As shown,

[0136] According to a second aspect of the embodiments of this application, an apparatus for determining the initial depth of shale oil reservoir formation is provided, comprising:

[0137] Curve plotting module 801: Used to calculate the curve of oil generation pressure value of mudstone changing with time using oil generation pressure test, to obtain the first curve; and used to calculate the curve of oil generation pressure value of carbonate rock changing with time using oil generation pressure test, to obtain the second curve.

[0138] The conversion module 802 is used to convert the first curve into the third curve, which is used to characterize the oil generation pressure value of mudstone as a function of burial depth. It is also used to convert the second curve into the fourth curve, which is used to characterize the oil generation pressure value of carbonate rock as a function of burial depth.

[0139] Calculation module 803 is used to calculate the capillary resistance of carbonate rocks;

[0140] The depth confirmation module 801 is used to overlay the third curve and the fourth curve to form an overlay curve, and to determine the initial depth of shale oil accumulation based on the overlay curve and capillary resistance.

[0141] Based on the same inventive concept, this application also provides a device for determining the initial depth of shale oil accumulation, referencing... Figure 9 The diagram shows a schematic of the structure of a device for determining the initial depth of shale oil accumulation in an embodiment of this application. The device for determining the initial depth of shale oil accumulation includes one or more memories 904, one or more processors 902, and at least one computer program (computer program instruction) stored in the memory 904 and executable on the processor 902. When the processor 902 executes the computer program, it implements the method described above.

[0142] Among them, Figure 9In this document, a bus architecture (represented by bus 900) is used. Bus 900 may include any number of interconnected buses and bridges, linking various circuits including one or more processors represented by processor 902 and memory represented by memory 904. Bus 900 may also link various other circuits such as peripheral devices, voltage regulators, and power management circuits, which are well known in the art and therefore will not be described further herein. Bus interface 905 provides an interface between bus 900 and receiver 901 and transmitter 903. Receiver 901 and transmitter 903 may be the same element, i.e., a transceiver, providing a unit for communicating with various other devices over a transmission medium. Processor 902 is responsible for managing bus 900 and general processing, while memory 904 can be used to store data used by processor 902 during operation.

[0143] Based on the same inventive concept, embodiments of this application provide a computer-readable storage medium storing computer program instructions, which, when executed by a processor, cause the processor to perform the steps of the method described above.

[0144] The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored as one or more instructions or codes on or transmitted via a computer-readable medium. Other examples and embodiments are within the scope and spirit of this application and the appended claims. For example, due to the nature of software, the functions described above may be implemented using software executed by a processor, hardware, firmware, hardwired, or any combination thereof. Furthermore, the functional units may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit.

[0145] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units can be a logical functional division, and in actual implementation, there may be other division methods. For instance, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling, direct coupling, or communication connection may be through some interfaces; the indirect coupling or communication connection between units or modules may be electrical or other forms.

[0146] The units described as separate components may or may not be physically separate. Similarly, the components of the control device may or may not be physical units; they may be located in one place or distributed across multiple units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0147] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) 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 computer program instructions, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0148] The above description is merely an embodiment of this application and is not intended to limit 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 for determining the initial depth of shale oil accumulation, characterized in that, include: The curve of oil generation pressure value of mudstone changing with time was calculated using oil generation pressure test, and the second curve was obtained by calculating the curve of oil generation pressure value of carbonate rock changing with time using oil generation pressure test. The first curve is converted into a third curve, which is used to characterize the oil generation pressure value of the mudstone as a function of burial depth. The second curve is converted into a fourth curve, which is used to characterize the oil generation pressure value of the carbonate rock as a function of burial depth. Calculate the capillary resistance of the carbonate rock; The third curve and the fourth curve are superimposed to form a superimposed curve. The initial depth of shale oil accumulation is determined based on the superimposed curve and the capillary resistance.

2. The method according to claim 1, characterized in that, The step of converting the first curve into a third curve includes: Obtain the burial history data of the well where the shale oil is located, including the relationship between the burial depth of the well and the change over time; Based on the relationship between burial depth and time, each time point on the horizontal axis of the first curve is converted into the corresponding burial depth, while the vertical axis remains unchanged. The curve is then redrawn to obtain the third curve.

3. The method according to claim 1, characterized in that, The step of converting the second curve into the fourth curve includes: Obtain the burial history data of the well where the shale oil is located, including the relationship between the burial depth of the well and the change over time; Based on the relationship between burial depth and time, each time point on the horizontal axis of the second curve is converted into the corresponding burial depth, while the vertical axis remains unchanged. The curve is then redrawn to obtain the fourth curve.

4. The method according to claim 1, characterized in that, The calculation of the capillary resistance of the carbonate rock includes: The pore size distribution of the carbonate reservoir was determined by high-pressure mercury intrusion porosimetry. The capillary pressure distribution is calculated based on the aforementioned aperture distribution. The capillary resistance of the carbonate rock is determined using the capillary pressure distribution.

5. The method according to claim 4, characterized in that, The calculation of capillary pressure distribution based on the pore size distribution includes: The orifice size value is converted into a capillary pressure value using the Young-Laplace equation, wherein the Young-Laplace equation includes: In the formula, P c σ is the capillary pressure encountered by oil and gas entering the reservoir; θ is the oil-water interfacial tension; θ is the wetting angle; r is the pore size of the tight reservoir. Keeping the ordinate of the aperture distribution unchanged, the aperture values ​​are converted into capillary pressure values ​​and redrawn to obtain the capillary pressure distribution.

6. The method according to claim 5, characterized in that, The determination of the shale oil reservoir initiation depth based on the superposition curve and the capillary resistance includes: In the superimposed curve, the depth of the abscissa corresponding to the point where the pressure increase of mudstone oil generation is greater than that of carbonate oil generation, and the difference between the pressure increase of mudstone oil generation and the pressure increase of carbonate oil generation is greater than the capillary resistance, is taken as the initial depth of hydrocarbon accumulation.

7. The method according to claim 6, characterized in that, The method for determining that the difference between the oil generation pressurization of the mudstone and the oil generation pressurization of the carbonate rock is greater than the capillary resistance includes: The capillary pressure value at which the maximum percentage of capillary pressure distribution is obtained; When the difference between the pressure increase of the mudstone oil generation and the pressure increase of the carbonate rock oil generation is greater than the capillary pressure value, it is determined that the difference between the pressure increase of the mudstone oil generation and the pressure increase of the carbonate rock oil generation is greater than the capillary resistance.

8. A device for determining the initial depth of shale oil reservoir formation, characterized in that, include: Curve plotting module: Used to calculate the curve of oil generation pressure value of mudstone changing with time using oil generation pressure test, to obtain the first curve; and used to calculate the curve of oil generation pressure value of carbonate rock changing with time using oil generation pressure test, to obtain the second curve; The conversion module is used to convert the first curve into a third curve, which is used to characterize the oil generation pressure value of the mudstone as a function of burial depth. It is also used to convert the second curve into a fourth curve, which is used to characterize the oil generation pressure value of the carbonate rock as a function of burial depth. A calculation module is used to calculate the capillary resistance of the carbonate rock; The depth confirmation module is used to overlay the third curve and the fourth curve to form an overlay curve, and to determine the initial depth of shale oil accumulation based on the overlay curve and the capillary resistance.

9. A device for determining the initial depth of shale oil reservoir formation, comprising a processor and a memory, characterized in that, The memory stores computer program instructions that can be executed by the processor, and when the processor executes the computer program instructions, it implements the steps of the method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer program instructions that, when executed by a processor, cause the processor to perform the steps of the method as described in any one of claims 1 to 7.

Images