Method for determining the volumetric oil content of free hydrocarbons in shales

Abstract

The present disclosure relates to a method for determining the volume oil content of free hydrocarbon in shale, belonging to the field of shale oil. The method comprises obtaining a plurality of core samples of the shale to be measured; measuring the total mass and total volume of each core sample in the plurality of core samples respectively; obtaining the free hydrocarbon unit mass and free hydrocarbon density of the free hydrocarbon in each core sample respectively; determining the volume oil content of the free hydrocarbon in each core sample based on the total mass, total volume, free hydrocarbon unit mass and free hydrocarbon density of each core sample; obtaining a plurality of types of logging data of the shale to be measured, the logging data comprising formation resistivity curve, compensated density curve, acoustic time difference curve and natural gamma curve; and determining the volume oil content of the free hydrocarbon in the shale to be measured based on the volume oil content of the free hydrocarbon in each core sample and the logging data. The method can determine the volume oil content of the free hydrocarbon in shale and quantitatively evaluate the volume oil content of the free hydrocarbon in shale.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of shale oil, and in particular, to a method for determining the volumetric oil content of free hydrocarbons in shale. BACKGROUND

[0002] Shale oil refers to oil resources contained in shale layer systems dominated by shale. Shale oil includes hydrocarbons in a free state (referred to as free hydrocarbons) contained in shale layers, hydrocarbons adsorbed in shale, and hydrocarbons dissolved in shale.

[0003] Currently, shale oil extracted from shale layers is mainly free hydrocarbons. The content of free hydrocarbons in shale oil can represent the reserves of shale oil, which is of great significance for guiding the exploration and development of shale oil. However, there is currently no good method for quantitatively evaluating the volumetric oil content of free hydrocarbons in shale. The volumetric oil content of free hydrocarbons refers to the volume of free hydrocarbons per unit volume of shale. SUMMARY

[0004] The present disclosure provides a method for determining the volumetric oil content of free hydrocarbons in shale, which is used to determine the volumetric oil content of free hydrocarbons in shale. The technical solution is as follows:

[0005] The present disclosure provides a method for determining the volumetric oil content of free hydrocarbons in shale, which includes: obtaining a plurality of core samples of a shale to be measured; measuring the total mass and total volume of each core sample in the plurality of core samples, respectively; obtaining the unit mass of free hydrocarbons and the density of free hydrocarbons of free hydrocarbons in each core sample, respectively; determining the volumetric oil content of free hydrocarbons in each core sample based on the total mass, the total volume, the unit mass of free hydrocarbons, and the density of free hydrocarbons of each core sample; obtaining a plurality of types of logging data of the shale to be measured, the logging data including a formation resistivity curve, a compensated density curve, a sonic time difference curve, and a natural gamma curve; and determining the volumetric oil content of free hydrocarbons in the shale to be measured based on the volumetric oil content of free hydrocarbons in each core sample and the logging data.

[0006] In an implementation form of the embodiment of the disclosure, the free hydrocarbon includes light hydrocarbon and light-medium hydrocarbon, and the free hydrocarbon unit mass and the free hydrocarbon density of the free hydrocarbon in each core sample are obtained, including: performing pyrolysis analysis on each core sample to obtain the first unit mass of the light hydrocarbon at a first temperature and the second unit mass of the light-medium hydrocarbon at a second temperature of each core sample, the second temperature is greater than the first temperature, and the free hydrocarbon unit mass includes the first unit mass and the second unit mass; based on the shale oil density analysis data of the shale to be measured, the first density of the light hydrocarbon and the second density of the light-medium hydrocarbon are obtained, and the free hydrocarbon density includes the first density and the second density.

[0007] In an implementation form of the embodiment of the disclosure, the pyrolysis analysis on each core sample includes: crushing the core sample in a frozen environment; heating the crushed core sample to a first temperature in a closed environment and maintaining for at least one minute to obtain the first unit mass of the light hydrocarbon; and continuing to heat the crushed core sample in a closed environment to a second temperature and maintaining for at least one minute to obtain the second unit mass of the light-medium hydrocarbon.

[0008] In an implementation form of the embodiment of the disclosure, the temperature of the frozen environment is between -50 degrees Celsius and -200 degrees Celsius.

[0009] In an implementation form of the embodiment of the disclosure, the heating of the crushed core sample in a closed environment includes: heating the crushed core sample in a closed environment at a heating rate of 20 degrees Celsius to 30 degrees Celsius per minute.

[0010] In an implementation form of the embodiment of the disclosure, the volume oil content of the free hydrocarbon in each core sample is determined based on the total mass, the total volume, the free hydrocarbon unit mass and the free hydrocarbon density of each core sample, including: calculating the volume oil content of the free hydrocarbon in each core sample according to the following formula:

[0011]

[0012] In the formula:

[0013] T f — the volume oil content of the free hydrocarbon in the core sample, unit: percentage (%);

[0014] S 1-1 — the first unit mass of the light hydrocarbon in the free hydrocarbon, unit: milligrams per gram (mg / g);

[0015] ρ 1-1— the first density, unit: gram per cubic centimeter (g / cm 3 );

[0016] S 1-2 — the second unit mass of light and medium hydrocarbons in the free hydrocarbons, unit: milligram per gram (mg / g);

[0017] ρ 1-2 — the second density, unit: gram per cubic centimeter (g / cm 3 );

[0018] m 样 — the total mass of the core sample, unit: gram (g);

[0019] V 样 — the total volume of the core sample, unit: cubic centimeter (cm 3 )。

[0020] In an implementation form of the embodiment of the present disclosure, the first temperature is between 190 degrees Celsius and 210 degrees Celsius, and the second temperature is between 340 degrees Celsius and 360 degrees Celsius.

[0021] In an implementation form of the embodiment of the present disclosure, determining the volumetric oil content of free hydrocarbons in the shale to be measured based on the volumetric oil content of free hydrocarbons in each core sample and the logging data includes: determining the correlation between each kind of logging data and the volumetric oil content of free hydrocarbons in the core sample by using a multiple regression software; determining the relevant logging data in the multiple kinds of logging data based on the correlation, the relevant logging data being the logging data in the logging data that has a correlation greater than 0.9 with the volumetric oil content of free hydrocarbons in the core sample; and determining a relationship between the volumetric oil content of free hydrocarbons in the shale to be measured and the relevant logging data, the relationship being used to represent the volumetric oil content of free hydrocarbons in the shale to be measured.

[0022] In an implementation form of the embodiment of the present disclosure, the sealing rate of the multiple core samples of the shale to be measured is greater than 90%.

[0023] In an implementation form of the embodiment of the present disclosure, the number of the core samples is between 15 and 40.

[0024] The technical solution provided by the embodiment of the present disclosure has the following beneficial effects:

[0025] In the embodiment of the present disclosure, a plurality of core samples of the shale to be measured are first obtained, then the total mass and total volume of each core sample are measured, the free hydrocarbon unit mass and free hydrocarbon density of free hydrocarbon in each core sample are obtained, then the volume oil content of free hydrocarbon in each core sample can be determined according to the total mass, total volume, free hydrocarbon unit mass and free hydrocarbon density of each core sample, and the volume oil content of free hydrocarbon in the shale to be measured can be determined according to the volume oil content of free hydrocarbon in each core sample and the logging data. The method can determine the volume oil content of free hydrocarbon in the shale, quantitatively evaluate the volume oil content of free hydrocarbon in the shale, and be used for characterizing the reserves of shale oil, so as to provide a guiding basis for the exploration and development of shale oil. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present disclosure, and other drawings can be obtained by those skilled in the art without creative labor.

[0027] Figure 1 is a flowchart of a method for determining the volume oil content of free hydrocarbon in shale provided by the embodiment of the present disclosure;

[0028] Figure 2 is a flowchart of a method for determining the volume oil content of free hydrocarbon in shale provided by the embodiment of the present disclosure;

[0029] Figure 3 is a flowchart of a core sample pyrolysis analysis provided by the embodiment of the present disclosure;

[0030] Figure 4 is an experimental curve of a core sample performing multi-stage pyrolysis analysis provided by the embodiment of the present disclosure;

[0031] Figure 5 is a graph of experimental data calculating the relationship between the volume oil content of free hydrocarbon and the formation resistivity;

[0032] Figure 6 is a graph of experimental data calculating the relationship between the volume oil content of free hydrocarbon and the compensated density;

[0033] Figure 7 is a graph of experimental data calculating the relationship between the volume oil content of free hydrocarbon and the volume oil content of free hydrocarbon in the calculation model of the volume oil content of free hydrocarbon. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present disclosure more clear, the embodiments of the present disclosure will be further described in detail with reference to the drawings.

[0035] Figure 1 This is a flowchart illustrating a method for determining the volumetric oil content of free hydrocarbons in shale, as provided in an embodiment of this disclosure. See also... Figure 1 The method includes:

[0036] In step S101, multiple core samples of the shale to be tested are obtained.

[0037] In this embodiment of the disclosure, core samples can be obtained by drilling from the shale to be tested. Since the core samples are obtained through drilling, they can accurately reflect the oil content of the shale formation being tested.

[0038] In this embodiment of the disclosure, the core sample is obtained from underground, where the pressure is relatively high. To prevent the release of free hydrocarbons from the core sample due to the decrease in pressure after it is taken out from underground, the sampling must be carried out in a closed environment.

[0039] In one implementation of this disclosure, the sealing ratio during sampling is greater than or equal to 90%.

[0040] In this embodiment of the disclosure, although sampling is carried out in a closed environment to reduce the possibility of free hydrocarbon precipitation, it is unavoidable that free hydrocarbons will still precipitate. The higher the temperature, the more free hydrocarbons will precipitate. After the core sample is taken out, it can be stored in a cold environment to reduce the amount of free hydrocarbons precipitated.

[0041] In one implementation of the present disclosure, after the core sample is taken out, it can be stored in a freezing environment between -50 degrees Celsius (°C) and -200 degrees Celsius.

[0042] For example, after the core sample is removed, it can be frozen in a sealed environment at -50 degrees Celsius to reduce the amount of free hydrocarbons released.

[0043] In this embodiment of the disclosure, in order to ensure the accuracy of the experiment and avoid increasing the workload of sampling, the number of core samples is between 15 and 40.

[0044] For example, the number of core samples is 24.

[0045] In step S102, the total mass and total volume of each core sample in the multiple core samples are measured respectively.

[0046] In this embodiment of the disclosure, after the core samples are removed, the total mass (m) of each core sample can be measured using a balance or scale. 样 ).

[0047] In this embodiment of the disclosure, after the core samples are extracted, the total volume (V) of each core sample can be measured using a rock sample total volume measuring instrument.样 )。

[0048] In step S103, free hydrocarbon unit mass and free hydrocarbon density of free hydrocarbon in each core sample are obtained respectively.

[0049] In the embodiment of the present disclosure, the free hydrocarbon unit mass of free hydrocarbon in each core sample can be obtained by experiment after the core sample is taken out.

[0050] In the embodiment of the present disclosure, the free hydrocarbon unit mass refers to the mass of free hydrocarbon in unit mass of core sample. For example, the free hydrocarbon unit mass can refer to how many milligrams of free hydrocarbon are included in each gram of core sample.

[0051] Illustratively, pyrolysis experiment can be performed on the core sample to obtain the free hydrocarbon unit mass of free hydrocarbon in the core sample.

[0052] In the embodiment of the present disclosure, the free hydrocarbon density can be obtained from the density analysis data of shale oil.

[0053] In step S104, the volumetric oil content of free hydrocarbon in each core sample is determined based on the total mass, total volume, free hydrocarbon unit mass and free hydrocarbon density of each core sample.

[0054] In the embodiment of the present disclosure, the free hydrocarbon unit mass multiplied by the total mass can obtain the free hydrocarbon mass in each sample, and then the free hydrocarbon mass divided by the free hydrocarbon density can obtain the free hydrocarbon volume, and then the free hydrocarbon volume divided by the total volume of the core sample can obtain the volumetric oil content of free hydrocarbon in each core sample.

[0055] In step S105, multiple types of logging data of the shale to be measured are obtained, and the logging data include formation resistivity curve, compensated density curve, acoustic time difference curve and natural gamma curve.

[0056] In the embodiment of the present disclosure, the formation resistivity, the compensated density, the acoustic time difference and the natural gamma are obtained during logging, and all belong to logging data.

[0057] In step S106, the volumetric oil content of free hydrocarbon in the shale to be measured is determined based on the volumetric oil content of free hydrocarbon in each core sample and the logging data.

[0058] In the embodiment of the present disclosure, by fitting analysis of the volumetric oil content of free hydrocarbon in each core sample and the logging data through the multiple regression software, it can be determined which type of logging data in the logging data has the highest correlation with the volumetric oil content of free hydrocarbon, that is, the logging data has a certain functional relationship with the volumetric oil content of free hydrocarbon, and the functional relationship can be obtained through the multiple regression software, so that the volumetric oil content of free hydrocarbon in the shale to be measured can be determined according to the logging data.

[0059] In the embodiment of the present disclosure, a plurality of core samples of the shale to be measured are obtained first, then the total mass and total volume of each core sample are measured, the free hydrocarbon unit mass and free hydrocarbon density of free hydrocarbon in each core sample are obtained, then the volumetric oil content of free hydrocarbon in each core sample is determined according to the total mass, total volume, free hydrocarbon unit mass and free hydrocarbon density of each core sample, and the volumetric oil content of free hydrocarbon in the shale to be measured is determined according to the volumetric oil content of free hydrocarbon in each core sample and logging data. The method can determine the volumetric oil content of free hydrocarbon in the shale, quantitatively evaluate the volumetric oil content of free hydrocarbon in the shale, and be used for characterizing the reserves of shale oil, so as to provide a guiding basis for the exploration and development of shale oil.

[0060] Figure 2 is a flow chart of a method for determining the volumetric oil content of free hydrocarbon in shale provided by the present disclosure. Referring to Figure 2 , the method comprises:

[0061] In step S201, a plurality of core samples of the shale to be measured are obtained.

[0062] In step S202, the total mass and total volume of each core sample in the plurality of core samples are measured respectively.

[0063] In the embodiment of the present disclosure, the free hydrocarbon includes light hydrocarbon and light-medium hydrocarbon.

[0064] The light hydrocarbon represents a part of the free hydrocarbon with less than 16 carbon atoms, and the light-medium hydrocarbon represents a part of the free hydrocarbon with less than 25 carbon atoms.

[0065] In step S203, pyrolysis analysis is performed on each core sample to obtain the first unit mass of light hydrocarbon at a first temperature for each core sample and the second unit mass of light-medium hydrocarbon at a second temperature for each core sample.

[0066] The second temperature is greater than the first temperature, and the free hydrocarbon unit mass includes the first unit mass and the second unit mass.

[0067] In the embodiments of the present disclosure, the ignition point of the light hydrocarbon in the free hydrocarbon is different from the ignition point of the light-medium hydrocarbon, and the ignition point of the light hydrocarbon is less than the ignition point of the light-medium hydrocarbon. The core sample is placed in a pyrolysis analysis experimental device, and pyrolysis analysis is performed on the core sample. When the temperature reaches a first temperature, the light hydrocarbon burns, causing the mass of the core sample to decrease. The decreased mass of the core sample can be read from the pyrolysis analysis experimental device. The decreased mass is evenly distributed to each unit mass of the core sample, and the decreased mass of each unit mass of the core sample, i.e., the first unit mass of the light hydrocarbon, can be obtained. When the temperature reaches a second temperature, the light-medium hydrocarbon burns, causing the mass of the core sample to decrease again. The decreased mass of the core sample can be read from the pyrolysis analysis experimental device. The decreased mass is evenly distributed to each unit mass of the core sample, and the decreased mass of each unit mass of the core sample, i.e., the second unit mass of the light-medium hydrocarbon, can be obtained.

[0068] In the embodiments of the present disclosure, when the core sample is subjected to pyrolysis analysis, it undergoes multiple temperature stages. This experiment can be referred to as a multi-temperature stage pyrolysis experiment.

[0069] Figure 3 is a flowchart of a core sample pyrolysis analysis provided by the embodiments of the present disclosure. Referring to Figure 3 , step 203 comprises:

[0070] In step S231, the core sample is crushed in a frozen environment.

[0071] In the embodiments of the present disclosure, the core sample is crushed, i.e., broken into pieces, which can increase the contact area between the free hydrocarbon in the core sample and the air, so that the free hydrocarbon burns completely and the accuracy of the experiment is improved.

[0072] At the same time, in order to avoid the precipitation of free hydrocarbon in the core sample, the core sample can be crushed in a frozen environment.

[0073] In the embodiments of the present disclosure, the temperature of the frozen environment when the core sample is crushed is between -50 degrees Celsius (℃) and -200 degrees Celsius.

[0074] For example, the core sample can be crushed in a liquid nitrogen environment. The temperature of the liquid nitrogen can reach -190 degrees Celsius, which can effectively reduce the amount of free hydrocarbon precipitation.

[0075] In step S232, the crushed core sample is heated to a first temperature in a closed environment for at least one minute, and the first unit mass of the light hydrocarbon is obtained.

[0076] In the embodiments of the present disclosure, the crushed core sample is transferred to the pyrolysis analysis experimental device, and the airtightness of the pyrolysis analysis experimental device is ensured. Then the crushed core sample in the pyrolysis analysis experimental device is heated, when the temperature reaches the ignition point of the light hydrocarbon, that is, the first temperature, the light hydrocarbon is burned, so that the mass of the core sample is reduced, and the pyrolysis analysis experimental device can determine the first unit mass of the light hydrocarbon (S 1-1 ) by measuring the mass of the core sample at this time.

[0077] In the embodiments of the present disclosure, the first unit mass of the light hydrocarbon represents the mass of the light hydrocarbon in the unit mass of the core sample.

[0078] In the embodiments of the present disclosure, when the temperature reaches the first temperature, the temperature in the pyrolysis analysis experimental device is ensured to be at the first temperature for at least one minute, so that the light hydrocarbon in the core sample can be fully burned, and the accuracy of the experiment is improved.

[0079] In the embodiments of the present disclosure, when the core sample is heated, the crushed core sample in the pyrolysis analysis experimental device is heated at a heating rate of 20 degrees Celsius per minute to 30 degrees Celsius per minute.

[0080] For example, when the core sample is heated, the temperature is raised at a rate of 25 degrees Celsius per minute.

[0081] In the embodiments of the present disclosure, the first temperature is between 190 degrees Celsius and 210 degrees Celsius. At this temperature, the light hydrocarbon in the core sample can be burned, and the light hydrocarbon in the core sample cannot be burned.

[0082] For example, the first temperature is 200 degrees Celsius.

[0083] In step S233, the crushed core sample is continuously heated in a closed environment, heated to a second temperature and maintained for at least one minute, and the second unit mass of the light hydrocarbon is obtained.

[0084] In the embodiments of the present disclosure, the crushed core sample in the pyrolysis analysis experimental device is continuously heated, when the temperature reaches the ignition point of the light hydrocarbon, that is, the second temperature, the light hydrocarbon is burned, so that the mass of the core sample is reduced again, and the pyrolysis analysis experimental device can determine the second unit mass of the light hydrocarbon (S 1-2 ) by measuring the mass of the core sample at this time.

[0085] In the embodiments of the present disclosure, the second unit mass of the light hydrocarbon represents the mass of the light hydrocarbon in the unit mass of the core sample.

[0086] In the embodiments of the present disclosure, when the temperature reaches the second temperature, the temperature in the pyrolysis analysis experimental device is guaranteed to last at least one minute at the second temperature, so that the light and medium hydrocarbons in the core sample can be fully combusted, and the accuracy of the experiment is improved.

[0087] In the embodiments of the present disclosure, when the core sample is heated, the heated core sample is heated in the pyrolysis analysis experimental device at a heating rate of 20 degrees Celsius per minute to 30 degrees Celsius per minute.

[0088] In the core sample, not only free hydrocarbons but also other types of hydrocarbons, such as hydrocarbons adsorbed in shale (referred to as adsorbed hydrocarbons) and hydrocarbons dissolved in shale (referred to as dissolved hydrocarbons). The ignition points of other types of hydrocarbons are all higher than that of light and medium hydrocarbons, so as long as the heating temperature does not reach the ignition point of other types of hydrocarbons, other types of hydrocarbons will not burn and thus affect the quality measurement of the aforementioned free hydrocarbons.

[0089] In the embodiments of the present disclosure, the second temperature is between 340 degrees Celsius and 360 degrees Celsius. At this temperature, the light and medium hydrocarbons in the core sample can be combusted, and other types of hydrocarbons in the core sample cannot be combusted.

[0090] Exemplarily, the second temperature is 350 degrees Celsius.

[0091] In step S204, shale oil density analysis data of the shale to be measured is obtained, a first density of light hydrocarbons and a second density of light and medium hydrocarbons are obtained, and the free hydrocarbon density includes the first density and the second density.

[0092] In the process of logging, a part of shale oil in the shale to be measured is extracted, and density analysis is performed on the shale oil in the shale. The shale oil is mainly free hydrocarbons, i.e., light hydrocarbons and light and medium hydrocarbons. The densities of various components can be determined through density analysis. For example, the lowest shale oil density obtained is the density of light hydrocarbons, i.e., the first density (ρ 1-1 ), and the highest shale oil density obtained from the density analysis data is the density of light and medium hydrocarbons, i.e., the second density (ρ 1-2 ).

[0093] In step S205, the volume oil-bearing rate of the free hydrocarbons in each core sample is calculated according to formula (1):

[0094]

[0095] In formula (1):

[0096] T f is the volume oil-bearing rate of the free hydrocarbons in the core sample, and the unit is percentage (%);

[0097] S 1-1— the first unit mass of light hydrocarbon in free hydrocarbon, unit: milligram per gram (mg / g);

[0098] p 1-1 — the first density, unit: gram per cubic centimeter (g / cm 3 ) ;

[0099] S 1-2 — the second unit mass of light-medium hydrocarbon in free hydrocarbon, unit: milligram per gram (mg / g) ;

[0100] p 1-2 — the second density, unit: gram per cubic centimeter (g / cm 3 ) ;

[0101] m 样 — the total mass of the core sample, unit: gram (g) ;

[0102] V 样 — the total volume of the core sample, unit: cubic centimeter (cm 3 ).

[0103] In the embodiments of the present disclosure, S 1-1 × m 样 is the mass of light hydrocarbon, is the volume of light hydrocarbon, is the volume oil content of light hydrocarbon.

[0104] Similarly, S 1-2 × m 样 is the mass of light-medium hydrocarbon, is the volume of light-medium hydrocarbon, is the volume oil content of light hydrocarbon. Adding the volume oil content of light hydrocarbon and the volume oil content of light hydrocarbon can obtain the volume oil content of free hydrocarbon in the core sample.

[0105] In step S206, the correlation between each kind of logging data and the volume oil content of free hydrocarbon in the core sample is determined by using a multiple regression software.

[0106] In the embodiments of the present disclosure, each kind of logging data can affect the volume oil content of free hydrocarbon in shale, and the depth of each core sample is recorded when the core sample is drilled. For example, step 206 can include:

[0107] Obtaining logging data at the corresponding depth from the curve of the logging data.

[0108] Fitting each kind of logging data and the volume oil content of free hydrocarbon in the core sample by using a multiple regression software, respectively.

[0109] The correlation between each kind of logging data and the volume oil content of free hydrocarbon in the core sample is determined by fitting the obtained graph.

[0110] Exemplarily, taking the formation resistivity as an example, the volume oil content of free hydrocarbon corresponding to one core sample is taken as the abscissa, the formation resistivity at the corresponding depth of the core sample is taken as the ordinate, a coordinate value is obtained, and the coordinate value is input into the multiple regression software. The volume oil content of free hydrocarbon and the formation resistivity corresponding to the remaining core samples are input into the multiple regression software in the same way. The multiple regression software displays a graph corresponding to the coordinate values, and the graph corresponds to a correlation value, which represents the correlation between the formation resistivity and the volume oil content of free hydrocarbon.

[0111] Exemplarily, the multiple regression software can be a statistical product and service solutions (SPSS) software.

[0112] In step S207, the relevant logging data in the multiple kinds of logging data is determined based on the correlation.

[0113] The relevant logging data is the logging data whose correlation value with the volume oil content of free hydrocarbon in the core sample is greater than 0.9.

[0114] In the embodiments of the present disclosure, the correlation value between each kind of logging data and the volume oil content of free hydrocarbon in the core sample can be obtained from the curve of the logging data and the volume oil content of free hydrocarbon in the core sample in the multiple regression software. When the correlation value is greater than 0.9, it is indicated that the logging data of this kind has a relatively large correlation with the volume oil content of free hydrocarbon in the core sample, and the logging data is the relevant logging data.

[0115] In step S208, a relationship between the volume oil content of free hydrocarbon in the to-be-detected shale and the relevant logging data is determined.

[0116] The relationship is used to represent the volume oil content of free hydrocarbon in the to-be-detected shale.

[0117] In the embodiments of the present disclosure, after the relevant logging data is determined, the volume oil content of free hydrocarbon of the core sample and the logging data at the corresponding depth are input into the multiple regression software, and the relationship between the relevant logging data and the volume oil content of free hydrocarbon in the to-be-detected shale can be fitted.

[0118] In the embodiments of the present disclosure, when the determined relevant logging data is one, it means that the one relevant logging data is related to the volume oil content of free hydrocarbon in the shale to be measured; when the determined relevant logging data is two, it means that the two relevant logging data are related to the volume oil content of free hydrocarbon in the shale to be measured; and when the determined relevant logging data is multiple, it means that the multiple relevant logging data are related to the volume oil content of free hydrocarbon in the shale to be measured.

[0119] In actual application, after the relationship between the volume oil content of free hydrocarbon in the shale to be measured and the relevant logging data is determined, the volume oil content of free hydrocarbon in the shale at different depths can be obtained according to the logging data at different depths in the relevant logging data, and then the volume of shale at the corresponding depth is obtained according to the change rule of the volume of shale and the depth in the geological data, the shale oil reserves at the depth are obtained by multiplying the volume of shale by the volume oil content of free hydrocarbon, and the total shale oil reserves can be obtained by adding the shale oil reserves at different depths.

[0120] The determination method of the volume oil content of free hydrocarbon in shale provided by the embodiments of the present disclosure will be further described below in combination with specific embodiments, taking G19-25 well in Cangdong Sag as an example, and the specific operation is as follows:

[0121] 1) For the continuous sealed coring of Kong 2 member in Cangdong Sag, the cumulative footage is 46.18 meters (m), the cumulative core length is 46.01 meters, the average recovery rate is 99.63%, the total sealing rate is 92.85%, and the core is quickly frozen in a sealed environment of-50 degrees Celsius after being taken out.

[0122] Among them, the cumulative footage is the total depth of the core, the cumulative core length is the total length of the core sample, and the average recovery rate is the cumulative core length divided by the cumulative footage.

[0123] 2) 28 sample points are selected, the sample mass and volume are measured, then the sample is crushed in a liquid nitrogen cold environment at-190℃, and the multi-temperature stage pyrolysis analysis is carried out immediately after crushing, the temperature is raised to 200 degrees Celsius at a rate of 25 degrees Celsius per minute (℃ / min), and the first unit weight of light hydrocarbon is detected, and then the temperature is raised to 350 degrees Celsius at a rate of 25 degrees Celsius per minute, and the second unit weight of light and medium hydrocarbon is detected.

[0124] Figure 4 is an experimental curve of a core sample for multi-stage pyrolysis analysis provided by the embodiments of the present disclosure. Referring to Figure 4 , wherein the upper abscissa represents temperature, unit: degrees Celsius (℃), the lower abscissa represents time, unit: minutes (min), and the ordinate represents unit mass, unit: milligrams per gram (mg / g). In the curve, the left shadow area represents the first unit weight S 1-1, the shadow area on the right represents the second unit weight S of light and medium hydrocarbon 1-2 .

[0125] From Figure 4 It can be seen that in shale not only includes free hydrocarbon, adsorbed hydrocarbon, dissolved hydrocarbon, but also includes pyrolysis hydrocarbon of kerogen.

[0126] 3) According to the density analysis data of shale oil in G19-25 well in Cangdong sag, the first density (ρ 1-1 ) of light hydrocarbon and the second density (ρ 1-2 ) of light and medium hydrocarbon in the sample are obtained.

[0127] 4) The volume oil content of free hydrocarbon in the sample is calculated by formula (1).

[0128] 5) Taking the volume oil content of free hydrocarbon calculated by formula (1) as the independent variable, reading the formation resistivity, compensated density, acoustic time difference, natural gamma and other types of logging values corresponding to the depth point, and applying multiple regression software for fitting. Through multiple regression software for multiple fitting, it is clear that the correlation between the volume oil content of free hydrocarbon and the formation resistivity and compensated density logging values of shale oil in the second member of Kong in Cangdong sag is the best.

[0129] Figure 5 is the experimental data to calculate the relationship between the volume oil content of free hydrocarbon and the formation resistivity. In Figure 5 , the horizontal coordinate represents the formation resistivity logging value, unit: ohm meter (Ω.m), the vertical coordinate represents the volume oil content of free hydrocarbon, unit: percent (%). Among them, the formation resistivity logging value can be directly read from the formation resistivity curve.

[0130] Figure 6 is the experimental data to calculate the relationship between the volume oil content of free hydrocarbon and the compensated density. In Figure 5 , the horizontal coordinate represents the compensated density logging value, unit: grams per cubic centimeter (g / cm 3 ), the vertical coordinate represents the volume oil content of free hydrocarbon, unit: percent (%). Among them, the compensated density logging value can be directly read from the compensated density curve.

[0131] Referring to Figure 5 and Figure 6 , the volume oil content of free hydrocarbon is approximately proportional to the formation resistivity, and the volume oil content of free hydrocarbon is negatively correlated with the compensated density, that is, the correlation between the volume oil content of free hydrocarbon and the formation resistivity and the compensated density is good, that is, the correlation logging data is the formation resistivity data and the compensated density data.

[0132] 6) According to the formation resistivity and compensated density data, the multiple regression software is used to establish the calculation model of the volume oil content of free hydrocarbon:

[0133] T f1 =0.665×lg(Rt)-4.73×DEN+11.72 (2)

[0134] In formula (2):

[0135] T f1 —Volume oil content of free hydrocarbons, in percentage;

[0136] Rt—formation resistivity logging value, unit: ohm-meter (Ω·m);

[0137] DEN—Compensated density logging value, unit: grams per cubic centimeter.

[0138] Figure 7 This is a graph showing the relationship between the volumetric oil content of free hydrocarbons and the volumetric oil content of free hydrocarbons calculated using experimental data. Figure 7 In the figure, the horizontal axis represents the volumetric oil content of free hydrocarbons obtained from experimental analysis, in percentage (%), which is the volumetric oil content of free hydrocarbons obtained by formula (1). The vertical axis represents the volumetric oil content of free hydrocarbons calculated by the calculation model, in percentage (%), which is the volumetric oil content of free hydrocarbons obtained by formula (2).

[0139] The relationship between the free hydrocarbon volumetric oil content calculated by the computational model and the free hydrocarbon volumetric oil content obtained from experimental analysis is as follows:

[0140] Y = 1.0001X + 0.0039 (3)

[0141] In formula (3):

[0142] Y—Free hydrocarbon volumetric oil content calculated by the computational model, in percentage;

[0143] X—Free hydrocarbon volumetric oil content obtained from experimental analysis, unit: percentage.

[0144] The correlation R between the free hydrocarbon volumetric oil content calculated by the computational model and the free hydrocarbon volumetric oil content obtained by experimental analysis 2 =0.9058. The free hydrocarbon volumetric oil content calculated by the free hydrocarbon volumetric oil content calculation model is not much different from the free hydrocarbon volumetric oil content obtained by experimental analysis, that is, the calculation model can be used to represent the free hydrocarbon volumetric oil content.

[0145] The method for determining the volume oil content of free hydrocarbon in shale provided by the embodiments of the present disclosure has a simple calculation model, involves parameters that can be obtained from oilfield production data, has high reliability, can quickly and continuously calculate the volume oil content of free hydrocarbon in a shale section, has good practicability for quantitatively evaluating the oil-bearing property of the shale section, and has important significance for guiding shale oil exploration and development.

[0146] The above merely describes optional embodiments of the present disclosure and is not intended to limit the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A method for determining the volumetric oil content of free hydrocarbons in shale, characterized by, The method for determining the volume oil content of free hydrocarbon in the shale comprises: obtaining a plurality of core samples of the shale to be measured; respectively measuring the total mass and total volume of each of the plurality of core samples; respectively obtaining the free hydrocarbon unit mass and free hydrocarbon density of free hydrocarbon in each of the core samples, the free hydrocarbon including light hydrocarbon and light-medium hydrocarbon, the free hydrocarbon unit mass including the first unit mass of the light hydrocarbon and the second unit mass of the light-medium hydrocarbon, the free hydrocarbon density including the first density of the light hydrocarbon and the second density of the light-medium hydrocarbon, wherein the first density is the lowest density of shale oil extracted from the shale to be measured, and the second density is the highest density of shale oil extracted from the shale to be measured; calculating the volume oil content of free hydrocarbon in each of the core samples according to the following formula: In the formula: T f Volume oil content of free hydrocarbons in core samples, in percent (%); S 1-1 - the first unit mass of light hydrocarbons in the free hydrocarbons, in milligrams per gram (mg / g); ρ 1-1 - the first density, in grams per cubic centimeter (g / cm 3 ); S 1-2 - the second unit mass of light to medium hydrocarbons in the free hydrocarbons, in milligrams per gram (mg / g); p 1-2 - the second density, in grams per cubic centimeter (g / cm 3 ); m 样 - total mass of the core sample in grams (g); V 样 - total volume of the core sample, in cubic centimeters (cm3) 3 ); obtaining a plurality of types of logging data of the shale to be measured, the logging data including formation resistivity curve, compensated density curve, acoustic time difference curve and natural gamma curve; determining the volume oil content of free hydrocarbon in the shale to be measured based on the volume oil content of free hydrocarbon in each of the core samples and the logging data.

2. The method of determining the volumetric oil-in-place of free hydrocarbons in shale of claim 1, wherein, respectively obtaining the free hydrocarbon unit mass and free hydrocarbon density of free hydrocarbon in each of the core samples, including: performing pyrolysis analysis on each of the core samples to respectively obtain the first unit mass of the light hydrocarbon at a first temperature and the second unit mass of the light-medium hydrocarbon at a second temperature of each of the core samples, the second temperature being greater than the first temperature; obtaining the first density of the light hydrocarbon and the second density of the light-medium hydrocarbon based on shale oil density analysis data of the shale to be measured.

3. The method of determining the volumetric oil-in-place of free hydrocarbons in shale of claim 2, wherein, performing pyrolysis analysis on each of the core samples, including: crushing the core samples in a frozen environment; heating the crushed core samples to a first temperature in a closed environment and maintaining for at least one minute to obtain the first unit mass of the light hydrocarbon; continuing to heat the crushed core samples in a closed environment to a second temperature and maintaining for at least one minute to obtain the second unit mass of the light-medium hydrocarbon.

4. The method of determining the volumetric oil-in-place of free hydrocarbons in shale of claim 3, wherein, The temperature of the frozen environment is between -50 degrees Celsius and -200 degrees Celsius.

5. The method of determining the volumetric oil-in-place of free hydrocarbons in shale of claim 3, wherein, heating the crushed core samples in a closed environment, including: heating the crushed core samples in a closed environment at a temperature rising speed of 20 degrees Celsius to 30 degrees Celsius per minute.

6. The method of determining the volumetric oil-in-place of free hydrocarbons in shale of claim 2, wherein, The first temperature is between 190 degrees Celsius and 210 degrees Celsius, and the second temperature is between 340 degrees Celsius and 360 degrees Celsius.

7. The method of determining the volumetric oil-in-place of free hydrocarbons in shale of any one of claims 1 to 6, wherein, determining the volume oil content of free hydrocarbon in the shale to be measured based on the volume oil content of free hydrocarbon in each of the core samples and the logging data, including: determining the correlation between each type of logging data and the volume oil content of free hydrocarbon in the core samples by using multivariate regression software; determining, based on the correlation, a relevant logging data in the multiple kinds of logging data, the relevant logging data being logging data in the multiple kinds of logging data having a correlation greater than 0.9 with the volumetric oil content of free hydrocarbon in the core sample; determining a relationship between the volumetric oil content of free hydrocarbon in the shale to be measured and the relevant logging data, the relationship being used to represent the volumetric oil content of free hydrocarbon in the shale to be measured.

8. The method of determining the volumetric oil-in-place of free hydrocarbons in shale of any one of claims 1 to 6, wherein, The sealing rate of the multiple core samples of the shale to be measured is greater than 90%.

9. The method of determining the volumetric oil-in-place of free hydrocarbons in shale of any one of claims 1 to 6, wherein, The number of the core samples is between 15 and 40.

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