A method for evaluating oil content in shale oil reservoirs

Abstract

The present disclosure provides a method for evaluating the oil content of a shale oil reservoir, comprising: performing waterless wire cutting processing on a shale sample after coring to obtain a plunger sample in an original state and a crushed sample; performing two-dimensional T1-T2 nuclear magnetic resonance testing on the plunger sample in the original state and the oil-water recovery state respectively; identifying the oil signal amplitude of the plunger sample in the original state and the oil-water recovery state according to the T1-T2 nuclear magnetic resonance spectrum, and determining the light hydrocarbon recovery coefficient; performing conventional pyrolysis and multi-temperature step pyrolysis on the crushed sample respectively to obtain conventional pyrolysis parameters and multi-temperature step pyrolysis parameters, and establishing a first equation, the first equation characterizing the relationship between the oil content in the original state and the conventional pyrolysis parameters; establishing a second equation according to the light hydrocarbon recovery coefficient and the first equation, the second equation characterizing the relationship between the oil content in the oil-water recovery state and the conventional pyrolysis parameters; and evaluating the oil content of the shale oil reservoir in the oil-water recovery state according to the second equation and the measured conventional pyrolysis parameters.

Description

Technical Field

[0001] The present invention relates to the technical field of shale oil exploration and development, and in particular to a method for evaluating the oil content of a shale oil reservoir. Background Art

[0002] Accurate evaluation of in-situ fluids in deep-sea and terrestrial shale oil reservoirs is the key to optimizing shale oil sweet spots. Conventional pyrolysis technology is widely used because of its simple operation, short time consumption and low cost. Conventional pyrolysis mainly obtains free hydrocarbon S1 by heating the sample to 300°C, and further heats it to 600°C to obtain thermally released hydrocarbon S2, among which S1 is often used as the main parameter to characterize the shale oil content. However, conventional pyrolysis technology has some problems, which leads to its underestimation of the actual content of shale oil.

[0003] First, due to the adsorption and swelling of organic matter and the high boiling point of some liquid hydrocarbons, conventional pyrolysis S1 will ignore these liquid hydrocarbons, resulting in an underestimation of heavy hydrocarbons. Second, the core will lose a large amount of light hydrocarbons and fluids such as water during the extraction, transportation and placement of the core from the wellbore, further exacerbating the underestimation of the amount of residual hydrocarbons in the rock by S1.

[0004] In order to solve this problem, the existing technology has proposed a method of heavy hydrocarbon compensation, such as compensation through the difference in conventional pyrolysis S2 before and after oil washing or combined with multi-stage pyrolysis. However, the most critical thing is to determine the amount of light hydrocarbon loss, which is still a challenge. The methods used by predecessors include hydrocarbon generation dynamics and pressure-maintained coring and liquid nitrogen freezing of samples, but these methods all have some problems. The hydrocarbon generation dynamics method is affected by the difference between laboratory conditions and in-situ formation conditions, and it is difficult to accurately restore the hydrocarbon generation characteristics of the in-situ formation. The pressure-maintained coring plus liquid nitrogen freezing operation process is complicated and costly, and the core will still lose fluid during extraction and migration. In addition, conventional or multi-stage pyrolysis technology cannot obtain shale pore water information, and therefore ignores the impact of pore water on shale oil occurrence. Summary of the invention

[0005] The present disclosure provides a method for evaluating the oil content of a shale oil reservoir, so as to at least solve the above technical problems existing in the prior art.

[0006] According to a first aspect of the present disclosure, a method for evaluating the oil content of a shale oil reservoir is provided, the method comprising:

[0007] The shale samples were processed by waterless wire cutting after coring to obtain the original plunger samples and crushed samples;

[0008] Two-dimensional T1-T2 NMR testing was performed on the original plunger sample;

[0009] Performing oil-water recovery treatment on the plunger sample in the original state, and performing a two-dimensional T1-T2 nuclear magnetic resonance test on the plunger sample in the oil-water recovery state;

[0010] According to the T1-T2 nuclear magnetic resonance spectrum, the oil signal amplitude of the plunger sample in the original state and the oil-water recovery state is identified to determine the light hydrocarbon recovery coefficient;

[0011] The crushed sample is subjected to conventional pyrolysis and multi-temperature-step pyrolysis respectively to obtain conventional pyrolysis parameters and multi-temperature-step pyrolysis parameters;

[0012] According to conventional pyrolysis parameters and multi-temperature-stage pyrolysis parameters, a first equation is established, wherein the first equation characterizes the relationship between the original state oil content and the conventional pyrolysis parameters;

[0013] According to the light hydrocarbon recovery coefficient and the first equation, a second equation is established, wherein the second equation characterizes the relationship between the oil content in the oil-water recovery state and conventional pyrolysis parameters;

[0014] According to the second equation and the measured conventional pyrolysis parameters, the oil content of the shale oil reservoir in the oil-water recovery state is evaluated.

[0015] Furthermore, the oil-water recovery process of the plunger sample in the original state includes:

[0016] placing the original plunger sample in a high humidity environment produced by a saturated potassium sulfate salt solution until the mass of the plunger sample remains unchanged;

[0017] After the plunger sample is evacuated, it is pressurized and saturated with n-dodecane so that the residual pores are filled with n-dodecane, thereby obtaining a plunger sample in an oil-water recovery state.

[0018] Furthermore, the oil signal amplitude of the plunger sample in the original state and the oil-water recovery state is identified according to the T1-T2 nuclear magnetic resonance spectrum, and the light hydrocarbon recovery coefficient is determined, including:

[0019] The signal amplitude of the total oil in the original state and the oil-water recovery state in the T1-T2 NMR spectrum is identified, and the signal amplitude ratio m of the total oil in the original state and the oil-water recovery state is determined as:

[0020] ;

[0021] According to the signal amplitude ratio of total oil in the original state and the oil-water recovery state, the light hydrocarbon recovery coefficient n is determined as:

[0022] ;

[0023] in, is the total oil signal amplitude of the sample in the oil-water recovery state; is the total oil signal amplitude of the plunger sample of the sample in the original state.

[0024] Furthermore, the conventional pyrolysis parameters of the crushed sample include: free hydrocarbons and thermally released hydrocarbons The multi-temperature pyrolysis parameters of the crushed sample include: free oil + , adsorption oil ; The first equation is established according to the conventional pyrolysis parameters and the multi-temperature pyrolysis parameters, including:

[0025] According to free hydrocarbon and free oil , the calculation formula of free oil content in the original state is established as:

[0026] ;

[0027] According to adsorption oil Pyrohydrocarbon , the calculation formula of adsorbed oil content in the original state is established as:

[0028] ;

[0029] The calculation formula for the total oil content of the crushed sample of the sample in the original state is established as follows:

[0030] , we get the first equation;

[0031] in, is the free oil content of the sample in its original state; is the adsorbed oil content of the sample in the original state; is the total oil content of the sample in its original state; a and b are constants.

[0032] Furthermore, the second equation is established according to the light hydrocarbon recovery coefficient and the first equation, including:

[0033] According to the light hydrocarbon recovery coefficient and the first equation, the light hydrocarbon recovery amount is determined for:

[0034] ;

[0035] A second equation is established based on the light hydrocarbon recovery amount.

[0036] Furthermore, if the free oil content of shale in the oil-water recovery state is evaluated, the second equation is established according to the light hydrocarbon recovery amount, including:

[0037] Establish the following equation:

[0038] ;

[0039] in, It is the free oil content of shale under oil-water recovery state.

[0040] Furthermore, if the total oil content of shale in the oil-water recovery state is evaluated, the second equation is established according to the light hydrocarbon recovery amount, including:

[0041] Establish the following equation:

[0042] ;

[0043] in, is the total oil content of shale under oil-water recovery state.

[0044] Furthermore, the evaluation of the shale free oil content under the oil-water recovery state further includes:

[0045] According to the second equation and conventional pyrolysis parameters , create a third-party program:

[0046] ;

[0047] Among them, the for The correction factor of .

[0048] Furthermore, a is between 1 and 1.3, and b is between 0.4 and 0.7.

[0049] Furthermore, the two-dimensional T1-T2 nuclear magnetic resonance test uses a saturation recovery pulse sequence.

[0050] The present invention discloses a method for evaluating the oil content of a shale oil reservoir. The method comprises the following steps: subjecting a shale sample to waterless wire cutting after coring, subjecting a plunger sample in an original state to a first two-dimensional T1-T2 nuclear magnetic resonance test, subsequently subjecting the plunger sample to an oil-water recovery treatment to recover the lost shale pore water and light hydrocarbons, and subjecting the plunger sample in an oil-water recovered state to a second two-dimensional T1-T2 nuclear magnetic resonance test; determining a light hydrocarbon recovery coefficient based on the T1-T2 nuclear magnetic resonance spectrum; subjecting the original pulverized sample to conventional pyrolysis and multi-temperature-step pyrolysis, respectively, to obtain conventional pyrolysis parameters and multi-temperature-step pyrolysis parameters, and establishing a first equation; and evaluating the oil content of the shale oil reservoir in an oil-water recovered state based on the light hydrocarbon recovery coefficient and the first equation; and based on the second equation and the measured conventional pyrolysis parameters. The evaluation method disclosed in the present invention combines two-dimensional T1-T2 nuclear magnetic resonance testing, oil-water recovery treatment, conventional pyrolysis and multi-stage pyrolysis technology, aiming to overcome the problems of conventional technology in underestimating light hydrocarbons and heavy hydrocarbons and ignoring the impact of pore water on shale oil storage when evaluating shale oil content.

[0051] Through the method for evaluating the oil content of shale oil reservoirs disclosed in the present invention, in the field of deep-sea oil and gas field exploration and development, the evaluation of oil and gas layers can be carried out, and the in-situ oil content of deep-sea oil and gas can be accurately evaluated by combining well logging or seismic prediction of organic parameters. In the field of shale oil and gas exploration and development technology, it can also be extended to major oil fields, making full use of a large amount of measured pyrolysis data to carry out in-situ oil content evaluation of shale oil and gas. Therefore, the present invention has broad market prospects and application needs.

[0052] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The above and other objects, features and advantages of the exemplary embodiments of the present disclosure will become readily understood by reading the detailed description below with reference to the accompanying drawings. In the accompanying drawings, several embodiments of the present disclosure are shown in an exemplary and non-limiting manner, in which:

[0054] In the drawings, the same or corresponding reference numerals represent the same or corresponding parts.

[0055] Figure 1 A schematic diagram of the implementation process of the method for evaluating the oil content of a shale oil reservoir according to an embodiment of the present disclosure is shown;

[0056] Figure 2a A schematic diagram of the T1-T2 nuclear magnetic resonance spectrum of the plunger sample in the original state of the embodiment of the present disclosure is shown;

[0057] Figure 2b A schematic diagram of the T1-T2 nuclear magnetic resonance spectrum of a plunger sample in an oil-water recovery state according to an embodiment of the present disclosure is shown;

[0058] Figure 3 A schematic diagram showing the signal amplitude correlation of total oil in the original state and the oil-water recovery state according to an embodiment of the present disclosure;

[0059] Figure 4 A schematic diagram showing the oil content of samples in conventional pyrolysis, multi-stage pyrolysis and nuclear magnetic resonance testing in an embodiment of the present disclosure is shown;

[0060] Figure 5a The multi-stage pyrolysis parameters of the disclosed embodiment are shown. Compared with conventional pyrolysis parameters Schematic diagram of correlation;

[0061] Figure 5b The multi-stage pyrolysis parameters of the disclosed embodiment are shown. Compared with conventional pyrolysis parameters Schematic diagram of correlation;

[0062] Figure 6 The free oil content of shale in the oil-water recovery state of the embodiment of the present disclosure and the conventional pyrolysis parameters are shown. Schematic diagram of the correlation;

[0063] Figure 7 A schematic diagram showing the results of a hydrocarbon generation thermal simulation experiment corresponding to a specific embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0064] In order to make the purpose, features, and advantages of the present disclosure more obvious and easy to understand, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present disclosure.

[0065] The present disclosure provides a method for evaluating the oil content of a shale oil reservoir. Figure 1 As shown, the method includes:

[0066] Step 101: After coring, the shale sample is subjected to waterless wire cutting processing to obtain an original plunger sample and a crushed sample.

[0067] In this example, after coring, the shale samples were processed into cylindrical plug samples using waterless wire cutting for nuclear magnetic resonance testing and oil-water recovery treatment; the remaining rock chips at both ends after cutting were crushed to obtain crushed samples for conventional pyrolysis and multi-temperature-step pyrolysis.

[0068] Step 102: Perform a two-dimensional T1-T2 nuclear magnetic resonance test on the plunger sample in the original state.

[0069] In this example, the two-dimensional T1-T2 NMR test refers to obtaining the T1 and T2 relaxation time data of the sample in one test, and displaying these data in the form of a two-dimensional spectrum. The two-dimensional T1-T2 NMR test is performed on the original plunger sample using a nuclear magnetic resonance instrument to obtain the T1-T2 NMR spectrum of the original plunger sample.

[0070] Step 103: Perform oil-water recovery treatment on the plunger sample in the original state, and perform a two-dimensional T1-T2 nuclear magnetic resonance test on the plunger sample in the oil-water recovery state.

[0071] In this example, the completed 2D T1-T2 NMR test was subjected to an oil and water recovery treatment to recover the lost shale pore water and light hydrocarbon fraction.

[0072] Specifically, the original state (AR) plug sample is placed in a high humidity environment created by a saturated potassium sulfate salt solution until the mass of the plug sample remains unchanged to recover the lost shale pore water; then the plug sample is evacuated and pressurized with saturated n-dodecane so that the residual pores are filled with n-dodecane to recover the lost light hydrocarbons, thereby obtaining a plug sample in an oil-water restored state (WOR) to approximately represent the in-situ state.

[0073] Then, the two-dimensional T1-T2 nuclear magnetic resonance test is performed on the plunger sample in the oil-water recovery state again, and the process is consistent with step 102 and will not be repeated here, thereby obtaining the T1-T2 nuclear magnetic resonance spectrum of the plunger sample in the oil-water recovery state.

[0074] Step 104: Based on the T1-T2 NMR spectrum, the oil signal amplitude of the plunger sample in the original state and the oil-water recovery state is identified to determine the light hydrocarbon recovery coefficient.

[0075] In this example, the signal amplitude of the total oil in the original state and the oil-water recovery state in the T1-T2 NMR spectrum is identified, and the signal amplitude ratio m of the total oil in the original state and the oil-water recovery state is determined as:

[0076] (one)

[0077] According to the signal amplitude ratio of total oil in the original state and the oil-water recovery state, the light hydrocarbon recovery coefficient n is determined as:

[0078] (two)

[0079] in, is the total oil signal amplitude of the sample under oil-water recovery state; is the total oil signal amplitude of the plunger sample in the original state.

[0080] The light hydrocarbon recovery coefficient n represents the correlation between the total oil signal amplitude of the sample in the original state and the oil-water recovery state. n will change due to factors such as region, formation and shale maturity.

[0081] Step 105: performing conventional pyrolysis and multi-temperature-step pyrolysis on the crushed sample respectively to obtain conventional pyrolysis parameters and multi-temperature-step pyrolysis parameters.

[0082] In this example, conventional pyrolysis parameters for the pulverized sample included: free hydrocarbons and thermally released hydrocarbons ; Multi-stage pyrolysis parameters of crushed samples include: free oil + , adsorption oil .

[0083] In conventional pyrolysis experiments, free hydrocarbons are first determined , and then the thermal release of hydrocarbons was determined after heating The multi-step pyrolysis was performed with four temperature gradients to measure (representing the light oil portion), (representing the medium oil portion), (representing the heavy oil fraction) and (Representing the kerogen part).

[0084] Among them, the light oil part and represents the medium oil fraction The sum is the free oil, which represents the heavy oil portion. To adsorb oil, conventional pyrolysis The medium oil components between 300℃ and 350℃ are usually ignored. + ) and conventional pyrolysis The relationship between the staged thermal desorption of oil Conventional pyrolysis relationship.

[0085] Step 106: According to conventional pyrolysis parameters and multi-temperature-step pyrolysis parameters, a first equation is established, wherein the first equation characterizes the relationship between the original state oil content and the conventional pyrolysis parameters.

[0086] In this example, based on the free hydrocarbon and free oil , the calculation formula of free oil content in the original state is established as:

[0087] (three)

[0088] According to adsorption oil Pyrohydrocarbon , the calculation formula of adsorbed oil content in the original state is established as:

[0089] (Four)

[0090] According to the above formulas (iii) and (iv), the calculation formula for the total oil content of the crushed sample in the original state is:

[0091] (five)

[0092] Formula (5) is the first equation; where, is the free oil content of the sample in its original state, mg / g; is the adsorbed oil content of the sample in the original state, mg / g; is the total oil content of the sample in its original state, mg / g; a and b are constants, which vary among shale oil reservoirs in different regions and strata. According to the conventional pyrolysis parameters and multi-temperature-step pyrolysis parameters measured in the above experiment, a is between 1 and 1.3, and b is between 0.4 and 0.7 after constructing a linear equation.

[0093] Step 107: A second equation is established based on the light hydrocarbon recovery coefficient and the first equation, wherein the second equation characterizes the relationship between the oil content in the oil-water recovery state and conventional pyrolysis parameters.

[0094] In this example, the light hydrocarbon recovery amount is determined based on the light hydrocarbon recovery coefficient and the first equation. The calculation equation is:

[0095] (six)

[0096] Subsequently, a second equation is established based on the light hydrocarbon recovery amount. In view of different types of oil content evaluation methods in shale, the present disclosure provides two types of oil content evaluation methods, specifically:

[0097] If the free oil content of shale in the oil-water recovery state is evaluated, the following second equation is established based on the light hydrocarbon recovery amount:

[0098] (seven)

[0099] in, The free oil content of shale in the oil-water recovery state, mg / g. and thermally released hydrocarbons When evaluating the free oil content of shale, and Substitute it into formula (VII) and calculate it.

[0100] If the total oil content of shale in the oil-water recovery state is evaluated, the following second equation is established based on the light hydrocarbon recovery amount:

[0101] (eight)

[0102] in, is the total oil content of shale in the oil-water recovery state, mg / g. and thermally released hydrocarbons When evaluating the total oil content of shale, and Substitute it into formula (8) and calculate it.

[0103] In addition, the shale oil content is mainly evaluated by conventional pyrolysis parameters of the samples. To characterize, when you want to quickly estimate the free oil content of shale, you can use the above-established formula (VII) and the conventional pyrolysis parameters measured in step 105 , establish the following third-party program:

[0104] (Nine)

[0105] in, for By establishing the correction factor of shale free oil in water recovery state and conventional pyrolysis parameters Relevance, according to Calculate the free oil content of shale.

[0106] Step 108: Based on the second equation and the measured conventional pyrolysis parameters, the oil content of the shale oil reservoir in the oil-water recovery state is evaluated.

[0107] The present invention provides a method for evaluating the oil content of a shale oil reservoir. The method comprises the following steps: subjecting a shale sample to waterless wire cutting after coring, subjecting a plunger sample in an original state to a first two-dimensional T1-T2 nuclear magnetic resonance test, subsequently subjecting the plunger sample to oil-water recovery treatment to recover the lost shale pore water and light hydrocarbons, and subjecting the plunger sample in an oil-water recovered state to a second two-dimensional T1-T2 nuclear magnetic resonance test; determining a light hydrocarbon recovery coefficient based on the T1-T2 nuclear magnetic resonance spectrum; subjecting the original pulverized sample to conventional pyrolysis and multi-temperature-step pyrolysis, respectively, to obtain conventional pyrolysis parameters and multi-temperature-step pyrolysis parameters, and establishing a first equation; and evaluating the oil content of the shale oil reservoir in an oil-water recovered state based on the light hydrocarbon recovery coefficient and the first equation; and based on the second equation and the measured conventional pyrolysis parameters. The evaluation method disclosed in the present invention combines two-dimensional T1-T2 nuclear magnetic resonance testing, oil-water recovery treatment, conventional pyrolysis and multi-stage pyrolysis technology, aiming to overcome the problems of conventional pyrolysis technology underestimating light hydrocarbons and heavy hydrocarbons and ignoring the impact of pore water on shale oil storage when evaluating shale oil content.

[0108] In the field of deep-sea oil and gas field exploration and development, the evaluation of oil and gas layers can be carried out, and the in-situ oil content of deep-sea oil and gas can be accurately evaluated by combining well logging or seismic prediction of organic parameters. In the field of shale oil and gas exploration and development technology, it can also be extended to major oil fields, making full use of a large amount of measured pyrolysis data to carry out in-situ oil content evaluation of shale oil and gas. Therefore, the evaluation method of the oil content of shale oil reservoirs disclosed in the present invention has broad market prospects and application needs.

[0109] In one example, a two-dimensional T1-T2 nuclear magnetic resonance test uses a saturation recovery pulse sequence, and the test parameters include: a waiting time of 3000 ms, a stacking number of 32 times, a number of echoes of 4096, and an echo interval of 0.07 ms.

[0110] Saturation-Recovery-Carr-Purcell-Meiboom-Gill (SR-CPMG) is a method for measuring T1 and T2 relaxation times. It combines saturation recovery technology and CPMG echo sequence to simultaneously obtain T1 and T2 information of the sample. Waiting time refers to the time interval from the end of the previous pulse sequence to the start of the next pulse sequence. In the SR-CPMG sequence, the waiting time is usually used to restore the magnetization vector in the sample to the initial state to ensure the accuracy of the measurement. 3000ms can ensure that the sample reaches a fully relaxed state before measurement. The number of stacking times refers to the number of times each data point is measured. By measuring multiple times and taking the average value, the signal-to-noise ratio and accuracy of the data can be improved. 32 stacking times can reduce the test time while ensuring data quality. The number of echoes refers to the number of echoes generated in the SR-CPMG sequence. Each echo corresponds to a specific relaxation time point. Therefore, the more echoes there are, the wider the relaxation time range that can be measured. 4096 echoes can provide high-resolution relaxation time distribution information. The echo interval refers to the time interval between two adjacent echoes, which determines the minimum value of the relaxation time range that can be measured. The echo interval of 0.07ms can balance the measurement range and noise level.

[0111] This disclosure will describe in detail the method for evaluating the oil content of the shale oil reservoir through the detection and evaluation of the oil content of the shale oil reservoir in the lower Teng section of the Cretaceous System in the Anan Sag of the Erlian Basin.

[0112] Step 1: The sampled samples are processed into cylindrical plunger samples with a diameter of 25 mm and a length of 30 mm using waterless wire cutting. The remaining rock chips at both ends after cutting are crushed to a size larger than 100 mesh to obtain a crushed sample.

[0113] Step 2: Nuclear Magnetic Resonance (NMR) test The original plunger sample was subjected to a two-dimensional T1-T2 NMR test using a MesoMR12-060H-I NMR instrument. The measured resonance frequency was about 12 MHz and the magnetic field strength was 0.3 T ± 0.05 T. The following results were obtained: Figure 2a T1-T2 NMR spectrum shown.

[0114] Step 3: Place the original plug sample in a high humidity environment created by a saturated potassium sulfate solution (the corresponding saturated vapor pressure is 98% at room temperature 296K) until the mass of the plug sample remains unchanged; then evacuate the plug sample for 1 hour and pressurize it with 10 MPa saturated n-dodecane for 24 hours, so that the residual pores are filled with n-dodecane to obtain a plug sample in an oil-water recovery state. The two-dimensional T1-T2 nuclear magnetic resonance test is performed on the plug sample in an oil-water recovery state again, and the following is obtained: Figure 2b T1-T2 NMR spectrum shown.

[0115] Among them, A is pore bound water, B is adsorbed oil, C is bound oil, D is movable oil, E is movable water, F is clay bound water, G is asphaltene, H is kerogen, and the sum of B+C+D is the total oil signal.

[0116] Step 4: By comparison Figure 2a and Figure 2b It can be seen that after oil and water recovery, the pore bound water in area A, the bound oil in area C, and the movable oil in area D all increased significantly, indicating that the pore water and oil in the original shale were lost. The oil signals in areas B, C, and D of the shale in the original state and oil and water recovery state were quantitatively extracted to determine the amplitude ratio m of the total oil signal in the oil and water recovery state and the light hydrocarbon recovery coefficient n.

[0117] Therefore, according to the signal amplitude of total oil in the original state and oil-water recovery state, combined with Figure 4 The oil content of the oil-water restored state and the original state in the NMR test is shown as well as Figure 3 The linear equation representing the correlation between the total oil signal in the oil-water recovery state and the original state is used to determine the signal amplitude ratio m of the total oil in the original state and the oil-water recovery state:

[0118] (ten)

[0119] According to the signal amplitude ratio of total oil in the original state and the oil-water recovery state, the light hydrocarbon recovery coefficient n is determined as:

[0120] (eleven)

[0121] Step 5: Use French Rock-Eval VI rock pyrolysis instrument to perform conventional pyrolysis and multi-step pyrolysis on the crushed sample to obtain conventional pyrolysis parameters and multi-step pyrolysis parameters. Figure 4 The oil content of different types of oil in conventional pyrolysis and multi-stage pyrolysis is shown, specifically:

[0122] The experimental process of conventional pyrolysis is as follows: free hydrocarbons are determined at a constant temperature of 300 °C for 3 min. Then the temperature was raised to 600℃ at a rate of 25℃ / min to obtain the thermally released hydrocarbons. .

[0123] Four temperature gradients were set for multi-step pyrolysis. The experimental process was as follows: the temperature was kept constant at 200 °C for 1 min. (representing the light oil part), then the temperature was raised to 350℃ at 25℃ / min and kept at this temperature for 1 min. (representing the medium oil part), then increase the temperature to 450℃ at 25℃ / min and keep it at this temperature for 1 min. (representing the heavy oil part), and finally heated to 600℃ at 25℃ / min for testing (Representing the kerogen part).

[0124] Step 6: Based on free hydrocarbons and free oil + ,like Figure 5a The correlation between the amount of multi-temperature pyrolysis oil and the amount of conventional pyrolysis oil in the original state is shown, and the calculation formula for the free oil content in the original state is established as follows:

[0125] (twelve)

[0126] According to adsorption oil Pyrohydrocarbon ,like Figure 5b As shown, the calculation formula for the adsorbed oil content in the original state is established as:

[0127] (Thirteen)

[0128] According to the above formulas (XII) and (XIII), the calculation formula for the total oil content of the crushed sample in the original state is established as follows:

[0129] (fourteen)

[0130] Step 7: According to the light hydrocarbon recovery coefficient and formula (XIV), the calculation equation for the light hydrocarbon recovery amount is determined as:

[0131] (fifteen)

[0132] This example provides two types of oil content evaluation methods, specifically:

[0133] If the free oil content of shale in the oil-water recovery state is evaluated, the following second equation is established based on the light hydrocarbon recovery amount:

[0134] (sixteen)

[0135] If the total oil content of shale in the oil-water recovery state is evaluated, the following second equation is established based on the light hydrocarbon recovery amount:

[0136] (Seventeen)

[0137] In addition, if the evaluation of shale free oil content under oil-water recovery state also includes: according to formula (16) and conventional pyrolysis parameters , establish as Figure 6The free oil content of shale and conventional pyrolysis parameters are shown The correlation of , we get the following equation:

[0138] (eighteen)

[0139] Step 8: Based on the above formulas (16), (17) and (18), as well as the measured conventional pyrolysis parameters, the oil content of the shale oil reservoir in the lower Teng section of the Cretaceous System in the Anan Sag of the Erlian Basin is evaluated.

[0140] In order to verify the accuracy of this method, low-maturity shale samples from the Anan Sag were selected to carry out thermal simulation experiments on hydrocarbon generation. Referring to the industry standard SY / T 7035-2016 "Golden Tube Thermal Simulation Experimental Method for Hydrocarbon Generation", the Golden Tube High-Pressure Thermal Simulation System-120 was used to carry out the test. The heating program was: from room temperature to 200°C in 1h, and then to 600°C at a heating rate of 2°C / h. Figure 7 This is the result of the thermal simulation experiment of hydrocarbon generation in the depression. According to the maturity Ro=0.67% corresponding to the formation depth, the light hydrocarbon loss accounts for 30% of the total residual oil, that is, the light hydrocarbon correction coefficient of the thermal simulation experiment is 0.3, which is very close to the light hydrocarbon recovery coefficient (0.3396) (Formula 11) obtained by nuclear magnetic fluid recovery, indicating the reliability of the light hydrocarbon correction results disclosed in the present invention.

[0141] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps recorded in this disclosure can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solutions disclosed in this disclosure can be achieved, and this document does not limit this.

[0142] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present disclosure, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0143] The above is only a specific embodiment of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A method for evaluating the oil content of a shale oil reservoir, characterized in that: The method comprises: The shale samples were processed by waterless wire cutting after coring to obtain the original plunger samples and crushed samples; Two-dimensional T1-T2 NMR testing was performed on the original plunger sample; Performing oil-water recovery treatment on the plunger sample in the original state, and performing a two-dimensional T1-T2 nuclear magnetic resonance test on the plunger sample in the oil-water recovery state; According to the T1-T2 nuclear magnetic resonance spectrum, the oil signal amplitude of the plunger sample in the original state and the oil-water recovery state is identified to determine the light hydrocarbon recovery coefficient; The crushed sample is subjected to conventional pyrolysis and multi-temperature-step pyrolysis respectively to obtain conventional pyrolysis parameters and multi-temperature-step pyrolysis parameters; According to conventional pyrolysis parameters and multi-temperature pyrolysis parameters, a first equation is established, wherein the first equation characterizes the relationship between the original state oil content and the conventional pyrolysis parameters, including: Conventional pyrolysis parameters of the crushed sample include: free hydrocarbons and thermally released hydrocarbons The multi-temperature pyrolysis parameters of the crushed sample include: free oil + , adsorption oil ; The first equation is established according to the conventional pyrolysis parameters and the multi-temperature pyrolysis parameters, including: According to free hydrocarbon and free oil + , the calculation formula of free oil content in the original state is established as: ； According to adsorption oil Pyrohydrocarbon , the calculation formula for the adsorbed oil content in the original state is established as: ； The calculation formula for the total oil content of the crushed sample of the sample in the original state is established as follows: , we get the first equation; in, is the free oil content of the sample in its original state; is the adsorbed oil content of the sample in the original state; is the total oil content of the sample in its original state; a is between 1 and 1.3, and b is between 0.4 and 0.7; According to the light hydrocarbon recovery coefficient and the first equation, a second equation is established, wherein the second equation characterizes the relationship between the oil content in the oil-water recovery state and conventional pyrolysis parameters; According to the second equation and the measured conventional pyrolysis parameters, the oil content of the shale oil reservoir in the oil-water recovery state is evaluated.

2. The method according to claim 1, characterized in that The oil-water recovery process of the plunger sample in the original state comprises: placing the original plunger sample in a high humidity environment produced by a saturated potassium sulfate salt solution until the mass of the plunger sample remains unchanged; After the plunger sample is evacuated, it is pressurized and saturated with n-dodecane so that the residual pores are filled with n-dodecane, thereby obtaining a plunger sample in an oil-water recovery state.

3. The method according to claim 1, characterized in that The method of identifying the oil signal amplitude of the plunger sample in the original state and the oil-water recovery state according to the T1-T2 nuclear magnetic resonance spectrum and determining the light hydrocarbon recovery coefficient includes: The signal amplitude of the total oil in the original state and the oil-water recovery state in the T1-T2 NMR spectrum is identified, and the signal amplitude ratio m of the total oil in the original state and the oil-water recovery state is determined as: ； According to the signal amplitude ratio of total oil in the original state and the oil-water recovery state, the light hydrocarbon recovery coefficient n is determined as: ； in, is the total oil signal amplitude of the sample in the oil-water recovery state; is the total oil signal amplitude of the plunger sample of the sample in the original state.

4. The method according to claim 1, characterized in that The second equation is established according to the light hydrocarbon recovery coefficient and the first equation, comprising: According to the light hydrocarbon recovery coefficient and the first equation, the light hydrocarbon recovery amount is determined for: ； A second equation is established based on the light hydrocarbon recovery amount.

5. The method according to claim 4, characterized in that If the free oil content of shale in the oil-water recovery state is evaluated, the second equation is established according to the light hydrocarbon recovery amount, including: Establish the following equation: ； in, It is the free oil content of shale under oil-water recovery state.

6. The method according to claim 4, characterized in that If the total oil content of shale in the oil-water recovery state is evaluated, the second equation is established according to the light hydrocarbon recovery amount, including: Establish the following equation: ； in, is the total oil content of shale under oil-water recovery state.

7. The method according to claim 5, characterized in that The evaluation of the shale free oil content under the oil-water recovery state also includes: According to the second equation and conventional pyrolysis parameters , create a third-party program: ； Among them, the for The correction factor of .

8. The method according to claim 1, characterized in that The two-dimensional T1-T2 nuclear magnetic resonance test adopts a saturation recovery pulse sequence.

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