Method for determining temperature thresholds of free oil and adsorbed oil in conventional pyrolysis experiments

Abstract

The present invention discloses a method for determining the temperature thresholds of free oil and adsorbed oil in a conventional pyrolysis experiment, which is characterized by including: obtaining a set of electrical signal data that changes with time, the free oil electrical signal value, and the adsorbed oil electrical signal value of a sample in the conventional pyrolysis experiment; by accumulating the electrical signal data set, using the free oil electrical signal value and the adsorbed oil electrical signal value as boundary values, determining the temperature thresholds of free oil and adsorbed oil of the sample in the conventional pyrolysis experiment; solving the problem that the existing conventional shale pyrolysis experiment can only distinguish the temperature thresholds of pyrolysis hydrocarbon S1 and cracked hydrocarbon S2, and cannot determine the temperature thresholds of free oil and adsorbed oil in the pyrolysis hydrocarbon, so the free oil and adsorbed oil in the conventional shale pyrolysis experiment cannot be effectively divided.

Description

Technical Field

[0001] The present invention relates to the conventional pyrolysis experiment of shale, specifically a method for determining the temperature thresholds of free oil and adsorbed oil in the conventional pyrolysis experiment, providing a basic guarantee for accurately determining the contents of free oil and adsorbed oil in shale. Background Art

[0002] As a major type of unconventional oil and gas resources, shale oil has huge resource potential, and the recoverable resource volume is 160×10 8 t, which is expected to solve the huge gap in current energy demand. However, according to practice, the exploitation effect of shale oil is not good, and there is often a phenomenon of high initial production but rapid decline. The reason for this phenomenon is the lack of understanding of the occurrence characteristics of shale oil in the exploitation area and the unclear content of the flowable part in shale oil.

[0003] In the shale layer rich in organic matter, the easily extractable crude oil that has been generated is called free oil. Free oil is the main target of current shale oil exploitation, and its content determines the exploitation value. In addition to free oil, there is also a type of oil called adsorbed oil that is difficult to flow and extract after generation. Adsorbed oil is usually adsorbed on the surface of kerogen or the inner surface of rock and has a strong adsorption force. Free oil and adsorbed oil are collectively called residual oil, and both belong to the type of pyrolysis hydrocarbons. There are significant differences in their properties, and reasonable methods are needed to distinguish them.

[0004] In the rock samples taken from underground drilling cores, there are both flowable free oil and difficult-to-flow adsorbed oil. How to correctly distinguish free oil and adsorbed oil in shale cores and determine their respective contents of free oil and adsorbed oil has become the key research content of shale oil resource evaluation.

[0005] Since the invention of the rock pyrolysis experiment instrument in the late 1970s of the last century, the rock pyrolysis experiment method has always been an important method for domestic and foreign scholars to evaluate the organic matter abundance, type and maturity of source rocks. The conventional shale pyrolysis experiment method is to place the shale sample in a pyrolysis furnace, first keep it at a constant temperature of 300°C for 3 minutes, collect the products and conduct quantitative analysis; then heat the sample to 650°C at a certain heating rate (25°C / min), and record the signal value of the volatilization of hydrocarbon substances in the sample over time ( Figure 1 ).

[0006] In the conventional pyrolysis experiment of shale, the product collected during the constant temperature process at 300°C is pyrolysis hydrocarbon S1, and the product collected from heating from 300°C to 650°C is the hydrocarbon substances generated by pyrolysis, that is, pyrolysis hydrocarbon S2.

[0007] Conventional pyrolysis experiments can only distinguish the temperature thresholds of pyrolysis hydrocarbon S1 and cracking hydrocarbon S2, and cannot determine the temperature thresholds of free oil and adsorbed oil in pyrolysis hydrocarbon. Therefore, it is impossible to effectively distinguish free oil and adsorbed oil. In addition, according to previous studies, there are errors in the contents of pyrolysis hydrocarbon S1 and cracking hydrocarbon S2 obtained by conventional pyrolysis experiments. The main reason is that the adsorbed oil contains more heavy components and is difficult to volatilize during the constant temperature process at 300 °C, resulting in the measured content of pyrolysis hydrocarbon S1 being smaller than the actual value and the content of cracking hydrocarbon S2 being larger than the actual value. Summary of the Invention

[0008] In view of this, the present invention provides a method for determining the temperature thresholds of free oil and adsorbed oil in conventional shale pyrolysis experiments, which solves the problem that existing conventional shale pyrolysis experiments can only distinguish the temperature thresholds of pyrolysis hydrocarbon S1 and cracking hydrocarbon S2, and cannot determine the temperature thresholds of free oil and adsorbed oil in pyrolysis hydrocarbon. Therefore, it is impossible to effectively distinguish free oil and adsorbed oil in conventional shale pyrolysis experiments.

[0009] To achieve the above-mentioned invention purpose, a method for determining the temperature thresholds of free oil and adsorbed oil in a conventional pyrolysis experiment is characterized by including:

[0010] Obtaining a set of electrical signal data that changes with time, the free oil electrical signal value, and the adsorbed oil electrical signal value of the sample in the conventional pyrolysis experiment;

[0011] By accumulating the electrical signal data set and using the free oil electrical signal value and the adsorbed oil electrical signal value as the boundary values, determining the temperature thresholds of free oil and adsorbed oil of the sample in the conventional pyrolysis experiment.

[0012] Further, the method for obtaining the free oil electrical signal value and the adsorbed oil electrical signal value of the sample in the conventional pyrolysis experiment is as follows:

[0013] Obtaining the free oil content and the adsorbed oil content of the sample;

[0014] Determining the signal conversion coefficient of the conventional pyrolysis experiment;

[0015] Using the free oil content and the adsorbed oil content, and combining the signal conversion coefficient to calculate the free oil electrical signal value and the adsorbed oil electrical signal value of the sample in the conventional pyrolysis experiment;

[0016] Further, the free oil content and the adsorbed oil content of the sample are obtained through a solvent extraction experiment.

[0017] Further, the calculation formulas for the free oil electrical signal value and the adsorbed oil electrical signal value of the sample in the conventional pyrolysis experiment are respectively:

[0018]

[0019]

[0020] Wherein: surf S 1a : Free oil electrical signal value (unit: μV); surf S 1b : Adsorbed oil electrical signal value (unit: μV); S 1a : Free oil content (unit: mg / g); S 1b : Adsorbed oil content (unit: mg / g); m1: Sample mass (unit: mg).

[0021] Furthermore, the method for determining the signal conversion coefficient of the conventional pyrolysis experiment is as follows:

[0022] Use a rock pyrolyzer to conduct a conventional pyrolysis experiment on the experimental standard sample of the rock pyrolyzer;

[0023] Obtain the cracked hydrocarbon content of the standard sample and the electrical signal value in the S2 region of the cracked hydrocarbon of the standard sample through the conventional pyrolysis experiment;

[0024] Use the following calculation formula to obtain the signal conversion coefficient:

[0025]

[0026] In the formula: Signal conversion coefficient K FID (unit: mg / μV); Mass of the standard sample std weight (unit: g); Cracked hydrocarbon content of the standard sample STD S2 (unit: mg / g); Electrical signal value in the S2 region of the cracked hydrocarbon of the standard sample surf S2 (unit: μV).

[0027] The present invention has the following beneficial effects:

[0028] The method of the present invention uses the same shale sample, based on the experimental results of solvent extraction, and based on the experimental principle of the Rock-Eval rock pyrolyzer, the temperature thresholds of free oil and adsorbed oil in the conventional pyrolysis experiment of the shale sample can be obtained by calculation, solving the problem that the existing conventional shale pyrolysis experiment can only distinguish the temperature thresholds of pyrolysis hydrocarbon S1 and cracked hydrocarbon S2, and cannot determine the temperature thresholds of free oil and adsorbed oil in the pyrolysis hydrocarbon, so the problem of effectively dividing free oil and adsorbed oil in the conventional shale pyrolysis experiment cannot be solved. Description of the Drawings

[0029] Through the following description of the embodiments of the present invention with reference to the drawings, the above and other objects, features and advantages of the present invention will become clearer. In the drawings:

[0030] Figure 1 is the conventional shale pyrolysis experiment spectrum of the background art of the present invention;

[0031] Figure 2is the technical flow chart of the method of the present invention;

[0032] Figure 3 is the relationship diagram between the electrical signal values of free oil and adsorbed oil and the data set in the conventional pyrolysis experiment of the embodiment of the present invention;

[0033] Figure 4 is the schematic diagram for determining free oil and adsorbed oil by the temperature thresholds T1 and T2 in the embodiment of the present invention;

[0034] Figure 5 is the correlation of the calculated temperature thresholds of free oil and adsorbed oil in the embodiment of the present invention. Detailed implementation manners

[0035] The present invention will be described below based on embodiments. However, it should be noted that the present invention is not limited to these embodiments. In the following detailed description of the present invention, some specific details are described in detail. However, those skilled in the art can also fully understand the present invention for the parts not described in detail.

[0036] In addition, those of ordinary skill in the art should understand that the provided drawings are only for illustrating the purpose, features and advantages of the present invention, and the drawings are not actually drawn to scale.

[0037] At the same time, unless the context clearly requires, the words such as "including" and "comprising" in the whole specification and claims should be interpreted as the meaning of inclusion rather than the meaning of exclusion or exhaustion; that is, the meaning of "including but not limited to".

[0038] Figure 2 is the technical flow chart of the method of the present invention; combined with Figure 2 as shown, the overall steps of the technical solution of the present invention are as follows:

[0039] 1. Determine the signal conversion coefficient K of the conventional pyrolysis experiment by using the rock pyrolysis experiment standard sample FID ;

[0040] 2. Take the shale sample with mass m1 for the conventional pyrolysis experiment to obtain the data set {x i} of the electrical signal values changing with time;

[0041] 3. Take the same shale sample with mass m2 as in step 2 for the solvent extraction experiment to obtain the free oil and adsorbed oil contents S 1a and S 1b ;

[0042] 4. Use the free oil and adsorbed oil contents S 1a and S 1b obtained in step 3, combine the sample mass m1 in step 2 and K in step 1 FIDCalculate the electrical signal values of free oil and adsorbed oil, surf S, of the sample in the conventional pyrolysis experiment 1a 、surf S 1b ;

[0043] 5. By accumulating the signal values that change with time obtained from the conventional pyrolysis experiment of the shale sample in step 2, and using surf S 1a and surf S 1b in step 4 as the demarcation values, determine the temperature thresholds T1 and T2 of free oil and adsorbed oil of the shale sample in the conventional pyrolysis experiment.

[0044] Furthermore, each step of the solution is described in detail.

[0045] Step 1: Calculate the signal conversion coefficient K FID

[0046] The signal conversion coefficient K FID The English name is the answer coefficient of FID, which is an important parameter for the Rock-Eval pyrolyzer to convert the hydrogen ion signal in the sample into an electrical signal in the pyrolysis experiment. The signal conversion coefficient K FID The parameter is obtained through a pyrolysis experiment with an experimental standard sample. The rock pyrolysis experimental standard sample is a special experimental sample with a definite pyrolysis hydrocarbon S2 value, so it is often used as the standard for instrument calibration.

[0047] Specifically, use the experimental standard sample to conduct a conventional pyrolysis experiment to obtain the signal conversion coefficient K in the conventional pyrolysis experiment FID .

[0048] Related parameters and calculation process involved: The signal conversion coefficient K FID (unit: mg / μV) in the conventional pyrolysis experiment is related to the mass of the standard sample, std weight (unit: g), the pyrolysis hydrocarbon content of the standard sample, STD S2 (unit: mg / g), and the electrical signal value of the pyrolysis hydrocarbon S2 region of the standard sample, surf S2 (unit: μV).

[0049] The calculation formula is:[[]]

[0050]

[0051] Step 2: Obtain the data set {x i}

[0052] Obtain the data set of the sample in the conventional pyrolysis experiment, including the temperature value and the electrical signal value that change with time. This obtaining method is a conventional technical means of the conventional pyrolysis experiment.

[0053] Specifically, a shale sample with a mass of m1 (unit: g) is selected for a conventional pyrolysis experiment. After the experiment, a data set {x i} can be exported from the computer, including the temperature T (unit: °C) and the electrical signal value surf S (unit: μV) that vary with time t (unit: s), that is, each time point corresponds to a temperature value and an electrical signal value.

[0054] Step 3: Determine the free oil and adsorbed oil content S 1a 、S 1b

[0055] Specifically, take the same shale sample with a mass of m2 (unit: g) as in Step 2. Through a solvent extraction experiment, the free oil and adsorbed oil content S 1a 、S 1b (unit: mg / g) of the sample can be obtained.

[0056] This solvent extraction experiment is also a conventional technical means in the field. The principle of the specific solvent extraction experiment is as follows: Since the components of adsorbed oil and free oil are different, the free state is generally mainly composed of light components, while the components of the adsorbed state are mainly large polar molecules or heteroatom compounds. Therefore, different polar organic solvent combinations + core treatment can be used to gradually extract and separate them to obtain the extracts in the adsorbed state and the free state respectively.

[0057] Step 4: Calculate the signal values surf S of free oil and adsorbed oil in the conventional shale pyrolysis experiment 1a 、surf S 1b

[0058] Since the same shale sample is used in Step 2 and Step 3, they have the same free oil and adsorbed oil content. Therefore, according to the free oil and adsorbed oil content of the shale sample obtained in Step 3, the electrical signal values of free oil and adsorbed oil in the conventional pyrolysis experiment can be calculated.

[0059] Specific relevant parameters and calculation formulas: The signal values surf S 1a 、surf S 1b (unit: μV) of free oil and adsorbed oil in the shale sample in the conventional pyrolysis experiment are related to the signal conversion coefficient K FID (unit: mg / μV) calculated in Step 1, the mass m1 (unit: mg) of the shale sample taken in Step 2, and the free oil and adsorbed oil content S 1a 、S 1b (unit: mg / g) in Step 3.

[0060] The calculation formula is:

[0061]

[0062]

[0063] Step 5: Calculate the temperature thresholds T1 and T2 of free oil and adsorbed oil in the conventional shale pyrolysis experiment

[0064] It should be noted that in Step 2, the electrical signal values varying with time obtained from the conventional pyrolysis experiment of the shale sample belong to a data set, and the electrical signal values of free oil and adsorbed oil in the conventional pyrolysis experiment calculated in Step 4 are the cumulative values in a certain interval of this data set, just like the relationship between the mother set and the subset in mathematics (as Figure 3 shown).

[0065] Therefore, through the conventional shale pyrolysis experiment on the shale sample in Step 2, the electrical signal value x i (i = 1, 2, 3,..., n) varying with time can be obtained, and then by the way of cumulative summation starting from x1, using the signal values surf S 1a and surf S 1b of free oil and adsorbed oil calculated in Step 4 as the boundary values, the temperature thresholds T1 and T2 of free oil and adsorbed oil in the conventional shale pyrolysis experiment of the sample are finally determined.

[0066] Specific relevant parameters and calculation process: The temperature thresholds T1 and T2 of free oil and adsorbed oil in the conventional shale pyrolysis experiment are related to the signal values surf S 1a and surf S 1b (unit: μV) of free oil and adsorbed oil calculated in Step 3 of the conventional shale pyrolysis experiment and the electrical signal value x i (i = 1, 2, 3,..., n) (unit: μV) varying with time obtained from the conventional shale pyrolysis experiment.

[0067] ① Temperature threshold T1 of free oil

[0068] Let two signal cumulative values SUM 游离1 and SUM 游离2 (similar to x and y in mathematics):

[0069]

[0070]

[0071] Starting from n = 1, is SUM 游离1 ≤ surf S 1a常规 ≤ SUM 游离2 , if so, then x1 is the signal value of free oil in the conventional shale pyrolysis experiment, if not, then n = n + 1, and then re - accumulate. Until at a certain n value, SUM 游离1 ≤ surf S1a常规 ≤SUM 游离2 If so, the signal values x1, x2, x3, …, x n are the signal value ranges of free oil in the conventional shale pyrolysis experiment, and the temperature corresponding to the signal value x n is the temperature threshold T1 of free oil in the conventional shale pyrolysis experiment.

[0072] ② Adsorbed oil temperature threshold T2

[0073] For the x in ① above n The remaining signal values that change with time are x n+i (i = 1, 2, 3, …, k). Similarly, set two signal cumulative values SUM 吸附1 and SUM 吸附2 :

[0074]

[0075]

[0076] Starting from k = 1, is SUM 吸附1 ≤surf S 1b常规 ≤SUM 吸附2 ? If so, then x n+1 is the signal value of adsorbed oil in the conventional shale pyrolysis experiment. If not, then k = k + 1, and then re-accumulate. Until at a certain k value, SUM 吸附1 ≤surf S 1b常规 ≤SUM 吸附2 ? If so, then the signal values x n+1 、x n+2 、x n+3 、…、x n+k are the signal value ranges of adsorbed oil in the conventional shale pyrolysis experiment, and the temperature corresponding to the signal value x n+k is the temperature threshold T2 of adsorbed oil in the conventional shale pyrolysis experiment.

[0077] Through the experiments and calculations in the above 5 steps, the temperature thresholds of free oil and adsorbed oil in the conventional pyrolysis experiment of the sample are determined, so as to distinguish the ranges of free oil and adsorbed oil in the conventional shale pyrolysis experiment, as specifically shown in Figure 4 shown.

[0078] Furthermore, taking the shale sample from the Qingshankou Formation in the Gulong Sag of the Songliao Basin as an example, the sample was taken from Well Nan 256-Xie 206, and multiple groups of experiments were carried out. The hydrocarbon content of the sample and the calculated temperature thresholds T1 and T2 obtained from the experiments are shown in Table 1.

[0079] Table 1 Statistical table of sample experiment calculation results

[0080]

[0081] To eliminate errors in this experiment, a total of 6 groups of experiments were conducted. For the 6 groups of conventional shale pyrolysis experiments obtained through calculation, the temperature thresholds T1 and T2 of free oil and adsorbed oil fluctuated within ±5°C. The average temperature thresholds T1 and T2 of free oil and adsorbed oil were 370°C and 468°C respectively, and they had a good correlation, with a correlation coefficient R 2 = 0.92 (as Figure 5 shown). This indicates that the technical solution is effective and feasible, and can reasonably divide free oil and adsorbed oil in conventional shale pyrolysis experiments.

[0082] From the above description, it can be seen that according to the method of the present invention, for existing shale samples, the temperature thresholds T1 and T2 of free oil and adsorbed oil in their conventional pyrolysis experiments can be determined through experiments and calculations to further reasonably divide free oil and adsorbed oil in conventional shale pyrolysis experiments.

[0083] The above-described embodiments are only for expressing the implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications, equivalent replacements, improvements, etc. can be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims

1. A method for determining the temperature thresholds of free oil and adsorbed oil in a conventional pyrolysis experiment, characterized in that, Including: Obtaining a set of electrical signal data that changes with time, a free oil electrical signal value, and an adsorbed oil electrical signal value of a sample in a conventional pyrolysis experiment; By accumulating the electrical signal data set and using the free oil electrical signal value and the adsorbed oil electrical signal value as boundary values, determining the temperature thresholds of free oil and adsorbed oil of the sample in the conventional pyrolysis experiment; The method for obtaining the free oil electrical signal value and the adsorbed oil electrical signal value of a sample in a conventional pyrolysis experiment is: Obtaining the free oil content and the adsorbed oil content of the sample; Determining the signal conversion coefficient of the conventional pyrolysis experiment; Using the free oil content and the adsorbed oil content and combining with the signal conversion coefficient to calculate the free oil electrical signal value and the adsorbed oil electrical signal value of the sample in the conventional pyrolysis experiment; The calculation formulas for calculating the free oil electrical signal value and the adsorbed oil electrical signal value of the sample in the conventional pyrolysis experiment are respectively: ； ； Among them: surf S 1a : Free oil electrical signal value, unit: μV; surf S 1b : Adsorbed oil electrical signal value, unit: μV; S 1a : Free oil content, unit: mg / g; S 1b : Adsorbed oil content, unit: mg / g; m1: Sample mass, unit: mg; The signal conversion coefficient is obtained by using the following calculation formula: ； In the formula: signal conversion coefficient K FID , unit: mg / μV; mass of the standard sample std weight, unit: g; pyrolysis hydrocarbon content of the standard sample STD S 2, unit: mg / g; pyrolysis hydrocarbon of the standard sample S electric signal value surf in area 2 S 2, unit: μV.

2. The method for determining the temperature thresholds of free oil and adsorbed oil in a conventional pyrolysis experiment according to claim 1, characterized in that: Obtaining the free oil content and the adsorbed oil content of the sample through a solvent extraction experiment.

3. The method for determining the temperature thresholds of free oil and adsorbed oil in the conventional pyrolysis experiment according to claim 1 or 2, characterized in that The method for determining the signal conversion coefficient of a conventional pyrolysis experiment is: Using a rock pyrolyzer to conduct a conventional pyrolysis experiment on the experimental standard sample of the rock pyrolyzer; Obtaining the cracked hydrocarbon content of the standard sample and the electrical signal value in the S2 region of the cracked hydrocarbon of the standard sample through the conventional pyrolysis experiment.

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