A method for correcting and restoring the original hydrocarbon content of shale

Abstract

The present invention provides a method for correcting and recovering the original hydrocarbon content of mud shale, comprising: step 1: establishing the relationship between conventional liquid nitrogen pyrolysis and staged liquid nitrogen pyrolysis, and performing heavy hydrocarbon correction on S1 of conventional liquid nitrogen frozen mud shale pyrolysis; step 2: performing heavy hydrocarbon correction on S1 of placed mud shale pyrolysis; step 3: performing light hydrocarbon correction on S1 of placed mud shale pyrolysis; and step 4: establishing light and heavy hydrocarbon correction models for S1 of liquid nitrogen frozen mud shale pyrolysis and S1 of placed mud shale pyrolysis, as well as evaluation models for adsorbed oil, free oil, and movable oil. This application enables the pyrolysis parameter S1 of mud shale wells to objectively characterize the oil content of mud shale, saving experimental test and analysis time and cost. The credibility of shale oil resource potential evaluation results is increased by an average of 35 percentage points, the accuracy of implementing "sweet spots" is increased by an average of 60 percentage points, and work efficiency is increased by an average of 50 percentage points.

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 correcting and recovering the original hydrocarbon content of mud shale. Background Art

[0002] The pyrolysis parameter (hereafter referred to as S1) is a key parameter for evaluating shale oil resources and their sweet spots. Evaluating resources and identifying these sweet spots are crucial for shale oil exploration and development. Because pyrolysis experiments are simple and easy to perform, and their results are informative, S1 is often used in shale oil resource potential assessments as an indicator of the free oil content in shale. Therefore, the ability of S1 to objectively characterize shale oil content directly impacts the credibility of shale oil resource potential assessment results.

[0003] In the actual experimental analysis process, due to the influence of core storage conditions, experimental test analysis technology, and kerogen adsorption and swelling, S1 has the loss of light hydrocarbons and heavy hydrocarbons, resulting in the measured S1 being lower than the in-situ shale oil underground oil content, making it difficult to directly reflect the in-situ oil content of underground shale oil. Therefore, it is necessary to perform light hydrocarbon and heavy hydrocarbon correction on the pyrolysis S1. Among them, the lost light hydrocarbon component ( <C 14 ) has low density, low viscosity, and good fluidity, making it the most recoverable portion of shale oil resources. Therefore, performing light hydrocarbon correction has a significant impact on shale oil resource evaluation, especially the evaluation of recoverable resources. In contrast, the lost components of heavy hydrocarbons in S1 have higher density, higher viscosity, and poorer fluidity, making them difficult to develop. However, they are also an important component of shale resources. With the maturity of shale oil development technology and the application of new development technologies (such as in-situ reforming), these resources still have development potential. Therefore, correcting and recovering light and heavy hydrocarbons in the pyrolysis parameter S1, and reasonably and objectively estimating the total shale oil resource, are of great significance to the long-term exploration and development of shale oil.

[0004] Li Jinbu et al. published “Correction of light and heavy hydrocarbons of pyrolysis parameter S1 and its significance: A case study of E2s in Damintun Sag, Bohai Bay Basin” in Oil & Gas Geology, Vol. 37, No. 4, 2016. 4(2) The article "Taking the shale section as an example" records that when using the pyrolysis parameter S1 (free hydrocarbon content) to evaluate shale resources, there is a phenomenon of light and heavy hydrocarbon loss, resulting in an underestimation of the calculated resource amount. Regarding the loss of heavy hydrocarbons, the S2 (pyrolysis content) obtained from the pyrolysis experiments before and after the extraction of the same shale sample was compared. The difference between the two is the heavy hydrocarbon content lost by S1. Regarding the loss of light hydrocarbons, based on the Rock-Eval and PY-GC of immature shale samples and the gold tube experiment on crude oil, the kinetic parameters were obtained according to the principles of chemical kinetics, and the C generated at different maturity levels was calculated using the EasyRo model.6-13 with C 13+ The ratio of C 6-13 with C 13+ The light hydrocarbon recovery is performed on the basis of S1 after heavy hydrocarbon recovery. Using S1 before and after light hydrocarbon and heavy hydrocarbon recovery as mud shale resource evaluation parameters will result in significant differences in resource calculation. 4(2) For example, the resource volume before recovery is 2.26×10 8 t, and the resource volume after recovery is 6.47×10 8 t, and the resource volume after recovery is 2.86 times that before recovery. Therefore, when using S1 to evaluate shale resources, the recovery of light and heavy hydrocarbons in S1 is of great significance.

[0005] Zhang Linye et al. published an article titled "Existence of recoverable oil and gas resources in the Paleogene shale of the Dongying Sag" in the Journal of Natural Gas Geoscience, Vol. 23, No. 1, 2012. They reported that the shale of the Shahejie Formation of the Paleogene in the Dongying Sag was systematically studied using geochemical, rock mineralogy, well logging and mud logging data. They concluded that the shale of the lower third and upper fourth sub-members of the Paleogene Shahejie Formation in the Dongying Sag is thick. The organic matter is rich in abundance, good in type, and has a wide range of maturity distribution. It is comparable to the geological and geochemical parameters of shale gas systems discovered in North America, and has the material basis for the formation of shale gas: the whole-rock mineral composition of the mud shale in the lower 3rd and upper 4th members of the Shahejie Formation in the Dongying Depression has high quartz and carbonate contents, and the clay mineral content is less than 50%. It has certain brittle characteristics and is generally characterized by the development of microcracks, which is conducive to the extraction of shale oil and gas. The investigation of gas logging data of the Paleogene lacustrine mud shale in the Dongying Depression found that the gas logging of the two sets of exploration wells drilled to the lower 3rd and upper 4th members of the Shahejie Formation showed high abnormalities. Well kicks and well leakage occurred frequently during drilling, indicating the presence of gas. The abundance of light hydrocarbons (C1-C4) in the top gas of the two sets of mud shale increases with increasing burial depth. The heavy hydrocarbon / light hydrocarbon ratio is low at a depth of 3400m, generally below 0.15. Combined with the study of the gas-oil ratio of the two sets of mud shales, it is believed that Exploration of mud shales in the Dongying Depression should adopt a strategy of concurrent exploration for oil and gas. Exploration of mud shales should primarily focus on oil reservoirs at depths shallower than 3,400 meters, while shale gas exploration should be conducted at depths deeper than 3,400 meters. Research indicates that recoverable oil and gas resources exist within the Paleogene mud shales of the Dongying Depression, making it a new area worthy of attention and risky exploration.

[0006] The OSI (S1 / TOC) method proposed by Jarive (2012) is currently the most commonly used method for evaluating adsorbed oil in shale. However, different recovery and verification methods for shale reservoirs in different regions will produce different results, affecting the exploration and development of shale oil in the region. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for calibrating and recovering the original hydrocarbon content of mud shale, establish the relationship between conventional liquid nitrogen pyrolysis and liquid nitrogen staged pyrolysis, and establish a liquid nitrogen frozen mud shale S1 heavy hydrocarbon correction model and a staged pyrolysis model based on conventional and staged pyrolysis of liquid nitrogen frozen samples and conventional and staged pyrolysis of stored samples, respectively. This allows the shale oil well pyrolysis parameter S1 to objectively characterize the oil content of the mud shale, saving experimental test and analysis time and cost. The credibility of shale oil resource potential evaluation results is increased by an average of 35 percentage points, the accuracy of "sweet spot" is increased by an average of 60 percentage points, and work efficiency is increased by an average of 50 percentage points.

[0008] The present application provides a method for correcting and restoring the original hydrocarbon content of shale, comprising:

[0009] Step 1: Establish the relationship between conventional liquid nitrogen pyrolysis and staged liquid nitrogen pyrolysis, and perform S1 heavy hydrocarbon correction for conventional liquid nitrogen frozen shale pyrolysis;

[0010] Step 2: Place the shale pyrolysis S1 heavy hydrocarbon correction;

[0011] Step 3: Place shale pyrolysis S1 light hydrocarbon correction;

[0012] Step 4: Establish the light and heavy hydrocarbon calibration model of liquid nitrogen frozen shale pyrolysis S1 and placed shale pyrolysis S1 and the evaluation model of adsorbed oil, free oil and movable oil.

[0013] Wherein: Step 1: Establish the relationship between liquid nitrogen conventional pyrolysis and liquid nitrogen staged pyrolysis, and perform S1 heavy hydrocarbon correction for liquid nitrogen frozen shale conventional pyrolysis, including:

[0014] The S1 correction coefficient of liquid nitrogen frozen shale can be established by comparing conventional pyrolysis and staged pyrolysis.

[0015] Wherein: Step 1: Comparing conventional pyrolysis and staged pyrolysis to establish the liquid nitrogen frozen shale S1 correction coefficient, including:

[0016] Analyze the distribution of adsorbed oil and free oil, establish a conventional thermal decomposition adsorbed oil and free oil evaluation model, and determine the liquid nitrogen conventional pyrolysis S 1L Free oil correction factor, that is, the total S1 content of staged pyrolysis and the S1 content of conventional pyrolysis 1L ratio.

[0017] Wherein: Step 2: Place shale pyrolysis S1 heavy hydrocarbon correction, including:

[0018] The loss of samples mainly results in the loss of light hydrocarbons, with no loss of heavy hydrocarbons. The correction coefficient ranges from 0.9 to 1.1.

[0019] Wherein: Step 2: Place shale pyrolysis S1 heavy hydrocarbon correction, including:

[0020] The heavy hydrocarbon correction coefficient of the placed sample is consistent with that of the liquid nitrogen frozen sample, and the heavy hydrocarbon correction coefficient is 0.82. The heavy hydrocarbon correction amount is 0.82S2, that is, 0.82S 2L =0.82S2.

[0021] Wherein: Step 3: Place shale pyrolysis S1 light hydrocarbon correction, including:

[0022] The S obtained by conventional pyrolysis of liquid nitrogen frozen samples 1L Contains all components of light hydrocarbons, and its ratio to the conventional pyrolysis S1 of the placed sample is the light hydrocarbon correction factor;

[0023] The light hydrocarbon correction factor is 1.73, that is, S 1L =1.73S1, so the total oil content of the shale sample after light and heavy hydrocarbon correction S TO For: S TO =S 1L +k2S 2L =1.73S1+0.82S2.

[0024] Among them: Place the sample and pyrolyze the total S1 content:

[0025] S 1m =1.33S 1L =1.33*1.73S1=2.3S1

[0026] Place sample for thermal desorption of oil volume: S a =0.82S 2L -0.33S 1L =0.82S2-0.33*1.73S1=0.82S2-0.57S1.

[0027] Among them: Step 4: Establishing the light and heavy hydrocarbon calibration model of liquid nitrogen frozen shale pyrolysis S1 and placed shale pyrolysis S1 and the adsorbed oil, free oil and movable oil evaluation model, including:

[0028] Model 1: Liquid nitrogen frozen shale sample

[0029] Total oil content: S TOL =S 1L +0.82S 2L

[0030] Free oil: S 1mL =1.33S 1L

[0031] Oil adsorption capacity: S aL =0.82S 2L-0.33S 1L

[0032] Model 2: Placing shale samples

[0033] Total oil content: S TO =1.73S1+0.82S2

[0034] Free oil: S 1m = = 2.3S1

[0035] Adsorption oil amount: S a =0.82S2-0.57S1

[0036] Movable oil volume: S ao =0.78S1.

[0037] The method for correcting and restoring the original hydrocarbon content of shale in the embodiment of the present application has the following beneficial effects:

[0038] The method for correcting and restoring the original hydrocarbon content of mud shale in the present application includes: Step 1: establishing the relationship between conventional liquid nitrogen pyrolysis and staged liquid nitrogen pyrolysis, and performing heavy hydrocarbon correction of S1 of conventional liquid nitrogen frozen mud shale pyrolysis; Step 2: heavy hydrocarbon correction of S1 of placed mud shale pyrolysis; Step 3: light hydrocarbon correction of S1 of placed mud shale pyrolysis; Step 4: establishing light and heavy hydrocarbon correction models of liquid nitrogen frozen mud shale pyrolysis S1 and placed mud shale pyrolysis S1, as well as evaluation models of adsorbed oil, free oil and movable oil. The present application enables the pyrolysis parameter S1 of mud shale wells to objectively characterize the oil content of mud shale, saving experimental test analysis time and cost, and improving the credibility of shale oil resource potential evaluation results by an average of 35 percentage points, the accuracy of implementing the "sweet spot" by an average of 60 percentage points, and the average improvement of work efficiency by 50 percentage points. (Place mud shale refers to mud shale that has been placed in the air for 15-180 days. This data is obtained from many years of experimental research.) BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 : Schematic diagram of segmented pyrolysis and conventional pyrolysis analysis of liquid nitrogen frozen samples;

[0040] Figure 2 : Schematic diagram of total organic matter content of liquid nitrogen frozen samples during conventional pyrolysis and staged pyrolysis;

[0041] Figure 3 : Schematic diagram of total oil content of conventional pyrolysis and staged pyrolysis of liquid nitrogen frozen samples;

[0042] Figure 4 : Schematic diagram of correction factors for heavy hydrocarbons in conventional pyrolysis of liquid nitrogen freezing;

[0043] Figure 5 : Schematic diagram of the correction factor for free oil in conventional pyrolysis of liquid nitrogen freezing;

[0044] Figure 6 : Schematic diagram of the calculation of conventional pyrolysis under liquid nitrogen freezing and the measured adsorbed / free oil amount under segmented pyrolysis;

[0045] Figure 7 : Schematic diagram of sample placement for segmented pyrolysis and conventional pyrolysis analysis;

[0046] Figure 8 : Schematic diagram of liquid nitrogen freezing and conventional pyrolysis of samples S2;

[0047] Figure 9 : Schematic diagram of light hydrocarbon correction coefficient for conventional pyrolysis of sample placement;

[0048] Figure 10 : Schematic diagram of movable oil coefficient for sample placement. DETAILED DESCRIPTION

[0049] The present application will be further described below with reference to the accompanying drawings and embodiments.

[0050] In the following description, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The following description provides multiple embodiments of the present invention, and different embodiments may be interchanged or combined. Therefore, this application is considered to include all possible combinations of the same and / or different embodiments described. Thus, if one embodiment includes features A, B, and C, and another embodiment includes features B and D, then this application should also be considered to include embodiments that include one or more of A, B, C, and D in all other possible combinations, even if such embodiments are not explicitly described in the following text.

[0051] The following description provides examples and does not limit the scope, applicability, or examples set forth in the claims. Changes may be made to the function and arrangement of the elements described without departing from the scope of this application. Various examples may appropriately omit, replace, or add various processes or components. For example, the described method may be performed in an order different from the order described, and various steps may be added, omitted, or combined. Furthermore, features described in some examples may be combined in other examples.

[0052] S1 is defined as the free hydrocarbon or residual hydrocarbon content in the rock, which is the content of hydrocarbons that have been generated and remain in the rock. Currently, S1 is obtained by rock pyrolysis instrument (Rock-Eval) test analysis. It is the thermally released hydrocarbons when the rock sample is heated to no more than 33°C. It mainly includes C 7-33 However, in current pyrolysis experiments, rock samples are usually placed in the core library for a long time, and the light hydrocarbon part (C 14-) has been basically lost. The S2 obtained by rock pyrolysis analysis is called cracked hydrocarbons, which are hydrocarbon products produced by cracking organic matter when the rock sample is heated to above 300°C. However, there are actually some liquid hydrocarbons in S2. Due to the adsorption of organic matter or inorganic minerals, and the high molecular weight, these hydrocarbons are difficult to be thermally released before 300°C. Therefore, the S1 directly tested by the rock pyrolysis experiment usually only represents a part of the residual hydrocarbons, lacking both the light hydrocarbons that were lost before the test and the heavy hydrocarbons that have not been thermally released before 300°C due to the high molecular weight and adsorption. Therefore, directly using rock pyrolysis S1 for shale resource evaluation will cause large experimental errors, and it is necessary to use liquid nitrogen to freeze the segmented pyrolysis S 1-1 With S 1-2 The sum of the light hydrocarbons and heavy hydrocarbons of the pyrolysis parameter S1 is used to recover the light hydrocarbons and compensate for the heavy hydrocarbons. This not only recovers the light hydrocarbon losses, but also tests the medium-light hydrocarbons released at 350°C, while also compensating for the organic products cracked by S2. In this application, placing shale, placing samples, and placing shale samples have the same meaning, and liquid nitrogen freezing shale, frozen samples, and frozen shale samples have the same meaning.

[0053] Example 1

[0054] In existing research, domestic and foreign scholars have ignored the process from core removal to experimental testing, failed to use liquid nitrogen to freeze the lost part, and failed to combine conventional pyrolysis and staged pyrolysis to compare the similarities and differences of hydrocarbons produced at different temperatures.

[0055] The method for correcting and recovering the original hydrocarbon content of mud shale in the present application includes: step 1: establishing the relationship between liquid nitrogen conventional pyrolysis and liquid nitrogen staged pyrolysis, and performing heavy hydrocarbon correction of liquid nitrogen frozen mud shale conventional pyrolysis S1; step 2: heavy hydrocarbon correction of placed mud shale conventional pyrolysis S1; step 3: light hydrocarbon correction of placed mud shale pyrolysis S1; step 4: establishing light and heavy hydrocarbon correction models for liquid nitrogen frozen mud shale conventional pyrolysis S1 and placed mud shale conventional pyrolysis S1, as well as adsorbed oil, free oil and movable oil evaluation models.

[0056] The method for calibrating and recovering the original hydrocarbon content of shale in this application is based on conventional and staged pyrolysis of liquid nitrogen-frozen samples and conventional and staged pyrolysis of stored samples. A calibration model for S1 heavy hydrocarbons from liquid nitrogen-frozen shale pyrolysis and a calibration model for S1 heavy and light hydrocarbons from stored shale pyrolysis are established, respectively. In this application, the formula obtained after calibration is also the recovery formula.

[0057] In this patent, the relationship between conventional pyrolysis and segmented pyrolysis is established. On this basis, liquid nitrogen samples and placed samples are analyzed. This technology can comprehensively cover different types of samples, and the inference process is rigorous and reliable.

[0058] Example 2

[0059] The SX84 well is taken as an example for detailed explanation.

[0060] Segmented pyrolysis is an effective method for analyzing the occurrence state of shale. It divides the organic matter into Figure 1 Part 4: Light oil (S 1-1 ), medium oil (S 1-2 ), heavy hydrocarbons (S 2-1 ) and kerogen (S 2-2 ), where S 1-1 Light hydrocarbons, S 1-2 Light-medium hydrocarbons, S 1-1 and S 1-2 Called free hydrocarbons / free oil, S 2-1 Conventional pyrolysis separates rock organic matter into two parts: retained hydrocarbons (S1) and pyrolyzed hydrocarbons (S2), of which S2 is called adsorbed hydrocarbons.

[0061] ① Total organic matter content (S TmL ): The sum of all organic matter in the rock sample after segmented pyrolysis. TmL =S 1-1L +S 1-2L +S 2-1L +S 2-2L

[0062] ② Place the sample and pyrolyze the total organic matter content (S Tm ): The sum of all organic matter in the rock sample after segmented pyrolysis. Tm =S 1-1 +S 1-2 +S 2-1 +S 2-2 (Place sample S 1-1 and / or S 1-2 After the loss, it will decrease or become 0)

[0063] ③ Total oil content of liquid nitrogen frozen sample by segmented pyrolysis (S TOmL ): Total oil content of segmented pyrolysis test. S TOmL =S 1-1L +S 1-2L +S 2-1L (Place sample S 1-1L and / or S 1-2L After the loss, it will decrease or become 0)

[0064] ④ Place the sample and pyrolyze the total oil content (S TO ): Total oil content of segmented pyrolysis test.

[0065] S TOm=S 1-1 +S 1-2 +S 2-1 (Place sample S 1-1 and / or S 1-2 After the loss, it will decrease or become 0)

[0066] ⑤ Liquid nitrogen frozen sample segmented pyrolysis total S1 content (S 1mL ): Segmented pyrolysis S 1-1L With S 1-2L The sum of the free oil content is S 1mL =S 1-1L +S 1-2L

[0067] ⑥ Place the sample and pyrolyze the total S1 content (S 1m ): Segmented pyrolysis S 1-1 With S 1-2 The sum of the two is the free oil amount. 1m =S 1-1 +S 1-2 (Place sample S 1-1 and / or S 1-2 After the loss, it will decrease or become 0)

[0068] ⑦ Liquid nitrogen frozen sample segmented thermal desorption oil amount: S 2-2L

[0069] ⑧Constant pyrolysis of liquid nitrogen frozen samples Total organic matter content (S TL ): The sum of all organic matter in conventional pyrolysis. TL =S 1L +S 2L

[0070] ⑨ Place the sample for conventional pyrolysis to determine the total organic matter content (S T ): The sum of all organic matter in conventional pyrolysis. T =S1+S2

[0071] ⑩Total oil content of liquid nitrogen frozen sample by conventional pyrolysis: S TOL

[0072] Place the sample for conventional pyrolysis. Total oil content: S TO

[0073] Movable oil volume for placing sample: S ao

[0074] Liquid nitrogen frozen sample thermal desorption oil volume: S aL

[0075] Place sample for thermal desorption of oil volume: S a

[0076] Light hydrocarbon compensation coefficient: k1

[0077] Heavy hydrocarbon compensation coefficient: k2

[0078] Step 1: Establish the relationship between liquid nitrogen conventional pyrolysis and liquid nitrogen staged pyrolysis, and perform S1 heavy hydrocarbon correction for liquid nitrogen frozen shale conventional pyrolysis.

[0079] The S1 correction coefficient of liquid nitrogen frozen shale can be established by comparing conventional pyrolysis and staged pyrolysis.

[0080] Total organic matter content (S TmL ) and the total organic matter content of conventional pyrolysis (S TL ) (liquid nitrogen frozen samples) both reflect the oil content of all organic matter in the shale, and the two should be in good consistency. Figure 2 The total of medium-stage pyrolysis has an excellent positive correlation with the total of conventional pyrolysis, y = 1.0117x, and the correlation coefficient R 2 =0.9546, slope 1.0117, the correlation coefficient and slope are close to 1, indicating good consistency between the two, that is, S TmL =S TL =S 1-1L +S 1-2L +S 2-1L +S 2-2L =S 1L +S 2L , both reflect the total organic matter content.

[0081] Figure 3 Total oil content of medium-stage pyrolysis (S TOmL ) and the total oil content of conventional pyrolysis (S TOL ) content has excellent consistency, y = 1.0138x, correlation coefficient R 2 =0.9363, slope 1.0138 (correlation coefficient and slope are close to 1), the two are consistent, that is, S TomL =S TOL =S 1-1L +S 1-2L +S 2-1L , indicating that conventional pyrolysis S 2L With staged pyrolysis S 2-2L The difference is the conventional heavy hydrocarbon compensation, that is, S TOL =S 1L +S 2L -S 2-2L .

[0082] Figure 4 Compensation amount of medium and heavy hydrocarbons (S 2L -S 2-2L ) and conventional pyrolysis S 2L Has an excellent linear relationship, y = 0.8172x, correlation coefficient R 2=0.9418, slope 0.8172, heavy hydrocarbon compensation (S 2L -S 2-2L ) is about the conventional pyrolysis S 2L 0.82 times of that, that is, the heavy hydrocarbon compensation amount k2 is about 0.82S 2L , thus determining that the heavy hydrocarbon compensation coefficient k2 of the shale in the study area is about 0.82, that is, S TOL =S 1L +0.82S 2L .

[0083] Further:

[0084] Analyze the distribution of adsorbed oil and free oil, establish a conventional thermal decomposition adsorbed oil and free oil evaluation model, and determine the liquid nitrogen conventional pyrolysis S 1L Free oil correction factor, i.e. total S1 content of staged pyrolysis (S 1mL )(Free oil content S 1-1L +S 1-2L ) and conventional pyrolysis S 1L The ratio of Figure 5 Total S1 content (S 1mL ) and conventional pyrolysis S 1L Excellent consistency, y = 1.3271x, correlation coefficient R 2 =0.8784, the slope is about 1.33, that is, the total S1 content (S 1mL )(Free oil content S 1-1 +S 1-2 ) is about the conventional pyrolysis S 1L 1.33 times, that is, S 1mL =1.33S 1L Total oil content S TOL Subtract free oil 1.33S 1L That is the amount of thermal desorption oil S aL :S 1L +0.82S 2L -1.33S 1L , that is, S aL =0.82S 2L -0.33S 1L .

[0085] Figure 6 In the conventional pyrolysis of liquid nitrogen freezing, the free oil is calculated as 1.33S 1L and adsorbed oil 0.82S 2L -0.33S 1L Free oil S measured by liquid nitrogen freezing and staged pyrolysis 1mL =S 1-1L +S 1-2L and adsorbed oil S 2-2LThere is good consistency. The free oil calculated by conventional pyrolysis of liquid nitrogen freezing is consistent with the free oil measured by segmented pyrolysis of liquid nitrogen freezing ( Figure 6 -left figure), y = 0.9728x, correlation coefficient R 2 =0.906, the slope is about 1, the adsorption oil calculated by conventional pyrolysis of liquid nitrogen freezing and the adsorption oil measured by staged pyrolysis of liquid nitrogen freezing ( Figure 6 -right figure), y = 1.0172x, correlation coefficient R 2 =0.7901, the slope is about 1.

[0086] The results show that the established liquid nitrogen freezing conventional pyrolysis model for evaluating free oil and adsorbed oil can effectively characterize the adsorption and free oil content of shale.

[0087] Step 2: Place shale pyrolysis S1 heavy hydrocarbon correction

[0088] Figure 7 Compared with the liquid nitrogen frozen samples, the total organic matter content of the shale decreased in the placed samples due to the loss of light hydrocarbons.

[0089] Figure 8 Place the sample in the conventional pyrolysis S2 and the liquid nitrogen frozen sample in the conventional pyrolysis S 2L Excellent consistency, y = 1.0052x, correlation coefficient R 2 =0.9256, the slope is about 1, and the two distributions are consistent, indicating that the loss of the placed sample is mainly light hydrocarbons, and there is almost no loss of heavy hydrocarbons. The correction factor is 1. The heavy hydrocarbon correction factor of the placed sample is consistent with the heavy hydrocarbon correction factor of the liquid nitrogen frozen sample, both of which are 0.82. The heavy hydrocarbon correction amount is 0.82S2, that is, 0.82S 2L =0.82S2.

[0090] Step 3: Place shale pyrolysis S1 light hydrocarbon correction;

[0091] The most effective and simple light hydrocarbon compensation method is to detect S1 light hydrocarbons in mud shale by using the liquid ammonia freezing method of core sampling. Since the core is frozen in liquid nitrogen after being taken out and ground in liquid nitrogen environment, the loss of light hydrocarbons can be ignored. Figure 9 The S 1L The light hydrocarbon correction factor is the ratio of the light hydrocarbon components to the conventional pyrolysis S1 of the sample placed in the well. 1L The conventional pyrolysis of the sample S1 shows that the light hydrocarbon correction factor is 1.73, that is, S 1L =1.73S1 Therefore, the total oil content of the shale sample of the second member of the Fuyang Formation in Well SX84 after correction of light and heavy hydrocarbons is S TO For: S TO =S 1L +k2S2L =1.73S1+0.82S2

[0092] Place the sample in sections for pyrolysis and calculate the total S1 content (i.e. total free oil content): S 1m =1.33S 1L =1.33*1.73S1=2.3S1

[0093] Place sample for thermal desorption of oil volume: S a =0.82S 2L -0.33S 1L =0.82S2-0.33*1.73S1=0.82S2-0.57S1

[0094] Among the components of shale oil, light oil has the best mobility, followed by medium oil, while heavy oil is mainly adsorbed oil. Therefore, the light oil lost from shale oil has the best mobility, and the light oil in residual oil also has good mobility. Figure 10 The movable oil volume is the loss oil 1.73S1-S1 and S 1-1L The sum of 1.73S1-S1+S 1-1L =S ao , S ao =K3S1,y=0.7758x, correlation coefficient R 2 =0.9971, the correlation is good, the slope is about 0.78, that is, K3 is 0.78, S ao =0.78S1.

[0095] Step 4: The light and heavy hydrocarbon calibration models for liquid nitrogen frozen shale pyrolysis S1 and placed shale pyrolysis S1, as well as the evaluation models for adsorbed oil, free oil and movable oil, were established.

[0096] Model 1: Liquid nitrogen frozen shale sample

[0097] Total oil content: S TOL =S 1L +0.82S 2L

[0098] Free oil: S 1mL =1.33S 1L

[0099] Oil adsorption capacity: S aL =0.82S 2L -0.33S 1L

[0100] Model 2: Placing shale samples

[0101] Total oil content: S TO =1.73S1+0.82S2

[0102] Free oil: S 1m = = 2.3S1

[0103] Adsorption oil amount: S a =0.82S2-0.57S1

[0104] Movable oil volume: S ao =0.78S1

[0105] The pyrolysis parameter S1 of Well SX84 can objectively characterize the oil content of shale, and the credibility of the shale resource potential evaluation results is improved by 38 percentage points.

[0106] The beneficial effects of this application are as follows: the pyrolysis parameter S1 of 10 shale wells can objectively characterize the oil content of the shale, the credibility of the shale oil resource potential evaluation results is increased by an average of 35 percentage points, the accuracy of implementing the "sweet spot" is increased by an average of 60 percentage points, and the work efficiency is increased by an average of 50 percentage points.

[0107] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for correcting and restoring the original hydrocarbon content of shale, characterized by: include: Step 1: Establish the relationship between liquid nitrogen conventional pyrolysis and liquid nitrogen staged pyrolysis, and perform liquid nitrogen frozen shale conventional pyrolysis S 1L Heavy hydrocarbon correction; Comparison of conventional pyrolysis of liquid nitrogen frozen shale and staged pyrolysis of liquid nitrogen frozen shale to establish liquid nitrogen frozen shale S 1L The amount of heavy hydrocarbon compensation; The heavy hydrocarbon compensation amount is S 2L -S 2-2L , compared with conventional pyrolysis S 2L The relationship is: y2=0.8172x2, x2 is the conventional pyrolysis S 2L , y2 is the heavy hydrocarbon compensation amount S 2L -S 2-2L The heavy hydrocarbon compensation coefficient k2 of mud shale is 0.82, and the heavy hydrocarbon compensation amount is 0.82S 2L ; Step 2: Place the S1 heavy hydrocarbon correction of conventional pyrolysis of shale; The heavy hydrocarbon correction factor of the placed sample is consistent with that of the liquid nitrogen frozen sample, which is 0.82, and the heavy hydrocarbon correction amount is 0.82S2; Step 3: Place the S1 light hydrocarbon correction of the conventional pyrolysis of mud shale; The S obtained by conventional pyrolysis of liquid nitrogen frozen samples 1L Contains all components of light hydrocarbons, and its ratio to the conventional pyrolysis S1 of the placed sample is the light hydrocarbon correction factor; Conventional pyrolysis of liquid nitrogen frozen samples 1L The relationship with the conventional pyrolysis S1 of the sample is: 1L =1.73S1, 1.73 is the light hydrocarbon correction factor; Step 4: Establishing conventional pyrolysis of liquid nitrogen frozen shale 1L and placement of the S1 light and heavy hydrocarbon calibration model for conventional pyrolysis of shale and the evaluation model for adsorbed oil, free oil and movable oil; include: Model 1: Liquid nitrogen frozen shale sample Total oil content: S TOL =S 1L +0.82S 2L Free oil: S 1mL =1.33S 1L Oil adsorption capacity: S aL =0.82S 2L -0.33S 1L Model 2: Placing shale samples Total oil content: S TO =1.73S1+0.82S2 Free oil: S 1m =2.3S1 Oil adsorption capacity: S a =0.82S2-0.57S1 Movable oil volume: S ao =0.78S1.

2. The method for correcting and restoring the original hydrocarbon content of shale according to claim 1, characterized in that: Step 3: Place the shale in conventional pyrolysis S1 for light hydrocarbon correction. According to the light hydrocarbon correction coefficient, the total oil content S of the shale sample after light and heavy hydrocarbon correction is obtained. TO For: S TO =S 1L +k2S 2L =1.73S1+0.82S2, k2 is the compensation coefficient of heavy hydrocarbons in shale.

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