Quantitative evaluation method for mixed source proportion of humus type crude oil and saprolite type crude oil

Abstract

The invention discloses a quantitative evaluation method for the mixed source proportion of humus type crude oil and saprolite type crude oil, and belongs to the technical field of oil-gas exploration. According to the technical scheme, the method comprises the steps that crude oil parameters are divided into crude oil physical property parameters, crude oil carbon isotope parameters and crude oil biomarker compound parameters, an analytic hierarchy process is adopted, the importance sequence of the three parameters is determined, then every two parameters are compared to determine the weight coefficient of each parameter, and a crude oil cause index OSI is established; oSI of all crude oil is calculated, according to the geological background, the OSI value of the crude oil only supplied by humic hydrocarbon source rock is determined and recorded as OSIh, the OSI value of the crude oil only supplied by saprolite type crude oil is recorded as OSIs, the OSIh and the OSIs serve as end members, and the mixed-source proportion of the mixed-source oil is calculated. The method is applied to the technical aspect of oil-gas exploration, solves the problem that the existing research method cannot quantitatively or accurately evaluate the mixed source proportion of humus type crude oil and sapropel type crude oil, can quantitatively evaluate the mixed source proportion of an oil-gas-containing area in which humus type and sapropel type hydrocarbon source rocks are developed at the same time, and is high in evaluation accuracy.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas exploration, and particularly relates to a method for quantitatively evaluating the mixing ratio of humic-type crude oil and sapropelic-type crude oil. Background Art

[0002] The formation conditions of strata in oil and gas-bearing basins in China are complex, and multiple sets of source rocks often develop. The formation of oil and gas reservoirs often involves the mixed contributions of multiple sets of source rocks. Accurately calculating the mixing ratio helps to clarify the source of oil and gas, optimize the selection of exploration target areas, and guide the evaluation of resource potential. In addition, changes in the mixing ratio may lead to differences in crude oil density, viscosity, and wax content, thereby affecting the production process and economic benefits. Since humic-type and sapropelic-type source rocks are significantly different in terms of hydrocarbon generation characteristics, biomarker compounds, carbon isotopes, etc., the corresponding humic-type crude oil and sapropelic-type crude oil are also significantly different. Therefore, establishing a reliable method for quantitatively evaluating the mixing ratio plays a key role in the efficient exploration and development of oil and gas resources.

[0003] At present, the quantitative research methods for the mixing ratio of crude oil at home and abroad mainly include biomarker analysis, stable carbon isotope composition, statistical modeling of geochemical parameters, and machine learning. Among them, biomarker compounds (such as steranes and hopanes) are widely used due to their sensitivity to the source of the parent material. However, this method is greatly interfered by factors such as maturity and biodegradation, and it is difficult to accurately quantify the mixing ratio. Stable carbon isotope (δ 13 C) can distinguish organic matter from different sources, but its resolution is limited due to the influence of secondary alteration. In recent years, methods based on multi-parameter statistical models (such as end-member mixing models) have improved the quantitative accuracy, but they still rely on high-quality end-member samples and are difficult to adapt to the mixing situation under complex geological backgrounds. At the same time, existing methods often rely on geochemical parameters and ignore the differences in crude oil physical properties. Therefore, there is an urgent need to develop a quantitative evaluation method for the mixing ratio that integrates multiple indicators and has high accuracy to support the decision-making of oil and gas exploration and development. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the technical problem to be solved by the present invention is to overcome the problem that the existing research methods cannot quantitatively or accurately evaluate the mixing ratio of humic-type crude oil and sapropelic-type crude oil, and propose a quantitative evaluation method for the mixing ratio of humic-type crude oil and sapropelic-type crude oil that can carry out quantitative evaluation of the mixing ratio in oil and gas-bearing areas where both humic-type and sapropelic-type source rocks are developed, and has high evaluation accuracy.

[0005] To solve the above technical problem, the technical solution adopted by the present invention is as follows:

[0006] The present invention provides a method for quantitatively evaluating the mixing ratio of humic-type crude oil and sapropelic-type crude oil, including:

[0007] Constructing the origin index of crude oil: Classify the crude oil parameters into three categories: physical properties of crude oil, carbon isotopes of crude oil, and biomarker parameters of crude oil. Using the analytic hierarchy process, determine the importance ranking of the three categories of parameters, and then compare them pairwise to determine the weight coefficients of each parameter. Establish the origin index of crude oil OSI. The calculation formula of OSI is as follows:

[0008] OSI = 0.0846D + 0.0846η + 0.4434C + 0.0482N + 0.0758H - 0.1167Z - 0.1467T

[0009] Where, D is the relative density of crude oil, dimensionless; η is the relative viscosity of crude oil, dimensionless; C is the relative carbon isotope of crude oil, dimensionless; N is the norhopane index, equal to Ts / Tm, dimensionless; H is the hopane index, equal to C 30 hopane / C 29 norhopane, dimensionless; Z is the regular sterane index, equal to C 27 regular sterane / C 29 regular sterane, dimensionless; T is the tricyclic terpane index, equal to tricyclic terpane / C 30 hopane, dimensionless;

[0010] Calculation of the mixed-source ratio: Calculate OSI for all crude oils. According to the geological background, determine the OSI value of the crude oil supplied only by humic-type source rocks, denoted as OSI h , and the OSI value of the crude oil supplied only by sapropelic-type source rocks is denoted as OSI s . Take these two as end members and calculate the mixed-source ratio of the mixed-source oil. The calculation formula is as follows:

[0011]

[0012] Where, M s is the contribution rate of sapropelic-type source rocks, dimensionless, with a value range of 0 - 100%; the contribution rate of humic-type source rocks is 1 - M s .

[0013] Preferably, the physical properties of crude oil include density and viscosity, the carbon isotopes of crude oil include the total oil carbon isotope, and the biomarker parameters of crude oil include Ts / Tm, C 30 hopane / C 29 norhopane, tricyclic terpane / C 30 hopane, C 27 regular sterane / C 29 regular sterane.

[0014] Preferably,

[0015]

[0016] where D is the relative density of crude oil, dimensionless; ρ is the density of crude oil measured at 20 °C, g / cm 3 ; ρ_water is the density of water under standard conditions, with a value of 1 g / cm 3 .

[0017] Preferably,

[0018]

[0019] where η is the relative viscosity of crude oil, dimensionless; μ is the viscosity of crude oil measured at 50 °C, mPa·s; μ 临界 is the critical value between medium-viscosity and high-viscosity crude oil, with a value of 100 mPa·s.

[0020] Preferably,

[0021]

[0022] where C is the relative carbon isotope of crude oil, dimensionless; δ 13 C 全油 is the total oil carbon isotope measured, ‰(PDB); δ 13 C 临界 is the critical carbon isotope value, with a value of -30‰(PDB).

[0023] Preferably, it also includes: experimental testing and data acquisition: performing physical property parameter testing, total oil carbon isotope testing, saturated hydrocarbon chromatography analysis, and saturated hydrocarbon chromatography-mass spectrometry analysis on crude oil to obtain the crude oil density ρ, viscosity μ, total oil carbon isotope δ 13 C 全油 , and calculating the biomarker compound parameters Pr / Ph, Ts / Tm, C 30 hopane / C 29 norhopane, tricyclic terpane / C 30 hopane, C 27 regular sterane / C 29 regular sterane.

[0024] Preferably, it also includes: standardizing the crude oil density, viscosity, and total oil carbon isotope to obtain the relative density D, relative viscosity η, and relative carbon isotope C.

[0025] Preferably, it also includes: parameter screening: through principal component analysis, eliminating parameters with low discrimination, and selecting 7 parameter indicators sensitive to the mixed-source ratio. The 7 parameter indicators include relative density D, relative viscosity η, relative carbon isotope C, Ts / Tm, C 30 hopane / C 29 norhopane, tricyclic terpane / C 30 hopane, C 27 regular sterane / C 29 regular sterane.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] The present invention provides a quantitative evaluation method for the mixing ratio of humic-type crude oil and sapropelic-type crude oil. From three dimensions of crude oil physical properties, crude oil carbon isotopes, and crude oil biomarker compounds, a comprehensive evaluation model is constructed, which can avoid the deviation of using a certain method or several methods. At the same time, this method fully considers the geological background and determines the end-member values of humic-type crude oil and sapropelic-type crude oil, making the evaluation results more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flowchart of the quantitative evaluation method for the mixing ratio of humic-type crude oil and sapropelic-type crude oil provided by the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] Next, the technical solutions in the specific embodiments of the present invention will be described in detail and completely with reference to the drawings. Obviously, the described embodiments are only partial specific embodiments of the overall technical solution of the present invention, rather than all embodiments. Based on the overall concept of the present invention, all other embodiments obtained by those of ordinary skill in the art fall within the protection scope of the present invention.

[0030] There are obvious differences between humic-type crude oil and sapropelic-type crude oil in terms of crude oil physical properties, carbon isotopes, biomarker compound compositions, etc. Therefore, typical parameters are selected for the calculation of the mixing ratio. The specific implementation steps are as Figure 1 shown, including:

[0031] (1) Experimental testing and data acquisition: Conduct physical property parameter testing, whole-oil carbon isotope testing, saturated hydrocarbon chromatography analysis, and saturated hydrocarbon chromatography-mass spectrometry analysis on the collected crude oil, and obtain the crude oil density ρ, viscosity μ, whole-oil carbon isotope δ 13 C 全油 , and calculate a series of biomarker compound parameters such as Pr / Ph, Ts / Tm, C 30 hopane / C 29 norhopane, tricyclic terpane / C 30 hopane, C 27 regular sterane / C 29 regular sterane; among them, Pr is pristane, Ph is phytane, and the percentage content can be obtained from the saturated hydrocarbon gas chromatography; Ts is 18α(H)-22, 29, 30-trinorhopane, Tm is 17α(H)-22, 29, 30-trinorhopane, C 30 hopane is 17α(H), 21β(H)-hopane, C 29 norhopane is 17α(H), 21β(H)-30-norhopane, and tricyclic terpane is 13β(H), 14α(H)-C 19Tricyclic terpanes, 13β(H),14α(H)—C 20 Tricyclic terpanes, 13β(H),14α(H)—C 21 Tricyclic terpanes, 13β(H),14α(H)—C 22 Tricyclic terpanes, 13β(H),14α(H)—C 23 Tricyclic terpanes, 13β(H),14α(H)—C 24 Tricyclic terpanes, 13β(H),14α(H)—C 25 Tricyclic terpanes, 13β(H),14α(H)—C 26 Tricyclic terpanes, 13β(H),14α(H)—C 27 Tricyclic terpanes, 13β(H),14α(H)—C 28 The sum of tricyclic terpanes and 13β(H),14α(H)—C 29 The above parameters can be obtained from the saturated hydrocarbon chromatogram-mass spectrum (m / z = 191); C 27 The regular sterane is 5α(H),14α(H),17α(H)—cholestane (20R), C 29 The regular sterane is 24-ethyl, 5α(H),14α(H),17α(H)—cholestane (20R), and the above parameters can be obtained from the saturated hydrocarbon chromatogram-mass spectrum (m / z = 217).

[0032] (2) Data normalization processing: Since the above biomarker compound parameters are all ratios, only the crude oil density, viscosity, and total oil carbon isotope need to be normalized to obtain the relative density D, relative viscosity η, and relative carbon isotope C. The calculation formulas are as follows:

[0033]

[0034] In the formula, D is the relative density of crude oil, dimensionless; ρ is the crude oil density measured at 20°C, g / cm 3 ; ρwater is the water density under standard conditions, with a value of 1 g / cm 3 .

[0035]

[0036] In the formula, η is the relative viscosity of crude oil, dimensionless; μ is the crude oil viscosity measured at 50°C, mPa·s; μ 临界 is the critical value of medium-viscosity and high-viscosity crude oil, with a value of 100 mPa·s.

[0037]

[0038] In the formula, C is the relative carbon isotope of crude oil, dimensionless; δ 13 C全油 is the total oil carbon isotope obtained by testing,‰(PDB);δ 13 C 临界 is the critical carbon isotope value, which is -30‰ (PDB).

[0039] (3) Parameter screening: Through principal component analysis, the parameters with low discrimination were eliminated and the indicators sensitive to the mixed source ratio were selected, including relative density D, relative viscosity η, relative carbon isotope C, Ts / Tm, C 30 Hopane / C 29 Norhopane, tricyclic terpane / C 30 Hopane, C 27 Regular sterane / C 29 7 parameters including regular steranes.

[0040] (4) Construction of crude oil genesis index: the above parameters are divided into crude oil physical properties (including density and viscosity), crude oil carbon isotopes (whole oil carbon isotopes) and crude oil biomarker compound parameters (including Ts / Tm, C 30 Hopane / C 29 Norhopane, tricyclic terpane / C 30 Hopane, C 27 Regular sterane / C 29 The three categories of crude oil (including regular steranes) are classified into three categories using the hierarchical analysis method. The importance of the three parameters is first determined, and then the weight coefficients of the above parameters are determined by pairwise comparison to establish the crude oil genesis index (OSI). The calculation formula is as follows:

[0041] OSI=0.0846D+0.0846n+0.4434C+0.0482N+0.0758H-0.1167Z-0.1467T (4)

[0042] Where OSI is the crude oil genesis index, dimensionless, and the larger the value, the more it indicates sapropel-type crude oil; N is the norhopane index, which is equal to Ts / Tm, dimensionless; H is the hopane index, which is equal to C 30 Hopane / C 29 norhopane, dimensionless; Z is the regular sterane index, equal to C 27 Regular sterane / C 29 Regular sterane, dimensionless, the larger the Z, the more it indicates humic organic matter, so the weight coefficient is negative; T is the tricyclic terpene index, which is equal to tricyclic terpene / C 30 Hopane is dimensionless. The larger the T, the more it indicates humic organic matter, so the weight coefficient is negative.

[0043] (5) Calculation of mixed source ratio: First, calculate the OSI of all crude oils. According to the geological background, determine the OSI value of the crude oil that only has humic source rocks as hydrocarbon source, which is recorded as OSI h , and the OSI value of crude oil with only sapropelic crude oil as hydrocarbon supplier, denoted as OSIs , taking the two as end-members, calculate the mixing ratio of the mixed-source oil, and the calculation formula is as follows:

[0044]

[0045] In the formula, M s is the contribution rate of sapropelic hydrocarbon source rock, dimensionless, 0 - 100%; the contribution rate of humic hydrocarbon source rock is 1 - M s .

[0046] To introduce the quantitative evaluation method for the mixing ratio of humic crude oil and sapropelic crude oil provided by the embodiments of the present invention more clearly and in detail, the following will be described in combination with specific embodiments.

[0047] Embodiment

[0048] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0049] Taking the Cangdong Sag as the study area and taking the Middle - Paleozoic oil reservoir as an example, evaluate the genetic index of the crude oil and determine the mixing ratio of the mixed-source oil. [[ID=2*]]

[0050] (1) Experimental tests and data acquisition: Test the physical properties of the collected crude oil, the carbon isotope of the whole oil, the saturated hydrocarbon chromatography analysis, the saturated hydrocarbon chromatography - mass spectrometry analysis, and obtain the crude oil density ρ, viscosity μ, the carbon isotope of the whole oil δ 13 C 全油 , calculate Pr / Ph, Ts / Tm, C 30 hopane / C 29 norhopane, tricyclic terpane / C 30 hopane, C 27 regular sterane / C 29 regular sterane and a series of biomarker parameter;

[0051] (2) Use formulas (1), (2), and (3) to standardize the crude oil density, viscosity, and the carbon isotope of the whole oil respectively, and obtain the relative density D, relative viscosity η, and relative carbon isotope C;

[0052] (3) Through principal component analysis, eliminate the parameters with low discrimination, and select the indicators sensitive to the mixing ratio, including 7 parameters such as relative density D, relative viscosity η, relative carbon isotope C, norhopane index N, hopane index H, regular sterane index Z, and tricyclic terpane index T.

[0053] (4) The above parameters are divided into crude oil physical properties (including density and viscosity), crude oil carbon isotopes (whole oil carbon isotopes) and crude oil biomarker compound parameters (including Ts / Tm, C 30 Hopane / C 29 Norhopane, tricyclic terpane / C 30 Hopane, C 27 Regular sterane / C 29 The OSI values of the 10 crude oil samples were calculated using formula (4), as shown in Table 1.

[0054] (5) Combined with the geological background, it was found that samples 7 and 8 were Permian reservoirs, with no faults connecting sapropelic source rocks. Only the Carboniferous-Permian humic source rocks provided hydrocarbons. The OSI was between 0.25 and 0.28, so the OSI h The value is 0.25; samples 1, 2, 3, and 4 are directly connected to the sapropelic source rock of the second member of Kong 2 through faults, and their OSI ranges from 1.03 to 1.38, so OSI s The value is 1.38.

[0055] Table 1 OSI calculation data of crude oil from the Mesozoic to Paleozoic in the Cangdong Sag

[0056]

[0057] (6) Using formula (5), the mixed source ratios of samples 5 and 6 were calculated, and the results are shown in Table 2. It shows that in sample 5, the contribution of sapropelic source rocks in the second member of the Kong Formation accounts for 41.81%, and the contribution of Carboniferous-Permian humic source rocks accounts for 58.19%. In sample 6, the contribution of sapropelic source rocks in the second member of the Kong Formation accounts for 38.93%, and the contribution of Carboniferous-Permian humic source rocks accounts for 61.07%, indicating that more humic source rock contributions were mixed into sample 6. This is consistent with geological knowledge. Samples 5 and 6 are both Permian crude oils and are located in close proximity, but sample 5 is directly connected to the source rock of the second member of the Kong Formation through a fault, so it has mixed more contributions from the sapropelic source rock of the second member of the Kong Formation.

[0058] Table 2 Calculation data of the mixed source ratio of crude oil in the Mesozoic-Paleozoic in the Cangdong Sag

[0059] Sample number Original oil source index OSI Contribution of sapropelic hydrocarbon source rock Contribution of humic hydrocarbon source rock 5 0.72 41.81％ 58.19％ 6 0.69 38.93％ 61.07％

[0060] In traditional research, through the comparison of biomarker compound scatter plots and the fingerprint comparison of chromatograms and chromatogram-mass spectra, it can be found that Crude Oil No. 5 and Crude Oil No. 6 have certain similarities with two sets of source rocks. For example, Pr / Ph is less than 1, the carbon isotope of the whole oil is relatively light, the regular steranes show an inverted "L" type distribution similar to sapropelic source rocks, the density and viscosity are relatively low, it contains a certain amount of tricyclic terpanes, C 30 hopane / C 29 norhopane is relatively high, similar to humic source rocks. It can be speculated that both Crude Oil No. 5 and Crude Oil No. 6 are contributed by humic and sapropelic crude oils, but the specific proportions cannot be determined. However, the present invention can accurately calculate the contribution proportions of each set of source rocks.

Claims

1. A quantitative evaluation method for the mixing ratio of humic-type crude oil and sapropelic-type crude oil, characterized in that Including: Constructing the crude oil genetic index: Classify crude oil parameters into three categories: crude oil physical properties, crude oil carbon isotopes, and crude oil biomarker compound parameters. Using the analytic hierarchy process, determine the importance ranking of the three categories of parameters, and then compare them pairwise to determine the weight coefficients of each parameter. Establish the crude oil genetic index OSI. The calculation formula of OSI is as follows: OSI = 0.0846D + 0.0846η + 0.4434C + 0.0482N + 0.0758H - 0.1167Z - 0.1467T Among them, D is the relative density of crude oil, dimensionless; η is the relative viscosity of crude oil, dimensionless; C is the relative carbon isotope of crude oil, dimensionless; N is the norhopane index, equal to Ts / Tm, dimensionless; H is the hopane index, equal to C 30 hopane / C 29 norhopane, dimensionless; Z is the regular sterane index, equal to C 27 regular sterane / C 29 regular sterane, dimensionless; T is the tricyclic terpane index, equal to tricyclic terpane / C 30 hopane, dimensionless; Mixed-source ratio calculation: Calculate the OSI for all crude oils. According to the geological background, determine the OSI value of the crude oil supplied only by humic-type hydrocarbon source rocks, denoted as OSI h , and the OSI value of the crude oil supplied only by sapropelic crude oil is denoted as OSI s . Take these two as end members and calculate the mixed-source ratio of the mixed-source oil. The calculation formula is as follows: Among them, M s is the contribution rate of sapropelic hydrocarbon source rock, dimensionless, with a value range of 0 - 100%; the contribution rate of humic hydrocarbon source rock is 1 - M s .

2. The quantitative evaluation method for the mixing ratio of humic-type crude oil and sapropelic-type crude oil according to claim 1, characterized in that, The physical properties of crude oil include density and viscosity. The carbon isotopes of crude oil include the carbon isotopes of whole oil. The biomarker compound parameters of crude oil include Ts / Tm, C 30 hopane / C 29 norhopane, tricyclic terpane / C 30 hopane, C 27 regular sterane / C 29 regular sterane.

3. The quantitative evaluation method for the mixing ratio of humic-type crude oil and sapropelic-type crude oil according to claim 2, characterized in that where D is the relative density of crude oil, dimensionless; ρ is the density of crude oil measured at 20°C, g / cm 3 ; ρ_water is the density of water under standard conditions, with a value of 1 g / cm 3 .

4. The quantitative evaluation method for the mixing ratio of humic-type crude oil and sapropelic-type crude oil according to claim 2, characterized in that In the formula, η is the relative viscosity of crude oil, dimensionless; μ is the viscosity of crude oil measured at 50 °C, mPa·s; μ 临界 is the critical value of medium-viscosity and high-viscosity crude oil, with a value of 100 mPa·s.

5. The quantitative evaluation method for the mixing ratio of humic-type crude oil and sapropelic-type crude oil according to claim 2, characterized in that In the formula, C is the relative carbon isotope of crude oil, dimensionless; δ 13 C 全油 is the total oil carbon isotope obtained by testing, ‰ (PDB); δ 13 C 临界 is the critical carbon isotope value, with a value of -30‰ (PDB).

6. The quantitative evaluation method for the mixing ratio of humic-type crude oil and sapropelic-type crude oil according to claim 1, characterized in that It further includes: Experimental tests and data acquisition: Physical property parameters of crude oil are tested, total oil carbon isotope is tested, saturated hydrocarbon chromatography analysis and saturated hydrocarbon chromatography-mass spectrometry analysis are carried out to obtain crude oil density ρ, viscosity μ, and total oil carbon isotope δ 13 C 全油 , and biomarker compound parameters Pr / Ph, Ts / Tm, and C 30 hopane / C 29 norhopane, tricyclic terpane / C 30 hopane, C 27 regular sterane / C 29 regular sterane.

7. The quantitative evaluation method for the mixing ratio of humic-type crude oil and sapropelic-type crude oil according to claim 1, characterized in that It further includes: Data standardization processing: Standardize the crude oil density, viscosity, and total oil carbon isotope to obtain the relative density D, relative viscosity η, and relative carbon isotope C.

8. The quantitative evaluation method for the mixing ratio of humic-type crude oil and sapropelic-type crude oil according to claim 1, wherein It further includes: Parameter screening: Through principal component analysis, parameters with low discrimination are eliminated, and 7 parameter indicators sensitive to the mixing source ratio are selected. The 7 parameter indicators include relative density D, relative viscosity η, relative carbon isotope C, Ts / Tm, C 30 hopane / C 29 norhopane, tricyclic terpane / C 30 hopane, C 27 regular sterane / C 29 regular sterane.

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