A method for determining the migration direction of petroleum by using the characteristics of trace elements in petroleum

Abstract

The present invention provides a method for determining the migration direction of petroleum based on trace element characteristics in the petroleum, comprising: step 1, selecting a certain amount of petroleum sample; step 2, pre-treating the sample by a combination of dry ashing and wet digestion to form a sample solution to be tested; step 3, determining the trace element content and calculating trace element-related parameter values for different samples; step 4, clustering the samples using a cluster analysis method to classify the petroleum types, including Class A and Class B; step 5, screening parameters with obvious gradient variation characteristics along the migration direction as effective migration direction tracing parameters; and step 6, determining the migration direction of the petroleum based on the spatial variation patterns of the parameters determined in step 5. This method for determining the migration direction of petroleum based on trace element characteristics in the petroleum overcomes the shortcomings of traditional methods in petroleum migration direction analysis, can effectively determine the migration direction of petroleum, and guide oil and gas exploration.

Description

Technical Field

[0001] The present invention relates to the technical field of petroleum geological exploration, and in particular to a method for judging the migration direction of petroleum by using the characteristics of trace elements in petroleum. Background Art

[0002] Underground oil reservoirs are the result of thermal evolution of organic matter in source rocks into petroleum, which then migrates and accumulates in traps. Determining the direction of oil migration can be used to track its path, identify its accumulation locations, and facilitate the discovery of new oil fields, thus playing a crucial role in oil and gas exploration. Using geochemical methods to determine the direction of oil migration is a key approach in oil and gas exploration. Oil migration within transporting layers leaves traces, which in turn alters its geochemical characteristics, including its physical properties and chemical composition. Compounds of varying molecular weights, polarities, and stereochemical structures experience varying adsorption capacities as they pass through transporting layers. The content of highly adsorbed compounds decreases with increasing migration distance. Traditional migration direction tracing indicators include crude oil physical properties, group composition, biomarkers, and nitrogen-containing compounds. However, these indicators have limitations in practical application. Crude oil physical properties and group composition are macroscopic characteristics of crude oil, limiting their accuracy in determining migration direction. Biomarkers and nitrogen-containing compounds, on the other hand, are microscopic characteristics of crude oil and are less suitable for crude oils with lower content. Furthermore, their analysis requires complex sample pretreatment procedures. Besides the organic components that make up the majority of the oil, inorganic elements present in lower concentrations in oil retain information about the elemental composition of the hydrocarbon-generating parent material and its depositional environment, providing specific indicative value. Oils generated from the same source rock have similar trace element compositions. During migration, different trace elements undergo adsorption and element exchange with the transporting layers, resulting in changes in the elemental composition. These changes in elemental composition can be used to track the migration direction of the oil.

[0003] Chinese patent application number CN201710362782.7 describes a method for determining the phase, timing, driving force, and direction of oil and gas migration. This method uses in-situ oxygen isotope and trace element data from the secondary quartz walls of oil inclusions to calculate the formation temperature of the oil inclusions and paleostratigraphic water oxygen isotopes, thereby determining the phase and timing of oil and gas migration. Furthermore, paleostratigraphic water oxygen isotopes and the oxygen isotopes and trace elements of the secondary quartz walls of the oil inclusions are used to determine reservoir connectivity during the oil and gas migration period. Furthermore, paleofluid pressures during oil and gas migration are determined from the oil inclusion formation temperature, phase diagrams, and isochoric lines. Combined with data on connected sand bodies, source rocks, and structures, this method reveals the driving force and direction of oil and gas migration. This invention, through in-situ geochemical testing of the secondary quartz walls of inclusions, can calculate and obtain comprehensive oil and gas migration information with high accuracy, broad applicability, and ease of implementation.

[0004] Chinese patent application number CN201811105568.4 discloses a method for reconstructing the migration and accumulation of natural gas using multi-parameter geochemical indicators. The method includes the following steps: determining the vertical and horizontal variation characteristics of natural gas geochemical indicators, formation water geochemical indicators, carbon and oxygen isotopes in carbonate cements, and trace elements in carbonate cements within the study area; determining the natural gas migration phase and direction based on the vertical and horizontal variation characteristics described in step one; and reconstructing the natural gas migration and accumulation process based on the natural gas migration phase and direction in step two, combined with pore characteristics, structural evolution characteristics, and fault evolution characteristics. Compared with similar studies, the method provided by this invention avoids the uncertainty and ambiguity of using each parameter independently to determine the natural gas migration phase, and reconstructs the natural gas migration and accumulation process. This research result has important guiding significance for natural gas exploration deployment in the study area, can better guide the selection of exploration targets in the study area, and improve the success rate of oil and gas drilling.

[0005] Chinese patent application number CN201710569903.5 discloses a method for analyzing oil and gas accumulation based on fracture structures. This method relates to the field of oil and gas accumulation and can effectively guide oil and gas exploration. The method includes the following steps: selecting fractures of varying degrees, observing their internal structural characteristics, and dividing the fracture zones into two structural unit layers: a fracture zone and a fracture zone based on the degree of rock fragmentation; taking samples from the fracture and fracture zones for field outcrop observation and microscopic observation. Based on the observation that more developed fractures indicate higher permeability of oil and gas fluids, the migration trajectories of the oil and gas fluids in the two structural unit layers are characterized; cementation materials containing oil and gas fluids in the different structural unit layers are analyzed and the source and phase of the oil and gas fluids are determined through inclusion homogenization temperature analysis, strontium isotope analysis, and in-situ trace element analysis. Based on the division of the structural unit layers, the migration trajectories of the oil and gas fluids, and the source and phase of the oil and gas fluids, an oil and gas accumulation pattern map is drawn, and the oil and gas accumulation effect is analyzed using the oil and gas accumulation pattern map.

[0006] The above existing technologies are significantly different from the present invention and fail to solve the technical problem we want to solve. Therefore, we have invented a new method for determining the migration direction of trace elements in petroleum based on their characteristics. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for effectively identifying the migration direction of oil and guiding oil and gas exploration by determining the migration direction of oil through the characteristics of trace elements in oil.

[0008] The object of the present invention can be achieved by the following technical measures: a method for determining the migration direction of oil by using the characteristics of trace elements in oil, the method comprising:

[0009] Step 1, select a certain amount of petroleum sample;

[0010] Step 2: Pre-treating the sample by combining dry ashing and wet digestion to form a sample solution to be tested;

[0011] Step 3: Determine the trace element content and calculate the trace element related parameter values of different samples;

[0012] Step 4: cluster analysis is performed on the samples using cluster analysis methods to classify the oil types, including Class A and Class B;

[0013] Step 5: Screen parameters with obvious gradient change characteristics along the migration direction as effective migration direction tracing parameters;

[0014] Step 6: Determine the migration direction of the oil based on the spatial variation pattern of the parameters determined in step 5.

[0015] The purpose of the present invention can also be achieved by the following technical measures:

[0016] In step 1, select the oil samples to be analyzed in the study area and organize and number them for analysis.

[0017] In step 2, a certain amount of sample is added to a crucible and heated to dehydrate, carbonize, decompose and oxidize the organic matter in the petroleum. It is then placed in a high-temperature ashing furnace and burned until the residue turns white or light gray. At this time, the residue is mainly inorganic components. The residue is then digested with an acid solution to remove the residual ash and form a solution of the sample to be tested.

[0018] In step 3, the prepared sample solution is analyzed on a plasma mass spectrometer to determine the trace element content. The operating temperature and relative humidity are 20°C and 30%, respectively. When the relative element content is greater than 1 ppm, the relative error is less than 5%, and when the content is less than 1 ppm, the relative error is less than 10%.

[0019] In step 3, the elements tested include vanadium (V), calcium (Ca), chromium (Cr), potassium (K), aluminum (Al), magnesium (Mg), manganese (Mn), sodium (Na), nickel (Ni), lead (Pb), iron (Fe), copper (Cu), tungsten (W), zinc (Zn), uranium (U), thorium (Th), titanium (Ti), scandium (Sc), cobalt (Co), molybdenum (Mo), thallium (Tl), bismuth (Bi), beryllium (Be), indium (In), cesium (Cs), rubidium (Rb), lithium (Li), strontium (Sr), gallium (Ga), gadolinium (Gd), yttrium (Y), samarium (Sm), neodymium (Nd), holmium (Ho), cerium (Ce), erbium (Er), europium (Eu), thulium (Tm), terbium (Tb), dysprosium (Dy), lutetium (Lu), lanthanum (La), praseodymium (Pr), and ytterbium (Yb).

[0020] In step 3, trace element parameters are calculated based on the trace element contents of different samples obtained from the test, including V / Ni, Co / Ni, U / Th, K / Na, Mn / Fe, V / Cr, Ni / Mo, Ni / Mn, Mo / Cr, Sr / Cu, V / Cu, Cr / Ni, Mn / Co, Zn / Co, Pb / Ni, La / Yb, La / Sm, Gd / Yb and the total amount of light rare earth elements / total amount of heavy rare earth elements LREE / HREE (∑(La+Ce+Pr+Nd+Pm+Eu) / ∑(Gd+Tb+Dy+Ho+Er+Tm+Yb+Lu)).

[0021] In step 4, based on the trace element parameter values of different samples obtained in step 3, the samples were clustered and classified into oil types. The systematic clustering method was used in the cluster analysis, the data were standardized by the standard deviation method, and the Euclidean distance was selected as the similarity measurement standard. The cluster dendrogram was obtained by analyzing the research samples.

[0022] In step 5, a certain type of oil with a clear migration direction is selected as a standard, and the variation characteristics of different trace element parameters along the migration direction are analyzed. Parameters with obvious gradient variation characteristics along the migration direction are selected as effective migration direction tracing parameters.

[0023] In step 5, the variation patterns of the trace element parameters of Class A petroleum with known migration directions in the migration direction are analyzed, and the effective parameters that can trace the migration direction are determined to be Al element content, Pb element content, Ca / Mg, Pb / Ni, Gb / Yb, and the total amount of light rare earth elements / total amount of heavy rare earth elements LREE / HREE.

[0024] In step 6, based on the migration parameters determined in step 5, the spatial variation patterns of different parameters of Class B oil are analyzed according to the magnitude variation of different parameter values to determine the migration direction of the oil.

[0025] The method of judging the migration direction of oil by the characteristics of trace elements in the present invention, based on determining the trace element content in the oil, selecting appropriate migration direction tracing parameters, systematically analyzing the trace element characteristics of oil derived from the same set of source rocks, and then determining the migration direction of oil, provides technical support for oil and gas exploration. The trace elements in oil are closely related to the changes in the origin and migration of oil. Currently, more than 80 trace elements can be identified, including alkali metals, alkaline earth metals, transition metals, lanthanides and actinides. Based on the pretreatment of oil samples, the trace elements of the samples are measured using a high-resolution plasma mass spectrometer (ICP-MS), the trace element parameters are calculated, the oil types are divided by cluster analysis, effective migration tracing parameters are selected, and the migration direction of oil is determined by the change pattern of the migration parameters. The oil migration direction determination of the present invention generally includes sample pretreatment, experimental analysis, sample classification, tracing parameter selection and migration direction determination.

[0026] The present invention determines the content characteristics of trace elements in petroleum through experiments, constructs and screens out parameters that can effectively reflect the migration direction of petroleum, and thus provides a method for determining the migration direction of petroleum. Trace elements in petroleum retain information about the sedimentary environment of the kerogen and source rock, and will undergo regular changes during the migration process. According to the changing patterns of the trace element composition, the migration direction of petroleum can be determined. The specific steps of the present invention are: pre-treating the petroleum sample, analyzing the treated sample by a plasma mass spectrometer, determining the trace element content, calculating various trace element parameters, dividing different types of petroleum by a cluster analysis method, and then determining the trace element parameters that can trace the migration direction of the petroleum, and determining the migration direction of the petroleum in the research target area based on the determined tracer parameters. The present invention overcomes the shortcomings of traditional methods in analyzing the migration direction of petroleum, and is a reasonable supplement to the conventional method of identifying the migration direction using organic geochemical means. It can effectively identify the migration direction of petroleum and guide oil and gas exploration. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart of a specific embodiment of the method of the present invention for determining the migration direction of trace elements in petroleum based on their characteristics;

[0028] Figure 2 This is a cluster dendrogram obtained by carefully classifying samples using a cluster analysis method in a specific embodiment of the present invention;

[0029] Figure 3 This is a graph showing changes in typical trace element content and related parameters of Type A oil along the migration direction in a specific embodiment of the present invention;

[0030] Figure 41 is a diagram showing the spatial variation pattern and migration direction of trace element parameters of Class B petroleum in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0031] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0032] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations and / or combinations thereof.

[0033] Different from the traditional method of judging the migration direction of oil by organic components in oil, this invention selects inorganic elements in oil as research means, determines the content of trace elements in oil through effective experimental analysis means, constructs migration direction tracer parameters, analyzes the variation characteristics of tracer parameters of oil from the same source, and thus determines the migration direction of oil. Figure 1 As shown, Figure 1 This is a flow chart of the method for determining the migration direction of trace elements in petroleum by using their characteristics. The method for determining the migration direction of trace elements in petroleum by using their characteristics comprises the following steps:

[0034] Step 1: Select a certain amount of petroleum sample.

[0035] Step 2: Pre-treating the sample by combining dry ashing and wet digestion to form a sample solution to be tested;

[0036] Step 3: Analyze the prepared sample solution on a plasma mass spectrometer to determine the trace element content and calculate the trace element related parameter values of different samples.

[0037] Step 4: cluster analysis is performed on the samples using a cluster analysis method to classify the oil types;

[0038] Step 5: Select a type of oil with a clear migration direction as a standard, analyze the variation characteristics of different trace element parameters along the migration direction, and select parameters with obvious gradient variation characteristics along the migration direction as effective migration direction tracing parameters;

[0039] Step 6: Determine the migration direction of the oil based on the spatial variation pattern of the parameters determined in step 5.

[0040] The following are several specific embodiments of the present invention:

[0041] Example 1

[0042] In a specific embodiment 1 of the present invention, the method for determining the migration direction of trace elements in petroleum by their characteristics includes the following steps:

[0043] Step 1: Select the oil samples to be analyzed in the study area and number them (SP1 to SP17 in this example);

[0044] Step 2: Pre-treat the sample using a combination of dry ashing and wet digestion. A certain amount of sample is placed in a crucible and heated to dehydrate, carbonize, decompose, and oxidize the organic matter in the petroleum. The crucible is then incinerated in a high-temperature ashing furnace until the residue turns white or light gray, which is primarily composed of inorganic components. The residue is then digested with an acid solution to remove the remaining ash and form a solution of the sample to be tested.

[0045] Step 3: The prepared sample solution was tested on an ICP-MS. The instrument used was an ELEMENT XR plasma mass spectrometer manufactured by Finnigan-MAT of Germany. The test method was based on the national standard "Chemical Analysis Methods of Silicate Rocks Part 30: Determination of 44 Elements". The working temperature and relative humidity were 20°C and 30% respectively. When the relative content of the elements was greater than 1ppm, the relative error was less than 5%. When the content was less than 1ppm, the relative error was less than 10%. The tested elements included vanadium (V), calcium (Ca), chromium (Cr), potassium (K), aluminum (Al), magnesium (Mg), manganese (Mn), sodium (Na), nickel (Ni), lead (Pb), iron (Fe), copper (Cu), and tungsten (W). ), zinc (Zn), uranium (U), thorium (Th), titanium (Ti), scandium (Sc), cobalt (Co), molybdenum (Mo), thallium (Tl), bismuth (Bi), beryllium (Be), indium (In), cesium (Cs), rubidium (Rb), lithium (Li), strontium (Sr), gallium (Ga), gadolinium (Gd), yttrium (Y), samarium (Sm), neodymium (Nd), holmium (Ho), cerium (Ce), erbium (Er), europium (Eu), thulium (Tm), terbium (Tb), dysprosium (Dy), lutetium (Lu), lanthanum (La), praseodymium (Pr), and ytterbium (Yb). According to the trace element contents of different samples obtained from the tests, trace element parameters were calculated, including V / Ni, Co / Ni, U / Th, K / Na, Mn / Fe, V / Cr, Ni / Mo, Ni / Mn, Mo / Cr, Sr / Cu, V / Cu, Cr / Ni, Mn / Co, Zn / Co, Pb / Ni, La / Yb, La / Sm, Gd / Yb and LREE / HREE (∑(La+Ce+Pr+Nd+Pm+Eu) / ∑(Gd+Tb+Dy+Ho+Er+Tm+Yb+Lu));

[0046] Step 4: Based on the trace element parameter values of different samples obtained in step 3, the samples were clustered using Origin software to classify the oil types into Class A and Class B. The system clustering method was used in the cluster analysis, and the data were standardized by the standard deviation method. The Euclidean distance was used as the similarity measurement standard. The cluster dendrogram was obtained by analyzing the research samples using the software (see Appendix). Figure 2 );

[0047] Step 5: Analyze the variation of trace element parameters of Class A petroleum with known migration direction in the migration direction, and determine that the effective parameters that can trace the migration direction are Al element content, Pb element content, Ca / Mg, Pb / Ni, Gb / Yb and LREE / HREE (see Appendix). Figure 3 );

[0048] Step 6: Based on the migration parameters determined in step 5, analyze the spatial variation of different parameters of Class B oil and determine the migration direction of oil (see Appendix). Figure 4 ).

[0049] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art may modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features therein. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

[0050] Except for the technical features described in the specification, all other technical features are known technologies to those skilled in the art.

Claims

1. A method for determining the migration direction of petroleum by using the characteristics of trace elements in petroleum, characterized in that: The method for determining the migration direction of oil by using the characteristics of trace elements in oil includes: Step 1, select a certain amount of petroleum sample; Step 2: Pre-treating the sample by combining dry ashing and wet digestion to form a sample solution to be tested; Step 3: Determine the trace element content and calculate the trace element related parameter values of different samples; Step 4: cluster analysis is performed on the samples using cluster analysis methods to classify the oil types, including Class A and Class B; Step 5: Screen parameters with obvious gradient change characteristics along the migration direction as effective migration direction tracing parameters; Step 6: Determine the migration direction of the oil based on the spatial variation pattern of the parameters determined in step 5; In step 5, a certain type of oil with a clear migration direction is selected as a standard, and the variation characteristics of different trace element parameters along the migration direction are analyzed. Parameters with obvious gradient variation characteristics along the migration direction are selected as effective migration direction tracing parameters; In step 5, the variation patterns of the trace element parameters of Class A petroleum with known migration directions in the migration direction are analyzed, and the effective parameters that can trace the migration direction are determined to be Al element content, Pb element content, Ca / Mg, Pb / Ni, Gb / Yb, and the total amount of light rare earth elements / total amount of heavy rare earth elements LREE / HREE.

2. The method for determining the migration direction of petroleum by using the characteristics of trace elements in petroleum according to claim 1, characterized in that: In step 1, select the oil samples to be analyzed in the study area and organize and number them for analysis.

3. The method for determining the migration direction of petroleum by using the characteristics of trace elements in petroleum according to claim 1, characterized in that: In step 2, a certain amount of sample is added to a crucible and heated to dehydrate, carbonize, decompose and oxidize the organic matter in the petroleum. It is then placed in a high-temperature ashing furnace and burned until the residue turns white or light gray. At this time, the residue is mainly inorganic components. The residue is then digested with an acid solution to remove the residual ash and form a solution of the sample to be tested.

4. The method for determining the migration direction of petroleum by using the characteristics of trace elements in petroleum according to claim 1, characterized in that: In step 3, the prepared sample solution is analyzed on a plasma mass spectrometer to determine the trace element content. The operating temperature and relative humidity are 20°C and 30%, respectively. When the relative element content is greater than 1 ppm, the relative error is less than 5%, and when the content is less than 1 ppm, the relative error is less than 10%.

5. The method for determining the migration direction of petroleum by using the characteristics of trace elements in petroleum according to claim 4, characterized in that: In step 3, the elements tested include vanadium (V), calcium (Ca), chromium (Cr), potassium (K), aluminum (Al), magnesium (Mg), manganese (Mn), sodium (Na), nickel (Ni), lead (Pb), iron (Fe), copper (Cu), tungsten (W), zinc (Zn), uranium (U), thorium (Th), titanium (Ti), scandium (Sc), cobalt (Co), molybdenum (Mo), thallium (Tl), bismuth (Bi), beryllium (Be), indium (In), cesium (Cs), rubidium (Rb), lithium (Li), strontium (Sr), gallium (Ga), gadolinium (Gd), yttrium (Y), samarium (Sm), neodymium (Nd), holmium (Ho), cerium (Ce), erbium (Er), europium (Eu), thulium (Tm), terbium (Tb), dysprosium (Dy), lutetium (Lu), lanthanum (La), praseodymium (Pr), and ytterbium (Yb).

6. The method for determining the migration direction of petroleum by using the characteristics of trace elements in petroleum according to claim 5, characterized in that: In step 3, according to the trace element contents of different samples obtained from the test, the trace element parameters are calculated, including V / Ni, Co / Ni, U / Th, K / Na, Mn / Fe, V / Cr, Ni / Mo, Ni / Mn, Mo / Cr, Sr / Cu, V / Cu, Cr / Ni, Mn / Co, Zn / Co, Pb / Ni, La / Yb, La / Sm, Gd / Yb and the total amount of light rare earth elements / total amount of heavy rare earth elements LREE / HREE (∑ (La+Ce+Pr+Nd+Pm+Eu) / ∑(Gd+Tb+Dy+Ho+Er+Tm+Yb+Lu)).

7. The method of determining the migration direction of petroleum by using the characteristics of trace elements in petroleum according to claim 1, characterized in that: In step 4, based on the trace element parameter values of different samples obtained in step 3, the samples were clustered and classified into oil types. The systematic clustering method was used in the cluster analysis, the data were standardized by the standard deviation method, and the Euclidean distance was selected as the similarity measurement standard. The cluster dendrogram was obtained by analyzing the research samples.

8. The method of determining the migration direction of petroleum by using the characteristics of trace elements in petroleum according to claim 1, characterized in that: In step 6, based on the migration parameters determined in step 5, the spatial variation patterns of different parameters of Class B oil are analyzed according to the magnitude variation of different parameter values to determine the migration direction of the oil.

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