A heavy mineral distribution track characteristic source tracing method

Abstract

The application provides a heavy mineral distribution track characteristic source tracing method, and belongs to the technical field of oil and gas field exploration and development, and comprises the following steps: selecting a research target area, and respectively selecting rock samples or researching heavy mineral data in the research target area; preparing, separating and identifying the selected rock samples, and classifying, collating and summarizing the heavy mineral data of the same layer; counting the content of stable heavy minerals in a single sample; drawing a distribution track trend graph of the stable heavy minerals; and horizontally comparing and analyzing the distribution track characteristics of the stable heavy minerals of a basin or a well (area) and a potential source area according to the drawn distribution track trend graph of the stable heavy minerals. The method can track the direction from each single source into a delta-sea basin, improves the accuracy of source tracing, and is suitable for local sources or multiple sources entering a basin at the same time.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field exploration and development technology, and in particular relates to a method for tracing the source of heavy mineral distribution trajectory characteristics. Background Technology

[0002] The provenance region refers to the source area or parent region of clastic material in a basin. Provenance analysis infers the petrological characteristics of the parent rocks in the clastic provenance region, as well as the tectonic setting and climatic conditions during sedimentation, based on the final products of sedimentation. Provenance analysis is of great significance in determining the location and nature of sediment sources, sediment transport pathways, and even the sedimentary processes and tectonic evolution of the entire basin. Currently, commonly used provenance analysis methods include thin section analysis, grain size analysis, heavy mineral assemblage analysis, rare earth element analysis, and zircon U-Pb dating.

[0003] Previously, scholars both domestically and internationally have used heavy minerals (heavy minerals refer to minerals with a density > 2.86 g / cm³, which are often used in provenance studies due to their stable physicochemical properties and resistance to attrition during transport) to analyze sediment provenance, primarily employing techniques such as stable heavy mineral assemblages, individual stable heavy mineral characteristics, heavy mineral maturity, and heavy mineral cluster analysis. However, in cases of sudden, localized geological events leading to abnormally high flow velocities that disrupt regional heavy mineral assemblages or stable heavy mineral distribution patterns, these techniques become ineffective in tracing the provenance. Furthermore, currently, there is no effective provenance tracing method available in the field for situations involving sudden, localized geological events. Summary of the Invention

[0004] In view of this, the present invention aims to propose a method for provenance tracing in multi-source basins and anomalously rapid sedimentary zones based on heavy mineral assemblages and ultra-stable heavy mineral distribution trajectory characteristics, referred to as a heavy mineral distribution trajectory characteristic provenance tracing method. Building upon traditional methods for identifying provenance using heavy mineral assemblages, this invention proposes a provenance tracing method based on the distribution trajectory characteristics of stable heavy minerals (zircon, tourmaline, anatase), which can improve the accuracy of provenance tracing and provide scientific and effective technical guidance for oil and gas field exploration.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows: a method for tracing the distribution trajectory characteristics of heavy minerals, comprising the following steps:

[0006] Step 1: Identify the study basin or well and potential source area, and select rock samples or conduct heavy mineral data surveys for the study basin or well and potential source area respectively.

[0007] Step 2: Prepare, separate and identify heavy minerals from the rock samples selected in Step 1, and classify, organize and summarize the heavy mineral data of the same stratigraphic layer.

[0008] Step 3: After classifying and summarizing the heavy mineral data from Step 2, calculate the content of stable heavy minerals in each individual sample.

[0009] Step 4: Based on the statistical results of Step 3, draw a distribution trajectory trend diagram of stable heavy minerals;

[0010] Step 5: Based on the distribution trajectory trend map of stable heavy minerals drawn in Step 4, conduct a horizontal comparative analysis to study the distribution trajectory characteristics of stable heavy minerals in the basin or well and the potential source area. Samples with the same stable heavy mineral distribution trajectory trend are presumed to belong to the same source direction, while samples with different heavy mineral distribution trajectory trend characteristics come from different source areas.

[0011] Furthermore, in step 1, when selecting rock samples, it is necessary to first determine the tectonic background of the study basin or well, the specific study stratigraphic level, and the potential source area.

[0012] Furthermore, the target area for the study should be selected, and the feasibility of selecting rock samples for the target area should be ensured, or that there is sufficient heavy mineral data for the target area.

[0013] Furthermore, it is necessary to select more than 50 rock samples or more than 50 heavy mineral data from the target area, and conduct a thorough investigation into the geological structure, water system, and major events in geological history surrounding the target area.

[0014] Furthermore, in step 2, the preparation, separation, and identification of heavy minerals are based on the "SY / T6336-2019 Methods for Separation and Identification of Heavy Minerals in Sedimentary Rocks".

[0015] Furthermore, in step 3, heavy minerals are classified into extremely unstable, unstable, moderately stable, stable, and ultra-stable heavy minerals according to their geochemical characteristics, lattice energy, and weathering resistance. The relative content of different heavy minerals in a single sample is then calculated.

[0016] Furthermore, in step 4, a distribution trajectory trend diagram of stable heavy minerals is drawn based on the different heavy mineral contents in a single sample.

[0017] Furthermore, in step 5, more than 50 samples are selected from the study basin or well and the potential source area respectively, and the stable heavy mineral distribution trajectory trend characteristics of the study basin or well and the potential source area are analyzed by comparison.

[0018] This invention is applicable whether the sediment source is localized or multiple sources simultaneously entering the basin, enabling directional tracing of each individual source from its deltaic entry into the sea basin. For anomalies where the distribution of heavy minerals does not conform to the overall zonal distribution patterns of submarine fans, traditional methods of determining source direction using only heavy mineral assemblage characteristics are infeasible. This is because abnormally high flow velocities caused by sudden local geological events can interfere with regional heavy mineral assemblage or stable heavy mineral distribution patterns. This invention innovatively proposes a dual-control source tracing method combining stable heavy mineral distribution trajectory characteristics with heavy mineral assemblage characteristics, which can effectively trace sediment sources.

[0019] Compared with existing technologies, the heavy mineral distribution trajectory feature source tracing method of the present invention has the following advantages: The present invention proposes a heavy mineral distribution trajectory feature source tracing method. This method can trace the direction of each single source from the delta into the sea basin, whether it is a local source or when multiple sources enter the basin at the same time. For anomalies where the distribution of heavy minerals does not conform to the overall distribution pattern of the zone and does not meet the heavy mineral assemblage characteristics of the submarine fan, this method can also be used to effectively trace the source by combining the dual-control source tracing of heavy mineral assemblage characteristics. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0021] Figure 1 This is a distribution trajectory diagram of heavy minerals in rock samples from the MS Group in the QX Basin.

[0022] Figure 2 A distribution trajectory diagram of heavy minerals in potential source region A;

[0023] Figure 3 This is a distribution trajectory diagram of heavy minerals in potential source region B. Detailed Implementation

[0024] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0025] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. However, the present invention is not limited to these embodiments.

[0026] This invention relates to a source tracing method based on the distribution trajectory characteristics of heavy minerals. Whether in cases of local sources or multiple sources entering a basin simultaneously, this method can trace the direction of each individual source as it flows from the delta into the sea basin. For anomalies where the distribution of heavy minerals does not conform to the overall zonal distribution pattern of the submarine fan heavy mineral assemblage, this method can also be used in conjunction with dual-control source tracing based on heavy mineral assemblage characteristics for effective source tracing. The method includes the following steps:

[0027] Step 1: Identify the study basin or well (area) and potential source areas, and select rock samples or conduct heavy mineral data surveys for the study basin or well (area) and potential source areas respectively. When selecting rock samples, the first step is to determine the tectonic background, specific study stratigraphic position, and potential source areas of the study basin or well (area).

[0028] Select a target area for study and ensure the feasibility of selecting rock samples or the availability of sufficient heavy mineral data. Select at least 50 rock samples (cores or wellbore cores) or at least 50 samples of heavy mineral data from the target area, and conduct a thorough investigation of the geological tectonic background, drainage systems, and major geological events in the surrounding area (east, west, south, and north). Select at least 50 rock samples from outcrops of relevant drainage systems in the potential source area, or conduct a thorough investigation and collection of heavy mineral data from rocks surrounding relevant drainage systems in the potential source area.

[0029] This step requires attention to two aspects. First, the selected research target area must have sufficient heavy mineral data, preferably core or wall core samples, to represent the most accurate information about the strata. If the existing heavy mineral data is less than 50 samples, the number of newly prepared heavy mineral samples plus the existing samples must exceed 50 to ensure the representativeness of the statistical data and research results. Second, the potential source area surrounding the selected research target area must have sufficient heavy mineral data, and this potential source area must meet the conditions for conducting on-site geological investigations and sampling for heavy mineral analysis.

[0030] Step 2: Prepare, separate and identify heavy minerals from the rock samples selected in Step 1. Classify, organize and summarize the heavy mineral data of the same stratum. The preparation, separation and identification of heavy minerals shall be carried out in accordance with the "SY / T 6336-2019 Method for Separation and Identification of Heavy Minerals in Sedimentary Rocks".

[0031] If resampling and analysis are required, the rock samples selected in step 1 will undergo heavy mineral preparation, separation, and identification according to "SY / T 6336-2019 Methods for Separation and Identification of Heavy Minerals in Sedimentary Rocks". Based on different heavy mineral geochemical characteristics, lattice energy, weathering resistance, and other indicators, heavy minerals will be classified into extremely unstable, unstable, moderately stable, stable, and ultra-stable heavy minerals. The relative contents of different heavy minerals in individual samples will be statistically analyzed. The classification table is shown below.

[0032]

[0033] Step 3: After classifying and summarizing the heavy mineral data from Step 2, screen and statistically analyze the content of stable heavy minerals such as zircon, tourmaline, and anatase in individual samples.

[0034] In this step, it's important to note that during data screening and statistical analysis, samples with poor representativeness, such as those containing high levels of iron ore or barite, should be removed to ensure that the selected samples accurately represent the true formation information. Additionally, when calculating the average content of a specific heavy mineral in a single well, individual samples with excessively high or low values ​​should be discarded.

[0035] Step 4: Draw the distribution trajectory trend of stable heavy minerals such as zircon, tourmaline, and anatase based on the different heavy mineral contents in a single sample.

[0036] Step 5: Based on the distribution trajectory trend map of stable heavy minerals drawn in Step 4, conduct a horizontal comparative analysis of the distribution trajectory characteristics of stable heavy minerals in the basin or well (area) and potential source areas. In actual operation, select more than 50 samples from each of the basin or well (area) and potential source areas for horizontal comparative analysis of the distribution trajectory trend characteristics of stable heavy minerals in the basin or well (area) and potential source areas. Samples with the same stable heavy mineral distribution trajectory trend are presumed to belong to the same source direction; conversely, samples with different heavy mineral distribution trajectory trend characteristics come from different source areas.

[0037] Application examples:

[0038] The study basin QX Basin, as well as potential source areas A and B, were identified. Rock samples were selected or heavy mineral data were collected for QX Basin, as well as potential source areas A and B.

[0039] Heavy minerals were prepared, separated, and identified from the selected rock samples. Heavy mineral data from the same stratigraphic layer were classified, organized, and summarized.

[0040] After classifying and summarizing the heavy mineral data, the content of stable heavy minerals such as zircon, tourmaline, and anatase in individual samples was screened and statistically analyzed.

[0041] Based on the different heavy mineral contents in individual samples, distribution trajectory trends of stable heavy minerals such as zircon, tourmaline, and anatase were plotted, such as... Figure 1 As shown, this illustrates the distribution trajectory characteristics of heavy minerals in rock samples from the MS Formation in the QX Basin. Figure 2 The image shows the distribution trajectory of heavy minerals in potential source region A. Figure 3 The figure shown is a distribution trajectory of heavy minerals in potential source region B.

[0042] Based on the plotted distribution trajectory of stable heavy minerals, a comparative analysis was conducted on the distribution trajectory characteristics of stable heavy minerals in the QX Basin and potential source areas A and B. Figure 1 As shown, the heavy mineral distribution pattern of rock samples from the MS Formation in the QX Basin is characterized by: tourmaline > zircon > anatase > garnet; for example... Figure 2 As shown, the heavy mineral distribution trajectory of potential source region A is characterized by: zircon > anatase > tourmaline > garnet; as... Figure 3 As shown, the heavy mineral distribution trajectory of potential source region B is characterized by: tourmaline > zircon > anatase > garnet.

[0043] A comparative analysis of the distribution trajectory of ultrastable heavy minerals in the QX Basin with potential source areas A and B reveals that the distribution trajectory of ultrastable heavy minerals in potential source area B is similar to that in the basin, indicating that the MS Formation in the QX Basin originated from potential source area B.

[0044] This invention innovatively proposes a source tracing method based on the distribution trajectory characteristics of heavy minerals. This method can trace the direction of each individual source from its deltaic entry into the sea basin, whether in local or multi-source simultaneous entry situations. For anomalies where the distribution of heavy minerals does not conform to the overall zonal distribution pattern of the submarine fan heavy mineral assemblage, this method, combined with dual-control source tracing based on heavy mineral assemblage characteristics, can effectively trace the source. The heavy mineral assemblage characteristic source tracing method is relatively common, using different stable heavy mineral assemblages to distinguish the source. For example, the stable heavy mineral assemblage of block A is zircon + leucoxene + garnet, excluding tourmaline, rutile, and anatase. The stable heavy mineral assemblage of block B is tourmaline + rutile + anatase, excluding zircon, leucoxene, and garnet. This indicates that blocks A and B originate from different source areas.

[0045] This invention is applicable whether the sediment source is localized or multiple sources simultaneously entering the basin, enabling directional tracing of each individual sediment source from its deltaic entry into the sea basin. For anomalies where the distribution of heavy minerals does not conform to the overall zonal distribution patterns of submarine fan heavy mineral assemblages, traditional methods of determining source direction using only heavy mineral assemblage characteristics are infeasible. This is because abnormally high flow velocities caused by sudden local geological events can interfere with regional heavy mineral assemblages or stable heavy mineral distribution patterns. This invention innovatively proposes a dual-control source tracing method combining ultra-stable heavy mineral distribution trajectory characteristics with heavy mineral assemblage characteristics, which can effectively trace sediment sources.

[0046] The beneficial effects of this invention are as follows: Previously, domestic and international scholars mainly used techniques such as stable heavy mineral assemblage characteristics, individual stable heavy mineral characteristics, heavy mineral maturity, and heavy mineral cluster analysis to analyze sediment sources. However, in cases of sudden local geological events leading to abnormally high flow velocities that disrupt regional heavy mineral assemblages or stable heavy mineral distribution patterns, these techniques are insufficient to trace the source. This invention innovatively proposes a source tracing method based on heavy mineral distribution trajectory characteristics. This method, whether for local sources or multiple sources entering the basin simultaneously, can trace the direction of each individual source from the delta into the sea basin. For anomalies where the heavy mineral distribution does not conform to the overall zonal distribution pattern of the submarine fan heavy mineral assemblage characteristics, this method can be combined with existing heavy mineral assemblage characteristic source tracing methods for dual-control source tracing, thereby effectively tracing the source.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for tracing the provenance of heavy mineral distribution trajectories, characterized in that, Includes the following steps: Step 1: Identify the study basin or well and potential source areas, and select rock samples or conduct heavy mineral data surveys for the study basin or well and potential source areas respectively; select the study target area and conduct a thorough investigation of the geological tectonic background, drainage system and major events in geological history around the study target area. Step 2: Prepare, separate and identify heavy minerals from the rock samples selected in Step 1, and classify, organize and summarize the heavy mineral data of the same stratigraphic layer. Step 3: After classifying and summarizing the heavy mineral data from Step 2, the content of stable heavy minerals in a single sample is calculated. According to the geochemical characteristics, lattice energy, and weathering resistance of different heavy minerals, heavy minerals are classified into extremely unstable, unstable, moderately stable, stable, and ultra-stable heavy minerals, and the relative content of different heavy minerals in a single sample is calculated. Step 4: Based on the statistical results of Step 3, draw a distribution trajectory trend diagram of stable heavy minerals; Step 5: Based on the distribution trajectory trend map of stable heavy minerals drawn in Step 4, conduct a horizontal comparative analysis to study the distribution trajectory characteristics of stable heavy minerals in the basin or well and the potential source area. Samples with the same stable heavy mineral distribution trajectory trend are presumed to belong to the same source direction, while samples with different heavy mineral distribution trajectory trend characteristics come from different source areas.

2. The method for tracing the distribution trajectory characteristics of heavy minerals according to claim 1, characterized in that: In step 1, when selecting rock samples, it is necessary to first determine the tectonic background of the basin or well under study, the specific stratigraphic level to be studied, and the potential source area.

3. The method for tracing the distribution trajectory characteristics of heavy minerals according to claim 2, characterized in that: Ensure the feasibility of selecting rock samples for the target area or that there is sufficient heavy mineral data for the target area.

4. The method for tracing the distribution trajectory characteristics of heavy minerals according to claim 3, characterized in that: It is necessary to select more than 50 rock samples or more than 50 heavy mineral data from the target area.

5. The method for tracing the distribution trajectory characteristics of heavy minerals according to claim 1, characterized in that: In step 2, the preparation, separation, and identification of heavy minerals are based on the "SY / T 6336-2019 Methods for Separation and Identification of Heavy Minerals in Sedimentary Rocks".

6. The method for tracing the distribution trajectory characteristics of heavy minerals according to claim 1, characterized in that: In step 4, a distribution trajectory trend diagram of stable heavy minerals is drawn based on the different heavy mineral contents in a single sample.

7. The method for tracing the distribution trajectory characteristics of heavy minerals according to claim 1, characterized in that: In step 5, more than 50 samples are selected from the study basin or well and the potential source area respectively, and the stable heavy mineral distribution trajectory trend characteristics of the study basin or well and the potential source area are analyzed by comparison.

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