Helium geological sweet spot prediction method
By combining the multi-source helium supply and multi-element migration models of the craton basin and utilizing various exploration data to identify helium geological sweet spots, the problem of inaccurate helium enrichment prediction was solved, and efficient development of helium exploration was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- PETROCHINA CO LTD
- Filing Date
- 2024-11-22
- Publication Date
- 2026-05-22
Smart Images
Figure CN122071942A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of helium exploration and development technology, specifically relating to a method for predicting helium geological sweet spots. Background Technology
[0002] Helium is a non-renewable and important strategic resource. Currently, China is heavily reliant on imports for helium resources, and demand is growing at an annual rate of over 10%. If the helium supply is cut off, it will cause a standstill in high-tech industries and scientific research activities. Therefore, conducting geological theory and technology research on helium resources to guide and support the exploration and development of helium resources in China has become one of the most urgent tasks in the field of resource geology research in China.
[0003] Helium in natural gas reservoirs differs significantly from hydrocarbons in origin and source, often exhibiting a "same reservoir, different origin" pattern. Hydrocarbons originate from sedimentary organic matter, representing an organic origin, while helium primarily arises from the radioactive decay of uranium (U) and thorium (Th) in source rocks such as granites in the Earth's crust and mantle, representing an inorganic origin. Because current oil and gas resource assessment and prediction technologies mainly target hydrocarbons, their genesis and reservoir formation theories cannot effectively guide helium resource exploration and development, and are not applicable to helium resource assessment and prediction. Therefore, predicting helium enrichment geological sweet spots remains a major challenge.
[0004] To address this issue, scholars in fields such as geology, natural gas resources, and gas geochemistry have taken various approaches. Some have focused on the distribution of helium source rocks in low-exploration areas to determine the scope of helium exploration and calculate helium resources. However, by focusing solely on the single factor of helium "source," they lack a comprehensive study of the "migration" and "storage" conditions of sedimentary strata, making it difficult to accurately predict sweet spots for helium enrichment.
[0005] Some methods, targeting mature exploration areas, summarize and analyze the formation models of different helium-rich natural gas reservoirs, predicting favorable helium exploration areas from aspects such as the basement, faults, and caprock. However, this is a relatively rough and broad prediction method, lacking in-depth quantitative research on helium reservoirs. Moreover, this prediction method mainly targets helium sources in basement metamorphic rocks and is not suitable for predicting sweet spots in helium-rich areas of cratonic basins with multiple helium sources, multiple migration patterns, and multi-level helium storage characteristics. Therefore, the geological sweet spot prediction method for helium-rich reservoirs in cratonic basins needs further improvement. Summary of the Invention
[0006] The purpose of this invention is to provide a method for predicting helium geological sweet spots. Based on the characteristics of cratonic basins, such as "multi-source helium supply from both basement-type and sedimentary-type helium sources," "multi-various migration patterns of helium through dispersion and fracture-fracture migration," and "multi-level reservoir helium storage," this invention addresses the three main controlling factors affecting helium reservoir formation: helium generation, helium migration, and helium storage. This solves the problem that existing methods for predicting helium geological sweet spots are not applicable to maturely explored cratonic areas and are difficult to accurately predict helium-enriched sweet spot regions.
[0007] This invention targets mature craton basins for helium geological sweet spot prediction. Mature craton basins have accumulated a wealth of exploration data over long-term exploration, including gravity and magnetic data, magnetic anomaly data, and well logging, well logging, and gas testing data. They also include various seismic geological structure data such as natural gamma spectral logging data, imaging logging data, drilling sampling experimental data, and seismic inversion profiles, as well as a large amount of lithological analysis data, all of which can be used in this invention for the analysis and prediction of helium geological sweet spot areas.
[0008] The technical solution adopted in this invention is a method for predicting helium geological sweet spots, characterized by the following implementation steps: Step 1: Collect magnetic anomaly data of the target craton basin area, draw ΔT contour maps based on the magnetic anomaly data, and identify areas with positive magnetic anomaly values in the ΔT contour maps as potential U and Th-containing areas; Step 2: In potential U and Th-bearing regions with magnetic anomalies ≥ 50 Nt, identify the basement helium source rock helium generation and supply zones; Step 3: In potential U and Th-bearing areas, identify the helium source rocks and helium supply zones in sedimentary strata, and draw helium generation intensity maps for each stratum in the sedimentary rock formations; Step 4: Collect logging, well logging, and gas testing data of the target craton basin area, and draw a contour map of hydrocarbon gas reservoir thickness based on the logging, well logging, and gas testing data, and mark the potential helium-enriched sweet spot areas on the map; Step 5: Collect seismic inversion profile data of the target craton basin area, and then determine the area of tectonic uplift in the target craton basin, as well as the extension of faults and fractures, through regional stratigraphic correlation. Step 6: Compare the area of the tectonic uplift with the helium-generating and supplying area of the basement helium source rock identified in Step 2, the helium generation intensity map of each rock layer in the sedimentary rock strata obtained in Step 3, and the reservoir thickness contour map obtained in Step 4. If the area meets condition 1, then the area is considered to be an advantageous area for helium migration and reservoir formation. Step 7: First, based on the relationship between the extension of fractures and cracks and the basement strata, determine the main channels for helium migration. Then, compare the main channels for helium migration with the basement helium source rock helium generation and supply areas determined in Step 2 and the reservoir thickness contour map obtained in Step 4. Find the areas that meet condition 2, and consider these areas as the advantageous areas for helium migration and reservoir formation. Step 8: Compare the helium generation intensity map of each rock layer in the sedimentary rock strata obtained in Step 3 with the reservoir thickness contour map obtained in Step 4, and find the area that meets condition 3. Then, the area is considered to be the advantageous area for helium migration and reservoir formation. Step 9: The advantageous areas for helium accumulation identified through Step 6, Step 7, or Step 8 are the geological sweet spots for helium.
[0009] A further feature of this invention is that step 2 includes the following sub-steps: Step 2.1: Taking the potential U and Th-bearing areas with magnetic anomalies ≥50 Nt in the ΔT contour map as the first target range, collect well logging data and drilling sampling experimental data within the first target range in the target craton basin to determine the stratigraphic information of the basement strata in the potential U and Th-bearing areas; Step 2.2: Based on the logging data and drilling sampling experimental data obtained in Step 2.1, further verify the location of the actual U and Th-containing basement strata within the first target area. If so, the basement area is considered to be the basement helium source rock helium generation and supply area.
[0010] Step 3 includes the following sub-steps: Step 3.1: Using the potential U and Th-containing areas identified in Step 1 as the second target area, collect well logging data and drilling sampling experimental data within the second target area of the target craton basin; Step 3.2: Based on the logging data obtained in Step 3.1, determine the stratigraphic information of various rock layers in the sedimentary rock formation within the second target area, and then verify the location of the actual U and Th-containing rock layers in the sedimentary rock formation within the second target area based on the drilling sampling test data obtained in Step 3.1. Step 3.3: Further determine the U and Th content data in the rock strata containing U and Th based on the drilling sampling test data obtained in Step 3.1. Among them, the rock strata with U content ≥ 2.7 ppm and Th content ≥ 10.5 ppm in the sedimentary rock strata are considered to be the sedimentary helium source rock helium generation and supply area. Step 3.4: Based on the U and Th content data of each rock layer in the helium source rock helium-producing and supplying zone of the sedimentary layer, the helium-producing intensity of each rock layer is calculated using the helium-producing intensity calculation formula. Based on the obtained helium-producing intensity data, a helium-producing intensity map of each rock layer in the sedimentary rock strata of the second target range is drawn.
[0011] The formula for calculating the helium production intensity used in step 3.4 is σ = (λC1 + δC2). Where σ is the helium generation intensity; λ is the uranium decay constant; C1 is the uranium content per gram of rock; δ is the thorium decay constant; and C2 is the thorium content per gram of rock.
[0012] Step 4 includes the following sub-steps: Step 4.1: Collect logging, well logging, and gas testing data of the target craton basin area, and determine the stratigraphic position and region of hydrocarbon gas reservoirs in the target craton basin area based on the logging, well logging, and gas testing data. Define a single hydrocarbon gas reservoir with a thickness ≥1m as an effective reservoir and as a layer. Draw a reservoir thickness contour map based on the cumulative thickness of all effective reservoirs. Step 4.2: Define the region with a hydrocarbon gas reservoir level ≥3 or a cumulative reservoir thickness ≥3m as a potential helium-enriched sweet spot region and mark it on the hydrocarbon gas reservoir thickness contour map.
[0013] Condition 1 in step 6 is: 1) A certain area is located within the helium-generating and helium-supplying zone of the basement helium source rocks; 2) In a certain region, a certain rock layer in a sedimentary stratum is located where the helium generation intensity is ≥1 cm⁻¹. 3 / year·gram rock area; 3) A certain area is located in a potential helium-rich sweet spot region on the reservoir thickness contour map; 4) A certain area is located within a tectonic uplift region.
[0014] Step 7 includes the following sub-steps: Step 7.1: Determine the relationship between each fracture and crack and the basement strata, and classify them as follows: A. The fractures and cracks extend downward to the basement and upward to the reservoir, but they do not penetrate the caprock. B. The fractures and cracks extend downward to the basement but do not extend upward to the reservoir, but the distance between the fractures / cracks and the effective reservoir is ≤100m; C. The fracture or crack does not extend downward to the base, or the fracture or crack extends upward and penetrates the cap layer, or other situations. Step 7.2: If the extension of the fracture or crack conforms to the A or B category in Step 7.1, then the fracture or crack is considered to be the main channel for helium migration. Step 7.3: If a region meets condition 2, then the region is considered to be an advantageous region for helium transport and accumulation.
[0015] Condition 2 in step 7.3 is: 1) A certain area is located within the helium-generating and helium-supplying zone of the basement helium source rocks; 2) A certain area is located in a potential helium-rich sweet spot region on the reservoir thickness contour map; 3) There is a major channel for helium migration in a certain area.
[0016] Condition 3 in step 8 is: 1) In a certain area, a certain rock layer in a sedimentary stratum is located where the helium generation intensity is ≥1 cm⁻¹. 3 / year·gram rock area; 2) A certain area is located in a potential helium-rich sweet spot region on the reservoir thickness contour map; 3) The distance between the helium source rock helium-generating and helium-supplying area of the sedimentary layer that meets condition 1) and the effective reservoir that meets condition 2) is ≤100m.
[0017] The beneficial effects of this invention are as follows: Based on fully considering the characteristics of craton basins, such as "multi-source helium supply from basement-type and sedimentary-type helium sources," "multi-various migration patterns of helium through dispersion and fracture-fracture transport," and "multi-level reservoir helium storage," the invention identifies basement helium source rock helium supply zones and sedimentary helium source rock helium supply zones. It also considers helium dispersion conditions and basement fracture-fracture transport conditions, as well as the fact that multi-level natural gas reservoirs are also reservoirs with helium capture and storage capabilities. Furthermore, it evaluates helium geological resources from the three main geological control factors of helium reservoir generation, migration, and storage, predicting helium-enriched sweet spots. This invention represents a comprehensive innovation in the prediction method for helium-enriched sweet spots in craton basins.
[0018] This invention can accurately predict sweet spots where helium is enriched, providing strong geological evidence and referable technology for efficient and high-quality helium exploration and development. It has important guiding significance for promoting helium exploration and development research in my country and ensuring the safety of helium use in my country. Attached Figure Description
[0019] Figure 1 This is an aeromagnetic ΔT contour map of a certain detection area; Figure 2 This is an example of a well logging response map for a certain detection area; Figure 3 This is a helium generation intensity map of a specific rock layer within a sedimentary rock stratum in a certain exploration area; Figure 4 This is a seismic inversion profile of a certain detection area; Figure 5 This is a diagram showing the distribution pattern of helium source rocks, fractures, and multi-level reservoirs within an ancient uplift area of a certain exploration zone. Figure 6 This is a schematic diagram of the helium escape, migration, and accumulation model in a certain detection area; Figure 7 It is a contour map of the reservoir thickness of hydrocarbon gas reservoirs and a distribution map of potential helium sweet spots in a certain exploration area. Detailed Implementation
[0020] This invention targets mature craton basins for helium geological sweet spot prediction. Mature craton basins have accumulated a wealth of exploration data over long-term exploration, including gravity and magnetic data, magnetic anomaly data, and well logging, well logging, and gas testing data. They also include various seismic geological structure data such as natural gamma spectral logging data, imaging logging data, drilling sampling experimental data, and seismic inversion profiles, as well as a large amount of lithological analysis data, all of which can be used in this invention for the analysis and prediction of helium geological sweet spot areas.
[0021] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.
[0022] Example 1: like Figure 1-7 As shown, the method for predicting helium geological sweet spots includes the following implementation steps: Step 1: Collect magnetic anomaly data for the target craton basin area, and plot ΔT contour maps based on the magnetic anomaly data, such as... Figure 1 As shown, the regions with positive magnetic anomaly values in the ΔT contour map are identified as potential regions containing U and Th, and the regions with larger magnetic anomaly differences tend to have higher U and Th content. Step 2: In potential U- and Th-bearing regions with magnetic anomalies ≥ 50 Nt, determine the basement helium source rock helium generation and supply zones, which includes the following sub-steps: Step 2.1: Using the potential U- and Th-bearing areas with magnetic anomalies ≥ 50 Nt in the ΔT contour map as the first target area, collect well logging data within the first target area of the target cratonic basin (e.g., Figure 2 (as shown) and drilling sampling test data; Step 2.2: Based on the logging data and drilling sampling experimental data obtained in Step 2.1, further verify the location of the actual U and Th-containing basement strata within the first target area. If the basement area is considered to be the basement helium source rock helium generation and supply area; Step 3: In potential U- and Th-bearing regions, identify the helium source rocks and helium supply zones in the sedimentary strata, and draw helium generation intensity maps for each stratum within the sedimentary rock formations. This includes the following sub-steps: Step 3.1: Using the potential U- and Th-bearing areas identified in Step 1 as the second target area, collect well logging data (e.g., ...) within the second target area of the target craton basin. Figure 2 (as shown) and drilling sampling test data; Step 3.2: Based on the logging data obtained in Step 3.1, such as... Figure 2As shown, the stratigraphic information of various rock layers such as black slate, argillaceous dolomite, bauxite, mudstone, sandstone and coal in the sedimentary rock strata within the second target range is determined. Then, based on the drilling sampling experimental data obtained in step 3.1, the location of the actual U and Th-containing rock layers in the sedimentary rock strata within the second target range is verified. Step 3.3: Further determine the U and Th content data in the rock strata containing U and Th based on the drilling sampling test data obtained in Step 3.1. Among them, the rock strata with U content ≥ 2.7 ppm and Th content ≥ 10.5 ppm in the sedimentary rock strata are considered to be the sedimentary helium source rock helium generation and supply area. Step 3.4: Based on the U and Th content data of each rock layer in the helium-generating and helium-supplying zone of the sedimentary helium source rocks, calculate the corresponding helium generation intensity of each rock layer using the helium generation intensity calculation formula. Then, based on the obtained helium generation intensity data, draw a helium generation intensity map of each rock layer in the sedimentary strata within the second target area, as shown below. Figure 3 As shown; Step 4: Collect well logging, well logging, and gas testing data for the target cratonic basin area, and draw a hydrocarbon gas reservoir thickness contour map based on the well logging, well logging, and gas testing data. Mark potential helium-enriched sweet spots on the map. This includes the following sub-steps: Step 4.1: Collect well logging, well logging, and gas testing data for the target cratonic basin area, and determine the stratigraphic positions and regions where hydrocarbon gas reservoirs are distributed within the target cratonic basin area based on the well logging, well logging, and gas testing data, such as... Figure 5 , Figure 6 As shown, an effective reservoir with a thickness ≥1m is defined as a single hydrocarbon gas reservoir, and it is considered as one layer. A reservoir thickness contour map is drawn based on the cumulative thickness of all effective reservoirs, as shown below. Figure 7 As shown; Step 4.2: Define regions with hydrocarbon gas reservoir layer level ≥3 or cumulative thickness ≥3m as potential helium enrichment sweet spots, and mark them on the hydrocarbon gas reservoir thickness contour map, such as... Figure 7 The shaded area indicated by the horizontal line; Step 5: Collect data such as seismic inversion profiles of the target craton basin area, such as... Figure 4 As shown, this study analyzes the geological structure, tectonic deformation, and subsidence information of the cratonic basin. Through regional stratigraphic correlation, it identifies the areas of tectonic uplift in the target cratonic basin and the extension of faults and fissures. Figure 5 The structural uplifts and fracture-crack development shown in the diagram; Step 6: Compare the area of the tectonic uplift with the helium-generating and supplying area of the basement helium source rock identified in Step 2, the helium generation intensity map of each rock layer in the sedimentary rock strata obtained in Step 3, and the reservoir thickness contour map obtained in Step 4. If the area meets condition 1, then the area is considered to be an advantageous area for helium migration and reservoir formation. Step 7: First, based on the relationship between the extension of fractures and cracks and the basement strata, determine the main channels for helium migration. Then, connect the main channels for helium migration with the basement helium source rock helium-generating and supplying areas determined in Step 2, and the reservoir thickness contour maps obtained in Step 4 (e.g., Figure 7 By comparing with the area shown, regions that meet condition 2 are identified, and these regions are considered to be advantageous areas for helium transport and accumulation. This process includes the following detailed steps: Step 7.1: Determine the relationship between each fracture and crack and the basement strata, and classify them as follows: A. The fractures and cracks extend downward to the basement and upward to the reservoir, but they do not penetrate the caprock. B. The fractures and cracks extend downward to the basement but do not extend upward to the reservoir, but the distance between the fractures / cracks and the effective reservoir is ≤100m; C. The fracture or crack does not extend downward to the base, or the fracture or crack extends upward and penetrates the cap layer, or other situations. Step 7.2: If the extension of the fracture or crack conforms to the A or B category in Step 7.1, then the fracture or crack is considered to be the main channel for helium migration. Step 7.3: If a region meets condition 2, then the region is considered to be an advantageous region for helium transport and accumulation. Step 8: Obtain the helium generation intensity map of each rock layer in the sedimentary rock strata obtained in Step 3 (e.g., ...). Figure 3 (as shown) and the reservoir thickness contour map obtained in step 4 (as shown) Figure 7 By comparing with the area shown in the figure, the area that meets condition 3 is considered to be an advantageous area for helium transport and accumulation. Step 9: The advantageous areas for helium accumulation identified through Step 6, Step 7, or Step 8 are the geological sweet spots for helium.
[0023] In this embodiment, the basis for the judgment in step 7.2 is as follows: the deeper the fractures and cracks extend into the basement, the more conducive it is for helium generated by the basement helium source to migrate up through the fractures and cracks, and the more conducive it is for helium accumulation; when the fractures and cracks extend upward without penetrating the caprock, the closer the fractures and cracks connecting the basement are to the reservoir, the better the reservoir's helium capture and accumulation capacity. Effective reservoirs within 100m of the fracture are more likely to accumulate and form reservoirs through the escape migration mode. The reason for not considering the C-type case is that if the fracture or crack does not reach the base, it is impossible to connect to the helium source; if the fracture or crack penetrates the caprock, the helium transported through the fracture or crack will escape into the atmosphere and will be difficult to accumulate into a reservoir.
[0024] The working principle of this embodiment: Step 2 of this invention involves determining the stratigraphic information of the basement strata within the first target range from well logging data. Based on this stratigraphic information, it further determines which drilling sampling data are from samples taken from the basement strata within the first target range, and whether the samples contain U and Th. The area where samples containing U and Th are located is the actual area containing U and Th basement strata, thereby identifying the basement helium source rock helium generation and supply zone.
[0025] Step 3 of this invention involves determining the stratigraphic information of various rock strata, such as black slate, argillaceous dolomite, bauxite, mudstone, sandstone, and coal, from well logging data. Based on the stratigraphic information of each rock stratum, it further determines which drilling sampling data pertains to which rock stratum within the second target area, and whether the samples contain U and Th. The rock strata and region containing U and Th are the actual U- and Th-bearing rock strata and their corresponding areas.
[0026] The drilling sampling test data includes not only information on whether the sample contains U and Th, but also the specific U and Th content data in the sample. Therefore, in step 3.3, the area where the rock strata with U and Th content reaches a certain value can be identified as the helium source rock helium generation and supply area of the sedimentary layer; in step 4, the corresponding helium generation intensity of each rock strata can be calculated based on the U and Th content data.
[0027] This invention, based on the identification of helium-generating and supplying zones in basement helium source rocks and sedimentary helium source rocks, considers helium escape conditions, helium migration conditions via basement fractures and fissures, and the fact that multi-level natural gas reservoirs also possess helium-capturing and storage capabilities. Then, based on these research conditions, it evaluates and predicts helium-enriched sweet spots. This invention, after determining that the main controlling factors for helium-rich reservoirs are helium source rock type, fractures and fissures, and reservoir characteristics, analyzes the relationship between these main controlling factors and helium-enriched sweet spots, and determines the helium-enriched sweet spots according to the correlation.
[0028] Example 2: Based on Example 1, the helium geological sweet spot prediction method uses the helium generation intensity calculation formula σ=(λC1+δC2) in step 3.4. Where σ is the helium generation intensity; λ is the uranium decay constant; C1 is the uranium content per gram of rock (measured value); δ is the thorium decay constant; and C2 is the thorium content per gram of rock (measured value).
[0029] The working principle of this embodiment is the same as that of Embodiment 1, and will not be repeated here.
[0030] Example 3: Based on Example 1, the condition 1 in step 6 of this helium geological sweet spot prediction method is: 1) A certain area is located within the helium-generating and helium-supplying zone of the basement helium source rocks; 2) In a certain region, a certain rock layer in a sedimentary stratum is located where the helium generation intensity is ≥1 cm⁻¹. 3 / year·gram rock area; 3) A certain area is located in a potential helium-rich sweet spot region on the reservoir thickness contour map; 4) A certain area is located within a tectonic uplift region.
[0031] In this embodiment, the basis for setting condition 1 is: if there is a tectonic paleo-uplift in the craton basin area, the paleo-uplift basement and sedimentary layers will rise accordingly, which will shorten the source-reservoir distance of helium and form a large number of tectonic fractures. Therefore, the paleo-uplift area is an important condition for judging the advantageous area for helium transport and accumulation.
[0032] The working principle of this embodiment is the same as that of Embodiment 1, and will not be repeated here.
[0033] Example 4: Based on Example 3, the condition 2 in step 7.3 of this helium geological sweet spot prediction method is as follows: 1) A certain area is located within the helium-generating and helium-supplying zone of the basement helium source rocks; 2) A certain area is located in a potential helium-rich sweet spot region on the reservoir thickness contour map; 3) There is a major channel for helium migration in a certain area.
[0034] The working principle of this embodiment is the same as that of Embodiment 1, and will not be repeated here.
[0035] Example 5: Based on Example 4, the condition 3 in step 8 of this helium geological sweet spot prediction method is: 1) In a certain area, a certain rock layer in a sedimentary stratum is located where the helium generation intensity is ≥1 cm⁻¹. 3 / year·gram rock area; 2) A certain area is located in a potential helium-rich sweet spot region on the reservoir thickness contour map; 3) The distance between the helium source rock helium-generating and helium-supplying area of the sedimentary layer that meets condition 1) and the effective reservoir that meets condition 2) is ≤100m.
[0036] The working principle of this embodiment is the same as that of Embodiment 1, and will not be repeated here.
[0037] Example 6: Based on Example 1, this method for predicting helium geological sweet spots uses airborne geophysical surveying technology in step 1 to obtain magnetic anomaly data of the target craton basin. The airborne geophysical surveying technology used is to use UAV aeromagnetic surveying to perform area measurements of the craton basin region and obtain the ΔT magnetic anomaly data of the region.
[0038] The working principle of this embodiment is the same as that of Embodiment 1, and will not be repeated here.
[0039] In other embodiments of the present invention, the magnetic anomaly data of the target craton basin in step 1 can also be obtained by using ground-based nuclear precession magnetometer observation technology to perform area measurements on the craton basin region and obtain the ΔT magnetic anomaly data of the region.
[0040] In other embodiments of the present invention, in step 3, the actual U and Th-containing areas and specific U and Th contents in each sedimentary rock stratum can also be determined by data such as natural gamma spectroscopy logging.
[0041] Example 7: Based on Example 1, the helium generation intensity map drawn in step 3.4 of this helium geological sweet spot prediction method is used not only to accurately predict the helium geological sweet spot area in the craton basin, but also to accurately evaluate the exploitable helium quantity in the sweet spot area, further enhancing the practical application value of this invention in helium exploration and development research.
[0042] The helium generation of the helium source rocks in each sedimentary layer was calculated using the helium generation calculation formula. The formula for calculating the amount of helium produced is: V1 = shρ × (λC1 + δC2) × N Where V1: helium production; s: area; h: thickness; ρ: density; λ: uranium decay constant; C1: uranium content per gram of rock; δ: thorium decay constant; C2: thorium content per gram of rock; N: year.
[0043] Among them, the area (s), thickness (h) and density (ρ) data are the area, thickness and density data of the helium source rock in the corresponding sedimentary rock strata, which can be obtained from drilling sampling test data, well logging data or seismic exploration data.
[0044] The working principle of this embodiment is the same as that of Embodiment 1, and will not be repeated here.
Claims
1. A method for predicting helium geological sweet spots, characterized in that, The implementation steps include the following: Step 1: Collect magnetic anomaly data of the target craton basin area, draw ΔT contour maps based on the magnetic anomaly data, and identify areas with positive magnetic anomaly values in the ΔT contour maps as potential U and Th-containing areas; Step 2: In potential U and Th-bearing regions with magnetic anomalies ≥ 50 Nt, identify the basement helium source rock helium generation and supply zones; Step 3: In potential U and Th-bearing areas, identify the helium source rocks and helium supply zones in sedimentary strata, and draw helium generation intensity maps for each stratum in the sedimentary rock formations; Step 4: Collect logging, well logging, and gas testing data of the target craton basin area, and draw a contour map of hydrocarbon gas reservoir thickness based on the logging, well logging, and gas testing data, and mark the potential helium-enriched sweet spot areas on the map; Step 5: Collect seismic inversion profile data of the target craton basin area, and then determine the area of tectonic uplift in the target craton basin, as well as the extension of faults and fractures, through regional stratigraphic correlation. Step 6: Compare the area of the tectonic uplift with the helium-generating and supplying area of the basement helium source rock identified in Step 2, the helium generation intensity map of each rock layer in the sedimentary rock strata obtained in Step 3, and the reservoir thickness contour map obtained in Step 4. If the area meets condition 1, then the area is considered to be an advantageous area for helium migration and reservoir formation. Step 7: First, based on the relationship between the extension of fractures and cracks and the basement strata, determine the main channels for helium migration. Then, compare the main channels for helium migration with the basement helium source rock helium generation and supply areas determined in Step 2 and the reservoir thickness contour map obtained in Step 4. Find the areas that meet condition 2, and consider these areas as the advantageous areas for helium migration and reservoir formation. Step 8: Compare the helium generation intensity map of each rock layer in the sedimentary rock strata obtained in Step 3 with the reservoir thickness contour map obtained in Step 4, and find the area that meets condition 3. Then, the area is considered to be the advantageous area for helium migration and reservoir formation. Step 9: The advantageous areas for helium accumulation identified through Step 6, Step 7, or Step 8 are the geological sweet spots for helium.
2. The method for predicting helium geological sweet spots according to claim 1, characterized in that, Step 2 includes the following sub-steps: Step 2.1: Taking the potential U and Th-containing areas with magnetic anomalies ≥50 Nt in the ΔT contour map as the first target range, collect well logging data and drilling sampling experimental data within the first target range in the target craton basin; Step 2.2: Based on the logging data and drilling sampling experimental data obtained in Step 2.1, further verify the location of the actual U and Th-containing basement strata within the first target area. If so, the basement area is considered to be the basement helium source rock helium generation and supply area.
3. The method for predicting helium geological sweet spots according to claim 1, characterized in that, Step 3 includes the following sub-steps: Step 3.1: Using the potential U and Th-containing areas identified in Step 1 as the second target area, collect well logging data and drilling sampling experimental data within the second target area of the target craton basin; Step 3.2: Based on the logging data obtained in Step 3.1, determine the stratigraphic information of various rock layers in the sedimentary rock formation within the second target area, and then verify the location of the actual U and Th-containing rock layers in the sedimentary rock formation within the second target area based on the drilling sampling test data obtained in Step 3.
1. Step 3.3: Further determine the U and Th content data in the rock strata containing U and Th based on the drilling sampling test data obtained in Step 3.
1. Among them, the rock strata with U content ≥ 2.7 ppm and Th content ≥ 10.5 ppm in the sedimentary rock strata are considered to be the sedimentary helium source rock helium generation and supply area. Step 3.4: Based on the U and Th content data of each rock layer in the helium source rock helium-producing and supplying zone of the sedimentary layer, calculate the corresponding helium-producing intensity of each rock layer using the helium-producing intensity calculation formula, and draw the helium-producing intensity map of each rock layer in the sedimentary rock strata of the second target range based on the obtained helium-producing intensity data.
4. The method for predicting helium geological sweet spots according to claim 3, characterized in that, The formula for calculating the helium generation intensity is σ=(λC1+δC2). Where σ is the helium generation intensity; λ is the uranium decay constant; C1 is the uranium content per gram of rock; δ is the thorium decay constant; and C2 is the thorium content per gram of rock.
5. The method for predicting helium geological sweet spots according to claim 1, characterized in that, Step 4 includes the following sub-steps: Step 4.1: Collect logging, well logging, and gas testing data of the target craton basin area, and determine the stratigraphic position and region of hydrocarbon gas reservoirs in the target craton basin area based on the logging, well logging, and gas testing data. Define a single hydrocarbon gas reservoir with a thickness ≥1m as an effective reservoir and as a layer. Draw a reservoir thickness contour map based on the cumulative thickness of all effective reservoirs. Step 4.2: Define the region with a hydrocarbon gas reservoir level ≥3 or a cumulative reservoir thickness ≥3m as a potential helium-enriched sweet spot region, and mark it on the hydrocarbon gas reservoir thickness contour map.
6. The method for predicting helium geological sweet spots according to claim 1, characterized in that, Condition 1 in step 6 is: 1) A certain area is located within the helium-generating and helium-supplying zone of the basement helium source rocks; 2) In a certain region, a certain rock layer in a sedimentary stratum is located where the helium generation intensity is ≥1 cm⁻¹. 3 / year·gram rock area; 3) A certain area is located in a potential helium-rich sweet spot region on the reservoir thickness contour map; 4) A certain area is located within a tectonic uplift region.
7. The method for predicting helium geological sweet spots according to claim 1, characterized in that, Step 7 includes the following sub-steps: Step 7.1: Determine the relationship between each fracture and crack and the basement strata, and classify them as follows: A. The fractures and cracks extend downward to the basement and upward to the reservoir, but they do not penetrate the caprock. B. The fractures and cracks extend downward to the basement but do not extend upward to the reservoir, but the distance between the fractures / cracks and the effective reservoir is ≤100m; C. The fracture or crack does not extend downward to the base, or the fracture or crack extends upward and penetrates the cap layer, or other situations. Step 7.2: If the extension of the fracture or crack conforms to the A or B category in Step 7.1, then the fracture or crack is considered to be the main channel for helium migration. Step 7.3: If a region meets condition 2, then the region is considered to be an advantageous region for helium transport and accumulation.
8. The method for predicting helium geological sweet spots according to claim 7, characterized in that, Condition 2 in step 7.3 is: 1) A certain area is located within the helium-generating and helium-supplying zone of the basement helium source rocks; 2) A certain area is located in a potential helium-rich sweet spot region on the reservoir thickness contour map; 3) There is a major channel for helium migration in a certain area.
9. The method for predicting helium geological sweet spots according to claim 1, characterized in that, Condition 3 in step 8 is: 1) In a certain area, a certain rock layer in a sedimentary stratum is located where the helium generation intensity is ≥1 cm⁻¹. 3 / year·gram rock area; 2) A certain area is located in a potential helium-rich sweet spot region on the reservoir thickness contour map; 3) The distance between the helium source rock helium-generating and helium-supplying area of the sedimentary layer that meets condition 1) and the effective reservoir that meets condition 2) is ≤100m.