A method for determining mineralization location using uranium reservoir porosity analysis

Abstract

The present invention discloses a method for determining the location of mineralization using uranium reservoir porosity analysis, comprising the following steps: Step 1: dividing mineralization units; Step 2: analyzing well logging data; Step 3: delineating favorable mineralization belt locations; Step 4: exploration deployment. The present invention has been applied to a certain mineral deposit in Qianjiadian, achieving good results. After applying the method of the present invention to delineate favorable mineralization locations, the exploration success rate in the research area increased from the original 27% to 75%, and the newly added resource volume exceeded 1,000 tons, which is equivalent to the discovery of a small uranium deposit. This method can effectively reduce exploration costs, improve exploration success rates, and has high application value.

Description

Technical Field

[0001] The present invention relates to the field of new energy technology, and in particular to a method for determining a mineralization location by using uranium reservoir porosity analysis. Background Art

[0002] In 2016, "World Nuclear Geology" published the application of comprehensive logging methods by Li Qiang et al. in the exploration of in-situ leaching sandstone-type uranium deposits in the Xinghuangqi area of ​​the Erlian Basin; in 2005, Luo Zhiming expounded on the application of comprehensive logging in the exploration of in-situ leaching sandstone uranium deposits in western Yunnan in his master's thesis; in 2010, Chen Ningning expounded on the study of heterogeneity of braided river delta-phase reservoirs in his master's thesis; in 2020, "Journal of Jilin University (Earth Science Edition)" published Yu Yang et al.'s logging evaluation of in-situ leachable sandstone uranium mineralization in the Sifangtai Formation of Changyuan in Daqing, Songliao Basin; in 2012, "Geological Science and Technology Information" published that Jiao Yangquan et al. studied the mineralization mechanism of sandstone-type uranium reservoirs through the superposition law of mineralization paleoflow field and uranium mineralization.

[0003] The above methods discuss the application of well logging technology in uranium exploration, including the division of lithologic profiles, including the changes and laws of different lithologic layers such as mineralized aquifers and upper and lower aquicludes; accurately locating the spatial location of uranium ore grades; studying the metallogenic environment and metallogenic laws of uranium mineralization, and also introduce the control of reservoir heterogeneity on uranium mineralization. However, there are the following limitations:

[0004] ① Although the determination of the heterogeneity of mineralized aquifers has been mentioned in the application of well logging technology, the research mainly focuses on evaluating the porosity range that is conducive to mineralization. However, the real control of mineralization is the location of porosity mutation rather than a specific porosity range; ② The permeability variation coefficient is an important indicator for evaluating the heterogeneity of mineralized aquifers, but previous studies have not established a quantitative correspondence between it and the uranium mineralization grade; ③ The main factor that constrains the heterogeneity of uranium reservoirs in braided rivers and braided river deltas is the distribution pattern of mudstones in microfacies such as interchannel bays. Previous studies mainly characterized the distribution pattern of sand bodies, and there have been no reports on the distribution pattern of dark mudstones, especially the relationship between the thickness of dark mudstones and their development scale. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a method for determining the mineralization location by using uranium reservoir porosity analysis.

[0006] To solve the above technical problems, the technical solution of the present invention is: a method for determining the mineralization location by using uranium reservoir porosity analysis, comprising the following steps:

[0007] Step 1: Divide the mineralization units; including:

[0008] A. Determine the scale of metallogenic unit division: one or more sedimentary cycles are used as a metallogenic unit;

[0009] B. Determine the top and bottom interfaces of the mineralization unit: If the mudstone at the top of the cycle is 0m < thickness < 1m, the bottom of the mudstone at the top of the cycle shall be taken as the top boundary of the mineralization unit; if the mudstone at the bottom of the cycle is 0m < thickness < 1m, the bottom of the mudstone at the bottom of the cycle shall be taken as the bottom boundary of the mineralization unit; if mudstone is not developed at the top and bottom of the sedimentary cycle, the top and bottom interfaces shall be divided according to the conventional division principles.

[0010] Step 2: Well logging data analysis; including:

[0011] A. Calculate the porosity curve;

[0012] B. Calculate the coefficient of variation of porosity of mineralization units;

[0013] C. Refer to the quantitative evaluation standards for uranium reservoir physical properties to evaluate the mineralization conditions and determine the favorable mineralization location of a single well.

[0014] Step 3: Delineate the location of favorable mineralization zones; including:

[0015] A. Given the thickness of mudstone in the logging data, the distribution range of mudstone can be delineated by combining the fitting relationship between mudstone thickness and its major and minor axes. The corresponding relationship between mudstone thickness and its plane distribution range is as follows:

[0016] W=68.755h 2 -126.62h+383.27

[0017] L=489.11ln(h)+549.2

[0018] Where h represents the thickness of mudstone, L represents the distance in the direction of the major axis of mudstone, and W represents the distance in the direction of the minor axis of mudstone;

[0019] B. Before drilling, use the known well as the center of the ellipse. The center of the ellipse can be adjusted at any time based on the drilling results.

[0020] Step 4: Exploration and deployment.

[0021] This method has been applied to a ore deposit in Qianjiadian, achieving excellent results. After using this method to delineate favorable mineralization locations, the exploration success rate in the study area increased from 27% to 75%, with over 1,000 tons of newly discovered resources, equivalent to the discovery of a small uranium deposit. This method effectively reduces exploration costs and increases the success rate, demonstrating its high application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a flow chart of the present invention;

[0023] Figure 2 It is a single well analysis diagram without a mine;

[0024] Figure 3 This is a single well analysis diagram of a mineralized well;

[0025] Figure 4 It is a single well analysis diagram of industrial wells;

[0026] Figure 5 It is the delineation of favorable mineralization locations Figure 1 ;

[0027] Figure 6 It is the delineation of favorable mineralization locations Figure 2 . DETAILED DESCRIPTION

[0028] The following is combined with Figure 1-6 The specific embodiments of the present invention are further described.

[0029] A method for determining the mineralization location by using uranium reservoir porosity analysis, comprising the following steps: Figure 1 ):

[0030] 1. Division of mineralization units

[0031] A mineralization unit usually refers to a set of mineral-bearing aquifers in a sandstone-type uranium deposit, with relatively stable aquicludes developed at the top and bottom. Sandstone-type uranium deposits in my country are usually found in braided river or braided river delta plain sand bodies. There is often no sedimentary discontinuity inside the target layer, and the stability of the sedimentary strata cycle is relatively strong. The sedimentary cycle comparison method is often used to divide the strata. However, when the sedimentary unit shows obvious positive cycle characteristics, the conventional division principle is to use the bottom of the positive cycle as the bottom interface of the stratum and the top of the positive cycle (usually the top boundary of the mudstone) as the top interface of the stratum. However, uranium ore bodies are often found at the interface between sandstone and mudstone, and 80% of them are found at the interface where the upper part is sandstone and the lower part is mudstone. Therefore, when the sedimentary cycle comparison method is used for stratigraphic comparison, the ore bodies developed at the sand-mud interface are often cut, thereby interfering with the study of the distribution law of the ore bodies. Therefore, the present invention proposes an innovative division principle in the division of mineralization units:

[0032] 1. Determine the scale of mineralization unit division: Sandstone-type uranium deposits are usually found in braided river or braided river delta sand bodies, with one or more sedimentary cycles as a mineralization unit, and the cumulative thickness generally does not exceed 30m.

[0033] 2. Determine the top and bottom interfaces of the mineralization unit: When performing stratigraphic correlation, the bottom of the sedimentary cycle is usually used as the bottom boundary, and the top of the sedimentary cycle is used as the top boundary. However, to avoid cutting the uranium ore body, the middle part of the mudstone at the top of the sedimentary cycle is used as the top boundary of the mineralization unit, and the middle of the mudstone at the top of the early sedimentary cycle at the junction with the sandstone at the bottom of the sedimentary cycle is used as the bottom boundary of the mineralization unit. If the mudstone at the top of the cycle is 0m < thickness < 1m, the bottom of the mudstone at the top of the cycle is used as the top boundary of the mineralization unit. If the mudstone at the bottom of the cycle is 0m < thickness < 1m, the bottom of the mudstone at the bottom of the cycle is used as the bottom boundary of the mineralization unit. If mudstone is not developed at the top and bottom of the sedimentary cycle, the top and bottom interfaces are divided according to the conventional division principles.

[0034] 2. Well Logging Data Analysis

[0035] For sandstone-type uranium deposits, uranium migration is controlled by interlayer oxidation, and the heterogeneity of the reservoir after entering the transition zone is an important factor controlling uranium accumulation. For reservoirs with braided river or braided river delta channel sandstone as the main rock type, porosity can accurately evaluate the physical properties of the mineralized aquifer, and the coefficient of variation of porosity can evaluate the heterogeneity of the mineralized aquifer. The porosity curve can reflect the changes in the porosity of the mineralized aquifer with high resolution. By calculating the porosity curve, the coefficient of variation of the porosity of the mineralized aquifer can also be calculated, and then the mineralization conditions of the mineralized unit can be evaluated. It is divided into the following steps:

[0036] 1. Calculation of porosity curve: The porosity curve is calculated from conventional logging data. It can be calculated using the acoustic transit time curve, density and neutron curves, or by the intersection of three porosity curves. The above are conventional methods and will not be described in detail.

[0037] 2. Calculate the porosity variation coefficient of the metallogenic unit: Taking the metallogenic unit divided in step 1 as the research unit, calculate the porosity variation coefficient of the completed target layer in the planned well deployment area. The calculation formula of the variation coefficient is: Porosity standard deviation SD Φ The calculation formula is: Average porosity The calculation formula is where Φ i Represents the porosity value, CV, of a point in the mineralization unit Φ represents the coefficient of variation of porosity, SD Φ represents the porosity standard deviation, represents the average porosity.

[0038] 3. Refer to the quantitative evaluation standard of uranium reservoir physical properties to evaluate the mineralization conditions and determine the favorable mineralization location of a single well. The enrichment and precipitation of uranium in sandstone-type uranium deposits are closely related to the heterogeneity of the reservoir. During the research process, the relationship between the physical properties of the target layer and the mineralization of different mineralization levels in four typical uranium deposits was statistically analyzed. The results show that the porosity variation coefficient has a significant corresponding relationship with the mineralization in the transition zone ( Figure 2 、 Figure 3 、 Figure 4 ), when the target layer is mainly sandstone, the average porosity is large, but the heterogeneity is not strong, and the mineralization is poor; when the target layer is sandstone partially interbedded with mudstone, the average porosity is large, the heterogeneity is weak, and it has certain mineralization, but does not meet industrial standards; when the target layer is interbedded with sandstone and mudstone, the average porosity is low, but the heterogeneity is strong, the mineralization is high, and it meets industrial standards; however, when the target layer is a large number of thin interbedded sand and mudstone, although the heterogeneity is strong, it is difficult for oxygen-containing uranium-containing water to advance, so it does not have a high mineralization. The specific quantitative relationship between reservoir mineralization potential and heterogeneity indicators is:

[0039] When the target layer has a low degree of mineralization, the porosity variation coefficient is generally <0.4; when the target layer reaches the mineralization level, the porosity variation coefficient is generally >0.4; when the target layer contains industrial ore sections, the porosity variation coefficient is generally 0.4 < <0.8.

[0040] It can be seen that the average porosity of the target layer is greater than 15%, and the porosity variation coefficient is 0.4 < 0.8, which is the most favorable for mineralization. This standard can be used to determine the favorable mineralization layer of a single well.

[0041] 3. Delineation of favorable mineralization zones

[0042] 1. Given the thickness of mudstone in the logging data, the distribution range of mudstone is delineated by combining the fitting relationship between the thickness of mudstone and its major axis and minor axis. Sandstone-type uranium deposits are mainly developed in braided river channels or braided river delta plain sand bodies. The ore-bearing layer is characterized by a large sand body thickness. The heterogeneity of the ore-bearing layer is often caused by the amount of mudstone in the stratum. The development of mudstone in both braided river channels and delta plains is mainly controlled by the sedimentary phase. Mudstone is developed in both inter-channel bays and floodplain phases, but the floodplain phase is widely developed in the region, and the relationship between its distribution range and thickness is not obvious. The thickness of the mudstone in the inter-channel bay phase has an obvious corresponding relationship with its distribution range. The present invention also established for the first time the corresponding relationship between the thickness of mudstone in the inter-channel bay microfacies in braided rivers or braided river delta plains and its planar distribution range:

[0043] W=68.755h 2 -126.62h+383.27

[0044] L=489.11ln(h)+549.2

[0045] Where h represents the thickness of mudstone, L represents the distance in the direction of the major axis of mudstone, and W represents the distance in the direction of the minor axis of mudstone.

[0046] Then the plane distribution range of the mudstone is regarded as an ellipse. The lengths of the major and minor axes are calculated according to the formula. The provenance direction is taken as the major axis and the vertical provenance direction is taken as the minor axis. The ellipse is circled with the known well as the center as the approximate distribution range of the mudstone.

[0047] 2. Before drilling, the known well is used as the ellipse center. The ellipse center can be adjusted at any time based on the drilling results. The specific method is as follows: ① Before exploration, the straight line L1 passing through the ellipsoid center in the direction of the vertical oxidation zone is used as the boundary. The ellipsoid range in the direction of the water surface of L1 is used as the favorable mineralization position ( Figure 5 ) ;② Each time a well is drilled, the center of the ellipsoid is adjusted according to the average porosity of the target layer and the porosity variation coefficient. If the evaluation index deteriorates, the center remains unchanged; if the evaluation index improves, the newly completed well is used as the center.

[0048] 4. Exploration deployment.

[0049] On the premise of fine division of mineralization units, the present invention calculates the logging data, describes the heterogeneity of each mineralization unit in the target layer by the porosity variation coefficient, and quantitatively characterizes the favorable mineralization parts in combination with statistical data. Then, combined with the mineralization of the favorable mineralization parts, the relationship between the thickness of the inter-channel bay phase mudstone and the plane distribution, etc., the distribution range of the favorable mineralization positions is delineated on the plane, thereby guiding scientific deployment.

[0050] Example

[0051] The southern part of a certain deposit in Qianjiadian is close to the boundary of the ore body. The ore body is thin and scattered, and exploration has not made any breakthroughs in the past 10 years. In 2022, the method of the present invention was applied to delineate favorable mineralization locations. Specifically, the following methods were used:

[0052] 1. Division of mineralization units

[0053] 1. Determine the scale of mineralization unit division: The uranium ore bodies in this area are hosted in braided river delta sand bodies. The main exploration target layer is the Y1 layer of the Yaojia Formation. Three sedimentary cycles are used as a mineralization unit, and the cumulative thickness generally does not exceed 30m.

[0054] 2. Determine the top and bottom interfaces of the mineralization unit: In the application of the present invention, the middle part of the mudstone at the top of the sedimentary cycle is used as the top boundary of the mineralization unit, and the middle of the mudstone at the top of the early sedimentary cycle where it connects with the sandstone at the bottom of the sedimentary cycle is used as the bottom boundary of the mineralization unit.

[0055] 2. Well Logging Data Analysis

[0056] 1. Calculation of Porosity Curve: Some of the completed wells in the work area have porosity curves interpreted by the logging company, while some have not. However, all of them have provided acoustic transit time (AC) curves. For those that do not have porosity curves, the porosity curves are calculated from the acoustic transit time curves and corrected based on lithologic samples to ensure that the two porosity curves have a unified standard.

[0057] 2. Calculate the porosity variation coefficient of the mineralization unit: Take the mineralization unit divided in step 1 as the research unit, and calculate the porosity variation coefficient of the completed target layer in the area where the well is to be deployed. There is one industrial well among the completed wells in the area, and the porosity variation coefficient of its Y1 layer is 0.69.

[0058] 3. Delineation of favorable mineralization zones

[0059] 1. The maximum thickness of mudstone near the industrial layer of the target layer in the known well logging data is 2m. Combined with the fitting relationship between mudstone thickness and its major axis and minor axis, the mudstone distribution range is delineated. According to the formula

[0060] W=68.755h 2 -126.62h+383.27

[0061] L=489.11ln(h)+549.2

[0062] Where h represents the thickness of mudstone, L represents the distance in the direction of the major axis of mudstone, and W represents the distance in the direction of the minor axis of mudstone.

[0063] The length of the mudstone plane distribution range in the long axis direction is 888m, and the length in the short axis direction is 405m.

[0064] 2. Before exploration, the straight line L1 passing through the center of the ellipsoid in the direction perpendicular to the oxidation zone is used as the boundary, and the ellipsoid range in the direction of the water surface of L1 is regarded as the favorable mineralization position ( Figure 5 ); deploy exploratory wells according to the exploration level in favorable mineralization locations; after each well is drilled, adjust the center of the ellipsoid based on the average porosity of the target layer and the porosity variation coefficient; if the evaluation index deteriorates, the center remains unchanged; if the evaluation index improves, the newly completed well is used as the center.

[0065] In the early stage of 2022, 5 exploration wells were deployed, of which 3 wells obtained industrial uranium ore indications. The uranium content per square meter of well 2 was significantly higher than that of well 1. Therefore, well 2 was used as the new ellipsoid center, and the above steps were repeated to delineate the new favorable mineralization zone, and a new round of deployment was carried out in the new favorable mineralization zone ( Figure 6 ), and two more industrial wells were obtained. This round of exploration completed 11 exploratory wells in the study area, of which 7 wells yielded industrial indications, with an industrial ore-finding rate of 63%, far exceeding the average level of the previous five years. The estimated resource volume exceeds 2,000 tons, demonstrating significant application results.

[0066] The above are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention within the technical scope disclosed in the present invention, and they should be covered by the scope of protection of the present invention.

Claims

1. A method for determining mineralization location using uranium reservoir porosity analysis, characterized in that: The following steps are involved: Step 1: Divide the mineralization units; including: A. Determine the scale of metallogenic unit division: one or more sedimentary cycles are used as a metallogenic unit; B. Determine the top and bottom interfaces of the metallogenic unit: If the mudstone at the top of the cycle is 0m < thickness < 1m, the bottom of the mudstone at the top of the cycle is taken as the top boundary of the metallogenic unit; if the mudstone at the bottom of the cycle is 0m < thickness < 1m, the bottom of the mudstone at the bottom of the cycle is taken as the bottom boundary of the metallogenic unit; if mudstone is not developed at the top and bottom of the sedimentary cycle, the top and bottom interfaces are divided according to the conventional division principles; Step 2: Well logging data analysis; including: A. Calculate the porosity curve; B. Calculate the coefficient of variation of the porosity of the mineralization unit; the formula for calculating the coefficient of variation is: CV Φ represents the coefficient of variation of porosity, SD Φ represents the porosity standard deviation, represents the average porosity; C. Refer to the quantitative evaluation standard for uranium reservoir physical properties to evaluate the mineralization conditions and determine the favorable mineralization location for a single well. The specific quantitative relationship between the reservoir mineralization potential and heterogeneity indicators is as follows: when the target layer has a low degree of mineralization, the porosity variation coefficient is generally less than 0.4; when the target layer reaches the mineralization level, the porosity variation coefficient is generally greater than 0.4; when the target layer contains industrial ore sections, the porosity variation coefficient is generally 0.4 < 0.8; when the average porosity of the target layer is greater than 15% and the porosity variation coefficient is 0.4 < 0.8, the mineralization is most favorable. This standard can be used to determine the favorable mineralization layer for a single well. Step 3: Delineate the location of favorable mineralization zones; including: A. Given the thickness of mudstone in the logging data, the distribution range of mudstone can be delineated by combining the fitting relationship between mudstone thickness and its major and minor axes. The corresponding relationship between mudstone thickness and its plane distribution range is as follows: W=68.755h 2 -126.62h+383.27 L=489.11ln(h)+549.2 Where h represents the thickness of mudstone, L represents the distance in the direction of the major axis of mudstone, and W represents the distance in the direction of the minor axis of mudstone; B. Before drilling, use the known well as the center of the ellipse. The center of the ellipse can be adjusted at any time based on the drilling results. Step 4: Exploration and deployment.

2. The method for determining the mineralization location using uranium reservoir porosity analysis according to claim 1, characterized in that: The cumulative thickness of item A in step 1 does not exceed 30m.

3. The method for determining mineralization location using uranium reservoir porosity analysis according to claim 1, characterized in that: The conventional division principle of item B in step 1 is to divide the top and bottom interfaces by taking the bottom of the positive cycle as the bottom interface of the formation and the top of the positive cycle as the top interface of the formation.

4. The method for determining mineralization location using uranium reservoir porosity analysis according to claim 1, characterized in that: Item A in step 2 can be calculated using an acoustic time difference curve, a density curve, a neutron curve, or can be obtained by the intersection of three porosity curves.

5. The method for determining mineralization location using uranium reservoir porosity analysis according to claim 1, characterized in that: Item B in step 2 is to calculate the porosity variation coefficient of the completed target layer in the planned well deployment area, taking the mineralization unit divided in step 1 as the research unit; the porosity standard deviation SD Φ The calculation formula is: Average porosity The calculation formula is where Φ i Represents the porosity value of a certain point in the mineralization unit, SD Φ represents the porosity standard deviation, represents the average porosity, and n represents the total number of data points.

6. The method for determining mineralization location using uranium reservoir porosity analysis according to claim 1, characterized in that: In item A of step 3, the planar distribution range of the mudstone is regarded as an ellipse. The lengths of the major and minor axes are calculated according to the formula, the provenance direction is used as the major axis, and the perpendicular provenance direction is used as the minor axis. An ellipse is drawn with the known well as the center to serve as the approximate distribution range of the mudstone.

7. The method for determining mineralization location using uranium reservoir porosity analysis according to claim 1, characterized in that: The specific method of item B in step 3 is as follows: ① Before exploration, the straight line L1 passing through the center of the ellipsoid in the direction perpendicular to the oxidation zone is used as the boundary, and the ellipsoid range in the direction of the water surface of L1 is used as the favorable mineralization position; ② After each well is drilled, the center of the ellipsoid is adjusted according to the average porosity value and the porosity variation coefficient of the target layer. If the evaluation index deteriorates, the center remains unchanged. If the evaluation index improves, the newly completed well is used as the center.

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