Salt lake basin brine mineral resource evaluation method

Abstract

The invention relates to a salt lake basin brine mineral resource evaluation method, and belongs to the technical field of liquid mineral resource quantity evaluation. The method comprises the following steps: on the basis of a to-be-evaluated mineral element enrichment rule and a formation mechanism, if to-be-evaluated mineral element enrichment is mainly evaporation and concentration, judging that a to-be-evaluated mineral element content contour line is annularly distributed by taking salt as a center; if the to-be-evaluated mineral element source is mainly based on fracture migration, judging that the content contour line of the to-be-evaluated mineral element is linearly distributed by taking the fracture as the center; if the to-be-evaluated mineral element substance is mainly sourced from volcano hydrothermal liquid, judging that the content contour line of the to-be-evaluated mineral element is distributed around the rock mass; and drawing a to-be-evaluated mineral element content contour map according to the to-be-evaluated mineral element content contour line distribution characteristics in combination with the actually measured mineral element content, and further calculating the to-be-evaluated mineral element resource quantity. According to the method, under the condition that seismic data and analysis test data are scarce, mineral resources such as lithium and potassium in brine of the salt lake basin can still be evaluated.

Description

Technical Field

[0001] The invention belongs to the technical field of liquid mineral resource evaluation, and in particular relates to a method for evaluating brine mineral resources in a salt lake basin. Background Art

[0002] Brine is rich in minerals, including trace elements such as lithium, bromine, iodine, and strontium. It is a valuable liquid mineral and is widely used in salt production, pharmaceuticals, chlor-alkali manufacturing (PVC, caustic soda) and other industries. The available resources of brine include sodium salt resources (NaCl), potassium salt resources (K 2 SO 4 , KCl, KNO 3 ), lithium salt resources (LiCl, Li 2 CO 3 ), magnesium salt resources (MgCl 2 , MgSO 4 ), Boron Resources (H 3 BO 3 ), bromine resources (Br 2 ) etc. According to the General Administration of Customs, my country's external dependence on lithium and potassium resources exceeds 50%, and the evaluation of lithium and potassium and other mineral resources is imminent. However, due to the locality and complexity of the distribution of lithium and potassium resources in salt lake basins, and the limitations of survey technology and survey areas, the spatial distribution and resource evaluation of brine-type mineral resources (such as lithium and potassium) are still limited to local surveys, lacking resource potential evaluation and prediction in large areas.

[0003] A Chinese invention patent application with publication number CN117849897A provides a method for determining the spatial distribution of brine-type potash and lithium mines and a method for estimating resource quantities, and a Chinese invention patent application with publication number CN112878998A provides a method for predicting the brine reservoir and evaluating resource quantities of underground brine-type potash and lithium mines. However, the above methods all require a geophysical work basis and a large amount of original undiluted brine lithium or potassium element content analysis test data results, so there are the following defects: 1) Under the condition of scarcity of seismic data and original undiluted brine mineral element content analysis test data, it will be impossible to accurately evaluate the mineral resources such as brine lithium and potassium in the salt lake basin, and the promotion is poor. 2) It is necessary to obtain a large amount of original undiluted brine lithium or potassium and other mineral element contents through multiple drilling of new wells or perforation water testing to improve the accuracy of the distribution characteristics of the mineral element content. However, drilling new wells or perforation water testing requires a lot of manpower and material resources, and the economic cost is high; and perforation water testing requires the occupation of the wellbore, affecting the normal production of oil and gas. Therefore, there is a lack of a simple and effective method for evaluating mineral resources such as lithium and potassium in brine in salt lake basins, which can take into account the accuracy of mineral element content distribution characteristics under the conditions of scarcity of seismic data and original undiluted brine mineral element content analysis and test data. Summary of the invention

[0004] The purpose of the present invention is to provide a method for evaluating brine mineral resources in a salt lake basin, so as to solve the problem that the prior art cannot effectively evaluate the brine mineral resources in a salt lake basin under the conditions of lack of seismic data and limited data on the element content of the original undiluted brine.

[0005] The present invention provides a method for evaluating brine mineral resources in a salt lake basin to solve the above technical problems, comprising: 1) Based on the enrichment law and genetic mechanism of the mineral elements to be evaluated, the distribution characteristics of the isovalue lines of the mineral elements to be evaluated are judged; if the salt lake basin has experienced an enrichment process of evaporation and concentration, the source of the mineral elements to be evaluated is mainly evaporation and concentration, and the isovalue lines of the mineral elements to be evaluated are judged to be distributed in a ring shape with salt as the center; if the brine in the salt lake basin communicates with the underlying salt-bearing strata through faults, the source of the mineral elements to be evaluated is mainly fault migration, and the isovalue lines of the mineral elements to be evaluated are judged to be distributed in a linear shape with the fault as the center; if the source of the mineral elements to be evaluated is mainly volcanic hydrothermal fluids, the isovalue lines of the mineral elements to be evaluated are judged to be distributed around the rock mass; 2) Based on the distribution characteristics of the element content contour lines of the mineral to be evaluated, the determined lower limit of the element content of the mineral to be evaluated and the value range of the element content contour lines of the mineral to be evaluated, combined with the measured mineral element content, draw a contour line map of the element content of the mineral to be evaluated; 3) Based on the contour map of the element content of the mineral to be evaluated, the volumetric method is used to calculate the resource quantity of the mineral element to be evaluated.

[0006] Furthermore, in order to reduce the economic cost of obtaining the content of mineral elements to be evaluated in the original undiluted brine, in step 2), for the rock salt development layer in the salt lake basin that has undergone the evaporation concentration enrichment process, according to the measured brine mineralization and mineral element content in the salt lake basin, a correlation between the content of the mineral element to be evaluated and the mineralization or the content of other mineral elements or other mineral element combinations except the mineral element to be evaluated is established, and the content value of the mineral element to be evaluated is calculated using the correlation.

[0007] Furthermore, the method for establishing the correlation between the content of the mineral element to be evaluated and the mineralization or the content of other mineral elements or other mineral element combinations except the mineral element to be evaluated is: first evaluate the correlation between the content of the mineral element to be evaluated measured in the brine of the water injection development wells in the same block and the mineralization or other mineral elements or other mineral element combinations; if the correlation is greater than the set threshold, then use only the original brine obtained from the new exploration well or perforation water test to determine the content of the mineral element to be evaluated and establish the said correlation.

[0008] Furthermore, when using a new exploration well to determine the content of mineral elements to be evaluated in the brine reservoir, after a set time is set for acid backwashing in the new exploration well, when the data of the content of mineral elements to be evaluated in the new exploration well to be determined stabilizes, the value measured at this time is used as the actual measured value of the content of mineral elements to be evaluated in the brine reservoir.

[0009] Furthermore, if the salt lake basin has undergone an enrichment process of evaporation and concentration, the source of the mineral elements to be evaluated is mainly evaporation and concentration. When the mineral elements to be evaluated are lithium or potassium, the content of the mineral elements to be evaluated is positively correlated with the mineralization.

[0010] Furthermore, in the step 2), the process of calculating the mineral element resource quantity to be evaluated by using the volumetric method includes: determining the lower limit of the porosity of the brine reservoir in the study area, defining the value range of the brine reservoir porosity contour line, and drawing the brine reservoir porosity contour line map; determining the effective thickness division standard and the lower limit of the brine reservoir in the study area, defining the value range of the brine reservoir effective thickness contour line, and drawing the brine reservoir effective thickness contour line map; according to the mineral element content contour line map to be evaluated and the brine reservoir porosity contour line map and the contour map of effective thickness of brine reservoir, determine the overlapping areas in the study area where the content of mineral elements to be evaluated, the porosity of brine reservoir and the effective thickness of brine reservoir are all greater than the corresponding lower limits, and then determine the distribution area of ​​brine reservoir in the study area; determine the water saturation value and brine volume coefficient value of brine reservoir in the study area; according to the effective thickness, porosity, water saturation, distribution area, brine volume coefficient and content of mineral elements to be evaluated in the study area, use the volumetric method to calculate the resources of mineral elements to be evaluated.

[0011] Furthermore, the arithmetic average method of well points, the well point area weighting method and the contour area weighting method were used to obtain the average effective content of mineral elements to be evaluated in brine, the average effective porosity of the brine reservoir and the average effective thickness of the brine reservoir. According to the average effective thickness of the brine reservoir, the average effective porosity and the average effective content of mineral elements to be evaluated in brine in the study area, the volumetric method was used to calculate the amount of mineral element resources to be evaluated.

[0012] Furthermore, the formula for calculating the mineral element resources to be evaluated using the volumetric method is: Where Q represents the potential resource of the mineral element to be evaluated, in tons; A represents the distribution area of ​​the brine reservoir, in m 2 ; It represents the average effective thickness of the brine reservoir, in m; represents the average effective porosity of the brine reservoir, expressed in percentage; Sw represents the water saturation of the brine reservoir, expressed in percentage; B represents the brine volume coefficient, dimensionless; It indicates the average effective mineral element content to be evaluated in brine, in mg / L.

[0013] Furthermore, the porosity value includes the porosity value interpreted by well logging, the porosity value measured by core, the porosity value under similar geological conditions, and the porosity value inferred by the relationship chart between porosity and depth.

[0014] Furthermore, the effective thickness contour lines of the brine reservoir are defined by combining the sand-to-formation ratio map, the oil and gas reservoir thickness map, the formation isothickness map, the sandstone thickness map and the sedimentary facies map.

[0015] The beneficial effect of the present invention is as follows: the present invention determines the distribution characteristics of the contour lines of the element content of the mineral to be evaluated according to the enrichment law and the genetic mechanism of the element to be evaluated, and draws the contour line map of the element content of the mineral to be evaluated according to the contour line distribution characteristics. In this way, under the condition that seismic data and original undiluted brine mineral element content analysis and test data are scarce, the resource amount of the mineral element to be evaluated can be calculated more accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a flowchart of a method for evaluating brine mineral resources in a salt lake basin according to an embodiment of the present invention; Figure 2 It is a flowchart of a method for evaluating lithium-potassium brine resources in a salt lake basin according to an embodiment of the present invention; Figure 3 This is a contour map of lithium content in a brine reservoir of the first segment of the Tertiary Shahejie Formation in a salt lake basin according to an embodiment of the present invention; Figure 4 A diagram showing the relationship between porosity and depth in a salt lake basin according to an embodiment of the present invention; Figure 5 The porosity contour map of the first brine reservoir of the Tertiary Shahejie Formation in a salt lake basin according to an embodiment of the present invention; Figure 6 The thickness contour map of the brine reservoir layer of the first section of the Tertiary Shahejie Formation in a salt lake basin according to an embodiment of the present invention; Figure 7 This is a graph showing the changes in brine volume coefficient with temperature and pressure according to an embodiment of the present invention; Figure 8 This is a distribution diagram of the brine reservoir area of ​​the first section of the Shahejie Formation of the Tertiary System in a salt lake basin according to an embodiment of the present invention. DETAILED DESCRIPTION

[0017] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

[0018] The basic idea of ​​the present invention is to determine the distribution characteristics of the content contour lines of the mineral elements to be evaluated based on the enrichment law and genetic mechanism of the mineral elements to be evaluated, according to the enrichment process of the mineral elements to be evaluated by evaporation and concentration, or the enrichment law of the underlying brine of the fault communication, or the material source of the volcanic hydrothermal fluid, so as to determine the method for drawing the contour line map of the content of the mineral elements to be evaluated. According to the contour line map of the content of the mineral elements to be evaluated, the resource amount of the mineral elements to be evaluated is calculated by the volumetric method.

[0019] Based on the above basic idea, the salt lake basin brine mineral resource evaluation method of the present invention comprises the following steps: Figure 1 As shown: 1. Based on the element enrichment law and genetic mechanism of the mineral to be evaluated, determine the distribution characteristics of the element content contour lines of the mineral to be evaluated.

[0020] Collect geological background data of salt lake basins, research literature on the genesis mechanism and enrichment law of the mineral elements to be evaluated, sedimentary phase diagrams, brine mineralization data at the beginning of drilling, current brine mineralization and test results of element content of the mineral elements to be evaluated, and determine the distribution characteristics of the contour lines of the mineral element content to be evaluated.

[0021] In the rock salt development section in the salt lake basin, if it has undergone repeated evaporation, concentration and enrichment processes, the source of the mineral elements to be evaluated is mainly evaporation and concentration, and the isovalue lines of the mineral elements to be evaluated are judged to be distributed in a ring shape with salt as the center; for the non-rock salt development section in the salt lake basin, if the main oil source lithology is consistent with the lithology rich in the mineral elements to be evaluated, it can be considered that the brine rich in the mineral elements to be evaluated communicates with the underlying salt-bearing strata through faults to form oil and gas-associated brine rich in the mineral elements to be evaluated, and it can be judged that the isovalue lines of the mineral elements to be evaluated are distributed in a linear shape with the faults as the center; when the source of the mineral elements to be evaluated is mainly volcanic hydrothermal fluids, it can be judged that the isovalue lines of the mineral elements to be evaluated are distributed around the rock mass.

[0022] 2. Based on the distribution characteristics of the element content contour lines of the mineral to be evaluated, the determined lower limit of the element content of the mineral to be evaluated and the value range of the element content contour lines of the mineral to be evaluated, combined with the measured mineral element content, draw a contour line map of the element content of the mineral to be evaluated.

[0023] Preferably, background information such as geological data, basic maps and analytical test data of the study area is obtained, and according to industry standards and / or economic evaluation results, combined with the actual content range of the mineral elements to be evaluated in the study area, the lower limit of the mineral element content to be evaluated is determined, the value range of the contour lines of the mineral element content to be evaluated is defined, and a contour line map of the mineral element content to be evaluated is drawn.

[0024] Preferably, for the rock salt development layer section in the salt lake basin that has undergone the evaporation concentration enrichment process, based on the measured brine mineralization and mineral element content in the salt lake basin, a correlation between the content of the mineral element to be evaluated and the mineralization or the content of other mineral elements (or other mineral element combinations) other than the mineral element to be evaluated is established, and the content value of the mineral element to be evaluated is calculated using the correlation. Among them, the content of other mineral elements (or other mineral element combinations) other than the mineral element to be evaluated refers to: the content of one other mineral element other than the mineral element to be evaluated, or the content of a combination of two or more other mineral elements other than the mineral element to be evaluated.

[0025] Preferably, when establishing a correlation between the content of the mineral element to be evaluated and the mineralization or the content of other mineral elements (or other combinations of mineral elements) except the mineral element to be evaluated, based on the principle of proportional dilution of the content of the mineral element to be evaluated and the mineralization or the content of other mineral elements (or other combinations of mineral elements) except the mineral element to be evaluated after water injection dilution, the correlation between the content of the mineral element to be evaluated measured in the brine of the water injection development wells in the same block and the mineralization or the content of other mineral elements (or other combinations of mineral elements) is first evaluated. If the correlation is greater than the set threshold, the content of the mineral element to be evaluated is determined using only the original brine obtained from the new exploration well or perforation water test to establish the said correlation.

[0026] In the salt lake basin, due to the water injection development of old oil fields, most of the formation brine is currently diluted. Since no perforation test is performed, the true mineral element content of the formation brine cannot be obtained. Preferably, when using a new exploration well to determine the mineral element content value to be evaluated in the brine reservoir, after setting the time for acid backflow in the new exploration well, when the data of the mineral element content to be evaluated in the new exploration well to be determined is stable, the value measured at this time is used as the actual measured value of the mineral element content to be evaluated in the brine reservoir. Among them, the setting time can be observed according to the actual situation, such as 30 days, 60 days, etc.

[0027] Preferably, if the salt lake basin has undergone an enrichment process of evaporation and concentration, the source of the mineral element to be evaluated is mainly evaporation and concentration. When the mineral element to be evaluated is lithium or potassium, the content of the mineral element to be evaluated is positively correlated with the mineralization. Preferably, in the enrichment process of evaporation and concentration in the salt lake basin, the lithium content contour can be defined by the lithium content in the lithium-rich mudstone.

[0028] The present invention is based on geological research foundations such as brine genesis, and indirectly estimates the content of the mineral element to be evaluated by establishing a correlation between the mineralization degree or the content of other mineral elements (or other mineral element combinations) except the mineral element to be evaluated and the content of the mineral element to be evaluated. It is no longer necessary to drill a large number of new wells or conduct multiple perforation tests to obtain the content of mineral elements such as lithium or potassium in the original undiluted brine. Therefore, while reducing economic costs and not affecting the normal production of the original wellbore, it can still accurately calculate the resource amount of the mineral element to be evaluated in the salt lake basin where the analysis test results of the mineral element content to be evaluated in the original undiluted brine are scarce, and the application scenarios are more extensive.

[0029] 3. Based on the contour map of the element content of the mineral to be evaluated, the volumetric method is used to calculate the resource quantity of the mineral element to be evaluated.

[0030] According to the contour map of the mineral element content to be evaluated, the process of calculating the mineral element resource quantity to be evaluated by volumetric method includes: 1) Determine the lower limit of the porosity of the brine reservoir in the study area, define the value range of the brine reservoir porosity contour line, and draw the brine reservoir porosity contour line map; Specifically, according to relevant data and the actual situation of the brine reservoir porosity value range in the study area, the lower limit of the brine reservoir porosity value is determined, the value range of the brine reservoir porosity contour line is defined, and the brine reservoir porosity contour line map is drawn.

[0031] Preferably, the relevant information includes industry standards, porosity values ​​of industrially developed reservoirs under similar geological conditions, economic evaluation results, water yield and production capacity evaluation results, etc.

[0032] Preferably, the porosity value includes the porosity value interpreted by well logging, the porosity value measured by core, the porosity value under similar geological conditions, the porosity value inferred by the relationship chart between porosity and parameters such as depth, etc.

[0033] 2) Determine the classification standard and lower limit of the effective thickness of the brine reservoir in the study area, define the value range of the effective thickness contour line of the brine reservoir, and draw the effective thickness contour line map of the brine reservoir; Preferably, when obtaining the effective thickness of the brine reservoir, it is necessary to first determine the sandstone and other reservoirs based on the natural gamma curve, and then select the reservoir based on the deep induction resistivity. At the same time, refer to the natural potential, well diameter, induced conductivity, three-porosity and other logging curves to determine the brine reservoir. The boundary is divided at the half-width point of the logging curve, and the effective thickness of the single layer is interpreted in combination with logging, logging, oil testing, test production and other data.

[0034] Preferably, when obtaining the effective thickness contour line of the brine reservoir, it can be limited by combining the sand-to-formation ratio map, the oil and gas reservoir thickness map, the formation thickness map, the sandstone thickness map, and the sedimentary phase map.

[0035] 3) According to the contour map of the element content of the mineral to be evaluated, the contour map of the porosity of the brine reservoir and the contour map of the effective thickness of the brine reservoir, determine the overlapping areas in the study area where the content of the mineral element to be evaluated is greater than the lower limit of the content of the mineral element to be evaluated, the porosity of the brine reservoir is greater than the lower limit of the porosity of the brine reservoir, and the effective thickness of the brine reservoir is greater than the lower limit of the effective thickness of the brine reservoir, and then determine the distribution area of ​​the brine reservoir in the study area.

[0036] 4) Determine the water saturation value and brine volume coefficient value of the brine reservoir in the study area; Preferably, the water saturation value of the brine reservoir is determined according to the logging interpretation results and / or experimental test results. The water saturation can be determined according to the logging principle. When the brine reservoir thickness is greater than 3 meters and the resistivity is less than 0.3Ω·m, the water saturation is usually 100%.

[0037] Preferably, water saturation, which is usually interpreted as oil saturation and gas saturation in well logging, can be calculated using the following formula if there is only oil and water in the pores: Sw=1-So Where Sw is water saturation, unit is cm 3 , So is oil saturation, unit is cm 3 .

[0038] If there is only gas and water in the pores, the following formula can be used for calculation: Sw=1-Sg Where Sw is water saturation, unit is cm 3 , Sg is gas saturation, unit is cm 3 .

[0039] If oil, gas and water coexist in the pores, the following formula can be used for calculation: Sw=1-So-Sg Preferably, the value of the brine volume coefficient is determined based on experimental test results or theoretical results. When calculating the brine volume coefficient, a chart showing that the brine volume coefficient usually changes with temperature and pressure can be established, and the brine volume coefficient value can be read based on the temperature and pressure data of oil testing and test production under similar geological conditions in the study area.

[0040] 5) Based on the effective thickness, porosity, water saturation, distribution area, brine volume coefficient and the content of mineral elements to be evaluated in the study area, the volumetric method is used to calculate the resources of the mineral elements to be evaluated.

[0041] In order to simplify the calculation process, the well point arithmetic average method, well point area trade-off method and contour area trade-off method are used to obtain the average effective mineral element content to be evaluated in brine, the average effective porosity of brine reservoir and the average effective thickness of brine reservoir. According to the water saturation, distribution area, brine volume coefficient, average effective thickness, average effective porosity and average effective mineral element content of brine in the study area, the volume method is used to calculate the mineral element resources to be evaluated. The formula is: Where Q represents the potential resource of the mineral element to be evaluated, in tons; A represents the distribution area of ​​the brine reservoir, in m 2 ; It represents the average effective thickness of the brine reservoir, in m; represents the average effective porosity of the brine reservoir, expressed in percentage; Sw represents the water saturation of the brine reservoir, expressed in percentage; B represents the brine volume coefficient, dimensionless; It indicates the average effective mineral element content to be evaluated in brine, in mg / L.

[0042] The above-mentioned isoline construction method and evaluation method of this embodiment can be applied not only to lithium and potassium resources, but also to the construction of isoline and resource evaluation of mineral elements such as boron, rubidium, bromine, strontium, iodine, and cesium.

[0043] The following is a further description of the technical solution of the present invention by taking the lithium-potassium brine resources of a salt lake basin as an example in conjunction with the attached drawings. During the sedimentary period of the Tertiary Shahejie Formation in a salt lake basin, the lake basin subsided and developed into a wide and shallow lake basin with a dry climate, closed flow, and sedimentary rock salt, gypsum, carbonate, mudstone, and sandstone strata. The mineralization of the sedimentary brine is distributed in a ring-shaped pattern around the rock salt deposition center.

[0044] This embodiment introduces a method for evaluating lithium-potassium brine resources in a salt lake basin by taking the lithium-potassium brine resources of the first section of the Shahejie Formation in a salt lake basin as an example, and includes the following steps: Figure 2 As shown: 1) Collect geological data, basic maps, analytical test data and other background information of the study area. Determine the lower limit of lithium-potassium content, define the value range of lithium-potassium content contour lines, and draw lithium-potassium content contour line maps.

[0045] In this embodiment, the geological background of a salt lake basin, research literature on the mechanism and enrichment of lithium and potassium, sedimentary phase diagrams, brine mineralization data in the early stage of drilling, current brine mineralization and mineral element content test results containing lithium and potassium elements are first collected to determine the distribution characteristics of lithium and potassium. According to the "Mineral Geological Exploration Specifications-Deep Brine Salts" DZ / T-2020, the lithium content of 25mg / L is the comprehensive utilization grade limit, and 50mg / L is the industrial grade limit for single mining. Combined with the actual lithium content of a salt lake basin, low lithium content (<25mg / L) has no industrial value and is not evaluated. The lithium content of 25-50mg / L, 50-75mg / L, and 75-100mg / L are used as the boundaries for drawing lithium content contour lines.

[0046] Since no perforation test was performed, the true lithium content of the formation brine could not be obtained. This embodiment combines the enrichment process of lithium ion evaporation and concentration in a salt lake basin, the distribution characteristics of a ring with salt as the center, and the positive correlation between lithium content and mineralization. Based on a large amount of measured data of lithium content and mineralization diluted by water injection, it is determined that the two have a strong positive correlation. Then, the value of the formation lithium content is roughly determined according to the fitting formula y=0.0003x+6.5024 of the lithium content and mineralization of the new exploration well. Finally, it is revised in combination with the measured data of lithium content in mudstone near the brine, and a contour map of lithium content in the first section of the sandstone in a salt lake basin is drawn accordingly, as shown in FIG. Figure 3 shown.

[0047] According to the "Mineral Geological Exploration Specifications - Deep Brine Salts" DZ / T-2020, the lower limit of potassium content is determined and the range of potassium content contour lines is defined. The method for drawing potassium content contour lines is the same as that for drawing lithium content contour lines, so it will not be explained in detail here.

[0048] 2) Determine the lower limit of the porosity value, define the value range of the porosity contour line, and draw the porosity contour line map.

[0049] In this embodiment, according to my country's petroleum and natural gas industry standard SY / T6285-2011 "Oil and Gas Reservoir Evaluation Method", combined with the relationship between porosity and permeability and the actual porosity range of a salt lake basin, Figure 4 As shown, the permeability below low porosity (porosity 10-15%) is considered too low and is not evaluated. Medium porosity (porosity 15-25%) is subdivided into 15-20%, 20-25%, and high porosity (porosity ≥ 25%) as the boundaries for drawing porosity contour lines.

[0050] The relationship between the measured porosity and depth of the Shahejie Formation core in a salt lake basin is shown in Figure 2. Figure 4As shown in the figure, when the porosity is 15%, the corresponding depth is 1700m~4000m, with an average depth of 3000m; when the porosity is 20%, the corresponding depth is 1600m~3500m, with an average of 2700m; when the porosity is 25%, the corresponding depth is 1500m~2800m, with an average of 2400m. Based on the corresponding relationship between the measured porosity of the Shahejie Formation core in a salt lake basin and the average depth, combined with the measured porosity data, a porosity contour map of the first member of the Shahejie Formation in a salt lake basin was drawn, as shown in the figure. Figure 5 shown.

[0051] 3) Determine the classification standard and lower limit of the effective thickness of the brine reservoir, define the value range of the effective thickness contour line of the brine reservoir, and draw the effective thickness contour line map of the brine reservoir.

[0052] In this embodiment, the effective thickness of the brine reservoir is divided mainly based on the natural gamma and deep induction resistivity logging curves. First, the sandstone and other reservoirs are determined according to the natural gamma curve, and then the reservoirs with deep induction resistivity less than 0.3Ω·m are selected. At the same time, the natural potential, well diameter, induction conductivity and other logging curves are referred to determine the brine reservoir. The division boundary is implemented at the half-width point of the logging curve. Combined with logging, logging, oil testing, test production and other data, the effective true thickness of the single layer is interpreted. The cumulative thickness is taken as a multiple of 10m as the boundary. Based on the logging data, brine genesis and sedimentary phase characteristics, the effective thickness contour map of the brine reservoir is drawn, as shown in FIG. Figure 6 shown.

[0053] 4) Determine the water saturation value of the brine reservoir based on well logging interpretation.

[0054] In this embodiment, according to the logging principle, when the brine reservoir thickness is greater than 3 meters and the resistivity is less than 0.3Ω·m, the water saturation is usually 100%, so the water saturation is taken as 100%.

[0055] 5) Determine the value of brine volume coefficient based on the theoretical diagram.

[0056] In this embodiment, the brine volume coefficient depends on the properties of water, and usually does not change much with temperature and pressure, and is generally slightly greater than 1. Figure 7 As shown, the brine volume coefficient is taken as 1.

[0057] 6) Use the superimposed areas that meet the lower limits of lithium content, porosity, and brine reservoir thickness to determine the distribution area of ​​the brine reservoir, draw a brine reservoir distribution area map, and read the brine reservoir distribution area.

[0058] In this embodiment, according to the above-mentioned lower limits of lithium content, porosity and effective thickness of brine reservoir, the lithium content contour map, porosity contour map and effective thickness contour map of brine reservoir are superimposed, and the contour lines with lithium content greater than 25 mg / L, porosity greater than 15% and brine reservoir thickness greater than 10 m are used as area boundaries to determine the distribution area of ​​brine reservoir, and draw a brine reservoir distribution area map, such as Figure 8 shown.

[0059] The method for determining the potassium-containing brine reservoir is consistent with the lithium content method and will not be described in detail here.

[0060] 7) Determine the average effective lithium and potassium content, average effective porosity, and average effective brine reservoir thickness in the formation by using three methods: well point arithmetic average, well point area weighting, and contour line area weighting.

[0061] 8) Based on the distribution area of ​​brine reservoir, water saturation, brine volume coefficient, average effective thickness of brine reservoir, average effective porosity, average effective brine reservoir thickness and average effective lithium and potassium content in the formation, the volumetric method is used to calculate the lithium and potassium resources of brine in the salt lake basin. The formula is: , where Q represents the potential resources of lithium and potash ore, in tons; A represents the distribution area of ​​brine reservoir, in m 2 ; It represents the average effective thickness of the brine reservoir, in m; represents the average effective porosity of the brine reservoir, in units of %; Sw represents the water saturation of the brine reservoir, in units of %; B represents the brine volume coefficient, dimensionless; It indicates the average effective lithium and potassium content of the formation, in mg / L.

[0062] In summary, the beneficial effects and advantages of the present invention may include: 1) Based on the element enrichment law and genetic mechanism of the mineral to be evaluated, the distribution characteristics of the contour lines of the element content of the mineral to be evaluated are determined. According to the distribution characteristics of the contour lines, the contour line map of the element content of the mineral to be evaluated is drawn. In this way, under the condition of scarce seismic data and analytical test data, the amount of mineral element resources to be evaluated can be calculated more accurately.

[0063] 2) Based on the geological research foundation such as the genesis of brine, by establishing a positive correlation between the mineralization (or the content of other mineral elements or other mineral element combinations except the mineral element to be evaluated) and the content of the mineral element to be evaluated, the content of the mineral element to be evaluated can be indirectly estimated. It is no longer necessary to drill a large number of new wells or conduct multiple perforation tests to obtain the content of mineral elements such as lithium or potassium in the original undiluted brine. Therefore, while reducing economic costs and not affecting the normal production of the original wellbore, it can still accurately calculate the amount of mineral element resources to be evaluated in salt lake basins where the analysis and test results of the mineral element content to be evaluated in the original undiluted brine are scarce, and the application scenarios are more extensive.

[0064] 3) Based on geological research foundations such as sedimentary phase characteristics, it is possible to more accurately predict the thickness and distribution area of ​​effective brine reservoirs in salt lake basins without seismic data, and effectively implement the distribution of mineral element resources to be evaluated.

Claims

1. A method for evaluating brine mineral resources in a salt lake basin, characterized in that: The method includes: 1) Based on the enrichment law and genetic mechanism of the mineral elements to be evaluated, the distribution characteristics of the isovalue lines of the mineral elements to be evaluated are judged; if the salt lake basin has experienced an enrichment process of evaporation and concentration, the source of the mineral elements to be evaluated is mainly evaporation and concentration, and the isovalue lines of the mineral elements to be evaluated are judged to be distributed in a ring shape with salt as the center; if the brine in the salt lake basin communicates with the underlying salt-bearing strata through faults, the source of the mineral elements to be evaluated is mainly fault migration, and the isovalue lines of the mineral elements to be evaluated are judged to be distributed in a linear shape with the fault as the center; if the source of the mineral elements to be evaluated is mainly volcanic hydrothermal fluids, the isovalue lines of the mineral elements to be evaluated are judged to be distributed around the rock mass; 2) Based on the distribution characteristics of the element content contour lines of the mineral to be evaluated, the determined lower limit of the element content of the mineral to be evaluated and the value range of the element content contour lines of the mineral to be evaluated, combined with the measured mineral element content, draw a contour line map of the element content of the mineral to be evaluated; 3) Based on the contour map of the element content of the mineral to be evaluated, the volumetric method is used to calculate the resource quantity of the mineral element to be evaluated.

2. The method for evaluating brine mineral resources in a salt lake basin according to claim 1, characterized in that: In step 2), for the rock salt development layer section in the salt lake basin that has undergone the evaporation concentration enrichment process, according to the measured brine mineralization and mineral element content in the salt lake basin, a correlation between the content of the mineral element to be evaluated and the mineralization or the content of other mineral elements or other mineral element combinations other than the mineral element to be evaluated is established, and the content value of the mineral element to be evaluated is calculated using the correlation.

3. The method for evaluating brine mineral resources in a salt lake basin according to claim 2, characterized in that: The method for establishing the correlation between the content of the mineral element to be evaluated and the mineralization or the content of other mineral elements or other mineral element combinations except the mineral element to be evaluated is as follows: firstly evaluate the correlation between the content of the mineral element to be evaluated measured in the brine of the water injection development wells in the same block and the mineralization or other mineral elements or other mineral element combinations; if the correlation is greater than the set threshold, then only use the original brine obtained based on the new exploration well or the perforation water test to determine the content of the mineral element to be evaluated and establish the said correlation.

4. The method for evaluating brine mineral resources in a salt lake basin according to claim 3, characterized in that: When using a new exploration well to determine the content of mineral elements to be evaluated in the brine reservoir, after a set time is set for acid backwashing in the new exploration well, when the data of the content of mineral elements to be evaluated in the new exploration well to be determined stabilizes, the value measured at this time is used as the actual measured value of the content of mineral elements to be evaluated in the brine reservoir.

5. The method for evaluating brine mineral resources in a salt lake basin according to any one of claims 2 to 4, characterized in that: If the salt lake basin has undergone an enrichment process of evaporation and concentration, the source of the mineral elements to be evaluated is mainly evaporation and concentration. When the mineral elements to be evaluated are lithium or potassium, the content of the mineral elements to be evaluated is positively correlated with the mineralization.

6. The method for evaluating brine mineral resources in salt lake basins according to claim 1, characterized in that: In the step 2), the process of calculating the mineral element resources to be evaluated by the volumetric method includes: determining the lower limit of the porosity of the brine reservoir in the study area, defining the value range of the brine reservoir porosity contour line, and drawing the brine reservoir porosity contour line map; determining the effective thickness division standard and the lower limit of the brine reservoir in the study area, defining the value range of the brine reservoir effective thickness contour line, and drawing the brine reservoir effective thickness contour line map; according to the content contour line map of the mineral element to be evaluated, the porosity contour line map of the brine reservoir and the effective thickness contour line map of the brine reservoir, determining the overlapping areas in the study area where the content of the mineral element to be evaluated, the porosity of the brine reservoir and the effective thickness of the brine reservoir are all greater than the corresponding lower limit values, and then determining the distribution area of ​​the brine reservoir in the study area; determining the water saturation value and the brine volume coefficient value of the brine reservoir in the study area; according to the effective thickness, porosity, water saturation, distribution area, brine volume coefficient of the brine reservoir in the study area and the content of the mineral element to be evaluated, the volumetric method is used to calculate the mineral element resources to be evaluated.

7. The method for evaluating brine mineral resources in a salt lake basin according to claim 6, characterized in that: The average effective content of mineral elements to be evaluated in brine, the average effective porosity of brine reservoir and the average effective thickness of brine reservoir are calculated by the well point arithmetic average method, the well point area weighting method and the contour area weighting method. According to the average effective thickness of brine reservoir, the average effective porosity and the average effective content of mineral elements to be evaluated in brine in the study area, the volumetric method is used to calculate the resources of mineral elements to be evaluated.

8. The method for evaluating brine mineral resources in a salt lake basin according to claim 7, characterized in that: The formula for calculating the mineral element resources to be evaluated using the volumetric method is: Where Q represents the potential resource of the mineral element to be evaluated, in tons; A represents the distribution area of ​​the brine reservoir, in m 2 ; It represents the average effective thickness of the brine reservoir, in m; represents the average effective porosity of the brine reservoir, expressed in percentage; Sw represents the water saturation of the brine reservoir, expressed in percentage; B represents the brine volume coefficient, dimensionless; It indicates the average effective mineral element content to be evaluated in brine, in mg / L.

9. The method for evaluating brine mineral resources in a salt lake basin according to claim 6, characterized in that: Porosity values ​​include porosity values ​​interpreted by well logging, porosity values ​​measured by core, porosity values ​​under similar geological conditions, and porosity values ​​inferred from the porosity-depth relationship chart.

10. The method for evaluating brine mineral resources in a salt lake basin according to claim 6, characterized in that: The effective thickness contour lines of the brine reservoir are defined by combining the sand-to-formation ratio map, oil and gas reservoir thickness map, stratigraphic thickness map, sandstone thickness map and sedimentary facies map.

Images