A borehole-based analytical method for quantitatively distinguishing deep-sea hydrothermal sulfides from their host rocks in situ

Abstract

The objective of the present invention is to provide a measurement and analysis method that utilizes a borehole to quantitatively distinguish deep-sea hydrothermal sulfides from host rocks in situ. [Solution] In order to achieve the purpose of accurately distinguishing the distribution and relative content of sulfide and host rock in the entire cross section of a borehole, a feasible borehole measurement and analysis method is proposed. The borehole measurement and analysis method for quantitatively distinguishing deep-sea hydrothermal sulfide and host rock in situ includes the following steps: Step 1: drilling and coring in a sulfide mining area, performing multi-parameter measurements in the borehole, and dividing rock layers from top to bottom based on the measurement curve; Step 2: performing laboratory physical property tests and microscopic layer identification and testing and calculations on the core samples; Step 3: establishing a discriminant equation for sulfide and host rock in a laboratory environment; and Step 4: substituting the average value of the drilling measurement curves of each layer into the discriminant equation obtained in Step 3, and calculating the relative content of sulfide and host rock in each layer of the entire cross section.

Description

[Technical field]

[0001] The present invention relates to the field of evaluation and research into deep-sea hydrothermal sulfide resources, and in particular to a measurement and analysis method using a borehole for quantitatively distinguishing deep-sea hydrothermal sulfides from host rocks in situ. [Background technology]

[0002] Deep-sea hydrothermal sulfides are metallic mineral resources widely distributed in deep-sea environments such as mid-ocean ridges, back-arc basins and island arcs, and have significant economic value and potential for development and utilization.

[0003] Deep-sea hydrothermal sulfides can coexist with and mix with host rocks (surrounding rocks) below the seafloor to form deposits with a thickness of over 100m. The poor consolidation of these deposits makes the collection efficiency of drilling cores extremely low, often less than 40%, and each layer of the coring is usually discontinuous, making it impossible to directly evaluate the resource potential with core samples. Based on the above reasons, using boreholes to carry out in-situ physical property measurements, combining the laboratory physical property test characteristics of drilling core samples with fitting analysis to analyze the distribution and relative content of sulfides and host rocks in each layer, is a necessary method for accurately evaluating the deep-sea sulfide resource potential.

[0004] At present, there are few drilling surveys in deep-sea hydrothermal sulfide areas, and even fewer borehole measurement studies, and the relevant theoretical foundations and methods for mineral content analysis of borehole rock layers are still immature, which has significantly limited the accurate understanding of the value of deep-sea sulfide resources in the scientific and industrial communities and the preparation for their development and utilization. At present, there is an urgent need to develop a borehole measurement and analysis method to quantitatively distinguish deep-sea hydrothermal sulfides and host rocks in situ.

[0005] In view of the above circumstances, this patent application is filed. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention relates to a measurement and analysis method using a borehole for quantitatively identifying deep-sea hydrothermal sulfides and host rocks in situ, and proposes a feasible measurement and analysis means using a borehole to solve the problems and needs existing in the above-mentioned prior art and to achieve the purpose of accurately identifying the distribution and relative content of sulfides and host rocks over the entire cross section of a borehole. [Means for solving the problem]

[0007] In order to achieve the above design objective, a measurement and analysis method is provided that utilizes a borehole to quantitatively distinguish deep-sea hydrothermal sulfides from host rocks in situ, Step 1: drilling and coring in the sulfide mining area, carrying out multi-parameter measurements in the borehole, and dividing the rock layers from top to bottom based on the measurement curve; Step 2: carrying out laboratory physical property testing, microscopic layer identification and testing, and calculations on the core samples; Step 3 to establish the discriminant between sulfides and host rocks in laboratory conditions; and Step 4: Substituting the average value of the drilling measurement curves of each member into the discriminant obtained in step 3 to calculate the relative content of sulfide and host rock in each member of the entire cross section; The method includes:

[0008] Also, the step 1 includes the following steps: drilling and coring at the ocean floor of a deep sea sulfide mining area; After coring is completed, a physical property measuring device is lowered vertically into the center of the borehole and measurements are started along the entire length of the borehole. If there are more measurement curves, selecting the most stable curve as a reference and correcting the depth range of the other curves; and The process includes a step of dividing the entire measured cross section from top to bottom into a plurality of layers using a point at a mid-depth value between the maximum value and the adjacent minimum value of the measured curve, or a point at a mid-depth value between the minimum value and the adjacent maximum value of the measured curve, as a boundary.

[0009] Also, the step 2 includes the following steps: A process of immersing a core sample taken from a deep-sea borehole in seawater of the same temperature and pressure as that used for coring, and carrying out continuous physical property tests from top to bottom; After the test is completed, the samples are taken out, and the layers are identified and tested under a microscope, and calculations are carried out to obtain the relative content of sulfide and host rock in each layer.

[0010] In step 2, the temperature of the seawater in the test chamber is measured by lowering a temperature probe of a measuring device into the borehole, and the surface pressure of the seawater in the test chamber is calculated from the water depth value of the single beam or the central beam of the multi-beam at the seabed surface of the borehole.

[0011] Also, step 3 includes the following steps: Establishing criteria for distinguishing sulfides from host rocks in laboratory conditions based on multi-parameter physical property measurement methods; and and performing a polynomial regression analysis based on the induced resistivity, sonic velocity, and relative sulfide content of each member measured in step 2, where the induced resistivity, sonic velocity, and relative sulfide content of each member are related by a polynomial function, and the following fitting equation is obtained:

[0012]

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[0013] Also, step 4 includes the following steps: reading curve values ​​corresponding to each depth value in different layers on the physical property exploration curve of the borehole cross section and calculating the average value of each physical property parameter of each layer; The process includes substituting the calculated average values ​​of the induced resistivity and sonic velocity of each member into the fitting equation (1) obtained in step 3 to determine the relative proportions of sulfide and host rock in each member on the full cross-sectional measurement curve of the borehole. Effect of the Invention

[0014] In summary, the advantages of the borehole measurement and analysis method proposed in this application for quantitatively identifying deep-sea hydrothermal sulfides and host rocks in situ are that it effectively solves the deficiencies in the relevant theories and methods for quantitatively identifying sulfides and host rocks in the longitudinal sections of deep-sea hydrothermal sulfide deposits in the prior art, proposes a specific and feasible borehole investigation and analysis means, and can accurately identify the distribution and relative content of sulfides and host rocks in the entire borehole cross section, thereby providing relevant theoretical basis and technical reference for the accurate assessment, development and utilization of deep-sea hydrothermal sulfide resources. [Brief description of the drawings]

[0015] [Figure 1] This is a flowchart of a measurement and analysis method using a borehole to quantitatively distinguish deep-sea hydrothermal sulfides and host rocks in situ. [Diagram 2] FIG. 1 shows the results of an analysis using the method described in this application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The present invention will be further described below with reference to the drawings and embodiments.

[0017] (First embodiment) The borehole-based measurement and analysis method proposed by the present application for quantitatively identifying deep-sea hydrothermal sulfides and host rocks in situ includes the following steps:

[0018] Step 1: Drill and coring in the sulfide mining area, carry out multi-parameter measurements in the borehole, and divide the rock layers from top to bottom based on the measurement curves. Select a flat seabed surface of the deep-sea sulfide mining area topography, and drill and coring vertically downward via a seabed drilling machine, a drilling survey platform or a drilling ship; After coring is completed, the physical property measuring device is lowered vertically into the center of the borehole and measurement work is started along the entire length of the borehole. Specifically, taking an example of a measuring device for induced resistivity (unit: Ω m) and sound wave speed (unit: μm / s), if there is a difference between the measurement curve when the measuring device is lowered and the measurement curve when it is pulled up, the measurement curve when the measuring device is pulled up is used as the final result. Since sonic measurement is relatively susceptible to external interference factors such as small particle deposits, pores on the borehole wall, etc., the relatively stable induced resistivity curve is used as the reference, and the depth value of the sonic velocity curve is corrected according to the induced resistivity curve to keep the depth range of the two measurement curves consistent; If there are more measurement curves, similarly select the most stable curve as the reference and compensate the depth range of the other curves, The entire section is divided into several layers from top to bottom by the boundary at the midpoint between the maximum value and the adjacent minimum value of the measurement curve, or the midpoint between the minimum value and the adjacent maximum value of the measurement curve. At this time, the sulfides and host rocks in each layer are evenly distributed, The maximum or minimum point of the measurement curve is identified by the following formula:

[0019]

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[0020] Step 2: Laboratory physical property testing, microscopic layer identification, and test calculations are performed on the core samples. The core samples taken from the deep sea borehole are immersed in seawater at the same temperature and pressure as when the core was taken, and continuous physical property tests are carried out from top to bottom. The temperature of the seawater in the test chamber is measured by lowering a temperature probe of the measuring device into the borehole, and the surface pressure of the seawater in the test chamber is calculated from the water depth value of the single beam or the center beam of the multi-beam at the seabed surface of the borehole. Take the measurement method of induced resistivity and sonic velocity as an example. When carrying out indoor physical property testing of core samples, the distance between the detector and the sample is the same as the distance between the equipment in the borehole and the borehole wall. Here, the sonic velocity is the longitudinal wave velocity, which is measured by the sonic detector, and this value is the sound distance of the sample divided by the time it takes for the sound wave to pass through the sample. The induced resistivity is measured by an electrical property measuring instrument, and this value is the product of the cross-sectional area of ​​the sample and the resistance value divided by the length between the two measuring electrodes. After the test, the samples were taken out and subjected to stratification identification and testing / calculation under a microscope to obtain the relative content of sulfide and host rock in each layer. Since these core samples are located under the seafloor of the hydrothermal field and the oxide content is extremely low, the oxide component can be ignored and only the relative content of host rock and sulfide is considered. After slicing the sample to a certain thickness, it is polished into optical sections, and the entire optical section is observed under a microscope. Because there is a significant difference in the reflective luster of the minerals that compose rocks and the minerals that compose sulfides, most of the rock minerals have a glassy or greasy luster, while the sulfide minerals have an obvious metallic luster. Therefore, the relative areal content of sulfides can be obtained by circling all minerals with metallic luster on the optical section, adding up the areas of the circled regions, and then dividing by the area of ​​the entire sample. The relative areal content of sulfides can then be multiplied by the density of the sulfide at the layer position and divided by the sum of the products of the densities of the sulfide and the host rock to obtain the relative content of sulfides and the host rock.

[0021] The densities of the sulfides and host rocks in the core samples at each layer were obtained by dividing the weights of the sulfide and host rock samples selected under a microscope by their volumes, where the weights were obtained by weighing with an electronic balance and the volumes were obtained by the drainage method.

[0022] The calculation formula for the sulfide content in the core sample is as follows:

[0023]

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[0024] The formula for calculating the host rock content in the core sample is as follows:

[0025]

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[0026] Step 3: Establish sulfide-host rock discriminants in laboratory conditions Establish criteria for distinguishing sulfides from host rocks in laboratory conditions based on multi-parameter physical property measurement methods; Taking the measurement methods of induced resistivity and acoustic velocity as an example, firstly, deep-sea hydrothermal sulfides are formed by the combination of metal cations and sulfide anions, so they have strong electrical conductivity and lower induced resistivity than the parent rock formed by magma condensation; secondly, deep-sea hydrothermal sulfides are formed by precipitation and deposition from hydrothermal fluids without compression or metamorphism, so they have a higher porosity than the parent rock and a slower acoustic propagation velocity than the parent rock; Based on the above relationship, it can be determined that there is a polynomial function relationship between the induced resistivity, sonic velocity, and the relative content of sulfide or host rock. By performing a polynomial regression analysis and fitting the induced resistivity, sonic velocity, and relative content of sulfide of each layer measured in step 2, the following equation can be obtained.

[0027]

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[0028] Step 4: Substitute the average values ​​of the drilling measurement curves for each layer into the discriminant obtained in step 3 to calculate the relative sulfide and host rock contents of each layer in the entire cross section. Reading the curve values ​​corresponding to each depth value in different layers on the physical property exploration curve of the borehole cross section, and calculating the average value of each physical property parameter of each layer; Taking the induced resistivity (R) and sonic velocity (S) as an example, the calculated average values ​​of the induced resistivity and sonic velocity of each member are substituted into the fitting equation (1) obtained in step 3 to determine the relative proportion of sulfide and host rock in each member on the full cross-sectional measurement curve of the borehole. The results of the measurement and analysis using the borehole are shown in Figure 1.

[0029] As mentioned above, by combining the contents of the means shown in the drawings and the description, similar technical means can be derived, which still falls within the scope of the technical means of the present invention.

Claims

1. A measurement and analysis method using a borehole for quantitatively distinguishing deep-sea hydrothermal sulfides and host rocks in situ, comprising: Step 1: drilling and coring in a sulfide mining area, carrying out multi-parameter measurements in the borehole, and dividing the rock layers from top to bottom based on the measurement curve; Step 2: Conduct laboratory physical property testing, microscopic layer identification, and testing and calculations on the core samples; The method includes the steps of: establishing a discrimination criterion for sulfide and host rock in a laboratory environment based on a multi-parameter physical property measurement method; and performing a polynomial regression analysis based on the measured resistivity, sonic velocity, and relative content of sulfide or host rock of each member in step 2 to obtain the following fitting equation, wherein the fitting equation is: [0010] where R and S represent the induced resistivity and sonic velocity values ​​of a rock formation, respectively; ｎ ~a ０ and b ｎ ~b ０ are the coefficients of the polynomial, which obtain constant values ​​after polynomial fitting, and P ｓ represents the relative content of sulfides in a given member, and P ｓ = [0, 1], and P ｓ When P = 1, the entire layer is sulfide, and P ｓ If = 0, the entire member is the host rock; Step 3 to establish sulfide-host rock discriminants in laboratory conditions; and Step 4 includes a step of reading the curve values ​​corresponding to each depth value in different layers on the physical property exploration curve of the borehole cross section, calculating the average value of each physical property parameter of each layer, and substituting the calculated average values ​​of the induced resistivity and sonic velocity of each layer into the fitting formula (1) obtained in step 3 to obtain the relative proportion of sulfide and host rock in each layer on the whole cross section measurement curve of the borehole, and substituting the average value of the borehole measurement curve of each layer into the discriminant obtained in step 3 to calculate the relative content of sulfide and host rock in each layer of the whole cross section; A measurement and analysis method using a borehole for quantitatively distinguishing deep-sea hydrothermal sulfides and host rocks in situ, comprising:

2. The step 1 includes: drilling and coring at the ocean floor of a deep sea sulfide mining area; After coring is completed, a physical property measuring device is lowered vertically into the center of the borehole and measurements are started along the entire length of the borehole. If there are more measurement curves, selecting the most stable curve as a reference and correcting the depth range of the other curves; and a step of dividing the entire measured cross section from top to bottom into a plurality of layers with a boundary being a point of mid-depth between a maximum value and an adjacent minimum value of the measured curve, or a point of mid-depth between a minimum value and an adjacent maximum value of the measured curve; A measurement and analysis method using a borehole for quantitatively distinguishing between deep-sea hydrothermal sulfides and host rocks in situ according to claim 1, comprising:

3. Step 2 includes: A process of immersing a core sample taken from a deep-sea borehole in seawater of the same temperature and pressure as that used for coring, and carrying out continuous physical property tests from top to bottom; After the test is completed, the samples are taken out and subjected to microscopic layer identification and testing and calculation to obtain the relative content of sulfide and host rock in each layer; A measurement and analysis method using a borehole for quantitatively distinguishing between deep-sea hydrothermal sulfides and host rocks in situ according to claim 1, comprising:

4. 4. The measurement and analysis method using a borehole for quantitatively identifying deep-sea hydrothermal sulfides and host rocks in situ as described in claim 3, characterized in that in step 2, the seawater temperature in the test chamber is measured by lowering a temperature probe of a measuring device into a borehole, and the seawater surface pressure in the test chamber is calculated from the water depth value of the central beam of a single beam or multi-beam at the seabed surface of the borehole.

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