A method for finding water and determining wells in magmatic rock hilly areas

Abstract

The present invention discloses a method for finding water and determining well positions in magmatic rock hilly areas, comprising the following steps: Step 1: Satellite image recognition; Step 2: Geomechanical analysis; Step 3: Field investigation tracking and on-site evaluation; Step 4: Geophysical exploration; Step 5: Well position determination. The present invention adopts new technical means such as satellite image recognition and geomechanical analysis, and combines conventional technical methods such as hydrogeological investigation, surface geophysical prospecting, and hydrogeological drilling. Aiming at main water storage structures such as fault zones, dikes, and lithologic contact zones, a set of easy-to-master and convenient-to-operate water-finding and well-position-determining technical methods of "satellite image recognition - geological stress analysis - investigation and verification - fracture network detection - well position confirmation - drilling and well completion" has been created, forming a three-dimensional comprehensive water-finding technical system from space to the ground, from plates to sections, from regions to local areas, and from the ground to underground.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogeology, and particularly to a method for finding water and determining well locations in magmatic rock hilly areas. Background Art

[0002] At present, there is no complete scientific and technical specification for finding water and determining well locations in magmatic rock hilly areas at home and abroad, and there is also a lack of systematic and mature working experience. The lithology in magmatic rock hilly areas is mainly granite, diorite, etc. The fractures in such rocks are not well developed, and the water-bearing property is poor. The development boundary of tectonic fractures has significant mutation characteristics, which is very different from that in limestone areas. Sometimes, two completely different well completion effects will appear when the position difference is less than half a meter. This is a long-term technical problem in finding water. Therefore, accurate positioning is the key to successful water finding. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for finding water and determining well locations in magmatic rock hilly areas, so as to solve the problems of relatively single means of finding water and determining well locations, difficult well location determination, and low well completion rate mentioned in the above background art.

[0004] To achieve the above purpose, the present invention provides the following technical solution: A method for finding water and determining well locations in magmatic rock hilly areas, which is characterized by including the following steps;

[0005] Step 1: Satellite image recognition;

[0006] On the basis of studying previous geological achievement data and fully mastering geological conditions, referring to the distribution directions of mountains, rivers, valleys and the hue differences of micro-topography images interpreted from satellite images, identify the positions and regional trends of faults, dikes and the contact zones of some rock masses, delineate the distribution ranges, combine the topographic slope direction, the directions of rivers and gullies to judge the groundwater runoff direction, analyze the groundwater recharge conditions, and delimit the water-finding targets or exploration ranges that are conducive to groundwater recharge and storage;

[0007] Step 2: Geological mechanics analysis;

[0008] Using geological mechanics, preliminarily delineate the water-rich target areas, generally there are three situations:

[0009] S1. According to the principles of geological mechanics, extensional tensile fractures develop along the direction of the main compressive stress during the tectonic period, while the strike of compressive or nappe fractures is basically perpendicular to the direction of the main compressive stress. There are secondary fractures of tensional shear and compressive shear developed between the tensile and compressive fractures. The fracture fracture zones and the tectonic influence fracture zones are the most favorable positions for groundwater storage. Generally speaking, in the NW and NWW fracture zones, the intersection zones of primary and secondary fractures, and the convex ends at the fracture turning points, the fractures in the rocks are relatively well developed, and there is a good groundwater storage environment.

[0010] S2. The cracks produced by stress in rocks are the main places for groundwater storage in igneous rock areas. The nature of the rock determines the degree of development of the cracks. Generally speaking, granite-like acidic rocks composed of light-colored minerals such as quartz and feldspar are rigid or brittle. Under the action of regional compression stress, they release stress by producing joints and cracks, and produce tensile cracks, forming a favorable space for groundwater storage. However, flexible or plastic rocks composed of dark-colored minerals such as hornblende, pyroxene and biotite release stress by internal compaction or deformation. The cracks are extremely undeveloped and do not utilize the storage of groundwater. Quartz and granite brittle dykes trending NW and near SN are basically all water-bearing dykes.

[0011] S3. The lithology changes in igneous rock areas have significant mutation characteristics, which creates favorable conditions for finding and utilizing the lithology contact zone of soft and brittle rock masses to find water and locate wells. When the rock mass is subjected to regional compressive stress, the interface of lithologies of different properties is the most concentrated part of the stress distribution. On the side of the flexible rock mass, the rock is compacted or plastically deformed, and sometimes metamorphism occurs in the surface zone; while in the brittle rock mass, joints and fissures are generated. In general, the joints and fissures in the surface zone (generally less than 10m) are relatively dense, and the tensile space is well developed. Going to the interior of the rock mass, the shear resistance is enhanced, the fissure development gradually worsens, and the closed shear joints are the main form. Therefore, the surface zone of the brittle rock mass is the target location for finding water and determining wells.

[0012] Step 3: Field investigation, tracking and on-site evaluation;

[0013] Based on the identification of regional lithology distribution and fracture and dyke development characteristics in step 1, combined with the water-rich target area determined in step 2, conduct field geological surveys to identify the types of water-bearing and water-controlling targets and their distribution characteristics, analyze the geomorphic locations and recharge ranges that are conducive to groundwater storage, and plan specific well locations on site where conditions are relatively clear. If geophysical exploration is required for further clarification, define the scope of geophysical exploration and plan the survey line layout;

[0014] Step 4: Geophysical survey;

[0015] The principle of finding low resistance among high resistance and high resistance among low resistance is mainly followed in finding water and wells in magmatic rock areas by using geophysical prospecting methods.

[0016] The joint profile method, electrical depth sounding method and high-density method are adopted, and the survey line is basically laid out along the strike of the vertical detection target body; the low-resistance orthogonal points of the joint profile curve, the synchronous V-shaped and U-shaped low-resistance belts, and the stepped abnormal belts are the characteristics of the existence of fault structures; the high-resistance anomalies formed by the synchronous vein-like bulges of the two curves are the reflection of the existence of brittle dykes; the electrical depth sounding and high-density section reflect the distribution range of underground high- and low-resistance rock masses along the survey line. In the same resistance lithology distribution area, the low-resistance belt is a display of fault development; the stepped resistance jump along the strike is the characteristic of lithology change; the abnormal characteristics of different geophysical exploration methods are compared and studied according to geological conditions, and the well location is selected by comprehensive analysis of the geomorphic environment and recharge conditions;

[0017] Step 5: Determine the well location;

[0018] S1. Using fractures to locate water and wells:

[0019] Fault structures are the most favorable locations for water control and water abundance in magmatic rock areas. Through investigation and geophysical exploration, we can find out their specific locations, scales, occurrences, and feather-shaped fault development, analyze and study the mechanical properties and lithological characteristics of different sections, and find the locations where fractures with recharge conditions are developed.

[0020] (1) Straight sections of tensile faults and tension-torsion faults: When passing through granite distribution areas, wells should be drilled in the fault zone or near the fault position in the upper plate; when passing through diorite and gabbro intermediate-basic rock areas, wells can be drilled in the fault zone at locations with good recharge conditions for large and medium-sized faults. Small faults and areas with poor recharge conditions are generally not suitable for well drilling;

[0021] (2) Compression, compression-torsion and tension-torsion faults: When passing through granite distribution areas, the wells are located in the cataclasite zone outside the impact zone; when passing through diorite and gabbro intermediate-basic rock areas, it is generally not suitable to locate the wells;

[0022] (3) The intersection zone of tensile and tension-torsion faults and feather-shaped secondary faults: located on the water-facing side of the intersection zone, close to the main fault, preferably in an area with granite rock distribution;

[0023] (4) Intersection zone of compressional, compression-torsional and feather-shaped secondary faults: It is located on the water-facing side of the intersection of the primary and secondary faults. The specific location is as follows: when the angle between the primary and secondary faults is less than 45°, it is located outside the intersection of the two fault influence zones; when the angle between the primary and secondary faults is between 45° and 90°, it is located outside the primary fault influence zone and in the secondary fault hanging wall influence zone;

[0024] (5) In gneissic granite and granite gneiss areas with well-developed lineation and foliation, when large or medium-sized tensile or tension-torsion faults are developed, wells can be located along the fault strike in areas with favorable recharge conditions and on the fault zone. In other cases, it is generally not appropriate to locate wells in this lithological area.

[0025] S2. Using rock veins to find water and locate wells:

[0026] To locate a well using a rock vein, we must first find out the length, width, occurrence, lithology changes along the strike of the rock vein, and the main geomorphic units it crosses, especially the conversion relationship between surface water and groundwater in the sections passing through large valleys and rivers; secondly, we must find out the conditions of the rock vein being cut by fractures or different directions, clarify the continuity and stability of the rock vein along the strike, the relationship between the overall strike and the direction of groundwater flow, and the depth of groundwater levels in different sections, so as to provide a basis for selecting a suitable well location;

[0027] (1) The length of the dyke used for well setting should be greater than 80-100m and the thickness should be more than 1m. If the thickness is less than 0.5m, well setting is not suitable;

[0028] (2) When the thickness of brittle rock veins such as quartzite and fine-grained granite is less than 20 m, the well can be located on the rock vein; when the thickness is larger, the well can be located at the edge of the rock vein on the water-facing side;

[0029] (3) When using inclined dykes to locate wells, it is necessary to find out the dyke inclination and the depth of the groundwater level, and to plan to expose the dyke below the groundwater level during the dry season;

[0030] (4) The well should be located by using the veins whose strike is perpendicular to the groundwater flow direction first, followed by the veins whose strike is oblique to the groundwater flow direction. When the well is located by using the veins whose strike is parallel to the groundwater flow direction, the well should be located in an area with a gentle terrain and a certain thickness of loose rock layer on the upper part before determining the well location.

[0031] (5) When a brittle dyke is interrupted by a fault or other dykes in the same direction, the well should be located in the dyke on the upstream side of the fault, preferably within the fault influence zone;

[0032] (6) In areas where there are many dykes or where the groundwater is not easily concentrated, wells should be located at locations with large catchment areas or where dykes intersect. If recharge conditions are met, the intersection of two brittle dykes and the upstream of where a brittle dyke is intercepted (cut) by a flexible dyke are good locations for wells (drilling on brittle dykes).

[0033] (7) Using water-blocking dykes to locate wells: When there is a large area of ​​coarse-grained granite and medium-coarse-grained monzonitic granite upstream of the diabase and lamprophyre dykes, the well site is located upstream of the water-blocking dykes and on the edge of the granite body facing the water;

[0034] S3. Using lithologic contact zones to locate water and wells:

[0035] In magmatic rock areas, the spatial lithology varies greatly and has poor regularity. There is basically no transitional phenomenon in the changes of different lithologies, and the lithologies on both sides of the interface have significant mutation characteristics. Since lithology is the main controlling factor for groundwater occurrence in magmatic rock distribution areas, when using lithology contact zones to find water and determine well locations, precise positioning must be ensured. Mylonite often develops at lithology interfaces, and the distance from the well location to the lithology interface should be controlled between 5 - 10m.

[0036] (1) High-resistance rock masses are distributed downstream of low-resistance rock masses; the well location is determined upstream of the high-resistance rock mass, close to the high-resistance body side, that is, in the surface fracture development zone of the high-resistance rock mass;

[0037] (2) High-resistance rock masses are distributed upstream of low-resistance rock masses; this situation is only suitable for areas where medium- to coarse-grained granite intruded later is distributed upstream and lineated or foliated gneiss is distributed downstream. The well location is determined in the surface fracture zone of the low-resistance rock mass upstream and the high-resistance rock mass;

[0038] Preferably, the satellite image recognition includes fracture structure image features, dike image features, and lithology contact zone image features.

[0039] The fracture structure image features:

[0040] (1) Present gray, gray-green lines or dark bands distributed along valleys, with an obvious color difference from the surrounding landform images. The lines are continuous or intermittent, and the overall trend is relatively stable;

[0041] (2) Between mountains and plains or between different geomorphic landscape areas, they are connected along a long straight line or smooth curve, forming an obvious distribution boundary; the ridge suddenly breaks or is displaced in its trend, and long linear cliffs or multiple cliffs are regularly arranged linearly on the mountain body;

[0042] (3) The river channel has a straight trend, with long strip-shaped or bead-shaped water bodies distributed along a certain direction, or the trend of the gully or river suddenly makes a straight turn;

[0043] (4) The mountain vegetation shows a significant strip-shaped distribution, and the white spots presented by the outcrops of mountain rocks suddenly break or turn along the trend.

[0044] The dike image features:

[0045] (1) Present white spots or white and light gray lines with a relatively stable overall trend, continuously or intermittently distributed, and green vegetation strips mostly develop on the side. When the white spots are larger or the lines are thicker, it indicates a larger thickness of the dike;

[0046] (2) Have a certain length, cross farmland or terraced fields with different arrangement directions along the trend, with continuous or intermittent white rock spots distributed along the line, developing intermittent spot-shaped green vegetation, or presenting dark steep bank strips;

[0047] (3) Small and medium-sized gullies developed along the hillside, with white lines or intermittent white spots appearing in the gullies, and intermittent green vegetation developing; the spotted lines still maintain a relatively stable direction when crossing large gullies or valleys;

[0048] Image features of the lithologic contact zone:

[0049] (1) There are ring-shaped or irregular light gray or gray-green scarps. When gullies develop along the joints and fissures of the hard rock mass, the scarps are distributed discontinuously. In areas with variable rock properties, there will be multiple concentrated scarps. There is obvious unevenness in hue and brightness on both sides of the scarps.

[0050] (2) In areas with a large distribution area of ​​granite, the surface or soil image is brighter, showing a white or yellowish phase, and the landform shows a distribution feature of raised strip-shaped hills and valleys. The width of the hills and valleys is generally narrow, and the slopes are steep. In areas with diorite distribution, the surface and soil color is darker, showing a gray or dark yellow phase, the hills and valleys are mostly wide, the slopes are gentle, and the direction consistency of the valleys or gullies is poor.

[0051] Preferably, the geomechanical analysis includes analysis of fracture structure conditions, analysis of dyke conditions and analysis of lithologic contact zone conditions;

[0052] Analysis of the fracture structural conditions:

[0053] In the area where granite brittle rocks are distributed, NW-trending and NWW-trending fault zones, the intersection of primary and secondary faults, and the outer convex end of the fault turning point, the cracks in the rocks are relatively developed, providing a good groundwater storage environment. The fault zone later invades and fills the granite section. The water-richness depends on the length of the rock mass and the recharge conditions. By selecting a geomorphic environment that is conducive to groundwater recharge and using geophysical exploration methods to identify the specific locations of the fault zone and crack development, the well location can be determined;

[0054] Analysis of the dyke conditions:

[0055] Brittle dykes have relatively developed fissures, some of which are generated during diagenesis and some are generated by the influence of later tectonic movements. Generally speaking, brittle dykes in flexible lithology areas have relatively developed fissures, and the degree of fissure development of dykes is related to their thickness. However, when the thickness is large, the shear resistance is enhanced, and the degree of fissure development is significantly deteriorated. Thick dykes of any lithology will play a water blocking role. However, if the dykes are thin, they are easily dislocated by stress, resulting in discontinuity along the strike. The water volume of dykes with a thickness of less than 20m is good, and the water volume gradually deteriorates when the thickness is greater than 20m. However, dykes with a thickness of less than 0.5m generally have poor continuity and low utilization value.

[0056] Generally, quartz and granite brittle veins with NW and SN trends are basically water-bearing veins. When locating wells, the thickness can be determined by using geophysical prospecting methods in concealed areas in combination with the recharge conditions and groundwater flow direction, and then a suitable well location can be selected.

[0057] Analysis of the lithologic contact zone conditions:

[0058] The lithology changes in magmatic rock areas have significant mutation characteristics, which creates favorable conditions for finding and utilizing the lithology contact zones of soft and brittle rock masses to locate water and wells.

[0059] When the rock mass is subjected to regional compressive stress, the interface between rock types of different properties is the place where stress distribution is most concentrated; on the side of the flexible rock mass, the rock is compacted or undergoes plastic deformation, and sometimes the surface zone becomes metamorphic; while in the brittle rock mass, joints and fissures are generated. In general, the joints and fissures in the surface zone (generally less than 10m) are relatively dense, and the tensile space is well developed. As you go deeper into the rock mass, the shear resistance is enhanced, the fissure development gradually deteriorates, and closed shear joints are dominant; therefore, the surface zone of the brittle rock mass is the target location for finding water and determining wells.

[0060] Preferably, the field investigation tracking and on-site evaluation include fault structure investigation, dyke investigation and lithologic contact zone investigation;

[0061] The fault structure investigation:

[0062] Verify and identify the geological characteristics of the abnormal sections in the satellite images. If it is confirmed to be displayed by the fault, track and find the outcrop of the fault along the strike direction, measure the cross-section occurrence and the width of the fault zone, identify the magma intrusion activity, filling section and lithology changes, lithology changes between the two plates along the strike direction, the width of the impact zone, the development and zoning characteristics of tectonic rocks, and the development of feather faults, analyze and study the mechanical properties of the fault structure, and delineate the key water-finding sections in combination with the geomorphic environment and recharge conditions, determine the geophysical exploration wiring plan, and select the well location by comprehensive analysis based on the results of geophysical exploration;

[0063] (1) In the straight section of the tensile fault and the tensile-torsion fault, when passing through the granite brittle rock area, a rock crushing zone of a certain width will appear along the strike. The rock blocks in the zone are uneven in size, and sometimes they are filled with fine rock debris or mud to present breccia. The lower part of the hillside and the front area are mostly buried. The section crossing the mountain presents U-shaped or V-shaped valleys, and sometimes gullies that are oblique to the terrain slope are developed along them. The well location of the tensile fault can be set inside the fault zone or in the upper plate fissure development zone, while the well location of the tensile-torsion fault should be set in the upper plate influence zone close to the fault;

[0064] (2) Compressive-shear, tensional-shear fractures and the torsional sections of tensional fractures (with tortuous strike and reversed dip of the fault plane); identify the lithology distribution along the fracture line, select the sections where granite rocks are distributed, find the outcrops of tectonites in the fracture influence zone and divide the lithology zones. Generally, from the fault center to the outer side of the influence zone, it can be successively divided into mylonite zone, mylonitized zone, cataclastic porphyry zone or breccia lens zone, schistosity zone and cataclasite zone. Sometimes, there may be a lack of certain lithology or incomplete zonation; cataclasite is distributed on the outermost side of the influence zone, connecting with the rock mass in the non-influence zone or weak influence zone. The compressive-shear stress causes the development of tensional fractures in it, forming the storage space for groundwater and becoming the main water-bearing part of this type of fracture structure; on the basis of identifying the characteristics of lithology zonation, combined with the groundwater recharge conditions, select the well location;

[0065] In addition, on the sides of compressive-shear and tensional-shear fractures, there are generally many feather-shaped secondary fractures developed. The rock mass at the intersection of the main and secondary fractures is broken and the fractures are developed, which is also a key consideration for selecting the well location;

[0066] (3) Fracture structures in the area of diorite flexible rocks; when the recharge condition is good and the fracture is obviously tensional, the well location target is selected in the fracture zone itself, but the water volume is generally less than 15m 3 / h; when the fracture is compressive-shear and tensional-shear, mylonite is mostly developed in the fracture zone and its influence zone. Generally, it is not suitable to locate the well;

[0067] The investigation of the dike:

[0068] The width of the fracture zone generated by the extrusion of the surrounding rock during the formation of the dike is generally very small, and its effect on groundwater storage is very small. Therefore, generally, the contact zone of the surrounding rock is not used as the target for finding water and locating wells, but the well location is determined in the brittle dike;

[0069] (1) According to the dike positions delineated on the geological map, combined with the display on the satellite image, trace along the strike on site to identify the lithology, occurrence and thickness of the dike, the strike, dip and development density of the tensional fractures and closed fractures. The field tracing distance should not be less than 200m; when finding a dike that is not marked on the geological map and not shown on the satellite image, try to trace along the strike to the end of the dike to determine the length, thickness and occurrence of the dike; when the dike passes through the shallow overburden area, there will generally be dike stones or debris distributed along a relatively stable strike on the surface or in the farmland. The length and thickness can be initially judged by tracing along the strike of the debris; when the strike of the dike is perpendicular or basically perpendicular to the groundwater flow direction, the groundwater in the dike is conducive to obtaining recharge, and generally good results can be achieved by locating the well on it;

[0070] (2) Identify the vertical lithology changes of the dyke. Outcrops can generally be found in places where the dyke passes through deep valleys. The vertical lithology changes should be observed in detail. If necessary, geophysical detection lines should be laid to identify the stability of the lithology along the strike and in the vertical direction. Homogeneous and stable lithology distribution is the key to successful water finding and well determination in the dyke. This is because magma differentiation occurs during the process of intrusion and condensation of magma. Most dykes have vertical lithology inhomogeneity and sometimes lithology mutations. When the dyke passes through the valley, the lithology from top to bottom is fine-grained granite, diorite or fine-grained granite, coarse-grained granite, diorite. This phenomenon is more common in field investigations.

[0071] (3) The effect of vein length on wellbore water output is significantly greater than that of thickness, because the longer the vein is, the more geomorphic units it crosses, the wider the source of recharge, and the richer the water storage capacity. In areas crossing river valleys, it is necessary to find out the recharge and discharge conversion relationship between groundwater and surface water in the vein, measure flow when necessary, analyze groundwater recharge conditions, and try to choose long brittle veins to locate wells.

[0072] The lithological contact zone survey:

[0073] Magmatic rock areas have brittle acidic granite rocks and soft intermediate-basic rocks, which will show different degrees of differential weathering characteristics. The contact zone is often distributed with irregular rock slops or intermittent rock outcrops with a certain regular arrangement on the surface. During the investigation, the lithological characteristics on both sides should be carefully identified, and the distribution range of different rock bodies should be traced and delineated along the slops and outcrops. When the lithological interface is covered by surface soil, the approximate contact zone boundary can be traced and delineated according to the changes in soil color and mineral particles contained. In the distribution area of ​​medium-coarse-grained granite, the soil color is mostly earthy yellow and light grayish yellow, and contains more coarse sand particles of feldspar and quartz rocks. In the distribution area of ​​diorite rocks, the soil color is mostly dark gray and dark yellow, which contains more dark mineral fragments or particles of biotite and hornblende. When the soil color and the rock particles contained show obvious changes, the vicinity is generally the contact boundary of soft and brittle (intermediate-acidic) rocks. Tracing and locating along the soil color belt, the boundary of lithological change is delineated.

[0074] Preferably, in step 4, the spatial lithology of the igneous rock area is variable, and the identification of structural low-resistance anomalies and lithological low-resistance anomalies is strengthened to eliminate the false and retain the true.

[0075] Preferably, in step 5, water is found and wells are determined based on major water storage structures such as faults, dykes, and lithologic contact zones.

[0076] The method for finding water and determining wells in igneous rock hilly areas proposed by the present invention has the following beneficial effects:

[0077] The present invention adopts new technical means such as satellite image recognition and geomechanical analysis, and combines conventional technical methods such as hydrogeological survey, surface geophysical exploration, and hydrogeological drilling. For main water storage structures such as fault zones, dikes, and lithologic contact zones, a set of water exploration and well location determination technical methods that are easy to master and operate, namely "satellite image recognition - geological stress analysis - investigation and verification - fracture network detection - well location confirmation - drilling and well completion", has been created, forming a three-dimensional comprehensive water exploration technical system from space to the ground, from plates to sections, from regions to local areas, and from the ground to underground; and it has been specifically applied in actual work, achieving good water exploration results, improving work efficiency and quality, effectively solving the long-standing problems of people's production and living water use difficulties in water-scarce mountainous areas, cracking the technical problems of water exploration and well location determination in water-scarce areas of magmatic rocks, and having popularization and application value in similar areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 Schematic diagram of suitable well locations for straight sections of tensional and tensional-shear fractures of the present invention;

[0079] Figure 2 Schematic diagram of suitable well locations for compressional, compressional-shear fractures and torsional sections of tensional-shear fractures of the present invention;

[0080] Figure 3 Schematic diagram of suitable well locations for the intersection zone of primary and secondary fractures of the present invention;

[0081] Figure 4 Schematic diagram of suitable well locations for wide fault zones of the present invention;

[0082] Figure 5 Schematic diagram of suitable well locations for nearly vertical dikes of the present invention;

[0083] Figure 6 Schematic diagram of suitable well locations for inclined dikes of the present invention;

[0084] Figure 7 Schematic diagram of suitable well locations for thick and large dikes of the present invention;

[0085] Figure 8 Schematic diagram of suitable well locations for lithologic contact zones of the present invention;

[0086] Figure 9 Satellite image map of Dongluotou Village of the present invention;

[0087] Figure 10 Regional geological map of Dongluotou Village of the present invention;

[0088] Figure 11 Schematic diagram of the layout position of geophysical exploration lines in Dongluotou Village of the present invention;

[0089] Figure 12 Joint profile ρ of Line DLT-01 in Dongluotou Village of the present inventionS Cross-sectional view;

[0090] Figure 13 For the combined section ρ of the Dongluotou Village DLT-02 line of the present invention S Cross-sectional view;

[0091] Figure 14 For the combined section ρ of the Dongluotou Village DLT-03 line of the present invention S Cross-sectional view;

[0092] Figure 15 For the cross-sectional view of the ZD33 borehole in Dongluotou Village of the present invention;

[0093] Figure 16 For the satellite image map of Shangdagucun of the present invention;

[0094] Figure 17 For the regional geological map of Shangdagucun of the present invention;

[0095] Figure 18 For the outcrop map of the Luxi granite vein of the present invention;

[0096] Figure 19 For the cross-sectional view of the ZD05 borehole in Shangdagucun of the present invention;

[0097] Figure 20 For the satellite image map of Dongnanhe Village of the present invention;

[0098] Figure 21 For the regional geological map of Dongnanhe Village of the present invention;

[0099] Figure 22 For the combined section DNH-L3 line ρ of the present invention S Cross-sectional view;

[0100] Figure 23 For the high-density DNH-G3 line ρ of the present invention S Profile contour map;

[0101] Figure 24 For the cross-sectional view of the ZD68 borehole in Dongnanhe Village of the present invention. Detailed implementation manners

[0102] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0103] Embodiment; Please refer to Figure 1 - 24The present invention provides a technical solution: a method for finding water and determining wells in a magmatic hilly area, comprising the following steps:

[0104] Step 1: Satellite image recognition;

[0105] Step 2: Geomechanical analysis;

[0106] Step 3: Field investigation, tracking and on-site evaluation;

[0107] Step 4: Geophysical survey;

[0108] Step 5: Determine the well location.

[0109] As shown in the following table:

[0110] Table 1 Technical methods for finding water and determining wells in magmatic hilly areas

[0111]

[0112]

[0113]

[0114]

[0115] More specific:

[0116] Example 1: Dongluotou Village - Using compression-torsion fractured rock belt to find water and locate wells

[0117] 1. Satellite image recognition:

[0118] Dongluotou Village is located in the south of Tianhuang Town and borders Zhangzhuang Town in the south. Through satellite image analysis, the village east and west are distributed along the valleys in the north-northwest direction. Figure 9 As shown in the figure, the lines are distributed continuously and in a stable direction, with obvious color difference from the topographic images on both sides, which is speculated to be a sign of fault development.

[0119] 2. Geomechanical analysis:

[0120] Combined with geomechanical analysis, it is speculated that the northwest-trending fault has tension-torsion and compression-torsion properties. The regional geological map (such as Figure 10 The Shengou-Loess Fault Zone passes through the eastern valley in the south of the village. The fault dips to the southwest with an angle of 75° to 85° and has left-lateral compression-torsion and left-lateral tension-torsion properties. The direction of the fault is basically consistent with the inferred direction and properties.

[0121] 3. Field investigation, tracking and on-site identification:

[0122] By tracing along the east gully, fault outcrops were found along the river on the southeast of the village. Obvious zonation was visible. Phyllonite and cataclasite zones could be seen on both sides of the outcrop. The rock fragments in the phyllonite zone were angular and cemented by the matrix. The rock had no orientation and showed obvious characteristics of compressional-shear fracture. The cataclasite zone was mainly composed of monzonitic granitic and granodioritic rocks with well-developed rock fissures, which was the main aquifer of this fault zone. However, it was hidden under the surface along the fault strike and the distribution of this section could not be determined.

[0123] 4. Geophysical exploration:

[0124] To verify the fault strike of the hidden section and provide sufficient basis for well location determination, the layout and measurement of the combined profile method were carried out. A total of 3 combined profile survey lines were completed. The electrode distances AO = BO = 60 - 110 m, MN = 20 - 40 m, and the measuring point distance was 10 m. Limited by the site conditions, they were all arranged on the southeast of the village (as Figure 11 shown).

[0125] Obvious abnormal characteristics appeared in the ρ S curves of the 3 combined profiles. Among them, at point 84 of the DLT-L1 line (as Figure 12 shown), point 81 of the DLT-L2 line (as Figure 13 shown), and point 33 of the DLT-L3 line (as Figure 14 shown), low-resistance positive intersection anomalies occurred under the AO = BO = 60 device. After changing the AO = BO = 110 device, the positive intersection still existed, and the separation on both sides was obvious, and there was a synchronous jump of the ρ s curve. The positive intersections of the large devices of the DLT-01 line and the DLT-02 line shifted slightly towards the smaller number direction, and the DLT-03 line shifted slightly towards the larger number direction, indicating that there was a NW-trending fault passing through this area. The southern side inclined to the southwest, and the northern side showed a torsional inclination to the northeast with a steep dip angle, belonging to a tensional-shear fracture.

[0126] Combined with the village's utilization requirements and construction condition limitations, the well position should be arranged near the DLT-L3 line. Judging from the curve characteristics, the ρ S value was larger in the direction of the smaller number at the positive intersection, basically reflecting the resistance characteristics of the primary magmatic rock. The ρ S value dropped steeply and tended to be flat in the direction of the larger number, presumably being the fault influence zone with relatively developed fissures. A low-resistance anomaly feature appeared at the 44th measuring point, which was analyzed as the cataclasite zone. This area was at the edge of the gully and could accept the groundwater gathering from the east and south directions to the greatest extent, with relatively good recharge conditions. The well position should be arranged near this point.

[0127] 5. Construction verification of the selected well position:

[0128] Finally, a borehole was drilled at the proposed hole position. The well depth was 82 m, and the single-well water inflow reached 8.5 m 3 / h, the drawdown is 25.4 m, the static water level is 7.5 m, and the dynamic water level is 32.46 m. There is a filled granite vein at 18 - 21 m, with a water - eroded surface, which is an aquifer; at 42 - 63 m is granodiorite, in the form of powdery blocks with scales, and the water inflow increases during drilling, which is an aquifer and is within the fault - affected zone (as Figure 15 shown).

[0129] Example 2: Shangdagucun - Finding water and determining well locations using fine - grained granite veins

[0130] 1. Satellite image recognition:

[0131] Shangdagucun is located in the southeast of Tianhuang Town. The village is in a NE - trending long and narrow valley surrounded by hills on the west, north, and east. It can be seen from the satellite image that there are dark - colored bands distributed along the valley from east to west, with an obvious color difference from the surrounding landform images. The lines are basically continuous and the overall trend is relatively stable, showing the image characteristics of fault development; two NW - trending gray - green bands can be seen north of the village, with a short length, and intermittent spotted green vegetation is developed along the line. The northern band shows a dark - colored steep - slope band near the village in the west, showing the image characteristics of dike development (as Figure 16 shown).

[0132] 2. Geomechanics analysis:

[0133] There is a wide distribution of magmatic rocks in the village, mainly diorite in lithology. The regional major fault passes through the territory of Shangdagucun in the south of the village. There are multiple dikes developed north of the village, generally trending NW, but with poor extensibility (as Figure 17 shown). Judging from the regional tectonic mechanics, the NE - trending fault is compressional - shear. The zonal characteristics and the development of cataclastic rock zones of this direction of fault need to be judged in combination with the outcrop situation of the fault. While the NW - trending brittle dikes in the area are generally water - bearing dikes, it is necessary to trace the outcrop of the dikes to judge the lithology of the dikes and the spatial distribution of the dike bodies.

[0134] 3. Field investigation tracking and on - site discrimination:

[0135] After investigation, an outcrop of fine - grained monzonitic granite can be seen on the steep slope on the west side of the road north of the village, with a width of 4 m, a strike of 130°, and a dip angle of 85°. The rock is flesh - red, pure and hard, making a clear sound when struck, and is weakly weathered. Tracing along the strike, an outcrop of a granite vein is found on the east side of the road, with a width of 4 - 5 m, a strike of 130°, a dip direction of NE, and a dip angle of 85°. Columnar joints can be seen on the outcropping surface, and the fissures are relatively developed. It can still be seen extending into the southeast field, with a large scale, and it is speculated to be the same granite vein. The terrain here is higher in the north and lower in the south, and the groundwater flows from northeast to southwest along the terrain. The distribution direction of the dike is nearly perpendicular to the groundwater flow direction, and it is suitable to locate a well on the dike (as Figure 18 shown).

[0136] 4. Selected well - location construction verification:

[0137] Combined with the construction conditions, the well location is determined within the open space south of the village committee. The well depth is 96m, the single-well yield is 18m 3 / h, the drawdown is 16.70m, the static water level is 8.32m, and the dynamic water level is 25.02m. The well reveals a pink fine-grained granite dike at 26.5 - 56m. The rock fractures are developed, and there are rock fall blocks during construction, and the water volume increases significantly. The aquifer thickness is 29.5m (as Figure 19 shown).

[0138] Example 3: Dongnanhe Village - Finding water and determining well location using lithological contact zone

[0139] 1. Satellite image identification:

[0140] Dongnanhe Village is located in the northeast of Chengqian Town. It can be seen from the satellite image that the geology here is relatively flat, and the granite-like rocks are distributed in a large area. The surface image color in the area from the southwest of Xinanhe Village to the south of Dongnanhe Village is relatively bright, with an overall yellowish hue, and the landform shows a characteristic of alternating convex strip-shaped hills and valleys, showing the granite image characteristics. To the east of this area, the surface color is darker, showing dark yellow, the hills are in a continuous sheet, the slopes are relatively gentle, and there is no obvious consistency in the valleys or gullies, showing the diorite image characteristics (as Figure 20 shown).

[0141] 2. Geomechanical analysis:

[0142] At the contact part of granite and diorite, stress is concentrated. Granite is brittle and is affected by regional extrusion force, and the joints and fractures are developed. The contact zone between the granite body and the diorite body is the target horizon here.

[0143] 3. Field investigation tracking and on-site discrimination:

[0144] After field investigation, this area is in the alluvial area of the ancient Yishui River channel. The overall terrain is high in the northeast and southwest and low in the middle, with a relative height difference of about 100m. The Yishui River flows from the low-lying area from northwest to southeast. The surface is covered by the Quaternary system with a thickness of 10 - 15m, and it is impossible to track the lithological changes on site. According to the geological map, Yishan series biotite granodiorite is developed here (as Figure 21 shown), and geophysical exploration work needs to be combined for discrimination.

[0145] 4. Geophysical exploration:

[0146] To find the contact part of different lithologies, one survey line each of the combined profile method and the high-density method was completed. According to the apparent resistivity ρ S The profile plan view reflects (as Figure 22 shown), the positive intersection point under the large device is at the 55th measuring point, and the positive intersection point of the small device moves to the 50th point, which is speculated to be due to developed fractures. According to the high-density DNH-G3 line ρ S Profile contour map (as Figure 23As shown, there is a low-resistance U-shaped anomaly at a depth of 1-77 m between measuring points 60-65 of the high-density measuring points. The position of this anomaly corresponds to the anomaly at the positive intersection point of the 56th line of the combined profile DNH-L1. The anomalies of the two methods correspond quite well. However, the lithology of the construction exploration hole is powdery, which is analyzed to be caused by compressive fractures. The resistance values change significantly on both sides of measuring point 45. It is speculated that this is a lithological contact zone. To the south of the measuring line is granite, and to the north is diorite. The groundwater here runs from southeast to northwest. It is recommended to place the well south of measuring point 45 to expose the granite surface appropriately.

[0147] 5. Construction verification of the selected well location:

[0148] Finally, a borehole was constructed at the recommended hole location. The well depth is 114 m, the single-well water inflow is 16.5 m 3 / h, the drawdown is 39.29 m, the static water level is 2.30 m, and the dynamic water level is 41.59 m. The well enters the lithological contact zone at 27 m (as Figure 24 shown), and monzogranite is encountered at 27-33 m, 45-63 m, and 84-90 m. The thickness of the aquifer is 33 m. Multiple fractures can be seen in the cuttings. Scratches can be seen on the surface of some fragments in some sections, which are caused by fracture dislocation surfaces.

[0149] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for finding water and determining wells in magmatic rock hilly areas, characterized in that, The following steps are involved: Step 1: Satellite image recognition Based on the study of previous geological data and a full understanding of geological conditions, refer to the distribution directions of mountains, rivers, and valleys interpreted from satellite images and the color differences of micro-relief images, identify the locations and regional trends of faults, dykes, and contact zones with some rock masses, delineate the distribution range, determine the direction of groundwater runoff based on the terrain slope, river and gully trends, analyze groundwater recharge conditions, and delineate water-finding targets or exploration ranges that are conducive to groundwater recharge and storage; Step 2: Geomechanical Analysis Using geomechanics, we can preliminarily define the water-rich target area in three situations: S1. According to the principles of geomechanics, extensional tensile faults develop along the direction of the main compressive stress during the tectonic period, while the direction of compressional or pushover faults is basically perpendicular to the direction of the main compressive stress. Between the extensional and compressive faults, there are secondary tensile-torsional and compressive-torsional faults. The fractured zones and structurally affected fracture zones are the most favorable locations for groundwater storage. The NW- and NWW-oriented fault zones, the intersection zones of the main and secondary faults, and the outer convex ends of the fault turning points have relatively developed cracks in the rocks, providing a good environment for groundwater storage. S2. The cracks produced by stress in rocks are the places where groundwater is stored in igneous rock areas. The nature of the rock determines the degree of development of the cracks. Granite-like acidic rocks composed of light-colored minerals such as quartz and feldspar are rigid or brittle. Under the action of regional compression stress, they release stress by generating joints and cracks, and generate tensile cracks, forming a favorable space for groundwater storage. However, flexible or plastic rocks composed of dark-colored minerals such as hornblende, pyroxene and biotite release stress by internal compression or deformation. The cracks are extremely undeveloped, which is not conducive to the storage of groundwater. Quartz and granite brittle dykes trending NW and near SN are basically all water-bearing dykes. S3. The lithology changes in igneous rock areas have significant mutation characteristics, which creates favorable conditions for finding and utilizing the lithology contact zone of soft and brittle rock masses to find water and locate wells. When the rock mass is subjected to regional compression stress, the interface of lithology with different properties is the most concentrated part of stress distribution. On the side of the soft rock mass, the rock is compacted or plastically deformed, and sometimes the surface zone is metamorphosed; while in the brittle rock mass, joints and fissures are generated. The lower surface zone is less than 10m, the joints and fissures are relatively dense, and the tensile space is well developed. Going to the inside of the rock mass, the shear resistance is enhanced, the fissure development is gradually poor, and the closed shear joints are the main form. Therefore, the surface zone of the brittle rock mass is the target location for finding water and determining wells; Step 3: Field investigation and on-site evaluation Based on the identification of regional lithology distribution and fracture and dyke development characteristics in step 1, combined with the water-rich target area determined in step 2, conduct field geological surveys to identify the types of water-bearing and water-controlling targets and their distribution characteristics, analyze the geomorphic locations and recharge ranges that are conducive to groundwater storage, and plan specific well locations on site where conditions are relatively clear. If geophysical exploration is required for further clarification, define the scope of geophysical exploration and plan the survey line layout; Step 4: Geophysical Survey The principle of finding low resistance among high resistance and high resistance among low resistance is mainly followed in finding water and wells in magmatic rock areas by using geophysical prospecting methods. The joint profile method, electrical depth sounding method and high-density method are used, and the survey line is basically laid along the direction of the vertical detection target body; the low-resistance orthogonal points of the joint profile curve, the synchronous V-shaped and U-shaped low-resistance belts, and the step-shaped abnormal belts are the characteristics of the existence of fault structures; the high-resistance anomaly formed by the synchronous vein-like bulges of the two curves is a reflection of the existence of brittle rock veins; Electrical depth sounding and high-density sections reflect the distribution range of underground high- and low-resistance rock masses along the survey line. In the same resistance lithology distribution area, the low-resistance zone is a manifestation of fault development; the step-like resistance jump along the strike is a characteristic of lithology change; the abnormal characteristics of different geophysical exploration methods are compared and studied according to geological conditions, and the well location is selected by comprehensive analysis of the geomorphic environment and recharge conditions; Step 5: Well location determination S1. Using fractures to locate water and wells: Through investigation and geophysical exploration, we can find out the specific location, scale, occurrence and development of feather fractures, analyze and study the mechanical properties and lithological characteristics of different sections, and find the fracture development sites with recharge conditions; S2. Using rock veins to find water and locate wells: Use the rock vein to locate the well, find out the length, width, occurrence, lithology changes along the strike of the rock vein, the main geomorphic units it crosses, and the conversion relationship between surface water and groundwater in large valleys and river sections; find out the situation of rock veins cut by fractures or different directions, clarify the continuity and stability of the rock vein along the strike, the relationship between the overall strike and the direction of groundwater flow, and the depth of groundwater level in different sections, to provide a basis for selecting suitable well locations; S3. Using lithologic contact zones to locate water and wells: In igneous rock areas, spatial lithology is variable and has poor regularity. There is basically no transition phenomenon in the changes of different lithologies, and the lithologies on both sides of the interface have significant mutation characteristics. Lithology is the main controlling factor for groundwater occurrence in the area. Therefore, the lithology contact zone is used to find water and locate wells.

2. The method for finding water and determining wells in magmatic rock hilly areas according to claim 1, characterized in that: The satellite image recognition includes fault structure image features, dyke image features and lithologic contact zone image features.

3. A method for finding water and determining wells in magmatic rock hilly areas according to claim 1, characterized in that: The geomechanical analysis includes fracture structure condition analysis, dyke condition analysis and lithology contact zone condition analysis.

4. A method for finding water and determining wells in magmatic rock hilly areas according to claim 1, characterized in that: The field investigation tracking and on-site evaluation include fault structure investigation, dyke investigation and lithologic contact zone investigation.

5. A method for finding water and determining wells in magmatic rock hilly areas according to claim 1, characterized in that: In step 4, the spatial lithology of the igneous rock area is variable, so the identification of structural low-resistance anomalies and lithological low-resistance anomalies should be strengthened to eliminate the false and retain the true.

6. The method for finding water and determining wells in magmatic rock hilly areas according to claim 1, characterized in that: In step 5, water is located and wells are determined based on the main water storage structures such as faults, dykes, and lithologic contact zones.

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