Inclined hole drilling method for detailed investigation of steep dip hidden movable fracture

Abstract

The invention discloses an inclined hole drilling method for detailed investigation of steep dip hidden active fractures, which is characterized by comprising the following steps of: S1, collecting data such as remote sensing, geophysics, drilling and regional geology of a target region; s2, preliminarily speculating the distribution position of the fracture according to previous data, and analyzing the movement property of the fracture; s3, laying a geophysical survey line, and further limiting a fracture position; s4, according to the fracture positions speculated in S1, S2 and S3, inclined hole drilling is arranged on the two fractured discs; and S5, analyzing an inclined hole drilling result, and determining a specific position, an accurate occurrence and an accurate width of the fracture. The method not only can adapt to the complex surface environment and improve the exploration precision, but also can effectively improve the fracture exploration efficiency and reduce the construction cost.

Description

Technical Field

[0001] The invention relates to the technical field of engineering investigation, and in particular to an inclined hole drilling method for detailed investigation of steeply inclined concealed active faults. Background Art

[0002] In the plains and basins of China, most of the surface is covered by loose Quaternary sediments. Most active faults are hidden faults. The surface does not show obvious signs of deformation, and it is difficult to locate the faults by surface survey alone. Active faults are related to earthquakes and various geological disasters, and have a great impact on engineering construction. As a linear project, railways are difficult to avoid active faults. The "Railway Engineering Geological Survey Code" (TB 10012-2019) requires that the specific location, occurrence, width and broken zone of active faults should be identified when selecting railway lines, and the positional relationship between active faults and lines should be clarified.

[0003] At present, the means of detecting hidden active faults mainly include geophysical exploration, drilling combined with profile, trenching, etc. Various methods have achieved certain results, but there are still shortcomings. Geophysical exploration is easily disturbed by the external environment, and the results are multi-solution. Geophysical exploration methods can be used to infer the approximate location of hidden faults, but drilling is still needed for verification. Drilling is the most direct means of detecting faults. According to "Active Fault Detection" (GB / T 36072-2018), the drilling combined with profile method requires a large number of drilling holes (generally at least 6), but the drilling workload is large and the operation cycle is long. Under complex surface environmental conditions, a large amount of drilling work is difficult to carry out. In addition, if the fault is steep (>60°), it is difficult for traditional drilling methods to effectively capture the fault surface. Therefore, a method for the exploration of the occurrence and width of the broken zone of steeply inclined hidden active faults is proposed. Summary of the invention

[0004] The present invention provides an inclined hole drilling method for detailed investigation of steeply inclined concealed active faults, which can not only adapt to complex surface environments and improve investigation accuracy, but also effectively improve fault investigation efficiency and reduce construction costs.

[0005] The invention discloses an inclined hole drilling method for detailed investigation of steeply inclined concealed active faults, comprising the following steps:

[0006] S1. Collect remote sensing, geophysical, drilling and regional geological data of the target area;

[0007] S2. Preliminarily infer the distribution of faults based on previous data and analyze the nature of fault movement;

[0008] S3. Lay out geophysical survey lines to further define the fault location;

[0009] S4. According to the fracture positions inferred by S1, S2 and S3, inclined holes are drilled on both sides of the fracture;

[0010] S5. Analyze the results of inclined hole drilling to determine the specific location of the fracture and its exact occurrence and width.

[0011] Preferably, S4 comprises the following sub-steps:

[0012] S4.1 Based on the location and occurrence of the fault, infer the extension structure of the fault below the surface;

[0013] S4.2 Based on the subsurface structure of the fault inferred from S4.1, two inclined drill holes are arranged in the upper plate of the fault and one inclined hole is arranged in the lower plate of the fault. The inclination angles and depths of the three inclined holes are required to be different, and the depth must be able to penetrate the fault.

[0014] Preferably, S5 includes the following sub-steps:

[0015] Step 5.1 The basis for judging the fracture from the drilling core includes mirror surface, scratch, core extrusion and crushing, and unconformity contact of the formation;

[0016] The angle between the drilling direction of the borehole and the xoy plane in step 5.2 is α, where 0 < α, and the angle between the projection of the borehole on the xoy plane and the true north direction is β; the spatial relationship between the starting point A(xa, ya, za) of a borehole ZK1 and the intersection point A1(xa1, ya1, za1) of the borehole and the fracture surface is:

[0017] x a1 =x a +La·cosα1·cosβ1;

[0018] y a1 =y a +La·cosα1·sinβ1;

[0019] z a1 =z z -La·sinα1;

[0020] Similarly, the spatial relationship between the borehole ZK2 B(xb,yb,zb) and the intersection point B1(xb1,ya1,za1) between the borehole and the fracture surface is:

[0021] x b1 =x b +Lb·cosα2·cosβ2;

[0022] y b1 =y b +Lb·cosα2·sinβ2;

[0023] z b1=z b -Lb·sinα2;

[0024] Similarly, the spatial relationship between the borehole ZK3 C(xc,yc,zc) and the intersection point C1(xc1,yc1,zc1) between the borehole and the fracture surface is:

[0025] x c1 =x c +Lc·cosα3·cosβ3;

[0026] y c1 =y c +Lc·cosα3·sinβ3;

[0027] z c1 =z c -Lc·sinα3;

[0028] In step 5.3, the surface formula of the fracture surface π is calculated using three points intersecting the fracture surface:

[0029]

[0030] In step 5.4, the intersection angle between the fracture surface π and the surface z=0 is used as the inclination angle θ of the fracture surface:

[0031]

[0032] 0≤θ≤90°, if θ>90°, the inclination angle is 180°-θ;

[0033] In step 5.3, the spatial extension direction of the intersection line of the fracture surface π and the surface z=0 is used as the fracture direction.

[0034] The intersection equation ι of the fracture surface π and the plane z=0 is:

[0035]

[0036] The angle between the intersection line ι and the true north direction is:

[0037]

[0038] The direction of the crack is determined based on the value of φ.

[0039] The advantages and technical effects of the present invention are:

[0040] The inclined hole drilling method for detailed investigation of steeply inclined hidden active faults of the present invention has a large lateral detection range and can easily detect the location of the fault, thus solving the problem that the traditional vertical drilling has a small detection range and is not applicable to the detection of steeply inclined faults.

[0041] The present invention adopts three inclined holes to determine the fracture surface, which can save at least half of the workload compared with the traditional folding method and can adapt to complex working environments.

[0042] The present invention realizes three-dimensional investigation of active faults, makes it easy to clearly judge the spatial position relationship between the faults and underground structures, and provides a basis for underground structure design. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a flow chart of the inclined hole drilling survey of the present invention;

[0044] Figure 2 It is a schematic diagram of the inclined hole drilling layout method of the present invention;

[0045] Figure 3 A spatial relationship diagram of a single inclined hole drilling of the present invention;

[0046] Figure 4 This is a fracture core map. DETAILED DESCRIPTION

[0047] The embodiments of the invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the invention, and cannot be understood as limiting the invention.

[0048] The present invention is a method for drilling inclined holes for accurately locating steeply inclined concealed active faults. Figure 1 As shown, the following steps are included:

[0049] S1 collects remote sensing, geophysical, drilling and regional geological data of the target area.

[0050] The target area is the edge of a city in South China, which is highly developed and has a lot of available data. We collected remote sensing, geophysical, drilling and regional geological data, especially structural data, from the area.

[0051] S2 preliminarily infers the location of the fault based on previous data and analyzes the nature of the fault;

[0052] Through the analysis of previous data, the target fault section is nearly east-west or slightly deflected to SEE or NWW, inclined to N, with a dip angle of 50-85°. It is a broken zone composed of multiple groups of compression fracture surfaces or small fault clusters with a width of several meters. The movement nature is normal fault and left-hand component. The regional distribution strata are Quaternary loose accumulation layers, Tertiary sandstone and muddy siltstone. Remote sensing images show that lakes and ponds along the fault are distributed in long strips. Based on the above information, the development location of the fault is inferred.

[0053] S3 arranged geophysical survey work to further define the fault location;

[0054] In order to further narrow the detection range of hidden faults, geophysical exploration profiles were laid out based on the previous analysis. The surface environment of the target area is complex, and external factors have a great interference with geophysical exploration. After a detailed investigation of the site and the surrounding area, a seismic reflection profile was laid out in an area with less interference and easy operation. Combined with the results of geophysical exploration, the location of the fault was further limited.

[0055] S4 arranges inclined holes for drilling on both sides of the fault according to the fracture positions inferred in steps 1, 2 and 3;

[0056] S4.1 Based on the location and occurrence of the fault, infer the extension structure of the fault below the surface;

[0057] S4.2 Based on the structure of the fault below the surface inferred by S4.1, the target fault is EW-oriented and dips N. Two drill holes are arranged on the upper wall (north side) of the fault and one inclined hole is arranged on the lower wall (south side) of the fault. The inclination angles and depths of the three inclined holes are required to be different, and the depths must be able to penetrate the fault.

[0058] The structure below the fault surface and the location of the inclined drilling are as follows Figure 2 shown.

[0059] S5 analyzes the results of inclined hole drilling to determine the specific location and occurrence of the fault.

[0060] S5.1 The basis for judging fractures from drilling cores includes mirror surface, scratches, core extrusion and crushing, and unconformity of formations ( Figure 3 ).

[0061] In S5.2, the angle between the drilling direction of the borehole and the xoy plane is α (0<α). The angle between the projection of the borehole on the xoy plane and the true north direction is β ( Figure 4 ). The spatial relationship between the starting point A(xa,ya,za) of a borehole ZK1 and the intersection point A1(xa1,ya1,za1) of the borehole and the fracture surface is:

[0062] x a1 =x a +La·cosα1·cosβ1;

[0063] y a1 =y a +La·cosα1·sinβ1;

[0064] z a1 =z z -La·sinα1;

[0065] Similarly, the spatial relationship between the borehole ZK2 B(xb,yb,zb) and the intersection point B1(xb1,ya1,za1) between the borehole and the fracture surface is:

[0066] x b1 =x b +Lb·cosα2·cosβ2;

[0067] y b1 =x b +Lb·cosα2·sinβ2;

[0068] z b1 =z b -Lb·sinα2;

[0069] Similarly, the spatial relationship between the borehole ZK3 C(xc,yc,zc) and the intersection point C1(xc1,yc1,zc1) between the borehole and the fracture surface is:

[0070] x c1 =x c +Lc·cosα3·cosβ3;

[0071] y c1 =y c +Lc·cosα3·sinβ3;

[0072] z c1 =z c -Lc·sinα3;

[0073] In S5.3, using three points intersecting the fracture surface, the surface formula of the fracture surface π is calculated as:

[0074]

[0075] In S5.3, the intersection angle between the fracture surface π and the surface z=0 is used as the inclination angle θ of the fracture surface;

[0076]

[0077] 0≤θ≤90°, if θ>90°, the inclination angle is 180°-θ;

[0078] In step 5.4, the spatial extension direction of the intersection line of the fracture surface π and the surface z=0 is used as the fracture direction.

[0079] The intersection equation l of the fracture surface π and the plane z=0 is:

[0080]

[0081] The angle between the intersection line l and the true north direction is:

[0082]

[0083] Calculate θ=68°, and the strike of the target fault is E82°S, with a dip angle of 68°.

[0084] The above are only embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. An inclined hole drilling method for detailed investigation of steeply inclined concealed active faults, characterized in that: The following steps are involved: S1. Collect remote sensing, geophysical, drilling and regional geological data of the target area; S2. Preliminarily infer the distribution of faults based on previous data and analyze the nature of fault movement; S3. Lay out geophysical survey lines to further define the fault location; S4. According to the fracture positions inferred by S1, S2 and S3, inclined holes are drilled on both sides of the fracture; S5. Analyze the results of inclined hole drilling to determine the specific location of the fracture and its exact occurrence and width.

2. The method for drilling inclined holes for detailed investigation of steeply inclined concealed active faults according to claim 1 is characterized by: The S4 comprises the following sub-steps: S4.1 Based on the location and occurrence of the fault, infer the extension structure of the fault below the surface; S4.2 Based on the subsurface structure of the fault inferred from S4.1, two inclined drill holes are arranged in the upper plate of the fault and one inclined hole is arranged in the lower plate of the fault. The inclination angles and depths of the three inclined holes are required to be different, and the depth must be able to penetrate the fault.

3. The inclined hole drilling method for detailed investigation of steeply inclined concealed active faults according to claim 1 is characterized by: The S5 comprises the following sub-steps: Step 5.1 The basis for judging the fracture from the drilling core includes mirror surface, scratch, core extrusion and crushing, and unconformity contact of the formation; The angle between the drilling direction of the borehole and the xoy plane in step 5.2 is α, where 0 < α, and the angle between the projection of the borehole on the xoy plane and the true north direction is β; the spatial relationship between the starting point A(xa, ya, za) of a borehole ZK1 and the intersection point A1(xa1, ya1, za1) of the borehole and the fracture surface is: x a1 =x a +La·cosα1·cosβ1; and a1 =and a +The thingα1·sinβ1; with a1 =with z -La·sinα1; Similarly, the spatial relationship between the borehole ZK2 B(xb,yb,zb) and the intersection point B1(xb1,ya1,za1) between the borehole and the fracture surface is: x b1 =x b +Lb·cosα2·cosβ2; <h2 style=";text-align:left;direction:ltr">y<h2 style=";text-align:left;direction:ltr"> b1 <h2 style=";text-align:left;direction:ltr"> =y<h2 style=";text-align:left;direction:ltr"> b <h2 style=";text-align:left;direction:ltr"> +Lb·cosα2·sinβ2; With b1 =from b -Lb sinα2; Similarly, the spatial relationship between the borehole ZK3 C(xc,yc,zc) and the intersection point C1(xc1,yc1,zc1) between the borehole and the fracture surface is: x c1 =x c +Lc·cosα3·cosβ3; y c1 =y c +Lc·cosα3·sinβ3; z c1 =z c -Lc·sinα3; In step 5.3, the surface formula of the fracture surface π is calculated using three points intersecting the fracture surface: In step 5.4, the intersection angle between the fracture surface π and the surface z=0 is used as the inclination angle θ of the fracture surface: 0≤θ≤90°, if θ>90°, the inclination angle is 180°-θ; In step 5.3, the spatial extension direction of the intersection line of the fracture surface π and the plane z=0 is used as the fracture direction. The intersection line equation l of the fracture surface π and the plane z=0 is: The angle between the intersection line l and the true north direction is: according to The value is used to determine the direction of the crack.

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