A method for designing well depths for seismic exploration wells in colluvial zones

Abstract

This invention relates to well depth design for seismic exploration wells in colluvial zones, and particularly to a method for well depth design for seismic exploration wells in colluvial zones. The method includes the following steps: Step 1, determining the wellhead coordinates P0 and bottom coordinates F of the microlog, the outcrop coordinates A and B of the bedrock layer at the bottom of the colluvial zone on both sides of the lateral direction of the colluvial zone, and the planned drilling point P of the seismic exploration well; the bottom coordinates F of the microlog are the horizontal projection of P0 onto the top interface of the bedrock layer; Step 2, establishing a geometric model including the inclined rock strata determined by the inclined lines FA, FB, and AB; Step 3, determining the well depth h = PP' of the seismic exploration well in the colluvial zone, using the projection point P' of the planned drilling point P onto the inclined rock strata. This invention solves the problem of significant uncertainty in the well depth design accuracy of seismic exploration wells in colluvial zones in the prior art.

Description

Technical Field

[0001] This invention relates to well depth design for seismic exploration wells in colluvial zones, and particularly to a method for well depth design for seismic exploration wells in colluvial zones. Background Technology

[0002] Colluvial deposits are geological formations formed by the deposition of weathered rock fragments under the influence of rainwater, snowmelt, and gravity. The upper part of a colluvial zone consists of clastic rock, which is relatively loose, highly porous, and compressible, with a stratification velocity typically between 800 and 1000 m / s. The lower part of the colluvial zone is bedrock, which is hard and has a stratification velocity typically between 3000 and 4000 m / s. The bedrock velocity depends primarily on the lithology. For example... Figure 1 The stratigraphic structure shown indicates that the colluvial zone lies above the limestone at the bottom of the slope, formed by the accumulation of debris from the weathered mudstone and sandstone above. Colluvial zones are generally located on gentle slopes or at the foot of slopes, and are typically small in size. They are characterized by being thicker in the middle and thinner at the edges, with significant variations in elevation and thickness along the slope direction, but slow variations in elevation and thickness in the transverse direction perpendicular to the slope.

[0003] In the exploration of seismic waves induced by well-blasting explosive sources, the depth of the seismic exploration well (i.e., the well-blasting induced seismic well) is a very critical parameter. A well depth below the high-velocity layer yields better seismic data quality. For example... Figure 1 In the stratigraphic structure shown, the preferred well depth is one that can reach the limestone layer. However, due to the varying thickness of the colluvial zone, the required depth of seismic exploration wells varies at different locations. If the well is too shallow, it is difficult to guarantee the quality of seismic data, while if it is too deep, it will increase the cost of seismic exploration.

[0004] Traditional well depth design first uses surface survey methods such as micrologging and small refraction to determine the depth of the interface between low-velocity and high-velocity layers. Then, spatial three-dimensional interpolation is used to obtain the interface of the high-velocity layer. Finally, the depth from the surface location of the wellhead to the interface of the underground high-velocity layer is calculated to obtain the design depth. In the above method, the number of micrologging wells corresponds to the number of spatial three-dimensional interpolation points. However, the number and location of micrologging wells are affected by factors such as cost and construction conditions, and cannot be set too many times. Furthermore, there will be sparse areas. The results obtained by this well depth design method are affected by the density of spatial three-dimensional interpolation points (micrologging wells) and the lateral variation of the surface lithology of the work area, thus restricting the accuracy of well depth design. When there are sparse areas of spatial three-dimensional interpolation points and lateral variations in the surface lithology of the work area, the accuracy of well depth design is low.

[0005] Chinese invention patent CN106569282B discloses a method for designing the excitation well depth in seismic acquisition. This method obtains a shallow surface velocity model through seismic data inversion under micrologging and low refraction constraints, and then determines the excitation well depth by combining this model with experimental data to obtain the optimal excitation velocity range. This method incorporates previously available seismic velocity information, overcomes the inaccuracies of three-dimensional interpolation in previous well depth designs, and increases the accuracy of well depth design. However, for work areas lacking prior seismic data, or areas with significant lateral variations in surface lithology, especially in colluvial zones, the accuracy of well depth design for seismic exploration wells remains highly uncertain. Summary of the Invention

[0006] The purpose of this invention is to provide a well depth design method for seismic exploration wells in colluvial zones, which solves the problem of significant uncertainty in the well depth design accuracy of seismic exploration wells in colluvial zones in the prior art.

[0007] The well depth design method for seismic exploration wells in colluvial zones in this invention adopts the following technical solution:

[0008] A method for designing well depths for seismic exploration wells in colluvial zones includes the following steps:

[0009] Step 1: Determine the wellhead coordinates P0(E0, N0, Z0), bottom coordinates F(E0, N0, Zh0), and the outcrop coordinates A(E0, N0, Zh0) of the bedrock layer at the bottom of the colluvial zone on both sides of the lateral side of the colluvial zone. A N A Z A ), B(E) B N B Z B The planned drilling locations of the seismic exploration wells are P(E, N, Z); the bottom coordinates F of the micro-logging wells are the horizontal projection of P0 onto the top interface of the bedrock layer.

[0010] Step 2: Establish a geometric model, which includes the inclined rock strata defined by the dip lines FA and FB and AB.

[0011] Step 3: Using the projection point of the planned drilling point P(E, N, Z) of the seismic exploration well onto the inclined rock layer as P'(E, N, Zh), determine the well depth h = PP' of the seismic exploration well in the colluvial zone.

[0012] The beneficial effects of the above technical solution are that, by introducing the exposure location information of the bedrock layer on both sides of the colluvial zone, the inclined rock strata determined by the geometric model established based on the exposure location information and the bottom coordinates of the micro-logging in the micro-logging interpretation results can more realistically reflect the rock strata conditions of the bedrock layer. Furthermore, the well depth h = PP' of the seismic exploration well in the colluvial zone can be determined based on the projection point P' of the planned drilling point P(E, N, Z) on the inclined rock strata. Compared with existing well depth design methods, for work areas without prior seismic data or areas with large lateral variations in surface lithology, the well depth design accuracy can be improved by relying on the exposure location information of the bedrock layer on both sides of the colluvial zone, solving the problem of significant uncertainty in the well depth design accuracy of seismic exploration wells in colluvial zones in existing technologies.

[0013] As a further defined technical solution: the plane formed by the X and Y axes in the coordinate system is parallel to AB, and the inclined line FA determined by point F is perpendicular to AB.

[0014] The beneficial effect of the above-mentioned further defined technical solution is that it facilitates the establishment of the model and its matching with the corresponding coordinate system, thereby facilitating data processing.

[0015] As a further defined technical solution: the geometric model in step two includes an inclined line BE that is parallel to the inclined line FA and of the same length as the inclined line FA, and the inclined rock layer is formed by ABEF; step three includes the step of determining the normal vector N(U, V, W) of the inclined rock layer ABEF according to the geometric model; it also includes the step of calculating Zh according to the normal vector equation U(E-E0)+V(N-N0)+W(Zh-Zh0)=0 passing through point F(E0, N0, Zh0), and then determining the well depth h=PP'=Z-Zh of the seismic exploration well in the colluvial zone.

[0016] The beneficial effect of the above-mentioned further defined technical solution is that Zh can be conveniently calculated through the equations of the normal vector N(U, V, W) and the normal vector passing through the point F(E0, N0, Zh0), reducing or avoiding dependence on computers.

[0017] As a further defined technical solution: the normal vector N(U, V, W) of the inclined rock layer is calculated based on the true dip angle α of the inclined rock layer, the angle ω between the dip direction FD of the inclined rock layer ABEF and the X-axis: U=sin(α)cos(ω), V=sin(α)sin(ω), W=cos(α).

[0018] The beneficial effects of the above-mentioned further defined technical solution are that the true tilt angle α and the included angle ω are easy to obtain, and the positive and negative values ​​are easy to determine according to the quadrant corresponding to FD, and the normal vector N(U, V, W) is easy to calculate.

[0019] As a further defined technical solution: the true tilt angle α is calculated from the apparent tilt angle β corresponding to the observation direction line FB, and the angle θ between the horizontal projection CD of AB and the horizontal projection of the observation direction line FB according to tan(α)=tan(β) / sin(θ).

[0020] The beneficial effect of the above-mentioned further defined technical solution is that the true tilt angle α can be calculated more easily.

[0021] As a further refined technical solution, the included angle θ is calculated using trigonometric functions based on a geometric model.

[0022] As a further defined technical solution: the included angle θ is calculated from the included angle ω and the azimuth angle η of the observation direction line corresponding to the projection FC of the inclined line FB on the horizontal plane passing through point F, according to sin(θ)=cos(ω-η).

[0023] The beneficial effect of the above-mentioned further defined technical solution is that the included angle θ can be calculated more easily.

[0024] As a further defined technical solution: the included angle ω is the azimuth angle of the inclined line FA corresponding to the dip direction FD. according to Calculated.

[0025] The beneficial effect of the aforementioned further defined technical solution is that the azimuth angle It can be obtained directly, making it easy to obtain the included angle ω.

[0026] As a further limiting technical solution: increase the length of the explosive column based on PP' to obtain the final seismic exploration well depth in field seismic exploration.

[0027] The beneficial effect of the aforementioned further defined technical solution is that it can directly obtain the actual depth of the seismic exploration well, which facilitates field operations.

[0028] As a further refined technical solution, the directions of the X and Y axes of the three-dimensional Cartesian coordinate system corresponding to each coordinate point are consistent with the corresponding actual geographical directions of the Earth.

[0029] The beneficial effect of the above-mentioned further defined technical solution is that no additional coordinate transformation is required, which facilitates the establishment of the geometric model. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the well location and characteristic points of the colluvial zone corresponding to Embodiment 1 of the well depth design method for seismic exploration wells in colluvial zones in this invention, and it is also a schematic diagram of a stratigraphic structure in the prior art.

[0031] Figure 2This is a schematic diagram depicting the attitude of the rock outcrops corresponding to the colluvial zone;

[0032] Figure 3 This is a schematic diagram of the geometric model corresponding to Embodiment 1 of the well depth design method for seismic exploration wells in colluvial zones in this invention;

[0033] Figure 4 This is a flowchart of Embodiment 1 of a well depth design method for seismic exploration wells in colluvial zones according to the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, not all embodiments. The components of the embodiments of the invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0035] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0036] It should be noted that, in specific embodiments of the present invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any actual relationship or order between these entities or operations. Furthermore, terms such as "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, the use of phrases such as "comprising a…" to define an element does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0037] In the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linkage" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0038] In the description of this invention, unless otherwise explicitly specified and limited, the term "provided with" should be interpreted broadly. For example, the object "provided with" can be a part of the body, or it can be separately arranged from the body and connected to the body. This connection can be a detachable connection or a non-detachable connection. Those skilled in the art can understand the specific meaning of the above terms in this invention through specific circumstances.

[0039] The present invention will be further described in detail below with reference to embodiments.

[0040] Example 1 of a well depth design method for seismic exploration wells in colluvial zones according to the present invention:

[0041] The colluvial belt corresponding to the well depth design method for seismic exploration wells in colluvial belts is as follows: Figure 1 As shown, the colluvial zone lies above the limestone below the slope, formed by the accumulation of debris from the weathering of purple mudstone and sandstone. The outcrop occurrence data of the limestone strata include outcrop locations A and B, with AB forming the strike line of the surface outcrops. As is common knowledge: a strike line is formed by the intersection of the bedding plane of a stratum and any imaginary horizontal plane. The strike, or the direction in which the two ends of the strike line extend, indicates the horizontal extension direction of the stratum in space. A stratum has two strike directions, differing by 180°. The straight line drawn perpendicular to the strike line and downwards along the slope on the bedding plane is called the dip line, which represents the maximum slope of the stratum. The direction indicated by the projection of the dip line onto the horizontal plane is called the dip direction of the stratum, also known as the true dip. There is only one true dip, indicating the direction in which the stratum dips. Any other straight line drawn obliquely to the strike line and downwards along the slope is called the apparent dip line; the direction indicated by its projection onto the horizontal plane is called the apparent dip. Both the dip and the apparent dip have a direction; that is, they only have one direction. The angle between a dip line on a rock stratum and its projection onto a horizontal plane is called the dip angle, also known as the true dip angle; the magnitude of the dip angle indicates the degree of inclination of the rock stratum. The angle between the apparent dip line and its projection onto a horizontal plane is called the apparent dip angle. Many dip lines can be drawn from any point on a plane, resulting in many apparent dip angles. The true dip angle is the angle between the dip surface and a horizontal reference plane measured on a cross-section perpendicular to the strike of the dip surface; all apparent dip angles are smaller than the true dip angle at that point, meaning the true dip angle is always greater than the apparent dip angle. Figure 1The strike, dip, and dip angle of the limestone strata are the three key elements of the strata's attitude, all of which can be measured using a geological compass. Figure 2 As shown. Additionally... Figure 1 In this context, P0 represents the wellhead coordinates of the micro-logging well, and P represents the planned drilling point of the seismic exploration well. The specific locations of P0 and P are determined using existing technology and can be determined based on factors such as grid division and formation conditions.

[0042] To determine the depth of seismic exploration wells, this invention provides a method for designing the depth of seismic exploration wells in colluvial zones, such as... Figure 4 As shown, the specific steps include:

[0043] 1. Read the micro-logging interpretation data, the coordinates of the rock strata outcrop location, and the rock strata occurrence data.

[0044] To facilitate model representation and calculation, a three-dimensional Cartesian coordinate system is first established. The plane formed by the X and Y axes of the three-dimensional Cartesian coordinate system is a horizontal plane. The X axis corresponds to the due east direction in the actual geographical direction of the earth, the Y axis corresponds to the due north direction in the actual geographical direction of the earth, and the Z axis is vertically upward and parallel to the depth direction of the micro-logging.

[0045] The micrologging interpretation data includes the coordinates of the wellhead location P0(E0, N0, Z0) = P0(500000, 3900000, 100), where E0 is the east coordinate, N0 is the north coordinate, and Z0 is the geodetic coordinate with an elevation of 100m. The thickness of the colluvial zone at P0 is h0 = 25 meters, meaning the bottom of the microlog is 25 meters below the surface at P0. The bottom of the microlog reaches the limestone strata, specifically the seismically high-velocity strata corresponding to rock outcrops A and B. The coordinates of the bedrock outcrops at the bottom of the colluvial zone on both sides of the lateral side of the colluvial zone are A(E0, N0, Z0) and B(E0, N0, Z0). A N A Z A ), B(E) B N B Z B The strata attitude data includes the strike line AB of the surface outcrop strata determined by the coordinates of points A and B. In order for AB to form the strike line of the surface outcrop strata, if the line connecting the coordinates of A and B is not parallel to the horizontal plane, elevation compensation can be performed on the coordinates of points A and / or B to obtain a strike line AB parallel to the horizontal plane.

[0046] In addition, the bottom coordinates of the micrologging well are determined in a three-dimensional Cartesian coordinate system: F(E0, N0, Zh0) = F(500000, 3900000, 75), where F is the horizontal projection of P0 onto the top interface of the bedrock layer. The coordinates of the planned drilling point near the wellhead of the micrologging well are determined: P(E, N, Z), which are the shot point coordinates of the seismic exploration observation system. The projection point P'(E, N, Zh) of the planned drilling point P(E, N, Z) of the seismic exploration well onto the top interface of the bedrock layer is determined, which is the bottom coordinate of the seismic exploration well. In this embodiment, the starting scale of the Z-axis is 75, corresponding to point F. Similarly, the starting scales of the X-axis and Y-axis also correspond to point F.

[0047] 2. Establish a geometric model

[0048] like Figure 3 As shown, the geometric model includes: a dip line FA perpendicular to the strike line AB of the surface outcrop strata; a dip line BE parallel to and of equal length to the dip line FA; a dipped stratum ABEF defined by E, F, and the strike line AB of the surface outcrop strata; the projection plane DCEF of the dipped stratum ABEF vertically onto the horizontal plane passing through F; and vertical lines AD and BC. A, B, C, and D form the vertical plane ABCD passing through the strike line AB of the surface outcrop strata. Additionally, FB forms an observation direction line, and planes BEC and FAD form planes passing through the dip line E, respectively. B The vertical plane, the vertical plane passing through the inclined line FA.

[0049] During field data collection, Figure 2 The rock strata shown are made of Figure 3 The inclined rock strata are represented by ABEF. Figure 2 In the line segment and angle attributes shown, lines AB and EF are... Figure 2 The strike lines of the rock strata shown are FA and E. B The lines are slanted, and rays DF and CE are slanted lines FA and E, respectively. B Projected onto the horizontal plane, DF and CE represent the dip of the rock strata.

[0050] exist Figure 3 In the middle, point M is the intersection of the inclined plane CE and the X-axis. In the horizontal plane MFK, planes BEC and FAD are sections perpendicular to the direction line AB, and plane BFC is any section oblique to the direction line. △E B C and △FBC are right triangles sharing a common side BC.

[0051] The azimuth angle is the angle of clockwise deviation from true north, inputting the azimuth angle of the bedrock dip line FA. that is, 30° north of east, the difference between the azimuth angle of the inclined line FA and the azimuth angle of the rock strike line AB is 90 degrees. Input the wellhead coordinates of the micro-logging P0(E0, N0, Z0) and the bottom point F(E0, N0, Zh0) of the micro-logging well, where F(E0, N0, Zh0) is the projection of point P0 on the top interface of the rock stratum. Input the coordinates of the rock outcrop position B(E B , N B , Z B )=B(500100, 3900075, 90).

[0052] 3. Calculate the azimuth angle η and the apparent dip angle β corresponding to the observation direction line FB

[0053] as shown in Figure 3 : the observation direction line FB is the connecting line between the bedrock point F under the micro-logging well and the rock outcrop position B, η, the included angle between the horizontal projection FC of the observation direction line FB and the X axis (due east direction) = ∠MFC, the apparent dip angle corresponding to the observation direction line FB is β, the included angle between the observation direction line FB and the horizontal projection FC of the observation direction line = ∠BFC.

[0054] 3.1 Calculate the azimuth angle η corresponding to the observation direction line FB

[0055] Alfa=(E B -E0) / sqrt[(E B -E0)*(E B -E0)+(N B -N0)*(N B -N0)]

[0056] =(500100-500000) / sqrt[(500100-500000)*(500100-500000)+(3900075-3900000)*(3900075-3900000)]

[0057] =100 / 125=0.8

[0058] where Alfa is the trigonometric function value, if the horizontal projection FC of the observation direction line FB is in the first quadrant or the second quadrant, then N B -N0≥0, η=arccosAlfa; if FC is in the third quadrant or the fourth quadrant, then η=180+arccosAlfa.

[0059] In this example, 1000075-<1000000>0, then η=arccos(0.8)=36.87°.

[0060] 3.2 Calculate the apparent dip angle β corresponding to the observation direction line FB

[0061] as shown in Figure 3As shown, the apparent tilt angle β corresponding to the observation direction line FB is ∠BFC.

[0062] BC = Z B -Zh0 = 90 - 75 = 15,

[0063] FC = sqrt[(E B -E0)*(E B -E0)+(N B -N0)*(N B -N0)]

[0064] =sqrt(100*100+75*75)

[0065] =125

[0066] tan(β) = BC / FC = 15 / 125 = 0.12, and the apparent tilt angle β is obtained by taking the arctangent.

[0067] 4. Calculate the angle θ between the strike line AB of the surface outcrop strata and the horizontal projection FC of the observation direction line FB.

[0068] like Figure 3 As shown:

[0069] The angle between the strike line AB of the rock strata and the horizontal projection FC of the observation direction line FB is θ = ∠DCF.

[0070] Sin(θ)=cos(ω-η)=cos(60-36.87)=0.92.

[0071] In the formula ω is the angle between the horizontal projection FD of the rock stratum dip line FA and the due east direction, and η is the azimuth angle corresponding to the observation direction line FB. It represents the azimuth of the dip line of the bedrock strata.

[0072] 5. Calculate the true dip angle α of the rock strata.

[0073] like Figure 3 As shown: The true dip angle of the rock strata is α=∠BEC, which can be obtained from tan(β)=sin(θ)*tan(α).

[0074] tan(α)=tan(β) / sin(θ)=0.12 / 0.92=0.13, taking the arctangent, we get α=7.43 degrees.

[0075] 6. Calculate the design well depth in the colluvial zone using the normal vector equation of the inclined rock strata.

[0076] 6.1 Calculate the normal vector N(A, B, C) of the inclined rock strata.

[0077] A=sin(α)cos(ω)=sin(7.43)cos(60)=0.064;

[0078] B=sin(α)sin(ω)=sin(7.43)sin(60)=0.111;

[0079] C=cos(α)=cos(7.43)=0.991;

[0080] In the formula, A, B, and C are the normal vector parameters.

[0081] Because ω and In other embodiments, complementarity can also be achieved through... Calculate the normal vector N(A, B, C) of the inclined rock strata.

[0082] 6.2 Calculation of the design well depth h in the colluvial zone using the normal vector equation of the inclined rock strata

[0083] The equation of the normal vector passing through the point F(E0, N0, Zh0) = F(500000, 3900000, 75) is:

[0084] A(E-E0)+B(N-N0)+C(Zh-Zh0)=0,

[0085] That is, 0.064(E-500000)+0.111(N-3900000)+0.991(Zh-75)=0;

[0086] Input the planned well shot location coordinates P(E, N, Z) = P(500075, 3900050, 95) to obtain the Zh value:

[0087] 0.064(500075-500000)+0.111(3900050-3900000)+0.991(Zh-75)=0

[0088] Zh = 64.55;

[0089] That is, P'(500075, 3900050, 64.55), where P' is the projection of P onto the inclined rock stratum.

[0090] The planned well depth at the well shot location P is h = PP' = Z - Zh = 10.45 meters.

[0091] The shallowest well depth in the colluvial zone was calculated in the above embodiments. The length of the explosive column was then increased during field seismic exploration to obtain the final field drilling depth.

[0092] Example 2 of a well depth design method for seismic exploration wells in colluvial zones in this invention:

[0093] The difference between this embodiment and Embodiment 1 is that in Embodiment 1, the Zh in the projection point P'(E, N, Zh) of the planned drilling point P(E, N, Zh) of the seismic exploration well onto the bedrock layer is calculated based on the normal vector N(U, V, W) of the inclined bedrock layer ABEF. In this embodiment, however, the Zh of P'(E, N, Zh) is directly obtained by the computer based on the geometric model in the coordinate system.

[0094] Example 3 of a well depth design method for seismic exploration wells in colluvial zones in this invention:

[0095] The difference between this embodiment and Embodiment 1 is that in Embodiment 1, the true dip angle α and the included angle ω of the bedrock layer, the angle θ between the horizontal projection CD of the strike line AB of the surface outcrop rock layer and the horizontal projection FB of the observation direction line, and the azimuth angle η of the observation direction line corresponding to the projection FC of the inclined line FB on the horizontal plane passing through point F are all calculated based on trigonometric functions. In this embodiment, however, the above angles can also be directly measured by the computer based on the geometric model in the coordinate system.

[0096] In the above embodiments, the X-axis of the three-dimensional Cartesian coordinate system corresponds to due east, the actual geographical direction of the Earth, and the Y-axis corresponds to due north, the actual geographical direction of the Earth. In other embodiments, the X-axis and Y-axis of the three-dimensional Cartesian coordinate system can also correspond to other directions, for example, the X-axis can be parallel to the direction of the directional line AB, and the actual geographical coordinates corresponding to the Earth can be obtained through coordinate transformation.

[0097] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. The scope of patent protection of the present invention shall be determined by the claims. Similarly, any equivalent structural changes made based on the description and drawings of the present invention shall also be included within the scope of protection of the present invention.

Claims

1. A method for designing the depth of seismic exploration wells in colluvial zones, characterized in that, Includes the following steps: Step 1: Determine the wellhead coordinates P0 (E0, N0, Z0) and bottom coordinates F (E0, N0, Zh0) of the micro-logging well, and the outcrop coordinates A (E0, N0, Zh0) of the bedrock layer at the bottom of the colluvial zone on both sides of the lateral side of the colluvial zone. A N A Z A ), B (E) B N B Z B ), and the planned drilling point P(E, N, Z) of the seismic exploration well; the bottom coordinate F of the micro-logging well is the horizontal projection of P0 on the top interface of the bedrock layer, the plane formed by the X and Y axes in the coordinate system is parallel to AB, and the inclined line FA determined by point F is perpendicular to AB. Step 2: Establish a geometric model. The geometric model includes the inclined rock strata defined by the inclined lines FA, FB, and AB. The geometric model also includes the inclined line BE, which is parallel to the inclined line FA and of the same length as the inclined line FA. The inclined rock strata are formed by ABEF. Step 3: Using the projection point of the planned drilling point P(E, N, Z) of the seismic exploration well onto the inclined rock layer as P'(E, N, Zh), determine the well depth h=PP' of the seismic exploration well in the colluvial zone; The normal vector N(U, V, W) of the inclined rock layer is calculated based on the true dip angle α of the inclined rock layer and the angle ω between the dip direction FD of the inclined rock layer ABEF and the X-axis: U=sin(α)cos(ω), V=sin(α)sin(ω), W=cos(α), where the true dip angle α is obtained by the apparent dip angle β corresponding to the observation direction line FB and the angle θ between the horizontal projection CD of AB and the horizontal projection of the observation direction line FB according to tan(α)=tan(β) / sin(θ); Zh is calculated based on the normal vector equation U(E-E0)+V(N-N0)+W(Zh-Zh0)=0 passing through point F(E0,N0,Zh0), and then the well depth h=PP'=Z-Zh of the seismic exploration well in the colluvial zone is determined.

2. The well depth design method for seismic exploration wells in colluvial zones according to claim 1, characterized in that, The included angle θ is calculated using trigonometric functions based on the geometric model.

3. The well depth design method for seismic exploration wells in colluvial zones according to claim 2, characterized in that, The included angle θ is calculated from the included angle ω and the azimuth angle η of the observation direction line corresponding to the projection FC of the inclined line FB on the horizontal plane passing through point F, according to sin(θ) = cos(ω - η).

4. The well depth design method for seismic exploration wells in colluvial zones according to any one of claims 1 to 3, characterized in that, The included angle ω is calculated from the azimuth angle φ of the inclined line FA corresponding to the dip FD, according to ω = 90° - φ.

5. The well depth design method for seismic exploration wells in colluvial zones according to any one of claims 1 to 3, characterized in that, By increasing the length of the explosive charge on the basis of PP', the final seismic exploration well depth in field seismic exploration is obtained.

6. The well depth design method for seismic exploration wells in colluvial zones according to any one of claims 1 to 3, characterized in that, The X and Y axes of the three-dimensional Cartesian coordinate system corresponding to each coordinate point are aligned with the corresponding actual geographical directions of the Earth.

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