阅读说明：本技术 基于高分辨率反演速度体的地震数据精细时深转换方法 (Seismic data fine time-depth conversion method based on high-resolution inversion velocity body ) 是由 常锁亮 张启帆 张生 陈强 于 2021-08-24 设计创作，主要内容包括：本发明提供了一种基于高分辨率反演速度体的地震数据精细时深转换方法,属于煤田勘探技术领域；首先,结合处理所得速度体的速度变化趋势与钻孔资料的精确速度值将反演速度体层段的典型标准层经时深转换后作为控制层；然后,利用反演层速度体及地震解释的时间域的层位计算其余各标准层深度信息,得到所有标准层的初步底板标高,利用钻孔资料对初步时深转换所得结果进行校正；最后,基于所得深度域标准层进行层间网格划分,获得目标层段深度域三维数据体；该方法利用反演速度体弥补了井间信息缺失,取得了更符合地质规律横向变化的数据,提高了时深转换横向精度；利用测井信息进行校正,提高纵向的转换精度,最终取得精度更高的深度域三维数据体。(The invention provides a seismic data fine time-depth conversion method based on a high-resolution inversion velocity body, belonging to the technical field of coal field exploration; firstly, combining the speed change trend of the velocity body obtained by processing with the accurate velocity value of the drilling data, and taking a typical standard layer of an inversion velocity body layer section as a control layer after time-depth conversion; then, calculating depth information of other standard layers by using the inversion layer velocity body and the horizon of the time domain of the seismic interpretation to obtain the initial bottom plate elevations of all the standard layers, and correcting the result obtained by the initial time-depth conversion by using drilling data; finally, carrying out interlayer mesh division based on the obtained depth domain standard layer to obtain a target layer interval depth domain three-dimensional data volume; according to the method, the inversion velocity body is used for making up for the information loss among wells, data which are more in line with the geological rule and change transversely are obtained, and the time-depth conversion transverse precision is improved; and the logging information is utilized to carry out correction, the longitudinal conversion precision is improved, and finally, a depth domain three-dimensional data body with higher precision is obtained.)

1. The seismic data fine time-depth conversion method based on the high-resolution inversion velocity body is characterized by comprising the following steps of:

s1 obtaining a depth domain target horizon:

s1.1: obtaining time domain interpretation results of each standard layer on the basis of fine interpretation of the standard layer and fine calibration of earthquake and geological layers; using one standard layer as a control layer, correcting the speed change trend of the obtained speed body at the control layer by using the average speed value at each drilling hole to obtain the bottom plate elevation H of the control layer₁；

S1.2: calculating the difference value of the two layers in the depth domain according to the difference value of the rest standard layers and the control layer in the time domain and the layer speed information corresponding to the difference value in the inversion speed body, and obtaining the bottom plate elevations of the rest standard layers according to the depth information of the control layer and the difference value;

s1.3: obtaining a standard interlayer thickness by subtracting the elevation values of two standard positions at the position of a drill hole p, obtaining a preliminary interlayer thickness by subtracting the elevation value of the bottom plate at the position of the drill hole p, and taking the ratio of the standard interlayer thickness to the preliminary interlayer thickness as the correction value of the preliminary bottom plate elevation at the position of p

M_p＝(h_p2-h_p1)/(H_pc2-H_p1) (3)

In the formula, M_pCalculating the elevation difference error between a layer and a standard layer at the position p of any drilling hole; h is_p2The elevation value of the bottom plate of a certain standard layer measured at the position of the drill hole p; h is_p1Calculating the elevation value of the bottom plate of the layer for the position measured by the drilling hole p; h_pc2Predicting the elevation of a bottom plate of a certain standard layer at the position p of the drill hole; h_p1For drilling holes pMeasuring the elevation of the bottom plate of the calculation layer;

calculating to obtain error information of a plurality of well points, and performing interpolation by a whole-area Cokriging method to obtain a corresponding interlayer thickness error grid M;

s1.4: correcting the preliminarily obtained elevation value of the bottom plate of the second standard floor by using the error grid M to obtain the elevation value of the bottom plate of the second standard floor

In the formula, H_ij2Predicting the bottom plate elevation of a certain standard layer at the plane position i, j; m_ijThe error value of the interlayer thickness at the plane position i, j is taken as the error value;

s1.5: interpolating the error grid to obtain a three-dimensional error body;

s2, depth domain mesh generation is carried out to construct a depth domain three-dimensional data volume:

on the basis of obtaining the elevation of the bottom plate of each standard layer, carrying out interlayer equal-interval grid division in a time domain, carrying out calculation on the grid thickness of a corresponding depth domain by utilizing the time difference represented by the corresponding inversion layer speed and the time grid thickness in the grid, and calculating from a shallow standard layer, subtracting the grid thickness of the depth domain from the elevation value of the standard layer corresponding to the next grid, and calculating downwards grid by grid; the elevation value of the bottom plate at any spatial position i, j, k is obtained by calculating (5)

h_ijk＝h_ij(k-1)-t/2×v_ijk×M_ij (5)

In the formula, h_ijkThe elevation values of the bottom plate in the depth domain at the space positions i, j and k are shown, and t is the length of the longitudinal grid in the time domain.

2. The seismic data fine time-depth conversion method based on the high-resolution inversion velocity volume according to claim 1, wherein in S1.1, the average velocity of the control layer is obtained by calculation at the drill hole:

in the formula, V_DrillThe average speed of the bottom plate elevation of the top control layer at the drilling position is obtained; a is a datum plane elevation value during processing; h is_DrillThe measured elevation value of the bottom plate elevation of the top control layer at the drilling position is used as the elevation value of the bottom plate elevation of the top control layer; t is_DrillThe time value of the top control layer at the drill hole is shown.

3. The seismic data fine time-depth conversion method based on the high-resolution inversion velocity body as claimed in claim 1, wherein in S1.2, at a plane position i, j, the floor elevation of a known control layer is H₁And the interval velocity values of each point are accumulated to obtain two longitudinal times t according to the sampling interval of the inversion velocity body₁,t₂The bottom plate elevation H of the standard layer is obtained by subtracting the calculated thickness value from the bottom plate elevation of the control layer_c2

In the formula: i is the ith grid in the x direction; j is the jth grid in the y direction; k is the kth grid in the z direction; v. of_ijkInversion layer velocities at spatial locations i, j, k; Δ t is a time domain sampling interval; t is t₁Time domain values for the starting layer; t is t₂Is the time domain value of a certain standard layer; h_ij1The elevation of the bottom plate of the calculation layer at the plane position i, j; h_ijc2To calculate the initial floor elevation of a standard floor at the resulting plane location i, j.

4. The seismic data fine time-depth conversion method based on the high-resolution inversion velocity volume according to claim 1, characterized in that a standard layer depth domain horizon is obtained when a correction result in S1.4 meets an accuracy requirement, and the S1.3 and the S1.4 are repeated for secondary correction when the correction result does not meet the accuracy requirement.

Technical Field

The invention belongs to the technical field of coal field exploration, and particularly relates to a seismic data fine time-depth conversion method based on a high-resolution inversion velocity body.

Background

The coal-based stratum formed by the transitional change of the marine facies-terrestrial facies deposition environment has the characteristic of rapid lithology and speed transverse change, and the depth domain result data obtained by using the traditional time-depth conversion method in the three-dimensional seismic exploration and development process of the coal field and the coal bed gas has low precision and the relative error is generally two percent. With the proposal of the accurate coal mining concept, the automatic and intelligent mining becomes a new development trend; in addition, horizontal well technologies are widely applied to coal bed gas development, the realization of the new technologies requires more accurate depth domain data provided by time-depth conversion, and the traditional time-depth conversion method is difficult to meet the precision requirement, so that more precise time-depth conversion is required.

The general idea of time-depth conversion is as follows: 1. obtaining an accurate time domain t0 value; 2. establishing an accurate speed field; 3. an appropriate speed conversion method is selected and then time-depth conversion is performed. When the seismic data are definite, the time domain t0 value obtained through three-dimensional seismic data interpretation is definite, and only by establishing a proper velocity field, selecting a proper time-depth conversion method is a necessary means for improving the time-depth conversion precision. The predecessors have made many studies on the aspect of improving the time-depth conversion precision, and with the continuous deepening of exploration and development, seismic data and well data are continuously abundant, and the construction method of the velocity field and the accompanying velocity conversion method are also richer. In the field of coal field exploration, or the average speed is calculated by using the buried depth of a drilling hole and the time domain interpretation result, then interpolation is carried out in the whole area, and then a depth domain value is obtained by simple operation, the reliability of the speed between wells is not high, so that the depth domain value in the transverse direction is not accurate; or the root mean square velocity obtained by processing is converted into the layer velocity according to a DIX formula, and then the layer velocity is converted into the average velocity to carry out time-depth conversion, but the DIX formula is only suitable for horizontal layered media and transverse non-variable-speed media, and the actual stratum can not meet the ideal conditions, so errors can be generated.

The technical scheme of the prior art I is as follows:

the common technical means in the field of three-dimensional seismic exploration of coal fields at the present stage is to calculate the average speed by using the buried depth of a drilling hole and the interpretation result of a time domain, then perform interpolation in the whole area, and then perform simple operation to obtain a depth domain value. As exploration is deepened, the number of drilled wells is increased, in areas with smooth construction and small longitudinal and transverse speed change, VSP logging information or basic speed information for time-depth conversion is determined according to the relation between the drilling depth and the time depth of a reflecting layer, a time-depth relation curve or a time-average speed relation curve at a well point is established, and then a speed field in a large area is established in an interpolation mode. The interpolation mode generally determines the contribution value of the speed data of each well in the speed field by taking the distance between the wells as a weight coefficient, and only considers the distance factor and does not consider the influence of the geological structure.

The first prior art has the following disadvantages:

the time-depth conversion method needs to have a certain number of drilling wells to facilitate the fitting of time-depth data, and also needs to be relatively stable in stratum. The interpolation method determines the contribution value of the speed data of each well in the speed field by taking the distance between wells as a weight coefficient, only considers the distance factor and does not consider the influence of a geological structure, and is feasible for stratum conditions with relatively shallow buried depth of an underground structure, small transverse change of stratum speed and small trap amplitude; however, in a fault block area or other complex structure areas with fracture development, due to factors such as fault dislocation, stratum folds and the like, stratums with different speed characteristics are mutually contacted at a fault or the same set of stratums are repeated for many times, the speed fields of underground space in the places can generate great changes in short distance, the speed fields become quite complex, the speed fields are generated in a purely mathematical distance interpolation mode on the basis of well point data, the influence of actual geological structure changes on the speed is not considered, the average effect is obvious, and the precision of the speed fields is still low.

The technical scheme of the prior art II is as follows:

in order to avoid the defect of low precision of velocity field caused by borehole interpolation, many scholars apply velocity data obtained by processing three-dimensional seismic data, which is called velocity volume method, also called DIX formula method. When the number of drilled holes in the exploration area is small, the distribution is uneven, and the geological condition is complex, a three-dimensional superposition velocity field which is provided by three-dimensional seismic data processing and is uniformly distributed in the whole area is utilized, and a Dix formula is adopted for operation to obtain the interval velocity; then, depth domain data is obtained through time-depth conversion.

The method is realized by the following steps: 1. outputting a velocity spectrum, selecting a section with good data, outputting the superposition velocity and the two-way time value from the processing system, and deleting velocity abnormal points; 2. outputting the horizon data, and outputting the interpreted horizon data from the interpretation system; 3. matching the horizon time value at the velocity spectrum, wherein X, Y of the velocity spectrum is the same as X, Y of the horizon file, putting the time value in one file, and calculating the time of the next velocity spectrum until the time is completely finished; 4. the destination floor average velocity is calculated, and the destination floor time value at each velocity spectrum is obtained through the above calculation, and then the average velocity at the destination floor is calculated, which can be calculated by the DIX (DIX) formula. Because the time and speed values at each speed spectrum are less in general explanation, interpolation or fitting processing is required to improve the precision; 5. correcting the layer velocity by using the drill hole; 6. and obtaining depth domain data through time-depth conversion calculation.

The second prior art has the following defects:

the method has two problems, namely firstly, when the underground structure is complex and the imaging quality of a seismic section is poor, energy clusters of a velocity spectrum are scattered, and the energy clusters of effective waves and energy clusters of multiple waves can not be distinguished almost, so that the interpretation precision of the velocity spectrum is difficult to guarantee. Meanwhile, the seismic velocity body established according to the velocity spectrum has many abnormal values, and the abnormal values are often greatly different from the well point velocity, which has great influence on time-depth conversion. The second problem is that because the DIX formula is only applicable to the velocity relation established under the conditions of horizontal laminar medium, transverse non-variable medium and vertical ray incidence, the preconditions are quite harsh, and the actual formation cannot meet such ideal conditions, when the underground medium is complex in shape, a large error is generated when the layer velocity or the average velocity is obtained by using the DIX formula. Therefore, the method is mainly used under the conditions of simple geological conditions and good velocity spectrum quality, and if the velocity spectrum interpretation precision is low, the well point depth error converted according to the method is large.

Disclosure of Invention

The invention overcomes the defects of the prior art and provides a seismic data fine time-depth conversion method based on a high-resolution inversion velocity body. The method achieves the purposes of improving the time-depth conversion precision of the target layer and obtaining the interlayer small-layer depth domain information.

In order to achieve the above object, the present invention is achieved by the following technical solutions.

1. Method for obtaining target horizon in depth domain

Step 1: obtaining time domain interpretation results of each standard layer on the basis of fine interpretation of the standard layer and fine calibration of earthquake and geological layers; selecting a certain standard layer as a control layer, calculating the average speed of the control layer according to the formula (1) in the drill holes, correcting the speed change trend of the obtained speed body at the control layer by using the accurate average speed value at each drill hole, and obtaining the bottom plate elevation H of the control layer₁

In the formula, V_DrillThe average speed of the bottom plate elevation of the top control layer at the drilling position is obtained; a is a datum plane elevation value during processing; h is_DrillThe measured elevation value of the bottom plate elevation of the top control layer at the drilling position is used as the elevation value of the bottom plate elevation of the top control layer; t is_DrillThe time value of the top control layer at the drill hole is shown.

Step 2: on the basis of the acquired control layer depth domain information, the difference value of the two layers in the depth domain can be calculated according to the difference value of the rest of standard layers and the control layer in the time domain and the layer speed information corresponding to the difference value in the inversion speed body, and the bottom plate elevations of the rest of standard layers can be obtained by operating the depth information of the control layer and the difference value.

At the plane position i, j, the floor height of the control layer is known as H₁And the interval velocity values of each point are accumulated to obtain two longitudinal times t according to the sampling interval of the inversion velocity body₁,t₂The bottom plate elevation H of the standard layer is obtained by subtracting the calculated thickness value from the bottom plate elevation of the control layer_c2

In the formula: i is the ith grid in the x direction; j is the jth grid in the y direction; k is the kth grid in the z direction; v. of_ijkInversion layer velocities at spatial locations i, j, k; Δ t is a time domain sampling interval; t is t₁Time domain values for the starting layer; t is t₂Is the time domain value of a certain standard layer; h_ij1The elevation of the bottom plate of the calculation layer at the plane position i, j; h_ijc2To calculate the initial floor elevation of a standard floor at the resulting plane location i, j.

Step 3: obtaining a standard interlayer thickness by subtracting the elevation values of two standard positions related to the previous step at the p position of the drill hole, obtaining a preliminary interlayer thickness by subtracting the elevation value of the bottom plate obtained by calculating the position of the drill hole in the same way, and taking the ratio of the standard interlayer thickness to the preliminary interlayer thickness as the correction value of the preliminary bottom plate elevation at the p position

M_p＝(h_p2-h_p1)/(H_pc2-H_p1) (3)

In the formula, M_pCalculating the elevation difference error between a layer and a standard layer at the position p of any drilling hole; h is_p2The elevation value of the bottom plate of a certain standard layer measured at the position of the drill hole p; h is_p1Calculating the elevation value of the bottom plate of the layer for the position measured by the drilling hole p; h_pc2Predicting the elevation of a bottom plate of a certain standard layer at the position p of the drill hole; h_p1The floor elevation of the layer is calculated for the prediction at the drilling hole p.

And (3) performing the calculation by using a plurality of drill holes to obtain error information of a plurality of well points, and performing interpolation by a whole-area Cokriging method to obtain a corresponding interlayer thickness error grid M.

Step4, correcting the preliminarily obtained elevation value of the bottom plate of the second standard floor by using the error grid M to obtain the elevation of the bottom plate of the second standard floor

In the formula, H_ij2Predicting the bottom plate elevation of a certain standard layer at the plane position i, j; m_ijThe above steps are shown in FIG. 2, which is the value of the interlayer thickness error at the plane position i, j.

And if the correction result meets the precision requirement, obtaining the standard layer depth domain horizon, and if not, repeating Step3 and Step4 to perform secondary correction.

And Step5, interpolating the error grids to obtain a three-dimensional error body, and preparing for correcting a subsequent depth domain three-dimensional data body.

2. Depth domain mesh generation method

On the basis of obtaining the elevation of the bottom plate of each standard layer, interlayer equal-interval grid division is carried out in a time domain, the grid thickness of a corresponding depth domain is calculated in the grid by utilizing the time difference represented by the corresponding inversion layer speed and the time grid thickness, the elevation value of the next grid corresponding to the standard layer is calculated from the shallow standard layer, the grid thickness of the depth domain is subtracted from the elevation value of the standard layer, and grid-by-grid downward calculation is carried out. Then, the elevation value of the bottom plate at any spatial position i, j, k can be obtained by (5)

h_ijk＝h_ij(k-1)-t/2×v_ijk×M_ij (5)

In the formula, h_ijkThe elevation values of the bottom plate in the depth domain at the space positions i, j and k are shown, and t is the length of the longitudinal grid in the time domain. The calculation is performed in the whole area, and the time domain and depth domain grids are corresponding as shown in fig. 3.

Compared with the prior art, the invention has the following beneficial effects:

the invention utilizes the high-resolution inversion layer velocity body to carry out time-depth conversion of each standard layer on the basis of the control horizon, further utilizes the time-depth conversion method of 'high-resolution inversion velocity body + standard horizon control + depth domain grid division' for constructing a depth domain three-dimensional data body by carrying out interlayer depth domain grid division on the basis of the standard layers, comprehensively utilizes the three-dimensional earthquake interpretation result, the high-resolution inversion velocity body, drilling and logging data and other data, adopts the comprehensive technology of fine borehole seismic calibration, fine interpretation of the standard horizon, time-depth conversion by utilizing inversion velocity body information and depth domain grid division, obtains better application effect, obtains the depth domain data with the error of tens of meters or even tens of meters by utilizing the traditional time-depth conversion method, by using the method, the error can be reduced to less than three meters, the obtained standard layer bottom plate elevation has higher precision, and the horizontal direction better conforms to the actual stratum change; meanwhile, the constructed depth domain three-dimensional data body makes up for the deficiency of standard interlayer information, and for some weakly-reflected interlayer small layers, accurate elevation information can be directly obtained as long as time domain data of the small layers are obtained, so that the final depth domain result of the three-dimensional seismic data is more accurate and richer. The method can better guide the exploration and development of the three-dimensional coal field and the coal bed gas subsequently, provide reliable guarantee for underground operation such as roadway tunneling, horizontal well drilling and the like, and provide support of precondition for realizing the accurate exploitation development concept of automatic and intelligent exploitation in the coal industry.

The method makes up for the information loss among wells by utilizing the inversion velocity body, obtains the data which is more in line with the geological rule and changes transversely, and improves the time-depth conversion transverse precision; meanwhile, the logging information is utilized to carry out correction, the longitudinal conversion precision is improved, and finally a depth domain three-dimensional data body with higher precision is obtained.

Drawings

FIG. 1 is a flow chart of a three-dimensional seismic data volume fine time-depth conversion method.

FIG. 2 is a schematic diagram of a fine time-depth conversion method.

FIG. 3 is a diagram illustrating the time domain and depth domain meshing correspondence; in the figure, (1) is time domain interlayer meshing; (2) the method is depth domain interlayer meshing.

Fig. 4 is a depth domain target layer bitmap obtained by time-depth conversion.

FIG. 5 is a three-dimensional data volume of a depth domain of a region of interest.

FIG. 6 is a comparison graph of the elevation of a 3M base plate obtained by the conventional time-depth conversion method and the new method in a research area; in the figure: (a) obtaining the 3M bottom plate elevation by a speed interpolation method; (b) obtaining the 3M bottom plate elevation by a DIX formula method; (c) the height mark of the 3M bottom plate obtained by the new method.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail with reference to the embodiments and the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The technical solution of the present invention is described in detail below with reference to the embodiments and the drawings, but the scope of protection is not limited thereto.

The method comprises the following specific steps:

step 1: and making a fine synthetic record, carrying out well seismic calibration, and matching a seismic reflection interface with a geological interface obtained by well logging to endow the geological significance to the seismic interface.

Step 2: and obtaining the accurate target horizon on the time domain through the fine interpretation of the three-dimensional seismic data.

And step 3: and selecting a control layer, and obtaining a control horizon in a depth domain by utilizing the speed change trend of the speed body obtained by the accurate average speed value correction processing at the drill hole at the control layer.

And 4, step4: and acquiring a high-resolution inversion layer velocity volume by using a phase control inversion technology.

And 5: and on the basis of the control horizon, performing time-depth conversion on the standard layer below the control horizon by using the high-resolution inversion layer velocity body.

Step 6: and carrying out interlayer depth domain mesh division based on the control horizon to construct a depth domain three-dimensional data volume.

The test is carried out by utilizing the existing data and the invention, the south foot low and middle mountain area of the Liu Bei mountain at the west side of the Taihang mountain in a certain mining area has complex surface topography, vertical and horizontal ditches, bare bedrock, high northwest and low southeast in the mining area. The structure in the mining area develops; the lithology and the speed of the formed coal-series stratum are changed transversely rapidly due to the deposition environment of sea-land transition, the speed of the whole stratum is changed obviously, unstable interlayers are distributed partially, the difference between the vertical lithology and the transverse lithology of the stratum is large, and the error of the elevation information of the bottom plate obtained by the traditional time-depth conversion method is large. Therefore, in this embodiment, the time-depth conversion of each standard layer is performed by selecting the internal sub-region of the mining area and using the above proposed fine time-depth conversion method, and the depth domain three-dimensional data volume is constructed by the interlayer depth domain meshing as shown in fig. 4, and the depth domain three-dimensional data volume is constructed by the interlayer depth domain meshing as shown in fig. 5.

The measured elevation result of the standard layer obtained by calculation and time-depth conversion methods commonly used in two industries, namely 1, a convergence interpolation method is utilized to carry out inter-well interpolation of average speed and then time-depth conversion is carried out to obtain a result; 2. and converting the processed root mean square speed into a layer speed by using a DIX formula, and comparing the result obtained by time-depth conversion with the actually measured standard layer elevation of the drill hole to test the application effect of the new method. The comparative effect of the 3M floor elevation map obtained by the three methods is shown in fig. 6.

The method comprehensively utilizes data such as three-dimensional seismic interpretation results, high-resolution inversion velocity bodies, drilling and logging data and the like, adopts comprehensive technologies of fine well seismic calibration, fine interpretation of standard horizon, time-depth conversion by utilizing inversion velocity body information and depth domain grid division, obtains good application effect, obtains depth domain data with an error of tens of meters or even tens of meters by utilizing the traditional time-depth conversion method, can reduce the error to less than three meters, and obtains a standard layer bottom plate with higher elevation precision which is more in line with actual stratum change in the transverse direction; meanwhile, the constructed depth domain three-dimensional data body makes up for the deficiency of standard interlayer information, and for some weakly-reflected interlayer small layers, accurate elevation information can be directly obtained as long as time domain data of the small layers are obtained, so that the final depth domain result of the three-dimensional seismic data is more accurate and richer.

While the invention has been described in further detail with reference to specific preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.