Predrilling stratum depth prediction method

Abstract

The invention relates to a pre-drilling stratum depth prediction method, and belongs to the technical field of oil and gas field exploration and development. According to the seismic interpretation result and the geological data, determining well position coordinates of a design well or an intention well in the target area, converting the well position coordinates of the design well or the intention well into geographic latitude and longitude coordinates, and obtaining well point elevation data values of the design well or the intention well according to the current latitude and longitude coordinates and the topographic data of the target area; performing well-seismic joint time-depth conversion work, determining sand body top and bottom positions and a horizontal section track of a well section of the design well according to the horizon after depth conversion and a transverse change trend of seismic inversion, and predicting a horizontal section track depth value of the design well or the intention well according to a seismic datum plane and an elevation data value of the design well or the intention well; according to the method, well point elevation data can be rapidly and accurately obtained, and the well point depth value can be rapidly and accurately determined.

Description

Technical Field

[0001] The invention relates to a method for predicting stratum depth before drilling, and belongs to the technical field of oil and gas field exploration and development. Background Art

[0002] With the acceleration of exploration and development, a large number of exploration and development wells need to be deployed every year in oil and gas exploration, development and production. Among them, the design of formation characteristics and depth prediction before well drilling is very critical, especially in the process of well site deployment demonstration. The quantitative and accurate prediction of structural trends and depths is crucial, which directly affects the drilling cost budget and construction cycle, and affects the accuracy of the initial drilling construction plan design.

[0003] The invention patent document with publication number CN107765309A discloses a pre-drilling depth prediction method based on vertical seismic data. This method obtains the stratigraphic segment velocity of the target layer based on the vertical seismic data of the adjacent wells adjacent to the predicted well, and calculates the stratigraphic reflection time difference of the target layer according to the top boundary reflection time of the target layer and the bottom boundary reflection time of the target layer, and calculates the predicted depth of the target layer using the stratigraphic reflection time difference of the target layer and the stratigraphic segment velocity of the target layer. This method has little research on the lateral characteristics and depth of the target layer structure of the designed well point. For well points in different areas, the existing method does not fully consider the difference in elevation values, resulting in inaccuracy in predicting the predicted depth of the target layer of the designed well, which in turn leads to the failure to achieve the expected effect due to inadequate drilling in the subsequent drilling process. Summary of the invention

[0004] The purpose of the present invention is to provide a method for predicting the depth of a formation before drilling, so as to solve the problem that the existing prediction method predicts the depth of a target layer inaccurately, thus affecting the drilling effect.

[0005] To achieve the above object, the solution of the present invention includes:

[0006] A method for predicting stratum depth before drilling of the present invention comprises the following steps:

[0007] 1) According to the seismic interpretation results and geological data, determine the well location coordinates of the designed wells and / or intended wells in the target area, convert the well location coordinates of the designed wells and intended wells into geographic longitude and latitude coordinates, and obtain the well point elevation data values ​​of the designed wells and intended wells according to the current longitude and latitude coordinates and the terrain data of the target area;

[0008] 2) Perform joint well-seismic time-to-depth conversion based on seismic data and well logging data, determine the top and bottom positions of the sand bodies and the horizontal trajectory of the designed well and intended well according to the lateral change trend of the layer position after depth conversion and seismic inversion, and predict the depth value of the horizontal trajectory of the designed well or intended well according to the seismic datum and the elevation data values ​​of the designed well or intended well.

[0009] Beneficial effects: The method for predicting the depth of the formation before drilling of the present invention mainly uses the elevation data obtained from satellite images to predict the depth of the target layer of the designed well and / or the intended well. When predicting the depth of the formation, the method fully considers the influence of the elevation value, and is more accurate in predicting the target depth of the formation of the designed well and / or the intended well, providing reliable support for subsequent drilling work.

[0010] Furthermore, the process of obtaining the elevation data values ​​of the designed wells and intended wells is as follows: importing the terrain data file of the target area into the satellite software, loading the latitude and longitude coordinates of the designed wells and intended wells in the target area into the satellite software, and obtaining the elevation data values ​​of the designed wells and intended wells.

[0011] Beneficial effects: The elevation value of the present invention uses existing three-dimensional seismic, satellite images and corresponding geographic information data and related technologies to quickly and accurately obtain the elevation data of the designed well or intended well, and the subsequent formation depth is more accurate.

[0012] Furthermore, the method also includes a step of correcting the elevation data value of the designed well or intended well point, and the correction process is: obtaining the actual coordinate values ​​and actual elevation values ​​of the known wells in the target area, and according to the actual coordinate values ​​of the known wells, using the method in step 1) to obtain the predicted elevation data value, calculating the verification value according to the actual elevation value of the known well and the predicted elevation data value of the well point, and adjusting the elevation data value of the designed well or intended well point according to the verification value.

[0013] Beneficial effect: The present invention also includes a step of correcting the elevation data value of the well point of the design well or the intended well using the verification value of the known well. The actual elevation value of the known well is compared with the elevation value calculated by the method of the present invention to obtain a verification value, and the elevation data value of the well point of the design well or the intended well is modulated by the verification value. The corrected elevation data value is more accurate, and the formation depth is predicted more accurately.

[0014] Furthermore, when correcting the elevation data value of the well point of the designed well or the intended well, the elevation data value of the well point of the designed well or the intended well is corrected by using the average calibration value of a plurality of known wells.

[0015] Beneficial effect: The average calibration value of multiple known wells is used to correct the elevation data value of the designed well or intended well point, and the predicted depth is more accurate and closer to the actual formation depth.

[0016] Furthermore, the acquired seismic root mean square velocity is converted into the seismic average velocity to obtain the seismic velocity pseudo-well curve; the logging average velocity is obtained by the Kriging interpolation method, and the linear relationship between the logging average velocity curve of each well and the corresponding seismic velocity pseudo-well curve is obtained according to the logging average velocity of each well; the seismic average velocity is converted into a unified value range with the logging average velocity, and the seismic average value of each well is spatially spliced ​​and smoothed and fused with the logging average velocity to obtain the well-seismic fusion velocity field, thus completing the time-depth conversion of the well-seismic joint.

[0017] Furthermore, the well point coordinates of the planned well or intended well are expressed in the form of a geodetic coordinate system.

[0018] Furthermore, the geodetic coordinate system adopts the Beijing 54 coordinate system or the Xi'an 80 coordinate system.

[0019] Beneficial effects: The well point coordinates of the present invention adopt the Beijing 54 coordinate system or the Xi'an 80 coordinate system, which makes the description of the well point more accurate and simpler when conducting well seismic research.

[0020] Furthermore, the seismic datum is the Yellow Sea elevation datum. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a flow chart of a method for predicting formation depth before drilling based on satellite images in a method embodiment of the present invention;

[0022] Figure 2 It is a seismic comprehensive interpretation result diagram in the method embodiment of the present invention;

[0023] Figure 3 is a satellite image of a deployment well in an embodiment of the method of the present invention;

[0024] Figure 4 It is a schematic diagram of establishing a well-seismic fusion velocity diagram and its velocity relationship in the method embodiment of the present invention;

[0025] Figure 5 It is the time-depth conversion seismic layer and inversion diagram in the method embodiment of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0027] Predrilling Formation Depth Prediction Method Embodiment:

[0028] like Figure 1The method shown is to determine the well location coordinates of the designed well or intended well in the target area based on the seismic interpretation results and geological data, convert the well location coordinates of the designed well or intended well into geographic longitude and latitude coordinates, obtain the well point elevation data value of the designed well or intended well based on the current longitude and latitude coordinates and the terrain data of the target area, perform the well-seismic joint time-depth conversion, determine the top and bottom positions of the sand body and the horizontal section trajectory of the designed well section based on the lateral change trend of the converted layer and seismic inversion, and predict the horizontal section trajectory depth value of the designed well or intended well based on the seismic datum and the elevation data value of the designed well or intended well. The specific implementation method is as follows:

[0029] This example takes a development well area on the northern edge of a basin as an example. This area needs to carry out multiple rounds of well site deployment work every year. In order to ensure the success rate of development wells, it is necessary to conduct multiple demonstrations during the well site deployment stage. This specific implementation combines the information of 30 known wells, determines the surface elevation of the design well or intended well, predicts the formation depth of the intended well, and takes the horizontal section trajectory design of a horizontal well as an example for depth prediction.

[0030] 1) According to the seismic interpretation results and geological data, determine the well location coordinates of the designed wells and / or intended wells in the target area, convert the well location coordinates of the designed wells and intended wells into geographic longitude and latitude coordinates, and obtain the well point elevation data values ​​of the designed wells and intended wells according to the current longitude and latitude coordinates and the terrain data of the target area.

[0031] Based on the seismic interpretation results and geological knowledge, the exploration and development well location demonstration is carried out and the coordinate information of the designed well (or intended well) is determined, such as Figure 2 As shown, the coordinate system of the target area has been converted to the same degree zone (19 degree zone). The coordinate systems of the known wells and the designed wells in the target area are converted, and the geodetic coordinate system is converted into the geographic longitude and latitude coordinate system using the coordinate conversion software.

[0032] The well location coordinate information obtained in this embodiment is geodetic coordinates, which are further represented by the Beijing 54 coordinate system or the Xi'an 80 coordinate system.

[0033] This example uses the coordinate conversion system in the Shuanghu commercial software to perform the conversion (the actual coordinate information is replaced by asterisks), and completes the coordinate conversion of 32 known wells and 4 designed wells, as shown in Table 1:

[0034] Table 1

[0035]

[0036]

[0037] The process of obtaining the elevation data values ​​of the designed wells and intended wells is as follows: importing the terrain data file of the target area into the satellite software, loading the latitude and longitude coordinates of the designed wells and intended wells in the target area into the satellite software, and obtaining the elevation data values ​​of the designed wells and intended wells.

[0038] Specifically, the coordinate data of the converted known wells and designed wells are converted into a universal vector format file, which is added to the map new software in the form of a layer, and the elevation data is obtained through the map new software, and the data file is imported into the software with satellite image display function. The terrain data file of the target area exported from the satellite image is the surface file type under the elevation benchmark.

[0039] Among them, commonly used map software includes two commonly used free software, MapNew Earth and Google Earth, as well as other software, while common vector format files include Google vector format (.kml, .kmz), CAD vector format (.dxf, .dwg) and other vector (.lgd, .mif) and other types of vector data.

[0040] The elevation data selected is the altitude value under the Yellow Sea elevation benchmark. The elevation data includes the national 30-meter and 90-meter precision DEM (digital elevation model). The elevation values ​​of the designed wells and known wells (Yellow Sea elevation) are derived. The normal distribution range of the known well elevation error is analyzed statistically, the error average is obtained, and the correction of the designed well points is completed to obtain data that is closer to the actual elevation.

[0041] Since the directly acquired elevation data values ​​have certain errors, they need to be corrected. The average error value is calculated using known wells to correct the elevation data values ​​of the designed wells. First, the actual coordinate values ​​and actual elevation values ​​of the known wells in the target area are obtained, and based on the actual coordinate values ​​of the known wells, the second elevation data value is obtained using the above-mentioned method of obtaining the elevation value of the designed well or intended well. The verification value is calculated based on the actual elevation value of the known well and the second elevation data value of the well point, and the elevation data value of the designed well or intended well point is adjusted based on the verification value. When correcting the elevation data value of the designed well or intended well point, in order to improve the accuracy of the corrected elevation data value, the average verification value of multiple known wells is used to correct the elevation data value of the designed well or intended well point.

[0042] Verify the accuracy of the converted longitude and latitude coordinates by using the actual location of the known well coordinates (the location traces of the well site on the surface of the satellite image). Figure 3The two known wells shown, YZ26 and YZ11 (not real well names), show that the surface well positions are clearly visible in the figure, which verifies the accuracy of the coordinate conversion. The surface elevation values ​​of all known wells are exported or read and the error statistics are analyzed with the actual measured elevations to calculate the average error value of the known wells in the target area. According to the average error value, the elevation value of the intended well is corrected. For example, the absolute average error value of 32 wells is 1.2 meters (excluding the maximum and minimum error values) in Table 1. According to the average error value, the elevation value of the intended well is corrected, as shown in Table 2:

[0043] Table 2

[0044]

[0045] The average error value is used to correct the elevation data values ​​obtained from the design well (intended well). In this embodiment, as shown in Table 3, the elevation values ​​read from the four intended wells (JY1, JY2, JY3, and JY4) are corrected to obtain the corrected elevation values.

[0046] Table 3

[0047]

[0048]

[0049] 2) Carry out the time-depth conversion of well seismic velocity, determine the top and bottom positions of the sand body and the horizontal trajectory of the designed well section according to the converted layer position and the lateral change trend of seismic inversion, and predict the depth value of the horizontal trajectory of the well according to the seismic fixed datum surface and the corrected elevation data value of the designed well.

[0050] Specifically, Figure 4 As shown in the figure, first, the three-dimensional seismic root mean square velocity is converted into layer velocity by using the Dicks formula, and then into seismic average velocity, and the seismic average velocity is extracted using the existing actual drilling points in the area as the pseudo-well curve. Second, through well seismic calibration, Kriging spatial interpolation is used to obtain the well logging average velocity curve (i.e., well control average velocity), as shown in formula (1):

[0051] V ave =2*H / T0 (1)

[0052] In formula (1), V ave is the average logging velocity, H is the vertical depth of the formation corresponding to the well point, unit, meter; T0 is the seismic two-way travel time corresponding to the well-seismic calibration.

[0053] Third, the average velocity body of the well logging is down-converted, and the intersection diagram is statistically analyzed to obtain the linear relationship between the average velocity curve of the well logging and the pseudo-well curve of the seismic velocity. The linear relationship is shown in formula (2), which converts the seismic velocity into a relatively uniform value range with the average velocity of the well control. For example, the seismic velocity of 2000-3000 m / s is corrected to the average velocity of the well control of 4000-5000 m / s by the method of well point intersection analysis. In the relationship of formula (2), different coefficients are obtained for different well control degree zones. Different column formulas can be obtained according to the coefficients obtained for different well control degree zones. Finally, the average velocity of each zone is calculated, and then spatial splicing and smoothing are performed, and it is fused with the average velocity body of the well control to form the final well-seismic fusion velocity field, and the time-depth conversion of the layer and seismic inversion is completed.

[0054] y=ax+b (2)

[0055] In formula (2), y is the average logging velocity, unit, m / s; x is the average seismic velocity after conversion from root mean square velocity, unit, m / s; a and b are fixed coefficients obtained by zoning analysis based on the well control degree.

[0056] According to the lateral change trend of the horizon after the depth conversion and the seismic inversion, the top and bottom positions of the sand body and the horizontal section trajectory of the horizontal well section are determined, such as Figure 5 As shown in Table 4, the top and bottom values ​​of the sand body determined by the horizontal well section, the top and bottom values ​​of the horizontal section, and other values ​​are derived, and the main stratigraphic positions of the well are obtained through seismic base calculation, and then the depth of the intended stratum is predicted, as shown in Table 4:

[0057] Table 4

[0058]

[0059] According to the intended formation depth and horizontal section trajectory depth values ​​predicted in Table 4, the more realistic depth value of the horizontal section of the horizontal well can be predicted as shown in Table 5. The calculation formula is:

[0060] D Z =D d -C+H (3)

[0061] In formula (3), Dz is the predicted formation depth at the Yellow Sea elevation; D d is the stratum depth value below the seismic datum plane; C is the seismic fixed datum plane (in this embodiment, the seismic datum plane is 1400 meters); H is the surface elevation value of the designed well.

[0062] Table 5

[0063]

[0064]

[0065] As shown in Table 5, the vertical depth, target point A and target point B are all calculated from the ground (i.e., the ground elevation is 1354.6 meters).

[0066] In summary, based on the detailed interpretation and timely depth conversion of 3D seismic structures, the surface type characteristics and elevation data of the designed wells can be quickly and accurately obtained by making full use of the existing 3D seismic, satellite images and corresponding geographic information data and related technical means, providing a basis for the description of the structural morphology between the deployed wells and the known wells and the depth prediction of the formation depth and horizontal trajectory of the designed wells, and more quickly and accurately determining the actual depth value of the well point, providing a more detailed seismic interpretation basis for the timely determination of the well location. Without the need for surveyors to conduct on-site surveys, the entire pre-drilling well site preparation time of 6 months is reduced to 3-4 months, greatly saving the drilling cycle, more accurately implementing the surface and underground geological information of the designed well site, accelerating the exploration and development process, optimizing the well site deployment process, and saving the cost of pre-drilling well site surveys.

Claims

1. A method for predicting formation depth before drilling, characterized in that: The following steps are involved: 1) According to the seismic interpretation results and geological data, determine the well location coordinates of the designed wells and / or intended wells in the target area, convert the well location coordinates of the designed wells and intended wells into geographic longitude and latitude coordinates, and obtain the well point elevation data values ​​of the designed wells and intended wells according to the current longitude and latitude coordinates and the terrain data of the target area; 2) Perform joint well-seismic time-to-depth conversion based on seismic data and well logging data, determine the top and bottom positions of the sand bodies and the horizontal trajectory of the designed well and intended well according to the lateral change trend of the layer position after depth conversion and seismic inversion, and predict the depth value of the horizontal trajectory of the designed well or intended well according to the seismic datum and the elevation data values ​​of the designed well or intended well.

2. The method for predicting stratum depth before drilling according to claim 1, characterized in that: The process of obtaining the elevation data values ​​of the designed wells and intended wells is as follows: importing the terrain data file of the target area into the satellite software, loading the latitude and longitude coordinates of the designed wells and intended wells in the target area into the satellite software, and obtaining the elevation data values ​​of the designed wells and intended wells.

3. The method for predicting stratum depth before drilling according to claim 1, characterized in that: The method also includes a step of correcting the elevation data value of the designed well or intended well point, and the correction process is: obtaining the actual coordinate value and actual elevation value of the known well in the target area, and according to the actual coordinate value of the known well, using the method in step 1) to obtain the second elevation data value, calculating the verification value according to the actual elevation value of the known well and the second elevation data value of the well point, and adjusting the elevation data value of the designed well or intended well point according to the verification value.

4. The method for predicting stratum depth before drilling according to claim 3, characterized in that: When correcting the elevation data value of the design well or the intended well point, the elevation data value of the design well or the intended well point is corrected using the average calibration value of multiple known wells.

5. The method for predicting stratum depth before drilling according to claim 1, characterized in that: The acquired seismic root mean square velocity is converted into the seismic average velocity to obtain the seismic velocity pseudo-well curve; the logging average velocity is obtained by the Kriging interpolation method, and the linear relationship between the logging average velocity curve of each well and the corresponding seismic velocity pseudo-well curve is obtained according to the logging average velocity of each well; the seismic average velocity is converted into a unified value range with the logging average velocity, and the seismic average values ​​of each well are spatially spliced ​​and smoothed and fused with the logging average velocity to obtain the well-seismic fusion velocity field, thus completing the time-depth conversion of the well-seismic combination.

6. The method for predicting stratum depth before drilling according to claim 1, characterized in that: The well point coordinates of the planned well or intended well are expressed in the form of a geodetic coordinate system.

7. The method for predicting stratum depth before drilling according to claim 6, characterized in that: The geodetic coordinate system adopts the Beijing 54 coordinate system or the Xi'an 80 coordinate system.

8. The method for predicting stratum depth before drilling according to claim 1, characterized in that: The seismic datum is the Yellow Sea elevation datum.

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