2022年petrel地质建模软件的曲率计算原理及方法 .pdf

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1、1Curvature Modeling BackgroundThis extensive workflow can calculate the curvature of a reservoir based on the geometry of the 3D grid. This in turn can be used in combination with fracture modeling. Curvature is often regarded a good indicator of fracture intensity for specify types of conjugate fra

2、cture pairs. Curvature can be used as a secondary variable in fracture modeling. It can also be used to spot irregularities in a 3D grid in general ResultA new, continues curvature property will be added to the 3D grid, the name of which will depend on the chosen method of curvature calculation (min

3、, max, mean or gauss). Prerequisites This workflow has been tested on simple and moderately complex grids. One needs a 3D grid with “segments ” modeled as a property under geometrical modeling. This segment property must be specified in the input. The workflow is most accurate when all the faults ar

4、e also segment boundaries. In case of (steep) faults not acting as a segment boundary (faults terminating or dying out within a segment), the modeling workflow becomes less accurate, because of the possibility of comparing depth values from both sides of the fault and thereby giving rise to an artif

5、icially high curvature. This can be partly counteracted by using the “distance from fault” property and a low value for the parameter “surface expansion”, but it is highly recommended to use a 3D grid with only segment dividing faults. If you do not have this, you can use trends set as segment bound

6、ary in the pillar gridding process. The workflow is fully compatible with the zone and segment filters. Curvature calculation itself is done per layer and per segment. The workflow itself works as follows. -The property “Curvature” is created, having values of zero everywhere. This property will pro

7、gressively be filled while the workflow is running. A suffix to the name will denote the curvature type -The property “K_Curve ” is created, giving an index to each layer. (0 to N from top to bottom) -The first loop will run from the min to the max layer index, starting with the top layer. -The seco

8、ndary loop progressively goes through all segments. -For the top layer in the first segment, the property Z (depth) will be calculated -An average map will be created from the Z values of that layer. Since map calculation is limited to only one layer, the map will simply represent the depth of the l

9、ayer (measured for cell center) -min, max, mean or gauss curvature is calculated for this layer and recreated as a separated surface -This calculation will return a curvature surface for one layer in one segment. Workflow SpecificsWorkflow Specifics Petrel Version 2009.1 Domain Geology Modules Geosc

10、ience Core or Combined Core Expert Level Advanced 名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 1 页，共 5 页 - - - - - - - - - 2-A property operation is used to extract the values of this surface and plot them back onto the grid, a calculator statement is used to limit

11、 the results to the proper layer in the correct segment. -The curvature results from the single layer will be added to the previously empty “Curvature” property. -The workflow will no go through the same layer in the next segment and run over again. -Once finished with all segments, the next layer (

12、below) is modeled, gradually populating the “Curvature”. Note that this workflow represents a 3D property for one layer as a surface, then performs a surface calculation and finally plots the results back in the grid. There are five adjustable numeric variables controlling the accuracy of the curvat

13、ure modeling process. In order of appearance these are: Input: The grid and the “segment index” have to be specified. $type: specify min, max, mean or gauss curvature. $Iterations: This variable gives the number of smoothing iterations that need to be performed on the extracted surface. A default sm

14、oothing is done, but additional smoothing can be specified with $Iterations. $Iterations should be in the preferred range of 1-10. Figure 1 shows the artificial spiking when the $Iterations is set too low. Quality-check the result and read the instructions in the workflow. Fig 1. Too few vs. enough

15、smoothing iterations. $Distance: An optional distance to fault property. If you do not want to use this option, deactivate this option by blanking the line. If all faults in the model are segment dividing, you will not need this $Interpolation: By default this variable is set to zero project distanc

16、e units, corresponding to no interpolation to faults. This variable can be used to exclude cell values near faults in the modeling process. It is the distance in project units from the fault for which the curvature should be interpolated from data further away from the fault. This should be used in

17、combination with a “distance to fault” property, which can be created under geometrical modeling. Use this variable when you have faults which are no segment boundary or faults that terminate within a segment. It is however strongly recommended to set all faults as a segment boundary and to avoid ha

18、ving terminating faults by joining them with segment-dividing trends. $minNdef: The minimum number of 3D grid cells in a layer to perform curvature calculation. The ideally, a cell in a layer is surrounded by eight other cells. The test using this variable only checks if the minimum number of cell c

19、riterion is met and not if these are adjacent. Visual final checking remains necessary. $Expand: How far the 3D grid will be expanded to ensure values near the edges in gridcells as specified in the make-edit surface process. Values of 5 are normally ok. Lower values can be used when you have intra-

20、segmental faults. 名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 2 页，共 5 页 - - - - - - - - - 3Troubleshooting. The property contains some extremely low negative values. These values are the original Z values and they are a result of too little data to perform curvatu

21、re calculation. When this happens, rerun the workflow with a higher $minNdef value. If the problem persists, use the calculator to clip the extremely high values (set them to undefined). Reasonable values do typically not exceed |0.01| and are often less, unless your model is heavily folded. An unex

22、plained increase in curvature occurs near faults. This fault is probably not segment divider. Look above for more information. An unexplained increase in curvature values occurs near the model corners. This is an artifact due to the absence of sufficient data near the model edges. Increase the $Expa

23、nd variable and optionally increase $Iterations, although the latter will also affect other cell values. Curvature modeling is in fact less accurate near the corners of the grid as well as near faults If the workflow is interrupted when running, the temporarily created properties and surfaces need t

24、o be deleted manually. (K_curve under properties and the average maps in the input) If these are not deleted, future runs may fail. 名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 3 页，共 5 页 - - - - - - - - - 4名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 4 页，共 5 页 - - - - - - - - - 5名师资料总结 - - -精品资料欢迎下载 - - - - - - - - - - - - - - - - - - 名师精心整理 - - - - - - - 第 5 页，共 5 页 - - - - - - - - -