OBJECTIVES • To become familiar with Surpac’s Block Modelling module and the concept of block modelling. • To learn to fill a block model from drillhole data from the geological database. • To learn to constrain a block model to filter out specific blocks. • To learn to report volume, tonnage, & grade from a block model.
BLOCK MODELLING _ FILES USED DISCUSSION FLOWCHART FOR SIMPLE USE OF BLOCK MODELLING Model Space User Block Size Sub-blocking None Standard Sub blocking Variable Sub Blocking Attributes Constraints Sub-celled Block Model BLOCKS AND ATTRIBUTES CONSTRAINTS ESTIMATION 10 ANISOTROPY ELLIPSOID PARAMETERS 11 CREATING BLOCK MODEL 14 CREATING MODEL ATTRIBUTES 21 CONSTRAINTS WITHIN A BLOCK MODEL 24 FILLING THE BLOCK MODEL 25 ASSIGN VALUE 26 INVERSE DISTANCE 27 BLOCK MODEL REPORTING 33 CALCULATED ATTRIBUTES 37 PARTIAL PERCENTAGE REPORTING 39 MODEL RE_BLOCKING 45 BASIC ACTIVITY 48 Add the attribute “gold_nn” to the block model 50 Add the attribute “sg” to the block model 50 Fill the “sg” attribute with the Assign Value method Assign a specific gravity of 2.5 to all blocks below the topography “topo1.dtm” 50 Fill the “sg” attribute with the Assign Value method Assign a specific gravity of 2.9 to all block in the solid ore body “ore1.dtm” 51 Fill the “gold_nn” attribute with Nearest Neighbour estimation method 52 Create a Block Model Report and report the following: 55 • Average weighted gold grade 55 • Average weighted specific gravity 55 • Tonnage (multiplication factor = sg) 55 • Organized by bench (0,250,10) 55 • Choose one of the available formats (.csv; not; htm; rtf; pdf) 55 • Constrain the report to all block within the solid “ore1.dtm” 55 1/83 ADVANCED BLOCK MODELLING TUTORIAL 58 Open the database DB1.DDB and display the drill holes – determine extents and become familiar with the dataset 61 Create an empty block model, ensuring to cover the area required totally 62 Export the centroid points to a string file and validate the model area 63 Create a graphical constraint of the qpy1.dtm & bif1.dtm and validate the user block size of your new block model 64 Add the attribute “gold” to the block model 66 Add the attribute “sg” to the block model 66 Add the attribute “gold_cut” to the block model 66 Add the attribute “orecat” to the block model 67 Create and save a constraint file for: 68 • Inside qpy1.dtm save as qpy1.con 68 • Inside bif1.dtm save as bif1.con 68 • Inside sand1.dtm save as sand1.con 68 • Combination of all above save as qpy_bif_sand.con 68 10 Fill the “sg” attribute with the Assign Value method Assign a specific gravity of 0.00 to all blocks above the topography “topo1.dtm” 69 11 Fill the “sg” attribute with the Assign Value method Assign a specific gravity of 1.68 to all blocks below the topography “topo1.dtm” and above “weath_ew1.dtm” 70 12 Fill the “sg” attribute with the Assign Value method Assign a specific gravity of 2.11 to all blocks below “weath_ew1.dtm” and above “weath_fresh.dtm” 70 13 Fill the “sg” attribute with the Assign Value method Assign a specific gravity of 2.46 to all blocks below “weath_fresh.dtm” 70 14 Fill the “sg” attribute with the Assign Value method Assign a specific gravity of 2.9 to all blocks in the ore solid “bif1.dtm” 70 15 Remove all graphical constraints and then constrain the block model below the topo1.dtm 71 16 Fill the “Gold” attribute with the Inverse Distance2 estimation method 72 17 Create a Block Model and Report the following: 78 • Average weighted gold grade 78 • Average weighted specific gravity 78 • Tonnage (multiplication factor = SG) 78 • Organized by bench (800,1000,10) 78 • Choose one of the available formats (.csv; not; htm; rtf; pdf) 78 • Constraints: Inside ore 3DM (bif1.dtm, qpy1.dtm,sand.dtm) 78 2/83 BLOCK MODELLING OBJECTIVES • • • • To become familiar with Surpac’s Block Modelling module and the concept of block modelling To learn to fill a block model from drillhole data from the geological database To learn to constrain a block model to filter out specific blocks To learn to report volume, tonnage, & grade from a block model FILES USED Files used in this lab exercise are found in the following folder: C:\GEOLOGY|BLOCKMODEL\DATA C:\GEOLOGY|BLOCKMODEL\ADVANCED_BM (for the advanced tutorial) DISCUSSION The Block Model is a form of spatially-referenced database that provides a means for modelling a 3-D body from point and interval data such as drillhole sample data, however it is interpolated values rather than true measurements.It is a method of estimating volume, tonnage, and average grade of a 3-D body from sparse drill data Previous history of block model had limitations to the block size and the resolution was restricted to 512 blocks Ver 5, the block model now has no limitations and is restricted only by your computer hardware A Block Model consists of cells of a specified size which at the core of the block centre contain a a centroid at which all the data is stored in an attribute ie Grade, sg, rock type This centroid point is what all data is reported on If you constrain your data, ie by pit design, the centroid point must lie within the constraint to be used within the calculation The effect of this on volumes if you have large parent sized blocks Generally the law of averages mean that the volume should be relatively accurate, however that is not always the case with some particular deposit geometries This is where sub-blocking and partial modeling can further refines your volume and reporting values Partial modeling checks the percentage of the centroid and writes this percentage of the block inside to an attribute This gives you a more refined volume for reporting Discuss: Block Size What will the model be used for Sub-blocking – governed by~1/4 of drill spacing Effect on Data Integrity 3/83 Flowchart for Simple Use of Block Modelling 4/83 The Block Model comprises of a number of components Model Space 3D coordinates spatially define the model extents Minimum Northing (Y), Easting (X) and Elevation (Z) Maximum Northing (Y), Easting (X) and Elevation (Z) User Block Size Schematic diagram showing how a block model space is defined Block size used for interpolation and reporting Sub-blocking Sub blocking is a method used by the Surpac block model to allow greater precision when applying geometric constraints (surfaces, solid models etc) to the model Allowing sub blocking allows the model to divide a user block (defined above) into smaller blocks, which will then be used in calculations All calculations are performed relative to the User block Centroid None No sub-blocking is applied to the model The largest and smallest interpolated block is the User Block Standard Sub blocking Standard sub blocking simply divides the parent block in half in all three dimensions This creates child blocks (always) This method of sub blocking is used widely when your deposit does not need smaller blocks in one (or two) particular directions 5/83 Variable Sub Blocking Variable sub blocking allows you to stop sub blocking in one or two directions, while still progressing in the other directions For example, if you have a user block size of 8x8x8m, standard sub blocking will allow minimum block sizes of 4x4x4, 2x2x2 and 1x1x1 (etc) However, using variable sub blocking, it is possible to have minimum block sizes of 4x4x2, 4x4x1, or even 4x2x1 This method allows you to get much finer resolution in one direction, without having to create potentially large numbers of blocks in the other two directions This method of sub blocking is particularly useful when modelling thin-seam deposits, as you can effectively model the "thin" direction, while still having fairly large blocks in the other two directions This saves a lot of memory by creating a smaller number of blocks, but still manages to model the resource very well Attributes The properties of the model space that are to be modelled are termed attributes These attributes may be nominal, ordinal, interval or ratio measurements expressed as numeric or character data Attributes may also be calculated from the values in other attribute fields, for reporting and visualising Constraints This is the engine of the block model Constraints are the logical combinations of spatial operators and objects that may be used to control the selection of blocks from which information may be retrieved and/or into which interpolations may be made Sub-celled Block Model A user block size is specified A minimum block size is specified When applying constraints, Surpac applies a “centroid rule” Blocks are sub-celled along the egde of the constraint If the centroid of the parent or of the sub-block is “inside” a constraint, the entire sub-block or parent block cell volume is reported, or a value is interpolated 6/83 Schematic diagram showing a constrained block model with parent blocks and sub-blocks NOTE: when Surpac is estimating values for a sub-celled block, the value is estimated on the original parent centroid and assigned to the sub-celled “inside” the constraint 7/83 Blocks and Attributes Records in the Block Model are related to blocks These are cuboid partitions of the modeled space and are created dynamically according to the operations performed on the Block Model Each block contains attributes for each of the properties to be modeled The properties or attributes may contain numeric or character string values Every block is defined by its geometric centroid and it’s dimensions in each axis Blocks may be of varying size defined by the user once the block model is created Figure 1: Block model of oil sands coloured by attribute values (bitumen) 8/83 Constraints All Block Model functions may be performed with constraints A constraint is a logical combination of one or more spatial objects on selected blocks Objects that may be used in constraints are plane surfaces, DTM’s, Solids, closed strings and block attribute values Constraints may be saved to a file for rapid re-use and may themselves be used as components of other constraints Blocks meet a constraint (e.g.: below a DTM as in the figures below) if its centroid meets that constraint This is true even if part of the block is above the DTM Figure 2: Unconstrained block model in relation to a DTM surface Figure 3: Same block model as in Figure but constrained by topography (DTM) 9/83 Estimation Once a Block Model is created and all attributes defined, they must be filled by some estimation method This is achieved by estimating and assigning attribute values from sample data which has X Y Z coordinates and the attribute values of interest The estimation methods that may be used are: Nearest Neighbour Inverse Distance Assign block values using an Inverse Distance estimator Assign Value Assign an explicit value to blocks in the model Ordinary Kriging Assign block values using Kriging with Variogram parameters developed from a Geostatistical study Indicator Kriging Functions concerned with a probabilistic block grade distribution derived from the kriging of indicators Assign from String Assign data from the description fields of closed segments to attribute values of blocks that are contained within those segments extended in the direction of one of the principal axes (X, Y or Z) Import Centroids Assign block values from data in a delimited or fixed format text file Assign the value of the closest sample point to a block 10/83 Fill Block Model with SG Values 10 Fill the “sg” attribute with the Assign Value method Assign a specific gravity of 0.00 to all blocks above the topography “topo1.dtm” a From the Block Model menu, choose Estimation, Assign value b Fill the subsequent forms as follows: 69/83 11 Fill the “sg” attribute with the Assign Value method Assign a specific gravity of 1.68 to all blocks below the topography “topo1.dtm” and above “weath_ew1.dtm” 12 Fill the “sg” attribute with the Assign Value method Assign a specific gravity of 2.11 to all blocks below “weath_ew1.dtm” and above “weath_fresh.dtm” 13 Fill the “sg” attribute with the Assign Value method Assign a specific gravity of 2.46 to all blocks below “weath_fresh.dtm” 14 Fill the “sg” attribute with the Assign Value method Assign a specific gravity of 2.9 to all blocks in the ore solid “bif1.dtm” 70/83 Display the block model by SG Attribute 15 Remove all graphical constraints and then constrain the block model below the topo1.dtm Colour display the block model on the SG attribute by selecting Block Model | Display | Colour By Attribute View the new attributes and values created above by selecting Attribute | View attributes for one block and then select a block 71/83 16 Fill the “Gold” attribute with the Inverse Distance2 estimation method Use the following estimation parameters: For QPY1.DTM ore solid I Composite file = cmpq1.str II Maximum search radius = 100m III Maximum vertical search distance = 9999 IV Bearing of major axis = 40 V Plunge of major axis = VI Dip of semi-major axis = 42 VII Anisotropy Ratios ii major / semi-major = iii major / minor = 10 VIII Constraints: Inside 3DM (qpy1.dtm) IX Ellipsoid Origin: Y:7260 X:1560 Z:900 For BIF1.DTM ore solid X Composite file = cmpb1.str XI Maximum search radius = 100m XII Maximum vertical search distance = 9999 XIII Bearing of major axis = 50 XIV Plunge of major axis = XV Dip of semi-major axis = 55 XVI Anisotropy Ratios iv major / semi-major = v major / minor = 10 XVII Constraints: Inside 3DM (bif1.dtm) XVIII Ellipsoid Origin: Y:7240 X:1670 Z:870 For SAND1.DTM ore solid XIX Composite file = cmps1.str XX Maximum search radius = 100m XXI Maximum vertical search distance = 9999 XXII Bearing of major axis = 27 XXIII Plunge of major axis = XXIV Dip of semi-major axis = XXV Anisotropy Ratios vi major / semi-major = vii major / minor = 10 XXVI Constraints: Inside 3DM (sand1.dtm) XXVII Ellipsoid Origin: Y:7335 X:1760 Z:1000 72/83 EXAMPLE: For QPY1.DTM ore solid Fill the “gold” attribute with Inverse Distance2 estimation method Use the following estimation parameters: I Composite file = cmpq1.str II Maximum search radius = 100m III Maximum vertical search distance = 9999 IV Bearing of major axis = 40 V Plunge of major axis = VI Dip of semi-major axis = 42 VII Anisotropy Ratios viii major / semi-major = ix major / minor = 10 VIII Constraints: Inside 3DM (qpy1.dtm) IX Ellipsoid Origin: Y:7260 X:1560 Z:900 a From the Block Model menu, choose Estimation, Inverse distance b Fill the subsequent forms as follows: Please note that the above form specifies source data In this case the gold grades are contained in the file cmpq.str in the second description field (D1) Feel free to open this string file and from the Inquire menu use Point Properties to view the description information contained in the D fields of each sample point 73/83 Select the Ellipsoid Visualiser button to view the ellipsoid To gain a visual representation of your ellipsoid save it by entering a string file name and string file origin coordinates Select save now prior to applying the form 74/83 Once you have viewed the ellipsoid, click on the Apply button Then click on the Apply button to move to the next stage of setting up the model filling Enter the inverse distance power to be used for the filling, and at the bottom of the form, make sure the debug output report and constraint option is ticked Click on the Apply button to be taken to the constraint form • Descretisation points If you leave these fields at 3, and 3, each user block in the model is subdivided into 27 subblocks and the grade estimated is at the centroid of each of the sub-blocks The mean of the grades for the 27 sub-blocks is then calculated and this is the grade assigned to the block This obviously increases processing time compared to x,y and z being set to 1).Using inverse distance there is often no appreciable benefit in making these extra calculations On the form, make sure you select to keep the blocks that are partially in the constraint This will keep all block that have a small part of the block inside the constraint, even if the centroid is outside the constraint 75/83 Once the filling has been completed you will be presented with a report which will summarise the filling parameters *Use the Inverse Distance method to fill the block model for the BIF and SAND zones Using the following estimation parameters: For BIF1.DTM ore solid X Composite file = cmpb1.str XI Maximum search radius = 100m XII Maximum vertical search distance = 9999 XIII Bearing of major axis = 50 XIV Plunge of major axis = XV Dip of semi-major axis = 55 XVI Anisotropy Ratios x major / semi-major = xi major / minor = 10 XVII.Constraints: Inside 3DM (bif1.dtm) XVIII Ellipsoid Origin: Y:7350 X:1840 Z:1000 For SAND1.DTM ore solid XIX Composite file = cmps1.str XX Maximum search radius = 100m XXI Maximum vertical search distance = 9999 XXII.Bearing of major axis = 27 XXIII Plunge of major axis = XXIV Dip of semi-major axis = XXV Anisotropy Ratios xii major / semi-major = xiii major / minor = 10 XXVI Constraints: Inside 3DM (sand1.dtm) XXVII Ellipsoid Origin: Y:7335 X:1760 Z:1000 76/83 Remove all graphical constraints and then constrain the block model by qpy_bif_sand.con Colour display the block model on the gold attribute by selecting Block Model | Display | Colour By Attribute View the inverse distance estimation in the gold attribute by selecting Attribute | View attributes for one block and then select a block 77/83 Create a Block Model Report 17 Create a Block Model and Report the following: • Average weighted gold grade • Average weighted specific gravity • Tonnage (multiplication factor = SG) • Organized by bench (800,1000,10) • Choose one of the available formats (.csv; not; htm; rtf; pdf) • Constraints: Inside ore 3DM (bif1.dtm, qpy1.dtm,sand.dtm) a From the Block Model menu, choose Block model, Report b Fill the subsequent forms as follows: To determine the overall grade of the deposit 78/83 Apply no constraints to give the average volume and tonnes for each grade range To determine the gold and grade in each solid (eg qpy1.dtm) then complete the form as follows: 79/83 Apply no constraints 80/83 If required the report can also break up the grade ranges for each bench to be mined, complete the form as follows: 81/83 82/83 83/83 [...]... extents, you can create your block model to cover this area Something you must keep in mind when creating your model is the smallest block size that you will allow In this exercise you will set the block model to have the smallest block at a size as shown in the table below User Block Y 10 X 10 Z 5 The smallest block size is going to be smaller than your user block size Smallest Block Y 10 X 5 Z 2.5 17/83... information within an individual block by clicking on it From the Block Model menu select the Display > View attributes for one block options Then click on any block that you can see on the screen You will see that the block has been given values for the attributes Click on several blocks to see that each has been given a value for the attributes 32/83 BLOCK MODEL REPORTING Report for entire deposit Based on... can be used to assign air blocks a specific gravity of zero 1 2 Open training.mdl Block Model | Estimation | Assign Value Nominate the attribute you wish to fill 3 Repeat this process for the constraints: Fresh, oxide and transitional 4 View this in graphics by constraining the block model by the ore zones qpy and bif and then colour the blocks based on numerical attributes BLOCK MODEL | DISPLAY | COLOUR... constraint form • Descretisation points If you leave these fields at 3, 3 and 3, each user block in the model is subdivided into 27 subblocks and the grade estimated is at the centroid of each of the sub-blocks The mean of the grades for the 27 sub-blocks is then calculated and this is the grade assigned to the block This obviously increases processing time compared to x,y and z being set to 1).Using... interpolation of blocks to QPY only Also, once the filling has been completed, save the block model View the model in graphics to validate that the gold values have been correctly filled 1 Choose Display - Display block model 2 Choose Display - New graphical constraint and nominate to view all blocks with a gold value >1 31/83 Now you can find out the information within an individual block by clicking... ``Save constraint to' 'box 24/83 FILLING THE BLOCK MODEL Several choices available: • • • • • • • Nearest neighbour (Assign the value from the closest sample point to the block centroid) Inverse distance (Interpolate block values using an inverse distance estimator) Assign value (Assign an explicit value to blocks in the model) Ordinary kriging (Interpolate block values using Kriging with Variogram parameters... expression NOT INSIDE When the word AND is used in a constraint combination, blocks that are common to the ANDed constraints will be selected When the word OR is used in a constraint combination, all blocks which related to either of the ORed constraints will be shown, not just those that are common Create a constraint file From the Block Modelling menu choose Constraints - New constraint file The ENTER CONSTRAINTS... make sure you select to keep the blocks that are partially in the constraint This will keep all block that have a small part of the block inside the constraint, even if the centroid is outside the constraint Once the filling has been completed you will be presented with a report which will summarise the filling parameters 29/83 Use the Inverse Distance method to fill the block model for the QPY zone Down... creation of the block model 18/83 If required – make changes This will now be created and displayed in the status bar SAVE IT From the Block Model menu, select the Save option Once the model is saved you will see it displayed in the file manager on the left of you screen It is now possible to display the model in graphics 19/83 From the block model menu select the Display > Display block model option... making any changes 21/83 From the Block Model menu select the Attributes > New option You will create four attributes at a single time in this step Select Model Summary to view the results 22/83 SAVE the block model 23/83 CONSTRAINTS WITHIN A BLOCK MODEL Constraints are the logical combinations of spatial operators and objects and may be used to control the selection of blocks from which information may