GridSTAT is an integrated 3D geostatistical reservoir description and seismic inversion software designed for both PC and UNIX. It is often more economical and convenient to use PC Windows software. It is much easier to send the output to printers and plotters through Windows. A Windows Metafile (WMF), CGM file, or VRML file is easily created to insert the picture into Word, Power Point, or any other Windows applications. GridSTAT files are compatible between PC version and UNIX version.
GridSTAT has been designed for both specialists and beginners. The step by step approach makes it easy to use. Field tested default setup avoids common mistakes. For experienced users, there are many additional options and functions. Field operation geoscientists and engineers have been using GridSTAT to analyze data, to normalize data, to make cross sections, and to build 3D models. Results from GridSTAT have been verified by comparing with conventional work and by infill drilling successes.
1. Point and click and step-by-step user interface with context sensitive help
2. Basemap, data traces, histogram, cross section, cloud plot, 3D volumes
3. Data statistics table and data quality control table
4. Variograms, structure/stratigraphic, deviated wells, faults
5. Data filter, data transformation and calibration
6. Three-dimensional kriging, cokriging, conditional simulation, cosimulation
7. Seismic time depth conversion and inversion
8. Volumetrics calculation, geobody identification, export to flow simulation format.
1. The ">" symbol to the right of a label means that there is an additional menu that appears when the mouse is clicked on the label.
2. The ". . ." symbol to the right of a label means that there is an additional screen that appears when the mouse is clicked on the label.
3. Inactive buttons are "grey'd out"; that is, they are lighter than normal.
4. Pull down menus can be closed by either clicking outside the menu box or hitting the Esc key. The Esc key may also be used to close a panel or stop some operations.
5. Typing is in insert mode initially. Use the Insert key to toggle between insert mode (vertical bar cursor) and overtype mode (underscore cursor).
6. When the File pull down menu is not available, you may print the panel with Ctrl-F9 key combination.
7. When the cursor is resting on a button or an active field, there is usually a one-line explanation displayed.
GridSTAT is controlled by a macro (scripting) language. Macros can be written to perform tasks that are not in the current user interface. Macros should have extension JDF (Job Description File) and can be executed from the Tools pull down menu Macros button. Rerun files records actual user actions of pressing a button of changing the content of an edit field. Several rerun files are provided to demo the examples. If you want to record a rerun file, keep in mind that when you run the rerun, the program should be in the same state as when you recorded it, otherwise the sequence of actions may be different and the rerun may fail.
Macros (scripts) can be written to convert data or execute another program from GridSTAT. The User pull down menu is setup to execute macros Program1.JDF, Program2.JDF, and Program3.JDF etc.
Macros (scripts) can be written to execute GridSTAT from another program and pass data between GridSTAT and the hosting program.
For developers wanting to write interface with GridSTAT, documentations are available for writing GridSTAT macros (scripts). Fortran or C libraries are also available for reading or writing GridSTAT binary data files.
Seven "steps" are listed in a box on the right hand side of each panel:
Project
Import
DataQC
Variogram
GridOption
GridSize
GridOutput
The list of steps serves two purposes. First, the list is a guideline for the way in which a geostatistics study is typically done. That is, it is a list of tasks that one needs to carry out to develop a grid of, for example, porosity. The arrow indicates where you are on the list.
Second, clicking on any of the elements of the list will take you to that GridSTAT panel. Thus the list allows you to move anywhere in the program that you want to.
If desired, the steps display can be toggled on and off by going to the View pull down menu and clicking on Show Steps. When the steps box is turned off, the steps will be listed as a pull down menu.
If 1 Graph view option is on, the graph in view is the active graph.
If multiple graph view is on, either two or four graphs, the active graph is identified with a blue frame. A graph may be empty or may be a table.
Click to activate the area where a graph or table is to be placed. Click on Graph or Table. Click on name of graph or table to be added. If that graph already exists, you will be offered the option to remove it.
Click on Select >. Turn Pick Well on. Click the wells you want to select in the active graph. Click a selected well again to remove it from selection list. To remove all the selections, click on Select > and select ResetPick.
Correct data is essential for building a good model. Quite often more than half of the project time is spent getting the data right. GridSTAT has many functions to help users spotting problems in data, removing bad data, and normalizing data, etc. Hundreds of wells can be handled in a short time. Equivalent software usually assumes input data is correct.
GridSTAT can normalize baseline drift in SP log and steam-affected resistivity logs. Other data transform functions include automatic correction of mixed decimal porosity and percentage porosity data, calibration of data, etc.
Correct horizon markers are essential for building a good reservoir model. GridSTAT has many functions to help users quality control horizon markers. It can automatically generate a horizon marker from well logs. Users can adjust horizon markers based on well logs, and interactively add and modify horizon markers. Equivalent software requires correct horizon markers to start.
Cross section is commonly used to visualize the reservoir. GridSTAT provides a powerful set of functions for drawing cross sections. A cross section can be drawn along any locations in a 3D model. Multiple curves can be displayed. Well stick includes depth labels, perforations, and casing information. Cross section is displayed either as structure or as stratigraphic section. A stratigraphic section can be drawn hanging on any one marker, or flatterning a combination of the available markers. Deviated wells can be turned on and off. A side distance can be specified to project wells off the section. A predicted log trace can be posted (when a grid has been generated) for a new well or a well without the log. Horizon markers can be interactively edited on the cross section. Other options include equal distance section, well header posting, etc. Such capability is hard to find in equivalent software.
The cokriging and cosimulation approach in GridSTAT requires only one additional parameter: reliability or coefficient of correlation. The same type of data and the same variogram are used. No collocation is required. This approach is more practical and robust than some other approaches.
GridSTAT treats seismic data as traces (like logs at a location), not only as a grid.
Correct depth is essential for integrating seismic data with well data. GridSTAT has functions to quality check and adjust depth correlation between seismic data and well logs. Other equivalent software assumes seismic depth is correct.