Version 1.1 (c) 2011 by Markku Pirttijärvi.
The PETROCK program is used to interpolate irregularly sampled petrophysical data, e.g. density or magnetic susceptibility, or geochemical data (K, Zn, Au) on an even grid. The two main purposes of the PETROCK program are: a) to create improved maps of the geographical distribution of petrophysical parameters, and b) to create initial 3-D models for potential field modeling and inversion. As a by-product the program gives statistical information for each lithological unit.
The program uses moving window strategy in which the gridded values are estimated from the nearest sample points using the mean and/or the inverse distance weighted mean. The program also uses the digital geological (lithological) maps to provide additional background weights for points inside the same lithological unit. A limiting condition can be defined to remove outliers from the petrophysical data inside the investigation area or inside each lithological unit. If the limiting condition is based on the mode (largest class) or the median the gridding can yield the base level of the lithological units better than if the mean of the samples was used. Thus, in areas where sampled data are not available the PETROCK gridding should be more reliable than normal interpolation would be. In addition, rock rejection rules can be defined that either reject certain rock types from certain lithological unit or allow only certain rocks in certain lithological unit.
The petrophysical data are read from column formatted text files. The polygon information of the geological maps is read from text files that have been converted from Mapinfo MID/MIF files into a special LIT file format using the MIF2BNA. Input processing parameters are given via keyboard or using a separate script file (PETROCK.INP). Output data are saved into column formatted text files.
Download the PETROCK_DISTRO.ZIP package (9.3 MB).
The distribution file contains a short description file, user's guide, an example dataset (taken from the Rock Geochemical Database of Finland, version 1.1). Two auxiliary programs MIF2BNA and PETRAUS, are provided for the manipulation of digital maps (saving MapInfo MIF/MID files in LIT-format) and petrophysical/geochemical data (redefining the lithological codes of the sample data).
User's guide PETROCK_GUIDE.PDF (930 kB).
Initial public release version 1.1 in November 2011