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Shale proportion can be calculated, based on either the gamma ray or the neutron and density porosity logs.
Calculation of Porosity
Porosity can be calculated using density, neutron, density/neutron, or sonic with and without correction for shale volume.
Shaly Sand Models for Sw Calculation
Sw model menu permit selection of Archie water saturation model (the default) and two shaly sand models, the Simandoux model and the dual-water model.
Hough Transform
The Hough transform is used for simultaneous solution of Archie equation constants and formation water resistivity.
Secondary Porosity
Secondary porosity is calculated as the difference between the total porosity (from density or neutron porosity) minus sonic porosity.
Moveable Hydrocarbon
Based on the assumption that the zone near the well is permeated with mud filtrate, the Archie equation is used to compute Sxo, the filtrate saturation of this flushed zone. Sxo is used to compute moveable and residual hydrocarbon saturations. PfEFFER generates a moveable oil plot consisting of bulk volume water, bulk volume fluid, and porosity. Difference between BVF and and BVW represents the moveable hydrocarbon saturation.
Lithological Analysis
Lithological analysis now includes two options in PfEFFER v. 2.0, one based on the RHOMAA-UMAA plot and the other allowing a more general selection of logs and system components. The general option allows user to compute up to six components based on up to five logs. Any log can be employed and the component selection is at the discretion of the user.
Zonation by Depth-constrained Cluster Analysis
Depth-constrained multivariate cluster analysis can be employed to segment the entire spreadsheet into subintervals based on user-specified set of logs. A hierarchical cluster (Ward's method) is used to produce subintervals that are as homogeneous as possible and distinct as possible from each other, in terms of their log characteristics. Option is useful in evaluating flow units and can be used as a blocking function.
Forward Modeling
Module implements equations developed by Pittman to predict values of rx, capillary pressure, and hydrocarbon column height for a range of water saturation values based on specific values of permeability and porosity.
Pay Flag Cutoffs
Pay flag cuttoff can be activated to add color to cells of selected variables used to determine pay (porosity, BVW, Sw, and Vsh) and to color cells in the pay column according to pay and non pay intervals.
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