PowerLog Statmin

Calculating Lithology, Mineralogy, Porosity

PowerLog® Statmin makes it easy to work with data that includes complex and varied minerals. It uses a probabilistic model to calculate lithology, mineralogy, and/or porosity and can easily adapt to the needs of the analyst. While PowerLog handles typical curves, Statmin hands any well log or computed curve that responds to lithology/mineralogy.

Statmin is based on a technique first presented at the 1988 Society of Professional Well Log Analysts Symposium and later reprinted in the June 1991 edition of World Oil in an article entitled "A Practical Approach to Statistical Log Analysis" by William K. Mitchell and Richard J. Nelson. Mr. Mitchell was instrumental in Statmin's development and continues to assist us with support.

Statmin solves balanced, over-determined, and under-determined models:

Over-determined models - More logs than necessary are used to calculate the mineral volumes. In this case Statmin will compute the answer that best fits all the logs by using the Maximum Likelihood Estimate of the mineral fractions.

Under-determined models - This is the more common case, where not enough logs are available to compute all the mineral fractions present at one time. Statmin provides the following techniques to address this problem:

• Sequential Models (Prior Matrix)
• Alternate Minerals
• Alternate Matrix
• Computed Data Input

Statmin uses linear response equations, which compute much faster than non-linear models. Non-linear solutions can be achieved through the use of computed curve inputs. For example, you can input SPHI (Hunt-Raymer) rather than DT. In addition to the computation of porosity and mineralogy, Statmin will output the reconstructed versions of all the input curves.

This picture shows the Statmin result with the computed lithology fractions in the right hand panel, and the input and reconstructed well log curves in the panels to the left of the lithology panel.