Recent advances in computer technology have allowed ever larger computer circuits to occupy ever smaller physical dimensions. As a result, it is now possible to include a large body of detailed log analysis logic on a small Read-Only-Memory chip (ROM). The Log Analysis ROM, which weighs 7 grams and occupies less than 7 ccs, plugs into a widely used programmable pocket calculator. The Log Analyst is thus afforded easy access to a library of complex interpretation routines equivalent to those found heretofore only on mainframe computers.

This paper describes the evolution of the log analysis ROM from a technical viewpoint including the general procedure for building a ROM and then details the architecture of the log analysis routines available. Methods used to make the system "user friendly" are described including the plain english prompting for input, computation options, and formatting of outputs together with audible cues.

Suggestions are offered to the practical log analyst for both wellsite and office formation evaluation using the log analysis ROM and related calculator and peripherals. These include shaly sand analysis, complex lithology solutions, dip and bore hole geometry related transforms, cased hole evaluation, and many utilities such as solution resistivity and concentration conversions.

The paper is illustrated with examples of the application of the Log Analysis ROM to practical formation evaluation problems.

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