Slide rules to freeware

Aug. 14, 2000
Your high-interest article "Oil scout humor" (OGJ, July 24, 2000, p. 17), might well become a regular feature.

Slide rules, nomograms, and logarithm tables were standard productivity tools before the mid-1960s.

Mechanical calculators that could handle floating-point decimals became available in the 1960s. Electronic scientific and programmable calculators displaced this technology in the 1970s.

In the 1970s and early 1980s, OGJ published numerous engineering programs that would run on programmable calculators. But one laborious task was to accurately key in steps that often numbered over 500-even in reverse Polish notation. Bar code options eventually helped with input.

Personal computers began displacing programmable calculators in the 1980s, initially with Basic programs and then with spreadsheets. Many OGJ articles described these calculations and let subscribers obtain free copies of the computer programs for executing them.

Initially subscribers had to send in a blank floppy disk for a copy of the program, but more recently, e-mail attachments have proven to be more efficient for distributing them.

Freeware on the net

Freeware on the internet now affords another source for obtaining computer programs that can improve an engineer's productivity.

Ryder Scott Co., Houston, a petroleum consulting company, has made available on its website,, six programs that can be downloaded for free. These programs use many of the "bells and whistles" of newer operating and spreadsheet software. In time, it plans to add more programs to its download list.

Ron Harrell, Ryder Scott CEO, said, "These programs are not designed to be substitutes for the more sophisticated suite of evaluation tools used by Ryder Scott for complete in-depth analyses. However, the six freeware applications constitute a suite of software tools that will enable a competent evaluator to prepare a reserves estimate for most properties."

Programs available

Ryder Scott currently offers these programs:

  1. ResGAS, for computing a gas stream's critical pressures and temperatures, specific gravities, and heating values.
  2. Reservoir solutions modules, for solving common problems that require the calculation of oil and fluid properties, such as pseudocritical properties, compressibilities, and formation-volume factors.
  3. QuickLook, for screening prospect economics, evaluating workovers and recompletions, and running preliminary lending economics.
  4. Material-balance, for calculating original gas in place; and estimating ultimate recovery, bottomhole pressure vs. cumulative gas production, and pseudocritical temperature and pressure properties from gas gravity while adjusting for contaminants.
  5. Flowing pressure analysis, for evaluating the performance of gas production or gas injection wells and calculating gas well flowing bottomhole pressures.
  6. LogWizard, for analyzing density-neutron or sonic logs with either of two templates and calculating the following petrophysical values based on user-selected methods:
  • Shale content, applicable to consolidated and unconsolidated formations.
  • Total porosity, using arithmetic-average or the sum-of-squares method.
  • Effective porosity, using arithmetic-average or the sum-of-squares method.
  • Formation water saturation, using Archie or modified Simandoux algorithms.

James Latham, Ryder Scott vice-president, developed these "add-in" visual basic programs that require Microsoft Excel 97 or newer spreadsheet software. The programs can run in either a Microsoft Windows or NT environment.

Latham indicates that most problems users have encountered with these downloads have been with the installation. He says that, depending on the Excel version and the operating system, the Excel start directory may be in a different place, unfamiliar to the user. Also, he says that other problems may result from the user not having downloaded all of Microsoft's service packs that correct bugs in its software.

Latham indicates that the programming code is protected, but he will furnish the user a copy, if requested.

As an added step to help users, Ryder Scott plans to offer free training sessions on running the freeware and understanding its limitations.


Users do need to obtain a password from Ryder Scott before they can run the programs. This requires them to fill out a form with their e-mail address and other information. But, according to Mike Wysatta, Ryder Scott business development manager, the company has no plans on doing mass mailings or sending out "spam" e-mails to program users.

He says the e-mail addresses provide a way for Ryder Scott to inform users of program updates, such as the one planned for its material balance program. According to Wysatta, Ryder Scott has used the e-mail addresses only once in 2 years to solicit feedback on the programs. It may decide to send its quarterly newsletter to the user, but Wysatta says users will have the option of removing their addresses from the mailing list.

He added, "Besides any altruistic motives, our business-development goal is to get recognition and publicity in the marketplace through these freeware releases. Our logo is displayed above the working templates. If there is any catch, that's it, but enduring a little unobtrusive advertising is not much of a price to pay for these highly beneficial programs."