SI systems

Mr. Timo Makinen's letter (OGJ, Nov. 1, 1999, p. 8) caught my eye rather quickly.

The statement that "the US, Liberia, and some other smaller nation" are the only countries that do not use SI units is simply not true, as I can say based on 40 years' experience in the oil industry.

Let's start with Canada. Here the SI units were introduced essentially "by decree" in the late 1970s. At present, the units used in the field are a mixture of the old and the new. SI units have an advantage over the "field" units, if one sticks to the standard SI units, for example "m3/s" for production rate. But that (like several other SI units) is unwieldy for everyday use (e.g., the world oil production is "only" 140 m 3/s).

So people talk in terms of "cubes per day," and the advantage of SI units starts to get lost. A gas production rate of 1 MMcfd is expressed as "28E+03 cubes per day," where the person would typically spell out "E+03." At one time, I, in vain tried to introduce "dam3/day" to avoid saying all that, but it never caught on.

Then there's permeability-darcy is still more commonly used than "micrometre squared"; some people who use it are not even sure whether the conversion to "metre square" is 10-6 or 10-12. (Careful about the spelling of "metre" for the purists in this country!)

This goes on and on.

From my experience, about the only country which is trying to use SI units in oilfield practice is Canada and maybe pockets of people in China and maybe even Libera.

In the US, standard SI units are used in pure sciences and other areas. When it comes to oilfield practice, the US has a more sensible approach, and the transition is slower to help out many other countries that still use field units, or a mixture. This includes Middle East and North African countries.

In South America, a mixture of units is used; for example, in Venezuela, field units are used, except that sometimes "metro" is used in place of "foot." In Mexico, and some other countries, things are not terribly helpful, when you see pressures in kg/cm2, or in Europe, you run into "bars." The US, being a freer country, is merely adapting the SI system as it suits the needs of the users.