Major oil companies maintain core testing laboratories equipped to evaluate
the oil producing potential of a given oilfield based on the testing of exploratory
oil cores. Test results will reveal the quantity of oil that will come out of
an oilfield; and whether the oilfield is worth developing once it is discovered.
An oil core is a sample of the oil-bearing rock obtained from
exploratory drilling. The recovered core is subjected to down-hole temperatures
and pressures, and the resulting flow of fluids through it is measured. Oil
producing rock typically has the density and porosity of cement, so the study
of fluid flow in these materials requires the ability to measure small
differential pressures (just a few psi) at very high static pressures (several
The oil core is prepared by fitting it into a special jacket that is heated
to down-hole temperature. A special high pressure pump forces brine through the
core. The static pressures around the core are typically 5000 to 10,000 psig.
The core has sealing packers placed along its length at regular
intervals. A Validyne variable reluctance transducer DP 303 is plumbed between
the packed-off sections so that the pressure drop through the core rock as a
function of flow rate can be measured.
Available from Bestech Australia, Validyne differential pressure sensors
feature a full scale of as little as 5 psi of differential pressure in several
models, while both ports of the transducer are at a static pressure of 10,000
A carrier demodulator displays the differential pressure digitally in
engineering units. The relationship between flow and pressure drop is a measure
of the permeability of the oil producing formation, and is used to determine
the amount of oil that can ultimately be brought into the well bore from the