Rock Compressibility System is designed specifically to demonstrate the reduction in
pore volume that occurs within the pore space of oilfield reservoirs during pressure
depletion to students. This pore reduction is the result of a change in balance
between the overburden pressure (caused by weight of the overlying sediment) and
the internal reservoir pressure normally estimated by hydrostatic gradient. The
pressure difference between overburden and internal pore pressure is called the
"Effective Overburden Pressure," or EOP.
During pressure depletion operations, the
internal pressure of the reservoir drops. Since overburden pressure remains constant,
the EOP is increased. The effect of increasing EOP is to reduce the bulk volume
of the reservoir while the sand grains within the pore spaces expand because of
the internal pressure drop. These two volume changes tend to reduce the pore space
and therefore, the porosity of the rock. Although these values are small, they become
important in reservoir calculations in deciding the economics of an oilfield.
Equipment includes a constant temperature air bath, overburden system, hydrostatic
core holder with necessary valves and plumbing with transducers and a digital readout
to monitor the internal and external pressures, high-pressure hand pump, vacuum
pump, the necessary equipment to encapsulate core samples before testing, and complete
operation and maintenance instructions. Specify voltage and frequency.