In th past, it was common for 60% of oil in a reservoir to be
unrecoverable although today that figure has fallen to slightly less
than 50% with horizontal drilling. However, the figure remains 60%
for older wells.
20% of US oil comes from so-called "Stripper wells", wells producing
less than 10 barells/day. Current regs say that if a well isnt
producing for a certain length of time that it must be plugged and
abandoned. If this happens, the remaining oil is lost forever because
it will never be economically feasible to re-drill the well.
Generally, it isnt feasible o take an older well and do horizontal
drilling to produce more because the reservoir is so depleted that you
would not recover your money. This means that the only way to get the
oil out is to continue to pump at ever reduced rates. Often, the cost
of producing the oil is so high that the operator, ussually and
independent person is forced to plug and abandon rather than simply
shut the well down and wait till prices go up. Clearly, what is
needed is new regs that allow an operator to wait for a long time
until prices rise enough to make pumping economically feasible,
perhaps years. A classic case of regulation causing a loss of oil for
INDEPENDENT operators ((majors rarely operate stripper wells).