flows to the wellbore under its own pressure. As a result, most gas wells are
equipped only with chokes and valves to control the flow through the wellhead
into a pipeline. When wellhead pressure is less than the pipeline pressure, a
compressor is installed to boost the low-pressure gas into the pipeline.
of crude oil is more complicated. Crude oil has larger molecules and moves
through rocks less easily. The percentage of the oil in the reservoir that can
be produced naturally, called the recovery factor, is determined by a large
number of elements. These include the density of the oil (how heavy it is), the viscosity (how sticky it is), the porosity and permeability of the rock, the
pressure in the oil reservoir, and the pressure of other fluids in the
reservoir, such as gas and
Petroleum Communication Foundation. Our Petroleum Challenge: Exploring Canada's Oil and Gas Industry, Sixth Edition. Calgary: Petroleum Communication Foundation, 1999. With permission from the Centre for Energy.