Page 115 - Primer on Enhanced Oil Recovery

Gas flooding 105

Figure 10.9 CO 2 flooding projects in the former USSR.

Volume of CO 2 for additional oil production is usually estimated during the
planning stage. Roughly it is assumed that for every additional barrel of oil the
demand for CO 2 will be:
3
for secondary oil recovery of light oil at around 400 m (0.8 t) and for heavy oil this rises
approximately two times;
3
for EOR of light oil it is around 500 m .
Later in this chapter we will provide an equation for the demand evaluation
A reliable CO 2 supply source is very important, since the gas must be supplied
on a continuous basis in large volumes over long periods of time. It is expected that
the project will last more than 5 years as the reservoir processes take some time to
develop and the injection well spacing is usually significant. The gas used must
have a purity of 90% or more. If impurities, other gases, are present, such as meth-
ane or nitrogen in high quantities a higher injection pressure will be required to pro-
vide miscible displacement.
The best sources are natural gas formations of high pressure with a high degree
of purity. Usually such CO 2 natural formations are found in the search for oil and
gas. In the United States, the oil producing basins of Wyoming, Utah, Colorado,
and New Mexico have the largest reserves of carbon dioxide.
However, estimations show that currently known natural sources of high purity
can provide only less than 15% of the total demand. Natural gas processing plants
(for instance in Delaware and Val Verde basins in southwest Texas) produce signif-
icant amounts of carbon dioxide. In addition, all CO 2 exhausts from manufacturing
can be used at the of energy “hungry” installations such as oil refineries, cement,