Page 373 - Standard Handbook Petroleum Natural Gas Engineering VOLUME2

Enhanced Oil Recovery Methods 339

the thermal efficiency. Steamf looding is possible in thin formations if the
permeability is high. High permeabilities (>200 md or preferably >500 md) are
needed to permit adequate steam injectivity; transmissibility should be greater
than 100 md ft/cp at reservoir conditions. Depths shallower than about 300 ft
may not permit good injectivity because the pressures required may exceed
fracture gradients. Heat losses become important at depths greater than about
2,500 ft. and steamflooding is not often considered at depths greater than 5,000
ft. Downhole steam generators may have potential in deeper formations if
operational problems can be overcome.

Graphical Representation of Screening Guides

From the summary of screening guides in Table 546, the viscosity, depth,
and permeability criteria are presented graphically in Figures 5-176 to 5-178.
The figures have some features which permit the quick application of screening
criteria but they cannot replace the table for detailed evaluations. In a sense,
the figures present a truer picture than the table because there are few absolutes
among the numbers presented as screening guides in the tables. Different
authors and organizations may use different parameters for the same process,
and most of the guidelines are subject to change as new laboratory and field
information evolves. In field applications, there are exceptions to some of the
accepted criteria, and the graphs accommodate these nicely. The “greater than”
and “less than” designations of the tables can also be displayed better graphically.

0
U U U
1,1111, I I 1111111 I I 1111111 I I I111111 I 1
HP GAS

SUR FACTA NT

POLYMER

ALKALINE

IN- SITU

STEAM

Figure 5-176. Viscosity ranges for EOR processes [386].