Introduction - Cased-Hole Log Analysis and Reservoir Performance Monitoring - page 3

Well Bore

Free gas production

GAS CAP

OIL ZONE
Dissolved gas
in produced oil.

Fig. 1.1 Gas produced with oil from associated gas-cap and solution in the oil. Reprinted with
permission of the Petroleum Engineer International from Cesak and Schultz (1956)

Well bore

Gas cap

Oil zone

Fig. 1.2 Coning of free gas into a well across bedding planes. Reprinted with permission of the
Petroleum Engineer International from Cesak and Schultz (1956)

Gas breakthrough
Inadequate pressure maintenance
Production rate too high
Formation pressure below bubble point
Incorrect completion

Water problems may be expected with water drive and gravity drainage reservoirs
as illustrated in Figs. 1.3 , 1.4 , and 1.5 —and can be traced to the following causes:

Coning of water
Permeability problems
Completion problems