Introduction - Cased-Hole Log Analysis and Reservoir Performance Monitoring - page 2

Completion Problems
Completion problems may arise due to the mechanical state of the completion
string. Relatively simple measurements can be made to pinpoint such problems as:
Casing leaks
Packer leaks
Bad cement jobs
Plugged perforations
Corrosion
Many different tools and techniques may be used in the search for mechanical
problems and each will be discussed later in the text.
Production and Injection Profiles
An important diagnostic tool for both producing and injecting wells is the ability to
derive fl ow profi les from production logging devices. These devices seek to answer
the questions, (1) How much of what comes from where? and (2) How much goes
where? In most wells a production or injection profi le will be a surprise to the opera-
tor. In few cases does the fl ow come from, or go to, the expected reservoir unit.
Gauging Treatment Effectiveness
Finally, productive logging can be used to establish the effectiveness of well treat-
ments such as frac jobs and/or secondary and tertiary fl oods.
Petroleum Reservoirs
In order to place these production/injection problems in perspective and illustrate
the conditions that may arise during the life of a well or fi eld, it is worthwhile to
recall the four principal types of petroleum reservoirs:
1. Solution-gas drive
2. Gas-cap expansion
3. Water drive
4. Gravity drainage (segregation)
Gas problems may be expected with solution-gas drive and gas-cap expansion
reservoirs as illustrated in Figs. 1.1 and 1.2 . Gas problems may be caused by: