Cased-Hole Logging Environment - Cased-Hole Log Analysis and Reservoir Performance Monitoring - page 13

Combinations of techniques can be used to ensure that the tools get to where they
need to be and the data is recorded. These can be classifi ed as:

• Conventional wireline : Tool string is gravity fed to TD and data is recorded in

real time as the wireline conductor cable is reeled up.

• Wired coiled tubing : Tool is “pushed” down-hole with coiled tubing and data is

recorded in real time as the coiled tubing is retrieved.

• Assisted wireline : Tool string is equipped with a motorized “tractor” that pulls

the tool string to the end of the well. Data is recorded as the tool is extracted from
the well in a conventional manner.

• Wireless conveyance : Tools are “pushed” via plain coiled tubing or heavy “slick

line” and data is recorded in a digital memory format for downloading later when
the tool is retrieved back at surface. In this case depth control is managed by
recoding the logging signals as a function of time which can then be keyed to a
known depth vs. time recording made at surface as the coiled tubing or noncon-
ducting line is recovered.

Figure 2.3 illustrates a motorized tractor that can be added to the lowered
production logging string and activated to mechanical crawl along the low side of
the casing to pull the tool string to the required depth even in horizontal holes.
The spring loaded drive wheels can be activated from surface to open up and engage
the pipe walls and then can be turned as drive wheels to propel the logging tool
string along the well path.

Fig. 2.3 Wireline tractor for production logging in highly deviated pipe. Courtesy Welltec ®