622 



Subsurface Geologic Methods 



always help the engineer evaluate subsequent work-over possibilities. One 

 of the earliest engineering uses of core-analysis data was for evaluating 

 and planning secondary oil recovery by water flooding. Today, in addi- 

 tion to that same use, it also aids in evaluating gas cycling and pressure 

 maintenance by gas-injection projects. Probably the latest and perhaps 

 one of the most valuable uses of modern core-analysis data for an engineer 

 is to provide basic data for reservoir-analysis studies. 



CI RCULATION HOLES 



BACK PRESSURE VALVE OPEN 



DRILL BARREL HEAD 



CORE 

 TUBE HEAD 



BACK PRESSURE VALVE CLOSED 



fLUI D PORTS 



BALL RELIEF VALVE BALL RELIEF VALVE 



DRILL Barrel 



DRILL BARREL SHOE 



CORE TUBE 



FINGER TYPE TRAP RING 



CORE TUBE TRIMVIE.R SHOE 



Figure 322. Cable-tool core 

 barrel in upstroke posi- 

 tion. 



DRILL BARREL SHOE 



Figure 323. Cable-tool core 

 barrel in downstroke posi- 

 tion. 



