Rafael Vasquez, 85543 W 180Th St APT 46, New York, NY 10033

5622223, Apr 22, 1997

Sep 1, 1995

8/522851

Rafael B. Vasquez - Katy TX

Haliburton Company - Houston TX

E21B 4900
E21B 4700

166264

This invention provides a closed-loop system for in situ testing of formation fluid conditions and for selectively collecting substantially mud filtrate free formation fluid samples at original formation conditions. The system contains an elongated member having a probe that is sealingly placed against the wellbore formation to withdraw formation fluids. A surface controlled pump controls the flow of a fluid from the formation into a flow line placed in the elongated member. A pressure sensor provides downhole hydrostatic pressure and differential pressure sensor provides difference in pressure across two fixed points across the flow line. A temperature sensor and resistivity device are utilized in a conventional manner to respectively provide downhole fluid temperature and the resistivity of the formation fluid. The system determines the density of the formation fluid in the flow line from the differential pressure and in response thereto controls the fluid flow into the flow line to selectively collect the formation fluid samples that are substantially free from any mud filtrates while maintaining the fluid pressure above the bubble point pressure of the fluid. This invention provides a method for retrieving and collecting formation fluids from a zone of interest in a wellbore at the original formation conditions.