1. Field of the Invention
The present invention pertains to an apparatus for obtaining samples of wellbore fluids, such as crude oils, and which may be actuated in the wellbore to trap a fluid sample in a chamber through which the fluid has been allowed to flow.
2. Background
The development of crude oil reservoirs containing relatively viscous fluids and the development of deeper wellbores which operate at higher temperatures and pressures has dictated the need for improvements in wellbore fluid sampling apparatus which are able to withstand such relatively high pressures and temperatures. Moreover, there has also been a need for sampling apparatus capable of trapping a sample of the wellbore fluid without improper filling of the sample cavity in the apparatus and without contamination of the sample when it is retrieved from the apparatus.
To this end, certain improvements have been developed in wellbore fluid sampling apparatus such as described in U.S. Pat. No. 4,766955 issued on Aug. 30, 1988 in the name of Steven G. Petermann and assigned to the assignee of the present invention. The apparatus described in the application is exemplary of certain improvements in wellbore fluid sampling apparatus for collecting samples of relatively viscous oils under moderate pressure and temperature conditions. However, it has further been recognized that an apparatus which permits throughflow of the wellbore fluid prior to trapping a fluid sample in the apparatus provides certain advantages and the need to provide such an apparatus which is capable of operating at relatively high pressure and temperature conditions with reliable operation has resulted in the development of the present invention.