Valve for use in a test string for the investigation of formations in a bore hole

摘要

An improved bypass valve for use with an oil well testing string is disclosed which includes a check valve means for allowing fluid flow from the interior of the test string to the well annulus when the interior pressure exceeds the well annulus pressure. The bypass valve further includes a blocking means which blocks interior communication with the check valve means when the well annulus pressure exceeds the string interior pressure. A delay means is included which delays the action of the blocking means for a predetermined length of time. The improved bypass valve is intended for use in a testing string for an oil well, and is to be placed in the testing string below a normally closed tester valve and above a seal assembly for insertion into sealing engagement with a preset production type packer. The time delay allows the seal assembly to be removed from the packer after the packer location is determined without activating the blocking means to move to its locked closed position.