Bottom Hole Compression

Bottom Hole Compression or Conventional drill stem tests use compression-set packers set above the formation, with tail pipe (drill collars or hevi-wate drill pipe) below the packers to the bottom of the hole. Placing weight on the tool string compresses the packers creating a seal before hydraulic valve opens, allowing the formation to flow.

The formation is flowed for a specified time period, after which the drill pipe is rotated five turns to the right to close the shut-in tool for a specified shut-in period (build-up). Five more right-hand rotations opens the shut-in tool for a second flow. Five more rotations (total 15) closes the shut-in tool for a final build-up. The tubing/drill pipe contents can be reversed out of the string though the pump-out-sub before pulling up on the drill pipe to close the Downhole Sampler and release the compression packers.