Patent ID: 6371204
Filing Date: 2002-04-16
Classification: E21B

Abstract:
An apparatus for detecting fluid transfer between an underground formation and a wellbore extending below a surface during drilling of said wellbore using a drilling rig, a trip tank fluidly connected to the interior of said wellbore, and a drill string positioned at least in part by said drilling rig and extending at least in part into said wellbore, said apparatus comprising:(a) an acoustic sensor for measuring changes in the depth of a string liquid level within said drill string, said acoustic sensor mounted proximate to said surface; (b) a string displacement sensor for measuring the changes in the position of said drill string; (c) an injected liquid sensor for measuring changes in liquid level in said trip tank; (d) means for calculating changes in liquid and drill string volumes within said wellbore using at least in part said measured changes in string position, tank liquid level, and string liquid level; and (e) means for totaling said calculated volume changes.