A method and apparatus for removing downhole well debris involves an elongate string operable to pump the debris from a well into the string. A pumping portion of the string includes a hollow piston with a hollow, splined piston rod fixed to the upper portion of the string, above the pumping portion,...http://www.google.fr/patents/US4478285?utm_source=gb-gplus-shareBrevet US4478285 - Method and apparatus for removal of downhole well debris
Method and apparatus for removal of downhole well debris
