Primary Cementing of Multiple Casing

Abstract

MARK A. CHILDERS· JUNIOR MEMBER AIME Recent work with controlled laboratory tests,' field experience and a new analytical approach indicate that casing centralization, pipe movement and relative rheolog-ical properties between the mud and cement (yield point and density) are the three controlling factors in successful primary cementing of dual casing. Turbulent flow has been demonstrated to be unnecessary under the severe displacement conditions of parallel dual strings of casing. Simultaneous reciprocation of dual casing in directionally drilled boreholes is highly dependent on centralization and on the rapid initiation of pipe movement once the casing has been run to total depth. Successful cementing of 30 out of 32 dual, 3lh-in casing wells substantiated these conclusions. A review of 15 dual, 3lh-in. casing wells completed prior to the adoption of these principles disclosed only one success. Mathematical and graphical techniques permit the engineer to analyze and anticipate the success or failure of a cementing operation. StandofJ, mud displacement and reciprocation can be analyzed mathematically and planned in deep, directional 'or straight boreholes by review of annular geometry, relative rheological properties between the mud and cement, and forces caused by casing weight, functional drag and difJerential sticking.