LOW-DENSITY FOAMED PORTLAND CEMENTS FILL VARIETY OF NEEDS.

FOAM CEMENT CAN BE ACCURATELY PREPARED, PLACED, AND CURED BOTH IN THE LABORATORY AND IN THE FIELD. CERTAIN GUIDELINES MUST BE FOLLOWED TO PROVIDE GOOD RESULTS FROM FOAM CEMENT JOBS. THESE HAVE BEEN IDENTIFIED AND ARE ACHIEVABLE. ONE MUST RECOGNIZE THAT LARGE VOLUMES OF FOAM SLURRY CAN EASILY BE LOST INTO A FRACTURED FORMATION BECAUSE MOST FOAM SLURRIES HAVELOW APL FLUID LOSS VALUES AND A VERY LOW SOLID VOLUME/SLURRY VOLUME RATIO - THE EXACT PROPERTIES DESIRED FOR AN EFFECTIVE FRACTURING FLUID. IN VIEW OF THIS, SUCCESSFUL LOST CIRCULATION CONTROL WITH FOAM CEMENT DEPENDS MAINLY ON ITS LOW DENSITY THIXOTROPIC PROPERTIES. BY CONTRAST, LIGHT WEIGHT SLURRIES THAT CONTAIN MICRO-SPHERES, GILSONITE OR WALNUT HULLS OWE MUCH OF THEIR LOST CIRCULATION CONTROL TO THEIR FRACTURE PLUGGING ABILITY. IN ADDITION TO OVERCOMING THE DENSITY LIMITATIONS MANDATED BY BREAKDOWN GRADIENTS, THE SUCCESSFUL FOAM CEMENT JOB SHOULD ALWAYS MEET TWO GENERAL OBJECTIVES. IT SHOULD PROVIDE SUFFICIENT HYDROSTATIC PRESSURE TO PREVENT ENTRYOF FLUIDS OR GAS INTO THE ANNULUS. FOAM CEMENT JOBS CAN BE EVALUATED BY THE STANDARD POST-JOB PROCEDURES BUT SPECIAL PRECAUTIONS SHOULD BE EXERCISED WHEN RUNNING OR INTERPRETING CEMENT BOND LOGS. TEMPERATURE SURVEYS HAVE PROVEN TO BE VALUABLE EVALUATION TOOLS. 9 RFS.