Maximum allowable pressure during heavy slurry displacement

Abstract

Heavy slurry pumping is facing enormous problems concerning pressure generation and casing limitations. Pumping high-density cement throughout narrow column, throttled at their extremity by the float equipment will generate more pressure, and could push casing to their limits of utilization. There are numbers of phenomena that could lead to casing length change as: piston, ballooning, temperature, tension and buckling. This work is oriented to study buckling effect on total casing length change. Generally, in conventional wells cementing, down hole conditions are referred to geological formation fracture pressure limit, which is lower than buckling limit. Heavy slurry displacement could make an exception, where buckling could appears at pressure inferior to geological fracture limit. While pumping heavy cement down, pressure inside casing increases progressively, pushing casing to extend, consequently risk of closing the narrow space out between casing and open hole total depth may appears. At this moment, buckling begins; pressure rise intensely to reach geological fracture limits and causes down hole loses. After passing the critical high pressure situation, casing will come back to their initial form. In order to overcome this situation, maximum allowable pressure during displacement together with problem indicators is proposed, to prevent and early detect the problem. Experimental and simulation results confirm the usability of assumption proposed.