The Anatomy of High Performance Float Equipment and Potential Failure Modes

Abstract

Float equipment comes in a variety of configurations incorporating such devices as poppet float valves and flapper valves to prevent cement from re-entering the casing at the end of displacement. Autofill functionality can be achieved by using various methods of flow and ball de-activation to either increase trip speed or reduce surge pressure on the formation. Float equipment performance is now loosely defined by the recommended practices in API RP10F. With the pending introduction of newly proposed API 10F standards, the industry recognizes the need to better define the performance properties for flow endurance, temperature, and back pressure. However, this much needed and improved specification does not address drillability and plug bump ratings. This seemingly simple technology has highly engineered nuances that may not be readily apparent. The careful balance of flow endurance, high pressure resistance, and debris tolerance while maintaining quick drill-out properties has been achieved through many years of refinement and testing. Even the concrete used in the manufacture of float equipment is highly engineered to provide ultrahigh compressive strengths and shear bonding, which not only create a drillable product but also produce a seal between the steel hull and the valve. If these nuances are not clearly understood, the selection of high-performance, cost-effective float equipment can be compromised, which can lead to poor cement placement, remedial intervention, added drill-out costs, and reduced well integrity. Failure modes are often attributed to design flaws or manufacturing errors. In some cases this is accurate, but a detailed understanding of performance properties and accurate compressibility calculations can mean the difference between allowing sufficient flow back and recording a float failure. Pipe management and standardized cementing practices are also important to success. This paper will explore the design practices and manufacturing methods for various types of float equipment and the need to dovetail the newly proposed API 10F standards and future iterations into the selection criteria for cost effective, reliable float equipment. This discussion will also review reasons for float failures and the causes behind these incidents.