New oil and gas reservoir discoveries in extreme deepwater conditions have become common. Constructing wells in these deepwater environments has challenged the industry to develop new technologies for reaching extended depths while focusing on limitations of the tubular goods due to excessive crushing loads from handling tools. To address this situation, a new landing string slip system with improved slip crushing capabilities has been designed and tested in the GOM. This hydraulically operated slip system was designed for 37 1/2-in. rotary profiles. It has a 1250-ton capacity and a pipe range of 5 1/2- to 7 5/8-in. Design considerations focused on limited maintenance, tubular guiding, and pipe centering capabilities. The main focus, however, was on reduced slip crushing forces to lessen the need of slip-proof pipe and to bring string capacities closer to tensile limitations.
To evaluate slip crushing capabilities, laboratory tests were performed on landing strings with varying wall thicknesses and yield strengths. Both strain gages and ID measurement tools were used to evaluate the slip crushing performance of this tool. The testing and results are detailed within this paper.
Applying results to field applications was the next challenge. The accepted application method is the Spiri-Reinhold equation; however, it is limited because it requires gross assumptions that do not accurately predict behaviors of critical load systems. The test data was used with the Spiri-Reinhold equation to produce a method of practical yet accurate evaluations of critical strings while highlighting important considerations for comparisons of results.
In this paper, the authors detail the operational advantages provided by this slip system, provide a comparison between the two testing methods, discuss the results obtained and their application to the Spiri-Reinhold equation, and highlight factors that must be considered when evaluating critical strings for which slip crushing forces are nearing pipe yield points.