Experimental study of drilling riser and wellhead force by small scale testing

Abstract

Small-scale model tests of a drilling riser were conducted, aiming at a better understanding of the mechanical transfer of forces from the drilling riser to the wellhead. The tests were conducted in a water tank with wave-making and flow-making functions, and strain gauges were installed along the riser model to estimate the riser curvature and stresses imposed on the wellhead. This paper discusses the effects of the environmental conditions, the platform offset, the dimensions of the riser and position of the buoyancy tube on the riser response and the stresses transferred to the wellhead. Obviously, the results indicate that increasing the riser dimensions, at more harsh environmental conditions, and increasing platform offsets will increase the stress at the wellhead. Among the four buoyancy tube arrangements (staggered, top, middle, and bottom arrangements), the staggered arrangement leads to the smallest wellhead stresses, whereas the wellhead stresses for the other three arrangements are also very close. The results of the small-scale experiments are found to be consistent with the results based on numerical calculations. By considering the results from the numerical simulations and full-scale experiments reported in the literature, the results of the present study are found to both confirm and extend the accumulated knowledge based on those studies.