Methodology for kick tolerance calculation and well killing in deepwater drilling

Abstract

Kick tolerance is a key parameter to indicate whether shut-in operation can be carried out safely and a proper well killing method should be chosen in well drilling. At present, however, the calculation of kick tolerance in deepwater drilling is not efficient enough. In this paper, a calculation method for volume kick tolerance of deepwater drilling was developed by means of theoretical derivation and example verification. Based on deepwater borehole temperature profile, choke manifold and annulus circulating pressure loss, the calculation model of volume kick tolerance was established under the constraint of the pressure-bearing capacity of the formation at the casing shoe, resistance to internal pressure of casing, blowout preventer (BOP) and choke control. Then, its reliability was verified by using the calculation results of a deepwater well in the South China Sea. It is indicated that the well can be shut in safely and the well killing will be safer if the Engineer's Method is used. The result is in agreement with the measures that were adopted on site. Finally, the newly developed calculation model was compared with those which don't take temperature and pressure loss into account, and the effect of choke manifold, annulus pressure loss and temperature inside wellbore on kick tolerance was analyzed. It is shown that the volume kick tolerance will get smaller if the effect of pressure loss and temperature is not taken into account, and the well killing conditions will be more rigorous. In addition, the technical measures to increase kick tolerance were proposed after the influential laws of pit gain and overflow depth on kick tolerance were analyzed.