Change law of standpipe pressure and formation stress during well killing by driller method in deepwater drilling

During deepwater drilling, the formation breakdown pressure is low and the window of drilling fluid density is narrow, so when driller’s method is used to kill a well for well kicks, the result is that the kick is not controlled but lost circulation incident may be induced. Hence, formation stress seems particularly important when driller’s method is used for well killing in deepwater drilling. This paper takes into account the effect of choke manifold, uses fluid dynamics to build a model to calculate standpipe pressure and formation stress when driller’s method is used to kill a well in deepwater drilling. Also, this paper analyzes the varying pattern of standpipe pressure and formation stress during well killing by driller’s method in deepwater drilling, provides the changing curves of standpipe pressure, casing pressure and formation stress relative to cumulative pumping length during well killing by driller’s method, and determines the optimal kill rate during well killing in conjunction with the limit of formation breakdown pressure. When the kill rate and BHA are the same, the deeper the casing shoe is, the greater the formation stress is at the casing shoe during well killing by driller’s method. The occurrence of maximum pressure at the casing shoe of great depth is earlier than that smaller depth. When the top of gas column reaches certain point in the hole, that point shall be under the maximum pressure. When the top of gas column reaches the wellhead, the casing pressure is the greatest, and the maximum value of formation stress is always earlier than that of casing pressure.