Calculation of safety pressure margins and circulation rate of well killing by deep water driller's method

Key words:  well killing  deep water driller's method  safety pressure margins  circulation rate

Abstract:

Deep water driller's method is a suitable well killing method for deep water well control. In response to the characteristics of deep water drilling and well control, the solution method of dynamic safety pressure margin was deduced and the recommended value of static safety pressure margin was given. And the solution method of circulation rate was developed. The results show that the dynamic safety pressure margin increases with well depth increasing and decreases with pit gain rising when the well depth and drilling fluid density window are constant. When the size of choke line is constant，the first and second maximum circulation rates increase with the well depth increasing. When the well depth is constant, the first and second maximum circulation rates decline with the size of choke line decreasing. With the pit gain decreasing, the first maximum circulation rate declines, but the second maximum circulation rate does not change. The choke line friction loss increases duo to low temperature in deep water. And with the temperature decreasing, the first and second maximum circulation rates decrease.