Master of Science in Petroleum Engineering (MSPE)
Managed pressure drilling is an innovative technique to precisely manage wellbore pressure. It is particularly applicable for reducing the risk of a kick or lost returns when drilling with a narrow window between pore pressure and fracture pressure. The constant bottomhole pressure method of managed pressure drilling uses annular frictional pressure and choke pressure in addition to mud hydrostatic pressure to achieve precise wellbore pressure control. This project investigated alternative initial responses to kicks to determine which would be most effective and reliable under different well scenarios when applying the constant bottomhole pressure method of managed pressure drilling. Three different initial responses to a kick, 'shut-in the well,' 'apply back pressure' and 'increase mud pump rate' were studied using an interactive transient multiphase flow simulator. The kick scenarios were varied by changing the hole size, type of kick fluid, initial kick volume, pressure differential at the kick zone, and fracture injectivity index. No single best response was identified for the kick scenarios that were studied. Nevertheless, some conclusions were reached. The validity of these conclusions may be limited to the range of scenarios studied. 'Increasing mud pump rate' is advantageous when it increases bottomhole pressure enough to stop formation flow because it results in the minimum casing and shoe pressures. Therefore, it should minimize the risk of lost returns or surface equipment failure. However, it is unlikely to be successful in large hole sizes. The 'apply back pressure' response has a similar but smaller advantage versus the 'shut-in' option because circulation creates friction in the annulus. However, in cases where lost returns occurred, no reliable way of identifying the loss of returns and avoiding unintentional formation flow to the surface was defined. The 'shut-in' reaction generally results in the highest casing and casing shoe pressures. Therefore, it may be most likely to cause loss of returns before stopping formation flow and consequently causing an underground transfer with continuous influx. Nevertheless, it is probably the least likely to unintentionally allow formation fluid flow to the surface or to cause loss of significant mud volume downhole.
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Das, Asis Kumar, "Simulation study evaluating alternative initial responses to formation fluid influx during managed pressure drilling" (2007). LSU Master's Theses. 3893.
John Rogers Smith