Through tubing rotary managed pressure drilling
Abstract
Managed pressure drilling (MPD) has been known to the industry for a few years. MPD with
the ability of coping with risky down-hole pressure situations has gained a great deal of
attention. Compared to MPD, the drilling method designated ‘’through tubing drilling’’
(TTD) is considerably younger. StatoilHydro, as one of the TTD pioneers, has drilled TTD
wells in its North Sea assets, of which the majority have been the ‘’through tubing rotary
drilling’’ (TTRD) wells.
The aim of initiating this technology was to access small and by-passed oil pools in mature
assets in a cost effective manner, since TTRD rules out the need of pulling the well
completion. From StatoilHydro’s experience we see that TTRD is one of the complex drilling
methods. Drilling by this technique has seen a number of challenges and drilling problems. In
fact, the majority of these problems are linked to system and down-hole pressure
environments, and thus to drilling hydraulics.
Pressure induced drilling problems can be solved by application of MPD. The idea in this
study is that the simultaneous application of TTRD and MPD will enable us to mitigate
problems relating to pressure conditions and drill cost effective TTRD. Therefore, this thesis
was initiated to study the hydraulics of ‘’through tubing rotary managed pressure drilling’’
(TTRMPD).
In this study two specially looked at MPD methods: back pressure and continuous circulation
system allow for the reduction of the static mud weight in order to manage circulating mud
weight and stay within available drilling window.
This study looks into hydraulics of the TTRMPD operation in terms of equivalent circulating
density (ECD), hole-cleaning, extended reach ability. In the TTRD, ECD management is
particularly challenging due to narrow annular clearance.
This master thesis focuses on the feasibility of combining MPD and TTRD to improve the
ECD management in TTRD. We will look into the effects that the reducing mud weight may
have on drilling parameters.
Description
Master's thesis in Petroleum engineering