ABSTRACT
One of the major barriers to the introduction of slimhole drilling technology to oilfield operations was perceived to be the maintenance of safe standards of well control. There were two parts to this problem. First, the reduced kick tolerance in a small annular capacity well dictated that the kick detection system must be able to detect an influx of approximately one barrel. Second, conventional well kill techniques such as the Wait and Weight Method depend on the annular pressure losses being a small fraction of the total circulating system pressure loss, such that while not causing fluid losses in the open hole, a small overbalance is maintained above formation pressure. This assumption is often not valid in slimhole wells.
This paper presents a safe method of modifying commonly practiced conventional well kill techniques to take account of the high annular pressure losses and circulate out the influx in a controlled manner. Previous solutions to the slimhole well kill problem have depended upon unpracticed dynamic techniques where neither the position and volume of the influx nor the pressure applied to the wellbore are precisely known.
The paper will analyse the forces occurring during a well kill operation and derive modified well kill equations.
In addition, situations unique to the slimhole scenario such as the effect of annular friction pressure losses which are greater than the shut in casing pressure, their effects on MAASP and the behaviour of surface circulating systems will be discussed.
The paper will go on to describe how the modified procedure is implemented. This section will include details of the well control training programme developed and the pre-kick data collection procedures established at the slimhole rigsite.
