This paper is an analysis of the well kicks recorded on the Wells IT database of the Offshore Safety Division (OSD) of the Health and Safety Executive (HSE). The purpose of the paper is to warn of failings that have led to kicks and suggest ways of avoiding these failings.
Kick frequencies have been calculated using the numbers of wells drilled and the numbers of kicks reported. The analysis indicates that kicks are taken in 11% of all wells drilled on the United Kingdom Continental Shelf (UKCS). This frequency has not decreased over the last eleven years. The frequencies are higher in wells drilling the Zechstein (13%) and for High Pressure High Temperature (HPHT) wells (22%). About 11% of the total kicks can be considered serious (That is out of 100 wells drilled in the UKCS 11 will have kicks of which 1 will be serious). Half the kicks take place during drilling operations with the others spread amongst cased hole, tripping and casing operations.
The appendix describes case histories of kicks which illustrate important lessons to be learnt. For well designers:-
anticipation of raised pressures in the reservoir from water injection;
assuming the worst when drilling the Zechstein;
make every effort to ensure the integrity of casing shoes and liner laps before displacing to a lower mud weight.
For well control training:-
emphasising the importance of monitoring pit volume during non-standard operations;
ensuring the driller has authority and confidence to shut the well in if there is any doubt;
the importance of a clear chain of command for kick control operations;
the Offshore Installation Manager (OIM) should not be too closely involved in technical aspects of killing the kick but should concentrate on the overall safety of the installation.
Kick simulators can be useful both in training personnel and planning wells.