DDV Reduces Time to Round-Trip Drillstring by Three Days, Saving £400,000

Abstract Fluid invasion of a reservoir during conventional overbalanced drilling operations can cause considerable formation damage. Increased awareness of the degree of damage possible has raised interest in the benefits that underbalanced drilling (UBD) offers. UBD techniques are not necessarily suitable for all reservoirs but can provide significant benefits in certain instances. During UBD operations, the formation is allowed to flow; so a surface pressure is ever present in the annulus. A rotating control head is used to control the pressure. As tripping begins and the pipe is stripped through the wellhead, the pressure must be managed to prevent a pipe-light situation. Killing the well to control it and allow for conventional tripping of drillstring is not always a viable solution; and, until recently, the only accepted method for tripping drillstring in a constant underbalanced state has been snubbing, which can have operational and economic drawbacks in some situations. This paper describes how implementation of the downhole deployment valve (DDV) in a Southern North Sea drilling program reduced overall program costs, set multiple records, and demonstrated successful integration of a new technology into one of the most critical underbalanced operations in the world.