UNDERBALANCE DRILLING - SURFACE CONTROL-SYSTEMS

A closed system of surface control equipment for underbalancing drilling is the safest method of controlling live wells. This new technology is particularly useful in both vertical and horizontal wells where invasion of drilling fluids into virgin formations can result in severe damage and low flow rate wells. The concept is to drill into these formations underbalanced so that there is no restriction to formation now, minimal damage and ultimately higher producing wells. This is achieved by utilizing a rotating BOP or double annular blowout preventers in combination with a choke manifold, sample catcher, low stage/high stage separator, flarestack and a ''live'' flow through control system. The ''closed system'' is particularly useful in drilling in low pressure and fractured reservoirs. It has been utilized to drill for oil and gas in carbonates and sandstone formations.