Baker Hughes Corporation

Gary E Cooper

David Cameron

Donald Murray

Jonathan Price

Alex Crabtree

A casing or tubing segment or segments are disclosed which can be used to create a parasite annulus during drilling. The cased wellbore receives a string containing valves and the drillstring operates through it. As the mud circulates, the segments of the tubing or casing provide communication at various depths from the parasite annulus (i.e., the outermost annulus) into the circulating mud, which is the innermost annulus. Each valve is adjustable to alter the amount of differential pressure required in order to open it. The valves are also in hydraulic pressure balance so that only the pressure added by the injected gas acts to open them. The valves close by a spring bias.

Balanced or underbalanced drilling method and apparatus

An insert tool for pre-existing casing is disclosed which allows the use of existing control line connections to facilitate independent operation of a pair of safety valves. The insert is particularly useful when a pre-existing well is converted to gas lift operation and requires the use of downhole valves, such as tubing safety valve in combination with an annular-type safety valve. The tool can be readily reconfigured if one of the control lines becomes obstructed so that continuing independent operation of the two valve components can continue. Normal and emergency release techniques are also included when it is time to retrieve the insert assembly.

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Aberdeen, United Kingdom

Gary E Cooper