Well Construction | AirLock Casing Buoyancy System
AirLock buoyancy system helps land horizontal casing
The AirLock® system facilitates landing casing strings in horizontal wells, at nominal cost and without altering casing and cementing operations. Unlike conventional float shoe systems, the unique AirLock seal allows the vertical casing section to be filled with fluid, while the lateral section remains air-filled and buoyant. The enhanced buoyancy reduces sliding friction up to 50% (see table below) while the enhanced weight of the vertical section provides the force needed to push the string all the way to the toe of the well.
The simple and passive AirLock system consists of only two components, which are made up in the casing string during run-in. The debris-trap is installed in a casing connection just above the float shoe, and the seal collar is installed at the optimal point in or above the radius. The seal collar contains a breakable ceramic seal that locks air in the lower section while the upper section is run and filled with fluid. After the casing is landed, surface pressure is increased to fragment the dome at a predetermined pressure, leaving the casing bore completely unrestricted. Seal fragments are collected by the AirLock debris trap, and conditioning and cementing operations are performed as usual.
More than 9,000 AirLock systems have been installed, and casing has landed on more than 99.9% of first attempts.
54% reduction in lateral casing weight and drag forces
|Casing weight in air||11.6 lb/ft (17.3 kg/m)|
|Casing weight in water||10.4 lb/ft (15.1 kg/m)|
|Casing weight with AirLock||4.8 lb/ft (6.9 kg/m)|
|4.5 in (114.3-mm) casing, 4-in (101.6-mm) ID; fluid in lateral casing is air; fluid in vertical casing and open hole is water|
lb/ft / kg/m
|4.5 / 114.3||11.6–15.10 / 17.26–22.47||L-80
|5.0 / 127.0||18.0 / 26.8||P-110*|
|5.5 / 139.7||17–23 / 25.3–34.23||L-80
|5.5 / 139.7||17–23 HTHP / 25.3–34.23||L-80
|6.0 / 152.4||23.95–25.0 / 35.6–37.2||P-110*|
|7.0 / 177.8||23.0-38.0 / 34.3-56.6||L-80
|*125 ksi MYS
5.5-in. x 4.5-in. (139.7-mm x 114.3-mm) available on request