Weatherford Liner System Suits Caspian

March 14, 2009

   The Monobore Open-Hole Liner system is made up of two components, a tieback shoe run on the bottom of the previous string of casing (13-3/8 or 13-5/8 in. conventional string) and the monobore expandable liner itself. The tieback shoe (Fig. 1) is made up of one or more joints of 14-1/2 in. or 15 in. semi flush joint casing that is crossed over to the 13-3/8 in. casing. Its outside diameter (O.D.) is approximately the same O.D. as the collars of the 13-3/8 in. casing. The tieback shoe utilizes a fibre glass inner-string so that its special drift is not exposed to cement during the cementing operation of the 13-3/8” string. After the 13-3/8 in. string is set and the next hole section is drilled, the 11-3/4 in. expandable casing is run and expanded. The top of the expandable liner is expanded into the 14-1/2 in. or 15 in. tieback shoe resulting in an expanded drift of 12-1/4 in., the same as the previous string of 13-3/8 in.

   Since the first conventional expandable liner was run in the GOM in 1999, solid expandable openhole liners have evolved to provide the industry with a large selection of sizes. However, these conventional expandable liners do not meet the demands of pore pressure and fracture gradients of the wells drilled in the region.

   For instance, the collapse of expandable liners is mostly driven by the thickness of the casing. The most effective path to creating an openhole expandable liner with a larger amount of collapse lies in building the liner from a tube manufactured with a thicker wall.

   Compared to a conventional 11-3/4 x 13-3/8 in. solid expandable liner, the 11-3/4 x 13-3/8 in. Monobore openhole liner system has the following features, advantages, and benefits:

Zero hole-size loss (post expansion drift equal to 12-1/4 in.);

Post-expansion collapse over twice that of the conventional expandable openhole liner of the same size (~2,000 psi versus ~900 psi) with tubular equal to 0.582 in.;
An expandable and collapsible cone;

Expandable metal-to-metal connectors qualified to ISO standards;
Seamless tubular;
~30 percent lower expansion pressure required;
System pressure contained using a valve.
The system’s ability to pass through the 13-3/8-in. conventional casing and expand large enough to have a post-expansion ID the same as the ID of the 13-3/8 in. conventional casing lies in two of the system’s attributes.
The first attribute consists of special-sized flush joint casing run on the bottom of the 13-3/8-in conventional casing, forming an oversized tieback shoe. The tieback shoe’s OD is similar to that of the 13-3/8 in. collars with an ID large enough (~13.642 in.) to accommodate the Monobore’s expanded 11-3/4-in. casing and still allow the Monobore liner to have an expanded drift of 12-1/4 in. (the same as the 13-3/8 in conventional casing).

   The second attribute is an expansion cone that is carried into the well in a transverse or collapsed mode and does not require an oversized launcher to house the cone. The cone