Multilateral Window Level 2
A side track well is one that is started down hole, from an existing well. A deflective devise is fixed within the existing well’s casing down hole, and the new well is started by drilling (deflecting) through the existing casing. A typical window is drilled through the casing by hydraulically setting a ramp at the deflection direction required. The drill bit will follow the ramp and drills through the casing. After the well is drilled, casing is run in the sidetrack well and is guided into the well by means of the ramp. This ramp has bypass capability so the original well below can produce past the ramp. This type of lateral window is considered a Level 2 well, where one well can’t be isolated from the other. Lateral windows that can allow a seal between each well are considered Level 6 wells.
This type of level 2 window does not allow entry into the lower well because the lateral casing and the ramp block entry. If entry to the lower well is required, the upper lateral casing and the ramp must be removed from the main well casing. If the ramp and casing is required to be put back in the well, it is difficult to line up the ramp at the exact location to reenter the lateral well. Typically it can take 8 to 12 hours to drill through the existing casing and to dress the drilled lateral window.
Knowing when a new Multilateral Window Level 2 (MW2) well is to be drilled, the main casing of the main well will contain an aluminum joint with a female spline sub attached below it. The ramp will contain a male spline sub below it. The ramp is installed (with MWD and drill bit) into the well and is set inside the female spline sub at the direction/orientation required. Drilling of the MW2 window (through the aluminum joint) is drilled and dressed in about 2 hours. The casing is run with a specific tool that places the top of the lateral casing at the inside of the window, and then removes the ramp. The lower well is accessible. When access is required to the material well, the ramp is reinstalled into the splines at the exact orientation and depth as it was when drilled, allowing easy access to the lateral well. This ramp also has through production capability.
The new ramp attaches to the drill string with a retractable shear pin sub. When the spline sub of the ramp is installed into its matting female spline sub at the desired orientation, weight is applied to shear the pins. The spline sub can’t pass through the matting sub when the splines are attached. Passage through the spline sub is allowed when the splines are detached. These splines can be locked and unlocked every 6°, for 360°.