Occasions arise where a well has to be plugged and abandoned. Typically, such wells will have a cemented casing and another tubular string inside the casing. The plug and abandon procedure involves severing the inner tubular followed by axially milling the severed tubular for a predetermined axial distance followed by setting a plug and depositing cement on top of the plug. The tubular to be severed has a nominal outer dimension between upsets at opposed ends where the joints occur. The axial milling has to cut the nominal dimension as well as the upset outer dimension. In either case it is not desirable to cut into the surrounding tubular as the integrity of the surrounding tubular is important to the functioning of the plug created as part of the abandonment process. On some occasions the tubular to be severed and axially milled is not disposed concentrically in the surrounding casing and sometimes the inner tubular lies on the casing. Axially milling the severed tubular involves using blades that extend a predetermined amount that is short of reaching the surrounding tubular.
The way this process is done today takes multiple trips. The first trip is with a mill with extending blades whose pointed ends radially penetrate the wall of a tubular until that wall is breached. These blades are limited in their radial extent to avoid damage to the surrounding tubular. The tool is then tripped out for a blade replacement to dress the tool with blades that will axially mill the nominal outside diameter of the tubular in a location where the severing took place, which is generally between upsets that have an even larger outer dimension. The axial milling continues between the upsets until an upset is reached. At that point there is another trip out of the hole to redress the tool with longer axial milling bladed that can reach further to the exterior of the larger upset dimension and yet not far enough to gouge the surrounding tubular. Should further axial milling be needed after an upset then another trip to swap back to the shorter axial milling blades is needed.
In one embodiment of the invention all three blade types are provided on a tool housing run into the tubular to be severed and then axially milled. The severing blades are initially extended for the radial cutting through the wall after which those blades are no longer needed. With the aid of specially configured darts that land in a profile either the shorter or the longer axial milling blades are extended. The uniquely configured darts are blown out into a catcher to allow selection of the longer or the shorter blades alternatively as many times as needed depending on the length of the axial milling distance and how many upsets need milling in that desired interval. No matter if the shorter or longer axial milling blades are extended, there is an open circulation path for the extended blades to cool them and for cuttings removal to a collection device or to the surface. While severing and milling is the preferred application, other uses are envisioned where there is a need to sequentially operate a variety of tools in a single trip particularly when two of the tools need to be alternatively operated multiple times. While the preferred actuation system is described in a hydraulic operating environment other ways to achieve the desired tool operating sequence are also contemplated with the objective being an economical and hence reliable design that can perform the required actions in a single trip and preferably without well intervention.
U.S. Pat. No. 8,955,597 shows a sequential use of a mill to make a radial cut with blades 76 followed by extension of a reamer 84 to enlarge the opening where the casing was earlier milled away. This application is limited to a single string in the hole and the sequence is executed but a single time. U.S. Pat. No. 5,765,640 describes a multipurpose tool where one or more pistons can be used to operate multiple tools at the same or different times but shows or describes no structure as to how that can be done one time, not to mention multiple times. U.S. Pat. No. 8,141,627 shows multiple rows of cleaning blades that extend at the same time and are spring retracted.
Those skilled in the art will have a better understanding of the preferred embodiment of the invention from the description below and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.