Method and device for injecting a fluid into a formation

A method of injecting a stream of treatment fluid into an earth formation in the course of underbalanced drilling of a borehole into the earth formation, so as to suppress fluid communication between the borehole and a fracture or a highly permeable region in the earth formation, using an assembly comprising a drill string extending into the borehole, the drill string being provided with at least one sealing means arranged to isolate a selected part of the borehole from the remainder of the borehole, each sealing means being movable between a radially retracted mode in which the sealing means is radially displaced from the borehole wall and a radially expanded mode in which the sealing means is biased against the borehole wall so as to seal the drill string relative to the borehole wall, the drill string further being provided with a fluid passage for the stream of treatment fluid, the fluid passage having an outlet debouching into the selected part of the borehole, which method comprises the steps of:

• operating the drill string in underbalance mode so as to progress the borehole until a treatment zone in the earth formation is reached, which treatment zone includes the fracture or the highly permeable formation, for which treatment is desired;
• stopping the drilling operation when the treatment zone is arranged adjacent to the part of the borehole which is selected by the arrangement of the sealing means on the drill string;
• moving the sealing means from the retracted mode to the expanded mode thereof so as to seal the drill string relative to the borehole wall;
• and
• pumping the stream of treatment fluid via the fluid passage and the outlet into the selected part of the borehole and from there into the treatment zone.

An assembly for injecting a stream of fluid into an earth formation using a borehole formed in the earth formation, the assembly comprising a drill string extending into the borehole, the drill string being provided with at least one sealing means arranged to isolate a selected part of the borehole from the remainder of the borehole, each sealing means being movable between a radially retracted mode in which the sealing means is radially displaced from the borehole wall and a radially expanded mode in which the sealing means is biased against the borehole wall so as to seal the drill string relative to the borehole wall, the drill string further being provided with a fluid passage for the stream of fluid, the fluid passage having an outlet debouching into the selected part of the borehole, wherein each sealing means includes an inflatable member movable between a radially retracted position when the sealing means is in the retracted mode and a radially expanded position when the sealing means is in the expanded mode, and wherein each inflatable member is arranged to be inflated by means of the pressure in the fluid passage when the stream of treatment fluid is injected, wherein each inflatable member includes a fluid chamber and an inflation channel having an outlet debouching into the fluid chamber, and wherein the drill string further comprises a means for selectively providing fluid communication between the inflation channel and the fluid passage, and wherein the means for selectively providing fluid communication comprises a tubular sleeve arranged on the inner surface of a tubular portion of the drill string, wherein the tubular sleeve is axially movable between a closing position and an opening position with respect to a port through the wall of the tubular portion, and wherein moving the tubular sleeve from the closing to the opening position opens fluid communication through the port, and thereby between the fluid passage, of which the interior of the tubular portion forms part, and the inflation channel.

A method of injecting a stream of treatment fluid into an earth formation in the course of drilling a borehole into the earth formation, so as to suppress fluid communication between the borehole and a fracture or a highly permeable region in the earth formation, using an assembly comprising a drill string extending into the borehole, the drill string being provided with at least one sealing means arranged to isolate a selected part of the borehole from the remainder of the borehole, each sealing means being movable between a radially retracted mode in which the sealing means is radially displaced from the borehole wall and a radially expanded mode in which the sealing means is biased against the borehole wall so as to seal the drill string relative to the borehole wall, the drill string further being provided with a fluid passage for the stream of fluid, the fluid passage having an outlet debouching into the selected part of the borehole, wherein each sealing means includes an inflatable member movable between a radially retracted position when the sealing means is in the retracted mode and a radially expanded position when the sealing means is in the expanded mode, and wherein each inflatable member is arranged to be inflated by means of the pressure in the fluid passage when the stream of treatment fluid is injected, wherein each inflatable member includes a fluid chamber and an inflation channel having an outlet debouching into the fluid chamber, and wherein the drill string further comprises a means for selectively providing fluid communication between the inflation channel and the fluid passage, and wherein the means for selectively providing fluid communication comprises a tubular sleeve arranged on the inner surface of a tubular portion of the drill string, wherein the tubular sleeve is axially movable between a closing position and an opening position with respect to a port through the wall of the tubular portion, and wherein moving the tubular sleeve from the closing to the opening position opens fluid communication through the port, and thereby between the fluid passage, of which the interior of the tubular portion forms part, and the inflation channel, which method comprises the steps of:

• operating the drill string so as to progress the borehole until a treatment zone in the earth formation is reached, which treatment zone includes the fracture or the highly permeable region, for which treatment is desired;
• stopping the drilling operation when the treatment zone is arranged adjacent to the part of the borehole which is selected by the arrangement of the sealing means on the drill string;
• moving the sealing means from the retracted mode to the expanded mode thereof so as to seal the drill string relative to the borehole wall;
• and
• pumping the stream of treatment fluid via the fluid passage and the outlet into the selected part of the borehole and from there into the treatment zone, wherein the drill string is rotated during pumping and/or during a curing period of the treatment fluid after pumping.