Devices and methods for formation testing by measuring pressure in an isolated variable volume

1. A device for formation testing while drilling, the device comprising a drill string with a packer arranged on the drill string above a drilling bit, the packer can be expanded and thereby isolate a lower open part of a wellbore,

wherein the packer is fastened sealingly but slideably over a distance of the drill string, such that the drill string can be brought up and down, with or without rotation, within said distance while the packer stands stationary and expanded in the wellbore, and

wherein the device comprises at least one pressure transmitter for measuring and transferring in real-time to the surface measured pressure in the isolated lower open part of the wellbore.

2. The device according to claim 1 , wherein the drill string can function as a piston rod.

3. The device according to claim 1 , wherein the device comprises a downhole micro pump, arranged to be able to pump fluid in or out of the isolated lower part of the well-bore, over the expanded packer.

4. The device according to claim 1 , wherein an increase of pressure in the isolated part takes place by bringing the drill-string down and/or by pumping in fluid through the drill-string and/or by pumping in fluid with the micro pump.

5. The device according to claim 1 , wherein lowering of the pressure in the isolated part of the well-bore takes place by bringing the drill-string up and/or pumping out fluid with the micro pump, or at high pressure in the lower isolated part of the wellbore, by controlled bleeding out the pressure through a valve arranged in the drill string.

6. The device according to claim 1 , further comprising one or more of: sensors/transmitters for pressure, differential pressure, temperature, resistivity, and sonic wave velocity.

7. A method for determination of pore pressure in a lower isolated open part of a well-bore, by use of the device according to claim 1 , the method including lowering the pressure in a controlled way by bringing up the drill-string within an available slideable distance, optionally by pumping out with a micro pump and/or repeated lowering of the drill-string, pumping out with a micro pump to previously achieved pressure and then further lifting of the drill-string for further pressure reduction, to observe non-linearity in a curve of measured pressure values as function of volume increase or drill-string movement in the lower isolated open part of the well-bore, as the point of non-linearity indicates pore pressure and beginning in-flow from the surrounding formation.

8. A method for determination of fracturing pressure in a lower isolated open part of a well-bore, by use of the device according to claim 1 , the method including increasing the pressure in a controlled way by bringing the drill string down within an available slideable distance, optionally by repeated lifting of the drill-string, pumping in of fluid through the drill-string to previously achieved pressure and then further lowering of the drill-string for further pressure increase, to observe non-linearity in a curve of measured pressure values as function of volume reduction or drill-string movement in the lower isolated open part of the well-bore, as the point of non-linearity indicates beginning fracturing in the surrounding formation.

9. The method according to claim 8 , wherein a pill of particles for rehabilitation of the well-bore's surface has been brought into the lower open part of the well-bore beforehand.

10. A method for determination of formation properties in a lower isolated open part of a well-bore, by using the device according to claim 1 , the method including pumping in fluid in a controlled way in a fractured isolated lower open part of the well-bore, and measuring pressure and optionally other parameters as function of time while fluid flows back to said part of the well-bore.

11. The method according to claim 10 , further including bringing the drill-string up an available slideable distance after fracturing, for controlled reduction of pressure and closure of fractures.

12. A device for formation testing of a production well, the device comprising a pipe means with a packer arranged on the pipe means above a lower end, which packer can be expanded and thereby isolate a lower part of the production well,

wherein the packer is fastened sealingly but slidably on a distance of the pipe means, such that the pipe means can be brought up and down, within said distance, while the packer stands stationary and expanded in the production well, and the device comprises at least one pressure transmitter for measuring and transferring to the surface in real-time measured pressure in the isolated lower part of the production well.

13. The device according to claim 12 , further comprising a valve in or close to the lower end of the pipe means, controllable from the surface.

14. The device according to claim 12 , further comprising a down-hole micro pump, arranged to be able to pump fluid in or out of the isolated lower part of the production well, over the expanded packer.