Fluid sampling methods and apparatus for use in boreholes

Apparatus for sampling the formation fluids in an earth formation surrounding a borehole, the region of the formation immediately surrounding the borehole being at least partially invaded by borehole fluids, the apparatus comprising a borehole tool adapted to be lowered into the borehole, the tool being adapted to receive any one of a plurality of interchangeable sampling probe devices and including means for urging a received sampling probe device into contact with the borehole wall, each sampling probe device comprising an inner probe and an outer probe surrounding the inner probe for withdrawing respective fluid samples from the formation, the ratio between the respective flow areas of the inner and outer probes being different for each sampling probe device.

Apparatus for sampling the formation fluids in an earth formation surrounding a borehole, the region of the formation immediately surrounding the borehole being at least partially invaded by borehole fluids, the apparatus comprising a borehole tool which is adapted to be lowered into the borehole and which is provided with a sampling probe device and means for urging the sampling probe device into contact with the borehole wall, the sampling probe device comprising an inner probe and an outer probe surrounding the inner probe for withdrawing respective fluid samples from the formation, wherein the sampling probe device is adapted to receive any one of a plurality of inner probes each having a different flow area.

A method of sampling the formation fluids in an earth formation surrounding a borehole, the region of the formation immediately surrounding the borehole being at least partially invaded by borehole fluids, using a borehole tool which is adapted to be lowered into the borehole and which is provided with a sampling probe device and means for urging the sampling probe device into contact with the borehole wall, the sampling probe device comprising an inner probe and an outer probe surrounding the inner probe for withdrawing respective fluid samples from the formation, the method comprising adjusting the ratio between the respective flow areas of the inner and outer probes so as to tend to reduce the time taken to obtain via the inner probe a sample of the formation fluids having a given level of contamination by borehole fluids.

Apparatus for sampling the formation fluids in an earth formation surrounding a borehole, the region of the formation immediately surrounding the borehole being at least partially invaded by borehole fluids, the apparatus comprising a borehole tool which is adapted to be lowered into the borehole and which is provided with a sampling probe device and means for urging the sampling probe device into contact with the borehole wall, the sampling probe device comprising an inner probe and an outer probe surrounding the inner probe for withdrawing respective fluid samples from the formation, and means for adjusting the ratio between the respective flow areas of the inner and outer probes so as to tend to reduce the time taken to obtain via the inner probe a sample of the formation fluids having a given level of contamination by borehole fluids.

Apparatus for sampling the formation fluids in an earth formation surrounding a borehole, the region of the formation immediately surrounding the borehole being at least partially invaded by borehole fluids, the apparatus comprising a borehole tool which is adapted to be lowered into the borehole and which is provided with a sampling probe device and means for urging the sampling probe device into contact with the borehole wall, the sampling probe device comprising an inner probe, an intermediate probe surrounding the inner probe, and an outer probe surrounding the intermediate probe, all for withdrawing respective fluid samples from the formation, the tool further comprising valve means selectively operable to combine the fluid sample withdrawn via said intermediate probe with the fluid sample withdrawn via the inner probe.