| 摘要 |
1. A method of retrieving a sample of formation fluid from a formation layer traversed by a cased borehole comprising the steps of: a) making a plurality of perforation sets through the casing wall into the formation layer, wherein the orientation of the perforation sets is so selected that the angle between adjacent perforation sets equals 360 degree divided by the number of perforation sets; b) lowering a sampling tool into the borehole to the first perforation set, which sampling tool comprises a central conduit having an inlet and a discharge, several fluid sample containers opening into the central conduit, and a system for discharging fluids from the central conduit and for moving fluids into the fluid sample containers, which sampling tool is provided with an upper and a lower packer arranged at either side of the inlet of the central conduit, wherein the discharge opens above the upper packer or below the lower packer, wherein the distance between the upper and the lower packer is larger than the height of a perforation set, wherein the length of the longest packer is smaller than the spacing between adjacent perforation sets; c) setting the packers so that the perforation set is straddled between the packers, taking a sample from the formation, storing the sample in the first fluid sample container and shutting off the first fluid sample container; d) positioning the sampling tool near the next perforation set, setting the packers so that the perforation set is straddled between the packers, taking a sample from the formation, storing the sample in the next fluid sample container and shutting off the next fluid sample container; and e) repeating step d) until samples from at most all perforation sets have been taken, and retrieving the sampling tool. 2. The method according to claim 1, wherein step d) is repeated until samples from all perforation sets have been taken. 3. The method according to claim 1, wherein the sampling tool further comprises a fluid analyser, and wherein step d) is repeated until formation fluid is detected. 4. The method according to any one of claims 1-3, wherein the lowermost perforation is marked, and the sampling tool comprises a device for detecting the marker. 5. The method according to claim 4, wherein the marker is a radioactive tracer, and wherein the sampling tool comprises a nuclear tool for detecting the radioactive tracer. 6. The method according to claim 5, wherein the nuclear tool is a gamma ray detector.
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