Abstract: Logging method and tool string for identifying and determining the concentrations of subsurface formation elements next to a borehole, by (i) using a broad energy spectra neutron source (such as a chemical source, like AmBe), and (ii) detecting and counting the delayed gamma rays resulting from the activation by the neutrons of atoms of least one element of interest (e.g. aluminum). Two gamma ray detectors may also be disposed on either side of the broad energy spectra neutron source, for detecting and counting the prompt gamma rays resulting from the capture of neutrons by atoms of elements, such as Si, Ca, Fe, S, H, or Cl, Gd, Ti, or K.The broad energy spectra neutron source is used for both the "activation" and the "capture" measurements. The tool string may also include a natural gamma ray tool for the determination of uranium, thorium and potassium, and for measuring the background to be subtracted from the gross Al activation measurement.

Abstract: A method for obtaining samples of connate fluids from formations traversed by a borehole, wherein a sample test chamber is brought in communication with an isolated portion of the borehole wall, and is opened so as to allow the connate fluids to fill the chamber, and wherein the connate fluids are filtered through porous material including particles of determined sizes. The particles are bound together so as to form a rigid porous member, and have an average diameter which is a multiple of the diameter of the formation particles. Filter includes sieved gravel/sand embedded in a thermosetting resin. Alternatively, the filter includes metal bound together by superficial melting or welding.