Perfluorocarbon tracer tagging of drilling muds for the assessment of sample contamination.

摘要

Perfluorocarbon tracers, PFTs, a multitracer technology of seven chemical tracers, were used to tag the drilling muds used in the Fourth Investigators Hole of the Deep Probe experiments. PFTs are fully fluorinated alkyl substituted cycloalkanes, which are inert, non-toxic and chemically non-reactive, detectable in these applications to 1 picoliter/gram of sample by gas chromatographic electron capture detection. PFTs were incorporated into the drilling muds at the 100,000 p1/gm level by addition of a 1% PFT microemulsion in H(sub 2)O during the periodic preparation of drilling muds. A total of four different PFTs were used to tag the drilling mud used in the stratigraphic core and sample wells; two PFTs were used in the core well and two further PFTs in the sample well. After sampling, a small aliquot of samples was forwarded to the Tracer Technology Center (TTC) for PFT analysis along with samples of the tagged muds. The samples were centrifuged and headspace sampled for PFT. Results of the PFT analyses were then used to assess the degree of drilling mud contamination of the retrieved samples. The results indicated some contamination of the retrieved samples and some transport of fluids from the core well to the sampling well, which are quantitated by the measured PFT concentrations. 8 refs., 3 tabs.