Mineral analysis of the heavy fraction via raman spectroscopy: insights from neogene deposits of the northeastern Sakhalin shelf

Introduction. In petroleum geology, heavy mineral analysis is an important tool for reconstructing sediment provenance, transport conditions, and diagenetic history of terrigenous rocks. However, the classical optical method has certain limitations that can be overcome by Raman spectroscopy, as this technique enables reliable identification of both transparent and opaque as well as well-rounded grains, and allows the detection of polymorphic modifications and micron-sized minerals. This significantly enhances the informational value of heavy mineral studies compared to conventional optical microscopy. The method was applied to wells drilled on the northeastern Sakhalin shelf—a key petroleum-bearing region with Neogene terrigenous reservoirs that have been only poorly investigated in terms of their heavy mineral composition.

Aim. To study the composition of heavy mineral assemblages in sandstones of the Neogene petroleumbearing succession (Nutov Horizon) on the northeastern Sakhalin shelf using Raman spectroscopy on core and cuttings samples from wells located at varying distances from the coast, in order to assess source area position, mineralogical maturity, and spatial variations in composition.

Materials and methods. A Raman spectroscopy study was carried out on core and drill cuttings material from the Nutov Horizon (Miocene–Pliocene) across five wells representing various fields on the northeastern shelf of Sakhalin Island.

Results. The results confi rm the assumption of a common provenance for the Lower and Upper Nutov deposits and indicate the proximal position of the source area. The identified heavy mineral associations can serve in the future as diagnostic markers for distinguishing between Lower and Upper Nutov subhorizons in well sections— particularly useful for young Neogene sediments that are difficult to stratify in the absence of index fossils, as well as for attributing core or cuttings samples that have lost their descriptive documentation.

Conclusion. Raman spectroscopy is an informative method for characterizing sediment provenance.

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