Material composition and formation conditions of productive sandstoons of the Pur-Tazov oil and gas-being region (on the example of Lodochnoe field, Krasnoyarsky Krai)

The article presents the results of the Lower Cretaceous sandstones lithological-facies analysis in the Lodochnoe oil and gas field. Petrographic analysis established the relationship between the composition of the sandstones detrital part and the epigenetic transformation features, made it possible to identify the main processes that affect the filtration-capacity properties. Particle size analysis by laser light diffraction and sedimentological analysis made it possible to clarify the formation conditions of productive sandstone layers in the field. Core material laboratory studies allow a better field structure understanding and answer a number of questions related to the features deposit formation. This paper presents the results of the sandstones material composition and post-sedimentary transformations study in the Lodochnoe oil-bearing reservoirs by the thin sections petrographic analysis using clay part rocks X-ray phase studies data. The article presents the main lithological characteristics of oil-bearing sandstones from Nizhnekhetskaya, Sukhodudinskaya, Malokhetskaya, Yakovlevskaya, Dolganskaya and Dorozhkovskaya suites. It was found that most of the studied productive layers are composed of quartz greywackes, arkoses and mesomictic sandstone varieties. The authors determined the interrelation between the features of the epigenetic sandstones transformation and the detrital part material composition. This interrelation manifested itself in the active kaolinitization of mesomictic and arkose sandstones, and quartz greywackes predominant secondary chloritization. As a result, the main processes that influenced the sandstone reservoir properties were established: there are deconsolidation, kaolinitization and carbonatization. The presence of these processes indicates a regressive-epigenetic transformation of terrigenous deposits due to the study area high tectonic activity. Conclusions were drawn about the positive effect of deconsolidation and mass kaolinitization on the studied sandstones reservoir properties, and that superimposed carbonatization contributed to the formation of some impermeable layers.

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