Composition of oils in Vereiskian and Bashkirian carbonate reservoirs of the Akanskoe oilfield in the Republic of Tatarstan

Abstract

The mineral and organic components of the core material from Vereiskian and Bashkirian depos its of the Akanskoe field in the Republic of Tatarstan have been studied by complex thermal analysis. The occurrence depth intervals with abnormally light oil have been revealed in the Bashkirian deposits. These facts together with the data on the composition of oils (high values of the ratio of light to heavy alkane homologues for heavier and more viscous Bashkirian crude oils, the bimodal MMD character of C 9 -C 20 n alkanes, and enrichment in high molecular mass asphaltenes at the bottom of the reservoir) suggest the influx of a lighter oil to the formed Bashkirian deposit. No facts of this sort have been identified for the Vereiskian oil.

Supramolecular Structures of Oil Systems as the Key to Regulation of Oil Behavior

“…This can be explained by the procedure of maltenes separation resulting in removing gasoline fractions that serve as a solvent of waxes, and asphaltenes inhibiting the wax crystallization process from crude oils. In maltenes from the oil of the bottom of the reservoir the crystal growth is not observed due to the fact that the oil is enriched in microcrystalline waxes with carbon atoms number from 40 to 60 (C40-C60), which are likely to disperse macrocrystalline waxes (C16-C40) [31]. The content of microcrystalline waxes in the oil from the top of the reservoir is substantially lower but the content of macrocrystalline waxes is higher.…”

“…Initial asphaltenes of oil from the bottom of the reservoir are enriched in A1 asphaltenes (64.6%) and depleted in A2 asphaltenes (8.1%) while asphaltenes from the top of the reservoir contains less A1 asphaltenes (49.4%) and twice the amount of A2 asphaltenes (15.7%) [31]. The rest part of asphaltenes is presented by the intermediate fraction-a mixture of A1 and A2 asphaltenes [12].…”

“…It should be noted that oil samples from one of the wells have been specially selected from the upper (top) and bottom parts of the reservoir [31].…”

“…Previously [31] we have shown the possibility of using the gradient of asphaltenes, as well as their structure, to confirm the influx of deep light hydrocarbons in carbonate reservoirs.…”

A new approach to identification of fluid-dynamic connectivity in an oil-bearing formation (on the example of the Akanskoe oil field)

“…Based on previously obtained results of studying the chemical composition of organic matter (OM) from the core material from the oil bearing formation of the Akanskoe oil field (**62 well), as well as the results of comparative analysis of oils produced from the upper and lower parts of the formation (**23 well), it was proposed that there is inflow of migrating light hydrocarbons into the formation [8]. The idea of (???)…”