Different types of void space and quality of unconventional reservoirs in the Upper Devonian domanic high-carbon deposits of Mukhanovo-Erokhovsky trough (Volga-Ural basin)

Abstract

Domanic deposits have already been studied in sufficient details. Various aspects of their study were described previosly in many works, but so far, these deposits have been considered mainly as source rocks. Domanic deposits are distributed in a wide stratigraphic range from the Middle Frasnian of the Late Devonian to the Tournaisian of the Early Carboniferous. In this paper, domanic formation is considered as an unconventional reservoir. Due to the complex and heterogeneous structure of rocks, their uneven saturation with organic matter and low porosity values, the methodology for assessing reservoir properties is at a low stage of production. An integrated study of the void space in such deposits, including macro- and microdescription of the core, analytical studies, makes it possible to predict zones with best quality of reservoirs and helped successfullу produce such deposits. In the section of domanic formation were identified the main lithotypes and characterized of each of them. Comparison of the types of void space identified in thin sections and reservoir properties made it possible to classify the main types of reservoirs and assess their quality.

From Clastics to Carbonates and Black Shales: Deciphering Sedimentary Continuity and Discontinuity in the Devonian Landscape of the Volga-Ural Petroleum Province

“…Many authors attribute the formation of sediments enriched in organic matter to the maximum level of basin flooding; and the formation of carbonate sediments, on the contrary, to basin regression (Stupakova et al, 2017;Chupakhina et al, 2022;Karpushin, Stupakova et al, 2022;Zavyalova, Karpushin, and Stupakova, 2023). Gatovsky et al (2015) considering Middle Frasnian organic rich black shales noted that these sediments are oversaturated with organic matter, and this circumstance could be the reason for the complete absence of the oxidative zone of diagenesis and the development of benthic anoxic conditions.…”