Depositional environments as a framework for genetic classification of the basic criteria of petroleum potential

Abstract

Most classifications of reservoirs, seals and source rocks based on the ability of the rock to generate, accumulate and preserve hydrocarbons, and the genesis of rocks is not always taken into account. The article presents a ranking scheme for continental, coastal-marine and marine sedimentation environments that determine the genesis and properties of the basic criteria of petroleum potential – source rocks, reservoirs, seals and pinch-out traps. Rocks, which can consider as source rock, reservoirs and seals are formed in each depositional environment. However, their structure, mineral composition and distribution area will differ from each other depending on the sedimentary environment and conditions. A combination of elements of the hydrocarbon system formed, corresponding to the sedimentation environment and are characteristic for basins of various types. Continental environments are favorable for the formation of reservoirs and local seals, while the accumulation of source rocks limited by lacustrine, floodplain, and swamp facies. The coastal-marine environment is favorable for the formation of all the basic criteria of petroleum potential, and the transgressive-regressive cyclicity determines the interbedding of source rocks, reservoirs and seals in the section. The marine depositional environments are most favorable for the formation of regional seals and source rocks, including high-carbon formations. The proposed ranking scheme of sedimentary environments and the basic criteria of petroleum potential genetically related to them is applicable in system analysis and selection for analogues of petroleum system elements in sedimentary complexes formed in similar depositional environments.

Correlations between Petroleum Reservoir Fluid Properties and Amount of Evolved and Dissolved Natural Gas: Case Study of Transgressive–Regressive-Sequence Sedimentary Rocks

“…(4) API defines the specific gravity by oAPI = (141.5/γo) − 131.5. (5) Reservoir fluid density at bubble-point pressure. The oil above bubble-point pressure tends to be undersaturated and acts as a single-phase liquid.…”

“…Also, it is reported that there is a greater proportion of higher-chain hydrocarbons in thermogenic natural gas relative to that in microbial gas, which mostly contains methane and carbon dioxide [4]. The presence of microbially mediated pathways that produce hydrocarbons with two or more carbon atoms has previously been highlighted [5].…”