GRANULOMETRIC ANALYSIS OF THE SARMATIAN SANDS FROM THE MOESIAN PLATFORM DESCRIBING ASPECTS OF THE DEPOSITIONAL ENVIRONMENT

Abstract

The Moesian Platform pertaining to Romania gathers numerous petroleum and gas reservoirs of various sizes and types of hydrocarbons, from black oil to shallow gas reservoirs. They are sited in reservoir rocks having different lithologies (limestone, sand, sandstone, microconglomerate etc) belonging to different ages from the Cretaceous up to the late Pliocene, all formations being characterized by the Paleogene hiatus. Sand formations studies for certain reservoirs indicate oceans rivers and deltas as depositional environments although lithologic analysis, and especially paleontological analysis, are very limited (sometimes missing) and could not be used to re-enact a detailed image. Using granulometric analysis performed on sand cored from different wells, clarification is brought onto the paleoecology of the zone and thus it was discovered which wells belonged to the ocean riverbed and riverbank. Paleoenvironmental studies require large quantities of data which in many cases are not available, but they help in clarifying further aspects such as regional geology, depositional environments and ultimately reservoir heterogeneity which would, in term, justify different production behaviors of the oil reservoirs. Production data has not been studied for this application, but it is confirmed to have ample fluctuations and wells on this structure require workover intervention very often. For data interpretation the classic Udden-Wentworth scale is used along with granulometries from different surface sites and artificial sand having one of the conclusions that the analyzed sand fits almost on the dot on the assumed paleoenvironment.

Keywords

• paleoenvironment
• granulometric sieving
• production potential resumption
• mean
• standard deviation
• skewness
• kurtosis