Clay minerals in fluvial shaley sandstone of upper Triassic reservoir (TAGS)-Toual field SE Algeria: identification from wireline logs and core data

摘要

The present investigation attempts to highlight clay minerals existing in fluvial shaley sandstones belonging to the upper Triassic (Rhaetian) reservoir using the French abbreviation "TAGS" for Trias argilo-greseux superieur. This reservoir is localized in the Toual field-SE of Algeria. In the absence of core samples, three main types of clay minerals are detected by wireline log analysis and core laboratory data (porosity and permeability measurements). To differentiate allogenic clay (laminated and structural clays) from authigenic clay (dispersed clay), Thomas and Stieber petrophysical model (shale volume versus total porosity) was applied. This model clearly shows that dispersed clay type has a leading presence in the reservoir's sandstone. The Neasham petrophysical model (porosity versus permeability) allowed us to find that authigenic illite (a dispersed type of clay) is dominant in TAGS sandstones. This model also shows that permeability is highly influenced by authigenic illite whereas porosity is less affected.