Diagenesis, provenance and reservoir quality of Triassic TAGI sandstones from Ourhoud field, Berkine (Ghadames) Basin, Algeria

Abstract

Diagenesis, provenance and reservoir quality of Triassic T AGI sandstones from Ourhoud field, Berkine (Ghadames) Basin, Algeria Also, this change has contributed to the significantly different diagenetic paths followed by the Lower TAG! quartz arenites and the MiddleUpper TAGI subarkoses.Grain-coating illitic clays are abundant in the Lower T AGl, where they exert a critical control on reservoir quality. These clays are interpreted as pedogenic and/or infiltrated in origin and to have had, in part, smectitic precursors. Shallow burial Fe-dolomite cementation was favored in the downthrown block of the field-bounding fault, where it contributed to the poor reservoir quality. Magnesite-siderite cements are multiphase. The earliest generation is composed of Fe-rich magnesite that precipitated during shallow burial from hypersaline fluids with high Mg/Ca ratios, probably refluxed residual brines associated with the Liassic evaporites. Later magnesite-siderite generations precipitated during deeper burial from waters with progressively higher FelMg ratios. Authigenic vermicular kaolin largely consists of dickite that replaced previously formed kaolinite. Dickitization was followed by late-stage illitization related to the dissolution of detrital and authigenic K-feldspar. Quartz, the most abundant cement, was mainly sourced by the pressure-or clay-induced dissolution of detrital quartz and is a critical factor controlling the reservoir quality. Overall, quartz cement is more abundant in the Lower TAGI than in the Middle Upper TAGI, and this increase correlates with a decrease in average porosity. Within the Lower TAGI, quartz cement abundance is stratigraphically very variable, which is in part related to facies controlled variations in grain-coating clay, resulting in major vertical variations in reservoir quality. Anhydrite and barite cements postdate quartz overgrowth. The sulfate necessary for their formation was likely sourced by deep subsurface dissolution of Late Triassic-Liassic evaporites.

Diagenesis and reservoir quality of the Sherwood Sandstone (Triassic), Corrib Field, Slyne Basin, west of Ireland

“…K-feldspar precipitation requires high silica activities and high K þ /H þ ratios (Morad, Ketzer, & De Ros, 2000). Rossi, Kälin, Arribas, and Tortosa (2002) discussed the supply of K þ by residual brines associated with halite evaporites and came to the conclusion that the K þ content can be significant but the aluminium and silica content is to low for precipitation. As a consequence, it is more likely that aluminium and silica were internally sourced by the alteration of detrital silicates, particularly feldspars.…”

Provenance of Upper Miocene to Quaternary sediments in the Yinggehai-Song Hong Basin, South China Sea: Evidence from detrital zircon U–Pb ages

“…The understanding of sediment provenance and its transport routes is a key element in establishing reservoir presence in clastic petroleum systems (Morton et al, 2001), because reservoir quality of sandstones in sedimentary basins is significantly influenced by the detrital compositions which mainly respond to the provenance distribution (e.g. Rossi et al, 2002). Valuable information about sedimentary direction during deposition is gained by reconstructing transport pathways, which provide useful knowledge when trying to locate hydrocarbon exploration targets (Olivarius et al, 2014).…”

Prediction of diagenesis and reservoir quality using wireline logs: evidence from the Upper Triassic (Raethian) fluvial reservoir tags - Toual field, Gassi Touil Area, SE Algeria

“…[2] and [3] in their reports indicate that TAGS has good petrophysical properties in almost fields. [4] details TAGI diagenesis in Ourhoud field (Berkine Basin) where TAGS is completely absent in stratigraphy. With the aim of helping to close this gap, this paper predicts some aspects on TAGS diagenesis using wireline logs.…”