Petrographic characteristics and reservoir quality of sandstone reservoirs from Enreca-3 well in Bach Long Vi island
Abstract
This paper presents the relation of petrographic characteristics and diagenetic process to the reservoir quality of sandstone units in the Enreca-3 well. The results of petrographic study show that almost all studied sandstones are fine- to medium-grained ones. All studied sandstones are quite clean and classified as arkose sandstone. The detrital grains of studied sandstones are mostly angular, subangular to subrounded in grain shape and mostly poor to moderate sorting. Arkose sandstones are composed of mostly quartz and feldspar with much smaller amount of rock fragments such as granite, volcanic, quartzite, schist, and sandstone. The sediments were derived mostly from continental block provenance. The sandstones were in the early diagenetic stage. The petrographic study also reveals that the visible porosity of studied sandstones has been strongly damaged by cementation, whereas the mechanical compaction has not significantly aff ected the
visible porosity of these reservoir sandstones. The visible porosity of studied sandstones is fairly good with mostly well preserved intergranular pores (7.6 - 19.4%, average ~15%) and minor micropores within clay patches (~1.0 - 2.0%), and further enhanced with secondary pores (1.4 - 1.8%) due to the dissolution of uncertain grains such as feldspar and lithic fragment.
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