Отправлено: 18.12.17 14:31. Заголовок: The role of diagenesis and depositional facies on pore system evolution in a Triassic outcrop analog

The role of diagenesis and depositional facies on pore system evolution in a Triassic outcrop analogue (SE Spain)
Marine and Petroleum Geology · December 2013

Saturnina Henares
Luca Caracciolo
Giuseppe Cultrone
Cesar Viseras

This study aims at unravelling the diagenetic history and its effect on the pore system evolution of the
Triassic redbeds exposed in SE Spain (TIBEM1), an outcrop analogue of the TAGI (Trias Argilo-Gréseux
Inférieur) reservoir (Berkine-Ghadames Basin, Algeria). Similar climatic, base level and tectonic conditions
of aforementioned alluvial formations developed analogue fluvial facies stacking patterns.

Furthermore, interplay of similar detrital composition and depositional facies in both formations resulted
in analogue early diagenetic features. Petrographic observations indicate lithic subarkosic (floodplain
facies) and subarkosic (braidplain facies) compositions which are considered suitable frameworks for
potential reservoir rocks. Primary porosity is mainly reduced during early diagenesis through moderate
mechanical compaction and formation of K-feldspar overgrowth, gypsum, dolomite and phyllosilicate
cements.
Early mesodiagenesis is testified by low chemical compaction and quartz cementation. Telodiagenetic
calcite filling fractures and K-feldspar dissolution determined the final configuration of analysed
sandstones.
Mercury injection-capillary pressure technique reveals overbank deposits in the
floodplain as the least suitable potential reservoirs because of their lowest open porosity (OP < 16%),
permeability (k < 5 mD) and small dimensions.
On the other hand, braidplain deposits show the highest
values of such properties (OP up to 31.6% and k > 95 mD) and greater thickness and lateral continuity, so
being considered the best potential reservoir.
The accurate estimation of TIBEM microscale attributes can
provide important input for appraisal and enhanced oil recovery performance in TAGI and in others
reservoirs consisting on similar fluvial sandy facies.