Porosity and Rock-Typing in Hydrocarbon Reservoirs Case Study in Upper Member of Dalan Formation in Kish Gas Field, South of Zagros, Iran

To estimate the volume of oil and gas in the hydrocarbon reservoirs, the rock-typing must be considered. The volume and type of available space in the reservoir rocks (porosity) and the ease of hydrocarbons flow (permeability) are important in the classification of rock-types. In the field study, touching-vug Porosities (intergranular, intercrystalline and brecciate) increase the total porosity and form high quality rock-types, on the other side, separated-vug porosities (such as moldic, intraparticle and vuggy) increase the total porosity but do not play a large role in the production of hydrocarbon. In this paper, based on the SCAL data (Special Core Analysis) and according to amount of irreducible water saturation (Swir) and capillary pressure, the reservoir rocks are divided into 4 classes including Reservoir Rock-Types 1 to Reservoir Rock-Types 4 (RRTs-1 to RRTs-4). By study of the prepared thin sections, we investigated the role of porosity in the rock-typing. Among the rock-types, category 1 is the best type-reservoir and category 4 is non-reservoir. Probably, the latest diagenetic process determines the quality rocks, not sedimentary environments.

Continental Trace Fossils in the Semnan Area (Northern Iran)

Continental ichnology has been taking an ever increasing importance in stratigraphy. In this paper, Continental Trace Fossils in Semnan area have been studied. Semnan Province is one of the 31 provinces which is located in the north of Iran. In the East of Semnan City, Quaternary deposits occupy about 93% of the surface area, of which the Alluvial represents one of the most important geomorphological features in the area. Nevertheless, the outspread ichnological studies in Semnan City have received lesser attention in Continental Trace Fossils. Based on the systematic ichnology, 6 trace fossils are distinguished, namely Celliforma isp, Coprinisphaera isp, Palaeophycus tubularis, planolithes isp, Tombownichnus plenus, and Skolithos isp. The existence of Rhizoliths along with the tetrapod footprints and the survey of lithofacies all indicate that the trace fossils are related to Coprinisphaera ichnofacies. Based on ichnological and sedimentary facies analysis, the Continental Trace Fossils, in the study area, are located in the flood plain, point bar, and playa environment.

Cretaceous Carbonate Deposits of Neotethys Ocean in the Northwest of Iran

Cretaceous carbonate deposits are considerably extensively distributed in the northwest of Iran and form most of the paleohighs of the region and different Cenozoic sedimentary units have deposited over these units with angular unconformity. Cretaceous stratigraphic units of northwestern Iran can be divided into three main categories： clastic, shallow carbonate and pelagic. Clastic facies include conglomerate, breccia and fine-grained clastic groups and carbonate facies are composed of series of microfacies of open sea（A）, bar（B）, lagoon（C）, and tidal flat. Relatively deep carbonate deposits with different trace fossils are also indications of deeper parts of the Cretaceous sedimentary environments in the northwest of Iran. With reference to the expansion of narrow Neotethys Ocean（Khoy-Zanjan）, shelf margin sedimentary environments of Neotethys Ocean can be assumed for the Azarshahr-Tabriz region, where flysch and clastics facies in the coasts of Varaghan deposited towards the northern parts with increase of depth. Investigation on the expansion of narrow Neotethys Ocean by using different sedimentary facies during the present study is considered as an important step to complete paleogeographic data of Cretaceous time in the northwestern region of Iran and Middle East.