IRANIAN JOURNAL OF PETROLEUM GEOLOGY
Year:2019 | Volume:9 | Issue:17|Papers Count:6

In order to identify foraminifera and determine the age of Dariyan Formation and the lower Cretaceous sediments of Central Iran, a section of Dariyan Formation in Lar Anticline (north east Gachsaran) (with a thickness of 111m, thick, medium and thin layer of limestone, marl and marly limestone) and a section of Kuh-e-Kolah Ghazi (south west Isfahan) (with a thickness of 260m, thick to medium layer limestone and shale) were studied. Based on biostratigraphic studies of Lar Anticline section, 28 benthonic foraminifera and 4 planktonic foraminifera have been identified in 4 biozones contains: Hedbergellids-Orbitolinids assemblage zone, Mesorbitolina texana zone, Mesorbitolina gr. subconcava zone, Favusella washitensis rang zone. Based on biostratigraphic of Lower Cretaseous sediments in Kuh-e-Kolah Ghazi, 21 benthonic foraminifera and 1 planktonic foraminifera have been identified and consequently 2 biozones are recognized contains: Mesorbitolina texana zone, Mesorbitolina gr. subconcava zonethe studied areas were correlated with some sections of the Dariyan in Kuh-e-Fahliyan, Kuh-e-Mangasht and Meymand. Accordingly, the sedimentation of two studied sections in Lar Anticline and Kuh-e-Kolah Ghazi were started from Late Aptian which were later than the other sections, and the end of sedimentation in the Kuh-e-Kolah Ghazi was earlier than the other sections in the Late Aptian age, while the end of sedimentation of Dariyan Formation in other sections was in Early Albian age.

The most seismic activities have observed around and along major fault systems of this zone in NE Iran that involving of an array active right lateral-strike slip faults have distributed by trending NW-SE. Neotectonic activities and mechanism changing of faults to reverse thrusting faults have caused to increase stress, shortening and increasing seismicity with high density of earthquakes in their ends bending. Structural relation faults between this zone and Binaloud through Meshkan thrusting-transfer zone which is major motion engine of Bakharden-Quchan zone to put it constantly under neotectonic stresses convergence of Arabia-Eurasia plates since last phase Alpine orogeny. In this paper fractal analysis through box counting method has done and D values change between 0-2. If D closes to zero, faults and earthquakes are focusing in a point with high tension and if D closes to 2 is shown low tension, dispersal faults and earthquakes in whole of region. In this paper values are closed to 2 and both surface/volume fractal dimensions distribution show higher seismicity activities in Central and Western parts of Kopeh Dagh in NE Iran.

Asmari Formation from the Gavarzin Gas Field (GGF), in the south Iran, shows uneven contact (probably as erosional unconformity boundary) with the marl and pelagic limestone of Pabdeh Formation and conformable overlain by the evaporate sediments of Gachsaran Formation, as a main cap rock of Asmari Formation reservoirs. Excavated cores from the one of the wells of GGF is 183 m in thickness, which includes 1. 30 m from the top of Pabdeh Formation, 162. 4 m from the Asmari Formation and 19. 30 m from the basal layers of Gachsaran Formation. Asmari Formation comprises alternation of limestone, calcite dolomitic, claystone and shale with green marl in this well. Petrography studies and facies analysis on the thin sections and cores led to identification of 12 microfacies, which formed in shallowing upward sequence of a carbonate ramp system from deep-sea basin to sabkha environments. The ramp includes deep environments, open sea, patch reef, bio-, clastic-bars, lagoon and tidal environments, and changed to the restricted environment, which confirmed by overlain evaporative sediments of Gachsaran Formation. Diagenesis processes are main factors on carbonate reservoir quality of GGF. The diagenesis history of the studied samples is summarized as A) vadose zone diagenesis, includes the crystallization, cementation, and dissolution processes. B) marine phreatic diagenesis, comprises bioturbation, micritization and cementation processes. C) burial diagenesis, confirmed by compression-induced, pressure dissolution and mechanical fracturing processes. The microfacies data show a wide varieties of reservoir characteristics and therefore a heterogeneous reservoir has been formed. Microfractures, however have strongly influence on the reservoir quality in this well of GGF. Confluence of dissolved and fractures porosities led to increase of permeability of the reservoir. The high-quality reservoir estimated for grainstone/packstone sediments of coated grains microfacies with moldic porosity. These microfacies formed by the dissolution of ooid-bearing packstone in the vadose zone.

Investigating the Status of oil potential distribution in the pay zone is one of the best ways to reduce drilling costs as well as quick access to the reservoir and optimal production of hydrocarbon resources. The purpose of this study, is to estimate the porosity, water saturation, thickness parameters and ultimately to reach to the potential state of the production zone that in the One of the southwestern oilfields is located 50 kilometers north of the port of Genaveh. Therefore, according to the data obtained from 76 wells of this field, variation of reservoir petrophysical parameters were modeled with variogram operation and using geostatistical methods. By using ordinary Kriging method, the values of the parameters were estimated in the whole field. Subsequently, by using the indicator kriging method, the field boundaries were separated in order to obtain the exact area of the oil zone and the volume of oil in place and finally by considering the 80% probability level, The definite boundary of the presence of the production zone was determined in the block model and In this zone the volume of reservoir's hydrocarbon was estimated about 147/5 million cubic foot.

In this study, Surgah Formation at Maleh-Kuh and Sarkan section in the southwest of Khoram Abad has been studied based on bio-event models. Surgah Formation at Sarkan well no. 1and Maleh-Kuh has 46 and 82-meter thickness respectively and was placed on the Sarvak Formation and under the Ilam Formation. In this study, Surgah Formation was composed of shale, limy shale with glauconite and pyrite. In this section, two Turonian-Coniacian and Coniacian-Santonian boundaries were recognized in Dicarinella concavata Interval Zone. Based on FADs Dicarinella concavata and Globotruncana lapparenti were detected Turonian-Coniacian boundary. Also based on FADs Dicarinella asymetrica and Globotruncana linneiana (Pill Box Like) were distinguished Coniacian-Santonian boundary in this section. All of main bio-events were realized around the Turonian-Coniacian and Coniacian-Santonian boundaries corrolable with the Coccioni and PremoliSilva and Lamolda respectively.

In the southwest of Iran there are large reservoirs of oil and gas including Jurassic and Cretaceous carbonates, in which they are suitable source rocks in the succession of the Early Cretaceous and Jurassic. The purpose of this Research was to evaluate the maturity of hydrocarbon fluids and to determine the migration path and properties of Pabdeh, Kazhdumi, Garu and Sargelu source rocks in the study area. For this purpose, one-dimensional burial history and thermal modeling in four oilfields and two-dimensional modeling for the study area were performed using Open Flow software to determine the maturity levels of the sedimentary, calving, and kerogen layers (s). Hydrocarbon outflow was evaluated. Comparison of measured vitrinite temperature and reflectance values with model results was used for model calibration. The results of one-dimensional modeling of the burial and thermal history in this study show that the kerogen (s) of the Sargelu, Garu, and Scorpion Formations have matured and have hydrocarbon outflow, but the organic matter or kerogen (s) of the Pabdeh Formation Not enough maturity to produce hydrocarbons. The results of migration model in the studied section show that the two Early Cretaceous and Middle Cretaceous hydrocarbon systems were separated by Kazhdumi Formation and therefore hydrocarbon migration in deeper layers of Kazhdumi was mostly lateral to Abadan plain. The hydrocarbon produced from the Kazhdumi Formation, in addition to charging the upper layers, migrated laterally to the Abadan plain due to the overall slope of the Ilam and Sarvak layers. In general, the maturation process of the source rocks decreased from east to west of the study area.