JOURNAL OF GEOTECHNICAL GEOLOGY (APPLIED GEOLOGY)
Year:2013 | Volume:9 | Issue:1|Papers Count:8

The South Pars Field, one of the largest gas and condensate resources in the Persian Gulf is located at the border of Iran and Qatar. The Dariyan Formation plays the role of a reservoir rock in this field, which is a sequence of limestone, shale and marl lithology. The most important processes affecting diagenetic facies are dissolution, cementation, compaction, and fracture development, while dissolution is the most important one for improving the reservoir quality of Dariyan Formation. Total porosity of Dariyan Formation is about 20 to 25%, while the effective porosity of the reservoir is considerably lower than total porosity due to blocked fractures. Consequently, the reservoir quality of Dariyan is poor. Open fractures are the main factors of high permeability. Porosity is a basic parameter determination of oil in place and characterization of rock fabrics. The neutron, density and sonic are the conventional porosity logs. The obtained porosity of these logs is not certainly equal to each other and real porosity of the rock because the logging tools do not measure the porosity. The tools measure physical reactions in well and then convert it to porosity. Porosity value is not only the output of these logs but also the pore type of reservoirs can be determined through these logs. Velocity deviation log, obtained from combination of neutron and sonic logs, is a tool from which some information can be obtained for determining the main pore types of carbonate rocks. This log curve is built using neutron-density and sonic logs, synthetically. First, velocity deviation log is built synthetically, and then the amount of log’s deviation represents the pore type. In this study, the results of velocity deviation log were compared to porosities from petrographic study to evaluate the performance of the method in pore type determination. The results show that thin section porosity shows a good agreement with velocity deviation log results. Therefore, velocity deviation log in conjunction with other logs is a useful tool for pore type determination in carbonate rocks. The data from two wells (Spo1, Spo2) of the Dariyan Formation, South Pars Gas Field was used. The Dariyan Formation in the studied wells is made of carbonates with lithology of mainly lime with shale interlayers.

The Behjatabad dam is located in Qazvin province at the 65 km away from the North West of Abyek city. The earthquakes occurred in this area had shallow depths and almost have a surface rupture. In this study, have been tried to specify features of dam seismicity using regional tectonic maps, aerial and satellite photos and set of seismic data. Earthquake hazard analysis based on the distribution, type and morphology of faults and, historical and current earthquakes performed. This analyzes have been done using EZ-Frisk software and using appropriate attenuation equations in deterministic and probabilistic methods. Based on deterministic method the most important seismic scenario is Abyek fault that if it's movement will create maximum acceleration at the site. However, the results have been showed that Taleghan, north Tehran and north Karaj faults far from the Abyek fault, have a maximum acceleration in new seismic separation method for controlling earthquake. According to dam designation based on the results of both methods, by usage of seismic separation method we could reduce economical budgets costs to 14 percent in Behjatabad dam.

The Persian Gulf among the areas with the greatest potential for exploration and development of hydrocarbon reservoirs in the word. The Gadvan Formation (Barremian to Early Aptian) is one of the formations with good source rock potential in this region. In this article, the hydrocarbon potential of the Gadvan Formation is investigated in the Iranian sector of the Persian Gulf. For this purpose, a total of 87 samples was taken from the Gadvan Formation in the 18 oil fields are analyzed by Rock-Eval pyrolysis. The thickness of the Gadvan Formation ranges from 35 to 354 meters. The Formation reaches a thickness of 354 m in the southern part of the study area and also in the Strait of the Hormuz. The results of Rock Eval pyrolysis indicate that the Gadvan Formation was deposited in a marine environment and its organic matter is mainly composed of kerogen III and II/III. The TOC ranges from 0.26 to 2.16 wt. % and the average TOC content of the Gadvan Formation is 0.97 wt. %. TOC content increases toward the west of the Persian Gulf. Tmax values range from 410 to 458°C, and in 86% of the samples the Tmax is less than 435oC.Moreover, a burial history and thermal maturity investigation were performed on the Gadvan Formation in 3 oil fields to assess its thermal maturity and evolution through time. The results confirm the Rock Eval results and indicate that the Barremian to Early Aptian-aged Gadvan Formation is currently immature in the center part of the Persian Gulf and reached to the early range of maturity for oil generation in the margin.

The Khuzestan province as a part of Afro-Asian stone belt and due to fall within warm and dry climates, it required extensive studies on mineralogy of urinary stones. In this way, mineralogical studied using X-ray diffraction and scanning electron microscope showed that urinary stones in the Khuzestan province can be divided in to six mineralogical groups: calcium oxalate, phosphate, calcium oxalate/ phosphate, urate, urate / calcium oxalate and urate/ calcium oxalate/ phosphate. Also the results which obtained from climate conditions effect investigation on the mineralogy of urinary stones, confirms that from Mediterranean sub-humid climates (northeastern area of the province) to warm and dry climates (south and southwest areas of the province), oxalate stones and urate stones concentration decreases and increases respectively. Presence of Niahite and Hydroxyapatite biominerals are the most important mineralogical feature in the study area. According to the negative relationship between Ca: Mg ratio and the formation of urinary stones, can be added magnesium to urban places cleaning water or passing resources of surface water from lithologies with high rate of magnesium (such as dolomite areas). Also urate stone can be dissolved by medicinal agents administered orally or parenterally, because chemolysis can be effective in the south and southwest area of province (highest distribution of urate stones in the province).

One of the methods used for mineral potential mapping in GIS is the fuzzy logic method. This method as one of knowledge-based methods is used especially when the mining and mineralization indices are restricted. In these cases, we can achieve acceptable results by assigning logical weights to the data layers or maps according to the expert opinion. In the present study, this method has been used for the integration of alteration map resulting from processing the satellite images, and airborne geophysical, geological, structural and geochemical stream sediment data or maps to determine hydrothermal gold mineralization potential map in Torbat-e-Heydarieh area, Khorasan Razavi province. As a result, the probability mineralization zones with order of their exploration preferences have been indicated on the potential map. Overlapping mineralization indices and major veins of the study area on the probability mineralization zones in the potential map of the area show the effectiveness of this method. Finally, we have compared the results obtained from applying five fuzzy operators on the data.

The study area, (Spharayen plain) is one of the sub-catchments of the central Kavir, in North Khorasan Province. According to decrease in groundwater quality in Espharayen aquifer particularly in recent years, this paper tries to consider the reasons for decreasing the groundwater quality in the southern parts of the study area. For this purpose, in December 2009 and July 2010 the number of 75 samples from water wells was collected and the values of pH, EC, and concentration of major ions measured and finally the EC map of study area drawn. The maximum, minimum, and average values of EC of collected samples are 14720, 661, and 3519, respectively. On the basis of field observations and EC map, the Espharayen aquifer has been divided into five hydrogeochemical areas. For each area the average of anions and cations, EC, saturation index of Halite, and HCO3/Cl were calculated and compared. Exception for HCO3, the values of all ions, EC, and saturation index of Halite in areas 4 and 5 were greater than those in other areas. To evaluate the prevailing cation and anion zones, the Piper diagram has been applied. The obtained results indicate that there is an intrusion of saline water to southern and southwestern of the Espharayen aquifer (4 and 5 regions). Considering the values of draw downs in the five-mentioned regions, it may be concluded that the main reason for intrusion of saline water in this aquifer is significant groundwater decline due to extra-exploitation from the aquifer.

Reconnaissance and interpretation of underground heterogeneity, particularly litho-facies, always plays an important role in evaluation and management of hydrocarbon resources. Between various developed methods for modeling discrete characteristics of hydrocarbon reservoirs such as litho-facies, one with a more proper conformity with actual condition of reservoir facies is of great advantage. Formed on basis of probability and presenting transition matrix, Markov method is widely applied as a powerful tool for modeling the facies. In the present study, first the method is introduced in details; then, generalizability of Markov for conditions without seismic horizons is investigated. Also, one suggestion is made based on changing the type direction of the chain in simulation procedure. The case study is a 12 km long 110 m thick section of Anhydrite and three major members of Asmari Formation from an oil field, South-West Iran. This section is modeled through Markov procedure and proposed solution. The models set indicated best result with the accuracy of 82% is for the proposed solution.