Geopersia
Volume:5 Issue: 1, Winter-Spring 2015

To evaluate the relationship between total organic carbon (TOC) and Rock-Eval S2 (petroleum potential) of petroleum source rocks، a total of 180 outcrop samples from the black organic matter–rich facies of Mesozoic strata from a locality of southwest of Iran were investigated using Rock-Eval VI pyrolysis and Leco Carbon Analyzer. The linear regression is applied to determine the correlation between Leco TOC and Rock-Eval S1 and S2. The accuracy of the proposed model by this method has approximately 95% conformity according to the Rock-Eval S2 and Leco TOC data (TOC = 0. 492 + 0. 174 S2). Then، by using the P value method، it was determined that TOC is a function of S2 and S1 only causes the fluctuations. By means of sensitivity analysis of TOC with respect to S1 and S2، it was shown that TOC has a linear relationship with S2 and does not have any noticeable correspondence to S1. The result of this study can be used to evaluate petroleum potential (S2) of organic matter–rich facies by using TOC obtained by Leco Carbon Analyzer. For the studied samples from the organic matter-rich facies، organic carbon richness is a quality and quantity index of petroleum potential.

Optimization of reservoir parameters is an important issue in petroleum exploration and production. The Ant Colony Optimization (ACO) is a recent approach to solve discrete and continuous optimization problems. In this paper، the Ant Colony Optimization is used as an intelligent tool to estimate reservoir rock properties. The methodology is illustrated by using a case study on shear wave velocity estimation from petrophysical data by the linear and nonlinear ACO models. The results of this research show that the ACO is a fast، robust and cost-effective method for rock properties estimation. It is proposed that ant colony optimization aids in future reservoir characterization studies.

Rhaetian strata from the Nayband Formation of the Tabas block، East- Central Iran، were studied palynologically. The material examined contained moderately diverse and well-preserved dinoflagellate cyst assemblages which lead to the identification of Rhaetogonyaulax rhaetica Zone. The assigned age of this dinozone (Rhaetian) is justified by plant fossils such as Equisetites arenaceus، Scytophyllum persicum، Pterophyllum bavieri، Pterophyllum aequale and Nilssoniopteris musafolia recorded from these strata. The dinoflagellate cysts show close similarities with assemblages reported from Australia، Northwest Europe، Arctic Canada and Northern Iran. Furthermore، the associated marine palynomorphs (dinoflagellate cysts، accompanied by spores grain indicate a nearshore depositional environment for the Late Triassic (Rhaetian) deposits in Tabas Block of Iran.

Jurassic deposits are well exposed in the Bazehowz area، South west of Mashhad city، East Alborz، Iran. It contains plant macrofossils belonging to eighteen species of eleven genera of various orders such as Equisetales، Filicales، Bennettitales، Cycadales، Corystospermales، Caytoniales، Ginkgoales and Pinales. Two biozones were recognized in the type section of Bazehowz Formation. Biozone I is an assemblage biozone with its lower and upper boundaries identified by first observed occurrence (FOO) and the last observed occurrence (LOO) of Nilssonia rigida، Nilsssonia sp. cf. N. bozorga and Nilssonia feriziensis. Since there are species from Liassic such as Nilssonia rigida and uppermost Liassic such as Nilssonia feriziensis and Nilssonia sp. cf. N. bozorga، a Toarcian age is suggested for this biozone. Biozone II is an interval zone with its lower and upper boundaries identified by FOO of Klukia exilis and Ptilophyllum vasekgahenses and Coniopteris hymenophylloides and Ctenozamites cycadea، respectively. According to occurrence of Klukia exilis، a lowermost Middle Jurassic age is suggested for the lower boundary and based on the occurrence of Coniopteris hymenophylloides Aalenian age is considered for upper boundary of Biozone II. On the basis of relative abundance of Filicales (%16. 6)، Bennettitales (%27. 7) and Cycadales it is considered a humid sub-tropical climate for this period of time.

This research was performed to determine the efficiency effect of sedimentary environment of Kerman City area on soil structure by comparing natural and reconstituted consolidation curves. In this regard، four different criteria such as sensitivity strength، stress sensitivity، Schmertman criteria and the result of the uniaxial compression test were used. The base of these criteria is to compare the results of natural and undisturbed soil consolidation tests. The position of undrained shear strength of Kerman City soils in Iv-Su space was located on the left side of the intrinsic strength line and this confirms that the stress sensitivity of soils is less than the unit. Therefore، the soils in the city subzone are mostly over consolidated، and cementation and chemical bonds have not developed. The swelling sensitivity of fine grained soils based on Schmertman criteria are often less than 2 or slightly larger than 2. 5 indicating that the soils of Kerman City subzones have underdeveloped swelling sensitivity due to poor cementation.

Clogging occurs during mechanical tunneling with a Tunnel Boring Machine (TBM) because of adhesion of clayey soils to the cutter head and conveyor system. The present study examined the effects of water and sand contents on clogging in Montmorillonite clayey soil. Testing was carried out using an adhesion test device on 28 samples with different water and sand contents to determine adhesion stress and degree of clogging. The results indicate that the consistency index (Ic) of the samples decreases as the sand and water content increases. The results for variation of adhesion stress versus water content at different sand contents formed similar bellshaped curves. In all graphs، an increase in sand content decreased adhesion stress. Adhesion stress increased until the water content increased to 138%، at which point it began to decrease. The results show that adhesion of the soil to the surface of the metal piston did not occur in samples having a sand content of >40% and in samples with >133% water content having a sand content of <40%، Ic>0. 5 adhesion occurred.

It is over two decades that groundwater flow models are routinely implemented for better management of groundwater resources. Modeling groundwater flow with the help of the ground water modeling system (GMS) in the Damghan plain aquifer in northern Iran، which experiences declining levels and numerous environmental hazards، has demonstrated that، (a) in the worst case scenario the aquifer will face 320 cm of drawdown by year 2019 and (b) land subsidence is observed mainly in areas that are subjected to an accelerated water level drawdown rate، such as، the southern part of the aquifer. Four different rainfall scenarios that have been modeled demonstrate that some areas of the aquifer are slightly impacted by climatic change in contrast to some other areas that are being influenced substantially. Together with GMS، Genetic Expression Programming (GEP) and Multiple Linear Regression (MLR) models were used to forecast land subsidence by applying developing functional relations to the long-term groundwater drawdown data. This segment of the study shows that a 35. 4 cm and 39. 45 cm settlement will occur if the groundwater level drops by 295 cm and 343 cm، respectively. This research shows that the water level in the Damghan aquifer continues to decline and the land subsidence will intensify. It is، therefore، needed to reduce groundwater pumping in high-risk areas.

The Shah-Kuh granitoid has intruded in the Triassic–Jurassic، pelitic and psammitic low grade metamorphic rocks of the NE Lut Block، in Central Iran. Cordierite porphyroblasts are common in the southern pelitic sediments، but are rare in the northern psammitic rocks، in the contact aureole. Deformation fabrics in the contact aureole are well preserved within the cordierite porphyroblasts. The relation of the cordierite porphyroblasts and deformation fabrics indicate that the time of growth has started and is synchronous with the first deformation phase and ends after the second deformation stage. The porphyroblasts are also generated in syn-intrusion ductile shear zones existing in the contact aureole and continue inside the Shah-Kuh granitoid. Shear zones in the contact aureole contain deformed cordierite porphyroblasts، with microstructures indicating clear shear sense. Structural analysis of various metamorphic rocks in the contact aureole of the Shah-kuh granitoid indicates a first stage، which is tight to the isoclinal folds، with well-developed axialplane foliation، and a second stage of crenulation cleavage. Sequential growth of cordierite porphyroblasts preserved fabric from various stages of a progressive deformation in the granite contact aureole. It is concluded that the Shah-Kuh granitoid has intrusions synchronous with progressive deformation، cordierite porphyroblasts growth، and shear zone development in the contact aureole of the granitoid.