جستجوی مقالات مرتبط با کلیدواژه "سازند داریان" در نشریات گروه "مهندسی شیمی، نفت و پلیمر"

Quantitative heterogeneity presentation is very important to compare the amount of heterogeneity in different reservoir characteristics in carbonate reservoirs. The aim of the present study is to quantify the heterogeneity by calculating the heterogeneity log and its application in investigating the heterogeneity of porosity and permeability in the Late Barremian-Early Aptian Darian carbonate Formation in the central part of the Persian Gulf. In order to calculate the heterogeneity logs, the well log data of gamma ray, bulk density, neutron porosity, acoustic and deep resistivity and the statistical methods of Lorenz coefficient and coefficient of variation have been used. Results show that the calculation of the heterogeneity log provides the possibility of quantitative comparison of the heterogeneity between different parts of the reservoir for different purposes. Heterogeneity calculation with both methods is efficient for calculating heterogeneity, but it should be noted that the coefficient of variation for the maximum heterogeneity does not have a specific range like the Lorenz coefficient. Also, increase in porosity is associated with a decrease in the amount of heterogeneity in the heterogeneity logs of deep resistivity, acoustic, neutron porosity and density. Unlike other logs, gamma ray heterogeneity log has little direct relationship with porosity in Darian Formation. Two types of neutron porosity heterogeneity and deep resistivity are the most used in determining the reservoir properties in this formation. Permeability shows a weak relationship with heterogeneity logs. In bioclast wackestone microfacies of carbonated units with high porosity, less heterogeneity is observed. Also, units with higher porosity are thicker and therefore exert stronger mean effects on heterogeneous areas. High variability in porosity and permeability causes higher heterogeneity. This is also the case about lithology and clay minerals. Heterogeneity changes at facies change boundaries. Therefore, heterogeneity log can be used to investigate geological heterogeneity, porosity, permeability and reservoir zoning.

Dariyan Formation (with Aptian age) is considered as one of the important oil reservoir of the Zagros and Persian Gulf sedimentary Basin. This formation in the studied field in southeast of the Persian Gulf, is considered as the most important oil reservoir rock. In this study, microscopic thinsections that prepared from the cores of the Dariyan Formation, were investigated. The study of the microfacies of the Dariyan Formation in this field led to identification of seven carbonate microfacies and one mixed carbonate-clastic microfacies, which were deposited in four facies belt including the inner ramp, middle ramp, outer ramp and deep basin. The investigating of the fauna in the studied microfacies shows a relatively shallow marine environment (in some intervals representing the deep marine environment), generally. Uniform facies changes and the absence of rudists and corals which are reef-building faunas as well as the replacement of Lithocodium algae with less ability to form the large reefs, represent the homoclinal carbonate ramp environment, which contain «patch reefs». Importanat diagenesis processes such as: cementation, bioturbation, pyritization, phosphatization, dolomitization, dissolution, Mechanical and chemical compaction and fracture has affected the carbonate rocks of this Formation. Correspondence of porosity and permeability data of the cores indicates that the reservoir quality of the Dariyan Formation in the studied field was affected by facies, sedimentary environment and diagenesis factors, so the lithocodium- bearing facies (boundstone-flootstone) have the most porous facies.

The Dariyan Formation with the Aptian age is one of the most important prolific oil reservoirs in the Zagros and Persian Gulf. In the current study, different rock typing approaches were integrated and applied for the reservoir characterization of this formation in an oil field in the eastern Persian Gulf. Petrographic studies on the thin sections of the studied formation have led to the recognition of nine microfacies grouped into four sub-environments, including basin, outer, middle and inner ramp. The observed facies indicate a carbonate ramp as the depositional environment of the Dariyan Formation. The most important diagenetic processes observed in thin sections are dissolution, dolomitization, fracturing, micritization, (mechanical and chemical) compaction, and bioturbation. Based on the porosity-permeability of cores, six hydraulic flow units (the flow zone indicators = FZI method), four Winland rock types, and three Lucia rock classes were identified. Predicted porosity and permeability from log data were used to identify five hydraulic flow units (from the FZI method) and based on the stratigraphic modified Lorenz plot (SMLP), six reservoir/non-reservoir units were identified. In addition, using the multi-resolution graph-based clustering (MRGC) technique, seven electrofacies were determined. A comparison between the results of all rock-typing methods and petrographic data also reveals close correspondence. In a general view, the reservoir potential of the Dariyan Formation is higher in the Highstand System Tracts, which are mainly composed of grain-supported fossil-bearing and boundstone facies of the inner ramp sub-environment that could be a target zone for the field development. In contrast, the mud-dominated facies of the basin and outer ramp sub-environments in the Transgressive System Tracts are the poor reservoir units within the Dariyan Formation.