جستجوی مقالات مرتبط با کلیدواژه « فرآیندهای دیاژنزی » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

Carbonate reservoirs are very complex and heterogeneous. Overcoming heterogeneity is important and necessary for accurate reservoir characterization. Dalan-Kangan formations, as the largest non-associated gas reservoir of the world, are heterogeneous and complex due to the influence of the sedimentary environment and diagenesis processes. Carbonate reservoirs are routinely studied using laboratory data. The use of well logging instead of using laboratory methods is very cost-effective in reducing time and cost. To overcome the heterogeneity by acoustic log, samples of Dalan-Kangan carbonate formations were prepared. A total of 87 limestone thin sections were evaluated by petrography, routine core analysis, and sonic velocity. Porosity, permeability, sedimentary textures, pore types, and diagenetic processes were determined precisely. From the studied well, well logging and acoustic logs were also available. After data quality control, the acoustic log was converted to velocity. Velocity-porosity model was constructed based on the differential effective medium (DEM) approach for different values of equivalent pore aspect ratio (EPAR). The results show that moldic, vuggy, interparticle, and microporosity pores have the largest aspect ratio, respectively. Due to their spherical shape and high aspect ratio at the given porosity, moldic and vuggy pores have higher velocity than flat and narrow pores. Through the geometrical shape and pore type and by using the acoustic log, the rock types were determined. These rock types clearly showed the porosity evolution, permeability changes and diagenetic processes that have been occurred in Dalan-Kangan reservoirs.

This investigation is focused on the Khaneh-Zu Formation as a hydrocarbon reservoir as a point of view of microfacies, depositional environment, diagenetic processes and their effects on reservoir characterization. This study is based on the integration of lithostratigraphy, field study and petrography of this formation in 2 surfaces (Abghad and Khaneh-Zu) and 2 subsurface sections (Chahchaheh and Afshar wells) in the Kopet-Dagh basin. According to petrographic studies, 9 microfacies has been identified which were deposited in 3 facies belts including mid ramp, outer ramp and basin. The lack of calciturbidites and gradual change of microfacies to each other indicates the deposition in a carbonate hompclinal ramp. Diagenetic processes which have been affected on the studied interval are bioturbation, micritization, cementation (blocky and drusy), compaction, dolomitization, dissolution, pyritization and silicification. Vuggy, intercrystalline and fracture are different identified types of porosity. The porosity types are non-facies selective and formed as a result of diagenetic processes include dissolution, dolomitization and fracturing. Cementation and compaction have negative effects on reservoir characteristics. Based on low porosity percentage and low permeability, the studied sections dose not show high reservoir quality since most of the pores are filled with calcite cements. Dissolution, chemical compaction as stylolite and cementation are the most important diagenetic processes in this formation that result burial diagenesis. As a matter of fact porosities in Khaneh-Zu Formation are vuggy type, and they are not connected to each other to make permeability and a good reservoir. However, this report would be able to introduce more information about sedimentary environment and diagenetic processes controller for Khaneh-zu formation in Kopeth Dagh area.

The Sarvak Formation is one of the most important carbonate reservoirs of Iran. This study presents an integrated geological and petrophysical reservoir characterization of the Sarvak Formation in a giant oil field in the Abadan Plain, SW Iran. On the basis of porosity-permeability data, core description and petrographic studies from two key wells, flow units were identified and interpreted. To identify flow units within the Upper Sarvak Formation, three different petrophysical methods including (1) Flow Zone Indicator (FZI), (2) Pore Throat Radius (R35) and (3) stratigraphic modified Lorenz plot (SMLP) were applied. The results indicate that the FZI and R35 methods cannot efficiently discriminate the different reservoir zones and flow units for this reservoir, because of the high changes in petrophysical properties have mainly inherited from the internal geological heterogeneity. In contrast, SMLP method successfully classifies the studied reservoir into discrete flow units by considering the relationship between petrophysical properties and depositional and diagenetic features. From depositional facies point of view, the best flow units are related to talus, shoal-biostrome and shallow open marine depositional facies, while lagoon and distal open marine commonly show low reservoir quality. In low reservoir quality units, calcite cementation and compaction are the dominant diagenetic processes, while dissolution is the main agent for enhancing of the reservoir quality in the reservoir units with high quality. The results indicate that the interpretation of flow units based on the depositional and diagenetic characteristics provides the crucial insight on distribution of reservoir zones within the heterogeneous carbonate reservoirs, such as, the Sarvak Formation.

Asmari Formation (Oligocene-Miocene) is one of the most important reservoir in the Aghajari oil field in the Dezful Embayment in south west of Iran which is composed of limestone, dolomite and sandstone units. The purpose of this study is to identify, differentiate and interpret the diagenetic processes and their impact on the reservoir quality of the Asmari Formation in wells 64, 30 and 149 of Aghajari oil field. The most important diagenetic processes that affected the Asmari Formation include dissolution, compaction, fracturing, dolomitization, cementation and anhydritization. Processes such as dissolution (by creating vuggy and moldic porosity), fracturing and dolomitization increase the reservoir quality while and processes such as anhydritization, compaction and cementation reduced the reservoir quality in zone of 3 and 4. Also one of the reasons for increasing the reservoir quality of Asmari Formation is the present of sandstone units in the Dezful Embayment. These increases in reservoir quality can be related to sorting and rounding of grain size, geometry and distribution of sandstone in this oil field. These processes led to creation of the best reservoir quality in quartzarenite and limy sandstones facies. Finally, zone 3 has a better reservoir quality than zone 4 that it is due to impact of diagenetic processes as well as increases sandstones thickness.