Thermal modelling of gas generation and retention in the Jurassic organic-rich intervals in the Darquain field, Abadan Plain, SW Iran

The petroleum system with Jurassic source rocks is an important part of the hydrocarbons discovered in the Middle East. Limited studies have been done on the Jurassic intervals in the 26,500 km2 Abadan Plain in south-west Iran, mainly due to the deep burial and a limited number of wells that reach the basal Jurassic successions. The goal of this study was to evaluate the Jurassic organic-rich intervals and shale gas play in the Darquain field using organic geochemistry, organic petrography, biomarker analysis, and basin modelling methods. This study showed that organic-rich zones present in the Jurassic intervals of Darquain field could be sources of conventional and unconventional gas reserves. The organic matter content of samples from the organic-rich zones corresponds to medium-to-high-sulphur kerogen Type II-S marine origin. The biomarker characteristics of organic-rich zones indicate carbonate source rocks that contain marine organic matter. The biomarker results also suggest a marine environment with reducing conditions for the source rocks. The constructed thermal model for four pseudo-wells indicates that, in the kitchen area of the Jurassic gas reserve, methane has been generated in the Sargelu and Neyriz source rocks from Early Cretaceous to recent times and the transformation ratio of organic matter is more than 97%. These organic-rich zones with high initial total organic carbon (TOC) are in the gas maturity stage [1.5–2.2% vitrinite reflectance in oil (Ro)] and could be good unconventional gas reserves and gas source rocks. The model also indicates that there is a huge quantity of retained gas within the Jurassic organic-rich intervals

Geochemical constraints and uranium potential of the younger granitic rocks in El Maghrbia area, Central Eastern Desert, Egypt

The present work deals with the mineralogy, geochemical behavior and uranium potentiality of the monzogranites of El Maghrbia area, which comprise G. El Maghrbia and G. El Eredyia and situated in the central Eastern Desert of Egypt. G. El-Erediya monzogranites represents a promising area for uranium mineralizations. These granites have shear zone filled with red and black silica veins containing many radioactive anomalies with visible yellow secondary uranium minerals. The shear zone is highly affected by different degrees of alterations such as silicification, kaolinitization, sassuritization and ferrugination. Monzogranites of El-Erediya area possess higher values of their radioactivity than in El Maghrbia monzogranites in which eU and eTh, reaches up to 792.3 and 66.81 ppm, whilst average content of eU and eTh in El Maghrabia granites are 3.86 and 8.55 ppm, respectively owing to the presence of radioactive minerals such as uraninite, uranothorite, uranophane, kasolite, betafite, zircon and monazite. Intensive geochemical analyses indicated that, the studied monzogranites are distinctly anomalous in U, where the average U is more than 620-fold the Upper Continental Crust (UCC), marked enrichment ([tenfold) of the elements Cd, Mo, Pb, Bi, Nb and W. The Th/U ratio decreases from 2.8, as a chondritic value, to 0.0023 for the studied granites, proposing extreme fractionation towards an extensive secondary migration-in of U. The Zr and Hf are depleted in the studied granites relative to the UCC, whereas Nb and Ta are strongly enriched. The content of Y is about sixfold enriched which reflects relative enhancement of the HREE during the alteration processes. Uranium correlates with Fe2O3 T, suggesting a possible association between uranium and ferrugination. Thus, the occurrences of uranium are epigenetic by remobilization from the host rock to the sheared zones, probably through metasomatic process where U–Fe–Mg replaced the feldspars in an oxidized condition. The high levels of radioactivity in the rocks being studied it them a priority for discovery and expanding the potentiality of the highly mineralized localities

Hydrogeochemical evolution of inland lakes’ water: A study of major element geochemistry in the Wadi El Raiyan depression, Egypt

Wadi El Raiyan is a great depression located southwest of Cairo in the Western Desert of Egypt. Lake Qarun, located north of the study area, is a closed basin with a high evaporation rate. The source of water in the lake is agricultural and municipal drainage from the El Faiyum province. In 1973, Wadi El Raiyan was connected with the agricultural wastewater drainage system of the Faiyum province and received water that exceeded the capacity of Lake Qarun. Two hydrogeological regimes have been established in the area: (i) higher cultivated land and (ii) lower Wadi El Raiyan depression lakes. The agricultural drainage water of the cultivated land has been collected in one main drain (El Wadi Drain) and directed toward the Wadi El Raiyan depression, forming two lakes at different elevations (upper and lower). In the summer of 2012, the major chemical components were studied using data from 36 stations distributed over both hydrogeological regimes in addition to one water sample collected from Bahr Youssef, the main source of freshwater for the Faiyum province. Chemical analyses were made collaboratively. The major ion geochemical evolution of the drainage water recharging the El Raiyan depression was examined. Geochemically, the Bahr Youssef sample is considered the starting point in the geochemical evolution of the studied surface water. In the cultivated area, major-ion chemistry is generally influenced by chemical weathering of rocks and minerals that are associated with anthropogenic inputs, as well as diffuse urban and/or agricultural drainage. In the depression lakes, the water chemistry generally exhibits an evaporation-dependent evolutionary trend that is further modified by cation exchange and precipitation of carbonate minerals