الملخص الإنجليزي
There are two main aquifer systems in Oman, the Tertiary aquifer system and the Paleozoic aquifers of Haushi and Haima Groups. The recharge of aquifer systems comes from the Oman Mountains. This research is about Tertiary aquifers in Yibal area. Yibal is one of the largest oil Fields in Northern Oman, which is located approximately 400 km to the Northwest Muscat. From old to young, the Tertiary Formations above the Field consists of Umm er Radhuma (UeR), Rus, Dammam and the Fars. In North Oman, all of these Formations except the Dammam are aquifers and they are used as a source for Field water supply and water injection for oil Fields.
The objective of this project is to study the aquifer system in the Tertiary Formations in the Yibal area. All gas and oil wells in Yibal penetrate the two aquifers, the Fars and the UeR. With a significant difference in salinity between the two aquifers, the tight Dammam limestone is recognized as providing the hydraulic barrier between the two aquifer regimes. A proper isolation during drilling in the Dammam Formation will provide a sealing between Fars and UeR aquifers.
In Yibal, no comprehensive study has so far been carried out, focusing on the shallow aquifers in terms of reservoir characterization and how the water moves in the aquifer. A recent review of data on shallow Formations revealed that there is a fundamental lack of understanding of overburden Formations and especially of the two overburden aquifers, the Fars and the UeR. The hydrogeological characteristics of the overburden Formations, lithology. hydraulic conductivity, storage capacity, and reservoir pressure behavior are poorly understood. It should be noted that there are little data available on aquifer parameters such as transmissivity, specific capacity, or storage coefficient.
Both periodic and continuous water-level data can yield valuable information about groundwater flow, but this information is limited either in time or in space. A groundwater flow model designed to simulate groundwater flow in an aquifer and can be used for a more comprehensive analysis. Such groundwater flow model can describe the paths that water follows as it flows through an aquifer. In this project, two types of simulators have been evaluated, an oil industry simulator (MoReS) and Modflow that is designed for water. Visual MODFLOW is a complete modeling environment for practical applications in three dimensional groundwater flow and contaminant transport simulations. Therefore, a schematic model was built in Yibal shallow aquifers using the visual MODFLOW simulator. The model built in this study can be used to test alternative configurations of boundary conditions, aquifer flow processes, parameter distributions and in identifying the key aquifer parameters controlling any further work such as water disposal. The model by itself is not fully calibrated but can be seen as a first step towards evaluating the aquifer characteristics in Yibal for any future conceptual design study. It is very sensitive to some hydrogeological parameters such as porosity, conductive features, distribution of conductivity (or permeability), boundary conditions and recharges data.
