Geology _ Geophysics in Oil Exploration

Primaryporosity secondaryporosity 4 permeability it

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Unformatted text preview: y buried, no hydrocarbons will be produced. 27 Geology & Geophysics in Oil Exploration Mahmoud Sroor Geology & Geophysics in Oil Exploration 2‐Migration Migration is the process of the oil and gas moving away from the source rock. This is a slow process. Migration is caused by burial, compaction, and increase in volume and separation of the source rock constituents. There must be space ‘porosity’ within the rocks to allow for movement. In addition, there is should be Permeability’ within the rocks. There are two types of migration: • Primary migration: is the process of movement from source rock. As sediments build up to greater thickness in sedimentary basins, Fluids are squeezed out by the weight of the overlying sediments. Fluids tend to move toward the lowest potential energy. Initially this is upwards, but as compaction progresses; there is lateral as well as vertical movement. Finally the mechanism that oil migrates is uncertain • Secondary migration: is movement to or within the reservoir entrapment. Once the water, oil and gas migrate into the trap, it separates according to density. Gas being the lightest, goes to the top of the trap to form the free gas cap. Oil goes to the middle and water that is always present, on the bottom 3‐Reservoir rocks It is a rock that contains connected pore spaces used to reserve the fluid inside To be commercially, productive it must have sufficient thickness, a real extent, and pore space and this pores must be interconnected (Permeable) Once oil and gas enter the reservoir rock, they are relatively free to move. Most reservoir rocks are initially saturated with saline groundwater. Saline ground water has a density of slightly more than 1.0 g/cm3. Because oil and gas are less dense than the ground water (density oil = 0.82‐0.93 g/cm3 and density gas = 0.12 g/cm3), they rise upward through the water‐saturated pore spaces until they meet a barrier of impermeable rock. Classification of the reservoir rocks: is based on 1. Type of rock: • Igneous Rocks: can be part of reservoirs (fractured ro...
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