Effect of fluid medium in source rock porosity on oil primary migration

With the self-designed simulation instrument for hydrocarbon generation and expulsion in formation porosity under controlled heating and pressuring conditions, a series of experiments was made with different systems such as nitrogen-water vapor, water vapor-liquid water, liquid water, and anhydrous. Oil discharge efficiency was compared to study the effect of the fluid medium in source rock porosity on oil primary migration. In the oil and gas generation phase, pore space in the source rock was charged by fluids (hydrocarbon gas, non-hydrocarbon gas, oil, formation water) with certain temperature and pressure. Liquid water was an indispensable transport carrier in oil primary migration process. Water might adsorb onto the surface of minerals, preventeding the adsorption of hydrocarbon and was favorable for hydrocarbon migration. CO₂ associated with hydrocarbon generation easily dissolved in oil, which reduced the interfacial tension between the oil and water, oil viscosity and oil migration resistance, and promoted oil primary migration.