ABNORMAL FORMATION PRESSURES AND OIL-GAS MIGRATION IN CHINA

Abnormal formation pressures occur not only in marine strata but also in terrestrial sedimentary basins in China. It develops most in Tertiary, followed by Mesozoic and Palaeozoic. Residual pressure decreases with the age of strata. Abnormal pressure mainly results from imbalanced compaction and hydrocarbon generation, and depends on various geological conditions. The secondary cause is the uplift of crust at the late stage and the transformation of day minerals. Practical data show that the abnormal formation pressure provides the dynamic force and passages for the primary migration of oil-gas, and in reservoirs, it can affect the distribution of flow potential, which controls the migration direction and the accumulation place of oil and gas.