HYDROGEOCHEMICAL REGULARITY OF PETROLIFEROUS BASINS

The hydrogeochemical evolution regularity of oil and gas accumulation in an artesian basin has been studied by taking the artesian basin as a whole.Some new understandings are gained as follows: 1) The horizontal movement of the underground water within the basin causes the hydrogeochemical compositions to change regularly from the water recharge area to the water discharge area,providing the hydrogeological basis for studying both the relationship among oil,gas and water,and the distribution regularity of oil and gas accumulations.2) Two distinct hydrogeological systems exist in the artesian basin,which are controlled by the sub-structures of the basin.3) The runoff characteristics,the drive energy and the geochemical compositions of the penetration water and the sedimentary water within the artesian basin may differ obviously,and may exert different effects on the generation,the migration,the accumulation and the dispersion of oil and gas.And the front interface of the two kinds of water can act as the geographical border of the oil accumulations with different properties.4) The shallow hydrogeochemical effects related to oil and gas may distribute in various hydrogeological units of the artesian basin,especially in the oil-controlling fault zones and the oil-generative centers.In a whole,the characteristics and the distribution regularity of the hydrogeochemical anomaly are closely related to oil and gas,and can be used to evaluate the oil and gas prospects,as well as to predict the favorable zones for oil and gas to accumulate.