The Evolution Of Chemical Characteristics Of Oilfield Water In Development Process

Oilfield water is the power and carriers that the hydrocarbon to migration, accumulation and forming reservoirs. Through studying the chemical characteristics of oilfield water and the evolution in the injection development stage, the migration, accumulation and the formation of oil and gas reservoirs can be analyzed, the water injection can be adjusted, the efficiency of water can be improved, the treatment and re-injection of the oilfield water can be guided, oil recovery can be enhanced.In the long-term developing of water injection, the rock matrix, pore network, and seepage characteristics of clay minerals of underground reservoir has evolved, the distribution and the nature of the fluid has changed. These changes mainly affected by the structural characteristics of oil pool and the properties and temperature of injection water.On the basis of research in national and abroad, according to 40 years'water quality monitoring data of the first block of Shengtuo Oilfield, the natural evolution and in the injection water, oily wastewater injection, polymer injection under the conditions of the different oil-water flooding and water chemistry characteristics of migration law and its evolution was be studied. The mainly results are as follows: (1) The main type of oilfield water is CaCl2 in the first block of Shengtuo Oilfield. With characteristics of high salinity and obvious ion differentiation phenomenon, it is considered as typical continental oilfield water.(2) During injection of Yellow River water, desalt dilute effect is obvious. Content of the major ion decreased on the earlier stage, but stabilized on the later stage. In this period, the type of water was NaHCO3. During injection of Oily wastewater, salinity, content of chloride ion and sodium ion increased. It is easy to produce H2S, and lead to water quality deterioration. During injection of polymer, effect of oil displacement was best when effective infused concentration was 1070mg/L and polymer concentration from recovery water was 200-300mg/L. Effect of oil displacement got better with a surge of chloride ion concentration.