Characteristics And Evaluation Of Brine In Lower Liaohe Plain, China

Brine is a kind of rare liquid resources, which has been extensively used in national economy. The Lower Liaohe River Plain, in Panjin city Liaoning province, has plenty of Quaternary brine resources, with the huge exploitation potential. So, it is necessary to carry out the characteristics analysis and resource evaluation.The study area, underlain by the Liaohe faulted sag, belongs to north of Bohai rift subsidence basin. The neotectonic movement has been dominated by subsidence and the frequent Quaternary sea level change has brought out multistep sedimentary cycle with respect to sea intrusion. The brine resource occurs in the Upper and Mid Pleistocene aquifer of Quaternary, the depth ranges from 20 to 200m. The Upper and Mid Pleistocene both are alluvial formation, the thickness respectively ranges from 50 to 60m or 40 to 50m.By analyzing hundreds of water samples, we summarize the chemical characteristics of brine in study area as followed:1) In the majority species, the ratio of Cl- in anion is more than 85%, and that of Na+ in cation is about 75%, the mean pH value is 6.6. The brine resource has patch distribution surrounding A1, A2 and A3. Analysis of AquaChem reveals that Na-Cl type brine extensively occurs in study area, region A1 enriches more Na-Mg-Cl type, so region A1 has more Mg²⁺ than A3.2) Analysis of ratio coefficient testifies that brine derives from seawater, and indicates intensive cation exchange process in the formation of brine. Correlation analysis between major cations and Cl^- confirms the above consequence, a great deal of Ca²⁺ turned into groundwater, while K⁺ was largely absorbed by rock and soil, Mg²⁺ slightly increased compared to seawater because of terrestrial sediment. Na⁺ showed decreased trend with increased concentration. 10 groups of chemical equilibrium simulations from seawater to the representative samples were conducted by PHREEQC, the results reveal that cation exchange plays more important role than mineral precipitation and dissolution plus to gas separation during the evolution of seawater. Simulations quantitatively approve the direction of ion exchange in water-rock interaction.3) Hydrogen and oxygen isotope analysis of 9 samples indicates there was mixing of meteoric water during the evolution; the aquifer system is slightly open to the modern water cycle.Finally, this dissertation set up a brine reserves model based on FdmGrid, theresult shows that liquid brine resource in region A1 and A3 counts up to 0.529 billion m³, and crystalline salt counts up to 2.77 million tons. The reserves of sodium salt, magnesium salt, potassium salt and bromine sum up ten thousand tons, with promising developing value.