Characteristics Of Enrichment And Resources Of The Subsurface Brines In The Deep-Seated Aquifers In The Ziliujing Brine-Beaing Structure Of The Sichuan Basin

The subsurface brines in the deep-seated aquifers is a kind of liquid deposits of high industrial value, which can be used for salt production and can also be used to extract Br-, K+, Li+, Li+, Sr2+ Ba2+ and so on. In this paper, we choose the Ziliujing brine-beaing structure of the Sichuan Basin as an example which has long history of salt production to analyze characteristics of enrichment and chemical characteristics and estimate the resources of the deep-seated subsurface brines.The subsurface brines in the Ziliujing brine-beaing structure can be divided into two kinds. The reservoir of the Upper Triassic Xujiahe Group is mainly composed of feldspar quartz sandstone and feldspar lithic quartzite sandstone and the buried depth is about 50 to 500 m. The reservoir of Middle and Lower Triassic Jialingjiang and Leikoupo Group are mainly composed of limestone and dolomite and the buried depth is about 920 to 1030 m. The porosity of clastic rock is 8.1% to 10.92% and the porosity of carbonate rocks is 6.33% to 12.98%. The reservoir is low porous and low permeable reservoir rocks. The storage space and communication Tunnel can be improved at anticline and fault zones. The enrichment of brines is mainly controlled by fracture. The bines occur mainly in the Huanggepo fault and the underground fault zone in the southeast. The production of the bines in the Huanggepo fault zone accounts for 74% of the whole production of the structure.This paper uses a variety of methods to do hydrochemical analysis for the deep-formation brines in the Ziliujing structure, such as the way of routine components analysis, ion proportional coefficient, and comparison with the curve of evaporated seawater, and so on. The TDS of the subsurface brines in Ziliujing brine-beaing structure ranges from 171.73 g/L to 238.48g/L. The hydrochemical type of the deep-formation brines are of Cl-Na type. The major component of the cations is Na+ and the major component of the anions is Cl-. The yellow brine is rich in Ca2+, Mg2+, Ba2+ and Sr2+ and the black brine is rich in K+, Na+, Li+. Tracelements, such as Br-, Li- and Sr2-, are in excess of the single mining industry standards. K+ that in the black bine is also in excess of the single mining industry standards. The stable isotopes of δ2H and δ18O of the brines and comparison with the curve of evaporated seawater show that the black bine is of paleo-marine origin. The black bine was formed during dolomitization, salt precipitation and the desulfurization acid effect. The results of ion proportional coefficient show that yellow bine is of continental syngenetic sedimentary water or ancient mereoric origin. The yellow bine was formed during membrane filtration, cation exchange adsorption and plagioclase albitization and so on.Calculation of the natural resources of the yellow bine with the volumetric method shows that there is brine of 7×108 m3 in the clastic aquifers. Comparion with the actual production of 1.6626×108 m3, yields the mining coefficient of 0.0803. We set up the three-dimensional unsteady flow model for the black brine in the study area and solve the model with the visual Modflow. We can determine the location and exploitation quantity of pumping wells accoding to the well yield distribution. Using the initial parameters of the reservoir to adjust aquifer parameter and make the values of head of pumping wells match the actual results. We can determine the exploitable volume of bines when the head value is the same as elevation of the aquifer roof. The exploitable volume of bines is 1.28×108m3 and the actual volume of bines is 1.12×108 m3. The actual head is a little lower than the calculated value. The possible reason for this is that the actual values of the hydrogeological parameters are less than the values of simulation. The whole exploitable volume of the aquifers has been pumped.