Characteristics Of Hydrochemistry Field And Its Relationship To Diagenesis In The Middle-Shallow Strata Of Northern Songliao Basin

Based on comprehensive collecting and sorting the analysis data in the middle-shallow strata of northern songliao basin, summarized the characteristics of formation water in vertical peace and surface distribution regularity and the main diagenetic characteristics of the sandstone.Through the research, we found that formation water can be vertically divided into three zones: free exchanging zone (0~800m), exchanging-retarded zone (800~1350m), a exchanging-stagnant zone (>1350m) and diagenetic water desalting zone (1350~1650m). The result of free water changing, diagenetic water desalting, water-rock reacting and other factors, chemistry characteristics of formation water changed regularly. Researching the distribution laws of plane, recognized that there is a close relationship between geological conditions and water chemistry, geological conditions similar, hydrochemistry characteristic also similar. Also found that during diagenesis sandstone particle, miscellaneous base, cementation, content and pore space changes closely related with diagenetic features of carbonate cementation, siliceous cementation, albitization, clay cementation and sandstone dissolution.For now the pH value of the formation water distortion, this paper established the acetic acid dissolution balance model, the application of organic acid recovery act of formation water in situ pH value, this method have certain limitation, it only applies to with organic acid decomposition for main buffer system formation. Through the recovery and measured the pH value of the comparison, its distribution area of the recovery pH value than the measured pH value is small to narrow. At the same time, use after restoring pH value income obtained the hydrogen ions concentration of dissolved feldspar with the contractor, reaction equilibrium constant comparison dissolution of feldspar, the dissolved state judge found in with organic acid decomposition for the main buffer system stratum, feldspar dissolved in balance.Through reseach the hydrochemistry characteristic and diagenesis characteristics, this process was mainly because potassium ion concentration of exorbitant prompting smectite and kaolinite to illite transformation in the middle-shallow strata of northern songliao basin. Formation water calcium and magnesium ions concentration change characteristics and carbonate cementation, the formation process of the corresponding with northern songliao basin in the diagenetic evolution characteristics of shallow calcite is consistent.Formation water sodium ions mineralization mechanism and chloride ions similar are mainly evaporation and concentration effect, it provides a rich source for potash feldspar and calcium feldspar albitization.