塔中古生界油田水化学与流体运移和演化

FLUID MIGRATION AND ALTERATION:CONSTRAINTS FROM CHEMISTRY OF PALAEOZOIC OILFIELD WATERS IN CENTRAL TARIM

对塔中地区石炭系、寒武-奥陶系油田水常量元素、氢氧同位素资料的研究表明，油田水中rCa／rMg值的高低可指示白云化或方解石溶解作用的强弱，与次生孔隙是否发育有关。rCa／rMg值、δ18O值正偏移是油田水封闭性、水-岩反应增强的结果。在高温、深埋条件下，储集层沥青与高丰度的有机酸共生，伴有石膏假晶、还原硫化物的出现，可能是由于烃类热化学硫酸盐还原作用。奥陶系油田水与石炭系油田水的氢氧同位素值相近，指示油田水发生了混合。

Based on major cation and isotope data of Carboniferous and Cambro-Ordovician oilfield waters, fluid-rbck interaction and flu-id migration in central Tarim are discussed. And it is suggested that rca/r.. ratio can indicate dolomization or dissolution ofcalcite, and is related to the secondary porosity. Positive shift of δ18O and high rca/rmg ratio are indicative of existence ofclosed system and enhanced water-rock interaction. And occurrence of reservoir bitumen, dolomite, calcite or pyrite as apseudomorphic replacement of gypsum, abundance of organic acids and anions and H2S gas, high homogenization tempera-tures of fluid inclusions are explained to be due to thermochemical sulfate reduction. Crossplot of δD and δ180 of Carbonifer-ous oilfield waters is close to those from Ordovician, suggesting occurrence of up-migration and mixing, which is also shownby relative proportions of major cations of waters from O, CⅡ, CⅠ unit.