大庆长垣北─断东地区葡Ⅰ油层组砂岩储层成岩环境对化学成岩作用的控制

DIAGENESIS ENVIRONMENT AND ITS EFLECT ON CHEMICAL DIAGENESES OF SANDSTONE RESERVOIR OF PI OIL BEARING GROUP TO THE EAST OF FAULT(NO.98)ON DAQING PLACANTICLINE

通过研究松辽盆地热演化史、孔隙水地球化学性质、地下水运移状态以及它们与成岩事件之间相互关系，探讨了成岩环境对砂岩储层化学成岩作用的影响。由于构造运动和古今地温梯度差异使葡Ⅰ油层组砂岩在埋藏成岩过程中所经历的最高古地温为８０～９０℃。这一温窗有效地控制了地层水中羧酸阴离了（ＣＡＡ）的浓度，砂岩中铝硅酸盐矿物和硅质岩屑的大量溶解充分地证实了这一点。溶解作用使某些砂岩储层具有较高的渗透率。在此热窗范围内，地下水中碳酸根系统被乙酸根缓冲，部分地抵消了ＣＯ＿２分压变化对ｐＨ值的影响，使砂岩中主要胶结物方解石趋于稳定。滞流盆地中地下水运移速度缓慢是葡Ⅰ油层组砂岩储层成岩作用单调的主要原因。

Based on the analysis of the geothermal evolution , the chemical properties of formationwate,the migration behavior of underground water in the Basin and their relation with dia-genetic events of the sandstone, this paper mainly deals with how the diagenetic environ-ment influences the chemical diageneses. Because of the tectonic background and geother-mal-gradient differences between the present and the Cretaceous,the sandstone reservoirhad been subjected to temperatures up to 80～90℃ during the burying process. This ther-mo-window limited the concentrations of CAA in the formation water,which is verified bythe dissolution of silicate grains and silicic rock fragments in the sandstones. This dissolutionmakes some sandstone highly permeable,In the thermo-window,the system of carbonicacid anion was buffered by the carboxylic acid anion in the formation water,which partlycounteracted the changes of the Pco_2 that affected the pH in the solution. The conditionsmade the calcite cements in the sandstone tend to be stable. Slow migration of the under-ground water in the detained basin is the main reason why the diagenesis of the sandstonereservoir of P I oil bearing group is monotonous.