塔里木盆地塔河地区上寒武统下丘里塔格组白云岩储层的热液改造效应OA北大核心

Hydrothermal dolomitization plays an important role on reservoir formation and evolution.Based on core and thin section examination,this study classifies the Upper Cambrian Lower Qiulitag dolostone in the Tahe area.Furthermore,elemental and isotopic geochemical analyses are employed to decipher the origins of various types of dolostones in the study area,aiming to evaluate the contribution of hydrothermal activity to reservoir evolution.Two types of matrix dolostones and dolomite cements of two stages are identified:very finely to finely crystalline matrix dolostone(D1),medium to coarsely crystalline matrix dolostone(D2),saddle dolomite cements with dull luminescence in the core(SD-1),and saddle dolomite cements with bright luminescence in the rim(SD-2).D1 is interpreted to have formed during shallow burial diagenesis,while D2 is interpreted as resulting from recrystallization during burial diagenesis.SD-1 is likely formed by local redistribution during burial diagenesis,whereas the rim of saddle dolomites(SD-2)formed through alteration by subsequent hydrothermal fluids.Consequently,we propose that the contribution of hydrothermal alteration to porosity enhancement seems negligible,with hydrothermal fluids largely confined to fractures and vugs.