中文摘要：

塔里木盆地塔中地区深埋碳酸盐岩储层显示出极强的非均质性。如灰岩地层孔隙度极低,而含酸性气藏的白云岩储层最大孔隙度高达27%。然而,造成这些现象的原因仍然不清楚。通过岩芯、薄片、扫描电镜观察,结合流体包裹体均一温度、盐度分析,方解石、白云石的碳氧同位素测定,试图解决这一问题。前人研究认为,塔中地区碳酸盐岩优质储层分布主要受控于原始沉积条件（如高能的礁滩相）和表生溶蚀,热液活动和断裂活动也起到重要作用。然而,多期流体活动和成岩作用导致大量同生期和表生期形成的溶蚀孔洞被破坏。在某些井区（如ZG9井和TZ75井）,埋藏溶蚀作用可能对优质储层形成起到重要作用。在寒武系和奥陶系岩芯中发现了大量硬石膏、重晶石、黄铁矿、沥青、方解石等,方解石交代硫酸盐,方解石具有较高的均一温度及较低的碳同位素值说明其形成与热化学硫酸盐还原作用（TSR）有关。在发生TSR的白云岩井段,储层物性较好,说明TSR可能对深埋储层的改善具有促进作用。这些认识有助于指导深层寒武系碳酸盐岩储层的进一步勘探。

英文摘要：

Deeply buried（ 4 500 to 7 000 m） carbonate reservoirs in the Tazhong area,Tarim basin,NW China show obvious heterogeneity with porosity from zero in limestones to 27.8% in sour dolostones. However,origin of the porosity remains puzzled. Petrographic features,C,O isotopes were determined,and fluid inclusions were analyzed on diagenetic calcite and dolomite from Ordovician reservoirs to solve the puzzle. Ordovician carbonate reservoirs in the Tazhong area are controlled mainly by initial sedimentary environments and primary and near- surface diagenetic processes. However,vugs and pores generated from eogenetic and telogenetic meteoric dissolution were observed to have partially been destroyed due to subsequent compaction,filling and cementation. In some localities or wells（ e.g.well ZG9 and TZ75）,mesogenetic dissolution（ e.g. thermochemical sulfate reduction,TSR） probably played an important role in pore production and reservoir quality improvement. The occurrence of TSR within Ordovician carbonate reservoirs are supported by TSR-originated calcite replacement of sulphate,and the association of sulfur species including acid gases（ H_2S）,pyrite,anhydrite or barite and elemental sulfur with hydrocarbon and ~（12）C-rich calcite with elevated homogenization temperatures. The TSR is observed to company with intensive dolomite dissolution,suggesting that TSR may have induced burial dissolution and thus probably increased the porosity of the sour dolostones reservoirs at least in some places. In contrast,no significant mesogenetic dissolution occurred in limestone reservoirs. The deeply buried sour dolostone reservoirs may therefore be potential exploration targets in Tarim basin.