南方震旦系灯影组热液白云岩化及其对储层形成的影响研究——以黔中隆起为例

我国南方地区，特别是四川盆地震旦系灯影组是我国当前高演化天然气勘探的热点，以黔中隆起为例，新揭示了其中发育的热液白云岩化现象，并探讨了其对储层形成的影响。研究区灯影组白云岩溶蚀孔洞或裂缝中见有白云石、石英、沥青充填，其中一种充填的粗晶白云石具有弯曲晶面、波状消光特征，在岩石学特征上初步反映热液成因。地球化学特征进一步揭示了这种热液成因。不同采样位置热液白云石样品中流体包裹体均一温度平均为157.5 ℃～205.8 ℃，最高为253.5 ℃。热液白云石具有较轻的氧同位素组成，δ¹⁸O_PDB 位于 -15.3‰～-8.6‰之间，平均值为 -11.2‰；较高的⁸⁷Sr/⁸⁶ Sr比值（0.709 445～0.713 131），其平均值为0.710 843，在稀土元素组成上，热液白云石具有典型的Eu正异常的特点，δEu值为1.11～7.46，平均值为2.37。因此，灯影组热液白云石发育。热液活动对储层形成具有积极影响，主要体现在对充填在早期岩溶孔洞和构造裂缝中的白云石产生了溶蚀作用，溶蚀孔中见沥青充填，反映为油气运移通道和聚集空间。因此，热液溶蚀改造作用对我国南方地区震旦系灯影组及下古生界碳酸盐岩储层发育可能具有重要意义，值得加强探索研究。

Hydrothermally dolomitized reservoir bed in Sinian Dengying Formation,northern China：An example from Central Guizhou Uplift

The Sinian Dengying Formation in the northern China, especially Sichuan Basin is a frontier for exploration of high evolution natural gas. Taking the Central Guizhou Uplift as an example, we found hydrothermal dolomitization and discussed the effect on reservoir development. Some dolomites, quartz and bitumen were found filled in dissolution caves or tectonic fractures in the Sinian Dengying Formation dolostones in the Central Guizhou Uplift. The coarse filling hydrothermal dolomites(HD)have features of curved crystal surface and wave extinction. Homogenization temperatures of fluid inclusions in HDs of different area are between 157.5 ℃ and 205.8 ℃, and the highest is 253.5 ℃. The oxygen isotope composition of the HDs is relatively light, and the δ¹⁸ O_PDB values are between -15.3‰ and -8.6‰ and -11.2‰ in average. The⁸⁷ Sr/⁸⁶Sr values of the HDs are relatively high, ranging from 0.709 445 to 0.713 131, and 0.710 843 in average. The HDs have a typical feature of Eu positive anomaly in REE composition. The δEu values are between 1.11 and 7.46, and 2.37 in average. The hydrothermal activities have also dissolved the dolomites filled in caves or fractures, and some bitumen can be found in the dissolution pores. The hydrothermal dissolution and alteration are very significant for development of the Sinian and Lower Paleozoic carbonate reservoir beds in the north area of China.