准噶尔南缘前陆盆地白垩纪—新近纪构造挤压作用与储层关系的新表征:镜质体反射率与颗粒填集密度

The interpretation of the controlling action of Cretaceous to Tertiary tectonic compression on the reservoir in the southern margin of Junggar Basin:vitrinite reflectance and grain packing density

镜质体反射率Ro是构造挤压作用对砂砾岩储集体产生热效应的重要反映,颗粒填集密度则是二者关系的具体体现。通过对准噶尔南缘白垩系—古近系样品镜质体反射率Ro的分析,结合白垩系—新近系霍001井等14口井76块样品统计颗粒填集密度分布规律与储层微观镜下研究,认为构造挤压作用对砂砾岩储集性的影响具有如下演化特征:白垩纪Ro值具有东部高、中西部低的特点,颗粒填集密度平面分布规律与其相近,表明位于前陆冲断带东部呼图壁地区储集层受构造侧向挤压影响较为强烈,西段的西湖—独山子地区储集层受构造影响弱,晚侏罗世—早白垩世博格达山隆升造成了这一结果。古近纪镜质体反射率Ro与颗粒填集密度展布与白垩纪显著不同,具有由冲断带中远端(第二、三排构造)安集海—玛纳斯—吐谷鲁背斜区向冲断带近端(第一排构造)与前渊带南北两方向降低趋势,表明古近纪储集层受构造侧向挤压影响弱,转变为主要受地层埋藏热效应影响。由于中新世以来的北天山强烈隆升,颗粒填集密度与古地温展布特点反映了储集层由古近纪主要受埋藏热效应影响,转变为受构造侧向挤压的影响。白垩系砂砾岩孔隙度与镜质体反射率Ro、颗粒填集密度呈明显负相关关系,也与成岩作用强度呈负相关关系;古近系镜质体反射率Ro、颗粒填集密度与砂砾岩孔隙度呈正相关关系,由此预测了准噶尔南缘较有利储层的分布。

Vitrinite reflectance is one of the important reflections of the controlling action of tectonic compression on the reservoir in the southern margin of Junggar Basin.Grain packing density is a direct result of tectonic compression that controls the reservoir.An analysis of the measured vitrinite reflectance of the Cretaceous-Neogene source rocks from the wells and outcrops and a study of the Cretaceous-Upper Tertiary micro reservoir and grain packing density in 14 wells reveal the evolution of tectonic compression controlling the reservoir in the southern margin of Junggar Basin from Cretaceous to Tertiary.The high Ro values were in the eastern Hutubi area in the southern margin of Junggar Basin,and the low Ro values were in the western area in Cretaceous.And the distribution of grain packing density is the same as the distribution of Ro values,as shown by the map.Because of the uplifting of the Bogeda Mountain in the Late Jurassic to early Cretaceous period,the tectonic compression in Hutubi area was stronger than that in Xihu-Dushanzi area in the southern margin of Junggar Basin.The distribution of vitrinite reflectance in Palaeogene was different from that in Cretaceous.The values of Ro and grain packing density in Anjihai-Manasi-Tugulu anticline area of the middle-distal thrust belt decreased in two directions,i.e.,the foot of the thrust belt and the foredeep.So the main reservoir-controlling factor was the buried thermal effect instead of the tectonic compression.Because of the re-uplifting of the Tianshan Mountains in Upper Tertiary,the tectonic compression changed the main reservoir-controlling factor through the distribution of grain packing density.An analysis of the micro-reservoir shows that the relationship between porosity and Ro was in negative correlation,so were the things at the diagenetic stage in Cretaceous;nevertheless,in Lower-Tertiary,the relationship between porosity and Ro was in positive correlation.