准噶尔盆地腹部白垩系底部不整合特征

UNCONFORMITY FEATURES OF CRETACEOUS BOTTOM IN THE BACK-LAND OF JUNGGAR BASIN

准噶尔盆地经历了海西、印支、燕山、喜马拉雅等多期构造运动,形成了多个不整合,这些不整合对于准噶尔盆地的油气运聚具有重要的控制作用.白垩系底部不整合在盆地腹部地区广泛分布,通过对该不整合面上下岩石组合、物质成分以及电性特征的研究,该不整合具有明显的3层结构特征,可以划分为不整合面之上的底块砂岩、不整合面之下的风化粘土层和半风化淋滤带.底块砂岩是一套好的储层;风化粘土层由于遭受了长期的风化作用,富Al3+、Fe3+,贫Si4+、Ca2+,是一套局部有效的盖层;半风化淋滤带由于长期遭受地表水的下渗淋滤溶蚀,储层物性得到了很好的改善,是一套好的储层.沿白垩系底部不整合形成了上下两套优质储盖组合,形成了大量隐蔽性的非构造圈闭组合,是盆地腹部最主要的勘探领域之一,通过该项研究为盆地腹部地区的油气勘探提供有益资料.

The Junggar basin suffered Hercynian,lndosinian,Yanshan and Himalayan tectonic movements,and formed more unconformities.These unconformities did important roles to the oil and gas migration and accumulation in Junggar basin.The Bottom Cretaceous unconformity is widespread in the backland of Junggar basin.Studying on the rock formation,material ingredient and the electric character feature of it indicates that the unconformity can be divided into three structures,ie, bottom block sandrock upper the unconformity, weathered argilic horizon and semi-weathered leached zone lower the unconformity.The bottom block sandrock is good reservoir, the weathered argilic horizon is a part effective cap formation because of suffering long time weather and leaching,rich Al^3＋, Fe^3＋and poor Si^4＋. Ca^2＋ in it.The semi-weathered leached zone is also a good reservoir because of suffering long time weather and leaching too,the reservoir＇s physical property gained great imProvement.There are two high quality reserveoir-cap combinations along the Bottom Cretaceous unconformity, and formed a lot of non structure subtle traps.It is one of the most important exploration area in the backland of Junggar Basin.The research will provide useful information for oil and gas exploration in this area.