陕北志丹地区前侏罗纪古地貌及其控制作用

综合运用印模法、残厚法及沉积法等将志丹地区前侏罗纪古地貌划分为侵蚀高地、侵蚀斜坡、侵蚀沟谷以及侵蚀残丘四个基本单元.研究结果表明:前侏罗纪古地貌对印支侵蚀不整合面上下之地层、构造、沉积、储层以及油气成藏特征等都具有重要的控制和影响.侵蚀面之下的长2油层组顶面剥蚀构造特征较好地反映了印支古地貌的基本格局;侵蚀面之上的延安组早期的沉积是前古地貌发育的镜像反映;而延10顶面构造则具有围绕古高地背景集中发育的特点.古高地与斜坡发育区是侵蚀面上下油气富集成藏的有利指向和主要场所,而深切的沟谷则为沟通下部油源以及油气运移提供了主要通道.油藏类型主要为地层-岩性油藏、构造-岩性油藏以及小而局限的构造、岩性油藏等.

Pre-jurassic palaeogeomorphology and its control action in Zhidan area,northern Shaanxi province

Comprehensive methods,such as impression method,residual thickness method,deposition method etc.,were used to divide Zhidan area into four basic units,i.e.erosion highland,erosion valley,erosion slop and erosion monadnock.The research results indicate that pre-ancient landform had an important control action and influence on the formation,structure,sedimentation and reservoir characteristics of the hydrocarbon accumulation of the areas located at upper and lower erosion surface.The top erosion structural features of Chang 2 oil bearing set under the erosion surface well show some basic configuration of the eroded ancient landform of Indo-China movement;the early deposition of Yan’an formation above the erosion surface is a mirror image of the pre-ancient landforms;Yan 10 oil bearing set’s top structure has a feature of centralized growth around an old upland background.Ancient erosion upland and erosion slope as well as the old upland background are major favorable sites of hydrocarbon accumulation located at upper and lower erosion surfaces, while the deep erosion valley has provided important channels to connect the lower oil source and upward hydrocarbon migration.The main reservoir types are strata-lithologic reservoir,structural-lithologic reservoir, relatively limited structure reservoir,lithology reservoir,etc.