鄂尔多斯盆地低丰度大型岩性气田成藏机理——以榆林气田为例  

Formation Mechanism of Large and Low-Abundance Lithologic Gas Fields in Ordos Basin——An example from Yulin gas field

作　　者：李艳霞[1] 田毓峰 李净红[1] 

机构地区：[1]西安石油大学油气资源学院非常规天然气资源研究中心,西安710065 [2]长庆实业集团有限公司,西安710018

出　　处：《新疆石油地质》2012年第4期408-412,共5页Xinjiang Petroleum Geology

基　　金：陕西省自然科学基金项目(2007D05)

摘　　要：鄂尔多斯盆地二叠系发育一系列低丰度大型岩性气田。对其中榆林气田形成机理的研究表明,大型平缓构造背景下,河流-三角洲砂体与烃源岩大面积分布且呈"三明治"式间互接触,为低丰度大型气田提供了成藏条件;区域性构造抬升剥蚀和大面积薄层致密砂岩储集层是导致榆林气田储量低丰度的根本原因;低丰度大型岩性气田的"甜点"主要受控于输导体系的质量,尤其在厚层带状砂体—裂缝型输导体系发育区,天然气富集程度高。利用流体包裹体、天然气组分等地球化学资料结合盆地构造-沉降演化将榆林气田形成划分为3个阶段:早中侏罗世,早期生烃侵位与储集层物性改造阶段;早白垩世,成藏要素达到最大优化配置,岩性气藏形成阶段;晚白垩世至现今,构造抬升与大面积薄层致密砂岩储集层有效耦合使气田保存至今成为低丰度大型气田阶段。A series of large and low-abundance lithologic gas fields developed in the Permian of Ordos basin are significant domains for natural gas exploration nowadays.The formation mechanism of Yulin gas field has revealed that under the large flat structural setting,fluvial-delta sands and source rocks are widely distributed and mutually contacted as a ＂sandwich-type＂,providing geologic conditions for large-scale gas accumulation in this area;regional tectonic uplift and denudation as well as large-sized thin sand reservoirs are the primary causes for forming low abundance in Yulin gas field;the distribution of ＂dessert＂ of such a field is controlled mainly by quality of transport system,particularly in areas with thick belt sand body and fracture transport systems in which gas concentration is normally high.Based on the geochemical data of fluid inclusion and gas component,combined with structural and depositional evolutions,the formation of Yulin gas field is divided into three stages： preliminary hydrocarbon emplacing and reservoir quality transforming stage in Early-Middle Jurassic;lithologic gas pool forming stage by optimized allocation of gas accumulation factors in Early Cretaceous;Late Cretaceous to nowadays,effective coupling of tectonic uplift and large-sized thin sand reservoir makes the surviving field become large gas field with low abundance until now since Late Cretaceous.

关 键 词：榆林气田 低丰度 大型岩性气田 形成机理 

分 类 号：TE112.111[石油与天然气工程—油气勘探]