准噶尔盆地陆东—五彩湾地区火山岩中天然气富集的主控因素

摘要

近年来准噶尔盆地陆东—五彩湾地区石炭系火山岩中发现了丰富的天然气资源,包括克拉美丽和五彩湾两个气田,因此石炭系成为北疆油气勘探的主要目的层之一,陆东—五彩湾地区天然气主要位于石炭系顶部的火山岩风化壳内,主要为煤成气,来自石炭系腐殖型烃源岩.本文在对陆东—五彩湾地区典型气藏剖面进行分析的基础上,探讨了石炭系火山岩中天然气富集的主控因素.结果表明,邻近烃源岩和生烃凹陷有利于形成气藏；风化淋滤和构造作用的改造是火山岩物性得到改善而发育有效储集空间的关键因素；断裂和不整合构成了油气垂向和侧向运移的有利通道；海西期以来的各个构造期,陆东—五彩湾地区石炭系圈闭和油气藏受到了不同程度的影响,其中火山岩气藏良好的生储盖配置定型于海西期,而燕山中期则是该区天然气成藏的关键时期.%Plentiful natural gas resource has been discovered in Carboniferous volcanic rocks in Ludong-Wucaiwan area in Junggar Basin in recent years. Kelameili and Wucaiwan gas fields were found in this area, and Carboniferous has been one of the major targets in oil and gas exploration in northern Xinjiang. As a special type of reservoirs, volcanic reservoirs have attracted wide attention. The natural gas in Ludong-Wucaiwan area was mainly preserved in the weathering crust of volcanic rocks at the top of Carboniferous,and was mainly coal-derived gas from Carboniferous humic-type source rocks. Ludong-Wucaiwan area could be divided into several secondary tectonic units,and the gas reservoirs were mainly located at the middle-west parts of Di' nan Uprise and Wucaiwan Sag. The accumulation properties of oil and gas in volcanic reservoirs are different from those in conventional ones. Besides the well reservoir quality, the matching of several favorable factors such as hydrocarbon generation, migration, and preservation were also necessary. Based on the analysis of typical gas reservoirs in Ludong-Wucaiwan area, this paper is focused on the major controlling factors on the enrichment of natural gas in Carboniferous volcanic rocks. The results indicate that it is favorable to form reservoirs if the volcanic rocks were adjacent to source rocks and hydrocarbon-generation sags; The reformation by and tectonism was a key factor to improve the reservoir quality of Carboniferous volcanic rocks in Ludong-Wucaiwan area and to develope effective reservoir space; The faults and the unconformity were the favorable pathways for vertical and lateral migration for oil and gas; The Carboniferous traps and reservoirs in Ludong-Wucaiwan area have been affected by different degrees in different stages since the Hercynian,in which the favorable source-reservoir-seal assemblages for the volcanic reservoirs were finalized in the Hercynian; while the Middle Yanshanian period was the key stage for natural gas accumulation.