CAJ | 학술논문

与石炭系相比,准噶尔盆地西北缘下二叠统火山岩岩性、岩相类型丰富,研究程度低.本文利用岩心、薄片及元素地球化学资料,开展了火山岩岩石学及其与储层关系研究.佳木河组以熔岩和火山碎屑岩共同发育为特征,岩性以玄武安山岩、安山岩、英安岩为主,相对稳定;风城组火山岩在不同地区变化明显,克百地区以火山熔岩为主,属于玄武粗安岩和碱玄岩,而乌夏地区以熔结火山碎屑岩或火山碎屑熔岩发育为特征,属于流纹岩、碱玄质响岩和粗安岩.在佳木河组及克百地区风城组,(沉)火山角砾岩储层质量最好,安山岩等熔岩其次;乌夏地区风城组熔结火山角砾岩和石泡构造火山角砾熔岩储层质量最好.此外,相同岩性可能因产出环境不同而储层特征有别.尽管各地成岩作用存在差异,但火山岩优质储层仍集中于溢流(爆溢)相上部亚相、爆发相空落亚相的弹射坠落堆积和火山碎屑流亚相的水下堆积和爆发相.全区佳木河组溢流相和爆发相共同发育,而克百地区风城组以溢流相为主、乌夏地区风城组以爆发相火山碎屑流亚相为主,不同地区不同层位的有利勘探目标差异明显.除断裂带的裂缝和大型不整合面之下的风化淋滤外,岩相是控制火山岩储层质量的关键因素.
여석탄계상비,준갈이분지서북연하이첩통화산암암성、암상류형봉부,연구정도저.본문이용암심、박편급원소지구화학자료,개전료화산암암석학급기여저층관계연구.가목하조이용암화화산쇄설암공동발육위특정,암성이현무안산암、안산암、영안암위주,상대은정;풍성조화산암재불동지구변화명현,극백지구이화산용암위주,속우현무조안암화감현암,이오하지구이용결화산쇄설암혹화산쇄설용암발육위특정,속우류문암、감현질향암화조안암.재가목하조급극백지구풍성조,(침)화산각력암저층질량최호,안산암등용암기차;오하지구풍성조용결화산각력암화석포구조화산각력용암저층질량최호.차외,상동암성가능인산출배경불동이저층특정유별.진관각지성암작용존재차이,단화산암우질저층잉집중우일류(폭일)상상부아상、폭발상공락아상적탄사추락퇴적화화산쇄설류아상적수하퇴적화폭발상.전구가목하조일류상화폭발상공동발육,이극백지구풍성조이일류상위주、오하지구풍성조이폭발상화산쇄설류아상위주,불동지구불동층위적유리감탐목표차이명현.제단렬대적렬봉화대형불정합면지하적풍화림려외,암상시공제화산암저층질량적관건인소.
Early Permian volcanic rocks in northwestern margin of the Junggar Basin have different rock types and lithofacies. In this paper, data from core, thin sections and element chemistry were used to study volcanic lithology and their relations to reservoir quality. The Jiamuhe Formation is characterized by lava and volcanoclastic rocks, which are mainly basaltic andesites, andesites and quartz andesites. The lithology of volcanic rocks in the Fengcheng Formation are different in different areas. Lava including basaltic andesitoid and tephrite was the main type in Kebai area, while welded pyroclastic rock and volcaniclastic lava of rhyolite, pollenite and andesitoid are the main types in Wuxia area. The high-quality reservoir developed in eruptive breccias and lava such as andesite in the Jiamuhe Formation and in the Fengcheng Formation of the Kebai area, and in welded pyroclastic rock and breccias lava with stone bubbles in the Fengcheng Formation of the Wuxia area. Besides, same volcanic rock would have different reservoir quality because of different volcanic environments. In the studied area, although diagenesis was diverse in different parts, high-quality volcanic rock reservoir developed mainly in the upper effusive sub-facies, air fall, and pyroclastic subfacies in explosive facies. Effusive and explosive facies were common in the Jiamuhe Formation, while effusive facies and pyroclastic flow subfacies in explosive facies were the main facies in Fengcheng Formation of Kebai area and of Wuxia area, respectively. Therefore, distinct explorative targets should be chosen in different layers in different areas. Lithofacies was another important controlling factor for volcanic reservoir besides fracturing in fault zones and leaching under the regional unconformable surface.