银根-额济纳旗及邻区石炭-二叠系的沉积特征及石油地质意义

长期以来,由于埋藏深、地质复杂及自然条件恶劣等原因,银根-额济纳旗及邻区石炭系-二叠系的油气勘查程度低,相关研究成果少.鉴于此,本文充分利用研究区的周缘露头,借助近30条剖面的详细调查,分析了本区石炭系-二叠系的沉积特征.研究表明,本区石炭系-二叠系包括了泥岩、砂岩、砂砾岩、碳酸盐岩和火山岩(或火山碎屑岩)等,海相生物丰富.暗色泥岩是石炭系-二叠系的主体,是潜在的烃源岩和盖层;火山岩(或火山碎屑岩)发育,碳酸盐岩多呈透镜状且硅化普遍,砂砾岩相对较少,三者构成石炭系-二叠系重要储层.岩石组成及展布特征表明,石炭纪-二叠纪期间,本区张裂频繁,火山作用强烈,远离陆源区,水体深而宁静,利于生烃物质发育.期间,区内主要发育了浅海相、广海海岸相、碳酸盐台地相、辫状三角洲相、扇三角洲相和火山喷发相等沉积类型.其中,浅海相和局限海岸相主要形成了烃源岩和盖层,其他沉积则形成了储层,为区内石炭系-二叠系造就了良好的油气地质条件.

Depositional Characteristic of Permo-Carboniferous System from Yingen-Ejinaqi and Their Surrounding Areas,Inner Mongolia,China and it Implications for Petroleum

A study of depositional characteristics is very important for petroleum geology exploration. For a long time, due to their deeply-buried, geological-complicated and bad-natural conditions etc, a study related to petroleum geology, because of poor exploration for oil and gas of Permo-Carboniferous formation from Yingen-Ejinaqi, was seldom done. Due to their deeply- buried, strongly-deformed and little of deeply-explored data, author, in purse of exploring oil and gas conditions of Permo-Carboniferous, researches into the depositional characteristics of Permo-Carboniferous formation by making full use of the outcrops from the study area and surveying in detail almost 30 sections of them. This paper shows that Permo-Carboniferous formation comprise the mudstones, volcanic rocks (or pyroclastic rocks), carbonate rocks, sandstones and conglomerates etc., accompanied by rich marine organism. The dark dominated mudstones of the formationg are potential source rocks and cap rocks. The ubiquitous volcanic rocks (or pyroclastic rocks) by which the Permo-Carboniferous formation is characterized, carbonate rocks of lenticular and prevalently-silicated, and fewer of sandstones and conglomerates make up the main reservoirs of the Permo-Carboniferous respectively. The composition and occurrence of the formations reveal that frequently-rifting and strongly-volcanism concurred in the study area through the Permo-Carboniferous age, the area, which were far from land, deep and quiet in water, are favorable to development of source rocks. The Permo-Carboniferous formation in the area includes 6 facies as follows: neritic shelf, open coast, carbonate platform, braided delta and fan delta etc. Among them, both neritic shelf and barrier coast form the source rocks and cap rocks, other facies else make up reservoirs for oil and gas respectively.