含凝灰质致密油层成岩作用与原油充注特点:以鄂尔多斯盆地西北部长4+5段为例  

Diagenesis and Oil Filling Characteristics of Tuffaceous Tight Reservoir:A Case Study of Chang 4+5 Member in Northwest of Ordos Basin

作　　者：宋世骏 柳益群[1,2] 郑庆华 翟亚若 Song Shijun;Liu Yiqun;Zheng Qinghua;Zhai Yaruo(State Key Laboratory of Continental Dynamics;Department of Geology,Northwest University,Xi＇an 710069,China;Energy Engineering Insistitute,Yulin University,Yulin Shaanxi 719000,China;3.The No.4 Gas Production Plant,PetroChina Changqing Oilfield Company,Xiran 710016,China)

机构地区：[1]西北大学大陆动力学国家重点实验室,西安710069 [2]西北大学地质学系,西安710069 [3]榆林学院能源工程学院,陕西榆林719000 [4]中石油长庆油田分公司第四采气厂,西安710016

出　　处：《地质科技情报》2018年第5期54-62,共9页Geological Science and Technology Information

基　　金：国家自然科学基金项目"新疆北东部三塘湖地区二叠纪地幔热液喷流沉积及其形成机理"(BJ08133-3)

摘　　要：鄂尔多斯盆地西北部含凝灰质的延长组长4+5致密油层勘探潜力巨大,但因成岩作用研究薄弱,相对高孔高渗储层成因机理认识不清,使该区勘探开发进程受到明显的制约。反射光识别、铸体薄片、扫描电镜、电子探针、微束荧光光谱、盐水包裹体测温等研究结果表明,研究区长4+5油层发育一类不含玻屑的凝灰岩和凝灰质岩,成岩阶段处于中成岩A晚期,经历了酸碱交替的成岩过程,早成岩A期碱性环境下绿泥石薄膜的胶结作用和早期油的充注有效抑制了机械压实作用和胶结作用,是储层孔隙得以保存的主要原因;中成岩A期酸性条件下,长石溶蚀孔、高岭石晶间孔扩大了储集空间;中成岩A晚期成岩环境逐渐向碱性转变,铁方解石等碳酸盐胶结作用使储层进一步致密。盆地西北部长4+5油层存在2期原油充注事件,均不遵循正常有机质热演化;早期油充注发生在早成岩A期,油包裹体发绿色荧光,伴生的盐水包裹体均一温度介于60～70℃间;晚期原油充注主要发生在中成岩A早期,原油成熟较早,成熟度差异较大,油包裹体发绿色、蓝绿色和亮蓝色荧光,具有交替充注的特点,伴生的盐水包裹体均一温度介于80～130℃间。综合研究表明,凝灰质沉积促进了相对高孔高渗储层的发育,而且对烃源岩成熟排烃也具有促进作用。The tuffaceous tight oil reservoir of the Chang 4＋5 of Yanchang Formation in the northwestern Ordos Basin has the enormous potential for exploration,the weak research and the little knowledge of the formation mechanism of the high porosity and permeability apparently restricted the process of exploration in this area.According to the reflected light recognition,casting thin section,scanning electron microscope,electronic probe,microbeam fluorescence spectra,and brine inclusion temperature measurement,this paper considers that the oil reservoir of the Chang 4＋5 develops a kind of tuff which not contains vitroclastic and crystal chip,and that the tuffaceous reservoirs are now at the end of the middle diagenetic A stage,experiencing the diagenesis of acid and alkali alternating.In the early stage A of diagenesis,the reservoir hole can be preserved owing to the cementation of the chlorite＇s film and the charging of the oil in early stage in the alkaline environment which effectively suppressed the mechanical compaction and cementation.In the middle stage A of diagenesis,the feldspar dissolved pore and kaolinite intracrystalline pore expanded the reservoir space in acidic condition.In the late middle stage A of diagenesis,the condition changed to the alkaline gradually,carbonate like iron calcite cementation made the reservoir tighter.There are two oil filling events in the oil reservoir of the Chang 4＋5 in the northwestern Ordos Basin,and they all did not follow the normal organic matter thermal evolution.The early oil filling happened in the early stage A of diagenesis when the oil inclusion emitted the green fluorescence and the brine inclusion temperature was between 60-70℃.The late oil filling happened in the early middle stage A of diagenesis,when the oil matured earlier,with mature period of oil varying among different individuals and having characteristics of alternate filling.the oil inclusion emits the green,blue,and blue-green fluorescence and the accompanying brine inclusion temperature was betwe

关 键 词：凝灰质 早期油 相对高孔高渗储层 致密油层 鄂尔多斯盆地 

分 类 号：P618.13[天文地球—矿床学]