摘要
彭阳油田位于鄂尔多斯盆地西南部,其上三叠统延长组长3段砂岩已发现商业油流,但是对其储层砂岩质量控制因素仍然缺乏了解。本文根据钻井、测井、岩心观察、铸体薄片、扫描电镜与岩心物性资料,研究了长3段层序格架与沉积相、砂岩成分与成岩作用特征及其对长3段砂岩储层质量的影响。长3段砂岩为发育在高位体系域早期的具有加积-进积准层序组特征的小型辫状河三角洲平原分流河道沉积,砂体孤立而不连续,成岩环境流体循环不畅而相对封闭,不利于早成岩期酸性大气水的普遍淋滤。长3段砂岩以长石岩屑砂岩和岩屑砂岩为主。高岩屑和长石含量使砂岩在早期成岩压实中损失了大量粒间孔,高白云岩岩屑含量促进了埋藏成岩期间硬石膏与铁白云石的大量胶结,进一步减少了粒间孔隙。三角洲平原环境促进了早期成岩过程中颗粒蒙脱石包膜的形成,并在埋藏成岩过程中转换为绿泥石包膜或伊利石,尤其是绿泥石包膜抑制了石英增生,使粒间孔得以保存。早成岩期的酸性大气水与埋藏成岩期的有机酸对长石、云母或岩屑的溶蚀对砂岩储层质量的贡献相对有限。长3段砂岩孔隙以残余粒间孔为主,这暗示长3段砂岩在晚三叠世末期剥蚀与侏罗纪末期-新生代的抬升(降低了长3段压实程度)以及埋藏成岩过程中绿泥石颗粒包膜的形成是长3段砂岩孔隙保存的最重要因素。成岩作用促进了长3段孤立砂体的致密化,加剧了该砂岩储层预测难度。
Pengyang oilfield is located within the southwestern part of Ordos Basin and has attained commercial petroleum production from sandstones of the Third Member of Upper Triassic Yanchang Formation. However, impacts on reservoir quality of these sandstones are still poorly understood. Characteristics of sequence stratigraphic framework and depositional facies of the Third Member of Yanchang Formation, compositions and diagenesis of sandstones and their effects on reservoir quality of the sandstones were comprehensively explored based on data of drilling, wall-logging, core description, cast thin section, scanning electron microscope and core plug analysis. The sandstones were deposited from delta-plain distributary channels of small braided-river delta during an early stage of the high stand system tracts with characteristics of aggradational to progradational parasequences. These sandstones are isolated within delta-plain interdistributary mudstones and have poor lateral continuities, which resulted in a relatively closed diagenetic environment with limited fluid circulation and did not contribute to extensive dissolution from meteor water during early diagenesis. The sandstones are principally composed of feldspathic litharenites and litharenites. High content of lithic grains and feldspars caused a large amount of damage to primary intergranular pores owing to their weaker resistance to compaction than quartzes during eodiagenesis. The high content of dolomitic rock fragments promoted cementation of a large quantity of anhydrites and ankerites during mesodiagenesis because these dolomitic precursors had supplied calcium and carbonate ions by dissolution or acted as nucleus for late carbonate cements, and further reduced intergranular pore volumes. The delta plain environment had induced formation of grain-coating smectites during the early diagensis that were transformed to illites or chlorites during the progressive buried diagnetic process; especially, the chlorite coatings helped preserving intergranluar pore
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2014年第6期1828-1840,共13页
Acta Petrologica Sinica
基金
国家自然科学基金项目(41172127)
中国石油天然气集团公司石油科技中青年创新基金项目(04E7023)联合资助
关键词
层序格架
砂岩成分
沉积相
成岩作用
砂岩储层质量
长3段
鄂尔多斯盆地彭阳油田
Sequence stratigraphic framework
Sandstone compositions
Depositional facies
Diagenetic alterations
Reservoirquality of sandstones
Third Member of Upper Triassic Yanchang Formation
Penyang oilfield of Ordos Basin
