摘要
玉北地区下奥陶统蓬莱坝组为塔里木盆地海相碳酸盐岩油气勘探的目的层系,发育了大量白云岩储层。由于白云岩埋藏深、勘探程度低,对其储层方面的认识有待进一步研究。在野外地质观察、岩心观察、薄片及物性等资料分析的基础上,结合扫描电镜和碳、氧、锶同位素测定等结果,对蓬莱坝组白云岩储层特征进行了分析,并探讨了储层发育的控制因素。蓬莱坝组白云岩由交代白云岩和重结晶白云岩组成,按晶粒大小可分为粉细晶白云岩、中晶白云岩及粗晶白云岩,其中中晶白云岩为最重要的储集岩。白云岩储集空间可分为晶间孔、晶间溶孔、晶内溶孔、溶蚀孔洞及裂缝,其中溶蚀孔洞和裂缝为比较重要的储集空间,裂缝还能作为运移通道,储集空间组合类型以裂缝-孔洞型为主。断裂作用及其伴生裂缝以及岩溶作用是影响研究区蓬莱坝组储层发育的关键因素。断裂活动控制了伴生裂缝的发育,使得地表淡水或深部热液沿断裂和裂缝下渗或上涌,并发生溶蚀作用;大气淡水岩溶作用有效改善了蓬莱坝组上部白云岩储层的物性,而热液岩溶作用致使大多数孔洞和裂缝被硅质等充填,导致蓬莱坝组下部储层发育欠佳。
Penglaiba Formation of Lower Ordovician in Yubei area becomes the target stratum for oil and gas exploration of marine carbonate rocks in Tarim Basin, and it developed large amounts of dolomite reservoirs. Due to the deep burial and low degree of exploration of dolomite, the cognition of its origin is not perfect and need further studying. Based on field geological inspection, core observation, identification of thin section, physical properties analysis, combined with SEM and the results of isotope geochemistry of carbon, oxygen and strontium, this paper analyzed the characteristics and controlling factors of dolomite reservoirs of Penglaiba Formation in Yubei area. The dolomites of Penglaiba Formation consist of replacement dolomite and recrystallization dolomite, which can be further subdivided into three categories, silty crystalline dolomite, medium grained dolomite and coarse crystalline dolomite in terms of grain size, and the most important reservoir rock is medium grained dolomite. The reservoir space in dolomites is subject to intercrystal pores, intercrystal dissolved pores, intracrystal dissolve pores, dissolved pores and fractures as migration channels. Dissolved pores and fractures are the most important reservoir space. The most common reservoir space is mainly the overlapped complex of cracks and cavities. Fracturing and its associated fractures and karstification are the keys for the development of dolomite reservoir of Lower Ordovician Penglaiba Formation. Fault activities control the development of associated fractures, which makes fresh surface water or deep hydrothermal infiltrate or upwell along faults and fractures, and then dissolution occurs. Atmospheric fresh water karstification effectively improves the dolomite reservoir properties at the top of Penglaiba Formation, while the hydrothermal karstification results in poor development of the lower reservoir of Penglaiba Formation, owing to filling with silica in the most holes and crakes.
出处
《岩性油气藏》
CSCD
2014年第3期59-66,共8页
Lithologic Reservoirs
基金
中国石油化工股份有限公司重大先导项目"玉北地区奥陶系储层发育规律与目标优选"(编号:2012KTXD04)资助
关键词
白云岩
储层特征
控制因素
蓬莱坝组
玉北地区
dolostones
reservoir characteristics
controlling factors
Penglaiba Formation
Yubei area
