塔中地区深层寒武系盐下白云岩储层特征及主控因素

摘要

塔中地区东部深层寒武系盐下白云岩勘探取得重大发现,但针对该层系白云岩储层的研究尚属空白.利用钻井、岩心、薄片、扫描电镜、测井及三维地震资料,对塔中寒武系盐下白云岩产层的储层类型、特征、主控因素及展布规律开展探索性研究,认为塔中寒武系盐下白云岩主要发育颗粒滩相白云岩储层和潮坪相膏云岩储层.颗粒滩相白云岩储层主要发育在下寒武统肖尔布拉克组以及中寒武统沙依里克组上段,岩性以台内藻砂屑滩相颗粒白云岩、藻白云岩及粉细晶白云岩为主,明显受岩相控制,形成于准同生期,并受后期层间岩溶作用改造优化.潮坪相膏云岩储层主要发育在中寒武统阿瓦塔格组及沙依里克组下段,岩性以含膏云岩、泥粉晶云岩、膏云质角砾岩为主,明显受岩相及裂缝控制,形成于准同生期,并受后期有机酸溶蚀作用形成微孔型储层.目前而言,下寒武统肖尔布拉克组台内藻砂屑滩相颗粒白云岩储层是最现实的勘探领域.%Studies on the Cambrian pre-salt dolomite reservoirs is still rare in eastern Tarim Basin,although the exploration there has made great discovery.Research on reservoir types and characteristics,main controlling factors and distributions of the Cambrian pre-salt dolomite reservoirs were presented on the basis of drilling data,cores,thin section SEPM,logging and 3-D seismic data.The results show that grain dolomite reservoir of beach facies and gypsodolomite reservoir of tidal fiat facies are two main reservoirs in the pre-salt dolomite of Cambrian in Tazhong Block,Tarim Basin.The former exists in the Lower Cambrian Xiaoerbulake Formation and the Middle Cambrain Upper Shayilike Formation.Lithologies include algae granular dolomite from shoals in platform proximate,algae dolomite and silty crystalline do lomite,and were mainly controlled by facies.The reservoir quality are mostly inherited from deposition and the porosity was improved by the later interlayer Karst processes.The latter mainly exists in the Middle Cambrian Awatage Formation and Middle Cambrain Lower Shayilike Formation.Lithology include gypsiferous dolostone,silty crystalline do lomite,gypsodolomite breccia and they were controlled by both petrography and later fracturing.For its microporous reservoir,the matrix formed during deposition while micropores formed due to later organic acid dissolution.Nowadays,the favorable objectives are most likely to be grain dolomite reservoirs of beach facies in Lower Cambrian Xiaoerbulake Formation.