渤海海域锦州25-A构造区中生界火山岩有利储层成因

Favorable Reservoir Genesis of Mesozoic Volcanic Rocks in Jinzhou 25 A Structure Area, Bohai Sea

渤海湾盆地辽东湾凹陷中生界火山岩勘探潜力较大,但是对于火山岩优质储层发育规律尚缺乏深入认识。针对探讨中生界火山岩有利储层成因这一难点,综合应用钻井数据、铸体薄片及物性测试资料,对渤海海域锦州25-A构造区中生界火山岩的储集空间类型、物性、孔隙微观结构等特征进行研究,分析火山岩优质储层发育的条件和储层发育模式。研究表明:锦州25-A构造区中生界火山岩主要发育中酸性溢流相下部亚相的粗安岩和安山岩,以及少量的基性溢流相玄武岩。有利储层主要发育在中酸性溢流相的粗安岩和粗面岩中,储集空间以次生成因为主,主要发育基质溶孔、晶内溶孔和裂缝,在火山岩顶部的风化砂砾岩中也可见一些粒间孔。储层孔隙度平均为20.3%,渗透率平均为0.209 mD~((1)),属于高孔-低渗型储层。火山岩体顶面经过长时间风化剥蚀顶部常发育厚层风化壳;同时在母岩带中还发育有喷发单元间次级风化壳的内幕储层;有效裂缝方向主要为NEE—SWW和NS向,为上述风化作用形成有利储层创造了良好条件。因此,本文建立了“以风化作用主控,火山岩顶部发育厚层风化壳储层,喷发单元顶部发育次级薄层风化壳内幕储层”的火山岩规模型储层发育模式。

The exploration potential of Mesozoic volcanic rocks in Liaodong Bay depression of Bohai Bay basin is great,but the development law of high-quality volcanic rocks reservoir is not well understood.Aiming at the difficulty of exploring the genesis of favorable reservoirs of Mesozoic volcanic rocks,the reservoir space types,physical properties,pore microstructure,and other characteristics of Mesozoic volcanic rocks in Jinzhou 25 A structure area in Bohai Sea are studied by a comprehensive application of drilling data,thin section,and physical property data,and the conditions and reservoir development model of high-quality volcanic rocks are analyzed and discussed.The results show that the Mesozoic volcanic rocks in Jinzhou 25 A structure area are mainly composed of trachyandesite and andesite in the lower subfacies of the intermediate-acid overflow facies,and a small amount of basalt in the basic overflow facies.Favorable reservoirs are mainly developed in trachyandesite and trachyte of the intermediate-acid overflow facies.The reservoir space is dominated by secondary origin,which mainly develops matrix pores,intracrystalline pores and fractures.Some intergranular pores can also be seen in the breccia on top of volcanic rocks.The average porosity and permeability of the reservoir are 20.3%and 0.209 mD respectively.It belongs to the high porosity and low permeability reservoir.Thick weathering crust is often developed on the top of volcanic rock mass after a long time weathering and denudation.At the same time,the inner reservoir of secondary weathering crust between eruptive units is also developed in the mother rock zone.The effective fracture direction is mainly NEE SWW and NS direction,which creates good conditions for the formation of favorable reservoirs.Therefore,this paper established a volcanic rock regular model reservoir development model of“weathering as the main control,thick weathering crust reservoir developed on the top of volcanic rock,and secondary thin weathering crust inside reservoir developed on the top of eruption unit”.