渤海歧南断阶带中下侏罗统碎屑岩潜山优质储层形成主控因素

Main controlling factors on the formation of high-quality reservoirs in the Middle and Lower Jurassic clastic rock buried hills in Qinan fault terrace belt,Bohai sea

渤海歧口凹陷歧南断阶带中下侏罗统碎屑岩潜山储层非均质性强、储层条件复杂。基于岩心和薄片观察、扫描电镜、电子探针、能谱分析、X衍射分析等资料,对研究区目的层储层特征和优质储层主控因素进行了分析。歧南断阶带中下侏罗统碎屑岩潜山储层主要为岩屑长石砂岩、长石岩屑砂岩和砂砾岩,储集空间以残余原生粒间孔、次生溶孔、晶间孔为主,属中孔低渗储层,不同层段储层物性差异明显。岩性、沉积相和成岩作用共同控制了优质储层的形成:砂砾岩储层物性最好,砂岩和含砾砂岩次之,凝灰质砂岩最差;三角洲水下分支河道砂体储集物性最好,河床滞留沉积和心滩砂体次之,水上分支河道、决口扇和河漫沉积物性较差;抗压实作用、表生风化淋滤作用和深部溶蚀作用是较高孔隙度储层普遍发育的主要原因,自生高岭石等黏土矿物充填和分布差异最终决定了储层渗透性和物性,优质储层主要发育在高岭石大量富集带内。本文研究结果可为歧南断阶带及渤海海域中生界碎屑岩潜山优质储层发育区及有利勘探区带预测提供参考。

The Middle and Lower Jurassic clastic rock buried hill reservoirs in Qinan fault terrace belt of Qikou sag,Bohai sea have strong heterogeneity and complex reservoir conditions.Through a series of core and slice observation,scanning electron microscopy,electron probe,energy spectrum analysis,X-ray diffraction analysis,the characteristics of the reservoirs in the target area and the main factors of high-quality reservoirs were analyzed.The Middle and Lower Jurassic clastic rock buried hill reservoirs in Qinan fault terrace belt is mainly composed of lithic feldspathic sandstone,feldspar lithic sandstone and glutenite,and the reservoir space is mainly composed of residual primary intergranular pores,secondary dissolved pores and intercrystalline pores;generally,it belongs to middle-low permeable reservoir.There are significant differences in reservoir properties of different intervals.Lithology,sedimentary facies,and diagenesis control the formation of high-quality reservoirs:the glutenite reservoir has the best physical properties,followed by sandstone and pebbly sandstone,and the worst is the tuff sandstone.The delta underwater distributary channel sand has the best physical properties,followed by the channel lag deposit and the channel bar,and the distributary channel,crevasse splay and alluvial deposit have poor physical properties.Ability to resist the compaction,surface weathering-leaching and deep dissolution are main reasons for the wide development of high porosity reservoirs.The difference in filling and distribution of clay minerals like authigenic kaolinite ultimately determines reservoir permeability and physical properties.High-quality reservoirs were mainly developed in a large kaolinite enrichment zone.The results of this paper can provide a reference for the determination of the distribution of high-quality reservoir development zones in the Mesozoic clastic rock buried hills in the Bohai sea and the prediction of favorable exploration zones.