山东桩海地区中生界碎屑岩储层特征及其控制因素

Characteristics and Controlling Factors of Mesozoic Clastic Reservoirs in Zhuanghai Area,Shandong Pvorince

采用岩芯观察、薄片鉴定、扫描电镜分析及X-衍射分析等手段,对桩海地区中生界碎屑岩储层的成岩作用、储集空间和控制因素进行了研究。结果表明,桩海地区中生界碎屑岩储层经历了强烈的压实压溶作用和胶结交代作用、多期次的溶解作用和裂缝形成作用;成岩作用阶段可划分为早成岩B,中成岩A1,A2和中成岩B期。储集空间以溶解孔隙和裂缝为主,裂缝主要有构造裂缝、压实裂缝和解理裂缝;溶解孔隙主要有长石溶解孔隙和碳酸盐胶结物溶解孔隙,其成因主要与大气降水溶解作用和沙河街组、东营组有机质演化过程中形成的有机酸溶解作用有关。桩海地区中生界碎屑岩储层的控制因素主要有沉积作用、成岩作用和构造作用。沉积作用控制了碎屑岩杂基、分选、磨圆等结构特征,进而控制了原生孔隙结构,为后期溶解作用的形成奠定了基础。断层和不整合面作为流体运移通道为溶解作用提供酸性介质,断层和不整合的规模越大对碎屑岩储层物性的控制作用越明显,距离断层和不整合面越近的储层物性越好。溶解作用受沉积作用和构造作用的控制,在原始孔隙结构好、压实作用和早期胶结作用弱以及裂缝发育的地区,溶解作用强烈、次生孔隙发育、储层物性好。在沉积作用、成岩作用和构造作用的综合控制下,中生界顶底及内部不整合面附近发育多个次生孔隙发育带,中生界顶部处于中成岩A1亚期的储层次生孔隙最发育。

The diagenesis,reservoir space and controlling factors of Mesozoic clastic reservoirs in Zhuanghai area have been researched in this paper through core observation,thin section determination,scanning electron microscope and X-diffraction analysis.The results show that,the clastic reservoirs experienced strong compaction,cementation and metasomatism as well as polyphase dissolution and crack formation.The diagenetic processes can be divided into four stages including early diagenesis B,middle diagenesis A1 and A2 and middle diagenesis B.There exist two chief types of reservoir space：the one is fractures including structural fractures,compaction fractures and cleavage cracks;the other is secondary pores including feldspar dissolution pores and carbonate cement pores which are related to atmospheric water dissolution and organic acid dissolution during the course of organic matter evolution in Shahejie Formation and Dongying Formation.The Mesozoic clastic reservoirs in Zhuanghai area are chiefly affected by sedimentation,diagenesis and tectonism.Sedimentation controlled the textures of clastic rocks such as matrix,sorting and rounding,and further affected the texture of primary pores,which served as basement for later dissolution.As the migration pathways of fluids,the faults and unconformity surfaces supplied acidic media for dissolution.Therefore,the scale of faults and unconformity surfaces controlled the properties of clastic reservoirs obviously.The closer the distance from faults and unconformities is,the better the reservoir properties are.In the areas of favourable sedimentation and geotectonic conditions with good primary pore structure,weak compaction and cementation,and well developed fractures,the strong dissolution,good primary pores and reservoir properties were formed,leading to development of several secondary pore zones around the unconformity surfaces,and the most favorable secondary pores occurred on the top of Mesozoic during the middle diagenetic stage A1.