乌尔禾—风南地区百口泉组碎屑岩储层成岩作用及孔隙演化

Diagenesis and porosity evolution of clastic reservoir of Baikouquan formation in Wuerhe-Fengnan area

利用铸体薄片、扫描电镜、粒度分析、XRD等测试分析方法,研究乌尔禾—风南地区三叠系百口泉组碎屑岩储层成岩作用特征和孔隙演化过程。结果表明:研究区百口泉组碎屑岩储层主要为岩屑砂岩和长石岩屑砂岩,储集空间类型主要为残余粒间孔、粒内溶孔、微裂缝和收缩缝,经历机械压实—压溶、胶结、溶蚀等成岩作用及裂缝破坏,整体处于早成岩阶段B期—中成岩阶段A期,成岩演化序列依次为早期绿泥石胶结—黄铁矿胶结—石英次生加大边—黏土矿物胶结—方解石胶结—长石溶蚀及高岭石胶结—石英溶蚀。孔隙演化早期以机械压实减孔作用为主,中期钙质、泥质胶结减孔作用发育,后期长石、石英溶蚀增孔作用较强,黏土矿物的收缩及晚期构造裂缝的发育提高储层渗透率。储层孔隙演化阶段划分为压实减孔、压实胶结减孔和溶蚀裂缝增孔3个阶段,压实减孔平均为18.54%,胶结减孔平均为3.96%,溶蚀裂缝增孔平均为7.06%,综合成岩作用和孔隙演化的研究,建立研究区孔隙演化模型。该结果可为研究区储层的形成演化及成藏研究提供依据。

On the basis of previous research,various analytical techniques,such as cores,casting thin sections,scanning electron microscopy,XRD,were used to target the clastic reservoirs characteristics of the T 1 b clastic reservior,and the diagenesis characteristics and porosity evolution process of clastic reservoirs were emphatically analyzed.The clastic rocks of the Baikouquan formation in the study area are mainly lithic sandstones and feldspar lithic sandstones.The pore types mainly include intergranular pores,intragranular dissolution pores,shrinkage and microcracks.These clastic reservoirs experienced early mechanical compaction,cementation,dissolution and other diagenesis reactions,the whole is in the stage B of the early diagenetic stage to the stage A of the middle diagenetic stage.The diagenetic evolution sequence is followed by pyrite cementation-quartz overgrowth-clay mineral cementation-calcite cementation-feldspar and quartz dissolution.In the early stage of porosity evolution,mechanical compaction dominated the reduction of pores,and then cementation reduced porosity of the clastic reservoir.In the late stage,feldspar dissolution and rock fracture reactions were strong,improving the porosity of the T 1 b reservoir.The development of late fractures greatly enhanced the reservoir permeability.The porosity evolution stage is divided into three periods,porosity reduction through compaction,porosity reduction through compaction and cementation,porosity increment through fracturation and dissolution.The average compaction porosity reduction is about 18.54%,the cementation porosity reduction is about 3.96%,the average porosity increase of dissolution and fracturation is about 7.06%.According to these researches above,we established the porosity evolution model of the T 1 b clastic reservoir.The results can provide a basis for the clastic reservoir evolution and hydrocarbon accumulation research in the study area.