摘要
【目的】准噶尔盆地车排子凸起东翼新近系沙湾组一段储层碳酸盐胶结严重,通过深入分析研究区碳酸盐胶结物发育特征和形成原因,明确其对储层物性、含油性及圈闭类型的影响。【方法】在岩心观察的基础上,综合运用薄片观察与鉴定、阴极发光(CL)、X射线衍射(XRD)等方法,对浅埋藏碳酸盐胶结物类型、分布特征、形成期次及成因进行研究。【结果】研究区沙湾组一段至少存在三期碳酸盐胶结物。第一期碳酸盐胶结物以栉壳状方解石及颗粒状菱铁矿为主,其形成主要受古气候及沉积水体影响,局部藻类发育。第二期及第三期碳酸盐胶结物以嵌晶状方解石为主,二者皆受到昌吉凹陷中下侏罗统烃源岩生排烃的影响,有机酸流体溶蚀早期碳酸盐胶结物及酸溶性颗粒,为后续碳酸盐胶结物的发育提供主要物质来源,其中第二期方解石分布广泛。研究发现,碳酸盐胶结物造成沙湾组储层早期物性差;储层孔渗性因后期酸性流体的注入而得到有效改善;碳酸盐致密胶结所形成的薄夹层在一定程度上控制了储层中油气运移及圈闭类型。【结论】明确了沙一段多期碳酸盐胶结物的类型、分布特征、形成原因及地质意义,为持续性勘探开发及寻找新的勘探目标提供支撑。
[Objective]The First member of the Neogene Shawan Formation located at the eastern side of the Che⁃paizi uplift in the Junggar Basin displays significant carbonate cementation and strongly heterogeneous oil-bearing po⁃tential.The reasons for the development of the carbonate cements in the study area were thoroughly analyzed,and its effects on the physical properties and oil content of the reservoir are discussed.[Methods]The types,distribution,formation stages and genesis of these shallow-depth carbonate cements were studied by core observation and cathode luminescence(CL)and X-ray diffraction(XRD)examination of thin sections.[Results]At least three stages of carbonate cementation were identified.The first stage is mainly dominated by shell-like calcite and granular siderite.Polarized microscopy indicated that the edges of some mineral particles have been replaced,and at the later stage the influence of acidic fluids has resulted in poor connectivity of the cement.The CL showed the calcite as bright yellow.The carbonate cement formation was mainly influenced by paleoclimate and depositional water;in the study area there is also evidence of the presence of algae.The second and third stages are dominated by poikilitic calcite,which is most widely distributed in the second stage.Also,CL of the second stage shows the calcite cement as almost nonluminous,and with a high Mg content.The calcite cement in the third stage is seen as orange-yellow color under CL.Signs of corrosion at the boundary between the second and third stages are clearly seen under the polarizing micro⁃scope.In both the second and third stages,the effect of hydrocarbon generation and expulsion from Middle and Lower Jurassic source rocks in the Changji Depression is indicated.Organic acid fluid dissolved the early carbonate cements and acid-soluble particles,providing the main material source for the development of subsequent carbonate cements.It was found that the carbonate cement causes the poor physical properties of the Shawan Formation reservoir in the early stage.Subsequent injection of acidic fluid in the later stages increased the porosity and permeability of the reservoir to a limited extent.Continuous planar development formed thin interlayers of carbonate cement sealed by capillary pressure,restricting hydrocarbon migration and trap types in the reservoir by blocking their migration path,so that migration and accumulation of oil and gas only occurs along a few structural fractures.This has led to obvious oil heterogeneity in the sandstone within the study area.Also,where high-carbonate cement occurs over large areas,it overlies the sand body.Because it is mostly basement cementation,it may form a better cap layer,affecting the accumulation of oil and gas.[Conclusions]The types,distribution,formation and geological significance of the multistage carbonate cements are defined,providing support for continued exploration and development as well as the search for new exploration targets.
作者
袁静
张宇翔
赵广昊
侯旭波
YUAN Jing;ZHANG YuXiang;ZHAO GuangHao;HOU XuBo(School of Geosciences,China University of Petroleum,Qingdao,Shandong 266580,China;State Key Laboratory of Deep Oil and Gas,Qingdao,Shandong 266580,China;Exploration and Development Research Institute of Shengli Oilfield Branch of SINOPEC,Dongying,Shandong 257015,China)
出处
《沉积学报》
北大核心
2025年第6期2015-2027,共13页
Acta Sedimentologica Sinica
基金
国家自然科学基金项目(42072134)。
关键词
碳酸盐胶结
浅埋藏
成因分析
地质意义
新近系
carbonate cementation
shallow burial
cause analysis
geological implications
Neogene
