姬塬油田砂岩储层成岩作用与孔隙演化

Succession of diagenesis and pore in sandstone reservoirs in Jiyuan Oilfield

目的研究姬塬油田延长组砂岩的成岩作用及其对储层物性的控制作用。方法采用了染色、铸体薄片鉴定、电镜扫描、阴极发光、X射线衍射、镜质体反射率测定及流体包裹体测温等多种分析测试手段。结果成岩作用主要有压实作用、胶结作用、溶解作用和交代作用,胶结物有硅质、碳酸盐和黏土矿物,成岩阶段已达中成岩A期;成岩作用对本区砂岩储层孔隙演化起着重要的控制作用,早期的机械压实和胶结作用使原生孔隙大量丧失,长石的溶蚀对储层物性起重要的改善作用,以铁方解石为主的胶结物又使砂岩孔隙再度降低。结论原生孔隙的大量丧失和胶结物中次生孔隙的不发育是造成砂岩低孔、低渗的主要原因。

Aim To ascertain Ascertain the control of diagenesis on reservoirs quality of the Yanchang sandstone,Jiyuan Oilfield.Methods Multiple analysis methods were adopted,including coloration and casting slice identification of sandstone,scan electron microscope,cathode luminescence,X-ray diffraction,reflection of vitrinite measurement,measurement of fluid inclusions,etc.Results Diagenesis includes compaction,cementation,dissolution and alteration.Cements are dominated by silicon,carbonate and clay minerals（chlorite,kaolinite,illite,illite/montmorillonite,and endellite）.Diagenesis reaches A-period of middle diagenetic stage.Conclusion Diagenesis has control of succession of pore in sandstone reservoirs in the region of interest.Primary porosity loses severely under compaction and cementation in early diagenetic stage.Porosity of sandstone reservoirs is improved by dissolution of feldspar.But it came down again caused by ferroan calcite cementation.Losing of a great deal of primary porosity and underdeveloped secondary porosity are the main reasons of low porosity and low permeability of sandstone reservoirs in Jiyuan Oilfield,Ordos Basin.