江汉盆地白垩系储集层中硬石膏的成岩作用及其对油气分布的控制

江汉盆地西南缘白垩系渔洋组砂岩储集层非均质性比较严重,储集物性除受沉积微相控制外还与成岩作用密切相关。各种常见的成岩作用类型在研究区均有出现,其中压实作用、压溶作用、胶结作用与交代作用对储集层孔渗性起破坏性作用;而溶解作用形成大量粒间、粒内溶孔和铸模孔,对改善储集层性质起到了较好的建设性作用。研究认为,引起区内储集层孔隙度和渗透率下降的关键成岩作用是硬石膏的胶结与交代作用,形成硬石膏的硫酸盐来自新沟咀组烃源岩中的膏盐段,其中的硫酸盐随油气的运移一起进入储集层,硬石膏的出现范围预示着油气的到达位置,因此它对研究区的油气分布有着明显的控制作用。图7参9

Diagenesis of anhedritite in the Cretaceous reservoir and its influence on the hydrocarbon distribution in southeast Jianghan Basin

The property of the Cretaceous Formation Yuyang reservoir in the southeast of the Jianghan basin,with great heterogeneity,is controlled by micro-facies and diagenesis.All diagenesis types can be found in the research area.The processes of compaction,pressure solution,cementation,and displacement reduce porosity and permeability,while the resolution process can form a quantity of intergranular,intragranular and fold pores,which improve the reservoir quality.The crucial factors that reduce the porosity and permeability are the cementation and displacement of anhedritite,which comes from the gypsum sector of the source rock in the Xingouzui Formation.The sulphate migrates into the reservoir together with the hydrocarbon.Where the anhedritite occurs tends to be the place where the hydrocarbon appears,implicating that the hydrocarbon distribution is controlled by the anhedritite.