姬螈地区长81地层水-岩作用机制

Discussion of interaction mechanism of formation water-rock in Chang81 reservoirs of Jiyuan oilfield

姬塬地区长81油藏属于典型的低孔一特低渗透油藏。薄片及扫描电镜下，长石溶孔占到整个面孔率的41．4％。与华庆油田长81储层对比，研究区黏土矿物组分富含高岭石。通过对研究区水岩作用相互机理研究发现：中成岩A期有机酸参与的溶蚀作用是研究区重要的溶蚀作用之一．相对开放的成岩体系以及较低的K＋／H＋活度比是造成研究区高岭石含量较高的主要原因；包襄体均一温度显示，研究区硅质胶结物主要为钾长石溶蚀产生．且主要为中成岩A期沉淀；碳、氧同位素研究表明，中成岩A期长石遭遇有机酸性水溶蚀．造成了研究区大量铁方解石沉淀；定量计算显示，钾长石溶解生成高岭石对研究区孔隙形成贡献最大，大约可以产生13．07％的额外体积。

The Chang81 reservoir of Jiyuan oilfield belongs to typical low-porosity and extra-low-permeability one, The thin sections and scanning electron microscopy （SEM） data show that the feldspar-dissolved pores account for 41.4% of the whole pore-section ar- ea ratio. Comparing with Chang81 reservoir of Huaqing oilfield, the clay minerals of the study area are rich in kaolinite. Through the study on the water-rock interaction mechanism in the study area, it is found that the dissolution of organic acid in the A period of the middle diagenetic stage is a main form of dissolution in the area. The relatively open diagenetic system and low K＋/H＋ activity ratio are main cause that leads to higher kaolinite content in the study area. The inclusion homogenization temperature measurement demonstrates the siliceous cements of the study area are mainly generated by potassium feldspar dissolution and mainly the deposits formed in the A period of mesogenetic stage. The carbon and oxygen isotope studies show the feldspar in the A period of mesogenetie stage was subject to dissolution from organic acid water, dissolution is the biggest contributor to the pore formation in the study area, producing about 13.07%extra volume.