柴达木盆地干柴沟地区E32Ⅱ油组储层伤害评价

Reservoir damage evaluation of E32Ⅱ oil formation in Ganchaigou area of Qaidam Basin

关键词:  储层特征  储层伤害  湖相碳酸盐岩  柴达木盆地

Key words:  reservoir characteristics  reservoir damage  lacustrine carbonate  Qaidam Basin

摘要:

目的 对干柴沟地区E₃²Ⅱ油组储层特征及储层伤害进行评价。方法 开展了岩心描述、薄片鉴定、扫描电镜分析、X衍射分析、储层伤害评价等实验。结果 干柴沟地区E₃²Ⅱ油组储层岩性为灰云岩、泥质灰云岩,主要由白云石、方解石组成,混杂少量陆源粉砂、黏土矿物、膏盐类矿物(硬石膏、钙芒硝、氯化钠)、黄铁矿等,碳酸盐岩为泥晶结构,碳酸盐晶体粒径为2～4 μm；岩石以块状结构为主,少量水平层理及纹层理；储集空间以白云石晶间孔为主,普遍发育,弥散状分布,孔径为0.5～2.0 μm；有机酸溶蚀作用普遍发育,局部溶蚀作用强,可形成溶蚀孔隙,溶蚀孔孔径为5～20 μm；块状结构岩石局部发育高角度裂缝,纹层状结构岩石发育层间缝；储层孔隙度平均值为8.3%,渗透率为1.38×10-3 μm²,属低孔特低渗储层；通过对储层伤害实验数据分析,研究区存在强速敏性,中等偏弱水敏性,弱碱敏性,无酸敏性,有针对性地提出了应对策略。结论 该研究成果对深化地质认识以及钻井、压裂、试油等施工作业过程中的储层保护具有一定参考作用。 

Abstract:

Objective Aiming at the reservoir characteristics and reservoir damage evaluation of E₃²II oil group in Ganchaigou area. Methods The experiments were carried out, such as core description, thin section identification, scanning electron microscope analysis, X-ray diffraction analysis and reservoir damage evaluation. Results It is concluded that the lithologies of E₃²Ⅱ oil reservoir in Ganchaigou area are dolomite and argillaceous dolomite, mainly composed of dolomite and calcite, mixed with a small amount of terrigenous silt, clay minerals, paste salt minerals (anhydrite, calcium glauber salt, sodium chloride), pyrite, etc. Carbonate rock has micritic structure and carbonate crystal size is 2-4 μm. The rock is dominated by massive structure with a little horizontal bedding and lamination. The reservoir space is mainly dolomite intercrystalline pores, which are widely developed and distributed with pore size of 0.5-2.0 μm. Organic acid dissolution is widely developed, and local dissolution is strong, which can form dissolution pores with pore sizes of 5-20 μm. Locally high Angle fractures are developed in massive rocks, interlayer fractures are developed in lamellar rocks. The average value of reservoir porosity is 8.3%, the permeability is 1.38×10-3 μm², which is a low-porosity and extra-low permeability reservoir. Through the analysis of reservoir damage experimental data, the study area has strong velocity sensitivity, medium and weak water sensitivity, weak alkali sensitivity and no acid sensitivity. The corresponding countermeasures are proposed. Conclusion sThe research results have a certain reference role in deepening geological understanding and reservoir protection during drilling, fracturing, oil testing and other construction operations.