临兴地区致密砂岩储层流体敏感性特征分析

Fluid sensitivity characteristics of tight sandstone reservoirs in Linxing area

临兴地区上古生界致密砂岩气纵向上多套成藏,各类敏感性伤害率不同,不同地层间敏感性也存在差异。综合X-衍射、薄片鉴定、扫描电镜、核磁共振及敏感性实验开展了储层流体敏感性特征及控制因素研究。结果显示,受岩石矿物组分、储层物性影响,研究区储层水敏、盐敏普遍较强,纵向上不同储层间酸敏、碱敏呈相反变化趋势;微观上储层敏感性受黏土矿物类型、含量、孔隙结构影响,水敏伤害主要受伊/蒙混层影响,酸敏和碱敏伤害率与绿泥石、高岭石含量呈正相关,随孔隙结构变差,搭桥式自生矿物易运移堵塞小孔喉储层产生伤害;宏观上储层敏感性受沉积微相变化及成岩作用的强弱控制,优势沉积微相水动力强,碎屑组分含量高,黏土矿物含量低,孔隙连通性好,速敏、水敏均较弱。依据成岩作用、孔隙类型、储层物性将研究区储层成岩相划分为四类,其中硅质胶结粒间孔成岩相(Ⅰ类)、长石溶蚀孔成岩相(Ⅱ类)敏感性相对较弱,是研究区优质储层类型。纵向上不同地层、不同成岩相敏感性差异可为储层保护措施优化提供参考依据。

Multiple sets of tight sandstone gas reservoirs are formed vertically in the upper Paleozoic in Linxing area,with various sensitivity damage rates and differences in sensitivity among different strata.Combined with X-ray diffraction,thin section analysis,scanning electron microscope,nuclear magnetic resonance and sensitivity test,the reservoir sensitivity and controlling factors were analyzed.The results showed that the water sensitivity and salt sensitivity in the study area are generally strong affected by rock mineral composition and reservoir physical properties.In vertical direction,the acid sensitivity and alkali sensitivity of different reservoirs show an opposite trend.Reservoir sensitivity is affected by clay mineral type,content and pore structure in microscopic view.The water sensitivity damage is mainly affected by illite-montmorillonite mixed layer.The acid sensitivity and alkali sensitivity damage rates are correlated with the content of chlorite and kaolinite.With the deterioration of pore structure,bridging authigenic minerals are easy to transport and block the small pore throat reservoir and cause damage.Reservoir sensitivity is controlled by sedimentary microfacies and diagenesis in macroscopic view.Good sedimentary microfacies have strong hydrodynamic force,in which the sandstone has high clastic content,low clay mineral content,good pore connectivity,and weak velocity sensitivity and water sensitivity.According to diagenesis,pore type,porosity and permeability,the diagenetic facies of the reservoir can be divided into four types.Among them,the sensitivity of the siliceous cemented intergranular(TypeⅠ)diagenetic facies and feldspar dissolution pores(TypeⅡ)diagenetic facies is relatively weak,and belongs to high-quality reservoir types.In vertical direction,the sensitivity difference of different formations and different diagenetic facies can provide reference basis for optimizing reservoir protection measures.