特低渗透砂岩储层敏感性评价与酸化增产液研制

酸化是特低渗透砂岩油藏的重要增产措施,若酸液体系使用不当,会对储层造成敏感性伤害。为此,以吐哈盆地鄯善油田三间房组砂岩储层为例,通过XRD衍射分析、扫描电镜、储层敏感性评价实验及现场资料整理等方法,研究储层敏感性特征及损害机理,并研发一种酸化增产液,该酸化增产液可与土酸组合使用,提高酸化效果。研究表明:三间房组储层岩石类型以长石岩屑砂岩为主,黏土矿物以高岭石和蒙脱石为主,属于高黏土矿物储层;储层物性整体表现为低孔特低渗特征,原油为轻质原油,油藏为正常地层压力的未饱和油藏;储层具有中等偏弱速敏、碱敏、水敏、盐敏以及弱酸敏特性;增产液与土酸组合酸液体系可溶蚀大孔隙、微孔隙等多种尺度孔隙后形成孔隙网络系统,可使目标储层岩心渗透率最大提高至原有渗透率的2.68倍。现场应用效果显著,与酸化前相比,平均单井日产油量增加1.29 t/d。研究成果可为特低渗砂岩油藏酸化增产提供技术支持。

Sensitivity Evaluation of Ultra-low Permeability Sandstone Reservoir and Development of Acidizing Stimulation Fluid

Acidizing is an important stimulation measure for ultra-low permeability sandstone reservoirs. If the acid fluid system is not used properly, it will cause sensitive damage to the reservoir. To this end, taking the sandstone reservoir of Sanjianfang Formation in Shanshan Oilfield, Turpan-Hami Basin as an example, the characteristics of reservoir sensitivity and damage mechanism were studied by means of XRD diffraction analysis, scanning electron microscope, reservoir sensitivity evaluation experiment and field data collation, and an acidizing stimulation fluid was developed, which could be used in combination with mud acid to improve the acidizing effect. The research shows: The rock types of the Sanjianfang Formation reservoirs are mainly feldspar lithic sandstone, and the clay minerals are mainly kaolinite and montmorillonite, which belong to high clay mineral reservoirs. The reservoir physical properties as a whole show the characteristics of low porosity and extra-low permeability, the crude oil is light crude oil, and the reservoir is unsaturated reservoir with normal formation pressure. The reservoir has moderate to weak velocity-sensitive, alkali-sensitive, water-sensitive, salinity-sensitive, and weak acid-sensitive properties. The combined acid fluid system of stimulation fluid and soil acid can dissolve pores of various scales such as macropores and micropores to form a pore network system, which can increase the permeability of the target reservoir core to a maximum of 2.68 times the original permeability. The field application effect is remarkable. Compared with that before acidizing, the average daily oil production of a single well increases by 1.29 t/d. The research results can provide technical support for acidizing stimulation of ultra-low permeability sandstone reservoirs.