【作者】 魏虎；

【导师】 孙卫；

【作者基本信息】 西北大学 ， 油气田地质与开发， 2011， 博士

【摘要】 低渗、致密砂岩气藏储层微观孔隙结构复杂、敏感性强、气井产能低,开展此项研究工作有助于对其微观孔隙结构进行系统地认识,揭示其对产能的影响。本文以岩心观察、铸体薄片鉴定、扫描电镜、高压压汞、恒速压汞、真实砂岩微观模型气水驱替、气水相渗和敏感性评价等实验结果为基础,对鄂尔多斯盆地低渗及致密砂岩气藏储层的岩石学特征、孔隙结构特征,微观孔隙结构与储层伤害关系,产能影响因素,等进行了深入研究。主要取得如下认识：(1)低渗致密砂岩气藏的岩石类型、岩石成分成熟度受物源和沉积环境影响明显。清水高能环境中的山2段岩石成熟度整体较高、石英砂岩比例高,而浑水和低能环境的盒8和山1层位石英砂岩比例则较低；西部气田的石英砂岩比例和成熟度高于东部气田,顺水流方向的石英砂岩比例和成熟度增加。(2)孔隙类型和孔隙结构受成分成熟度、成岩作用等影响。孔隙类型多样化,溶蚀孔发育,微观孔隙结构特征分可为Ⅰ-Ⅳ类。Ⅰ类至Ⅲ类孔隙结构变差,孔隙半径变化不大而喉道半径逐渐偏细,Ⅳ类孔隙结构的孔隙和喉道分布与前3类的孔喉分布有很大差别。(3)分形维数及形态多样化,孔喉分布形态也多样化。分形维数与分选系数、最大进汞饱和度具有很好的相关性,而与表征孔喉大小的各参数无明显的相关性。孔喉分布形态能定性反映孔隙度和渗透率大小。(4)储层的水敏、压敏程度与微观孔隙结构的关系密切,随着孔隙结构变差、敏感性对储层的伤害程度变大。酸化以增加大孔喉半径和渗流区间的孔喉半径为主,土酸的改善效果最好。(5)微观孔隙结构决定了气水渗流规律和潜在伤害因素,需采用特定的生产方式,微观孔隙结构类型越差,生产方式对气井的生产能力影响越明显。生产压差山2小于10MPa、盒8和山15MPa左右既可解除水锁,又可防止水窜,是合理的范围。针对微观孔隙结构的类型采取相应的排水采气措施,可采出近井地带被水圈闭的残余气。频繁的关开井制度,恶化了压敏和水锁效应,使得气水分布和渗流特征更加复杂,应当避免。更多还原

【Abstract】 Gas reservoir with less permeability and tight sandstone has low productivity in wells and strong sensitivity, which is caused by its complex micro-pore structure. The aim of this work is to study the micro-structue of the low permeability and tight sandstone and its impact on gas production. Based upon the analyzes and experimental results of gas-water displacement in microscopic model of real sandstone, gas-water relative permeability and sensitivity test, core observation, identification of casting tin sections, electron scan microscope (ESM), mercury injection in high pressure and controlled rate, four aspects contents, which conclude the characteristics of rock, influence factor of gas production, pore structure and the relationship between sensitivity and micro-pore texture, are studied in Low permeability sandstone and Tight gas reservoir of the Ordos Basin. And then following results are obtained:(1) Types and compositional maturity of low permeability tight sandstone gas reservoir rock is affected by provenance and depositional enviromental obviously. The compositional maturity and rate of quartz sandstone in Shan2 formation, which lies in high-energy and clear water enviroment, is higher than that in He8 & Shanl formation, which lies in turbid water and low-energy water enviroment. The rate of quartz and compositional is increasing along the flow direction, and that in the western part is higher than that in the eastern part of gas pool in basin.(2) For the type and structure of pore is affected by compositional maturity and diagenisis, so the pore type is variegated, especially the dissolution pore is the most important type. The characteristics of micro-pore structure are divided into four types, typeⅠtoⅣ, and each type has its own pore types and pore structure. From typeⅠtoⅢ, the pore texture became worse, with the similar radius of pores, but the radius of throats become thinner. While the distribution of pores and throats in type IV is different from the three types.(3) The fractal dimension and feature is variegated. Fractal dimension has a very good correlation with the separation factor and the maximum saturation of mercury invasion, while no significant correlation with the characteristic parameters of pore size is found. The distribution of pore throat, which is variegated also, can be used to evaluate the value of porosity and permeability qualitatively.(4) Reservoir’s sensitive degree of water and pressure is close tied up with micro-pore structure, and it becoming seriously with the pore structure becomes poor. The radius of main flow room and big pore throat room increasing after acidulations, and the best effect is proved by clay acid treatment.(5) The specific rule of gas-water percolation and potential damage factors are decided by micro-pore structure. For production model has an impact on gas well perforation, which becoming obviously with the pore structure goes poor, so specific production mode is drawn. The proper production pressure differential is about 5MPa in He8 & Shanl formation and less than lOMPa in Shan2 formation, which can remove water locking and prevent water breakthrough. To produce the gas trapped near wellbore area, the measures of recovery gas by discharge water should be adopted according to the type of micro pore structure. The strategy of well opening and shutting frequently, made the pressure-sensitive and water-blocking effect more serious, and made the seepage character and distribution of water-gas more complex, should be avoided.更多还原