摘要
针对CO_(2)驱油过程中气窜现象严重且缺乏气窜形成的力学机理解释的问题。通过分析超低渗油藏致密砂岩CO_(2)驱气窜缝网形成的能量演化规律,研究了天然裂缝型气窜通道随注入能量累积而两端同时转向的临界能量规律,进一步建立了气窜缝网形成的能量判别准则。现场注CO_(2)气窜的示踪剂动态监测结果验证了该准则的适用性和准确性。研究结果表明:临界能量与天然裂缝尺寸、应力强度因子等成正相关关系,与弹性模量成负相关关系,而与自身倾角和井筒夹角成三角函数关系;气窜缝网连通所需的能量均随注入压力和注入排量的增大而增大;通过与2个井组气窜的示踪剂监测情况对比,发现该能量判别准则适用于300 m左右的井间距离。该能量准则可避免气窜通道前缘复杂流固耦合计算,并弥补了经典应力判别准则无法反映作用时间效应的缺陷,为超低渗油藏注CO_(2)气窜提供力学机理支撑。
Aiming at the serious channeling during CO_(2)flooding and the lack of a mechanical mechanism explanation for channeling formation,by analyzing the energy evolution law of CO_(2)channeling fracture network formation in tight sandstone during CO_(2)flooding in ultra-low permeability reservoirs,the critical energy law for the simultaneous diversion of both ends of natural fracture-type channeling pathways with accumulated injection energy was studied.Furthermore,an energy criterion for the formation of channeling fracture networks was established.The applicability and accuracy of this criterion were verified by tracer dynamic monitoring results of field CO_(2)channeling.The study results show that critical energy is positively correlated with natural fracture size,stress intensity factor,etc.,negatively correlated with elastic modulus,and exhibits a trigonometric function relationship with its own dip angle and wellbore angle;the energy required for channeling fracture network connectivity increases with increasing injection pressure and injection rate;by comparing with tracer monitoring of channeling in two well groups,it was found that this energy criterion is applicable to inter-well distances of about 300 m.This energy criterion can avoid complex fluid-solid coupling calculations at the front of the channeling pathway and compensate for the defect of classical stress criteria in reflecting the effect of action time,providing mechanical mechanism support for CO_(2)channeling in ultra-low permeability reservoirs.
作者
刘志远
赵海峰
甘贵鹏
张旺
LIU Zhiyuan;ZHAO Haifeng;GAN Guipeng;ZHANG Wang(China University of Petroleum(Beijing),Beijing 102249,China)
出处
《特种油气藏》
北大核心
2025年第4期94-103,共10页
Special Oil & Gas Reservoirs
基金
国家自然科学基金“一种复杂缝网的能量断裂准则及其在致密砂岩压裂模拟中的应用”(11672333)。
关键词
超低渗油藏
注CO_(2)驱
气窜缝网
能量判别准则
ultra-low permeability reservoir
CO_(2)flooding
channeling fracture network
energy criterion
