特低渗透油藏二氧化碳驱气窜影响因素及规律

Gas Channeling Influencing Factors and Patterns of CO_2-flooding in Ultra-Low Permeability Oil Reservoir

针对特低渗透油藏CO_2驱存在气窜、注气开发效果差、气窜影响因素认识程度低、气窜治理不及时等问题,从储层发育特征、原油物性及注采井生产情况出发,利用数值模拟方法揭示了不同因素影响规律,运用灰色综合评估法定量评价了诸因素影响强弱,明确了气窜主要影响因素,制订气窜程度分类界限,建立气窜程度评估模型。研究表明,气窜主要影响因素(由强到弱)为:裂缝密度、非均质性、渗透率、注入强度、地层原油黏度及孔隙度;当评估值大于0.55时,气窜程度非常严重,当评估值小于0.25时,未出现气窜;气窜程度评估模型计算结果符合率达到90.6%,证明该模型的准确性。研究成果为现场及时采取气窜防控措施、改善注气开发效果提供理论基础。

In view of the gas channeling,poor gas-flooding performance,defective understanding of gas channeling influencing factors,ineffective treatment of gas channeling and other challenges,reservoir numerical simulation is used to analyze different influencing factors from reservoir development patterns,oil properties and injection-production well performances.Comprehensive grey evaluation is adopted to quantitatively assess the sensitivities of different factors and clarify the key controlling factors.The classification limits of gas channeling are formulated to establish an evaluation model of gas channeling level.Research indicates that the key influencing factors from high to low are fracture density,permeability,injection intensity,formation oil viscosity and porosity.There is serious gas channeling when the evaluation value exceeds 0.55.There is no gas channeling when the evaluation value is less than 0.25.The agreement rate of gas channeling level evaluation model is up to 90.6%,which proves the model accuracy.This research could provide a theoretical reference for the field gas channeling treatment and improvement of gas-flooding performance.