储层流体非均质性在重油评价及开发生产上的应用

Application of Fluid Heterogeneity in Heavy Oil Reservoir Appraisal and Production

原油化学组成和物理性质的剧烈变化在重质油藏内非常普遍,了解引起这种变化的原因及控制因素对深化油藏地质评价、优化重油开发方案设计及提高重油采收率都有非常重要的意义。在重油评价方面,根据原油组成和物性的梯度变化可以帮助判别油层非均质程度和隔层的出现;在混层开采时,原油地球化学组成可以用来判别各层的贡献。在重油开发方面,黏度的梯度变化是造成油藏模拟结果与生产历史难以拟合的主要原因,用均一黏度模型进行油藏数值模拟,过高地估计了蒸汽辅助重力泄油(SAGD)和循环注汽开采(CSS)的累计产油量。油相组成变化必须像渗透率、孔隙度和含油饱和度一样结合到常规油藏描述和数值模拟中去,能否准确预测生产行为就取决于上述变化与数值模拟工具相结合的有效性。流体物性的梯度变化同时表明,目前工业界普遍采用的把SAGD生产井置于油水界面之上1～2m并不是一个完善的设计,按照黏度梯度变化、累计产量和目前油价进行的优化计算显示,在西加拿大盆地Peace River地区理想的完井位置应该在油水界面之上8m。由于原油黏度对生产行为有着非常重要的影响,因此重油生产必须考虑黏度的变化,为此提出了一种新的完井设计思路,把J型生产井与SAGD相结合(JAGD),JAGD生产不仅提高了经济效益,还能降低对环境的影响。同时,由于重油开采主要受流动性控制,在热采之前对油藏进行预处理,待黏度降低后再进行开采也是提高重油采收率、降低能耗的有效手段。

The defining characteristic of heavy and super heavy oil reservoirs is the large spatial variation in fluid properties,such as oil viscosity.Understanding chemical composition and physical property variations within heavy oil reservoirs has broad applications in geological appraisal,developing optimization and enhancing recovery efficiency.Based on the continuity of molecular compositions and physical properties across the oil column,the degree of reservoir heterogeneity and the occurrence of barriers or baffles can be recognized.Using oil compositional differences can allocate commingled production from a single well.Without knowing chemical composition and physical property heterogeneity in heavy oil reservoir causes a lot of problems in reservoir simulation and history match performance.Numerical thermal reservoir simulations reveal that oil viscosity heterogeneity makes the cumulative oil production volumes be lower from thermal recovery process（such as SAGD and CSS） in geologically realistic reservoirs,compared to results from equivalent models run with uniform viscosity profiles.The impact of oil viscosity variations on recovery process performance promotes the notion that heavy oil production processes must take advantage of the viscosity variations to more efficiently produce these reservoirs.Lateral variation of the physical property of the fluid shows that common SAGD well lies upon 1-2m of the oil-water interface is not a perfect design.Optimization calculation on viscosity variation,cumulative oil production and current oil price presents that the best position of well completion should be upon 8m of the oil-water interface in Peace River area,west Canada basin.Oil viscosity has very important impact on production performance,so its variation should be considered in the heavy oil production.A new well configuration we have developed is the J-well and Gravity Drainage recovery process（called JAGD）.JAGD process takes into account the oil phase viscosity variations to improve the economic and environmental performance of the production process.Due to oil mobility the key for recovery processes,precondition with organic solvent to reduce viscosity before recovery is another option for enhancing recovery efficiency and decreasing energy consumption.