致密油注气吞吐优化

近年来，注气吞吐成为致密油体积压裂水平井衰竭式开采基础之上的一种有效的提高采收率的方法。本文通过数值模拟新疆玛湖地区玛131井区典型井注气吞吐过程，对该过程机理进行分析，对相关参数进行优化。首先，建立体积压裂水平井的组分油藏数值模拟模型。接着，对不同的注气量、不同的注入时长、不同的注入气体以及不同闷井时间进行了数值模拟。最终，通过对累计产油量和油藏平均压力的分析，优选合适的注气方案。结果发现，保持油藏压力在地层破裂压力以下并尽可能增加每轮次注气量可提高采收率，注入时长对采收率影响微弱，注入气体组成对吞吐效果影响巨大，闷井时长对采收率影响微弱。最终给出了该致密油藏优化的注气方案的建议。总之，数值模拟可以对致密油注气吞吐过程进行分析和优化，对生产实践具有一定的参考意义。

Optimization Study of Tight Oil Cyclic Gas Injection

In recent years, cyclic gas injection has become an effective enhanced oil recovery method for tight oil reservoirs developed with hydraulically fractured horizontal wells after primary depletion. In this work, through numerical simulation of the cyclic gas injection process for one domestic tight oil reservoir, we study the mechanisms for such process and optimize the relevant parameters. First, a compositional numerical reservoir simulation model is constructed. Then, simulations are conducted for cases with different gas injection amount, different injection durations, different types of injection gas and different shut-in durations. At the end, through analyzing the cumulative oil production and average reservoir pressure, we optimize the gas injection strategy. The results have shown that increasing the gas injection amount while keeping the reservoir pressure lower than the limit can improve oil recovery. Different injection duration has minimal impact on the recovery. Different injection gas compositions, have strong influence on the result. The shut-in duration also has minimal impact. Finally, we demonstrate the suggestions for optimized cyclic gas injection in this tight oil reservoir. In conclusion, through numerical reservoir simulation, optimization and analysis have been conducted for tight oil cyclic gas injection process. This work shall have its value in guiding field production and practice.