考虑启动压力梯度的断块油藏CO2/N2复合气体吞吐注采参数优化

冀东油田高12断块油藏砂体规模小、渗透率较低、难以建立有效驱替关系,注入压力高,注水困难,水驱开发效果较差,但油藏温度和压力较高,适宜通过注气来提高油藏采收率。低渗油藏普遍存在启动压力梯度,对实际油藏开发造成影响,针对高12断块油藏,建立高12断块注气开发的三维地质模型,在室内启动压力梯度实验的基础上,得到启动压力梯度与渗透率的公式,在数值模拟软件考虑启动压力梯度与渗透率的变化关系。但长期注入CO2导致的管线腐蚀问题日益突出,N2作为良好的增能气体,将二者结合形成复合气体进行吞吐,可缓解对管线的损害。利用数值模拟方法,进行了衰竭阶段单井产量、段塞比、转注时机、注入量、焖井时间、注气阶段采油速度优化。最终得到该区块最优吞吐注采参数：衰竭阶段单井产量为15m3/d；段塞比为7：3；转注时机为衰竭阶段的日产油速度降为4m3/d时；注入量为60 000 m3；焖井时间为15天；注气阶段采油速度为25m3/d,为高12断块油藏提高采收率提供了方法技术借鉴。

Optimization of Injection-production Parameters for CO2/N2 Composite Gas Huff and Puff in Fault-block Reservoirs Considering Starting Pressure Gradient

The Gao 12 fault block reservoir in Jidong Oilfield is small in scale, low in permeability, and difficult to establish an effective displacement relationship. The injection pressure is high, water injection is difficult, and the water flooding development effect is poor, but the reservoir temperature and pressure are high and suitable Improve oil reservoir recovery through gas injection. Low-permeability oil reservoirs generally have a starting pressure gradient, which has an impact on actual reservoir development. Aiming at the high 12 fault block reservoir, a three-dimensional geological model for the high 12 fault block gas injection development is established. Based on the indoor starting pressure gradient experiment, it is obtained For the formula of starting pressure gradient and permeability, the relationship between starting pressure gradient and permeability change is considered in the numerical simulation software. However, the problem of pipeline corrosion caused by long-term injection of CO2 has become increasingly prominent. As a good energizing gas, N2 combines the two to form a composite gas for throughput, which can alleviate the damage to the pipeline. Using numerical simulation methods, the optimization of single well production, slug ratio, injection timing, injection volume, simmering time, and oil recovery rate during gas injection stage in the depletion stage was carried out. Finally, the optimal injection-production parameters of the block are obtained: the single well production in the depletion stage is 15m3/d; the slug ratio is 7:3; the transfer timing is when the daily oil production rate in the depletion stage drops to 4m3/d; the injection volume is 60000m3 ; The simmering time is 15 days; the oil recovery rate in the gas injection stage is 25m3/d, which provides a method and technology reference for improving the oil recovery of high 12 fault block reservoirs.