页岩气藏注CO2渗透率界限及开发参数优化研究

根据页岩气井的现场生产情况,压裂水平井产量会迅速下降,注CO2技术是改造储层提高产量的有效手段。连续驱替与吞吐式注入作为注CO2提高页岩气采收率的两种常见方式,却在相同页岩气藏中驱替效果存在差异。为了对不同储层条件下注CO2开发方式进行优选,本文基于现场页岩气藏实际情况建立了双孔介质气藏机理模型,并通过建立采收率影响因素的正交试验,分析了渗透率、孔隙度、储层厚度、CH4和CO2最大吸附量以及Langmuir压力等的影响规律。将渗透率作为主控因素,划分了五个不同渗透率条件,进行直接驱替与吞吐注CO2模拟,并针对不同CO2注入驱替开发方式进行了布缝模式、井位排列、闷井时间等开发参数优化。结果表明：不同渗透率条件下两种开发方式驱替效果不同,以0.001mD为界限,渗透率低于0.001mD时,直接驱替效果更优；渗透率高于0.001mD时,选择吞吐式注CO2为宜；针对连续注气,交叉布缝模式具有更高的采收率,在多井同产同注时,应将生产井置于内部；另外,吞吐式注气应该选择较短的焖井时间来节约成本获得更好的经济效益。

Research on Permeability Demarcation and Process Parameter Optimization of Shale Gas Recovery with on CO2Injection

According to situations in the shale gas reservoir, Production will decreased rapidly in fractured horizontal well. Continuous injection and Huff-n-Puff injection are commonly used to develop shale gas reservoir, but the results are different. In order to optimize the way of CO2 injection under different reservoir conditions, we based on the actual situation of shale gas reservoir, a mechanism model of dual-porosity and dual-permeability is established. And we have established orthogonal test considering permeability, porosity, thickness of reservoir, methane maximum absorption, carbon dioxide maximum absorption and Langmuir pressure. We choose the permeability to research. And then five different permeability conditions are divided to simulate continuous injection and Huff-n-Huff CO2 injection. In addition, the technological parameters such as cloth pattern, well location and soak time wert optimized according to different CO2 injection. The results show that the continuous injection effect is better when the permeability is lower than 0.001 mD and the Huff-n-Huff CO2 injection is better when the permeability is higher than 0.001 mD. For CO2 continuous injection the cross pattern has a higher recovery rate, and the production wells should be placed inside when multiple wells are simultaneously produced and injected. In addition, the CO2 Huff-n-Puff injection should choose shorter soaking time to save cost and get better economic benefits.