二维核磁共振技术评价CO_(2)吞吐对不同状态页岩油的动用率

Evaluation of the Utilization Rate of Shale Oil in Different Occurrence States During CO_(2) Huff-n-puff Process by Two-dimensional Nuclear Magnetic Resonance Technology

游离态和吸附互溶态页岩油动用的难易程度不同,不同状态页岩油动用程度的准确表征对于页岩油的高效开发具有重要意义。结合二维核磁共振技术和CO_(2)吞吐实验,建立了CO_(2)吞吐过程中不同赋存状态页岩油划分及动用率的评价方法。采用该方法处理得到的CO_(2)吞吐过程中页岩油总动用率与质量变化计算得到的总动用率基本一致,验证了该方法的准确性。此外,可以直观地看到吸附互溶态页岩油和游离态页岩油二维核磁共振图谱随吞吐轮次的变化,游离态页岩油的动用要比吸附互溶态页岩油更容易,而提高压力和吞吐轮次可以明显提高吸附互溶态页岩油的动用率,10 MPa吞吐5个轮次后,吸附互溶态页岩油的动用率和总动用率分别达到73.6%和91.1%。该方法可对吸附互溶态页岩油动用率进行定量评价,有助于优化页岩油CO_(2)吞吐增产工艺,大幅提高页岩油采收率。

The complexity of the development of shale oil with the state of free oil and adsorbed-absorbed oil is different,and the exact measurement of the utilization rate of shale oil with different state is of great significance for the efficient development of shale oil.An evaluation method for the utilization rate of shale oil at different occurrence states during CO_(2) huff-n-puff process has been founded by two-dimensional nuclear magnetic resonance technology and CO_(2) huff-n-puff experiments.The total utilization rate obtained from this method is almost the same as the values calculated by the mass variation of shale core saturated with oil,which verifies the accuracy of the method.Furthermore,the variation of the adsorbed/absorbed oil and free oil with CO_(2) huff-n-puff cycles can be clearly observed in the t_(2)-t_(1) two-dimensional nuclear magnetic resonance spectrum.The free oil in shale core is easier to be extracted by CO_(2) than the adsorbed/absorbed oil.The increase of pressure and huff-n-puff cycles can enhance the utilization rate of adsorbed/absorbed oil.At 10 MPa after 5 cycles of CO_(2) huff-n-puff,the utilization rates of adsorbed/absorbed oil and total can reach 73.6%and 91.1%.The exact evaluation on the utilization rate of shale oil with the state of adsorbed-absorbed oil is conducive to the optimizing of the production technology and enhancing the shale oil recovery.