致密砂岩气运移的临界动力学条件探讨

Critical dynamic conditions for gas migration in tight sandstone

王若谷 乔向阳 周进松 雷裕红 曹军 银晓 朱耿博仑

WANG Ruogu QIAO Xiangyang ZHOU Jinsong LEI Yuhong CAO Jun YIN Xiao ZHUGENG Bolun

1. 陕西延长石油(集团)有限责任公司 天然气研究院, 西安 710065; 2. 中国科学院 地质与地球物理研究所, 北京 100029

1. Natural Gas Research Institute of Shaanxi Yanchang Petroleum (Group) Co., LTD., Xi'an, Shaanxi 710065, China; 2. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China

物理模拟是认识地下油气运移和聚集机理的重要方法和手段，为了更深入地认识深层条件下致密储层天然气运移的机理，以延安气田上古生界山西组致密砂岩气为例，设计了实验模型和边界条件。基于超低渗岩石多相渗流核磁共振在线模拟实验，探讨致密砂岩中天然气运移的临界压力、临界物性动力学条件，进而分析影响天然气运聚的控制因素。选取山西组不同砂岩类型包括石英净砂岩、富石英低塑性颗粒岩屑石英砂岩、富塑性颗粒岩屑砂岩和富凝灰质杂基石英砂岩样品，代表不同孔渗分布区间的岩石相储层，进行了恒定低注入流量、不同流速(流量)和不同压差充注实验。结果表明，致密砂岩储层的临界充注压力主要受岩石相和渗透率控制，渗透率较高的优势岩石相具有更低的临界充注压力，石英净砂岩天然气临界注入压力一般小于1.2 MPa，即使是物性很差的富塑性颗粒岩屑砂岩和富凝灰质杂基石英砂岩的天然气临界注入压力一般也小于1.5 MPa。同时，致密砂岩也没有绝对的天然气充注物性下限，但致密砂岩的充注效率、含气饱和度与储层物性，尤其是渗透率呈正相关，优势岩石相越发育、渗透率越高，充注效率和含气饱和度也越高。

Physical simulation serves as a crucial method for understanding the mechanisms of underground oil and gas migration and accumulation. To gain a deeper understanding of gas migration mechanisms in tight reservoirs under deep geological conditions, experimental models and boundary conditions were designed using the tight sandstone gas reservoirs of the Upper Paleozoic Shanxi Formation in the Yan’an Gas Field as a case study. Based on ultra-low permeability rock multiphase flow nuclear magnetic resonance online simulation experiments, the study investigated the critical pressure and dynamic conditions governing gas migration in tight sandstone, while also analyzing the factors influencing gas migration and accumulation. Different types of sandstones from the Shanxi Formation were selected, including quartz clean sandstone, quartz-rich low-plasticity particle detrital quartz sandstone, plastic particle-rich detrital sandstone, and tuffaceous matrix-rich quartz sandstone samples, representing reservoir rock facies with different porosity and permeability distributions. Experiments with constant low injection flow rates, different flow velocities (flow rates), and different pressure differences were conducted. The findings indicate that the critical charging pressure of tight sandstone reservoirs is primarily influenced by rock facies and permeability. Dominant rock facies with higher permeability exhibit lower critical charging pressures. For instance, the critical injection pressure of pure quartz sandstone gas typically falls below 1.2 MPa, while it generally remains below 1.5 MPa even for plastic-rich granular lithic sandstones and tuff-rich hybridquartz sandstones with inferior physical properties. Furthermore, there exists no absolute lower limit for the gas charging physical properties of tight sandstone. However, the charging efficiency and gas saturation of tight sandstone are positively correlated with reservoir physical properties, particularly permeability. The more developed the dominant rock facies and the higher the permeability, the higher the charging efficiency and gas saturation.

国家科技重大专项“延安地区陆相页岩气勘探开发关键技术”(2017ZX05039)资助。

https://doi.org/10.11781/sysydz202403532