砾石充填介质复合堵塞对天然气水合物储层产能的影响规律研究

砾石充填层堵塞是影响天然气水合物储层砾石充填防砂井产能优化的关键因素。在考虑泥质粉砂与二次生成水合物对砾石充填层复合堵塞情形的基础上，针对人造陶粒与石英砂充填介质，分别开展了泥质粉砂和水合物二次生成堵塞充填层的模拟试验，系统分析了堵塞过程。基于复合堵塞充填层机理及渗透率变化规律，构建了天然气水合物砾石充填防砂井砾石充填层堵塞后的产能预测模型并进行了案例分析。研究结果表明，在泥质粉砂和二次生成水合物堵塞条件下，充填层渗透率的降幅分别达93%与98%；复合堵塞造成充填层渗透率降低对产能的影响显著，堵塞后防砂井产能比的降幅达97%。大粒径砾石充填虽然能缓解产能受损，但效果不明显。研究认为，预防复合堵塞的关键是优化生产制度，避免水合物二次生成。 

Influence Law of Hybrid Plugging of Gravel-Packed Media on Productivityin Natural Gas Hydrate Reservoirs

The influence brought by the plugging of gravel-packed media on productivity is the key to optimizing the productivity of gravel-packed sand control wells for natural gas hydrate production. Primary consideration was given to the hybrid plugging of gravel-packed media by argillaceous silt and secondary hydrates. For the packing media of artificial ceramsite and quartz sand, medium plugging by argillaceous silt and medium plugging caused by secondary hydrate formation were respectively experimentally simulated, and the plugging processes were systematically analyzed. A productivity prediction model for plugged gravel-packed sand control wells for natural gas hydrate production was built according to the hybrid medium plugging mechanism and the permeability variation law, and a case study was carried out with the proposed model. The results showed that under the conditions of plugging by argillaceous silt and secondary hydrate formation, the permeability of the packing layer decreased by 93% and 98%, respectively. The decrease in the permeability of the packing layer caused by hybrid plugging had a significant impact on productivity, and the productivity ratio of the sand control wells after plugging dropped by 97%. Although packing with gravels of large particle sizes can alleviate the loss of productivity, the effect is insignificant. Instead, optimizing the production system to avoid secondary hydrate formation is the key to preventing hybrid plugging.