页岩气及致密砂岩气藏由于其特殊地质构造,在大体积压裂开发后井筒出砂现象频发且严重影响生产。针对川南气区页岩气和天府气区致密气井生产中出砂及井筒砂堵危害进行了动态分析,基于大型水平井实验装置开展了井筒内气水携砂实验,结合数值仿真进行了水平井内气、水、砂三相流动特性研究,分析了产气量、产水量、井口压力等主要因素对气液携砂的影响规律。结果表明:砂在井筒内沉积形成砂床或间断砂丘;井筒携砂能力随产气量增大而增强;产水量为0~1.4 m³/h,井筒携砂能力随产水量增大而增强,产水气井的携砂能力明显强于不产水气井的携砂能力,产水量增大1倍,气井完全携砂临界产气量可降低15%左右;井口压力增大,井筒压差减小,携砂能力降低。最后基于研究数据建立了一种井筒内气水携砂率预测模型,携砂率表征了井筒携砂能力及积砂风险的大小,通过计算携砂率实现对气井携砂状况实时评估,并提出携砂率计算+反馈调控井口产气量的出砂气井控砂稳定生产方法。预测模型及控砂方法现场实践效果良好,有望为页岩气、致密气稳产上产提供相关支持。

Due to the special geological structure of tight sandstone gas reservoirs and shale gas reservoirs, sand production from the wellbore becomes a frequent phenomenon after the large-scale fracturing development, seriously affecting the production. A dynamic analysis was conducted on sand production and wellbore sand plugging hazards during the production of shale gas wells in South Sichuan gas area and tight gas wells in Tianfu gas area. A large-scale experimental apparatus simulating horizontal wellbore conditions was set up to conduct gas-liquid sand transport experiments within the wellbore. Numerical simulation was applied to study the three-phase flow characteristics of gas, liquid, and sand within the entire wellbore of horizontal wells. The effects of key parameters such as gas production, water production and wellhead pressure on the gas-liquid sand transport were analyzed. The results showed that sand deposition formed sand beds or intermittent sand dunes in the horizontal and inclined sections of the wellbore. The sand-carrying capacity of wellbore increased with increasing gas production. Within the water production range of 0~1.4 m³/h, the sand-carrying capacity of wellbore increased with increasing water production. The sand-carrying capacity of water-producing gas wells was significantly higher than that of gas wells without water production. With a doubling of water production, the critical gas production for gas wells to fully carry sand could be reduced by approximately 15%. Higher wellhead pressure resulted in lower wellbore differential pressure and reduced sand-carrying capacity. Based on extensive experimental and simulation data, a predictive model for sand-carrying rate of gas and water within the wellbore was developed. This model characterizes the sand-carrying capacity of the wellbore and the risk level of sand accumulation. Real-time prediction of sand-carrying condition of gas well is realized through the calculation of the sand-carrying rate. A control strategy combining sand-carrying rate calculation with feedback regulation of wellhead gas production is proposed to stabilize sand production in sand-producing gas wells. The field application of the model and control method has achieved positive results and is expected to support the stable and enhanced production of shale gas and tight gas wells.