研制一种新型的油田防砂用可脱离式充填筛管,其技术关键是实现井下PLA-T管体的快速有效脱离。以PLA-T的降解程度和降解速率为评价指标优选出一种降解剂配方,并在模拟油藏条件下对降解剂进行耐温、耐盐、耐稀释等性能的评价。通过扫描电镜观察反应过程中PLA-T表面的微观变化,分析PLA-T的降解机制。结果表明：最优降解剂配方为w(丙酮)： w(二甲基甲酰胺)： w(乙二胺)=3：2：5；在温度为50~80℃、矿化度为10~100 g/L、稀释质量分数为70%~90%的模拟油藏条件下,PLA-T管体降解时间为6~92 min,表明该体系在复杂环境中具有优良的降解性能；在降解剂的作用下,PLA-T的表面结构形态从光滑表面逐步向裂纹、裂缝、不规则裂缝、裂缝-孔洞形态转变,导致PLA-T的降解速率先增大后减小；这种高效降解剂可以通过对PLA-T管体快速降解,实现井下充填筛管的有效脱离,达到疏松砂岩油气藏无筛管防砂的目的。%A novel detachable filling screen tube was developed for oilfield sand control. The key to this technology is to detach the PLA-T tube quickly and effectively downhole. In this study, an efficient degradation agent of PLA-T was proposed and its performance was evaluated under various oilfield conditions. Microscopic changes of the PLA-T surface structure were observed by SEM to analyze the degradation mechanism. The experimental results show that an optimized formula of the agent consists of w(acetone) : w(DMF) : w(ethylenediamine)=3 : 2 : 5. Under simulated reservoir conditions with temperature of 50-80℃, salinity of 10-100 g/L and diluted mass fraction of 70%-90%, the degradation time of the PLA-T tube is 6-92 min, which indicates that the agent has a good degradation performance in rigorous environments. The SEM results reveal that the surface of the PLA-T can be gradually transformed from smooth to cracks, and then successively to crevices, irregular crevices and crev-ice-holes induced by the degradation agent, which leads to the degradation rate of the PLA-T increasing firstly and then de-creasing. This degradation agent can dissolve the PLA-T tube downhole so that the filling screen tube can be quickly and effec-tively detached, therefore screenless sand control can be applied in unconsolidated sandstone reservoirs.
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