Design and performance of degradation agent for detachable filling screen tubes in oilfield sand control

Key words:  detachable filling screen tube  degradation agent  degradation degree  degradation rate  screenless sand control

Abstract:

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 crevice-holes induced by the degradation agent, which leads to the degradation rate of the PLA-T increasing firstly and then decreasing. This degradation agent can dissolve the PLA-T tube downhole so that the filling screen tube can be quickly and effectively detached, therefore screenless sand control can be applied in unconsolidated sandstone reservoirs.