防砂井投产初期砾石层渗透率损害规律

摘要

Wells with gravel packing for sand control may experience dramatic productivity decline shortly after production. Tests are conducted to highlight changes in permeability of compacted gravel-packing layers and plugging of such layers due to absorption. Eventually, patterns of permeability loss in gravel-packing layers during initial production are determined. Test results show, down-hole compaction and crude oil absorption and plugging are main contributors for permeability loss in gravel-packing layer during initial production. Permeability of gravel-packing layer may decrease signiifcantly with increase in external pressure. Permeability of gravel-packing layers compacted under pressure 40 MPa may be approximately 5%~11%of original permeability;Water permeability of gravel-packing layer may decrease rapidly after alternative displacement with permeability loss factor of approximately 0.75~0.85. Ratio of permeability loss in short duration may vary slightly with changes in displacement time and temperature. Based on relevant test results, prediction model and technique for prediction of permeability loss in gravel-packing layer during initial production have been constructed. The innovative model and technique may provide valuable guidance for research and production in relevant ifelds.%砾石充填防砂井在投产后经常在短期内发生产量明显下降的现象。通过压实条件下砾石层渗透率变化规律实验和砾石层吸附堵塞实验，对投产初期砾石层渗透率损害规律进行研究。实验结果表明，砾石充填防砂井的井下压实作用与原油吸附堵塞作用是导致投产初期砾石层渗透率下降的主要原因，随着外加压力的增大，砾石堆积渗透率明显降低，40 MPa压实下的砾石层渗透率约为初始渗透率的5%~11%；砾石层进行交替驱替后水相渗透率迅速下降，渗透率损害系数约在0.75~0.85之间；短时间内堵塞渗透率比随驱替时间及驱替温度变化不大。根据实验结果建立了投产初期砾石层渗透率损害程度预测模型与方法，对相关领域的生产研究具有一定指导意义。