形状记忆效应对水合物开采井防砂用聚合物性能的影响

The influence of shape memory on the performance of polymers used for sand control in hydrate production wells

摘要:

形状记忆聚合物防砂筛管在日本第二轮天然气水合物试采中成功应用，但形状记忆效应对聚合物孔渗特征和防砂性能等影响的研究较少。基于此，本文研发了一种以聚氨酯作为基质的形状记忆聚合物防砂材料，探究了聚合物形状记忆特性、形状记忆前后的孔渗特性和力学强度等的变化规律，并评价了防砂性能。实验结果表明：研制的多孔聚氨酯具有良好的形状记忆特性和孔渗特性，形状固定率>98%，形状恢复率为100%，形状记忆温度为59.8 ℃；回弹前后渗透率均维持在10 D左右，且回弹前后抗压强度均维持在1 MPa左右；压汞测试表明形状记忆是一个对材料内部大孔的压缩-回弹过程，会导致材料内部结构发生变化，造成抗压强度略有降低，但完全回弹后，渗透性会小幅度增加；防砂性能测试表明仅在实验初期会有少量砂产出，砂粒的产出会对聚氨酯渗透性有一定的损伤，但对完全回弹的聚氨酯的渗透率仍可保持在10 D左右。综合材料性能分析认为，研制的形状记忆聚氨酯材料可配合机械防砂筛管使用，能满足水合物开采井防砂的需求。

关键词:天然气水合物;形状记忆聚合物;多孔聚氨酯;防砂;渗透率;孔隙结构

Abstract:

The shape memory polymer sand control system has been successfully applied in the second phase of natural gas hydrate production in Japan. However， the effects of the shape memory on the pore-permeability characteristics and sand control performance of polymers is rarely researched. Therefore， in this paper， a shape memory polymer sand control material taking the polyurethane as the matrix is developed. The polymer’s shape memory characteristics as well as the changes in pore-permeability and mechanical strength before and after the shape memory process are investigated and the sand control performance is also evaluated. The results revealed that the developed porous polyurethane shows excellent shape memory characteristics and pore-permeability properties： the shape fixed rate exceeded 98%， the shape recovery rate reached 100%， the shape memory temperature was 59.8°C， the permeability remained at approximately 10D before and after the shape memory process， and the compressive strength was maintained at around 1MPa. The mercury injection tests indicated that the shape memory process is a compression-rebound process for the polyurethane material with large pores， which will lead to some changes in the internal structure of the material， resulting in a slight decrease in compressive strength and a small increase in permeability after complete shape recovery. The sand control performance tests indicated that a small amount of sand production occurred only in the initial test， and the presence of sand particles caused some damage to the permeability of the polyurethane material， however， the permeability could still be maintained at around 10 D for the fully recovered polyurethane. According to the comprehensive performance analysis of the above materials， the developed shape memory polyurethane material can be used in conjunction with a mechanical sand control screen pipe， which could meet the requirements of sand control in hydrate production wells.

Key words:natural gas hydrate;shape memory polymer;porous polyurethane;sand control;permeability;pore structure