降阻剂聚集形态与降阻性能研究

Study on Aggregation Morphology and Resistance Reducing Properties of Drag Reducing Agents

为明确滑溜水压裂液降阻剂宏观降阻性能的微观控制机制,利用环境扫描电镜对不同类型的聚合物降阻剂形成的聚集体结构进行大量微观表征,结合体系降阻性能测试,从聚合物分子聚集态层次揭示浓度对不同降阻剂体系降阻性能作用的微观机理。研究发现,滑溜水降阻剂在极低浓度下聚集形成丝状结构,随着降阻剂浓度的不断提高,这些丝线状结构逐渐缠结连接形成骨架,最终围成多层次的“蛛网状”聚集体网络结构。同时不同类型的滑溜水降阻剂所形成的网络结构又具有各自的特点,其中以乳液型和悬浮液型降阻剂网络结构最为完整,而粉剂型降阻剂由于溶解速度较慢,形成聚集体网络结构分布不均,网络强度普遍不高。降阻剂浓度对降阻剂聚集状态影响极大,在低浓度条件下,3种降阻剂形成的网络结构平均骨架厚度约为0.1~0.3μm。随着降阻剂浓度的增大,体系网眼形状由不规则逐渐转变为多边形,部分降阻剂可形成强度较高、稳定性较好的圆形网络支撑结构,网眼尺寸减小,骨架厚度增加。当降阻剂浓度增加为0.05%时,骨架厚度可达0.3~0.9μm,网络结构强度显著提高。滑溜水降阻剂形成的聚集体网络结构会对体系降阻性能产生重要影响,降阻剂加量与体系降阻性能之间并非表现出简单的线性关系,只有在合适浓度下形成的适中尺寸的聚集体网络结构才能与体系中的水分子紧密作用,稳定溶液流动状态,减少湍流脉动,降低湍流流动过程中的能量耗散,最终实现高效降阻的效果。

In order to clarify the micro control mechanism of the macro drag reduction performance of slick-water drag reducer,a large number of micro characterization of the aggregate structure formed by different types of polymer drag reducing agents were carried out by environmental scanning electron microscope.Combined with the test of the drag reduction performance of the system,the micro mechanism of the effect of concentration on the drag reduction performance of different drag reducing agents systems was revealed from the level of polymer molecular aggregation structure.It was found that the slick-water drag reducer aggregated to form a filament structure at very low concentration.With the increasing concentration of the resistance reducer,these filament structures gradually entangled and connected to form a skeleton,and finally form a multi-level"spider net"aggregate network structure.At the same time,the network structure formed by different types of slick water resistance reducer had its own characteristics.Among them,emulsion and suspension type drag reducing agents had the most complete network structures,while powder type drag reducing agents had uneven distribution of aggregated network structures and low network strength due to slow dissolution speed.At low concentration,the average mesh wall thickness of the network structure formed by the three drag reducing agents was about 0.1-0.3μm.With the increase of the concentration of drag reducing agents,the mesh shape of the system gradually changed from irregular to polygonal.Some drag reducing agents can form a circular network support structure with high strength and good stability.The mesh size decreased and the mesh wall thickness increased.When the concentration of drag reducing agents increased to 0.05%,the mesh wall thickness can reach 0.3-0.9μm.The strength of network structure had been significantly improved.The aggregate network structure formed by the slick-water drag reducer will have an important impact on the resistance reducing performance of the system.The addition of the resistance reducing agent and the resistance reducing performance of the system did not show a simple linear relationship.Only an appropriate size aggregate network structure formed at a suitable concentration can closely interact with the water molecules in the system,stabilize the solution flow state,reduce the turbulence pulsation,and reduce the energy dissipation in the turbulent flow process,Finally,the effect of high-efficiency resistance reduction was realized.