表面活性剂对煤层气压裂伤害研究

Fracturing Damage of Coal Bed Methane Caused by Surfactants

为评价压裂液中表面活性剂对煤层气压裂过程的影响,利用煤岩样品针对阳离子、非离子、阴离子表面活性剂和表面活性剂复配体系,开展膨胀性、润湿性、吸附性能、表面张力、煤岩伤害和煤层气吸附解吸附物理模拟实验。将不同表面活性剂和复配体系的煤岩膨胀高度、接触角、煤粉中吸附形态和吸附量、措施前后表面张力和煤岩渗透率、吸附和解吸附曲线进行对比分析,进而优选表面活性剂体系。研究结果表明:水和表面活性剂溶液对所选煤岩膨胀性影响不大;阳离子可以增加憎水性,非离子保持煤岩水润湿性,阴离子会增加煤岩水润性;非离子表面活性剂有利于扩大煤岩孔隙进而提高煤层气的解吸附作用;双子表面活性剂(GM)为点状吸附,烷基酚聚氧乙烯醚(OP)为平铺吸附,十八烷基三甲基氯化铵(1831)为连体状吸附;双子-烷基酚聚氧乙烯醚(GMOP-4)复配体系措施前后表面张力较低,大幅度降低了GM的吸附量且对煤层气解吸附过程具有促进作用;GMOP-4复配体系实现了阳离子表面活性剂在煤层气压裂措施中低成本、高性能的应用。

The coal expansibility, wettability, adsorption, surface tension, damage, adsorption and desorption experiments of cationic surfactant, nonionic surfactant and anionic surfactant were performed to investigate the effect of surfactants on hydraulic fracturing in coal bed methane （CBM） reservoir. The expansion height, contact angle, adsorption forms and absorbance, the surface tension and permeability of coal samples before and after damage, adsorption and desorption of different surfactants and compounded systems were compared and analyzed to identify the optimal system. The investigation shows that the surfactants and water have little effect on coal expansibility. The cationic surfactant increases the coal sample＇s hydrophobicity, the nonionic surfactant maintains the coal wettability, and the anionic surfactant increases the coal hydrophilia. The nonionic surfactant enlarges coal porosity and accelerates coal gas desorption. The GM is dot adsorption, OP is tile adsorption, and 1831 is conjoined structure adsorption. The GMOP-4 compounded system with low surface tension significantly decreases the GM adsorption volume and accelerates coal gas desorption. The GMOP-4 compounded system realizes the low-cost and high-performance application of cationic surfactants in CBM hydraulic fracturing.