非常规储层液氮低温致裂理论及研究进展

Theory and Research Progress of Cryogenic Cracking with Liquid Nitrogen in Unconventional Reservoirs

液氮压裂是一种极具前景的无水压裂技术,可为非常规油气水力压裂所面临的耗水量巨大、储层伤害和环境污染等问题提供解决方案。低温致裂岩石是液氮高效改造储层的基础和关键。基于作者前期在液氮压裂方面的研究成果,重点针对液氮低温致裂研究进行归纳总结,系统地阐述了液氮超低温作用下岩石物理及力学特性变化规律,分析了影响液氮低温致裂效果的关键因素及主要机制,从矿物学角度揭示了岩石损伤破裂的微观模式和特征,剖析了液氮对于不同岩性类型、不同原生孔隙结构、不同储层原位状态(高温/饱水)岩石的适用性。本研究旨在帮助读者更加全面、深入了解液氮低温致裂岩石的基本理论及研究进展,为后续液氮压裂技术研究及工程应用提供基础理论指导。

Liquid nitrogen(LN_(2))fracturing is a promising waterless stimulation method,which could provide solutions for issues accompanying hydraulic fracturing in unconventional reservoirs,such as large water consumption,formation damage and environmental risks.Cryogenic cracking is the primary advantage for applying LN_(2) in reservoir stimulation.Based on previous studies of LN_(2) fracturing,this paper puts particular focus on the cryogenic cracking.Physical and mechanical property changes of rocks subjected to LN_(2) cooling are elaborated,and the primary parameters influencing cryogenic cracking performances and corresponding mechanisms are analyzed in detail.Microscopic patterns and characteristics of rock damage are revealed from the perspective of mineralogy.Additionally,we also evaluate the applicability of LN_(2) to rocks with various lithology,various primary pore structures and various in-situ states(high temperature,water saturation).The purpose of this paper is to help readers better understand the theory and research progress of cryogenic cracking with LN_(2) and provide some theoretical guidance for future studies and applications of the LN_(2) fracturing technique.