低渗透油气储层裂缝-孔隙型双重网络介质多相渗流细观机理研究

Since oil and gas exploitation will potentially focus on the low permeability fractured reservoirs in the recent future in China, the improvement and development of the performance and recovery yield are one of the substantial research topics widely used in many fields such as geology of petroleum and gas. Fractures and pores of Underground reservoir are fractals that exhibit complex flow and transport properties and capillary effects. This project would combine theoretical and experimental methods, and characterize fracture- and pore- networks based on fractal technology. This project firstly studies the multiphase fluids flow in multiscale pore network of porous rock with the compressibility and capillarity are considered. Secondly, develops the funtion for fluids transfer between fracture network and pore network of matrix, in which the fluids can be transfer between the maxtrix and fracutre. Thirdly, under the spontaneous and forced conditions, analyzes the Darcy and non-Darcy mesoscopic mechanism of the flow and transport in fracture-pore network of low permeability fractured reservoirs with consideration of the effect of capillarity, microstructure of pores and its compressibility. Lastly, the study will quantify the multiphase flow in fractured porous medium as a function of the flow characteristics and related influence factors, and established a systematic mathematical model to characterize the flow and transfer properties in complex fractured oil and gas reserovirs with low permeability, and the method for upscaling the mesoscopic multiphase seepage to oil recovery model of field scale, research also help to reveal the influcnce mechanism of complex reservoir microsturutre on enhance oil revovery. It is anticipated that the results achieved from this study will contribute to a complete understanding the mechanisms of multiphase flow and transport in the low permeability fractured porous media and promote the development of oil and gas, mechanics of flow through porous media, and offer a theoretical basis to improve the recovery of low permeability reservoirs.

裂缝性低渗透油气储层是我国未来油气勘探开发的主要场所，提高其开发效果和采收率是石油天然气开发及地质学等领域的热点课题之一。储层裂缝、孔隙结构复杂，具有分形特征和复杂的毛细效应，细观流动与传输规律复杂。本课题将理论与实验相结合，采用分形技术表征裂缝和孔隙网络，研究考虑压缩性和毛细效应的岩心孔隙网络中流体多相流动，发展裂缝与孔隙网络耦合形成的双重流体流动网络间的流体交换函数，分析驱替条件下裂缝性多孔介质达西和非达西细观渗流机理，建立岩心细观多相渗流方程与裂缝性低渗透储层采收率模型，进而量化裂缝性多孔介质中流动特性与各影响因素的函数关系，建立一套表征裂缝性低渗透油气储层中复杂流动规律的系统性数学模型，揭示储层复杂微结构影响采收率关键机理，最终将细观多相渗流模型应用于油田开采数据分析。研究结果将有助于推动油气田开发及渗流力学学科的发展，为提高油藏采收率提供理论支持。

致密和裂缝性油气储层及地热储层中的多相复杂流动及传热规律是我国资源勘查开发领域热点和基础问题之一。岩石微观孔隙结构非常复杂、具有极强的微观非均质性特征，从实验室测量得到的岩石输运参数受到各种结构因素影响。岩石宏观传输特性从根本上取决于其微观结构特征，造成流体在其内部流动异常复杂，单一的孔隙模型不能很好的模拟多种不同岩石类型的输运特性，造成预测模型的精度不高。因此，如何对多孔介质输运性质进行参数表征以及不同尺度/岩性/饱和状态的实验数据拟合及系数关联，是定量预测与评价储层岩石物理特性的重要内容。本项目提出了岩石分形维数与孔径分布的关系表达式；综合使用分形维数、缺项、进相等参数表征低渗储层岩石微观结构的差异及研究该类差异对渗透率的影响；采用分形技术表征裂缝网络，得到了裂缝网络演化过程中分形维数与时间、开度、润湿度和裂缝孔隙度之间的关系；推导了一种基于自发渗吸的KC常数分形模型，数值模拟研究了不同边界条件下的渗吸驱替规律；提出了关于孔隙岩石渗透率与地层因子的分形解析表达式，建立了关于孔隙岩石电传导与水力传导特性的关系；提出了考虑粘性流和扩散输运线性叠加的体相气体输运模型，并建立了页岩气输运的三维分形模型；基于纳米颗粒及其聚集分形特性，系统分析了纳米流体热传导和纳米颗粒聚集应力特性的分形研究进展；考虑固体颗粒服从分形特征，建立了不同液体饱和度下多孔介质等效热导率分形模型；总结了多尺度孔隙结构对电流的流动过程的影响及饱和多孔介质的电传导特性理论模型。项目以理论分析为主，结合实验验证，并辅以数值模拟分析，系统地开展了低渗透储层多尺度裂缝-孔隙型双重网络介质的细观输运特性研究，建立了一套系统描述裂缝性低渗透储层中流体复杂输运规律的多参数数学模型，为低渗透油藏的高效开发及优化决策提供理论基础和技术支撑。