含纳米尺度孔隙的致密油储层和含水致密气储层中，流体流动呈现显著的低速非线性渗流特征，存在启动压力梯度现象。前期研究表明该特征对致密油气藏开发具有较大影响，但尚未明确低速非线性渗流的产生机理。本项目将围绕含纳米尺度孔隙致密油气储层低速非线性渗流机理这一亟待解决的科学问题，拟采用分子动力学、计算物理化学、流体力学、分形几何学等多学科研究手段，针对纳米尺度空间单相油流动，构建液固分子动力学模拟方法，阐明纳米尺度孔道单相流体正负滑移特征，结合分形表征模型，建立考虑滑移特征的单相油低速非线性渗流模型，搞清致密油流动存在启动压力梯度的微观机理；针对纳米尺度空间气水两相流动，构建气液固分子动力学模拟方法，明确气液界面附加阻力特征，建立考虑壁面特征和相界面效应的气水相对渗透率模型，揭示纳米尺度孔隙气水两相流体低速非线性渗流规律。该研究成果有助于完善渗流理论体系，为非常规储层开发提供理论基础，具有重要意义。

The fluid flow in tight oil reservoirs and water-bearing tight gas reservoirs with nanoscale pores presents remarkable low-velocity nonlinear seepage characteristic, namely there exists threshold pressure gradient (TPG). Previous studies have shown that the existence of TPG has a great impact on the development of tight reservoirs, but the mechanism about why TPG exists has not been figured out. This project will focus on the scientific problem about mechanism of nonlinear flow characteristics in tight reservoirs with nanopores using methods relating different disciplines like molecular dynamics, computational physics and chemistry, fluid mechanics and fractal geometry. For the single-phase oil flow in nanoscale pore, a liquid-solid molecular dynamics simulation method was constructed to elucidate the characteristics of positive and negative slip near the wall. Furthermore, combined with fractal characterization model, a low-velocity nonlinear flow model for single-phase oil considering slip effects was established. The mechanism about why TPG exists in the tight oil flow was clarified. For the gas-water two-phase flow in nanoscale pore, a gas-liquid-solid molecular dynamics simulation method was constructed to elucidate the characteristic of additional resistance in the gas-liquid interface. Furthermore, considering the solid-liquid and gas-liquid interfacial effects, the relative permeability model of gas-water two-phase flow was established. Then the low-velocity nonlinear flow characteristic of nanoscale gas-water two-phase flow was figured out. The research results can be helpful to enrich seepage theory and provide theoretical basis for the development of unconventional reservoirs.