Dissipative particle dynamics (DPD) is modified by introducing attractive force. Attractive interaction of liquid and solid and micro-scale flow in nano throats is simulated to discuss mechanism of boundary layer. It is found that thermal motion affects velocity significantly in molecular scale while pressure gradient is leading function as greater than molecular scale. However, thermal motion cannot change integral moving direction. As throat radius becomes larger, parabola shape of velocity distribution becomes more and more obvious. Boundary layer thickness is affected by pressure gradient, throat radius and fluid viscosity. As pressure gradient increases and fluid viscosity decreases, boundary layer thickness decreases. As throat radius decreases, boundary layer thickness increases first and then decreases. Boundary layer is essential reason of nonlinear flow behavior and thickness of boundary layer increasing makes nonlinear flow behavior more obvious.

For reservoirs with high rock brittleness coefficient and uniform development of natural fractures, three basic modes are developed to characterize fracture network created by volume fracturing in horizontal wells. Flow from reservoir to wellbore is divided to two parts:reservoir flow and network flow. Principle of potential superposition is used to derive reservoir flow equation. Finitedifference method is adopted to establish flow equation within finite conductivity network. Star-Delta transformation is used to tackle interplay of flow between hydraulic and natural fractures. A comprehensive flow model is presented by coupling matrix equations of two flows. It indicates that as stimulated horizontal length is kept constant, effect of quantity of fracture stages and perforation clusters in each stage on production is more significant than that of half-length and flow conductivity of hydraulic fracture, which is, in turn, more dominant than that of density and flow conductivity of natural fractures. Finally, a field example shows that little difference exists between measured and calculated results.

A model to calculate stress sensitivity is established based on theory of accumulation of geology, geomechanics and theory of flow through porous media. Compared with experimental results, the model is accurate and reliable. Distribution range of tight oil reservoir in Daqing Field is narrower than that of Changqing Field. It results in that stress sensitivity of Daqing Field is severer than that of Chaingqing Field. And productivity of Daqing Field is lower than that of Changqing Field. We make a quantitative description on mechanism of stress sensitivity in tight oil reservoirs.