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.

An unsteady model of fractured horizontal wellbore coupling with a box-shaped reservoir is constructed with consideration of anisotropy in a low permeability reservoir. Solution of the model is shown. Pressure drops of friction and acceleration are considered under different types of constraints. Flow condition in fractured horizontal well is divided into early transient period and pseudo-steady period. In transient period, the output from each fracture differs little, and total production rate increases linearly with fracture number. In pseudo-steady phase, production rate of fractures at the toe and heel is higher than that in the middle. Fractures in symmetrical position have different yield due to frictional and accelerational pressure drops. Pressure loss along the wellbore results in decrease of production in horizontal well and non-uniform distribution of pressure in wellbore. Under constant flow rate followed by constant bottom-hole pressure constraints, production plateau stays longer with increase of fracture number.