Transient pressure analysis of horizontal well in low permeability oil reservoir

Low permeability reservoirs occupy a large proportion in the remaining reserves all over the world. So, it is urgent to research the seepage law of fluid flow in low permeability reservoirs intensively. Fluid flow in these reservoirs deviates from the classical Darcy law and conforms to the one of nonlinear seepage instead. Horizontal well is one of the key technologies to exploit the low permeability reservoir. According to this characteristic, this paper presents a mathematical model for the analysis of pressure behaviour of a horizontal well in low permeability reservoirs, which takes into consideration of threshold pressure gradient (TPG). The solution of the non-homogeneous Bessel equation is obtained through Laplace and Fourier cosine transform and the Green Function methods. Integrating along the horizontal well and using Stehfest numerical inversion method, the dimensionless pressure response and type curves of horizontal well with the consideration of TPG are obtained, and the sensitivities of related parameters are discussed. The results of this paper have significance in the well test analysis, production performance prediction and production data analysis of horizontal well in low permeability reservoirs.