Non-Linearity Seepage Productivity Model and Influential Factors' Analysis in Tight Sandstone Gas Reservoir

Abstract

The tight sandstone gas is the most precious unconventional natural gas resource which has massive reserves all over the world. However, poor formation physical properties, extremely lower permeability, and complex pore-throat structure make it difficult to effective displacement in the tight gas formation. As a result, fracturing of horizontal wells is an effective technique for the tight gas. Based on the natural gas non-linearity unsteady seepage theory, the pseudo-pressure pattern and the overlay principle, this paper sets up the fractured horizontal well productivity model in the tight sandstone gas reservoir, which takes fracture interferences into consideration. Combined with the productivity model above, the relation curves between cumulative gas production and different factors have been drawn, and the sensitivity analysis of productivity influential factors has been carried on as well. Research shows that: the best length of horizontal well is 900 m and the corresponding optimal number of fractures is 6, while the optimal half-length of the fracture is 80 m. The length of horizontal well is the most sensitive influential factor to the productivity, while other factors are half-length of the fracture and the fracture conductivity in turn. Seeing from the sensitivity analysis curve, the fractured horizontal well productivity is not sensitive to fracture conductivity in tight gas formation. The study has an important guiding significance to productivity prediction and parameters optimization of fractured horizontal wells in the tight sandstone gas reservoir. Key words: Tight gas; Non-linearity seepage; Productivity prediction; Fractured horizontal well