The Study Of Seepage Flow Law On Horizontal Wells Developing In Low Permeability Reservoir

During the Oil fields development of our country, the low-permeability reservoirs account for more than half of the proved reserves, so the development of low-permeability oil fields will be of great potentiality. The horizontal wells technology which develops speedily in recent years is the one of the more effective measures in low-permeability reservoirs. Because of inherent features of low-permeability reservoirs and complexity of internal flow in horizontal wells, how to combine them to study the seepage flow law on development of horizontal wells in low-permeability reservoir is very significant.On the basis of relevant theory of horizontal well, the article describes the analysis of the seepage characteristics in horizontal wellbore and the effect of wellbore pressure drop on dynamics of production.Several models which are used for calculating single-phase flow pressure drop in horizontal wellbore are summed up in it. Moreover a case by su method is giving and the sensitive factors are analyzed. The results show that the total pressure drop increases with the increase of length of horizontal segment, perforation density and single-hole flow rate, but decreases with the increase of hole diameter.After considering threshold pressure gradient, pressure drop losses in horizontal wellbore and the impact of reservoir deformation, the mathematical model which takes the coupling of low-permeability reservoir seepage and horizontal wellbore flow into account is built. The impacts of threshold pressure gradient, pressure drop losses and reservoir deformation on seepage law is analyzed in this paper.The results show that the wellbore losses of horizontal wells has little effect on seepage flow law. But threshold pressure gradient has a great influence. The impact of reservoir deformation on development of horizontal wells in low-permeability reservoirs is great, but not larger than threshold pressure gradient. At last the recovery ratio of horizontal well is higher when length is longer. But increasing velocity decreases from some value. The results in the paper are meaningful to horizontal wells applied in low-permeability oil fields.