Production Research Of Partially Penetrated Directional Wells

In recent years, with the reservoir geological conditions tending to be more complicated, directional wells and partially perforated wells are more and more widely applied. Directional wells are usually applied in offshore oil and gas reservoirs. In gas cap reservoirs or reservoirs with bottom water, partially perforated wells must be used to avoid premature breakthrough of gas and water. So perforated wells, directional wells or partially perforated directional wells have important practical significance.In this paper, we study the pressure and production of several different boundary conditions of normal vertical wells, partially perforated vertical wells, directional wells and partially perforated directional wells respectively. Pressure solutions of various mathematical models are based on Laplace transform, Fourier transform, point source function method, mirror inversion method, the stress superposition principle and numerical inversion methods of Stephen and so on.Firstly, we solve dynamic solutions of the wellbore pressure of completely perforated vertical wells under three kinds of boundary conditions. And then we divide fluid flow stages of every model and analyze the causes of each flow period. The existence of closed boundaries outside the reservoir causes the pseudo-steady flow. In addition, for a model with closed boundaries, the distance between the well and boundaries will affect the occurrence time of the pseudo-steady flow in late time.Then this paper solves dynamic of wellbore pressure and production of partially perforated vertical wells under three different boundary conditions. We find that partially perforated vertical wells are different from fully perforated vertical wells in the flow patterns because of the spherical flow. The anisotropy factor of reservoir and the penetrating degree of vertical wells are two important factors which affect pressure dynamic and production dynamic. The bigger the anisotropy factor, the greater the occurrence time of midterm spherical flow and radial flow will be delayed, besides, the production will decrease. The greater the perforating degree of perforated vertical wells, the longer the duration time of early radial flow will be, but the shorter the duration time of the medium-term spherical flow will be. Until the well becomes fully perforated well, the spherical flow will disappear. In contrast, the production will increase with the increase of the penetrating degree and the decline speed will speed up in late time too.The productivity of directional wells is mainly affected by reservoir thickness, the anisotropy factor and the angle of well. The study find that when other conditions are certain, the productivity increases with the increase of the thickness of reservoir, decreases with the increase of the anisotropy factor and increases with the increase of the well angle. We add pseudo skin factor to the solution of partially perforated vertical wells and find that the productivity of partially perforated directional wells increases with the increase of the angle of directional well, but decreases with the increase of the anisotropy factor.A series of research shows that the productivity of partially perforated directional wells is mainly affected by the perforating degree of well, the angle of well and the anisotropy factor of the reservoir. The greater the perforating degree is, the greater the production will be. The bigger the angle is, the greater the production will be. But the bigger the anisotropy factor is, the lower the production will be.