Horizontal wells which are characterized by large drainage area, small pressure drawdown and high production rate are more influenced by reservoir heterogeneity and wellbore pressure loss than vertical wells. These factors may lead to unequilibrium development and premature water breakthrough, resulting in shortened production period, reduced production and ultimate recovery. Perforated completion is a widely used completion technology of horizontal wells. As the only flow channel between the formation and the wellbore, perforation plays an important role on the inflow performance. This paper aims to develop a perforation optimization method for regulating production profile of horizontal wells in heterogeneous reservoirs.
Based on an improved evaluation approach of permeability heterogeneity, a reservoir/wellore coupling model of perforated horizontal wells in heterogeneous, anisotropic parallelepiped reservoirs is presented, and hence a perforation density optimization method aiming at regulating production profile is proposed. The example optimization shows that, the lower perforation density has a wider pressure regulating range. With the increase of perforation length, both the converged pressure drop and pressure regulating range decrease. To obtain an ideal production profile, the perforation density in low-permeability region should be higher than that in high-permeability region. The stronger the near-well permeability variability, the greater the density range and the proportion of low density are. The smaller the density, the greater the impact of rounding error is, and hence the less satisfactory the regulating effect is. This study provides a theoretical basis for the perforated completion design of horizontal wells in heterogeneous, anisotropic reservoirs.