The optimal reservoir configuration for maximum productivity index of gas reservoirs depleted by horizontal wells under Darcy and non-Darcy flow conditions

The outcomes of this study can be summarized in: 1) Productivity index of gas reservoirs in pseudo-steady state is affected by the dominant flow type in the reservoirs: Darcy or non-Darcy flow. 2) Wellbore length, reservoir configuration, and anisotropy affect the productivity index as well as wellbore asymmetricity. 3) Productivity index of Darcy flow is greater than non-Darcy flow. 4) Wellbore horizontal penetration ratio with respect to reservoir length may have significant impact on productivity index as well as reservoir width. The most interesting points in this study are: 1) The maximum productivity index could be reached for reservoir length of (xeD=0.55−0.65) regardless reservoir width. 2) The anisotropy may affect productivity index for short and moderate wellbores, however, it does not have significant effects in long wellbores. 3) Productivity index might be affected by wellbore location with respect to reservoir width and length but not wellbore location in the vertical direction. 4) Pseudo-steady state productivity index can be estimated by the proposed models using reservoir configuration and wellbore length with a full consideration to the formation anisotropy and wellbore asymmetricity.