Easy technique for calculating productivity index of horizontal wells

In recent years, horizontal well technology have evolved as the more favorable option in the state of Kuwait over the conventional vertical and deviated wells. Several models have been published in the literature to estimate the productivity index of horizontal wells. Generally, all of these models require two factors which are the shape and pseudo-skin factors. Also, most of these models require parameters that are not always easy to determine. This study presents easy and quick technique for calculating the productivity index of a horizontal well. The new technique has been established based on the instantaneous source solutions for the pressure response of a horizontal well. The pseudo-steady state flow is expected to develop because the horizontal well is assumed to be acting in finite reservoirs. Two parameters were derived and their influences on the productivity index were investigated. The first one is the pseudo-skin factor due to asymmetry of a horizontal well. The second one is the shape factor group. The study emphasizes that the productivity index for horizontal wells are strongly affected by the two parameters: the shape factor group and the pseudo-skin factor. Shape factor group is mainly affected by the drainage area configuration while pseudo-skin factor is mainly affected by vertical penetration. The study confirms that the productivity index is affected by the penetration ratio in the horizontal plane and reservoir geometry. In addition, square-shaped reservoir produces at maximum productivity index while channel-shaped reservoir produces at minimum productivity index. The study finds that wellbore eccentricity (wellbore location in the horizontal plane) does not affect the pseudo-skin factor and vertical penetration ratio does not affect the shape factor group. The results obtained from the new technique have been compared with the results from Babu & Odeh model and Economides model. Numerical examples will be included in the paper.