Effects of Partial Completion on Productivity Index

Abstract

A new method for analysing productivity index (PI) on vertical wells is the main objective of this study. Well performance is often measured in terms of the well’s productivity which is dependent on a number of factors such as the reservoir’s configuration, the type of completion, petrophysical and fluid properties, formation damage, etc. The effect of partial completion is the main focus of making the productivity index analysis since almost all vertical wells are partially completed due to the reasons of water coning or gas cap issue, etc. It is also very expensive to fully complete a well especially when the formation thickness is so large. Pressure behaviour solutions for both closed boundary and constant pressure boundary have been obtained, taking into consideration the effect of partial completion. Productivity of a well is usually evaluated on the long time performance behaviour, thus the pseudo-steady state (late time) approach has been employed for calculation of the productivity index. Several key factors have been tested on productivity index such as pseudo skin, shape factors, penetration ratio, reservoir drainage area and etc. The effects of these factors have been analysed on PI. Theoretical data were used in carrying out the analysis with results indicating that, productivity index increases with increasing completion interval and vice versa, whiles pressure drop due to skin as a result of restricted entry to fluid flow increases tremendously with decreasing completion interval. Shape factors of various well positions in bounded reservoirs were computed and compared with results obtained by Dietz, and Babu and Odeh.