Abstract

Knowing the production contribution from individual zones in a multi-layer environment is very critical in optimizing initial completions and subsequent workovers. The old trial and error method to determine the maximum well productivity is very inefficient due to unnecessary repetitions in workovers resulting in higher operating costs.

The possible maximum production rate of each layer can be estimated by calculating its productivity index and applying the maximum allowable pressure drawdown. Data to calculate the productivity index for each layer is not always available. Production logging (PLT) or individual zone production testing (IZT), the source of data, is not run in every well. These common problems could be addressed by instituting a production zone allocation system.

This paper reports a practical approach to estimate absolute horizontal permeability and the specific productivity index (SPI) by correlating to density porosity (Φ_d)and Volume Shale Gamma Ray Index (Vsh_GR) for Minas Sihapas formations. The Φ_d and Vsh_GR are calculated from open hole log data, which is usually available. The correlation is principally generated by using the permeability - density porosity transform, relative permeability curve and Darcy's law for radial flow in porous media. The calculated SPI is a fair match with actual field data obtained from PLT and IZT. In some conditions the calculated SPI is under estimated compared to actual data. This slight disagreement will also be reviewed in this paper. The method to generate this practical correlation can also be applied to data from other fields.