An Investigation of Using Different Saturation Height Functions in an Iranian Oil Reservoir

Abstract

An important application of the concept of capillary pressures pertains to the fluid distribution in a reservoir prior to its exploitation. The capillary pressure-saturation data can be converted into height-saturation data by using the capillary pressure equation and solving for the height (h) above the free water level. Estimation of the water saturation greatly impacts oil-in-place calculations. Saturation-height function is used to predict the saturation in the reservoir for a given height above the free water level. The authors investigate performance of eight saturation-height methods (i.e., Leverett, Cap-Log, Modified Cap-Log, Johnson, Cuddy, Modified Cuddy, Skelt-Harrison, and Sodena methods) employed in the oil industry. They collected measured capillary pressure data and core properties from a well in one of the Southern Iranian reservoirs. The authors review advantages and disadvantages of each method while comparing the output of each method with saturation obtained from the log data. The results indicate that the Skelt-Harrison and Leverett methods, with coefficients independent of core properties, would be the best and worst option, respectively.

Keywords:

• capillary pressure
• Iranian oil reservoir
• saturation height function
• water saturation