Impact of water saturation model on the reservoir estimation ; a case study on dorado and Barracuda Wells in Mannar Basin, Sri Lanka

Abstract

Fluid carrying properties of rocks (permeability) and the interaction between fluid and rock that influence the flow of the fluids(porosity and saturation) are required to evaluate the maximum recovery and producibility of any petroleum reservoir. Determination of Water Saturation (Sw) is a critical and complex petro physical calculation, as there are number of independent methods used to calculate the same. The objective of this research was to analyse the impact of water saturation model on the reservoir estimation, using the well-log data of Dorado-1 well and Barracuda well in Mannar Basin, Sri Lanka. First, quick look analysis was done with the welllog data. Then the saturation of water in pay zones were calculated using five water saturation calculation approaches namely Archie’s equation, Equivalent Model, Indonesia model, Dual Water Model and Juhasz model. For both wells the highest water saturation values were found with Dual Water Model and Juhanz model, 0.89 for the Dorado well and 0.83 for Barracuda well. While Equivalent model gave the lowest saturation value, 0.46, for Dorado well and the Archie’s model estimated the lowest value of 0.60 for Barracuda well. Except the results of Dual Water Model and Juhasz model, all other models estimated different values for water saturation. This leads to a considerable difference in reservoir estimation. Therefore, for a reservoir it is important to establish the most suitable water saturation calculation method to estimate the volume of reservoir correctly.