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Accurate Calculation of Hydrocarbon Previous HitSaturationNext Hit Based on Log Data in Complex Carbonate Reservoirs in the Middle East

Tawfiq A. Obeida1*, Faisal Al-Jenaibi2, Sami Rassas1, and Samy Serag El Din1
1ADCO
2ADNOC
*[email protected]

To generate Previous HitsaturationNext Hit functions (capillary pressure drainage curves or J-functions) to initialize complex carbonate Previous HitreservoirNext Hit simulation models always presents challenges to petrophysicists and Previous HitreservoirNext Hit engineers. This is especially the case when Special Core Analysis Laboratory (SCAL) data is neither available, nor rock-property trends such as the porosity-permeability relationship, which are used to assign a Previous HitsaturationNext Hit function in 3-D models. As a start, the proposed method required the initial Previous HitwaterNext Hit-Previous HitsaturationNext Hit Previous HitdistributionNext Hit in the 3-D model. It can be calculated by log-derived J-functions if the permeability Previous HitdistributionNext Hit is available. Otherwise, it can be calculated using a software program that is based on Previous HitwaterNext Hit-Previous HitsaturationNext Hit log data. For each Previous HitreservoirNext Hit rock type (RRT), the capillary pressure calculated from the height function, was plotted versus log-derived Previous HitwaterNext Hit-Previous HitsaturationNext Hit. Depending on the data scatter, ranges of Previous HitwaterNext Hit Previous HitsaturationNext Hit can be determined in order to generate a capillary pressure (Pc) curve for each range. The Pc curves per RRT were based on Previous HitwaterNext Hit-Previous HitsaturationNext Hit ranges regardless of the rock properties trends. To differentiate between such Previous HitsaturationNext Hit functions, a script file was written to discriminate between these regions per RRT. Previous HitSaturationNext Hit numbers were then assigned for each region and these were used to initialize a massive and complex carbonate Previous HitreservoirNext Hit simulation models (Shu’aiba Formation) in the United Arab Emirates. The initial Previous HitwaterNext Hit-Previous HitsaturationNext Hit profile from log data matched the Previous HitwaterNext Hit-Previous HitsaturationNext Hit calculated by the dynamic model in 90% of the wells (more than 100 wells at initial Previous HitwaterNext Hit Previous HitsaturationTop). The difference in original-oil-in-place calculations between the static and dynamic models was less than 2%.

 

AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain