ارتباط اشباع آب كاهش نيافتني و شاخص كيفيت مخزني در يكي از مخازن كربناته هيدروكربوري جنوب ايران

Relationship between irreducible water saturation and reservoir quality index in a carbonate hydrocarbon reservoirs, Southern Iran

One of the most important parameters in hydrocarbon reservoir evaluation is irreducible water saturation; commonly determined from capillary pressure or relative permeability experiments. Real reservoir rock samples are needed for doing these experiments. Usually such samples are hardly available and their preparation is expensive. In this study, estimation of irreducible water saturation has been done by combining capillary pressure data and hydraulic flow units. In this article the number of hydraulic flow units has been determined based on measured porosity and permeability on the samples of a carbonate reservoir. First by calculating reservoir quality index and pore to matrix ratio, flow zone indicator determined for each sample and then by histogram and sum square errors analyses the number of hydraulic flow units was clarified. By using mercury capillary pressure data for each sample and converting them to reservoir condition, the values of irreducible water saturation for each sample is obtained and relationship between irreducible water saturation and reservoir quality index has been studied in each hydraulic flow units. The results show that there is reasonable match between irreducible water saturation and reservoir quality index, such that the average correlation coefficient between irreducible water saturation and reservoir quality index in different hydraulic units is about 0.95. Therefore it is possible to use presented method to estimate irreducible water saturation when necessary data is not available.