عنوان مقاله [English]
The aim of this article is to represent a new method to determine the cementation exponent in carbonate reservoirs. For this purpose, the matrix density and relevant factor between matrix density and cementation factor was calculated. Then a log was generated that estimates the variation of cementation factor around the borehole. The method was applied on well log and petro-physical data of an oil well in Darkhovin oil field in southwest Iran and the cementation factor log around the borehole was calculated.
There are two approaches for measuring hydrocarbon saturation; well log interpretation and usual developed formulas. Archie’s equation is one of the most fundamental equations for water saturation calculation. Archie’s equation includes three factors: cementation factor, tortuosity and saturation exponent. Archie determined those factors based on lab results in sandstone and provided fixed value for them. Carbonate reservoirs have variety of texture, shape and distribution of pores, therefore mentioned factors, especially cementation are not considered constant. Several methods are presented for calculation of cementation factor continuously. In all of the methods, change in lithology type and converting limestone to dolomite are not considered.
Methodology and Approaches
Cementation factor can be defined as a parameter that has a close relation with density. By calculating the matrix density and relevant factor between matrix density and cementation factor from core’s analysis, a log will be generated that estimates the variation of cementation factor around the borehole. In this research the well logging and petro-physical data of well no.DQ14 have been used in order to calculate cementation factor. This well is located in Darkhovin oil field in southwest of Iran. Available well log data were: calliper, sonic, resistivity, neutron, photoelectric, density and gamma-ray. Also, ten core data were available for these analyses.
Results and Conclusions
The method was applied on an oil borehole and the cementation factor log around the borehole was calculated. The regression of calculated values with the core data is 84.09 percent, that shows this method is useful for calculating the cementation factor in carbonate rocks.