Journal issues: 2/2013
New cementation factor correlation in carbonate parts of south-west iranian oil fields
Petrophysical parameters such as porosity, water and oil saturations, formation resistivity factor, etc. describe the storage capability of the porous media or the capacity of rocks to hold fluids. The modified Archie’s equation also called the saturation equation is used to determine the water saturation. Archie’s parameters, m, n and a, are sometimes assumed constant to simplify petrophysical measurements. But these parameters are not constant, particularly in heterogeneous reservoirs. Inaccurate estimates of these parameters can cause significant errors in the calculation of water saturation when using and lead to discrepancies between log interpretation and production test results. There are many factors affect cementation factor, m such as porosity, pore throat size, type of rock grains, type and distribution of clay content, degree of cementation and overburden pressure. In the present paper results of electrical resistivity experiments are used to derive a new cementation factor correlation that can be applied to carbonate parts of Asmari and Sarvak formations located in south-west Iran. In Iran, the cementation factor is traditionally measured by Shell formula or is taken equal to two to avoid difficulty. In the new formula, m increases with increasing porosity but in the Shell formula, m decreases with increasing porosity especially in the low porosity range (<10%), in disagreement with the current paper results. Also it is demonstrated that it is not possible to introduce constant m values or separate cementation factor correlations versus porosity for different petrofacies and rock types. Petrophysical evaluations are done to quantify hydrocarbon resources in formations under study. Then the water saturation is calculated with different calculation methods of m. The calculated water saturations compared with measured water saturations of preserved cores. Finally appropriate proposals are presented for the specified reservoirs.
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Archie’s equation; cementation factor; formation resistivity factor; water saturation; водонасыщенность; коэффициент сопротивления пласта; коэффициент цементации; уравнение Арчи References to this article (GOST) Saeed Rafiee, Abdolnabi Hashemi, Mohammad Shahi New cementation factor correlation in carbonate parts of south-west iranian oil fields // Electronic scientific journal "Oil and Gas Business". 2013. №2. P.227-253. URL: http://ogbus.ru/eng/authors/RafieeS/RafieeS_1.pdf