Accurate estimation of the reservoir parameters is a basic problem in reservoir studies and reservoir scheduling. So consideration of the parameters which would affect the reservoir parameters is too much important for such estimation. In the present paper, several tools such as petrophysics evaluation stages, ptrophysical logs, saturation equations and corresponding parameters were used for determination of reservoirs parameters. One of the most prominent and effective parameters is the group of Archi coefficients (m, n and a). These coefficients play an important role in calculation of reservoir values. Any error made in the calculation of these parameters, can change the reservoir volume to an unacceptable value. Within the above mentioned group, the cementation exponent (m) acts as an essential value which under affect porosity, Saturation and rock types determination. In the present study an effort is made to investigate the effects of this parameter on results of the petrophysics evaluation carried out in one of the fields of the Sarvak formation. To do so, first using several tools, the cementation exponents were estimated and then the variation trends of the reservoir parameters, which were posed by the m values were studied. Finally the best tool which gave the most convenient values for m was recommended for the Sarvak formation in particular studied field.
The main goal of the present study is to determine two important parameters of the Sarvak formation including: porosity and water saturation. Here an effort is made to execute a sensitivity analysis considering the Archi parameters which are known as some important parameters in evaluation of the characteristics of the above mentioned reservoir. To do so, different tools such as core analysis results, governing equations, default parameters and mathematical methods have been used. Archi parameters including: a, m and n are usually gained through the core analysis [1], otherwise the default values are used in this manner. Such parameters vary for different kind of rocks. Following is the Archi parameters for the Carbonates and sandstones: For the carbonates the a, n and m are equal to 1, 2 and 2 respectively and for the sandstones these values change to 0.62, 2 and 2.15.[4] Cementation factor (m) is one of the factors involved in the calculation of the water saturation and as a result the in evaluation of the initial Hydrocarbon in place. Various methods are created for the computation of the m value and using it in the evaluation of the hydrocarbon reservoirs. Some of these methods get use of the default values. The bases of such values are different equations such as: Archi, Homble, Shell and etc. using the default values which means the constant value for parameter m in each case, gives a proportional distribution of the possible error over the entire reservoir.
