One of the fundamental equations in calculate the saturation of fluid in hydrocarbon reservoirs is the Archie’s equation. In addition to the parameters measured by well logging such as porosity and resistivity, there are others parameters that called Archie’s coefficients. Archie provides constant values for this coefficient base on experimental core’s data, accordance with saturation formula in sandstone. In carbonate reservoirs nevertheless the sandstone reservoirs, high heterogeneity, variety in lithology and texture, shape and distribution of pores, due to this coefficient is not constant. So, variation of tortuosity as a coefficient that depends on the way correlation between pores, is high and considering a constant value due to error in calculation of fluid saturation. In this study, with the stoneley waves measured from DSI tools and required calculation, the value of tortuosity coefficient calculated continuously in well no.10 Darkhovin field. The regression of calculated values with the core data is 83.16 percent, that showed this method is useable for calculation the tortuosity.
Mineral exploration is done by different methods. Geophysical and geochemical studies are two powerful tools in this field. In integrated studies, the results of each study are used to determine the location of the drilling boreholes. The purpose of this study is to use field geophysics to calculate the depth of mineral reserve. The study area is located 38 km from Zarand city called Jalalabad iron mine. In this study, gravimetric data were measured and mineral depth was calculated using the Euler method. 1314 readings have been performed in this area. The rocks of the region include volcanic and sedimentary. The source of the mineralization in the area is hydrothermal processes. After gravity measuring in the region, the data were corrected, then various methods such as anomalous map remaining in levels one and two, upward expansion, first and second-degree vertical derivatives, analytical method, and analytical signal were drawn, and finally, the depth of the deposit was estimated by Euler method. As a result, the depth of the mineral deposit was calculated to be between 20 and 30 meters on average.
Permeability is one of the petrophysical properties of oil and gas reservoirs and is defined as the ability of rock to transmit fluids through the porous media. After exploration of any reservoir, permeability information is necessary to optimize the well completion method, oil and gas production and field development. Permeability is determined by both direct and indirect methods. Direct methods are core analysis, well testing, and modular dynamic tester (MDT) and the indirect method is using well logging data such as nuclear magnetic resonance (NMR) and porosity. Determination of permeability from the Stoneley slowness is one of the indirect and continuous methods in the whole well-bore and has been chosen as the goal of this study. The result of this correlation has been plotted against other well logging data and there is a very good match between this result and other petrophysical properties. Due to the complex nature of permeability in carbonate reservoirs, most of the time there is not a good match between this parameter and other petrophysical properties. This study has been conducted on the data of a single well and correlation has been determined. The results show that in calculation of permeability from Stoneley waves, the effective parameters are porosity, lithology, Stoneley slowness and accuracy of the MDT tool. For more precise correlation in a reservoir or a specific geological area, more data from other wells or reservoirs are necessary.
There are two approaches for measuring hydrocarbon saturation: well log interpretation and usually developed formulas. Archie’s equation is one of the most fundamental equations used for water saturation calculation. Archie’s equation includes three factors: cementation factor, tortuosity and saturation exponent. Archie determines these factors based on lab results in sandstone and provides fixed value for them. Carbonate reservoirs have a variety of textures, shapes and distribution of pores; therefore, the mentioned factors, especially cementation are not considered constant. In this study, the relationship between cementation factor and density log was examined because cementation factor is defined as a parameter that has a close relationship with density. By calculating the matrix density and accordance factor between the matrix density and cementation factor from core’s analysis, a log will be generated that can estimate the variation of cementation factor around the borehole. This method is useable for calculating the cementation factor in carbonate rocks. Keywords: Cementation factor, carbonate reservoir, density, new method, exponents.
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