Abstract
Over the time by increasing global demand for source of energy and decreasing hydrocarbon production from reservoirs, recovery methods have become important. The surface area and porosity are central physical characteristics that highly affect the estimation of original oil and gas in place and understanding the mechanisms incorporating in production. The surface area is the internal surface area per unit of pore volume and determines the amount of space in rocks exposed to injectant during injection operation. The occurrence of fractures system in carbonated reservoirs increases the complexity and decreases the homogeneity; hence, it is difficult to determine the correct surface area of reservoir. Therefore, the existence of a local correlation which relates effective porosity to specific surface area is needed and it can help to estimate effective surface area exposed to chemicals during Enhanced Oil Recovery (EOR) process. In this study, the specific surface area in carbonate reservoir rocks was measured by gas adsorption (nitrogen) method and petro-graphical image analysis. In addition, the effective porosity was determined by a gas porosimeter, followed by plotting specific surface area measured by the Brunauer, Emmett and Teller (BET) method versus specific surface area determined from core scan and calibration curve. According to this calibration curve, a new relationship was developed (with R2 = 0.92) that could give BET data for a known data of core scan. The relationship between porosity and specific surface area was analyzed statistically and a relationship with accuracy of R2 = 0.89 was proposed. This relationship was compared with other models such as Pirson and Kotyakhov. Results show that the latter one is more accurate than other models and is more compatible with experimental data (with R2 = 0.84). The results obtained from the experiment indicate that the specific surface area shows an initial decrease upon increasing of porosity up to 0.2. After this decrease, the curve indicates an increasing trend. Moreover, a novel relationship was developed depending on the specific surface area, porosity and permeability and some constant parameters for carbonate rocks (with R2 = 0.95).
Highlights
Because of high rate of energy consumption and challenges and high expenses of petroleum production, researchers are continually seeking effective methods to enhance its Department of Petroleum Engineering, Abadan Faculty of Petroleum Engineering, Petroleum University of Technology (PUT), Abadan, IranDiscipline of Chemical Engineering, School of Engineering, University of KwaZulu-Natal, Howard College Campus, King George V Avenue, Durban 4041, South Africa recovery (Evbuomwan 2009)
The results from experimental data measured by core scan DMT3 device and the BET test indicate that as porosity increases from 0 to 0.2, the specific surface area decreases and reaches a minimum and again the trend becomes increasing
A calibration curve was developed based on core scan DMT3 and BET tests with R2 = 0.92
Summary
Discipline of Chemical Engineering, School of Engineering, University of KwaZulu-Natal, Howard College Campus, King George V Avenue, Durban 4041, South Africa recovery (Evbuomwan 2009). Through the producing life of a reservoir, recovery is summarized in three phases: primary, secondary and tertiary. The predominant mechanism is natural drive energy of the reservoir. In this phase, the injection of any external fluids or heat as a driving energy is not necessary. An external fluid, such as water and/or gas, is injected for purpose of pressure maintenance and volumetric sweep of reservoir fluid. Tertiary recovery is described by the injection of special fluids such as chemicals, miscible gases and/or the injection of thermal energy (Sheng 2010)
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