Carbonate Reservoir Characterization Experimental and Numerical Study of Overburden Pressure, Pore Size Distribution, Capillary Pressure, Porosity and Permeability in Ab-Teymur Oil Field

Carbonate reservoirs contain more than 50% of the world's hydrocarbons and consist of 30% of the world's sedimentary rocks. In carbonate rocks, the processes of sedimentation and diagenesis, particularly dissolution, produce a wide range of pore sizes resulting in a complex pore distribution and pore connectivity. By employing core analysis and advanced methodologies such as NMR measurements, CT scanning images and ultracentrifuge the characterization of reservoir including the effects of overburden pressure, pore size distribution, capillary pressure, pore structural design, porosity, permeability and water saturation in heterogeneous carbonate reservoirs are determined.;The amount of calcium carbonate organic and inorganic, level of salinity, temperature, and pH of water can control the types of carbonate facies. There are different types of pore-size distributions and porosities due to wide variations of carbonate facies. Because of their reactive nature, carbonates go through a more complicated deposition and diagenesis compared to siliciclastic sandstones. Precipitation, diagenesis and dissolution on carbonates can control porosity, permeability, and fluid saturation which are primary characterization parameters of carbonate reservoirs.;In this research, pore size distribution and pore structural design in heterogeneous carbonate reservoirs are studied. There are different compositions and minerals in carbonate rocks, which form a complicated pore system with primary, secondary, and tertiary porosity. Additionally, the dissolution phenomena increase the vuggy, moldic, channel, and cavernous pore structures. These can lead to modified porosity and permeability. The prediction of pore size distribution, pore connectivity and dissolution can clarify issues that are regularly a critical control on reservoir quality.;Recent studies have recognized the significant role of pH behavior in carbonate rocks through precipitation, lithification and diagenesis. It has been shown that different fluid pH levels in the rock result in various dissolution scenarios. Reduction of pH to acidic levels in carbonate reservoirs can increase dissolution. This could also take place in the forms of reaction or ionic processes.;In this research, core analysis is the methodology to characterize reservoir rocks experimentally. Core samples are provided from different oil carbonate formations of Ab-Teymur in Iran. Characterizations of these reservoirs are obtained by conducting different tests on various core samples. This study is carried out by employing different sophisticated techniques such as Low Field NMR, CT scanner and ultracentrifuge.;The result of the mapping of relationships between rock properties including porosity and permeability in this work has shown that the carbonate formations are complicated. Moreover, these characterizations associate with high degree of pore structures including vug, mold, cavernous and fracture and contain distribution of tight matrix in impermeable layers to permeable layers with different capacity storage. Furthermore, the degree of agreement of correlation between porosity, permeability, pore size distribution and thin section analysis are demonstrated.;The carbonate reservoirs pore structural design has been modified by the diagenetic processes specifically compaction, cementation and dissolution phenomena. The obtained result has shown that permeability variation is not a simple function of porosity and it is not easy to predict the values of permeability only from pore architecture or rock capacity storage.;The fundamental of reservoir characterization could be distinguished by understanding the rock properties. In hydrocarbon standard reservoirs, these properties could be determined fast and easy with routine methodology. The heterogeneous carbonate reservoirs characterization cannot be determined with simple ordinary methods. Therefore, it would be necessary to employ more than one advanced technology in the process. Although the results of this research are unique based on modern methodology, the outcome of this thesis work have been shown that complicated carbonate reservoirs still require more efforts and investigations.;Extensive experimental works have been performed with modern technology to produce detailed qualitative and quantities analysis of the results. The new NMR permeability model, as well as pore size distribution, pore structural design and new classification of porosity, permeability, saturation profile and capillary pressure were developed. The outcomes of research can be very beneficial in studies of reservoir quality, capacity, capillary pressure and reservoir recovery. Furthermore, this research carried out analysis in regards to development of technologies to measure the carbonate reservoir characterization.;The principle objective of this study is to perform fundamental research on pore size distribution classification, capillary pressure analysis, reservoir capacity storage model, permeability variation based on permeable-impermeable layers and evaluation of the NMR new permeability model to give a better description of carbonate reservoir characterization and provide insights to increase the producibility and improve oil recovery.