ABSTRACT
Nuclear Magnetic Resonance (NMR) is one of the primary techniques used in the oil industry for logging operations and in the laboratory environment to study rock formations due to its reliability in offering a reliable estimation of oil well productivity. Two types of well-logging operations exist, Wireline Logging and Logging While Drilling (LWD). Wireline Logging involves NMR measurements taken under static conditions. In contrast, LWD involves measurements taken during the drilling process while the tool is in motion, translating, rotating, and vibrating relative to the formation. To understand the behavior of NMR signals measured under LWD conditions on a laboratory scale, we developed a setup that includes a single-sided magnet, rf probes, and a mechanical system that emulates a relative sinusoidal motion between the sample and the applied magnetic field. Four representative rock samples were selected according to their relaxation times, which were short, intermediate, and long compared to the oscillation period of the LWD simulator: three sandstone, Fontainebleau, Berea Sandstone, and Portland Red, and one carbonate, Indiana Limestone. The results show that even with the modifications observed in the relaxation times distribution, which could lead to misinterpreting the geological formation parameters, the total porosity remains unaffected and independent of the sample motion during the NMR measurements, even under severe conditions and using the standard procedures of the data processing.
ABSTRACT
We report a dataset containing full-scale, 3D images of rock plugs augmented by petrophysical lab characterization data for application in digital rock and capillary network analysis. Specifically, we have acquired microscopically resolved tomography datasets of 18 cylindrical sandstone and carbonate rock samples having lengths of 25.4 mm and diameters of 9.5 mm. Based on the micro-tomography data, we have computed porosity-values for each imaged rock sample. For validating the computed porosity values with a complementary lab method, we have measured porosity for each rock sample by using standard petrophysical characterization techniques. Overall, the tomography-based porosity values agree with the measurement results obtained from the lab, with values ranging from 8% to 30%. In addition, we provide for each rock sample the experimental permeabilities, with values ranging from 0.4 mD to above 5D. This dataset will be essential for establishing, benchmarking, and referencing the relation between porosity and permeability of reservoir rock at pore scale.
ABSTRACT
This article was written in honor of Prof. Bernhard Blümich, who has heavily impacted many areas of Magnetic Resonance and, in particular, low-field and portable NMR with numerous advances, concepts, innovations, and applications of this impressive technology. Many years ago, we decided to research and develop single-sided magnets for the area of petroleum science and engineering to study oil reservoir rocks in the laboratory under well-logging conditions. The global urge to exploit oil reserves requires the analysis of reservoirs, intending to characterize the yields before starting the production. Thus, well-logging tools have been developed to estimate the quality of oil and reservoir productivity. NMR logging is included in these analytical tools, and numerous operations using this kind of device were performed since the early 1950s. To contribute to this vital research area, we show the development of a new benchtop single-sided NMR system, with well-logging tool characteristics, a cylindrical sweet spot with 4 cm of diameter and length, with magnetic field of 47 mT centered at 11 cm from the magnet's surface and a constant gradient of 35.7 G/cm along z. This system was used in self-diffusion, T1-T2, and D-T2 measurements of standard liquids and rock cores, demonstrating its functionality.
