Browsing by Author "Chen, Zeliang"
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Item Core Analysis and Core-Log Integration for Evaluation of Unconventional Formations(2019-08-09) Chen, Zeliang; Hirasaki, George JUnconventional resources are of great importance in the global energy supply. This thesis develops new techniques and presents fundamental research serving unconventional formations evaluation for the petroleum industry. First, hydrocarbon composition is a critical input to formation evaluation. In this thesis, a new technique using laboratory Nuclear Magnetic Resonance (NMR) core-analysis integrated with downhole NMR logging is developed to estimate the hydrocarbon composition in an organic-rich chalk prospect. More specifically, the contrasts in T2 and T1/T2 distributions between fluids are used for fluid typing. Meanwhile, another technique based on the NMR laboratory-measured restricted diffusion of light hydrocarbons is proposed to estimate the mean pore size, heterogeneity length scale, and tortuosity of the hydrocarbon-filled porosity. Second, it has been commonly observed that in organic-rich shale, the saturating hydrocarbons have higher NMR T1/T2 ratio than the saturating water. However, the origin of the high T1/T2 ratio was not clearly understood until now. In this thesis, the organic matter (i.e., kerogen) in the organic-rich shale is isolated for investigation. It is confirmed that the saturating heptane in kerogen has higher T1/T2 ratio than water in kerogen and clays, which validates the fluid typing technique providing the wettability. This thesis also proves that the high T1/T2 ratio originates from dissolved heptane in kerogen and/or bitumen, where the dominant relaxation mechanism can be the 1H-1H dipole-dipole interaction, as a result of nanopore confinement. Last but not least, permeability is an indicator of the producibility of reservoirs, and thereby a critical petrophysical property during formation evaluation. The existing ultralow-permeability measurement approaches for unconventional formations, including both steady-state and unsteady-state approaches, confronting various challenges. In this thesis, a novel unsteady-state method is proposed to determine the permeability by history matching, which consists of 1D transient-pressure experiments and numerical simulation incorporating real-gas pseudo pressure and table lookup. This novel method helps to improve the experimental efficiency, simplify the set-ups, reduce the interpretation complexity, and alleviate the pressure-limit constraint. These new technologies and fundamental understandings could in principle be used to improve the evaluation of unconventional formations.Item Determination of fluid-phase-specific petrophysical properties of geological core for oil, water and gas phases(2024-03-05) Vinegar, Eva; Singer, Philip M.; Hirasaki, George J.; Chen, Zeliang; Wang, Xinglin; Vinegar, Harold J.; Rice University; Vinegar Technologies LLC; United States Patent and Trademark OfficeThe following invention is used for determining the relative permeability of a fluid in a rock for three different phases: water, oil, and gas, in both conventional and unconventional formations. The permeability of a phase describes how much it can flow in porous media given a pressure gradient and is useful in evaluating reservoir quality and productivity. The following invention is a method to determine the three-phase relative permeabilities in both conventional and unconventional formations using NMR restricted diffusion measurements on core with NMR-active nuclei, combined with centrifugation of the core. In addition, the tortuosity, pore size (surface-to-volume ratio), fluid-filled porosity, and permeability is determined for each of the three phases in a rock.Item Method for determining the composition of natural gas liquids, mean pore-size and tortuosity in a subsurface formation using NMR(2021-08-24) Vinegar, Harold J.; Singer, Philip M.; Hirasaki, George J.; Chen, Zeliang; Wang, Xinglin; Rice University; Vinegar Technologies LLC; United States Patent and Trademark OfficeNew methods for determining the volumetric composition and saturation of methane and NGLs (natural gas liquids: ethane, propane, butane, and pentane) in a petroleum reservoir combining NMR (nuclear magnetic resonance) logging and NMR core analysis and for determining the mean pore-size and tortuosity of the light hydrocarbon-filled porosity in a petroleum reservoir using NMR core analysis.Item Method of estimating permeability using NMR diffusion measurements(2024-03-19) Vinegar, Harold J.; Singer, Philip M.; Hirasaki, George J.; Chen, Zeliang; Wang, Xinglin; Vinegar, Eva; Rice University; Vinegar Technologies LLC; United States Patent and Trademark OfficeThis invention is useful for determining the permeability of a geological formation using 1H NMR diffusion measurements acquired in the laboratory and using downhole 1H NMR well logging. The current technology for obtaining formation permeability downhole using NMR is not adequate for low-permeability, unconventional source rock formations with high organic content. This new method uses laboratory 1H NMR diffusion measurements for creating continuous downhole well logs of the mobile-hydrocarbon permeability of the hydrocarbon-filled pore space of downhole geological formations.Item NMR Characterization of Fluids in Unconventional Formations(2018-07-12) Chen, Zeliang; Hirasaki, George J.; Chapman, Walter G.This thesis presents a fundamental research on unconventional formations where it has been empirically observed that the saturating hydrocarbons have higher Nuclear Magnetic Resonance (NMR) T1/T2 ratio than saturating water. This empirical rule has been exploited as a powerful logging technique for oil and gas industry. But the origin of the high T1/T2 ratio were not clearly understood until now. This research confirms that the saturating heptane in kerogen has higher T1/T2 ratio than water in kerogen and clays, which validates the fluid typing technique providing the wettability. This research also proves that the origin of the high T1/T2 ratio observed on heptane is that the heptane absorbed in kerogen and/or bitumen, where the relaxation mechanism involves the 1H-1H dipole-dipole interaction. The findings in this thesis provide key insight into the high T1/T2 ratio, which can be used to improve the interpretation of NMR logs in terms of fluid typing and saturation estimation.