Thesis (M. S.)--Texas A&M University, 2005. / "Major Subject: Petroleum Engineering" Title from author supplied metadata (automated record created on Apr. 27, 2007.) Vita. Abstract. Includes bibliographical references.

Thesis (M. S.)--Texas A&M University, 2006. / "Major Subject: Petroleum Engineering" Title from author supplied metadata (automated record created on Apr. 27, 2007.) Vita. Abstract. Includes bibliographical references.

Thesis (M. S.)--Texas A&M University, 2005. / "Major Subject: Petroleum Engineering" Title from author supplied metadata (automated record created on Apr. 27, 2007.) Vita. Abstract. Includes bibliographical references.

Thesis (M. S.)--Texas A&M University, 2007. / "Major Subject: Petroleum Engineering" Title from author supplied metadata (automated record created on Oct. 13, 2008.) Vita. Abstract. Includes bibliographical references.

Thesis (Ph. D.)--Texas A&M University, 2008. / "Major Subject: Petroleum Engineering" Title from author supplied metadata (automated record created on Oct. 13, 2008.) Vita. Abstract. Includes bibliographical references.

Thesis (M. S.)--Texas A&M University, 2008. / "Major Subject: Petroleum Engineering" Title from author supplied metadata (automated record created on Oct. 13, 2008.) Vita. Abstract. Includes bibliographical references.

Thesis (M. S.)--Texas A&M University, 2008. / "Major Subject: Petroleum Engineering" Title from author supplied metadata (automated record created on Oct. 13, 2008.) Vita. Abstract. Includes bibliographical references.

Thesis (M. S.)--Texas A&M University, 2007. / "Major Subject: Petroleum Engineering" Title from author supplied metadata (automated record created on Oct. 13, 2008.) Vita. Abstract. Includes bibliographical references.

<p> Nuclear magnetic resonance (NMR) has become an increasingly important tool for estimating porosity, permeability, and fluid characteristics in oil and gas reservoirs since its introduction in the 1950s. While NMR has become common practice in <i>conventional</i> reservoirs, its application is relatively new to <i>unconventional</i> reservoirs such as the Eagle Ford Shale. Porosity and permeability estimates prove difficult in these exceptionally tight rocks and are routinely below the detection limit and/or resolution of low frequency (2 MHz or less) NMR. High frequency (400 MHz) NMR has been applied to address these issues; however, previous studies have been limited to crushed rock samples or millimeter-sized core plugs. </p><p> In response, a custom-built NMR probe has been constructed, capable of measuring 0.75-inch diameter, 0.45-inch length core plugs at 400 MHz, to determine if larger core plug sizes yield higher resolution <i>T</i>₂ distributions in the Eagle Ford Shale. The tool is composed of two primary elements, the structural framework and the radio frequency circuit. Each element was designed and constructed iteratively to test various layouts while maintaining functionality. The probe's structural design was initially based on retired, commercial probes then modified to operate within a Bruker Ascend&trade; 400WB NMR spectrometer. Designs were drafted and 3D-printed multiple times to determine proper physical dimensions and clearances. Once designs were deemed satisfactory, structural components were manufactured and assembled to create the structural framework. A radio frequency circuit was then built to measure <i>T</i>₂ distributions at the desired frequency and sample size. Multiple inductor designs and capacitor combinations were tested until a stable circuit, capable of matching impedance and tuning to the proper frequency, was achieved. The probe's stability and data quality were then confirmed by measuring the NMR spectra of deuterated water in a Teflon container. </p><p> The NMR probe was validated by comparing high frequency (400 MHz) data acquired in-house to low frequency (2 MHz) data measured at a commercial laboratory. Twelve core plugs (0.75-inch diameter, 1-inch length) were cut from two Eagle Ford Shale subsurface cores located in Gonzales and La Salle counties, Texas. Low frequency <i>T</i>₂ distributions were measured twice: first after drying core plug samples in a vacuum oven and again after spontaneous imbibition with various brine solutions (deionized water, 8 wt.% KCl, or 17.9 wt.% KCl) for one week. These contrasting saturation states were applied to highlight immovable water in the core plugs. For high frequency data measurements, samples were trimmed to 0.45-inch lengths to fit inside the newly-built NMR probe, leaving two sub-samples for each of the original core plugs. <i> T</i>₂ distributions were first acquired "as-is" (e.g., without drying or imbibition). After as-is data acquisition, samples were dried in a vacuum oven then allowed to spontaneously imbibe the same brine solutions used in the low frequency study. <i>T</i>₂ distributions were measured again after imbibition and compared to the low frequency data acquired by the commercial laboratory. </p><p> Qualitatively, high frequency <i>T</i>₂ distributions resemble low frequency data; however, the absolute <i>T</i>₂ values are routinely higher by one order of magnitude. The difference may be caused by data acquisition, data processing, fluid-rock interactions, magnetic field inhomogeneities, or some combination thereof. In spite of not attaining the higher-resolution <i>T</i>₂ distributions desired, the project still provides a proof-of-concept that <i>T</i>₂ relaxation times can be measured in conventional-sized core plugs using 400 MHz NMR. Although limited in its outcomes, the study delivers promising results and elicits future research into utilizing high frequency NMR spectroscopy as a petrophysical tool for unconventional reservoirs.</p><p>

<p> Reactive transport phenomena, such as CO2 sequestration and Microbial EOR, have been of interest in streamline-based simulations. Tracing streamlines launched from a wellbore is important, especially for time-sensitive transport behaviors. However, discretized gridblocks are usually too large as compared to the wellbore radius. Field-scale simulations with local-grid-refinement (LGR) models often consume huge computational time. An embedded grid-free approach to integrate near-wellbore transport behaviors into streamline simulations is developed, which consists of two stages of development: tracing streamlines in a wellblock (a gridblock containing wells) and coupling streamlines with neighboring grids. The velocity field in a wellblock is produced based on a grid-less virtual boundary element method, where streamlines are numerically traced using the fourth-order Runge-Kutta (RK4) method. The local streamline system is then connected with the global streamline system which is produced by Pollock&rsquo;s algorithm. Finally, the reactive transport equation will be solved along these streamlines. </p><p> The presented algorithm for solving near-wellbore streamlines is verified by both a commercial finite element simulator and Pollock-algorithm-based 3D streamline simulator. A series of computational cases of reactive transport simulation are studied to demonstrate the applicability, accuracy, and efficiency of the proposed method. Velocity field, time-of-flight (TOF), streamline pattern, and concentration distribution produced by different approaches are analyzed. Results show that the presented method can accurately perform near-wellbore streamline simulations in a time-efficient manner. The algorithm can be directly applied to one grid containing multiple wells or off-center wells, as well. Furthermore, assuming streamlines are evenly launched from the gridblock boundary or ignoring transport in the wellblock is not always reasonable, and may lead to a significant error. </p><p> This study provides a simple and grid-free solution, but is capable of capturing the flow field near the wellbore with significant accuracy and computational efficiency. The method is promising for streamline-based reservoir simulation with time-sensitive transport, and other simulations requiring an accurate assessment of interactions between wells in one particular gridblock.</p><p>