archives@tulane.edu / 1 / Omolola Akintomide

Temperate forests are an important carbon sink, yet there is debate regarding the net effect of forest management practices on carbon storage. Few studies have investigated the effects of different silvicultural systems, and the relative strength of in-situ forest carbon versus wood products pools remains in question. Our research (1) describes the impact of harvesting frequency and degree of post- harvest structural retention on carbon storage in northern hardwood-conifer forests, and (2) tests the significance of including harvested wood products in carbon accounting at the stand scale. We stratified Forest Inventory and Analysis (FIA) plots to control for environmental, forest structural and compositional variables, resulting in 32 FIA plots distributed throughout the northeastern U.S. We used the USDA Forest Vegetation Simulator to project stand development over a 160 year period under nine different forest management scenarios. Simulated treatments represented a gradient of increasing structural retention and decreasing harvesting frequencies and included a “no harvest” scenario. The simulations incorporated carbon flux between aboveground forest biomass (dead and live pools) and harvested wood products (including carbon storage in landfills). Mean carbon storage over the simulation period, including carbon stored in harvested wood products, was calculated for each silvicultural scenario. We investigated tradeoffs among scenarios using a factorial treatment design and two-way ANOVA. The predictive strength of management scenarios relative to site-specific variables was evaluated using Classification and Regression Trees. Mean carbon sequestration was significantly (a = 0.05) greater for “no management” compared to any of the active management scenarios. Of the harvest treatments, those favoring high levels of structural retention and decreased harvesting frequency stored the greatest amounts of carbon. In order to isolate the effect of in-situ forest carbon storage and harvested wood products, we did not include the emissions benefits associated with substituting wood fiber for other construction materials or energy sources. Modeling results from this study show that harvesting frequency and structural retention significantly affect mean carbon storage. Our results illustrate the importance of both post-harvest forest structure and harvesting frequency in carbon storage, and are valuable to land owners interested in managing forests for carbon sequestration.

Global warming due to anthropogenic emission of greenhouse gases notably carbon dioxide, could lead to the irreversible melting of the polar ice and significant increases in global mean temperature. One of the mitigating strategies that can be carried out on a larger scale is the capture and geological sequestration of this gas. Notable among proven geological resources is deep unmineable coal seams. Geological sequestration in these systems has a value added advantage because of coal bed methane production which is a source of cleaner burning fuel than coal. Accordingly the injection of carbon dioxide to a coal seam for long term storage accompanied by the production of methane requires adequate knowledge of the two phase flow characteristics of the methane/brine and carbon dioxide/brine systems. The most important characteristics of the two phase flow are relative permeability and capillary pressure. The coal core was characterized by proximate and ultimate ASTM measurements, x-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses. These analyses identify the existence of clay minerals in the coal structure, which shows that origin of coal formation was from swamp plants. These minerals were used to fill the pores and reduce the permeability. Relative permeability and capillary pressure data for Sydney basin coal samples were collected. This study has also obtained pore size distribution and its indexes both from capillary pressure data and statistical methods based on the hyperbolic model of capillary pressure versus saturation data. The elaborate experimental design and precise measurements using capillary pressure unit (TGC-764) with a pressure control module makes the acquired petro-physical data a valuable asset for future carbon dioxide enhanced coal bed methane production.

Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xiii, 133 p.; also includes graphics (some col.). Includes bibliographical references (p. 125-133).

The Cranfield field, located in southwest Mississippi, is an enhanced oil recovery and carbon sequestration project that has been under a continuous supercritical CO₂ injection by Denbury Onshore LLC since 2008. Two 3D seismic surveys were collected in 2007, pre-CO₂ injection, and in 2010 after > 2 million tons of CO₂ was injected into the subsurface. The goal of this study is to characterize a time-lapse response between two seismic surveys to understand where injected CO₂ is migrating and to map the injected CO₂ plume edge. In order to characterize a time-lapse response, the seismic surveys were cross equalized using a trace-by-trace time shift. A normalized root-mean-square (NRMS) difference value was then calculated to determine the repeatability of the data. The data were considered to have “good repeatability,” so a difference volume was calculated and showed a coherent seismic amplitude anomaly located through the area of interest. A coherent seismic amplitude anomaly was also present below the area of interest, so a time delay analysis was performed and calculated a significant added velocity change. A Gassmann-Wood fluid substitution workflow was then performed at two well locations to predict a saturation profile and observe post-injection expected changes in compressional velocity values at variable CO₂ saturations. Finally, acoustic impedance inversions were performed on the two seismic surveys and an acoustic impedance difference volume was calculated to compare with the fluid substitution results. The Gassmann-Wood fluid substitution results predicted smaller changes in acoustic impedance than those observed from acoustic impedance inversions. At the Cranfield field, time-lapse seismic analysis was successful in mapping and quantifying the acoustic impedance change for some seismic amplitude anomalies associated with injected CO₂. Additional well log data and refinement of the fluid substitution workflow and the model-based inversion performed is necessary to obtain more accurate impedance changes throughout the field instead of at a single well location. / text

This thesis compares 23 anthropogenic charcoal deposits to 19 corresponding control sites, along a European climatic gradient from Temperate Maritime (South Wales) to Mediterranean (southern Italy) environments.

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The safe sequestration of CO2 is pivotal to a successful carbon capture and storage scheme. Saline aquifers and depleted hydrocarbon fields in the North Sea are currently used as storage repositories for captured CO2 from anthropogenic sources. This is because they are deemed safe due to the presence of a sealing cap rock and large storage volume they provide. One such field is the Sleipner field, with over 13 million tonnes of CO2 injected into the Utsira Saline +Formation from 1996 to date. Careful monitoring of the injected CO2 into the formation has revealed growing reflections on nine identified sub-horizontal horizons, referred to as intra reservoir shales. The enhanced reflectivity of the shale layers is mainly caused by the high compressibility of the CO2, trapped beneath them, and by constructive tuning effects of the top and bottom reflections at the CO2 accumulations. Within the same data are chimneys – high permeability pathways that show up in the time lapse seismic images as zones of disturbed layering that cut nearly vertically through the interbedded thin shale layers in the reservoir sands. The presence of these intra-reservoir shales and chimneys affects the distribution pattern of CO2 in the reservoir and distorts the verification of known injected mass of CO2. The aim of the research is to interpret intra-reservoir shales and chimneys on the pre-injection seismic data, these features have previously only been identified in the post-injection time lapse seismic data. The characterisation of the 3D geometry of a reservoir from seismic data is crucial to understanding the parameters that control fluid distribution. The 1994 3D pre injection dataset was interpreted with the help of volumetric seismic attributes tied to a well log. This led to the characterisation of layers from the Utsira top layer to intra-Utsira Shales (IUTS) one to ten and Utsira base layer. A multi-attribute analysis was also used to identify chimneys within the data set. The results from the interpretation workflow were then tested, against the post-injection seismic image data. The CO2 plume visualised across the 4D seismic data set were recreated into geobodies to delineate their form and extent across the reservoir. These geobodies were analysed alongside the interpreted geometry (layers) to understand the effect the layers have in controlling the spatial distribution of the injected CO2. Further analysis was conducted on the geobodies (CO2 plume) to calculate the reservoir volume of CO2 and compare against the known injected amounts of CO2. The interpreted geometry of the plume was used to simulate the impact of the reservoir geometry on injected CO2. Models were created with input parameters derived from well logs and published data. Although limited (real time measurements), results from simulations reveal close resemblance with 4D seismic data set. This study has highlighted the possibility of identifying intra-reservoir shales and chimneys to inform site characterisation that can be performed before any CO2 injection project commences. Attribute and spectral analysis can be used to add resolution to seismic data to enable detailed interpretation of the geometry of a reservoir and the volume of CO2 within a reservoir can be verified using seismic geobodies. The current monitoring techniques can employ the characterisation and verification procedure described in this study to characterise a reservoir, verify and quantify the injected amounts of CO2 to avert and mitigate for CO2 leakage.