The objective of this project was to design a prototype field air permeameter that can be used to track changes in the hydraulic conductivity within soil covers with time. The evolution of soil structure in reclamation soil covers at the Syncrude Canada Ltd. oilsands mine is currently being studied. The Guelph permeameter is currently used to measure hydraulic conductivity, but gathering the data is a very time consuming task due to the relatively low hydraulic conductivity of the cover materials. The use of a faster, more efficient method would increase the capabilities for tracking changes in hydraulic conductivity of reclamation soil covers with time. <p>Three air permeameter design options were evaluated. One design was chosen and a prototype was built. Preliminary field trials were conducted at the Syncrude Canada Ltd. oilsands mine in August 2005. Air permeability measurements were taken on various soil cover treatments and slope positions. Improvements to the air permeameter were implemented in 2006, and additional data gathered. Guelph permeameter testing was carried out alongside the air permeameter in both field seasons. The air permeameter and Guelph permeameter were also tested under controlled laboratory conditions and compared to standard constant head column tests. <p>Results include correlations of air and water permeability for various materials and soil structures. Using dry uniform sand in a laboratory setting, the full scale air permeameter provided permeability values within 21% of a standard constant head column test. Testing of the air and Guelph permeameters on a cover constructed of peat-mineral mix over tailings sand revealed a difference of approximately one order of magnitude in permeability values. A difference of approximately two orders of magnitude existed between permeability values measured with the air and Guelph permeameters on till/secondary soil covers. <p>Further investigation into the difference between values of permeability measured with both methods is necessary. If successful, the air permeameter could prove to be a viable alternative to the Guelph permeameter for use in long-term monitoring of soil covers used in mine reclamation or waste containment. A more efficient air permeability method would allow a greater number of measurements to be made in a shorter time and could be used to track temporal as well as spatial variability in hydraulic conductivity.

Multiphase and non-Darcy flow effects in hydraulically fractured gas wells reduce effective fracture conductivity. Typical proppant pack laboratory experiments are oriented in such a way such that phase segregation is not possible, which results in mixed flow. Tidwell and Parker (1996), however, showed that in proppant packs, gravity segregation occurs for simultaneous gas and liquid injection at laboratory scale (1500 cm2). Although the impact of gravity on flow in natural fractures has been described, previous work has not fully described the effect of gravity on multiphase non-Darcy flow in hydraulic fractures. In this work, reservoir simulation modeling was used to determine the extent and impact of gravity segregation in a hydraulic fracture at field scale. I found that by ignoring segregation, effective fracture conductivity can be underestimated by up to a factor of two. An analytical solution was developed for uniform flux of water and gas into the fracture. The solution for pressures and saturations in the fracture agrees well with reservoir simulation. Gravity segregation occurs in moderate-to-high conductivity fractures. Gravity segregation impacts effective fracture conductivity when gas and liquid are being produced at all water-gas ratios modeled above 2 Bbls per MMscf. More realistic, non-uniform-flux models were also run with the hydraulic fracture connected to a gas reservoir producing water. For constant-gas-rate production, differences in pressure drop between segregated cases and mixed flow cases range up to a factor of two. As the pressure gradient in the fracture increases above 1 to 2 psi/ft, the amount of segregation decreases. Segregation is also less for fracture half-length-to-height ratios less than or close to two. When there is less segregation, the difference in effective conductivity between the segregated and mixed flow cases is reduced. I also modeled the water injection and cleanup phases for a typical slickwater fracture treatment both with and without gravity effects and found that for cases with segregation, effective fracture conductivity is significantly higher than the conductivity when mixed flow occurs. Gravity segregation is commonly ignored in design and analysis of hydraulically fractured gas wells. This work shows that segregation is an important physical process and it affects effective fracture conductivity significantly. Hydraulic fracture treatments can be designed more effectively if effective fracture conductivity is known more accurately.

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xii, 99 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 53-54).

A sizable amount of literature exists analyzing the effect of confining stress on fracture conductivity in sandstones. This thesis attempts to answer similar questions with regard to shale formations. The low Young’s Moduli and Brinell hardness values characteristic of many prospective shale formations may lead to a great deal of embedment and fines production which can drastically reduce fracture conductivity. Furthermore, shales exhibit sensitivity to aqueous fluids which may cause them to be weakened in the presence of certain fracturing fluids. Previous work analyzing shale fluid sensitivity has failed to preserve the shales’ formation properties by allowing the shale to dry out. This paper presents a study of propped fracture conductivity experiments at reservoir temperature and pressure using various North American shale reservoir cores. Exposure to the atmosphere can alter the mechanical properties of the shale by either drying or hydrating the samples, so care was taken to preserve these shales in their native state by maintaining constant water activity (relative humidity). Variations in applied closure stress and aqueous fluid exposure were analyzed and in certain cases altered the propped fracture conductivity by crushing proppant, embedding the proppant into the fracture face, and producing fines. The damage to fracture conductivity is correlated to mineralogy for the various shale samples. These findings show that a one-size-fits-all frac design will not work in every shale formation, rather a tailored approach to each shale is necessary. In the future, the results of this work will be analyzed alongside easier to perform Brinell hardness tests, swelling tests, and other characterization techniques incorporated into the UT Shale Characterization Protocol. Correlations were developed to relate the simpler tests to the fracture conductivity experiments which yield a straight forward method to determine the role embedment and fluid sensitivity have on post treatment fracture conductivity in shales. The UT Shale characterization Protocol can then be used to optimize the design and execution of fracing treatments. / text

No description available.

This study had three primary aims. Firstly, to establish the flow resistance characteristics of meandering channels in flood with different inner channel sinuosities and morphology. Secondly, to gain a better understanding of the coherent flow structures and energy loss mechanisms present within such flows. Third, to establish a link between the identified energy loss mechanisms and the flow resistance behaviour of channels with different geometry. The study begins with a review of current literature appertaining to three flow systems. These were; Inbank flow through meandering channels, overbank flow through channels comprising a straight channel with straight parallel floodplains, and meandering channels with floodplain flow. The available literature with regards to flooded meandering channels was limited to a handful of studies. It was clear there existed a deficiency in stage-discharge data over a range of inner channel sinuosities, and the flow descriptions given were limited to inner channels of relatively low sinuosity i.e. 1.25 - 1.3, rectangular or trapezoidal cross-section and unrealistically low width to depth (aspect) ratio. In addition, the influence of roughened floodplains also required further study. To address these needs, a small-scale laboratory investigation was undertaken at Aberdeen, together with a large-scale collaborative experimental study centred at the SERC Flood Channel Facility. These two experimental studies, in which two inner channels of sinuosity 1.4 and 2 were investigated in detail, are described. The experimental techniques and data collection procedures used are also described. The data types collected include: stage- discharge data, flow visualisation, flow velocity measurement, water surface profiles and bed shear stress analysis using an erodible bed. The stage-discharge data were used for the following; to establish the relationship between inner channel sinuosity and overall channel flow resistance; to establish the effect of inner channel morphology on overall channel resistance: and to assess the implications of roughened floodplains on resistance behaviour. The analysis of these data, together with existing related overbank data, yielded a number of conclusions; i). Overall flow resistance increases as inner channel sinuosity increases, ii). At deep floodplain flows, a floodplain comprising a trapezoidal inner channel was less efficient than one comprising a smaller natural inner channel, iii). Roughening the floodplains has a significant effect on channel resistance characteristics. The flow description data, of overbank flow, revealed the presence of coherent flow structures in flows over inner channels of sinuosity 1.4 and 2, and at a number of flow depths. It is suggested these coherent flow structures are a source of additional energy loss, and a link is proposed between the vigour and frequency of these structures for several flow conditions and channel geometries, and the overall resistance behaviour. Contour maps of water surface elevation are presented for several flow conditions and channel geometries. An increase in surface relief was observed as floodplain depth, and therefore velocity, increased. These maps and earlier related work were then discussed. Plots of near bed velocities, secondary circulation patterns and erodible bed observations strongly indicated a change in sediment erosion and deposition patterns, and thus a change in inner channel morphology during overbank flow. Implications of this change are proposed and discussed. Finally, suggestions for future work are presented. with particular emphasis on a 3-dimensional numerical model presently under development at the University of Aberdeen.

No description available.

In this work, we present methodologies for optimization of hydraulic fracturing design under uncertainty specifically with reference to the thick and anisotropic reservoirs in the Lower Tertiary Gulf of Mexico. In this analysis we apply a stochastic programming framework for optimization under uncertainty and apply a utility framework for risk analysis. For a vertical well, we developed a methodology for making the strategic decisions regarding number and dimensions of hydraulic fractures in a high-cost, high-risk offshore development. Uncertainty is associated with the characteristics of the reservoir, the economics of the fracturing cost, and the fracture height growth. The method developed is applicable to vertical wells with multiple, partially penetrating fractures in an anisotropic formation. The method applies the utility framework to account for financial risk. For a horizontal well, we developed a methodology for making the strategic decisions regarding lateral length, number and dimensions of transverse hydraulic fractures in a high-cost, high-risk offshore development, under uncertainty associated with the characteristics of the reservoir. The problem is formulated as a mixed-integer, nonlinear, stochastic program and solved by a tailored Branch and Bound algorithm. The method developed is applicable to partially penetrating horizontal wells with multiple, partially penetrating fractures in an anisotropic formation.

No description available.

No abstract available. / Thesis (Ph.D.)-University of Natal, Durban, 1984.