2,305 research outputs found
Questions on uncertainties in parton distributions
No full textA discussion is presented of the manner in which uncertainties in parton distributions and related quantities are determined. One of the central problems is the criteria used to judge what variation of the parameters describing a set of partons is acceptable within the context of a global fit. Various ways of addressing this question are outlined. (From the workshop 'Advanced Statistical Techniques in Particle Physics', 18–22 March 2002
A Cooper Basin simulation study of flow-back after hydraulic fracturing in tight gas wells
No full textAfter fluid injection (slickwater) during hydraulic fracturing, the flow-back of fracture fluid is necessary before gas production starts. A review of fracture treatments indicates that the incomplete return of treating fluids is a reason for the failure of hydraulic fracturing and is associated with poor gas production. The aim of this study is to investigate the parameters that limit flow-back in low permeability gas wells in the Cooper Basin.
The authors used numerical simulation to find the critical controlling parameters to introduce the best practice for maximising the flow-back in the Cooper Basin. Several 3D and multiphase flow simulation models were constructed for three wells in the Patchawarra Formation during fracture fluid injection, soaking time and during flow-back. All models were validated using history matching with the production data.
The results show that the drainage pattern is distinctly different in the following directions: vertically upward, vertically downward, and horizontal along the fracture half-length and along the matrix. The lowest recovery is observed during the upward vertical displacements due to poor sweep efficiency. Furthermore, it is observed that drawdown does not influence the recovery significantly for upward displacements. Surface tension reduction, however, can improve sweep efficiency and improve recovery considerably. Also, the wettability of the rocks has a significant impact on ultimate recovery when the effect of gravity is dominant. The authors conclude that a significant amount of injected fluid is trapped in the formation because of poor sweep efficiency and formation of gas fingers, which results from low mobility ratio and gravity segregation.S. Sarkar, M. Haghighi, M. Sayyafzadeh, D. Cooke, K. Pokalai and F. Mohamed Ali Sahi
Search for resonances decaying into top-quark pairs using fully hadronic decays in pp collisions with ATLAS at root s=7 TeV
No full textContains fulltext :
111244.pdf (Publisher’s version ) (Open Access
Uncertainties in parton related quantities.
No full textI discuss the issue of uncertainties in parton distributions and in the physical
quantities which are determined in terms of them. While there has been significant
progress on the uncertainties associated with errors on experimental
data, there are still outstanding questions. Also, I demonstrate that in many
circumstances this source of errors may be less important than errors due to
underlying assumptions in the fitting procedure and due to the incomplete nature
of the theoretical calculations
Parton Distribution Functions of the Charged Pion Within The xFitter Framework
No full textUsing xFitter, we extract parton distribution functions of charged pions from currently available Drell-Yan and photon production data. While the valence distribution is well-constrained, we find that the considered data are not sensitive enough to unambiguously determine sea and gluon distributions. In the used approximation, we find the high-x behavior of the valence distribution to be linear in (1-x) at high x. Fractions of momentum carried by the valence, sea and gluon components are discussed
Simulation of hydraulic fracturing with propane-based fluid using a fracture propagation model coupled with multiphase flow simulation in the Cooper Basin, South Australia
No full textIn many unconventional reservoirs, gas wells do not perform to their potential when water-based fracturing fluids are used for treatments. The sub-optimal fracture productivity can be attributed to many factors such as effective fracture length loss, low load fluid recovery, flowback time, and water availability. The development of unconventional reservoirs has, therefore, prompted the industry to reconsider waterless fracturing treatments as viable alternatives to water-based fracturing fluids.
In this paper, a simulation approach was used by coupling a fracture propagation model with a multiphase flow model. The Toolachee Formation is a tight sand in the Cooper Basin, around 7,200 ft in depth, and has been targeted for gas production. In this study, a 3D hydraulic fracture propagation model was first developed to provide fracture dimensions and conductivity. Then, from an offset well injection fall off test, the model was tuned by using different calibration parameters such as fracture gradient and closure pressure to validate the model. Finally, fracture propagation model outputs were used as the inputs for multiphase flow reservoir simulation.
A large number of cases were simulated based on different fraccing fluids and the concept of permeability jail to represent several water-induced damage effects. It was found that LPG was a successful treatment, especially in a reservoir where the authors suspected the presence of permeability jails. The authors also observed that total flowback recovery approached 76% within 60 days in the case of using gelled LPG. Modelling predictions also support the need for high-quality foam, and LPG can be expected to bring long-term productivity gains in normal tight gas relative permeability behaviour.Y. Fei, M.E. Gonzalez Perdomo, V.Q. Nguyen, Z.Y. Lei, K. Pokalai, S. Sarkar and M. Haghigh
Zeus Nlo QCD fits
No full textNLO QCD fits using the DGLAP formalism have been made to the high precision ZEUS reduced cross-section data and to fixed target structure function data, in order to detrmine parton distribution functions and the value of , taking full account of correlated systematic errors. Preliminary results are reported
Microwave Experiments and Noise in Mesoscopic Devices
No full textThis thesis is a compilation of several works in the area of condensed matter physics, and with devices based on superconducting Josephson junctions (JJ) as the common denominator for the presented projects apart from the work on diffusive systems. Microwave measurements were conducted on a Superconducting Cooper pair transistor to explore its current-phase relationship. Measurements on a JJ-based qubit coupled to a LC resonator revealed the vibronic transitions obeying the Franck-Condon principle. The main body of the thesis is the work done on the Bloch Oscillating Transistor (BOT), an ultra low noise quantum amplifier. In the present work, we investigated the dynamics of the BOT near the bifurcation threshold as well as implemented differential BOTs to check its capability to reject common mode signals. To account for our studies of quantum features in mesoscopic systems other than JJs, we performed an experiment similar to the Hanbury-Brown and Twiss interferometry in optics. For this mesoscopic interference experiment we selected a multiterminal diffusive system. We developed a low temperature noise measurement scheme to study current-current correlations in the GHz frequency range. In our experiments we found a small positive HBT exchange correction factor in the non-interacting limit at low bias voltage in the presence of quantum interference. We found negative exchange correction factor in the hot electron case for similar structures, which agrees well with the theory. Altogether, our experiments demonstrated the theoretically predicted HBT exchange effects in non-interacting and interacting regime of electron transport in a diffusive mesoscopic system
Impact of low- resummation on QCD analysis of HERA data
No full textFits to the final combined HERA deep-inelastic scattering cross-section data within the conventional DGLAP framework of QCD have shown some tension at low x and low . A resolution of this tension incorporating -resummation terms into the HERAPDF fits is investigated using the xFitter program. The kinematic region where this resummation is important is delineated. Such high-energy resummation not only gives a better description of the data, particularly of the longitudinal structure function , it also results in a gluon PDF which is steeply rising at low x for low scales, , contrary to the fixed-order NLO and NNLO gluon PDF.Fits to the final combined HERA deep-inelastic scattering cross-section data within the conventional DGLAP framework of QCD have shown some tension at low and low . A resolution of this tension incorporating -resummation terms into the HERAPDF fits is investigated using the xFitter program. The kinematic region where this resummation is important is delineated. Such high-energy resummation not only gives a better description of the data, particularly of the longitudinal structure function , it also results in a gluon PDF which is steeply rising at low for low scales, GeV, contrary to the fixed-order NLO and NNLO gluon PDF
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