Time-dependent coupled oscillator model for charged particle motion in the presence of a time varyingmagnetic field

The dynamics of time-dependent coupled oscillator model for the charged particle motion subjected to a time-dependent external magnetic field is investigated. We used canonical transformation approach for the classical treatment of the system, whereas unitary transformation approach is used when managing the system in the framework of quantum mechanics. For both approaches, the original system is transformed to a much more simple system that is the sum of two independent harmonic oscillators which have time-dependent frequencies. We therefore easily identified the wave functions in the transformed system with the help of invariant operator of the system. The full wave functions in the original system is derived from the inverse unitary transformation of the wave functions associated to the transformed system.Comment: 16 page

PERMEABILITY ANISOTROPY DISTRIBUTIONS IN AN UPPER JURASSIC CARBONATE RESERVOIR, EASTERN SAUDI ARABIA

Most classical reservoir engineering concepts are based on homogeneous reservoirs despite the fact that homogeneous reservoirs are the exception rather than the rule. This is especially true of carbonate reservoirs in the Middle East which are known to be highly heterogeneous. The realistic petrophysical characterization of these kinds of reservoirs is not an easy task and must include the study of directional variations of permeability. Such variation can be incorporated into engineering calculations as the square root of the ratio of horizontal to vertical permeability, a parameter known as the anisotropy ratio. This paper addresses the distribution of anisotropy ratio values in an Upper Jurassic carbonate reservoir in the Eastern Province of Saudi Arabia. Based on whole core data from a number of vertical wells, statistical distributions of horizontal and vertical permeability measurements as well as anisotropy ratios were determined. The distributions of both permeability measurements and anisotropy ratios have similar patterns characterized by considerable positive skewness. The coefficients of variation for these distributions are relatively high, indicating their very heterogeneous nature. Comparison of plots of anisotropy ratios against depth for the wells and the corresponding core permeability values indicate that reservoir intervals with lower vertical permeability yield consistently higher ratios with considerable fluctuations. These intervals are represented by lower porosity mud-rich and/or mud-rich/granular facies. Granular facies, on the other hand, yielded considerably lower ratios without significant fluctuations

PERMEABILITY ANISOTROPY DISTRIBUTIONS IN AN UPPER JURASSIC CARBONATE RESERVOIR, EASTERN SAUDI ARABIA

Most classical reservoir engineering concepts are based on homogeneous reservoirs despite the fact that homogeneous reservoirs are the exception rather than the rule. This is especially true of carbonate reservoirs in the Middle East which are known to be highly heterogeneous. The realistic petrophysical characterization of these kinds of reservoirs is not an easy task and must include the study of directional variations of permeability. Such variation can be incorporated into engineering calculations as the square root of the ratio of horizontal to vertical permeability, a parameter known as the anisotropy ratio. This paper addresses the distribution of anisotropy ratio values in an Upper Jurassic carbonate reservoir in the Eastern Province of Saudi Arabia. Based on whole core data from a number of vertical wells, statistical distributions of horizontal and vertical permeability measurements as well as anisotropy ratios were determined. The distributions of both permeability measurements and anisotropy ratios have similar patterns characterized by considerable positive skewness. The coefficients of variation for these distributions are relatively high, indicating their very heterogeneous nature. Comparison of plots of anisotropy ratios against depth for the wells and the corresponding core permeability values indicate that reservoir intervals with lower vertical permeability yield consistently higher ratios with considerable fluctuations. These intervals are represented by lower porosity mud-rich and/or mud-rich/granular facies. Granular facies, on the other hand, yielded considerably lower ratios without significant fluctuations

Cross-layer architecture for congestion control in Vehicular Ad-hoc Networks

Vehicular Ad-hoc Networks (VANETs) are special kind of Mobile Ad-hoc Networks (MANETs). The distinctive characteristics of the VANETs include high speed of vehicular nodes and high variability in node density. Congestion detection and control protocols have been proved to be an efficient method for improving network performance and are well studied for the MANET environment. However, they often result in sub-optimal network performance for the vehicular network environment due to the specialized characteristics of VANET. In this paper we present an adaptive and distributed cross-layer congestion detection and control protocol for the VANET environment. During the congestion detection phase, information from each layer of the network protocol stack is combined and mapped on to congestion levels. In the subsequent congestion control phase parameters like contention window, transmission rate and transmit power are jointly adjusted to improve on the network performance. The effectiveness of the proposed model is evaluated through mathematical analysis and simulation-based studies. © 2013 IEEE

USE OF A NON-DESTRUCTIVE METHOD TO ESTIMATE DRILLING FLUID INVASION DEPTH IN CORES, APPLICATION TO FORMATION DAMAGE

ABSTRACT Formation damage results each year in substantial losses for the oil industry. Most of the damage is due to drilling and completion operations during well construction. This is particularly true when the drilling fluids used are not chosen meticulously. It has been proven that well impairment is due to drilling fluids invasion in the formation, which in turn induces a permeability reduction in the vicinity of the well. One of the main characteristics of a drilling fluid is its bridging ability, which depends on the size of the particles present in the mud. A rule of thumb in order to minimize invasion of the formation is that the average diameter of the solid particles present in the mud, should be no smaller than the third of the median pore throat diameter. Since the source of the solid particles is diverse; weighting agents, cuttings etc, an efficient solid control mechanism is needed. In fact, a compromise solution between an adequate bridging and an efficient solid transport and removal is sought. Laboratory measurements are conducted in order to determine the optimum conditions for a minimum invasion depth and consequently limited damaging effects of drilling fluids