bluuebunny/crossref_metadata_2025 huggingface dataset:
Developing a Fatigue Risk Management System: Case Studies on Education and Mitigation Strategies
Authors: Acton Sarah
Published: October 2014

"Fatigue" is neither easy to define nor measure. Symptoms include a lack of alertness and reduced mental and physical performance but identifying these symptoms can be challenging. Despite the difficulty of recognizing the symptoms of fatigue, they have in fact contributed to many major accidents in numerous safety-critical industries. Due to the safety-critical environment of industries, such as oil and gas, fatigue can lead to catastrophic consequences when symptoms begin to affect works' decision-making capabilities. Implementing a Fatigue Risk Management System can help reduce worker fatigue and improve situation awareness, especially during shifts with high risk of fatigue.

A successful system which eliminates emerging symptoms and prevents overexaustion includes two main focus areas for eliminating or mitigating the effects of fatigue: fatigue education for workers and on-duty alertness strategies. Understanding the human body and how environmental factors can affect sleep are important to helping workers achieve and maintain good sleep hygiene. Employing fatigue alertness strategies, especially during night shifts, is crucial to helping employees stay alert and focused during high-workload tasks. This paper will explore fatigue education and mitigation strategies in various industries to determine what factors contribute to a successful Fatigue Risk Management System.
Foams Stabilized by In-Situ Surface Activated Nanoparticles in Bulk and Porous Media
Authors: Singh Robin , Mohanty Kishore K.
Published: October 2014

The goal of this work is to study foam stabilization by in-situ surface activation of hydrophilic nanoparticles for subsurface applications. The interfacial properties of the nanoparticles were modulated by attachment of short chain surface modifiers which render them partially hydrophobic. Static foams were generated using nanoparticles with varying concentrations of surface modifiers. The decay of foam height with time was studied and half-lives were determined. Optical micrographs of foams stabilized by surface-modified nanoparticles (SM-NP) and surfactants were recorded. Aqueous foams were created in-situ by co-injecting the SM-NP solutions with nitrogen gas through a Berea sandstone core at a fixed quality. Pressure drop across the core was measured to estimate the achieved mobility reduction factor (MRF). The results were then compared witha typical surfactant under similar conditions. Oil displacement experiments were conducted in Berea cores using surfactant and SM-NP solutions as foaming agents. Bartsch shake test revealed strong foaming tendency of SM-NP even with a very low initial surface-modifier concentration (0.05 wt%), whereas hydrophilic nanoparticles alone could not stabilize foam. The bubble texture of foam stabilized by SM-NP was finer than that with surfactant which indicated a stronger foam. As the degree of surface coating increased, mobility reduction factor (MRF) of SM-NP foam in a Berea core increased significantly. The core floods in the sandstone cores with a reservoir crude oil showed that immiscible foams using SM-NP solution can recover significant amount of oil over water flood.
Modeling Adsorption of Gases in Nanoscale Pores Using Grand Canonical Monte Carlo Simulation Techniques
Authors: Al Ismail Maytham I. , Horne Roland N.
Published: October 2014

Shale gas and liquid-rich shales have become important energy sources in the US and other parts of the world. Shale rocks contain a very heterogeneous pore system. The pore size varies between micro-, meso- and macroscales. One critical phenomenon that governs the flow of hydrocarbons and is strongly affected by pore size is the adsorptive behavior. The adsorbate packing and density is influenced strongly by the force fields of the closely opposing pore walls.

In this study, molecular simulation was applied to generate adsorption isotherms of pure methane, pure n-butane and methane/n-butane mixtures using grand canonical Monte Carlo (GCMC) techniques. The simulations were conducted on a slit pore model composed of parallel planar graphitic surfaces. Various pore sizes were studied ranging from 1 nm to 20 nm. The nonbonded interactions between the molecules, as well as between the molecules and the pore walls were described with Lennard-Jones potentials. To verify the model, the simulated adsorption isotherms were compared with adsorption isotherms obtained from published experimental data where the adsorption measurements of methane and n-butane were conducted on a Marcellus shale sample and carbon materials; respectively.

In the pure molecule cases, results indicate that as the pore width increases, the density of the adsorbed molecules decreases due to the reduction of the fluid-wall interaction. For example, above 10 nm pore-width, the density of methane inside the slit pore becomes comparable to the methane density in the bulk. In the methane/n-butane mixture case, results indicate that the selectivity of n-butane over methane was greater than 1 at low pressures (~200 psi). Therefore, n-Butane is the more favorable component to adsorb and form a layer near the pore walls. However, at high pressures (~1,000 psi), "selectivity reversal" was observed due to size entropy effects. Preferential adsorption leads to compositional variations in the gas produced from the shale.

This study provides insights on the adsorptive behavior of light and heavy hydrocarbon molecules. Determining the effect of fluid confinement on adsorption will lead to better understanding of the fluid behavior in rocks with nanoscale pores such as shales. This is especially important when the compositional behavior of confined multicomponent gas-condensate mixtures is investigated during depletion to develop strategies for more effective hydrocarbon recovery.
A Guideline to Calculate Erosional Velocity due to Liquid Droplets for Oil and Gas Industry
Authors: Arabnejad H. , Shirazi S. A. , McLaury B. S. , Shadley J. R.
Published: October 2014

In the oil and gas industry, pipe size and material are selected so that the flow velocity is below the so called "erosional velocity," presumably a flow velocity at which it is safe to operate. The American Petroleum Institute Recommended Practice 14E (API RP 14E) guide describes a method for calculating an erosional velocity for clean service. For oil and gas industry applications, some authors assume that the basis for API RP 14E is erosion due to liquid droplet impact. However, there is no experimental or theoretical evidence supporting this idea. The goal of present work is to provide a guideline to calculate erosional velocity due to liquid droplets in oil and gas production and transportation facilities. This paper describes how liquid droplet erosion can be calculated for a variety of materials that are commonly used in oil and gas industry pipelines. The calculation methodology developed previously has been extended to predict erosion of the oilfield materials due to water droplets with and without impurities using experimental data that was collected for specimens impacting a liquid jet. The erosion equation for liquid impact presented in American Society for Testing and Materials (ASTM) standard G73-10 has been modified based on experimental data to consider velocity exponent changes with droplet size. Based on the new erosion model, a procedure has been developed to predict erosional velocity due to liquid droplet impact utilizing the entrainment fraction and droplet size calculated from two-phase flow correlations and the impact velocity of the droplets within a pipe elbow or a tee that is estimated using stagnation length model which is basically a one-dimensional particle tracking model and an alternative for complex Computational Fluid Dynamic (CFD) simulation of multiphase flow and incorporated particle tracking scheme. Experimental data that was obtained at the Erosion/Corrosion Research Center (E/CRC) for several engineering materials such as stainless and carbon steels, chromium alloys and Inconel are used to calculate a threshold velocity using the data and method developed in this study. The erosional velocities computed using this model are compared with the erosional velocities computed using API RP 14E. It is shown that the trend of the erosional velocity calculated by the API guideline is extremely conservative as compared to the new model predictions for erosion due to liquid impact and does not correlate with erosion due to small entrained particles. Thus, oil and gas producers can use this method and provided equations and graphs to determine erosional velocities for cases when no sand is being produced or when small particles are entrained in the liquid.
A Mechanistic Model for Wettability Alteration by Chemically Tuned Water Flooding in Carbonate Reservoirs
Authors: Qiao C. , Li L. , Johns R. T. , Xu J.
Published: October 2014

Injection of chemically tuned brines into carbonate reservoirs has been reported to enhance oil recovery by 5% to 30% OOIP in core flooding experiments and field tests. One proposed mechanism for this improved oil recovery (IOR) is wettability alteration of rock from oil wet or mixed-wet to more water wet conditions. Modeling of wettability alteration experiments, however, are challenging due to the complex interactions among ions in the brine and crude oil on the solid surface. In this research, we developed a multiphase multicomponent reactive transport model that explicitly takes into account wettability alteration from these geochemical interactions in carbonate reservoirs.

Published experimental data suggests that desorption of acidic oil components from rock surfaces make carbonate rocks more water wet. One widely accepted mechanism is that sulfate (SO42−) replaces the adsorbed carboxylic group from the rock surface while cations (Ca2+, Mg2+) decrease the oil surface potential. In the proposed mechanistic model, we used a reaction network that captures the competitive surface reactions among carboxylic groups, cations, and sulfate. These reactions control the wetting fractions and contact angles, which subsequently determine the capillary pressure, relative permeabilities, and residual oil saturations.

The developed model was first tuned with experimental data from the Stevns Klint chalk and then used to predict oil recovery for additional un-tuned experiments under a variety of conditions where IOR increased by as much as 30% OOIP, depending on salinity and oil acidity. The numerical results showed that an increase in sulfate concentration can lead to an IOR of over 40% OOIP, while cations such as Ca2+ have a relatively minor effect on recovery (about 5% OOIP). Other physical parameters, including the total surface area of the rock and the diffusion coefficient, control the rate of recovery, however not the final oil recovery. The simulation results further demonstrate that the optimum brine formulation for chalk are those with relatively abundant SO42− (0.096 mol/kg water), moderate concentrations of cations, and low salinity (total ionic strength less than 0.2 mol/kg water). These findings are consistent with the experimental data reported in the literature. The new model provides a powerful tool to predict the IOR potential of chemically tuned waterflooding in carbonate reservoirs under different scenarios.
Advances in Understanding Wettability of Tight and Shale Gas Formations
Authors: Lan Qing , Xu Mingxiang , Dehghanpour Hassan , Wood James
Published: October 2014

This paper aims at understanding the factors controlling the wettability of unconventional rocks. In the first part, we report the results of comparative imbibition experiments on several binary core plugs from the Montney tight gas formation, which is an enormous tight gas fairway in the Western Canadian Sedimentary Basin. Both contact angle and imbibition data indicate that the formation is strongly oil-wet. However, the ratio between oil and water imbibition rate of these samples is higher than what capillary-driven imbibition models predict. This discrepancy can be explained by the strong adsorption of oil on the surface of a well-connected organic pore network that is partly coated by pyrobitumen. We also define a wettability index by using the equilibrium imbibed volume of oil and water in binary plugs. Oil wettability index is in general positively correlated to the total organic carbon (TOC), measured by the Rock-Eval technique. In the second part, we report similar imbibition experiments on several binary core samples collected from the cores drilled in the shale members of the Horn River Basin. In contrast to the Montney (MT) samples, the Horn River (HR) samples imbibe significantly more water than oil. This observation contradicts the contact angle results which suggest that the HR samples are strongly oil-wet. Clay hydration, imbibition-induced microfractures, depositional lamination, and osmotic potential are collectively responsible for the excess water uptake. We also measure and compare spontaneous imbibition of oil and water into the crushed packs of the similar HR samples. Interestingly, in contrast to the intact samples, the crushed samples consistently imbibe more oil than water. The comparative study suggests that the connected pore network of the intact HR samples is water-wet while the majority of rock including poorly connected pores is oil-wet.

Overall, the results suggest that the well-connected pore network of the MT samples is dominantly hydrophobic and is very likely to be coated by pyrobitumen. This is the main reason why these samples imbibe more oil than water. On the other hand, the well-connected pore network of the HR samples is strongly hydrophilic primarily due to the presence of clay minerals and precipitated salt crystals coating the rock grains.
Assessment of Hydrocarbon Saturation in Organic-Rich Source Rocks using Combined Interpretation of Dielectric and Electrical Resistivity Measurements
Authors: Chen Huangye , Heidari Zoya
Published: October 2014

Complex pore geometry and composition as well as heterogeneous and anisotropic behavior of organic-rich source rocks significantly affects physical properties of the rock measured by well logs such as electrical resistivity and dielectric permittivity. These physical properties are used to estimate in situ petrophysical properties of the formation such as hydrocarbon saturation. Conventional methods for assessment of hydrocarbon saturation include interpretation of (a) electrical resistivity logs through resistivity-porosity-saturation models (e.g., Archie's equation and the dual-water model) and (b) dielectric permittivity measurements using volumetric techniques such as the Complex Refractive Index Model (CRIM). In the application of these approaches to formations with complex pore structure and mineral composition such as organic-rich formations, the impact of complex pore-structure (e.g., kerogen porosity and inter-granular pores), pyrite, and conductive mature kerogen have not been taken into account. The aforementioned limitations cause significant uncertainty in estimates of water saturation.

The method proposed in this paper improves the assessment of hydrocarbon saturation using combined interpretation of dielectric and electrical resistivity measurements. We start with pore-scale numerical simulations of electrical resistivity and dielectric permittivity of fluid-bearing porous media to investigate the impact of structure of pore and matrix constituents on these measurements. The inputs to these simulators are three-dimensional (3D) pore-scale rock images. We then introduce an analytical model that combines conductivity and permittivity measurements for assessment of water-filled porosity and hydrocarbon saturation. We applied the new method on actual sandstone and synthetic organic-rich source rock samples. We observed an improvement in estimates of water-filled porosity compared to conventional methods in both cases of conventional and unconventional rock samples. This improvement was more significant in the case of organic-rich source rocks with complex pore structure. In the case of synthetic organic-rich source rock samples, the simulation results confirmed that not only the pore structure, but also spatial distribution and tortuosity of water, kerogen, and pyrite networks, affect the dielectric permittivity and electrical resistivity. Taking into account these parameters through the joint interpretation of dielectric and electrical resistivity measurements significantly improves assessment of hydrocarbon saturation.
Going Beyond the Tally book: A Novel Method for Analysis, Prediction and Control of Directionally Drilled Wellbores using Mechanical Specific Energy
Authors: Noynaert S. , Gildin E.
Published: October 2014

The following paper covers work completed at Texas A&M University regarding an innovative method to quantify the rate of change in a wellbore trajectory using mechanical specific energy or MSE. The use of MSE to anticipate the rate of change is a fresh approach to wellbore trajectory prediction using surface drilling data and is shown in our work to be an accurate predictor of dog-leg severity.

The use of horizontal drilling has expanded at an almost exponential pace as it has been applied to unconventional reservoirs, and yet, the process is still done in a reactive fashion. This is to say that, many horizontal drilling decisions are still made by the directional driller using only his tally book with simple records showing the results of his prior actions. Using the correlation presented in this paper, a system has been developed which allows for accurate prediction of the rate of change of wellbore deviation while a drillstring is being rotated ahead.

Predictive models, typically centered on WOB or RPM, have been in existence for many years. However, one parameter whose effect on wellbore deviation has not been investigated is mechanical specific energy. MSE is a measure of the efficiency of the drilling process and has primarily been used for vibration analysis and rate of penetration optimization. Using published experimental data, a correlation was developed which shows a clear relationship between the dog-leg severity, rate of penetration (ROP) and MSE. The correlation requires only a few hundred feet of drilling before it is able to be tuned to match an individual well's results. With minimal tuning throughout the drilling of a well, good results can be obtained with regards to forecasting dog-leg severity as the wellbores were drilled ahead. The correlation was tested using data from multiple, geo-steered wells drilled in a shale reservoir. The analysis of the correlation using real-world data proved it to be a robust and accurate method of predicting the magnitude of dog-leg severity.

This work is a part of the overall industry push to understand the mechanics of what is occurring downhole and their effect on the many aspects of the drilling process. The correlation allows for the prediction of what is now becoming a vital part of many of the wells we drill: the wellbore's trajectory while rotating. It works particularly well in horizontal or near-horizontal portions of the well, which is where the wellpath trajectory matters the most with regards to overall well productivity. In addition, there are no special data requirements, only standard surface drilling parameter data. Overall, the use of this correlation results in a smoother wellbore, drilled with a faster overall ROP with a better chance of staying within the geologic targets.
Understanding Mechanisms for Liquid Dropout from Horizontal Shale Gas Condensate Wells
Authors: Altman Raphael , Fan Li , Sinha Shekhar , Stukan Mikhail , Viswanathan Anup
Published: October 2014

The presence of nanopores in tight, rich-gas-condensate wells (3,000 to ~10,000 scf/STB) may hold long-term gas/oil ratio (GOR) trends constant with time as observed in production data from some North American shales. This finding contrasts with some of the numerical simulation forecasts performed on calibrated pressure/volume/temperature (PVT) models based on bulk laboratory PVT data. Research efforts have pointed to a decrease in the PVT phase envelopes of hydrocarbon fluids confined in nanopores. This would delay the onset of dew point pressure and condensate liquid dropout and could be one of the causes of the observed constant producing GOR in the wells studied.

An understanding of fluid properties in nanopores is fundamental to predicting the onset of condensate dropout in shale reservoirs. One approach may be molecular dynamics simulations that can shed the light on the difference in behavior of larger-chain hydrocarbon molecules at kerogen surfaces and bulk pore space. Additionally, shale gas condensate production management may be more fully optimized by understanding both the effects of hydraulic fracture degradation with drawdown and liquid dropout in the production string. An integrated approach of this kind can help optimize liquid-rich shale reservoir production management.
Recovery Mechanism of Thermal Process in Naturally Fractured Tight Diatomite Heavy Oil Reservoir
Authors: Harness Paul , Tang Guo-qing , Inouye Art , Lowry Dustin
Published: October 2014

The Monterey siliceous diatomite resource is an unconventional resource which traps several billion barrels of heavy oil in San Joaquin Valley. Thermal processes, such as steam injection, have been successfully used to stimulate heavy oil production from diatomite reservoirs since the 1990's. Significant improvements in oil production have been achieved using the steam injection process however, the recovery mechanism remains unclear. This work is aimed at uncovering the recovery mechanism for steam injection in diatomite heavy oil reservoirs.

A comprehensive experimental study focused on the recovery mechanisms utilizing a specially designed high temperature and pressure core test system, integrated with high resolution CT-scan imaging technology with advanced test protocols to simulate reservoir conditions. Reservoir rocks with different lithologies (sandy, clean, and clayey), various viscous crude oils (API=14-22), and synthetic formation brines were used in this study. Imbibition core tests at elevated temperatures up to 400°F were conducted to study the recovery mechanism by the steam injection process.

Our study showed that oil recovery is dominated by hot water imbibition from fracture networks in the tight matrix where oil is stored. As the temperature is increased from reservoir temperature to steam temperature (400 °F), the oil recovery is symmetrically increased from less than 10% to around 60%. A proportional linear relation between oil recovery and temperature is observed which can be used to optimize field steam injection operations. Results indicate that thermal processes alter wettability toward increasing water-wetness. Wettability alteration experiments at elevated temperatures were also observed with a high resolution industrial CT-scanner.
New Approaches to Transferring Skills to the Next Generation
Authors: Lomas Adam. T.
Published: October 2014

Author's speak recently of a "disruptive shake-up" in the energy industry. The relationship between NOC's IOC's and service companies has changed beyond recognition, but one parameter has remained the same throughout these turbulent years – the need for talent to develop the increasingly complex oil and gas fields.

The constraint on being able to invest in mega projects, is often not the lack of capital or even the increasingly complex technology required to drill deeper, horizontal or in (sub) arctic conditions, it is the lack of talent to deliver them.

The oil industry has experienced a number of "boom and bust" cycles since the 1970's and each oil price crash has led to cuts to keep operating costs low. The first cuts almost always hit training and travel budgets and the 10$ oil in the early 90's led to a freeze on hiring new graduates into the industry and massive cuts in training and development.
A New Approach for Fast Evaluations of Large Portfolios of Oil and Gas Fields
Authors: Castiñeira David , Mondal Anirban , Matringe Sebastien
Published: October 2014

This paper presents a new systematic process for the evaluation of large portfolios of oil and gas fields where the performance and economic value of an entire portfolio is very rapidly derived. The automation of this workflow relies on some key technological developments, namely an automated algorithm for decline-curve analysis, and data mining studies of workovers and new well performance.

The automated decline-curve analysis tool presented here uses an event detection algorithm combined with quantile regression technique design to provide a robust probabilistic estimate of future PDP (proved-developed-producing) reserves on a well-by-well basis. Individual well behaviors are then aggregated stochastically to provide expected field and portfolio declines, with uncertainty ranges. Future well trends are estimated using probabilistic type-curves computed by data mining algorithms. Wells and fields are then individually assessed and ranked in terms of reserves and production metrics and financial information can be used to assess the value of the portfolio with a high-level of granularity.

A large portfolio of oil and gas fields in Texas and Louisiana is analyzed in this paper using the proposed methodology. For this portfolio computed decline rates, PDP reserves and cash flows are provided. Analysis of expected production from new wells and estimates of workover performance are also presented.

The analytical approach presented in this work is being used daily for comprehensive portfolio evaluations in the US and represents a significant change in the way divestitures and acquisitions evaluations are currently performed in the industry.
Mathematical Modeling of Production Decline For Conventional and Unconventional Reservoir
Authors: Mikolajczak Edyta
Published: October 2014

The determination of reservoir flow rate is the key issue during the planning phase of hydrocarbon production in conventional and unconventional reservoirs. Production change forecasts are presented with decline curve based on analytical or empirical dependencies. Curve matching depends on the appropriate mathematical model which was used.

The aim of this paper is the possibility to implement various mathematical models analysing production process for hydrocarbon wells. The idea of this paper is to use Logistic equation, which has widespread use in modeling the growth of the population, for modeling production decline and test results for the Arps model and the Logistic equation for predicting gas production for both conventional and unconventional resources.

This paper presents a study on the forecasting of gas well production. Part one focuses on the conventional reservoir, while part two presents predicting the production of unconventional gas wells. New mathematical formula has been proposed taking into account effect of gas desorption from organic matter of the shale.

Analytical models provide more reliable forecasting capability. The logistic curve was successfully applied to conventional and unconventional reservoirs. Once, it is useful to understand the dynamic behavior of the decline resulting from phenomena for unconventional reservoir. The modeling results were verified by the real industrial data.
Enzyme Penetration Tests on Carbonaceous Rocks for Application to Enhanced Oil Recovery
Authors: Haastrup Birgit
Published: October 2014

Many different Enhanced Oil Recovery (EOR) methods have been applied on reservoirs with declining oil production. Currently there is a demand for new and green technologies in order to increase oil recovery. One of the technologies in focus is Enzymatic EOR (EEOR).

One of the newest proposals for the application of enzymes utilizes their ability to alter the wettability of the reservoir rock. Both laboratory experiments and pilot plant tests have been carried out (although mainly for sandstone rocks) to study this effect. However little is known about the applicability of enzymes on carbonate reservoirs.

The aim of this paper is to outline the penetration behavior of two different enzymes on carbonate cores, in order to check whether the enzymes get irreversibly adsorbed in the rock and, thus, would "get lost" close to injection sites if injected for EOR. This is an important study in order to investigate the feasibility of EEOR application in the North Sea carbonate reservoirs.

Two enzymes, an esterase and a lipase, were selected based on their ability to change the wettability and adhesion properties and also desorption rates on cleaned cleaved chalk surfaces. The penetration tests were conducted on North Sea chalk reservoir cores.

The tests showed that the esterase does not penetrate chalk whereas the lipase does. When the core is previously unused a recovery rate of up to 35% of the lipase is achieved.
Experimental Study on Stress Sensitivity of Naturally Fractured Reservoirs
Authors: Tian Ye
Published: October 2014

Stress sensitivity of a naturally fractured reservoir is regarded as pronounced where pressure decrease induced by production is believed to cause significant changes in fracture apertures. Most laboratory investigations suggest that decrease in reservoir pressure would lead to great loss of fracture conductivity and rapid production decline. But till today, no such evidence from the production practices has been documented; on the contrary, there are some reported cases where depletion could potentially maintain even increase the extraction rate.

To solve the discrepancy, experiments were performed when permeability of fractured cores was measured in the process of increasing confining pressure with a constant pore pressure. In production, formation overburden pressure represented by laboratory confining pressure seldom alters and it is the pore pressure that virtually changes. To cope with that, effective stress was applied in the study, where Biot's coefficient for fracture effective stress was theoretically derived and found equal to fracture porosity. Improved evaluation method was then given based on effective stress and stress-dependent permeability correlations. At last, a general evaluation criterion was established where stress sensitivity levels were classified based on Stress-sensitivity Index.

The evaluation of four cores reveals that, the stress-dependence of fracture permeability turns out to be weak if evaluated with a low value of Biot's coefficient directly resulting from small fracture porosity. The study also indicates that fracture is strongly sensitive to confining pressure change in laboratory, but only weakly sensitive to the reservoir pressure change in production, which might reconcile the discrepancy between laboratory study and production practice.
Analysis of Reservoir Pressure Transients: A Wave Physics Approach
Authors: Vitus Ohazuruike Lotanna
Published: October 2014

This research work presents an investigation on a wave physics approach to pressure transient analysis. It is hinged on the view that a pressure transient phenomenon has an associated wave behaviour. A Reservoir pressure transient partial differential equation is developed by importing the pressure transient velocity into the general wave partial differential equation. The equation is then solved using the Boltzmann transformation. The resulting equation presents a mathematical definition of a reservoir pressure transient from a wave physics viewpoint. Spectral and Time Series plots of the model and field data predicted pressure transients are presented. Observation shows a similar trend in behaviour for both plots and discrepancies possibly due to reservoir heterogeneities, noise in data and the likelihood of a counterpressure effect from the restrictions.
Economic Analysis of Solar-Based Thermal Enhanced Oil Recovery
Authors: Anderson Timothy
Published: October 2014

One of the most promising technologies that has been developed to reduce the cost of thermal enhanced oil recovery (TEOR) is solar-based TEOR, where solar energy, instead of natural gas or other fossil fuels, is used to heat the steam or fluid used in TEOR. Previous studies have shown that solar-based TEOR is significantly more environmentally advantageous than traditional TEOR, but none has thoroughly analyzed the economic viability of solar-based TEOR. This study analyzes the cost effectiveness of solar-based TEOR in comparison with traditional TEOR setups in both the early-time (first ∼30 years of production) and late-time (after capital has been paid out) production stages. For the early-time, production data from the Kern River Oil Field was analyzed, as this field has a typical TEOR setup and complete record of steam injection and oil production data over its lifetime. The early-time analysis focused on the effect that optimization of the size of a steam generation setup has on the net present value (NPV) of various solar-based and traditional TEOR setups. The late-time analysis focused on deriving and analyzing a cost model for TEOR in the late-time. The cost model was based on calculating the total energy needed by the system (heating, lift, and maintenance), and then calculating the cost of this energy. The results of the analysis for the early-time and late-time was that a 100% solar setup is the most economical setup in both cases. In the early-time, the analysis showed that 100% solar TEOR consistently had the highest NPV for various scenarios of optimizing the production data. NPV for 100% solar was also the highest except at moderate (∼8%) interest rates. In the late-time, 100% solar was the least costly, as it had the lowest operations and maintenance costs, assuming that these costs were the same for all solar fractions. Further work would include a more rigorous analysis of the maintenance costs and efficiency degradation of TEOR systems in the late-time. This analysis can be carried out once industry data becomes available for maintenance costs and efficiency degradation. This study shows that solar-based TEOR is not only environmentally viable, but also offers substantial economic advantages. Overall, TEOR is a very promising technology that offers an opportunity to make petroleum extraction cleaner, more economical, and more effective.
Precise Modeling of Seismic Responses from Fractured Geological Media
Authors: Golubev Vasily
Published: October 2014

The goal of this article is the investigation of seismic responses from fractured medium through the precise simulation of dynamic processes in heterogeneous elastic media. The base of the method proposed is the direct solution of a system of elastic equations in full 3D case. For describing the geometry of rock massif parallelepided meshes are used. For taking into account the internal mathematical features of the govern system of eqations the grid-characteristic method is used. It allows us to set correct boundary conditions and to describe full set of elastic seismic waves: Rayleigh and Love surface waves and all body waves. In this work the direct modeling of the internal geometry of fractured media is used. All cracks consist of two parallel borders and contain two different saturators: nothing and fluid. In the first case the corrector for setting of day-surface (normal zero-force) condition is used and in the second one – the approach of free gliding is used. With the usage of proposed method the seismic response from a set of 31 vertical geological cracks was obtained. This cluster was placed at 2 km below the day-surface and has fractured density equals to 1 crack \ 100 m. Dynamic wave fields for successive times were obtained and synthetic multi-component seismograms were drawn. The detailed analysis of these results provided interesting facts. The main part of the seismic response from a system of geological cracks consists of complex combination of scattered P-waves and S-waves. The intensity of reflected waves is less than the intensity of propagated waves approximately by the factor of 1,8 for empty cracks and 0,2 for fluid-filled cracks. In general, seismic response from empty cracks is significantly higher than from fluid-filled cracks. The dominant component of seismic response for empty cracks is the S-wave registered on X-component, for fluid-filled cracks – P-wave registered on Z-component. After the arrival of first responces of P ans S-waves following them tail may be clearly identified connected with the crack-crack interaction.
Exploring the Diagnostic Capability of RTA Type Curves
Authors: Mishra Siddharth
Published: October 2014

The cost intensive oil and gas industry dictates the use of techniques which maximize quality information while minimising rig time. Continuous improvement in data acquisition techniques as well as data interpretation methods has been seen in the recent past. One such modern data interpretation method is the "Rate Transient Analysis (RTA)".

Pressure Transient Analysis (PTA) and Rate Transient Analysis (RTA) has been the industry practice for analysis of pressure data. PTA is mainly used for analysis of short-term conventional well test while RTA is used mainly for analysis of pressure and rate data over a long time span. RTA can also be termed as a modern Decline Curve Analysis (DCA) method. Traditional DCA deals with pseudo steady state flow regime and is an empirical / semi empirical method. However RTA deals with transient state flow and the RTA flow equations have analytical origin. RTA is known to give convincing estimates of reservoir parameters when low frequency (weekly or monthly) production data is available. However recently, considerable amount of work has been done to study the applicability of RTA on high frequency well test data.

The utility of PTA for well test interpretation is well known among reservoir engineers and it has a rich literature base. However there exists several "complex scenarios" where conventional PTA interpretation becomes non feasible. Under these scenarios RTA proves to be a promising interpretation tool.

Also a large pool of literature is available on the diagnostic capabilities and sensitivity analysis of the PTA type curves. What is not available in literature is the diagnostic power and sensitivity analysis of RTA diagnostic plots. Owing to the need of RTA as a modern data interpretation tool, this paper discusses the diagnostic capability of RTA type curves by generating synthetic models of complex reservoir systems (numerical well test modelling & simulation) and studying the sensitivity of various reservoir parameters on the RTA type curves.
Assignment for genes encoding the terminal complement components to porcine chromosome
Authors: Anh Khoa , Wimmers K.
Published: October 2014

One of the major goals of the porcine genome projects is building a physical
map. To assign the porcine genes encoding the complement components C6, C7,
C8 and C9 to porcine chromosomes, we used a porcine 7000Rad Radiation Hybrid
panel (IMpRH) containing 118 clones provided by INRA-University of Minnesota.
It resulted in assignment of the porcine C6, C7 and C9 genes to chromosome
16q1.4, the porcine C8A and C8B genes to chromosome 6q3.1-q3.5 as well as the
porcine C8G gene lonely to chromosome 1q2.13.
The effect of parental genotype and parity number on pigs litter size
Authors: Lukac D. , Vidovic V. , Visnjic V. , Krnjaic J. , Sevic R.
Published: October 2014

The aim of this study was to investigate the effect of parental genotype and
parity number on the litter size properties of sows (number of live born,
stillborn and weaned piglets). The investigation was conducted on a farm in
Vojvodina. The analysis included 65535 litters that originated from five
genotypes of dams (sows with unknown origin, n = 20980; Yorkshire, n = 3189;
Landrace, n = 22426; F1(YxL), n = 14251; F1(LxY), n = 4689) and five
genotypes of sires (Yorkshire, n = 21641; Landrace, n = 26623; Pietrain, n =
485; Duroc, n = 13463; Hampshire, n = 3323). Based on the obtained results
it can be concluded that the genotypes of the dams had statistically
significant (p<0.01) influence on the observed litters properties. Landrace
sows achieved the highest average number of born alive piglets (10.12) with
a statistically significant difference (p<0.01) compared with sows of other
genotypes. The observed effect of sire genotype on litter size properties
was statistically significant (p<0.01), where the terminal genotypes were
superior when it comes to the number of live born and weaned piglets.
Regression analysis of dependence between parity and litter size recorded
positive regression coefficients: number of live born (b = 0.007), stillborn
(b = 0.09) and weaned piglets (b = 0.07). Influence of parity on the
observed traits of litter size was highly statistically significant
(p<0.01).
The effect of genotype and lactation on yield and physicochemical properties of ewe milk
Authors: Ilic Z.Z. , Jevtic-Vukmirovic A. , Petrovic Caro , Petrovic M.P. , Petrovic M.M. , Ristanovic B. , Stolic N.
Published: October 2014

Two genotype of sheep have been utilized in the conduct of the experiment
composed of 60 ewes from Pirot x Virtemberg as genotype 1 and 60 ewes of
Improved Pirot as genotype 2. All the ewes were reared under identical
conditions and without any differences in nutrition and management during the
whole period under study. The collection of Milk sampling was done in morning
and evening during periods (1, 2, 3) of lactation duration. The average
lactation duration and average total milk of the two genotypes were very
close and has a minimal difference of 0.467 day and 1.562 kg, in favor of
genotype 2. The differences between genotypes were not significant (P>0,05).
Regarding physical and chemical properties of milk for both genotypes, the
difference were very minimal such as follows; viscosity Pa x s - 0.006,
electrical conductivity ? - 0.018, density kg/m3 -0,001, freezing, t 0C -
0.013, LD number - 0.028 total solids, % - 0.014, fat,% - 0,026, protein,% -
0.085, lactose,% - 0.038, ash,% - 0,021, acidity, 0SH - 0.209. The results
indicated that the properties of milk for both genotypes were very near to
each other. It can be interpreted that the breeds utilized in the experiment
were comparable due to similar characteristics perhaps. The effect of
genotype was very significant only for the % protein of the milk. The
lactation periods were highly significant in all physical and chemical
properties of milk.
Forage quality and energy content of perennial legume-grass mixtures at three level of n fertilization
Authors: Bijelic Z. , Tomic Z. , Ruzic-Muslic D. , Krnjaja V. , Mandic V. , Vuckovic S. , Niksic D.
Published: October 2014

The aim of this study was to investigate fodder quality and nutritive value
of different grass-legumes mixtures influenced by various level of N
fertilization. Studied factors had an impact only on the content of crude
protein (CP), crude protein yield (CPY) and nitrate content in the forage.
The level of N fertilizer showed a highly significant and positive impact on
the CP and nitrate content. Treatment with 210 kg N ha-1 is characterized by
the highest content of CP and nitrate of 189.7 g kg-1 DM and 2524 ppm,
respectively, and the highest protein yield of 1.95 t ha-1. The value of
nitrate in the forage does not exceed the limit that is considered hazardous
to the health of animals. Energy value of forage obtained from the grasslands
of ME ?7.75 and NEL?4.32 MJ kg-1 DM is lower than values obtained in other
studies.
Practical Differences Among Aggregate-Level Conditional Status Metrics
Authors: Castellano Katherine E. , Ho Andrew D.
Published: October 2014

Aggregate-level conditional status metrics (ACSMs) describe the status of a group by referencing current performance to expectations given past scores. This article provides a framework for these metrics, classifying them by aggregation function (mean or median), regression approach (linear mean and nonlinear quantile), and the scale that supports interpretations (percentile rank and score scale), among other factors. This study addresses the question “how different are these ACSMs?” in three ways. First, using simulated data, it evaluates how well each model recovers its respective parameters. Second, using both simulated and empirical data, it illustrates practical differences among ACSMs in terms of pairwise rank differences incurred by switching between metrics. Third, it ranks ACSMs in terms of their robustness under scale transformations. The results consistently show that choices between mean- and median-based metrics lead to more substantial differences than choices between fixed- and random-effects or linear mean and nonlinear quantile regression. The findings set expectations for cross-metric comparability in realistic data scenarios.
A comparative study between single layer versus double layer closure in ileostomy reversal
Authors: Mittal Sushil , Singh Harnam , Singh Gurpreet , Munghate Anand , Garg Anjna , Yadav Manish
Published: October 2014

Background:  Ileal perforation peritonitis is a common surgical emergency in the Indian subcontinent and in tropical countries. Formation of an intestinal stoma is frequently a component of surgical intervention for diseases of the small bowel. The technique for stoma reversal has remained controversial is the use of either one or two layers of sutures for anastomosis.Methods:  Sixty patients with ileostomy were taken for study .These patients divided in two groups A and B, 30 each. These patients were taken up for ileostomy closure in single layer (group A) (n-30) &double layer (group B) (n-30). Results: 60 Patients of ileostomy were studied, divided equally in 2 groups, A decreased intra operative time was seen in Group A when compared with Group B with no any significant comparative complication in these groups. Conclusion: Two-layer anastomosis for ileostomy closure offers no definite advantage over single layer anastomosis in terms of postoperative leak and other complications. Single layer ileostomy closure technique is safe, easy to perform and simply to taught. Considering duration of the anastomosis procedure and medical expenses single-layer intestinal anastomosis may prove the choice of procedure for most of the surgeons. DOI: http://dx.doi.org/10.3126/ajms.v6i2.10080Asian Journal of Medical Sciences Vol.6(2) 2015 44-47
Physician’s dilemma in treating Acinetobacter baumanii: A combination of art and science
Authors: Khadanga Sagar , Tadepalli Karuna , Thatoi Pravat Kumar , Mohanty Rina , Mohapatra Namita
Published: October 2014

Acinetobacter are gram negative coccobacilli and ubiquitous in nature1. Quiet frequently they are recovered from inpatients who are hospitalized for prolonged illness and often multiple times.  Although originally considered to be a low grade opportunistic pathogen Acinetobacter species has emerged to be one of the common nosocomial pathogen. These isolates are often MDR1. It still remains a physician’s dilemma whether to treat or not such isolates, considering them pathological or commmensals.  In one of our case it was isolated as a commensal and the patient did not require any antibiotic. On the hand the second case succumbed just after we started the susceptible antibiotic. DOI: http://dx.doi.org/10.3126/ajms.v6i2.10405Asian Journal of Medical Sciences Vol.6(2) 2015 105-107
Four semesters of medical humanities at the Xavier University School of Medicine, Aruba
Authors: Shankar P. R.
Published: October 2014

Introduction: Medical humanities is using subjects traditionally known as the humanities for specific purposes in medical education.Methods: In this report the author shares his experience of facilitating a module for four semesters at the Xavier University School of Medicine, Aruba.Results: The sessions were conducted in small groups and used case scenarios, role-plays, paintings and debates among other modalities to explore various aspects of medical humanities.Conclusion: The author has been successful in conducting medical humanities sessions in an offshore Caribbean medical school. DOI: http://dx.doi.org/10.3126/ajms.v6i2.10455Asian Journal of Medical Sciences Vol.6(2) 2015 124-128