bluuebunny/crossref_metadata_2025_split huggingface dataset:
Complexity in Storm Choke Operation: Caspian Sea Experience
Authors: Faiz Wan Mohd , Fablillah Wan Mohd , Rahman Hazrina A. , Melayev Arslan , Ali Zulkifli , Atajanov Merdan , Baijuri Asri 
Published: October 2015

Abstract
The control line for CZ-5 well became plugged due to contaminants in the hydraulic control line fluid. As a result, CZ-5 well remained shut in with the deferment of 2000 bbls/day. Remedial solution was planned and it involved the installation of subsurface controlled safety valve or storm choke. Since the failed subsurface safety valve is in the jammed close position, the mechanism to lock open the flapper and to keep the valve open permanently must be done before the installion of the storm choke. The special tubing with smaller ID, or better known as straddle, was then set across the flapper and hang inside. Without the realization that the pressure setting of the storm choke calculation would become complicated with the smaller tubing/straddle inside, the closing and opening pressure were determined based on NODAL Analysis.
The flapper of CZ-5 ScSSV was also expected to dislocate severely and a special flip open tool is designed to position the dislocated flapper back to its housing. Flapper flip open tool is the in-house designed tool that can be run using slickline for 2 7/8″, 3½″ or 4½″ tubing. This unique tool has enabled many lock open jobs in our operation and it has totally eliminated the need for flapper milling.
The unexpected outcome of valve closing pressure and operating speed was experienced for a few times after the installation, causing the multiple intervention work to retrieve and to re-set the storm choke with different setting pressure. Though all minimum data required to design the storm choke for CZ-5 has been rightly considered, its performance is still very unpredictable and shocking. Determined to make the valve to work properly for a desired certain period of time, all operational data were gathered and studied. During the last rectification attempt, the storm choke has finally worked as intended.
The paper will describe more on the challenges encountered during the set-up of flip open tool and modified straddle, the engineering design of both of them and the storm choke unique behaviour from the experience at Caspian Sea Operation.
History of History Match in Azeri Field
Authors: Ibrahimov Turan 
Published: October 2015

Abstract
Modern reservoir development could not happen without building and using 3-phase 3-D simulation models and predicting the future performance of the field using powerful computer technologies. Long term production and injection profile forecasts for the Azeri field have been carried out through usage of simulation models from 2001. Since production from 2005 Azeri models have been history matched on an annual basis. While matching the model data to the actual field observed data, surveillance and performance learnings have been an integral part of the process in order to obtain representative and satisfactory results.
In the current work, the challenges and problems faced, as well as the success of the history match process for the Azeri field are described. Along with discussion of applied techniques and obtained results, recommendations on matching complex reservoir simulation models based on several years experience of history matching process in the Azeri field are offered.
Practical Aspects of Modeling of Water Coning in Carbonate Reservoirs
Authors: Ilya Breslavich , Diana Shigapova 
Published: October 2015

Abstract
An important step in the design development of carbonate reservoirs is the understanding and simulation of well flooding mechanism particularly water coning. The significance of coning is due to the fact that an incorrect account of the flooding mechanism may lead to the following negative consequences: overstatement of the target oil production inaccurate forecast of remaining reserves and the mechanism of their production, selection of unsuitable well-workover methods and other negative results.
The paper discusses different approaches to the water coning simulation: local grid refinement; non-neighbour connection with the bottom water; water flooding through a vertical fracture using method of allocating drains; use of additional completions; use of the non-diagonal permeability tensor; the verticallu directed change in rock permeability and pore volume with pressure decreasing; dual porosity model.
It is recommended that in case of the typical orthogonal grid, local grid refinement should be used for hydrodynamic model water coning. It is possible to obtain appropriate results using dual porosity method and non- neighbour connections, but these methods have bad forecasting power.
If water coning were not repeated then: oil production total would increase up to 10-15% (for a 5 year forecast) or up to 5-35% (for a 25 year forecast);water-free period well production would be prolonged;oil production rate would increase.
The implementation of the recommendations made it possible to optimize new wells targeting and well operation, which provided an increase of water-free periods of the wells for the Urals-Volga region oilfields.
Seismic Virtual Reality: High-Fidelity Finite Difference Modelling of the Azeri-Chirag-Gunashi Field
Authors: Crosby Alistair , Jackson Joseph 
Published: October 2015

Abstract
Seismic finite-difference (FD) modelling is a term that describes the propagation, recording and processing of virtual seismic waves through a computational model. It is an important tool for addressing a wide variety of questions related to seismic acquisition, processing and interpretation for the simple reason that seismic images are best assessed when the subsurface is well defined. FD modelling is particularly useful when data is to be acquired over targets that present complex imaging challenges, such as those underneath salt bodies or a highly heterogeneous shallow section (e.g. Regone, 2007; Kabir et al., 2009).
This paper discusses the application of finite-difference modelling to the central part of the Azeri-Chirag-Gunashli (ACG) field offshore Azerbaijan (Figure 1) and builds on the earlier work of Crosby et al. (2014). ACG is a steeply-dipping NW-SE oriented anticline approximately 10 km wide and 50 km long. The targets reside within a series of Late Miocene stacked braided fluvio-deltaic sequences with intervening shales (e.g. Reynolds et al. 1998). Imaging is complicated by the presence of steep dips on the flanks and a highly heterogeneous shallow section including mud volcanoes, complex faults and shallow gas bodies at the crest. It is clear that any model must capture these details if it is to be useful.
Historically, the principal limitations of seismic modelling have not just been computational, but have also resulted from the level of detail in the model itself. Models have either been constructed manually using a set of interpreted framework surfaces or derive their properties from existing seismic images (e.g. Regone, 2007; Kabir et al,. 2009). In the first case, reflectivity is often too simplistic; whilst in the second case artefacts and bandwidth limitations are introduced as truth into the model. A better approach is to simulate geological features directly when building the model. Two recent papers (Etgen and L'Heureux, 2013; L'Heureux and Etgen, 2013) present an automatic, probabilistic method for generating stochastic stratigraphy using a set of facies templates, and then morphing the resultant layering to structure. This approach can generate geologically realistic models to arbitrary levels of detail. Here we show the result of applying this method to Central Azeri, together with some preliminary synthetic seismic images.
Composition-Transient Analysis in Shale-Gas Reservoirs With Consideration of Multicomponent Adsorption
Authors: Li Daolun , Zhang Longjun , Wang John Yilin , Lu Detang 
Published: October 2015

Summary
Rate-transient analysis (RTA) has been widely studied to evaluate the shale-gas-reservoir parameters. However, few attempts have been made on composition-transient analysis (CTA) to evaluate formation properties about shale-gas reservoirs. In this work, we proposed a new CTA method and provided a physical interpretation of CTA.
We first established a compositional simulator incorporating slip flow and extended Langmuir (EL) isotherm with multiple components. Then, a fully implicit iterative numerical solution of the nonlinear model was developed on the basis of perpendicular-bisection (PEBI) gridding. Finally, we defined the composition change and derivative as functions of pressure change and derivative.
One important finding is that the free-gas composition is obviously different from the desorped-gas composition because of the different desorption capacity of different gas components. This contributes to the changes of composition of the produced gas over time.
Another finding is that ultimate adsorption capacity determined the value of the composition change and composition derivative, which made adsorption content be easily determined by CTA. If the flow regimes are defined by composition, several flow regimes could be identified from the composition change and the composition derivative, which may not exist on the curves of pressure change and pressure derivative.
The findings in this study could provide a more-effective and practicable way to identify reservoir parameters than the traditional well-test method. Furthermore, gas compositions could be measured at the wellhead, which makes the CTA feasible in practice.
Risk Factors of Cardiovascular Diseases in HIV/AIDS Patients on HAART
Authors: Nsagha Dickson Shey , Assob Jules Clement Nguedia , Njunda Anna Longdoh , Tanue Elvis Asangbeng , Kibu Odette Dzemo , Ayima Charlotte Wenze , Ngowe Marcelin Ngowe 
Published: October 2015

Background :The introduction and widespread use of combination antiretroviral therapy referred to as highly active antiretroviral therapy (HAART) in the mid 1990’s, has led HIV-infected individuals to experience a dramatic decline in immunodeficiency-related events and death. There is growing concern on metabolic complications associated with HIV and HAART which may increase cardiovascular risk and disease. The aim of this study was to investigate the cardiovascular risk profile of HIV/AIDS patients receiving HAART and those not receiving HAART at HIV/AIDS treatment centres in the South West Region of Cameroon.Methods :Consenting participants, who had been receiving HAART, were compared with HAART naive participants. A questionnaire was administered; anthropometric and blood pressure measurements were recorded under standard conditions. Blood samples were obtained for the determination of plasma glucose and lipid levels.Results :Two hundred and fifteen participants were recruited, 160 (74.4%) were on HAART and 55 (25.6%) were HAART naive. Among the individual lipid abnormalities, increased total cholesterol was the most prevalent (40.0%). Participants on HAART were significantly about 8 times at risk of developing hypercholesterolemia when compared to the HAART inexperienced group (OR 8.17; 95% CI: 3.31-20.14; p<0.001). Hypertension had a prevalence of 25.6% (95% CI: 15.3%-35.9%) and was about 2 times significantly higher in the HAART treated than the HAART untreated group (p=0.033). The prevalence of low HDL-c was significantly higher in males (24.1%) compared to females (11.2%) (p=0.0196). Many females (27.3%) were obese compared to males (7.4%) (p=0.0043). HAART use and treatment duration of more than five years were significantly associated with higher prevalence of CVD risk factors.Conclusion :HAART treatment was associated with significantly higher prevalence of hypercholesterolemia, increased LDL-c and hypertension, hence the risk of cardiovascular diseases.
Folkloric uses of <i>Jatropha gossypifolia</i> in emesis and gut motility disorders: Pharmacological validation
Authors: Hussain Musaddique , Raza Shahid Masood , Majeed Abdul 
Published: October 2015

<p class="Abstract"><em>Jatropha gossypifolia</em> is used in folkloric system to manage emesis and gastrointestinal motility disorders such as constipation and diarrhea. The present study was undertaken to provide pharmacological evidences for these folkloric uses by <em>in vivo</em> and <em>in vitro</em> experimental setting. Ethanolic extract of <em>J. gossypifolia</em> showed the significant antiemetic potential (p&lt;0.05) against different emetogenic stimuli, when compared with chlorpromazine. The extract (0.01-1.0 mg/mL) on application to isolated rabbit jejunum preparation exerted spasmogenic effect, followed by the spasmolytic effect (3-10 mg/mL). In the presence of atropine, spasmogenic effect was blocked while spasmolytic effect was emerged, suggesting the involvement of muscarinic receptor activation.<em> J. gossypifolia</em> caused relaxation of high K<sup>+ </sup>(80 mM)-induced contraction and shifted the Ca<sup>2+ </sup>concentration-response curve to the right in a manner similar to verapamil, thus conforming its Ca<sup>2+</sup>-channel blocking activity. These findings provide pharmacological validation for the presence of antiemetic and gut modulator (spasmogenic and spasmolytic) activates, validating its folkloric uses.</p><p> </p>
Studying antimicrobial-induced morphostructural damage of bacteria by Scanning Electron Microscope
Authors: Shukla Shruti 
Published: October 2015

<p>In this investigation, a scanning electron microscopy (SEM) method was used to examine the morphostructural changes in bacterial cells induced by antimicrobial agents. SEM-based visual approach is referred the study of bacterial cells and their physiological consequences when affected by antibiotics or antibacterial agents permitting the observation of characteristic morphological defects of cell wall, and provides valuable insights into processes involved in bacterial cell death. This experiment visualized various step-by-step techniques used in the slide preparation of bacterial cells treated with specific antimicrobial agent for analyzing the morphological alterations such as increase of cell wall roughness, cell disruption, cell swelling and lysed cell formation due to loss of intracellular material using SEM analysis when compared with untreated normal cells as a control. The SEM approach used in this visual experiment may analyze the antimicrobial effect of any commercially known or new compounds in a very conducive manner.</p><p><strong>Video Clips</strong></p><p><a href="https://youtube.com/v/WQtp1fV3Zuc">Culturing of bacteria</a> 2 min 54 sec</p><p><a href="https://youtube.com/v/U3RUXFWDgtw">Treatment of bacterial culture by antimicrobials</a> 4 min 21 sec</p><p><a href="https://youtube.com/v/AgeuJg_afeE">Sample pre-treatment</a> 4 min 23 sec</p><p><a href="https://youtube.com/v/SI7PU0Uw7Bo">Microscopic slide preparation</a> 9 min 27 sec</p><p><a href="https://youtube.com/v/ilX91i4afVM">Critical point drying and ion sputter coating of slides</a> 5 min 52 sec</p><p><a href="https://youtube.com/v/iOp9Mi_O3KE">Scanning Electron Microscopic analysis of coated slides</a> 4 min 18 sec</p>
Phase Behavior of CO2-Rich Live Oil Samples From High Pressure Reservoirs
Authors: Cardoso F. M. R. , Viegas C. C. B. , Fleming F. P. , Freitas R. S. , Vieira A. J. M. , Rosa P. T. V. , Carrier H. , Daridon J-L 
Published: October 2015

Abstract
Oil production activities are strongly dependent on the phase behavior of produced fluids. Among the usual phase changes, those that lead to the appearance of one or more solid phases are among the main focus of flow assurance studies. The flocculation of asphaltenes, the heaviest and most polar fraction of crude oil, usually occurs downhole at high pressure and temperature conditions. To assess the live oil phase behavior, four samples were evaluated using a high pressure microscope (HPM). The results obtained from HPM isothermal depressurization experiments revealed the existence of four different phase behavior patterns, suggesting the existence of a liquid-liquid equilibrium at elevated temperatures and pressures in CO2-rich fluids. The pictures and videos acquired from the HPM showed that the the second liquid phase droplets hardly coalesce, suggesting either a low interfacial tension between the two coexisting liquids or the presence of a natural surfactant at the interface. This unusual phase behaviour is not promptly antecipated by thermodynamic simulations, rendering unavoidable the experimental characterization of live oil samples. In light of this new scenario, techniques that only evaluate the appearance of a different phase like the solid detection system (SDS) analysis based on the light scattering in the NIR region are not conclusive when used independently. HPM analysis or the combination of different techniques like SDS and isobaric filtration, become indispensable in order to assess solids formation in live oil samples above their bubble points.
Identification While Drilling of Drill-String Dynamic Model for Diagnostics and Optimization
Authors: Veltman A. , Stulemeijer I. , Catena A. 
Published: October 2015

The main objective of this paper is to improve drilling performance by obtaining a representative dynamic model of a drilling system: top-drive, controls, drill-pipe and bottom hole assembly (BHA). High-fidelity simulations with a representative analytical model are a goal necessary to optimize controller-settings while or before drilling. Goals such as ‘lowest sensitivity to torque disturbance at the bit’ or ‘best reaction to stick-slip events’ can be pursued while guarding stability limits of the full system.
The method is based on spectral correlation between at least two signals: a broad-band signal with frequencies in the relevant band (0.05Hz to 5Hz) added to the top-drive's torque command and second: the measured top-drive speed. Mathematical tools from seismic exploration and control-theory are used to determine key parameters of this closed-loop system. Correlation techniques allow identification even during high background noise generated by varying friction and bit-cutting forces in most cases.
Experimental results from a number of wells in Oman, Malaysia, and USA show that the transmission-line based model can be accurately matched at all depths. Besides the eigen frequency, a number of higher modes of the drill sting are found, including their effective damping. The identified response agrees with expected response based on pre-computed mechanical drill-string composition parameters. In one well a substantial increase in friction and bit-inertia was identified at certain depth intervals. Logs taken afterwards showed wash-outs at these depths, suggesting diagnostic potential of this estimation technique.
Novel is the ability to identify a dynamic drill string model without advance information, yielding auto-tuning capability for most stick-slip mitigation technologies such as ‘softtorque’. A very welcome benefit is the estimation of the string's characteristic impedance and length but also internal and external friction components along the string and at the bit. Traditionally, these damping terms are often neglected, exaggerated or set to an agreeable value to limit the amplitude of resonances in the calculated model. The presented identification method generates updates of these different damping terms every ten minutes or so. During drilling several wells, the found damping terms are spread over a wide range due to mud-pipe, pipe-wall interaction and bit-formation variability. We conclude that damping terms cannot be ignored without severely compromising the dynamic fidelity of the model. Future diagnostic and drilling optimization tools may be based on this new way of harvesting information from down hole.
Inlet Effects on Flow Regimes in Downwards Inclined Pipes
Authors: Diaz M. , Nydal O. J. 
Published: October 2015

Abstract
Multiphase flow models require models for each flow regime, and models for the transition between the regimes. Dynamic slug flow models also aim at predicting the slug formation and decay as well as the statistical distributions of lengths, frequencies and velocities.
Previous experimental studies have demonstrated the existence of a region in the flow regime map where both stratified and slug flow can be stable flow regimes, typically for low pressure systems. This phenomenon can also lead to large flow transients at the point of stratified-slug transition, with excess liquid transported out of the pipeline in the form of a large liquid slug, with length depending on the pipe geometry and length.
This phenomenon is experimentally investigated for 3 degrees downwards air-water flow in a 16 m long pipe of 60 mm internal diameter. An inlet section of 3 m long was configured at 14.6 degree downward and 25 degrees upward, in order to generate either stratified flow or slug flow. The statistical analysis of the slug frequency and length distribution was examined, and the results show a premature stratified-slug transition when slug flow is set as inlet condition. The slug formation and evolution along the pipeline was studied by tracking the slugs at different locations in the downward pipe. Results were compared against flow patterns predicted by a commercial simulator.
Simplified Hydraulic Design Methodology for a Subsea Inline Oil-Water Pipe Separator
Authors: Stanko M. , Golan M. 
Published: October 2015

This paper introduces and demonstrates a simplified hydraulic design methodology of an oil water pipe inline separator for subsea deployment in a hydrocarbon production system. The oilwater pipe separator consists of an inclined tube section with evenly spaced tapping points at the bottom from where water rich streams are withdrawn.
Two main steps of the hydraulic design process are discussed in detail and demonstrated using numerical modeling, synthetic and literature data. The steps are: 1) assessing the potential production gain of installing the inline separator in a subsea production system and identifying the required separator performance and 2) Quantifying the separation performance of a single tapping and predicting the separation performance of a group of tapping points.
The results show that the proposed methodology can be successfully used to: Evaluate the potential gain in oil production when installing a subsea oilwater separator; Obtain a rough approximation of the required performance of the separator (required drained water flow rate and associated oil content) to achieve a given desired production increase; and estimate the approximate number of tapping points required and their operating conditions.
The concepts and methodology discussed in the present work can be easily generalized to other subsea separation techniques. They allow to determine the feasibility of installing a separator on a subsea production system and a concept to measure and predict the performance of separation techniques based on tapping.