bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of diesel engine for low exhaust emissions with different combustion chambers
Authors: Ghodke Pundlik , Suryawanshi Jiwak
Published: December 2015

Upcoming stringent Euro-6 emission regulations for passenger vehicle better
fuel economy, low cost are the key challenges for engine development. In this
paper, 2.2L, multi cylinder diesel engine have been tested for four different
piston bowls designed for compression ratio of CR 15.5 to improve in cylinder
performance and reduce emissions. These combustion chambers were verified in
CFD at two full load points. 14 mode points have been derived using vehicle
model run in AVL CRUISE software as per NEDC cycle based on time weightage
factor. Base engine with compression ratio CR16.5 for full load performance
and 14-mode points on Engine test bench was taken as reference for
comparison. The bowl with flat face on bottom corner has shown reduction 25%
and 12 % NOx emissions at 1500 and 3750 rpm full load points at same level of
Soot emissions. Three piston bowls were tested for full load performance and
14 mode points on engine test bench and combustion chamber ?C? has shown
improvement in thermal efficiency by 0.8%. Combinations of cooled EGR and
combustion chamber ?C? with geometrical changes in engine have reduced
exhaust NOx, soot and CO emissions by 22%, 9 % and 64 % as compared to base
engine at 14 mode points on engine test bench.
Techno-economic analysis of stand-alone photovoltaic/wind/battery/hydrogen systems for very small-scale applications
Authors: Stojkovic Sasa , Bakic Vukman
Published: December 2015

The paper presents the results of a technical and economic analysis of three
stand-alone hybrid power systems based on renewable energy sources which
supply a specific group of low-power consumers. This particular case includes
measuring sensors and obstacle lights on a meteorological mast for wind
measurements requiring an uninterrupted power supply in cold climate
conditions. Although these low-power (100 W) measuring sensors and obstacle
lights use little energy, their energy consumption is not the same as the
available solar energy obtained on a daily or seasonal basis. In the paper,
complementarity of renewable energy sources was analysed, as well as one of
short-term lead-acid battery-based storage and seasonal, hydrogen-based
(electrolyser, H2 tank, and fuel cells) storage. These relatively complex
power systems were proposed earlier for high-power consumers only, while this
study specifically highlights the role of the hydrogen system for supplying
low-power consumers. The analysis employed a numerical simulation method
using the HOMER software tool. The results of the analysis suggest that solar
and wind-solar systems, which involve meteorological conditions as referred
to in this paper, include a relatively large number of lead-acid batteries.
Additionally, the analysis suggests that the use of hydrogen power systems
for supplying low power-consumers is entirely justifiable, as it
significantly reduces the number of batteries (two at minimum in this
particular case). It was shown that the increase in costs induced by the
hydrogen system is acceptable.
Aerodynamic shape optimization of guided missile based on wind tunnel testing and computational fluid dynamics simulation
Authors: Ocokoljic Goran , Rasuo Bosko , Bengin Aleksandar
Published: December 2015

This paper presents modification of the existing guided missile which was done by replacing the existing front part with the new five, while the rear part of the missile with rocket motor and missile thrust vector control system remains the same. The shape of all improved front parts is completely different from the original one. Modification was performed based on required aerodynamic coefficients for the existing guided missile. The preliminary aerodynamic configurations of the improved missile front parts were designed based on theoretical and computational fluid dynamics simulations. All aerodynamic configurations were tested in the T-35 wind tunnel at the Military Technical Institute in order to determine the final geometry of the new front parts. The 3-D Reynolds averaged Navier-Stokes numerical simulations were carried out to predict the aerodynamic loads of the missile based on the finite volume method. Experimental results of the axial force, normal force, and pitching moment coefficients are presented. The computational results of the aerodynamic loads of a guided missile model are also given, and agreed well with.
New non-orthogonality treatment for atmospheric boundary layer flow simulation above highly non-uniform terrains
Authors: Mirkov Nikola , Stevanovic Zarko
Published: December 2015

In this paper we validate an improved finite volume approximation of Reynolds
Averaged Navier-Stokes equations for simulation of wind flows in body-fitted
grids generated by algebraic extrusion from digital terrain elevation data,
proposed in N. Mirkov et. al. J. Comput. Phys. 287, 18-45(2015), [1]. The
approach is based on second-order accurate finite volume method with
collocated variable arrangement and pressure-velocity coupling trough SIMPLE
algorithm. The main objective is the attenuation of spurious pressure field
oscillations in regions with discontinuity in grid line slopes, as
encountered in grids representing highly non-uniform terrains. Moreover, the
approach relaxes the need for grid generation based on elliptic PDEs or grid
smoothing by applying fixed point iterations (i.e. Gauss-Seidel) to initial
grid node positions resulting from algebraic grid generators. Drawbacks of
previous approaches which ignored treatment of finite volume grid cell cases
with intersection point offset in non-orthogonality corrections are removed.
Application to real-life wind farm project at Dobric (Srvljig, Serbia) is
used to assess the effectiveness of the method. The results validate the view
in which accurate discretization of governing equations play more important
role than the choice of turbulence modelling closures.
Influence of high injection pressure on fuel injection perfomances and diesel engine worcking process
Authors: Shatrov Mikhail , Golubkov Leonid , Dunin Andrey , Yakovenko Andrey , Dushkin Pavel
Published: December 2015

In MADI, investigations are carried out in the field of diesel engine working
process perfection for complying with prospective ecological standards such
as Euro-6 and Tier-4. The article describes the results of the first stage of
experimental research of the influence of injection pressure up to 3000 bar
on working processes of diesel engine and its fuel system. Justification of
the design of a Common Rail injector for fuel injection under 3000 bar
pressure is presented. The influence of raising injection pressure (up to
3000 bar) on the fuel spray propagation dynamics is demonstrated. The
combined influence of injection pressure (up to 3000 bar) and air boost
pressure on fuel spray propagation dynamics is shown, including on engine
emission and noise.
Pregnancy Outcomes in Youth With Type 2 Diabetes: The TODAY Study Experience
Authors: Klingensmith Georgeanna J. , Pyle Laura , Nadeau Kristen J. , Barbour Linda A. , Goland Robin S. , Willi Steven M. , Linder Barbara , White Neil H. ,   for the TODAY Study Group
Published: December 2015

OBJECTIVE

We evaluated pregnancy outcomes, maternal and fetal/neonatal, during the Treatment Options for type 2 Diabetes in Adolescents and Youth (TODAY) study.

RESEARCH DESIGN AND METHODS

The TODAY study was a randomized controlled trial comparing three treatment options for youth with type 2 diabetes. Informed consent included the requirement for contraception, including abstinence; this was reinforced at each visit. Following informed consent, self-reported data related to the mother’s prenatal care and delivery and the infant’s health were retrospectively collected. When permitted, maternal medical records and infant birth records were reviewed.

RESULTS

Of the 452 enrolled female participants, 46 (10.2%) had 63 pregnancies. Despite continued emphasis on adequate contraception, only 4.8% of the pregnant participants reported using contraception prior to pregnancy. The mean age at first pregnancy was 18.4 years; the mean diabetes duration was 3.17 years. Seven pregnancies were electively terminated; three pregnancies had no data reported. Of the remaining 53 pregnancies, 5 (9.4%) resulted in early pregnancy loss, and 7 (13%) resulted in loss with inadequate pregnancy duration data. Two pregnancies ended in stillbirth, at 27 and 37 weeks, and 39 ended with a live-born infant. Of the live-born infants, six (15.4%) were preterm and eight (20.5%) had a major congenital anomaly.

CONCLUSIONS

Despite diabetes-specific information recommending birth control and the avoidance of pregnancy, 10% of the study participants became pregnant. Pregnancies in youth with type 2 diabetes may be especially prone to result in congenital anomalies. Reasons for the high rate of congenital anomalies are uncertain, but may include poor metabolic control and extreme obesity.
Effects of Handedness on the Hand Grip Strength Asymmetry in Turkish Athletes
Authors: Ziyagil M. Akif , Gürsoy Recep , Dane Şenol , Türkmen Mehmet , Çebi Mehmet
Published: December 2015

This study aims to evaluate hand grip strength with respect to handedness in Turkish male and female athletes. Data were collected from 268 female and 1,234 male participants. There was no significant difference between right- and left-hand grip strength only in male left-handers. Right-hand grip strength was greater than left-hand grip strength without regard to handedness in both genders, but left-handed athletes had stronger non-dominant hands.
The Power of Micro Urban Structures, Theory of EEPGC - the Micro Urban Energy Distribution Model as a Planning Tool for Sustainable City Development
Authors: Tkáč Štefan
Published: December 2015

To achieve the smart growth and equitable development in the region, urban planners should consider also lateral energies represented by the energy urban models like further proposed EEPGC focused on energy distribution via connections among micro-urban structures, their onsite renewable resources and the perception of micro-urban structures as decentralized energy carriers based on pre industrialized era. These structures are still variously bound when part of greater patterns. After the industrial revolution the main traded goods became energy in its various forms. The EEPGC is focused on sustainable energy transportation distances between the villages and the city, described by the virtual “energy circles”. This more human scale urbanization, boost the economy in micro-urban areas, rising along with clean energy available in situ that surely gives a different perspective to human quality of life in contrast to overcrowded multicultural mega-urban structures facing generations of problems and struggling to survive as a whole.
Research of Rainwater Infiltration in Eastern Slovakia
Authors: Hudáková Gabriela , Zeleňáková Martina , Tometz Ladislav
Published: December 2015

Today precipitation water in the majority of built up and other sealed surface areas no longer reach the water circulation system via natural routes. This can lead to long-term changes to the soil and water resources, reduce the natural local regeneration of the groundwater and have effects on the chemical and biological conditions above and below the ground surface. Reasonable rainwater management leads to maintain or recover a sound and sustainable water cycle. The purpose of this paper is to present objectives and monitoring of a drainage project in Eastern Slovakia, in Kosice city. The paper focuses on percolation facilities in the research area of campus of Technical University and measurements connected with rainwater infiltration.
Influence of Building Material Solution of Structures to Effectiveness of Real Estate Development
Authors: Somorová Viera
Published: December 2015

Real estate development is in its essence the development process characterized by a considerable dynamics. The purpose of the development process is the creation of buildings which can be either rented by future unknown users or sold in the real estate market. A first part of the paper is dedicated to the analysis of the parameters of buildings solutions considering the future operating costs in a phase of designing.

Material solution of external structures is a main factor not only in determining the future operating costs but also in achieving the subsequent economic effectiveness of the real estate development. To determine the relationship between economic efficiency criteria and determine the optimal material variant of building constructions for the specific example is the aim of the second part of paper.
Effect of Selected Alternative Fuels and Raw Materials on the Cement Clinker Quality
Authors: Strigáč Július
Published: December 2015

The article deals with the study of the effects of alternative fuels and raw materials on the cement clinker quality. The clinker quality was expressed by the content of two principal minerals alite C3S and belite C2S. The additions of alternative fuels ashes and raw materials, in principle, always increased the belite content and conversely reduced the amount of alite. The alternative fuels with high ash content were used such as the meat-bone meal, sewage sludge from sewage treatment plants and paper sludge and the used alternative raw materials were metallurgical slags - granulated blastfurnace slag, air cooled blastfurnace slag and demetallized steel slag, fluidized bed combustion fly ash and waste glass. Meat-bone meal, sewage sludge from sewage treatment plants and paper sludge were evaluated as moderately suitable alternative fuels which can be added in the amounts of 2.8 wt. % addition of meat-bone meals ash, 3.64 wt. % addition of sewage sludge ash and 3.8 wt. % addition of paper sludge ash to the cement raw mixture. Demetallised steel slag is suitable for production of special sulphate resistant cement clinker for CEM I –SR cement with addition up to 5 wt. %. Granulated blastfurnace slag is a suitable alternative raw material with addition 4 wt. %. Air cooled blastfurnace slag is a suitable alternative raw material with addition 4.2 wt. %. Waste glass is not very appropriate alternative raw material with addition only 1.16 wt. %. Fluidized bed combustion fly ash appears not to be equally appropriate alternative raw material for cement clinker burning with less potential utilization in the cement industry and with addition 3.41 wt. %, which forms undesired anhydrite CaSO4 in the cement clinker.
The Use Potential of Traditional Building Materials for the Realization of Structures by Modern Methods of Construction
Authors: Spišáková Marcela , Mačková Daniela
Published: December 2015

The sustainable building has taken off in recent years with many investors looking for new and different methods of construction. The traditional building materials can be made out of natural materials, while others can help to lower energy costs of the occupant once built. Regardless of what the goal of the investor is, traditional building materials and their use is on the rise. The submitted paper provides an overview of natural building materials and possible modern building systems using these construction materials. Based on the questionnaire survey is defined the use potential of traditional building materials for the realization of the construction by methods of modern constructions and then are determined the drivers and barriers of traditional materials through using modern methods of construction. Considering the analysis of the achieved results, we can identify the gaps in the construction market in Slovakia and also to assess the perception of potential investors in the field of traditional building materials use, which is the purpose of submitted paper.
Comparative Analysis of Houses Built from Insulating Concrete Formwork – case Study
Authors: Mačková Daniela , Spišáková Marcela
Published: December 2015

More and more, people are looking to build and live in different ways. They want houses with a high standard of living and reasonable production and maintenance costs. However, they also want to build a way that does not adversely affect their quality of life. Currently, the using of modern methods of construction (MMC) expands consistently year on year. MMC include prefabricated products made in the factory and also new methods of building that are site-based and they are regarded as a means of achieving higher quality, reducing time spent onsite, increasing safety and overcoming skills shortages in the industry. Aim of this paper is to analyze and compare, trough case study, technical, cost and technological parameters of house built by modern method of construction (from insulating concrete formwork) and by traditional method (from brick system). The subject of case study is house modeled in two variants of insulating concrete formwork and a variant bricks and ceiling system. In conclusion, there is selected optimal method and system for house construction through multicriteria optimization.
Permeability Computations of Shale Gas by the Pore-Scale Monte Carlo Molecular Simulations
Authors: Li Jun , Sultan Abdullah S.
Published: December 2015

The permeability variation of shale gas with pressure is an important input data in the predictions of well performance for optimizing production. We present a novel pore-scale simulation scheme to accurately compute the permeabilities at different pressure conditions by using the Fortran parallel software NanoGasSim, which was developed with a recent Monte Carlo molecular simulation method (i.e., the DSBGK method that is based on the Bhatnager-Gross-Krook (BGK) equation and has been comprehensively verified against the traditional direct simulation Monte Carlo (DSMC) method). The influence of adsorption layer on the permeability can be considered at each given pressure by adjusting the effective pore space according to the adsorption-layer thickness and specifying a potential moving velocity for adsorption layer. Then, the Klinkenberg slippage effect at high Knudsen numbers (Kn) is accurately modeled in the DSBGK simulations of free gas inside the effective pore space and the permeability can be computed from the steady-state flow velocity distribution. Linear variation of permeability with reciprocal pressure is observed in the range of high Kn with low pressure and the permeability becomes almost unchanged at low Kn with high pressure, where a large number of simulated molecules move inside hundreds of millions of cells and message passing interface (MPI) parallel computations are employed to reduce the computational time. Our computed permeability data can be directly used for industrial applications and also provide a reference to calibrate empirical correlation models as fitting formulas (e.g., the Klinkenberg model) and to validate other pore-scale simulation methods based on artificial corrections at high Kn (e.g., the lattice Boltzmann method).
Flow Regime Prediction Using Fuzzy Logic and Modification in Beggs and Brill Multiphase Correlation
Authors: Rammay Muzammil Hussain , Alnuaim Sami
Published: December 2015

An accurate prediction of Liquid Hold-up and pressure drop in multiphase flow is required in designing of million or billion dollars surface and subsurface facilities projects in Petroleum industries. These projects include building of offshore Oil and Gas pipelines, Oil and Gas field's process plants, multiphase separators, Oil and Gas wells equipments such as tubing, completion equipments. Therefore accuracy in prediction of Liquid Holdup and Pressure drop has a lot of importance and one of most primarily concerns in petroleum and chemical industries.

Beggs and Brill multiphase flow correlation is one of the most widely used multiphase flow correlations in the industry [19] due to its applicability for horizontal, vertical and inclined multiphase flow modeling. It also takes into account the different horizontal and vertical flow regimes. [4] It uses the general mechanical energy balance and the average in-situ density to calculate the pressure gradient. But due to the complex flow regimes and its wide transition, the method prediction becomes poor in certain practical conditions especially, when flow pattern classification parameters are near to the boundaries of the flow regime limits usually due to the inaccurate prediction of slip liquid hold-up. [18]

In this paper modification to Beggs and Brill correlation is proposed by predicting horizontal pipe flow regime using fuzzy logic instead of the one presented by the correlation. A fuzzy model is designed and tested to predict horizontal pipe flow regime and used in Beggs and Brill Correlation. The fuzzy model developed in this study is made by the technique of "Learning from example", which is basically used for rule base construction in automated methods for fuzzy systems [3]. For this purpose the fuzzy logic toolbox of MATLAB is used [17]. In this new proposed method, mixture Froude number and no slip liquid hold up, which were used by Beggs and Brill correlation for flow pattern calculation, are fuzzified. By using these parameters, the coefficients for liquid holdup calculations in Beggs and Brill correlation are modified and eventually produced by this fuzzy model. The new proposed correlation was verified using sets of published data in [1], [2] to predict flow pattern from no-slip holdup and Froude number. Some datasets in [1] were used to further refine the given fuzzy model, particularly high Distributed and low segregated flow regimes, which were not captured by Beggs and Brill data set.

This new proposed fuzzy model indicated that the generated fuzzy model empirical coefficients improve the liquid hold up prediction, which can improve pressure drop prediction of Beggs and Brill correlation; hence improve the accuracy of this widely used multiphase flow correlation. This fuzzy model outperforms the published models and Beggs and Brill multiphase correlation in terms of the lowest absolute average percent error 12.55 % and 9.94 % for Dataset in [1] and [2] respectively.
Removal of Pyrite and Different Types of Iron Sulfide Scales in Oil and Gas Wells without H2S Generation
Authors: Mahmoud M. A. , Kamal M. , Bageri B. S. , Hussein I.
Published: December 2015

Iron Sulfide scale is a significant problem in oil and gas industry where the iron sulfide depositions have adverse impact to the production operations. Typically, iron sulfide scale formed as result of the reaction between the hydrogen sulfide and iron. Iron sulfide scale has several forms; pyrrhotite (Fe7S8), troilite (FeS), pyrite (FeS2), greigite (Fe2S4), and mackninawite (Fe9S8). Pyrite, which has good thermal stability, tends to deposit at shallower places downhole and is inert to acid. Other iron sulfides react with acids. Thermal stable species are much harder to be removed by acids. Thus the iron sulfide downhole are mainly pyrrhotite, pyrite, marcasite and mackinawite, in which pyrite cannot be removed by acid treatment. Both pyrite and marcasite have very low solubility in HCl, and the only available method of removal in the oil industry is to mill these types of scale.

In this paper we introduced new formulations that can be effectively used to remove the pyrite and marcasite scales with removal efficiency reaches 85%. The new formulation will not release H2S during the removal of pyrite scale or any other iron sulfide scale as HCl, therefore, no need for H2S scavenger and also no HSE consideration are required during the removal because the new formulation can be considered as environmentally friendly. No need for additives such as corrosion inhibitors because these fluids pH is above 11 and they are not corrosive. The new formulation consists of high pH chelating agents such as DTPA (di ethylene tri amine penta acetic acid) at pH range from 11 to 14 and catalytic or converting agent such as potassium carbonate (K2CO3), (Cesium Carbonate) Cs2CO3, or (Cesium formate) CsCOOH. The optimum concentration of the chelating agents is 20 wt % DTPA and 7 wt% for the catalyst/converter. In the oilfield treatment water wetting surfactant or solvent should be injected first to remove the organic scale that covers the iron sulfide scale and then DTPA/Converting agents can be injected. No gases will be released during the scale removal process and this will not increase the pressure of the well during the treatment process.

Currently the removal efficiency of the pyrite scale type is maximum 20 % by HCl. Using the new formulations the solubility of actual field samples of pyrite reached 85%. The new formulation can be used effectively to remove all types of iron sulfide scales especially those cannot be removed by HCl. One more advantage of the new formulation is that the H2S will not evolve during the treatment and that will cut the cost of safety considerations bedside the cost of H2S scavengers.
Using Free Surface VSP Downgoing Multiples to Obtain Unconventional VSP Image Above the Well Trajectory - A Case Study in Offshore Vietnam
Authors: Dac The Nguyen , Sanders Michael , Ngo Anh Tuan Nguyen , Millot Pascal , Rehman Sadu-ur , Suzuki Katsuko , Lawson Michael , Jeow Foo Say , Tran Van Khanh
Published: December 2015

The Vertical Seismic Profile (VSP) technique is routinely used to create seismic images near the wellbore; traditionally, only the up-going wavefield is used to image the subsurface below the receivers. The standard VSP technique does not provide seismic image information above the well trajectory. The objective of this study was to produce a seismic image above the top receiver depth up to the seafloor by using the downgoing multiples recorded in the VSP data for a more complete seismic-to-well tie.

In VSP acquisition, the seismic source is positioned below Mean Sea Level and deployed above a downhole receiver. The source signal is recorded by a downhole receiver that is moved to cover a large number of depth levels in the well. The upgoing and downgoing arrivals are separated during processing; the up-going wavefield is used for subsurface illumination, whereas the downgoing wavefield and multiples are normally excluded from the processing. The standard VSP technique using the VSP upgoing wavefield gives a seismic image along the range of receiver depths and below the well trajectory. However, a VSP image can also be obtained from the downgoing multiple sequences in deep water.

The processing of sea surface multiple is used mainly to obtain a VSP image of formations above the top receiver depth; such an image is unattainable with the standard VSP technique. Our results show that illumination coverage increases significantly when using multiples versus primaries. In addition, reflectors above the shallowest receiver can be imaged by multiples, including the seabed itself. This can be useful for shallow hazard identification for sidetracks or to avoid the expense of infill nodal seismic below the rig (Farmani et al., 2012). We also show that the image obtained from the VSP multiples can have good resolution comparable to the surface seismic image, with better signal to noise ratio especially for the shallower reflectors. The VSP data is true amplitude, zero-phase, and perfectly tied in depth and in time. In very deep water, the seafloor-sea surface multiple is completely separated in time from the air gun signature and is out of the time range of the conventional processing and interpretation steps.

By using the deepwater surface-related VSP multiples and the mirror-imaging technique, the VSP image was extended successfully above the well trajectory upward to the seafloor and shows a good correlation with the surface seismic section (Marques et al., 2011). We present a case study using the sea surface downgoing multiples for this unconventional VSP imaging technique.
3D and 4D Seismic Data Integration for Geomodel Infilling: A Deep Offshore Turbiditic Field Case Study.
Authors: Silva V. , Cadoret T. , Bergamo L. , Brahmantio R.
Published: December 2015

When seismic data is of good quality and that it can be related to useful geological properties it can become a useful driver to distribute spatial heterogeneity within the geomodel. This paper describes a workflow to incorporate efficiently seismic data during the geomodel infilling process. We propose to combine the seismic facies probability attribute (obtained after 3D pre-stack inversion) with 4D attributes. This is done by increasing the seismic facies probability where 4D information highlights the presence of permeable reservoir facies. Afterward the obtained attribute is combined with well information using Total in-house workflow to generate the final facies proportion cubes. Finally, Associated Facies (AF) simulation is performed using SIS (Sequence Indicator Simulation) algorithms. Comparison is performed between the AF obtained using 3D seismic data only and AF obtained using combined 3D and 4D seismic data.

The integration of 4D information early in the geomodeling workflow (i.e. in facies modelling stage) improves the efficiency of the dynamic back-loop by allowing an early combination of Static and dynamic information. Thanks to this, history matching of dynamic reservoir simulation is facilitated.
Geochemical Applications for Identifying the Source of Hydrocarbons in Well Annuli
Authors: Aly Maher , Clancey Byron , Montgomery John K. , Bugti Mehboob A. , Ahmadzamri Ahmad F. , Al-Meraikhi Ajlan A. , Lawson Michael
Published: December 2015

Pressure build-up in the annuli of oil and gas wells could be an indication of a well integrity problem, in particular if determined to be sustained. In order to implement an effective remediation strategy for sustained annuli pressure, the source(s) of annuli fluids need to be determined so that the root cause of the problem can be identified and effectively mitigated.

This paper describes an approach developed to attempt to identify the possible sources of hydrocarbon fluids observed in some annuli of gas condensate wells located in Field A. During the initial phase of the investigation, it was not possible to determine the source of annuli hydrocarbon fluids from routine compositional analysis alone because the outer casing strings of the wells intersect multiple hydrocarbon bearing reservoirs and aquifers whose fluids have non-unique compositions. A multidisciplinary approach was therefore adopted that incorporated all of the available data and non-routine fluid analyses. A detailed fluid sampling and analysis program was also conducted to better understand and characterize the possible sources of the observed hydrocarbons in each well's annuli.

In one case study, interpretation of routine fluid compositional data indicated that non-hydrocarbon and hydrocarbon gas composition data alone did not provide a clear indication of the source of intermediate and surface casing fluids. Detailed geochemical analysis was therefore required to gain a better understanding of the annuli fluid source. In another case study, comparing the gas composition of the annuli fluid to the gas composition of a produced fluid allowed for the indication of the source of annuli fluid. In both cases, the compositional signature of the annuli source fluids was found to be sensitive to contamination as a result of changes in the pressure and temperature conditions in the annuli and through mixing with aqueous annuli drilling or completion fluids. However, more comprehensive geochemical screening that included molecular geochemistry and isotope analysis was shown to help in understanding the processes controlling the fluid composition and in reducing the uncertainties associated with the derived interpretation based on routine fluid compositional analysis alone. Conclusions from this work have now been incorporated into the annuli pressure management guidelines and in planning of future drilling and completion activities.
The HSSE Journey of Qatar Shell and GDI on Al-Khor Rig
Authors: Dakik A. , Attar F. , Babi B. , Stephenson B.
Published: December 2015

In continuous pursuit of improving safety and operational standards in the drilling industry, Shell took a major step forward in the Middle East when Qatar Shell Services Company W.L.L. partnered with the local drilling contractor, Gulf Drilling International (GDI) in 2011 for operating the Al-Khor Jack up drilling rig.

During the course of this partnership, HSSE was identified as one of the main pillars to be recognized, developed, and reviewed continuously for compliance against key HSSE targets.

GDI the local drilling contractor in Qatar aspires to become one of the best in class drilling contractors. Qatar Shell is committed to assist GDI in achieving that goal by refining the safety leadership attributes within the GDI crew, developing the skills for effective use of HSSE tools, and focusing on performance and people.

Shell's vision in safety is "Goal Zero" which means having an incident free workplace. Qatar Shell's safety journey with GDI started with improving the safety culture in the workforce and focusing on preventing incidents. This was a crucial step in the beginning of the journey as the team had new staff, new rig and a new contract to cope with. In addition, the rig was supporting well testing operations and did not drill wells for the previous 2 years.

Qatar Shell has successfully implemented and contributed to both personal and process safety roadmaps on Al-Khor Rig by adopting, and continuously evolving the learnings and safety procedures that are implemented globally by Shell. A successful implementation of DROPS (Dropped Objects Prevention Scheme), Red Zone management, Hands Free working, and barrier ownership has had a significant impact on Shell operations globally. On the GDI Al Khor, the implementation of these safety drivers in the appraisal wells program led to a reduced number of incidents, comprising a total of 3 recordable incidents in 4 years of operations. In addition, to promote the safety culture onboard the reporting of unsafe STOP cards was encouraged.

On the rig, compliance continues to be measured, and leading HSSE indicators continue to be developed. The goals set by GDI and Qatar Shell will be achieved through continuous commitment and safety leadership. With the vision to constantly improve and uplift the safety culture on Al-Khor rig to become best in class, Qatar Shell's journey with GDI continues.
Sweet Spots For Hydraulic Fracturing And Oil Or Gas Production In Underexplored Shales Using Key Performance Indicators: Example Of The Posidonia Shale Formation In The Netherlands
Authors: ter Heege J. H. , Zijp M. H. A. A. , Nelskamp S.
Published: December 2015

While extensive data and experiences are available for hydraulic fracturing and hydrocarbon production from shales in the U.S.A., such a record is lacking in many underexplored shale basins worldwide. As limited data is usually available in these basins, analysis of shale prospectivity and identification of sweet spots for oil & gas production needs to be based on upfront geological characterization and modelling before drilling, hydraulic fracturing and gas production has commenced. In this paper, different reservoir characterization techniques and modelling approaches are combined to quantify key performance indicators that describe potential shale productivity across the formation. The performance indicators describe the potential for hydrocarbon generation, storage, and flow stimulation based on a limited number of shale properties, and are benchmarked using data from the prospective Barnett Shale Formation in the U.S.A. The approach has been applied to the underexplored Posidonia Shale Formation in the South of the Netherlands (West Netherlands Basin). Local maxima of the mean performance indicator across the formation correlate with local maxima in vitrinite reflectance and depth. Average performance for the Posidonia is lower than for the Barnett shale, mainly due to lower maturity and brittleness. Besides higher clay content and associated lower brittleness, the potential for hydrocarbon generation and storage capacity of the Posidonia are comparable to oil mature Barnett shale from noncore areas. Predictions of gas production in the Posidonia based on simulations of hydraulic fracturing and gas flow using well-based models are in rough agreement with gas production observed in noncore Barnett areas, but low brittleness may hamper succesfull hydraulic fracturing. The example shows that the approach can be applied to underexplored shales worldwide to quantify prospectivity, map out sweet spots, point to preferred drilling sites, and optimize field development planning.
Engineered Formic Acid Precursor Helps Operator Successfully Stimulate Longest Open Hole Section in Carbonate Reservoir to Date
Authors: Degouy Didier , Sofyan Muhammad , Jaffar Mohd Bin , AL-Naimi Abdulaziz , Mohamed Monir , Pavia Linneth
Published: December 2015

A formic acid precursor (FAP) was used in a carbonate reservoir in offshore Qatar to achieve uniform filter-cake breaker treatment over the entire openhole section to improve wellbore productivity. Wells with a moderate wellbore length have been stimulated using a FAP with a delay time of ±3 hours, which is sufficient for spotting the precursor pill into the openhole reservoir section before the filter cake is broken by the treatment reaction (resulting in downhole completion fluid losses). In late 2014, a FAP cake-breaker treatment job was designed and performed for a 3741-m (12,270 ft) section of an 8½-in. open hole. This job required spotting a 159-m3 (1,000 bbl) FAP stimulation pill in the entire openhole section without incurring downhole losses while pumping. Thus, the delay time required for the precursor to convert to acid had to be increased to 8 hours.

Extensive laboratory tests were performed to increase the delay time for mixing and spotting the precursor pill before converting to acid and causing a significant reaction with the reservoir. These tests showed that an additional 5 hours of delay time could be achieved by a redesigned formulation. Mixing time also improved by delivering the liquid precursor in tote tanks, rather than in drums.

By performing the new fluid design and handling precursor material in tote tanks, the job was successfully run with an actual delay time of 8 hours, as compared to 5 hours for previous jobs. In addition, the retarded acid precursor pill was mixed and spotted into the entire open hole in 5 hours without downhole losses while pumping, indicating a successful mixing and spotting plan for the job. The downhole loss rate increased from zero at the end of spotting the precursor fluid to 2.5 m3/hr after 3 hours, signifying that the acid precursor was releasing acid, which reacted with the filter cake. An increase in downhole losses was observed after three more hours, when the loss rate increased from 2.5 m3/hr to 20 m3/hr. This increase indicated that the entire filter cake had reacted with the acid and that the acid had begun to enter the formation, acting as a stimulation fluid and enhancing well productivity.

This job was classified as the largest acid-delay precursor job performed globally to date by volume pumped and by interval length. Extensive laboratory tests were conducted to redesign the precursor fluid to achieve a sufficient delay time to mix and spot 159 m3 (1,000 bbl) of the FAP pill into the entire open hole before the acid reaction began. Using a liquid-precursor material in tote tanks helped to minimize the mixing time by 50% and resulted in a more efficient use of limited rig deck space.
A New Approach for Optimization of Long Horizontal Wells’ Performances
Authors: Al Qahtani Abdullah , Al Hashim Hasan , Al Yousef Hasan
Published: December 2015

Initially, it was believed that a horizontal well should be drilled as long as possible. This was motivated by the advancements in horizontal well drilling, which allows horizontal wells to be drilled several thousands of feet long. However, field experience and flow meter surveys in long horizontal drain-holes revealed that the frictional pressure loss in the wellbore is an important factor limiting the effective length of long horizontal wells and consequently hindering the full use of the entire length of the horizontal wells. Flow meter surveys revealed that the productivity of long horizontal wells is not proportional to well length because the increase in the length of horizontal section results in significant frictional losses in the wellbore. The frictional pressure losses may be comparable with the drawdown at the producing end of the well rendering a portion of the horizontal drain-hole unproductive.

This paper presents a new approach to maximize the use of the full length of long horizontal drain-holes by producing these long horizontal wells from both ends (heel and toe) and/or intersecting the second half of the horizontal well at an optimized location. This approach is supported by development of a rigorous semi-analytical model for the transient pressure analysis and well productivity evaluation for the horizontal well producing from both wings at the desired rates from both wings. The model incorporates the impact of wellbore hydraulics into the solution and used to calculate the flux distribution and pressure profile along the horizontal section. The developed model can also be used to evaluate the impact of reservoir parameters on the horizontal well performance. Furthermore, the model can be used as an optimization tool to optimize the production of long horizontal well by producing the well at the desired flow rates from both wings. Also presented, are some results showing the impact of wellbore hydraulics on the flux profile along the horizontal wells. These results show that the flux profile is a function of combination of reservoir flow characteristics and well conductivity. Wellbore hydraulics changes the flux distribution (flow ingress profile) along the wellbore and, thus, results in additional pressure drop in the well. The proposed method is found to be superior to the conventional horizontal well in terms of productivity and flux profile.
First True Two-Stage Cement Treatment Using an Expandable Liner Hanger
Authors: Jaramillo Andres , Jackson Tance
Published: December 2015

As wells increase in complexity, new challenges must be addressed in order to produce hydrocarbons in the best way possible. Some wells should be cemented in two stages because of the risks of fracturing the lower zone. Running a long casing string increases the equivalent circulating density (ECD) and also increases the chance of damaging that zone, so running a liner is the best option.

Cementing liners in two stages has been performed with conventional liner hangers for some time because of their capability to run an inner string and their capacity for manipulation after the hanger is set. Now, new technologies allow those treatments to be completed with expandable liner hangers (ELH).

The ELH provides a premium liner top seal (Williford, Smith, 2007) and excellent tensile capabilities. They also help to improve the cement bond by allowing the movement of the string while the cement is being pumped in place. ELHs have proven to be a reliable tool (Jimenez, C., et al., 2009), and every year their popularity increases tremendously.

This paper discusses the first true two-stage cement job with an ELH performed in Kazakhstan. The use of the ELH helped the operator reach total depth (TD), cement the two zones without issues, and create a premium barrier at the top of the liner.
Reservoir Filling Paths Revealed By Kinetic Modeling of Biodegradation at Basin Scale
Authors: Haeseler F. , Levache D. , Lamirand B.
Published: December 2015

This paper presents a methodology contributing to describe the filing of petroleum reservoirs based on the quantification of fluid alteration processes.

Biodegradation of hydrocarbons in oil reservoirs is one of the important alteration processes of petroleum. Described by Bastin in 1926, it is a widespread mechanism. Hydrocarbon degrading microorganisms have been found until 4 km depths and temperatures ranging up to 80 °C . The alteration of oil leads to an increase of sulphur and metal compounds, and also to the increase of acidity, viscosity and density. The level of biodegradation is classically described by the presence of biomarkers presenting specific resistivity to biodegradation (Peters and Moldowan, 1993). Haeseler et al. proposed in 2010 a quantitative numerical model based on stoichiometric equations, describing, step by step, the evolution of hydrocarbon composition and physical properties in biodegraded oils.

This tool was applied successfully to different African Basins (Lower Congo Basin, Niger Delta Basin and Albert Lake Basin) showing excellent correlation between the computed and the analysed composition of oils presenting increasing biodegraded grades. The biodegradability coefficients of the different hydrocarbon classes were shown to follow always the same rules. In the present paper, we applied the dynamic version of this model. In addition to the compositional data, parameters provided by Basin simulators like expulsion history from the source rock, reservoir temperature curves, reservoir volumes… were integrated. Applied to a biodegraded play located offshore Africa, this biodegradation model allowed various parameters describing the filling history of the Oligocene and Miocene reservoirs to be determined:

total quantities of hydrocarbons lost by biodegradation,

total quantity of methane generated. This allowed to calculate the methane losses over geological times by taking into account presently measured GOR and GOR expected from the numerical simulation,

gas loss fluxes: providing a geological description of reservoir sealing efficiency,

the kinetic parameters of the biodegradation for each compound class,

oil filling path in the reservoirs. The oils from the Miocene reservoirs must have previously been stored (and altered) in the Oligocene reservoirs. A direct arrival in the Miocene reservoirs from the source rock was excluded,

the storage time of the oils in Oligocene and Miocene reservoirs.

This multidisciplinary work allows to be optimistic about the possible existence of a general law governing the kinetics of the biodegradation and applicable for sedimentary Basins. It also showed that a qualitative and quantitative description of an oil alteration process contributes to a better understanding of fluid paths and the nature of fluids in place. It builds a strong scientific base for the description of fluid differences at reservoir scales that can be applied for various geochemical applications.
Challenges in Uncertainty Management: Scenarios vs. Realizations and Their Impacts on Projects - How to Deal With That?
Authors: Tawile E. , Schirmer P. , Rolando J-P
Published: December 2015

In an uncertainty evaluation process, making sure that critical uncertainties are captured is crucial. This paper aims at showing the difficulties in defining critical uncertainties because 1) definitions are not necessarily clear and 2) capturing the whole range of uncertainties is impossible. Indeed, if we place ourselves in the appraisal and development screening phase of an E&P project , the main objective is to reduce uncertainties and hence risk to an acceptable level which then allows triggering investments in such a project.