bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of protein source and crossing system of lambs on wool quality parameters
Authors: Ruzic-Muslic Dragana , Petrovic Milan , Petrovic Milan , Bijelic Zorica , Caro-Petrovic Violeta , Maksimovic Nevena , Mandic Violeta
Published: May 2016

The experiment included 30 lambs-crosses F1 generation: Pirot Pramenka (50%)
x W?rttemberg (50%) and 30 crossbred F1 generations: Pirot Pramenka (12.5%) x
W?rttemberg(37.5) x Ille de France (50%), weaned at 60 days of age, the
average body weight of 18.0 kg. The mixtures varied in protein source: I -
sunflower meal, II - soybean meal and III - fish meal. The share of
undegradable protein was 43 : 51 : 58 %. The average diameter of the fibres
in lambs on treatments I:II:III was 26.14 : 24.96 : 25.20 ?m, and of
two-breed (PxW) and threebreed (PxWxIDF) crosses: 25.38 and 25.49 ?m. The
average height of the wool fibre in lambs on treatments I:II:III was: 2.97 :
3.06 : 3.17 cm, and in two-breed (PxW) and three-breed (PxWxIDF) crosses 2.98
: 3.15 cm. The average length of the fibre in lambs on protein sources
I:II:III was 4.62 : 5.08 : 5.11 cm and in twobreed (PXW) and three-breed
(PxWxIDF) crosses 4.77 : 5.11 cm. Protein source in feed mixtures, and
genotype of lambs significantly influenced the quality of wool expressed
through diameter, height and length of the fibres.
Impact of agro-ecological conditions on protein synthesis in hexaploid wheat - spelt (Triticum spelta)
Authors: Ikanovic Jela , Popovic Vera , Jankovic Snezana , Drazic Gordana , Pavlovic Slobodanka , Tatic Mladen , Kolaric Ljubisa , Sikora Vladimir , Zivanovic Ljubisa
Published: May 2016

Technological quality of wheat is defined by physical and chemical indicators
of quality and its baking properties. To make wheat a commodity, there are
certain requirements to be met, defined by minimum values of trade quality
indicators. As hexaploid wheat, spelt (Triticum spelta L.) belongs to a group
of alternative cereal grains high in gluten, and its flour is therefore used
for making most pastries. Due to its high nutritional value, spelt flour is
used to enhance the quality or flavour of wheat bread and other bakery
products. Two-year research was conducted during 2011 and 2012 to investigate
protein content in crops grown on the Eutric Cambisol soil type. The research
was conducted on two spelt cultivars: Hungarian Ek? 10 and Serbian NS
Nirvana. The results showed that NS Nirvana averaged a statistically
significantly higher proteins content (16.76%) than Hungarian cultivar Ek? 10
(15.65%). Climatic factors, temperatures, the intensity of light and duration
of seed filling had an impact on the investigated parameter.
Algorithm for uptake assessment in small lesions based on dynamic scintigraphy scans
Authors: Jankovic Milica , Miler-Jerkovic Vera , Koljevic-Markovic Ana , Popovic Dejan
Published: May 2016

The aim of our research was to develop an algorithm for estimation and
visualisation of radiopharmaceutical uptake based on time-activity-curve
(TAC) analysis in small regions of interest (ROI) in scintigraphic studies.
The algorithm is implemented in Lab view environment (National Instruments,
Texas, Austin) and comprises the following steps: 1) delineation of grid of
small ROIs over the examined tissue and corresponding TAC processing; 2)
background vs tissue separation; 3) the extraction of all ?suspected? ROIs
where TACs are not exponentially descendent; 4) correlation analysis between
a TAC corresponding to the central suspected ROI and TACs of neghboring ROIs;
5) the extraction of representative TAC for ?suspected? area by Principal
Component Analysis technique; and 6) visual interpretation of
radiopharmaceutical distribution in the ?suspected? area. The application of
algorithm is presented in data recorded in case of histopathologically proven
parathyroid tumors.
Design of IIR digital filters with critical monotonic passband amplitude characteristic: A case study
Authors: Mirkovic Dejan , Andrejevic-Stosovic Miona , Petkovic Predrag , Litovski Vanco
Published: May 2016

A case study is reported related to the design of IIR digital filters
exhibiting critical monotonic amplitude characteristic (CMAC) in the pass
band. This kind of amplitude characteristic offers several advantages as
compared to its non-monotonic counterparts, although it has not been studied
thoroughly so far, if at all. After giving a short overview of the way of
CMACs generation, arguments will be listed in favor of the IIR version of the
digital filter function realization. Next, the IIR implementation of the
digital filters will be considered in short. The main part of the paper will
be devoted to the design sequence of this kind of filters which will be
illustrated on the example of a band-pass filter obtained by a set of
transformations from an all-pole low-pass analogue prototype. This will be
the first time a CMAC band-pass IIR digital filter is reported.
Dielectric properties of La/Mn codoped barium titanate ceramics
Authors: Paunovic Vesna , Mitic Vojislav , Marjanovic Milos , Kocic Ljubisa
Published: May 2016

La/Mn codoped BaTiO3 ceramics with various La2O3 content, ranging from 0.3 to
1.0 at% La, were investigated regarding their microstructure and dielectric
properties. The content of MnO2 was kept constant at 0.01 at% Mn in all
samples. La/Mn codoped and undoped BaTiO3 were obtained by a modified Pechini
method and sintered in air at 13000C for two hours. The homogeneous and
completely fine-grained microstructure with average grain size from 0.5 to
1.5mm was observed in samples doped with 0.3 at% La. In high doped samples,
apart from the fine grained matrix, the appearance of local area with
secondary abnormal grains was observed. The dielectric properties were
investigated as a function of frequency and temperature. The dielectric
permittivity of the doped BaTiO3 was in the range of 3945 to 12846 and
decreased with an increase of the additive content. The highest value for the
dielectric constant at room temperature (er= 12846) and at the Curie
temperature (er= 17738) were measured for the 0.3 at% La doped samples. The
dissipation factor ranged from 0.07 to 0.62. The Curie constant (C),
Curie-Weiss temperature (T0) and critical exponent (g) were calculated using
the Curie-Weiss and the modified Curie-Weiss law. The highest values of Curie
constant (C=3.27?105 K) was measured in the 1.0 at% La doped samples. The
obtained values for g ranged from 1.04 to 1.5, which pointed out the sharp
phase transformation from the ferroelectric to the paraelectric phase.
Evaluation of normal heights by the means of global navigation satellite systems and global geopotential model
Authors: Odalovic Oleg , Joksimovic Danilo , Grekulovic Sanja , Todorovic-Drakul Miljana , Popovic Jovan
Published: May 2016

This paper presents geometrically and physically defined height systems,
along with their evaluation by the means of Global Navigation Satellite
Systems (GNSS) and Global Geopotential Models (GGM). The paper defines
ellipsoid heights as an instance of geometrically defined heights; with
physically defined heights being represented by definitions of orthometric
and normal heights. Methods of normal heights calculation by the means of
ellipsoid heights are presented in detail, as determined using the GNSS and
height anomalies calculated from the GGM application. Apart from the above,
numerical part of the paper evaluates normal height values and compares them
to their conditionally accurate values at 1073 points with relatively uniform
distribution over the entire territory of Serbia. Conditionally accurate
values had been determined by the means of classical geodetic terrestrial
methods. Under the procedure of evaluating normal height values, GGM - GGM05C
was used, as created in 2016 by the Center for Space Research, University of
Texas at Austin. In order to evaluate the quality of applying the model
above, data on normal heights evaluation were also presented, using the GGM
EGM96, created in 1996 by the National Imagery and Mapping Agency (NIMA),
Goddard Space Flight Center (GSFC - NASA) and Ohio State University,
presently being the most commonly used model. The comparison above indicates
that application of the GGM05C model provides 50 % greater quality of normal
heights evaluations against the ones obtained using the EGM96 model.
Spatial development analysis of the Danube region in Serbia in the function of sustainable development
Authors: Petrovic Ljubica
Published: May 2016

The Danube river represents one of the most important European development
potentials and the stemming point leading towards the European Integration.
Although the water testings of the Danube river show that the Danube is, on
its way out from the country, of better quality that on its entering, and
that the presiding state of parametres of the living environment had
deteriorated and is endangered by possible influences of anthropogenic origin
which represent limiting factor of development of this area. This paper
analizes the Danube significance in the territorial development of Serbia
which is the main axis of development with the best developmental
possibilities and economic potentials. The paper also shows that an evaluation
of Danube river basin developmental potential has been carried out, which
states the fact that inequalities in the degree of the region development and
the evaluation of the living environment together with the identification of
the worst pollutants, imply that the worst pollutants can be found in the
regions which belong to the group of the stabile regions. The categorization
of the living environment has been carried out on the basis of the condition
evaluation and analysis according to the Spatial Plan of the Republic of
Serbia after which the precaution measures are installed , on whose basis the
further sustainable development of this area would be realized.
Community hygiene problems and environmental protection measures in the area of natural monument "Zvezdara forest"
Authors: Samardzic Ivan
Published: May 2016

Community hygiene conditions and equipment represent significant indicators
of the quality management of green areas. As a space of exceptional
importance for protection of forest complex and biodiversity in an urban
environment, Zvezdara forest is placed under protection as a natural monument
by an act of the Assembly of the City of Belgrade, where measures of
environmental protection and preservation of this area, as one of the most
important green areas in this part of the city, are also defined (wind
protection role, enrichment of the air with oxygen, thermoregulation, etc.),
but as well as a space for sports, recreation, picnics. This research
presents the community hygiene problems (?illegal landfills?, lack of garbage
cans, hydrants, public toilets and drinking fountains, etc.) and
environmental issues (?wild? construction, landslides, etc.). The aim of this
research is the recommendations of environmental protection measures and
removal of community hygiene and environmental issues, presented in the final
part of this research paper, which could be used in the future during
preparation of planning documents, in order to achieve better environmental
management in the area of Zvezdara forest.
Culture of giving birth: Research on the issue of violence against women during delivery
Authors: Sekulic Nada
Published: May 2016

The paper deals with the issue of the fragile connection between social
sciences, humanistic sciences and feminism, arguing in favor of their closer
mutual influence. In the framework of this approach, paper presents the
results of the part of the research ?Politics of Parenthood?, based on the
feminist approach. The paper analyzes the delivery (giving birth) as an
important ritual in the life cycle of the largest number of women, through
which power relations in society manifest, and women are subdued. Research on
the issue of violence against women during delivery is part of the broader
research dealing with the social construction of women?s bodily experience
and female body as a social resource, in the processes that reflect and at
the same create gender inequality.
Synthesis, structure and properties of nickel-iron-tungsten alloy electrodeposits - Part II: Effect of microstructure on hardness, electrical and magnetic properties
Authors: Cirovic Natasa , Spasojevic Pavle , Ribic-Zelenovic Lenka , Maskovic Pavle , Maricic Aleksa , Spasojevic Miroslav
Published: May 2016

Nanostructured nickel-iron-tungsten alloys were produced by electrodeposition
from an ammoniacal citrate bath. The tungsten content of the alloy ranged
from 0.8 wt.% to 11 wt.%, and the crystal grain size of the FCC phase of the
solid solution of iron and tungsten in nickel was between 14 nm and 3.3 nm.
The amorphous phase content of the alloy increases with decreasing crystal
grain size. As the amorphous phase content increases, the magnetization,
electrical conductivity and hardness of the alloy decrease. Annealing the
alloy to crystallization temperature results in structural relaxation during
which the alloy undergoes short-range ordering in conjunction with decreases
in the density of chaotically distributed dislocations and internal
microstrain level, which increases the exchange integral value, the
electronic density of states at the Fermi level, the mean free path of
electrons, the ordering and the mean size of cluster in the sliding plane
and results in more uniform orientation of dipole moments of certain
nanoparticles. These changes: a) increase the mobility of magnetic domain
walls, facilitate the orientation of domains in the external magnetic field
and cause an increase in magnetization; b) cause a decrease in electrical
resistance, and c) impede the sliding of grain boundaries and increase the
hardness of the alloy. Annealing the alloys at temperatures above 400?C
results in amorphous phase crystallization and larger crystal grains of the
FCC phase, along with a decrease in the density of chaotically distributed
dislocations and a decrease in internal microstrain level. The formation of
larger crystal grains reduces the hardness of the alloy, decreases its
specific electrical resistance and impedes both the orientation of certain
magnetic domains and the shift of walls of already oriented domains, thus
inducing a decrease in magnetization. The heat released during the milling
of Ni87.3Fe11.3W1.4 alloy with FCC-phase crystal grains 8.8 nm in average
size causes amorphous phase crystallization, FCC crystal grain growth and an
increase in magnetization. Alloys with relatively high tungsten content (11
wt. %) have an inhomogeneous composition, a high proportion of the amorphous
phase and FCC crystal grains with an average size of 3.3 nm. This
microstructure results in magnetic domains that have different and
relatively low thermal stabilities and relatively low degrees of
magnetization.
Removal of Cs ions from aqueous solutions by using matrices of natural clinoptilolite and its safe disposal
Authors: Omerasevic Mia , Ruzic Jovana , Vukovic Nikola , Jovanovic Uros , Mirkovic Miljana , Maksimovic Vesna , Dondur Vera
Published: May 2016

The possibility to use natural zeolite - clinoptilolite as a host material
for radioactive Cs immobilization has been investigated. Cs-exchanged form of
clinoptilolite which was prepared by treatment of clinoptilolite powder with
0.25 M CsCl solution was compacted. Both, powder and powder compact of
exchanged clinoptilolite were thermally treated at 1200?C. The XRPD analysis
showed that Cs was successfully immobilized after heat treatment by formation
of stable cesium dodecaoxo-alumopentasilicate in both, powder sample and
compact. The newly formed compound showed satisfactory Cs ions retention
during leaching test. The sintered compact showed somewhat better resistance
to Cs leaching than the thermally treated powder. The compressive strength of
sintered compact was close to 200 MPa which is more than enough for easy
handling and safe storage.
Drillable PDC Casing Bit Defies Challenging Onshore Drilling Environment and Sets Longest Single Trip Drilling with Casing Record
Authors: Utama Budi , Won Keith
Published: May 2016

Orubadi formation in Permit PRL 21 at Western Province Papua New Guinea(PNG) was known for its challenges to drilling and casing-running operations on the surface section. A waterflow event occurred when drilling the offset well through the formation, consequently requiring the flow to be diverted. In addition, the surface casing-running operation was time-consuming due to tight-hole conditions, which led the operator to perform extra trips to reamthrough the ledges.

An approach using the drilling-with-casing technique was presented and identified as the most suitable drilling method for setting the 13 3/8-in. surface casing safely and improving drilling efficiency through trip-time reduction and elimination of conventional drilling BHA handling. A unique, reliable and easily operated top-drive casing-running and drilling system, which had been used regularly for surface casing-running operations, has contributed to the first successful drilling-with-casing operation on the rig. The casing-bit selection has appeared to be an important process in this challenging project. Ultimately, a newly-developed polycrystalline-diamond-compact (PDC) drillable casing bit with PDC cutters was selected based on the estimated hard formation rock strength characteristic of the field, in order to achieve the targeted total depth in a single trip.

The drilling-with-casing system was deployed through the problematic zone and mitigated the expected borehole problem with variations in the drilling penetration rate. Recommended drilling parameters were used to achieve optimum performance in combination with sufficient mud properties to maintain good hole cleaning and bit hydraulic performance until total depth.

This paper presents the drilling-with-casing project in the field, covering the planning stage, equipment selection, preparation, implementation, and operational aspects of the longest nonretrievable 13 3/8-in. drilling-with-casing project performed in the world to date.
New Offshore Sidetrack Practices Reduced Significantly Stuck Pipes in KSA
Authors: Al-Dossary Abdulla
Published: May 2016

This paper demonstrates the causes of the major issue of stuck pipes in offshore sidetracks in Saudi Aramco & also explains the new drilling practices implemented to reduce the number of stuck pipes while drilling or running completion systems. Out of three wells sidetracked, two stuck pipes occurred. Year after, this number of stuck pipe has declined significantly after revised and corrected drilling practices. In year 2005, oil demands went up and therefore, Saudi Aramco converted vertical and deviated wells to horizontal in order deliver more oil to the oil market. Sensitive shale instability problem was present almost in every well where drill pipe got stuck. Also, it is worth mentioning that development of humps while drilling contributed to inability of cleaning the hole very efficiently. Typically, every single well is sidetracked and drilled across shale formations of different pressures up to the productive zone. After drilling the horizontal section, the whole well is reamed with stiff assembly during which obstructions and tight spots are cleared. Then, ICD system is deployed to TD. This paper will highlight the main causes of stuck pipe and following that, successful solutions will be presented and explained in detail.
Casing While Drilling (CwD): Surface Hole Optimisation in Mature Field of Offshore North West Java
Authors: Taufiqurrachman H. , Tanjung E.
Published: May 2016

Offshore North West Java (ONWJ) is one of Indonesia's mature fields. Mature field developments in this level require a simple, fast and cheap well design to be economically interesting. The highlight in this paper is drilling top-hole section optimization by applying Casing while Drilling (CwD).

The main 2 challenges in drilling top-hole section in ONWJ are gumbo attack and loss circulation. Past mitigation was drilled a small pilot hole to reduce cutting amounts then enlarge the open-hole by hole opener. However it did not solve the problem completely. The gumbo attack still occurred, some associated non-productive rig times still happened and safety concern to clean the plugged flowline still existed. KCl Polymer mud system was not an option due to loss circulation existence, where hole will collapse when seawater is displaced to keep hydrostatic.

CwD were executed successfully at 2 exploration wells in Q3 2011 by implementing Vertical-CwD (VCwD). First trial of VCwD was run only in surface section with a simple cutters casing shoe mounted on the end of a casing string. Further improvement in drillshoe, BHA and mud design was made on the second trial to extend the interval and improve overall ROP. The second trial of VCwD managed to safely drilled almost 3000ft of combine surface and intermediate vertical section with overall ROP of 60fph, where at surface section CwD was performed blindly due to total loss circulation and it was successfully cemented (no annulus pressure trap so far). The second trial has saved the company over 1MMUSD compared to conventional drilling.

In 2012, numerous trials of Vertical Casing while Drilling (VCwD) have been performed for exploration and development wells in offshore North West Java. CwD is heralding the way to the future of drilling in mature fields of Offshore North West Java.
Carbonate Rock Types Matrix, the Ultimate Rock Properties Classification Catalogue
Authors: Al-Farisi Omar , Belhaj Hadi , Ghedan Shawket , Negahban Shahin , Gomes Jorge , Yammahi Fatmeh , Amr Mohamed , Khamissa Hocine , Ibrahim Khalil , Al-Shamsi Abdullah
Published: May 2016

The heterogeneity in carbonate rocks, made it hard for Geoscientists and Reservoir Engineers to define a universal classification methodology that is able to honour the critical reservoir static properties. Most classifications, like, lithofacies, capillarity and textural methods have based their rocktyping concept on one or two static properties, then tried to find an analog to other static properties to cluster or group them, then worked to populate the rock types across the whole field. However, from field observations and experiences of utilizing these conventional techniques, it was obvious that they suffered from several gaps, like inability to have the properties analog consistent throughout the whole reservoir. Moreover, the groups or clusters have big dispersion that produced overlaps, and then theoretically they could not fully honour the physics and rock properties links.

Therefore, in this study, rock typing is made to honour static properties all together through changing the classification concept to resolve the gaps of the traditional methodologies. The ultimate objective of all reservoir characterization and rock classification is to enable building geological and simulation models, with optimum honouring of rock properties. To achieve this objective, the established framework in this research is based on analyzing the effects of each of the rock properties on another and the value and impact that each can add to the models most critical parameters. By this technique, the gap of pore and pore-throat network is resolved through Multiple Properties Intersection.

This Integrated Carbonate Rock Typing technique starts with capturing the heterogeneity of carbonate rock by generating matrix of core permeability, capillary pressure (end point, threshold pressure and Plateau), pore-throat size distribution and porosity. Then intersecting this matrix to construct weighted links between these properties and identify unique groups. Resulted classes are novel carbonate rock type classes that entered to feedback analysis node to explore and validate the logic of linked physics to tune the classes'thresholds and assure no overlap between any of classification properties. Finally for utilizing this technique in non-cored wells, an analog with logging data is structured through novel permeability, capillary pressure and saturation function called the C-Function to be the replacement of the J-Function in Carbonate.
Unlock Shale Oil Reserves Using Advanced Fracturing Techniques: A Case Study in China
Authors: Liu Hai , Luo Yin , Zhang Ning , Yang Dong , Dong Wanbai , Qi Dunke , Gao Yinjun
Published: May 2016

Development of unconventional resources has become major focus in China in the recent years as the growth of energy demands. Many pilot projects on shale oil reservoirs have been initiated to seek for economic development with modern hydraulic fracturing technologies. Fracturing these reservoirs is quite challenging and requires not only large reservoir contacts but also high fracture conductivity in both primary fracture and fracture networks since oil viscosity is several magnitudes higher than natural gas. Vertical fracture connectivity is also an issue in many cases due to lamination of shale-rich layers with thin siliceous and calcareous beds. This typical sedimentary feature may result in either short fracture height or pinch-point in vertical fracture profile due to proppant embedment in shale-rich layers.

The paper presents a shale oil case study in Northern Songliao Basin in China in which many fracturing treatments have been attempted in the past without success. Two existing vertical wells drilled in 1989 were used to study appreciate fracturing techniques and demonstrate the possibility of economic production before evaluating horizontal well completion. The paper illustrates optimization of treatment strategy and design by integrating detailed reservoir characterization, fracture simulation using unconventional fracture model and numerical reservoir simulations. It also introduces an innovative fiber diversion technique for improved vertical fracture coverage and proppant placement together with real time fracture monitoring for treatment optimization.

After increased understanding from the treatment on the first well, the treatment on the second well was quite successful and the well produces 30 bopd after the treatment, which is the first ever economic production in the field. The first month production history also matches with the forecast very well, which increases the confidence of extending the practice to the entire field as well as subsequent horizontal well evaluation.
Assessing Unconventional Resources Using an Integrated Petroleum Systems Approach
Authors: Roy Ananda Shankar , Neber Alexander , Kadir Zailani Abdul
Published: May 2016

Petroleum system modeling has matured in the past few years and is now a valuable component in conventional exploration. It has become best practice to mitigate risks by using petroleum system modeling to predict the presence, types, and volumes of hydrocarbons in prospective areas or structures before drilling. An adaptation of this methodology has been successfully applied to unconventional resource plays. Petroleum system modeling may be applied to predict: the type and quantity of hydrocarbon remaining in the source rock, proportion of adsorbed gas, porosity, and geomechanical properties of potential unconventional reservoirs.

A new methodology has been developed to integrate trap, reservoir, charge, seal, and other risk (sub-) elements to evaluate play risk. Chance-of-success (COS) maps are created by transforming the physical propertiy maps to maps with probability units. As data, interpretations and related COS maps are in the same software system, the evaluation can be kept alive and dynamic as new data interpretations become available. Within the same application, prospect COS can be evaluated using a consistent approach

This paper illustrates this methodology using examples from shale plays in North America, data-rich plays from the North Slope of Alaska and data-poor plays that are more representative of many Asia-Pacific basins from the north-eastern and southern regions of the United States. The examples demonstrate the application of the methodology in both frontier and mature areas, either in quick data-room reviews or for delineating prospects.
Oil-Based Fracturing Fluid: First Results in West Africa Onshore
Authors: Perfetto R. , Melo R.C.B. , Martocchia F. , Lorefice R. , Ceccarelli R. , Tealdi L. , Okassa F.
Published: May 2016

Hydraulic fracturing operations in West Africa are not as common as in the US, Latin America and the Middle East. In the Republic of Congo fracturing technology is spreading and has overcome more than few difficulties since the practice began. The most significant challenge has been the formation, which has shown through laboratory testing to be soft and water-sensitive.

The fracturing project started in the laboratories, identifying critical issues, such as formation heterogeneity, hardness, water sensitivity, clay content and particularly the risk of proppant embedment.

The fracturing fluid chosen for the project was a water-based, borate-crosslinked guar fluid, with specific chemicals added to minimize formation softening and clay swelling issues. A specific pumping strategy was implemented when using water based fracturing fluid to limit the effects of proppant embedment. Several wells were treated with this system.

In an effort to improve well productivity, a pilot test was designed with oil-based fracturing fluid. This fluid was pumped in two wells, resulting in improvements in terms of cleanup time and economics, compared to the water-based treatment fluids in the same field.

Part of the economic benefit was gained because of the reduced hydrostatic head of the oil-based fracturing fluid, which eliminated the need for a coiled tubing gas lifting operation. Economics were also improved by minimizing rentals of well cleanup equipment because the broken fracturing fluid can be sent directly to production facilities. In this paper, design and application results for the oil-based fracturing fluid operations are presented with all the operational and logistical challenges overcome.
Imaging Earth
Authors: Zhu Hejun , Luo Yang , Bozdag Ebru , Peter Daniel , Tromp Jeroen
Published: May 2016

Harnessing high-performance computers and accurate numerical methods to better constrain physical properties of Earth's interior is becoming one of the most important research topics in structural and exploration seismology. We use spectral-element and adjoint methods to iteratively improve 3D subsurface images ranging from continental to exploration scales.

The spectral-element method, a high-order finite-element method with the advantage of a diagonal mass matrix, is used to accurately calculate three-component synthetic seismograms in a complex 3D Earth model. An adjoint method is used to numerically compute Frechet derivatives of a misfit function based on the interaction between the wavefield for a reference Earth model and a wavefield obtained by using time-reversed differences between data and synthetics at all receivers as simultaneous sources. In combination with gradient-based optimization methods, such as a preconditioned conjugate gradient method, we are able to iteratively improve 3D images of Earth's interior and gradually minimize discrepancies between observed and simulated seismograms. Various misfit functions may be chosen to quantify these discrepancies, such as cross-correlation traveltime differences, frequency-dependent phase and amplitude anomalies as well as full-waveform differences.

Various physical properties of the Earth are constrained based on this method, such as elastic wavespeeds, radial anisotropy, shear attenuation and impedance contrasts. We apply this method to study seismic inverse problems at various scales, from continental-scale seismic tomography to exploration-scale full-waveform inversion. Two examples are utilized to illustrate the applications of this method, namely, 1) application of adjoint tomography in improving 3D elastic wavespeeds of the European crust and upper mantle, and 2) application of the impedance gradient in elastic reverse-time migration for a 2D salt dome model.
First Horizontal Openhole Gravel Pack Installation in a Clastic Gas Reservoir: KM Field
Authors: Izzat M. , Nizam M. , Azmi Mahadi K. , Ogbonna C. , Jadid M.B. , Chen Y. , Chia I.
Published: May 2016

The KM field is part of the KM cluster development project, which plans to deliver 100 MMscf/D of gas to liquefied natural gas (LNG) from five horizontal wells. Four of the wells were completed with 4 1/2-in. production tubing using horizontal openhole gravel packs (HZOHGPs) as sand control, which was the first application of this technology for the operating company. Based on geomechanical modeling, the KM field is an unconsolidated clastic gas reservoir that requires active sand control. The particle size distribution (PSD) suggests that the KM clastic formation is a poorly sorted sand with a high uniformity coefficient and very high fines content; thus, justifying the need to use a gravel pack completion rather than a screen-only completion. The conventional internal gravel packed (IGP) technique has been widely applied because it provides a reliable means of abating sand production. However, it does not provide the same productivity as a HZOHGP. IGP is also highly prone to increasing skin throughout the production life of the well. Nodal analysis indicates that HZOHGP would give the highest production index (PI) with low production drawdown compared to a cased-hole gravel pack completion, in addition to potential cost savings realized from the elimination of the casing, cementation of the casing, and perforation of the casing. Running a screen in conditioned, solids-free mud, avoiding premature bridging during the job execution, proper removal of the mud filter cake, and limiting flow to below critical drawdown pressure (CDP) play important roles in the successful implementation of a HZOHGP completion in the KM field. This paper describes the planning of the first openhole gravel pack installation for an unconsolidated gas formation while highlighting the risk assessment, the lessons learned, and the excellent production performances achieved. Use of OLGA® transient simulators for estimating drawdown during well cleanup is also briefly discussed.
Optimum Development on Low Permeability Reservoir - New Phase Opportunity for Mature Badak Field
Authors: Hermawaty Irma , Permana Robhy , Silitonga Frans , Wijanarko Andre , Soenoro Amireno
Published: May 2016

VICO Indonesia is the operator of Sanga Sanga Production Sharing Contract (PSC) area in the onshore Mahakam Delta, East Kalimantan, Indonesia since 1968. Over 40 years, the PSC has produced more than 12 TSCF of gas through more than 800 wells to feed the Bontang LNG Plant and domestic market. One of the major fields in the contract area is the Badak Field, which has contributed more than 6 TSCF of gas production.

Badak Field's reservoirs are the analog of the present day's Mahakam delta, and comprise of stacked distributary channel sands deposited in the deltaic environment draping on a four-way dip closure anticline. The shallower stratigraphic interval is dominated by fair to good quality upper delta plain, amalgamated channel sands, with a combination of water and depletion drive mechanism. The deeper stratigraphic intervals are dominated by fair to poor quality lower delta plain, more isolated distributary channel sands and mouth bar. The main reservoir drive mechanism is depletion drive.

As the early development strategy of the Badak Field had been focused mainly on drilling the best reservoirs, those shallow reservoirs in the crestal area, the majority of these reservoirs are now depleted. In contrast, low permeability deeper reservoirs with relatively higher reservoir pressure, still contain significant remaining resources. VICO's depletion challenge is to balance between increasing the recovery from the deeper intervals, whilst continue optimizing the recovery from shallow intervals.

An Integrated subsurface study has been conducted to understand the geological description of the reservoirs, ultimately to unlock the reserves of the deeper low permeability intervals. Several development options have been carefully evaluated, which lead to the implementation of new technologies to optimize recovery, including cluster wells, horizontal wells, and hydraulic fracturing. The results of the implementation of the development strategy and technology have been outstanding. This has helped sustain the Badak Field's decline rate at around 25% annually compared to a 45% natural decline. In 2011, the gas production was successfully maintained at 75 MMSCFD or 3 times the base line of the "do nothing" case prediction, with more than 55 BSCF of reserves progressed.
Assimilating Microseismic and Welltest Data Using EnKF for Accurate Reservoir Characterisation
Authors: Han Mei , Li Gaoming , Chen Jingyi
Published: May 2016

The pressure trainsient data in welltest can only resolve the thickness-weighted average permeability but are more sensitive to the high productive (high permeability) layers. The mircroseismic data between fracture simulation treatment well and the monitor wells can only resolve the average velocity along its wave path but are more sensitive to the layer (or region) with high wave velocity (low productivity). Therefore, these two types of data are complimentary to each other in reservoir characterization. In this paper, we assimilate these two types of data using the state-of-the-art ensemble Kalman filter (EnKF) method. Layered homogeneous and heterogeneous reservoir examples verified the complimentary nature of these two types of data. The porosities and permeabilities in the layered reservoir obtained after assimilating both types of data are comparable to assimilating pressure trainsient and layer rate data. As EnKF is a stochastic process, we generated 10 different ensembles for each example for better uncertainty quantification. Assimilating only one type of data may yield biased estimates in porosity and log-permeability and hence biased prediction in the layer rates, while assimilating both pressure and microseismic data yield good estimates in reservoir properties with smaller uncertainty bound and hence more accurate layer rate prediction.
Innovative Method for Exploring Potential Reservoirs in Areas with Limited Data - Case Study from Deepwater South China Sea
Authors: Mukherjee Anubrati , Jiao He , Fang Yin Cheng , Wu Pei Shu , Hinz Curtis , Bo Zhang Zhen
Published: May 2016

The study area is in deep water offshore South China. Only one well has been drilled so far. There are 2 target intervals. The shallow interval encountered gas bearing sands with low porosity (average 5%) and high volume of clay (average 55%) and the deep interval carbonates and volcanics with no sand. Gas found in shallow interval was not of commercial saturation. Two key issues needed to be resolved from this study: a) Are there better quality sands away from the drilled well within the seismic block in the shallow interval? b) Are there sands in the deeper target interval? If so how are the qualities of the sands? The study looked at ways of using recent advances in seismic inversion and rock physics unravel most information from seismic in absence of sufficient hard data.
A Journey Towards Operational Excellence - from Effective Plant Performance Monitoring to Capturing Opportunities
Authors: Amminudin Kamarul A. , AbdulMohsin Mohammed T. , Muaibed Mohammad F.
Published: May 2016

Since being commissioned in June 2009 and being the largest crude increment program undertaken in recent history, Saudi Aramco's Khurais Central Processing Facility (KhCPF) has positioned itself for a greater leap by embarking on various operational excellence initiatives. This includes various optimization initiatives ranging from maximizing crude yield to optimizing energy efficiency performance. Nonetheless, to ensure a sustainable optimum performance following the implementation of these initiatives, which proves to be the greatest challenge for the facility, an in-house engineering dashboard was created to provide engineers and operations with plant performance monitoring capabilities.

To reinforce this drive for operational excellence, a multidisciplinary team member task force was formed with the objective of realizing the opportunities identified during the process improvement. The focus of the task force is to capture "low hanging fruit" opportunities that can be implemented immediately and require little or no cost. Today, after implementing these initiatives, the KhCPF is realizing the benefits of the operational excellence initiatives in the most sustainable way and has achieved significant improvement in the plant energy performance index by 3% and enhanced its crude recovery by around 0.2% without incurring any capital cost. Such value creation initiatives do not stop the task force from setting out on a journey of continuous improvement as part of its ongoing operational excellence effort.

Introduction

Saudi Aramco successfully commissioned the KhCPF in June 2009 as being the world largest crude increment program in history. This mega facility is located approximately between Riyadh and Dammam expressway in Saudi Arabia (Figure 1). Its facilities are intended to produce oil at 1.2 million barrels per day together with associated gas and condensate from three major fields in the area; namely, Khurais, Abu Jiffan and Mazalij. It also has the facility to cater for the water injection requirement for these fields, which is being supplied from the seawater treatment plant.
Sand Detection Using Integrated AVA and Rock Property Analysis: Applications in Horizontal Well Drilling
Authors: Romli Gunawan
Published: May 2016

An integrated methodology to characterize sandstone reservoirs in offshore Arabian Gulf oil fields is described in this paper. The methodology incorporates amplitude vs. angle (AVA) inversion and rock property analyses with the objective of defining optimum elastic properties to separate sandstone from shale and limestone. A set of elastic property cutoffs is determined from the rock property analysis and used to interrogate the AVA volumes to detect sandstone reservoirs and map their lateral and vertical distributions. The detected AVA sand images have been used to support planning and drilling of more than 100 wells in the last five years. Several examples from recent drilling results will be shared to show the application and limitation of the technique as well as recommendations for future improvements.

Introduction

Offshore Arabian Gulf oil fields make a significant contribution to overall Saudi Arabian oil production. Three major offshore oil fields produce from the mid-Cretaceous Wasia Formation. Figure 1 shows the stratigraphic column and type logs of the Wasia Formation. The Safaniya and Khafji Members of the Wasia Formation are the main oil reservoirs. They were deposited in a fluvio deltaic environment and consist of multiple sandstone and shale sequences with a few thin limestone beds. The sandstone facies range from shaly to very clean sands, with thicknesses ranging from 5 ft to 150 ft and an average porosity of about 20%.
Integration of Multi Functional Disciplines to Optimally Develop a Greenfield Gas Development Project: Example from T Field, Malaysia
Authors: Sunhaji Iman , Gorden William C. , Khalid Khadijah , Liew Alex , Jaynes Scott
Published: May 2016

A multidisciplinary teamwork approach has been taken to plan the development and execution of a greenfield gas project offshore Peninsular Malaysia. Domestic demand for gas in Peninsular Malaysia remains strong mainly to fuel growing electricity demand. Timely execution of the T Gas Development project is critical to supplementing declining capacity from existing developed fields and ensuring the ability to meet gas supply obligations.

The T field is a faulted, compressional anticline comprised of lower to middle Miocene sandstone reservoirs. The major reservoir in T consists of shallow, fluvio-deltaic to near-shore marine sediments containing a dry, non-associated gas. Discrete channel meanders and faulted segments within the field contribute to uncertainties in reservoir connectivity and compartmentalization. Incorporation of conventional seismic volumes with a derivative sand/shale indicator volume, and combined with an understanding of the environment of deposition and seismic stacking geometries, were used to better capture the range of predictive uncertainty in the lateral and vertical heterogeneities observed in the seismic data.

Installation of down-hole pressure gauges in the production wells are expected to increase understanding of dynamic reservoir connectivity during production. Due to shallow reservoir burial depth, the development wells were designed with ERD (extended reach drilling) ratios of up to 2.9 in order to optimize well placement and reserves capture. Furthermore, installation of downhole sand control in these high-angle wells will be challenging, but is critical to ensure production sustainability and minimize future wellbore interventions. Alternate Path Technology (APT) screens will be utilized to ensure successful frac pack completions at high well angles.

The T Field project utilizes the 'Design One, Build Multiple' concept via replication of proven design components to optimize cost and schedule. This paper describes key challenges for T Field development planning, including managing reservoir compartmentalization and connectivity uncertainties, optimizing well design, and the use of 7" tubing completions in high quality sands to maximize well deliverability and meet gas supply requirements with optimum well count for reserves capture.

Early stakeholder-alignment and detailed execution planning have been pursued to meet aggressive project schedule reflecting the need to rig-up before monsoon season and to tie into a major gas compression hub during a limited shut-down window.
Rock Typing for a Fractured Carbonate Reservoir with Low Resistivity in Middle East
Authors: Mu H. , Sun X. , Lin S. , Feng Z. , Xu F.
Published: May 2016

The T reservoir is a fractured carbonate reservoir located in Middle East with low resistivity and high total porosity. Fractures of various scales and dip-azimuth are well developed. The storage space for matrix consists of intragranular pores and micro fractures. Effective porosity interpretation suggests that less than 20 percent porous volume in total porosity is effective. FMI log interpretation of more than 120 wells show that fractures are well developed with various apertures, dip and strikes.

Three types of the reservoir rock were distinguished according to the combination of range of effective porosity and scale of fractures. Rock Type 1 is the fractured limestone in lower part of reservoir characterized by development of large scale fractures. The effective porosity is less than 5% with total porosity over 20%. Rock Type 2 is the fracture-matrix mixed limestone in middle part of reservoir characterized by smaller scale fractures and pores connected to fractures. Rock Type 3 is the matrix limestone in upper part of reservoir with higher effective porosity (over 20%). Dynamic data show that the major productivity is contributed by Rock Type 1 and Rock Type 2, which are distributed in lower and middle intervals of T reservoir.

Introduction

Reservoir rock typing is one of the most challenging subjects in carbonate reservoirs. Definition of significant reservoir rock types petrophysically and geologically is critical in the reservoir characterization, which is also fundamental in providing a link to geological modeling. If the reservoir rocks are properly classified and defined, the real dynamic characteristics of the reservoir will be provided in reservoir simulation modeling.