bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of retinoids during oocyte maturation diminishes apoptosis in caprine embryos
Authors: Conceição Juliana C. Z. , Moura Marcelo T. , Ferreira-Silva José C. , Ramos-Deus Pamela , Silva Priscila G. C. , Cantanhêde Ludymila F. , Chaves Ricardo M. , Lima Paulo F. , Oliveira Marcos A. L.
Published: June 2015

Exposure of caprine oocytes and embryos to retinoids enhances embryonic development, but the mechanisms governing this phenomenon have not been characterised. The aim of the present study was to evaluate if the incidence of apoptosis is affected by the addition of retinyl acetate (RAc) and 9-cis-retinoic acid (RA) during in vitro maturation (IVM) of caprine oocytes. Embryonic development was recorded on days 3 and 8 post-fertilisation, and apoptosis was measured by caspase activity and DNA fragmentation (TUNEL assay). Control zygotes had lower capacity to cleave and reach the blastocyst stage (24.45 ± 2.32 and 5.32 ± 0.81, respectively) than those of RAc- (29.96 ± 1.62 and 7.94 ± 0.93, respectively) and RA-treated groups (30.12 ± 1.51 and 7.36 ± 1.02, respectively). Oocytes and blastocysts positive for TUNEL assay were more frequent, respectively, in the controls (8.20 ± 0.78, 8.70 ± 1.05) than in RAc (5.60 ± 0.52, 4.80 ± 0.51) and RA (6.40 ± 0.69, 5.40 ± 0.69). Caspase activity did not differ between control oocytes (7.20 ± 0.91), RAc (6.60 ± 0.68) and RA (7.30 ± 0.67), but it was reduced in RAc- (5.05 ± 0.62) and RA-treated blastocysts (5.75 ± 0.22) compared to controls (8.35 ± 0.71). These results indicate that the addition of retinoids during IVM increases the developmental potential of goat embryos with a concomitant reduction in apoptosis rates.
Urokinase-type plasminogen activator does not affect in vitro bovine embryo development and quality
Authors: Krania Fotini , Dovolou Eleni , Rekkas Constantinos A. , Heras Sonia , Pappas Ioannis , Soom Ann Van , Amiridis Georgios S.
Published: June 2015

The effects of modification of the in vitro embryo culture media (IVC) with the addition of urokinase-type plasminogen activator (u-PA) on the yield and/or quality of bovine embryos were examined in two experiments. In Experiment 1, denuded embryos were cultured in semi-defined synthetic oviductal fluid (SOF) for seven days, while in Experiment 2 embryos were co-cultured with cumulus cell monolayer in a serum-containing SOF medium. Plasminogen activator activity (PAA) and plasminogen activator inhibition (PAI) were determined in all spent IVC media. At the activity used (5 IU/ml), u-PA had no effect either on in vitro embryo production rates or on embryo quality as revealed by gene expression analysis of 10 important mRNA transcripts related to apoptosis, oxidation, implantation and metabolism. PAA and PAI analysis indicated the need for wellbalanced plasminogen activators and inhibitors as a culture environment for embryo development. However, more research is needed to unveil the mechanism by which u-PA is involved in in vitro embryo production systems.
A jobb pitvar és bal kamra méretének és funkciójának összefüggései egészségesekben. Eredmények a háromdimenziós speckle-tracking echokardiográfiás MAGYAR-Healthy Tanulmányból
Authors: Piros Györgyike Ágnes , Domsik Péter , Kalapos Anita , Lengyel Csaba , Orosz Andrea , Forster Tamás , Nemes Attila
Published: June 2015

Introduction: Heart cycle includes systole and diastole when heart chambers are characterized by a complex motion. Aim: The present study was designed to test whether relationships exist between three-dimensional speckle-tracking echocardiography-derived right atrial and routine two-dimensional echocardiography-derived left ventricular volumetric and functional parameters is healthy subjects. Method: The present study comprised 20 healthy volunteers. Complete two-dimensional echocardiography and three-dimensional speckle-tracking echocardiography were perfomed in all cases. Results: Left ventricular ejection fraction showed correlations with systolic and diastolic right atrial volumes and area strain characterzing atrial contraction in diastole. Right atrial volumes respecting cardiac cycle correlated only with left ventricular end-systolic diameter and volume, while similar relationships could not be confirmed with end-diastolic parameters. Conclusions: Relationships could be demonstrated between three-dimensional speckle-tracking echocardiography-derived right atrial and two-dimensional echocardiography-derived left ventricular volumetric and functional parameters in healthy subjects. Orv. Hetil., 2015, 156(24), 972–978.
A folyóiratcikkek súlya a különféle tudományterületek szakirodalmában: az elmúlt két évtized trendjei
Authors: Schubert András , Soós Sándor
Published: June 2015

Trends of preferred publication channels in selected categories of Sciences, Social Sciences and Arts & Humanities were studied by determining the percentage share of references in reviews to serials (journals) in all references. It was found that in the period 1995–2014, the fraction of articles published in journals was increasing in all selected areas of science and scholarship. The most dynamical increase was found in Social Sciences. Orv. Hetil., 2015, 156(24), 985–987.
Egyenlőtlenségek a méhnyakszűrésben
Authors: Döbrőssy Lajos , Kovács Attila , Budai András
Published: June 2015

Theoretically, the cytology-based cervical screening is capable of early detection of precancerous epithelial lesions of cervix uteri and its cancer, and of early referral to treatment. In this way, screening can inmprove the quality of life of the patients and reduce mortality from the target disease. Unfortunately, this often remain unexploited, because there might be inequalities on both “supply” and “demand” side of screening. In addition to the geopolitical situation of a country, inequalities might result from differences in the health care systems, and heavy access to the screening services. On the other hand, the socioeconomic status, the health-conciousness of the target population, and their knowledge and information of the benefits and potential harms of screening examination might have a bearing on the acceptance or refusal of the offered screening. Efforts need to be made to increase the uptake of cervical screening programmes. Orv. Hetil., 2015, 156(24), 955–963.
Intestinal helminth parasites of the grey wolf (Canis lupus L.) in Serbia
Authors: Ćirović Duško , Pavlović Ivan , Penezić Aleksandra
Published: June 2015

The grey wolf (Canis lupus L.) is the most widespread large carnivore in Europe with large populations in the Eastern part of Europe and the Balkan Peninsula. In this study, a total of 102 wolves were examined for intestinal helminth parasites. The carcasses were collected within the Serbian part of the wolf’s range during the period 2009–2014. Nine helminth species were found: one nematode, Toxocara canis (3.9%), one trematode, Alaria alata (1.0%), and seven cestodes, Taenia pisiformis (1.0%), T. hydatigena (9.8%), T. polyacantha (2.9%), T. taeniaeformis (2.0%), T. (syn. Multiceps) multiceps (3.9%), T. serialis (1.0%) and Mesocestoides litteratus (1.0%). Taenia (syn. Hydatigera) taeniaeformis has been registered for the first time in a wolf from Europe. An overall moderate prevalence (16.7%) of infected wolves was recorded. There was no statistically significant difference in prevalence between sexes. Of the years studied, the highest prevalence was found in 2014 (57.1%). The maximum number of helminth species per host specimen was four.
Clinical babesiosis and molecular identification of Babesia canis and Babesia gibsoni infections in dogs from Serbia
Authors: Davitkov Darko , Vucicevic Milos , Stevanovic Jevrosima , Krstic Vanja , Tomanovic Snezana , Glavinic Uros , Stanimirovic Zoran
Published: June 2015

Canine babesiosis is a frequent and clinically significant tick-borne disease. Sixty symptomatic dogs with clinical findings compatible with babesiosis were included in this study conducted in Serbia. After clinical examination, blood samples were taken for microscopic examination, complete blood count (CBC), Canine SNAP 4Dx Test, DNA analyses and sequencing. The main clinical signs included apathy, anorexia, fever, brown/red discoloration of urine, pale mucous membranes, icterus, splenomegaly, and vomiting. The main clinicopathological findings in Babesia infections were a slight to severe thrombocytopenia and a mild to very severe normocytic normochromic anaemia. Microscopic evaluation revealed 58 positive samples with the presence of large and small intraerythrocytic piroplasms in 57 and 1 sample(s), respectively. No co-infections were found using SNAP test. Two Babesia species, B. canis (58/60) and B. gibsoni (2/60), were differentiated by polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP). Species identification was further confirmed by sequencing PCR products of B. gibsoni samples and six randomly selected B. canis samples. All dogs were treated with imidocarb dipropionate (6.6 mg/kg of body weight), given intramuscularly twice at an interval of 14 days. This report presents the first molecular evidence of the occurrence of B. gibsoni and B. canis, confirmed by DNA sequencing, in sick dogs from Serbia.
Immediate and Early Loading of Hydrothermally Treated, Hydroxyapatite-Coated Dental Implants: 2-Year Results from a Prospective Clinical Study
Authors: Simmons David E. , Palaiologou Archontia , Teitelbaum Austin G. , Billiot Susan , Popat Lomesh J. , Maney Pooja
Published: June 2015

This investigation was undertaken to determine if multithreaded implants partially coated with plasma-sprayed hydroxyapatite (HA) could be effectively loaded earlier than 3–6 months after placement. Forty-eight patients (22 men, 26 women) were enrolled in the study and received 48 implants. The population was divided into 2 groups: A implants (n = 23) were loaded immediately on the day of surgery and group B implants (n = 19) were loaded 3 weeks after surgery. Cone beam computerized tomography (CBCT) scans were taken preoperatively to aid in treatment planning. Bone density was evaluated by tactile feedback during surgery. Insertion torque was recorded at time of implant placement. Resonance frequency analysis, performed on the day of surgery, at the time of loading, and at 6, 12, and 24 months, was used to record implant stability according to the unit's implant stability quotient (Osstell ISQ). Standardized radiographs were taken at time of implant placement and at 6, 12, and 24 months to measure crestal bone stability. Bone level changes were measured by software (Image J). Bone quality was judged as either type 1 (n = 1), 2 (n = 31), 3 (n = 15), or 4 (n = 1). There were no failures in the group A (survival = 100%, n = 23/23) and 1 failure in group B (survival = 94.7%, n = 18/19). After 2 years in function, cumulative mean radiographic bone loss was 0.75 ± 0.50mm (maxillae: 0.92 ± 0.49 mm, n = 14; mandibles: 0.67 ± 0.49 mm, n = 28). No differences in bone levels were noted between implants placed in previously augmented and nonaugmented sites, and there were no periodontal or soft tissue complications. After 2 years in function, implants partially coated with plasma-sprayed and hydrothermally treated HA were clinically predictable when restored in occlusion immediately after or within 3 weeks of implant placement.
Zagospodarowanie turystyczne jako ekonomiczny czynnik kształtowania produktu turystycznego obszaru
Authors: Guzik Halina , Strzelczyk Wojciech
Published: June 2015

As a multidimensional phenomenon, tourism is an important determinant of the economic development of cities and regions. This study pays particular attention to the development of tourism, which is part of the supply side of the tourism market. It presents the economic aspects of the management of tourism space, highlighting the optimal use of assets and resources a given spatial unit has, including the substantial and constantly evolving development of tourism. The purpose of this article is to present tourism development as part of the tourism product area, constituting one component of a city's mega-product, and the presentation of the economic aspects of tourism area management. The discussion introduces the basics of a marketing approach to the development of the tourism specific reception area product, and more precisely a methodical concept for defining such a product. The article is of a mainly theoretical nature.
Ekonomiczna wartość obszarów chronionych. Zarys problematyki i metodyka badań
Authors: Zawilińska Bernadetta
Published: June 2015

Theoretical in nature, this paper provides an overview of issues concerning the economic value of protected areas, including methodological problems relating to the valuation of natural assets. It discusses the total economic value concept, which defines the value of natural areas as consisting of use values (direct use values, indirect use values and option values) and non-use values (bequest values and existence values). Selected methods used in the valuation of use and non-use values of natural areas are also presented (e.g. travel cost method, hedonic prices method, contingent valuation method).
Anthropogenic nitrogen deposition predicts local grassland primary production worldwide
Authors: Stevens Carly J. , Lind Eric M. , Hautier Yann , Harpole W. Stanley , Borer Elizabeth T. , Hobbie Sarah , Seabloom Eric W. , Ladwig Laura , Bakker Jonathan D. , Chu Chengjin , Collins Scott , Davies Kendi F. , Firn Jennifer , Hillebrand Helmut , Pierre Kimberly J. La , MacDougall Andrew , Melbourne Brett , McCulley Rebecca L. , Morgan John , Orrock John L. , Prober Suzanne M. , Risch Anita C. , Schuetz Martin , Wragg Peter D.
Published: June 2015

Humans dominate many important Earth system processes including the nitrogen (N) cycle. Atmospheric N deposition affects fundamental processes such as carbon cycling, climate regulation, and biodiversity, and could result in changes to fundamental Earth system processes such as primary production. Both modelling and experimentation have suggested a role for anthropogenically altered N deposition in increasing productivity, nevertheless, current understanding of the relative strength of N deposition with respect to other controls on production such as edaphic conditions and climate is limited. Here we use an international multiscale data set to show that atmospheric N deposition is positively correlated to aboveground net primary production (ANPP) observed at the 1‐m2 level across a wide range of herbaceous ecosystems. N deposition was a better predictor than climatic drivers and local soil conditions, explaining 16% of observed variation in ANPP globally with an increase of 1 kg N·ha−1·yr−1 increasing ANPP by 3%. Soil pH explained 8% of observed variation in ANPP while climatic drivers showed no significant relationship. Our results illustrate that the incorporation of global N deposition patterns in Earth system models are likely to substantially improve estimates of primary production in herbaceous systems. In herbaceous systems across the world, humans appear to be partially driving local ANPP through impacts on the N cycle.
Forest census and map data for two temperate deciduous forest edge woodlot patches in Baltimore, Maryland, USA
Authors: Dandois Jonathan P. , Nadwodny Dana , Anderson Erik , Bofto Andrew , Baker Matthew , Ellis Erle C.
Published: June 2015

This data set reports on a census of all trees within two 6.25‐ha plots (250 m × 250 m) of temperate deciduous woodlot patch on the campus of the University of Maryland Baltimore County (UMBC), Baltimore, Maryland, USA. Woodlot patches are primarily of the tulip poplar association. From 2011–2012, a 25 m × 25 m quadrat grid was established for each plot by total station surveying equipment. From 2012–2014, the location and DBH (diameter at breast height, 1.37 m) of all woody stems ≥ 1 cm DBH that reached ≥1.37 m tall were censused, whether living or dead. All such stems were also marked with numbered metal tags. All living stems were identified at least to genus and to species when possible. All censused stems and associated data (tag number, DBH, location, species, status) were entered into a geographic information system (GIS) map layer based on stem location within a Universal Transverse Mercator (UTM) projected coordinate system where each stem was represented as a unique point feature. The primary objective of these data is to provide a reference for stem location and diameter for the calibration and evaluation of ground‐based 3D remote sensing technologies based on computer vision and personal digital camera or cell phone image collections. With regular re‐census, the data could also be used for tracking growth, mortality, and recruitment of patchy forest woodlots within a suburban landscape mosaic.
Home ranges of Recent mammals
Authors: Kelt Douglas A. , Van Vuren Dirk H.
Published: June 2015

The data provided here include home range and body sizes for 285 species of mammals in 177 genera. Data were extracted from 552 published sources, and have been used in multiple papers since we originally published results of analyses in 1999 and 2001. While this likely is the most comprehensive such data set available, it is arguably biased taxonomically and geographically. While some mammal orders are well represented taxonomically most are not. Hence, while all genera in Monotremata, Proboscidea, and Pholidota are represented, these comprise only 60, 66, and 20% of species, respectively; moreover, these are relatively minor radiations. In contrast, we have no species of Paucituberculata, Microbiotheria, Notoryctemorphia, Tubulidentata, Hyracoidea, Cingulata, Scandentia, Dermoptera, and Primates (the latter likely reflecting a bias in data acquisition). The modal proportion of genera and species across 27 terrestrial orders is zero; the median values are 10.8% (genera) and 3.7% (species), suggesting that further data should be sought to confirm generalizations provided by these data.
Connectivity structures local population dynamics: a long‐term empirical test in a large metapopulation system
Authors: Castorani Max C. N. , Reed Daniel C. , Alberto Filipe , Bell Tom W. , Simons Rachel D. , Cavanaugh Kyle C. , Siegel David A. , Raimondi Peter T.
Published: June 2015

Ecological theory predicts that demographic connectivity structures the dynamics of local populations within metapopulation systems, but empirical support has been constrained by major limitations in data and methodology. We tested this prediction for giant kelpMacrocystis pyrifera, a key habitat‐forming species in temperate coastal ecosystems worldwide, in southern California, USA. We combined a long‐term (22 years), large‐scale (~500 km coastline), high‐resolution census of abundance with novel patch delineation methods and an innovative connectivity measure incorporating oceanographic transport and source fecundity. Connectivity strongly predicted local dynamics (well‐connected patches had lower probabilities of extinction and higher probabilities of colonization, leading to greater likelihoods of occupancy) but this relationship was mediated by patch size. Moreover, the relationship between connectivity and local population dynamics varied over time, possibly due to temporal variation in oceanographic transport processes. Surprisingly, connectivity had a smaller influence on colonization relative to extinction, possibly because local ecological factors differ greatly between extinct and extant patches. Our results provide the first comprehensive evidence that southern California giant kelp populations function as a metapopulation system, challenging the view that populations of this important foundation species are governed exclusively by self‐replenishment.
NMR Logs Help Formation Testing and Evaluation
Authors: Hursan Gabor G. , Deering James S. , Kelly Francis N.
Published: June 2015

A large-scale formation evaluation program has been conducted in multiple fields to enhance reservoir description and fluid characterization. Well-logging targets include siliciclastic and carbonaceous formations that pose numerous challenges to petrophysical interpretation and wellsite operations. First, it is difficult to select formation pressure points as permeability prediction by conventional logs is hindered by complex lithology, grain size variations and microporosity. The second challenge is the complex distribution of fluids where hydrocarbons may vary from heavy oil to gas within a single reservoir section. This often necessitates a number of fluid pumpouts or samples that are by far the most time-consuming and expensive element of the logging program.

Nuclear magnetic resonance (NMR) logs noticeably reduce the uncertainties of log interpretation and increase operational efficiency in multiple ways. Formation tester measurements demonstrate that the readily available NMR Free Fluid Index (FFI) predicts fluid mobility with remarkable consistency especially in complex shaly sand intervals. Advanced NMR T1, T2 and diffusivity measurements also helped identify distribution of formation water, oil and gas.

This work presents case studies to demonstrate each of the above benefits with notes on principal limitations and areas of improvement. It also reviews technical lessons from NMR logging performed by different vendors in several evaluation wells in the area from the viewpoint of everyday tasks. Practical guidelines are formulated for logging tool and activation selection, log quality-control, and NMR data processing with standard basic and advanced algorithms followed by recommendations for future reservoir description studies.
Can Proppants Do More Than Hold The Fracture Open?
Authors: Saldungaray Pedro , Palisch Terry , Leasure Josh
Published: June 2015

In the 1940's experimental fracture treatments were performed without proppant. However in most formations unpropped fractures heal quickly with no sustained benefit, and in 1947 river sand was introduced as proppant. The first evolution in proppants came in the 1950's, when river sands started to be replaced by higher quality mined sands from Illinois and Texas. This was the early recognition that employing more uniform, rounder, stronger - and ultimately more conductive proppant - produced larger production gains. From this point on efforts concentrated on improving sand performance and finding new propping materials that could cope with harsher conditions. In the 1960's, petroleum engineers incorporated walnut hulls, glass and plastic beads into frac designs. The 1970's saw the introduction of resin coated proppants and the first commercial bauxite based ceramic proppant, followed by low and intermediate density ceramics in the 1980's. However, throughout this time, proppants still served one primary purpose – to prop open the fractures and provide a conductive flowpath for hydrocarbon production.

Placement of proppant deep into the formation brings a unique opportunity of conveying new functions, additional to the primary roles of keeping the frac mechanically open and providing a conductive path for production enhancement. For decades most proppant development efforts concentrated on developing proppants that could either cope with higher stress and deliver higher conductivity or improve proppant transport via lower density, while minimal effort was put in adding other functionalities. Recently it has been recognized that other functions can be incorporated into manmade proppants during the industrial manufacturing process, thereby exploiting the placement opportunity. These functions might include assuring flow in the production system, providing reservoir surveillance or monitoring fracture properties.

This paper will review the latest technology developments that enable the incorporation of these functions into proppants, including how the new proppant delivered technologies permit users to cost effectively deploy additional functionalities in the initial completion of hydraulically fractured, frac-packed and gravel-packed wells. The paper will also present recent case histories of field implementations of these technologies which illustrate how these high function proppants can reduce overall operating costs, enhance production and diagnose hydraulic fractures.
Chelating Agent for Uniform Filter Cake Removal in Horizontal and Multilateral Wells: Laboratory Analysis and Formation Damage Diagnosis
Authors: Al-Ibrahim Hussain , AlMubarak Tariq , Almubarak Majed , Osode Peter , Bataweel Mohammed , Al-Yami Abdullah
Published: June 2015

An impermeable mud cake layer, created on the formation face while drilling may be favorable for drilling operations but detrimental to well productivity. In vertical high pressure wells the layer is cleaned out while flowing back the well at adequate pressure drawdown. On the other hand, low pressure differential at the sand face in horizontal wells makes well cleanup treatments a necessity. Not all filter cake components are acid soluble. Commonly used inorganic acids and oxidizers are very reactive and cause uneven filter cake removal, which can affect the well's performance. As a result, there was a need to evaluate slow-reacting chemicals that can produce delayed uniform filter cake removal in horizontal wells. These treatment chemicals vary from the nonreactive acid-free microemulsion fluid systems to the weak organic acids, acid precursors, enzymes and chelating agents.

The objective of this paper is to evaluate two chelating agent based treatments, NTA and EDTA, as filter cake removal treatments for a sandstone reservoir utilizing oil based mud (OBM) drill-in fluid (DIF) in Saudi Arabia. Coreflooding experiments were run under reservoir conditions to evaluate fluid-rock interaction. In addition, fluid-fluid compatibility was conducted between chelating agent and drill-in fluids base brines and between the chelating agent and formation fluid using high temperature, high pressure (HTHP) see-through cell. Solubility and static fluid-loss tests were conducted to evaluate the filter cake removal efficiency.

Experimental results indicated that the NTA-based treatment was effective in removing up to 91% of the filter cake uniformly after soaking treatment for 24 hours. Fluid-fluid compatibility tests showed that the NTA-based chelating agent, when mixed with reservoir fluids, was free from precipitation or emulsion. On the contrary, mixing the chelating agent with the DIF carrier brine resulted in severe precipitation of insoluble permanently damaging byproducts. The laboratory study also observed that pH has a direct proportional relationship with the amount of precipitation.

EDTA-based treatment results showed a removal efficiency of 93% after soaking treatment for 90 hours. Fluid-fluid compatibility tests showed that the EDTA-based treatment, when mixed with OBM DIF was free from precipitation or emulsion. On the contrary, mixing the chelating agent with the reservoir formation water resulted in severe precipitation of insoluble permanently damaging byproducts.
Laboratory Evaluation of Different Mode of Supercritical CO2 Miscible Flooding for Carbonate Rocks
Authors: AlOtaibi Fawaz M. , Zhou Xianmin , Kokal Sunil L.
Published: June 2015

Field application of supercritical CO2 (sc- CO2) miscible flooding continues to grow. Optimization of sc- CO2 injection during miscible flooding modes represents one of the dominant factors affecting its performance in carbonate oil reservoirs. The main objective of this study was to investigate the impact of different modes of sc- CO2 miscible injection on oil recovery and injectivity in carbonate rocks. Several modes of sc- CO2 injection modes were investigated including continuous CO2 miscible flooding, water-alternating-gas (WAG), and tapered WAG injection. Five coreflooding experiments were conducted to evaluate oil recovery for different modes of CO2 injection under reservoir conditions. Composite cores of 25 cm length from a specific, producing carbonate reservoir were used in the study. Both horizontal and vertical coreflooding experiments of continuous CO2 injection mode were carried out to compare oil recovery and injectivity during CO2 flooding. Horizontal core flooding experiments under WAG mode was performed at pore pressures of 3,200 psi and 3,800 psi.

The experimental results indicate that tertiary oil recovery was influenced significantly by different CO2 injection modes and the direction of displacement. 18.4% and 26.74% of original oil in cores were recovered for horizontal and vertical experiments of continuous CO2 injection modes, respectively. In horizontal WAG experiments with different pore pressures, higher oil recovery was observed at a pore pressure of 3,800 psi compared to 3,200 psi. The marginal increase in incremental oil recovery indicates that pressure increase beyond 3,200 psi will not have a significant impact. The injectivity of different CO2 injection modes is reported in this paper.
Measurements of Volumetric Phase Behavior of Mixtures of n-decane and CO2 at High Pressures and High Temperatures
Authors: Rahman Saifur , Kandil Mohamed E. , Al-Saifi Nayef , Sultan Abdullah S.
Published: June 2015

The use of CO2 as an enhanced oil recovery agent is ever increasing as CO2 is becoming widely used for heavier oil production. The environmental burdens of CO2 also encourage that it should be disposed of in a way that those liabilities are minimized. Hence there is a need for understanding the phase behavior of Hydrocarbon-CO2 systems and mechanism by which the hydrocarbon rich phase is displaced. Accurate data on phase behavior of mixtures containing hydrocarbons and CO2 will not only help in oil recovery and production but also will help in designing infrastructure for transportation and downstream separation.

Solubility of CO2 in hydrocarbons at low and moderate pressures is pretty good. This phenomenon reduces the density of the mixture and volume swelling is observed. At high pressure range there is a dramatic increase in the density of CO2 with pressure, which can produce a complete miscibility. In some complex mixtures of hydrocarbon and CO2 a second liquid CO2-rich phase can also exist.

Development of experimental methods and technique for measurements of volumetric properties for binary mixtures of CO2+ n-decane will be discussed. The phase behavior properties measured include isothermal compressibility, mass density, bubble points at temperatures from (313 to 410) K and pressures up to 76 MPa (11000 psi). Our data are compared with the predictions from equation of state (EOS) models commonly used in software simulators. The accuracy of experimental data and challenges in development of the experimental technique will also be discussed.
Successful Installation of Multistage Choke Valve Technology in Water Flowlines to Reduce High Pressure Drop across Choke Valves
Authors: Al Saeed Abdullah J. , Al Mousa Salah A. , Al Ajmi Mohammed A. , O'Donnell Martin
Published: June 2015

Reasons for internal and external valve damage are varied in the industry. Valve damage can occur due to irregular preventive maintenance, sand erosion, internal and external corrosion, improper materials selection, and/or due to operating the valve outside of its operating pressure and temperature ranges1. This paper will focus only on valve cavitation related damage, which happens on water choke valves.

The main purpose of this paper is to demonstrate a trial installation of multistage choke valve technology in water lines that reduces high pressure drops across water injection choke valves. The trial test was conducted on two single-stage choke valves installed upstream of two water injection wellheads, which were completed in two different reservoirs. The selected single-stage choke valves were experiencing high noise and vibration levels where operators could barely meet the required water injection rate for each well.

Different surface mitigation measures were evaluated to overcome this serious issue prior to conducting the trial installation of the multistage chokes. The field water injection system was studied from the water injection plant (WIP) where the water injection centrifugal pump (3000 psig) is located, through the water lines, fittings and valves all the way to the water injection wellheads. Results from the trial test show that implementing multistage choke valve technology can prevent high noise and vibration levels and allow the target water injection rate per well to be met.
An Integrated Approach for Downhole Leak Detection
Authors: Al-Hussain Ali Musa , Hossain M. Enamul , Abdulraheem Abdulazeez , Gajbhiye Rahul
Published: June 2015

Effective well integrity practices ensure the protection of people, facilities and the environment from the risk of uncontrolled release of formation fluids throughout the life cycle of a well, so petroleum engineers are always required to ensure well integrity. Part of well integrity is to make sure downhole equipment and barriers are in excellent condition. Identifying the downhole leak source of pressure communication between tubingcasing and casing-casing annuli in any well is a huge challenge for petroleum engineers. Detecting any leak at the early stage is an important key to well integrity management. Two objectives were set in this paper as follows: The first objective is to develop a method that can detect downhole leaks by utilizing only rigless data based on full interpretation and evaluation of different logs in the field: temperature, noise, and corrosion log in different scenarios. The first scenario is shut-in condition while the second scenario is in flowing condition. The flowing condition will be either after bleeding off Tubing-Casing-Annulus or Casing-Casing-Annulus. This approach was implemented in a specific operation order to ensure job success. Also, the corrosion log was run to evaluate the condition of tubing and casing separately. The second objective of this study is to compare rigless approach results with the conventional rig approach for downhole leak detection, which will be completed by statistically analyzing corrosion, temperature, and noise surveys. Moreover, guidelines were set in each step of these surveys to confirm leak occurrence. This objective was achieved through developing a method and program for leak detection. Based on the conducted temperature, noise, and corrosion surveys, the integrated approach identified the leakage zones through the developed module in this report. The obtained results from the rigless approach were almost similar to the rig approach. The only difference between both approaches is that the developed method is more accurate, compared to the rig approach, since it can identify any corrosion or leak depth, while the rig approach will identify only leak zones. The paper will discuss in details the development of this method and its successful implementation in a few selected offshore wells in the same field of the Arabian Gulf.
Assessment of Water Injection-Related Scale Risks for an Onshore Carbonate Oilfield Incremental Development Project in Central Arabia
Authors: Osode P. I. , Almubarak T. A. , Bataweel M. A. , Al-Faifi M. G. , Al-Khaldi M. H.
Published: June 2015

Water flooding has been widely used in the industry as a secondary recovery technique to improve recovery from oil reservoirs. One of the major operational challenges is addressing the compatibility between injected water and formation water in order to proactively lower the probable risk of scale formation near wellbore. A thorough investigation was conducted to evaluate the probability of scale formation and identify the effective mitigation options for a Central Arabian incremental development project.

A holistic approach was implemented at this study to achieve the objective through reviewing analogue reservoirs, running numerical predictions of scale tendency, carrying out laboratory experiments to evaluate the compatibility of the formation water with the injected mix water and conducting in-situ coreflood experiments to quantify the potential risk of formation damage.

This study identified an inherently high calcium sulfate scale risk associated with the planned seawater injection in the new reservoir development and within the surface production fluid process facilities. Appropriate scale mitigation options including the potential impact of an injection seawater sulfate removal process facility will be discussed in this paper.
Analysis of High Temperature Sour Gas Wells to Mitigate Corrosion and Scale Formation
Authors: Ramachandran Sunder , Gupta Anuj , Al-Muntasheri Ghaithan , Leal Jairo , Syafil Irfan
Published: June 2015

In this paper a review of the thermodynamics of gas/condensate and water systems with hydrogen sulfide and water/hydrocarbon wetting and its influence on corrosion is presented.

Compositional analysis is used to provide information on the variation of different material streams and composition as a function of depth. Although on the surface, the liquid stream of a well can predominately consists of hydrocarbon, the liquid stream downhole can have a very different composition. The variation of liquid composition, pressure, temperature, ionic composition and flow regime can have interesting implications on sour corrosion and scale formation.

Calculations on scaling conditions and thermodynamic conditions that cause corrosion are done on a well under bottom hole and well head conditions. Iron sulfide films that are formed during high temperature CO2/H2S corrosion of carbon steel and often layered structures of scale are formed where the composition of scale varies with depth. The calculations provide guidance on the types of iron sulfide and iron oxyhydride scales that may form.
Compositional Analysis and Treatment of Oilfield Scales
Authors: El Hajj Hicham , Pal Omprakash , Zoghbi Bilal
Published: June 2015

Scale formation in the wellbore and pipelines during upstream processes can result in production disruptions and declines in revenue. Hence, treatment and removal of oilfield scales are important for avoiding production depreciation. Scale varies in chemical composition, being composed of layers of scale adhering to the inside of tubing and deposited during the well life cycle. Identifying the location and composition of scale deposits is the first step in designing a cost-effective remediation program. Scale removal could be mechanical or chemical. Scale removal techniques should be quick, non-damaging to the wellbore, tubing, or formation environment, and effective at preventing reprecipitation. There have been many significant advances in scale control and remediation in recent years. Improvements in placement technology, reservoir chemistry, and intelligent fluids provide more cost-effective options for chemical scale inhibition or removal in downhole tools. The purpose of the present study was to analyze scale composition and then develop and recommend a solution to effectively remove specific oilfield scale from downhole tools. In this study, scale samples were collected from downhole tools and compositional analysis conducted to characterize both crystalline and non-crystalline compounds. Composition of scale samples was determined by X-ray diffraction (XRD), X-ray fluorescence (XRF), and acid solubility for more accurate analysis. XRD and XRF results showed that the scale composition was mostly carbonate. Based on the scale composition, an acid-free carbonate scale dissolver was evaluated, and the results are presented in this paper.
Comparative Analysis of Feature Selection-Based Machine Learning Techniques in Reservoir Characterization
Authors: Akande Kabiru O. , Olatunji Sunday O. , Owolabi Taoreed O. , AbdulRaheem AbdulAzeez
Published: June 2015

Comparative study and analysis of the generalization performance and predictive capability of machine learning (ML) techniques in reservoir characterization and modeling is presented in this work by utilizing two distinct Oil well data sets. The performances of the ML techniques (artificial neural network (ANN) and support vector regression (SVR)) have been boosted by proposing a correlation-based feature selection approach which employs fewer datasets resulting in less computing time and processing power. Predictive accuracy of both ML techniques in permeability prediction has been improved as a result of the feature-selection approach. Furthermore, ANN shows superior performance in case of large dataset while SVR shows better performance in case of small dataset. The results of this work provide excellent insight and guidance to practitioners in improving ML performance and determining the most appropriate technique in cases of small and large datasets.
A Methodology for Identifying & Quantifying Uncertainties (Seismic to First Phase Field Development) in Reservoir Simulation: Case Study of Two Fields in Saudi Arabia
Authors: Moriwawon Babatunde , Al-Turki Ali , Al-Shawaf Ali , Radhey Bansal
Published: June 2015

Understanding and management of subsurface uncertainties has become increasingly important for oil and gas companies to optimize reserve portfolios, make better field development decisions and improve day-to-day technical operations such as well planning. In this paper, the authors developed models, workflows and methodologies for multiple development scenarios that span the range of uncertainties for all stages of reservoir description and simulation for two fields (Field A and Field B) in Saudi Arabia. These processes are based on responses to uncertainty parameters in order to capture and quantify uncertainties. Uncertainty quantification for the two reservoirs was performed using experimental design (ED) approach taking into account seismic interpretation, geological uncertainty, and dynamic data. ED is an intelligent way of sampling parameter space by selecting combination of predefined variables to minimize the number of "experiments" to characterize the behaviour of a system, and to limit the number of models to be run. As a result, robust and responsive reservoir models were constructed to predict the field performance as well as to evaluate various future development strategies alongside better risk-assessments.
Step Change in Hydraulic Fracturing Methodology by Analyzing Clastic Gas Reservoir Field Experience to Achieve Production Enhancement
Authors: Al-Ali Ammar H. , Islam Ashraf
Published: June 2015

The clastic non-associated gas reservoirs are encountered in one of the Saudi Arabian oilfields. There is a wide variation in permeability in this Devonian age formation, varying from tight rocks with 0.1 md or less to more than few Darcie's in highly unconsolidated sandstones. While the prolific areas are easily producible at sustained high gas rates by conventional drilling and using sand control completion mechanisms, the relatively tighter areas require hydraulic fracturing to sustain commercial flow rate.

During the last 10 years, the field A focused on exploiting gas reservoirs is being developed with vertical or S-shaped wells, and completed using a monobore tubular assembly. Proppant fracturing treatments are routinely conducted in multiple stages along the vertical wellbore. Fracture treatment parameters are adjusted over time by the introduction of different fracture fluids to enhance stability and avoid premature screen out. Proppant flow back measures were taken with the use of resin-coated proppants. A large database was developed on stimulation treatments and results that allowed conducting a detailed analysis to understand the behavior and effect of hydraulic fracturing trends on the reservoir performance to optimize the design parameters and further increase reservoir potential.

This paper documents the analysis of the pre- and post-fracture treatment data, production analysis and thorough evaluation of petrophysical and geomechanical measurements from this massive database of 10-year long operational period. This study shows that there is a room to improve fracturing treatments and fluid chemistry and recommends a step change in the well stimulation strategy by modifying some existing technologies and also applying novel technologies that have been carefully studied and approved using laboratory and field trial testing. The results from the application of this new strategy are presented in the paper using actual examples.
Feasibility Study of Photovoltaic Microgrids and Their Application in Powering Remote Onshore Oil and Gas Surface instrumentation
Authors: Vidal Faez Angelo M. , Ruvalcaba Velarde Salvador A.
Published: June 2015

A new remote onshore well site development requires electrical energy to power instrumentation, cathodic protection and communications equipment. Although this equipment is generally not power intensive, it is still a common practice to deploy transmission lines to connect the well site to the electrical grid, no matter how far away it can be. This procedure is usually expensive and time consuming.

In this study, we propose a distributed energy generation scheme using a solar photovoltaic (PV) microgrid which can be rapidly deployed and can power one or several well sites. For this purpose, we utilized the microgrid modeling software HOMER (Hybrid Optimization of Multiple Energy Resources), which allowed us to develop a techno-economical evaluation as well as an environmental impact study of the initiative. Furthermore, we present the conceptual design of the system, which can be easily scaled to the power requirements of any number of well sites.

Using this approach, we show the feasibility of a remote area renewable energy microgrid along with its levelized cost of energy (LCOE). In addition, we show that this method can significantly reduce the reliance on conventional sources of energy, while maintaining the reliability of the system.

In summary, this proposal depicts how onshore surface equipment power requirements can be reliably met by using distributed energy generation. The use of renewable energies provides an alternative path which enables energy efficiency optimization while providing a reduction in CO2 emissions through a clean environmental solution.
Well Engineering Schematics for Design & Analysis using Digital Well Files
Authors: Al-Sanie Faisal S. , Al-Khudiri Musab M. , Radhwi Asem O. , Mubaireek Hussain , Kashif Muhammad , Jovin Tony
Published: June 2015

The advancements in tools and technology with the variety of data available in drilling industry has increased drastically. It is quite important to manage them in the best form so that we could effectively use this for several constructive purposes such as planning, execution and post processing analysis in drilling. For many years data has been majorly classified as static and real time where Real time from sensors lives feed is often visualized for operational decision making. Static information such as casing design, tubular design, well head design, BOP design are often stored as static files at database level.

It is often a tedious process for a drilling expert to replicate a similar design in engineering that he had created before for reference modelling or analysis. This is mainly due to the fact that the data is often not available in a flexible format.

To address such issues Saudi Aramco has decided to build a Drilling Engineering schematics package that serves in visualizing all of the available drilling data types. These data types significantly assist us to uncover many uncertainties such as when the data is captured or analyzed.

The system is designed is in flexible format such that it could be accessible for all users across the same platform. Industrial format WITSML and Representational State transfers web services are used together to construct a data converter that converts any form of data into WITSML objects. These WITSML objects are then referenced using an image library set of components before they reach the final output for users.

The system will be so useful for the drilling professionals for design and analysis as it can detect anomalies in the data such as casing, Cementing, Bottom Hole Assembly to name a few.