bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heavy Oil Viscosity Measurements; Accuracy, Reliability, and Repeatability
Authors: Alkandari Hassan , Alomair Osamah , Elsharkawy Adel 
Published: April 2012

Abstract
The aims of this work is to present consistent and reliable viscometer measurements for heavy oil samples and to draw a comprehensive comparison amongst the several viscosity measuring procedures for the same solo crude oil sample. Viscosity measurements were preformed for temperatures over the range of 25°C to 80 °C with three apparatuses. These apparatuses include an Oscillating Piston Electromagnetic Viscometer (OPV), Rotational Rheometer using Cone and Plate (RCV), and Oscillating U-tube of rotating concentric cylinders (OUV). More than 36 heavy dead oil well head samples were collected from different Kuwaiti fields to perform this study. The API gravity of oil samples collected, ranges from 13 to 23 degrees with a good assortment of composition. It was concluded that each viscosity measurement is environment as well as apparatus operational principle limited. These expected errors in laboratory-measured oil viscosity are the main factors in the degradation of the oil viscosity correlation equation's efficiency. Homogenized sample aliquots are analyzed at various test conditions; hence corresponding data is precisely collected. The measurements are verified and assured by the National Institute of Standards and Technology (NIST) tractable Standard Referenced Materials.
Anisotropy and True Formation Resistivity Measurements with a New LWD Resistivity Sensor
Authors: Bittar Michael , Wu Hsu-Hsiang , Li Shanjun , Bayrakdar Mohammed 
Published: April 2012

Abstract
The determination of true formation resistivity is always a challenging component of oil field exploration. The electromagnetic (EM) resistivity tool, one of the most well-known logging tools, provides geological information by detecting electrical properties of the formation downhole. Accurate geophysical knowledge assists petrophysicists to develop a better reservoir and to enhance oil production. However, it is often critical to know the hydrocarbon saturation, which requires reliable horizontal and vertical formation resistivities. During the last decade, wireline triaxial induction logging has successfully provided resistivity anisotropy in vertical wells, whereas logging-while-drilling (LWD) azimuthal EM tools have demonstrated similar field results in deviated wells with only high relative dip angles. Low dipping drilling conditions have posed difficulties regarding conventional LWD measurements for resistivity anisotropy determination because of simple antenna structures.
This paper describes the development of a new LWD EM resistivity sensor that uses an antenna configuration with tilted transmitter and receiver antenna orientations rotated relative to the borehole by rotary steerable drilling. Measurements made by this antenna configuration are obtained by unique processing schemes that enable the determination of the dip angle, strike angle, and vertical and horizontal resistivity of the formation at any relative dip angle while drilling. The paper discusses the design concept of the sensor and the environmental parameters that influence tool responses.
Several test results, with data processing and the inversion schemes, are shown and compared to various resistivity logging tools. These results indicate that the new LWD EM resistivity tool provides reliable conventional resistivity readings and determines resistivity anisotropy and dip at any relative dip angle. The paper also highlights additional discussions about the calculation of anisotropy and dip angle and about related applications using the sensor.
Dependency of Remaining Oil Saturation on Wettability and Capillary Number
Authors: Abeysinghe Kumuduni Prasangika , Fjelde Ingebret , Lohne Arild 
Published: April 2012

Abstract
Wettability is a major factor that affects the flow behavior and recovery efficiency in oil reservoirs. In this study, the effects of wettability on water-oil relative permeability (kr), capillary pressure (Pc) curve and capillary desaturation curve (CDC) have been investigated in laboratory on core scale.
Water floods and surfactant floods at different capillary numbers (Nc) were carried out in sandstone rock at different wettability conditions. These floods were followed by oil floods. The kr and Pc curves were estimated by history matching the experimental production and pressure drop.
The recovery after water flood was higher at non water-wet conditions but a higher throughput of water was needed. Estimated kr and Pc curves vary with the wettability of the rock. The relative permeability of the wetting phase is more curved than that of the non wetting phase. The measured CDC for oil in mixed-wet condition and the CDC for water in water-wet condition deviate from the typical CDC shape. In these cases, it is found that the measured remaining oil or water saturation is a function of the number of pore volumes injected and also it is largely affected by capillary end effects. Since the residual saturation is difficult to be obtained in core floods at non water-wet conditions, the measured CDC in laboratory experiments does not represent the true CDC. More focus should be directed at relative permeability (corrected for capillary end effects) than the residual oil saturation.
The results presented in this paper demonstrate the importance of the wettability of rock on recovery efficiency and also the importance of correcting the laboratory data especially predicting the flow behaviour of non water-wet conditions. Remaining oil saturation based on relative permeability should be used instead of residual oil saturation in evaluation of the potential for tertiary recovery, e.g. surfactant.
A New Viscoelastic Surfactant for High Temperature Carbonate Acidizing
Authors: Wang Guanqun , Nasr-El-Din Hisham A. , Zhou Jian , Holt Stuart 
Published: April 2012

Abstract
Diverting agents have been widely used during matrix acidizing treatments to accomplish the uniform distribution of acid solutions across the target zones. One of the most popular formulas is based on viscoelastic surfactants (VES) which showed good results in the lab and field tests. A major limitation with the conventional VES is temperature. Most of these surfactants do not hold viscosity at temperatures greater than 250°F.
A new VES that can be used at higher temperatures was developed. The apparent viscosity of the spent VES-based acids was measured as a function of temperature and shear rate at 300 psi. Various corrosion inhibitors were mixed together with the new VES to find out the most compatible formula. A coreflood test was conducted on a 20 in. long carbonate core to examine the performance of the new surfactant. The core was CAT scanned before and after the experiment to observe the wormholes created by the new system. The acid contained 20 wt% HCl and 4 vol% VES.
Spent acids of the new VES had a high viscosity up to 325°F. Several corrosion inhibitors were identified that can be mixed with the new system without affecting the apparent viscosity of the spent acid. Similar to current VES, mutual solvent is recommended in the post flush to reduce the fluid viscosity and remove any gel from the core. CAT scan of the core show wider and tortuous wormholes, indicative of good retardation of the new VES-based acid system.
Improved Understanding of Proppant-Formation Interactions for Sustaining Fracture Conductivity
Authors: Rayson Neelam , Weaver Jim 
Published: April 2012

Abstract
A recent paper published data describing interactions between shale and commercial ceramic proppants. It reported that the diagenetic outgrowth materials formed were zeolites. The creation of these zeolites was reported to largely depend on the characteristics of the formation mineralogy and the fluid medium. It was further reported that when tested under dynamic conditions, these diagenetic-type reactions were not observed. The standard API crush test was used to indicate the percentage of fines generated.
This paper presents the results of extensive laboratory testing with sandstone and bauxite proppants at moderate reservoir temperatures and normal reservoir pH in which dramatic loss of proppant-pack permeability and proppant strength were observed. Zeolites were identified and responsible for much of the fines material created during the testing cycle. Zeolite deposits were also detected, even when bauxitic proppants were aged in the aqueous fluid medium alone. In both cases, the fluid medium was DI water, which is not a source of any metallic element. These results indicate that zeolite formation is also dependent on the chemistry of the proppant. Similar results have been reported for tests conducted under dynamic flow conditions. It is crucial to ensure that the true value of proppant strength degradation is determined; however, it is questionable that the API conductivity testing procedure is the best method.
This paper presents repeatable data generated from laboratory tests at reservoir temperatures, as well as at elevated temperatures, that indicate conditions under which zeolites are formed and the effect on proppant strength degradation using both single-grain crush-strength analysis and the API conductivity procedures. This data provides better information for the proper selection of proppant for given formation conditions.
Forecasting and Monitoring Water Cut Utilizing ESP Pump Discharge Pressures and Fluid PVT Analysis
Authors: Al Enezi Sultan M. , Warlick Mickey L. , Almusabeh Muzher I. , Kaba Abdullah A. 
Published: April 2012

Abstract
In some fields, the ability to obtain reliable water production numbers is hard to do. Case in point is one Saudi Aramco offshore field. This particular field has all wells on electrical submersible pumps (ESPs) and has supervisory control and data acquisition recorded real time. Oftentimes the timing of getting the samples to shore, the lab, and to the desktop of the engineer takes a very long time. By modeling and using the pressure-volume-temperature (PVT) data from the reservoir and the pump discharge pressure of a well we can determine what water cut is necessary to match the surface flowing wellhead pressure (also taking into account frictional losses). Utilizing this method allows Saudi Aramco to monitor water production in the field and then to verify it with actual water samples whenever the data becomes available.
Stimulation Strategies to Guard against Uncertainties of Carbonate Reservoirs
Authors: Bukovac Tomislav , Nihat M. Gurmen , Jauregui Jairo Leal , Malik Ataur R. , Bolarinwa Simeon , Al-Ghurairi Fadel 
Published: April 2012

Abstract
Due to the complex nature of carbonate reservoirs, reservoir characterization often leaves many uncertainties. Finding the right balance between risks associated with these uncertainties and optimum stimulation makes acid fracturing and matrix acidizing treatments challenging. The stimulation objectives become even more difficult in highly slanted, layered, naturally fractured reservoirs exhibiting high permeability contrast. In this environment, adequate fluid diversion and leak-off control have always been the key design elements for stimulation. Achieving diversion and leak-off with a degree of control to make treatments applicable to a wide range of reservoir uncertainties presents challenges.
A novel, polymer-free degradable diversion system has been in use for the last three years in the largest carbonate reservoirs of the world, namely the Khuff formation in Saudi Arabia's Ghawar field. The self-diverting fluid combines viscoelastic surfactant in HCl with degradable fiber technology. The fluid develops viscosity as the acid spends, while the fibers bridge across perforation tunnels and fissures to form a filter cake. Because the fibers completely degrade with time and the spent fluid breaks when it comes into contact with hydrocarbons or solvents during flowback, the fluid temporarily limits injectivity into thief zones without damaging the reservoir.
More than 50 wells have been stimulated with this fluid system covering a wide range of single and multi-stage matrix acidizing and acid fracturing treatments. The controllable nature of diversion from well to well and on-the-fly adjustment capabilities of the fluid system have successfully ensured stimulation performance despite the uncertainties of carbonate reservoirs in Saudi Arabia. In essence, this novel fluid became the standard insurance policy for stimulation treatments of carbonate formations where the permeability models are inherently underestimating the contrast due to difficulties of placing natural fractures and quantifying their impact.
Preparation and Characterization of Colloidal Gas Aphron based Drilling Fluids Using a Plant-Based Surfactant
Authors: Nareh`ei M. Arabloo , Shahri M. Pordel , Zamani M. 
Published: April 2012

Abstract
Colloidal gas aphron (CGA) based drilling fluids, because of their non-coalescing nature, excellent capability in minimizing deep invasion, and also behaving like a flexible bridging material, are indicated for drilling permeable and fractured formations. Their unique feature is to form a solid free, tough, and elastic internal bridge in pore networks or fractures to minimize deep invasion by means of air microbubbles, which can be removed easily during the initial stage of production.
CGA based fluids combine certain surfactants and polymers to create the system of microbubbles. Surfactant is used to produce the surface tension to contain the aphron as it is formed, build the multilayer bubble wall, and create interfacial tension to form a non-bonding network capable of bridging openings in permeable and fractured formations. Polymer is used as viscosifier and aphron stabilizer. The surface activity and aggregation behavior of the surfactant affects the stability and also other physico-chemical properties of generated microbubbles. Therefore, selection of a suitable surfactant is important for the generation of microbubbles with the desired rheological and filtration properties.
The goal of this paper is to investigate the potential use of a new plant-derived surfactant as an aphronizer surfactant in preparation of CGA based drilling fluids for accomplishing desirable rheological and filtration properties. For this purpose, natural surfactant obtained from leaves of special tree namely Zizyphus Spina-Christi and used for preparation of aphron-based fluids. To evaluate the potential use of new plant-derived surfactant as an aphronizer, various physico-chemical properties of aphron-laden muds were investigated. To achieve the research objectives, laboratory tests of suspension generation, microscopic visualization, initial yield, filtration loss, and rheological behavior with varying concentrations of surfactant and polymer were performed.
Effect of base fluid viscosity and surfactant concentration on size/size distribution of microbubbles, rheology, and yield of CGA based drilling fluids will be presented. Three rheological models, namely, Bingham Plastic, Power Law and Casson models were used for characterizing rheological properties of the muds studied.
Transient Pressure Analysis of Gas Wells in Unconventional Reservoirs
Authors: Wu Yu-Shu , Wang Cong , Ding Didier 
Published: April 2012

Abstract
Unconventional gas reservoirs have shown the potential to be the next world primary energy resource and have received a lot of attention in the past few years in the world. Even with the significant progress that has been made world-wide towards commercial development of natural gas from these unconventional resources, understandings or modeling tools of gas flow in these extremely low-permeability reservoirs are far behind the industry needs. In this paper, we present a numerical model for modeling transient gas flow behavior and its application to well testing analysis in unconventional gas reservoirs. Specifically, the numerical model simulates realistic reservoir gas flow processes, including Klinkenberg effect, non-Darcy flow behavior, and adsorption under reservoir flow condition, in addition to wellbore storage and skin effect. We use the numerical model to generate various type-curves for nonlinear gas flow for well testing analysis in unconventional porous and fractured reservoirs and demonstrate the conventional well testing analysis approach may still be applicable for analysis of unconventional gas reservoirs.
Effect of Acid Gas on Cement Sheath Integrity: Experimental Findings
Authors: Garnier Andre , Laudet Jean Benoit , Patil Sandip , Patil Rahul , Ravi Kris , Ferreira Luis 
Published: April 2012

Abstract
Long-term cement sheath integrity is important to maintain wellbore stability and effective zonal isolation. Various factors influence cement sheath integrity, such as effective placement of cement, mechanical and thermal stresses, and interaction with corrosive gases. Corrosive gases are known to chemically attack Portland cement. However, the challenge is designing a cement system that can sustain CO2 and H2S attack.
Acid-gas-resistant systems are useful in various applications, including producers and CO2 injector wells. To understand how the cement sheath is affected by prolonged exposure to corrosive gases, detailed studies should be performed at different temperatures and pressure conditions.
This paper documents a resilient cement system that was exposed to CO2 and H2S gas environments for a period of three months. For comparison purposes, a neat cement system was used as a reference and tests were conducted at 194 (90°C) and 284°F (140°C). X-ray density profiles obtained using tomography techniques were used to analyze samples. The cement samples responded differently to CO2 and H2S environments. Formation of CaCO3 on exposure to CO2 was evident and was reflected in X-ray density profiles. Conversely, leaching of neat cement was observed on exposure to H2S gas. In both cases, the resilient cement system specially designed for the work described proved to be a better option when compared to neat cement because the destruction was less prominent in the former case.
Sedimentary environment and palaeogeography of the ?Palaeocene-Middle Eocene Kashkan Formation, Zagros fold-thrust belt, SW Iran
Authors: Yeganeh Bizhan , Feiznia Sadat , van Loon A. 
Published: April 2012

Sedimentary environment and palaeogeography of the ?Palaeocene-Middle Eocene Kashkan Formation, Zagros fold-thrust belt, SW IranThe Kashkan Formation (?Palaeocene to Middle Eocene) in the Zagros fold-thrust belt, SW Iran, which is intercalated between to marine limestone formations, consists of conglomerates, sandstones and siltstones. The sedimentology and the palaeogeography of the Kashkan Formation had not received any attention thus far, but have now been studied in seven sections, situated in the province of Lorestan. The sediments form twelve lithofacies, three ichnosubfacies and seven architectural elements, which are described, depicted and analysed. The analysis leads to the conclusion that most sediments accumulated in a low-sinuosity, low-gradient braided-river system (characterised by mainly unidirectional palaeocurrent directions, and by sheetfloods), that occasionally showed meandering characteristics (represented by overbank deposits and large bars). The deposits of this system closely resemble those of the South Saskatchewan River in Canada, which is considered as the classical example of a sand-bed braided river. The river flowed roughly from North to South, as deduced by palaeocurrent indicators such as imbrication and large-to medium-scale trough cross-stratification (direction measured in the trough axes). This current direction is supported by the southward to south-westward thinning of the formation and by the diminishing average grain size in the same direction. The trace fossils in the Kashban Formation fit all in theSkoyeniaichnofacies, which has here three ichnosubfacies which allow a more detailed palaeoenvironmental reconstruction, indicating that the braided stream passed into the low-energy shoreface zone of a tidally-influenced sea.
Mesozoic mass extinctions and angiosperm radiation: does the molecular clock tell something new?
Authors: Ruban Dmitry 
Published: April 2012

Mesozoic mass extinctions and angiosperm radiation: does the molecular clock tell something new?Angiosperms evolved rapidly in the late Mesozoic. Data from the genetic-based approach called ‘molecular clock’ permit an evaluation of the radiation of flowering plants through geological time and of the possible influences of Mesozoic mass extinctions. A total of 261 divergence ages of angiosperm families are considered. The radiation of flowering plants peaked in the Albian, early Campanian, and Maastrichtian. From the three late Mesozoic mass extinctions (Jurassic/Cretaceous, Cenomanian/Turonian, and Cretaceous/Palaeogene), only the Cretaceous/Palaeogene event coincided with a significant, abrupt, and long-term decline in angiosperm radiation. If their link will be further proven, this means that global-scale environmental perturbation precluded from many innovations in the development of plants. This decline was, however, not unprecedented in the history of the angiosperms. The implication of data from the molecular clock for evolutionary reconstructions is limited, primarily because this approach deals with only extant lineages.
Ultrasonography as a diagnostic and prognostic approach in cattle and buffaloes with fatty infiltration of the liver
Authors: Tharwat M. 
Published: April 2012

Ultrasonography as a diagnostic and prognostic approach in cattle and buffaloes with fatty infiltration of the liver
The aim of the present study was to determine whether ultrasonographic evaluation of the hepatic parenchyma could be used as a diagnostic and prognostic approach in cows and buffaloes with hepatic lipidosis. For this purpose, cows (n=16) and buffaloes (n=10) with fatty infiltration of the liver were examined by ultrasonography. Treated cows and buffaloes were monitored for hepatic changes ultrasonographically, biochemically and histologically. Clinical findings were non-specific and included anorexia, recumbency, muzzle necrosis, and icteric mucosal membranes. Laboratory data revealed neutrophilia, hyper γ-globulinemia, elevated activities of aspartate aminotransferase, γ-glutamyl transpeptidase, creatine kinase and lactate dehydrogenase, and high concentrations of insulin, total bilirubin, non-esterified fatty acids and β-hydroxyl butyric acid. Laboratory results 7, and 21 days after treatment showed progressive improvement in the chemistry profile. On admission, ultrasonographic examination of the hepatic parenchyma in cows and buffaloes revealed either increased or decreased hepatic echogenicity; histologic examination revealed marked fatty infiltration of the hepatocytes. One week after treatment, the hepatic parenchyma was visualized easily, liver boundaries were clearly imaged, and histologic examination of hepatic specimen showed a moderate degree of fatty infiltration. Three weeks after treatment, the hepatic parenchyma was almost similar to normal, the hepatic and portal blood vessels could be easily imaged, and the histologic picture had greatly improved where the liver resembled the normal organ. Six cows and seven buffaloes made a full recovery while the remaining ten cows and three buffaloes were slaughtered and thoroughly examined postmortem. Ultrasonography showed a good correlation with histologic and laboratory findings.