bluuebunny/crossref_metadata_2025 huggingface dataset:
Understanding the Impact of Production Slugging Behavior on Near-Wellbore Hydraulic Fracture and Formation Integrity
Authors: Lu Haidan , Anifowosh Olatunbosun , Xu Lili
Published: January 2018

Numerous studies on unconventional shale well production data have shown that downhole pressure fluctuations can exceed 300 psig during a slugging period. Such pressure fluctuation will result in very high drawdown and could lead to near-wellbore formation damage when the rock failure criterion was met. An engineering workflow was developed to investigate the impact of multiphase slugging events on cemented casing plug and perforation (CCPP)and open hole sliding sleeves (OHSS) completions. Based on transient pressure analysis and geomechanical evaluation, safety operational envelope was generated to minimize the risk of formation damage due to slugging behavior.

In this study, a dynamic multiphase flow simulator was used to predict the pressure amplitude and frequency during the slugging events in both a CCPP and OHSS completion configuration. The results from the simulation were then incorporated into a geomechanical model to analyze and identify potential hydraulic fracture closure and formation damage concerns, which can compromise well performance.

The results from this study show that OHSS completion is more vulnerable to damage during the downhole slugging period than a CCPP completion. However, severe formation and fracture damage could occur during downhole slugging for CCPP well if the well is operated outside the safety operational envelope. Results from the two case studies led to the conclusion that it is crucial to consider the effect of downhole slugging on near-wellbore fracture and formation integrity to avoid permanent and irreversible damage.
Application of Solid Scale Inhibitor in Annular Space to Reduce Well Intervention Cost
Authors: Bhaduri Sumit , Shen Dong , Gupta D. V.
Published: January 2018

Formation damage caused by mineral scale development is one of the major reasons resulting in reduction of hydrocarbon production during a well's life cycle. Scale inhibitors are most widely used to control scale deposition in producing wells either by adding them directly to fracturing fluids in wells where stimulation treatment is planned or by performing remedial squeeze treatments. Prolonged protection can be achieved by adding proppant-sized solid inhibitor during the stimulation treatment. The current study addresses the benefits of alternate methods of placing solid inhibitor depending on the well completion system. In the case where stimulation treatment is not planned, the solid inhibitor can be placed in the annular space between the production tubing and formation in the long open-hole horizontal well to provide extended protection as the well starts to produce. This solid inhibitor once depleted as evidenced by residual analysis can be recharged effectively by injecting liquid inhibitors that restores the effectiveness, allowing extension of protection life-times.

An appropriate inhibitor chemical was first identified for the treatment from the produced water scaling analysis. A suitable solid scale inhibitor was prepared by adsorbing this chemical onto a high surface area water/oil insoluble substrate, and multiple surface modifications made to control the inhibitor release rate. The long term inhibitor chemical release profile was evaluated by packing this solid inhibitor into a column and eluting with synthetic produced water at expected bottom-hole temperatures of 200°F.

The solid inhibitor elution tests show long protection times when solid inhibitor was applied. The projected inhibitor protection would be more than 60,000 pore volumes (PVs) of produced water before the inhibitor chemical was substantially depleted. In a well, 3000 pounds of this inhibitor can be potentially placed in the annular space, which would result in preventing scaling for 330 thousand barrels of water being produced, with protection life-time of more than 5 years (at 170 barrels of water per day). The presence of high surface area substrate allows inhibitor to be recharged after inhibitor depletion. The efficiency of the inhibitor recharge application was investigated by a series of column experiments.

Placing the solid inhibitor into the annular space will delay the requirement for scale squeeze treatments significantly, and reduce the overall well maintenance cost for the operator, particularly in an offshore environment. The ability of the solid inhibitor to be re-charged using conventional scale squeeze chemistry enables more chemicals to be retained when subsequent squeeze is potentially performed on the wells.
Successful Installation of Horizontal Openhole Gravel-Pack Completions in Low Fracture Gradient Environment: A Case History from Deepwater West Africa
Authors: Jeanpert J. , Banning T. , Abad C. , Mbamalu I. , Hardy J.
Published: January 2018

This paper presents the design and execution of an openhole gravel-pack completion campaign in deepwater West Africa. Based on field history and past challenges, a novel approach was implemented to address the low fracture gradient.

Various aspects of the gravel pack design are discussed - drilling and gravel pack fluid selection, screen selection, openhole displacement, filtercake removal, placement technique, and pumping design. The placement method uses screens with shunt tubes, an existing technology, that was deployed in an unconventional manner. Post treatment evaluation and analysis are also presented. Results are compared to conventional gravel pack placement and to previous wells from this field.

The success of the first completion enabled an increase in openhole length in subsequent wells. The understanding of the packing sequence was consolidated after each well, driving the optimization of the pumping schedule.
Fracture Permeability of Activated Calcite Veins to Water and Gas
Authors: Mokhtari Mehdi , Tutuncu Azra N.
Published: January 2018

Many shale and limestone formations exhibit natural fractures in the form of calcite veins. Although these natural fractures might be sealed, they are prone to activation in hydraulic fracturing operation due to their low mechanical properties. Once these fracture are activated, the flow in such fractures without proppants play a role not only in production performance but also in analyzing the mechanisms responsible for the low recovery of water flowback. To address this issue, we created induced fractures within calcite veins of Niobrara formation using indirect tensile experiment and fracture permeability experiments were conducted by injecting both water and gas. The results of fracture permeability tests in Niobrara formation were compared with the results of fracture permeability tests in granite sample. The effective fracture permeability to water is significantly lower than the fracture permeability to gas in calcite veins while the fracture permeability of granite sample to both water and gas is almost similar. Comparing the fracture permeability of the Niobrara sample with the granite sample provides some insights into the possibility of water trapping microfractures as a possible reason for low water-flowback recovery. Besides the interaction of water with rock, fracture roughness can be another mechanism affecting fracture permeability. To this end, the topographic surface of samples were measured by laser profilometer and the fluid flow in rough fractures were simulated numerically to analyze the effect of roughness on fracture permeability.
How Does Mixing Water Quality Affect Cement Properties
Authors: Saleh F. K. , Rivera R. , Salehi S. , Teodoriu C. , Ghalambor A.
Published: January 2018

The integrity of a well is a crucial component for the longevity of a well. Cement isolates the casing and protects the well from fluids, pressure, and other components that may jeopardize its stability. Extreme care and research should be invested in analyzing the water quality that is used to mix cement. In this study, the effects of water quality on API Class G-Portland cement were studied to understand the relationship between water quality, rheology, thickening time, and compressive strength. Although extensive research has been made on well cement in general, no previous research focused on oilwell cement water quality was available until now. Thus, this paper is intended to serve as reference as well as motivation for future research. Cement thickening time was recorded using a cement consistometer and compressive strength using a universal testing machine. We tested several samples including soft to very hard, very saline and field waters. We also tested the hard water at different temperatures to investigate the effect of temperature on thickening time. A positive correlation occurred between the temperature of the mixing water and consistency, the higher the temperature was of the mixing water, the faster the consistency rose. In contrast, a negative correlation between water hardness and thickening time occurred. As water hardness increased, thickening time decreased and vice versa. A percentage change up to 2.4% was recorded between different water qualities making soft water (0 gm/L) have a longer thickening time in comparison to very hard water (180 gm/L+). Variations on the pH of the different waters used did not seem to have a significant impact on the results obtained. Compressive strength results showed that soft water (water with no hardness) is the strongest among the other samples prepared with different waters. In addition, a similar trend cannot be observed at different curing times. For instance, some samples show high strength on the first day but drops as cement hydration time increases.
Injectivity Decline During Waterflooding and PWRI due to Fines Migration
Authors: Borazjani Sara , Chequer Larrisa , Russell Thomas , Bedrikovetsky Pavel
Published: January 2018

Injectivity decline by fines migration with two-phase flow is important in low-salinity and smart waterflooding in oilfields. The complexity of detachment of the natural reservoir fines, their mobilization, migration and straining in two-phase environment preclude simple formulae for injectivity decline prediction. The objective of the present study is to derive of the semi-analytical model for two-phase axi-symmetric flow with variation of injected salinity, fines migration, and consequent permeability damage. A simple and robust model allows investigating the effects of injection rate, injected salinity, oil viscosity, relative permeability, and kaolinite content in the rock on skin-factor growth.
Treating Liquid Banking Problem to Increase Shale Gas Wells Productivity
Authors: Phan Tri , Kazempour Mahdi , Nguyen Duy , Champion Nalco
Published: January 2018

One of the common causes of gas wells productivity loss is attributed to liquid accumulation near the wellbore over the production life of the wells. For gas condensate reservoirs, when the bottomhole pressure falls below the dew point pressure, liquid hydrocarbon drops out of the gas phase, residing in the near wellbore region and causing condensate block. Fracturing fluid also contributes to liquid blockage as only 5 to 30% of fracturing fluids are recovered from the reservoir. For a tight shale formation where the pore sizes are as small as nanometers, capillary pressure is large enough to cause liquid entrapment in the pore body reducing the relative permeability to the gas phase.

A variety of methods such as gas cycling, super critical CO2 injection, solvent injection, and wettability alteration using fluorinated surfactants/polymers have been suggested to treat liquid block or banking (i.e., water and condensate). However, these methods are either not effective or expensive, and do not provide a good return on investment. As capillary pressure depends on surface/interfacial tension (ST/IFT) and the contact angle, a treatment method that combines the effect of ST/IFT reduction and wettability alteration can be applied to lower capillary pressure, thus, to enhance liquid unloading. In addition, reducing the ST between gas and the liquid phase (water/gas condensate) will increase the carrying capacity of the gas phase with respect to the banked liquid phase.

This paper presents a practical laboratory testing procedure developed to screen and recommend cost effective production enhancement formulations to treat liquid blocking. Based on laboratory test results obtained from this testing procedure, a non-fluorinated production enhancement formulation was recommended for a field trial. The recommended formulation was tested at two gas wells: one vertical and one horizontal in North Texas. The proposed formulation was used in the fracturing fluids when the wells were re-fractured. Production data from the two wells have shown a sustained increase in gas production and water recovery rate. The lessons learned here can be used as a guideline to increase production life of existing gas wells and to maximize hydrocarbon (gas and associated condensate) recovery rates.
Economic Evaluation of Wettability Alteration towards the Alleviation of Condensate Blocking
Authors: Ajagbe Oluwatobi , Weiss Maxine , Fahes Mashhad
Published: January 2018

Wettability alteration has been investigated by research groups over the past two decades as a possible answer to the problem of condensate blocking in order to mitigate its effect on productivity loss, however, very limited field applications have been attempted with one case of success and two cases of failure. A volume of experimental and simulation studies have been published, but these papers rarely identify the factors that can contribute towards the success or failure of such a stimulation method. The absence of an actual economic analysis of this method in the literature is also evident. In this study, we build upon the experience of the research team in this area in order to produce a comparative study to be able to identify the conditions under which wettability alteration can be recommended as a suitable approach to address condensate blocking.
Well Productivity Impairment Due to Fines Migration
Authors: You Zhenjiang , Bedrikovetsky Pavel
Published: January 2018

Compressibility needs to be accounted for when estimating productivity decline in closed gas and oil reservoirs, and in closed aquifers. Previous works derived an analytical model and well index for inflow performance accompanied by fines migration and consequent permeability damage for incompressible flow towards well. In the present work, we account for fluid and rock compressibility. The problem with given and constant well production rate is investigated. Mathematical model is developed, which provides well productivity index decline with time. Under this model, the solution of damage-free compressible flow in a closed reservoir is matched with the impedance growth formulae for incompressible flow in the well vicinity. The well production data have been successfully matched by the model; the tuning parameters have the common values. It allows indicating the fines mobilization, migration and straining as possible well impairment mechanism in wells under investigation.
Methodology for Evaluating Drag Reduction Characteristics of Friction Reducer
Authors: Shah S. , Asadi M. , Wheeler R. , Brannon H. , Kakadjian S. , Ainley B. , Chen Y. , McElfresh P. , Ghalambor A. , Kaufman P. , Archacki D.
Published: January 2018

Friction reducers have been an integral part of the oil and gas industry for many years. They possess very unique properties of reducing friction pressure associated with the flow of fluid in tubulars. Friction pressure loss or hydraulic characteristics of friction reducers depend greatly on how they are tested and evaluated in the laboratory. Today, there is no standard procedure for their evaluation. American Petroleum Institute (API) oversees the development and publication of industry standard practices for various fluids and materials. Recognizing the need for a standard testing procedure for friction reducers, a Committee made up of members from industry and academia was formed and charged to develop a document outlining the standard procedure.

Round-robin tests were conducted by four industry organizations and one academic institution, employing their in-house flow loops and were requested to report the results. Tests were to conduct friction pressure measurements of friction reducers, and to develop and deliver to the industry a standard procedure and method to measure and analyze friction reducers data in straight pipes. The test fluids chosen were two friction reducers: one anionic and the other cationic. Water data were also gathered as base line. Same fluid samples were submitted to all laboratories. The calibration procedure and fluid testing procedure was developed and distributed to all involved in fluid testing. The analysis for data reduction and for reporting results was also developed and distributed to all.

It was found that the calibration procedure was more critical than originally thought. The determination of internal diameter of the circular tube is the most important parameter that influences the friction pressure loss results greatly. In this paper, the details of various flow loops, calibration procedure, data analysis procedure, and results obtained with water as base line and two friction reducers are presented and discussed. A standard procedure for testing and evaluating friction reducers for their friction loss properties is outlined.

Following this standard procedure and carefully performing the testing with friction reducers will yield very similar results among various laboratories in the industry. This will make it easy when comparing the performance of friction reducers for their friction loss properties from different organizations.
Comparative Study on the Performance of Different Stand-Alone Sand Control Screens in Thermal Wells
Authors: Fattahpour V. , Mahmoudi M. , Wang C. , Kotb O. , Roostaei M. , Nouri A. , Fermaniuk B. , Sauve A. , Sutton C.
Published: January 2018

Stand-alone sand screen (SAS) is proven to be effective for sand control in unconsolidated sands in thermal wells. The characteristic design parameter to specify SAS is the aperture size, while the Open to Flow Area (OFA) is chosen to balance between the mechanical integrity of the screen, the completion cost, and the plugging risk. The objective of this study is to compare the performance of common SAS types for a certain geological condition.

A series of three-phase large-scale sand retention tests (SRTs) is performed on slotted liner, wire-wrapped screen, and punched screen coupons. The tests are performed using two common representative PSDs of the McMurray Formation. The test matrix includes the common aperture sizes and OFA for each screen and PSD based on the current best practices in the industry. The test procedure is designed to mimic the near wellbore flow velocities, with three-phase flow ranging from 0%-100% water cut and produced gas-oil ratio ranging from 0-277 scf/bbl. The gas flow was supposed to simulate the steam breakthrough incidents. Live measurements are obtained of the sanding amount and pressure drops along the sand-pack and across the screen. Screen plugging is assessed after the completion of each test.

The sanding and flow performance are shown to be a function of the aperture size, PSD, near-wellbore flow velocities, and the water cut. In low fluid flow rates, all the screen types show minimal pressure drops and perform similarly. As near-wellbore velocities increase or gas flow occurs, pressure drops show a significant increase for all devices. Results show OFA, aperture size, and screen type affect the pressure drop and sanding. In all cases, the produced sand in three-phase flow is the determining design parameter for the upper-bound acceptable aperture. The gas flow is observed to accompany large amounts of sanding for larger aperture sizes. Further, test results indicate high pressure drops for three-phase flow conditions. Test results reveal the complexity of the interaction between different design parameters, which affect the sand and flow performance, hence, necessitating an SRT test for each specific case.

This paper presents the results of physical model testing of different standalone screens in terms of flow performance and sand control. This will help to identify the main factors that influence the performance of each specific screen type and develop the rationale for the screen type selection in new developments.
Improving Wormholing Efficiency in Carbonates with a Novel System Based on Hydrochloric Acid
Authors: Daeffler Christopher S. , del Valle Julia Fernandez , Kariampally Jacob , Elkhoury Jean E. , Max Nikolaev , Panga Mohan
Published: January 2018

This paper presents a single-phase alternative to widely used emulsified acid systems. The performance of the new single-phase acid was evaluated for both fracturing and matrix operations and benchmarked against hydrochloric acid and emulsified acid. Wormhole experiments were performed in Indiana limestone cores up to 300°F. The rate of wormhole propagation was used a measure to compare the performance of the acid systems. Diffusion constants were measured with a rotating disk experiment (RDE) at different temperatures. Laboratory measurements characterized the viscosity and friction pressure of each of the acid systems. Two single-phase retarded acid concepts were evaluated. In wormhole experiments with Indiana limestone, the best single-phase retarded acid possesses lower pore volume to breakthrough (PVBT) than unmodified HCl across all injection rates. The PVBT are substantially decreased for the single-phase retarded acid at low injection rates, meaning that when HCl enters the conical wormhole regime, the single-phase retarded acid is still efficiently forming dominant wormholes. At many injection rates, the single-phase retarded acid possesses similar PVBT to emulsified acid. These observations are confirmed up to 300°F. Diffusion coefficients obtained from the RDE are up to 10 times lower for the single-phase retarded acid at 220°F. Friction reducers hydrate quickly and show low friction pressures in the single-phase retarded acid. The new single-phase system matches the performance of emulsified acids while eliminating issues that confront them.
Salt Precipitation in the Near Well Bore Region of Gas Wells
Authors: Egberts P. J. , Nair R. , Twerda A.
Published: January 2018

A numerical model was created to predict timing and location of salt precipitation near the well bore region of mature gas wells. The model provides quantitative insight into the relevant reservoir and well properties that govern salt precipitation and its remediation. The model is used to predict the well's gas production and improve mitigation strategies.

The numerical model has been developed using DumuX, a simulator developed by the University of Stuttgart. The model has been extended to incorporate several additional features essential to model salt precipitation and dissolution.

A sensitivity study has been conducted to evaluate the impact of varying parameters such as initial liquid saturation, permeability, salinity, well pressure and drawdown on the model. Production loss mitigation strategies used can differ depending on the location and timescales of precipitation.

A study of the parameters controlling the productivity of wells plagued by salt precipitation shows scope for improving reservoir management strategies which can delay the onset of salt clogging thereby improving gas production.
Novel Chelation Opens the Door for Redeployment of Sea Water Based Fracturing Fluids in High Temperature Wells.
Authors: Gupta D. V. , Carman Paul S. , Nguyen Susan
Published: January 2018

Exploration for unconventional reservoirs has begun in various countries in the Middle East. Widely recognized as the bastion of conventional crude oil and gas production, the area's exploration for natural resources –– in particular unconventional resources –– is in its infancy. The lack of fresh water may derail some of the exploration and production of unconventional resources in the Middle East. One of the solutions is to use the abundant availability of nearby sea water for fracturing treatments.

This paper will discuss the applicability of sea water for fracturing fluids for without the need for separate treatment of the water. Rheological data with synthetic sea water as well as source sea water from Saudi Arabia, identification of any potential precipitation and remediation and compatibility with produced water and proppant pack conductivity data, of applicable fluids to show the effectiveness of the systems to the high temperatures of the reservoirs in the kingdom, 325°F will also be presented.

The concept of using seawater as a base fluid is not new. Because of the problems associated with substituting seawater for freshwater in polymer-based fracturing fluids, many operators are apprehensive about using seawater for fracturing. There have been noted attempts to mix polymer-based fluids on the fly with seawater, but treatment results have varied widely. Seawater contains dissolved inorganic salts, adversely affecting hydration and viscosity development of polymer-based fluids. High content of calcium and magnesium in seawater can reduce viscosity. These salts also buffer and strongly influence pH control and may inhibit or deactivate certain gel breakers. To gel effectively, polymer fluids need a specific mixing environment with distinct pH windows. Borate crosslinking normally requires a high pH. Rheology and breaker profiles will be shown that provide the desired properties and regain conductivity to establish the non-damaging clean-up of a properly designed fluid.

The technology presented uses chemical chelation of the problem ions in the sea water, resulting in the fracturing fluids with enhanced fluid and proppant pack properties, including thermal stability, retained fracture conductivity, pH buffering capacity, scale inhibition and fluid loss control. Further, the addition of the novel additives to the fluid does not interfere with the crosslink delay time and does not complicate the preparation of the fluid. The technology discussed eliminates the need for traditional water treatment and nano-filtration of sea water and associated disposal issues.
Tunu: From Lab to Field Application with a New Hybrid Inorganic-Organic Sand Consolidation Fluid as Primary Treatment on Shallow Reservoirs
Authors: Andrieu J. , Kutzky B. , Schackmann B. T. , Mahardhini A. , Abidiy I. , Poitrenaud H. M.
Published: January 2018

Tunu field, which is located in Mahakam area, consists of sandstone reservoir. Due to the maturity of the field, producing layer has moved from the deep zone, which has consolidated sand, into shallow zone, which has unconsolidated sand. Hydrocarbon production from shallow zone is unmanageable without having primary sand control downhole.

Here, we present a new type of sand consolidation composite (or hybrid) low-viscous binding material, based on combination of both inorganic and organic components. After describing the properties of this material, like low viscosity and strong adhesion to sand surface, we introduce the models used in the laboratory to stay as close as possible to the injection parameters on the field. We present the results of consolidation and regained permeabilities obtained in the laboratory with this binder on several substrates (loose sand and sand stone cores) with various porosities. The formulation was tested with success on samples ranging from several darcys down to 80 millidarcys. It is also noteworthy that samples display strong consolidation after extensive brine-based overflush.

Then, this paper discusses the results obtained during eight field trials divided into three successive campaigns. The volume of water-based overflush was identified as the main parameter to find the right balance between consolidation strength without sand production and expected productivity. We achieved improvement of the formulation as well as learning curve from each campaign. After first campaign with 6 pore volumes overflush, three wells out of five produced sand free. During second campaign (1.5 pore volume overflush), two wells were treated and able to produce sand free with average gas rate 1 MMscfd (million standard cubic feet per day), after productivity impairment was solved. The trial on one well in a third campaign with 3 pore volumes overflush was successful, with the well producing sand free with average gas rate 0.8 MMscfd.
Mechanisms of Perforation-Induced Damage in Carbonates and the Effect on Injection Flow Performance
Authors: Seagraves A. N. , Smart M. E. , Ziauddin M. E.
Published: January 2018

Fluid diversion in heterogeneous carbonate formations is critical to the design of successful stimulation treatments. In cased andperforated wells, microstructural damage around the perforated tunnels represents a significant challenge for the analysis of flow distribution along the wellbore. While this damaged or"crushed" zone has been a subject of numerous studies involving sandstones, the specific mechanisms of perforation damage in carbonates and theeffect on flow efficiency are not well understood. We examine the carbonate crushed zone at a fundamental level by interpreting the results of flow experiments on perforated cores using direct observation and analysis of the crushed zone at the porescale.

Injectivity index was recorded in Indiana limestone (IL) cores perforated using a gas-filled wellbore, an approach that suppresses wellbore dynamics and produces worst-case damage conditions. After the flow test, continuum modelsof the perforated coreswere constructed fromcomputerized tomography (CT) scans and used to calculate core flow efficiency (CFE) andaverage crushed zone permeability. Novel image analysis algorithms extracted the radial variation of pore-scale quantities across the crushed zone from high-resolution scans of thin sections at multiple axial locations along the tunnel. A correlation wasthen developed which estimates the radial variation of permeability in the near-tunnel region from each thin section. The permeability model is calibrated using analytical solutions that connect the crushed zone and virgin rock permeability profiles to experimental measurements made in the core test. The calibration approach makes use of a new approximate analytical solution for the flow field around a perforation with nonuniform tunnel geometry and crushed zone damage.

In the flow experiments, we observe a persistent drop in CFE for multiple charge types and test fluids as the initial core permeability is increased over two orders of magnitude. This is found to coincide with a decreasing ratio of average crushed-zone to virgin-rock permeability. Thin section analysis reveals that crushed zone damage is dominated by pore compaction near the tunnel edge, which has a characteristic signature in terms of the radial variation of porosity and pore-perimeter to surface-area ratio. Analysis of the spatial distribution of permeability suggests that flow efficiency is controlled by a low-porosity zone near the tunnel edge in which the damage is dominated by porecompaction.
A Novel Viscoelastic Surfactant Fluid System Incorporating Nanochemistry for High-Temperature Gravel Packing Applications
Authors: Vaidya Nirupama , Lafitte Valerie , Makarychev-Mikhailov Sergey , Panga Mohan Kanaka , Nwafor Chidi , Gadiyar Balkrishna
Published: January 2018

Viscoelastic Surfactant (VES) fluids have been used in many openhole gravel packing applications with the shunt tube technique as they offer several advantages over polymeric fluids. However, existing VES fluids have temperature limitations. The objective of this work was to develop a new viscoelastic surfactant (VES) based fluid for gravel packing wells with temperature up to 325°F while retaining the advantages of existing VES fluids.

The new fluid system consists of a surfactant, a cosurfactant, and a nanoadditive. The performance of the new fluid system was evaluated in laboratory experiments up to 325°F. The properties studied and discussed in this paper are shear recovery time, rheology (viscosity versus shear rates), gravel suspension, and core retained permeabilities. The optimization of the final fluid formulation based on sensitivity of the target properties to concentration of each component is also detailed in the paper.

The new VES-based gravel pack carrier fluid incorporating a nanoadditive showed significantly improved performance at elevated temperatures compared with conventional fluids. In particular, while the conventional VES fluids do not meet the gravel suspension requirement, the new fluid system is able to suspend the gravel under static conditions up to 325°F. In addition, the viscosity at low shear rates is improved while the viscosity at high shear rates is comparable to existing VES fluids. Tests with outcrop cores of varying permeabilities demonstrated the fluid's minimal formation damage. The complete VES fluid system with nanoadditive was found to be compatible with both monovalent and divalent brines at densities up to 14.0 lbm/gal. As such, it is a more cost-effective alternative to xanthan-based carrier fluids, which are incompatible with inexpensive calcium brines and thus necessitate sodium bromide or formate brines depending on the density requirements. Based on the extensive laboratory study, it can be concluded that the new fluid system outperforms conventional VES gravel pack carrier fluids at high temperatures while retaining the benefits of the conventional VES fluids.

The new fluid system significantly extends the temperature limit of VES-based gravel packing carrier fluids. The fluid system can also be used with many completion brines and mixed at a wide density range, making it an excellent alternative to conventional polymeric fluids used in gravel packing applications.
Optimising Sand Control and Production Strategies in a Low Permeability Sandstone Oil Field
Authors: Daramola B. , Alinnor C. M.
Published: January 2018

This paper presents how the sand control and management strategies of an oil field were optimised after multiple well failures between 2014 and 2016. It describes the impact of the new strategies on oil production and net present value. Field E is a sandstone field with oil and gas-cap gas at initial conditions, and has been developed with 5 production wells, 2 water injection wells, and 2 gas injection wells.

The first nine wells were drilled from an offshore platform and completed with sand screens between 2012 and 2013. Production commenced in late 2013, and by the end of 2016, multiple sanding events had been reported and four of the five production wells had died. The asset team was tasked with diagnosing the cause of the well failures and developing solutions. Pressure data suggested that three of the failed wells had tubing restrictions, and the fourth failed well had a blockage upstream of the BHP gauge. The sand count data suggested significant sand production prior to well failures, and sand was also recovered from the separators.

Pressure transient analysis suggested that the field had a lower permeability than the pre-development estimate, and higher pressure drawdowns were needed to produce economic oil rates from the field. It was concluded that the well failures were most likely caused by the high pressure drawdowns, which pulled sand from the reservoirs, and led to screen breakage in at least two wells and screen plugging in one well. A decision was made to re-drill the failed wells in 2016, and complete them with frac-pack sand control solutions. The drilling and production performance of the first two new wells are presented in this paper. The asset team also implemented a new and improved sand management strategy in Field E.

This paper presents the lessons learnt from a new oil field impacted by sand production. It also outlines practical well diagnosis and sand management strategies, and presents simple methods of preserving well integrity and cash flow in oil fields struggling to manage sand production in a 40 USD/barrel oil price environment.
Encapsulating Biopolymer for Control of Clay and Fines Generation in Unconventional Reservoirs
Authors: Landis C. , Maley D. M. , Nelson J. , Blackmon M. , Madduri A .V. , Rodencal C.
Published: January 2018

The current trends to re-evaluate the need for traditional clay control additives and the interest in increasing hydrocarbon production from secondary fracture networks are leading to the use of more appropriate fluid compositions. Additives historically used to dehydrate or exchange interlayer cations in water-reactive phyllosilicates introduce instability in the reservoir matrix and have been used in shale reservoirs without thorough assessments of potential formation damage. Framing the need for clay control in these reservoirs solely on the need to control water-reactive clays led naturally to the removal of clay control additives from fluids during the recent downturn. While justified from a cost perspective, these simplified fluids were introduced without assessments of the impact of near colloidal (10-40um diameter) fines generation. Completion experts who realize the formation damage risk of fines generation recognized these problems.

This paper updates the industry on an approach to proportion clay control and shale stabilization with fluid design better aligned to reservoir mineralogy and the stress introduced on the reservoir during hydraulic fracturing. The paper reports swelling clay control and near colloidal fines evaluations from four world class unconventional oil & gas reservoirs in North America. Reproducible fundamental trends in CST and near-colloidal fines generation data are correlated to clay control additive type and use of oxidative breaker. Additionally, this new test method has the potential to be easily and commercially viable for rapid field evaluation to assess formation damage due to fines generation.
THE ISSUES OF THE USE OF INDIGENOUS SACRAL OBJECTS IN TOURIST INDUSTRY (EXPERIENCE OF THE ALTAI-SAYAN REGION)
Authors: Чайкина Елизавета , Chaikina Elizaveta , Осипов Константин , Osipov Konstantin
Published: January 2018

Religious objects play an important role in the vital activity of the indigenous peoples of the North, as they accumulate information about the history, traditional culture and the use of local communities. Currently, many of them are gradually fading away or in an unsatisfactory state. Sacred places are getting more and more popular with tourists, which turns them into touristic destinations. That is why the article raises the pressing challenge of including the sacred places of the Northern indigenous peoples into tourist routes.

The article examines the experience of the regions ofSouthern Siberiain organizing tourism near religious sites.

As a result of the research, the author comes to the conclusion that the development of tourism in places of power of the indigenous peoples of the North has both positive and negative aspects. The paper gives a number of practical recommendations that would prevent negative consequences of the use of religious objects in tourism. In the conclusion of the article it is said that, with proper organization, tourism can be one of the most effective tools for maintaining and developing the sacred sites in the Altai-Sayan region.
Primary productivity and climate change in Austrian lowland rivers
Authors: Zoboli Ottavia , Schilling Katerina , Ludwig Anna-Lena , Kreuzinger Norbert , Zessner Matthias
Published: January 2018

There is increasing evidence of water temperature being a key controlling factor of stream ecosystem metabolism. Although the focus of research currently lies on carbon emissions from fluvial networks and their potential role as positive climate feedback, it is also important to estimate the risk of eutrophication streams will be exposed to in the future. In this work, a methodological approach is developed to create a scientific basis for such assessment and is applied to two Austrian lowland rivers with significantly different characteristics. Gross primary productivity (GPP) is determined through the open diel oxygen method and its temperature dependence is quantified based on the metabolic theory of ecology. This relationship is combined with the outcomes of a climate change scenario obtained through a novel integrated modelling framework. Results indicate that in both rivers, a 1.5°C warming would provoke an increase of GPP of 7–9% and that such an increase would not be limited by nutrient availability. The results further suggest that the situation for the relatively shallow river might be more critical, given that its GPP values in summer are five times higher than in the deeper murky river.
Protein Sequence Comparison and DNA-binding Protein Identification with Generalized PseAAC and Graphical Representation
Authors: Li Chun , Zhao Jialing , Wang Changzhong , Yao Yuhua
Published: January 2018

Aim and Objective:

The rapid increase in the amount of protein sequence data available
leads to an urgent need for novel computational algorithms to analyze and compare these sequences.
This study is undertaken to develop an efficient computational approach for timely encoding protein
sequences and extracting the hidden information.

Methods:

Based on two physicochemical properties of amino acids, a protein primary sequence was
converted into a three-letter sequence, and then a graph without loops and multiple edges and its
geometric line adjacency matrix were obtained. A generalized PseAAC (pseudo amino acid
composition) model was thus constructed to characterize a protein sequence numerically.

Results:

By using the proposed mathematical descriptor of a protein sequence, similarity
comparisons among β-globin proteins of 17 species and 72 spike proteins of coronaviruses were
made, respectively. The resulting clusters agreed well with the established taxonomic groups. In
addition, a generalized PseAAC based SVM (support vector machine) model was developed to
identify DNA-binding proteins. Experiment results showed that our method performed better than
DNAbinder, DNA-Prot, iDNA-Prot and enDNA-Prot by 3.29-10.44% in terms of ACC, 0.056-0.206
in terms of MCC, and 1.45-15.76% in terms of F1M. When the benchmark dataset was expanded
with negative samples, the presented approach outperformed the four previous methods with
improvement in the range of 2.49-19.12% in terms of ACC, 0.05-0.32 in terms of MCC, and 3.82-
33.85% in terms of F1M.

Conclusion:

These results suggested that the generalized PseAAC model was very efficient for
comparison and analysis of protein sequences, and very competitive in identifying DNA-binding
proteins.
Recurrent Oral Eosinophilic Ulcers of the Oral Mucosa. A Case Report
Authors: Sugaya Norberto , Martignago Fernanda , Pinto Decio , Migliari Dante
Published: January 2018

Objective:

This article describes a case of an Oral Eosinophilic Ulcer (OEU) in an otherwise healthy 31-year-old white woman.

Introduction:

The importance of reporting this case was the presence of recurrent episodes with lesions appearing in different areas of the oral mucosa, a type of manifestation not commonly associated with this disease. A typical manifestation of OEU occurs as a single ulceration that goes into healing after an incisional biopsy, a procedure usually required for a proper diagnosis of the disease. In spite of trauma being suggested as the main culprit of OEU, the exact pathogenesis mechanism of this disease remains controversial.

Case report:

The pattern of the present case contradicts the usually common course of the disease, as the patient had experienced many recurrent episodes for almost 2.5 years, with the recurrences occurring even after biopsies performed during some of the relapses. Differential diagnosis included recurrent aphthous stomatitis, recurrent intra-oral herpes, autoimmune disease, Crohn’s disease and malignancy.

Conclusion:

Fortunately, the patient has been free of any recurrences for 1.5 years since the last biopsy was taken at the time she came to our clinic seeking treatment.
Pulpal and Periodontal Tissues Changes Associated with Le Fort I and Sagittal Split Ramus Osteotomies: A review
Authors: Lazaridis Konstantinos , Lazaridou Maria , Athanasiou Athanasios E.
Published: January 2018

Introduction:

Le Fort I and sagittal split ramus osteotomies are the most commonly performed orthognathic surgery procedures on the maxilla and mandible, respectively.

Techniques:

Despite progress in the techniques, these procedures may still be associated with morbidity, expressed as inflammation, inadequate bony union, periodontal damages or in extreme cases even total bone loss.

Discussion:

Through a comprehensive review of the literature, the influences of maxillary and mandibular surgery on Pulpal Blood Flow (PBF), pulp sensitivity and pulp vitality are examined. Moreover, adverse effects of maxillary surgery on tooth color and periodontal tissues are also reported. The effects had a variety of expression. Concerning maxillary surgery, some studies showed an initial increase in PBF followed by a decrease to the baseline or even lower levels after 1-3 months. Other studies found an initial decrease in PBF followed by an increase soon after. There were also studies that showed no significant PBF changes, in contrast.

Conclusion:

Concerning mandibular surgery, a recent study showed a decrease in PBF immediately after sagittal split ramus osteotomy. Some authors detected tooth discoloration of maxillary teeth after Le Fort I osteotomy. Root resorption and root injury were also detected, but were of minor significance. Usually, these adverse effects derive from injury of the vessels of the palatal pedicle. This pedicle should be maintained intact for the avoidance of blood flow impairments. In addition, the descending palatine artery should be protected during maxillary surgery procedures in order to maintain the highest possible blood flow on the maxillary teeth.
Islamic Boarding School based vocational education: a case study on SMK Syubbanul Wathon Tegalrejo Magelang
Authors: Rochayati Umi , Zamroni Z. , Sudira Putu
Published: January 2018

This study aims to: (1) describe the conception of vocational education by the Islamic boarding school community; (2) describe the education system at SMK Syubbanul Wathon Tegalrejo Magelang. The study was conducted at SMK Syubbanul Wathon Tegalrejo Magelang using qualitative approach of a case study. The data collection used interviews, participant observation, and documents. The research informants consisted of the chairman of the foundation of Syubbanul Wathon, the caretakers, the principal, the vice principal, the teachers, the cleric, and the students. The results of the study were: (1) The conception of vocational education by Islamic Boarding School community is ngluru ngilmu which means sincerity between teachers and students, (2) The system of vocational education based on Islamic boarding school in SMK Syubbanul Wathon Tegalrejo Magelang include: (a) the context: SMK Syubbanul Wathon Tegalrejo Magelang has internalized the dynamics of context into formulation of school vision, mission, goals, and activities; (b) input: SMK Syubbanul Wathon Tegalrejo Magelang applies KTSP and Islamic boarding school curriculum; (c) process, SMK Syubbanul Wathon Tegalrejo Magelang integrates the school and Islamic boarding school system; (d) output, SMK Syubbanul Wathon Tegalrejo Magelang graduates have vocational skills, strong religiosity, independence, discipline and skills in foreign languages; (e) outcome: 44% of SMK Syubbanul Wathon Tegalrejo Magelang graduates worked, 42% went to college, and 14% went to salaf boarding school or entrepreneurship.