bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of the factors influencing primary hypertension in childhood
Authors: GİRİŞGEN İlknur , SÖNMEZ Ferah
Published: April 2018

Aim: Primary hypertension is the most important risk factor for chronic kidney disease in adulthood. The genesis of essential hypertension is likely to be multifactorial. The aim of this study is to investigate the causing factors of primary hypertension detected by ambulatory blood pressure monitoring in children.Materials and Methods: Fifty-six patients who had blood pressure higher than 90 percentile during the healthy children follow-up and 27 healthy children with the normal blood pressure were included in the study. Twenty-four hour blood pressure measurements with the blood pressure monitor were recorded as the day-night mean blood pressure, the blood pressure loads and the dipper-non-dipper characteristics. Plasma renin levels, serum aldosterone, nitric oxide and endothelin levels and amounts of sodium and potassium excretion in the 24 hour urine and were investigated in all patients and the control group.Results: Laboratory evaluations of the patients showed that the patient group has higher mean levels of plasma renin, lower mean levels of blood endothelin and mean levels of urinary sodium excretion than the control group.Conclusion: In the pathogenesis of childhood primary hypertension and white coat hypertension, which were seen in the half of the children diagnosed as primary hypertension, plasma renin and urinary sodium excretion had important roles.
Interventional radiology for hemorrhage due to tuberous sclerosis associated angiolipoma rupture
Authors: KIZILAY Fuat , AKINCIOĞLU Emir , ALİYEV Elmir , ŞİMŞİR Adnan
Published: April 2018

Renal angiomyolipomas are rare tumors that may be seen with tuberous sclerosis and cause massive retroperitoneal hemorrhage. In this paper, we present a case with massive hemorrhage due to angiomyolipoma in the left kidney and treated with selective arterial embolization by interventional radiology. Even in cases of massive bleeding, the angiographic procedure can be successfully performed and thus the kidney can be spared.
Variant anatomy of sciatic nerve and their clinical implications
Authors: AKTAN İKİZ Z. Aslı , BİLGE Okan , ÜÇERLER Hülya , ÇELİK Servet , BODUÇ Erengül
Published: April 2018

Aim: The
aim of present study was to demonstrate the variations of piriformis muscle,
sciatic nerve and its branches and discuss their clinical importance.Materials and Methods: Fifty-two gluteal and lower limb regions of 26 formalin fixed male
cadavers were evaluated in Ege University Faculty of Medicine, Department of Anatomy.
The anatomical relationship between the sciatic nerve and the piriformis
muscle, and division level of sciatic nerve in thigh was recorded. Results: The
sciatic nerve exited the pelvis as a single branch through the infrapiriform
foramen with no variation in 84.62% of the lower limbs. The division variations
of sciatic nerve were determined in 23.08%. In 8 of 12 high divisions were
observed in gluteal regions (15.38%). The common peroneal nerve and the tibial
nerve entered deep gluteal region via the greater sciatic foramen below
piriformis muscle separately in four lower limbs (7.69%). Two separate nerve
divisions passed above and through (or below) the piriformis muscle and then
combined together to form common peroneal nerve while tibial nerve passing
below the piriformis muscle in 4 lower limbs (7.69%). In 2 of 12, high division
occurred in the 1/3 upper portion of the thigh unilaterally (3.85%). The division
of sciatic nerve in the popliteal fossa was seen in two lower limbs (3.85%).

Conclusion: The clinical importance of the sciatic nerve around the piriformis
muscle or in the thigh was discussed for piriformis syndrome, palsy after total
hip arthroplasty, intramuscular injections in gluteal region and failed
popliteal nerve block.
NBPT Kaplamalı Ürenin Buğday ve Mısırda Etkinliğinin Belirlenmesi
Authors: İPEK Volkan Ahmet , ÇOKUYSAL Burçin
Published: April 2018

Bu çalışma NBPT kaplamalı üre azotunun buğday (Triticum aestivum)  ve
mısırda (Zea mays) etkinliğinin denenmesi
amacıyla İzmir İli Aliağa İlçesi’nde ve İzmir İli Tire İlçesi’ne bağlı Derebaşı
Köyü’nde olmak üzere iki farklı lokasyonda kurulmuştur. İzmir İli Aliağa
İlçesinde yürütülen denemede Ziyabey 98 ekmeklik buğday (Triticum aestivum) çeşidi İzmir İli Tire İlçesi Derebaşı Köyünde
yürütülen denemede ise Limagrain 30,709 silajlık mısır (Zea mays) çeşidi kullanılmıştır. Denemeler 2014–2015 yetiştirme
sezonunda tesadüf blokları deneme desenine göre 4 tekerrür olacak şekilde
kurulmuştur. Çalışmada NBPT kaplı üre azotunun ekmeklik buğday bitkisinde tam
doz ve yarım doz şeklinde uygulanarak başak boyu, başakta tane sayısı, azot
içeriği ve toplam verim üzerine olan etkileri, silajlık mısır bitkisinde ise
tam doz şeklinde uygulanarak koçan uzunluğu, sap kalınlığı, koçanda tane
sayısı, azot içeriği ve toplam verim üzerine olan etkileri araştırılmıştır.Araştırma
sonuçlarına göre, NBPT kaplı üre azotunun ekmeklik buğday ve silajlık mısır
bitkileri üzerinde verim ve verime bağlı öğelerde önemli artışlar sağladığı
belirlenmiştir.
Effects of Lyophilization and Storage Temperature on Wuchereria bancrofti Antigen Sensitivity and Stability
Authors: Agbozo Edem Y. , Dumashie Edward , Boakye Daniel A. , de Souza Dziedzom K.
Published: April 2018

Antigen-based rapid diagnostic tests for Lymphatic filariasis do not come with quality control (QC) materials, and research and disease control programmes rely on stored positive plasma samples. This study was undertaken to evaluate the use of freeze-dried Wuchereria bancrofti antigen positive plasma samples to serve as QC materials for LF RDTs. 10 well characterized W. bancrofti positive samples were lyophilized and stored at 4°C, 28°C and 40°C. The samples were evaluated using the Filaria Test Strips before lyophilization and after one and three (3) months of storage. The sensitivity and stability of the lyophilized samples were evaluated. The results revealed a loss of sensitivity and stability with increasing temperature and duration of storage. The results are further discussed in terms of the use of Dried Blood Spot (DBS) in diagnostics studies on LF requiring quantitative assessments, and the need for thoughtful DBS preparation and storage.
MEMBANGUN KONSEP BERTAHAP DANMODEL PEMBELAJARAN PENDIDIKAN KEWARGANEGARAAN DI SEKOLAH MENEGAH ATAS
Authors: Hasyim Adelina
Published: April 2018

The leanring model of civic edition, developed to enhance students active participation in learning is “Building Concept Staged”which is a modification of the concept attainment model, and investigation groups. Based on the draft modifications to the model, the model of learning that enable students designed the scenario as follows: 1) Preliminary Activities (2) The presentation of data, 3) achievement of concept testing, (4) Implementation of strategic thinking, (5) Finding a problematic situation, (6) exploration and investigation, and (7) Analysis of progress and determination of the position.

Abstrak

Model pembelajaran pendidikan kewarganegaraan (PKn) yang dikembangkan untuk meningkatkan partisipasi belajar siswa secara aktif adalah “Membangun Konsep Bertahap”yang merupakan modifikasi dari model pencapaian konsep, dan investigasi kelompok. Berdasarkan rancangan modifikasi model, maka model pembelajaran yang mengaktifkan siswa dirancang dengan scenario sebagai berikut: 1) Kegiatan pendahuluan (2) Penyajian data; (3) Pengetesan ketercapaian konsep; (4) Penerapan strategi berpikir; (5)Menemukan situasi bermaslaah; (6) Eksplorasi dan investigasi; dan (7) Analisis kemajuan dan penetapan posisi.
MODEL PENDIDIKAN INKLUSIF UNTUK SISWA TUNAGRAHITA DI SEKOLAH DASAR
Authors: Supena Asep
Published: April 2018

The research aims to produce a model’s implementation of inclusive education for students who are syndromic Mental Retardation in elementary school. Research conducted by the method of research and development (R&D). The research has produced two major findings: (1) a description of the facts and issues of implementation for inclusive education for students who are Syndromic Mental Retardation in elementary school today.; (2) konsep pelaksanaan model pendidikan inklusif bagi siswa tunagrahita di sekolah dasar. The resulted models include 5 main products (1) general guidelines for the implementation of inclusive education, (2) model of curriculum and learning, (3) model lesson plans, (4) evaluation model, (5) syllabus’ lessons in elementary school that have been modified for students who are Syndromic Mental Retardation

Abstrak

Penelitian ini bertujuan untuk menghasilkan implementasi model tentang pendidikan inklusif bagi siswa yang Tunagrahita di sekolah dasar (SD). Penelitian dilakukan dengan metode penelitian dan pengembangan (R & D). Penelitian ini menghasilkan dua temuan utama, yaitnu (1) deskripsi fakta dan isu-isu implementasi pendidikan inklusif bagi siswa tunagrahita di sekolah dasar saat ini; (2) konsep pelaksanaan model pendidikan inklusif bagi siswa yang Tunagrahita di sekolah dasar. Model hasil meliputi 5 produk utama:  (a) panduan umum untuk pelaksanaan pendidikan inklusif, (b) model kurikulum dan pembelajaran, rencana Model (c) pelajaran, (d) model evaluasi, pelajaran (e) silabus 'di sekolah dasar yang telah dimodifikasi bagi siswa yang Tunagrahita.
ANALISIS DIAMETER KRITIS DAN SUHU CURIE BAHAN PARMALLOY FECOB BERBENTUK BOLA-NANO SERTA PENGARUH TEMPERATUR (HEAT ASSISTED) DENGAN MENGGUNAKAN PROGRAM SIMULASI MIKROMAGNETIK NMAG DAN VAMPIRE
Authors: Nursiyanto W. , Rohman L. , Eko M A.
Published: April 2018

Abstrak

Bahan paduan magnet (parmalloy) FeCoB bersifat magnet kuat karena memiliki koersivitas medan magnetik yang kuat. Dari sifat yang dimiliki ini, FeCoB sangat cocok digunakan sebagai bahan piranti penyimpan data. Namun demikian, bahan parmalloy FeCoB ini akan mengalami perubahan sifat magnetnya ketika mendapat pengaruh temperatur (heat assisted) yang berubah-ubah dan dimensi (diameter bola) yang berbeda. Dengan adanya kondisi tersebut, diperlukan informasi yang cukup dari bahan parmalloy FeCoB agar menjadi efektif dan efisien ketika bahan ini digunakan sebagai bahan dasar hard-disk. Oleh karena itu, dilakukan analisis bahan parmalloy FeCoB yang terdiri dari dimensi diameter yang mempengaruhi perubahan sifat magnet (diameter kritis), suhu Curie akibat perubahan temperatur dan diameter bahan, serta kurva histerisisnya. Penelitian ini dilakukan dengan menggunakan program simulasi mikromagnetik Nmag dan Vampire. Hasil yang didapatkan dari bahan parmalloy FeCoB ini adalah memiliki diameter kritis sebesar 10 nm dan suhu Curie sebesar 700 K. Dari hasil ini dapat disimpulkan bahwa bahan parmalloy FeCoB akan efektif dan efisien sebagai bahan dasar hard-disk bila dimensi diameter yang digunakan di bawah diameteri kritis dan dioperasikan di bawah suhu Curie.

 

Kata-kata kunci: parmalloy, kurva histerisis, suhu Curie, heat assisted.

Abstract

The  magnetic alloy material (parmalloy) FeCoB is strongly magnetic material category because it has strong coercivity. So, FeCoB is suitable for use as data storage device. However, the FeCoB will be changed of its magnetic properties when it used to varying temperatures (heat assisted) and different dimensions (spherical diameter). Therefore, some sufficient information is required from the material when this material is used as a hard-disk base material. An analysis of FeCoB parmalloy material consisting of diameter dimensions influencing the change of magnetic properties (critical diameter), Curie temperature due to changes in temperature and material diameter, and hysteresis curve. This research was using simulation of program micromagnetic  are Nmag and Vampire. The results of this research are the critical diameter is 10 nm and value of Curie temperature is 700 K. The conclusion from that results is the material will be effective and efficient as the hard-disk base material when the diameter dimension is used under critical diameter. And it will be operated under Curie temperature.

Keywords: parmalloy, hysterisis curve, Curie temperature, heat assisted.
PENGEMBANGAN ALAT PERAGA BINTIK MATAHARI MENGGUNAKAN LED BERBASIS ARDUINO
Authors: Silta Yoky Novra , Pramudya Yudhiakto
Published: April 2018

Abstrak

Bintik matahari yang terjadi dalam kehidupan sehari-hari merupakan hal menarik untuk divisualisasikan melalui alat peraga dalam proses belajar menganjar. Alat peraga bintik matahari menggunakan software Arduino dilengkapi oleh lampu LED pada alat peraga tersebut. Perhitungan periode rotasi diketahai melalui jejak-jejak bintik matahari sehingga dapat divisualisasikan oleh alat peraga bintik matahari berdasarkan data tanggal jejak bintik matahari tersebut. Peneliti membatasi tanggal jejak bintik matahari selama 8 hari terhitung dari tanggal 6 Oktober 2016 sampai 13 Oktober 2016. Penggabungan jejak bintik matahari dari tanggal 6 Oktober 2016 sampai 12 Oktober 2016 (7 hari) dan tanggal 7 Oktober 2016 sampai 13 Oktober 2016 (7 hari) menghasilkan data I dan data II. Perhitungan hasil periode rotasi matahari pada data A dan data B adalah sama 28 hari sehingga divisualisasikan kedalam alat peraga bintik matahari. Alat peraga beroperasi dengan baik terlihat dari lampu LED pada alat peraga menyala/mati sesuai perintah program Arduino dengan tampilan serial monitor.    

Kata-kata kunci: Alat Peraga, Bintik Matahari, Arduino

Abstract

Sunspots in daily life is an interesting object to be visualized into an instrument applied in the teaching and learning process. The sunspots instrument applied Arduino software completed with LED light. The calculation of the periodic of rotation was discovered through the sunspots traces, so that it could be visualized by the sunspots instrument based on the sunspots traces. The researcher limited the date of the sunspots traces into 8 days ,started from October, 6th 2016 until October, 13th 2016. The merging of sunspots traces started from October 6th 2016 until October 12th 2016 ( 7 days) and at the date of October 7th 2016 until October 13th 2016 (7 days ) produced data I and data II. The calculation result of the sun periodic of rotation were equally 28 days, so that it could be visualized into the sunspots instrument. The instrument was successfully operated, indicated from the LED light which was turning on and off accordingly to the instructions of the Arduino program with the display of serial monitor.Keywords : Instrument, Sunspots, Arduino

Keywords: Instrument, Sunspots, Arduino
INTEGRATED AVO, ELASTIC SEISMIC INVERSION AND PETROPHYSICAL ANALYSIS FOR RESERVOIR CHARACTERIZATION: A CASE STUDY OF GAS FIELD, SOUTH SUMATERA BASIN
Authors: Haris Abdul , Sandrina Ressy , Riyanto Agus
Published: April 2018

Integrated Amplitude Versus Offset ( AVO), elastic seismic inversion and petrophysical analysis have been successfully applied to estimate the elastic parameters of the reservoir for a case study of the gas field in south Sumatera basin. This paper aims to have better understanding the petrophysical properties of the reservoir. The petrophysical analysis was carried out by performing routine formation evaluation that includes calculation of shale volume, porosity, and water saturation of basic well log data. Sensitivity analysis was conducted to evaluate the sensitivity parameters of the log for changing in lithology, porosity, and fluid content in the reservoir. For completing the availability of elastic parameter from well log data, shear wave logs were derived from Castagna’s mudrock line relationship. Further, P-impedance, S-impedance, VpVs ratio, LambdaRho (λρ), MuRho (μρ) and density(ρ) were then calculated through a Lambda-Mu-Rho (LMR) transformation. Prior to performing AVO analysis and elastic seismic inversion, super gather technique was applied to improve the reliability of pre-stack seismic data. Elastic seismic inversion was carried out to extract the lateral elastic properties to capture lithology and fluid changes in the reservoir. In addition, AVO analysis of pre-stacked data was applied to identify hydrocarbon-bearing sandstone at target zone. The petrophysical analysis shows that porosity versus density crossplot is able to distinguish sand-shale based on 34% shale volume cutoff, while LMR crossplot is able to delineate hydrocarbon zone at water saturation value under 65%. The predicted lateral elastic parameter shows slightly higher value compare to overlying layer.
Parametric Probabilistic Models for Fluid Diffusivity Inversion and Forward Microseismic Generation Using Seismicity Rates
Authors: Li Qi , Aguilera Roberto
Published: April 2018

Fluid diffusivity inversion and injection-induced microseismicity provide useful means of evaluating unconventional reservoirs. When taking into consideration geomechanics, linear poroelasticity equations provide the key connection between diffusion and microseismicity. This work explores microseismicity generation from a probabilistic point of view, embedding uncertainty assessment in its quantification. Bayesian framework serves as the base for probabilistic analysis.

The primary objective of this work is to develop a new microseismicity probabilistic model framework that can be used for uncertainty quantification in data analysis as well as to provide forward modeling of microseismicity. Results are tested against real data of Horn Rives shales in Western Canada, and show good prediction of the number of actual microseismicity occurrences against time.

The novel probabilistic model is derived from Directed Graphic Model using a statistical learning framework. Stochastic Poisson process combined with a specific rate model is integrated to generate a likelihood function. Both, parameter inference and microseismic event forecast are assisted by Bayesian theorem. The model has an intrinsic statistical learning root, which specifically uses observed microseismic data to update model parameters and then is applied for microseismicity prediction.

The model is extended to take into account basic geomechanical principles. Dieterich (1994) relative seismicity rate model is integrated into the aforemantioned probabilistic model. We use a synthetic case to demonstrate how the probabilistic model can be connected with stress and pressure information from geomechanical calculations.

The novelty of this study is the development of a probabilistic microseismic prediction model which obeys rate-and-state law based relative seismicity rate constitutive equations. The model inherently considers time dependence of nucleation and fault geomechanics. It can be used for planning purposes in the pre-hydraulic fracturing stage.
Well-Testing Challenges in Unconventional and Tight Gas Reservoirs
Authors: Azari Mehdi , Hamza Farrukh , Hadibeik Hamid , Ramakrishna Sandeep
Published: April 2018

Traditionally, newly drilled wells are tested using a drillstem test (DST) or wireline formation test (WFT) to evaluate production potential and help make development and completion decisions. These methods are typically designed to flow the well under controlled conditions and then shut in the flow to achieve a pressure buildup (PBU). Depending on how it is conducted, testing could involve a typical DST, closedchamber DST, slug test, or surge test. Later, during the life of a well, other tests, such as standard drawdown-buildup, reservoir limit, flow-after-flow, interference, and pulse tests are conducted to evaluate productivity, remaining reserves, amount of damage, depletion, and production allocation.

Even though injection/falloff (IFO) is also an established testing type, it is not conducted as often as a standard pressure drawdown (PDD) and PBU test within the petroleum industry because of possible formation damage resulting from a noncompatible injection fluid. Such tests are usually conducted to determine injection efficiency for water injection wells, communication between an injection and a production well during a secondary oil recovery project, such as waterflooding, in mini- or microfracturing to determine formation and rock mechanics properties, and in nonproducing wells where a standard PDD and PBU test would not work.

Because of controlled rates with an IFO test in low-permeability wells, faster flow stabilization can be achieved, resulting in shorter wellbore-storage durations. This technique can obtain well and reservoir information faster than a conventional PBU test.

One issue with unconventional wells, particularly tight gas wells, is that the wellbore storage lasts significantly longer than in standard wells. A downhole shut-in tool or any test that minimizes the wellbore storage effects can greatly reduce the duration of such tests and help improve the quality of the analysis results. An extended diagnostic fracture injection test (DFIT) conducted with a downhole wireline operation that minimizes high wellbore storage issues is also discussed.

This paper discusses several well-testing applications with corresponding analyses pertaining to unconventional wells. The results provided valuable information to help optimize production and evaluate reservoir potential.
Safe Boundaries of High-Temperature Fracturing Fluids
Authors: Ogunsanya Tony , Li Leiming
Published: April 2018

In successful hydraulic fracturing operations, fracturing fluids should possess sufficient viscosity in order to transmit high pumping pressure downhole. This pressure creates fractures in formation and transports proppants that help to keep the fractures open after treatment. Fluid viscosity may drop when polymers in fracturing fluids suffer degradation due to, for example, oxidative species, especially in wells with elevated bottomhole temperatures. Fluid stabilizers are often needed in fracturing fluids to mitigate this effect.

Commonly used fluid stabilizers in oil field operations are thiosulfate oxygen scavengers, such as sodium thiosulfate. Thiosulfate can quickly neutralize oxidative molecules, thus protecting polymers from being decomposed and extending the lifetime of fracturing fluids. Thiosulfate, however, may react to release hydrogen sulfide, especially at elevated temperatures. Hydrogen sulfide is poisonous to human and can also damage oil field assets by corrosion and scaling. To minimize hydrogen sulfide release, a series of lab tests were conducted to study hydrogen sulfide generation in high-temperature fracturing fluids.

Extensive lab tests suggested that the hydrogen sulfide generation in fracturing fluids could be influenced by factors including test temperature, oxygen scavenger concentration, fracturing fluid formula, etc. At test temperatures of 350°F or below, the hydrogen sulfide generated was well below 10ppm. Without cooldown, most fracturing fluids prepared with crosslinked polysaccharides are limited to downhole temperatures up to 350°F. It is therefore less risky to use thiosulfate in these fluids without much concern for generating hydrogen sulfide. We observed that the dosage of thiosulfate influenced the outcome of the hydrogen sulfide generated at elevated temperatures above 350°F. Usually the more thiosulfate was added, the more hydrogen sulfide was produced. Without using excessive dosage of thiosulfate, the hydrogen sulfide generated, for example, could be less than 10ppm even at about 375°F or higher. With optimized selection of the fluid compositions, the amount of hydrogen sulfide produced could therefore be reduced significantly.

The illustrative experiments include the search for safe boundaries of fracturing fluids used at high temperatures without producing hydrogen sulfide over regulatory permissible exposure limit. Guidelines on how to mitigate hydrogen sulfide generation will be recommended based on lab results.
Lab Testing Cement-Steel Bonding at Shallow Temperature and Pressure Conditions
Authors: Wilson D. C. , Eustes A. W. , Fleckenstein W. W.
Published: April 2018

The Cohesive Zone Experiment (CZE), captured the effect of time, temperature, and pressure on the behavior of adhesive bonding between oilwell cements and casing. The CZE captured the behavior of bond failure as a function of displacement, showing the degree of compliance in the bond. Interpretation of the compliance behavior suggests an appropriate material property model of bond failure, suitable for mechanical FE analysis. The two failure models considered are the critical fracture energy (maximum area-specific energy) and the critical shear strength (maximum area-specific force).

Two Class G cement compositions were tested: a 15.8 ppg neat cement (Class G neat) and a 14.2 ppg gelled cement (Class G with 7% bentonite). The testing was done at temperature and pressure regimes designed to conform to environments typical to onshore surface casing shoe conditions, both shallow and deep. The neat cement is tested at conditions typically assumed at shallower surface casing setting depth (~600’ TVD): 92°F and 262 psi. The gelled cement was tested at conditions typically assumed at deeper setting depths (~1800’ TVD): 101°F and 786 psi. Each composition was tested at two hydration times: an early time of 4 to 6 hours and a late time of 22 to 24 hours.

The CZE results suggest cement at early hydration time (~5 hours) has a compliant bond. The adhesive bond of such an immature cement does not fail acutely when stressed to failure; the bond fails "intermittently" and retains some strength through displacement past the initial fracture. However, cements at late hydration time (~23 hours) do not show this compliance. The bond at late times fails acutely; displacement sufficient to initiate fracture is sufficient to fail the bond.

The compliant bond behavior observed at early hydration times should be modeled with a specific energy value: the critical fracture energy. The non-compliant bond observed at late hydration times should be modeled with a specific force value: the critical shear strength. Values for each property are reported from mean values observed in the CZE.
Investigation of Well Management on Hydrocarbon Recovery in Reservoirs With Pressure Dependent Permeability
Authors: Song Y. , Ehlig-Economides C. A.
Published: April 2018

Production rate and pressure transient data recorded in multiple transverse fracture horizontal wells (MTFHWs) suggested that well productivity is lost when wells are produced with excessive pressure drawdown. Pressure dependent permeability (PDP) may be a reason for this behavior. Moreover, in stress sensitive reservoirs, some models suggested that the pressure dependent permeability can result in productivity reversal. These models implied there is an optimum flowing pressure point which can lead to the maximum flow rate, and flowing at any other pressure will reduce the flow rate. The objective of this study is to discover how to quantify the inputs required to manage the well production.

This study is divided into two main parts. From the results of the first part, we learned that our simulation model can reproduce published results and can be used for the second part of the study. Using the model, we established that successive buildups must be acquired under different flowing pressures to provide meaningful results and can be used for permeability modulus estimation. We also learned that the behavior of the buildup transients distinctly depends on whether the pressure dependent permeability is mainly in the fractures or in the stimulated rock volume (SRV). Finally, we concluded that a rigorous model applying pressure dependent permeability phenomenon in space and time does not confirm the well management practices proposed in the literature. While these practices are likely well advised, PDP models do not justify them.
An Assessment of Model-Based Multiobjective Optimization for Efficient Management of Subsurface Flow
Authors: Fu Jianlin , Wen Xian-Huan
Published: April 2018

The making of development plan to produce an oil or gas field usually involves several distinct stakeholders (e.g., the operator, partners and the government) with many engineering, economic, environmental, and/or political considerations. The interests of these stakeholders may be potentially in conflict with each other, entailing that a robust development plan should take into account all these concerns. Multiobjective optimization (MOO) can be used to find a set of optimal solutions (i.e., the so-called Pareto front) to balance all these interests. This work reviews and presents several typical applications of MOO to illustrate its value for efficient and robust reservoir management (RM) and asset development. These applications include: (i) simultaneous optimization of oil recovery and unwanted fluids, (ii) states-constrained optimization, (iii) short-term and long-term optimization, and (iv) optimization under uncertainty (OUU) for risk mitigation. Particularly, the MOO solution is compared with a conventional single-objective optimization (SOO) method in handling these problems. Results show that MOO is a solution of choice for comprehensive RM when a project involves optimizing multiple metrics or multiple drivers.
Comparative Simulation Study and Economic Analysis of Thermal Recovery Processes in Athabasca Reservoirs
Authors: Iyogun C. O. , Chen Z.
Published: April 2018

Simulation studies of three thermal recovery processes used in Athabasca reservoirs have been carried out for a 10-year production period. The recovery processes studied are Steam-Assisted Gravity Drainage (SAGD), Fast-SAGD, and Expanding Solvent-SAGD (ES-SAGD). Normal pentane (n-C5) was the solvent of choice used in ES-SAGD simulations with its molar concentration varied from 2% to 5.9%. The main objective of this study is to conduct an economic analysis of the three recovery processes with the goal of determining the most economically viable process. The economic indicator that will be assessed to ascertain the most viable recovery process is their Net Present Value (NPV.)

2D simulation studies based on homogeneous Athabasca reservoirs have been performed. Results obtained show that of the three recovery processes, Fast-SAGD had the lowest cumulative oil produced, followed by SAGD and ES-SAGD, the highest. The cumulative oil produced also increased with increasing molar concentration of n-C5. Furthermore, it was shown that as expected, the CSOR of ES-SAGD was the lowest of them while that of Fast-SAGD was the highest. The CSOR of the ES-SAGD processes reduced as the concentration of the n-C5 increased.

The economic analysis showed that of the three recovery processes, ES-SAGD is the most economically viable process. Furthermore, the effect of solvent on the viability of ES-SAGD over the other recovery processes is dependent on the price regime of pentane. In this analysis, two extreme price regimes were chosen and the result showed that for a low price regime, varying the molar ratios of n-C5 had a significant effect on the NPV up to a point before its effect diminishes. In fact, increasing the molar concentration of n-C5 from 2% to 3.76% significantly increased the NPV while further increasing it from 3.76% to 4% and thereafter to 5.9% had no noticeable effect. However, it seems that increasing it from 3.76% to 5.9% had a diminishing effect especially after the 3-year period. Nevertheless, the significant NPV improvement ES-SAGD has over SAGD and Fast-SAGD diminishes once the price regime of pentane is more than 3 times that of oil. In fact, this high price regime showed that 5.9% molar concentration of n-C5 is no longer more viable than the SAGD counterpart. There is still some benefit up till about 4% molar concentration of n-C5 but this benefit is greatly diminished.

In conclusion, ES-SAGD has been shown to be the best recovery process for Athabasca reservoirs based on economics but further research is needed to evaluate the molar concentration that will provide the most economic benefit for a real Athabasca reservoir.
Controlling Microwave Penetration and Absorption in Heavy Oil Reservoirs
Authors: Liao H. , Morte M. , Bloom E. , Huff G. , Hascakir B.
Published: April 2018

Microwave heating has great potential to recover heavy oil reservoirs, because it significantly reduces the heating time and consequently the cost of heavy oil extraction. Moreover, heavy crude oils contain high amounts of polar molecules (asphaltenes) and polar functional groups, making them great microwaving candidates. This study investigates the microwave effectiveness for a specific heavy oil reservoir focused on its polar components.

Furthermore, the impact of asphaltene precipitants and dispersants on microwave efficiency was investigated. A crude oil sample from Canada was subjected to microwave experiments for 30 seconds. Dielectric properties of the crude oil before and after exposure to microwave were mostly measured by using a vector network analyzer to quantify the overall polarity changes in the bulk crude. The impact of asphaltene precipitants (nC5 and nC7) and a dispersant (toluene) on microwave efficiency was also investigated. The crude oil sample was blended with nC5, nC7, or toluene at three varying doses (10%, 20%, or 50%) to investigate the impact of solvent dose on microwave efficiency. Microwave absorption and penetration depth were calculated to quantify the effectiveness of microwave heating.

It has been observed through dielectric property measurements that microwave energy was absorbed by mainly the asphaltenes. Dielectric constant and loss tangent values of the blends prepared with asphaltene precipitants (nC5 and nC7) and toluene were measured before and after exposure to microwave to quantify the microwave absorption in different blends. Although precipitant mixtures had higher dielectric constants, the dispersant mixtures had much higher microwave absorption due to higher loss tangents. This finding was further supported by penetration depth measurements, in which dispersant mixtures had lower values, which led to higher microwave absorption of the crude oil mixtures.

Microwave heating as a thermal enhanced oil recovery method is promising, however, complicated due to the uncontrollable nature of microwave penetration and absorption. This study reveals that while injection of an asphaltene precipitant to the desired reservoir locations can enhance the microwave penetration, injection of asphaltene dispersants will increase the microwave absorption. Cyclic injection of asphaltenes dispersants and precipitants may achieve the creation of effective heating spots within the reservoir by using only one microwave source.
Analysis of Critical Operational and Reservoir Parameters in Carbonate Acidizing Design
Authors: Safari R. , Fragachan F. , Smith C. S.
Published: April 2018

This work employs an integrated analysis method to quantify the impact of operational parameters and subsurface conditions on the acid stimulation efficiency of a carbonate reservoir. Examined parameters include reservoir type, completion design (initial skin), reservoir thickness, reservoir liquid properties (viscosity and compressibility), reservoir temperature, reservoir heterogeneity, acid type, acid volume, injection rate, and diversion technique.

In general, a combination of operational parameters and local geological conditions control the efficiency of carbonate acidizing. The operational parameters include acid type, injection volume, injection rate, and diversion technique. Optimizing these parameters maximizes stimulation efficiency and consequently hydrocarbon recovery. However, optimization needs to be evaluated within the context of local geology and subsurface conditions. For instance, the presence of natural fracture swarms or a high permeability zone along a limited length of the wellbore can present acid placement challenges that only advanced analysis can carefully address.

In our study, an integrated wellbore and reservoir model is used to simulate carbonate reservoir acidizing. The model first simulates the movement of stimulation fluid in a wellbore and couples it with transient reservoir flow. This analysis provides the distribution of reactive fluid along the well and calculates dynamics of skin evolution of a wellbore during stimulation. The model simulates the local change of injectivity and the interactions of different reservoir zones along the completed length of the well during stimulation time.

The analyzed results show that the interactions between wellbore flow and reservoir flow along the completed length of the wellbore is a dominant governing factor for stimulation efficiencies. It shows that at a limited volume of acid or low injection rate, most of the acid stimulates the upper sections of the reservoir while inadequate amounts of acid reach the bottom of the reservoir. The results show that the reservoir porosity system (i.e. porosity and permeability), pay-zone height, initial skin (i.e. completion design), reservoir temperature, and heterogeneity have governing effects on the optimum acid volume and injection rate. The reservoir condition might impose a wasteful acid volume and injection rate for a bullheaded treatment that can be optimized further with diversion technology. The latter situation being important in optimizing the volume of acid needed to efficiently stimulate the reservoir to obtain higher production.
Experimental Study on Oil and Solids Removal in Nutshell Filters for Produced Water Treatment
Authors: Rawlins C. H.
Published: April 2018

Nutshell filters composed of black walnut or pecan granular media are an established produced water treatment technology for tertiary oil removal. Guidelines for the size and operation of nutshell filters have evolved mainly by trial and error, with limited published operating data. This laboratory research program tested a nutshell filter to determine the operating flux limits (flow rate per unit area) that provide suitable oil removal performance. The separation efficiency target was defined as 5 ppmv oil in the outlet stream. The variables tested included medium type (black walnut shell or pecan shell), medium size, filtration flux, water salinity, and oil concentration. The flux limit for common 12/20 media is 12.0 gpm/ft2 for fresh water operation and 13.0 gpm/ft2 for saline water. Decreasing the medium size to 20/30 mesh increased the allowable flux limit but at the expense of a substantial increase in the pressure drop. Oil droplet penetration into the filter bed proceeds via a near plug-flow profile, with the top 18 inches of the bed providing 99% of the oil removal. Full breakthrough is a function of inlet oil concentration, with 20-30 hours of operation expected for a 48-inch-deep bed. Testing for removal of fine sand particles showed a average 5 µm separation size for 12/20 media at 13.5 gpm/ft2 flux.
A Cost-Effective Application of New Surfactant/Oxidant System to Enhance the Removal Efficiency of Oil-Based Mud Filter Cake
Authors: Zhou J. , Nasr-El-Din H. A. , Socci D. , Holcomb J.
Published: April 2018

Removing oil-based mud (OBM) filter cake is a difficult task. Low removal efficiency of filter cake may result in pay zone damage, including drilling fluid filtrate incompatibilities with reservoir fluids, fines migration, and undesirable change of permeability. This paper proposes a cost-effective and single-stage application of a new surfactant/oxidant system to enhance the removal efficiency of OBM filter cake.

A qualitative wettability experiment was performed to test wetting property of OBM emulsion before and after being cleaned by non-ionic surfactants. Phase behavior of the new surfactant/oxidant system was also shown when the variables were the concentration and type of coated persulfates. Filter press simulated various high-pressure/high-temperature (HP/HT) well conditions in laboratory to form and remove the OBM filter cakes. Average permeability ratio (Kfinal / Kinitial) of Berea sandstone disks was calculated by static filtration test to show the degree of formation damage.

Surfactant used in the new removal system ensures OBM emulsion to be water-wet and promotes it to flow more easily in contact with the rock surface. Coated persulfate can be circulated out of wellbore after the removal work, based on its low density and tightly coated property. HP/HT filter cake removal tests indicate the optimized new system can disperse and remove the filter cake by up to 98 wt% removal efficiency. The optimized surfactant/oxidant system affects the formation permeability slightly because Kfinal / Kinitial ratio is consistent in the 0.99~1.09 range.

With optimized formulation and soaking time, the cleaning solutions will benefit the oilfield industry significantly by removing OBM filter cake under challenging well conditions. Cost-Effective and single-stage application of the new removal system makes the oilfield industry more efficient and economical to remove OBM filter cake. The new surfactant/oxidant system minimizes the effects of drilling fluid on formation properties, based on its compatibility with OBM emulsions, quick removal steps, high removal efficiency, and acceptable Kfinal / Kinitial results.
A New Method to Assess Stimulation of Sandstone Cores Damaged by Fines Migration
Authors: Hanafy A. M. , Nasr-El-Din H. A.
Published: April 2018

Sandstone stimulation faces multiple challenges due to the heterogeneity of the formation and the sensitivity of its clay minerals. Fines migration results in lowering the formation productivity and complicates the stimulation process. Multiple field studies showed that treatment of fines migration is critical and can result in permanent damage of the wellbore. This study aims to locate, quantify, and describe the damage resulting of fines migration damage and its stimulation in sandstone formations and examine the impact of the clay content and its nature on the stimulation process.

This work is structured to evaluate the stimulation of fines migration damage in Bandera, Berea, and Kentucky sandstones. Fines migration was induced by injecting deionized water to trigger the mobilization of the clay minerals in the core. Both HCl or formic acid, and mud acid stages were injected following the fines migration induction. The new formation damage evaluation methodology utilizes computed tomography (CT) and nuclear magnetic resonance (NMR) scanning before and after the fines migration induction and its stimulation. The data from CT and NMR were combined and processed to generate a 3D representation of the cores pore structure, which gives an insight on how the clay nature impacts the stimulation process and the pore system.

The developed technique exhibited an excellent ability to visualize the core porosity distribution and the changes in the pore structure following the fines migration damage and the acid treatment. The 3D representation succeeded to assess the magnitude and the location of the formation damage due to fines migration and its stimulation. The injection of deionized water in the studied formations resulted in a different petrophysical responses, which came matching the prediction built on the mineralogy and porosity mapping using computed tomography data. These changes in pore structure prevailed as a controlling variable of the acidizing process. The stimulation of the damaged cores at 150 and 250°F resulted in the deposition of the alumino silicates toward the core outlet. These deposits are attributed to the acid leaching of the aluminum and iron ions from the alumino silicate structures. The high temperatures resulted in the deposition of alumino silicates closer to the injection point. The enhancement in permeability noticed in all of the studied formations showed to be due to the induction of narrow channels in between heavily deformed pore structures.

This work added to the sandstone stimulation technology a new tool to assess the true impact of acid stimulation on fines migration damage. The high level of resolution of tracking the changes in the pore structure lay the road to optimize the treatments to enhance the productivity and lower the cost. This technique has a potential as a formation evaluation technique to evaluate other types of formation damage, such as fracturing fluids and water blockage.
Detection of Fault Reactivation in Compartmentalized Reservoirs Using Pressure Transient Analysis
Authors: Molina Oscar M , Zeidouni Mehdi
Published: April 2018

A pressure transient model to detect fault reactivation is presented in this paper. The central assumption of the fluid flow model is that fault permeability gets suddenly altered upon fault slip. The fault is modeled as a linear interface segmenting an infinite, homogeneous and isotropic reservoir into two semi-infinite regions. A constant-rate well induces pressure changes in the reservoir by either fluid withdrawal or injection that lead to fault reactivation. The mathematical model is solved via integral transforms and the analytical solution is examined at the well with the purpose to find the characteristic bottomhole pressure and pressure derivative response to a fault slip event. Typical diagnostic plots and type curves used in well testing analysis are presented. A reservoir characterization approach summarizes the application of the model presented in this paper.
Reservoir Performance Optimization under Uncertain Future Development Plans
Authors: Jahandideh A. , Jafarpour B.
Published: April 2018

Optimization workflows have received considerable attention in oilfield management and development. A major difficulty in field development optimization is the significant uncertainty and risks from various sources, especially at the early stages of the reservoir life. While field development optimization under geologic and economic uncertainties have been studied and investigated in the literature, future development plans and their associated uncertainties have not yet been considered. In life-cycle optimization, reservoirs are likely to undergo extensive development activities in the future. Disregarding the possibility of future developments can lead to field performance predictions and optimization results that do not represent real field conditions. Alternatively, future development activities may be considered either as decision variables to optimize or as uncertain input parameters that must be accounted for. In many cases, even when future development activities are optimized, for a variety of (often unpredictable) reasons, the implementation in real field may not follow the optimized plan.

In this paper, we demonstrate that it is important to consider future development plans with their associate uncertainty when optimizing the field performance. We present stochastic formulations to account for the uncertainty in future development activities, necessitating the need to consider multiple possible development scenarios. Using stochastic optimization formulations, we optimize decision variables (e.g. well locations and operational settings) at the current stage of development while accounting for the uncertainty in possible future development plans. In this work, we assume that infill drilling uncertainty evolves over reservoir development stages as a discrete time stochastic process, resulting in a decision tree representation of future drilling scenarios. The performance of the developed stochastic framework is evaluated and discussed relative to existing approaches that do not account for future field development plans in the optimization procedure. The results show significant improvements in the production performance when the uncertainty in future field development planning is considered in the optimization problem. We conclude that incorporating the uncertainty in future development offers flexibility and robustness to accommodate alternative development options and can avoid solutions that significantly underperform when future reservoirs development (drilling) activities do not go as planned.