bluuebunny/crossref_metadata_2025 huggingface dataset:
International Student Migration: Regional Aspect
Authors: Vartanyan A.
Published: February 2021

The article provides a profound analysis of the main trends of international student migration for tertiary education, discusses the key factors influencing the choice of destination for studying abroad, and reveals the regional peculiarities of instruments for student migration regulation. The first part of the paper highlights the official statistics showing that in recent decades the world witnessed the steady increase in the number of international students, concentrating mainly in the USA and the European Union. Almost 48% of all international students in the world study in the European Union. This region also shows the highest internal student mobility. Among others, such countries as Austria, Luxemburg, Switzerland, Australia and New Zealand demonstrate the biggest shares of foreign students in the total number of university students. As for donor countries, the dynamics proves the major role of the Asia region, with a half of all international students originated from it. The largest number of foreign students come from China, India and South Korea. Nonetheless, the Asia region becomes a popular destination of student mobility nowadays. The second part of the article concerns different coordination policies of tertiary migration in the regional context. Mostly in developed countries, practices of attracting foreign students to study in professional programs and degree programs with a perspective to enter a national labor market after graduation become more and more popular. Postgraduate migration remains a priority. Most countries encourage job-searching for foreign graduate students, as they are considered to have a high-skill level, international views and an opportunity to live and work in a variety of socio-cultural conditions. Further analysis refers to the main factors determining the choice of destination for foreign students, which are: geographical proximity, language skills, cultural proximity, the cost of education, and a country's reputation in the field of higher education. The paper reveals the leading role of the EU in the developed intraregional educational mobility, the regional asymmetry of migration processes in other regions of the world, and Asian countries actively promoting temporary educational and labor migration to developed countries with incentives to return to a home-country in the future. In recent years, due to positive dynamics of the return migrants number, an interest in the creation of the returnees strategy grows as well as desire of developed and developing countries to benefit most from the return migration.
Russia’s Foreign Economic Ties in IMEMO Studies
Authors: Zagashvili V.
Published: February 2021

The publication provides an overview of 60-yeasr history of IMEMO’ studies in the field of world economy and foreign economic activities of USSR/Russian Federation. The basic stages and directions of these studies are presented. The author outlines the main theoretical ideas of the Institute’s specialists that contributed into the practical foreign economic policy of our country.
US Economic Growth: Trends and Factors
Authors: Varnavskii V.
Published: February 2021

The article considers the main trends and factors of US economic growth. Economic and technological reasons for slowdown of US Gross Domestic Product (GDP), GDP per capita and productivity are discussed. The author focuses on the estimates of key macroeconomic indicators published by the Bureau of Economic Analysis, Bureau of Labor Statistics and other government agencies for analyzing historical growth and identifying factors contributions. Also, the article discusses points of view on the potential factors for continued economic growth in the future, including the statistics and calculations of the American economists. It is shown that the United States is nowadays facing fundamental problems of productivity, not just a cyclical downturn. A number of disturbing tendencies in the US economy, such as negative trends in both labor productivity and multifactor productivity (MFP) emerged well before the economic and financial crises of 2008 (Great Recession). As the author note, the US has entered into a period of relatively low GDP growth rate in comparison with 1990 – early 2000s. A reduction also occurred in the growth rate of GDP per capita, labor productivity and other indicators. Special attention is addressed to the roles of the Information and Communication Technologies (ICT). Since mid-1990 the large-scale investments into the ICT provided a great portion of US economic growth and productivity. However, in the last 10 years the contribution of ICT to productivity growth noticeably reduced from its maximum value in 1995–2004. Nonetheless, it remains sizable and still contributes about one-fifth of the GDP growth and more than 40% of the growth in labor productivity. The author’s general conclusion is that, despite the existing problems in economic growth, United States remains the world’s most productive economy and the largest market for ICT goods and services. This is likely to continue encouraging the nation’s economic growth and productivity, although at a slower pace.
Pengendalian serangan rayap tanah pada bebak gewang menggunakan bahan pengawet alami ekstrak tuba (Derris elliptica)
Authors:   Balai Penelitian dan Pengembangan Lingkungan Hidup dan Kehutanan Kupang, B. Prabawa Sigit , E. Koeslulat Ermi , Muliastuty W.O. ,   Pusat Penelitioan dan Pengembangan Hasil Hutan Bogor
Published: February 2021

People from East Nusa Tenggara generally use gewang midribs for walls and ceilings. However this midribs contains ingredients that can be attacked by organisms such as soil termites. To overcome this, preservation action is needed. Conventional preservatives commonly contain ingredients that are less environmentally friendly, expensive and not easily available. Therefore, it is necessary to find a natural preservative from the species more suitable for people. The purpose of this study was to obtain data about the effect of the concentration of natural preservatives from Tuba extract on the gewang midribs. Tuba extract was obtained through the maceration using methanol. Preservation was carried out by soaking the Gewang midribs samples in to tuba extract solution with the consentration (gr/liter) of 0 (control), 4, 9, 16, 25 and 36 for 24 hours at room temperature. The effectiveness of preservatives was done using soil termites test. The results showed that tuba extract had a very significant effect on decreasing the weight of the sample and increasing the quality of gewang midribs from class IV to II. It is recommended that preserving gewang midribs can use tuba extract with a concentration at least of 4 gr/liter of water.
Asosiasi vegetasi tanaman rambatan ketak (Lygodium circinatum (Burm.) Sw.) di KPHL Rinjani Barat, Pulau Lombok, Nusa Tenggara Barat
Authors:   Universitas Mataram, Wahyuningsih Endah , Faridah Eny ,   Universitas Gadjah Mada, Budiadi Budiadi , Syahbudin Atus
Published: February 2021

Ketak (Lygodium circinatum (Burm.) Sw. is a fern plant and its growth requires other plants as a host plant for climbing of tendrils to get light. Information of vegetation association of host plant is needed, due to it is considered to have an influence on growth and productivity. This data and information is important to develop a strategy of ketak for cultivation and conservation. This research was aimed to determine vegetation association of ketak host plant in its habitat. The study applied purposive systematic sampling by survey technique based on altitude i.e. 0-249, 250-499 and 500-750 m asl. There are 10 of observation plot with dimension of 20 m x 20 m. In each plot, an analysis of vegetation association of ketak host plant to determine association between species, type of interaction and index of association between species of ketak host plant. The results showed that vegetation association of ketak host plants in each altitude classification which had a positive and strong association were 14 pairs species in altitude of 0-249 m asl, and 8 pairs species in altitude 250 – 499 m asl, and also in altitude 500 – 750 m asl had 15 pairs species. Altitude 500 - 750 m asl, shows the association of vegetation with the highest combination of species pairs.
Pengaruh pemupukan dan pemangkasan tanaman terhadap produktivitas daun murbei di kota Tomohon, Sulawesi Utara
Authors:   Balai Penelitian dan Pengembangan Lingkungan hidup dan Kehutanan Manado, Nurrani Lis , Tabba Supratman , Wildah Andi
Published: February 2021

Mulberry is remain the only important feed determined the productivity of cocoons on silkworm cultivation. Development of hybrid mulberry that contain high nutrition is very important because their nutritional value is the most influences key factor toward the quality and quantity of cocoons and silk. This study aimed to determine the effect of fertilization and trimming on the leaves productivity of three species of mulberry in a demonstration plot in Rurukan village, Tomohon city, North Sulawesi. This study used a completely randomized design with a factorial research design of three species of mulberry leaves (SULI 01, M.cathayana dan M.kanva) with three types of fertilizer (Taikam, Petroganik dan Kandang) to determine the effect of fertilizing. Two species of mulberry (M.cathayana dan M.kanva) with three different trimming heights (30 cm. 45 cm dan 60 cm from the ground) to determine the effect of trimming techniques. The source of mulberry genetic material comes from The Forest Productivity Research and Development Center in Bogor. The parameters measured include diameter growth, height and leaves production. The results showed that in general the fertilization aplication had no effect on leaves productivity in all species of mulberry tested. Application of Taikam fertilizer and manure only affects the growth of diameter and height of mulberry plant. The trimming treatment has an influence on leaves productivity. The highest leaf production resulted by M.kanva (639.61 gr) on high trimming 45 cm, on the other side the highest leaf production of M.cathayana on high trimming 60 cm from the ground (482.40 gr).
Pengaruh pohon induk dan bahan stek terhadap pertumbuhan stek cabang Timoho ( Kleinhovia hospita L)
Authors:   Balai Besar Penelitian dan Pengambangan bioteknologi dan Pemuliaan tanaman Hutan, Hakim Lukman , Yuliah Yuliah , Adma Adinugraha Hamdan
Published: February 2021

Timoho (Kleinhovia hospita L) is a rare plant that has high economic and cultural value for the Javanese people, especially in Yogyakarta. Timoho wood has a beautiful pattern called pelet and is used as a raw material for keris sheath. In Yogyakarta, timoho trees are difficult to find, currently, so that plant propagation in a generative way also has difficulty due to scarcity of seeds. Therefore, it is necessary to conduct timoho propagation research through vegetative methods. The purpose of this study was to determine the origin of stem cuttings to the success of timoho stem cuttings. Stem cuttings come from three timoho trees in the Arboretum of the Center for Forest Biotechnology and Tree Improvement Yogyakarta. The research method used a factorial experimental design using 3 mother trees and 3 stem parts (base, middle and end). The parameters observed were percentage of shoots, number of shoots, length of shoots, and number of leaves. The results showed the percentage of live cuttings varied from 10.9-60.0%, number of shoots 1-7 pieces, number of leaves 3-26 strands and length of shoots 2.00-17.7 cm. The mother tree has a significant effect on the percentage of sprouts and shoot length, while the cuttings material has a significant effect on the length of shoots at the cuttings measurements of the age of 2 months since planted in polybags.
Fungi Mikoriza arbuskula (FMA) yang berasosiasi dengan Durio zibethinus di Kabupaten manokwari, Papua Barat, Indonesia
Authors:   Universitas Cendrawasih Jayapura, suharno Suharno , Agustini Verena , H.R. Tanjung Rosye , Sufaati Supeni
Published: February 2021

Arbuscular mycorrhizal fungi (AMF) is a symbiosis between fungi and plants. This association is mutualism,AMF contributes to increased plant growth while fungi obtain energy sources from plant assimilation. The purpose of this study was to determine the association of AMF with durian plants (Durio zibethinus) in Manokwari, West Papua. The survey was conducted in 10 villages located in 4 districts known as the center for producing durian. Observation of the presence of AMF spores in the plant's rhizosphere was carried out by the wet sieving method. Furthermore, to find out the association between the two symbionts is done by observing AMF colonization in plant roots. The types of AMF found in the plant's rhizosphere are morphologically identified based on spore characteristics. The results showed that durian was associated with AMF. The percentage of AMF colonization ranged from 39.29 to 80.00%, while the number of spores was 112-336 spores per 100 grams of soil sample. Based on the spore morphological characteristics, AMF found is dominated bythe genus Glomus, Scutellospora, and Acaulospora.
UJI ANTIBAKTERI TEPUNG UMBI PORANG (Amorphophallus konjac) TERHADAP Staphylococcus aureus dan Escherichia coli DENGAN METODE DIFUSI DISK
Authors: Sulkarnain Sulkarnain , Agustina Laily , Jamilah Jamilah
Published: February 2021

Umbi porang (Amorphophallus konjac) termasuk salah satu jenis tanaman talas-talasan dan merupakan tanaman lokal Indonesia yang banyak tumbuh di hutan. Umbi porang memiliki kandungan glukomanan yang cukup tinggi, yaitu sekitar 55% dari berat kering umbi. Umbi porang juga memiliki kandungan berupa protein yang memiliki peran penting dalam mencegah pertumbuhan mikroba. Jenis protein yang dapat berfungsi sebagai antimikroba adalah lektin. Penelitian ini bertujuan untuk mengetahui efektifitas antibakteri dari tepung umbi porang dalam menghambat Staphylococcus aureus dan Escherichia coli yang dapat menyebabkan penyakit pada unggas. Bahan yang digunakan dalam penelitian ini yaitu tepung umbi porang, isolat kuman, Staphylococcus aureus strain ATCC 25923, Escherichia coli strain ATCC 25922, media muller hinton agar (MHA), blood agar dan mac conkey agar, antibiotik disk, kertas disk kosong, alkohol 70% dan aquades. Data yang diperoleh dianalisis dengan RAL (Rancangan Acak Lengkap) yang terdiri atas empat perlakuan dan empat ulangan. Hasil penelitan menujukkan bahwa luas zona hambat berpengaruh nyata (P<0,05) baik pada bakteri S.aureus maupun E. coli.. Dari hasil tersebut dapat disimpulkan bahwa pemberian tepung umbi porang hingga level 4,5% mampu menghambat pertumbuhan S.aureus dan E. coli.. Daya hambat tertinggi terdapat pada bakteri Gram positif dan daya hambat terendah terdapat pada bakteri Gram negatif. Kata Kunci: Antibakteri, Tepung Umbi Porang, S.aureus, E. coli.
PENGGUNAAN UMBI TALAS SEBAGAI BAHAN ADDITIVE TERHADAP BEBERAPA UNSUR KIMIA SILASE RUMPUT GAJAH MINI
Authors: Nompo Syamsuddin , Rinduwati .
Published: February 2021

Penelitian bertujuan untuk mengetahui pengaruh umbi talas sebagai bahan additive terhadap beberapa unsur kimia silase rumput gajah mini. Penelitian ini menggunakan rumput gajah mini dan tepung umbi talas sebagai zat additive. Penelitian disusun berdasarkan  Rancangan Acak Lengkap (RAL) sebanyak 16 unit percobaan, yang terdiri dari 4 perlakuan dan 4 kali ulangan. Perlakuan terdiri dari : T0 = Rumput gajah mini tanpa tepung umbi talas (control); T1 = Rumput gajah mini + 6% tepung umbi talas jepang; T2 = Rumput gajah mini + 6% tepung umbi talas bogor; dan T3 = Rumput gajah mini + 6% tepung umbi talas sutra. Hasil penelitian menunjukkan bahwa pemberian tepung umbi talas berpengaruh nyata ( P<0,05 ) terhadap kandungan protein kasar, serat kasar dan ADF tapi  tidak berpengaruh nyata ( P>0,05 ) terhadap kandungan NDF silase rumput gajah mini. Kesimpulan bahwa kandungan protein kasar silase rumput gajah mini yang menggunakan tepung umbi talas lebih tinggi daripada silase tanpa tepung umbi talas. Kandungan serat kasar pada perlakuan tanpa tepung umbi talas lebih tinggi dibanding silase yang menggunakan tepung umbi talas. Kandungan NDF dan ADF silase dari rumput gajah mini yang menggunakan tepung umbi talas lebih rendah dibanding silase tanpa tepung umbi talas. Silase yang menggunakan tepung umbi talas sutra lebih baik daripada perlakuan lainnya.
PENGARUH TINGKAT PEMBERIAN PUPUK UREA DAN UMUR PANEN TERHADAP PRODUKSI HIJUAN SORGUM MANIS (Sorghum bicolor (L.) Moench)
Authors: Saputra Ardian , Nohong Budiman , Rinduwati .
Published: February 2021

Penelitian ini dilakukan untuk mengetahui pengaruh umur panen dan level pemberian pupuk urea terhadap produksi hijauan sorgum manis. Penelitian disusun dalam rancangan acak lengkap pola faktorial 2 x 3 dan tiga kali ulangan. Faktor pertama terdiri atas umur panen, yaitu 35 hari setelah tanam (35 HST) dan 55 hari setelah tanaman (55 HST).  Faktor kedua adalah level pupuk urea, yaitu 0 kg urea/ha (0 g urea/polybag), 150 kg urea/ha (0,75 g urea/polybag) dan 250 kg urea/ha (1,25 g urea/olybag). Setiap unit perlakuan diberi pupuk dasar bokashi masing-masing 300 g/polybag. Hasil penelitian menunjukkan bahwa umur panen dan level pemberian pupuk urea berengaruh terhadap produksi hijauan segar dan bahan kering sorgum manis. Tidak ada interaksi antara tingkat pemupukan dengan umur panen.  Produksi hijauan segar dan bahan kering sorgum manis lebih tinggi ada umur panen 55 hari dan pada level pemberian pupuk 250 kg urea/ha (1,25 g urea/olybag).
PENGARUH MIKROORGANISME, BAHAN BAKU, DAN WAKTU INKUBASI PADA KARAKTER NATA: REVIEW
Authors: Putri Sherly Novia Yuana , Syaharani Wahyu Fajri , Utami Cindy Virgiani Budi , Safitri Dyah Retno , Arum Zahra Nur , Prihastari Zulfa Shafira , Sari Anjar Ruspita
Published: February 2021

Nata is an organic food product that has a high fiber content. Nata is a fermented produce by Acetobacter xylinum. There is very limited review article that discussed the making process of nata using different starter, raw material, and the length of incubation time in once. So that, this review discusses the comparison of various parameters that affect the fermentation process of nata. This review aims to discuss the effect of using several types of microorganisms, different raw materials, and different fermentation time on nata production. Factors that influence the success of nata fermentation process include fermentation time, the addition of ingredients (sugar, vinegar, and urea), the use of hollow caps, avoiding products from shocks, and the use of sterile equipment. The bacteria that can be used for making nata include Acetobacter xylinum and Acetobacter sp. Several raw materials can be used to make nata, such as coconut water, seaweed, banana peels, tofu water, cassava, and jackfruit straw. The best raw material to make nata from color parameters is seaweed, aroma parameter is jackfruit straw, and taste parameter is cassava. Based on chemical and physical tests, the best raw material for moisture content parameters is seaweed, fiber content parameter is cassava, thickness parameter is banana peel, and yield parameter is coconut water followed by cassava. The length of fermentation affects the thickness and weight of nata, chewier texture of nata, and the darker color of nata. The best thickness of nata produced on the 14th day of fermentation was 1.7 cm. The best overall weight of nata on produced the 10th day of fermentation was 600 g/L. The texture of nata was the chewiest in the fermentation time of 14 days with the value was 72.33 g/5mm. The lowest degree of nata whiteness produced on the 14th day of fermentation with the value was 72.307%.
Determinants of Exclusive Breastfeeding Practices of Female Healthcare Workers in Jakarta, Indonesia
Authors: Rapingah Siti , Muhani Nova , Besral Besral , Yuniar Poppy
Published: February 2021

The World Health Organization (WHO) recommended that mothers worldwide exclusively breastfeed their infants for the child's first six months to achieve optimal growth, development, and health. Indonesia had not fulfilled the global standard of breastfeeding rate so that there was low coverage of exclusive breastfeeding in East Jakarta, especially for female healthcare workers. This study aimed to determine the factors associated with exclusive breastfeeding practices of healthcare workers. This was a quantitative study using a cross-sectional design. The recruited sample consisted of 85 female public health center workers with infants aged 6-24 months. Data were collected using self-administered questionnaires. Logistic regression analysis was applied to identify factors associated with exclusive breastfeeding. The results showed that the proportion of exclusive breastfeeding was 54.1%. Variables associated with exclusive breastfeeding were knowledge, attitude, family support, co-worker support, and healthcare worker support. Multivariate analysis showed that knowledge and age were the dominant factors of exclusive breastfeeding practices with an odds ratio (OR) adjusted OR of 14 and 5, re¬spectively. Knowledge was an influential factor in the success of exclusive breastfeeding. Therefore, creating a training program related to breastfeeding would be expected to improve knowledge. Besides, a supportive policy such as providing breastfeeding facilities was needed.
Exclusive Breastfeeding History Risk Factor Associated with Stunting of Children Aged 12–23 Months
Authors: Sari Nurhalina , Manjorang Marlida Yuliza , Zakiyah Zakiyah , Randell Madeleine
Published: February 2021

Stunting (low height-for-age) remains a global and national health problem because it increases the risk of disturbances in growth and development and mortality. Banjar Margo District, Tulang Bawang Regency, has the second-highest prevalence in Lampung Province, Indonesia. This study aimed to analyze the association of exclusive breastfeeding history and stunting in children aged 12–23 months in Banjar Margo District. This study used a cross-sectional design on 193 children aged 12–23 months. It was primary data conducted between April and May 2018 with a questionnaire. Data analysis was performed using the chi-square test and multiple logistic regression. The result showed that of 193 children, 29.5% were stunted. Children who were not exclusively breastfed were 3.1 times (95%CI = 1.5–6.4) more at risk of stunting than those exclusively breastfed, after controlling for mothers with low education and unemployment factors as confounding variables. Health promotion activities in primary/integrated health care should be focused not only on mothers but also on other people involved in child care, such as grandparents, at-home caregivers, and day carers.
Analysis of Measles Vaccination Refusal on Social Media (Facebook) among Anti-Vaccine Communities in Indonesia
Authors: Meilani Dwi , Martha Evi , Pratomo Hadi , Hasanah Indah Jamiatun , Rungreangkulkij Somporn
Published: February 2021

Measles is one of the main causes of global mortality in the under-fives. The existence of groups that reject immunization caused a decrease in immunization coverage. Anti-vaccine messages are widely delivered on social media. Identification of vaccine rejection behavior can be used as the basis to formulate effective program strategies. The design of this study used rapid assessment procedures (RAP). The informants were from two anti-vaccine communities in the Facebook group. In-depth interviews and observations were done for data collection, and data analysis was performed using the Framework Method. The results found that determinants, such as knowledge, beliefs in health behavior and disease prevention, religion, culture, and government policies play a role in shaping informants’ perceptions of vaccines and disease risks. The design factors of vaccination programs and the reliability of vaccine producing sources were found to be inhibiting factors for informants to receive vaccines. Also, experience with vaccines, health workers' role, and lobbying by anti vaccine groups strengthened informants' attitude who initially doubted vaccines, causing them to reject vaccines ultimately. It is suggested to the Ministry of Health to improve vaccination campaigns through social media, conduct vaccine development study, and increase health workers' knowledge related to vaccines and make their communication techniques more effective.
Evaluation of Added Sugar and Sugar-Sweetened Beverage Consumption by University Students
Authors: Meric Çağdaş Salih , Ayhan Nurcan Yabanci , Yilmaz Hacı Ömer
Published: February 2021

Today, increased intake of sugar and sugar-sweetened beverages is seen today as an important factor in the growing prevalence of chronic diseases, such as obesity, obesity-related diabetes, and coronary heart diseases. This study involved 214 university students from the Department of Nutrition and Dietetics of Ankara University, Faculty of Health Science, which was intended to evaluate the consumption of sugar and sugar-sweetened beverages. The frequency of student consumption of beverages and the quantities and amounts of sugar taken with beverages were questioned. The average total amount of sugar added to drinks by the students was 4.69 ± 6.35 gram, while the average total amount of sugar taken with sugar-sweetened beverages was 11.34 ± 15.32 gram. Female students relative to male students, students in grade 4 compared to grades 2 and 3, and students who had daily breakfast compared to those who did not had lower average sugar consumption (p-value < 0.05). As class grades increase, the amount of sugar added to beverages and fruit juice and sweetened soft drinks and carbonated beverages decreased (p-value < 0.05). The consumption of herbal teas and dietary beverages increased and eating habits of students generally changed positively (p-value > 0.05). It is important to educate university students about the reduction in sugar intake and sugar-containing food in order to avoid many chronic diseases that may be seen in older ages.
Geomechanics Without Sonic In Tight Gas Reservoirs In The North Of Oman
Authors: Lukmanov Rinat , Aamri Mohammed
Published: February 2021

Barik and Miqrat are the main two deep tight gas clastic reservoirs in several fields of Oman. In the area of the current Study, these reservoirs are encountered at depth 4500-5200 m and contain rich gas/condensate. Average permeability for different units ranges from 0.02 to 4 mD, porosity up to 14% with averages values within the range 5-10%. In order to produce economically, hydraulic fracturing is applied in these reservoirs. Geomechanics calculations are essential for the fracturing design. One of the particular challenges is fracture containment within the gas zone because in view of low stress contrast between different lithologies. Sonic data are normally used for these calculations. However, based on the analysis of the Sonic data available, a simple workflow was developed for Geomechanics calculations which don't require Sonic. A good restoration of compressional Sonic was achieved using the total porosity and the rock volumetrics as the input data. The analysis reveals good correlation between the complex rock constituents and the Poisson's ratio. These findings resulted in good Shear Sonic restoration and fir for purpose calculations of Geomechanics parameters. The Minimum horizontal stress data obtained based on actual Sonic data matches very well with the Minimum horizontal stress derived without Sonic resulting in practically the same hydraulic fracturing design.

The normalization of Gamma Ray and Neutron and rigorous multimineral analysis was a key to success for this methodology. A fit for purpose methodology was developed which enabled to perform identification of 3 key rock constituents even from the basic Triple Combo.

The methodology for Geomechanics without Sonic was used for frac design in several wells. The proposed model is found to be very robust.
Beyond Volumetrics: Unconventional Petrophysics for Efficient Resource Appraisal (Example from the Khazzan Field, Sultanate of Oman)
Authors: Spain David R. , Merletti German D. , Dawson William
Published: February 2021

The Middle East region holds substantial resources of unconventional tight gas and shale gas. The efficient extraction of these resources requires significant technology and expertise across numerous disciplines, including reservoir description and geomechanical characterization, hydraulic fracture modelling and design, advanced numerical simulation capabilities, sensor and surveillance technologies, and tightly integrated workflows.

The effective application of these integrated subsurface and completion workflows leads to improved capital efficiency and well performance through increased well potential, increased ultimate recovery, and reduced costs. Key elements include dynamic rock typing to highlight potential flow units that will maximize gas deliverability, geomechanical modelling to provide a calibrated stress profile, and an integrated model that demonstrates the importance of understanding both dynamic flow properties and geomechanical response in complex tectonic environments.

Dynamic rock typing focuses on using both depositional and petrophysical properties including rock type, porosity, and effective gas permeability at reservoir conditions to divide the reservoir into flow units in the context of their saturation history. The geomechanical profiling generates a tectonics-corrected minimum horizontal stress (SHmin) and the net confining stress (NCS). The rock-log-test calibration requires the evaluation and integration of subsurface fracture tests, including After-Closure Analysis (ACA), Data Fracs and Micro Fracs. All three involve different injection volumes and sampled reservoir volumes.

Tight gas petrophysical studies must go “beyond volumetrics”, and should consider not only the static (storage) and dynamic (flow) properties within the context of the petroleum system and evolution of the current day pore geometry and fluid saturation distribution, but also the geomechanical stress regime and its implications for efficient completion optimization. Alternative interpretations test the range of uncertainty and are useful in designing field trials and surveillance strategies to reduce the subsurface uncertainty and to mitigate development risks.
Production Forecasting Using Flow Back Data
Authors: Kurtoglu Basak , Salman Ahmad , Kazemi Hossein
Published: February 2021

In unconventional reservoirs, the well life cycle includes drilling, completion, flowback, and production. The analysis of the fracturing pressure, flowback, and production data provides an early estimate of the stimulated rock volume (SRV) and reservoir flow capacity. In this paper, we present a methodology for using the average treatment pressure and hourly flowback data to characterize reservoir connectivity as an early indicator for long-term productivity. We will also show that performing flow regime analysis during the flowback period provides a greater understanding of the initial fracture conductivity (via bilinear flow) and reservoir connectivity (via linear flow). This early time analysis also sheds light on sweet spots (or geologically favorable areas) and effectiveness of the completion practices for business decisions. In this paper, we have modified the well-known single-phase diffusivity equation to include simultaneous flow of oil, water, and gas in the reservoir. Furthermore, we used fracture treatment pressure, flowback and production data from several Eagle Ford and Bakken wells to demonstrate the value of completion and flowback data and their relation to the long-term performance of wells.
Hydraulic Percussion Drilling System with PDC Bit Increases ROP and Lowers Drilling Costs
Authors: Powell Scott W. , Hu Ertai
Published: February 2021

Drilling the Severnaya Truba Field in Aktobe, Kazahkstan, has proved to be a costly and time consuming challenge for operators trying to maximize profits. The formation is typically drilled with roller cone bits that take multiple runs to complete an interval. To increase effectiveness and drilling efficiency, a hydraulically powered percussion drilling system along with a fixed cutter PDC bit were added.

In place of a conventional drilling system, a new energy distribution system was introduced that would induce axial oscillations and percussion impacts while applying the same weight and torsional energy to the bit. In combination with a drilling fluid powered percussion hammer (FPPH), a fit for application polycrystalline diamond compact (PDC) bit with depth of cut (DOC) control features was used to minimize the exposure of the cutting structure and prevent breakage.

The system combines the torsional power of a conventional positive displacement motor with a high frequency axial pulse created with each rotation. The torque is transferred directly to the bit and 100% of the hydraulic flow is utilized by the bit nozzles to maintain hole cleaning and keep PDC cutters cool. The mechanical lifting and falling action creates a rapid variation in weight on bit (WOB), allowing the bit's depth of cut to fluctuate while overcoming different stresses. These variations, along with the percussion pulse created with each stroke, lead to increased rates of penetration.

This system has been used throughout the world on a variety of formations, using both PDC and roller cone insert bits. This paper will focus on an 8½ in interval drilling operation in the Severnaya Truva field, located 60 km from Zhanazhol field in Kazakhstan. The formations consisted of soft to medium siltstone, red/grey clays, sandstone, hard cemented dolomite, limestone, and very dense clay stone. This new technology proved to increase both ROP and interval drilled, saving seven days of drilling compared to offset wells.
Production Performance Analysis of Unconventional Gas Reservoirs with Different Well Trajectories and Completion Techniques
Authors: Erturk Mehmet Cihan , Sinayuc Caglar
Published: February 2021

The significance of unconventional gas reservoirs has been increasing for recent years owing to economic viability of their development, therefore assessment of the challenges and common pitfalls regarding those resources have been gaining importance at the same time. In this regard, the optimization of production performance of these reservoirs with the different well trajectories and completion techniques and identifying the best case scenario become more significant. That is absolutely challenging process due to the several reasons such as ultra-low permeability, desorption effect, and complex geological characteristics. However, it is possible to analyze the various parameters and observe their impact on each system with the help of advances in algorithms, computer power, and integrated software.

The objective of this work is to investigate and understand the effect of some reservoir and completion parameters on the future production performance of shale gas and coal bed methane (CBM) reservoirs. A practical model is constructed with the field and synthetic data for the analysis of gas production rate and cumulative gas production versus time in multi-layered shale gas and CBM reservoirs respectively. Changes in the thickness of various stratified layers, permeability, wellbore position, number of hydraulic fracture stage, and also production profile of each system are studied using different well trajectories. The results are obtained by running a series of reservoir simulation conducted by a commercial numerical simulator with dual porosity model for CBM and shale gas reservoirs.
Evaluation of Synthetic Acid for Wells Stimulation in Carbonate Formations
Authors: AlDahlan Mohammed N. , Obied Marwa A. , Marshad Khalid M. , Sahman Faisal M. , Yami Ibrahim S. , Alhajri Abdullah M.
Published: February 2021

Acid treatments of carbonate formations are usually carried out using mineral acid (HCl), organic acids (formic and acetic), mixed acids (HCl-formic, HCl-acetic), or retarded acids. The major challenges when using these acids are their high corrosivity, fast reaction rate and health hazard. The improvement in corrosion inhibitors makes the use of a strong acid as high as 28 wt% HCl possible. The acid reaction rate can be controlled by increasing acid viscosity using gelling agent or emulsifying acid droplets, acid-in-diesel emulsion. While the issues of stimulation acids reaction and corrosion rates are relatively controlled, these acids health hazard rating of 3 by the National Fire Protection Association (NFPA) is a major concern. A health hazard rating of three is defined as an extreme danger where short exposure could cause serious injury.

An acid replacement chemical that has no or minimum health hazard rating while still has the ability to dissolve carbonate rock would be a major forward step in stimulation technology. This paper presents the results of the study conducted on a synthetic stimulation acid (Syn-A) chemical, with health hazard rating of one and dissolving power similar to 15 wt% hydrochloric acid (HCl). An extensive experimental scheme including: thermal stability, dissolving power, acidity, compatibility, corrosion rate & inhibition and coreflooding on carbonate formation core plugs was conducted. The Syn-A was found to be thermally stable with similar dissolving power to 15 wt% HCl and lower corrosion rate. In addition, the Syn-A developed a breakthrough on core plugs with an average pore volume (PV) of 2.7 and approximately 3 folds increase in permeability.
Hydraulic Fracture Initiation and Propagation Model Provides Theoretical Ground for Hybrid-Type Fracturing Schedules in Unconventional Gas Reservoir in the Sultanate of Oman
Authors: Briner Andreas , Moiseenkov Alexey , Prioul Romain , Abbas Safdar , Nadezhdin Sergey , Gurmen Nihat
Published: February 2021

A recent series of tight gas discoveries in the Amin formation of the greater Fahud area represents some of the most exciting exploration success of this decade in the Sultanate of Oman. The structures have been evaluated as containing very significant amounts of gas locked in a challenging deep and hot environment requiring hydraulic fracture stimulation. Since their discoveries, the two primary challenges have been difficult breakdown of the formation and limited proppant placement during stimulation attempts. The early experience in the exploration and appraisal campaigns from 2009 to 2014 has led to fracture designs with conservative proppant amounts that could limit the full potential of the field. Several geomechanical studies have been commissioned in the past to guide completion strategies in well placement, perforation, and fracture stimulation design.

The objectives of this study were to model hydraulic fracture initiation and breakdown in the three Amin zones (upper, middle, and lower) to provide some theoretical understanding of the impact of the different parameters on the observed field breakdown pressures. In agreement with field observations, the model showed that lowering the viscosity of the pad has a major impact in lowering the breakdown pressures. Consequently, current best practices include formation breakdown and hydraulic fracture propagation with low-viscosity fluids followed by proppant placement with high-viscosity fluids. When applied to tight gas formations in the Sultanate of Oman, the hybrid fracturing evolves from conventional designs for the purpose of successful fracture initiation, while still placing a successful job.
Comprehensive Spectral and Thermal Characterization of Oil Shales
Authors: Guven S.. , Akin S.. , Hascakir B..
Published: February 2021

The heterogeneous nature of oil shale resources associated to the depositional environments, lithology, and organic content make the reserve estimation complex and unpredictable. However, comprehensive laboratory studies on organic rich shale samples collected from different regions can increase the understanding about the organic content of oil shales, interaction of shale with organic matter and injected fluid used during enhanced oil recovery method. This study investigates the characterization of eight different Turkish and American oil shale samples with several spectral methods and a thermal analysis. The main purpose of this study is to characterize the oil shale samples to increase the understanding about the organic content and interaction of shale with organic matter.

In this study, we used Thermal Gravimetric Analysis/Differential Scanning Calorimetry (TGA/DSC) analysis to estimate organic content of each oil shale sample in air and nitrogen environments. X-Ray Diffraction (XRD) was used to define minerals in oil shale. Fourier Transform Infrared Spectroscopy (FTIR) was used to detect the mineral and kerogen in oil shale before and after the TGA/DSC analysis. Scanning Electron Microscope (SEM) was used to characterize the depositional environment of each oil shale samples. TGA/DSC results verified that oil shale samples have up to 50% of organic matter. XRD and FTIR results helped to identify the organic and inorganic compounds. Effects of minerals and ions were recognized by comparing TGA/DSC curves and FTIR spectra. It was recognized that the more carbonate ion in the oil shale the more increase in weight loss occurred. Diatoms identified from SEM results showed that depositional environments of the some oil shale samples are marine environments.

This study provides insight for the reserve estimation of the eight different oil shale samples with comprehensive spectral and thermal characterization.
Realtime Drilling Geomechanics Service, Case Study, Offshore Malaysia
Authors: Heidari Babak , Leong Sook Ting , Son Nguyen Truong , Aznor M Zafril
Published: February 2021

Real Time Drilling Geomechanics (RTDG) provides relevant real time information and integrated workflow to help clients in reducing operational risk and nonproductive time (NPT) through drilling in marginal economical and technically challenging environments. Dulang-B field is a technical challenge due to its complex structural geological environment. All the existing wells failed to penetrate into deep reservoir F40 sands due to wellbore instabilities issues. Overpressure in F-sands remains always the main concern and challenge which led to unsafe drilling environment and significant nonproductive time in the field. Avoiding drilling surprises means more than being prepared for problems when they occur; it means averting them in the first place. Appropriate safe mud weight to drill each formation, must be defined to overcome different overpressure zones and identify the best position for casing seat of each hole section of the well. With the knowledge acquired through pore pressure and fracture gradient modeling, well behavior could be foretold with enough advance notice to allow drilling team to calmly make technically sound operational decisions that lead to optimal drilling performance.

This study presents the challenges and the main results of the collaborative drilling approach via RTDG (Real Time Drilling Geomechanics) operation in well DL-B28 ST2. This study focuses on the overpressure and narrow safe mud weight window as well as level of uncertainty over prognosis formation tops which has to be managed by integrating LWD seismicVISION* and RTDG which had clear impacts on decision making process. The real time measurement approach by utilizing actual well data provided the best solution to accurately constrain pre-drill pore pressure and fracture gradient model.
Identification of Well Completion and Hydraulic Fracturing Performance Factors of Initial Development Wells within a Tight Oil Project in West China
Authors: Zhang Jing , Jiangwen Xu , Jiang Hong , Judd Tobias , Liu Yuan , Liu Hai , Palacio Juan Carlos
Published: February 2021

The early development of a systematic approach to well completion practices centralized around multistage hydraulic fracturing treatments is often the critical component to sustainable reservoir exploitation and development. Unfortunately, the exploitation of either exploratory or underdeveloped resources often has a number of issues that include the understanding of geological heterogeneity with different results observed within close proximity and the need to optimize completion techniques to offset the potential rapid decline in well productivity. For these cases, well completion and stimulation practices are of utmost importance with the optimization and evaluation of such designs to include and account for the integration of all reservoir and geomechanical parameters.

Recent vertical well results from initial exploratory wells combined with single-well horizontal pilot wells has accelerated the development plans for the Jimusaer field located in the Junggar basin of western China. This field covers a surface area of 300,000 acres with the targeted reservoir being located between 2,300 to 4,255 m true vertical depth (TVD). The application of horizontal wells from multiwell pads with each well consisting of up to 23 hydraulic fracturing treatments was meant to exploit large volumes of hydrocarbon reserves that were previously thought unattainable. Operationally, the first four wells consisted of 62 hydraulic fracturing stages and were executed within a 28-day period.

The project included the application of an integrated workflow including reservoir characterization along the length of the horizontal well lateral, deployment of novel multistage openhole completion techniques with dissolvable isolation technology, factory fracturing approach with all stages being monitored by microseismic monitoring, and application of chemical tracers on selected stages to identify zonal contribution during flowback and cleanup operations.

This paper describes how the acquisition of crucial reservoir and fracturing data combined with operational performance can identify areas for improvement of future completions while strengthening existing ones.