bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morfologi dan Produksi Beberapa Aksesi Sagu (Metroxylon spp.) di Distrik Iwaka, Kabupaten Mimika, Papua / Morphology and Production of Some Sago Palm Accessions in Iwaka, Mimika District, Papua Province
Authors: Ahmad Fendri , Bintoro Mochamad Hasjim , Supijatno Supijatno 
Published: February 2018

<p>Sago is a carbohydrate-producing palm witharea about 382.198 ha in Mimika Regency. So far, research on the characterization of sago palm in this area has not existed, therefore it is necessary to do. The diversity of sago accessions in Mimika District is expected to be a source of germplasm and superior sago selection to support sago development. This study aims to obtain information about morphological characters and starch production of some sago accessions. The study was conducted using observation method of seven sago accessions, namely Mbupuri, Monepikiri, Mbapare, Tuwae, Aute, Iyaremeta and Bakaketemeta in Iwaka District, Mimika Regency, Papua Province. The result showed that the seven accessions sago differed based on morphological character namely stem, leaves and spine, and starch production. The Monepikiri accession has the longest stem and large stem diametre, namely 13.75 m and 59.00 cm, respectively. Accession Mbupuri has more leaves and wider leaves than the others. Accession Monepikiri has a production potential of more than 300 kg’s dried starch/palm and accession Mbupuri more than 200 kg’s dried starch/palm. Both accessions of this sago can be further investigated the stability of yield starch to be released as superior varieties. The morphological characters, especially the length of the stem affect the starch production because the starch is present in the pith of the stem.</p><p><strong>ABSTRAK</strong></p><p>Sagu merupakan tanaman sumber karbohidrat dengan luas areal di Kabupaten Mimika 382.198 ha. Penelitian tentang karakterisasi aksesi sagu di Kabupaten ini belum ada, oleh karena itu perlu dilakukan. Keragaman aksesi sagu di Kabupaten Mimika diharapkan menjadi sumber plasma nutfah sagu, dan untuk seleksi sagu unggul untuk menunjang pengembangan sagu. Penelitian ini bertujuan untuk mendapatkan informasi mengenai karakter morfologi dan produksi pati beberapa aksesi sagu. Penelitian menggunakan metode observasi terhadap tujuh aksesi sagu, yaitu Mbupuri, Monepikiri, Mbapare, Tuwae, Aute, Iyaremela dan Bakaketemeta. Penelitian dilakukan di Distrik Iwaka, Kabupaten Mimika, Provinsi Papua. Hasil penelitian menunjukkan bahwa ketujuh aksesi tersebut berbeda karaktermorfologinya, yaitu batang, daun dan duri. Aksesi Monepikiri memiliki batang yang paling panjang dan diameter paling besar berturut-turut, yaitu 13,75 cm dan 59,00 cm. Aksesi Mbupuri memiliki jumlah daun paling banyak dan daun paling luas.Aksesi Monepikiri memiliki potensi produksi lebih dari 300 kg pati kering/pohon dan aksesi Mbupuri &gt;200 kg pati kering/pohon. Kedua aksesi ini dapat diteliti lebih lanjut kestabilan hasilnya untuk dilepas sebagai varietas unggul. Karakter morfologi khususnya panjang batang mempengaruhi produksi, karena pati terdapat dalam empulur batang.</p>
Measures to Control the Prevalence of Pneumoconiosis in Coal Mining: A Review of the Literature
Authors: Ayaaba Esther , Liu Yi , Li Yan , Han Lei , Yedu Quasanh Dan , Chunhui Ni 
Published: February 2018

Background: There are enormous health problems associated with the use of coal as energy. Dust emitted during the mining processes is identified as a specific risk factor for Coal Worker Pneumoconiosis (CWP) and other respiratory health problems. There is little published evidence on various health measures and their effectiveness in controlling CWP. This review seeks to provide a summary of the published literature on various health measures taken to reduce CWP in coal mines.
Methods: We searched Google Scholar, PubMed, MEDLINE, EMBASE and occupational health databases for published research articles, evaluation reports, official documents and regulations. Reference lists of relevant papers were hand-searched. We retrieved a total of 1, 049 articles out of which 17 merited criteria for inclusion. Papers presenting evidence of the prevention of CWP among coal miners were included.
Results: Many technological interventions are currently available to promote primary prevention of CWP by ensuring reduction in inhalable dust. This review identified laws and regulations, surveillance, direct dust control measures, risk assessment and compensations as ways of minimizing exposure to dust among coal workers, as means of preventing CWP.
Conclusion and Implications for Translation: There is little evidence on the various measures stipulated in mining regulations that are adhered to and the extent to which they have been effective. The public health strategy that combines various health measures, including training of workers on safety measures, may be effective in preventing CWP.

[This article has been republished with minor changes. These changes do not impact the academic content of the article.]

Copyright © 2017 Ayaaba et al. Published by Global Health and Education Projects, Inc. This is an open-access article distributed under the terms of the Creative Commons Attribution License CC BY 4.0.
Knarr Field - Optimization of Wellbore Clean-Up Through Dynamic Transient Modeling
Authors: Dimude M. , Wane B. , Lu H. 
Published: February 2018

Abstract
Optimized well clean-up planning and procedures are crucial for the effective development of offshore subsea wells and their subsequent production stage to host facilities. The objective of the well cleanup is aimed at ensuring a successful removal of the completion fluids and drill-in fluid out of the wellbore to restore connectivity with the reservoir, maximize well productivity while minimizing tensile sand failure, and properly conditioning the sand face completion (in a standalone screen scenario). To achieve this goal, the well clean-up time, bean-up procedure, rate and fluid volumes to be produced should be appropriately estimated to properly size the surface testing equipment required for the operation.
Due to the highly dynamic and transient nature of the cleanup process, the use of a dynamic simulator was required to effectively capture the physics of the concurrent flow of the various phases present in the system. An extensive modelling and simulation of the unload process has been performed through the use of a dynamic multiphase simulator to assess the transient displacement of the various wellbore fluids according to several unload strategies. Potential clean-up times and volumes were assessed using flowrate ramp-up schedules designed for different completion fluid distributions in the wellbore. The constrained flowrate cases were considered to represent the constraint on the rig (restricted because of surface handling capacity issues).
The well clean-up procedure was developed to minimize clean-up time, avoid formation damage, and minimize volume of formation liquids on flow back during the rig well tests. During the execution, the movement of fluids along the wellbore, surface production rates, the drawdowns and duration of clean-up to predefined targets were monitored and recorded. The acquired field data from the clean-up operation was compared against simulation prediction and validated the reliability of the predictive model.
This study proves the transient multiphase simulation to be effective in capturing the physics of the multiphase flow process involved in the clean-up operation. It also demonstrates that, when appropriately done, it could be an effective tool for the planning and strategy selection for the well cleanup operation.
Quantifying Reservoir Permeability in Shale Reservoirs Using After-Closure Analysis of DFIT by Considering Natural Fractures, Fissures, and Microfractures: Field Application
Authors: Chen Zhiming , Sun He , Liao Xinwei , Wang Shuhua , Yu Wei , Zuo Lihua , Wu Keliu , Li Jing 
Published: February 2018

Abstract
Natural fractures, fissures, and microfractures are well-known contributors to production performance of shale reservoirs. Complex fracture geometries can be generated by either small-scale fracturing, DFIT, or large volume fracture stimulation, because the activation of pre-existing natural fractures, fissures, and microfractures plays a significant role on generation of induced hydraulic fractures. Therefore, much more attention should be paid to the model development of DFIT complexity.
In previous work, Chen et al. (2017a) built a complex fracture-network model for after-closure analysis of DIFT by considering natural fractures. Based on that, this paper introduces a generalized model with random fracture geometry caused by natural fractures, fissures, and microfractures. First, the model flexibility is demonstrated by different complex fracture cases, namely opening-fissure fracture network, tree-like fracture network, radial multiple fracture network, and mutually orthogonal fracture network. It is found that the pressure derivative reaches constant level, no matter what the fracture geometry is. Furthermore, the reservoir permeability of field examples from actual DFIT tests in Marcellus shale reservoir is quantified using the log-log diagnostic plots based on the model solutions. Finally, the Nolte G-function is applied to verify the estimated results. We find that the results from the two methods are consistent. This work primarily focuses on quantifying the reservoir permeability, while in the future more efforts will be made to identify the fracture properties using the proposed model.
A Laboratory Study of CO2 Interactions Within Shale and Tight Sand Cores - Duvernay, Montney and Wolfcamp Formations
Authors: Reynolds Murray , Britten Derek , Cui Xiaojun , Twemlow Cory , Cook Mike 
Published: February 2018

Abstract
The most commonly used technology for development of unconventional reservoirs is horizontal wells combined with large multi-stage hydraulic fracture treatments. However, even with these technological advancements, primary recovery factors are generally less than 10 percent of the hydrocarbon in place. Water is currently the primary fracturing fluid used in most commercial developments. There is growing interest in non-aqueous (e.g. CO2) fluid systems not only to reduce water usage, but to increase well productivity and recovery factors.
Use of carbon dioxide (CO2) as a fracturing fluid and an enhanced oil recovery (EOR) agent is also attractive from an environmental point-of-view. Organic rich shale reservoirs can be targets for carbon storage, due to their high CO2 adsorptive abilities and multiple mechanisms for gas storage. Therefore, use of CO2 can have both economic (increased recovery) and environmental (sequestration) benefits.
This laboratory study investigates the interactions of CO2 with various cores from three formations (Duvernay, Montney, and Wolfcamp). Multiple core plugs were prepared from each of the three reservoirs. The mineralogy of the samples was measured with x-ray diffraction (XRD), and total organic carbon (TOC) and thermal maturity were determined with a SRA (Source Rock Analyzer). Porosity was also measured under as-received conditions and cleaned and dried conditions with a helium pycnometer. For each sample, its initial baseline permeability to helium was tested under a full cycle of net confining pressures (1,500 psia → 4,500 psia → 1,500 psia) with pressure steps of 1,000 psia using the pressure pulse-decay method. Subsequently the sample was vacuumed for 12 hours, and was then soaked with CO2 for more than 48 hours. Afterwards, the permeability to CO2 was measured under another cycle of confining pressures. Finally, the sample was vacuumed again and the regain permeability to helium was measured.
Results indicate that the permeability to helium is generally recovered after CO2 soaking stages for tight-sand samples (e.g., Montney) and may be elevated for some samples enriched in organic matter and clay minerals (e.g., Wolfcamp). Overall the study shows favorable interaction between rock and organic material and CO2, which supports the use of CO2 as a fracturing or EOR fluid in these three reservoirs.
Pressure Depletion’s Impact on Induced Strain During Hydraulic Fracturing in Child Wells: The Key to Mitigate Fracture Hits and Pressure Interference
Authors: Vargas-Silva S. , Khodabakhshnejad A. , Paryani M. , Venepalli K. , Ouenes A. 
Published: February 2018

Abstract
Productivity of hydraulically stimulated unconventional wells depends greatly on the successful interconnection of the enhanced permeability and the natural fracture system. Such success is achived by proper understanding of the distribution of mechanical properties of the rock, presence of natural fractures, and regional stresses characterisitcs. With this understanding of the reservoirthe response of the rock to the stimulation can be quantified. Currrently, there are multiples approaches adopted by the industry to support such a process, making fracture designs more robust and reliable. However, theseworkflows often neglect the underlying physics of pressure wave propagation throughout the reservoir, crossing geological features such as faults, natural fractures, ash and karst layers among others.
Pressure depletion caused by production of the first well in a section (parent well) generates continuous changes in stress magnitude and orientation. Simplistic geomechanical models ignore such effects and usually are built based on original conditions, resulting in overestimation of induced strain which will be reflected in oversized hydraulic fracture jobs that negatively affect not only the subsequent wells (child wells) but also the first well in section itself. Negative effects such as frac hits are usually irreversible, and proper estimation of the potential damage needs to be quantified and understood in order to put in place a mitigation plan.
This work presents a workflow where changes in the pressure field are incorporated and taken into consideration during geomechanical modeling of induced strain using full continuum mechanics. As a result, hydraulic fracture designs are adjusted to the reservoir conditions at the time a new child well will be drilled and completed, thus reducing thepotential for negative effects such as frac hits.
A fracture design for a planned child well to be drilled after two years of production of its parentis presented under two scenarios: first, ascenario ignoring the effect of pressure depletion, second, a scenario using the full continuum geomechanical solution to account for the effects of parent depletion.
Results of the fracture design are migrated to dynamic simulation to estimate the effect on the resulting EUR.
Reconciling Empirical Methods for Reliable EUR and Production Profile Forecasts of Horizontal Wells in Tight/Shale Reservoirs
Authors: Yu Shaoyong , Jiang Zhixiang , Lee W. John 
Published: February 2018

Abstract
Confidently establishing single well and/or aggregated production profiles, particularly estimated ultimate recovery (EUR), is both an important and challenging process in unconventional reservoirs. Numerous papers have proposed forecasting techniques, but four fundamental approaches dominate:
Empirical decline curve analysis (DCA), such as multisegment Arps, the modified stretched exponential production decline (YM-SEPD) model, Duong's method, and power-law methods. Rate-transient analysis (RTA), which can include corrections for special dynamic mechanisms (e.g., stress-sensitivity, multiphase flow, adsorption/desorption). Numerical simulation for history-matching and forward modeling. Volumetrically determining in-place resources based on geological data and then applying a recovery factor deemed suitable for the reservoir system and depletion scheme.
Each of these approaches can be implemented using either probabilistic or single-point estimates. Seidle et al. (2016) recently outlined recommended methodologies to accurately forecast time-series volumes and ultimate recovery in unconventional systems. A key recommendation in Seidle et al. (2016) is that the multiple approaches listed previously should be reconciled to establish confidence in forecasts and ultimate recovery estimates. However, Seidle et al. (2016) does not detail the means to achieve this goal. This paper establishes a methodology/workflow to reconcile the different types of empirical DCA methods, which should serve as a starting point for the ultimate goal of reconciling the four fundamental approaches listed.
This paper compares and contrasts the DCA methods applied to various field cases in prominent Canadian [Western Canadian Sedimentary Basin (WCSB)] and US unconventional (oil and gas) plays (Bakken, Barnett, Cadomin, Eagle Ford, and Niobrara). Data sets are selectively chosen based on data quality and history length to increase confidence in the appraisal of the DCA approach. Hindcasting is applied to validate the results and conclusions.
From analysis of a number of wells in different types of reservoirs, a new workflow (methodology) is proposed and validated with hindcasting that allows practically and accurately reconciling EURs based on various empirical methods.
This manuscript is the first paper to discuss systematic reconciliation of EURs from varying approaches for horizontal wells in tight/shale reservoirs.
Dual-Permeability Matrix–Fracture Corefloods for Studying Gas Flooding in Tight Oil Reservoirs
Authors: Luo Peng , Knorr Kelvin D. , Li Sheng , Nakutnyy Petro 
Published: February 2018

Abstract
Laboratory evaluation of tight oil production processes requires a unique coreflood apparatus that portrays both the tight rock matrix and fractures—a dual-permeability system. However, with some tight formations such as the Bakken having no available outcrop, full-sized actual cores are very difficult and sometimes impossible to obtain. In this study, a large-volume coreflood apparatus was developed to incorporate the detailed physics of ultra-tight, dual-porosity, dual-permeability flow in porous media. Also, large synthetic cores were made to represent the permeability, porosity, and mineralogy of actual tight reservoir rocks. To generate the desired dual-permeability system, fractures are simulated by creating sand-filled branched pathways in the large synthetic core. During a coreflood test, fluids are injected through the peripheral high-permeability belt into the tight matrix and recovered through the central fracture. This simulates the flow of matrix to fracture, or vice versa, seen in an ultra-tight reservoir. As well, either continuous gas/water injection or cyclic gas injection modes can be tested with the model. Two large-volume dual-permeability corefloods were conducted to study the effectiveness of immiscible field-produced gas flooding using recombined reservoir oil and synthetic tight cores. The corefloods simulated a practical field production sequence that included primary recovery (pressure depletion), injection of field-produced gas, pressurizing and soaking with this gas, and pressure depletion. The higher-recovery run produced 28.3% original oil in place (OOIP) including primary and tertiary (enhanced) processes. The dual-permeability corefloods demonstrated more representative performance of actual field operations than do traditional one-dimensional corefloods.
The new matrix–fracture coreflood system better reflects the extreme permeability contrast between matrix and fractures that characterizes tight oil reservoirs. Therefore, history matching of its results using a numerical simulator is expected to provide much better representation in scaling up and predicting realistic field operations.
A Markov-Chain-Based Method to Characterize Anomalous Diffusion Phenomenon in Unconventional Reservoir
Authors: Liu Shuai , Li Han , Valkó Peter P. 
Published: February 2018

Abstract
The recent success in developing unconventional reservoirs has caused many new challenges to the theory of reservoir engineering. In this paper, we try to investigate the anomalous diffusion phenomenon caused by the heterogeneity due to the fracture network on the reservoir scale. Firstly, we revisit the physical background of the single-phase flow diffusivity equation by discussing the equivalent single particle diffusion. Combining the characteristics of single particle diffusion with complex fracture geometry, it is indicated that anomalous diffusion phenomenon will be dominant on the reservoir scale, even for single phase production behavior. Then a model based on Markov chain is presented to demonstrate the proposed anomalous diffusion by simulating the partical normal diffusion on a geometric graph and then calculating the relation of the mean square displacement vs. time in the embedding Euclidean space. Based on the simulation results, in consequence, we make a discussion on the characteristic size of the heterogeneity due to the fracture network on the reservoir scale, summarize 2 types of pattern for the anomalous diffusion, and provide a supportive argument for using the fractional diffusivity equation, in place of the classical one, to model the flow and production behavior in highly fractured unconventional reservoirs.
Evaluating Human-Machine Interaction for Automated Drilling Systems
Authors: Farhangfar A. , Torre A. M. , Shor R. J. 
Published: February 2018

Abstract
The efficient utilization of automation systems necessitates a clear understanding of the interaction of the human operator, the automation system and any automated routines being run. If automated routines perform actions not desirable to the human operator, time is lost as the routine is interrupted and human control re-engaged. In addition, automatic handoff back to the human operator, both due to human intervention and due to exist conditions or anomalies must also be managed. Activity data from rigs across North America is analyzed to understand automation process utilization and interrupt timing. Realtime and historic data is tagged, either automatically, semi-automatically using machine learning, or manually, to create a minute-by-minute timeline of rig operations. Operations are then classified both by operation – steering, reaming, making hole, etc. – and well plan to understand how operational demands change automation system utilization. This results in a new set of metrics which can be used to precisely quantify the performance metrics of both the human and automated drilling systems. Performance of the automation system is found to be a strong function of hole deviation with the system outperforming during simple operations and in the vertical hole, but with reduced performance while in the curve and horizontal, due to high interruption of certain tasks. It is found that standard performance metrics, such as slip to slip or weight to weight are affected by standard practices and if these are used to grade system performance, these practices must be account for. This paper presents a detailed investigation of the interaction of the driller with an automated drilling automation system and lays out the utilization of the automation system as a function of rig operations and well path. It is specially noted that standard performance metrics must consider standard practices which may differ between operations.