bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural, Magnetic and Mossbauer studies of Transition metal doped Gd2Fe16Ga0.5TM0.5 intermetallic compounds (TM=Cr, Mn, Co, Ni, Cu, and Zn)
Authors: Dahal Jiba Nath , Sikkanther Syed Ali , Alam Jahangir , Mishra Sanjay Ram
Published: October 2018

The effect of transition metal substitution for Fe and the structural and magnetic properties of Gd2Fe16Ga0.5TM0.5 (TM=Cr, Mn, Co, Ni, Cu, and Zn) compounds were investigated. Rietveld analysis of X-ray diffraction indicates that all the samples crystallize in the hexagonal Th2Ni17 structure. The lattice parameters: a, c and unit cell volume show TM ionic radii dependence. Both Ga and TM atoms show preferred site occupancy for 12j and 12k sites. The saturation magnetization at maximum room temperature was observed for Co, Ni, and Cu of 69, 73, and 77 emu/g, respectively while minimum value was observed for Zn (62emu/g) doping Gd2Fe16Ga0.5TM0.5. Highest Curie temperature of 590 K was observed for Cu doping which is 15% and 5% and thesehigher than Gd2Fe17 and Gd2Fe16Ga compounds, respectively. The hyperfine parameters viz. hyperfine field and isomer shift, show systematic dependence on the TM atomic number. The observed magnetic and Curie temperature behavior in Gd2Fe16Ga0.5TM0.5 is explained on the basis of Fe(3d)-TM(3d) hybridization. The superior Curie temperature and magnetization value of Co, Ni, and Cu doped Gd2Fe16Ga0.5TM0.5 compounds as compared to pure Gd2Fe17 or Gd2Fe16Ga makes Gd2Fe16Ga0.5TM0.5 a potential candidate for high-temperature industrial magnet applications.
MISR-GOES 3D Winds: Implications for Future LEO-GEO and LEO-LEO Winds
Authors: Carr James , Wu Dong , Kelly Michael , Gong Jie
Published: October 2018

Global wind observations are fundamental for studying weather and climate dynamics. Most wind measurements come from atmospheric motion vectors (AMVs) by tracking the displacement of cloud or water vapor features. These AMVs generally rely on thermal infrared (IR) techniques for their height assignments, which are subject to large uncertainties in the presence of weak or reversed vertical temperature gradients around the planetary boundary layer (PBL) and with tropopause folding. Stereo imaging can overcome the height assignment problem using geometric parallax for feature height determination. In this study we develop a stereo 3D-Wind algorithm to simultaneously retrieve AMV and height from geostationary (GEO) and low Earth orbit (LEO) satellite imagery and apply it to collocated Geostationary Operational Environmental Satellite (GOES) and Multi-angle Imaging SpectroRadiometer (MISR) imagery. The new algorithm improves AMV and height relative to products from GOES or MISR alone, with an estimated accuracy of <0.5 m/s in AMV and <200 m in height with 2.2 km sampling. The algorithm can be generalized to other LEO-GEO or GEO-GEO combinations for greater spatiotemporal coverage. The technique demonstrated with MISR and GOES has important implications for future high-quality AMV observations, for which a low-cost constellation of CubeSats can play a vital role.
Review of the Progress and Process of Satellite Imagery and Road Databases Conflation
Authors: Z.Jber Mohamed , Fritsch Dieter
Published: October 2018

Spatial data conflation plays a fundamental role in in many aspects of modern Geographic Information Systems (GIS) research and development such as geospatial data visualization, incremental updating of databases and disaster evaluation. The primary objective of conflation is to derive valuable information based on the comparison of multiple spatial data sources of homogeneous or heterogeneous nature. This paper reviews the state of art of the concept of conflation, feature matching, the most important progresses of conflation between image and road network data, and the complexity of spatial conflation.
Influence of Disease Duration on Circulating Levels of miRNAs in Children and Adolescents with New Onset Type 1 Diabetes
Authors: Samandari Nasim , Mirza Aashiq H , Kaur Simranjeet , Hougaard Philip , Nielsen Lotte Broendum , Fredheim Siri , Mortensen Henrik B , Pociot Flemming
Published: October 2018

The objective of this study was to identify circulating miRNAs affected by disease duration in newly diagnosed children with type 1 diabetes. Forty children and adolescents from The Danish Remission Phase Cohort were followed with blood samples drawn at 1, 3, 6, 12 and 60 months after diagnosis. Pancreatic autoantibodies were measured at each visit. Cytokines were measured only the first year. miRNA expression profiling was performed by RT-qPCR and quantified for 179 human plasma miRNAs. The effect of disease duration was analyzed by mixed models for repeated measurements, adjusted for sex and age. Eight miRNAs (hsa-miR-10b-5p, hsa-miR-17-5p, hsa-miR-30e-5p, hsa-miR-93-5p, hsa-miR-99a-5p, hsa-miR-125b-5p, hsa-miR-423-3p and hsa-miR-497-5p) were found to significantly change expression (adjusted p-value < 0.05) with disease progression. Three pancreatic autoantibodies ICA, IA-2A, GADA65 and 4 cytokines IL-4, IL-10, IL-21, IL-22 were associated with the miRNAs at different time points. Pathway analysis revealed association with various immune-mediated signaling pathways. Eight miRNAs, involved in immunological pathways changed expression levels during the first five years after diagnosis in children with type 1 diabetes, and were associated with variations in cytokine and pancreatic antibodies, suggesting a possible effect on the immunological processes in the early phase of the disease.
Suitable Combination of Direct Intensity Modulation and Spreading Sequence for LIDAR with pulse coding
Authors: Kim Gunzung , Park Yongwan
Published: October 2018

In the coded pulse scanning light detection and ranging (LIDAR) system, the number of laser pulses used at a given measurement point changes depending on the modulation and the method of spreading used in optical code-division multiple access (OCDMA). The number of laser pulses determines the pulse width, output power, and duration of the pulse transmission of a measurement point. These parameters determine the maximum measurement distance of the laser and the number of measurement points that can be employed per second. In this paper, we evaluate the performance and characteristics of combinations of modulation and spreading technology that can be used for OCDMA, and study optimal combinations according to varying operating environments.
The Effect of Petrographic Characteristics and Physico-Mechanical Properties of Aggregates on the Quality of Concrete
Authors: Petrounias Petros , Giannakopoulou Panagiota P. , Rogkala Aikaterini , Stamatis Panagiotis M. , Lampropoulou Paraskevi , Tsikouras Basilios , Hatzipanagiotou Konstantin
Published: October 2018

This paper examines the effect of the aggregate type on concrete strength and more specifically how the petrographic characteristics of various aggregate rocks as well as their physico-mechanical properties influences the durability of C 25/30 strength class concrete. The studied aggregate rocks are derived from Veria-Naousa and Edessa ophiolitic complexes as well as granodiorite and albitite rocks from their surrounding areas in central Macedonia (Greece). Concretes are produced with constant volume proportions, workability, mixing and curing conditions using different sizes of each aggregate type. Aggregates were mixed both in dry and water saturated states in concretes. Six different types of aggregates were examined and classified in three district groups according to their physicomechanical properties, petrographic characteristics and surface texture. The classification in groups after the concrete compressive strength test verified the initial classification in the same three groups. Group I (ultramafic rocks) presents the lowest concrete strengths, depending on their high alteration degree and the low mechanical properties of ultramafic aggregates. Group II (mafic rocks and granodiorite) presents a wide range of concrete strengths, depending on different petrographic characteristics and mechanical properties. Group III (albite rocks) presents the highest concrete strengths, depending on their lowest alteration degree and their highest mechanical properties. Therefore mineralogy and microstructure of the coarse aggregates affects the final strength of the concrete specimens.
Influence of the technology of aluminum waste melting on the composition and the possibility of using the generated dust
Authors: Tribushevskiy L. V. , Nemenenok B. M. , Rumiantseva G. A.
Published: October 2018

It is shown that the amount of flux used in melting significantly influences the composition and volume of dust and gas emissions. Based on the results of the chemical analysis of dust a solution was adopted for the fluxless melting of aluminum waste. In this case, the proportion of chlorine-containing compounds is 1.4% at 75% of aluminum oxides, which makes it possible to use the formed dust to produce a deoxidizing mixture or a refiner slag. On the basis of balance melting, it is shown that with fluxless melting of aluminum waste, a waste-free processing technology is realized, ensuring ecological and economic effects.
Generation, structure and properties of the modified welding seams
Authors: Lovshenko F. G. , Khabibulin A. I.
Published: October 2018

Preparation, structure and properties of modified welds by using electrodes with coatings, which contain, along with classical components, a modifying ligature. The ligature is mechanically and thermally synthesized composite submicrocrystalline powders with nanosized inclusions of aluminum oxides. Reactionary mechanical alloying is an effective technology of obtaining nanocrystalline modifying ligatures and modifiers. The use of electrodes with an experimental coating containing a mechanically alloyed, composite ligature to resolve transcrystalline type of structure of the weld metal and reduce the grain size by 2,5–3,0 times (from № 8–9 to № 11–12) reduces by 20–30% the threshold of cold brittleness and increase by 15–25% of mechanical properties of the weld metal.
Labour safety in foundry production
Authors: Lazarenkov A. M.
Published: October 2018

The issues of safety of workers in the foundry production ate considered. The results of the analysis of occurrence rate industrial injuries in foundries with different nature of production are given.
Furnace ecology
Authors: Rovin S. L. , Rovin L. E. , Rusaya L. N. , Gerasimova O. V.
Published: October 2018

The article studies the issues of dust and gas cleaning of emissions from smelting units, the analysis of the relationship of furnaces energy efficiency and their environmental parameters, the complex systems that insure high efficiency of gas purification which are aspirated from the melting units are provided, with minimal energy and investment costs.
The sharpness of the images in metallography
Authors: Anisovich A. G.
Published: October 2018

The article presents the issues of sharpness of images of the structure of materials in metallographic studies. The use of the concept of depth of field to obtain images of the structure of various objects – fractures, microsection polished specimen, optically transparent materials is illustrated. The errors of focusing on the sharpness for metal specimens are considered; it is shown that in the case of inclined arrangement of the specimen, the zone of sharp image is a strip with parallel boundaries formed by a fuzzy visible structure. Particularities of focusing out-of-flatness samples and replicas are shown. It is noted that the location of the areas of the non-sharply visible structure in the image is the result of external influence. The possibilities of varying sharpness for the quantitative analysis of austenite grain, as well as the visualization of dendritic structures are demonstrated.
Peculiarities of laser cladding with feeding of the filler tape
Authors: Yelistratov A. P.
Published: October 2018

Semiconductor laser has some features that make it an efficient tool for surface treatment of metals, in particular for surface strengthening. It provides high enough concentration of energy in the heat spot, possibility to adjust process parameters in wide range. Insignificant, compare to other types of laser, energy density eliminates an extensive penetration and internal melting of the metal, which is very important for surface treatment and for the wear resistant covering.

Method of metal layers deposition by feeding a metal strip and its melting by laser beam was developed. Metallurgical processes of the deposit lay forming were investigated; method of feeding the filler strip was optimized.
AR Headsets Give Oil and Gas Sector the Quicker Fix
Authors: Jacobs Trent
Published: October 2018

Predictive algorithms have captured the imagination of industrial firms the world over because of the promise they hold for predicting show-stopping machine failures. But no matter when a digitally-prophesized breakdown comes, you still need someone to go out and fix the equipment the old-fashioned way—or maybe not.

 Augmented reality (AR) headsets are challenging the status quo by enabling faster repairs of mission-critical systems such as topdrives and gas compressors. Their arrival into the oil and gas sector is being led by the largest equipment manufacturers that say the technology’s chief contribution is its ability to mitigate the industrywide bane of downtime.

Attached to a typical hardhat, these industrialized wearable computers combine video cameras, AR displays, and solid networking systems into a single unit. This gives the dispersed engineering team, vs. a lone technician in the field, a new way to collaborate on the toughest equipment-related problems.

Earlier this year, a rig crew working in south Texas ran into trouble with a piece of equipment supplied by NOV that had stopped working correctly, and no one on-site knew how to fix it. “So they fired up the communications box, put the hard-hat and headset on, and had an answer from engineering within 10 minutes,” said Christopher Boehm, a service manager with NOV’s control systems group.

Boehm is leading the implementation of the AR headsets at NOV, which have been rolled into a maintenance service it has branded TrackerVision.

The voice-recognition software running inside these units enables users to call out commands like “wiring layout,” which prompt the headset to pull up a relevant engineering diagram. The user can move his or her head to scan the diagram, or say “zoom” to focus in on a key area and then “freeze document” to maintain a hold on the image as they do the work.

But people can still get lost in the maze of wires and circuit boards found in a lot of modern oilfield equipment. This is when it is a good idea to use the headset’s two-way communications, using cell service or low-Earth-orbit satellites, to dial up the on-call expert. As the technician holds his or her view over a piece of equipment, the expert watching on the other end can even use a telestrator to draw circles around the components to replace, or which ones to leave alone.

Industry Shows Strong Interest

NOV is so confident about these enabling features that it is using AR headsets to support the successful implementation of one of its most important new products, the NOVOS automated rig control system, and has sent units to each of the rigs running on the platform.
Technology Focus: Reservoir Simulation (July 2018)
Authors: Bailey William
Published: October 2018

Technology Focus

A radical digital revolution is happening all around us (or so we are told). This digital domain is moving so rapidly that new acronyms are being added to our lexicon almost weekly (BD, DA, DNN, GAN, and ML, to name but a few). So how will this affect reservoir simulation? Speaking for myself, I really do not know. However, I came across an interesting article from the Harvard Business Review that examined the effect of innovative information technology (IIT) on some large US-based consumer businesses, and, while specific benefits of IIT were clearly stated, the authors opined, “In times of radical technological change, there’s a lot of figuring out to do. [We] have to understand what new technologies can do.” Applying this to reservoir simulation, we apparently need to understand better when and, more importantly, when not to use such technology—to appreciate its bounds, its limitations, its range of validity, and so on.

Deep neural networks (DNNs), for example, are excellent at labeling images (cat, dog, axolotl, etc.). However, some futurists have an impression that IIT can solve almost any kind of problem, sometimes leading to extravagant claims about its potential utility.

Futurists are optimists in nature (the ones I have seen certainly are). However, such buoyant proclamations require some counterbalance through honest questions, healthy discussion, and a reluctance to accept such bold assertions as dogma.

Without wishing to appear too skeptical, I came across an article from The Royal Society that is well worth quoting directly: “No matter their ‘depth’ and the sophistication of data-driven methods, in the end, they merely fit curves to existing data. Not only do these methods invariably require far larger quantities of data than anticipated … they can also fail in circumstances beyond the range of the data used to train them because they are not designed to model the structural characteristics of the underlying system.” While this article focuses on biology and medicine, the authors apply their keen insight to any multiscale and complex system, which covers our domain of interest. I feel that a tempered, modestly restrained approach to IIT is indeed wise (as applied to reservoir simulation), at least until we have had time to fathom where this digital revolution is leading.

Recommended additional reading at OnePetro: www.onepetro.org.

SPE 186079 Implicit Modeling for Permeability Enhancement in Carbonate Reservoirs: A Novel Approach To Bridge Data Gaps for Honoring Dynamic Observations by Arthur P.C. Lavenu, 

Abu Dhabi Marine Operating Company, et al.

SPE 187046 Integrated Reservoir-Network Simulation Improves Modeling and Selection of Subsea Boosting Systems for a Deepwater Development by Gaurav Seth, Chevron, et al.

SPE 187453 Assessing Single EOS Predictability Using PVT Properties of a Wet-Gas Reservoir on a Compositional Simulator by Bander N. Al Ghamdi, Saudi Aramco, et al.
Rapid Evaluation of Development Ideas has Engineers Thinking: What If?
Authors: Rassenfoss Stephen
Published: October 2018

What started as a project to automate the tedious task of creating and updating well production forecasts at Range Resources led to a system that challenges engineers there to question the status quo.

The program has evolved from predicting future well output to showing engineers the many ways their ideas could affect asset performance, including a feature often missing from engineering software, instant estimates of the likely cost and return of each option considered.

“As Range was developing the Marcellus, they knew their teams of engineers and geologists were being creative and effective, but as the volume of data and number of databases grew, so did the painstaking job of merging and manipulating data.

One of the things that struck me about a year ago was that engineers were coming to me with ideas, with more thoughts and creative solutions than a year or two before,” said Ken Brown, Vice President of Reservoir Engineering for Range’s Appalachian Division. The independent operator is primarily focused on the Marcellus, where production is mostly natural gas and NGLs.

Automation has given engineers more time to think. “Because of the sheer volume of data, we were spending an enormous amount of time on a routine task, thus reducing the time available for critical thinking,” he said.

The new tools allow the team to quickly determine if ideas, that might otherwise be viewed as long shots, are actually worth pursuing. Each idea is evaluated based on a variety of measures, including widely used financial performance metrics.

The Range system relies on what computers do well, keep track of more variables and how they interact than a human can in real time. And it can offer alternatives. As a result, Brown said, “it might provide you with options you have not thought of before.”

For example, the analysis may point out that rather than drilling and completing a five-well pad, it would be better to drill four wells and use the proppant that would have been used in the fifth well to more intensely fracture the other four wells.

The program can quickly predict how production would be affected by various versions of that approach, as well as how that would affect the costs and returns on the investment.

If increasing proppant by a significant amount improves recoveries and returns, what if we add even more? Setting up that simulation would take less than 5 minutes, said Matt Ockree, Senior Reservoir Engineer for Range who is the liaison to Novi, the company developing the software.

Convincing analysis generated quickly greatly enhances the consideration of ideas that require changes in the operation, and people’s habits.
Technology Focus: Formation Evaluation (August 2018)
Authors: Ma Shouxiang (Mark)
Published: October 2018

Technology Focus

The future is here; a machine can learn games and beat the world’s best players. What a fascinating time we are living in—Industrial Revolution 4.0.

In December 2017, news broke that AlphaZero decisively beat the world’s best players in chess after its older sibling, AlphaGo, defeated the world champions in the ancient game of go a couple of years earlier. These games have been won by machine learning and artificial intelligence.

What effects will Industrial Revolution 4.0 have on the upstream oil and gas business in general and petrophysics in particular? We should see more intelligence and automation in measurements, processes, work flows, and operations, which should result in more-consistent results, better-quality answer products, and less nonproductive time (i.e., improved quality, efficiency, and productivity with less cost).

Historically, petrophysics is based on physical principles or empirical relationships, as illustrated in paper SPE  191296 on predicting crude-oil viscosity. With Industrial Revolution 4.0, a new era in petrophysics has begun. The logging tools are smarter (as demonstrated in paper SPE 190062 dealing with environmental corrections to some of the deliverables of pulsed-neutron logs that can be performed automatically). And the operational and data-interpretation work flows are more automated (as shown in paper SPE 187040, which details formation testing and sampling jobs that can be done semiautomatically through standardizing terminologies, measurement uncertainties, and data quality-control criteria).

In playing games such as go and chess, machines learn on the basis of man-made game rules. In petrophysics, rules are often data-driven, so data quality becomes critically important. It is always true that having bad data is worse than having no data.

Density, representativeness, and coverage are other parameters of the data besides data quality that are required for data-driven petrophysics.

Recommended additional reading at OnePetro: www.onepetro.org.

SPE 189807 Characterization of Reservoir Quality in Tight Rocks Using Drill Cuttings: Examples From the Montney Formation, Alberta, Canada by A. Ghanizadeh, University of Calgary, et al.

SPE 188804 Low-Resistivity Pay Identification in Lower Cretaceous Carbonates, Onshore UAE by J.L. Ruiz, ADCO, et al.

SPE 187371 Saturation Mapping in the Interwell Reservoir Volume: A New Technology Breakthrough by Alberto F. Marsala, Saudi Aramco, et al.
Three Unconventional Startups Offer New Clues on Shale’s Biggest Well Spacing Mysteries
Authors: Jacobs Trent
Published: October 2018

It can be fairly argued that the most important question being asked today by shale producers is: How close can horizontal wells be placed together? The right answer is worth billions of dollars to the sector.

Among the unsolved mysteries with well spacing are how and why hydraulic fractures from neighboring wells interact with each other. These events, described as frac hits, can be beneficial to oil production (as has been documented in the Bakken Shale) but the more pressing concern is focused on the cases where they harm production (often the case in the Permian Basin and Eagle Ford Shale).

Petroleum engineers know that production-depleted zones within their reservoirs play a big role, but predicting the effects this has on their well designs will require completely new diagnostic approaches.

To solve this grand challenge, an increasing number of industry startups have put their technologies, ones originally developed with a different purpose in mind, under the microscope. The clues they have discovered so far could reshape how the industry understands highly complex shale plays—where profits and losses can be decided by landing a well 100 ft in one direction or the other.

These young companies are among those coming up with some of the most compelling pieces to the puzzle. Fracture ID invented a measurement-while-drilling tool that can detect depleted reservoir sections; Reveal Energy Services has a monitoring system that may be able to diagnose interwell fracture activity; and ResFrac Corp. is using its new modeling software to help operators better estimate permeability, which ties right into well spacing and fracture cluster design.

Can You Measure Depletion While Drilling?

Founded in 2014, Fracture ID offers a new service called “drill bit geomechanics” that could become an early warning system for frac hits caused by pressure and hydrocarbon depletion from older producing wells.

The wellbore-focused service has been used by more than three dozen operators to improve on several different aspects of completion efficiency, including helping to make sure proppant effectively moves into perforations. 

While a lot of its work is focused on what is happening around the wellbore, over the course of its 350-well track record the company has determined, “what we’re measuring in the near-field has some extension out into the farfield,” said Chris Neale, the chief executive officer and founder of Fracture ID.

He explained that the downhole data the firm gathers during drilling show correlations to the pressures that operators monitor during and after stimulating a fracture stage. This relationship is seen as one key to predicting which stages will most likely lead to fracture interference.

At the core of Fracture ID’s service is a foot-long accelerometer device that sits behind a drill bit and enables the Denver-based firm to translate drilling vibrations into critical rock descriptions, including stress and strain, two performance-driving factors for completions.
Getting to Zero and Beyond
Authors: Hinton Jack
Published: October 2018

The Society of Petroleum Engineers (SPE) technical report, Getting to Zero and Beyond: The Path Forward, sets the stage for continuing the discussion across the industry of the essential actions the industry must undertake to attain and sustain zero harm. The report is a compilation of discussions from various SPE sessions and expands on those discussions to identify and evaluate actions that may aid the industry by exploring current thinking and views; incorporating experiences and learnings from other industries that are mature in the application of human factors; and suggesting the next steps that will enable the oil and gas industry to meet an expectation of zero harm.

Introduction

The goal of health, safety, and environment (HSE) programs and departments is to eliminate incidents that produce harm whether to people, the environment, or property. But somehow the industry has settled into a comfort zone, a zone that tolerates incident occurrence and satisfaction with incremental improvement.

Phrases such as “you should have seen the way it was before” or “but we are better than we were” are heard and some-how enable us to accept that what we are doing is sufficient, good, and OK.

Industry safety statistics were the subject of an analysis conducted using International Association of Oil & Gas Producers (IOGP) member company annual safety data. The findings showed that in the period from 2014 to 2016, the lost-time injury frequency and total recordable injury frequency both posted an incremental decrease (Fig. 1). However, during the same period, the fatal accident rate showed an increase (Fig. 2).

In June, IOGP released its annual Safety Performance Indicators for 2017. Although the 2017 statistics illustrate an improvement in the number of fatalities, the number of fatal incidents increased in 2017 (IOGP 2018).

Most striking is the realization that the top three causes of fatal incidents that occur in the global upstream oil and gas industry have remained the same since IOGP first began collecting the data in 2010. Fundamentally, fatalities are occurring despite the industry implementing traditional HSE efforts such as IOGP’s Life-Saving Rules, management systems, training programs, and targeted injury campaigns. What needs to occur is to challenge the current mindset, the ingrained culture. What if we could reject this incremental mindset and make the leap to be satisfied only when we are attaining and sustaining zero harm?

That is exactly what a group of SPE members did. They united, starting in 2010, to change industry thinking—to challenge incremental HSE performance improvement, and to create “zero thinking,” not as the end or long game, but as the starting point to defining HSE performance. Their work and efforts have culminated into a recently issued SPE technical report titled Getting to Zero and Beyond: The Path Forward.
From the SPE President: Oil and Gas Industry: Bringing Prosperity and Happiness to the World
Authors: Alnuaim Sami
Published: October 2018

President's column

I vividly recall a trip with my family when I was 10 years old from my hometown Hofuf to Dammam city on the east coast of Saudi Arabia. This was the early 1970s, and we passed through the northern part of Ghawar, the largest oil field in the world. We also drove through Abqaiq city, which was established by Aramco as a crude-handling facility. During that trip I was wondering what oil and gas would bring to me and to my country, Saudi Arabia. During that time, Saudi Arabia was at the initial stage of educational, industrial, and scientific evolution, trying to catch up with the more advanced West. I remember Saudi Aramco (Aramco back then) was the company where most of the people in Eastern Province of Saudi Arabia dreamt of working. Not only was Aramco a source of a reliable job with good pay, but also health, education, sport, food, and entertainment. To my generation in Saudi Arabia, the oil and gas industry was everything a young person dreamt of. During that trip, while gazing through the drilling rigs and flares on both sides of the highway at night, I created for myself a goal to be part of this great industry.

My thoughts back then were limited to myself and my family, hoping for more economic prosperity and happiness. Today, after 45 years, I can observe how oil and gas has brought economic prosperity not only to myself and my family, but to my country.  I also see the positive impacts globally.  

Saudi Arabia has evolved in a very short time to be one of the top developing countries, one of the top 20 global economies, primarily because of oil and gas. In a few decades, Saudi Arabia achieved extraordinary advancements in many areas—economy, health, education, manufacturing, agriculture, sport, and entertainment. It isn’t just exporting countries though. South Korea is an example of an importing country that has also developed due to oil and gas. Imported energy supplied the fuel for its development in advanced electronics, automobiles, and heavy industry. In mid-March, the SPE Board of Directors held a meeting in Ghana. Just days before, The New York Times published an article projecting that Ghana will be the world’s fastest-growing economy in 2018. This is primarily due to the recent offshore natural gas discoveries and the high potential for more oil and gas development in the region. Like many parts of Africa, Ghana does not have a countrywide electrical grid, and most current electric power comes from diesel major changes in the quality of the environment and the lives of people throughout Ghana. A number of other African countries have also had recent discoveries, meaning that even more people may benefit as these resources are developed.
Guest Editorial: Growth in Unconventional Resources Adds to Technical Literature
Authors: Teletzke Gary
Published: October 2018

Guest editorial

Unconventional resources require technologies typically not used to produce conventional oil and gas reservoirs. In particular, starting in the late 1990s, the combination of horizontal wells and multistage hydraulic fracturing has been key to rapidly increasing success in exploiting unconventional resources. While the well completions in unconventional resources may be more expensive than those typically applied in conventional reservoirs, the advantage is access to the very large volumes of these resources, which include tight (low-permeability) gas in sandstone or carbonate rock, coalbed methane, and organic-rich source rocks classed as shale gas and tight oil.

The exploitation of shale gas, along with tight gas and coalbed methane, enabled a stunning increase in US natural gas production of approximately 4 Tcf/D from 2005 to 2010. A similar story followed a few years later for US crude oil production. Tight oil production ramped up nearly 5 million B/D over approximately 5 years, starting in 2008, and continues to rise. And it is not just the US that is benefiting—unconventional resource development is now beginning to spread to other countries around the world.

The technologies that accomplished these near miracles were developed, implemented, and continue to be improved largely by SPE members, and this has been reflected in an upsurge in conference presentations and journal publications related to unconventional resources over the past decade. This is illustrated by the chart (Fig. 1), which shows a dramatic increase in the percentage of peer-reviewed papers related to unconventional resources published in SPE Reservoir Evaluation & Engineering (SPEREE) beginning in 2011. Before 2011, there were only a handful of publications related to unconventional resources each year, primarily dealing with coal-bed methane and fundamentals of fluid flow in tight pore systems. Beginning in 2011, publications related to the analysis and prediction of shale gas reservoir production performance showed a sharp increase, followed a few years later by publications related to tight oil reservoir performance analysis and prediction. In addition, enhanced oil recovery from tight oil reservoirs has become an increasing area of focus. This year, over half of the publications in SPEREE will be related to unconventional resources. As further indication of the increasing importance of unconventional resources, in July SPE released Unconventional Gas and Tight Oil Exploitation, the first SPE monograph devoted exclusively to the topic.
A Study of Proppant Transport With Fluid Flow in a Hydraulic Fracture
Authors: Blyton Christopher A. , Gala Deepen P. , Sharma Mukul M.
Published: October 2018

The effective placement of proppant in a fracture has a dominant effect on well productivity. Existing hydraulic-fracture models simplify proppant-transport calculations to varying degrees. A common assumption applied is that the average proppant velocity caused by flow is equal to the average carrier-fluid velocity, while the settling-velocity calculation uses Stokes’ law. To more accurately determine the placement of proppant in a fracture, it is necessary to account for many effects not included in previous assumptions.

In this study, the motion of particles flowing with a fluid between fracture walls is simulated with a coupled computational-fluid-dynamics/discrete-element method (CFD/DEM) code that uses both particle dynamics and CFD calculations to account for both particles and fluid. These simulations (presented in metric units) determine individual particle trajectories as particle-to-particle and particle-to-wall collisions occur, and include the effect of fluid flow. The results show that the ratio of proppant diameter to fracture width governs the relative average velocity of proppant and fluid.

A proppant-transport model developed from the results of the direct numerical simulations and existing correlations for particle-settling velocity has been incorporated into a fully 3D hydraulic-fracturing simulator. This simulator couples fracture geomechanics with fluid-flow and proppant-transport considerations to enable the fracture geometry and proppant distribution in the main hydraulic fracture to be determined. For two typical shale-reservoir cases, the proppant placement and width distribution have been determined, allowing comparison at the hydraulic-fracture scale, including effects observed at the particle scale. This allows for optimization of the treatment to a specific application, and the results are presented in oilfield units, considered more familiar to our readers.
Thermodynamic Analysis of Phase Behavior at High Capillary Pressure
Authors: Rezaveisi Mohsen , Sepehrnoori Kamy , Pope Gary A. , Johns Russell T.
Published: October 2018

High capillary pressure has a significant effect on the phase behavior of fluid mixtures. The capillary pressure is high in unconventional reservoirs because of the small pores in the rock, so understanding the effect of capillary pressure on phase behavior is necessary for reliable modeling of unconventional shale-gas and tight-oil reservoirs. As the main finding of this paper, first we show that the tangent-plane-distance method cannot be used to determine phase stability and present a rigorous thermodynamic analysis of the problem of phase stability with capillary pressure. Second, we demonstrate that there is a maximum capillary pressure (Pcmax) where calculation of capillary equilibrium using bulk-phase thermodynamics is possible and derive the necessary equations to obtain this maximum capillary pressure. We also briefly discuss the implementation of the capillary equilibrium in a general-purpose compositional reservoir simulator. Two simulation case studies for synthetic gas condensate reservoirs were performed to illustrate the influence of capillary pressure on production behavior for the fluids studied.
Novel Application of Cationic Surfactants for Foams With Wettability Alteration in Oil-Wet Low-Permeability Carbonate Rocks
Authors: Ghosh Pinaki , Mohanty Kishore K.
Published: October 2018

Carbonate rocks are typically heterogeneous at many scales, leading to low waterflood recoveries. Polymers and gels cannot be injected into nonfractured low-permeability carbonates (k < 10 md) because pore throats are smaller than the polymers. Foams have the potential to improve both oil-displacement efficiency and sweep efficiency in such carbonate rocks. However, foams have to overcome two adverse conditions in carbonates: oil-wettability and low permeability. This study evaluates several cationic-foam formulations that combine wettability alteration and foaming in low-permeability oil-wet carbonate cores. Contact-angle experiments were performed on initially oil-wet media to evaluate the wettability-altering capabilities of the surfactant formulations. Static foam-stability tests were conducted to evaluate their foaming performance in bulk; foam-flow experiments (without crude oil) were performed in porous media to estimate the foam strength. Finally, oil-displacement experiments were performed with a crude oil after a secondary gasflood. Two different injection strategies were studied in this work: surfactant slug followed by gas injection and coinjection of surfactant with gas at a constant foam quality. Systematic study of oil-displacement experiments in porous media showed the importance of wettability alteration in increasing tertiary oil recovery for oil-wet media. Several blends of cationic, nonionic, and zwitterionic surfactants were used in the experiments. In-house-developed Gemini cationic surfactant GC 580 was able to alter the wettability from oil-wet to water-wet and also formed strong bulk foam. Static foam tests showed an increase in bulk foam stability with the addition of zwitterionic surfactants to GC 580. Oil-displacement experiments in oil-wet carbonate cores revealed that tertiary oil recovery with injection of a wettability-altering surfactant and foam can recover a significant amount of oil [approximately 25 to 52% original oil in place (OOIP)] over the secondary gasflood. The foam rheology in the presence of oil suggested propagation of only weak foam in oil-wet low-permeability carbonate cores.
Unlocking the Potential of the Monterey Shale Resource: An Analysis of Geological Characteristics, Completion Techniques, and Production Behaviors
Authors: Saini D.. , Wright J.. , Mantas M.. , Gomes C..
Published: October 2018

A critical analysis of the key geological characteristics, completion techniques, and production behaviors of the Monterey Shale wells and their comparisons with analogous major US shale plays—namely, the Bakken and the Eagle Ford—may provide insights that could eventually help the petroleum industry unlock its full potential. The present study reports on such efforts.

The Monterey Shale is very young and geologically heterogeneous compared with the Eagle Ford and the Bakken. Oil viscosity in the Monterey Shale is significantly higher, and one can also notice that Monterey oil production has declined over the years. The Monterey Shale has a field-dependent completion strategy (pattern spacing and fracturing stage), while a horizontal, uncemented wellbore completion is common in the Bakken and the Eagle Ford. In the Monterey, nonhydraulically fractured zones of horizontal and hydraulically fractured wells appear to be making approximately equal contributions to the well's cumulative production. The ongoing water-disposal operations in overlying injection zones, up to a certain extent, have affected the productivity of both types (long and short production histories) of wells. The geology also appears to have an effect on the production behaviors of horizontal and hydraulically fractured wells.

A preliminary economic analysis suggests that exploitation of the Monterey Shale is still a profitable venture. However, for sustainable development in a current price regime of USD 50/bbl of crude oil, it is necessary that production costs be reduced further. Also, compared with the Bakken and the Eagle Ford, the Monterey sits in regions of extremely high water stress (i.e., frequent occurrences of drought or drought-like conditions). However, oilfield-produced water associated with current steamflooding-based oil- and gas-production operations in the region as a base fluid suggests that it can potentially meet most of the water demand for future fracturing jobs. Also, combined use of a centralized water-management system; a less-costly, more energy-efficient, and high-capacity solar-powered desalination system; and a final sludge-management and/or residual-brine-disposal mechanism might assist the petroleum industry in managing flowback and produced waters while keeping water-handling costs low.

A combination of new enhanced-oil-recovery (EOR) methods for releasing the remaining oil from both nonfractured and fractured zones of horizontal wells and the use of oilfield-produced and recycled water for completing hydraulically fractured horizontal wells might prove to be a significant change for the future exploitation of California's Monterey Shale resource, which is subject to the toughest hydraulic-fracturing regulations in the nation and is in a region of extremely high water stress.
A Variable-Switching Method for Mass-Variable-Based Reservoir Simulators
Authors: Alpak Faruk O. , Vink Jeroen C.
Published: October 2018

Field-scale simulations of complex processes often suffer from long simulation times. One of the main reasons is that the Newton-Raphson (NR) process used to solve each simulation timestep requires many iterations and small timestep sizes to converge. Because the selection of solution variables affects the nonlinearity of the equations, it is attractive to have a practical method to rapidly explore the use of alternative primary variables in general-purpose reservoir simulators.

Many reservoir simulators use pressure, saturations, and temperature in each gridblock as the primary solution variables, which are referred to as natural variables. There is also a class of reservoir simulators that uses pressure, total component masses (or moles), and internal energy in each gridblock as primary variables. These simulators are referred to as mass-variable-based reservoir simulators. For a given choice of primary variables, most simulators have dedicated, highly optimized procedures to compute the required derivatives and chain rules required to build the Jacobian matrix. Hence, it is usually not possible to switch between mass and natural variables. In this work, however, we establish a link at the numerical-solution level between natural- and mass-variable formulations and design a novel (nonlinear) block-local method that transforms mass-variable shifts (computed at each NR iteration) into equivalent natural-variable shifts.

We demonstrate on a number of simulation models of varying complexity that by use of the proposed approach, a mass-variable-based flow simulator can still effectively use natural variables, where the change of variables can be made locally per gridblock. Results indicate that in some models the total number of NR iterations, linear-solver (LS) iterations, and timestep-size cuts (caused by the nonconvergence of the NR procedure, also known as backups) are reduced when using natural variables instead of mass variables. However, the improvement is relatively modest and not generally observed. Our findings also signify that depending on the specific characteristics of the simulation problem at hand, mass-variable-based simulators may perform comparably or outperform natural-variable-based simulators.

The proposed variable-switching method can be used effectively to evaluate the effect of using different primary solution variables on problem nonlinearity and solver efficiency. With this method, the effect of interchanging primary solution variables on problem nonlinearity can be rapidly evaluated.