bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Comparison of Multi-Objective Optimization and Optimization with Constraints as a Tool for Reservoir History Matching and Characterization: Application to an Aquifer Gas Storage Case
Authors: Thomas Schaaf , Delphine Sinoquet 
Published: June 2020

Abstract
One of the final goals of any reservoir characterization study is to deliver reliable production forecasts. This is definitely a challenging task as the fluid flow dynamics is governed by non-linear equations: a small perturbation in the reservoir model inputs might have a large impact on the modelling outputs, thus the forecasts. Also, depending on the maturity of a project, engineers have various amounts and types of data to deal with and to history match through an optimization process.
Considering the case of a mature asset, for which massive datasets of various types are available, the standard history matching process is based on the minimization of a single objective function (history matching criteria), computed through weighted least squares formulation. The difficulty is then to (user) define properly the weight of each data set before the summation itself into the single objective function is performed.
To avoid this difficulty, two currently available but yet prospective – in geosciences application - optimization techniques are considered. The former is based on the definition of multiple objective functions (based on data types and/or location on the field) coupled to an optimization process. If all the objective functions minimize trends together, the user has still the flexibility to assess one by one the individual objective functions minimization. On the contrary, if the objective functions are minimizing/maximizing trends in competition (e.g. because of noisy data), then the derived Pareto front (in 2D case) would identify the location of optimal compromises. The latter is a sequential optimization approach based on single-objective constrained optimizations: optimize each objective at a time with constraints on the other objectives. The thresholds defined for the constraints on the objectives are derived from the results of the previous optimization results. This pragmatic approach allows to prioritize the objectives and tunes the expected accuracy on each data type.
Both approaches are applied to a real field gas storage asset with more than 40 years of exploitation history and various data types e.g. pressures, saturations as well as gas breakthrough of control wells, leading to the definition of multiple (possibly more than 2) objective functions. Both show promising results in terms of history matching quality and in terms of flexibility as the user might be able to consider, define and update dynamically alternative history matching strategies. These approaches might be considered as alternatives to the standard one for the history matching process, preliminary to the production forecasts computation, even if the associated challenges and complexity are growing accordingly to the number of objective functions.
A New Methodology for Naturally Fractured Reservoir Characterization: Use of Multi-Well Interference Tests Interpretation
Authors: Vincent Philippe , Portier Eric 
Published: June 2020

Abstract
Reservoir characterization is a key aspect during the appraisal and production phases of a field development. Understanding the reservoir property distribution and dynamic behavior reduces uncertainties and helps to improve recovery while optimizing investments. Modern seismic and logging tools, combined with core data, provide multi-disciplinary teams with better data quality. However, the reservoir heterogeneity and connectivity, often remain uncertain until several years of production have been achieved. This is true of naturally fractured reservoirs, for which fracture connectivity can only be characterized dynamically. In order to provide earlier dynamic connectivity information in a field development, interference tests have been developed to define whether parts of a reservoir are in communication, and to estimate reservoir properties between wells which is not possible from log measurements and correlations.
Interference tests are ideally conducted when a reservoir is in equilibrium with homogeneous and fully stabilized pressure through the entire field. This paper describes a new methodology for interference test interpretation when reservoir pressure is not stabilized, and also describes how to optimize multi-well interference operation sequencing. First, the observation well is tested, and second, active wells are produced in a sequence while the observation well bottom hole pressure (BHP) is still building up. Pressure changes only related to the interference are extracted from the pressure measurements at the observation well by removal of the build-up effects. Interpretation is subsequently performed to quantify reservoir properties such as matrix and fracture permeability and porosity to match interference time lag (also named time of flight), pressure and depletion amplitude. Permeability anisotropy and fracture connectivity are defined and quantified at the field scale.
The application of this new methodology to multi-well interference tests performed on a naturally fractured gas reservoir is presented in this paper. Using this methodology can prove connectivity through open natural fractures and quantify the fracture network properties even when there is a very small interference amplitude. Defining the extent of a natural fracture network and its contribution to the hydrocarbon production is crucial for naturally fractured reservoir development and reservoir management. In addition the described methodology was applied to calculate gas volumes dynamically connected to the wells.
The capability to interpret an interference test performed while the pressure measured at the observation well is still building up allows a significant operational time and cost reduction while ensuring accurate interpretation of reservoir parameters. This methodology can be applied to an interference test including a well pair or multiple wells.
Static and Dynamic Considerations for Perched Water and the Consequence in Reservoir Modelling
Authors: Larsen Alex , Ahmadhadi Faram , Øian Erlend , Nerbøvik Sivert 
Published: June 2020

Abstract
The initial water saturation in a reservoir is important for both hydrocarbon volume estimation and distribution of multi-phase flow properties such as relative permeability. Often, a practical reservoir engineering approach is to relate relative permeability to flow property regions by binning of the initial water saturation. The rationale behind this approach is that initial water saturation is related to both the pore-throat radius distribution and the wettability of the rock, both of which impact relative permeability. However, pore-throat radius and wettability are usually not explicitly included in geomodel property modelling. Therefore, the saturation height model (SHM) should not only capture an average hydrocarbon pore volume (HCPV), but also reflect the underlying mechanisms from hydrocarbon migration history and its impact on initial water saturation distribution.
This work defines a new terminology, "excess water", for more precise classification of SHM-scenarios in reservoirs where multiple mechanisms have interacted and caused a complex water saturation distribution. The physical basis for drainage and imbibition transition zones connected to both regional and perched aquifers is given. The distribution of initial water saturation in reservoirs containing excess water is demonstrated through numerical modelling of oil migration over millions of years.
High permeable reservoirs are more likely to have locally trapped water due to lower capillary forces. A static situation occurs in areas where the capillary forces cannot maintain a high enough water saturation for further water drainage. On the other hand, both high and low permeability reservoirs may have significant excess water due to still ongoing dynamical effects. In both cases, long distances for water to drain laterally to a regional aquifer enhances the possibility for a dynamic excess water situation.
The impact of excess water on well test results are demonstrated with focus on calculation of the product of permeability and sand thickness.
Numerical Modelling of Radial Crack Propagation in Cement Sheath During Hydraulic Fracturing
Authors: Yan Yan , Guan Zhichuan , Xu Yuqiang , Zhang Xuan , Yan Weijun 
Published: June 2020

Abstract
The cement sheath are damaged around the hole after perforation, and the micro-cracks in the cement sheath will cause fluid channeling during hydraulic fracturing. Focused on this problem, a numerical model was set up to calculate the crack propagation length in cement sheath during hydraulic fracturing by using the Cohesive Zone Method (CZM). Then the influence of different parameters on the unsealing length of cement sheath during hydraulic fracturing was analyzed. The results show that higher casing pressure can help to reduce the unsealing length of cement sheath. It is significant to perforate with lower density and phase to ensure the sealing integrity of the cement sheath. This research can evaluate the sealing performance of the cement sheath during hydraulic fracturing and give some guiding for the design of fracturing schemes.
Increasing Oil Recovery from Unconventional Shale Reservoirs Using Cyclic Carbon Dioxide Injection
Authors: Fakher Sherif , El-Tonbary Ahmed , Abdelaal Hesham , Elgahawy Youssef , Imqam Abdulmohsin 
Published: June 2020

Abstract
Unconventional shale reservoirs have become and large unconventional supplier of oil and gas especially in North America. They are usually produced from using hydraulic fracturing which produces and average of 7-10% per well. This research studies the application of carbon dioxide (CO2) enhanced oil recovery (EOR) in shale reservoirs to increase oil recovery to more than 20%. Cyclic CO2 injection was used to conduct all experiments rather than flooding. The main difference between both procedures and the advantage of cyclic injection over flooding in shale reservoirs is explained. A specially designed vessel was constructed and used to mimic the cyclic CO2 injection procedure. The effect of CO2 soaking pressure, CO2 soaking time, and number of soaking cycles on oil recovery was investigated. Results showed that cyclic CO2 injection can increase oil recovery substantially, however there are some points that must be taken into consideration including optimum soaking pressure and time in order to avoid a waste of time and capital with no significant increase in oil recovery. This research not only provides an experimentally backed conclusion on the ability of cyclic CO2 injection to increase oil recovery from shale reservoirs, it also points to some major issue that should be considered when applying this EOR method in unconventional shale in order to optimize the overall procedure.
Conformance Gel Design for High Temperature Reservoirs
Authors: Juárez José Luis , Rodriguez María Rosario , Montes Jesús , Trujillo Francisco Daniel , Monzòn Jorge , Dupuis Guillaume , Gaillard Nicolas 
Published: June 2020

Abstract
A gel conformance treatment is a complex process that has to be adapted to reservoir conditions such as pH, temperature and salinity. For instance, high temperature and low salinity reduce gelation time making field operations difficult. Understanding the interactions between functional groups of polymers, crosslinkers and retardants is essential to control the gelation process considering kinetic, strength and stability of the gel.
The objective of this work is to better understand chemistry mechanisms in gel formation to design an optimal gelation system for in-depth conformance treatment in a high temperature reservoir.
The target reservoir conditions are a low salinity water (TDS 6 g/L) and a temperature of 100°C. The ultimate goal is to select a polymer / crosslinker / retardant system with a gelation time above 7h, and Sydansk's gel strength of "G" that is stable over more than one week.
This work contains a stepwise process to design a conformance gel based on the understanding of the chemical interactions between polymers and crosslinkers. In a first step, a rheology evaluation of different polymers containing ATBS was performed. Then, a wide range of combinations between polymers and crosslinkers with and without retardants was studied. The study of the formation of gels was carried out in bottle test (Sydansk's gel-strength code) in order to provide information about the gel formation, the gel kinetics, the gel strength and the stability of gel as function of time.
Finally, the best gelant solutions were selected to further study the evolution of the complex viscosity over time using a rheometer with a high pressure cell that mimics the reservoir conditions.
This study provides new knowledge of polymer gelation at high temperature; the main findings are the following: Gelation depends on the chemical composition of polymer and crosslinker.Gelation time depends on the particular polymer / crosslinker system and not only on whether the crosslinker is organic or not.Concentration plays a very important role in the formation of certain gels.The polymer molecular mass dependence is not as clear as it might be assumed at first. The kinetics of the polymer / PEI crosslinker systems can be delayed by retardants that contain inhibitor groups.
This positive laboratory results will be complemented with simulation studies to assess the field implementation of these new conformance gels.
The main novelty of this work is the use of thermal resistant polymers that combined with the adequate crosslinkers and retardants allowed the generation of a conformance gel at 100°C. The information provided in this study will be useful for the design of conformance treatment for other field conditions. The close communication and integration between polymer manufacturers and operators was crucial for the interpretation of the results and gel optimization.
Autonomous NanoSurfactant for Enhanced Oil Recovery Applications
Authors: Shi Nan , Mashat Afnan , Abdel-Fattah Amr 
Published: June 2020

Abstract
Enhanced oil recovery (EOR) techniques often involve delivering chemicals, macromolecules, or particles in oil reservoirs to improve oil mobility and production. The harsh environment typical to the reservoir poses a great challenge to maintaining long-term stability of these agents. Moreover, accessing constricted regions in the reservoir with extremely tight pores and pore throats, and where large volumes of resources exist, require more efficient delivery methods than diffusion.
We have developed an in-house EOR nano-agent (NanoSurfactant) platform using the inexpensive and abundant petroleum sulfonate salt surfactant. NanoSurfactants are chemically and colloidally stable at high salinity (&gt; 56K ppm) and high temperature (&gt; 90°C) conditions. Their structure, size, and surface properties suggest different transport mechanisms for enhanced delivery in oil reservoirs compared to conventional surfactants. We seek to improve the delivery of NanoSurfactants to regions in the reservoir that are inaccessible to conventional waterflood. Here, we explore diffusiophoresis (DP) as a mean to efficiently deliver NanoSurfactants to flow-restricted regions.
Direct microscopic visualization experiments are conducted to study the migration of NanoSurfactants in different chemical gradients. These transient gradients are established in microfluidic channels mimicking dead-end pores in the reservoir. In addition, we study the effect of adding dilute macromolecules to the NanoSurfactant solutions on their DP migration. NanoSurfactants are labeled with a fluorescent dye to enable microscopic visualization and quantification of DP migration. Results showed that salinity gradients yield faster and deeper delivery of NanoSurfactants into the dead-end channels compared to diffusion without any gradients. A more pronounced migration is observed when small concentrations of macromolecules are added.
Our findings expand the understanding of DP migration in an extremely high salinity environment. In addition, they provide insights into the utilization of natural or induced gradients in oil reservoirs to harness the DP migration for EOR applications.
Optimization of Liquid Pipeline Control for Economic and Efficient Operations
Authors: Khlebnikova Elena , Zlotnik Anatoly , Sundar Kaarthik , Ewers Mary , Tasseff Byron , Bent Russell 
Published: June 2020

Abstract
Pipelines perform a critical function in the petroleum business by transporting hydrocarbon commodities between oil fields, refineries, and consumer markets. We formulate an optimization problem for determining the optimal pumping modes and flow configuration for liquid pipeline operations. Based on requested flow rates and commodity prices submitted by users of the pipeline system, the system manager can solve an optimization problem to determine flow rates allocated to all customers, flows on each pipeline section, and pumps station operating settings in order to maximize economic value provided by a pipeline while adhering to limitations of pump machinery and the physics of fluid flow. In particular, the optimal solution will maximize the economic benefit for the pipeline transport network users and utilization of system capacity while also minimizing the energy expended in operation. This problem is nonconvex, and solutions are only guaranteed to be locally optimal. In this study we pose a mathematical optimization formulation with minimal modeling that captures the basic phenomena involved, and an algorithm based on general-purpose interior point optimization is proposed for efficient solution. We demonstrate our approach on a realistic case study based on a pipeline system in the United States.
Improving the nursing informatics competency of critical care nurses: results of an interventional study
Authors: Jouparinejad Somayeh , Foroughameri Golnaz , Khajouei Reza , Farokhzadian Jamileh 
Published: June 2020

Abstract

Background Along with growth and development of health information technology (HIT), nursing informatics (NI) is becoming a fundamental part of all domains of nursing practice especially in critical care settings. Nurses at different levels of the nursing continuum are expected to equip with NI competency for providing patient-centered evidence-based care. Therefore, improvement of the nurses’ NI competency through educational programs is important and necessary for effective using of HIT. This study aimed to evaluate the impact of a training program on NI competency of critical care nurses. Methods In this interventional study, 60 nurses working in critical care units at hospitals affiliated with a large University of Medical Sciences in the southeast of Iran were randomly and equally assigned to the control and intervention groups. NI competency was trained to the intervention group in a three-day workshop. Data were collected using demographic questionnaire and Nursing Informatics Competency Assessment Tool (NICAT) before and one month after the intervention. Results In the pretest stage, both intervention and control groups were at the “competent” level in terms of the NI competency, and no significant difference was observed between them ( p =0.65). However, in the posttest, the NI competency and its dimensions significantly increased in the intervention group with a large effect size compared with the control group ( p = 0.001). This difference showed that the intervention group achieved the “proficient” level in posttest stage. Conclusions The improved scores of NI competency and its dimensions after using the training program implied the effectiveness of this method in enhancing the NI competency of nurses working in the critical care units. The higher efficiency of the training program can be determined by its application in diverse domains of nursing practice. The project is a fundamental for improving nurses’ NI competency through continuous educational programs in Iran, other cultures and contexts.
An Innovative Strategy to address shortages of healthcare personnel in South Africa
Authors: Gumede Dumsani Mandla , Taylor Myra , Kvalsvig Jane 
Published: June 2020

Abstract
Background: In order to improve health in low- and middle- income countries the basic health infrastructure needs to be upgraded. Part of the problem is the shortage of skilled healthcare professionals (HCP) particularly in rural areas. The Umthombo Youth Development Foundation (UYDF) is a non-profit organisation (NPO) established in 1999 to assist in addressing shortage of HCPs in rural areas. The aim of this study is to measure the success of the UYDF bursary scheme in achieving this goal by calculating the cost of supporting rural students and estimating the benefits in relieving the shortage in terms of the financial return on investment.Methods: The sources of the data were the UYDF organisational records (finance, human resources and procurement), supplemented by the published and unpublished UYDF reports. The return on investment was estimated through the use of an Internal Rate of Return (IRR) calculation.Results: The UYDF database of beneficiaries showed that by the year 2017 a total of 337 HCPs had graduated and a further 254 were still studying. An average of R17 million was spent every year on the students or R102 015 per student per year. The IRR was 63% higher than interest rates on commercial loans. These graduates are expected to generate an estimated R15 billion in lifetime earnings, which would be equal to R4 billion at current prices.Conclusion: The UYDF scheme relieved the shortage of HCPs in rural hospitals, and the hospitals were able to retain the service of many of the locally sourced HCPs. The costs of implementing the bursary scheme were outweighed by the income generated from salaries, and taxes contributed to the country’s economic development.
Spatial Analysis of Mangrove Forest Management for the Reduction of Air Temperature and Co2 Emission
Authors: - Sumarmi , - Purwanto , Mutia Tuti 
Published: June 2020

Abstract
Surabaya is one of the developing cities in term of coastal area. Like other developing cities, Surabaya highlysuppresses the mangrove forest for the residential area, industry and so forth. Mangrove forest as a conservation land has an essential function as an oxygen source for people in Surabaya and it absorbs CO2. Mangrove forest functions to decrease the impact of global warming and maintain the coastal ecosystem sustainability. This research aimed to 1) Map the dynamics of temperature in Surabaya during the last twenty years (1996-2016) by using Remote Sensing and GIS. 2) Examine the ability of mangrove forest in absorbing CO2 and heat energy in decreasing the impact of global warming in Surabaya. The research results showed that 1) based on the analysis result of temperature surface extent, the temperature has changed since 1996 up to 2016. The trend of the temperature change can be classified into three surface temperatures which are low, moderate and high. The low temperature with the category of 21 o-30 oC had a differenttrend. Every year, the trend of the area extent of which surface temperature was highly categorized was 31-42 oC. The trend was highly increasing in the period of 2006-2016. Such condition showed that, in 2016, Surabaya had a high temperature increase. (2) There was a correlation between mangrove forest change and the temperature change; the content of CO2 in the mangrove, vegetation and water areas was reduced and it increased in the areas used for buildings such as factory, residential, road and so on. The content of CO2 in the air of Surabaya showed the distribution grouping in the “high” and “extremely high” categories. The highcategory was 27.5% and the extremely high category was 67.5%. There was one sample point in each of moderate and low categories which was 2.5% respectively.