bluuebunny/crossref_metadata_2025 huggingface dataset:
Los albores del Derecho penal: la regulación del poder punitivo en los códigos sumerios, acadios y semitas
Authors: García Falconí Ramiro J. , Larenas Cortez Melissa
Published: October 2016

El Derecho en general y en específico, y la regulación del poder punitivo, aparecen desde las primeras codificaciones que se conocen en la historia de la humanidad, siendo claros su carácter religioso, la lógica sacrificial y el componente de violencia que impregnan al mismo. Esta matriz punitiva se presenta tanto en los códigos sumerios y acadios, como en la legislación hebraica posterior, en las que se fusionan lo violento y lo sagrado. La ley talional ya hace su aparición, así como las estructuras sobre las cuales se construirá posteriormente el sistema inquisitivo y algunos rasgos que sobreviven hasta nuestros días.
Self-Care Motivation Among Patients With Heart Failure: A Qualitative Study Based on Orem’s Theory
Authors: Abotalebidariasari Ghasem , Memarian Robabe , Vanaki Zohreh , Kazemnejad Anoshirvan , Naderi Nasim
Published: October 2016

Background and Purpose: Initiating and adhering to self-care activities necessitate self-care motivation. This study was undertaken in Iran to explore self-care motivation among patients with heart failure (HF). Methods: This qualitative study was done in 2014 and 2015. Study participants were patients with HF and their family members who were purposively selected from Shaheed Rajaei Cardiovascular, Medical and Research Center, Tehran, Iran. The study data were collected from December 2014 to May 2015 by doing in-depth semistructured face-to-face interviews and were analyzed via the directed content analysis approach. Results: Eleven primary codes were generated which reflected motivations for self-care among patients with HF in the Iranian sociocultural context. To enhance the clarity of the findings, these primarily codes were summarized and grouped into 7 subcategories including fear of death and love of life, returning to previous physical health status and preventing or alleviating symptoms, understanding the value of self-care behaviors and trusting them, having the desire for remaining independent, relying on God, reassuring and supporting family members, and preventing family members from feeling irritation. Implications for Practice: The findings of this study indicate that patients with HF have different motivations for doing self-care activities. Fear of death, love of life, wish to return to previous health status, and prevention or alleviation of HF symptoms were the participants’ strongest motivations for self-care. Understanding the motivations for self-care among patients with HF, based a holistic approach and evidence-based practice, can help nurses and physicians develop motivational programs for promoting self-care behaviors.
Avaliação de cardápio e identificação de alimentos funcionais: estudo qualitativo de restaurante popular de Araraquara, São Paulo, Brasil
Authors: Ramírez Yudi Paulina García , Moreira Raquel Regina Duarte , Oliveira José Ricardo Soares de
Published: October 2016

Este estudo avalia qualitativamente o cardápio e a presença de alimentos funcionais nas preparações do restaurante popular do município de Araraquara, São Paulo. Esse estabelecimento integra a rede de ações e programas da Fome Zero, política de inclusão social, administrada pelo Ministério do Desenvolvimento Social e Combate à Fome, visando à oferta de refeições prontas saudáveis e a preços acessíveis, reduzindo assim, o número de pessoas em situação de insegurança alimentar. Realizou-se um estudo de caso descritivo, de caráter qualitativo, durante o período de fevereiro a abril de 2014. Analisou-se qualitativamente o cardápio do almoço de 12 semanas pelo método Análise Qualitativa das Preparações do Cardápio. A presença de alimentos funcionais foi avaliada por meio da identificação, quantidade e frequência oferecida nas preparações do cardápio, seguindo as recomendações da American Dietetic Association de 2004. O cardápio apresentou como aspectos positivos, oferta de frutas como sobremesa 89,7%, carnes gordurosas 6,9%, doces 12,1% e não foi observada oferta de frituras e doces no mesmo dia. A baixa oferta de saladas de folhosos e a monotonia de cores das preparações foram evidentes, sendo um aspecto negativo do cardápio. Os alimentos funcionais foram identificados principalmente em frutas e verduras, oferecidos todos os dias. Conclui-se que o restaurante popular avaliado ofereceu um cardápio adequado quanto aos itens analisados. Destaca-se que a introdução de uma alimentação saudável e de alimentos funcionais na dieta de cada indivíduo deve ser contínua, auxiliando na prevenção de doenças e na busca da saúde.
Odds Ratio versus Razão de Prevalências ou Modelo de Lógite versus Regressão de Poisson
Authors: Hoffmann Rodolfo
Published: October 2016

São analisadas as limitações e as vantagens do uso da Regressão de Poisson, em comparação com o modelo de lógite, quando o desfecho é uma variável binária. São discutidos exemplos nos quais todas as variáveis são binárias e também um exemplo com variável explanatória contínua. O modelo deve ser escolhido considerando as características do fenômeno analisado. A preferência pelo uso da razão de prevalências, e não da odds ratio, na análise dos resultados, não deve ser motivo decisivo na escolha do modelo de relação entre as variáveis.
Portaria CVS no 5/2013 como ferramenta de prevenção e controle de doenças transmitidas por alimentos
Authors: Ferrão Luana Limoeiro , Morais Isabela Cristina Lobo de , Ferreira Elisa Helena da Rocha
Published: October 2016

A vigilância em saúde possui como objetivo a observação e análise constantes da situação de saúde da população. As doenças transmitidas por alimentos e seus surtos são um dos maiores desafios para a Saúde Pública. Estes surtos devem ser notificados, segundo o Sistema Nacional de Vigilância Epidemiológica vigente, sendo que, paralelamente à investigação, devem ser tomadas medidas de prevenção e controle. No Brasil esse perfil epidemiológico ainda é pouco conhecido, presumindo-se alta morbidade sem conhecer sua real magnitude. Buscando diminuir os casos destes surtos, a Secretaria do Estado de São Paulo aprovou em abril de 2013 a Portaria CVS no 5. Neste regulamento foram acrescidas medidas de prevenção e controle importantes para assegurar a diminuição do risco de contaminação do alimento. Este trabalho teve como objetivo discutir os avanços da legislação em relação à segurança dos alimentos, analisando as diretrizes da nova Portaria CVS no 5/2013. Constatou-se que é uma legislação mais rígida e detalhada que as revogadas CVS no 6/1999 e CVS no 18/2008 e até mesmo que a legislação federal em vigor, RDC no 216/2004, principalmente no que tange a saúde e segurança do manipulador, processamento e armazenamento dos alimentos.
Technology Update: Flexible, Single-Skin Completion Concept Meets Well Integrity, Zonal Isolation Needs
Authors: Sidle Brian
Published: October 2016

Technology Update

As deeper and more complex well designs proliferate throughout oil and gas fields, well completion methods are challenged and new technologies are emerging to ensure safe, cost-efficient, and optimized completions.

The Welltec Flex-Well completion concept is a flexible, single-skin (monobore) system that allows fit-for-purpose completion designs that can be as minimal or intricate as needed for optimal reservoir drainage and do not require the use of cement or swellable packers (Fig. 1).

Reliable and effective annular barriers continue to be crucial to well management for safety and performance. Cementing has been the industry’s conventional means of creating these barriers, having been used for almost 100 years (American Oil & Gas Historical Society 2015). However, the industry is not drilling and completing wells the way that it did a century ago.

The advances in drilling, particularly those related to horizontal well technology, have led to well designs and completion environments that often exceed the capabilities of cement to provide a reliable annular barrier that will last as long as the well. Efforts to overcome the challenges of many of today’s wells with cement can lead to complicated, expensive, and time-consuming operations.

The use of certain swellable packers has arisen as an accepted alternative, primarily because of time savings. However, their degradable polymer content has a significant risk of failure in harsh downhole well environments. Wells with swellables have been shown to leak approximately 50% of the time after 5 years from the time of installation (Plessing and Arnskov 2011).

With more than half of the world’s rigs drilling highly deviated or horizontal wells, and an increasing number of mature fields with depleted well zones, the challenges of such wells call for barriers that not only are cost-efficient but will also remain effective throughout the well’s lifetime.

Expandable Annular Barrier

A key component of the flexible, singleskin completion system is the Welltec Annular Barrier (Fig. 2), an all-metal expandable barrier with a large expansion ratio that was developed for a wide variety of applications in well construction, including well integrity and zonal isolation. Designed for the specific well during its construction phase, before the well is spudded, the barrier delivers reliable annular isolation and maximizes the ability to handle pressure change across the entire borehole, without internal restrictions, over the life of the well.
Acoustic Measurements Aid Mechanical-Damage Characterization in Proppant Packs
Authors: Wilson Adam
Published: October 2016

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper IPTC 18092, “Mechanical-Damage Characterization in Proppant Packs Using Acoustic Measurements,” by Aderonke Aderibigbe, SPE, Clotilde Chen Valdes, and Zoya Heidari, SPE, Texas A&M University, and Tihana Fuss, Saint-Gobain Proppants, prepared for the 2014 International Petroleum Technology Conference, Kuala Lumpur, 10–12 December. The paper has not been peer reviewed.

The strength and conductivity of proppant packs are key parameters for assessing their performance. Mechanical damage of proppants usually is analyzed by crush tests. However, measurements from these tests remain questionable because of discrepancies in procedures and test results. This paper introduces a new technique based on interpretation of acoustic measurements to quantify mechanical damage in propping agents.

Introduction

Mechanical damage that leads to compaction and crushing is studied for sands by measuring ultrasonic velocities. Elastic properties can be estimated from compressional- and shear-wave velocities calculated from acoustic measurements. The elastic properties of unconsolidated sands usually are studied by use of effective-medium models for granular media. Effective- medium-theory approaches such as the Hertz- Mindlin model are often used to derive the effective elastic moduli of packings of identical and spherical granular materials. This model combines the Hertzian contact model, which is used to estimate the normal (compressional) stiffness for two identical spheres, and the Mindlin contact model, which is used to estimate the tangential (shear) stiffness of the spheres.

Work investigating the relationship between the ratio of compressional- to shear-wave velocities and pressure as a result of preconsolidation and sorting in unconsolidated sands showed that the Hertz-Mindlin model overestimated the shear moduli and underestimated the pressure dependence of the moduli and the velocities of the unconsolidated sands when compared with experimental data from ultrasonic measurements. The discrepancy was attributed to the inability of the model to account for rotation of grains and slip at their boundaries. The work applied a modified Hertz-Mindlin model, in which it is assumed that there is no friction between the grains (hence, the tangential stiffness is negligible), to obtain a reasonable match between the model and experimental results. The disparities were attributed to the angularity of the sand grains and the assumption of no slip at the grain contacts. The disparities were modified by introducing an average- angularity parameter and assuming slip at the grain contacts.

Previous publications documented applications of effective-medium models for assessment of elastic properties in rocks and unconsolidated sands. However, effective-medium models have not been applied in the assessment of elastic properties of proppant packs.
Optimizing Spacing of Multistage-Fractured Horizontal Wells in Gas Reservoirs
Authors: Carpenter Chris
Published: October 2016

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 171688, “Optimizing Spacing of Horizontal, Multistage-Fractured Wells in Gas Reservoirs,” by Maryam Alghannam and Zillur Rahim, Saudi Aramco, prepared for the 2014 Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, 10–13 November. The paper has not been peer reviewed.

The growing demand for gas in Saudi Arabia and the availability of multistage-fracturing (MSF) horizontal-well technology have spurred the development of tight gas reservoirs throughout the country. Draining the reservoir efficiently by use of MSF strongly depends on well spacing, especially for low-permeability reservoirs. This paper gives the recommended MSF horizontal-well spacing for several development scenarios in Saudi Arabian gas-reservoir environments.

Theoretical Background

There are four different flow regimes for multiple-fracture systems without wellbore storage: early linear, early radial, formation linear, and pseudoradial flow (Fig. 1). The initial flow period observed is the linear flow, where fluid flow toward the fractures in the formation is perpendicular to the fracture planes. This flow exists when each fracture behaves independently and most of the fluid entering the wellbore comes from the fractures (when the fracture-tip effects have not yet affected the pressure behavior). After the start of the flow into the fracture tips, the early radial flow develops while there is still no communication between fractures. This flow regime may occur briefly or it may not occur at all, depending on the fracture length and spacing. Subsequently, formation linear flow develops after the fracture interference has been felt and the flow becomes normal to the horizontal well. Finally, the pseudoradial-flow regime develops in the formation, where the flow appears radial toward the entire well/fracture system. During this flow period, the composite fracture system behaves as if it were a single fracture. The flow eventually will reach pseudosteady state when it hits the reservoir boundaries or interferes with surrounding wells.

The rate at which the flow regime develops, from the start of production under transient conditions until it reaches reservoir depletion under pseudosteady state, is highly dependent on well spacing and well and reservoir characteristics.
Controlled-Freeze-Zone Technology for the Distillation of High-CO2 Natural Gas
Authors: Carpenter Chris
Published: October 2016

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 171508, “Controlled-Freeze-Zone Technology for the Commercialization of Australian High-CO2 Natural Gas,” by Jaime A. Valencia, Robert D. Denton, P. Scott Northrop, Charles J. Mart, and Ransdall K. Smith, ExxonMobil, prepared for the 2014 SPE Asia Pacific Oil and Gas Conference and Exhibition, Adelaide, Australia, 14–16 October. The paper has not been peer reviewed.

The simple separation of carbon dioxide (CO2) from natural gas by distillation would involve cryogenic temperatures at which CO2 solidifies. Most CO2-separation processes instead use solvents that bind to CO2 molecules. For solvent regeneration, the binding process is reversed. The technology described by the authors provides the simplicity of a single-step distillation process for the separation of CO2 from natural gas. The technology has shown the potential to separate CO2 and other impurities from natural gas more efficiently and more cost-effectively.

The Process

In the gas industry, separations based on differing relative volatility and phase behavior are relatively simple, easy to implement, and widely used. The significant difference in relative volatility of methane and CO2 makes this system an ideal candidate for separation by distillation, were it not for some cold-temperature conditions leading to solidification of CO2. At 600 psig, conventional distillation is interfered with, for liquid-methane concentrations between approximately 25 and 85%, by the presence of this solid phase. Raising the pressure to 800 psig shifts the operating conditions away from the solidification boundary but into a new limitation: critical conditions. The critical pressure of pure methane is 667 psia; thus, methane-rich mixtures become supercritical. A high-purity methane-product stream cannot be obtained by distillation at 800 psig, and the overhead product purity is limited to 80 to 85% methane with a residual CO2 content of 15 to 20%. This is the basis for CO2 bulk fractionation.

The technology described in this paper, rather than avoiding the solidification of CO2, allows CO2 to freeze, though under carefully controlled conditions and in a specially designed section of an otherwise conventional distillation tower.

The tower normally incorporates three zones: the specially designed section that addresses the solidification region and two conventional distillation sections, one for rectifying and one for stripping, which cover the vapor/liquid areas above and below the CO2-solidification region. The relationship between the three sections of the column and the methane/ CO2 phase diagram is illustrated in Fig. 1.
A Real-Field Multiscale Black-Oil Reservoir Simulator
Authors: Kozlova A.. , Li Z.. , Natvig J. R. , Watanabe S.. , Zhou Y.. , Bratvedt K.. , Lee S. H.
Published: October 2016

Simulation technology is constantly evolving to take advantage of the best-available computational algorithms and computing hardware. A new technology is being jointly developed by an integrated energy company and a service company to provide a step change to reservoir-simulator performance.

Multiscale methods have been rapidly developed during the past few years. Multiscale technology promises to improve simulation run time by an order of magnitude compared with current simulator performance in traditional reservoir-engineering work flows. Following that trend, the two companies have been working in collaboration on a multiscale algorithm that significantly increases performance of reservoir simulators.

In this paper, we report the development of multiscale black-oil reservoir-simulation technology in a reservoir simulator used by the industry, as well as the performance and accuracy of the results obtained by use of this implementation. The multiscale method has proved to be accurate and reliable for large real-data models, and the new solver is capable of solving very-large models an order of magnitude faster than the current commercial version of the solver.
Cold CO2 Injection for Balancing Interfacial Tension Decrease and Viscosity Increase
Authors: Hamdi Zakaria , Awang Mariyamni , Bataee Mahmood , Kamyab Mohammadreza
Published: October 2016

CO2 injection has been used for decades in the petroleum industry as a successful tertiary recovery method. The main impact of CO2 on the reservoir is interfacial tension (IFT) reduction between the crude oil and CO2 which leads to better sweep. Decrease in the temperature can cause lower IFT between CO2 and hydrocarbons. Yet, lowering the temperature will cause an increase in oil viscosity which negatively affects the oil recovery. In this study, we have calculated the change in IFT and viscosities of crude oil and CO2 to examine if a low IFT optimum point does exist where a low viscosity ratio between the two fluids is observed.

To obtain IFT between CO2 and crude oil, the Parachor model is used. Viscosities of the fluids are calculated using a commercial simulator. Then, simulations of CO2 injection is conducted as a tertiary recovery method to calculate the overall recovery as well as investigating the existence of the optimum point.

The results show that based on the composition of the crude oil, there is an optimum temperature beyond which the IFT would not decrease as well as the viscosities are at the optimum point suitable for recovery. Therefore, it is concluded that IFT has a more important role in the ultimate recovery than the viscosity of the fluids.
An Investigation of Fe2O3 Nanoparticles Diffusion into Oil for Heat Transfer Optimisation on Electromagnetic Heating for Well Stimulation and EOR
Authors: Santoso R. K. , Rachmat S. , Resha A. H. , Putra W. D. , Hartowo H. , Setiawati O.
Published: October 2016

The use of iron oxide nanoparticles in electromagnetic heating application has been proven through several investigations to increase the electromagnetic absorption properties of reservoir, then, significantly increase the generated temperature. A factor that affects the temperature build-up is nanoparticles transport mechanism. When the nanoparticles carrier fluid is in contact with oil, it is possible for mass transfer to occur. Thus, nanoparticles can diffuse from its carrier fluid to oil in the reservoir. This mechanism is advantageous in increasing the oil temperature because it reduces the heat loss. In this study, we investigate the diffusion mechanism of iron oxide nanoparticles from brine to oil. We used 1% NaCl solution as the brine and nanoparticles carrier. The experiments are done with variation of the type of oil, nanoparticles concentration and sonication time. Heavy and asphaltic oil creates barrier for nanoparticles to diffuse, therefore, diffusion of nanoparticles from brine to oil is very small. Increase in nanoparticles concentration and sonication time provides more driving force for nanoparticles to move to oil. However, it is not always as ideal as those conditions, interaction among nanoparticles, such as aggregation creates various unpredictable results in the experiments.
When to Refrac? Combination of Reservoir Geomechanics with Fracture Modeling and Reservoir Simulation Holds the Answer
Authors: Pankaj Piyush , Gakhar Kush , Lindsay Garrett
Published: October 2016

A workflow has been developed for a shale play in North America for the strategic deployment of refracturing in an unconventional reservoir. Although it is clearly understood in the industry that refracturing in tight unconventional reservoirs can have a dramatic impact on the productivity and longevity of economic production, until now there has been no workflow that could be counted on to deliver consistent results. The impact of production and stress re-orientation plays a significant role in adding a fourth dimension of time to the existing three-dimensional problem of hydraulic fracture modeling in these reservoirs.

We examined the re-orientation of reservoir stress and the change in stress magnitude with production in a case from the Eagle Ford. The stress redistribution occurring due to poroelastic effects was simulated using a finite element geomechanical simulator and then tied back to predict the new hydraulic fracture growth. Fracture geometry as it relates to draining the unstimulated domain was found to play a significant role in fracturing success. The impact of adding new perforations in the wellbore and application of a suitable diversion technique were also considered in the study. Our numerical investigation of the potential increase in productivity with selection of the optimum refracturing treatment timing and technique led to development of a methodology that solves the complex four-dimensional problem.

By adopting the guidelines from the case study application of the end-to-end workflow, operators can avoid the futility of too early or too late fracturing and thereby maximize their return on investment.
Electric Impulse Technology: Less Energy, Less Drilling Time, Less Round Trips
Authors: Voigt Matthias , Anders Erik , Lehmann Franziska
Published: October 2016

The paper presents a new drilling technology. With the Electric Impulse Technology it is possible to drill boreholes with less energy demand, more drilling speed and less drill bit changes. Drilling results, calculations und further steps will be presented.

The new technology uses high voltage impulses to destroy rock with almost no wearing of the drill bit. Engineering a drill bit with this technology will advance the drilling activity for oil and gas as well as geothermal drilling and mining. The objective is to develop a whole drilling system suitable for a conventional drilling rig. Within the first step an impulse voltage generator including a drill electrode was engineered, tested and evaluated. Drill performance under pressure with OBM was investigated. Next steps will include the developing of the energy supply for the system and field tests.

The impulse voltage generator designed as a downhole tool was developed to drill bore holes with a diameter of 12 ¼ inch in hard rock with a drill speed of 1 to 2 m/h which is comparable to conventional drilling bits. Furthermore it withstands temperatures up to 200 °C and pressures of 1000 bar. The components of the generator have a lifetime about 350 h, so a bit could be used almost seven times longer than a conventional drilling bit. In laboratory tests a block of granite was drilled on a length of 50 cm with a diameter of 12 ¼ inch. Additionally further materials like limestone, sandstone, marble and iron ore were successfully destroyed. Pressure tests up to 500 bar with WBM and OBM were performed and analyzed. The whole design process of the generator and the electrodes was accompanied by network analysis and FEM calculation.

The paper presents the new results of the development of a drill bit based on the Electric Impulse Technology. After the engineering of the impulse voltage generator and promising results the development of the power supply get into focus. The pressure tests show that the Electric Impulse Technology will work under borehole conditions. In addition to early processing the drill bit will be configured for drilling with WBM concerning environmental and financial issues.
Physical Simulation of Storage Threshold of Shale Oil
Authors: Jin Xu , Bi Lina , Wang Xiaoqi , Sun Liang , Li Jianming , Liu Xiaodan
Published: October 2016

In this contribution, a nano-pore template with controllable pore size was used to simulate pore-throats in shale. Considering the wettability at the solid-liquid contact, the seepage of oil in channels with different pore sizes was examined to figure out the effect of pore diameter on oil storage capacity scientifically and systematically for the first time. The simulation shows that the lower threshold of pore-throat to store oil can be 20nm under certain conditions. The new threshold value of pore size for oil storage has brought about revolutionary changes in the estimation of geologic reserves, recoverable reserves and economically recoverable reserves of shale oil.
Production Surface Network Modelling and De-Bottlenecking Analysis for Gathering Center in Kuwait
Authors: Almohammad Humoud , Al-Saqabi Mishari
Published: October 2016

One of the major challenges facing Kuwait mature oil fields is to maintain their current production and maximize recoverable reserves; to achieve Kuwait 2030 target: 4 MMSTBO. The challenging production environment in the selected area from Kuwaiti fields is not an exception, where high pressure and H2S wells are existing. Connecting wells, to the same processing facility, with varying in reservoir pressure, high, medium and low, create bottlenecks in the surface network.

To find bottlenecks in flowlines and have an optimum distribution of wells; the engineers have built and studied flowline network model in-house using a commercial steady-state multiphase flow simulator for the wells connecting to one of Kuwait companys' Gathering Centre (GC). GC-XY was considered as its eight headers are ranging between high and low pressure headers, and receiving production from several fields in Kuwait. The project started by data collection, followed by quality check the flowing conditions for each well and reservoir fluid models. Next, the physical network model was built using the simulator. After that, the flowing correlations factors were tuned.

The modeled results were compared with the actual testing results. The results findings show a significate potential of bottlenecks in 15 wells out of 83 oil production wells, mainly in the high pressure headers. Also, a possible production enhancement, of approximately 30,000 barrels per day. That to be achieved by implementing the explained optimum well distribution between the high pressure headers and low pressure headers. Furthermore, asphaltene and bitumen deposition are existed and deposited over time in the flowlines, making it essential to flush the flowlines with a solvent mixture to clean the inner flowing section. To successfully implement the flushing job, it is also required to have an awareness of the backpressure existence in the flowlines, which was achieved using the simulated model.

The project explains a complete procedure to build a reliable network model, to identify bottlenecks and minimize production loss. Bottlenecks in flowline can increase wellhead pressure; hence, it is crucial to find bottlenecks to detect and reduce backpressure effect on the flowline network. Implementing flowline flushing job successfully is important to maximize the production deliverability and prevent flowline blockage and backpressure; which will also cause the existing electrical submersible pumps to trip.
Oil Well Cement Static Gel Strength Development Comparison Between Ultrasonic and Intermittent Rotational Measurement Methods
Authors: Ashraf Shameed , Hamilton Paul , Salehpour Amir Gheisar , Azwar Cinto , Bogaerts Martijn
Published: October 2016

Disclaimer: This paper includes forward-looking statements, Actual future conditions...

The publication of the API Standard 65-2 "Isolating Potential Flow Zones During Well Construction" places strong emphasis on measuring the Critical Gel Strength Period (CGSP). The CGSP is the time period starting from when laboratory measurements indicate the slurry has developed Critical Static Gel Strength (CSGS), to when it has developed strength of 500 lbf/100ft2. As per the API standard, CGSP of 45 minutes or less has proven effective in isolating zones with severe flow potential therefore, the CGSP has been identified as a crucial parameter to qualify slurry systems for many oil and gas operators. The API 10B-6 "Recommended Practice on Determining the Static Gel Strength of Cement Formulations" indicates there are three measurement methods; continuous rotation, intermittent rotation, and ultrasonic-type static gel strength. This paper will review a comparative laboratory- based study between two measurement devices commonly used in the industry to measure the CGSP. One device uses the intermittent rotation, and the other uses the ultrasonic method.

The slurry systems selected for the study covers a density range of 11.5 to 18 lbm/galUS within the temperature range of 27 to 121 deg C. The selected slurries comprise of Class G cement, silica flour with extenders or weighting agents paired with antifoam, fluid loss additives, dispersant and retarder to represent the typical slurry systems used in cementation of potential flow zones. Additionally, each slurry system is designed for two scenarios; one is to cover a short placement time(3 to 4 hours) and the other for a longer placement time (7 to 8 hours). While some of the slurry systems passed the CGSP criteria based on the ultrasonic method of measurement, they did not pass the criteria when measured by the intermittent rotation method. Possible reasons for this mismatch are further explained in this paper.

Results of this study are applicable to all oil and gas service operators involved in cementation of potential flow zones. One would expect that both of these methods would predict the same slurry behavior in either passing or failing the CGSP criteria, however and on the contrary that was not observed on all of the slurry systems selected for this study.
Geomechanical Sweet Spot Identification in Unconventional Resources Development
Authors: Rahman Khalil , Gui Feng
Published: October 2016

Sweet spot identification in unconventional fields generally involves the identification of clusters and intensities of parameters that indicate the resource volume and production-related parameters, i.e., reservoir quality parameters such as total organic content (TOC), porosity, permeability, pay zone thickness, etc. The process usually incorporates interpretation of seismic data, well logs and other data to develop a 3D model that is used to suggest locations for productive wells. While understanding these parameters is essential in unconventional resource development, the potential to achieve productive hydraulic fractures, or the potential to exploit natural fractures, or the potential to achieve both simultaneously determines the feasibility of developing an unconventional resource. There are geomechanical conditions that are favourable to achieve the maximum productivity from stimulation operations. Identifying the geomechanical sweet spots within the field-wide reservoir quality sweet spots is, therefore, essential for optimum placement of wells and hydraulic fractures in unconventional reservoirs. This identification requirement is gaining more and more attention in the industry, which is helping the technique and workflow development. This paper discusses the workflow to identify the existence and properties of geomechanical sweet spots including rock mechanical properties and natural fracture distribution and how they help to decide the vertical location and direction of horizontal wells for optimal reservoir development. The workflow requires a multidisciplinary data set comprising drilling, geology, geophysics, production, geochemistry and geomechanical information. Based on detailed geological understanding, either a 1D or a 3D geomechanical model is built as the foundation for further analysis. Images, seismic data and structural information are the key to develop the understanding of natural fracture distribution. A discrete fracture network (DFN) model, or other definitive models, is required to identify stress-sensitive fracture distributions under different stress conditions. Due to the fact that local in-situ stress and natural fracture properties can be altered by production operations, initial unsweet spots may turn into sweet spots at some stage of production or injection operations. Based on the results of comprehensive geomechanical sweet spot analysis, an optimal development decision can be made based on integrated geomechanics, production and net present value analyses within the identified sweet spots. This paper includes results and illustrations from several case studies completed for a number of fields in the Asia Pacific to demonstrate the concept.
Downhole Real-Time Monitoring for Conventional Waterflooding Wells
Authors: Pei Xiaohan , Sun Fuchao , Jia Deli , Zheng Lichen , Yang Junzheng , Wang Jinzhong , Zhang Jianzhong
Published: October 2016

Waterflooding is the main development mode in China. 80% production comes from waterflooding. Nowadays, there are two conventional waterflooding techniques called eccentric bridge waterflooding and concentric bridge waterflooding. However both these two techniques can not obtain real-time parameters of each layer while injection such as zonal tubing pressure, after-choke pressure, temperature and etc. Lacking of downhole real-time data results in poor reservoir dynamic modeling. In this paper, a downhole real-time monitor was developed. It was placed downhole permanently in each layer. The real-time monitor was composed of battery, rechargeable unit, temperature sensor, two pressure sensors, antenna, and control unit. The downhole tubing pressure, after-choke pressure, temperature and battery power could be monitored continuously and stored on the control unit. Once the data were needed to read, set down communication sub from ground and wireless communication was used to realize data transfer between sub and regulator. The downhole battery could be charged on line to meet the need of different sample time. The downhole real-time monitor has been implemented in a four-layer waterflooding wells in Daqing Oilfield in China. The results show that the monitor could realize downhole tubing pressure, after-choke pressure, temperature and battery power monitoring. On-line battery charging technique was used to ensure its long working time whatever the sample time was. For this well, the sample time was set to 5min according to geological engineer’s advice. All the real-time data were obtained through a short distance wireless way by a communication sub. The results showed its apparent advantage that the downhole real-time monitor had no effect on conventional regulator. All the conventional measurement and adjustment method was the same. The management was also the same as before. Existing conventional waterflooding wells can only obtain real-time data while testing through instruments. Usually there is only totally one hour data per year. The technique in this paper can offer long term real-time data which were used to offer basis for better reservoir understanding and optimization. It is suitable for conventional eccentric bridge and concentric bridge regulator which is most widely used in China, more than 40,000 wells.
The Far-Field Deformation Induced by a Fracture in a Poroelastic Layer with Application to Tiltmeter Monitoring of Hydraulic Fractures in Coal Seams
Authors: Chen Zuorong , Pandurangan Venkataraman , Jeffrey Robert G.
Published: October 2016

Measurements of deformations by using tiltmeters located at large or moderate distances from a hydraulic fracture (HF) have often been used to monitor fracture geometry. The fracture is generally represented as a singular point displacement discontinuity (DD) source, or as a constant DD over a rectangular plane, or as a distributed DD across a fracture plane, and the analytical solution for the induced deformation by a DD in a homogeneous elastic half-space is commonly used directly as a forward model for representing a simple fracture or as a building block for constructing a more complex fracture in mapping the fracture geometry. The mechanical properties of the coal seam in which an HF is placed are typically very different from those of the surrounding rocks. In addition, the poroleastic response associated with fracturing fluid leakoff from the fracture surface into the coal layer may also influence the HF growth and the induced deformation. In order to obtain a correct interpretation of the created fracture geometry and better understanding of the treating pressure behaviour in hydraulic fracturing stimulation of coal to enhance gas production, the mechanical property contrasts and the poroelastic effect induced by fluid leakoff need to be recognised and taken into account.

In this paper, a mechanical model based on the concept of eigenstrain and the equivalent inclusion method is presented and applied to the problem of calculating the far-field deformation and stresses induced by a horizontal fracture located in a formation layer with mechanical properties different from those of the surrounding homogeneous elastic half-space. The fracture is modelled as a constant opening DD across the fracture plane, and the corresponding mathematically equivalent eigenstrain is defined based on the fracture opening and formation layer geometry. A simple one-dimensional hydromechanical model has been presented to approximate the fluid leakoff through the surface of a stationary fracture. The analytical solutions allow for estimating the importance of the poroelastic effect associated with an HF in a coal seam. The variation of the pore fluid content due to fracturing fluid leakoff is characterized by the poroelastic eigenstrain. A relationship connecting the induced far-field deformation and stresses with the fracture and formation layer geometry, the fluid leakoff volume, and the mechanical properties has been established. The proposed method offers a simple and computationally efficient forward model to take into account the effect of mechanical property contrasts and poroelasticity on the deformation induced by the fracture when using tiltmeter monitoring to map the geometry of an HF in a coal seam.
A New Method for Estimating the Production Performance of Water Flooding
Authors: Li Kewen , Liu Changwei , Zhang Qiaoliang , Jiang Ping , Lei Xiao , Gao Hongyi , Jing Fengjiang
Published: October 2016

Pore volumes injected (PVI) has been found to be difficult to represent the longevity and intensity of water flooding in oil reservoirs. In order to find a better parameter to characterize fluid flooding, a new concept referred as to "flushing coefficient" has been proposed, which is a function of time and position. The effects of the viscosity, relative permeability of water phase, pressure gradient, and flooding time are considered in the flushing coefficient. Water flooding experiments were conducted in sandstone rock samples with different permeabilities ranging from about 1.0 to over 1000 md at room temperatures. The experimental data were used to test the new concept.
Old Technique New Insights: Reservoir Properties society of Petroleum Engineers from Pulse Testing
Authors: Filippi Bert , Nabipour Amin , Fukuda Naoki
Published: October 2016

Pulse testing, introduced in the 1960's, is a useful analytical technique to detect communication between wells and estimate interconnected reservoir properties. Despite its potential, it is rarely included in data acquisition programs. This is probably because engineers prefer to use interference testing, which can be easily detected and interpreted by reservoir simulation. Regretfully, the latter cannot analyse pulses which are so subtle that they are hidden within the tidal effects of pressure measurement.

In pulse testing, interconnected permeability is calculated from the time the pulse takes to travel from the producer to the observation well. In this paper, new formulations are presented for both linear and radial flow regimes. These are straightforward, making their application easy. Furthermore, they can detect whether pressure is propagated along channels or more extensive areal systems. The magnitude of the pulse can also provide invaluable reservoir characterisation. For a relatively homogenous system, this amplitude is easily calculated using either radial or linear coordinates. For more complex geometries, such as communication between different sands, detailed studies are required to quantify where and how the connectivity occurs between the producer and the observation well.

Often the pulse is significantly less than 0.1 psi which makes detection difficult, because of tidal effects, and analysis hard to interpret by finite difference simulation. Searching for such subtle changes in pressure takes perseverance. Calculating interconnected permeability by a single equation and determining the geometry of a channel by simple algebra makes the effort rewarding.

Three examples are presented to show how the following equations can be used to determine interconnected reservoir characteristics. Although the data is real, it refers to different fields, the interpretation of which is yet to be finalised. For this reason they are referred to as hypothetical cases A, B and C. These were selected because of the high frequency and the excellent quality of the data.  For linear flow k=79⋅x2ϕμc⋅(1tl−1t)/ln⁡ttl For radial flow k=79⋅r2ϕμc2(1tl−1t)/ln⁡ttl

In oil field units: k, x, r,ϕ, μ, c are permeability, distances (x and r), porosity, viscosity and compressibility. The times, t and tl are the hours from the beginning and the end of production pulse (of duration t - t1) to the maximum pressure disturbance at the observation well.
Laboratory and Mathematical Modelling of Fines Production from CSG Interburden Rocks
Authors: Badalyan A. , Beasley T. , Nguyen D. , Keshavarz A. , Schacht U. , Carageorgos T. , You Z. , Bedrikovetsky P. , Hurter S. , Troth I.
Published: October 2016

Twelve clastic core samples from the Walloon Coal Measures, Surat Basin were tested for disintegration in artificially produced fluids varying in ionic strength. XRD data confirm the presence of smectite (water sensitive clay) in the samples. Flow-through rock disintegration experiments demonstrate that the higher the concentration of smectite and soluble plagioclase is, the quicker rock disintegrates in artificial low ionic strength fluid. Pre-soaking of rocks with high ionic strength fluid reduces rock disintegration rate in low ionic strength fluids. This is explained by very strong clay-clay and clay-sand attraction forces, evidenced through zeta-potential measurements, which inhibit rock degradation. For the studied samples it is clear that rock disintegration rate is proportional to fluid velocity. Experimental rock disintegration data are fitted by a power erosion model with two adjusted parameters: fluid ionic strength and Reynolds number. The experimental results satisfactorily agree with theoretical data. Rock disintegration rates are calculated as released particle volume per thickness of interburden layer per day at a fixed Reynolds number and low ionic strength. The laboratory work suggests that keeping wells under strong ionic fluid during shut-in times and a reduction of water production rate will preserve rock integrity for a longer period of time.
Laboratory Study on Surfactant Induced Spontaneous Imbibition for Carbonate Reservoir
Authors: Qi Ziyuan , Han Ming , Fuseni Alhasan , Alsofi Abdulkareem , Zhang Fan , Peng Yuqiang , Cai Hongyan
Published: October 2016

Chemical flooding has been successfully applied in sandstone reservoirs using surfactant-related formulations due to their abilities to reduce interfacial tension (IFT) between injection fluid and oil. This scheme need to be modified to fit the requirement of effective application in carbonate reservoirs that present preferably oil-wet or mixed wet. In this case, the wettability alteration should be triggered by a kind of surfactants that can change the wettability towards water-wet and induce the spontaneous imbibition of injection fluid into the carbonate matrix for higher oil recovery. In this study, 16 surfactant samples were screened aiming at an Arabian carbonate reservoir, among which 3 surfactant samples were selected for spontaneous imbibition experiments using Amott cells at 95°C. The experimental results presented the imbibition was induced by the surfactant solutions compared to effect of the brine. It also showed that brine imbibition recovery decreases with the increase of permeability and initial water saturation. Surfactant can effectively improve imbibition recovery, and cores with higher permeability show better increased imbibition recovery. Imbibition can be divided into three types based on the value of bond number, and recovery as well as recovery rate can also be correlated with bond number. The imbibition model is validated by two imbibition modes – surfactant imbibition and brine imbibition then surfactant imbibition – using UTCHEM simulator. This paper demonstrates the effect of surfactant induced spontaneous imbibition on oil recovery, which should be taken into account in the chemical flooding application for carbonate reservoirs.