bluuebunny/crossref_metadata_2025 huggingface dataset:
PROPOSTA DE INTERSECÇÃO DE LINHAS GEODÉSICAS SOBRE A SUPERFÍCIE ESFÉRICA E SOBRE O ELIPSÓIDE DE REVOLUÇÃO
Authors: Basso Marcos Aurélio , Morescki Junior Luiz Fernando Macedo , Siguel Alyne Raminelli , Nadal Carlos Aurélio
Published: March 2015

A Lei 8.617 de 1993 define a Zona Econômica Exclusiva como uma faixa de até duzentas milhas náuticas ao longo do mar territorial, na qual os recursos existentes podem ser explorados, rendendo royalties aos estados que confrontam com essas áreas. A demarcação das águas territoriais será efetivada através da intersecção entre duas linhas geodésicas. Neste trabalho, propõe-se uma solução para o problema da intersecção de linhas geodésicas nas superfícies esférica e elipsoidal. Inicialmente, fundamentaram-se os cálculos na trigonométrica esférica, fornecendo resultados preliminares, que servem como uma primeira aproximação. Na sequência, propôs-se um método computacional recursivo, baseado nas formulações de Vincenty, onde são realizadas discretizações de azimutes de pequenos segmentos de arco, servindo como aproximação à intersecção por meio da obtenção do lugar geométrico do ponto oriundo da intersecção dos últimos segmentos obtidos.
MODELAGEM DO ERRO SISTEMÁTICO DE DISTÂNCIA NAS MEDIÇÕES REALIZADAS COM A CÂMARA PMD CAMCUBE 3.0
Authors: Silva Felipe Martins Marques da , Centeno Jorge Antonio Silva
Published: March 2015

As câmaras de distância são capazes de medir a distância entre o sensor e a superfície dos objetos para cada pixel da imagem. Comparando com os equipamentos de varredura a laser possuem a vantagem de obter a distância de vários pontos em um único instante, sem equipamento de varredura. As medidas obtidas pela câmara possuem erros sistemáticos que devem ser minimizados. Alguns fatores como o tempo de integração, a distância a ser medida, bem como a iluminação da cena, influenciam na obtenção da medida. Neste estudo foi analisada a influência da variação do tempo de integração e da distância câmara-alvo na exatidão do cálculo da distância, procurando modelar os erros sistemáticos das medições feitas com uma câmara PMD Camcube 3.0. A modelagem foi feita por meio da Transformada Discreta de Fourier e permitiu diminuir o erro médio quadrático (RMSE) de 15,01 cm para 5,05 cm, para das observações feitas com tempo de integração de 4000 (s. Também foi verificado que a amplitude do erro é diretamente proporcional ao tempo de integração utilizado.
Three historic railway bridges in Katanga, DR Congo
Authors: Espion Bernard , Provost Michel , Bastin Olivier , Bouillard Philippe
Published: March 2015

The crossing of rivers in Katanga (Democratic Republic of Congo) by railway lines in the 1920s and 1930s gave Belgian engineers and contractors the opportunity to build record spans for railway bridges. The crossing of the Lualaba River at Bukama consists of four Vierendeel steel girders each with a 62 m span, which were the largest of their type at the time of their erection in 1925. The crossing of the Lualaba at Kongolo, built in 1937–1939, required a 495 m long reinforced concrete continuous beam bridge with 14 spans, the largest measuring 70 m. It was the first significant concrete beam bridge constructed with a travelling gantry supporting movable formwork. The crossing of the Lukaga River (1938–1939) is a three-span concrete bridge with the 70 m long central span built using the cantilever method, which makes this bridge the oldest of its type in the world. This paper highlights the landmark characteristics of these forgotten bridges.
Flow-rate measurements in meter-size multicomponent geosynthetic clay liners
Authors: Bannour H. , Touze-Foltz N.
Published: March 2015

ABSTRACT: To quantify the flow rate through multicomponent geosynthetic clay liners (GCLs), three different meter-sized specimens from different manufacturers were characterized in a dedicated experimental column. This study allows quantification of the interface transmissivity of multicomponent GCLs when the coating or attached film is damaged over an area large enough to make edge effects negligible. For all multicomponent GCLs characterized, the coating or attached film was less than 0.7 mm thick. Steady-state results indicated flow rates ranging from 4.61 × 10−12 to 3.01 × 10−11 m3/s with interface transmissivities ranging from 1.20 × 10−11 to 7.59 × 10−11 m2/s, which are broadly in line with flow rates obtained from conventional geomembrane (GM)–GCL composite liners. Consequently, when the coating or attached film is damaged, the thickness and rigidity of the coating or attached film appears not to affect the steady-state flow rate and interface transmissivity, which leads to a good contact at the interface.
The role of soil stiffness non-linearity in 1D pile driving simulations
Authors: Salgado R. , Loukidis D. , Abou-Jaoude G. , Zhang Y.
Published: March 2015

Drivability studies and determination of pile static capacity from driving resistance are an integral part of present foundation engineering practice. The success of both pile driving simulations and back-calculation of static resistance from pile driving resistance (signal matching analyses) depends on the model used for the interaction of the shaft and base of the pile with the soil. In this paper, a set of advanced base and shaft dynamic reaction models is formulated that accounts explicitly for soil stiffness non-linearity. Comparisons between predictions of the proposed soil reaction models and of various existing reaction models used in practice with measured pile driving data from two well-instrumented field cases allow assessment both of the importance of stiffness non-linearity in accurate pile driving simulations and of the usefulness of various levels of sophistication in the shaft and base reaction models.
Comparison of finite-element limit analysis and strength reduction techniques
Authors: Tschuchnigg F. , Schweiger H.F. , Sloan S.W. , Lyamin A.V. , Raissakis I.
Published: March 2015

In practical geotechnical engineering the factor of safety is still determined by means of simple limit equilibrium analysis in many cases. However, because displacement finite-element analysis is routinely applied for assessing displacements and stresses for working load conditions, this technique is increasingly being used to calculate ultimate limit states and, consequently, factors of safety, usually by means of the so-called strength reduction technique, and results which are comparable to those obtained with limit equilibrium methods have been reported in the literature. However, owing to the inherent assumptions of limit equilibrium analyses, they do not always provide unique factors of safety. The purpose of this paper is on the one hand to compare the strength reduction method with rigorous limit analyses which are based on collapse theorems of plasticity, and on the other hand to investigate if a shortcoming of the strength reduction method, namely possible numerical instabilities for non-associated plasticity, can be overcome. Two examples are considered, namely slope stability and tunnel face stability. Finally an important note on the definition of the factor of safety for effective and total stress analysis under undrained conditions is provided.
5. A DINÂMICA EMOCIONAL DO DESVIO: UMA ANÁLISE EM CRIMINOLOGIA CULTURAL
Authors: ROCHA Alvaro Oxley , Da SILVA Simone Schuck
Published: March 2015

O artigo apresenta uma a análise da inserção cultural do crime, do controle da criminalidade e das emoções envolvidas nesses fenômenos, pelo prisma da Criminologia Cultural, uma abordagem recente nos estudos criminológicos, oferecendo uma base necessária para qualquer estudo das necessidades para a formação da cidadania, realizado no contexto das sociedades urbanas pós-moderna, e pois, de modernidade tardia. Nesse sentido, apresentam-se esses fenômenos em relacionados ao individualismo, à criatividade e à geração de estilo de vida, em um período de privações materiais e ontológicas, enfatizando a força da mídia de massa como influenciadora da subjetividade humana.
PREFÁCIO AO V.2., N.4 DA REVISTA JURÍDICA DO DIREITO
Authors: KRETSCHMANN Angela , SELAYARAM Renato
Published: March 2015

A Revista Jurídica do Cesuca alcança seu quarto número com uma coleção de artigos cuidadosamente selecionados e avaliados e que vêm a público agora, em dezembro de 2014. A Revista cresceu ainda mais em estrutura, em qualidade, e neste quarto número, que a faz completar 2 anos de nascimento,  acrescentou mais indexadores internacionais e popularizou-se mais entre os cientistas pesquisadores da área jurídica, em especial na América Latina.

É importante lembrar que a Revista insere-se dentro da política de acesso aberto promovida pela Faculdade Inedi – Cesuca, e dessa forma, o acesso à produção é livre, sem necessidade sequer de qualquer cadastro prévio para acesso aos exemplares.
Prey size structure diminishes cascading effects by increasing interference competition and predation among prey
Authors: Geraldi Nathan R.
Published: March 2015

The size of an organism can change by orders of magnitude during its lifespan. Size can determine whether an individual consumes, is consumed, competes, or avoids individuals of the same or different species. Two complementary mesocosm experiments with a tri‐trophic food chain (top predator, toadfish, Opsanus tau; intermediate prey, mud crab, family Xanthidae; basal resource, oyster, Crassostrea virginica) were conducted to measure how the size of both the top predator and the intermediate prey affects consumptive and behavioral interactions in trophic cascades. In the first experiment, I systematically varied the sizes of predators and prey, respectively. The amount of crab biomass consumed was dependent on crab size and not toadfish size, but the effect of crab size did not cascade to alter oyster survival. Increased oyster survival from crab interference competition in the absence of toadfish was similar to oyster survival from predator‐avoidance behavior in the presence of a toadfish. When all crab size classes were present, crab mortality was similar in the presence and absence of toadfish, highlighting the importance of intraguild predation in food‐web dynamics. The second experiment separated crab mortality by other crabs from crab mortality by predatory toadfish and found that crab mortality generally switched from intra‐ to interguild predation when a toadfish was present. In addition, field surveys indicated mud crab abundance and size was primarily influenced by mud crab recruitment, but not by toadfish abundance, which supports our experimental results that interactions among mud crabs have similar effects to predator–prey interactions. These findings indicate that changes in size or abundance of intermediate prey may be comparable to changes in top predator abundance in terms of trophic interactions and their transmission to lower levels, which suggests that certain types of relatively simple food chains can be resilient to the loss of higher trophic levels.
Dermatologic Surgical Pearls: Enhancing the Efficacy of the Traditional Elliptical Excision
Authors: Nantel-Battista Melissa , Murray Christian
Published: March 2015

Dermatologic surgery procedures can sometimes be time consuming in an office setting. We present a series of tips for dermatologists and dermatologic surgeons that will enhance the efficiency of simple procedures.

Les interventions en chirurgie dermatologique peuvent parfois prendre beaucoup de temps en cabinet. Nous présentons une serie de conseils à l'intention des dermatologues et des chirurgiens dermatologues, qui accroîtront l'efficacité de petites interventions.
Dermatologic Surgical Pearls Part 3: Tips for Labial Excisions and Repairs
Authors: Nantel-Battista Melissa , Murray Christian
Published: March 2015

Dermatologic surgery procedures can sometimes be time consuming in an office setting. We present two tips for dermatologists and dermatologic surgeons that will enhance the efficiency of procedures around the lip.

Les interventions en chirurgie dermatologique peuvent parfois prendre beaucoup de temps en cabinet. Seront présentés aux dermatologues et aux chirurgiens dermatologues deux procédés qui auront pour effet d'accroître l'efficacité des interventions touchant les lèvres.
The Prevalence of Anxiety and Depression in Arab Dermatology Patients
Authors: Alshahwan Mohammed A.
Published: March 2015

Background

Psychiatric disorders are common among patients with physical illnesses.

Objectives

To estimate the prevalence of anxiety and depression in Arab dermatology patients and to study its association with the patients’ characteristics.

Materials and Methods

A cross-sectional study was carried out on 875 patients attending the Dermatology Clinic at King Khalid University Hospital in Riyadh, Saudi Arabia. Each patient was asked to complete the Hospital Anxiety and Depression Scale and the demographic-clinical questionnaire.

Results

The frequency of anxiety and depression in Arab dermatology patients was 29% for anxiety and 14% for depression. These frequencies were not related to sociodemographic and clinical variables (p > .05), except skin disease type (p < .05). Patients suffering from hair loss had the highest anxiety and depression scores (OR 1.725 [95% CI 1.247-2.386] and OR 1.686 [95% CI 1.101-2.581], respectively). On the other hand, patients suffering from psoriasis had the highest depression scores (OR 2.909 [95% CI 1.611-5.254]).

Conclusion

Anxiety and depression are frequent among Arab dermatology patients.
Money-in-the-Utility-Function: Model Simulations and Money Demand Estimation in the Case of the Republic of Macedonia
Authors: Ivanov Mile , Petkovski Mihail , Naumovska Elena
Published: March 2015

This paper aims to reassess and analyze the dynamic interactions between money, prices and economic activity in the case of the Republic of Macedonia. The first part of the paper simulates the property of the superneutrality of money, based on Sidrauski’s (1967) framework. The second part presents the money demand estimations on the monetary aggregate M2 for the period from 2002 to 2012, using the cointegration approach. Following Cziráky and Gillman (2006), we examine the validity of the Fisher equation in the case of Macedonia. The Fisher equation does not hold in the case of Macedonia, so the inflation rate must be included in the money demand specification. The estimated cointegration equation is in line with economic theory. The cointegration equation shows income elasticity less than unity (0,81), small and negative interest rate semi-elasticity (-0.17) and negative elasticity with respect to inflation. The short-run dynamics reveal that only 2,70% of the disequilibrium is corrected in a single quarter. The properties of stability imply that the M2 aggregate may serve as a proper policy indicator.
Forecast of Sand Deposition at Low Points of a Riser - Jubilee Field Case Study
Authors: Anthony William , Nadu Stephen Langmatey
Published: March 2015

The Jubilee Field is located at about 60 km offshore Tano Basin, Ghana. It produces from an average water depth of about 1100 m through subsea components such as manifolds, flowlines and flexible risers into a Floating Production, Storage and Offloading (FPSO) platform at surface. The paper examined the flow dynamics and sand deposition pattern in the east loop riser of the Jubilee Field under a given operating conditions.

It employed computational fluid dynamics technique aimed at forecasting the possible deposition areas of sand in the riser. Eulerian discrete phase model was adopted in predicting sand flow pattern at areas encompassing the low points of the riser.

It was observed that for the given flow conditions, there is the possibility of sand deposition and/or accumulation in some sections of the riser. The study predicted the possibility of sand deposition within the vicinity of 14 m from the riser base, and also at sections from the touchdown point up to 2 m downstream of that point. It established that low points in riser bathymetry are possible sources for onset of sand deposition. Sand dispersion decreases from the point of injection towards the lower region of the flow domain downstream from the injection point.

The study would aid in proposing effective riser bathymetry to mitigating the impacts of sand deposition in a riser. It will contribute significantly in developing an effective sand management strategy.

Introduction

The Jubilee Field is a 'green' field located approximately 60km offshore Tano Basin of Ghana with an estimated recoverable reserves of over 370 million barrels and an upside potential of about 1.8 billion barrels. Cased Hole Frac Pack (CHFP) completions were performed on the Jubilee wells; as a long term insurance to mitigate sand production although studies showed the reservoir was generally competent and consolidated.
Mechanistic Modelling for Field Trial of Enhanced Water-Alternating-Gas (EWAG) Injection in Malaysian Oilfields
Authors: Foo Yoong Yow , Zhafri Ridhwan , Tewari Raj Deo , Hunter Thomas
Published: March 2015

Application of gas injection to displace crude oil for pressure maintenance and improving oil recovery often suffer from severe viscous fingering and gravity override. As such, Water-Alternating-Gas (WAG) injection mode is usually promoted, in order to improve macroscopic and microscopic displacements. The improvement in oil recovery due to WAG injection is attributed to the contact of the unswept zones and modification of residual oil saturations, targeting the attic oil. Hysteretic effects which changes saturation paths, due to sequential injection of water and gas, additionally improve the recovery. The gas flow may, however, still develop preferential paths that bypass many unswept regions because of its inherent viscosity and density differences against water. Foam as gas mobility controller has been studied and introduced to enhance WAG displacement process. It acts as a blocking agent in high-permeability zones and diverts the gas flow to the other oil-trapped regions. Foam is a discontinuous phase which consists of liquid lamella and foam gas. Having intermediate behaviours between water and gas, its stability is strongly dependent on the component saturation, strength, size, gas quality etc. As a result, it poses a great challenge to simulate these complex mechanisms and behaviours, not to mention the pertaining effects in the porous media. At present, foam mechanisms are widely modelled via simple quasi-equilibrium approach using interpolation parameters, such as oil saturation, capillary number etc. to correlate the corresponding Mobility Reduction Factor (MRF). This paper presents the foam model results which intend to predict the foam injectivity at wellbore conditions, subsequently developing an injection proposal scheme for the field trial of EWAG process in Malaysia oilfields. In turn, the field trial results later will be history-matched, aiming to improve the prediction model for successive full-field modelling. The mechanistic modelling approach employed in this study takes into account of changes of lamella densities, allowing foam degradation and regeneration via stoichiometric reaction expressions. The mobility control is modelled throughinterpolation of relative permeability using foam gas concentration as interpolator andpermeability blockage in the presence of trapped lamella in solid form.
Innovative Non-Aqueous Fluids Technology Improves Drilling Efficiency Significantly in Dealing with Divalent Complex Salt Formation Under HTHP Conditions
Authors: Yin Da , Peng Shuangjiu , Liu Guoqing
Published: March 2015

This paper presents a case study on the successful application of Non-Aqueous Fluids (NAF) in the Tian Mountain Front Block in North Border of Tarim Basin. Traditionally the wells in this area are drilled with water based mud. Due to the unpredictable divalent complex salt formations, the high temperature (up to 180 °C) and high pressure (mud weight up to 2.6 s.g.) conditions, significant non-productive time (NPT) and low rate of penetration (ROP) were encountered in dealing with wellbore instability, kicks, stuck pipe and downhole losses in the salt formations and fractured pay zone. The water base fluids would become unstable when they are heavily contaminated by divalent salts and/or brine influx.

Introduction

Tarim Basin is the biggest oil and gas bearing basin in China. Total area is approximately 560,000 km2, including "dead sea" desert of around 337,000 km2. One of the most challenging field in terms of drilling difficulties lies in the north border of Tarim Basin: the Tian Mountain Fronts. The reservoir depths are over 7000 meters TVD and bottom hole temperatures are up to 180 °C. Analysis of a large quantity of offset well data1,2, operator internal reports3,4,5 and presentations6 was comprehensively carried out and it was observed that frequent downhole complications were encountered in three major formation sequences / intervals:Shallow formations above the salt formations:Heavy losses and extremely low ROP are common in drilling the hard conglomerates above the salt formations. In the event that the salts are inadvertently penetrated, the high pressure brine influx would require higher mud weight to kill the well. This is normally followed by downhole losses and stuck pipe events.Inside the salt formation sequences:When the water base mud is used, downhole losses and stuck pipe events would normally follow a high pressure brine influx. Stuck pipe is also often encountered when the highly mobile divalent salt formation is penetrated, depending on the mud weight and time exposed. It is believed that the salts are dominantly divalent and their creep rate is much higher than the monovalent salts (believe to be 20 times faster). The risk of stuck pipe is significant higher when divalent mobile salts are drilled.

Another hazard causing the heavy downhole losses and pipe stuck in drilling the salts formation is when the pay zone is inadvertently penetrated, since the mud weight required in drilling the salts is much higher than the mud weight required in drilling the pay zone. It has been a long standing problem to confirm the bottom of the salt sequences. It is common that the number of salts sequences is unpredictable and hence require technology for confirming the end of salt sequences is highly challengeable. Often salts are encountered again in the next interval after the casing has been set to isolate all salt sequences, because the determination of the end of the salt sequences has been made mistakenly.
Minimizing Hydrate Inhibitor Injection Rates
Authors: Yang Jinhai , Mazloum Vajari Saeid , Chapoy Antonin , Tohidi Bahman
Published: March 2015

Inhibitor injection is probably the most popular option for avoiding gas hydrate problems. However, inhibitor injection rates are normally designed based on worst operating conditions (i.e., maximum pressure and minimum temperature) with significant safety margin (e.g., 3–5 °C). Although the system pressure normally drops with time, the injection rates are not normally changed. Furthermore, large quantities of inhibitors are used during start-ups and maintained until the system conditions at monitoring point is well outside the hydrate stability zone. This is completely understandable considering the costs and risks associated with hydrate blockage which outweigh any savings associated with reducing inhibitor injection rates.

However, high inhibitor injection rates are not sustainable later in the life of the reservoir when the water cut increases, hence there is significant interest in developing monitoring and warning systems that can adjust inhibitor injection rates and warn against any potential hydrate blockage.

This laboratory has been investigating various techniques for monitoring hydrate safety margin and detecting early signs of hydrate formation for a number of years through several JIPs. After screening many techniques we have developed two main techniques for monitoring hydrate safety margin (i.e., how far the system is outside the hydrate stability zone) and detecting early signs of hydrate formation. The techniques have now been tested and implemented in many places around the world. These techniques enable us to adjust inhibitor injection rates based on system parameters, hence a more reliable and cost effective hydrate prevention strategy. In this communication we will present the developed techniques and some of the case studies.

Introduction

Injection of hydrate inhibitors is the most common measure to prevent hydrate blockages apart from dehydration and thermal insulation (including heating). There are three types of hydrate inhibitors in terms of inhibition mechanisms, including thermodynamic hydrate inhibitors (THIs), kinetic hydrate inhibitors (KHIs), and anti-agglomerants (AAs). THIs inhibit hydrate formation by shifting the hydrate phase boundary to lower temperature and higher pressure, moving the operation conditions outside the hydrate stability zone (HSZ), while KHIs do not prevent hydrate formation but delay hydrate nucleation and hinder hydrate crystal growth within a certain degree of subcooling, which allows the hydrocarbon fluids sufficient time to pass through the length of a transport pipeline where the thermodynamic conditions are inside the HSZ [1–5]. Contrary to THIs and KHIs, AAs allow hydrate formation but prevent individual hydrate crystals from agglomerating together, therefore, maintain the hydrocarbon system transportable [5, 6].
Acquiring and Maintaining Social License to Operate During the Lifecycle of Major Oil and Gas Operations
Authors: Gilbert Katherine , Canning James W.
Published: March 2015

Introduction

This paper addresses some of the key considerations and activities required in order to acquire and maintain a Social License to Operate (SLO) throughout the full life-cycle of major upstream oil and gas projects and operations (hereafter referred to as a Project or Operation). Operations in both Papua New Guinea and Chad, representing different phases of the lifecycle, were examined in order to identify key strategies and lessons learned.

Overview

The upstream lifecycle of an oil and gas project typically begins with exploration activities, moves into the design and construction of facilities and infrastructure following discovery of commercial quantities of oil and gas, transitions into production operations and then ends with decommissioning. It is important to identify and address the socioeconomic aspects and risks associated with each phase of the operation as early as possible and with a long-term, strategic view. Any commitments, expectations and relationships established with local stakeholders during one phase can have positive or negative impacts on successive phases of the operation. Since there are often significant changes to the scope of activities that take place within a given community throughout the life-cycle, it is imperative to identify a strategy that allows for both the successful acquisition and long-term maintenance of a SLO. Stakeholders and issues will likely change during the life-cycle, so the SLO Strategy must take that into consideration.

What is a Social License to Operate?

There are varying definitions of SLO which are used by different entities depending on the context of the country in which they operate. One way to define SLO is the degree to which a company and its activities are accepted by the local network of stakeholders, including government, landowners, the local communities and any other people directly affected by an Operation. This unwritten social contract is earned and maintained through relationships based on honesty, transparency and respect. Ongoing approval by stakeholders is based on the company's on-the-ground performance.
Prediction of Critical Gas Velocity of Liquid Unloading for Entire Well Deviation
Authors: Li Jeff , Almudairis Fahad , Zhang Hong-quan
Published: March 2015

Liquid loading is a common production problem in mature gas wells. As the formation pressure decreases and gas flow rate also decreases, the gas kinetic energy is unable to lift the liquid phase completely to the surface. Liquid starts to accumulate at the bottom of the well, which increases the back pressure of the reservoir. This is reflected in a fluctuated production of liquid and gas rates. At the same time, it significantly reduces the production rate and eventually kills the well. Correct prediction of critical gas velocity at which the well starts to load is very important to the operators since they could take appropriate measures to prevent liquid loading and extend the well production life.

In the past, most studies on liquid loading focused on vertical wells. Only recently have a few studies been conducted to deal with the liquid loading for deviated and horizontal wells. To date, there are few published studies discussing how to predict the critical gas velocity across a wide deviation angle range. In fact, there are contradictory conclusions made by different researchers. In this paper a database related to the critical gas velocity is compiled with data from published literature. A new model is developed and evaluated with the experimental data. The gaps in the previous studies and modeling are also discussed.

Introduction

Gas wells often produce water and other condensate. In the early production stage, the gas flow rate is high enough to carry the produced liquids to the surface. As the reservoir pressure is depleted, the produced gas flow rate decreases until the gas reaches a critical condition at which time the liquid loading is initiated. At the inception of liquid loading, the gas flow rate is not enough to carry the liquid completely to the surface and the liquids start to accumulate at the bottom of the well. Then, the back pressure builds up and the increased reservoir pressure will eventually be sufficient to lift the liquid to the surface. Once the liquid slug is pushed out by the gas, the liquid starts to reload the well again and the cycles are repeated again and again until the well is eventually loaded completely and gas production stops. Accurate prediction of liquid loading in the well is very important to the operators since this will allow them to take the necessary measures to void liquid loading and extend the well production life. The most common liquid loading symptoms observed in the field are pressure (or pressure gradient) fluctuations and reduction of gas production.

In general, there are two different liquid loading principles proposed in the literature: liquid droplet fall back and liquid film reversal. The liquid droplet mechanism is based on the falling back of liquid droplets while the liquid film concept is related to the partial or full reversal flow of the liquid film.
Electro-Magnetic Sensitivity in the Bengal Basin: Implications for Exploration in Myanmar, Bangladesh and NE India
Authors: Filipov Allan , Dilindi Robert , Drage Magne
Published: March 2015

The Ganges Brahmaputra Delta and the associated Bengal Fan is the world's largest delta/submarine fan complex. The deepwater areas of the Bengal and Rakhine Basins are relatively underexplored frontier areas. In 2003 the large Shwe gas field was discovered in Lower Pliocene turbidite fan sediments with reserve estimates of 6–9 tcf. As additional blocks are licensed, new data will be acquired to evaluate the area including 3D CSEM which is being considered as a complementary exploration method to seismic data.

The controlled-source electromagnetic (CSEM) method has been applied to oil and gas exploration and production for more than 10 years. EM data are used to indicate the presence of hydrocarbons, since hydrocarbon saturated rocks display higher electric resistivity compared to water-filled reservoirs. CSEM is an excellent technique to define the lateral extent of hydrocarbon accumulations and is particularly useful in determining the existence and extent of stratigraphic accumulations.

3D modelling indicates CSEM is sensitive to the Shwe Field reservoirs and can define the lateral extent of the pay zones. 3D CSEM forward modelling has been performed over a range of target sizes within the economic limitations of deepwater drilling, and the modelling shows that CSEM would be sensitive to those targets.

Based on these results, it is concluded that CSEM 3D data will detect the presence of hydrocarbon accumulations and thus, high-grade exploration areas in the greater Bengal Basin.

Introduction

In this paper we describe how the deepwater reservoir sediments in the Bay of Bengal, dominated by a deepwater turbidite depositional process, is the ideal geologic setting for detecting resistive anomalies related to hydrocarbon accumulations. Turbidites, by nature, are anomalous deposits of sand encased in shale. When saturated with hydrocarbons, they are more resistive than the surrounding shales, allowing them to be detected using the marine controlled source electromagnetic (CSEM) method. CSEM is sensitive to the large Shwe field accumulation on the shelf, offshore Myanmar and is used in this study to illustrate the ranges of detectability in the adjacent deepwater areas (Fig. 1).
Aligning Shutdown Plans of Multiple Projects to Minimise Production Loss - 3 Years Look Ahead Model
Authors: Al-Jabri Saleh Mohammed , Kumar Kenneth Prem , Al-Qazweeni Mahdi Mohammad
Published: March 2015

Description: Marked by rapid expansion and revamp, year 2012–13 for KOC's NK directorate experienced situation wherein each of the operating facility (3 Gathering Centers- 450MBOPD, 1 Water Injection plant-300 MBWPD; 1 Sea Water Treatment Plant-300 MBWPD) required multiple Shutdowns to cater for Tie In requirements of 5 different projects (different time lines) & Preventive Maintenance.

Catering to individual project shutdown requirements meant huge production loss and the only way feasible to minimize the same was to accommodate Tie In requirements of all projects, in parallel within a single or maximum two shutdowns per facility. To minimize these losses, KOC concentrated on program management focusing on interfaces between projects to develop a feasible aligned shutdown plan and to accomplish it successfully across all facilities.

The paper intends to highlight critical elements of the planning & implementation phases of the aligned shutdown plan like; Tie In scopes (all disciplines) & schedules specific to each project, tools used for decision making, Identification & management of risks and project interfaces, communication management, resource management, monitoring progress and coordination (12 KOC Teams & 5 Contractors).

APPLICATIONS: All Brownfield projects

RESULTS & CONCLUSIONS:Savings of more than 1000 million USDSafety Enhancement by avoiding repletion of hot works on critical Hydrocarbon lines (Tank Vapor header, Flare header etc.)Reduction in Flaring.Reducing the number of shutdowns helped minimizing numerous startup & shutdown problems associated with ageing facilities.

With the availability of PM shutdown every year, aligning project Tie had been relatively easier; however with the concept of partial shutdown for Preventive Maintenance, shutdowns of long durations won't be available. Thus, in future Facility Shutdowns of long durations will have to consider addressing Tie In requirements of all projects (3 years look ahead) irrespective of project stage.
Sedimentology and Diagenesis of Deeper Clastic Reservoirs: Some Insights from Recent Exploration Wells in Offshore Sarawak, Malaysia
Authors: Pendkar Narender , Bt. Zainun Fakhitah , Parsuram Satyabrata Nayak , Bin A. Aziz Anuar , Bin Ali Mohd Firdaus , Bt. Embi Rahida
Published: March 2015

The present study integrates the laboratory data from sidewall cores (RCA, petrography, XRD and SEM) with sedimentological observations (cores, wireline and image logs). Compositionally the sandstones are fine to medium grained sublitharenites to litharenites, with lithic fragments of metamorphic, reworked sedimentary and volcanic rock types. The diagenetic events observed in the sandstones are compaction, dissolution of feldspar and lithics, cementation (pyrite, silica, calcite, siderite dolomite and ferroan carbonate), and clay formation (kaolinite and illite). The porosity type comprises of primary intergranular, secondary and microporosity. The environment show a gradual change from upper reaches of the lower coastal plain with fluvial dominant regime for Cycle I to lower reaches of the lower coastal plain with increasing marine influence in Cycle II. The reservoir quality is controlled by both petrofacies and grain size variations.

Introduction

The ongoing drilling campaign in offshore Sarawak has resulted in the discovery of potential reservoirs from deeper Cycle I and II, previously considered tight and thus opening new frontiers for exploration. The study area lies within several geological provinces of Central Luconia, SW Luconia and West Balingian (Figure 1 and 2). The generalized stratigraphy, tectonics and paleogeographic evolution for the Cycle I and II are depicted in Figure 1 (Madon, 1999). In the subsurface the Cycle I and II sediments can be recognized using biostratigraphy, well logs and to a limited extent on seismic datasets; the concept of Cycle as originally defined by Ho Kiam Fui (1978) has been used for defining the cycle boundaries. Accordingly, the base of a cycle is taken for practical reasons at the base of the most transgressive interval. The electrolog signatures across the block show good lateral correlations and can be used with reasonable confidence (Figure 2).

Methodology

The present study was undertaken to comprehensively evaluate the sedimentological controls for understanding the reservoir quality from eight exploratory wells obtained during the last few decades. The observations and datasets from limited conventional and sidewall cores form the basis of this study. Laboratory data (RCA, petrography, XRD and SEM), wireline and image logs were integrated to understand the petrofacies, diagenesis and depositional trends. The petrographic, mineralogical and textural data is limited especially for the deeper Cycle I sandstones. The analytical datasets have been standardized and plotted to make meaningful interpretations and comparisons. For understanding the sandstone compositions, the modal data obtained from petrographic examination was plotted using Folk (1980) techniques for classification of sandstones and lithic grains.
Integration of Rock Physics Model in Reservoir Characterization - a Case Study from Malay Basin Malaysia
Authors: Pathak Ravi Kant , Ali Zulfiqar , Bakar Rizal
Published: March 2015

Introduction

Rock physics is considered as essential link between reservoir & seismic properties that allows improved reservoir characterization. While petro-physical evaluation provides information about 1D lithology, porosity and saturation information, rock physics add value in their interpretation in terms of geological control over reservoir development and fluid mixing model such as uniform or patchy saturation. Rock physics models developed based on integration of well and core data facilitates reliable prediction of reservoir properties beyond the well control from elastic properties estimated from seismic data. In the paper, authors demonstrate the value gained through establishment of rock physics model from well and core data and its potential application for improved prediction of reservoir properties in Malay basin.

The study area is a part of Malay basin located 170 Km offshore Terengganu at about 76 M water depths. The field is an E-W elongated four way structural closure. The reservoirs are 3–10 M average net thickness comprised of middle to upper Miocene fine-grained sand and silts inter-bedded with clay & coals deposited in a coastal plain setting.

Rock Physics Diagnostics

Rock Physics diagnostics (RPD) has emerged as a tool to establish the relationship between seismic velocity and porosity consistent with geological control over reservoir development to support the development of Rock Physics Model. In the study, the solid phase components and their proportions have been established from Sand-Slilt-Clay (SSC) model. Figure 1 shows the reservoir lithology and fluid characteristics as established from Petro-physical evaluation of a representative well within the study area.
Imaging on the Edge - Processing Challenges of a Sparsely Acquired 3D-2C OBC Survey, Offshore Malaysia
Authors: El Kady Nabil , Ghazali Ahmad Riza , Hoong Tang , Widjianto Yeni P. , Chandola Sandeep Kumar , Sharma Sachin Kumar , Abdul Rahman Mohd Ramzi , Nyein Glenn , Sazykin Artem , Goswami Saumya Kanti , Hamdani Ahmed
Published: March 2015

Introduction

Seismic data acquisition using ocean-bottom cable (OBC) methods, whilst capturing valuable azimuthal information, often presents challenges in the signal processing sequence for successful removal of unwanted noise and multiples-related energy. Herein, we present the results of methods that have enhanced the standard noise and multiple attenuation workflows. We present results on linear noise and shear-wave removal utilizing wavelet scale decompositions to complement tau-p transforms, receiver and source line interpolations using a "beyond-aliasing" approach for improved multiple model prediction and also subsequent imaging, and wavefield extrapolation to sea level plus adaptive subtraction for long-period multiples removal.

Whilst it is always desirable to acquire data with uniform and dense coverage, acquiring 3D OBC wide-azimuth surveys can be challenging and expensive due to limits imposed by operational complexity and safety, time scheduling due to weather windows and environmental considerations, in-situ infrastructure and obstructions, and others. This typically results in compromises to surface acquisition grid sampling, i.e., large source and/or receiver line spacing. To mitigate the sparseness of OBC acquisition, an innovative and cost-effective staggered-grid source-receiver survey design was implemented, with the goal of improving spatial sampling without incurring the need for more equipment or increased operational complexity (Chandola et al., 2014). In this work, we show the effect of the surface grid on seismic processing and imaging and illustrate seismic data processing techniques to improve surface coverage further to overcome the acquisition limitations efficiently.

Survey Geometry

The survey geometry was oriented north-south for receiver lines, and east-west for source lines. The nominal spacing between receiver lines was 300 m and 250 m for source lines, whilst the receiver interval was 50 m and the source point interval was 25 m. Water depths within the survey area ranged from 8 m to 50 m (Figure 1).

An innovative staggered grid source plus receiver layout was implemented within the development area. The goal was to increase spatial subsurface sampling from 12.5- x 25-m bins within the exploration areas, to 12.5 m x 12.5 m within the developmental areas without incurring additional acquisition cost. This staggered design was coupled with denser source line spacing in the developmental area to improve the coverage fold and near-offset distribution.
Mechanical Damage Characterization in Proppant Packs Using Acoustic Measurements
Authors: Aderibigbe Aderonke Abiodun , Valdes Clotilde Chen , Heidari Zoya , Fuss Tihana
Published: March 2015

The strength and conductivity of proppant packs are key parameters for assessing their performance. Mechanical damage in the propping agents, leading to compaction and crushing, significantly reduces the conductivity of the proppant pack. Mechanical damage of proppants is usually analyzed using crush tests. However, measurements from these tests remain questionable because of discrepancies in procedures and test results. Therefore a need emerges to develop techniques for characterizing the properties and mechanical damage in proppant packs.

In this paper, we introduce a new technique based on interpretation of acoustic measurements to quantify mechanical damage in propping agents. We performed uniaxial compression tests in the laboratory and measured the compressional- and shear-wave velocities in proppant packs loaded at axial stress ranging from 10 MPa to 110 MPa. After unloading the tests in which maximum axial stress of 28, 55, 69, 97 and 110 MPa were applied, we conducted sieve analysis on the proppant packs. We applied an effective medium theory based on the Hertz-Mindlin model to approximate the effective elastic properties. We then calibrated the model using the elastic properties estimated from the experimental measurements to characterize the mechanical damage of the proppant packs.

Introduction

Proppants are used to create conductive pathways for reservoir fluids by keeping the created fractures propped open in hydraulic fracture stimulation treatments. The application of proppants in stimulation treatments is largely influenced by properties such as permeability, conductivity, and resistance to crush. The reduction in fracture conductivity is usually associated with proppant failure and fines migration. The failure of proppants can occur as a result of geochemical reactions and/or mechanical damage.
An Innovated Approach for History Matching by Reliable Fracture Modeling - Case Study of NKJ Gas Field
Authors: Ben Amor Faical , Amari Mustafa , Sharifzadeh Najafi Ahmad , Dashti Qasem , Al-Saffar Ali
Published: March 2015

Introduction:

The North Kuwait Jurassic Complex (NKJC) is composed of six fields and situated in the Northern part of Kuwait (Figure 1). The field is characterized by dual porosity/permeability in deep HP/HT conditions, with wide variety of hydrocarbon fluids ranging from volatile oil to gas condensate. The primary recovery mechanism and the recovery efficiency strongly rely on fractures. Therefore, reliable and calibrated fracture model is required in getting a representative dynamic model.

Using a wide range of 2D/3D seismic, geometrical and petrophysical attributes, a hybrid natural fractured reservoir static geomodel, made of Discrete Fracture Network (DFN) and Implict Fracture model (IFM), has enabled a reasonable 3D representation of three sets of fractures, identified based on well and seismic data:Fracture corridors associated to geophysically interpreted faults;Medium scale layer bound geomechanically controlled fractures; andFolding related fractures.

The new hybrid fracture model was calibrated using PLT, MDT and PBU data from more than 60 wells drilled in the reservoir.

This paper demonstrates how a calibrated hybrid fracture model has shortened the process of the history match significantly, which required only very small adjustments/alterations to the initial static model. The uncertainty and the challenges faced while calibrating the model were addressed, together with the highly sensitive parameters that were adjusted to match the dynamic data. Succeeding a smooth and timely history match resulted in significant CPU time gain, and an optimized well count that went into the Asset Action Plan.