bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Neutron Irradiation on Brittle Fracture Initiation in VVER-1000 Reactor Pressure Vessel Materials
Authors: Kuleshova E. A. , Artamonov M. A. , Erak A. D.
Published: July 2014

This work contains fractographic analysis of base metal and weld metal specimens of a VVER-1000 reactor pressure vessel (RPV) in initial state and after neutron irradiation. In this work, two main types of brittle fracture origins were discovered for VVER-1000 RPV materials in different states—non-metallic inclusions and grain or subgrain boundaries, as well as the correlation between the cleavage initiation distance and critical stress-intensity factor KJc values for each type of fracture origin. In this paper, evolution of relative proportion between these two types of origins under neutron irradiation was also studied.
Prolonged Adenosine A1 Receptor Activation in Hypoxia and Pial Vessel Disruption Focal Cortical Ischemia Facilitates Clathrin-Mediated AMPA Receptor Endocytosis and Long-Lasting Synaptic Inhibition in Rat Hippocampal CA3-CA1 Synapses: Differential Regulation of GluA2 and GluA1 Subunits by p38 MAPK and JNK
Authors: Chen Zhicheng , Xiong Cherry , Pancyr Cassandra , Stockwell Jocelyn , Walz Wolfgang , Cayabyab Francisco S.
Published: July 2014

Activation of presynaptic adenosine A1 receptors (A1Rs) causes substantial synaptic depression during hypoxia/cerebral ischemia, but postsynaptic actions of A1Rs are less clear. We found that A1Rs and GluA2-containing AMPA receptors (AMPARs) form stable protein complexes from hippocampal brain homogenates and cultured hippocampal neurons from Sprague Dawley rats. In contrast, adenosine A2A receptors (A2ARs) did not coprecipitate or colocalize with GluA2-containing AMPARs. Prolonged stimulation of A1Rs with the agonist N
6
-cyclopentyladenosine (CPA) caused adenosine-induced persistent synaptic depression (APSD) in hippocampal brain slices, and APSD levels were blunted by inhibiting clathrin-mediated endocytosis of GluA2 subunits with the Tat-GluA2–3Y peptide. Using biotinylation and membrane fractionation assays, prolonged CPA incubation showed significant depletion of GluA2/GluA1 surface expression from hippocampal brain slices and cultured neurons. Tat-GluA2–3Y peptide or dynamin inhibitor Dynasore prevented CPA-induced GluA2/GluA1 internalization. Confocal imaging analysis confirmed that functional A1Rs, but not A2ARs, are required for clathrin-mediated AMPAR endocytosis in hippocampal neurons. Pharmacological inhibitors or shRNA knockdown of p38 MAPK and JNK prevented A1R-mediated internalization of GluA2 but not GluA1 subunits. Tat-GluA2–3Y peptide or A1R antagonist 8-cyclopentyl-1,3-dipropylxanthine also prevented hypoxia-mediated GluA2/GluA1 internalization. Finally, in a pial vessel disruption cortical stroke model, a unilateral cortical lesion compared with sham surgery reduced hippocampal GluA2, GluA1, and A1R surface expression and also caused synaptic depression in hippocampal slices that was consistent with AMPAR downregulation and decreased probability of transmitter release. Together, these results indicate a previously unknown mechanism for A1R-induced persistent synaptic depression involving clathrin-mediated GluA2 and GluA1 internalization that leads to hippocampal neurodegeneration after hypoxia/cerebral ischemia.
Constructing Glinka
Authors: Zavlunov Daniil
Published: July 2014

After more than a century and a half of studying Glinka, we hardly know Glinka: he remains ever elusive and illusive. And that is because Glinka is a construct, one that came into existence in the stories of those who knew him. In this study I examine the posthumous construction of Glinka by the members of his circles, concentrating on the primary sources that originated as obituaries and commentaries to the publications of Glinka’s letters and his autobiography, the Zapiski. The enigmatic image that Glinka left behind compelled many of his acquaintances to rush in to control the damage, offer their correctives, preserve their perception of the true Glinka, and claim him for their ideological causes; they also aimed to uphold and partake in his legacy. The result was a series of astonishingly diverse and conflicting representations of Glinka that laid the foundation of the Glinka mythology, without which the subsequent canonization(s) of the composer would have been impossible. Although I consider in some detail the historiographic problems in the way the sources have been used in Glinka scholarship, my primary concern is with the sources themselves, with the questions of who speaks for Glinka, why they do so, and how. In answering these questions I seek to deconstruct and contextualize the hagiographies by looking at the writers who produced them, specifically through the lens of the social circles to which they and Glinka belonged.
Sharpening rhomboid specificity by dimerisation and allostery
Authors: Strisovsky Kvido , Freeman Matthew
Published: July 2014

In this issue of The EMBO Journal, mechanistic analyses of substrate cleavage by rhomboid intramembrane proteases suggest that catalytic efficiency towards natural, transmembrane substrates is allosterically stimulated by initial substrate interaction with an intramembrane exosite, whose formation depends on rhomboid dimerisation. In the realm of intramembrane proteolysis, dimerisation and allosteric cooperativity represent new concepts that, once confirmed more broadly, should radically alter our view of how these proteases work.
Symptomatic Lipoma of the Internal Auditory Canal: CT and MRI Findings
Authors: Filli Lukas , Huber Alexander , Husain Nader Al-Haj
Published: July 2014

We describe the case of a 39-year-old man in whom diagnostic work-up for combined right-sided hearing loss revealed a lipoma of the internal auditory canal (IAC). This very ran diagnosis has significant implications for therapeutic management because lipomas, unlike other lesions in the IAC, should not be surgically removed in most cases. We emphasize the importance of the combined use of magnetic resonance imaging and computed tomography to reliably establish the diagnosis of a lipoma, differentiate it from other potential lesions of the internal auditory canal and exclude additional pathologies in the petrosal bone.
Representações e estereótipos das pessoas com deficiência como consumidoras: o drama dos personagens com deficiência em telenovelas brasileiras
Authors: Faria Marina Dias de , Casotti Leticia Moreira
Published: July 2014

A despeito de serem importantes meios de comunicação da cultura, dos valores e das perspectivas vigentes em uma sociedade, os textos culturais configuram possibilidades pouco exploradas em pesquisas acerca do comportamento do consumidor com deficiência. No Brasil, novelas televisivas parecem ser textos culturais adequados para esses estudos, tendo em vista a importância apresentada pelas telenovelas como programas transclassistas de abrangência nacional. Definiu-se como objetivo do estudo discutir as representações e os estereótipos das pessoas com deficiência (doravante PcD) como consumidoras apresentados em telenovelas brasileiras. Para atingir o objetivo foram analisadas cenas de 22 telenovelas brasileiras que mostram personagens com deficiência em situações de consumo. Os resultados do estudo alertam para a necessidade de que empresas, instituições públicas e a sociedade em geral revejam a forma como lidam com esses consumidores quase invisíveis que, muitas vezes, não são considerados como potenciais clientes e são excluídos de ações de políticas públicas.
Oldest Omaliini (Coleoptera: Staphylinidae: Omaliinae) Discovered in the Opaque Cretaceous Amber of Charentes
Authors: Peris D , Thayer M K , Néraudeau D
Published: July 2014

Belonging to the Staphylinidae, the largest animal family known, recent Omaliinae are a diverse and widespread group of rove beetles. There are omaliine representatives known since Early—Middle Jurassic compressions, but members of the tribe Omaliini have been known only from the Cenozoic. Duocalcar geminum Peris and Thayer gen. et sp. nov. is described as the oldest definitive fossil of the tribe Omaliini worldwide, originating from opaque mid-Cretaceous (latest Albian) amber of Charentes, south-western France. The discovery and description were made possible with the use of the propagation phase-contrast X-ray synchrotron imaging technique, which allows the detailed study of otherwise invisible specimens in opaque amber.
China clay waste as aggregate in alkali-activated cement mortars
Authors: Zografou Adamantia , Heath Andrew , Walker Pete
Published: July 2014

Every 1 t of china clay produced in the UK generates 9 t of waste material. A limited quantity of the coarser waste has beneficial use as a building stone or secondary aggregate in concrete and asphalt, but there are currently limited uses for the finest waste fraction. ‘Mica’ waste is a mixture of fine minerals and is one of the forms of waste with little beneficial use other than the restoration of old quarries. With an aim to find new commercially viable and low environmental impact uses in construction, this paper focuses on the use of china clay waste as an aggregate in alkali-activated cement mortar. Based on preliminary analysis of the compressive strength of binders using slag and fly ash, optimum binders were selected to produce mortars using mica and other forms of china clay waste as aggregate. The mortars were then compared in compression with control specimens using standard sand. Although the results show that the test mortars were generally weaker than the control samples, the paper concludes there are opportunities for their use.
Artificial ground freezing of a volcanic ash: laboratory tests and modelling
Authors: Casini Francesca , Gens Antonio , Olivella Sebastia , Viggiani Giulia M. B.
Published: July 2014

The use of artificial ground freezing (AGF) to form earth support systems has had applications worldwide. These cover a variety of construction problems, including the formation of frozen earth walls to support deep excavations, structural underpinning for foundation improvement and temporary control of ground water in construction processes. On one hand, the main advantage of AGF as a temporary support system in comparison to other support methods, such as those based on injections of chemical or cement grout into the soil, is the low impact on the surrounding environment as the refrigerating medium required to obtain AGF is circulated in pipes and exhausted in the atmosphere or re-circulated without contamination of the ground water. On the other hand, the available methods may vary significantly in their sustainability and complexity in terms of times and costs required for their installation and maintenance. The ability to predict the effects induced by AGF on granular materials is therefore crucial to assessing construction time and cost and to optimising the method. In this work, the thermo-hydro-mechanical processes induced by artificial freezing of a soil body are studied using a constitutive model that encompasses frozen and unfrozen behaviour within a unified effective-stress-based framework. It makes use of a combination of ice pressure, liquid water pressure and total stress as state variables. The model is validated and calibrated using the results of a series of laboratory tests on natural samples of a volcanic ash (Pozzolana) retrieved during construction of Napoli underground, where the technique of AGF was used extensively to stabilise temporarily the ground and control the ground water.
Centralised Produced Water Treatment in the Niger Delta; A Cure-All for Disposal and Re-Injection Requirements?
Authors: Murray Graeme
Published: July 2014

When developing marginal fields, the maximisation of production and the minimisation of cost are two key drivers. This paper is concerned with one of the main cost streams in terms of capex, opex, environmental threat and management time; the treatment and disposal of produced water. Whilst many of the concepts are applicable to any marginal field development, the thrust of the paper is aimed at the Niger Delta's particular situation.

To effectively design water treatment and injection systems, a wide range of skills is needed. If water is required for pressure maintenance or sweep, the decision must be taken whether to use produced, aquifer, sea or commingled water. The water needs to be accurately characterised (a difficult task in itself). The potential for scale formation and souring must be assessed. The geology of the injection zone should be understood and its injectivity measured. The best techno-economic treatment and injection system needs to be designed; this should be robust and well-proven for use in local conditions.

Worldwide, there is a shortage of ‘available’ oilfield water management expertise. It is therefore unrealistic to expect fledgling oil companies to have such expertise in-house. If each oil company in the Delta Region ‘goes it alone’ the repercussions will include: a) fewer available experts; b) greater capital expenditure and environmental damage across the region due to ‘sparing’, construction and drilling; c) lack of water trading; d) less ability to provide community services of substance; e) greater risk of environmental incidents, and; f) increased regional opex.

This paper describes the rationale for a small number of centralised water processing systems: each taking water from several oil companies; disposing or re-supplying it responsibly and providing in-depth assistance to the local communities; with expected savings in project studies, implementation time, capex, opex, environmental clean-up and water resources.
Evaluation of Safety Performance and Compliance of Workers in Selected Oil and Companies in Nigeria
Authors: Stella Anumadu Ugochi , Dosunmu Adewale , Anyanwu Chimaroke , Ekeinde Evelyn , Odagme Baridor
Published: July 2014

In both developed and developing countries, the oil and gas industries are considered to be one of the most significant industries in terms of its impact on health and safety of the working population. Oil and Gas industries are both economically and socially important. However, the oil and gas industries are also recognized to be the most hazardous. This research was set out to assess accident rate, safety performance and compliance in three different sectors of oil and gas producing companies in Nigeria (indigenous, national and international oil and gas industries) and to know DPR standard of safety for the oil and gas company.

The study populations were 474 staff of the three different sectors of oil and gas companies and 96 for DPR. 700 questionnaires were designed and administered. The response rate was 81.43%. The collected data was analysed descriptively to determine accident rate amongst the three different oil and gas sectors and using Kendall's coefficient of concordance to establish the level of correspondent of the respondents on awareness and compliance to safety standard and procedure.

The study revealed that the respondents of indigenous oil and gas companies has low safety standard when compared to DPR standard, low level of awareness (44%) and compliance (47%) to safety standard and procedures and high accident rate, national oil and gas companies respondents revealed safety standard above average, good level of awareness (56%) and compliance (53%) to safety standard and procedures and low accident while for the international oil and gas
Sodium Silicate Cement Squeeze Best Practice
Authors: Garba M. D. , Petitt I. , Macphee D. E.
Published: July 2014

Setting a conventional cement plug is nearly unsuccessful when there is any wellbore flow especially for the zechstein formations. As such, the used of sodium silicate remain the common option. The silicate polymerization and gelation has been used in well formation to plug holes and reduce the catastrophic flow which cause a lot of production loses. This is usually encountered during drilling rocks zone producing large amount of water or brine. This could result in large volume of the drilling fluid lost into the formation and consequently reduce the effectiveness of the drilling operations. The total successfulness of sodium silicate/cement squeeze depends strongly on whether the cement placed in the desired place without any contamination. Contamination from Oil Base Mud (OBM), Brine influx in the formation can affect the properties of the cement and lead to the failure of it is placement. Other factors include too low concentration of the silicate and or fresh water dilution may also contribute to some extent as tentatively drawn from a bottle test. The thesis focuses on the laboratory evaluation of the likelihood of this contaminant resulted in the sodium silicate/cement squeeze failure in Swift well. The chemistry of their interaction with the cement slurry is discussed. The zechstein brine is prepared using a programmed spread-sheet provided by Shell UK Company based on typical Molln formation as produced from a well in Germany

Compressive strength, thickening time and consistency of the source contaminant were measured varying the volume of the contaminant to see their influences comparing to the neat cement and to see how the extent of these contaminations affected the cement properties. Conclusions were made base on the change of these properties observed on what potentially contribute to it is failure
Improving Oil Production and Recovery Using WAG Injection; A Niger Delta Case Study
Authors: Mayowa Sunmonu Rasak , Ajiboye Oluwatosin , Olominu Oluwafemi
Published: July 2014

The days of easy oil are going. The frontier of oil and gas exploitation continues to be pushed further as a result of oil price volatility, new technologies, and an ever dynamic political and economic atmosphere. Production by primary and secondary recovery have been known to only recover a limited fraction of the oil in place thus the need to look into more innovative ways to improve recovery especially in declining assets through suitable EOR methods.

Several EOR techniques have been developed for improving oil recovery from reservoirs one of which is Water Alternating Gas (WAG) injection. In this work, WAG is presented as a potential candidate to increase oil productivity in the Niger delta. WAG involves the cyclic injection of water and gas into the reservoir so as to squeeze out more oil. By decreasing gas mobility and capillary forces, guaranteeing effective microscopic displacement due to gas flooding and reducing the mobility ratio thus improving the macroscopic sweep created by water injection, it combines the advantages of water flooding and gas injection in optimizing residual oil production.

This study aims at investigating the possible increase in oil production and reserves from a Niger Delta field through the use of Immiscible WAG injection as an EOR process. In conducting this study, various development strategies such as Gas Injection, Water Injection and Immiscible WAG were proposed in exploiting the reservoir. Using a conventional 3-D numerical simulator to mimic the process, comparison was then made between the various strategies where results such as field oil recovery, cumulative oil recovery and production rate were analysed. With Immiscible WAG injection, an increase in recovery above the very popular gas injection or water injection was observed. Parameters critical to the success of a WAG enhanced oil recovery process such as three-phase flow, hysteresis effect, WAG cycle, WAG ratio, and Injection rates and their effects was also studied.
Feasibility Study of Improved Gas Recovery by Water Influx Control in Water Drive Gas Reservoirs
Authors: Ogolo N. A. , Isebor J. O. , Onyekonwu M. O
Published: July 2014

Gas recovery factor from water drive gas reservoirs is very low compared to recovery made from depletion drive gas reservoirs. Other problems associated with gas recovery from water drive mechanism include high residual gas saturation in the water invaded zone of the reservoir, high volume of produced water, abandonment at high reservoir pressures and high possibility of hydrate formation in pipe lines. The use of carbon dioxide (CO2) in displacing natural gas from volumetric gas reservoirs has been studied, practised and is successful. In this paper, it is proposed that extending this practice to gas reservoirs under strong water drive mechanism can improve recovery and control water influx.

CO2 is denser than natural gas and water is denser than CO2. The different densities of these fluids can be taken advantage of to boost natural gas recovery from water drive gas reservoirs. The continuous CO2 injection process at the gas water (g/w) contact can partially prevent water encroachment into the system. The technique can change the water drive mechanism to full or partial depletion drive where CO2 will separate the natural gas zone from direct contact with the water zone. Any eventual water invasion into the reservoir affects the CO2 zone, not the upward moving natural gas zone.

This technique was studied by simulation using data from a lean gas reservoir under strong water drive. Two cases were considered. In the first case, which is the reference case, gas production under water drive was allowed for 30years. In the second case, CO2 was injected at the initial gas water contact for the same number of years. Simulation results showed that water production from the reservoir was drastically reduced to about 60% in the second case because the rate of water influx into the reservoir was controlled. Gas recovery from two producer wells out of three that were considered improved above 10% and gas condensate recovery was improved to about 4% over the period of production that CO2 was injected.
A New Approach to Water Saturation Modeling and Distribution in Dynamic Models Using Log Derived Saturation Height Function (SHF) (A Case Study of Niger Delta Province)
Authors: Omeke James E. , Ugwoke Marcel , Aihumekeokhai Basil O.
Published: July 2014

Complex variations in pore geometrical attributes, which in turn, defines the existence of distinct zones or hydraulic unit within a mappable geological facie or “rock type (RRT)' which have similar dynamic behavior is “masked” when “rock types (RRT's)” in reservoir simulators are assumed to be different geological facies of similar dynamic behavior. To effectively and accurately distribute water saturation (Swi) in the cells of dynamic model, capillary pressure (Pc) vs.Swi and relative permeability curves must be assigned such that they honor the pore system structure as well as the saturation from well logs. Therefore it might not be enough to assign one SHF for a given geological RRT. These poses a challenge, for example, in Niger Delta sandstone reservoir comprisingmainly alternating deltaic sandstone with shale suggesting two or three consistent RRT's with wide variability in Swi.

The proposed approach tends to develop a correlation that will consistently replicate the behavioral relationship between reservoir quality index ((RQI=0.0314K/∅ϵ)), effective water saturation S* = (Sw − Swirr)/(1 − Swirr) and Height above free water level(HAFWL) of both routine core and log data. This correlation is used to develop drainage log derived Pc and relative permeability curves for each class of RRT. Rock classification employed in this work was based mainly on irreducible water saturation(Swirr) classes. The SATNUM keyword in ECLIPSE was used to assign each SHF and relative permeability curve to the grid cells of the dynamic model based on the rock classification.

The developed SHF yielded an excellent match, both vertically and laterally, with log derived Swi and within 1% difference between static and dynamic hydrocarbon-in- place for some Niger-delta reservoirs studied. Also, a plot of Swi generated from the newly developed SHF at well points on the Y-axis and those from well logs on the X-axis yielded a 45° straight line through the origin with an R-square of 0.9935. The dynamic model stability and running performance was greatly improved using the developed SHF.
A Strategic Cost Saving Initiative for Dual-Zone Completions in Marginal Fields
Authors: Ogbunuju E. , Ekeigwe A. , Pepple B. , Ogaji D. , Yahaya I.
Published: July 2014

Dual zone gravel pack completions, mostly the preferred sand control mechanism of choice in unconsolidated stacked reservoirs, can be quite expensive in marginal field environment, particularly in the Niger Delta region due to high logistics and security costs associated with rig costs. This cost escalation (Rig spread, logistics, security and associated costs) progresses from land to swamp and ultimately offshore locations. Conventional techniques for such completions involve multiple trips in and out of the hole with gravel pack and isolation tools, with pumping stages and a wireline trip to set the sump packer. This process typically takes between 12-14 days and has often resulted in border line economics, when this technique is applied in a marginal field.

In this paper, we present a different sand control technique for carrying out a cost-effective completion for a two zone well in a marginal field, situated in the Niger Delta. This technique involves the use of Multi Mesh Screen (MMS) and can eliminate the use of gravel pack pumping treatments for several applications. It has specific design criteria for enhancing sand control and has found great application as standalone screen in cased hole.

The proposed system involves the combination of a special MMS with engineered electric-line deployed perforating technique. The entire deployment of a two zone completion required only about four days of rig time. Post completion, the deeper interval has been producing at an average oil rate of 220 bopd and associated gas production of 0.35 MMscf/d while the shallow interval has average production of ca. 500 bopd with associated gas production of 0.35 MMscf/d. Both intervals have performed at an order of magnitude higher than the predicted sand-free production rate without any or other conventional sand control methods. Overall, the use of this adaptive completion technique resulted in some 50% cost savings to the operator compared to the conventional gravel packing of both zones. This has greatly enhanced the economics of the well. The details of the installation design, field procedures along with an analysis of the production data and an economic comparison to the alternatives are presented herein.
Using Robust Torque and Drag Modelling Software For Efficient Well Planning and Operations Monitoring. Paradigm Sysdrill for OML 126 Wells – A Case Study
Authors: Ugochukwu Okoli , Verity Simon
Published: July 2014

The quest to appraise un-stacked reservoir sands and other surface location constraints has given rise to complex wellbore profiles due to the requirement of building angles and azimuth changes through these targets. This has increased the length and inclination of the wells drilled in the past decades. There are also larger departures and more tortuous wellbore. These trajectories can give rise to excessive torque and drag during the well delivery.

Excessive drill string torque and drag is one of the major limitations of horizontal and extended reach wells, and when unplanned is a primary limiter. Because of the increased costs and risks in these wells, torque and drag analyses is recognized as an important part of the risk management process.

Torque and drag models have proven to be very useful in the planning, drilling and post analysis of these difficult wells. During the planning stage they are used to optimize the trajectory design to minimize the torque, drag and contact forces between the drill string and the borehole wall. They are used during operations to monitor the hole conditions while drilling, diagnosing hole cleaning problems, watching out for impending differential sticking, and monitoring for high torque in planned highly tortuous trajectories. In post analysis the models help to determine the true causes of the hole problems, which will further be highlighted, documented and used to optimize operations.

Accurate torque and drag analysis gives an opportunity to build reliable well trajectories, as it will take into account the capabilities of the rig and the geological complexity of the formation to be traversed. Ideally the model must be able to predict with minimal error the forces and along the wellbore. Generally the discrepancy between torque and drag prediction and actual measurements in conventional wells is within 20% depending on the variables used. This percentage error might increase or decrease depending on the variables used for these models.

In this paper, a general overview of the torque and drag model is presented. It is then discussed how the Paradigm Sysdrill software has been able to accurately predict the torque and drag values of a planned wellbore. The error margin between the predicted and actual values was very minimal. This software has been able to effectively aid in the planning, monitoring and helped to give a reasonable and concise post mortem of the subject well that will be used as the case study in this paper.
Spreadsheet Modeling and Simulation Analysis of Production Sharing Contract Terms and Instruments in Nigeria
Authors: Echendu Joseph C. , Onwuka Emmanuel I. , Iledare Omowumi
Published: July 2014

This paper evaluates the economics of petroleum exploration and production (E&P) projects within the context of the expected economic value of a portfolio of blocks/fields owned and developed under the existing petroleum production sharing contracts (PSC), the jettisioned Inter Agency Team (IAT) memorandum on PIB 2008, and the Petroleum Industry Bill (PIB) 2012. The study incorporates important key variables in the determination of the expected or realized economic values from E&P projects including but not limited to location, technical cost & price, and field size. The model framework adopted for this paper is the Discounted Cash Flow (DCF) Model. The model framework is estimated by coding each segment of the DCF model equations in Microsoft Excel Spreadsheet to calculate deterministic economic and sytem performance measures, Government Take (GT), Discounted Government Take (DGT), and Front-end Loading Index (FLI). Two popular economic measures, the net present value (NPV) and internal rate of return (IRR), are derived and adopted to evaluate investment performance; and to account for uncertainties inherent in the data assumptions. A spreadsheet simulation tool is applied to quantify the impact of selected variables on relevant performance indicators using Monte Carlo simulation approach. Sensitivity analysis of decision variables and stochastic variables in the model is applied. The paper reports the P50 value of selected economic and system performance indicators. Simulation results show that for a viable deepwater project the unit technical cost (UTC) has to be within global average range of $27 and $35 per bbl; and contractor domiciling much of its cost at home. This enables the contractor to have a better IRR and helps to impact positively on local content. The result from this study shows that the PIB is less regressive than the earlier PSCs keeping in perspective our study assumptions.
The Effects of Natural Gas Flaring on Climate Change in Nigeria
Authors: Bisong Anthony Oso
Published: July 2014

Nigeria is a major producer and exporter of oil and gas in the world. Most oil and gas exploration activities takes place in the Niger Delta region of the country where there is high rate of gas flaring from oil and gas production. Although the federal Government of Nigeria had directed all oil and gas producing companies to reduce gas flare to a minimum by 2008 and stop total gas flaring by 2010 due to its effects on the environment and climate. Oil and gas companies are yet to implement these directives, making the country suffer intensive climate change, environmental degradation, revenue losses, chronic energy shortage, e.t.c. Despite the directive passed by the Nigerian Government declaring gas flaring technically, economically, environmentally and totally unacceptable, the oil and gas companies still flares billions of cubic meters of gas yearly. A huge amount of suffering, repression, depression, degradation, pollution and climate change have accompanied this long practice of gas flaring. Natural gas flaring emanating from hydrocarbon exploration has been internationally and locally acknowledged as a significant source of greenhouse gas emission and a major contributor to climate change. During combustion process, gaseous hydrocarbons react with atmospheric oxygen to form carbon monoxide (CO) – Incomplete combustion and carbon dioxide (CO2) – Complete combustion. Gas flaring also causes acid rain, produces air pollution and causes severe impact on the environment. This paper will extensively highlight the negative effects and impact of gas flaring, how greenhouse gases emission from gas flaring affects climate change, the environment and human lives and also proffer pragmatic and strategic measures to combat this unsafe, unhealthy and unfriendly practice in Nigeria.
Innovative Compact Sand Removal Technology: Developments, Qualifications and Successful applications
Authors: Opawale Adekunle , Abdalla Tarig
Published: July 2014

Sand particles are usually produced with oil, gas and water from the reservoir, constituting several operational challenges. Presence of sand in the production stream can cause erosion of upstream facilities and – even more commonly – clogging of flowlines and accumulation in production vessels; reducing residence time and thereby performance of separator internals. Operators have experienced expensive plant shut downs due to excessive sand production and hence demand for highly efficient, robust and compact solution for upstream sand removal from production streams.

This paper presents a recent advancement in the design of compact sand removal equipments, for applications in subsea separation systems, offshore topsides and onshore process plants. The FMC Technologies' inline desander technology is based on an innovative cyclonic separation principle, utilizing a smart stationary swirl element to develop an enhanced separation force.

The desander design is governed by mechanistic models which describe the dynamics of sand particles dispersed in a radial flow field. Produced sand particles are separated from process stream by virtue of their inertia, and radial acceleration developed within the motion field. They are extracted as concentrated slurry through the reject outlet of the desander. The unique geometry of the desander and its internal design enables development of a low pressure core inside it, which initiates a reversed flow of the clean separated fluid into an underflow outlet. As part of the development process of the inline desander, CFD simulation studies were also carried out to study the flow patterns developed in the desander and model the trajectory of the sand particles inside it.

Extensive technical information about the technology development process of the compact desander is discussed in this paper; with reference to qualification tests and R&D reports. Some of its successful applications in challenging situations and advanced production facilities are also discussed.
Chemical Compromise: A Thermodynamic and Ionic Solution for Hydrate Control
Authors: Olabisi Odutola Toyin , Sunday Ikiensikimama , Appah Dulu
Published: July 2014

In recent times, polymers and surfactants have been used to influence the kinetics of hydrate growth and coagulation. However, these Low Dosage Hydrate Inhibitors are limited in terms of water-cut and sub-cooling. This work considers using a blend of Thermodynamic Hydrate Inhibitor and Ionic Inhibitor for hydrate inhibition. A comparative study was carried out to evaluate the combined effect of Ionic and Thermodynamic Hydrate Inhibitors in preventing hydrate formation by combining their temperature depression using Hammerschdmidt and Østergaard equation. This work finds application in hydrate inhibition by reducing the dosage of inhibitors. This will be useful for deepwater reservoirs and flowlines having large subcooling temperature and (or) high water-cut. The Thermodynamic Hydrate Inhibitors used are Methanol, Monoethylene Glycol and Diethylene Glycol while the Ionic Inhibitors used are Calcium Chloride, Sodium Chloride and Potassium Chloride salts. It was observed that the dosage of Thermodynamic Hydrate Inhibitors reduced by over 14% when it was combined with Ionic Inhibitors. The best blend was the hybrid of Methanol and Sodium Chloride salt which saved about 34% of methanol. This simple approach to hydrate inhibition will enable the Engineer reduce the use of methanol or glycols based on the salinity of the formation water. The operator can also save a lot by using the hybrid instead of methanol or glycol alone.
New Techniques for Estimating Solution-Gas Drive Reservoir Properties Using Production Data
Authors: Mosobalaje Olatunde O. , Tiab Djebbar
Published: July 2014

A number of attempts have been made to establish the theories of rate decline in solution-gas drive reservoirs with multiphase flow, and to formulate techniques for reservoir properties estimation using production data. Until recently, none of the attempts have established a consistent functional link between the empirical and the theoretical domains of decline analysis for such reservoirs. The absence of such link has inhibited the formulation of simple techniques for reservoir properties estimation.

This work presents a new, simple technique for estimating reservoir permeability in solution-gas drive reservoirs, using production data. The technique is based on a recently-established relationship between the empirical and the theoretical domains of decline curve analysis for solution-gas drive reservoirs. The technique has been applied to a number of cases and found to yield excellent estimates of reservoir permeability, even for heterogeneous reservoirs. In addition, this work presents a new technique for estimating a well's drainage area, using production data in solution-gas drive reservoirs. This is based on a 2-phase material balance equation. Analyses have been performed on the sensitivity of the techniques to some key parameters.
A Simple Approach to Determining Original Gas-in-Place Using Production Data
Authors: Mohammed S.
Published: July 2014

A simple approach is presented that utilizes production data to determine original gas-in-place (OGIP). In particular, we propose a "modified" Agarwal-Gardner rate/cumulative decline type curves that yield an anchor point of unity, instead of 1/2π. The advantage of this unit anchor point is that, the normalized pseudopressure drop ratio, which is a plotting function on the abscissa, need not be modified; hence, providing a simpler approach than the traditional methods.

The computation of pseudopressure drop ratio (or pseudocumulative function) requires a prior knowledge of average reservoir pressure history, or indirectly, OGIP. Consequently, various methods have been proposed in the literature to solve OGIP. This paper utilizes an approximate gas flowing material balance equation, which was previously presented by this author, to make an initial estimate or provide a "true window" for OGIP. This approximate plot yields two negative slopes during boundary-dominated flow regime – early-time pseudosteady state and late-time pseudosteady state lines. The early-time pseudosteady state line is shown to yield a reasonable initial estimate of OGIP while the late-time pseudosteady state line yields an optimistic result.

The proposed approach is applicable to general variable pressure and/or variable rate case for single- and multi-well systems during boundary-dominated flow regime. The method is validated with two simulated data; and then, applied to two field data – one from a single-well system and the other from a multi-well system.
Fast Algorithm for Calculating Present Values and Rate of Return on Investment
Authors: Adeniji A. , Idigbe K. I
Published: July 2014

The popular yardsticks for ranking ventures in order of their profitability, among others, are rate of return on investment and present value. This paper describes applications of polynomial algorithms for fast and efficient determination of present-day value of total profit for a fixed interest rate and internal rate of return. Thus, establishing the value of the cash flow backs compared to the expenditures and the time value of money become trivially algebraic formulated using a discount rate compatible with the average rate of return on equity.

Average rate of return on investment based on predicted cash flow backs compared to force value of investment to balance value of cash-flow-back at some common reference time, the time of investment. This leads to another definition; the internal rate of return is the rate of interest that makes the present-day value of the total income equal to the capital investment. Emphasis is placed on the proper utilization of the results in development of realistic mathematical model and proper consideration of profitability in economic evaluation. Application of digital electronic computer simplifies the extremely cumbersome calculation in 3-step algorithm.
Improved Method of Predicting and Monitoring Flow Assurance Problems in the Niger Delta Using PROSYS
Authors: Osokogwu U. , Emuchay D. , Ottah D. G. , Aliu S. , Ajienka J. A.
Published: July 2014

Flow Assurance – a term used to evaluate the effects of fluid hydrocarbon solids (i.e. asphaltene, hydrate and wax) and their potential to disrupt flow of hydrocarbon fluids in the flow lines due to deposition in the flow system. This study presents a quick and easy tool – PROSYS - that helps in the preliminary screening of asphaltene to determine if the operator will experience severe or mild problems arising from deposition of asphaltene and also estimates the dissociation temperature of hydrate in a pipeline during depressurization and the thickness of the melted ice in the pipeline. The models used in the development of PROSYS was validated with several experimental results from literature. PROSYS predicted the severity of asphaltene deposition in an analysis carried out on a field having asphaltene issues. Furthermore, PROSYS estimated the thickness of ice melted of a hydrate plug using Osokogwu and Ajienka model as well as the dissociation temperature of a hydrate plug which compared very well with Peter (1999) and Bollavaram (2003) experimental results with less than 5% error.
Developing A New Analytical Tool for the Quantification of Oil Slick on Waters
Authors: Ogwo O. U.
Published: July 2014

Offshore spillage is an attendant problem to offshore oil operations. As offshore oil operations continue to expand, the search for a more precise and cost-effective method for offshore oil spillage quantification becomes more imperative. Effective monitoring and control of polluted waters requires the knowledge of the extent of the area polluted and the quantity of the pollutants (which includes produced and/or transported crude oil, refinery/petrochemical plant disposals, industrial machinery waste oil, and automobile crank case oil disposal). A number of methods have been proposed for use in the determination of the quantity of oil spilled on waters. Unfortunately these methods would not be cost-effective when the volume of oil spilled is not on the high side. There is therefore the need for a tool that would be suitable for use in the petroleum industry under all conditions of hydrocarbon quantity, quality and economics. A new analytical tool has been developed for the quantification of oil slick on waters. The new tool (a relationship between the volume of crude oil floating on the water surface and its surface area, termed the Spread Equation) is the result of extensive research on the minimum thickness of oil on the water surface. From the research, oil-on-water colour spectrum has been developed that has proved reliable in the determination of the quantity of oil slick on waters, given the area covered by the slick. This work presents the analytical tool – the functional form, the experimental data and result of the investigations.
Integration of 3D Seismic in the Absence of Core Data to Mitigate Porosity Uncertainty in a Deep, Over Pressure Reservoir in Niger Delta
Authors: Basak Prahlad , Abdul-Kareem Abiola , Anyaehie James C , Esho Muyiwa
Published: July 2014

Determining reservoir porosity from density logs is possibly the most common practice in the industry over the years. Computation of porosity from density is largely affected by the grain density and fluid density used in the models. There are many best practices available in the industry to compute the grain density and fluid density with reasonable certainty. There are also many different models available which takes into account other available log responses like neutron porosity, resistivity, and shale volume to account for the uncertainties in the porosity computation. However, one of the areas that need some special attention is to integrate non-petrophysical data like seismic which can help reducing the porosity uncertainty significantly especially when no other calibration reference is available. Log measurements from the padded tools like density, neutron porosity are generally quality checked against caliper and other lithology indicators like gamma ray, resistivity, sonic etc. This paper demonstrates that porosity computation could also go wrong in a true gauge hole where density log reading apparently looks good and also showing right kind of deflection for changes in lithology. The situation can get quite complicated if the reservoir is highly over pressured and if there is no core data or regional data available.

In a deep, over pressured reservoir in the niger delta, with only two well penetrations, no core measurements, and no regional calibration reference, top quality recent 3D seismic data was integrated with the well data to mitigate uncertainties in reservoir porosity. The formation evaluation challenge was that log in one of the wells showed a relatively low density reading (hence high porosity) compared to the second well density over the same reservoir. However seismic amplitude did not support the porosity variation between the two wells hence leading to further investigation on identification and management of the observed uncertainties. This paper showcased in details how the seismic data was used to identify the wrong well log reading that lead to wrong prediction of porosity distribution and the accuracy of the integrated seismic and well log predicted properties when compared to actual well log result from a well that was later drilled in the same reservoir.