bluuebunny/crossref_metadata_2025 huggingface dataset:
What's in a copy?
Authors: Ribeiro Gustavo Lins
Published: July 2013

I will answer the question "What's in a copy?" by considering three sets of related issues: the importance of copies in academia; in cultural life; and in the economic world. In academia the current capability of making copies is challenging pedagogical practices and the trust of its members, plagiarism being the most immediate problem. The notion of authorship is also undergoing changes provoked by a proliferation of authors and new possibilities opened up by cyberspace. In cultural life, imitation and mimesis have long been fundamental engines of socialization. Our enhanced capacity of copying problematizes, with new intensity, the relationships between homogeneity and heterogeneity, between the genuine and the spurious. In the economic world, the digital era is threatening some of the fundamental tenets of capitalism, especially of its variant called the "knowledge society", regarding the control of intellectual property rights. The gap between normativity and social practices is widening. The many dilemmas and tensions identified in the text are understood as symptoms of two major characteristics of the current times: hyperfetishism and hyperanimism.
Kuahí: the indians of the Lower Oiapoque and their museum
Authors: Vidal Lux
Published: July 2013

In recent decades we have witnessed a proliferation of museums, including indigenous museums, with an emphasis on regionalization and active participation of the collectivities in which they are inserted. This article involves the implementation of the Museum of the Indigenous Peoples of Oiapoque, which was a request made by the four ethnic groups that inhabit the region - the Palikur, Galibi Kali'na, Karipuna and Galibi Marworno - to the governor of Amapá in 1998. Since then, projects and actions have been realized for the revival and strengthening of the cultural heritage of these peoples that inhabit the far north of Brazil, on the border with French Guyana. We present these actions, their consequences and the articulation among partnerships (with indigenous organizations, government agencies and NGOs), which led to the development and operation of a regional museological institution that is dedicated to housing, preserving and promoting the cultural archives of these peoples, and to training indigenous museology technicians, teachers and researchers. Finally we address the importance of the different collections about these indigenous peoples that have been formed over the past two decades and report of the exhibitions mounted at the Kuahí Museum in Oiapoque and at the Museum of the Indian in Rio de Janeiro, emphasizing the specificity of each.
Scientific research in the natural sciences in South Africa: A scientometric study
Authors: Sooryamoorthy Radhamany
Published: July 2013

As a leading producer of scientific publications on the African continent, South Africa has made remarkable progress. However, attempts are yet to be made to comprehend the empirical reality of scientific production in South Africa. One way to do this is to analyse specific science disciplines (such as the natural sciences), publication outputs and their features. A bibliometric study was undertaken of the publication trends and patterns of South African researchers in the natural sciences from 1975 to 2005 (choosing selected sample years), using the Thomson Reuters’ Web of Knowledge database of selected indexed natural science journals. Characteristics of natural science publications, such as the trends over the years, were revealed as well as the collaborative dimensions involved in the production of scientific papers in these disciplines in South Africa. The connection between collaboration and publication, as well as between collaboration and sectors of authors was evident. The key findings of this study were that authors were based mostly in universities and were collaborative in their research endeavours. In addition, the participation of international collaborators has increased.
Effect of farming activities on seasonal variation of water quality of Bonsma Dam, KwaZulu-Natal
Authors: Shabalala Ayanda N. , Combrinck Ludwig , McCrindle Robert
Published: July 2013

Agriculture has both direct and indirect effects on the quality of surface water and groundwater and is among the leading causes of water quality degradation, mainly as a result of the excessive use of agrochemicals. Water samples were collected in a selected catchment area (Bonsma Dam) in KwaZulu-Natal and analysed for physicochemical variables. The concentrations of most of the elements and total dissolved solids, as well as the pH and electrical conductivity values, met the water quality requirements for domestic, agricultural, livestock and aquatic ecosystem uses. However, the inlet streams feeding the dam were found to be eutrophic during the wet season. Analysis of nitrate in the water body of the study area indicated that agricultural applications of manure and fertilisers may be a potential source of nitrate contamination. Most elements were more concentrated in the dam during the wet season. The overall ionic conductivity values were also higher in the wet season, while the pH was lower. The outcome of this work links the concentrations of physicochemical variables to land use, agricultural practice and local geomorphology. Seasonal patterns in the concentration of physicochemical variables occur, as land use, rainfall and farming activities change seasonally, and these concentrations should therefore be determined periodically.
Photo-induced switchable TiO2 thin films for biological applications
Authors: Berger Olena , Fischer W.-J.
Published: July 2013

Titanium and its alloys are key materials for biomedical applications due to their unique combination of high biocompatibility and mechanical strength. The interface between implant and tissue can be improved by titanium oxide coatings. Titanium oxide thin films prepared by electron beam deposition with well-defined structure, phase composition, morphology and local surface chemistry have been used in a study of the correlation between physicochemical surface characteristics and their biocompatibility, which have been shown dependent on preparation method and deposition parameters. In this study, three independent measurement methods were used for the determination of surface groups and charge: X-ray photoelectron spectroscopy, electrokinetic and contact angle measurements. The behavior of the thin titanium oxide films exposed to fibroblast L929 cells was studied. The aim of this study was to functionalize the oxide surfaces by controlling their properties through either defects introduced using high-temperature annealing, UV-light and/or modifier atoms as well as by molecules adsorbed at the surface, in particular, the formation of hydroxide groups. It was found that UV-light drives a switchable biocompatible titanium oxide surface, changing the surface charge polarity which increases or decreases the wettability of the films and the growth of the cells on the film’s surface correspondingly.
Large effects of consumer offense on ecosystem structure and function
Authors: Chislock Michael F. , Sarnelle Orlando , Olsen Brianna K. , Doster Enrique , Wilson Alan E.
Published: July 2013

Study of the role of within‐species adaptation in ecological dynamics has focused largely on prey adaptations that reduce consumption risk (prey defense). Few, if any, studies have examined how consumer adaptations to overcome prey defenses (consumer offense) affect ecosystem structure and function. We manipulated two sets of genotypes of a planktonic herbivore (Daphnia pulicaria) in a highly productive ecosystem with abundant toxic prey (cyanobacteria). The two sets of consumer genotypes varied widely in their tolerance of toxic cyanobacteria in the diet (i.e., sensitive vs. tolerant). We found a large effect of tolerant D. pulicaria on phytoplankton biomass and gross primary productivity but no effect of sensitive genotypes, this result stemming from genotype‐specific differences in population growth in the presence of toxic prey. The former effect was as large as effects seen in previous Daphnia manipulations at similar productivity levels. Thus, we demonstrated that the effect of consumer genotypes with contrasting offensive adaptations was as large as the effect of consumer presence/absence.
Phenology effects on invasion success: insights from coupling field experiments to coexistence theory
Authors: Godoy Oscar , Levine Jonathan M.
Published: July 2013

Ecologists have identified a growing number of functional traits that promote invasion. However, whether trait differences between exotic and native species promote invasion success by enhancing niche differences or giving invaders competitive advantages is poorly understood. We explored the mechanisms by which phenology determines invasion success in a California annual plant community by quantifying how the seasonal timing of growth relates to niche differences that stabilize coexistence, and the competitive ability differences that drive dominance and exclusion. We parameterized models of community dynamics from experimentally assembled annual communities in which exotic plants displayed earlier, coincident, or later phenology than native residents. Using recent theoretical advances from the coexistence literature, we found that differences in phenology promote stabilizing niche differences between exotic and native species. However, phenology was more strongly related to competitive ability differences, allowing later invaders to outcompete earlier native competitors and native residents to outcompete earlier invaders in field experiments. Few of these insights could be inferred by comparing the competitive outcomes across invaders, highlighting the need to quantify niche and competitive ability differences when disentangling how species differences drive invasion success.
Women’s Perceptions Using the CenteringPregnancy Model of Group Prenatal Care
Authors: Risisky Deb , Asghar Syed Masood , Chaffee Madeline , DeGennaro Nancy
Published: July 2013

A qualitative nonexperimental thematic analysis was conducted at a hospital-based midwifery practice to explore the views of participants in group prenatal care and its impact on pregnancy, birth, and postnatal care. Ten women and three support people, recruited through purposive sampling, shared their feedback on the program. The findings conveyed three broad themes: program experience, midwife relationship, and support. Women enjoyed the opportunity for in-depth learning, and peer-group support led to normalizing of pregnancy concerns. Having support people as participants also helped during pregnancy, birth, and child care. The findings showed the enhanced opportunity for education, learning, and interpersonal support provided by CenteringPregnancy to expectant mothers had a positive impact on their pregnancy experiences.
Supporting Maternal Transition: Continuity, Coaching, and Control
Authors: Rowe Jennifer , Barnes Margaret , Sutherns Stephanie
Published: July 2013

The transition from maternity services to community child health services on discharge from hospital occurs at a potentially vulnerable time for women in their transition through the childbearing/early parenting continuum. Their experiences contribute to their developing maternal efficacy and parenting skill. The ideal attributes of services that aim to support women and their families during this time include continuity of care, service integration, and birth in accessible, community-based contexts. The purpose of this study was to investigate aspects of maternal experience of mothers attending with their infants a publicly funded drop-in postnatal health-care service, as well as their reasons for attending and their perceptions of its usefulness to them as a mechanism of continuity and a source of support.
Trapping Mechanism of Nanofluids on Migrating Fines in Sand
Authors: Ogolo N. A. , Onyekonwu M. O. , Akaranta O.
Published: July 2013

Some nanoparticles and fluid dispersants that have the capacity to control migrating fines in formations have been investigated. The primary mechanisms through which fines were trapped and prevented from migrating were electrostatic forces of adsorption of which the pH value of the nanofluids played a significant role. The pH values and zeta potential of the nanofluids, the points of zero charge of the nanofluids and the surface charge density were used to explain the trapping of fines in the presence of some nanoparticles. The likely forces between the nanoparticle compounds and clayey fines that results in trapping and preventing fines migration were also studied. It is speculated that two or more forces of attraction contribute together to trap and prevent fines in sands from further migration.

Results indicate that aluminium oxide nanoparticle has a high capacity to trap fines and prevent them from migrating in sands. The pH value of aluminium oxide in distilled water, brine and ethanol were the lowest, implying that their zeta potentials were high and so contributed to the good performance of the nanoparticles. The high surface charge density of aluminium was also a contributing factor. With distilled water, brine and ethanol, more fines were trapped in the absence of crude oil than in the presence of crude however, in the presence of crude oil, diesel trapped the most fines. These could have occurred mainly as a result of various intermolecular interactions. It was concluded that the pH values of the nanofluids and its related properties work together with electrostatic forces of attraction to trap migrating fines in sands.
Promises of Artificial Intelligence Techniques in Reducing Errors in Complex Flow and Pressure Losses Calculations in Multiphase Fluid Flow in Oil Wells
Authors: Adebayo Abdulrauf R. , Abdulraheem Abdulazeez , Al-Shammari Ahmad T.
Published: July 2013

Empirical correlations normally used to calculate pressure losses in vertical and horizontal pipes involve complex calculations that normally rely on estimation of other complex parameters such as liquid hold up and flow regimes before arriving at values of pressure losses. Errors in estimation of hold up and flow regimes using empirical correlations propagate to error in pressure loss calculation. Hence, available empirical correlations perform pressure loss calculations with certain degree of errors which can translate to poor design of production systems. Our objective is therefore to use new techniques-artificial intelligence techniques- to calculate pressure losses during natural flow of multiphase fluid through tubing in vertical wells. The method uses some real multiphase fluid flow data (such as pressure losses, flow and fluid properties) with which an artificial intelligence is developed and trained to understand the relationship between pressure losses with fluid and flow properties. The artificial intelligence is subsequently used to perform similar calculations under new fluid properties and flowing conditions. In the literature, many papers have shown that artificial neural network (ANN) technique can estimate multiphase pressure loses more accurately than some selected empirical models. However, to the best of our knowledge, none or few papers have shown the applicability of support vector machine which is another powerful AI technique. In this paper, we applied two AI techniques-artificial neural network (ANN) and support vector machine (SVM) to predict bottom-hole pressure in a multiphase flow well using field data and we then compared results with some commonly used empirical correlations commonly used in the industry using graphical and statistical error analysis. The empirical correlations used are: Duns and Ros; Hagedorn and Brown; Fancher and Brown; Mukherjee and Brill; Beggs and Brill; Orkizewski; and Petroleum experts II. Our results showed that the two AI methods predicted bottom-hole pressure with accuracies higher than the empirical models. The correlations of coefficient and results error analysis for all the models are presented in tabular and graphical forms for ease of comparison. Finally, it is worth mentioning that artificial intelligence is an emerging technology currently used in the petroleum industry to solve complex engineering problems and its application in multiphase pressure calculations is promising as shown in this paper.
The Efficiency of Hurt Based Approach in Improving Personnel Safety
Authors: Darlington Etaje , Abdulkarim Mohammed , Ibe James
Published: July 2013

Treatment Based Approach is the traditional approach used in personnel safety which is to "classify" actual incident consequence into categories based on the type of treatments. These includes: Loss Time Incident, LTI; Restricted Work Incident, RWI; Medical Treatment Incident, MTI; and First Aid Incident, FAI. Although treatment based approach gives historical metrics that are common across entire industries, provides comparisons on a similar basis and is consistent with many government reporting requirements. However, it has shortcomings because it's not descriptive of actual injury severity and it does not include potential injury severity therefore low consequence-high potential safety events (minor hurt, near misses) are often overlooked or simply not reported, investigated, or shared for lessons. It does not enable a culture of care. This implies that workforce can view safety focus to be on reducing the number of recordables (often by minimizing treatment) and not on the elimination of injuries. Therefore, there is a need to address potential severity in order to identify low consequence incidents that could have been severe or fatal and help determine the depth of investigation requirements (in addition to actual severity).

This paper analyzes the efficiency of a highly reputable company's ‘Hurt Based Approach’ to safety and the intention is to share this good practice with all interested parties hence the reason for this paper. The hurt based approach is used to identify the integral potential and consistent actual severity of an incident and also used as a cultural enabler. A comparison between ‘treatment based approach’ and ‘hurt based approach’ will be shown in this proposed paper using the selected company as a case study. Results and historical statistics revealed that there were significant reduction in number of workforce hurt and rate of workforce hurt (THIR) when using the ‘hurt based approach’.
Breakthrough Time Correlations for Coning in Bottom Water Supported Reservoirs
Authors: Amarfio Eric Mensah , Igbokoyi A. O
Published: July 2013

This paper investigates the development and behaviour of cones (both water and gas cones) in oil reservoirs supported by strong aquifer, and from which analytical correlations are developed for quick engineering estimates of the time for water/gas cones to break into the perforations of the producing wells. The studies treated the cone development and breakthrough times in both horizontal and vertical well producing reservoirs and made analysis on them. The Ozkan and Raghavan (1990) method was employed as the base approach in the modeling of the cones in both horizontal and vertical well. The developed models were then run on field data, the results were graphically represented in both the horizontal and vertical well cases. Analytical correlations were then developed from the results obtained for the breakthrough time estimations, which are simpler, compared to literature (Ozkan et al correlations, 1990) but give close results on same example case. This work actually employs the dimensionless (or the normalized approach) system to curtail the units complexities and represent the results in a more generalized form. These analytical correlations can be leveraged on to plan better future recompletion strategy as they provide an engineering estimate of when water breaks into the production wells.
Education and Training: A Sine Qua Non for Professionalism in the Oil and Gas Sector
Authors: Anekwe Ifeoma Eucharia , Orodu Oyinkepreye D.
Published: July 2013

A number of countries in Africa are leveraging on her oil and gas as the major source of government revenue. As such, if these natural resources are produced and exploited in an unsustainable manner and depleted, these could lead to adverse effect on the economy in terms of the much needed revenue and host communities' livelihood. The activities in upstream, middle stream and downstream of the industry; the further discoveries offshore, particularly in deep waters; the spring up of local players in the E&P for marginal and brown field development; the local content drive; sustainable refined petroleum products capacity for the nation and the expectations of the Petroleum Industry Bill (PIB) in Nigeria requires ‘fit-for-purpose’ caliber of human resources/manpower in the skilled and semi-skilled cadre. As such the human capital within this sector must be highly trained and skilled to meet up with the needed production increase, global demands, standards and best practices in the industry. Professionalism is a long and wide concept; even though, it is often neglected by most individuals and organizations. It is made up of education, training, technical assistance and time. It is the dividing line between the developed and underdeveloped communities. It is the hallmark of all laudable solutions, creativities, and innovations. It is hard for Africa's oil and gas sector to meet up with the growing trends of globalization without professionalism. In the light of the foregoing, this research work seeks to carry out a comprehensive diagnosis and dialysis on how to boost educational training and professionalism in the oil and gas sector in Africa.
An Application of Experimental Design to Increase the Likelihood of Success in a Brown Field Re-Development
Authors: Sonde Adekoyejo , Ayeni Olumide
Published: July 2013

Oil reservoirs developed under a natural depletion scheme usually leave behind a significant portion of the discovered oil and while in-fill drilling is a logical choice to recovering more oil from these reservoirs, there is always the challenge of locating the remaining oil and optimally placing new wells within these ‘sweet spots’.

3-Dimensional (3-D) dynamic modelling and 4-D seismic are well developed methods of establishing post-production saturation distributions and a combination of both methods further increase the confidence of the post-production saturation distributions predicted. Even then however, these methods are not infallible. Experimental design methods when integrated into dynamic modelling enable a logical and systematic interpretation/utilisation of all available data to understand the extent and impact of uncertainties, an understanding which can help make robust decisions about these re-developments.

The reservoir of interest (Level 1X) is an oil rim reservoir with a 36-year production history from 6 wells. All the existing completions in the reservoir were used to develop the oil-rim. To evaluate the option of developing the gas cap of the reservoir, a technical review of the oil rim had to be carried out to assess the existing developments and evaluate the possibility of further development opportunities in the oil rim prior to the gas cap blow down.

Over the area of this field, 4-D seismic was not available and while the traditional dynamic reservoir modelling method could be used to plan further development, the oil rim nature of the reservoir coupled with reservoir uncertainties (such as oil-water and gas-oil contacts) meant a second method would give further credence to any analyses of the reservoir and the proposals resulting from such analyses. This paper demonstrates how experimental design, incorporated into dynamic simulation, has been applied to the reservoir study to achieve the following:

Integration of practically all data into the study (not a pre-selected value for each uncertainty) Allowing available data to guide the history match of the reservoir (History matches evolve/drop out of data) thus increasing confidence in the calibrated (low, mid and high case) models. Allowing a selection of a high confidence case re-development strategy.
First Commercial Installation of MazeFlo™ Technology for Remedial Sand Control Application in Ubit Field
Authors: Okoroh K. , Hommema J. , Igwebike C. , Oguamanam U.
Published: July 2013

This paper describes the successful installation of the first commercial MazeFlo™ in a remedial sand control application and post job well performance. MazeFlo technology is an enhanced reliability sand screen with applications for remedial sand control and new completions. The reliability enhancement is achieved through a secondary sand screen in combination with a set of compartments to self-mitigate sand breakthrough from primary screen damage. The candidate well is located offshore West Africa with a high angle reservoir interval length of 1500 ft measured depth. It was originally completed with a 4-1/2" pre-perforated liner across the open hole interval without sand control and historically became a sand producer post initial completion. Though a high rate producer, the well was subsequently shut-in for sand production and a MazeFlo screen was installed to restore production.

This paper will share installation results and learnings from the rig-based intervention that was required to install the 2-3/8" MazeFlo screen inside the existing 4-1/2" pre-perforated liner. Handling and running of the MazeFlo screens was flawless due to front-end engineering, planning, and collaboration with key service providers. Post job well performance will also be discussed.
Design Of A Microreactor For Biodiesel Production From Algae
Authors: Ajilo V. I. , Falode O. A.
Published: July 2013

There is a growing interest in the production of biofuels mainly because of environmental protection and energy supply reasons. Currently, most research into efficient biofuel production is being carried out and predictions from small-scale production experiments bear out that using algae (microalgae, among other biofuels) to produce biodiesel may be the only viable method by which enough automotive fuel can be produced to replace current world conventional diesel usage. Also, studies show that some species of algae can produce up to 60% – 80% of their dry weight in the form of oil. Because the cells grow in aqueous suspension where they have more efficient access to water, CO2 and dissolved nutrients, microalgae are capable of producing large amounts of biomass and usable oil in either high rate algal ponds or photo-bioreactors. This oil can then be turned into biodiesel which could be sold for use in automobiles. Economic wise, regional production of microalgae and processing into biofuels will provide great benefits to rural communities. Hence, there is need for optimal, efficient and safe production of biodiesel from microalgae.

In this work, we propose a project for the design and construction of a biodiesel microreactor. It is drawn using the PDMS software. The design of the reactor requires the modelling of the complex series of reversible reactions which are known to take place; process characterization of the biodiesel production system by dividing it into unit processes; design of a process model; derivation of thermodynamic equations that govern the whole system; and algorithm using FORTRAN 95 to enhance the estimation and proper management of the productivity of any quantity (mass) of algal biomass to be converted to useful volume of biodiesel. Finally, a test of the use of this biodiesel in vehicles is presented.
Compilation of Instantaneous Source Functions for Varying Architecture of a Layered Reservoir with Mixed Boundaries, Horizontal and Vertical Well Completions; Part V: Letter ‘H’ Architecture
Authors: Adewole E. S.
Published: July 2013

If a reservoir is layered and the layering precipitates an architecture in the form of letter ‘H’, then modeling pressure distribution or understanding the character of the influencing external boundaries can be achieved through a study of instantaneous source functions for a horizontal and vertical wells completed in the layers of the reservoir. This is the main objective of this compilation. In this paper, both crossflow and no-crossflow layers are considered, and the external boundaries are varied as sealed and constant-pressured. Only the vertically top layer has a vertical well in all the models considered.

The study shows that a two-layered reservoir of latter ‘H’ architecture has no inverted form in terms of external boundary variation, no matter the axis of symmetry considered for inversion. The reservoir architecture presents one (1) mandatory infinite-acting boundary each at the bottom and at the top of the composite, vertically-stacked reservoir. There are a maximum of two (2) opposite external boundaries in each layer that may be considered sealed or subject to external fluid drive (constant-pressure). In all, sixteen (16) different external fluid and sealed boundary combinations are possible assuming crossflow interface. Fifteen (15) different combinations of edged fluid drive are also possible assuming crossflow interface. No bottom or top external fluid drive is possible for this architecture. For crossflow interface, only one (1) architecture may be subject to double edged external fluid drive in both layers, while six (6) architectures may have double edged external fluid drive possibility for no-crossflow interface reservoir architecture. Therefore, every well enjoys an infinite-acting source strength of the kind I(z), whether the interface is sealed or permits crossflow.
Analysis Of Wellbore Stability In Multilateral Well Design And Construction
Authors: Anyanwu Chimaroke , Dosunmu Adewale , Fekete Paul , Ekeinde Evelyn , Odagme Baridon
Published: July 2013

The number of multilateral wells drilled in the Niger Delta all geared towards increasing recovery as well as other field development objectives. However, a major challenge facing the successful drilling of these special trajectory wells is hole instability. The cost of instability according to some operators can be as high as $ 600MM per Year. Wellbore instability poses a unique threat in multilateral wells such that the tendency for collapse or fracture increases at the bore hole junctions. Casing deformation, difficulty in through-put of drilling tools and equipments, to mention but a few, are among the major problems associated with this instability.

This research revisits the issue of wellbore stability with emphasis on multilateral wells. A modified failure model is developed by including a stress concentration factor based on the junction configurations. The Mogi criterion was applied to account for intermediate stress and predict the minimum mud pressure below which shear failure will occur. A risk and uncertainty factor is attached to this model for sensitive model parameters including stress concentration factors, and lateral bore entry angle.

Results from two case studies presented in this work showed that collapse gradient prediction by Mogi based model were more reliable than those of Mohr based model. In case 1, a minimum mud weight of 0.52 psi/ft was predicted to be sufficient to maintain stability. A mud weight of 0.53 was used to drill the lateral section and hole pack offs were encountered at build angle of 30°. However, the Mogi prediction was 0.57 and sufficiently prevented hole collapse. In case 2, the Mogi predictions are all well above the actual mud weight used as against the underestimation with Mohr's.
An Improved Predictive Tool for Liquid Loading in a Gas Well
Authors: Fadairo Adesina , Femi-Oyewole Damilola , Falode Olugbenga
Published: July 2013

As the search for natural gas becomes increasingly high due to its high demand worldwide, the oil and gas industry is faced with the challenge of liquid loading in gas or condensate wells. It is imperative to properly design and predict the operational parameters necessary for handling flow assurance challenges due to simultaneous flow of gas with liquid. The model of Guo et al is the most recent systematic approach for predicting liquid loading in gas well. However, it did not account for the accumulation and kinetic terms in the momentum energy equation used to estimate bottom-hole pressure in a gas/oil/water/solid four phase flowing well. The two neglected terms in Guo et al formulation have significant effects on the gas well operational parameters such as the minimum gas flow rate for preventing liquid loading.

This paper presents an improved model that describes a systematic approach for estimating liquid loading in a gas well without neglecting any term in the fundamental momentum equation. The results obtained showed that at the early production time where initial transience at the onset of flow is experienced, the critical gas flow rate obtained from the new model is lower than that predicted from Guo et al model due to inclusion of accumulation term while at the later production time, the critical gas flow rate obtained becomes higher than that predicted from Guo et al model and increases as the transient period elapses. Results further show that at some point during production, the minimum energy required to lift liquids out of the wellbore is more than that required at the earlier stage of production. The new model is reasonable, reliable and better when compare with Turner et al and Guo et al models. It is useful for operators to refine their procedures and better manage the risk of liquid loading during natural gas production.
Enhancing Reservoir Surveillance and Management in Mature Depleted Reservoirs Using Reservoir Operating Envelopes: The Sofad Field Case-study
Authors: Sonde Adenike , Osho Rotimi , Ayeni Kayode
Published: July 2013

Operating envelopes are used in many industries, including the oil industry, to define appropriate operating boundaries and limits for production systems. In the oil industry, the boundaries generally include minimum and maximum operating rates, as well as minimum and maximum operating pressures and temperatures for the different components of the production system. Today, the use of operating envelopes has been extended to the subsurface (specifically hydrocarbon-bearing reservoirs) with the aim of identifying optimum limits for production rates and reservoir pressure depletion.

The Sofad field is one of the biggest and most structurally complex oil fields in the Western Niger Delta straddling land, swamp and shallow offshore. The high offtake rates from the reservoirs, coupled with the high fault density, have inhibited the response of the otherwise active aquifer especially in the key producing reservoirs. As a result, the key reservoirs have suffered severe pressure depletion over the years.

Analyses of the historical production/pressure trends of these reservoirs clearly indicate that the reservoir pressures are generally sensitive to the rates of production from the reservoirs. Thus, it became essential to evaluate the maximum production rates for these reservoirs in order to manage the reservoir pressure depletion and consequently maximise oil recovery (pending the execution of the water injection project for pressure maintenance).

This paper presents how the operating envelopes for the reservoirs were designed. It also showcases how the operating envelopes are being used in ensuring the maintenance of reservoir pressures, which has led to an improvement in the recovery from these reservoirs over the last 3 years (2010 – 2012).
Application of Injection Fall-Off for Reservoir Characterisation and Production Optimisation: Cases from a Deepwater Field
Authors: Ojeke Akpoebi N. , Lawal Kazeem A. , Ibianga Deri
Published: July 2013

In producing assets, the drive to reduce production deferments is increasing the interests in injection fall-off (IFO), as against pressure build-up, tests for reservoir characterisation. The IFO, which entails the measurement and analysis of pressure transients due to the shut-in of an injector after a period of continuous injection, provides estimates of important subsurface parameters such as static pressure, transmissibility and, where applicable, induced-fracture characteristics. This paper documents the application of IFO in selected cases from an oil-producing deepwater field.

The pressure fall-off curves obtained for two water injectors in the subject deepwater field are analysed. Particular attention is paid to the analysis of the fall-off curves and the identification of the various flow regimes. The estimation of key subsurface parameters such as skin factor, transmissibility, and boundary characteristics is detailed.

To reduce interpretation uncertainties, an integrated application of geoscience data has been employed to constrain the possible range of IFO interpretations. In addition, the IFO results have been used to rationalise the declining injectivity indices observed in the subject injectors, while providing clues for these observations at the pore scale. In essence, this work reechoes the credentials of IFO, as a credible and cheaper alternative to pressure build-up tests, for the characterisation of subsurface systems.
Integrated Production System Modeling (IPSM) as an Opportunity Realization and Optimization Tool for Improved Asset Management
Authors: Eli Awan , Aboaja Ugochukwu , Ajayi Ayo
Published: July 2013

This paper presents the Mede & Mafe field Integrated Production System Modeling (IPSM) strategy, synopsis of work done and benefits derived from the model. The IPSM provided a simple fit-for-purpose tool for understanding, diagnosing and tracking the fields’ performance as well as optimizing well production and facility throughput.

The main areas which the IPSM was used are:

Opportunity identification and validation Optimization and Prediction of field performance.

The IPSM enabled the integration of flow assurance with subsurface deliverability using well and reservoir operating conditions as boundary conditions & separators static pressures as topside constraints. The IPSM modeling strategy was aligned to meet the requirements of Well and Reservoir Management (WRM) minimum standard.

Opportunity realization and optimization from the existing wells were achieved after calibrating the model to match actual field performance within ±5% error margin. Additionally, the opportunities generated from the Integrated Drainage Point Reviews (IDPR) were ranked and validated with the IPSM model to quantify Short Term Oil Gains (STOG) within calculated well and reservoir operating envelopes.

The model is also used as a standard tool for quarterly Production System Optimization meeting with continual update made to enhance well and reservoir management of these fields.

The IPSM has been used in four PSO reviews with seven (7) bean-up opportunities identified/validated delivering oil gain of 1500bopd. An opportunity to improve flow assurance and de-bottleneck the Mafe bulklines with a potential to deliver 1700bopd was also identified.
Seismically Driven Reservoir Characterization
Authors: Fehintola Tope , Umeh Emeka , Obieke Chris
Published: July 2013

Integration of well and seismic data is a key component of optimal reservoir characterization for field development. In a green, partially appraised ultra deepwater field with few wells, the proper use of well data as calibration points for the seismic data becomes more important. The workflow can be complicated in instances of multi loop reservoirs with differing AVA signatures. An alternative to existing workflows is required for such reservoirs.

The current integrated workflow involves carrying out seismic inversion for reservoir properties; this is typically done for each reservoir model because of rock property differences between reservoirs. Reservoir properties are estimated from inverted PImpedance and S-Impedance through the use of rock property models. The rock models describe how the reservoir PImpedance and S-Impedance changes with variations in a particular reservoir property, such as net:gross or porosity.

With reservoirs of differing Amplitude Variation with Angle (AVA) signatures, different rock models must be applied to the inverted P and S-Impedance to generate varying versions of the same reservoir property, e.g. the rock model of an acoustically hard low porosity sand will vary from an acoustically soft high porosity sand. The varying version of the reservoir property will then be applied to different portions of the reservoir model.

While seismic inversion gives a non-unique solution, the integration of well data allows for derivation of a technically best fit solution, as well as an estimate of the associated uncertainty. The resulting inversion aids in the building of a reservoir model that honours geophysical, petrophysical and geologic data. This paper will present how the integration of well and seismic data was used to optimally characterize an offshore green field development and create a fit-for-purpose reservoir model.
A Holistic Approach to Defining Well Operating Envelopes
Authors: Hamzat Kassim , Adenike Sonde , Olukayode Ayeni , Juliet Njoku , Ayotunde Ajayi , Adebisi Akande
Published: July 2013

Well performance management is a critical aspect of production system optimisation in an oil and gas field. Accurately defining the well operating envelope will not only ensure asset integrity, but will also ensure realistic production performance expectations (forecasts) from available well resource. This paper discusses an approach to defining well operating envelopes that incorporates the technical limits and constraints of the various components of the producing well (i.e. reservoirs, sand face completions, tubing erosion and surface production facility, etc.). The methodology employs a visualization tool to graphically represent the operating envelope for the wells based on these constraints.

This approach has been implemented in several fields and wells in Shell Nigeria with varying completion types and field-wide constraints. It has also been proven to be flexible enough to accommodate the possible variations between well types and field peculiarities. The case study of five fields in SPDC Swamp West Asset presented in this paper will demonstrate this flexibility. Some of the benefits realized include improved reservoir management and water cut control. Furthermore, the visualization tool has been used to carry out exception based well surveillance that has proven to improve our response time to well deviations for better deferment management.
Case Histories of Drilling Challenges and Prediction of Equivalent Static Density of HPHT Wells in Niger-Delta
Authors: Madu S. O. , Akinfolarin A. A.
Published: July 2013

Instability of drilling fluid density downhole in the high pressure, high temperature hole section of a HPHT well has been posing many drilling challenges like well control (kick/blowout) or high ECD that could lead to the fracturing of formation especially where the operational window between the pore pressure and fracture gradient is very narrow which is often the case for HPHT wells. Accurate prediction of dominant effect of temperature or pressure on the change in the equivalent static density of drilling mud prior to drilling is important to benchmark with the real time pressure measurement.

This study uses Kutasov empirical model and subsurface data to predict the behavior of equivalent static density (ESD) of the anticipated drilling fluid in Niger Delta.

Furthermore, the equivalent static density of drilling fluids of some HPHT wells are modeled to investigate some drilling issues that were experienced during the drilling of these wells. Finally some HPHT case histories and their specific drilling challenges are discussed as part of this study.
Modeling Gas Water Contact Effects in Pressure Transient Behavior using Analytical Aquifer modeling and Numerical Simulation
Authors: Kehinde Dare , Ikwan Ukauku , Oghene Nkonyeasua , Afolayan Olatunbosun , Awa Chukwunweike
Published: July 2013

Interpretation of reservoir boundary conditions and well drainage areas have been historically done conventionally; using analytical and numerical simulation approaches with constant pressure, no flow, leaky and conductive boundaries. This paper investigated the effect of Gas Water Contact (GWC) boundary on the pressure transient behavior.

The novel approach adopted involves building numerical simulation well test models that investigate the effect of using Carter Tracy analytical aquifer model to simulate the response at the aquifer interface of a gas reservoir using SAPHIRE software. Bourdarot1 and Kuchuk2 stated that the effect of an aquifer can be modeled with a constant pressure boundary model. This model assumes that the pressure at the boundary of the reservoir consistently remains at the initial reservoir pressure during the drawdown and build up phases of the well test. Hence, it suggests that the pressure support from gas cap is very strong due to expansion and that the multi phase flow effects can be neglected. These assumptions work well for gas cap depletion systems. However, in the case of a water drive system, they may be incorrect.

The result of this investigation indicates that pressure transient at Gas Water Contact boundary behaves like a constant pressure boundary for gas reservoir with small sized aquifer or a radial composite system for gas reservoir with large or infinite aquifer respectively. The former is due to the change in fluid diffusivity and very high mobility contrast. (Khμ)1→(Khμ)2 (with 2>>1) coupled with expansion of active gas cap while the later is due to mobility contrast coupled with expansion from the active water influx. The result of this investigation was compared with the conventional analytical method of using a constant pressure boundary assumption.

It is recommended to apply the results of this investigation in: (i) estimating the Gas Water Contact in a down-dip reservoir and therefore help in the quantification of reservoir volumes to support existing reliable technology for determining the Lowest Known Hydrocarbon (LKH) in a Gas Down To (GDT) scenario by applying shrinking box technique to a recognized onset of constant pressure or radial composite effect in a DST or multi rate test in a down dip gas well (ii) Analytical Aquifer boundary modeling in well test designs as it affects drainage area and volume.
Comparative Study Of Different Salts On Hydration Of Bentonite
Authors: Uti L. O , Joel O. F
Published: July 2013

The make up water is one of the main building blocks of the drilling mud. The pH, hardness, and salt content of the make up water determine the yield and performance of the bentonite clay. hydration and dispersion of dry clay are greatly affected if the makeup water contains salt or various metallic ions. Many drilling muds are prepared with seawater for economy and convenience. This research study therefore details a comparative study of different salts namely sodium chloride, potassium chloride and calcium chloride on the hydration of bentonite. The rheological values were determined using FANN viscometer with different concentrations of NaCl, KCl and CaCl2((0%,0.5%, 1.0%,1.5%,2.0%, 2.5%, 3.0%, 4.0%, 4.5% and 5.0%) respectively by weight of bentonite. Test results indicated that plastic viscosity for NaCl, KCl and CaCh ranged from 11 to 5 cP, 9 to 8 cP and 9 to 4 cP respectively. Also the yield point ranged from 13 to 2 lb/100ft2,17 to 8 lb/100ft2 and 17 to 1lb/100ft2 respectively. The fluid loss also ranged from 15 to 20ml/30mins for NaCl, 12 to 16ml/30mins for KCl and 18 to 30ml/30mins for CaCh respectively. Test results indicated that increase in the concentration of the salts resulted to decrease in rheological properties and increase in fluid loss respectively. The effect was more pronounced with CaCl2 than the other two salts. It is imperative to introduce fluid loss and viscosifying additives when using mix water with high salt concentrations.