bluuebunny/crossref_metadata_2025 huggingface dataset:
Conserved Single Residue in the BK Potassium Channel Required for Activation by Alcohol and Intoxication in
C. elegans
Authors: Davis Scott J. , Scott Luisa L. , Hu Kevin , Pierce-Shimomura Jonathan T.
Published: July 2014

Alcohol directly modulates the BK potassium channel to alter behaviors in species ranging from invertebrates to humans. In the nematode
Caenorhabditis elegans
, mutations that eliminate the BK channel, SLO-1, convey dramatic resistance to intoxication by ethanol. We hypothesized that certain conserved amino acids are critical for ethanol modulation, but not for basal channel function. To identify such residues, we screened
C. elegans
strains with different missense mutations in the SLO-1 channel. A strain with the SLO-1 missense mutation T381I in the RCK1 domain was highly resistant to intoxication. This mutation did not interfere with other BK channel-dependent behaviors, suggesting that the mutant channel retained normal
in vivo
function. Knock-in of wild-type versions of the worm or human BK channel rescued intoxication and other BK channel-dependent behaviors in a
slo-1
-null mutant background. In contrast, knock-in of the worm T381I or equivalent human T352I mutant BK channel selectively rescued BK channel-dependent behaviors while conveying resistance to intoxication. Single-channel patch-clamp recordings confirmed that the human BK channel engineered with the T352I missense mutation was insensitive to activation by ethanol, but otherwise had normal conductance, potassium selectivity, and only subtle differences in voltage dependence. Together, our behavioral and electrophysiological results demonstrate that the T352I mutation selectively disrupts ethanol modulation of the BK channel. The T352I mutation may alter a binding site for ethanol and/or interfere with ethanol-induced conformational changes that are critical for behavioral responses to ethanol.
Intercellular network structure and regulatory motifs in the human hematopoietic system
Authors: Qiao Wenlian , Wang Weijia , Laurenti Elisa , Turinsky Andrei L , Wodak Shoshana J , Bader Gary D , Dick John E , Zandstra Peter W
Published: July 2014

The hematopoietic system is a distributed tissue that consists of functionally distinct cell types continuously produced through hematopoietic stem cell (HSC) differentiation. Combining genomic and phenotypic data with high‐content experiments, we have built a directional cell–cell communication network between 12 cell types isolated from human umbilical cord blood. Network structure analysis revealed that ligand production is cell type dependent, whereas ligand binding is promiscuous. Consequently, additional control strategies such as cell frequency modulation and compartmentalization were needed to achieve specificity in HSC fate regulation. Incorporating the in vitro effects (quiescence, self‐renewal, proliferation, or differentiation) of 27 HSC binding ligands into the topology of the cell–cell communication network allowed coding of cell type‐dependent feedback regulation of HSC fate. Pathway enrichment analysis identified intracellular regulatory motifs enriched in these cell type‐ and ligand‐coupled responses. This study uncovers cellular mechanisms of hematopoietic cell feedback in HSC fate regulation, provides insight into the design principles of the human hematopoietic system, and serves as a foundation for the analysis of intercellular regulation in multicellular systems.
Long-Term Endovascular Treatment Outcome of 46 Patients with Cavernous Sinus Dural Arteriovenous Fistulas Presenting with Ophthalmic Symptoms
Authors: Pashapour Ali , Mohammadian Reza , Salehpour Firooz , Sharifipour Ehsan , Mansourizade Reza , Mahdavifard Ali , Salehi Mohamadgharib , Mirzaii Farhad , Sariaslani Payam , Ardalani Ghasem Fatahzade , Davaraltafi Ghasem Fatahzade
Published: July 2014

Ocular symptoms are regularly observed inpatients with cavernous sinus dural arteriovenous fistulas (cDAVF). We aimed to evaluate the long-term efficacy and safety of endovascular approaches in patients with cDAVF presenting with different ocular symptoms. In a prospective study between June 2008 and March 2013, 46 patients with ocular symptoms due to cDAVF who were not eligible for conservative therapy, met the inclusion criteria and underwent endovascular treatment. They underwent a transarterial approach with histoacryl glue injections or transvenous coil embolization, all in one session. They were followed up for a mean period of 17.3 months (range 7 to 30 months) clinically and using angiography. The mean age of patients was 36.8 years (18–60) and 65% of them were male. All patients showed venous drainage into the superior and inferior orbital veins. Access to the cavernous sinus was transvenous in ten patients, transarterial in 26 patients, and mixed in ten patients. Initial symptoms were improved in 97.8% of patients and did not recur during the study follow-up. The procedural complications included: blurred vision, transient sixth nerve palsy and exacerbation of chemoproptosis in two, one and two patients respectively that completely resolved in initial weeks with no recurrence. No patient worsened or developed new symptoms suggestive of a recurrent fistula during the follow-up period. One patient experienced intracranial dissection of the internal carotid artery and ischemic stroke with an unfinished procedure. The relief of early presentation was durable in long-term follow-up and the cured lesions were stable in angiographic controls. Favorable and durable outcomes could be obtained following endovascular approaches for cDAVF presenting with different ocular symptoms.
Nação, região e a unidade nacional uma leitura baseada em dois livros didáticos de história publicados na Primeira República
Authors: Silva Cristiani Bereta da
Published: July 2014

Este artigo objetiva discutir os sentidos de nação e região e a questão da unidade nacional presentes nos discursos sobre a história do Brasil e a história de Santa Catarina, construídos e divulgados na Primeira República. A proposta é analisar dois livros destinados ao público escolar: História do Brasil. Curso Superior, de João Ribeiro, publicado em 1900; e Pequena história catarinense, de Lucas Alexandre Boiteux, de 1920, com base em seu contexto de produção e circulação. A história e a geografia serviram ao propósito de legitimação das fronteiras estabelecidas entre os estados, assim como o da construção de um passado e tradição comuns que destacassem as especificidades de cada região e respectiva contribuição para a grandeza da nação. Espera-se contribuir para evidenciar as bases políticas sobre as quais se assentaram as histórias regionais no passado em relação à história do Brasil, bem como para adensar o debate sobre a produção didática de história regional no presente.
A organização de um corpo disperso uma análise da atividade jesuítica em terras brasílicas (1583)
Authors: Faria Marcos Roberto de
Published: July 2014

O artigo investiga a pedagogia da vigilância instaurada pela Companhia de Jesus na segunda metade do século XVI. Com o intuito de organizar o corpo disperso, o centro da Companhia em Roma manda visitar a província do Brasil, a fim de reforçar a vigilância e estabelecer a ordem sobre as coisas. Para verificar essa tese, faz-se uso de uma documentação muito pouco explorada, pesquisada no Archivum Romanum Societatis Iesu (ARSI), em Roma, sobretudo a correspondência entre o visitador e o Geral da Companhia. Nessa direção, o artigo aponta que o reforço da ortodoxia instaurado pela Companhia de Jesus é perceptível em várias direções, como na rígida regulamentação das normas que passam a sistematizar o cotidiano dos colégios e casas que os jesuítas mantinham em terras brasílicas.
O blefe na vida cotidiana: o jogo (de truco) enquanto mecanismo imaginário para evasão do real
Authors: Santos-Pinheiro Alexandre , Carrieri Alexandre de Pádua
Published: July 2014

Este trabalho discute o jogo de truco como elemento que permitiria a própria existência dos sujeitos jogadores ao tornar suas realidades minimamente suportáveis. Estudamos as dimensões simbólicas de um jogo de truco que acontece há 23 anos em uma organização empresarial, em que jogavam do "peão do chão de fábrica" ao "vice-diretor geral da empresa". O método de estudo utilizado foi a etnografia em organizações, a qual recebeu auxílio da observação participante e de entrevistas em profundidade. Os jogadores parecem significar sua realidade de trabalho através de movimentos do jogo que o conduzem a ser aquilo que sempre desejaram ser nessa realidade.
Performance evaluation of expenditure in primary care: the case of Brazil's southeastern cities
Authors: Santos Lucas Maia dos , Gonçalves Márcio Augusto , Ferreira Marco Aurélio Marques
Published: July 2014

This study aimed to analyze the performance of cities of Brazil's southeastern region on primary care expenditure, from 2007 to 2010. In order to do the performance analysis we used the technical efficiency scores produced by the Data Envelopment Analysis (DEA) methodology and the Ray and Desli Malmquist Index as the quantitative metrics. Before starting the cities' efficiency analysis, the cluster analysis was applied to group similar cities. This study proposes an analytical model of the comparative performance of 1097 cities, based on the National Primary Care Policy. The efficiency scores obtained highlights the disparities in the allocation of resources and lost in productivity through the years analyzed. This fact could be justified due the absence of procedures of relative comparison between cities and the decentralization of public expenses in public healthcare. The results shed light on the possibility to improve the quantity of primary care services, given the current level of expenditure.
The Influence of Subsoil Structure and Acquisition Parameters in MASW Mode Mis-identification
Authors: Boaga Jacopo , Vignoli Giulio , Deiana Rita , Cassiani Giorgio
Published: July 2014

Inversion of surface wave dispersion properties is commonly used to derive shear wave velocity depth profiles. However, one of the critical and yet rarely considered issues in this ill-posed inversion process is mode contamination. Rayleigh dispersion modes are the theoretically possible solutions of motion. Experimentally, we define Rayleigh dispersion properties from spectra energy maxima in some domain (as f–k), thus possibly producing only apparent experimental dispersion curves, where energy spreads onto several modes. If this phenomenon is not recognized, the inversion of an apparent dispersion curve can produce results unrelated to the actual subsurface structure. In this work, we present the results of synthetic tests that highlight the most common subsoil conditions and acquisition pitfalls that can give rise to surface wave mode contamination. In particular, we consider three typical subsoil structures that can produce this phenomenon: 1) a simple two-layer system with a strong impedance contrast, 2) a layered system with velocity inversion, and 3) a two-layer system having a lateral discontinuity. It is known that all such systems produce, to some extent, situations in which Rayleigh wave energy propagates at higher modes rather than on the fundamental mode. We also consider the impact of acquisition parameters, which influence mode contaminations mainly as a consequence of inadequate spatial sampling. This exercise leads to identifying the most critical subsoil characteristics that control ambiguous mode inversion. We finally propose possible a priori detectors and warnings for the most critical subsoil conditions leading to mode contamination.
Pelican Lake Field: First Successful Application of Polymer Flooding In a Heavy-Oil Reservoir
Authors: Delamaide Eric , Zaitoun Alain , Renard Gérard , Tabary René
Published: July 2014

The Pelican Lake heavy-oil field in northern Alberta (Canada) has had a remarkable history since its discovery in the early 1970s. Initial production by use of vertical wells was poor because of the thin (less than 5 m) reservoir formation and high oil viscosity (800–80,000-plus cp). The field began to reach its full potential with the introduction of horizontal drilling and was one of the first fields worldwide to be developed with horizontal wells. However, with primary recovery at less than 10% and 6.4 billion bbl of oil in place (OIP), the prize for enhanced oil recovery (EOR) is large.

Initially, polymer flooding had not been considered as a viable EOR technology for Pelican Lake because of the high viscosity of the oil, until the idea came of combining it with horizontal wells. A first—unsuccessful—pilot was implemented in 1997, but the lessons drawn from that failure were learned and a second pilot was met with success in 2006. The response to polymer injection in this pilot was excellent, with oil rate increasing from 43 BOPD to more than 700 BOPD and remaining high for more than 6 years; the water cut has generally remained at less than 60%. Incremental recovery over primary production is variable but can reach as high as 25% of oil originally in place (OOIP) in places.

This paper presents the history of the field and then focuses on the polymer-flooding aspects. It describes the preparation and results of the two polymer-flood pilots, as well as the extension of the flood to the rest of the field (currently in progress).

Polymer flooding has generally been applied in light- or medium-gravity oil, and even currently, standard industry-screening criteria limit its use to viscosities up to 150 cp only. Pelican Lake is the first successful application of polymer flooding in much-higher-viscosity oil (more than 1,200 cp), and as such, it opens a new avenue for the development of heavy-oil resources that are not accessible by thermal methods.
Theoretical Breakthrough Time of Vertical and Horizontal Wells Subject to External Fluid Drive in a Layered Reservoir with varying Architecture; Part VI: Letter ‘H’ Architecture
Authors: Adewole E. S.
Published: July 2014

Theoretical breakthrough times for a vertically-stacked two layered reservoir with letter ‘H’ architecture and completed with vertical and horizontal well at the top and bottom layer, respectively, have been compiled. Both crossflow and no-crossflow interface cases were considered.

Fifteen (15) different combinations of only edged fluid drive are possible. No bottom or top external fluid drive is possible for this architecture.

Layered reservoirs with no-crossflow interface are characterized by functions viii(x), x(x) and ix(x) only. But when the two layers are contributing to flow through the interface, breakthrough times are identified by the function v(z), vi(z), viii(x), x(x) and ix(x) only.

Theoretical breakthrough times derived were found to be directly proportional to reservoir extents in two (2) directions and inversely to reservoir layers diffusivity. Therefore, external fluid would finally reach the wellbores earlier if the fluid diffusivity is low and would be delayed if larger vertical reservoir areas are exposed to flow. The vertical reservoir area is suggested because of the infinite-acting boundaries bounding the upper and lower layers along the vertical axis. Irrespective of the number of sides of the reservoir and well type exposed to external fluid drive, the delay may be enhanced using perforation modification along the vertical axes or a rate selection based on estimated breakthrough time. Rate selection in the horizontal wells in this architecture is mandatory, since length modification is limited by lateral reservoir boundaries.
A Review of Erosion-Corrosion Monitoring and Inspection Techniques for Amenam High Pressure (HP) Header
Authors: Alum M. A. , Nworah C. , Omolegbe A
Published: July 2014

The Amenam high pressure Header is a 16" Carbon steel (API 5L gr. X60) network of flow-lines that collect crude oil gathered from the manifold of high pressure wells and convey them to the HP separator. With the combination of an ageing platform and production activities, severe internal erosion-corrosion issues are being experienced on the HP header of AMD2 (Amenam Drilling Platform 2), with estimated corrosion rates within 3 to 5 mm/year.

This erosion-corrosion is resulting from the very high velocities experienced on the HP header of AMD2, certainly combined with some production of sand. Also from a design perspective, using the highest available grade of Carbon Steel in conveying such a seriously corrosive fluid is always seen as the best viable economically because of the lengths of such headers, however considering the changing fluid compositions and conditions of an ageing field in contrast to design parameters, Carbon steel usually do have limitations in the long run.

In November 2010, a Shutdown was carried out to replace a failed section of the piping.

As part of the recommendation of a 2012 study by the Technology-Corrosion team of Total HQ, a periodic monitoring of this header in addition to a continuous inhibitor injection was advised until a more permanent solution of a more corrosion resistant Duplex stainless steel material is used to replace the carbon steel.

This paper highlights the Inspection techniques applied for the corrosion monitoring, results and trending analysis, as well as the advanced Non-destructive techniques (NDT) used for the period starting from December 2012 to December 2013. The results have helped in predicting which methods has the best reliability in detecting internal corrosion, while also helping to predict when a possible loss of containment is expected thereby giving the Operators a measure of proactive planning for sectional replacement; vis-à-vis assess the efficacy of the inhibitor injection and extrapolating the corrosion rates of similar configuration.
Maximizing Oil Production from a Reservoir Benefiting from an Adjacent Water-Flooded Reservoir
Authors: Nwankwo Kenechukwu , Ambastha Anil , Eme Vincent
Published: July 2014

Two reservoirs, the saturated Main area and the under-saturated Horn area, were discovered in 1965 and 1966, respectively. The original oil-water contact of the Main area is 6761 ft ss, while that of the Horn area is likely between 6994 and 7133 ft ss. Production started from both reservoirs in 1968 with almost same initial reservoir pressures, but significant pressure differences were observed when waterflood was initiated in 1991. Material balance can only be achieved with combined model of the two reservoirs and not with separate models of the Main or the Horn area.

The purpose of this study is to optimize oil recovery from the Horn area reservoir by optimizing waterflood performance and/or drilling infill wells to drain the identified remaining reserves. A black-oil simulation model was used to simulate the two reservoirs in a single model. Aquifer pore volume and aquifer transmissibility for both reservoirs are uncertain along with transmissibility for the fault separating the two reservoirs. These and other uncertain parameters were studied in a systematic manner to achieve a high-quality history-match.

Water cut, GOR and pressure matches were obtained by constraining simulated oil production to that of the historical. Oil net flux rate and oil cumulative net flux for each reservoir were derived from the simulation making it possible to calculate the recovery factor of each reservoir as a function of time. Also, since much of the oil has migrated over time from the Main to the Horn area, forecasts were made to evaluate future opportunities in the Horn.

Material balance calculation to reduce the uncertainty range in OOWC for the Horn area was carried out. A systematic evaluation of impact of uncertain parameters like aquifer pore volume and aquifer transmissibility for the Main and Horn areas along with fault transmissibility on history-match quality was deployed.
Cement Spacer Technology Eliminates Costly Remedial Jobs While Providing Excellent Bond Logs
Authors: Ilesanmi Oluwagbemiga , Gill Stephen , Hilal Bashar , Kulakofsky David
Published: July 2014

The significant and continuing loss of mud and/or cement slurry to a formation during drilling operations is one of the most troublesome problems affecting the oil industry. These problems impart a substantial negative impact on well economics.

Loss circulation problems have been identified as one of the most costly and time consuming problems faced in the oil and gas industry. It has been globally estimated that these problems causes drilling industries close to a billion dollars annually in rig time, materials, and other resources.

This paper will describe in detail the nature of the losses and application used to resolve the problem. The use of this unique cement spacer technology is a viable means of resolving most of these problems. This technology, can be applied to strengthen a wellbore, even with when a degree of losses are expected, as a preventive method where fractureing during cementing may occur due to predicted increases in hydrostatics, frictional factors, or both (ECD). In addition, it can also be used as a corrective method in cases where the wellbore is already experiencing losses.

Case histories will be presented describing how this novel spacer cured losses from seepage, moderate, severe and complete loss of returns. The applications include very low fracture gradients wells, where it was impossible to cement with dual slurry with lightweight slurries.

Additional benefits of the spacer is that it is 1) non-damaging, 2) minimizes filtrate invasion from the cement, 3) eliminates or at least drasticly reduces induced losses while cementing, and 4) it forms a permeability barrier membrane on the inside face of the wellbore (Figure 1) wall in-affect strengthening the wellbore allowing successful placement of the cement slurry which in-turn can provide long-term zonal isolation. Formation damage testing with this spacer shows near 100% return permeability.

The spacer rheological can be adjust from low values which minimize increases in ECD to higher YPs as required to enhance mud removal
Comparative Analysis of Geomecahnical Parameters Using Cores, Sonic and Gamma Ray Logs for Optimal Well Design
Authors: Dosunmu Adewale , Odagme B. S , Paul Fekete , Anyanwu Chimaroke , Ekeinde Evelyn , Odusegun Olufela C
Published: July 2014

Geomechanics data are usually dependent on log data and reservoir rocks often deforms due to depletion in the life of a field. These changes occur as a result of changes in the stress on such rocks which are imposed by drilling, production and injection activities and these changes can be unfavourable to the operators when drilling new wells in the same field. Thus, these changes have to be accurately predicted and mitigated (if undesirable). In this study, the accuracy of these vital geomechanical parameters obtained through sonic and gamma ray logs were compared and a correlation between both was established. Comparison was also made with respect to key indices including cost, safety, ease of acquisition etc. Only Unconfined Compressive Stress (UCS) as a geomechanical parameter was evaluated using several logging methods. The correlation coefficient range of 0.993 to 1 for various well logs analysed from the unconfined compressive stress obtained from the Sonic and Gamma ray logs. This would prove very useful especially for the marginal field operators in Nigeria and mature fields that do not have sonic logs as it would enable a more accurate derivation of geomechanical properties and the accruing benefits of a geomechanical analysis study. The nagging limitation of the Petrophysical log approach is the accuracy of the logs as spurious correlations were noticed from defective logs.
Investigating the Effects of Contaminants on the performance of Mineral Oil Based Versathin Dispersant
Authors: Kumapayi Olamide , Bello Kelani , Adekomaya Olufemi , Akintola Abidemi , Dala Joshua , Mohammed Ismail , Olafuyi Olalekan
Published: July 2014

Flocculation occurs when particles in the drilling fluid agglomerate due to particle to particle attraction thus leading to uneven distribution of weighting material within the fluid. Dispersants majorly are used to deffloculate fluids that have these tendencies, and their performance lies in the ability to minimize sagging and hence control drilling fluid rheology(Yusuf et al).

This work was undertaken to investigate the effect of clay and sea water (containing calcium and magnesium ions) contaminations on dispersant performance used in an oil based invert emulsion drilling fluid system. Barite (Ba2SO4) was used as the weighting agent; the based fluid used for the oil based invert emulsion mud was EDC-99, a specialized kind, different from the conventional diesel oil.The fluid were analysed before and after aging using, rheometer, filtration and emulsion stability tests.

The dispersant employed for the fluid system was Versathin ®. Versathin is an oligomeric fatty acid in mineral oil, an oil-based dispersant which tend to also perform excellently in the invert emulsion system. From the experimental results, a general decrease in fluid rheology was observed in the dispersant sample as compared with the blank sample. The emulsion stability of the fluid decreased as contaminants were added, fluid loss increased when contaminants were added to the dispersant samples. Contaminations also increased the plastic viscosity and yield point for the dispersant sample but all were still within the API range. Increase in LSYP in the presence of sea water and clay revealed that sag may be less noticeable when drilling reactive formations, confirming earlier studies on water based mud and the suitability of clay as rheology controllers. Cumulatively the result shows that Versathin oil based dispersant can control flow behaviour of fluids when employed in the oil based invert emulsion system.
Antimony Sulphide Stibnite and Potash as Local Substitute to Barite and Lignosulfonate as Drilling Mud Weighting Additives
Authors: Onu Ogbonnaya Victor , Ikponmwosa Ohenhen
Published: July 2014

A modified Antimony sulphide, locally called Tiro (stibnite) was employed as a drilling mud weighting material due to its relative weight and apparent health safety, as a substitute to expensive and imported Barite. Potash, commonly known as Kaun or Akaun in Nigeria, better called ‘Cooking Potash’ was also employed as a substitute to Lignosulfonate as a thinner in drilling mud.

The implication of using the Tiro and Potash were compared with that of conventional Barite and Lignosulfonate respectively in this project. Result obtained showed that Barite gave better weighting strength than tiro, it was also observed that the effect Barite on mud pH is lower than that of Tiro. Unfortunately, it was observed that the effect of barite on mud viscosity as weight of Barite increases has a severe effect on the viscosity of the mud. In that of Tiro, viscosity was maintained until some percentage weight of Tiro in the mud. For mud used in drilling dangerous zone, Tiro may be a better substitute to Barite due to Tiro's lower negative effect on viscosity if the safety of the well is of high consideration.

For the thinners, it was noticed that both Potash and Lignosulfonate have similar reducing influence on the mud weight, after which the Potash caused a radical reduction in mud density with increasing weight percentage of the additive. Both thinners had a reducing effect on the pH of mud at first after which the mud pH remained constant irrespective of additive increment. Mud pH is desirable between 8–10 for optimum hydration, since the percentage reduction of Potash is lower compared to Lignosulfonate, this puts Potash more relevant than Lignosulfonate. Also when there is need to quickly reduce the mud density due to the possibility of loss circulation as a result of over weight mud, especially when an abnormal low pressure zone is encountered during drilling operation, Potash would be a better alternative thinner as it causes rapid reduction in mud density.
Maximising Oil Production by Well Operating-Envelope Review to Arrest Production Decline in a Deepwater Field
Authors: Okosun Joshua , Ajayi Ayotunde , Olatunji idris , Lawal Kazeem , Ogunsina Oluseye
Published: July 2014

Well operating envelopes are defined to ensure optimal production performance, while maintaining completions integrity. Operating envelopes (OE's) however, have to be kept live to reflect the dynamic nature of well performance. This paper presents how the operating envelops of subsea production wells in a deepwater field are being monitored and utilised as enablers to realising production targets without compromising relevant constraints such as reservoir pressure, drawdown and well integrity.

A review of the current parameters employed to determine the required well operating envelope was carried out with a view to ascertain any window of opportunity for optimization. Downhole velocities, drawdown, produced sand/fines data were evaluated to help mitigate completion impairment and loss of installed sand control equipments.

An extensive post implementation analysis was also carried out to help revalidate the basis of well operating envelope. This provides a platform for remedial action, as any deviation from expectation is found out. This paper will provide an overview of how the operating envelope for Producer 1 was reviewed and implemented to maximize production from reservoir Z. The methodologies and workflow will be discussed extensively to demonstrate how the Field team has effectively arrested production decline in the Z reservoir by proactive review and update of its wells operating envelopes.
Distinguishing Strategies for Hydrocarbon Value Maximization in Africa's Energy Corridor: A Case Study of Zerkel Asset.
Authors: Maduawia Emmanuel , Matemilola Saka , Kaars-Sijpesteijn Casper , Enu Emmanuel
Published: July 2014

Although organizations spend lots of money to acquire assets for her legitimate and profitable use; observations have shown that some organizations hardly manage their assets efficiently and effectively; hence many firms have and if not, will in no distance time face significance asset management challenges.

Using Zerkel asset as a case study, this paper presents a description of how vision re-enactment via leadership, staff re-orientation and timely delivery of processes served as effective management strategies to rejuvenate hydrocarbon production within a short time frame.
High Prevalence of Modifiable Cardiovascular Risk Factors Among Male Off-shore Workers in Nigeria-A Preliminary Study
Authors: Chijioke Iroezindu Israel , Raymond Ruthvin , Michael Felfernig
Published: July 2014

Background: Internationally, Cardiovascular diseases (CVD) constitute a major cause of morbidity and mortality and it is estimated that by 2020 a majority of the global burden of CVD will be in developing countries. Offshore workers are often more prone to CVD due to unhealthy lifestyles however, the risk of CVD to this population is largely unknown in sub-Saharan Africa. Our study determined the prevalence of modifiable cardiovascular risk factors among off-shore workers in Nigeria.

Methodology A descriptive cross-sectional study was carried out amongst male off-shore workers in the Niger delta area of Nigeria from January to December 2012. Participants of the study were recruited consecutively during periodic medical fitness for work examinations where sociodemographic data, anthropometric measurements and blood pressure were obtained in a standardized manner.Venous blood samples were collected in the fasting state for glucose and lipid profile including total cholesterol, triglyceride, HDL and LDL, all of which were analaysed using dry chemistry technique (Reflotron® System, Roche Diagnostics, Germany).

Results This study looked at 375 male offshore workers with a mean age of 42.6 ± 7.1 years. Forty-one (10.9%) and 196 (52.3%) had a history of cigarette smoking and alcohol consumption respectively. The prevalence of modifiable cardiovascular risk factors screened for were: hypertension 139 (37.1%), diabetes mellitus 30 (8.0%), obesity 154 (41.1%), hypercholesterolaemia 80 (21.3%), lowHDL 30 (8.0%), highLDL 66 (17.6%), and hypertriglyceridaemia 53 (14.1%). Disorders that occurred more frequently in older patients were hypertension (p=0.002), diabetes (p=0.002), obesity (p=0.02) and hypercholesterolaemia (p=0.04). About 19 (63.3%) of subjects with diabetes mellitus and 52 (37.4%) with hypertension were unaware of the diagnosis prior to the on-site screening.

Conclusion The prevalence of modifiable cardiovaascular risk factors among off-shore workers in Nigeria is high. In order to prevent unwanted cardiovascular events in this group, a healthy lifestyle, frequent health screenings and other work place-based health promotion activities should be ensured.
Production Analysis for Solution Gas-Drive Reservoirs: General Variable Pressure/Variable Rate Case –Theory
Authors: Mohammed S. , Amarfio E. M. , Dankwa O. K.
Published: July 2014

Presently, analytical models for estimating reservoir parameters for solution gas-drive are restricted to either constant pressure or constant rate assumption. Thus, current models for solution gas-drive do not allow for rigorous analysis of simultaneous variations in pressure and rate. In addition, the traditional material balance time or pseudotime, which models variable pressure and/or variable rate case, is limited to single-phase flow.

This paper proposes a normalized multiphase pseudotime function that is capable of modeling general variable pressure and/or variable rate data for solution gas drive reservoirs during boundary-dominated flow. In particular, we present a multiphase flow equation that incorporates this pseudotime function. This flow equation is expressed in a form that traces the rate/time harmonic depletion curve. Thus, the proposed approach allows analysts to use a single depletion curve to model constant rate, constant pressure and variable pressure/variable rate cases for solution gas drive reservoir systems.

In addition, we propose a multiphase pseudocumulative function that is normalized by pseudopressure drop to permit the extension of flowing material balance method to solution gas drive. This is essential since analysis using flowing material balance method offers a better resolution than decline type curves. It also permits the computation of initial-oil-in-place.

The significant contribution of this paper is the generality of the proposed model that allows the rigorous handling of variable pressure and/or variable rate case for solution gas drive reservoir systems. Thus, the proposed approach, as opposed to existing models, is not limited to production constraints.

Only the appropriate equations and the methods of analyses and interpretation are presented in this paper. Illustrative examples are deferred to a subsequent writing.
OML-XYZ Production System Debottlenecking Using IPM
Authors: Ekeke Davis , Basu Subhayu
Published: July 2014

OML-XYZ is one of the largest producing and mature assets in Addax Petroleum Nigeria Limited and for a number of years, as drilling activity and the attendant well production potential have increased, has experienced bottlenecks in its production system (production potential recorded during testing of new wells was not fully released at FPSO after hook-ups to production line, even factoring in expected pipeline losses).

In some cases, after new producers were brought on stream, there was no noticeable increase in throughput at FPSO. Combining the complexity in the field architecture layout (evidenced by the number of well head platforms, well hook-up points, oil and gas-lift pipelines network & other surface facilities) and the lack of access to real-time pressure & production data, it was difficult to establish reason behind bottlenecks detected in the system.

A production system network model was constructed with the purpose of simulating functional relationships between fluid flow and pressure drop at critical nodes in the production system, such as well head, manifolds, pipelines and separators for different operating conditions.

This paper addresses the OML-XYZ production system and reviews the methodology of capturing flow behavior from reservoir to FPSO, utilizing an integrated production model (IPM). In identifying OML-XYZ production bottlenecks using the IPM, daily field data was reasonably matched and was subsequently used for short and medium term production forecasting, field monitoring, production optimization and facilities requirements. Results of production optimization studies showed that considerable production gains could be achieved through gas-lift optimization and targeted facilities upgrade.

Some examples of preliminary gains from this optimization are also presented.
Well Testing: A Geological Interpretation Tool
Authors: Animashaun M. B. , Nwakaji N. F
Published: July 2014

We acknowledge well testing as a reservoir engineers' tool and the importance of geological information in most aspects of interpreting well tests. Conversely, the well testing provides more reliable geological information and dynamically verifies the proposed geological model and sometimes updates the contents of geological description. This paper aims at reviewing the geological interpretation of the reservoir using well testing though it is subjective.

The first section of this paper is a review of essential geological data to get prior studies, static and dynamic modelling. The potential risks of a reservoir engineer working in isolation from the geoscientists are highlighted.

The second section evidences more detailed geological information about the reservoir such as reservoir continuity/compartmentalization, channels, facies, initial reservoir pressure, permeability and anisotropy (heterogeneity)

The third section emphasizes the importance of the geological description from well testing interpretation conforming to the static model.
Dynamic Modelling of Stacked Complex Reservoirs Using Experimental Design for Full Scale Smart Field Development in Niger Delta: Lessons Learned
Authors: Nwonodi Chike , Onwuchekwa Chukwuma , Campero Manuel , Eke Kenneth , Madu John , Adenaiye Niyi , Umoh Magdalene , Oluwaseyi Adekoya , Igogo Arit , Anosike Ebere
Published: July 2014

3D reservoir modelling of stacked reservoirs is often difficult, due to interplay of various uncertainties related to heterogeneity of the sand units modelled together within the stack. In the past, reservoir simulation had been used to model stacked reservoirs for commingled wells with varying predictive capacity. Typically, dynamic models use conventional approach in assessing uncertainties, involving discrete sensitivity of uncertain parameters and often lack robust subsurface uncertainty management. Additionally, handling dynamic cross flow issues by modelling of control valves in such cases presents production allocation challenges. Huge man-hours are needed for several run times, without achieving relatively good history-match and predictive capacity. As a result, only base-case history-matched model is developed; thus robust assessment of impact of sub-surface uncertainties on the predictions is usually inadequate.

This paper details a multidisciplinary approach adopted in integrated dynamic modelling of stacked reservoirs in a Niger Delta field using experimental design methodology. The phased development was aimed at full-scale reservoir development of multi-zone and commingled wells. Instead of single average for each sand unit, facies-dependent kvkh values were required to adequately capture reservoir heterogeneity for the complex depositional environment. Field-wide history-matches for 23 reservoir blocks and over 70 individual conduit matches were done to calibrate the simulation models. Model robustness was conducted through blind-testing and calibration with carbon-oxygen and openhole log data from newly drilled wells.

From the model predictions, recoveries for existing conduits from simulation models were benchmarked against Decline Curve Analyses and the results compared closely. Response Surface Models were used in selecting best history-matched realizations. 1P, 2P and 3P models were selected from the ultimate recovery probability distribution curves of these history-matched realizations. The modelling of interval control valves settings within the stacked models and use of smart well routines assisted evaluation of recoveries from planned commingled wells.
Managing Injectors Impairment in a Deepwater Field
Authors: Olatunji Idris , Ogunsina Oluseye , Okosun Joshua , Kazeem Lawal , Ajayi Ayotunde , Adenuga Ademola , Abiola Olayinka
Published: July 2014

In this deepwater soft rock field injected water is equivalent to oil as the reservoir management strategy is to maintain 100% voidage replacement and keep reservoir pressures above bubble point. The producers are high rate wells operating at 10-50kbpd range. This means the injectors are always expected to inject reliably at high rates.

However, over the life history of the field, waterflood performance has been one of the limiting constraints on achieving full potential of the field. Water injectors' impairment and failure has contributed immensely to this challenge of waterflood performance. A lot of efforts have gone into understanding the cause of these impairments and failures and the means to eliminate them. At the beginning of the field life, the impairment observed was mostly attributed to poor injection water quality. Water hammers resulting from trips were also identified as another cause of impairment.

The earlier wells were completed as Frac & Pack wells and there were attempts to understand how this completion types impact the impairment particularly as regards whether the proppants will be intact after significant amount of injection. In recent times, horizontal wells are being drilled and though the data from them is still limited, possible impairment models are being developed for them as well. The choice of the mode of injection – fractured or matrix – also seems to impact on the impairment mechanism of injectors.

Increase of the injection pump discharge pressure have been attempted to manage wells' rate and pressure interaction with each other through the subsea flowlines. The extent to which this can be carried out is limited by the pressure rating of topsides, the subsea equipment and the shale (cap rock) strength.

Consideration of all these factors has improved understanding of impairment mechanism which in combination with learning's from operational procedure that led to failure of injector wells has resulted in better management and improved the operating envelope for these wells. Reduced failure rates have been observed in longer well's life for newer wells than earlier ones. It has also led to development of mitigation measures like backflushes, refracs and acid stimulation when impairment is being observed.

There is still a large area of uncertainties or gaps in current understanding, although plans are being made for data gathering e.g. HUD checks, downhole gauges, injection profile logs and temperature warm- back logs to further to close the gaps in the existing impairment models for the water injectors.
Production Forecast Improvement Using Vertical Lift Performance Curves: Deep Offshore Niger Delta
Authors: Mogbolu Emmanuel , Turan Halil , Rey-Fabret Isabelle , Okereke Onyedikachi
Published: July 2014

Improving the production forecast of a hydrocarbon resource using reservoir simulation models, allows us to have a better prediction of reserves. This is important in asset development due to uncertainties that can reduce the expectation ultimate recovery after development. The resulting optimized production forecast allows for a better reservoir management plan.

This paper presents the methodology and reservoir tools to improve production forecast for fields under development. This methodology was applied in the case of HMS Field and the information obtained can be applied in optimizing the production forecast for other fields.

In the case of HMS field, the estimation of the production forecast was initially given by a first reservoir model (RMV1) of the field. After the acquisition of new seismic data, the production forecast needed to be improved.

The field studied is composed of 3 main reservoirs. Therefore, the improvement of the global production forecast has been made by generating up to date vertical lift performance (VLP) curves representative of the oil producers and water injectors based on the new data, and by connecting these VLPs on one hand to the 3 individual reservoir models, on the other hand to the new version of the global reservoir model (RMV2). Moreover, VLPs for the network (from the Well heads to the FPSO) have been built in order to test their impact on the merged model (RMV2).

The results show that for the individual reservoirs and merged model, there is marginal improvement in the reserves.

Sensitivity analysis and pressure gradient comparison for the wells were also investigated to manage uncertainties in the study. The results obtained were benchmarked against RMV1.

The integrated approach used in the study across the Reservoir Engineering, Drilling Engineering, Completions and Geosciences disciplines allowed for seamless delivery.
4D Seismic Feasibility Study for Well and Reservoir Monitoring in a Deepwater Nigeria Field
Authors: Osayande Francesca I. , Poon Becky B. , Horst Peter A. , Quadt Edwin , Otoh George A.
Published: July 2014

A 4D feasibility study was carried out to evaluate seismic detectability and the application of 4D technology in a green field in deepwater Nigeria. A 3D seismic survey, acquired prior to production, will serve as a baseline for future follow-up 4D survey if the production induced changes are sufficiently detectable.

The objective of this study was to assess if production-induced changes and fluid movement, using time-lapse seismic technology, are detectable. The seismic differences between monitor seismic and modeled time stamps are analyzed for 4D responses in the presence of realistic noise levels. This 4D feasibility study will provide technical basis for incorporating 4D seismic monitoring into the reservoir surveillance plan.

The 4D seismic will assist in placement of new wells, to optimize fluid flow between producer/injector pairs, and to locate by-pass oil areas. This will further support the current effort to improve the ultimate recovery by optimising phased development activities and in-field drilling using time-lapse monitor survey.

A dynamic reservoir simulation model was used to generate several time-stamps, the first being base and later time-stamps acts as monitor models. These models were converted to acoustic properties through a suitable rock and fluid model, and acoustic impedances were calculated. Synthetic seismograms were subsequently generated for the various base and monitor combinations, and the difference between the base and monitor synthetic seismic was analyzed for production-induced 4D signals (after the baseline synthetic was calibrated to the existing baseline seismic). The synthetics were corrupted with realistic noise levels, derived from the existing baseline seismic and existing 4D difference seismic volume from a nearby deepwater field.

The results showed that production-induced 4D signals due to changes in fluid saturation are clearly mapable in the field after one or two years of production in the presence of expected noise (NRMS of 15%) levels. However, the pressure drawdown is of relative small magnitude and has no significant impact on the 4D response. This information serves as a good guide for planning 4D acquisitions and reducing costs of unnecessary intervention in the field. The results of the study will be applied in updating Wells/Reservoir surveillance plan and optimising field development.

Based on the study, the plan is to acquire a minimum of three (3) seismic monitor surveys in the life cycle of the field. The first monitor will take place after two years from start of production and should show already significant 4D (time-lapse) signals.