bluuebunny/crossref_metadata_2025 huggingface dataset:
Active Versus Passive Cooling During Neonatal Transport
Authors: Chaudhary Rajiv , Farrer Kate , Broster Susan , McRitchie Louise , Austin Topun
Published: October 2013

BACKGROUND AND OBJECTIVE:

Therapeutic hypothermia is now the standard of care for hypoxic-ischemic encephalopathy. Treatment should be started early, and it is often necessary to transfer the infant to a regional NICU for ongoing care. There are no large studies reporting outcomes from infants cooled passively compared with active (servo-controlled) cooling during transfer. Our goal was to review data from a regional transport service, comparing both methods of cooling.

METHODS:

This was a retrospective observational study of 143 infants referred to a regional NICU for ongoing therapeutic hypothermia. Of the 134 infants transferred, the first 64 were cooled passively, and 70 were subsequently cooled after purchase of a servo-controlled mattress. Key outcome measures were time to arrival at the regional unit, temperature at referral and arrival at the regional unit, and temperature stability during transfer.

RESULTS:

The age cooling was started was significantly shorter in the actively cooled group (46 [0–352] minutes vs 120 [0–502] minutes; P <.01). The median (range) stabilization time (153 [60–385] minutes vs 133 [45–505] minutes; P = .04) and age at arrival at the regional unit (504 [191–924] minutes vs 452 [225–1265]) minutes; P = .01) were significantly shorter in the actively cooled group. Only 39% of infants passively cooled were within the target temperature range at arrival to the regional unit compared with 100% actively cooled.

CONCLUSIONS:

Servo-controlled active cooling has been shown to improve temperature stability and is associated with a reduction in transfer time.
Infant Hospitalizations for Pertussis Before and After Tdap Recommendations for Adolescents
Authors: Auger Katherine A. , Patrick Stephen W. , Davis Matthew M.
Published: October 2013

OBJECTIVE:

Recent universal vaccination efforts among children in the United States have markedly changed hospitalization patterns for many vaccine-preventable diseases. Infants with pertussis often require hospitalization to monitor for potentially life-threatening respiratory failure. In 2006, tetanus-diphtheria-acellular pertussis (Tdap) vaccination was recommended for universal administration to adolescents, a known source of pertussis in infants. By 2011, 78% of adolescents in the United States had received Tdap. We sought to understand if patterns of pertussis hospitalization for infants changed with adoption of Tdap vaccination among adolescents.

METHODS:

Infants (aged <1 year) diagnosed with pertussis were identified in the Nationwide Inpatient Sample by using diagnostic codes. We used variance-weighted least-squares regression over preimplementation years (2000–2005) to estimate pertussis hospitalization patterns if Tdap had not been available. We compared expected hospitalization rates with observed rates for 2008–2011. Two years (2006 and 2007) were excluded from analysis during early Tdap implementation.

RESULTS:

The incidence of hospitalization for pertussis in 2000 was 5.82 (95% confidence interval: 4.51–7.13) discharges per 10 000 infants in the US population. The rate increased during pre-Tdap years by a mean of 0.64 pertussis discharges per 10 000 infants per year (P for trend = .004). Observed hospitalization rates for pertussis among infants were significantly lower than expected in 2008, 2009, and 2011, but in 2010 the observed and expected rates of hospitalization were not significantly different.

CONCLUSIONS:

Adolescent Tdap vaccination appears to be partially effective in preventing pertussis hospitalizations among infants. However, broader Tdap immunization coverage may be necessary to achieve sustainable reductions in infant pertussis burden.
Neonatal ECMO Study of Temperature (NEST): A Randomized Controlled Trial
Authors: Field David
Published: October 2013

BACKGROUND:

Despite evidence to support the use of extracorporeal membrane oxygenation (ECMO) in defined groups of newborn infants, rates of impairment among survivors remain high. Therapeutic hypothermia has been shown to provide neuroprotection in mature infants exposed to perinatal asphyxia. We hypothesized that therapeutic hypothermia during ECMO would reduce the proportion of infants with brain injury, and thus later impairment.

METHODS:

We conducted a randomized trial in the United Kingdom to compare ECMO with cooling (34°C for the first 48 to 72 hours) with standard ECMO (37°C). The primary outcome was the cognitive composite score of the Bayley Scales of Infant and Toddler Development, 3rd edition, at 2 years. Prespecified secondary outcomes included death, neonatal morbidity, and other neurodevelopmental and behavioral outcomes at 2 years.

RESULTS:

A total of 111 infants were entered into the study, 14 died before 2 years of age (16% who received ECMO with cooling vs 9% who received ECMO alone). Two infants were lost to follow-up, and 8 were unable to complete the full range of tests. For 45 evaluated infants who received ECMO with cooling, mean cognitive scores at 2 years were 88.0 (SD: 16.2) compared with 90.6 (SD: 13.1) for 48 infants receiving ECMO only (difference in means: −2.6; 95% confidence interval: −8.7 to 3.4). The various secondary outcomes were not significantly different between the groups, but most favored ECMO without cooling.

CONCLUSIONS:

In newborn infants treated by ECMO, the use of mild hypothermia for the first 48 to 72 hours did not result in improved outcomes up to 2 years of age.
A total thyreoidectomia hatásossága és biztonságossága a jóindulatú multinodularis golyvák kezelésében
Authors: Gál István , Solymosi Tamás , Lukács-Tóth Gyula , Wéber György
Published: October 2013

Absztrakt

Bevezetés: A megfelelő sebészi kezelési módszer vitatott a benignus multinodularis golyvák kezelésében. Klinikai tapasztalatainkról számolunk be, amelyeket a multinodularis golyvák total thyreoidectomiával történő kezelésében a műtétek kimenetelére, szövődményeire fókuszálva szereztünk, majd értékeljük a módszer hatásosságát és biztonságosságát. Anyag és módszer: Retrospektíve elemeztük 264, 2000 és 2006 között multinodularis golyva miatt total thyreoidectomiával kezelt beteg adatait. Vizsgáltuk a műtéti indikációkat, az átlagos kórházi ápolási időt, a korai és késői szövődményeket, a szövettani vizsgálat eredményeit különös tekintettel az incidentális pajzsmirigyrákok gyakoriságára és átlagosan 6,2 évvel a beavatkozást követően a rekurrencia előfordulását. Az eredményeket az irodalmi adatokhoz hasonlítottuk. Eredmények: A sebészeti beavatkozást 174 betegnél (65,9%) kompressziós és/vagy dislocatiós tünetek, 74-nél (28%) hyperthyreosis, a többinél kozmetikai probléma indokolta. Az átlagos kórházi ápolási idő 4 nap volt. Harmincegy betegnél (11,7%) alakult ki átmeneti hypocalcaemia, azonban ez csak 1-nél (0,3%) okozott klinikai tüneteket, és csupán 4 betegnél (1,5%) vált permanenssé. Egyéb szövődmények a 4 esetben (1,5%) kialakult haematoma, 7 esetben (2,6%) átmeneti egyoldali n. recurrens paresis – melyből 2 (0,75%) vált permanenssé – és a 8 (3%) betegnél észlelt seroma voltak. A szövettani vizsgálat 9 esetben (3,5%) fedezett fel incidentális pajzsmirigyrákot. Az utánkövetés során rekurrenciát nem észleltünk. Következtetés: A multinodularis golyvák sebészi kezelésében a total thyreoidectomia lehet a választandó műtéti eljárás.
Ciclos de comércio exterior: um estudo comparativo entre Brasil e Espírito Santo
Authors: Magalhães Matheus Albergaria de , Toscano Victor Nunes
Published: October 2013

O presente trabalho tem como objetivo documentar as principais regularidades empíricas ("fatos estilizados") relacionadas ao comércio exterior do Brasil e do estado do Espírito Santo em frequências cíclicas. Para tanto, constrói-se uma base de dados referentes a variáveis dos setores externos estadual e nacional ao longo de um período de dez anos (2002-2011), atentando para seu desempenho de curto prazo, com ênfase na volatilidade e persistência das flutuações observadas. Os resultados obtidos permitem concluir que, além das variáveis de comércio exterior serem mais voláteis que as medidas de nível de atividade, eles apresentam um padrão procíclico e defasado. Adicionalmente, constata-se que o saldo da balança comercial apresenta um padrão marcadamente contracíclico e que as flutuações das variáveis de comércio exterior são, em média, mais voláteis no caso espírito-santense do que no caso brasileiro. Por outro lado, não há evidências robustas voltadas para a possível ocorrência de uma "curva-S" relacionando saldo da balança comercial e termos de troca. Estes resultados são importantes por constituírem uma primeira tentativa de documentação de regularidades do comércio exterior estadual e nacional em horizontes de tempo correspondentes a ciclos de negócios.
Does Non‐Surgical Periodontal Therapy in Overweight and Obesity Result in a Change in Body Mass Index? A Review of Current Evidence
Authors: Geisinger Maria L. , Holmes Carolyn M. , Geurs Nicolaas C. , Reddy Michael S.
Published: October 2013

Focused Clinical Question

In patients with chronic periodontitis (CP) classified as overweight or obese who receive non‐surgical periodontal therapy, is a change in body mass index (BMI) associated with periodontal treatment?

Clinical Scenario

A 47‐year‐old male presents to your office with a chief complaint of “I was told I have periodontal disease.” He is missing tooth #9 and has significant supragingival and subgingival calculus deposits (Fig. 1). After examination, you assign a diagnosis of generalized moderate to severe CP. His probing depths (PDs) range from 2 to 8 mm, and his clinical attachment levels range from 2 to 8 mm, with 56% of sites demonstrating PD ≥4 mm. His medical history is significant for hypertension, osteoarthritis, gastroesophageal reflux disease, and obesity, with a current BMI of 31 kg/m2. He reports taking 5 mg enalapril every day, ibuprofen as needed for pain, and 20 mg omeprazole every day. Your treatment plan includes non‐surgical therapy and periodontal reevaluation before possible phase II surgical treatment. The patient states that he recently read an article in lay media discussing the link between obesity and periodontal disease and is interested in optimizing his health.
Randomized Trial of Intensive Housing Placement and Community Transition Services for Episodic and Recidivist Homeless Families
Authors: Levitt Aaron J. , Mitchell Kristen , Pareti Lauren , DeGenova Joe , Heller Anne , Hannigan Anthony , Gholston Jennifer
Published: October 2013

Objectives. We compared Home to Stay, a pilot of intensive housing placement and community transition services for episodic and recidivist homeless families, with a standard services approach.

Methods. Using intention-to-treat analyses, we conducted a modified randomized trial of 138 Home to Stay client families and a control group of 192 client families receiving standard shelter services.

Results. Home to Stay clients exited shelter more quickly than clients in the control group (Cox regression, P < .001), more commonly exited shelter with housing subsidies (75% vs 56%), stayed out of shelter longer (Cox regression, P = .011), and spent fewer total days in shelter (376 days vs 449 days). Home to Stay performed best with clients who entered shelter within 180 days of the pilot’s start date and had less impact on clients entering shelter before that time.

Conclusions. Relative to standard services, Home to Stay services can accelerate exit from shelter and reduce return to shelter and total sheltered days for episodic and recidivist homeless families. Standard shelter services may be able to narrow this performance gap by incentivizing work with all episodic and recidivist homeless families.
Intelligent Monitoring Technology of Production Parameters in CO2 Flooding Production Wells
Authors: Changyu Liu , Shuying Song , Deping Zhang , Qing Li , Shuai Xing
Published: October 2013

CO2 flooding experiment is conducted on the old well after water flooding, without taking into account such designs as CO2 corrosion control and gas seal. There are more wellbore weak links. In order to meet the demand of the long-term safe CO2 flooding, safety risk assessment is required.

Wellbore risk assessment process and evaluation template is established.. Integrated application of cementing quality detection, casing condition and annual pressure evaluation technology, safety risk assessment technology of CO2 flooding has formed and established wellbore risk assessment on CO2 flooding wells converted from water flooding mature wells.

This technology has been widely applied in CO2 flooding test in Daqinzi, jilin oilfield, comprehensively evaluating safety condition of old wellbore, screening suitable CO2 flooding well and assessing annulus pressure condition of injection well to ensure the long-term safe CO2 flooding.
Selection Criteria for Successful Water Shut-Off Treatment - Brown Field Success Story
Authors: Permana D. , Fakhrizal Fakhrizal , Nurwibowo M. P.
Published: October 2013

A brown-field which is located in Sumatra has been producing for more than 40 years. This field currently has high water production with average field water cut 98%. This condition is really burdening operating cost of this field since water production is continuously increasing. In order to reduce water production, reduce operating cost and increase profitability of the field, water shut-off treatments were preferred to be applied to several wells in this field. Those treatments successfully achieved good result which was decreasing water production (from 20,688 BWPD to 4,719 BWPD) and maintaining or even increasing oil production (219 BOPD to 525 BOPD) due to reduction of water-cut of water shut-off wells from 99% WC to 88% WC.

Prior to executing water shut-off treatments program, all data, including historical well-work job and completion, production data, and reservoir data, were thoroughly reviewed to ensure the wells were properly selected for water shut-off treatments. After the treatments were completed, those data were reanalyzed to extract lesson learned for upcoming water shut-off treatments. Based on previously analyzed data and results of water shut-off treatments, in order to have higher probability of success ratio of water shut-off treatments, following things are must-have items that need to be considered: well’s diagnostic plot (WOR and WOR′) should clearly show that wells have water coning or channeling problem, well’s historical completion has not been treated with the same method of water shut-off treatment, and wells should have interval which is located above current oil-water contact (COWC).

This paper describes the analysis method, candidate selection, and lesson learned of success and failure that may be used as selection criteria for selecting water shut-off treatments candidate to ensure higher probability of success.
Gas to Liquids: Beyond Fischer Tropsch
Authors: Lewis Philip E.
Published: October 2013

The oil and gas industry has long sought ways of converting difficult to transport natural gas into easily transported liquids, especially from remote locations where local opportunities to market natural gas are limited. In recent years, interest in Gas To Liquids (GTL) has expanded beyond such "stranded" gas because of a widening spread between the market value of natural gas and hydrocarbon liquids even in locations with mature natural gas markets such as the USA. The Fischer Tropsch (FT) process is a well-known and established method of producing hydrocarbon liquids from natural gas; for some, it has become synonymous with GTL. This paper points out that commercial and near commercial alternatives to the FT process exist and may be commercially superior in somesettings. The focus is on technologies that have been successfully piloted.

Available alternatives to FT are primarily natural gas to methanol and methanol derivatives. Methanol synthesis is one of the most mature industrial processes and methanol annual production volume ranks among the top three products in the petrochemical industry. Traditionally, methanol has been primarily a precursor to formaldehyde and acetic acid. In recent years, methanol has achieved added importance as an precursor to olefins and motor fuels, including direct blending into the gasoline pool, and also as a precursor to many motor fuel products such as gasoline and MTBE, a gasoline additive still very important outside the U.S., and DME, a diesel fuel substitute.

Natural gas to ethanol, ammonia, and ammonia derivatives will also be considered.
Fatigue in BHA Connections: How to Cope with It and Extend Product’s Life
Authors: Plessis Guillaume , Brock James , Muradov Andrei , Youngson Steven
Published: October 2013

Bottom-hole assembly (BHA) drill stem components and tools are heavy and have increased wall thickness compared to drill pipe. These components are typically run in compression, which can result in buckling, subjecting the BHA components to bending. Rotation under bending creates cyclic stress, fatigue, and can lead to possible failure. Changes in cross section and the presence of sharp corners and geometric discontinuities in the BHA thread/connection profile produce a higher localized stress state, a stress concentration, in comparison with the tube body of the BHA component. As a result, the connection is almost always the point of fatigue failure in drill collars (DC) and the point of failure in heavy weight drill pipe (HWDP) about half of the time. Therefore, increasing the fatigue life of the connection is beneficial. To increase BHA connection fatigue life, stress reducing features such as pin stress relief grooves, box borebacks, and a cold-rolling of the thread roots (creating a compressive stress state) have been incorporated into BHA connection design.

Additional connection designs have been developed that provide additional stress reduction and extend the connection fatigue life. Besides improving the resistance to fatigue crack initiation, these designs provide an added benefit of reducing the material loss when repairing (recutting) the connection. Three different field proven connection technologies are presented in this paper. The connection features that contribute to improved fatigue performance are described. The first is a modification to an API rotary shouldered connection. The second is a proprietary double-shoulder connection developed specifically for BHA tools. The benefits of both are discussed, including the results of full-scale comparative fatigue testing. The amount of material loss from repairing the connection and the impact on product life are also examined. Third, the use of streamline proprietary double-shouldered connections on heavy weight drill pipe (HWDP) is discussed. Recommendations are presented.
Experience with Formate Fluids for Managed Pressure Drilling and Completion of Subsea Carbonate Gas Development Wells
Authors: Carnegie A. W. , Omar M. , Colman G. , Supriyono H.
Published: October 2013

This paper reviews the outcome of the first-ever deployment of low-solids formate fluids for the managed pressure drilling (MPD) and overbalanced open-hole completion of two subsea gas wells in a highly-pressured carbonate reservoir. The field development plan required the use of low-solids well construction fluids to minimise formation damage and ensure maximum rates of gas production from the reservoir. The deployment of low-solids fluids was also required to minimise the amount of solids that would pass through the gas processing facilities on production start-up.

The high pressure of the reservoir required fluids of an equivalent mud weight of >15 pounds per gallon (ppg) - 1.80 Specific Gravity (SG) to maintain well control. Previous drilling experience in the area suggested there was a high probability of losing large volumes of fluid to the reservoir while drilling conventionally in overbalance. The strategy adopted to mitigate the risk of massive fluid losses was to use a 12.7 ppg (statically and dynamically underbalanced) potassium / sodium formate drilling fluid in combination with MPD technology to control the level of overbalance through backpressure. The reservoir section of each well was successfully and safely drilled with the low-solids potassium / sodium formate fluid at 150 psi overbalance in less than 2 days at an average ROP of 15-17 metres/hour with no measureable fluid losses to the formation.

On reaching Total Depth (TD) the potassium / sodium formate drilling fluid was displaced to kill weight (15.1 ppg) low-solids cesium formate brine as the tripping fluid before running the 7" pre-drilled liner. The tripping fluid was then displaced to 15.1 ppg clear cesium formate brine for the upper completion operation. These open-hole completion operations in cesium formate brine took 67 hours for the first well and 72 hours for the second. Both wells cleaned up naturally at start- up and tested at gas production rates of > 150 MMscfd, exceeding expectations by 50%.

The results of these trials confirm that low-solids formate brines used in combination with MPD can help deliver highly productive wells in fractured carbonate reservoir developments without incurring excessive fluid losses during drilling and without requiring acid stimulation. From an economic perspective this first-ever deployment of an underbalanced formate brine system for drilling a carbonate reservoir in MPD mode reduced costs by: -Eliminating lost circulation events and associated fluid losses-Allowing the use of a lower-cost (i.e. lower density) brine for drilling-Providing early kick and loss detection

It is concluded that the successful use of MPD with low-solids formate fluids in two subsea gas wells have provided a new cost-saving technique for safely drilling and completing high-pressure carbonate reservoirs that are prone to severe circulation losses.
US Shale Gas and Tight Oil Boom - The Opportunities and Risks for America
Authors: Madden Brian , Vossoughi Shapour
Published: October 2013

Shale gas and tight oil from unconventional deposits is now a very attractive target in the UnitedStates. Thanks to the technological revolution brought about by the combined use of horizontal drilling and hydraulic fracturing the US is now exploiting shale gas and tight oil formations in record numbers. The success of these exploitations were indicated in the most recent report released by the International Energy Agency (IEA) announcing the United States will overtake Russia as the biggest gas producer by 2015 and will become the largest oil producer by 2017.

The Energy Information Administration (EIA) estimates that the US has more than 750 trillion cubicfeet of technically recoverable shale gas, and estimates that there could be in excess of 24 billion barrels of on-shore technically recoverable tight oil resources. Already the Barnett Shale play in Texas produces 6 percent of all natural gas produced in the United States, and Leonardo Maugeri predicts the natural endowment of the initial Bakken/Three Forks American shale play could become a big Persian Gulf producing country within the United States on its own.

The risks concerning shale plays are the effects of hydraulic fracturing on the environment, whichisperceived as contributing to both land and water contamination among other health and community impacts. The pros and cons of this aspect will be scrutinized in this paper.

The analysis in this paper will examine the prospects of the major shale plays in the US and the technology being used to enhance the potential opportunities this boom has for American jobs and the economy. This paper will also review a series of federal laws governing most environmental aspects of shale gas and tight oil development, and the full range of environmental and health risks this potentialshale revolution may hold for the United States.
Clastic Reservoirs Productivity Index Estimation with Well Log Data
Authors: Kozhevnikov Dmitry , Kovalenko Kazimir , Deshenenkov Ivan
Published: October 2013

Fluid filtration and mass transfer processes description are the key issue of the geological modeling and oilfields development design for reservoirs with complex structure. The well log data interpretation results are the basis of reservoir characterization.

The advanced application of the effective porosity value provides description of reservoir properties for dynamic (absolute, effective and relative permeabilities, capillary pressures, free fluids) reservoir simulation. The outcome values of effective porosity and clay swelling index are properties, which confidently reflect filtration reservoir parameters.

It is stated that effective porosity determined with log data provides evaluation of relative/phase permeability values and hydrocarbon distribution in transition zones using capillary pressure models. The application of Buckley Leverett function for known effective permeability gives evaluation of oil share in production. It is established that effective porosity has strong correlation with productivity index for wide range of clastic reservoir rocks from different region. Thus, the determination of effective porosity from well logs is resulted in prediction of oil and water amounts in production.

The effective porosity determination with log data is complex task, which could be solved with NMR log or conventional log data interpretation. Authors of stated work developed petrophysical models and appropriate algorithms (adaptive log data interpretation) for effective porosity determination based on adaptation to well logging tools metrology and reservoir conditions. These algorithms provide determination of effective porosity values with conventional well logs (spontaneous potential log, formation density log, gamma-ray log, neutron log and sonic log). Proposed models of capillary pressure and relative/phase permeabilities are used in dynamic reservoir properties prediction algorithms. Dynamic properties are transferred in digital geological and hydrodynamic models for reservoirdevelopment process simulation.

The well log derived effective porosity is used for reservoir rocks productivity index prediction. Oil and water effective/relative permeabilities have close relation to effective and dynamic porosity and this fact provides determination of oil and water effective/relative permeabilities in reservoirs as well as oil and water amounts in production. Obtained results are applied for fluid filtration processes modeling and reservoir development technology design.
Integrated Unconventional Play Solution — A Case Study in Developing Very Thin Low-Permeability Gas Reservoir and Shale Gas Reservoir in Sichuan Basin, Central China
Authors: Qiang Jiang Yu , Run Peng Hai , Yang Yang , Halomoan Parlindungan Monris , Zhao Jing Kai , Wang Yue
Published: October 2013

abstract

Exploration and production of unconventional reservoirs have been conducted in the Sichuan basin since the 1950s. In that time, the relatively thicker low-permeability (tight) gas reservoirs have been developed, and a very thin tight reservoir and a shale gas reservoir are now being targeted. An operator has planned to develop these unconventional reservoirs with long horizontal drilling combined with multistage hydraulic fracturing. However, the management of the subsurface uncertainties appears as the biggest challenge.

Since the basin rests in a major compressional tectonic area, the target reservoirs are very sensitive to abrupt structural dip changes and faulted standoffs. Precise landing and lateral placement of horizontal wells are critical to the success of this program. Advanced logging-while-drilling (LWD) acquisition and real-time data transmission have been applied to overcome these challenges. A new LWD imaging technology delivers high-resolution electrical borehole images, azimuthal gamma ray, and multidepth measurement of formation resistivity for well placement and fracture identification purposes in the thin tight gas reservoirs. A multifunction LWD formation evaluation delivers the elemental capture spectroscopy in addition to triple- combo measurements for well placement and real-time formation evaluation in the shale gas reservoir.

Based on these real-time data and advanced interpretation or analysis techniques while drilling, structural features including dips, faults, and fractures could be clearly identified. Improved elemental composition from elemental capture spectroscopy and enhanced formation grain density evaluation could also be obtained. As a result, the team has been able to accurately place the well and significantly reduce the probability of erroneous lateral placement and optimize the completion design and planning of the hydraulic fracturing staging and segmentations. The successful implementation of this solution has led to the conclusion that the very thin tight gas reservoir and shale gas reservoir can be profitably developed in Sichuan Basin.
A Simplified Model for Desorption Area Prediction in Coalbed Methane Reservoir
Authors: Xu Bingxiang , Li Xiangfang , Xu Hanbing , Haghighi Manouchehr , Du Xiyao , Yang Xinzhou , Chen Dong , Zhai Yuyang
Published: October 2013

Production forecasting, well spacing, and well pattern optimization are key tasks in coal-bed methane field development plan. Desorption area around a production well is an important factor in well performance and reserve estimation. Analytical models are found to be simple and practical tools for drainage area calculation and well deliverability in conventional reservoirs. However, up to now, we have found no such analytical model for coal-bed methane wells with two-phase flow in which the gas desorption in coal is the controlling mechanism while the water is flowing in the cleat system.

In this paper, we present a mathematical model to predict how the size of desorption area is changing with pressure propagation during gas and water production. The pressure profiles at different production stages are determined using diffusivity equation which is solved using the known method of "continuous succession of steady states". For the case of two- phase flow of gas-water system, the pressure squared concept is used for linearization in middle and late times, while the pressure concept is used in early times when water flow is dominated. We have combined pressure from the solution of diffusivity equation with the material balance equation in order to develop our predictive model which is applicable for vertical wells for both cases of with or without hydraulic fractures.

This model is verified by numerical simulation and is in excellent agreement with the numerical solutions. Furthermore, the developed model is applied in one coal-bed methane well group in Hancheng field in China. It is found that desorption area is expanded outward in elliptical shape and the area can be calculated by the gas production data. The results show that two sample wells in the group have interfered with each other after producing for 525 days.
Enhanced Magnetic Surveying Technique Allows Tight Target Requirements to Be Achieved While Maintaining Drilling Efficiency
Authors: Aziz Intan Azian , Mondali Mondali , Mohammad Mahzan B , Tajuddin M Taufiq , Sapidih M Firdaus , Amir M Syafeeq , Brahmanto Edwin , Subroto Bramanta
Published: October 2013

Enhanced Magnetic surveying technique was introduced to Field Q in Malaysia allowing the tight geological target requirements to be achieved without impacting the operator’s drive for drilling efficiency.

Managing wellbore uncertainty is a significant challenge in Field Q, West Malaysia, where the Subsurface Team defines tight reservoir targets to accommodate the uncertainties that they have in a long step out well. Accurate well positioning becomes crucial in this situation to allow the penetration of multiple small targets. Historical approaches would have involved either running gyro surveys (which introduce more risk and time to the drilling process), or having to "over engineer" the wells (by creating tortuous well paths and drilling on the line to achieve the small drilling targets) due to the uncertainties of standard MWD surveys. Both of these approaches are against the drive to continually improve drilling efficiency while reducing risks.

Magnetic surveying has become increasingly accurate and now provides a cost-effective alternative to gyroscopic surveys in real-time drilling applications. New techniques for identifying and compensating for these errors involve a better understanding of the natural variations in the earth’s magnetic field, and new methods of mapping local variations improve magnetic modeling. The enhancement involves a multi-station analysis technique that provides compensation for drillstring magnetic interference and further improved when used in conjunction with geomagnetic referencing, which takes account of localized crustal effects in the earth’s magnetic field.

With a Geomagnetic Referencing System in Field Q, magnetic survey reduced uncertainty by 60% on average compared to a standard MWD error model. The benefits from this real-time drilling surveying process also means drilling is more accurate, with a reduced need for correction runs, or post-drilling changes to the planned well trajectory.
Drill Pipe Riser Intervention System Successful Experience in Offshore West Africa
Authors: de Fonvielle Henri , Bordet Laurent , Campbell William , Susak Nenad , Marajh Mitra
Published: October 2013

While offshore intervention on subsea equipment is quite common, the increasingly deeper water operations require light weight intervention systems while meeting safe and stringent operating specification. For these new deep offshore challenges, the conventional risers are becoming a more costly and less desirable solution.

Starting with a recollection of the main drivers that motivated the development of drill pipe riser intervention systems (DPRISi), the paper details the technical and economical challenges in West Africa that have led to the design of such a solution. When non-productive time and financial aspects are taken into account, it makes sense to develop a dedicated system in order to provide fast and reliable intervention.

Depending on the field requirements, two different types of drill pipe riser systems using a proprietary double shoulder connection were used by operators. A first solution was developed in 1999 featuring a seal ring close to the external shoulder. Subsequently, a new solution featuring a gas-tight metal to metal seal on the pin nose was developed in order to address increasingly demanding and challenging operations.

Intensively used in West Africa since 1999, the solution using the seal ring has shown robustness and reliability while being used for several projects in Angola such as Girassol and Rosa and now GirRI. The paper draws a summary of these operations and the feedback on the field use and maintenance. Also it emphasises the successful qualification process for the metal to metal seal solution that has been used in offshore Nigeria since 2010 for the USAN project.
Stress Analysis of Hollow Sucker Rod Screw Thread Joint and Shape Optimization of Screw Thread
Authors: Suling Wang , Yang Gao , Fangchao Liu , Siyuan Wangyuning Huang
Published: October 2013

In recent years, the screw pump is used as a new artificial method for it has the advantages of less investment, simple device structure, conventional operation, obvious energy saving and strong adaptability. It could reduce the cost of production effectively and improve production efficiency. Now it has become the main method of oil field mining machine. With the maturity of the ground drive screw pump oil recovery technology, many new forms of injection-production technology gradually applied to the screw pump well, such as, the downhole double screw pump oil-water separation system. For the torque which load on the whole system increases considerably than conventional screw pump, Higher mechanical property requirement of the supporting hollow sucker rod is needed, the failure area mainly concentrated on the screw thread joint. The Stress analysis was applied to the 34 hollow sucker rod which is supported on the on and off attachment of the downhole double screw pump oil-water separation system. According to the stress analysis results, shape optimization was applied on the root shape of the screw thread, the stress distribution of the screw thead on hollow sucker rod joint was improved, the mechanical property of the screw thread joint of hollow sucker rod was improved.
Metal Foam Sand Control Screen
Authors: Pei Xiaohan , Shi Bairu , Chen Lin , Zheng Lichen
Published: October 2013

Metal foam is recently being applied in down-hole sand control. The open pore substrate has a very permeable structure, the porosity and the pore size of the metal foam can be varied in a large range to meet the sand control demand. The three dimension open pore of metal foam results a very permeable structure to prevent plugging risks. The open pore metal foam is wrapped around a cylindrical geometry perforated base pipe. The number of foam layers and the pore sizes can be varied in order to achieve optimum flexibility for different sand control applications.

The effects of pore size and relative density on the metal foam mechanical properties and the relationship between the pore size and the sand control size have been studied. This paper compares the sand control characteristics of metal foam with two different conventional mechanical sand control screens supplied by manufactory, under similar conditions, loads, and formation sand. The metal foam based sand control screen improves the sand retention, and reduces the flow resistance by 16.6%. The metal foam based sand control screen was successfully used in the Liaohe Oilfield in China.
Opportunities and Challenges of CO2 Flooding in Indonesia
Authors: Muslim A. , Bae W. , Permadi A. K , Gunadi Bambang , Saputra D. D , Widyaningsih R. , Gunadi T. A.
Published: October 2013

Indonesia’s oil production has been constantly decreasing since 1995 and it is in need of another way to increase it. The oil production has been dominated by primary and secondary recovery techniques, while tertiary recovery techniques have rarely been used. The OOIP has been estimated at 75 billion barrels, the cumulative production is about 23 billion barrels, and proven reserve is 4.04 billion barrels. Therefore, remaining reserve is 49.5 billion barrels and the EOR potential is approximately 3.3 billion barrels. Looking at this potential, there is an excellent opportunity to implement a new suitable EOR method in order to increase the oil production.

Most of Indonesian crude oil is medium to light oil, with some fields containing heavy oil. Many researchers have been studying about CO2 flooding by experimental or simulation. The result shows that some of oil fields are favorable for CO2 flooding. Several studies on CO2 miscibility pressure revealed that the pressure ranges from 2150 to 3200 psig. This paper discusses and evaluates the opportunities and challenges of CO2 flooding in Indonesia. CO2 can be obtained from natural sources, natural gas processing, power plant, refinery and petrochemical industries. CO2 generated from power plant, refinery and petrochemical are need carbon capture technology. Sources of CO2 from natural gas processing are approximately 132.5 MMscfd, oil processing 899.41 MMscfd and power plant 6.817,91 MMscfd. Based on sources of CO2, oil categories, remaining oil reserves and previous studies, CO2 flooding is favorable in Indonesia especially in Central Sumatra and South Sumatra. Some of the challenges should be considered, such as depleted reservoir pressure to achieve MMP, infrastructure for CO2 transportation and surface facilities to process CO2 (recycling) that are not available, and also the unavailability comprehensive data of CO2 from gas field.
Innovative PDC Bit Designs With Improved Cutter Technology Deliver Significant Performance Improvements in Arabian Deep Gas Applications
Authors: Teasdale P. , Holalkere Markandeya S. , Djaoui M. , Ahmad R. T. , Roberts T. , Herron A.
Published: October 2013

This paper details the step by step process undertaken by a dedicated focus group established to provide a solution to inconsistent drilling performance with the 16" section in two deep gas fields in the Arabian Peninsula. The paper reviews the analysis undertaken as well as focusing on new design concepts and improved technology introduced.

Drilling in these deep gas fields, especially the 16" sections has always been a challenge for Polycrystalline Diamond Compact (PDC) drill bits due to the complex lithology that consists of a variety of carbonates with high interfacial severity, abrasive sandstones and compact shales. Despite improving the ability to consistently drill the 16" sections in a single run over the past few years, the new challenge is further improve consistency and rate of penetration.

Having experienced inconsistent performance and a series of premature PDC bit failures in these applications over the last few years the vendor assembled an integrated project team to investigate the issue. This team carried out an in depth analysis of all the available field data and identified several key factors that were responsible for PDC bit damage, such as bit/BHA whirl, poor operating parameters and their associated vibrations, and the limited ability of existing PDC cutters to drill such formations.

The findings led to the development of a new PDC bit design solution with high lateral and torsional stability capable of drilling with high drilling efficiency, and the introduction of new cutter technology, along with optimised operating parameters. The successful implementation of the new drill bit and recommended drilling parameters have enabled the operators to more consistently drill these challenging 16"sections in a single run at higher ROPs than previously achieved. This has resulted in significant cost saving for the operator.
Saturation Height Function in a Field Under Imbibition: A Case Study
Authors: Seth K. , Beales V. , Kawasaki A. , Namba T.
Published: October 2013

This paper presents a case study on the reconciliation of the water saturation computed using electrical logs and a saturation height function when the field is under imbibition. It is noted that wireline log evaluations suggest that the reservoir system cannot be adequately described using primary drainage capillary pressure in the field, and structure restoration study supports that the reservoir is under the imbibition process.

Gas in place (GIIP) has the largest impact on the development planning of this offshore gas field. GIIP is computed using the gas saturation, area and thickness of the reservoir making gas saturation a critical evaluation parameter. To compute the gas saturation accurately, typically, two sources of data, wireline logs and core measurements are integrated and reconciled. Wireline log based saturation is computed by using density, neutron porosity, resistivity as well as dedicated electrical core measurements, Archie’s exponents m and n. In addition, core based saturation is computed using saturation height functions established from capillary pressure measurements acquired using various techniques: Mercury Injection, Centrifuge and Porous Plate experiments. For imbibition conditions, special spontaneous and forced imbibition measurements were acquired on the core samples. These data sets represent two independent evaluations of the gas saturations.

In this paper, an imbibition function is computed from drainage capillary pressure data from core measurements and reconciled with wireline log estimates in a systematic workflow. This workflow has been applied to the Ichthys field, Browse Basin, on the NW shelf of Australia for generating the pre-development drilling base case model.

Overall, a good match is obtained between the saturation computed by the imbibition function and the wireline log interpretations, however mismatch is observed across some zones. Methods are proposed toclarify the origin of the mismatch and validate the resultant saturation whilst also serving as a guide for establishing a robust workflow to achieve these results.
Theoretical Prediction on the Volumetric Efficiency of Progressive Cavity Pumps via Finite Element Simulations with a Fluid-Solid Interaction Model
Authors: Chen Jie , Liu He , Wang FengShan , Shi GuoCheng , Cao Gang , Sun YanAn , Sun ChunLong , Ge WeiTao , Wu HengAn
Published: October 2013

During the operation of Progressive Cavity Pumps (PCPs), the problem of internal slip which defines the pump performance in terms of volumetric efficiency and lifting capacity always occurs. However, due to the complex geometrical structure and coupling interactions between the stator and the oil lifted, it is difficult to solve the internal slip analytically.

In our study, a new finite element model of PCP with fluid-solid interaction is developed to investigate the internal slip. We established the simulation models of fluid and solid respectively, solved the control equations of them in different solvers and exchanged the results through the fluid-solid interface. Partitioned solution algorithm is employed to tackle the problem of two-way fluid-solid interaction.

Two leakage mechanisms, longitudinal slippage and transversal slippage, were found from our numerical simulation results. For specified design parameters, the fluid leakage can be computed with different hydraulic pressure, thus the volumetric efficiency of PCPs can be obtained. Our computed volumetric efficiency is consistent with experimental results of laboratory test, which can verify our model and simulation method. Furthermore, we studied the influence of different material and structure parameters on internal slip of PCP. The developed model could also be used to compare the volumetric efficiency of different PCPs and optimize the design of PCPs. Our work can be of great significance for the optimization design of new specified PCPs.
Life Extension of Offshore Assets – Balancing Safety & Project Economics
Authors: Brandt H. , Mohd Sarif S.
Published: October 2013

The oil and gas industry in the Asia Pacific region has matured, and the number of aging offshore facilities is increasing. Changes in reservoir conditions and enhanced oil recovery technologies result in more hydrocarbons available than originally anticipated. Further, new discoveries in more remote or deepwater areas are often developed and tied into existing infrastructures as subsea tiebacks. These trends result in a need to extend the life of the existing offshore installations and facilities beyond their original design life. The decision to extend the service life of an offshore asset is based on detailed technical analyses, assessing the status and the integrity of the structures, the equipment and systems combined with detailed economical evaluations of the required investment needed for upgrades and modifications. It is essential that these evaluations assures safe and reliable future operations of the assets, while at the same time provide sound project economics for the life extension period.

DNV has for a number of years been a leading provider of technical life extension analyses and integrity management services, assessing structures, hulls of floating installations and platforms, mooring lines, pipelines, subsea equipment and well integrity. Together with the industry, DNV has further enhanced these life extension services by developing an integrated approach which combines the technical assessments with risk and reliability analysis into a Value Chain Assessment (VCA) which can be used to better evaluate the project economics related to a life extension project and provide decision support for assessing investments required for upgrades and modifications. This economic value chain model combines all the relevant cost elements into an economic lifecycle model, considering operational and maintenance costs, expected project revenue and capital investment costs required for any upgrades and modifications.

This paper will, based on project experience, highlight key challenges and issues related to life extension of offshore installations and will demonstrate the benefits related to applying an integrated and more economic approach to life extension projects. Key technical challenges related to offshore life extension projects will be addressed and possible solutions presented.