bluuebunny/crossref_metadata_2025 huggingface dataset:
Clocks for all seasons: unwinding the roles and mechanisms of circadian and interval timers in the hypothalamus and pituitary
Authors: Wood Shona , Loudon Andrew
Published: June 2014

Adaptation to the environment is essential for survival, in all wild animal species seasonal variation in temperature and food availability needs to be anticipated. This has led to the evolution of deep-rooted physiological cycles, driven by internal clocks, which can track seasonal time with remarkable precision. Evidence has now accumulated that a seasonal change in thyroid hormone (TH) availability within the brain is a crucial element. This is mediated by local control of TH-metabolising enzymes within specialised ependymal cells lining the third ventricle of the hypothalamus. Within these cells, deiodinase type 2 enzyme is activated in response to summer day lengths, converting metabolically inactive thyroxine (T4) to tri-iodothyronine (T3). The availability of TH in the hypothalamus appears to be an important factor in driving the physiological changes that occur with season. Remarkably, in both birds and mammals, the pars tuberalis (PT) of the pituitary gland plays an essential role. A specialised endocrine thyrotroph cell (TSH-expressing) is regulated by the changing day-length signal, leading to activation of TSH by long days. This acts on adjacent TSH-receptors expressed in the hypothalamic ependymal cells, causing local regulation of deiodinase enzymes and conversion of TH to the metabolically active T3. In mammals, the PT is regulated by the nocturnal melatonin signal. Summer-like melatonin signals activate a PT-expressed clock-regulated transcription regulator (EYA3), which in turn drives the expression of the TSHβ sub-unit, leading to a sustained increase in TSH expression. In this manner, a local pituitary timer, driven by melatonin, initiates a cascade of molecular events, led byEYA3, which translates to seasonal changes of neuroendocrine activity in the hypothalamus. There are remarkable parallels between this PT circuit and the photoperiodic timing system used in plants, and while plants use different molecular signals (constans vsEYA3) it appears that widely divergent organisms probably obey a common set of design principles.
KATP channel as well as SGLT1 participates in GIP secretion in the diabetic state
Authors: Ogata Hidetada , Seino Yusuke , Harada Norio , Iida Atsushi , Suzuki Kazuyo , Izumoto Takako , Ishikawa Kota , Uenishi Eita , Ozaki Nobuaki , Hayashi Yoshitaka , Miki Takashi , Inagaki Nobuya , Tsunekawa Shin , Hamada Yoji , Seino Susumu , Oiso Yutaka
Published: June 2014

Glucose-dependent insulinotropic polypeptide (GIP), a gut hormone secreted from intestinal K-cells, potentiates insulin secretion. Both K-cells and pancreatic β-cells are glucose-responsive and equipped with a similar glucose-sensing apparatus that includes glucokinase and an ATP-sensitive K+(KATP) channel comprising KIR6.2 and sulfonylurea receptor 1. In absorptive epithelial cells and enteroendocrine cells, sodium glucose co-transporter 1 (SGLT1) is also known to play an important role in glucose absorption and glucose-induced incretin secretion. However, the glucose-sensing mechanism in K-cells is not fully understood. In this study, we examined the involvement of SGLT1 (SLC5A1) and the KATPchannels in glucose sensing in GIP secretion in both normal and streptozotocin-induced diabetic mice. Glimepiride, a sulfonylurea, did not induce GIP secretion and pretreatment with diazoxide, a KATPchannel activator, did not affect glucose-induced GIP secretion in the normal state. In mice lacking KATPchannels (Kir6.2−/−mice), glucose-induced GIP secretion was enhanced compared with control (Kir6.2+/+) mice, but was completely blocked by the SGLT1 inhibitor phlorizin. InKir6.2−/−mice, intestinal glucose absorption through SGLT1 was enhanced compared with that inKir6.2+/+mice. On the other hand, glucose-induced GIP secretion was enhanced in the diabetic state inKir6.2+/+mice. This GIP secretion was partially blocked by phlorizin, but was completely blocked by pretreatment with diazoxide in addition to phlorizin administration. These results demonstrate that glucose-induced GIP secretion depends primarily on SGLT1 in the normal state, whereas the KATPchannel as well as SGLT1 is involved in GIP secretion in the diabetic statein vivo.
Innate immunity and inflammation of the bovine female reproductive tract in health and disease
Authors: Sheldon I Martin , Cronin James G , Healey Gareth D , Gabler Christoph , Heuwieser Wolfgang , Streyl Dominik , Bromfield John J , Miyamoto Akio , Fergani Chrys , Dobson Hilary
Published: June 2014

Mammalian reproductive physiology and the development of viviparity co-evolved with inflammation and immunity over millennia. Many inflammatory mediators contribute to paracrine and endocrine signalling, and the maintenance of tissue homeostasis in the female reproductive tract. However, inflammation is also a feature of microbial infections of the reproductive tract. Bacteria and viruses commonly cause endometritis, perturb ovarian follicle development and suppress the endocrine activity of the hypothalamus and pituitary in cattle. Innate immunity is an evolutionary ancient system that orchestrates host cell inflammatory responses aimed at eliminating pathogens and repairing damaged tissue. Pattern recognition receptors on host cells bind pathogen-associated molecular patterns and damage-associated molecular patterns, leading to the activation of intracellular MAPK and NFκB signalling pathways and the release of inflammatory mediators. Inflammatory mediators typically include the interleukin cytokines IL1β and IL6, chemokines such as IL8, interferons and prostaglandins. This review outlines the mechanisms of inflammation and innate immunity in the bovine female reproductive tract during health and disease condition.
The Mystical Figure of Haji Ahmad Mutamakin from the Village of Cebolek (Java)
Authors: Wieringa Edwin
Published: June 2014

History of the Islamization process in rural Javanese society has given birth to a mystic figure named Haji Cebolek Mutamakin of the village; a village in the North Coast region, Pati, Central Java. This figure is estimated to live around the beginning of the 18th century. He is widely known by the public-especially among students through a Java-written book Yasadipura I (1729-1803), a poet Sultan palace Pakubuwana IV, entitled Fiber Cebolek.DOI: 10.15408/sdi.v5i1.759
Al-Ma‘ahid al-Turāthīyah wa Shuyū‘īyah wa al- Ṭuruq al-Ṣūfīyah
Authors: Anwar Khoirul
Published: June 2014

This paper will reveal images Pesantren tradition, Kyai, and the congregation that has not been studied by scholars such as van den Berg, Hurgronje, and Clifford Geertz thus able to capture the real power of intellectual tradition and religious boarding schools. Kyai (charismatic religious teachers/scholars) and pesantren (traditional Islamic boarding schools owned and run by kyai) have become common subjects of research among scholars studying Islam in Indonesia.DOI: 10.15408/sdi.v5i1.761
Al-Ma‘had al-Turāthī wa Taqwim al-Jamā‘ah: Tajribah Ma‘had Hidayatullah
Authors: Abbas Sirojudin
Published: June 2014

This article discusses some of the characteristic peculiarities of the pesantren as in Pesantren Hidayatullah, Balikpapan, East Kalimantan, which does not make Arabic reviewing activities as part of the daily staple of his students.During the last three decades, pesantren in Indonesia have shown  a variety of institutional developments. The identification of pesantren as Islamic learning institutions-especially in term of their specific role in preserving intellectual tradition and reproducing 'ilama' may no longer be sufficient to explaint that development. Such a trend can be seen in the establishment of a significant number of Islamic learning institution in the country with different visions and characteristics of learning. One of the leading institutions representing this new form of pesantren is Pesantren Hidayatullah, Balikpapan, East Kalimantan.DOI: 10.15408/sdi.v5i2.756
Baby-MONITOR: A Composite Indicator of NICU Quality
Authors: Profit Jochen , Kowalkowski Marc A. , Zupancic John A. F. , Pietz Kenneth , Richardson Peter , Draper David , Hysong Sylvia J. , Thomas Eric J. , Petersen Laura A. , Gould Jeffrey B.
Published: June 2014

BACKGROUND AND OBJECTIVES:

NICUs vary in the quality of care delivered to very low birth weight (VLBW) infants. NICU performance on 1 measure of quality only modestly predicts performance on others. Composite measurement of quality of care delivery may provide a more comprehensive assessment of quality. The objective of our study was to develop a robust composite indicator of quality of NICU care provided to VLBW infants that accurately discriminates performance among NICUs.

METHODS:

We developed a composite indicator, Baby-MONITOR, based on 9 measures of quality chosen by a panel of experts. Measures were standardized, equally weighted, and averaged. We used the California Perinatal Quality Care Collaborative database to perform across-sectional analysis of care given to VLBW infants between 2004 and 2010. Performance on the Baby-MONITOR is not an absolute marker of quality but indicates overall performance relative to that of the other NICUs. We used sensitivity analyses to assess the robustness of the composite indicator, by varying assumptions and methods.

RESULTS:

Our sample included 9023 VLBW infants in 22 California regional NICUs. We found significant variations within and between NICUs on measured components of the Baby-MONITOR. Risk-adjusted composite scores discriminated performance among this sample of NICUs. Sensitivity analysis that included different approaches to normalization, weighting, and aggregation of individual measures showed the Baby-MONITOR to be robust (r = 0.89–0.99).

CONCLUSIONS:

The Baby-MONITOR may be a useful tool to comprehensively assess the quality of care delivered by NICUs.
Comparison of Rapid Cranial MRI to CT for Ventricular Shunt Malfunction
Authors: Boyle Tehnaz P. , Paldino Michael J. , Kimia Amir A. , Fitz Brianna M. , Madsen Joseph R. , Monuteaux Michael C. , Nigrovic Lise E.
Published: June 2014

OBJECTIVES:

To compare the accuracy of rapid cranial magnetic resonance imaging (MRI) with that of computed tomography (CT) for diagnosing ventricular shunt malfunction.

METHODS:

We performed a single-center, retrospective cohort study of children ≤21 years of age who underwent either rapid cranial MRI or cranial CT in the emergency department (ED) for evaluation of possible ventricular shunt malfunction. Each neuroimaging study was classified as “normal” (unchanged or decreased ventricle size) or “abnormal” (increased ventricle size). We classified a patient as having a ventricular shunt malfunction if operative revision for relief of mechanical causes of altered shunt flow was needed within 72 hours of initial ED evaluation. Our primary analysis tested noninferiority of the accuracy of rapid cranial MRI to CT for diagnosing shunt malfunction (noninferiority margin 10%).

RESULTS:

We included 698 ED visits for 286 unique patients, with a median age at visit of 10.0 years (interquartile range 5.9–15.5 years). Patients underwent CT in 336 (48%) or rapid cranial MRI in 362 (52%) of ED visits for evaluation of possible shunt malfunction. Patients had operative revision for ventricular shunt malfunction in 140 ED visits (20%). The accuracy of rapid cranial MRI was not inferior to that of CT scan for diagnosing ventricular shunt malfunction (81.8% MRI vs 82.4% CT; risk difference 2.0%; 95% confidence interval, –4.2% to 8.2%).

CONCLUSIONS:

Rapid cranial MRI was not inferior to CT for diagnosing ventricular shunt malfunction and offers the advantage of sparing a child ionizing radiation exposure.
Was Sarah Murnaghan Treated Justly?
Authors: deSante Jennifer , Caplan Arthur , Hippen Benjamin , Testa Giulano , D. Lantos John
Published: June 2014

Lung transplantation is a potentially life-saving procedure for patients with irreversible lung failure. Five-year survival rates after lung transplantation are >50% for children and young adults. But there are not enough lungs to save everyone who could benefit. In 2005, the United Network for Organ Sharing developed a scoring system to prioritize patients for transplantation. That system considered transplant urgency as well as time on the waiting list and the likelihood that the patient would benefit from the transplant. At the time, there were so few pediatric lung transplants that the data that were used to develop the Lung Allocation Score were inadequate to analyze and prioritize children, so they were left out of the Lung Allocation Score system. In 2013, the family of a 10-year-old challenged this system, claiming that it was unjust to children. In the article, we asked experts in health policy, bioethics, and transplantation to discuss the issues in the Murnaghan case.
Paleo‐MARSPEC: gridded ocean climate layers for the mid‐Holocene and Last Glacial Maximum
Authors: Sbrocco Elizabeth J.
Published: June 2014

Understanding how species have responded to climate change during recent glacial cycles has the potential to inform our understanding of how species will respond to future climate change over the next century. Glacial refugia and historical range shifts over geological time have traditionally been inferred by examining the fossil record or the distributions of sister species using phylogeographic approaches and, more recently, with species distribution models. Species distribution modeling has become a popular tool for projecting range expansions and contractions under climate‐change scenarios in terrestrial ecosystems; however, such models are less commonly applied to the study of marine ecosystems despite a similar need for understanding species' vulnerabilities to fluctuating climates. Here I present gridded climatologies for the world ocean representing the annual mean, range, variance, and extremes in sea surface temperature and salinity for the mid‐Holocene (6 ka) and the Last Glacial Maximum (LGM; 21 ka) obtained from coupled ocean–atmosphere general circulation models available through the second phase of the paleoclimate modeling intercomparison project (PMIP2). Furthermore, I present geophysical layers representing bathymetry, distance to shore, and six measures of topographic complexity during the LGM, when sea level was approximately 120 meters lower than today. All data layers are global in spatial extent, are downscaled to a 5‐arc‐minute spatial resolution, and are provided in ESRI raster grid format suitable for analysis in ArcGIS or in R using the raster package. These paleoclimatic data layers complement the modern bioclimatic and geophysical data layers contained in the MARSPEC database and should facilitate further studies on the historical response of marine species to late‐Quaternary climate change, including but not limited to inferences based on species distribution models.
Late-Life Production Boost for BP Miller With Combined Scale Squeeze and Chemical Water-Shutoff Treatments
Authors: Williams G. , MacDonald A. , Wylde J. , Shields C. , Smitton C. , Frampton H. , Morgan J. , Morris A.
Published: June 2014

The current, late life production on the Miller field is characterised by high water cut wells that need frequent scale inhibitor squeezes to manage the production of scale. In addition, the wells are often choked back due to plant water constraints. The key to managing the decline in oil production is therefore to reduce water production. This allows the wells to flow un-choked and also lightens the fluid column, increasing drawdown and oil rate in the well. Other advantages include increased scale inhibitor squeeze (SISQ) life, reduced OPEX costs and reduced environmental impact of overboard discharge of produced water and production chemicals. However, the presence of scale in the wells means that intrusive surveillance and mechanical water shut off would require costly milling to gain access. The field is therefore ideal for the use of chemical selective water shut off (SWSO) treatments, which can be deployed without access to production logging data. BP Miller and Clariant have progressively applied SWSO treatments on a range of wells. A dilute solution of cross-linkable polymer is bullheaded down the wells and reacts with added cross-linker in situ. After cross-linking, the web of polymer is inflated in the presence of water, effectively blocking the flow path, whilst deflating in the presence of oil. Since the whole producing zone is treated, water will be retarded without the need to know where it is coming from. Providing due precautions are taken, this can be highly successful. For example, in May 2005 on Slot 32, oil production increased from 800 bopd to 2,800 bopd, whilst water cut reduced from 92% to 77%. The most likely explanation for this is a combined effect of the treatment stimulating production from the J-sand region while limiting water flow potential from wetter areas.
Deliverability of Gas-Condensate Reservoirs — Field Experiences and Prediction Techniques
Authors: Kamath Jairam
Published: June 2014

Distinguished Author Series articles are general, descriptive representations that summarize the state of the art in an area of technology by describing recent developments for readers who are not specialists in the topics discussed. Written by individuals recognized as experts in the area, these articles provide key references to more definitive work and present specific details only to illustrate the technology. Purpose: to inform the general readership of recent advances in various areas of petroleum engineering.

Introduction

Predicting and assuring well deliverability often are important concerns when developing gas-condensate reservoirs. Many gas-condensate projects are in deep, hot, low-permeability reservoirs for which well costs are a significant part of the project economics. It is well known that the deliverability of gas-condensate wells can be impaired by the formation of a condensate bank once the bottomhole pressure drops below the dewpoint. This paper outlines the five steps—appropriate laboratory measurements, fitting laboratory data to relative permeability models, use of spreadsheet tools, single-well models, full-field models (FFMs)—to predict deliverability loss caused by condensate banking. It then discusses integrated laboratory/simulation field studies used to validate these steps. Finally, options to improve well deliverability are explored.

Gas Condensate and Banking

Typically, gas-condensate reservoirs are single-phase gas in the reservoir at discovery, but yield small amounts of oil at the surface (approximately 10 to 300 STB/MMscf). They have a composition consisting largely of methane and small fractions of intermediate and heavy ends (typically, approximately 87% C1, 9% C2-6, and 4% C7+). The temperatures encountered in these reservoirs (200 to 400°F) are higher than the critical temperature of the fluid, but lower than the maximum temperature extent of its two-phase region. As Fig. 1 shows, the gas is extracted, the pressure declines isothermally, and at the dewpoint, the first droplets of liquid formed from the heavier hydrocarbon components appear.

A gas-condensate system is also characterized by a liquid-condensation curve such as that shown in Fig. 2. A lean system may have a yield of approximately 10 STB/MMscf (2% maximum condensate), and a rich system could yield as much as 300 STB/MMscf (20% condensate).

When the flowing bottomhole pressure falls below the dewpoint of the reservoir fluid, liquid condensate builds up (condensate banking) near the wellbore, as shown in Fig. 3.
Coalbed- and Shale-Gas Reservoirs
Authors: Jenkins Creties D. , Boyer Charles M.
Published: June 2014

Distinguished Author Series articles are general, descriptive representations that summarize the state of the art in an area of technology by describing recent developments for readers who are not specialists in the topics discussed. Written by individuals recognized as experts in the area, these articles provide key references to more definitive work and present specific details only to illustrate the technology. Purpose: to inform the general readership of recent advances in various areas of petroleum engineering.

Introduction

Annual natural-gas production from coalbed- and shale-gas reservoirs in the US is approximately 2.7 Tscf, which represents 15% of total natural-gas production. Approximately 1.7 Tscf of this gas comes from more than 40,000 coalbed gas wells completed in at least 20 different basins. The remaining 1.0 Tscf comes from more than 40,000 shale gas wells completed in five primary basins. While the pace of coalbed-gas drilling is starting to slow, shale gas continues to be one of the hottest plays in the US, and drilling is expanding rapidly, especially in the south-central US (the Barnett shale and its equivalents), the Appalachian basin, and numerous Rocky Mountain basins.

Outside the US, more than 40 countries have investigated the potential of coalbed gas, resulting in commercial projects in Australia, Canada, China, and India. No commercial shale-gas projects currently exist outside of the US, but work continues to identify both new shale-gas reservoirs and to add incremental shale-gas production in existing reservoirs. Given that worldwide coalbed-gas resources are estimated to exceed 9,000 Tscf and shale-gas resources are estimated to exceed 16,000 Tscf, it is clear that tremendous potential exists for future growth (Kawata and Fujita 2001).

Reservoir Fundamentals

Coals are sedimentary rocks containing more than 50 wt% organic matter, whereas shales contain less than 50 wt% organic matter. Methane is generated from the transformation of this organic matter by bacterial (biogenic gas) and geochemical (thermogenic gas) processes during burial. The gas is stored by multiple mechanisms including free gas in the micropores and sorbed gas on the internal surfaces of the organic matter. Nearly all coalbed gas is considered to be sorbed gas, whereas shale gas is a combination of sorbed gas and free gas.

Coalbed-gas reservoirs contain an orthogonal fracture set called cleats that are oriented perpendicular to the bedding and provide the primary conduit for fluid flow. Gas diffuses from the matrix into the cleats and flows to the wellbore. In shale-gas reservoirs, gas is sometimes produced through more-permeable sand or silt layers interbedded with the shale, through natural fractures, or from the shale matrix itself. In some cases, natural fractures are healed by a mineral filling and must be forced open by hydraulic-fracture stimulation. It also is possible to have both shales and coals interbedded in a single reservoir, resulting in gas contributions from both lithologies.
The Marlim Field: Incorporating 4D Seismic in Reservoir-Management Decisions
Authors: Oliveira Rildo M.
Published: June 2014

Distinguished Author Series articles are general, descriptive representations that summarize the state of the art in an area of technology by describing recent developments for readers who are not specialists in the topics discussed. Written by individuals recognized as experts in the area, these articles provide key references to more definitive work and present specific details only to illustrate the technology. Purpose: to inform the general readership of recent advances in various areas of petroleum engineering.

Many brownfields have had 4D-seismic technology applied successfully to optimize reservoir production and recovery. This paper describes how 4D-seismic results were incorporated into the geological model and illustrates applications in reservoir- management decisions, thereby mitigating drilling risks in Marlim deepwater turbidite heavy-oil field. It highlights the repositioning of many planned wells and the improvement in the history match by use of the updated geological model.

The Marlim field is off the eastern Brazilian coast in water depths varying from 2,000 to 3,600 ft (Fig. 1). The field is the largest producing oil field in Brazil. Three seismic surveys cover the Marlim field. The first was acquired in 1986 and the others in 1997 and 2005. The most recent survey was acquired specifically for reservoir-characterization and -monitoring purposes.

Introduction

The Marlim field was discovered in 1985. The reservoir is an Oligocene/Miocene turbidite with excellent rock characteristics. Relative permeabilities are favorable to water injection, and well productivities are very high (Pinto et al. 2001). The field area is 56 sq miles. The oil gravity ranges from 18 to 24°API, the reservoir-oil viscosity is between 4 and 8 cp, the original pressure was 4,082 psi, and the saturation pressure was 3,769 psi.

Initial oil production from the Marlim field was in March 1991. Water injection started in 1994. Currently, oil production is approximately 390,000 B/D, water injection is 705,000 B/D, and the actual recovery factor is 25%. The water production is 252,000 B/D (bottom sludge and water=39%). A total of 205 wells were drilled in the Marlim field, of which 125 wells are operating—81 producers and 44 injectors. The production peak (615,000 B/D) in Marlim field was achieved in early 2002.

Three seismic surveys cover the field. The appraisal survey was acquired in 1986. A reservoir-characterization survey was acquired in 1997. The most recent survey, in 2005, was acquired specifically for reservoir-monitoring and -characterization purposes (Johann et al. 2006).

The initial development phase ended in 2002, and a new phase of complementary development is under way. This new phase is characterized by projects of border wells and infill-drilling wells. The 4D seismic was identified as the best technology to minimize risk and optimize the new projects, mainly the infill-drilling projects. A new seismic acquisition, for monitoring purposes, is planned for 2009.
Case Study: Integrated Study for Assessing Production Enhancement from a Matured Large Carbonate Reservoir in Kuwait
Authors: Al-Maraghi Eisa , Nair Cholamcottu V. G.
Published: June 2014

An integrated study has been conducted to build a reservoir management tool to evaluate feasibility of enhancing the production and maintaining the plateau rate long for the Umm Gudair field, a large carbonate reservoir located in Kuwait and the Partitioned Neutral Zone. A comprehensive data gathering campaign was made during initial phase of infill drilling and an appreciable volume of rock and fluid data were obtained which assisted the geoscientists and engineer in developing an improved static and dynamic model.

A team of geoscientists developed a complex geostatistical geologic model, considering 3D seismic, large suit of log data from 170 wells, core description of about 6000 ft of cores collected from 31 wells, etc. The detailed fine scale geologic model was built using one of the latest software and upscaled using a hybrid procedure involving statistical methodologies and upscaled models were sense-checked through streamline simulations to ensure that the selected simulation model preserves the features of the finescale model. The simulation model was history matched with 45 years production and surveillance data.

An optimum development plan was developed meeting the Company's strategic production requirements and a scheme that would provide extension of the current peak rate for another 5 years was recommended along with the necessary facility modifications and contingencies to mitigate uncertainties in long term production scenario. This paper highlights the critical steps of building a comprehensive reservoir simulation model through integration of the geological studies, engineering and production data and application of the model for planning production enhancement with the current and modified surface facilities in accordance with the Asset's long-term production strategy.
Fracture Acidizing of a HTHP Exploratory Well in Deep Carbonate Reservoir: A Case Study
Authors: Al-Omair F. S. , Siddiqui M. A. , Singh J. R. , Manimaran A. , Liu Hai , Razouqi Maen
Published: June 2014

The Jurassic carbonate reservoirs in Kuwait are deep, characterized with extremely low porosity and permeability. The temperature of these reservoirs ranges between 250-300°F. High production from these types of reservoirs will be possible if the oil filled fractures can discharge into large connected fractures during drawdown. Hence, these reservoirs are well suited for fracture stimulation to be exploited properly.

Fracture acidization of a deep HTHP exploratory well producing from limestone reservoir was performed successfully without any operational problem. The well was drilled to a depth of above 16,000 ft using high density oil-based mud (OBM). The well was tested in three intervals out of which the middle section produced high API gravity oil with gas. Initially, the well flowed at low rates but little increase in production was observed after matrix stimulation with emulsified acid. Lack of flow channels in the matrix was indicated by the continuous increase in bottomhole pressure during long shut-in period with a consistent drawdown pressure of 8,000 psi.

The low production of the well was investigated using borehole image logs, mud logs, daily drilling reports and core examination study. The findings of the study combined with data of the offset wells prompted fracture acidizing treatment. The well was fracture acidized using emulsified acid due to which the oil and gas production increased by several folds. Prior to the main fracturing treatment a step rate test, using 2 wt% KCl brine with surfactant, was conducted to determine reservoir parameters such as fracture extension pressure, fracture closure pressure and instantaneous shut-in pressure.

The paper highlights the usefulness of old data in deciding and designing the fracturing treatment to enhance reservoir deliverability. Additionally, a procedural mechanism for the selection of stimulation techniques, acid or proppant, in deep limestone reservoirs is discussed in this paper.
Beyond the Damkohler Number: A New Interpretation of Carbonate Wormholing
Authors: Talbot M. S. , Gdanski R. D.
Published: June 2014

Optimizing matrix acidizing is important to obtain the most effective stimulation treatment. Finding the optimum flow rate has been the subject of many papers and several of those focus on finding an optimum Damkohler number. This approach finds a unique solution only for a given linear core aspect ratio. Additionally, the pore volumes to breakthrough at the optimum Damkohler number are different between different laboratories and only scale to a master curve. This paper bridges the gap between data sets from different laboratories that have been performed using different aspect ratios. This paper uses the approach of minimizing the pore volumes to breakthrough as a function of interstitial velocity. To use the Damkohler number, the reactivities of all the rocks would need to be known, and they are generally not available from published work. Therefore, temperature is used in this model instead of reactivity.

This paper analyzes many plain hydrochloric acid test results and takes into account differences in temperature, acid concentration, core aspect ratio, porosity, and permeability. Having obtained a global function to describe all the data, the data can be collapsed to form a master curve. From this master curve, one can predict the optimum pump rate given a set of experiments conducted on a given rock regardless of aspect ratio. The new methodology allows improved optimization of acid wormholing using linear core test data from various laboratories by taking into account acid concentration, core aspect ratio, test temperature, and rock morphology in a single mathematical description.
Optimization of Completion Interval to Minimize Water Coning
Authors: Tabatabaei M. , Ghalambor A. , Guo B.
Published: June 2014

Horizontal wells have been found not ideal in many cases for solving water coning problems due to premature water breakthrough. This promoted a revisiting of the optimization of completion interval of vertical wells in bottom water-drive oil reservoirs. This paper presents a new approach to determining the optimum wellbore penetration for achieving the maximum water-free production rate of vertical well.

After reviewing the mechanism of water coning and the deluge of extremely sophisticated mathematical models in the literature, a simple analytical model has been derived in this study for completion engineers to optimize their water coning wells. The new model estimates the maximum water-free production rate (critical rate) considering the effect of limited wellbore penetration on the oil productivity of the well. To maximize the critical rate, an optimum wellbore penetration into an oil zone has been determined theoretically. This analytical model shows that the optimum wellbore penetration into the pay zone is less than half the total oil zone thickness, depending on the radius of wellbore, radius of drainage area, and pay zone thickness. Finally, this paper provides a tool in form of a set of curves which can be used for determining the optimum completion interval to make this approach easy to use for practice.
Behavior of Flow Through Low-Permeability Reservoirs
Authors: Lei Qun , Xiong Wei , Yuan Jiangru , Gao Shusheng , Wu Yu-Shu
Published: June 2014

While pores and throats of low-permeability reservoir rock are very tiny, they have significant influence on flow behavior in those reservoirs. There may be large differences in throat sizes and their distribution in low-permeability formations, even though they have similar storage space and flowing channels. Equivalent radii of flowing throats for low-permeability reservoirs with similar permeabilities may be very different. Stronger liquid-solid interaction within finer pore throats having a large interface area and abundant hydrophilic clay tends to prevent water from flowing through.

This paper presents a systematic study of flow behavior in low-permeability reservoirs using (1) a constant-rate mercury injection test, (2) a nuclear magnetic resonance (NMR) core analysis, and (3) a seepage experiment. NMR results show that mobile fluid saturation in low-permeability formations is very different from that in normal reservoirs. In general, the less clay content and larger throat radii of the low-permeability rock, the larger the mobile fluid saturation. We conducted a series of seepage tests, with the results showing that at low velocity, the flow rate in low-permeability rock is not linearly correlated with pressure gradient, but rather is a function of pressure gradient. Based on experimental results, we propose a modified Darcy's law for describing the observed nonlinear flow phenomenon, which is implemented into a black-oil model simulator. Simulation results incorporating the nonlinear flow-behavior show that effective permeability near production and injection wells is higher, whereas the permeability further away from the wells is lower. Well performance predicted by the linear model overestimates production rates, while that predicted by the new, nonlinear model better matches the field production data.
Reservoir Management of the Gullfaks Main Field
Authors: Talukdar Saifullah , Instefjord Rune
Published: June 2014

The giant Gullfaks Main Field comprises Statfjord, Cook and Brent Formations of Early to Middle Jurassic. The reservoir is complex due to large number of faults and extreme permeability contrast ranging from several Darcies in the Tarbert to milli-Darcy in the Cook. The highly productive sands are poorly consolidated causing sand production problem. Reservoir fluid in some of the areas contains high H2S. Uncertainties associated with structures, degree of communication, extreme contrast in reservoir properties and effective control of sand and H2S pose a great challenge for reservoir management.

Despite the challenges, the recovery factor on Gullfaks Main Field is high. A total of 335 Sm3 of oil has so far been produced, which amounts to an overall recovery factor of 56% (60% in the Brent Formation). This high recovery factor is attributed to effective reservoir management. The management strategy involves conservation of reservoir energy, implementation of simple and advanced strategies, systematic and sustained collection of data, and continuous application of improved recovery technologies.

Conservation of energy is achieved through water and gas injection. Simple and advanced strategies include selective perforation of wells, sand control, zone isolation, multi-target wells, controlled drainage through DIACS technology, through-tubing drilling, etc. Data collection involves 3D and 4D seismic, core and well log, RFT/MDT pressure, PLT, RST saturation, well completion, production and injection, etc. Improved recovery techniques, studied and some of them implemented, consist of infill-drilling, water and WAG injections, polymer assisted surfactant flooding, microbial injection, CO2 injection, etc. The current IOR initiatives are meant to extend the production life of the field to 2030 and thus meet the ambition of recovering 400 MSm3 of oil.

This paper summarizes the reservoir management challenges, techniques and technologies applied to evaluate and monitor the reservoir performance, and the strategies to enhance oil production.
Sand Cleanout with Coiled Tubing: Choice of Process, Tools, or Fluids?
Authors: Li J. , Misselbrook J. G. , Seal J.
Published: June 2014

Cleaning sand from wellbores is a major part of the coiled tubing (CT) industry. The process is a function of multiple variables including fluid properties, flow velocities, hole size and deviation, pipe eccentricity, particle properties and fill penetration rate and wiper trip speed. It becomes even more challenging to successfully remove fill from wells with low bottom hole pressure (BHP) especially if the well is completed with smaller diameter production tubulars which reduce circulation flow cross-section and choke flow. The problem is further compounded by high deviation or horizontal well trajectories especially in large diameter wellbores.

Several cleanout options have been developed in the past, employing a variety of different approaches. CT or conventional jointed pipe often incorporates high circulation rates, special fluids, wiper trip, or reverse circulation mode to remove solids. Many of these conventional sand cleanout methods often apply excess hydrostatic pressure on the formation, resulting in lost circulation in low formation pressure reservoirs. The conventional solution to overcome excess hydrostatic has been to include nitrogen to reduce fluid density and thus lessen the hydrostatic head. Sand vacuuming technology combines a concentric coiled tubing (CCT) string with a downhole jet pump to remove fills without placing hydrostatic loads on the reservoir.

This paper reviews the individual sand cleanout systems and discusses the advantages and limitations related to each method. Compared with other processes, cleaning sand using a wiper trip has become the most common and efficient mehtod. However, it needs an appropriate pump rate and reservoir pressure to maintain a proper return flow rate to carry the sands to the surface. For a depleted reservoir and especially for horizontal heavy oil wells, a sand vacuuming system can be used to efficiently remove the debris without circulating nitrogen and without high pump rates. The main application for the reverse circulation technique is cleaning sand from large diameter wellbores and when the necessary pump rates for conventional "forward" circulation are not achievable. Fluids with high solids suspension capability (under shear conditions) may be an economic option when the debris cannot be removed from a large diameter deviated wellbores using more conventional, but lower cost, cleanout fluids. The venturi junk bailer is often used to retrieve larger material or junk which is typically not circulated out by any other methods. Field cases are provided, demonstrating how to select the proper cleaning method and how to efficiently remove sands from a wellbore based on both operational and logistical conditions.
Using Monobore Systems to Lower Completion Costs in Short-Life Wells
Authors: Chapman Walt
Published: June 2014

A large percentage of the wells completed today are classified as short life or harvest wells. Many of these would not economically feasible utilizing high end completion components, and methods. Mono-Bore wells can be a solution to this dilemma.

This paper will discuss several methods and case histories used to complete these wells. Systems discussed and presented in this paper demonstrate how considerable time can be eliminated which will lower the overall completion cost as well. Several methods will be discussed and case histories provided to substantiate the results and savings. Methods will include the following:

Disposable completions utilizing the minimal completion components. Cemented Mono-Bore's utilizing Cement tolerant components, and methods/procedures of completing these wells. Staged cementing completion designs for open hole mono-bores. Simple water injector completions utilizing new technology. Low cost gas well unloading Case histories of the methods above discussing the advantages, and disadvantages of each method.

Illustrations along with detailed procedures will be discussed to better understand how each completion method can address the numerous opportunities, and problems associated in well completion design. Case histories will be provided to validate the each method. What if technologies will also be discussed in order to gain insight on what the future holds for these low cost wells.
An Alternative Method in Determining Permeability in Fractured Tight Gas Wells Dominated by Either Linear or Bilinear Flow
Authors: Bachman Robert C. , Hawkes Robert V.
Published: June 2014

Pressure transient tests are routinely performed on wells that have been hydraulically fractured. During the build-up, wells typically exhibit linear or bilinear flow, depending on the fracture conductivity. For high permeability wells radial flow may also be evident. For low permeability gas wells, the time to radial flow can often be impractically long. As a result many pressure transient analysis (PTA) tests end before radial flow happens. Without radial flow a unique value for reservoir permeability cannot be determined. To compound the problem low permeability wells often do not flow before being stimulated, so that pre-fracture tests require very specialized testing procedures and are not always possible. Unfortunately permeability dominates the productivity index calculation and without a reasonable value for permeability, the resultant production forecast will be significantly off. Furthermore, the ability to diagnose the success or failure of the actual stimulation treatment without prior knowledge of permeability will be diminished. This paper will show a technique, called the matrix method, which significantly reduces the uncertainty in permeability estimation for such cases. The essence of the technique is to generate a plausible set of matches considering the build-up data only. Then one takes this group of solutions and utilizes additional data, namely the pressure and rate history during the drawdown period, to determine the best possible match of the drawdown data.
Improved Water Saturation Estimation Using Equivalent Rock Element Model and Application to Different Rock Types
Authors: Shang Bruce Z. , Hamman Jeffry G. , Caldwell Donald H.
Published: June 2014

The second Archie equation relates water saturation to formation resistivity index through a power function. This important relationship has been widely used to evaluate hydrocarbon saturation. However, many rocks don't obey this empirical rule. The best Archie fit to these data may not comply with physical bounds and create significant bias in the computed hydrocarbon saturation.

This paper develops a new method for water saturation estimation based on the equivalent rock element model (EREM) that has been demonstrated to work well for rock transport properties to the first order effect. EREM contains two orthogonal pore components, one parallel and the other perpendicular to the direction of transport. Pore structure efficiency is defined as the volume ratio between the two components. When pores contain conductive and non-conductive fluid phases, the pore structure efficiency for the conductive phase changes with saturation due to fluid and mineral properties and pore structure variations. The conductive phase may become discontinuous below a certain critical saturation due to pore structure, wetting characteristics, interfacial tension, etc. The proposed algorithm incorporates this critical saturation phenomenon and relates capillary pressure data with electrical measurements. Approximating the pore structure efficiency of conductive phase as a function of saturation, we formulated a theoretical relationship between resistivity index and water saturation.

For some rocks, additional conductive meachanisms may exist in addition to electrolytic conductivity, in which case the Archie's equation would not apply. Many proposed formulas can be found in the literature regarding non-Archie rocks, but each only works well for a particular type of rocks. This paper demonstrates that the EREM approach can account for the additional conductivity and work well regardless of rock type.

This new approach expands the applications of the equivalent rock element model. It has several advantages over existing methods. (1) The approach is based on a simple physical model that reflects the two main components in a pore structure and accounts for the first order transfer effect. This ensures compliance with physical boundary conditions and increases the predictiveness. (2) The innovative inclusion of critical water saturation avoids the underestimation of water saturation at low water saturations. It links electrical measurements with capillary pressure measurements and allows the two observations to cross-validate and complement each other. (3) The proposed method is demonstrated to match core measurements from different rock and pore types with a single model.
The Art of Mentoring as told by Both Sides of the Three Decade Old Struggle in the Petroleum Industry
Authors: Edwards J. T. , Woo G. T.
Published: June 2014

Along with the dramatic price changes in the petroleum industry including gas and oil, there is one resource that has been seriously overlooked and undervalued: experienced personnel in the field, including engineers and other technical specialties. The real challenge is how this lack of experience is overcome in the short term, rather than just waiting for the passage of time. The petroleum industry can make significant gains quickly by investing in true, on the job mentoring. It could mean the difference between success and failure. Companies could be focusing less on headcount, and more on effective and well organized mentoring programs.

The shifts in supply and demand over the past three decades have at times left many within the technical side of the industry barely holding onto their jobs or looking at other vocations in order to maintain employment. Hoping to ride out the waves of boom and bust, those with valuable experience are not passing on their knowledge at a rate that can sustain our industry. These trends have led many colleges and universities to back away from true Petroleum degrees. Now that a demand is increasing again, how can the voids be filled quickly in the field with qualified and well-trained personnel, while the slow process of ramping up academic programs begins?

The only way to fill the void is through hiring from other engineering fields along with the inclusion of like-minded individuals with technical backgrounds. But now that they have been hired and are on the job, how can we maximize their success? The answer is mentoring. This paper will present the case with a personal perspective as told by mentors in the petroleum industry on both sides of the struggle, spanning three decades.