bluuebunny/crossref_metadata_2025 huggingface dataset:
Place of Cabergoline in Acromegaly: A Meta-Analysis
Authors: Sandret Laure , Maison Patrick , Chanson Philippe
Published: February 2011

Context:

Cabergoline is widely considered to be poorly effective in acromegaly.

Objective:

The aim of this study was to obtain a more accurate picture of the efficacy of cabergoline in acromegaly, both alone and in combination with somatostatin analogs.

Design:

We systematically reviewed all trials of cabergoline therapy for acromegaly published up to 2009 in four databases (PubMed, Pascal, Embase, and Google Scholar). We identified 15 studies (11 prospective) with a total of 237 patients; none were randomized or placebo-controlled. A meta-analysis was conducted on individual data (n = 227).

Results:

Cabergoline was used alone in nine studies. Fifty-one (34%) of the 149 patients achieved normal IGF-I levels. In multivariate analysis, the decline in IGF-I was related to the baseline IGF-I concentration (β = 1.16; P <0.001), treatment duration (β = 0.28; P < 0.001), and baseline prolactin concentration (β = −0.18; P = 0.01), and with a trend toward a relation with the cabergoline dose (β = 0.38; P =0.07). In five studies, cabergoline was added to ongoing somatostatin analog treatment that had failed to normalize IGF-I. Forty patients (52%) achieved normal IGF-I levels. The change in IGF-I was significantly related to the baseline IGF-I level (β = 0.74; P < 0.001) but not to the dose of cabergoline, the duration of treatment, or the baseline prolactin concentration.

Conclusion:

This meta-analysis suggests that cabergoline single-agent therapy normalizes IGF-I levels in one third of patients with acromegaly. When a somatostatin analog fails to control acromegaly, cabergoline adjunction normalizes IGF-I in about 50% of cases. This effect may occur even in patients with normoprolactinemia.
The Future of Literary Study: An Experiment in Guesswork
Authors: Gorman David
Published: February 2011

The fundamental structure of literary study has stayed remarkably constant during the last seventy-five years: professional teaching and research have revolved around “criticism,” or the exegesis of individual works, and every other aspect of literary study has been treated as contributory to “reading.” There is almost no precedent for this pattern of activity in anything now recognized as the history of criticism. If these claims are at all correct, then studying literature differently would likely mean a redistribution of status among the subdisciplines, with such traditional fields as poetics, erudition (roughly, literary scholarship), and even evaluation pursued alongside criticism, as ends in themselves.
Selection in Insurance Markets: Theory and Empirics in Pictures
Authors: Einav Liran , Finkelstein Amy
Published: February 2011

Government intervention in insurance markets is ubiquitous and the theoretical basis for such intervention, based on classic work from the 1970s, has been the problem of adverse selection. Over the last decade, empirical work on selection in insurance markets has gained considerable momentum. This research finds that adverse selection exists in some insurance markets but not in others. And it has uncovered examples of markets that exhibit “advantageous selection”—a phenomenon not considered by the original theory, and one that has different consequences for equilibrium insurance allocation and optimal public policy than the classical case of adverse selection. Advantageous selection arises when the individuals who are willing to pay the most for insurance are those who are the most risk averse (and so have the lowest expected cost). Indeed, it is natural to think that in many instances individuals who value insurance more may also take action to lower their expected costs: drive more carefully, invest in preventive health care, and so on. Researchers have taken steps toward estimating the welfare consequences of detected selection and of potential public policy interventions. In this essay, we present a graphical framework for analyzing both theoretical and empirical work on selection in insurance markets. This graphical approach provides both a useful and intuitive depiction of the basic theory of selection and its implications for welfare and public policy, as well as a lens through which one can understand the ideas and limitations of existing empirical work on this topic.
Priceless: The Nonpecuniary Benefits of Schooling
Authors: Oreopoulos Philip , Salvanes Kjell G
Published: February 2011

Increasing wealth provides key motivation for students to forgo earnings and struggle through exams. But, as we argue in this paper, schooling generates many experiences and affects many dimensions of skill that, in turn, affect central aspects of individuals' lives. Schooling not only affects income, but also the degree to which one enjoys work, as well as one's likelihood of being unemployed. It leads individuals to make better decisions about health, marriage, and parenting. It also improves patience, making individuals more goal-oriented and less likely to engage in risky behavior. Schooling improves trust and social interaction, and may offer substantial consumption value to some students. We discuss various mechanisms to explain how these relationships may occur independent of wealth effects and present evidence that nonpecuniary returns to schooling are at least as large as pecuniary ones. Ironically, one explanation why some early school leavers miss out on these high returns is that they lack the very same decision-making skills that more schooling would help improve.
Retrospectives: The Phillips Curve: A Rushed Job?
Authors: Sleeman A. G
Published: February 2011

Half a century ago, Economica published what its webpage claims is “the most heavily cited macroeconomics title of the 20th century”—the paper by A. W. H. “Bill” Phillips (1958) that introduced the Phillips curve. Based on admittedly circumstantial evidence, I will argue that Bill Phillips was not satisfied with the paper and had not intended to publish it in 1958. I believe that Phillips was persuaded to allow his paper to be published in 1958 by James Meade. After a brief overview of Phillips' early life and career, I attempt to show why Phillips was probably unhappy with the paper that introduced the curve that came to be identified with his name and how, nevertheless, it came to be published.
Consumer Financial Protection
Authors: Campbell John Y , Jackson Howell E , Madrian Brigitte C , Tufano Peter
Published: February 2011

The recent financial crisis has led many to question how well businesses deliver services and how well regulatory institutions address problems in consumer financial markets. This paper discusses consumer financial regulation, emphasizing the full range of arguments for regulation that derive from market failure and from limited consumer rationality in financial decision making. We present three case studies—of mortgage markets, payday lending, and financing retirement consumption—to illustrate the need for, and limits of, regulation. We argue that if regulation is to be beneficial, it must be tailored to specific problems and must be accompanied by research to measure the effectiveness of regulatory interventions.
Identification, localization and expression of LPXRFamide peptides, and melatonin-dependent induction of their precursor mRNA in the newt brain
Authors: Chowdhury Vishwajit Sur , Ubuka Takayoshi , Osugi Tomohiro , Shimura Taichi , Tsutsui Kazuyoshi
Published: February 2011

The existence of RFamide peptides with a C-terminal LPXRFamide (X=L or Q) motif has been identified in the brain of various vertebrate species. However, the presence of LPXRFamide peptides in the urodele brain is not yet known. In this study, we cloned a cDNA encoding the precursor of LPXRFamide peptides from the newt brain by a combination of 3′ and 5′ rapid amplification of cDNA ends. The deduced LPXRFamide peptide precursor consisted of 233 amino acid residues, encoding four putative LPXRFamide peptides. All the peptide sequences were flanked by a glycine C-terminal amidation signal and basic amino acid on each end as an endoproteolytic site. Mass spectrometric analyses detected a nonapeptide, two decapeptides and an octapeptide produced from the precursor polypeptide in the brain as endogenous ligands. In situ hybridization further revealed the cellular localization of newt LPXRFamide (nLPXRFa) precursor mRNA in the suprachiasmatic nucleus (SCN) in the newt hypothalamus. Immunocytochemistry showed a cluster of cell bodies restricted to the SCN and their terminals in the median eminence. To understand the regulatory mechanism of nLPXRFa peptide expression, we further analyzed the effect of melatonin on the expression of nLPXRFa precursor mRNA. Melatonin administration to newts increased the expression of nLPXRFa precursor mRNA in the diencephalon. These results indicate that the urodele hypothalamus possesses LPXRFamide peptides and the expression of LPXRFamide peptides is regulated by melatonin. The localization of nLPXRFa peptides further suggests that these peptides may be involved in the regulation of pituitary hormone release in newts.
The State of Crayfish in the Pacific Northwest
Authors: Larson Eric R , Olden Julian D
Published: February 2011

We summarize the state of knowledge on crayfish in the Pacific Northwest region of the United States and Canada, emphasizing distributions and conservation status of native species, as well as known introductions and distributions of alien crayfishes, and reviewing fishing regulations relevant to crayfish across five states and provinces. We found the present distribution and ecology of native crayfishes in this region to be poorly known, inhibiting accurate conservation assessments and management. The number of alien crayfishes established in the region, ranging in distribution from localized to widespread and including several major invasive species, now exceeds the diversity of native crayfishes. The treatment of crayfish by fishing regulations and laws varies among states and provinces, potentially impairing successful management and conservation of these species in shared ecosystems such as the Snake and Columbia rivers. We conclude with recommendations for crayfish management and regulation, and a call for more research on the ecology of crayfish in the Pacific Northwest.
The Aquarium Trade as an Invasion Pathway in the Pacific Northwest
Authors: Strecker Angela L , Campbell Philip M , Olden Julian D
Published: February 2011

The aquarium trade moves thousands of species around the globe, and unwanted organisms may be released into freshwaters, with adverse ecological and economic effects. We report on the first investigation of the ornamental pet trade as an invasion pathway in the Pacific Northwest region of the United States, where a moderate climate and a large human population present ample opportunities for the introduction and establishment of aquarium trade species. Results from a regional survey of pet stores found that the number of fish (n=400) and plant (n=124) species currently in the aquarium trade is vast. Pet stores import thousands of fish every month, the majority of which (58%) are considered to pose an ecological threat to native ecosystems. Our propagule pressure model suggests that approximately 2,500 fish (maximum 21,000 individuals) are likely released annually to the Puget Sound region by aquarists, and that water temperatures in many parts of Washington are suitable for establishment of populations. In conclusion, the aquarium trade may be a significant source of past and future invasions in the Pacific Northwest, and we recommend enhanced public education programs, greater regulation of the aquarium industry, and improved legislation of nonnative species in the ornamental trade.
Unique Hydrajet Tool Provides Cost Savings and Improved Performance in Placing Many Perforations and Proppant Fractures in Horizontal Wellbores
Authors: Van Gijtenbeek K. A. , Surjaatmadja J. B. , Heitman C.
Published: February 2011

Hydrajet perforating and subsequent fracturing-stimulation placements using jointed pipe to sequentially create many propped fractures in a horizontal well can be challenging. When proppants are pumped through hydrajetting equipment for initial cutting and then also for the fracturing operation, tool failures could occur, possibly leading to a situation whereby the complete bottomhole assembly (BHA) needs to be replaced several times during these treatments. A service provider conducted an extensive analysis of some of these failures that revealed multiple damage mechanisms that could lead to internal and external erosion of the hydrajetting equipment. This analysis resulted in the design and construction of a new-concept hydrajetting tool that addresses these erosion issues adequately. This has been demonstrated by several recent case histories showing that the newly designed tool drastically outperformed the old-style tools, resulting in considerably fewer requirements for BHA replacements throughout the job. In fact, most cases have only required one trip in the hole, even for very large proppant volumes being pumped. This has provided considerable cost savings to the well operators.
Application of Nitrogen Foam for Profile Modification in a Heterogeneous Multi-layer Sandstone Oilfield
Authors: He Liu , Peng Ye , Wei Li , Li Song , Yan Zhong
Published: February 2011

Daqing Oilfield is a heterogeneous multi-layer sandstone oilfield. The main pay zone of the oilfield has entered into high water-cut (over 90%) development stage after more than 30 years of water injection. According to intrusive mercury tests on 104 pieces of sealed coring samples, permeability increased by 32% after water flooding; the pore volume increased by 5.9%. This may indicate a change in pore structure affected by long-term water injection. In thick layers, water bypasses oil and flooding efficiency decreases.

Fine geology research results show that in main pay zones and thick layers of non-main pay zones, there are certain amounts of remaining oil. Vertically, the remained oil gathers on the top of positive rhythm thick formations. For this portion of the remaining oil, it is difficult to develop by conventional stimulation measures. Therefore, study on nitrogen foam injection technology was carried out to control fingering. Core experiments indicated that nitrogen foam injection is suitable for enhancing oil recovery rate of heterogeneous reservoirs. Field pilot gave positive results.

This paper briefly introduces profile modification mechanism of nitrogen foam to control fingering and enhancing oil recovery rate. Static tests of foam adaptability to temperature, salinity, and oil saturation are evaluated in the paper.

Nitrogen foam can select automatically the high permeability zone and high water cut layer and realize fluid diversion after foam plugging, and then the gas component may provide gravitational differentiation when the foam bubbles break off, so as to increase the sweep volume and enhance the flooding efficiency[1][2] [3] [4] [5]. At present, Sabei Oilfield in Daqing has entered into the extra high water-cut development with its total water-cut up to 96%. Vertically, the water out behavior in layers differs greatly and massive water injected advances suddenly along high permeability positions, resulting in serious channeling. Therefore, in view of the geologic characteristics and fluid properties, three sets of foam system are developed, and the field pilots for nitrogen foam injection technology to control water fingering are conducted successively in Xing 7-1-33 and Bei 2-Ding 2-59 well cluster in Sabei Oilfield.
Understanding First, Simulation Later: Using Basic and Modern Reservoir-Engineering Techniques to Understand Reservoir Dynamics: A Proven Case
Authors: Alonso Gomez
Published: February 2011

In this paper is described a mature field in which water production is seen very early on in production life and rapidly increased to the current level of 80%. At well level a similar behavior has been a noticed, high initial oil rates with subsequent strong decline once water breakthrough occurs. This type of behavior has been observed in most of the wells completed among the different reservoirs that make up the field. Long term production data and modern decline analysis strongly indicated the presence of two systems in the reservoir.

Initially it was considered normal water production behavior. Petrophysical interpretation indicated the presence of five different facies. The production data was imported directly into the simulation model and with some "adjustments" a reasonable match was achieved. This resulted in highly optimistic forecasts, never reproduced by the new wells. This paper presents an analysis and explanation of the production behavior observed in the field. Which proved to be in line with the subsequent acquisition of field data. Indicating the reservoir shows a behavior similar to a dual porosity dual permeability one, with two systems dominating the production behavior in the wells.

This paper shows how important it is to have a strong understanding of reservoir dynamics before using 3D reservoir simulation models, and specially in this case, how the use of simple and modern analytical techniques, like for instance Chan plots, transient tests, conventional and modern decline analysis among others, can provide the reservoir engineer with a enough background to confidently take the next step. This paper also describes how pseudo-steady state calculations provided information regarding the characteristics of the second system. Which helped to optimize the original petrophysical interpretation in the static model. This represents a simple approach at the time to consider how detailed a geological model should be to reproduce production behavior.

This work had a direct impact on completion strategies and future IOR projects to be evaluated through the use of reservoir simulation, and it clearly represents a new "way of thinking" by integrating and making sense of different analytical techniques as input for building new models (static and dynamic). Similar production behavior has also been observed in other fields in the same area, which can be explained following the methodology here presented.
Improved Technique for Wireline Oil Sampling of a Tight Carbonate Reservoir in the Partitioned Zone (Kuwait/Saudi Arabia): A Case Study
Authors: Omar Mosaad Hamdalla , Bouyabes Ahmed , Al-Haimer Mohamed Salem , Al-Busairi Ahmed , Boon Cheng Cheong , Rampurawala Mansoor Ali , Hussein Azhar
Published: February 2011

The South Fuwaris Field is located in the Partitioned Zone of Kuwait and Saudi Arabia. The main reservoir is the Lower Cretaceous Ratawi, which commenced production in 1963. The reservoir is an elongated anticlinal structure, with good porosity (15-20%) but low permeability (1-10 md). The Ratawi Oolite was historically ranked as a lower priority compared to Ratawi Limestone due to poor productivity from the vertical wells. In recent years, the well performance has improved significantly through the use of open hole horizontal wells and Electric Submersible Pumps (ESPs). The reservoir is currently undergoing further development, with critical reservoir inputs being reviewed to enhance the reservoir model. One of the key model uncertainties is related to oil properties, as no representative PVT samples had been available.

Multiple attempts to collect downhole oil samples using Wireline Formation Tester (WFT) in this reservoir had failed due to low formation permeability, low fracture density and high pressure drawdown. A new technique was developed from comprehensive review of log and core data including:

Nuclear Magnetic resonance (NMR) for identification of mobile hydrocarbons, presence or absence of bitumen, estimation of oil viscosity, pore size distribution and permeability with core data integration. Review of sonic and core data to optimise perforation design. Open hole perforation in the zone of interest to bypass the damaged zone, increase the area open to flow and intersect natural fractures. Reduction of perforation damage due to mud reinvasion, through reduction of hydrostatic overbalance (from WFT pressure data) and the replacement of the wellbore mud system with clean completion fluid, during perforation and sampling operations.

This paper presents a case study of successful downhole oil sampling in a very tight carbonate reservoir through the use of innovative techniques and detailed job planning. The potential of applying this technique to heavy oil reservoirs within our asset portfolio is under evaluation.
Numerical Study of PDL-Induced Fracture-Face Damage Using a Fracturing Mimicator
Authors: Gdanski Rick
Published: February 2011

Simulations with a fit-for-purpose fracture-cleanup model have previously explored the impact of matrix relative-permeability quality on cleanup and productivity in tight-gas sands. Gas-water relative-permeability curves that have a crossover in the range of 0.1% of rel-perm have a region of "rel-perm jail." Previous simulations demonstrated that water invasion in such situations can cause cleanup problems. However, a low rel-perm quality should also act as a fluid-loss-control mechanism during fracturing, thereby preventing deep invasion in the first place. The fracture-cleanup model was upgraded to mimic fracturing treatments to explore the impact of rel-perm quality on fluid efficiency, fluid invasion, and cleanup. The model explored certain aspects of pressure-dependant leakoff (PDL) that might bypass rel-perm jail restrictions.

The causes and prevention of poor-performing fracturing treatments in tight-gas sands have plagued the industry, with many mechanisms suggested and various solutions attempted as cures. Verifying the mechanisms and solutions often requires a trial- and-error approach because of the physical and chemical complexities involved. This model has a unique capability of exploring physics of flow and chemical physics of overall complexity that cannot be effectively studied in the laboratory. The upgraded model was used to study a new mechanism by which PDL might induce fracture-face damage.

Fracturing and PDL were successfully modeled using the method of pressure-dependant porosity and permeability for the fracture and matrix. Details of the method are presented. Simulations show that in the absence of PDL, poor quality rel-perms provide effective fluid-loss control and should prevent deep-matrix invasion. Under certain circumstances, PDL can bypass the fluid-loss-control mechanism causing rel-perm-induced matrix damage once the fracture has closed. Fortunately, there is currently no strong evidence that this damage mechanism is common.
Petrophysical Evaluation for Enhancing Hydraulic Stimulation in Horizontal Shale Gas Wells
Authors: Buller Dan , Hughes Simon , Market Jennifer , Petre Erik , Spain David , Odumosu Tobi
Published: February 2011

The economic recovery of gas from shale reservoirs requires optimal multistage hydraulic stimulation in horizontal wells. Important parameters to consider in shale-gas evaluation include gas-filled porosity and total organic content. Mechanical rock properties, including a calculated brittleness index, along with mineralogy, are also required to target and design individual horizontal fracture stages in the best zones. This type of formation evaluation in horizontal wells requires careful correlation and calibration to petrophysical measurements obtained in either vertical pilot holes or direct offset wells. This paper presents a comprehensive approach to the evaluation of an unconventional resource play drilled in the Haynesville Shale in east Texas.

Using openhole and logging-while-drilling (LWD) logs, conventional core analysis, and a chemostratigraphy analysis of drill cuttings, a shale analysis linking mineralogy, free gas, effective porosity, a shale brittleness index, and a clay linked transverse anisotropy is verified on separate vertical and horizontal control wells. Beyond that, pulsed neutron spectroscopy logs were run to develop a cased-hole evaluation solution from N-N (neural network) modeling that could replicate openhole wireline or LWD logs, and chemostratigraphy mineralogy results.

Subsequently, two horizontal wells were logged with LWD tools and afterward, through casing, using the pulsed neutron log and neural network calibration. Fracture stages for the logged horizontal wells were then evaluated vs. the log data. Generally, lower normalized treating pressures per fracture stage are noted where lower clay volumes exhibit less transverse anisotropy and a higher calculated shale brittleness index. Radioactive tracer and production log data also confirm lower amounts of gas production from zones that are apparently fractured, but are more ductile and clay-rich.
Production Enhancement of Hilly Terrain Onshore Remote Field
Authors: Hanbzazah Shadi M. , Merwat Mohammed N. , Al-Khamis Mohammed N.
Published: February 2011

Developing and producing remote fields in a hilly terrain environment economically and effectively poses a great challenge to oil operators1. Transporting hydrocarbon fluids in these fields from the wells to the processing facilities and then to shipping terminals requires a detailed assessment of the flow hydraulics of the entire production network2–6. Moreover, a viable optimizing flow option needs to be considered and thoroughly evaluated prior to implementation for cost optimization, effectiveness and long-term impact on reservoir sweep7.

Saudi Aramco has recently embarked on the development of several fields, including remote fields, such as Shaybah, which is located in a remote, hilly terrain desert area in the Empty Quarter of the Arabian Peninsula. The crude from Shaybah oil producing wells must travel a long distance from wellheads located in Sabkhah (flat terrain) to the Gas-Oil Separation Plant (GOSP), passing across high sand dunes rising up to 200 meters, and then through a 638 km cross- country pipeline to reach a final stabilization facility. Due to the aberrant topography of the area, high back pressure and changes of flow regime leading to huge slugs have been observed, affecting the overall performance of the wells and the operation of the processing facilities. Consequently, three innovative technologies: Horizontal Thrust Boring (HTB), Multiphase Pumps, and Drag Reducing Agents, have been evaluated and implemented to circumvent these problems.

This paper will discuss in detail the realized benefits from these three technologies where results have shown a reduction in the flow and pipeline pressure drops of 230 psig and 300 psig from the application of HTB and drag reducing agents, respectively. Moreover, an overall production increase of about 50 thousand barrels of oil per day (MBOD) was realized from the utilization of HTB technology and an incremental increase of 250 MBOD in the capacity of the 638 km cross- country pipeline from the utilization of the drag reducing agent. On the other hand, the results of the trial test of the multiphase pump have indicated unsatisfactory performance due to the frequent maintenance needs and pump failures.
Evaluating Hydraulic Fracture Effectiveness in a Coal Seam Gas Reservoir from Surface Tiltmeter and Microseismic Monitoring
Authors: Johnson Raymond L. , Scott Michael P , Jeffrey R. G. , Chen Zuorong , Bennett Les , Vandenborn Craig , Tcherkashnev Sergei
Published: February 2011

In developing new coalbed methane (CBM) or coal seam gas (CSG) fields or reservoirs, the effect of many parameters are important in understanding the success or potential areas for improvement of hydraulic fracturing treatments. Estimating fracture geometry relative to the reservoir architecture is critical to understanding production variability. The Walloon Coal Measures, in the Surat Basin of Eastern Queensland, Australia, are a complex reservoir containing interbedded sandstone, siltstone, carbonaceous shale and coal seams where initial attempts at hydraulic fracturing in early pilot areas of the Surat Basin yielded poor results. Thus, when a hydraulic fracturing program was planned for this reservoir, it was decided to integrate a group of diagnostics that would be useful in understanding past results as well as deriving future improvements.

Data is presented from two wells in the Walloon Sub Group (WSG) where tiltmeters and microseismic monitoring were used to evaluate fracture effectiveness relative to the reservoir architecture and to assist further design work. The treatments carried out in the studied wells were typical of CSG frac treatments used in other producing areas, incorporating stages of treated, gelled and crosslinked-gelled water with increasing concentrations of sand, up to six (6) lbm/gal. During the treatments, complex fractures were inferred based on analyses of data from both tiltmeter and microseismic monitoring methods. The collaborative data set for these wells also included a large amount of other analyses and diagnostic data. It was only possible to fully explain the treatment results through the combination of multiple diagnostics and an in-depth understanding of how the created fracture interacted with the complex reservoir and stress environment.

In this paper, we outline the steps used to plan the monitoring program and describe how geological data was integrated to better understand the results observed during the treatments. We describe each of six (6) stages performed across the two wells, and how the diagnostics did or did not support the overall conclusions as to the effectiveness of each stage. Finally, this paper presents a logical framework to evaluate and integrate these technologies for use in future CSG well stimulation.
Coupled Hydro Geomechanical Simulation and Analysis of Fault Reactivation: Influence of Fault Geometry
Authors: Asadi M. S. , Rasouli V. , Zhang Y.
Published: February 2011

Fault reactivation is one the unfavourable incidents during drilling and production due to changes in in-situ stresses and reservoir pressure. Only a few studies, in their analysis, have included the effects of fault geometrical properties, in particular length, dip angle and surface geometry, while these are important parameter controlling fault slippage.

In this paper, the significant influence of fracture morphology on the mechanical behaviour of rock masses is explained through virtual coupling of FDM/DEM numerical simulations. It will be shown how changes in fracture roughness and inclination angle lead to different failure mechanisms. DEM numerical simulation of synthetic fractures shearing in a bonded particle model was performed to investigate the effects of surface roughness on the creation of damage zones around the pre-existing fractures as a result of broken bonds between particles. Moreover, the effects of the ratio of shear to normal stresses on fracture sliding will be discussed analytically.

In the second part of this study, synthetic data from a sandstone reservoir was used for a field-scale FDM modelling to analyse fault reactivation and plastic deformation. Our focus is on shear failures close to the fault plane, which intersects the reservoir rock horizon in a field with normal fault stress regime being dominant. Pressures associated with fluid injection were increased until the fault being reactivated, and this was then analytically confirmed with the Mohr-Coulomb failure criterion. Sensitivity analyses were performed to examine the effects of state of in-situ stress, injection pressure, fault inclination angle, and surface properties on the potential of fault reactivation.

The results show that the extent of damage zone along a reactivated fault is highly influenced by fault surface geometry and injection pressure. The higher the inclination angle, the lesser the fault sliding strength. Sensitivity analysis of injection pressure and fault surface properties showed that fault reactivation potential is a function of multiple parameters, but more sensitive to the injection pressure than fault infills properties. It was also observed that the hydrocarbon flow path after fault reactivation is towards the sheared segments of a fault zone, where the permeability was increased. Large displacements were recorded where a large dip angle (here 63º) and a small friction angle (here 10º) were assigned to the fault surface. Distributions of shear strain are clearly heterogeneous along and near fault planes. This suggests that specific fault segments might be prone to experience leakage when others might retain a hydrocarbon column.
Dual Porosity Processes in Coal Seam Reservoirs: The Effect of Heterogeneity of Coal Matrices
Authors: Lu Meng , Connell Luke D.
Published: February 2011

The heterogeneous effect of coal matrices on flow profiles in coal seam reservoirs was discussed in this paper. To this end the flow equations in cleats were formulated to couple with a new fracture (cleat)-matrix transfer function that incorporates the statistical details of the heterogeneity regarding the diverse matrix block's sizes. The resultant flow equations were then described by a set of integral-(partial) differential equations, and we developed a novel quatrature scheme to deal with them. An enhanced-coalbed-methane-recovery (ECBM) problem was taken as an excise example, where the statistical data measured for a coal sample from a literature was used. With this example we discussed the relative errors of the flow profiles that were predicted with and without considering the statistical variances relevant to the heterogeneous effect, respectively. These profiles discussed include the methane production rate, the carbon dioxide injection rate, and the pressure transient response at the bottomehole of the production well. The relative errors for the cleat methane recovery in the field were also examined. It was shown that, for the flowrates and the pressure response at the wells, considerable errors (around 5% to 60%) may be observed when the heterogeneous effect concerned is neglected, especially in earlier times of operations (e.g., 0 to 15 days), whilst large errors (e.g., over 50%) for the cleat methane recovery may still exist in some areas in the subsurface after a much longer time (e.g., 400 days).
Case Study of Improved Oil-In-Place Determination from Petrophysical Evaluation of Resistivity Anisotropy Logging Data in a Malaysian Deepwater Turbidite Field
Authors: Manescu Adrian , Kho Sze-Fong , Ha Kwong-Tak
Published: February 2011

Deep-water turbidites can hold significant amounts of hydrocarbon reserves. One principal element of reserves estimation is accurate hydrocarbon-in-place determination. In this type of reservoir this value is often difficult to obtain as turbidites are primarily composed of thinly bedded shale and sand beds. When shale and sand lamina are below a tool's vertical resolution, petrophysical properties, for example porosity, are averaged across the shale and sand lamina. Also, resistivity measured by conventional induction devices is biased toward the low-resistivity lamina-component, e.g. shale. This creates the classical low-contrast, low-resistivity predicament where quantification of hydrocarbon saturations and net-to-gross is problematic.

Tensor resistivity measurements provide both horizontal and vertical resistivities. The vertical resistivity is more representative of the high-resistivity lamina component, e.g. hydrocarbon-saturated sand. The tensor resistivity measurements are also used to measure large-volume (cubic meters) formation dip and azimuth.

Tensor resistivity and nuclear magnetic resonance data were acquired in this deep-water turbidite field. The data were used to provide a more accurate hydrocarbon–in-place value than was obtainable using conventional resistivity measurements in low- contrast, low-resistivity shaly sand formations and to obtain formation dips and azimuths. A methodology directed at the sand- lamina petrophysical properties was used. Work was performed in a total porosity system, using dry-shale density calculated by comparing nuclear magnetic resonance (NMR) porosity data with the neutron-density porosity in shale.

By comparing the final analysis with core data, it is shown that the integration of tensor resistivity and NMR data accurately computes oil saturations, sand fraction porosity and net sand thickness. There is a large increase in the calculated cumulative hydrocarbon volume over conventional petrophysical approaches due to increased precision and accuracy in the sand-lamina porosity, hydrocarbon saturation, and net sand thickness determination.
The "Extreme Lean Profile" Concept as a Crucial Technology for Multilateral, Long Extended-Reach Wells: The Case History of Cerro Falcone 4 OR
Authors: Burini A. , Poloni R. , Valente P. , Cavallaro G. , Mattioli L.
Published: February 2011

Following the many successful applications of the "Lean Profile" (LP) technique, developed by Eni E&P some ten years ago, a further step towards production maximization with simultaneous increase of operational safety and decrease of the overall drilling cost has been recently achieved with the introduction of the "Extreme Lean Profile" (XLP).

Compared to a conventional profile, the LP has allowed running an additional casing between the 18 ⅝" and 13 ⅜" strings, the XLP introduces a further casing also between the 13 ⅜" and 9 ⅝" strings.

Previous papers have described this new concept. Instead, our main intent herein is to highlight how the use of the XLP can really make the difference for the success of drilling operations when it comes to drill long extended-reach wells.

This is the case of the onshore well Cerro Falcone 4 Or in the Val D’Agri field (Italy), the first ever deviated well being drilled by applying the XLP concept, without which the target could not be reached with the borehole size required for constructing the planned multilateral well.

The need to apply the XLP technology required overcoming many challenges due to the severe operational conditions experienced in drilling previous wells (hard, unhomogeneous and abrasive formations, hole instability, severe vibrations, mud losses).

This paper provides a comprehensive description of the well profile requirements, the associated operational issues, the chosen solutions and the actual challenges encountered during drilling operations. The achieved results are also described.

Based on the success of this XLP application, Eni E&P is considering to further develop this concept of narrow annuli, to insert additional casing strings: for instance a 8 ⅛" casing between the 9 ⅝" and 7" strings and a 5 ¾" casing between the 7" and 4 ½" strings.
Shale Gas Horizontal Production Logging Measurements and Challenges
Authors: Heddleston D. C. , Haggerty M.
Published: February 2011

Traditional shale formations are presently being produced via horizontal well completions. These horizontal wells consist of numerous selectively stimulated stages containing as many as 20 stages spread out across 2000 ft to 9000 ft interval.

The well completions have been stimulated using low technology methods such as high volume water / slick water & sand. The initial production of the well requires a short period of flowback of the injected load water prior to the wells being kicked off with hydrocarbon production. The load water flowback can range from as little as 2% load return as high as 70% returns. Since these types of formations are far from being homogeneous, these horizontal laterals can intersect existing natural fractures or faults in the formation or an aggressive stimulation could induce fractures into existing natural fracture or faulting network.

This paper will showcase horizontal well production logging measurements ideal for this flowing environment in order to deliver a high confidence, representative flow profile.

In addition, deployment techniques & the logging challenges will be discussed to establish the best possible representative flowing environment for measuring these types of well completions.
Permeability Prediction from Wireline Well Logs Using Fuzzy Logic and Discriminant Analysis
Authors: Nashawi I. S. , Malallah A.
Published: February 2011

The goal of this paper is to predict formation permeability from readily available wireline well log data measurements. The proposed method has many advantages. It is cost effective compared to permeability obtained from core analysis, and most importantly it provides a continuous permeability profile throughout a particular formation horizon as opposed to the permeability obtained from well test analysis, which provides an average value for the entire drainage area of the well.

The method presented in this paper delineates a general methodology for permeability prediction from well log data. First, principal components analysis, cluster analysis, and discriminant analysis are consistently used to identify and categorize clusters based on the unique characteristics of well log measurements reflecting reservoir mineralogy, fluid content, and hydraulic properties within the logged interval; then, fuzzy-logic model is applied to each cluster to determine the formation permeability within the specified interval. Actual field data obtained from a highly complex heterogeneous sandstone reservoir are used to demonstrate the applicability and competence of the proposed technique.
Debottlenecking through Heat Integration Case Study: Crude Distillation Unit
Authors: Aseeri Ahmed S. , Amin M. Shahid , Ibrahim Mahmoud S.
Published: February 2011

Heat Integration of process plants leads to better energy conservation. This energy conservation can be utilized for increasing the capacity. In many plants the energy supply is the bottleneck for expansion. In such cases better heat integration can be used to overcome this bottleneck. In this paper we will talk about a case study that was done for debottlenecking a Refinery Crude Distillation Unit (CDU) through heat integration. The energy sources in this case are the furnaces. The maximum heat duty of the furnaces is limited by its design. The conventional solution for such a case is addition of another furnace or replacement by other furnaces of higher capacity.

The unit consists of the crude preheat train Heat Exchanger Network (HEN) in which the heat recovery shall be increased through better integration. The better integration is achieved at two levels, namely the network level and the exchanger level. For retrofit projects the modifications shall be minimal in order to achieve economic feasibility. For this reason the preheat train was divided in three sections depending on the plant layout. The analysis was first done for each section individually followed by the analysis for the whole preheat train, the three sections collectively.

The outcome of this study was a heat-integration-based retrofit design that will give a 20% increase in throughput utilizing the same existing furnaces and hence same energy consumption. This means a 20% more energy-efficient design yielding the saving of about 100 million Btu/hour of fuel gas and an estimated CO2 emissions reduction of 40,000 tons/year. Moreover the capital cost of this proposal is estimated to be 40% less than the traditional solution of adding a new train. Other components of the CDU including columns, vessels, furnace, piping and pumping systems were also analyzed and modified in accordance to the proposed new design.
Performance Assessment of the DC All-Electric Subsea Production Control System
Authors: Abicht Daniel , Braehler Johannes
Published: February 2011

This Paper describes the performance assessment program initiated for the first operating DC All Electric Controls System. An overview of the applied method considering both model and data uncertainties will be provided. Also the experience gained through operation after successful installation and commissioning of the system to date will be addressed.

While presently collecting operational experience subsea, significant data and processing capabilities of the first operating DC All Electric Controls System can be assessed. Key parameters of interest and their context are investigated in a thorough detail. This allows a permanent observation of the state of the system. By means of this approach expert confidence level increases as additional decision support is provided. This systematic condition evaluation is based on a continuous probabilistic investigation which complex physical phenomena tend to impose. Preventive planning of maintenance is enabled and leads to long term cost reduction.

The CameronDC™ system allows continuous condition monitoring which next to several others can be seen as a key enabler for All Electric Subsea Controls Systems. The presented one uses the concept of end to end redundancy, consistently from surface to the subsea actuators. It also employs high voltage DC electrical supplies, providing the advantages of minimized energy losses, and a true environmental friendly design, in line with the zero discharge concept.
Well Productivity Index Degradation - Applied Modeling Workflow
Authors: Saputelli L. , Perez J. , Chacon A. , Lopez C. , Patino J. , Eggenschwiler M.
Published: February 2011

Productivity index (PI) reduction is a recognized phenomenon in oil and gas production to the extent that production becomes uneconomic. Productivity index (PI) decrease may be caused by several factors arising from reservoir, completion, and operational issues. The reservoir-related factors include compaction, fines migration, pressure support and multi-phase fluid flow. The completion-related issues arise from frac-pack geometry and stress-sensitivity of proppant conductivity. Finally, operational issues such as pressure drawdown at the sandface and induced flux (the movement of fluids across the completion) may also play a large role in PI degradation. Understanding the interactions of different parameters controlling the PI behavior and the resultant well performance is paramount for maximizing the ultimate recovery and net-present value or NPV. PI modeling may offer several challenges because it involves non-unique solutions for reservoirs and near-wellbore and well-completion status, in addition to manual data entry subject to human errors, uncertainties in reservoir parameters, and poor quality field data.

This study presents a workflow for modeling well PI degradation for an over-pressured gas/condensate reservoir in deep offshore Gulf of Mexico. An automated procedure was tailored and applied to match production history by adjusting both the reservoir and well completion parameters. Among the reservoir parameters considered were horizontal stresses, rock compressibility, absolute permeability, relative-permeability endpoints and curvature, porosity, stress-sensitive permeability and porosity. The well completion parameters included fracture length, height, width, conductivity, and stress. A "Tabu Scatter Search" optimizer engine (April et al, 2003) selected the optimal values of a set of input parameters to minimize the objective function, i.e. the error between the measured and calculated PI values.

Both reservoir and well completion parameters contributing to PI degradation were identified, and compared to those obtained by alternate methods. The relative and combined contributions of stress-sensitive reservoir compressibility, permeability, porosity, and fracture conductivity all helped understand well performance and guide decisions towards optimum well operating envelope.