bluuebunny/crossref_metadata_2025 huggingface dataset:
The Drosophila Planar Polarity Proteins Inturned and Multiple Wing Hairs Interact Physically and Function Together
Authors: Lu Qiuheng , Yan Jie , Adler Paul N
Published: March 2010

The conserved frizzled (fz) pathway regulates planar cell polarity in both vertebrate and invertebrate animals. This pathway has been most intensively studied in the wing of Drosophila, where the proteins encoded by pathway genes all accumulate asymmetrically. Upstream members of the pathway accumulate on the proximal, distal, or both cell edges in the vicinity of the adherens junction. More downstream components including Inturned and Multiple Wing Hairs accumulate on the proximal side of wing cells prior to hair initiation. The Mwh protein differs from other members of the pathway in also accumulating in growing hairs. Here we show that the two Mwh accumulation patterns are under different genetic control with the early proximal accumulation being regulated by the fz pathway and the latter hair accumulation being largely independent of the pathway. We also establish recruitment by proximally localized Inturned to be a putative mechanism for the localization of Mwh to the proximal side of wing cells. Genetically inturned (in) acts upstream of mwh (mwh) and is required for the proximal localization of Mwh. We show that Mwh can bind to and co-immunoprecipitate with Inturned. We also show that these two proteins can function in close juxtaposition in vivo. An In∷Mwh fusion protein provided complete rescue activity for both in and mwh mutations. The fusion protein localized to the proximal side of wing cells prior to hair formation and in growing hairs as expected if protein localization is a key for the function of these proteins.
Degradation of the Saccharomyces cerevisiae Mating-Type Regulator α1: Genetic Dissection of Cis-determinants and Trans-acting Pathways
Authors: Nixon Christina E , Wilcox Alexander J , Laney Jeffrey D
Published: March 2010

Mating phenotype in the yeast Saccharomyces cerevisiae is a dynamic trait, and efficient transitions between alternate haploid cell types allow the organism to access the advantageous diploid form. Mating identity is determined by cell type-specific transcriptional regulators, but these factors must be rapidly removed upon mating-type switching to allow the master regulators of the alternate state to establish a new gene expression program. Targeted proteolysis by the ubiquitin–proteasome system is a commonly employed strategy to quickly disassemble regulatory networks, and yeast use this approach to evoke efficient switching from the α to the a phenotype by ensuring the rapid removal of the α2 transcriptional repressor. Transition to the a cell phenotype, however, also requires the inactivation of the α1 transcriptional activator, but the mechanism by which this occurs is currently unknown. Here, we report a central role for the ubiquitin–proteasome system in α1 inactivation. The α1 protein is constitutively short lived and targeted for rapid turnover by multiple ubiquitin-conjugation pathways. Intriguingly, the α-domain, a conserved region of unknown function, acts as a degradation signal for a pathway defined by the SUMO-targeted ligase Slx5–Slx8, which has also been implicated in the rapid destruction of α2. Our observations suggest coordinate regulation in the turnover of two master regulatory transcription factors ensures a rapid mating-type switch.
Benign Neonatal Sleep Myoclonus: A Review of the Literature
Authors: Maurer Valeria O. , Rizzi Mattia , Bianchetti Mario G. , Ramelli Gian Paolo
Published: March 2010

OBJECTIVE:

Neurologically normal term infants sometimes present with repetitive, rhythmic myoclonic jerks that occur during sleep. The condition, which is traditionally resolved by 3 months of age with no sequelae, is termed benign neonatal sleep myoclonus. The goal of this review was to synthesize the published literature on benign neonatal sleep myoclonus.

METHODS:

The US National Library of Medicine database and the Web-based search engine Google, through June 2009, were used as data sources. All articles published after the seminal description in 1982 as full-length articles or letters were collected. Reports that were published in languages other than English, French, German, Italian, Portuguese, or Spanish were not considered.

RESULTS:

We included 24 reports in which 164 term-born (96%) or near-term–born (4%) infants were described. Neonatal sleep myoclonus occurred in all sleep stages, disappeared after arousal, and was induced by rocking the infant or repetitive sound stimuli. Furthermore, in affected infants, jerks stopped or even worsened by holding the limbs or on medication with antiepileptic drugs. Finally, benign neonatal sleep myoclonus did not resolve by 3 months of age in one-third of the infants.

CONCLUSIONS:

This review provides new insights into the clinical features and natural course of benign neonatal sleep myoclonus. The most significant limitation of the review comes from the small number of reported cases.
25-Hydroxyvitamin D Status of Healthy, Low-Income, Minority Children in Atlanta, Georgia
Authors: Cole Conrad R. , Grant Frederick K. , Tangpricha Vin , Swaby-Ellis E. Dawn , Smith Joy L. , Jacques Anne , Chen Huiping , Schleicher Rosemary L. , Ziegler Thomas R.
Published: March 2010

OBJECTIVES:

The goals were to determine the prevalence of vitamin D deficiency among minority children in a southern US city, to examine differences in serum 25-hydroxyvitamin D levels between non-Hispanic black and Hispanic children, and to determine dietary sources of vitamin D.

METHODS:

Low-income, minority children (N = 290; mean age: 2.5 ± 1.2 years) were recruited during well-child clinic visits. Serum 25-hydroxyvitamin D and calcium levels were measured and dietary information was assessed.

RESULTS:

The mean 25-hydroxyvitamin D3 level was 26.2 ± 7.6 ng/mL, whereas 25-hydroxyvitamin D2 was not detected. Overall, 22.3% of children had deficient serum 25-hydroxyvitamin D3 levels (≤20 ng/mL), 73.6% had less-than-optimal serum 25-hydroxyvitamin D levels (≤30 ng/mL), and 1.4% had low serum calcium levels (≤9 mg/dL). A significantly larger proportion of non-Hispanic black children, compared with Hispanic children, had vitamin D deficiency (26% vs 18%; P < .05). Age and season of recruitment were significantly associated with vitamin D deficiency and low serum calcium levels. Older children (≥3 years) were less likely to have vitamin D deficiency (odds ratio [OR]: 0.89 [95% confidence interval [CI]: 0.81–0.96]; P < .001). Study enrollment during spring and summer reduced the likelihood of vitamin D deficiency by ∼20% (spring, OR: 0.85 [95% CI: 0.73–0.98]; P = .03; summer, OR: 0.82 [95% CI: 0.73–0.92]; P < .01). Fortified milk provided most dietary vitamin D (62%), with Hispanic children reporting greater intake.

CONCLUSIONS:

Suboptimal vitamin D status was common among apparently healthy, low-income, minority children. Age and season were significant predictors of vitamin D deficiency.
Pediatric Organ Donation and Transplantation
Authors:   Committee on Hospital Care, Section on Surgery, and Section on Critical Care
Published: March 2010

This Policy Statement was revised. See https://doi.org/10.1542/peds.2023-062923.

Pediatric organ donation and organ transplantation can have a significant life-extending benefit to the young recipients of these organs and a high emotional impact on donor and recipient families. Pediatricians, pediatric medical specialists, and pediatric transplant surgeons need to be better acquainted with evolving national strategies that involve organ procurement and organ transplantation to help acquaint families with the benefits and risks of organ donation and transplantation. Efforts of pediatric professionals are needed to shape public policies to provide a system in which procurement, distribution, and cost are fair and equitable to children and adults. Major issues of concern are availability of and access to donor organs; oversight and control of the process; pediatric medical and surgical consultation and continued care throughout the organ-donation and transplantation process; ethical, social, financial, and follow-up issues; insurance-coverage issues; and public awareness of the need for organ donors of all ages.
Ghrelin attenuates kainic acid-induced neuronal cell death in the mouse hippocampus
Authors: Lee Jiyeon , Lim Eunjin , Kim Yumi , Li Endan , Park Seungjoon
Published: March 2010

Ghrelin is an endogenous ligand for GH secretagogue receptor type 1a (GHSR1a), and is produced and released mainly from the stomach. It has been recently demonstrated that ghrelin can function as a neuroprotective factor by inhibiting apoptotic pathways. Kainic acid (KA), an excitatory amino acid l-glutamate analog, causes neuronal death in the hippocampus; previous studies suggest that activated microglia and astrocytes actively participate in the pathogenesis of KA-induced hippocampal neurodegeneration. However, it is unclear whether ghrelin has neuroprotective effect in KA-induced hippocampal neurodegeneration. I.p. injection of KA produced typical neuronal cell death in the CA1 and CA3 pyramidal layers of the hippocampus, and the systemic administration of ghrelin significantly attenuated KA-induced neuronal cell death in these regions through the activation of GHSR1a. Ghrelin prevents KA-induced activation of microglia and astrocytes, and the expression of proinflammatory mediators tumor necrosis factor α, interleukin-1β, and cyclooxygenase-2. The inhibitory effect of ghrelin on the activation of microglia and astrocytes appears to be associated with the inhibition of matrix metalloproteinase-3 expression in damaged hippocampal neurons. Our data suggest that ghrelin has a therapeutic potential for suppressing KA-induced pathogenesis in the brain.
A New Finite-Volume Approach to Efficient Discretization on Challenging Grids
Authors: Aavatsmark I.. , Eigestad G.T.. T. , Heimsund B.-O.. -O. , Mallison B.T.. T. , Nordbotten J.M.. M. , Øian E..
Published: March 2010

Multipoint-flux-approximation (MPFA) methods were introduced to solve control-volume formulations on general simulation grids for porous-media flow. While these methods are general in the sense that they may be applied to any matching grid, their convergence properties vary.

An important property for multiphase flow is the monotonicity of the numerical elliptic operator. In a recent paper (Nordbotten et al. 2007), conditions for monotonicity on quadrilateral grids have been developed. These conditions indicate that MPFA formulations that lead to smaller flux stencils are desirable for grids with high aspect ratios or severe skewness and for media with strong anisotropy or strong heterogeneity. The ideas were pursued recently in Aavatsmark et al. (2008), where the L-method was introduced for general media in 2D. For homogeneous media and uniform grids, this method has four-point flux stencils and seven-point cell stencils in two dimensions. The reduced stencils appear as a consequence of adapting the method to the closest neighboring cells.

Here, we extend the ideas for discretization on 3D grids, and ideas and results are shown for both conforming and nonconforming grids. The ideas are particularly desirable for simulation grids that contain faults and local grid refinement.

We present numerical results herein that include convergence results for single-phase flow on challenging grids in 2D and 3D and for some simple two-phase results. Also, we compare the L-method with the O-method.
Stress-Corrosion Cracking as an Alternative Time-Dependent Shale-Stability Model
Authors: Park N.. , Olson J.E.. E. , Holder J..
Published: March 2010

Wellbore stability in shale has been a crucial issue for drilling in all kinds of environments. The analysis of time-dependent wellbore stability in shales has largely concentrated on the influence of fluid chemistry and filtrate invasion into the formation to predict compressive failure using poroelasticity and continuum models. This paper presents another possible mechanism for time-dependent behavior—stress-corrosion cracking (subcritical crack growth). Using the discrete-element method (DEM) to simulate grainscale processes, we apply the concept of time-dependent cracking to hole enlargement for vertical wellbores. We use a published example from the North Sea to verify the stress-corrosion model and demonstrate the application to wellbore stability in shale. Laboratory results on rocks indicate a wide range of susceptibility to stress-corrosion cracking related to rock petrology and contact-fluid chemistry. Using laboratory calibrated rock properties, we run 2D, plane-strain simulations of vertical-wellbore stability in shale, where hole enlargement is tracked through time. As a result of stress-corrosion cracking, the numerical models show a time-dependent failure history, with an initial stable period of varying duration (influenced by mud weight, rock properties, and in-situ stress), followed by a brief period of combined shear and tensile failure, and ending with stabilization at an enlarged, elliptically shaped geometry. Time to failure increases with increasing mud weight. Enlarged-hole shape changes from elliptical to roughly circular with decreasing stress anisotropy. These behaviors simulated by the stress-corrosion model coincide with previously reported field experience. This new modeling approach for time-dependent wellbore failure can be readily constrained with straight forward fracture-mechanics tests on rock samples and has the potential to also be applied to time-dependent, intermittent sand or fines generation during production.
Analysis of Control Lines Strapped to Tubing
Authors: Mitchell Robert F. , Ellis S.T.. T. , Siappas G.. , Colyer A..
Published: March 2010

Hydraulic control lines are commonly used to actuate surface- controlled subsurface safety valves (SCSSVs), and new applications include choke operation and the control of more-complex "smart-well" completions. In general, control lines are not subject to routine failures. However, the analysis of worldwide completion failures indicates control lines to be a critical component of failure. In fact, control lines and associated components, such as clamps and fittings, are not engineered with the same rigor as the rest of the well completion.

The first step in understanding control-line failure is predicting the loads and stresses in a control line strapped to the tubing. Tubing movement causes loads in the control line through stretching and bending. To a lesser degree, the tubing is loaded by the control lines. To determine this interaction, a calculation is performed in which the control line and the tubing are treated as a composite, with axial displacement constrained to be the same in both. This analysis provides the average stress state in the control line. Because the control line is fixed at only certain points along the tubing, the variation in stress from the average must be determined between clamps. This paper provides the technical details for both calculations.

Several example cases based on field data are presented that give insight into the potential problems that typical production scenarios create for control lines.
A Mixing Rule of Self Diffusivities in Methane Hydrocarbon Mixtures and the Determination of GOR and Oil Viscosities from NMR Log Data
Authors: Chen Jiansheng , Chen Songhua
Published: March 2010

A new mixing rule is described for the prediction of the self diffusivities of gas- and liquid-hydrocarbon molecules in methane/oil mixtures. Unlike macroscopic fluid properties, such as density and viscosity, molecular self diffusivity is a microscopic parameter associated with individual molecular species. Thus, a self diffusivity of a binary mixture of gas and oil is a misnomer. Instead, the self diffusivity of each species in the binary system is affected by the presence of the other species. For that reason, the commonly used log-mean based mixing rule that applies to macroscopic properties of the mixtures is unsuitable for self diffusivity when the reference states are pure Components 1 and 2. We found that it is necessary to introduce two new reference states: One is the infinite dilution of Component 1 in Component 2; the other is the infinite dilution of Component 2 in Component 1. The component can be a single-molecule species or a mixture, as long as its self diffusivity or self diffusivity distribution can be measured. Using this approach, the self diffusivity of each component in the mixture follows the log-mean based mixing rule. This new mixing rule is verified with literature data of methane/hexane, ethane/hexane, methane/octane, ethane/octane, methane/decane, and ethane/decane mixtures over a wide range of temperatures, pressures, and solutiongas concentrations.

The new mixing rule is applied, and a detailed procedure is developed, to determine the gas/oil ratio (GOR) and the live-oil viscosity for in-situ volatile oils from nuclear-magnetic-resonance (NMR) log data. First, the self diffusivities and proton fraction of the methane and oil mixture are determined by fitting the NMR-measured diffusivity distribution with a bimodal distribution. Then, the self diffusivities for the four reference states are calculated using the mixing rule. Finally, the GOR is calculated from the proton ratio, while the live-oil viscosity is calculated from the self diffusivity of pure oil and the GOR. The calculated GOR and oil viscosities are compared to the pressure/volume/temerature (PVT) measurement of the oil sample taken from downhole and show good agreement. GOR and oil viscosities from this new technique can be used for optimizing testing and sampling programs, for reservoir-simulation studies, and for the design of surface production facilities.
A New Look at Wellbore-Collision Probability
Authors: Brooks Andrew G.
Published: March 2010

Given the potentially catastrophic human and environmental results of an unplanned well collision, a meaningful estimate of the probability of wellbore intersections provides a valuable risk-management tool. A number of estimation techniques are currently in use in the industry; however, all of these have limitations that may not be clearly understood. For example, many computations currently in use fail when the two wells are parallel; they ignore the fact that the drilled well may have reached its current location without collision, or they return an identical result regardless of whether the drilling well is thought to be approaching or departing from the existing well.

A rational approach to the problem begins by clearly defining the probability to be estimated. This paper presents a method to ascertain the probability that a particular interval of the well being drilled might intersect an existing adjacent wellbore. An overall collision probability can then be obtained by combining the probabilities associated with successive intervals along the reference well. The estimates of probability are based on knowledge of the surveyed well paths and their survey uncertainties, expressed in the form of position covariance matrices.

A body of relevant research exists in the field of astrodynamics concerned with estimating the risk of collision between orbiting satellites. This paper draws on previous work from both the oil field and aerospace in developing a more rigorous assessment of collision probability, overcoming the limitation of previous methods. Examples demonstrate that the new method agrees with analytic results for both parallel and nonparallel well paths in simple cases where both wells are straight in the region of interest.
Probabilistic Aggregation of Oil and Gas Field Resource Estimates and Project Portfolio Analysis
Authors: van Elk Jan F. , Gupta Ritu , Wann David
Published: March 2010

Probabilistic aggregation and dependency estimation are essential in portfolio methods, production forecasting, and resource estimation. The use of arithmetic addition understates the true value of the resource estimates within a portfolio of fields. Potentially, this could result in deferral of a project, or loss of lucrative business and commercial opportunities, such as project investment, facilitysizing decisions, or incremental gas-supply commitments.

A statistically robust method for aggregation of resource estimates that appropriately uses expert opinion is presented in this paper. Using two integrated-project examples, this paper introduces new methods for (1) probabilistic aggregation of the resource estimates for multiple fields and (2) estimating a measure of dependency between the resource estimates of individual fields.

The new analytical method for probabilistic aggregation is based on multivariate skew-normal (MSN) distributions, which can model a wide range of skewness through a shape parameter and are used heavily in financial and actuarial applications.

In studies of the fields in which the multiple-realizations approach is used as a basis for the uncertainty framework, tornado diagrams are generated routinely to describe the dependence of the field resources on reservoir parameters. The improved method for evaluating measures of dependency between the resource estimates within a portfolio of fields uses these tornado diagrams as a basis. Incorporating the expertise and knowledge of geologists and petroleum engineers is a critical element of the method.

These methods for probabilistic aggregation and estimating dependencies were developed within the context of the oil industry, but their use is not limited to the oil industry. They are general and can be used in other probabilistic-aggregation problems. Application of these techniques requires limited time and effort, compared to individual-field studies, and can have a profound impact on the uncertainty range of the total resources for the portfolio of fields.
Challenges in Completing Long Horizontal Wells Selectively
Authors: Abbasy Imran , Ritchie Barry , Pitts Michael , White Brendan , Jaafar M. Rushdan
Published: March 2010

Although drilling technology is now able to deliver ultra long horizontal wells (LHWs), completion technology has been slower to evolve. Running long liners, effective stimulation, and completions are some of the areas that require more attention. This paper discusses some of the challenges in the development of the Al Shaheen reservoirs offshore Qatar and how they were overcome. Some of these wells have a stepout in excess of 30,000 ft with a total vertical depth of 3,100 to 3,500 ft, and thus, they offer some unique challenges. Running and cementing liners to these depths is difficult, and some of the methods to achieve this effectively are discussed. Perforating guidelines are presented that allow sand control without having to resort to conventional sand-control practices. Stimulation of such long reservoir sections is a particular challenge, and a fine balance must be struck between acid coverage and cost, both for barefoot and perforated intervals. The so-called Q-CAJ technique of acid distribution, which has allowed acceptable stimulation despite these conditions, is presented. The technique also offers opportunities to stimulate long horizontal boreholes more effectively and at lower cost. Some of the wells are completed with multizone selective completions, which push the design limit of equipment. A number of such intelligent wells have been completed successfully, and more aggressive wells are planned. To optimize the development cost, dual-lateral wells have also been drilled with complete control over each lateral. Discussed are some of the underlying completion techniques such as running completion in stages, use of mechanical latches, hydraulic-control-line wet connects, interval control valves, and limitations imposed by control lines. The paper concludes with some of the challenges that have yet to be overcome.
A Guide to Successful Backreaming: Real-Time Case Histories
Authors: Yarim G.. , Ritchie G.M.. M. , May R.B.. B.
Published: March 2010

Backreaming is the practice of pumping and rotating the drillstring while simultaneously pulling out of the hole. When reliable topdrive drilling systems (TDSs) on conventional drilling rigs were introduced more than 25 years ago, the practice of backreaming became a popular technique in the driller's toolbox for tripping out of hole initially in deviated wells.

In general, backreaming operations have become a popular solution to poor hole conditions while pulling out of hole, but they are also notorious for causing the very same problems they are supposed to prevent, such as stuck pipe. If backreaming is not performed properly, it may complicate the operations, cause wellbore-stability issues, cause higher equivalent circulating densities (ECDs), and cause stuck-pipe incidents caused by packoffs.

As part of the company's stuck-pipe prevention initiative, it became clear that when backreaming is carried out in a wellbore that has a large amount of cuttings and/or cavings, it can cause problems rather than solve them if it is not done with sufficient care. Also, backreaming and tripping operations were usually occasions when the rig-based team went to a "low-vigilance" level. On the basis of historical cases, it was concluded that in the majority of instances, there were no clear guidelines on when to start, how to do it, when to slow down, and when to stop backreaming operations. A review of industry literature also indicated a lack of procedures generally for backreaming.

As a result of the analysis of the real-time data from several case histories, a plan was put in place to improve backreaming operations, define the situations that require backreaming, and focus on tripping practices to prevent stuck-pipe incidents and tool failures.

This paper focuses on one of the industry's most controversial subjects, reviews the implications of backreaming by using real-time data and case histories, and suggests proven procedures to trouble-free backreaming. It recommends the conditions that require backreaming and also suggests wellbore conditions that are not recommended for backreaming. More importantly, it proposes key drilling parameters that need to be monitored when backreaming. These include pump pressure, torque, hookload, cuttings rate, and downhole measurements (if available) to detect and prevent backreaming-induced operational problems. In addition, this paper provides guidelines for successful backreaming operations and defines conditions that may be resolved without needing to backream. Backreaming guidelines have been developed on the basis of the company's worldwide operations, supported by real-time case histories and an extensive stuck-pipe prevention program.
Miscible Interaction Between Matrix and Fracture: A Visualization and Simulation Study
Authors: Er V.. , Babadagli T..
Published: March 2010

CO2 injection has been applied in naturally fractured reservoirs (NFRs) for the purpose of enhanced oil recovery (i.e., the Wey-burn and Midale fields, Canada; the Wasson and Slaughter fields, USA; and the Bati Raman field, Turkey). The matrix part of these types of reservoirs could potentially be a good storage medium as well. Understanding the matrix/fracture interaction during this process and the dynamics of the flow in this dual-porosity system requires visual analyses. We mimicked fully miscible CO2 injection in NFRs using 2D models with a single fracture and oil (solute)/hydrocarbon solvent pairs. The focus was on the visual pore-scale analysis of miscibility interaction, breakthrough of solvent through fracture, transfer between matrix and fracture, and the dynamics of miscible displacement inside the matrix.

First, matrix/fracture interaction was studied intensively using 2D glass-bead models experimentally. The model was prepared using acrylic sheets and glass beads saturated with oil as a porous medium while a narrow gap of 1-mm size containing filter paper served as a fracture. The first contact miscible solvent (pentane) was injected into the fracture, and the flow distribution was monitored using an image-acquisition and -processing system. The produced solvent and solute were continuously analyzed for compositional study. The effects of several parameters, such as flow rate, viscosity ratio (oil/solvent), and gravity, were studied. Next, the process was modeled numerically using a commercial compositional simulator, and the saturation distribution in the matrix was matched to experimental data. The key parameters in the matching process were the effective diffusion coefficients and the longitudinal and the transverse dispersivities. The diffusion coefficients were specified for each fluid, and dispersivities were assigned into gridblocks separately for the fracture and the matrix.
Gas-Condensate Pseudopressure in Layered Reservoirs
Authors: Singh Kameshwar , Whitson Curtis H.
Published: March 2010

This paper presents verification of the Fevang and Whitson (1996) gas-condensate pseudopressure method for layered reservoirs. Layers may be characterized by widely varying permeability and composition, and they may be communicating or noncommunicating. The pseudopressure method is used in well calculations for coarse-grid models with relatively large areal grid dimensions (>50 m), capturing near-well condensate blockage without local grid refinement, thereby reducing run time and model size.

The paper presents examples from several field studies and from two synthetic systems using a commercial reservoir simulator. The field studies include rich- and lean-condensate reservoirs.

The study was conducted using a commercial compositional reservoir simulator. Three-dimensional multilayer, fine-grid (radial and Cartesian) models and equivalent coarse-grid models were used. Both depletion and gas-injection cases were simulated for a wide range of reservoir fluids. Reservoir performance of fine-grid models and coarse-grid models was compared using the gas-condensate pseudopressure method and showed comparable results in all cases studied, including relative permeabilities with capillary-number dependence and high-velocity (β) flow treatment.

The coarse-grid model with pseudopressure is somewhat dependent on coarse-grid size, generally requiring Δx=Δy≈50-100 m for lean gas condensates and Δx=Δy≈100-200 m for rich gas condensates.

The paper verifies for the first time that the gas-condensate pseudopressure method as proposed by Fevang and Whitson (1996) is valid and accurate for layered systems with significant heterogeneity (permeability variation), with and without crossflow, with and without capillary-number modification of relative permeabilities, and for widely ranging fluid compositions in each layer.
Use of Liner Drilling Technology as a Solution to Hole Instability and Loss Intervals: A Case Study Offshore Indonesia
Authors: Jianhua Liao , Chao Zhao , Jinxiang Li , Rosenberg Steve , Hillis Keith , Utama Budi , Gala Deepak M.
Published: March 2010

The Banuwati field offshore southeast Sumatra, Indonesia, presents major challenges to both drilling and liner running operations because of the problematic lower Baturaja limestone formation, which is a carbonate reef structure known for severe lost-circulation conditions. The operator previously had experienced severe losses with wellbore-stability issues while drilling this formation with the inability to set the 7-in. drilling liner at the planned depth in Well A-3. The liner had to be pulled out of the hole, leading to the eventual abandonment of the existing openhole section and resulting in the sidetracking of the well. Liner-while-drilling technology was identified as the most suitable solution for setting the planned 7-in. drilling liner through the loss interval because of the following: Documented lost-circulation problems have been minimized or eliminated through the use of liner drilling technology possibly attributed to the "smear effect" (Fontenot et al. 2004) phenomenon.The liner system selected provided for high torsional capability as well as the requirement for both a mechanical and a pressure event to release the setting tool, thus minimizing the chances of premature release.A drill shoe with a displaceable polycrystalline-diamond-compact (PDC) cutting structure was used to drill the 8½-in. hole section and subsequently displaced before cementing so as to allow drill out with a conventional drill bit and bottomhole assembly (BHA).

This paper will discuss the implementation of liner drilling technology in the Banuwati field project. This technology was used to drill successfully through the known lost-circulation zone with the 7-in. liner cemented in place, allowing the operator to reach the completion objectives while realizing a savings of more than USD 1 million.
Embedding a Petroelastic Model in a Multipurpose Flow Simulator To Enhance the Value of 4D Seismic
Authors: Fanchi John R.
Published: March 2010

Time-lapse (4D) seismic can be effectively integrated into the reservoir-management process by embedding the calculation of seismic attributes in a flow simulator. This paper describes a petroelastic model (PEM) embedded in a multipurpose flow simulator. The flow simulator may be used to model gas, black-oil, compositional, and thermal systems. The PEM can calculate reservoir geophysical attributes such as compressional-wave (P-wave) and shear-wave (S-wave) velocities and impedances, dynamic and static Young's moduli, and dynamic and static Poisson's ratios. Examples illustrate how to use the PEM to facilitate the integration of 4D seismic and reservoir flow modeling.
Investigation of Flow Behavior of Slickwater in Large Straight and Coiled Tubing
Authors: Shah S.N.. N. , Ahmed Kamel A.H. H
Published: March 2010

Low-damage fracturing fluids are normally used for better fracture-dimension confinement and lower residue. This leads not only to longer fracture lengths, but also to higher fracture conductivity. Slickwater fracturing technology, developed in the 1980s, is less expensive than gel treatments. Fluid and proppant volumes can be reduced, and treatment flow rates can be increased significantly. When compared to conventional gel treatments, slickwater fracturing can generate similar or better production responses.

In frac treatments, slickwater is pumped through straight tubing (ST) and coiled tubing (CT). As a result of secondary flow, frictional pressure losses in CT are higher than in ST. Determining these losses is of the utmost importance for successful treatments. Customarily, laboratory-generated flow data are used to develop correlations to predict frictional pressure loss of fluids flowing in ST and CT. These correlations are then, without verification, applied to field applications, which employ much larger conduit sizes.

The present study is aimed to experimentally investigate the hydraulic properties of a commonly used drag reducer—Nalco ASP-820—in larger tubing sizes. This is a modified partially hydrolyzed polyacrylamide (PHPA). Previously, we reported flow data gathered employing ½-in. ST and CT (varying curvature ratio) and the correlations developed to predict frictional pressure losses of fluids in ST and CT. In this investigation, the large-scale flow data acquired from 200-ft ST and 1,000-, 2,000-, and 3,000-ft,1½-in. CT, and 1,000-ft 2⅜- and 2⅞-in. CT, are compared with the predictions from the correlations developed from ½-in.-pipe data. The effects of shear intensity, shear duration, and pipe roughness on flow properties of the ASP-820 fluid are also investigated.

Results show significantly lower drag reduction in CT than in ST because of secondary flow caused by the CT curvature. Polymer degradation because of shear (shear intensity and duration) and/or tubing roughness can reduce drag reduction significantly. The results are discussed in light of a recently developed "drag-reduction envelope" to evaluate the drag reduction characteristics of slickwater fluid in ST and CT.
Feedback Controllers for the Simulation of Field Processes
Authors: Güyagüler B.. , Papadopoulos A.T.. T. , Philpot J.A.. A.
Published: March 2010

Control systems with feedback controllers are useful in reservoir simulation because they enable the maintenance of desired operating conditions of a field. This, in turn, helps to establish the value of implementing automated mechanisms in the field, and also in determining long-term field operating strategies. A generic controller framework is constructed within a reservoir simulator that enables the usage of different kinds of controller algorithms for managing a variety of field processes. In this study, three field processes are considered. First, average pressure within a reservoir region is maintained by adjusting the voidage-replacement ratio between a group of injectors and producers. Second, control systems are used for the prevention of gas/water coning for single and multiple wells. Finally, the average temperature within a reservoir region is maintained at a critical value by controlling flow into the formation, so as to operate with the desired mobility of heavy oil. Traditional proportional, integral, derivative (PID) controllers, as well as linear and nonlinear fuzzy controllers, are considered. The advantages and disadvantages of the approaches are discussed. Tuning control systems is a difficult process in practice. Several methods for tuning the parameters of these controllers are investigated, and rule-of-thumb values are suggested in this study. Synthetic and real reservoir models are used.
Tie-Simplex Parameterization for EOS-Based Thermal Compositional Simulation
Authors: Iranshahr A.. , Voskov D.V.. V. , Tchelepi H.A.. A.
Published: March 2010

Thermodynamic equilibrium computations are usually the most time-consuming component in compositional reservoir flow simulation. A compositional space adaptive tabulation (CSAT) approach was developed as a preconditioner for equation of state (EOS) computations in isothermal compositional simulation. The compositional space is decomposed into sub- and supercritical regions. In the subcritical region, we adaptively parameterize the compositional space using a small number of tie-lines, which are assembled into a table. The critical surface is parameterized and used to identify supercritical compositions. The phase-equilibrium information for a composition is interpolated as a function of pressure using the tie-line table. We extend the CSAT approach to thermal problems. Given an overall composition at a fixed temperature, the boundary between sub- and supercritical pressures is represented by the critical tie-line and the corresponding minimal critical pressure (MCP). A small set of subcritical tie-lines is computed and stored for a given temperature. This process is repeated for the pressure and temperature ranges of interest, and a coarse (regular) tie-line table is constructed. Close to the critical boundary, a refined tie-line table is used. A combination of regular and refined interpolation improves the robustness of the tie-line search procedure and the overall efficiency of the computations. Several challenging problems, including an unstructured heterogeneous discrete fracture field model with 26 components, are used to demonstrate the robustness and efficiency of this general tie-line-based parameterization method. Our results indicate that CSAT provides accurate treatment of the near-critical region. Moreover, the computational efficiency of the method is at least an order of magnitude better than that of standard EOS-based reservoir simulation approaches. We also show the efficiency gains relative to standard techniques as a function of the number of gridblocks in the simulation model.
Fractional-Flow Theory of Foam Displacements With Oil
Authors: Ashoori E.. , van der Heijden T.L.M.. L.M. , Rossen W.R.. R.
Published: March 2010

Fractional-flow theory provides key insights into complex foam enhanced-oil-recovery (EOR) displacements and acts as a benchmark for foam simulators. In some cases with mobile oil present, the process can be represented as a two-phase displacement. We examine three such cases.

A first-contact-miscible (FCM) gasflood with foam injection includes a chemical shock defining the surfactant front and a miscible shock defining the gas front. The optimal water fraction for the foam, that which gives the fastest oil recovery in 1D, maintains the gas front slightly ahead of the foam (surfactant) front.

The success of a foam process with FCM CO2 and surfactant dissolved in the (supercritical) CO2 depends on the strength of foam at very low water fractional flow, such as for a surfactant- alternating-gas (SAG) process with surfactant dissolved in water. The speed of propagation of the foam front depends on surfactant adsorption on rock and on the partitioning of surfactant between water and CO2 but is always less than the velocity of the foam front in a SAG flood with surfactant ahead of the gas. A foam with surfactant that partitions preferentially into water rather than into CO2 would propagate slowly, regardless of the surfactant's absolute solubility or the level of adsorption on rock. An aqueous surfactant preflush can speed the advance of foam, however.

An idealized model of a surfactant flood pushed by foam suggests that it is best to inject a relatively high water content into the foam to ensure that the gas front remains behind the surfactant front as the flood proceeds. Any gas that passes ahead of the surfactant front would finger through the oil and be wasted.

We present simulations to verify the solutions obtained with fractional-flow methods and illustrate the challenges of accurate simulation of these processes.
Design and Development of a Novel Process To Treat Drilling-Fluid Slops: A Positive Environmental and Economic Impact
Authors: Dixit Rahul , Patel Arvind
Published: March 2010

Slop mud, created by water contamination of invert drilling fluids during displacement and cleaning activities, has been successfully treated at source to recover the drilling-fluid phase and water phase. This method included treating the slop mud with a biodegradable demulsifier. The recovered drilling fluid can be reconditioned to acceptable properties for reuse or can be sent for disposal. The recovered/separated slop water phase is contaminated with hydrocarbons and cannot be discharged in an offshore environment unless it meets the discharge criteria of < 30 mg/L of oil in water. Thus, it becomes imperative for the operator to treat the water at source, reduce the enormous expenses associated with transportation/disposal, and embark upon a potentially significant environmental issue. This was achieved by development of an on-site treatment process including filtration, ozonation, and phase separation.

A synthetic-based drilling fluid contaminated with water was separated with a biodegradable demulsifier. The addition of the surfactant resulted in phase separation (i.e., separated drilling-fluid and water phases). As tested by the approved International Organization for Standardization (ISO) method, the separated water phase was found to have oil-in-water content of 4,000 mg/L, which is unacceptable for discharge. The separated water then was treated with ozone. The ozone-treated water was allowed to separate in two phases (i.e., clarified water phase and organic rich phase). The oil-in-water content of the clarified ozone-treated water phase was found to be 30 mg/L, thus reducing the oil-in-water content by 99%.

This paper will present the demulsification methodology, the chemistry of ozonolysis, and the results obtained to meet or exceed the oil-in-water discharge limits of 30 mg/L. The environmental and economic impact of the process will be discussed.
Water Quality and Well Injectivity: Do Residual Oil-in-Water Emulsions Matter?
Authors: Buret S.. , Nabzar L.. , Jada A..
Published: March 2010

The present work is a part of a thorough and systematic laboratory study of oil-in-water emulsion flow in porous media that we have undertaken recently to investigate the mechanisms of oil-droplet retention and its consecutive effect on permeability. One of our main objectives was to see how the in-depth propagation of produced- water (PW) residual dilute emulsion could impair the permeability during PW reinjection (PWRI). During this casework, we used granular packs of sharp-edged silicon carbide grains and stable and dilute dodecane-in-water emulsions. The flow experiments were performed under well-controlled conditions, and we studied the effect of most of the relevant parameters, including flow rate, salinity, droplet size, and permeability of the porous medium.

A careful monitoring of the salinity and the jamming ratio (JR) allowed us to consider and work separately on the two main mechanisms of droplet capture (i.e., surface capture and straining capture). In a previous paper (Buret et al. 2008), we reported on the effect of salinity and flow rate on emulsion flow through porous media where the pore-size/droplet-size ratio (JR) was very high, ensuring that only droplet capture on pore surface is operative. This paper reports on the effect of salinity and JR on both mechanisms, with the main focus being on the induced permeability impairment.

We demonstrated that surface capture could induce significant in-depth permeability losses even at a high JR. The maximum reached permeability loss is very sensitive to salinity and flow rate (shear-thinning effect). This maximum is always lower than a limiting value dictated by the surface-coverage jamming limit of random sequential adsorption (RSA) theory. This limiting value increases while decreasing the JR, according to a simple formula extracted from Poiseuille's law with a mean hydrodynamic thickness of the deposited layer close to the droplet diameter (monolayer deposition). Regarding the straining capture, we determined a critical JR of 7 for this mechanism to occur. Preliminary results using only two JR values and one flow rate are presented. Compared to surface capture, the results show that straining capture induces more severe plugging with a lower rate of propagation. The lower the JR is, the more severe the plugging is and the lower the propagation rate is. However, more investigations are still required, notably using various JRs and flow rates to characterize this important mechanism better.
Plunger-Lift Modeling Toward Efficient Liquid Unloading in Gas Wells
Authors: Chava G.. , Falcone G.. , Teodoriu C..
Published: March 2010

This paper is a follow-up to Chava et al. (2008), which introduced a preliminary plunger-lift model built around the availability of smart-plunger (PCS 2005) data. The latter devices are equipped with internal gauges to record pressure and temperature with time, which can be downloaded whenever the plunger is at surface.

We present an updated model that accounts for pressure drop caused only by gravitation but satisfactorily reproduces the dynamics of a field installation in east Texas.

We also present a comparison of the predictions from the new model with the corresponding results from some earlier plunger-lift models available in the public domain.