bluuebunny/crossref_metadata_2025 huggingface dataset:
Successful Application of a New Solids-Free Fluid Loss System in Acid Fracturing Treatments Achieved Significant Well Productivity Improvements in Saudi Arabian High Condensate Gas Producers
Authors: Leal Jairo , Solares J. Ricardo , Taq Ali , Duarte Jorge , Al-Shammari Nayef , Al-Ruwaished Azmi , Eoff Larry , Izquierdo Guillermo
Published: June 2011

Controlling fluid matrix leakoff into the formation is of critical importance during fracture stimulation treatments to ensure objectives are met. Decreasing the amount of fluid leakoff increases the volume that is available to maintain and propagate a hydraulic fracture. The need to minimize fluid leakoff is even more significant during acid fracturing since maintaining the fracture is difficult because of the ability of acid to spend quickly as it enters the formation. Traditional approaches utilize solids-laden viscous gels to reduce the volume of fluid leakoff as a fracture is propagated; however, it has been amply documented that the solids typically used are capable of damaging the formation if not properly removed after the treatment. Moreover, removal of treatment gels, which is required to minimize formation damage, is contingent on selection and design of breakers or other compounds, which are often chosen based on a number of uncertain reservoir parameters.

This paper will present both laboratory and field application results from a new solids-free fluid loss (SFFL) system designed to reduce matrix permeability to aqueous fluids, thereby resulting in longer fracture propagation caused by a significantly lower fluid-leakoff rate. This fluid loss system does not require the use of breakers, which eliminates the potential negative impact on post-stimulation well productivity. Laboratory test data will show the ability of the material to control fluid leakoff and its ability to achieve high levels of regained permeability to hydrocarbon.

Field results from the application of the new system during acid fracturing treatments in high condensate gas producers in Saudi Arabia, in which achieving long half-length fractures with acid is very difficult due to excessive fluid leakoff, are also discussed. Post-treatment analysis showed that utilization of the new system resulted in significant reduction of fluid leakoff, thereby allowing treating pressure to remain above closure pressure throughout the treatment and achieve a longer fracture extension. A post treatment performance comparison between gas producers treated with the new system and those stimulated using conventional fluids will show that using the new system consistently exhibited better productionperformance (normalized for reservoir characteristics).
Investigation of Asphaltene Deposition Mechanisms During Primary Depletion and CO2 Injection
Authors: Jafari Behbahani T. , Ghotbi C. , Taghikhani V. , Shahrabadi A.
Published: June 2011

Asphaltene deposition causes serious problems in the oil industry. Variation of oil composition and reservoir pressure is reported to be the most important factors that influence asphaltene deposition from reservoir oil. In this study, a mathematical model was developed to simulate asphaltene deposition during primary depletion and CO2 injection. The main purpose of this study is to investigate and to compare asphaltene deposition mechanisms due to primary depletion and CO2 injection. The solid model as thermodynamic model was applied to investigate asphaltene precipitation. A numerical model was established to the governing equations both in space and time and model parameters were determined by history matching. Because of the implicit and coupling nature of equations in the model, an iterative method was applied to solve the numerical equations. Results show that surface deposition, entrainment and pore throat plugging have occurred during primary depletion and CO2 injection. Deposit re-entrainment and surface deposition proceed against each other. So, in most situations one of these two mechanisms is dominant, and the other one might be ignored. Enhanced re-entrainment deposition allows flocculated asphaltene to change into precipitated asphaltene, or be dispersed into the oil phase. Also, surface deposition rate during CO2 injection is more important than due to primary depletion. Result shows that entrainment of asphaltene deposit and pore throat plugging are predominant mechanisms of physical deposition in CO2 injection. A thermodynamic modeling show that because of CO2 is a precipitant, asphaltene precipitation is more important during CO2 injection than primary depletion.
Improvement of the Criteria for Expandable Sand Screen Well Candidate Selection
Authors: Salehi-Moorkani Reza , Ghasemzadeh Amir
Published: June 2011

One of the new techniques to prevent sand production is completing well with Expandable Sand Screen (ESS). This technique is used in some sand stone reservoirs in Iranian onshore fields and the results of this technique were acceptable in reducing sand production and increasing productivity of the wells. Therefore, oil companies tend to complete more wells using this method. Selecting the suitable well to install ESS is one of production engineers concern which needs good knowledge of both technology concept along with well and reservoir conditions like perforation interval, critical flow rate, water oil contact level, etc. In this study previous wells which were completed with ESS have been studied and based on field experiences; the criteria for well candidate selection are developed. The results of this paper will provide engineers with a better knowledge of when and under which well and reservoir conditions this technique should be applied.
Application of Genetic Algorithms to the Optimization of Pressure Transient Analysis of Water Injectors using Type Curves
Authors: Zakaria Ahmed S. , Hafez Mohamed M. , Ochi Jalel , Zaki Karim S. , Loloi Mehdi , Abou-Sayed Ahmed
Published: June 2011

Injection pressure fall-off (PFO) test analysis has proven to be a reliable vehicle for understanding and evaluating well performance. Recently the methodology has been extended to the understanding of injectors. This paper presents an optimization model for analysis and interpretation of PFO tests for fractured water injectors. An elliptical composite flow model mathematically represents the fractured injector well. The optimization scheme couples the mathematical model of the well with a Genetic Algorithm (GA) to reach the final solution. The pressure transients representing the behavior of an injector a closing fracture and the discontinuity in fluid mobility are best developed in elliptical coordinates. The methodology derives the dimension of the induced fractures, formation permeability, fracture conductivity and fracture face skin.

The current paper illustrates the solution methodology by showing the attained match for a West Africa offshore field case. The field case provides reasonable agreement for the fracture dimensions and characteristics as verified by other techniques.

Genetic Algorithms are one of the most common artificial intelligence techniques for optimization. The reported solution is obtained by applying a GA with a non-linear least square error function as an objective function. A special penalty function, mutation, crossover probabilities, and stopping criterion are used to obtain the global minimum of the objective function. The test data analysis is done through type curve matching of the pressure and its derivative by minimizing the objective function to help determine the parameters that provide the best match between the field data and the presented novel fractured injector type curves.
Advancements in Screen Testing, Interpretation and Modeling for Standalone Screen Applications
Authors: Chanpura Rajesh A. , Fidan Selcuk , Mondal Somnath , Andrews Jamie S. , Martin Frederic , Hodge Richard M. , Ayoub Joseph A. , Parlar Mehmet , Sharma Mukul M.
Published: June 2011

Slurry type sand retention tests (SRT) that simulate gradual rock failure around the wellbore have been widely used in the industry to evaluate the performance of sand control screens for standalone screen (SAS) applications. Using the test results, screen selection is generally done based on the relative ranking of screen performances rather than absolute performance.

A recent paper by Chanpura et al. (2011) highlighted the drawbacks of the current practices in slurry type SRT procedures and proposed a new testing and interpretation methodology. Another recent work by Mondal et al. (2010) proposed simulation methods and results that, to the best of our knowledge, modeled screen performance numerically for the first time and presented comparisons to physical experiments. However, the approach used by Mondal et al. considers cases where hole collapse occurs on wire wrap screens and simulates "prepack" testing as opposed to slurry type tests considered in this work.

In this paper, we review the recent advancements in screen testing, interpretation and modeling for standalone screen applications, and present an analytical as well as a statistical (Monte Carlo) approach for prediction of sand production through sand screens with slot geometry. We show that the proposed methods can estimate both mass and size distribution of the produced solids in a slurry type SRT taking into account the full particle size distribution (PSD) of formation sand for wire wrap screens. Simulations show that once the slot opening is covered by particles bigger than the slot opening, sand production becomes negligible unless there is a true "fines" problem, which is characterized by a bimodal size distribution. The effect of slot size variation in screen coupons on sand production demonstrates the importance of proper quality control or at least accurate determination of slot sizes in these tests. The proposed methods can be used to estimate sand production in slurry type SRT for different screen sizes and thereby enable screen size selection based on defined acceptable level of sand production. Final screen selection can be confirmed through a sand retention test.
Determining Perforation Parameters from Single-Shot Tests: Radial vs. Axial Flow
Authors: Harvey J. , Kokel P. , Zhan L. , Grove B. , Huang H. , Atwood D.
Published: June 2011

Flow laboratories have been used for six decades to evaluate and optimize perforating systems for downhole environments. A key experimental variable is the pressure/flow boundary condition on the target core. Two standard configurations are axial flow, and radial flow. The implications of each configuration have been addressed somewhat in the literature in the context of steady flow with identical but prescribed tunnels. There has never been a careful comparison of the influence of boundary conditions on the actual tunnels.

In this paper we summarize the state of understanding regarding these two flow regimes by primarily focusing on the sensitivity of each to perforation damage and cleanup. In addition to addressing the differences under steady flow conditions, we also experimentally investigated the influence of target boundary conditions on the transient flow regime (i.e. during dynamic underbalance perforation cleanup). This was primarily an experimental investigation, supported by numerical simulations to determine baseline flow performance.

We find that radial flow provides the most meaningful measure of perforation damage (as indicated by post-shot steady flow). Indeed, radial flow is indispensable to parameterize skin and productivity models as they are currently formulated.

Axial flow yields steady production flow which is most sensitive to penetration depth, and relatively insensitive to perforation damage.

Finally, and perhaps most significantly, the transient perforation cleanup process is different for radial vs. axial boundaries. The intrinsic inflow characteristic of the tunnel is itself a function of the boundary conditions at shot time.

Proper selection of laboratory flow geometry is essential to yield meaningful measurements of perforation damage. In addition to this diagnostic purpose, target boundary conditions play a critical role in the removal of perforation damage, evolution of open tunnel length and diameter, and the resulting perforation flow efficiency.
Water-based, Frac-Pack Remedial Treatment Extends Well Life
Authors: Nguyen P. D. , Weaver J. D.
Published: June 2011

A solvent-based surface modification agent (SMA) has been very successful in precoating proppants to improve their performance in fracture stimulation treatments. To a far lesser degree, it was also used as an aggregating agent applied to formations and/or proppant packs to stabilize fines in a remedial method. However, its incompatibility with some aqueous wellbore fluids and the safety concerns due to the solvent base has limited its field applications. This paper presents the development of a new formulation of an SMA-aggregating agent that is aqueous-based, and includes results obtained from extensive laboratory studies. The new aqueous-based surface-modification agent (ASMA) provides significant improvements in health, safety, and ease of operation for the treatment of proppant, formation surfaces, and unconsolidated formations to control proppant and fines aggregation. Additionally, this ASMA will function to moderate undesirable diagenetic reactions that effect proppant strength, proppant pack permeability and formation permeability.

A unique property of this ASMA is that the rate of release of the active SMA ingredient can be controlled allowing it to be used for primary fracturing treatments or as a remedial treatment of damaged proppant packs or inhibiting continued formation fines production. This means the ASMA can be added directly to frac fluid during a treatment to coat proppant, to a fracture stimulation treatment prepad to treat the formation face, or at a later time as a remedial treatment.

As a remediation application, once injected into the proppant pack and formation matrix, the ASMA forms a thin film on the particulates, covering the fines and anchoring the particulates in place. In addition to controlling fines, ASMA coating forms a hydrophobic film that encapsulates the particulate surfaces, inhibiting the chemical reactions that lead to scale formation in the pack matrix and subsequent productivity loses.

Experimental testing using packed beds of proppant, formation sands, and various fines were used to simulate proppant pack conditions and formation fines before and after remedial treatments. It was observed that only a very thin film was formed, which encapsulated the proppant or formation particulates and created cohesion between grains without plugging the pore spaces. Additionally, laboratory results show that ASMA treatments effectively mitigate the buildup of scale in various sand packs as well as successfully control the migration of formation fines into proppant packs to maintain fluid flow paths.
Critical Assessment of Microemulsion Technology for Enhancing Fluid Recovery from Tight Gas Formations and Propped Fractures
Authors: Champagne Lakia M. , Zelenev Andrei S. , Penny Glenn S. , Travis Kerry
Published: June 2011

In recent years numerous case studies documenting the use of microemulsions in hydraulic fracturing of tight gas formations have appeared in the literature. Field case studies and supplemental laboratory data have illustrated that microemulsions enhance core permeability to gas and enhance fluid flowback mainly due to lowering capillary pressure and altering wettability in reservoirs and propped fractures. Although proven successful for enhancing gas production, many aspects of the microemulsion behavior in propped fractures are still poorly understood. In the present study we have performed numerous experiments on microemulsion-assisted fluid recovery from columns packed with sand proppant and shale, using microemulsions of different chemical composition. Our results indicate that the extent to which microemulsion additives promote foaming is an important factor in achieving highest possible levels of fluid recovery. By using properly formulated microemulsion compositions one can achieve significant improvement in fluid recovery at commercially viable doses of treatment.
Interactions of Organic-HF Systems with Aluminosilicates: Lab Testing and Field Recommendations
Authors: Al-Harbi B. G. , Al-Khaldi M. H. , Al-Dossary K. A.
Published: June 2011

Mixtures of HCl-HF, known as mud acid, have been extensively used in sandstone matrix stimulation. However, mud acid treatments were applied with poor success rate. This is mainly due to complex acid/rock interactions and other factors, such as the presence of HCl-sensitive clays and poorly consolidated formations. In addition, precipitation of reaction products of sandstone minerals dissolution in HF, especially at elevated temperatures, is another common factor limiting the mud acid effectiveness. These limitations associated with the use of typical HCl-HF mixtures warrant the use of organic-HF acids. These mixtures are used as an alternative to the HCl-HF blends to stimulate formations with HCl-sensitive clays and corrosion concerns. Various organic-HF blends have been extensively used; however, the studies of their interactions with sandstone rocks have been relatively limited. This work, for the first time, provides a systematic investigation of the chemical interactions of various sandstone minerals with three different organic-HF acids over a wide range of parameters.

Organic-HF systems based on acetic, formic, and citric acids were studied. Using static solubility tests coupled with chemical analysis of spent acid solutions, the dissolution of different sandstone minerals in each system was evaluated as a function of organic acid/HF weight ratio, reaction time, and temperature values of 50 and 75°C. The Scanning Electron Microscopy (SEM) and the X-ray fluorescence (XRF) techniques were used to explore the possibility of the presence of any precipitated reaction products.

Results based on this study showed that all organic-HF acids tested have a retarded nature with sand and clay minerals when compared to regular HCl-HF mixtures. In general, the dissolution of different sand and clay minerals in each organic-HF system is dependent on the type, ratio of the organic acid/HF used, and the temperature value. The reaction rate of different organic-HF acids with sand and clay minerals increased when the temperature value was increased from 50 to 75°C.

Findings based on this study addresses various chemical interactions and precipitation mechanisms involved with the reaction of organic-HF acids with sand and clay minerals. This work highlights the effects of the initial acid concentration, temperature, and soaking time on the performance of organic-HF acids. In addition, it provides new insights into the field application, and potential limitations of organic-HF acids.
Effect of Spent Acids on the Wettability of Carbonates at High Temperature and Pressure
Authors: Saneifar M. , Nasralla R. A. , Nasr-El-Din H. A. , Fahes M. , Hill A. D.
Published: June 2011

Accumulation of spent acid in the wellbore area after acidizing causes severe formation damage that would result in loss of productivity. This would cause reduction of relative permeability to gas, especially in tight gas wells. Capillary forces are the key parameters that affect trapping of spent acid in the formation. This work provides a comprehensive study of the effect of acid additives in spent acid on contact angle in tight gas carbonates. All experiments were conducted using the Drop Shape Analysis (DSA) at high temperature and pressure.

Different types of commonly used additives including corrosion inhibitors, iron control agents, mutual solvents, methanol, acetic acid and formic acid were tested at different concentrations. Experiments were conducted at temperature of 100 °C and pressure of 1000 psi.

Acid additives such as methanol, corrosion inhibitors, formic and acetic acids reduced the contact angle. Both iron control agents showed no impact on contact angle at concentration of 0.3 wt.% while at the lower concentration of 0.03 wt.% they decreased contact angle. A study was also done on the effect of temperature on contact angle of spent acid. The results showed that increasing temperature up to 100 °C increased contact angle, while beyond this temperature contact angle was decreased.

This work would help to better understand the ability of acid additives in altering wettability of carbonate rocks, which would consequently result in better designing the acid formulae and enhancement in well productivity by minimizing capillary forces.
New Insights into the Removal of Calcium Sulfate Scale
Authors: Al-Khaldi M. H. , Al-Juhani A. M. , Al-Mutairi S. H. , Gurmen M. N.
Published: June 2011

Calcium sulfate has been one of the major scales which cause many significant and serious operating problems in producing oil/gas wells and in water injectors. Impermeable hard scale deposits of calcium sulfate can severely impair the formation permeability or lead to down-hole equipment failure. Typically, preventative treatments, such as use of scale inhibitors, are the best economical methods for calcium sulfate mitigation. However, application of a cost-effective treatment is needed, in case of emergency, when calcium sulfate precipitation occurs.

A comprehensive lab investigation was conducted in order to assess the effectiveness of several remedial methods for calcium sulfate removal. This work shows the amount of calcium sulfate dissolved after its exposure to different reactive fluids at 25 and 50°C. In addition, it discusses the effect of different factors on the efficiency of each remedial treatment. These factors include: pH, temperature, reactive fluid concentration and presence of magnesium/iron ions.

Based on obtained results, several new findings were identified. The presence of gypsum (CaSO4.2H2O) has negative impact on the performance of mud acid treatments. After initial dissolution of gypsum in live mud acid, dissolved calcium will precipitate as both calcium fluoride and calcium sulfate in spent HCl/HF solutions. Similarly, gypsum has higher solubility limit in live HCl acid compared to its spent solutions. This resulted in re-precipitation of calcium sulfate in spent HCl. This solubility trend of gypsum in acidic solutions could result in severe formation damage. Live acids can initially dissolve any precipitated calcium sulfate solids in wellbore area and then it will re-precipitate in the formation rocks as the acid spends.

Gypsum has higher solubility limit in EDTA solutions, compared to acidic solutions. No re-precipitation of calcium sulfate occurred in these solutions due to the fact that calcium ions exist as complex ions and not free to interact with other ions. The dissolving power of EDTA was found to be a function of the solution pH value. Higher dissolving power of EDTA for gypsum was observed at high pH values. The presence of both magnesium and iron (III) ions had negative effect on gypsum dissolution in EDTA fluid. Compared to magnesium, iron (III) ion resulted in significant decrease in gypsum solubility in EDTA. Dissolved magnesium ions in EDTA solutions could re-precipitate as magnesium sulfate when gypsum is dissolved. This re-precipitation is more at low pH EDTA solutions.
Reduced Solids Oil-Based Completion Fluid for Horizontal HPHT Openhole Completions
Authors: van der Zwaag C. H. , Svanes G. S. , Schiefloe B. S. , Ibragimova Z. , Austmo Moeller K. , Vikanes H. , Lund Smørdal C. , Pedersen G. E. , Bringsjord K. L.
Published: June 2011

A 1.9 SG oil-based fluid for suspending open-hole pre-perforated liner completions in 1100 m long, horizontal openhole sections, under HPHT conditions (162°C, +800 bar reservoir pressure) has been engineered for the Morvin field development. The main challenge was to provide this fluid with sufficient stability so that it still was mobile when wells were backproduced after up to 4 weeks of subsequent well completion activities.

The main drivers for the development were the constraints that alternative fluid concepts pose under such conditions. Standard oil-based fluids weighted with barite, under the prevailing conditions up to 1.4 tons per cubic-meter of fluid, showed to be highly instable under simulated reservoir conditions. Barite settled out and deposited thick immobile mud bodies that were potentially completion damaging. Other fluid alternatives such as Cesium-formate weighted water-based suspension fluids were suspected to be incompatible with the selected oil-based reservoir drilling fluid.

Based on previous experiences with low solids (barite free) oil-based completion fluids (screen running and perforation fluids), a so-called "reduced solids oil-based completion fluid" was engineered in cooperation with the fluids contractor. The main features of the fluid were a close-to 50/50 oil-to-brine ratio, a Cesium-formate internal brine phase and fine barite to weigh up the fluid to approach the required weight. Several variations of this fluid were rigorously tested to evaluate stability and mobility of fluid sample samples.

The fluid has so far successfully been used on three completions. This paper reports in detail on the fluid development process, operational experiences and well-clean-up observations.
Reduction of Fines Migration by Nanofluids Injection, an Experimental Study
Authors: Habibi A. , Ahmadi M. , Pourafshary P. , Ayatollahi Sh.
Published: June 2011

Formation damage of the oil reservoirs because of fines migration is a major reason for productivity decline. Formation fines are defined as unconfined solid particles present in the pore spaces of the formations. Their migration because of fluids flow in the reservoir would cause pore plugging or permeability reduction. In the last three decades, many studies have been done for the characterization of fines and their migration effect on permeability reduction. There are many techniques in the industry to remediate the damage, especially near well bore regions.

Nanofluids that contain nanoparticles show specific properties such as high tendency for adsorption and good candidate for the injection into the near wellbore regions because of their very small sizes. In this paper, a packed column is utilized to study the use of different types of nanoparticles to reduce fines migration in synthetic porous materials. Three types of nanoparticles; MgO, SiO2 and Al2O3 are used here to investigate their effects on the fines movement. The results indicate that the fines could stick into the grains hindering their migration when the porous materials are already soaked with nanofluids. Besides, to check the mechanisms of this remediation technique, the effect of nanoparticle concentrations and fluid flow rates in the medium on the fines detachment was studied. A theoretical model was employed to calculate the total energy of interaction for the surfaces to check the experimental results, which was also validated by using SEM pictures for samples from the synthetic cores.

The results showed that the addition of 0.1 wt% of MgO and SiO2 nanoparticles would reduce the fines migration by 15% compared to the reference state. MgO nanoparticles were found to be more effective even at high fluid rates when it is used at higher concentration as it is noticed in the macroscopic and microscopic results.
New Analysis Tool to Assess the Need for Enhanced Pumping Technologies for FrackPacks
Authors: Bhamidipati Srikalyan , Karadkar Prasad , Fitzpatrick Harvey , Hailey Travis
Published: June 2011

When frac packing as a completion technique, long treating intervals or heterogeneous lithology within the intervals being treated have led to the use of various methods, equipment, and techniques for ensuring the complete treatment of the intervals. Shunt tubes attached to sand screens can provide an alternate path for fracpack slurry to flow past a bridge if it were to form in the borehole-screen annulus. A concentric annulus packing system using a specific design of perforated liner around the sand screens has also been used to successfully fracpack producing intervals that were thought to have a high risk of forming a bridge inside the borehole before all parts of the interval were properly treated (Lemesnager et al. 2008).

Though using these technologies has led to successful completions, it is less clear how to determine when the fracpack enhancing technologies are actually required. The use of any of the enhancing technologies will likely require some compromise to the flow area (reduction to inner diameter), complexity in installation, or risk to potential retrieval, and at least adds to the cost of the completion. Thus, some means of analyzing when the technologies are required is desirable. A new treatment design analysis software tool has been developed for estimating the amount of liquid leak-off which will occur to a screened-out fracture and corresponding annular bridge if such were to form in the upper (or upstream in the case of high deviation or horizontal wells) portion of a long-treating interval. By determining the amount of liquid leak-off from the slurry being pumped during a fracpack to a bridged-off fracture, a better estimation of the likelihood of successfully packing or fracpacking the remaining portion(s) of the interval with the resulting slurry can be made. Alternatively, by estimating the leak-off in advance with this design tool, we can modify the slurry design to account for the anticipated liquid loss (e.g., by increasing the ratio of liquid to proppant), thus enhancing the likelihood of success. With this new analysis tool, more reliable decisions can be made about the need for treatment-enhancing alternate path or concentric path screens.
Optimizing the Displacement Design - Mud to Brine
Authors: Javora Paul H. , Adkins Mike
Published: June 2011

Displacing drilling mud with clear solids-free completion brine is one of the most critical steps during well completion. Drilling deeper below the mudline (25,000+ feet) and exploring deeper water depths requires critical evaluation of conventional displacement methods and testing procedures and leads to a more rigorous displacement scenario.

Deep wells generally contain greater volumes of working fluid, larger diameter wellbores and drill strings, more feet of casing, and significantly increased surface area that require effective cleaning of mud residue and debris during the displacement process. Therefore, such wells typically require larger volumes of displacement spacers, enhanced pumping rates, and enhanced cleaning chemicals that tolerate substantial mud contamination while maintaining cleaning effectiveness. In order to properly design displacement spacer systems, these parameters must be incorporated into the evaluation and testing scenarios.

This paper describes methods and processes that incorporate the key wellbore parameters, including temperature and density requirements, into the displacement spacer system in order to define the size of spacers, amount of cleaning chemical included in each spacer, number of spacers required, and test methods used to validate the displacement design for the target well. Case histories illustrate how to design and execute an efficient and effective displacement job and the cost savings involved when a displacement system is properly developed.

Failure to complete properly the displacement process can lead to complications in subsequent completion and tool operations, and contribute to wellbore control issues. Furthermore, increased formation damage due to residual solids and time lost to resolve any issues can significantly increase the cost of the completion.
Remedial Sand-Control in Mature Field: Results & Lessons Learnt from through-Tubing Sand Screens Operations in the Gulf of Guinea
Authors: Poitrenaud H. , Djomou S. , Poumerol F.
Published: June 2011

The field in which took place the remedial intervention discussed in this article is located offshore West-Africa, in the gulf of Guinea. Oil is produced from unconsolidated sandstone formations of Miocene/Pliocene reservoirs. Currently, out of 360 wells drilled in the field, about 140 wells are still in production and nearly all of them are equipped with sand-control. Historically, the wells were completed as vertical or slightly deviated Internal Gravel-Packs (IGP), Open-Hole Gravel Pack (OHGP) with milled-windows or with Pre-Pack screens, then since 2001 as Frac-Pack and High Rate Water-Pack (HRWP).

With the first development dating back from 1978 (over 30 years of production) and 50% of the producing wells older than 20 years, this asset is clearly a mature field. Therefore, the durability of sand control systems has been dearly challenged and on some wells, failure of the sand-control has occurred before the production had been exhausted.

This paper will present several rig-less operations that have been performed for sand-control remediation in this mature offshore field environment and the results obtained.

We will first discuss possible scenarios of failure of the existing sand-control completions and then present the choices that have been made for the sand-control remediation, in particular the use of premium through-tubing sand screens with no gravel placement and the use of swell packers for the screen anchoring rather than mechanical devices.

We will then present the productivity and longevity achieved with such equipment and will demonstrate that even in some unorthodox cases, as can be often found in mature fields, remedial sand-control operations can still prove successful. Practical aspects that are important when considering such operations will also be covered.

Finally, recommendations and lessons-learnt derived from successes and failures will be presented.
Privatization and Delegation of State Authority in Asylum Systems
Authors: Kritzman-Amir Tally
Published: June 2011

One of the measures taken by states to relieve the burden of providing for asylum seekers and refugees is privatization and delegation of asylum regimes. I analyze the privatization and delegation of authority that is taking place within asylum systems and describe three tiers of privatization/delegation: 1. admission at points of entry or criminalization of undocumented entry, 2. status determination, 3. social integration and provision of social and economic rights and benefits. I then ask why states are privatizing and delegating authority within the context of asylum systems and argue that privatization and delegation of authority are intended to be used to maintain control and reduce immigration and integration of asylum seekers. Governments are often helpless in their attempts to manage refugee migration and need to recruit other sectors to assist them in regaining control over immigration. This tool is particularly instrumental as it allows governments to maintainto a large extentcontrol of immigrations and at the same time distance themselves from their responsibilities, from human rights violations, etc. Governments attempt to have private or other actors carry out acts that they cannotwhether because of practical reasoning or due to legal constraints. Finally, I argue that asylums systems are a special locus; thus, special care, great caution, much regulation, or complete refrain from privatizing at all, is paramount since privatization of asylums systems carries unique and severe consequences.
On the gravitodynamics of moving bodies
Authors: Mol Anderson
Published: June 2011

In the present work we propose a generalization of Newton’s gravitational theory from the original works of Heaviside and Sciama, that takes into account both approaches, and accomplishes the same result in a simpler way than the standard cosmological approach. The established formulation describes the local gravitational field related to the observables and effectively implements the Mach’s principle in a quantitative form that retakes Dirac’s large number hypothesis. As a consequence of the equivalence principle and the application of this formulation to the observable universe, we obtain, as an immediate result, a value of Ω = 2. We construct a dynamic model for a galaxy without dark matter, which fits well with recent observational data, in terms of a variable effective inertial mass that reflects the present dynamic state of the universe and that replicates from first principles, the phenomenology proposed in MOND. The remarkable aspect of these results is the connection of the effect dubbed dark matter with the dark energy field, which makes it possible for us to interpret it as longitudinal gravitational waves.
Secondary carbonates in loess-paleosoil sequences: a general review
Authors: Barta Gabriella
Published: June 2011

The literature dealing with secondary carbonates in loess-paleosoil sequences is in many cases ambiguous, which means that different concepts are used for the same features, whereas certain concepts referring to different types are used as collective nouns. The aim of this study is to give a review on this nomenclature and to draw comparision between the various types and concepts. As a main guiding principle the article of Becze-Deák et al. (1997) is used, because it has formulated a proposition of a nomenclature which would be worthwhile to adopt. The terms and concepts introduced by their work are exact, referring to certain separated secondary carbonates and are of decisive importance with a view to paleoenvironmental reconstruction.

The research of secondary carbonates in loess-paleosoil sequences is of great importance, through providing detailed information on the paleoenvironment, especially on the former moisture conditions (including leaching processes). Secondary carbonates originate from the vertical, horizontal or in situ resettlement of carbonates during pedogenesis in the soil-sedimentary environment. Among others, calcified root cells, hypocoatings and needle-fiber calcite are classified into the microscale category, while concretions (e.g. loess dolls) belong to the macroscale types.
Efficacy of Trunk Balance Exercises for Individuals With Chronic Low Back Pain: A Randomized Clinical Trial
Authors: Gatti Roberto , Faccendini Simone , Tettamanti Andrea , Barbero Marco , Balestri Angela , Calori Giliola
Published: June 2011

Study Design

Randomized clinical trial.

Objectives

To determine the efficacy of trunk balance exercises for individuals with chronic low back pain.

Background

The majority of exercises focusing on restoring lumbopelvic stability propose targeting the feedforward control of the lumbopelvic region. Less attention has been paid to feedback control during balance adjustments.

Methods

Seventy-nine patients were randomly allocated to 2 different groups. The experimental group performed trunk balance exercises in addition to standard trunk flexibility exercises. The control group performed strengthening exercises in addition to the same standard trunk flexibility exercises. The primary outcome measures were pain intensity (visual analogue scale), disability (Roland-Morris Questionnaire), and quality of life (12-Item Short-Form Health Survey). Secondary outcomes were painful positions, use of analgesic drugs, and referred pain. Analysis of variance and relative risk were used to analyze the data for the primary and secondary outcome measures, respectively. The number of participants reaching the minimal clinically important difference in the 2 groups for each outcome measure was compared using relative risk.

Results

A significant difference in scores on the Roland-Morris Questionnaire (P = .011) and the physical component of the 12-Item Short-Form Health Survey (P = .048), and in the number of participants reaching the minimal clinically important difference for the Roland-Morris Questionnaire (relative risk, 1.79; 95% confidence interval [CI]: 1.05, 3.04) and the secondary outcome of painful positions (relative risk, 1.37; 95% CI: 1.03, 1.83) were found in favor of the experimental treatment.

Conclusions

Trunk balance exercises combined with flexibility exercises were found to be more effective than a combination of strength and flexibility exercises in reducing disability and improving the physical component of quality of life in patients with chronic low back pain.

Level of Evidence

Therapy, level 1b-. J Orthop Sports Phys Ther 2011;41(8):542–552. Epub 7 June 2011. doi:10.2519/jospt.2011.3413
An Exploration of the Relationship Between Back Muscle Endurance and Familial, Physical, Lifestyle, and Psychosocial Factors in Adolescents and Young Adults
Authors: Campbell Amity C. , Briggs Andrew M. , O'Sullivan Peter B. , Smith Anne J. , Burnett Angus F. , Moss Penny , Straker Leon M.
Published: June 2011

Study Design

Cross-sectional investigation.

Objectives

To explore the relationship between back muscle endurance (BME) and a range of familial, physical, lifestyle, and psychosocial variables in adolescents and young adults.

Background

There is evidence that low back pain interventions which focus on improved BME are effective. However, the mechanisms associated with BME performance in adolescents and young adults are largely unclear. In particular, the potential familial relationship between parents and their children remains unexplored.

Methods

This study utilized a subset of participants from the Joondalup Spinal Health Study cohort. One hundred nine children (47 boys, 62 girls) and 101 parents (39 fathers, 62 mothers) completed a series of physical, lifestyle, and psychosocial assessments. The univariable relationship between each covariate and BME was explored. Those found to have an association with child BME (P<.2) were included in an initial multivariable model and sequentially removed, until all remaining covariates were statistically significant (P<.05).

Results

Mothers' BME performance was related to children's performance, accounting for 14.4% of the variance in the children 's BME. Fathers’ BME performance had a similar, albeit nonsignificant effect. Children's sitting trunk angle, pain sensitivity, percent trunk fat, waist girth, and body mass index were associated with their BME performance, accounting for between 5.2% and 20.9% of BME.

Conclusions

The final multivariable model, including mother's BME, percent trunk fat, and sitting trunk angle, explained 28% of the variance in BME performance, suggesting that for successful BME intervention a range of multidimensional variables should be considered. J Orthop Sports Phys Ther 2011;41(7):486–495, Epub 7 June 2011. doi:10.2519/jospt.2011.3638
Total Number and Severity of Comorbidities Do Not Differ Based on Anatomical Region of Musculoskeletal Pain
Authors: Coronado Rogelio A. , Alappattu Meryl J. , Hart Dennis L. , George Steven Z.
Published: June 2011

Study Design

Secondary analysis, cross-sectional study.

Objectives

To (1) compare differences in individual comorbidity rates among patients with cervical, lumbar, and extremity pain complaints and (2) compare rates based on total number and severity in these same patient groups.

Background

Comorbidities can impact recovery, prognosis, and potentially hinder participation in rehabilitation. Few studies have compared comorbidity rates among patients with different anatomical region of pain, to determine whether specific screening is warranted in physical therapy settings.

Methods

Included in the analyses were 2375 patients who reported complete demographic, clinical, and comorbidity information using Patient Inquiry software. Comorbidity data were collected from the Functional Comorbidity Index (18 items) and 6 additional comorbidities, to assess the presence of medical disease across multiple body systems. Comorbidities were further classified as “nonsevere” or “severe,” based on inclusion in the Charlson Comorbidity Index. Chi-square analyses investigated differences in the rates of total number and severe comorbidities. Odds ratios (OR) and 95% confidence intervals (CIs) were calculated on rates with statistically significant differences (P<.001), using the lumbar spine as the reference group.

Results

Of the 24 comorbid conditions included in this analysis, 3 nonsevere medical conditions (degenerative disc disease, obesity, and headache) had different rates among anatomical region. A lower rate for degenerative disc disease was associated with the extremity conditions (x2 = 66.3; OR = 0.40; 95% CI: 0.32, 0.50). Higher rate of headache (x2 = 115.3; OR = 3.01; 95% CI: 2.45, 3.70) and lower rate of obesity (x2 = 16.2; OR = 0.64; 95% CI: 0.51, 0.80) were associated with cervical conditions. There were no differences among the 3 anatomical regions for total number or severe comorbidities.

Conclusions

Focused screening for degenerative disc disease, obesity, and headache may be warranted. However, the same strategy was not supported for total number or severe comorbidities, at least when considering comparative rates from this cohort. Physical therapists should consider the potential influence of total number and severe comorbidities equally for all anatomical regions of musculoskeletal pain.

Level of Evidence

Differential diagnosis/symptom prevalence, level 3b. J Orthop Sports Phys Ther 2011;41(7):477–485, Epub 7 June 2011. doi:10.2519/jospt.2011.3686
Robust Means Modeling
Authors: Fan Weihua , Hancock Gregory R.
Published: June 2011

This study proposes robust means modeling (RMM) approaches for hypothesis testing of mean differences for between-subjects designs in order to control the biasing effects of nonnormality and variance inequality. Drawing from structural equation modeling (SEM), the RMM approaches make no assumption of variance homogeneity and employ robust estimation/rescaling strategies in order to alleviate reliance on normality. A Monte Carlo simulation is conducted to compare the Type I error rate and the power of the proposed six RMM test statistics to five analysis of variance (ANOVA)-based statistics, the latter of which have also employed trimmed means and Winsorized variances to enhance robustness. Various simulation factors manipulated include variance inequality, sample-size pairings with group variances, degree of nonnormality, alpha level for hypothesis tests, and effect size. Results show that the proposed RMM methods are indeed superior to the traditional ANOVA-based methods.
“Let's Hear it for the Men”: A Men's Studies Curriculum in the School System
Authors: Weber Gordon , Kitchenham Andrew
Published: June 2011

This qualitative research explored the impetus, implementation, and barriers to the creation of a men's studies program in a rural Canadian school district. Student engagement in several countries and continents has drawn significant academic attention over the last decade and statistical evidence of lack of engagement, poor attendance, inappropriate behaviour, school suspension, special education enrolment, and low graduation rates demonstrates an oversubscription by male students. Using a synthesis of international research literature and supporting materials from a variety of sources, and to answer the research question, “Grounded in the professional literature, what characteristics might be the scope and sequence of a curriculum of Men's Studies 12, designed for identified at-risk youth?”, we outlined an actual men's studies program based on curriculum design guidelines and grounded in the professional literature.