bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of alloyed Bi2TexSe(3-x) nanoparticles and thermoelectric characterization of bulk nanostructured materials obtained by their assembly
Authors: Bude Romain , Divay Laurent , Bisaro Renato , Servet Bernard , Leveugle Elodie , Wyczisk Frédéric , Carisetti Dominique , Ziaei Afshin , Galindo Christophe 
Published: May 2015

ABSTRACTThe optimization of the figure of merit of thermoelectric materials requires the simultaneous control of the material composition and microstructure. Assembly of nanoparticles obtained by a solution route is an attractive bulk fabrication method because size and shape of the nanoparticles can be tuned by variation of the synthesis conditions. Recently, new synthetic pathways were reported among which reducing agent assisted, surfactant free processes. We report here the evaluation of this method for the synthesis of Bi2TexSe3-x alloyed nanoparticles with varying selenium concentrations. X-ray diffraction studies conducted on powder and pellet samples show that two alloyed phases are present in the sample even at low selenium content. The careful study of the position of the diffraction peaks as function of the formulation shows that this behaviour could arise from the difference in reactivity of selenium and tellurium. Moreover, the electrical conductivity of the samples is shown to increase upon selenium addition while the Seebeck coefficient is reduced. Power factor shows an optimum value around 20% selenium content with a large tolerance in composition.
Insulated Polyacetylene Chains in an Inclusion Complex by Photopolymerization
Authors: Dincă Steluţa A. , Allis Damian G. , Lashua Amanda F. , Sponsler Michael B. , Hudson Bruce S. 
Published: May 2015

ABSTRACTThe properties of a material often depend on the degree of order of their atomic, molecular, or crystalline domain components. This is expected to be especially true for the case of polyacetylene, whose properties are highly anisotropic. For many applications, it may be necessary to have macroscopic order but not necessarily crystalline order. Having polyacetyelene chains fully extended and aligned parallel to each other may be sufficient for these applications even without order of the chains around their long axis. We report here progress in the use of an inclusion crystal containing a photo-reactive precursor to prepare high molecular weight polyacetylene. Raman spectroscopy was performed to probe the resulting conjugated polyene chains. Ultraviolet irradiation of a 1,4-diiodo-1,3-butadiene/urea inclusion complex results in the appearance of new resonance-enhanced Raman modes at 1125 and 1509 cm-1. The Raman spectra of the resulting confined polyene chains are very similar to freestanding isolated trans-polyacetylene prepared by solution methods.
Biohybrid Fibro-Porous Vascular Scaffolds: Effect of Crosslinking on Properties
Authors: Thomas Vinoy , Nozik Danna , Patel Harsh , Singh Raj K. , Vohra Yogesh K. 
Published: May 2015

ABSTRACTTubular grafts were fabricated from blends of polycaprolactone (PCL) and poly(glycolide-co-caprolactone) (PGC) polymers and coated with an extracellular matrix containing collagens, laminin, and proteoglycans, but not growth factors (HuBiogel™). Multifunctional scaffolds from polymer blends and membrane proteins provide the necessary biomechanics and biological functions for tissue regeneration. Two crosslinking agents, a natural crosslinker namely genipin (Gp) and a carbodiimide reagent namely 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), were used for further stabilizing the protein matrix and the effect of crosslinking was evaluated for structural, morphological, mechanical properties using SEM, DSC and DMA. SEM images and fiber diameter distribution showed fiber-size between 0.2 μm to 1 μm with the majority of fiber diameters being under 500 nm, indicating upper range of protein fiber-sizes (for example, collagen fibers in extracellular matrix are in 50 to 500 nm diameter range). HB coating did not affect the mechanical properties, but increased its hydrophilicity of the graft. Overall data showed that PCL/PGC blends with 3:1 mass ratio exhibited mechanical properties comparable to those of human native arteries (tensile strength of 1-2 MPa and Young’s modulus of <10 MPa). Additionally, the effect of crosslinking on coating stability was investigated to assure the retention of proteins on scaffold for effective cell-matrix interactions.
Stimulating High-Temperature Dolomitic Limestone Reservoirs with Chelant Fluids
Authors: de Antuñano Yuri , Losada M. , Milne A. 
Published: May 2015

Abstract
Oil production in southern Mexico is mainly from deep (&gt;16,000 ft) high-temperature (&gt; 300°F), naturally fissured dolomitic limestone reservoirs with clays present. With increasing depth, the dolomitization increases and the porosity and permeability decrease. These reservoirs must be stimulated to produce, and treatments are traditionally repeated to maintain production.
Although there is a substantial body of published research on stimulating carbonate formations, there is little on treating dolomites specifically. In general, the smaller the volume of reactive fluid required to penetrate into the formation to create a wormhole—a function of reactive fluid used, injection rate, and temperature—the more efficient the treatment. Hydrochloric acid (HCl) has both a high dissolution rate and dissolution capacity which, at high temperature, results in dissolution of the face of the formation, as opposed to wormholing, and uncontrollable corrosion rates. Organic acids have lower corrosion rates and limited dissolution capacity, but have a relatively high rate of dissolution, which also results in face dissolution at high temperature. Although, clays present in the formation may slow the rate of dissolution.
Chelant-based fluids are less corrosive, have lower dissolution rates, and are capable of creating effective wormholes at temperatures up to 400”F in carbonates. Although dolomite retards the dissolution rate of both acids and chelants, the difference is less with chelants. The wormholing efficiency of chelants in dolomites is also less rate dependent than is that of inorganic acids.
Acidic hydroxyethylethylenediaminetriacetic acid (HEDTA) fluids were developed to stimulate high-temperature carbonates and dolomites. These fluids have been highly effective in stimulating both carbonate, and even sandstone, formations worldwide. However, the optimum pH and injection rate for wormholing is markedly different for carbonates and dolomites. In addition, a low pH may result in emulsions and corrosion downhole or at surface when flowing back the treatment. Recent studies show that the efficiency of diammonium EDTA (DEA) with the correct pH is similar whether stimulating a high-temperature limestone or a dolomite formation, at similar injection rates.
A direct comparison has been made by performing treatments in the same reservoirs using the two chelant systems. In every case, the initial post-treatment production with the DEA-based fluid has been significantly higher and the production decline slower. This is attributed to stimulating both the dolomite and limestone intervals and removing the potentially damaging clay and fines. The fluid also eliminates the possible issues with using a low-pH fluid.
Operator Uses Advanced Perforation Flow Laboratory to Support HMX Perforating by Coiled Tubing in HPHT Field
Authors: Haggerty D. , Christie S. 
Published: May 2015

Abstract
By using the advanced perforation flow laboratory (APFL), the depth of penetration performance of shaped charges can be measured at downhole conditions to confirm whether or not the formation penetration will exceed the depth of formation damage attributable to drilling. In tubing-conveyed perforating, HNS explosive shaped charges have historically been used in elevated temperature environments. The option of using deeper penetrating, but less heat-resistant, HMX explosive shaped charges is possible in the Hejre field wells in the North Sea because the depth to the reservoir interval to be perforated is within the reach of coiled tubing. This process requires less time for the perforating guns to tolerate elevated temperatures, and coiled tubing provides a means of circulating cooling fluid, further increasing the charge lifespan. Based on conservative run times for deploying guns on coiled tubing (estimated to be 4 to 6 hours from surface), there will be sufficient time to position the guns at depth before detonation, and sufficient time to retrieve the gun string from the wellbore in the event of a misfire.
All perforation flow lab tests in the APFL were run at Hejre pressures, with overburden stress at 17,500 psi and pore pressure at 14,600 psi; several tests were run at the reservoir temperature of 160°C (320°F). Aligned with American Petroleum Institute Recommended Practice 19B Section 4 (2006), the APFL tests were conducted to closely match the expected conditions in the Hejre field, requiring minimal scaling of the results.
Tests in the APFL comparing the different explosive powder charges showed a nearly 50% increase in formation-analog target penetration using the HMX charge vs. the HNS charge. This depth of penetration increase improves the prospect of penetrating the estimated drilling damage zone to vastly improve production and the effectiveness of further stimulation. This paper discusses the methodology, obstacles encountered and means of addressing them, and the test program results.
Before the construction and development of testing equipment to shoot a shaped charge at elevated temperatures and high pressures, extrapolations had to be used to predict perforator performance with a higher level of uncertainty.
Exploitation of Danish Sector North Sea Chalk Field: A Case Study of the Hess South Arne Field – Acid Stimulation Design, Optimization and Execution
Authors: Miller Rory , Jakobsen Erik , Kalfayan Leonard , Troelsen Benny 
Published: May 2015

Abstract
The South Arne Field, located in the Danish sector of the North Sea, has been producing oil and gas since 1999 with an active waterflood since 2000. Producers and injectors are primarily horizontal with sliding sleeve completions targeting both the Ekofisk and Tor chalk formations. South Arne is currently in exploitation modewith a new (Phase III) development program. Phase III includes two new platform installations, a two-kilometer umbilical bundle and an eleven-well drilling program targeting the northern extension of the field. This paper discusses the first five Phase III wells, focusing on stimulation design, lessons learned from the fluid testing, experiences, and the continuous improvement of the operational execution process.
New producer and injector stimulation designs are generally based on a pad-acid procedure in which a cross-linked gel pad is followed by an in-situ cross-linked hydrochloric (HCl) acid treatment, to create viscosity contrast for diversion and differential acid fracture etching for sustained conductivity. The acid fracture treatment is then followed by a closed fracture acidizing (CFA) step to enhance near-wellbore fracture conductivity. For wells completed in zones that have the potential of short-circuiting to neighboring wells, lower rate and smaller volume HCl matrix treatments are pumped. The Phase III stimulations to date have been conducted through ball drop sliding sleeves, with the number of zones ranging from 10 to 14.
Establishing Phase III success has required extensive QA/QC testing to optimize the stimulation fluid systems and, in particular, the acid corrosion inhibition program. Use of real-time bottom-hole temperature measurements during stimulation treatments has enabled optimization of corrosion inhibitor loadings, resulting in both an environmental benefit and financial savings. The stimulation treatments are performed simultaneously with drilling operations, therefore extensive work was required to ensure that stimulation and drilling activities are safely executed without interference. Both platforms were initially designed to optimize productive time during stimulation operations, however as the project evolved, thorough risk evaluations pointed to the need to modify operating plans. Rigorous marine and vessel audits were performed to ensure that stimulation vessels could operate safely and effectively from both a marine and stimulation job execution standpoint. The design, testing and advance preparation for the South Arne Phase III program has resulted in safe and effective treatment execution.
The Effect of Stress Sensitive Permeability Reduction on the Evaluation of Post-Fracture Welltests in Tight Gas and Unconventional Reservoirs
Authors: Shaoul J. R. , Ayush A. , Park J. , Pater C. J. 
Published: May 2015

Abstract
The interpretation of well performance in propped fractured tight gas reservoirs is a topic that has been studied for decades, but still presents a number of difficulties. These issues are becoming more important as unconventional reservoirs with even lower permeabilities are developed (micro and nano- Darcy).
One of the most troublesome issues in tight-gas fracturing is that post-frac welltests often show very short effective fracture lengths. This is often blamed on gel damage due to poor proppant pack cleanup in the fracture or loss of propped width due to embedment and filtercake in the fracture. It has also been attributed to formation damage, due to “phase trapping” of fracture fluid filtrate along the fracture face. Much work has already been done on these topics, which show that extreme damage to the proppant pack or the fracture face would be needed to explain the short effective fracture lengths that are often seen. Regained permeability testing, when available, in many cases does not indicate that this much damage is expected, either in the proppant pack or on the fracture face, under normal circumstances.
In this paper, a large number of high resolution 3D numerical simulations have been performed, based on realistic reservoir parameters for a typical tight-gas reservoir, using stress sensitive permeability data derived from core testing. By modeling both the propped fracture and the reservoir with fine grid refinement, it is possible to simulate drawdown and buildup pressures with and without the effect of stress sensitive permeability in the reservoir matrix. The simulations also include the effect of the effective stress on the proppant pack, which is generally not significant in tight gas, unless the proppant concentration is extremely low. These synthetic drawdown and buildup data sets with known parameters are then analyzed using a standard welltest analysis package, and the results are compared.
The results of this work show that for tight and ultra-tight reservoirs, conventional welltest analysis methods will always show a smaller fracture length and a larger permeability, compared to the “correct” values used to generate the test data sets. This behavior is partly due to the rectangular fracture geometry assumed in the welltest solutions. An additional reduction in length can be explained by stress sensitive permeability, without any need for damage to the proppant pack or the fracture face. The results from the incorrect welltest analysis are used for a long-term forecast simulation (with a short fracture length, higher permeability and ignoring stress sensitive permeability), which is compared to a forecast based on the model with the correct fracture length and stress sensitive permeability. This shows a significant overestimation of the ultimate recovery when using the welltest derived parameters.
Applying Method of Characteristics to Study Utilization of Nanoparticles to Reduce Fines Migration in Deepwater Reservoirs
Authors: Yuan Bin , Ghanbarnezhad Moghanloo Rouzbeh , Pattamasingh Purachet 
Published: May 2015

Abstract
This paper examines an application of method of characteristics (MOC) to evaluate utilization of nanoparticles to mitigate fines migration. Deepwater reservoirs are poorly consolidated, strongly heterogeneous and less consolidated with high pressure, temperature, porosity and permeability. All these features increase the possibility of troublesome sand production. It has been shown that nanoparticles can effectively reduce double layer repulsive forces between sand particles through changing the associated zeta potentials; the reduction of repulsive forces between loose particles would maintain integrity of the rock texture. However, our understanding on the effectiveness of nanoparticles to mitigate sand production has been limited to some experimental studies serving as proof of concept. In practice, this paper also provides an efficient and simple model to optimize fines migration treatment via injection of nanoparticles.
In this paper, we develop an analytical model to study the interplay between adsorption of nanoparticles and their geochemical effects on fines migration and the consequent sand production. There are two governing mechanisms: 1) adsorption of nanoparticles on the surfaces of fines particles; 2) the positive contribution of adsorbed nanoparticles on integrity of the rock texture. We define a fictitious attachment reaction for which we interpret the existing lab results as the rate of reaction.
We consider nanoparticle adsorption front as borders of distinct regions. At upstream of adsorption front, adsorbed nanoparticles improve coalescence of particles; whereas at the downstream, dynamic detachments of fine particles occur. Similarly, adsorption of nanoparticles on the grain surface occurs only at the upstream of adsorption front. The main contribution of this work is to evaluate the propagation of adsorption front, and fine particles and nanoparticle concentration profile along the sand pack. We use method of characteristics and present a graphical solution to determine optimal concentration of nanoparticles required to reduce maximum sand production. We define mitigation index (MI) to describe the contribution of nanoparticles to mitigate fines migration.
The analytic solution is verified by numerical simulation. This model provides a novel and efficient approach to describe the impact of nanoparticles to mitigate fines migration. In practice, this method can be used to design an effective treatment for sand control in deepwater reservoirs as well as other type of reservoirs that suffer from fines migration problems.
Perforating on Wireline: Maximizing Productivity and Minimizing Gunshock
Authors: Baumann Carlos , Gultom Denny , Salsman Alan , Smart Moises , Primasari Indah , Rahman Risal , Warsito Sandy 
Published: May 2015

Abstract
We present perforating on wireline with dynamic underbalance (DUB) to simultaneously maximize productivity and minimize gunshock. We focus on perforating on wireline with DUB because, when compared with other approaches, perforating with DUB is probably the best method to deliver lower tunnel plugging and lower formation rock damage, with lower risk of tool damage due to gunshock or guns blown uphole. Specifically, we present two important aspects of perforating on wireline using DUB: prediction of wellbore dynamics to assess perforation tunnel and formation cleanup and gunshock prediction to assess the risk of tool damage. We present the latest models used to evaluate perforating jobs for well productivity and for operational risks.
It is well known that the DUB produced when perforating with the right gun system can remove formation rock damage and tunnel plugging produced by shape charges. What is not so well known is how much DUB (amplitude and duration) is necessary, and how to predict how much DUB will be generated by a gun system. To achieve formation tunnel cleanup, we need a DUB of large amplitude but short duration to remove perforating rock damage and plugging while minimizing gunshock loads. In the pre-job design, we simulate/predict the transient fluid pressure waves in the wellbore and formation rock to predict formation rock damage cleanup and also the associated gunshock loads. DUB amplitude and duration depend on job parameters that can be adjusted, such as type and size of guns, loading of standard perforating charges and DUB charges, and placement of packers, if present. Important physics included in the model are: gun filling, wellbore pressure waves, transient reservoir fluid flow, and the dynamics of all relevant solid components (cable, shock absorbers, tools, and guns).
The reliability of the DUB prediction model is demonstrated by comparing downhole fast-gauge pressure data with the corresponding simulated values. When the reservoir properties are well known, the predicted DUB amplitude and duration are very close to the field data values, typically within 15% or less. The reliability of the gunshock loads is demonstrated with residual shock absorber deformation and cable tension logs. We also demonstrate how gunshock simulations have been useful to explain equipment failures due to gunshock loads.
Reliable predictions of wellbore dynamics, transient reservoir flow, and gunshock loads enable operators to select perforating equipment capable of removing perforating formation damage and reduce the risk of unexpected release of tools and guns due to dynamic loads, thereby minimizing the probability of nonproductive time and fishing operations.
Selection of Non-damaging Phosphonate-Based Scale Inhibitors for Field Application in a Reservoir Containing Reactive Iron Minerals
Authors: Tahir M. A. , Orme Mike , Kidd Samuel , Hoeth Laurien Wichers , Wright Rob , Graham Gordon 
Published: May 2015

Abstract
Core flood testing of phosphonate-based scale inhibitors in reservoir sandstone containing iron minerals revealed potential formation damage caused by unmodified acid phosphonates, which are reactive toward the iron minerals. The mechanism of formation damage was shown to be due to dissolution and re-precipitation of iron phosphonate species, together with fines mobilized (also thought to be due to dissolution effects) which propagated some distance through the core, leading to pore throat blockages. In an example case, complete blockage occurred as the front of the injection chemical reached the outlet of the core due to a combination of silica fines and iron phosphonate chemical.
To mitigate the potential issue, different chemical formulations were prepared based on the same phosphonate scale inhibitor, in order to mitigate / minimise the potential for in-situ dissolution of iron bearing minerals within the reservoir formation. This allowed a less aggressive formulation to be prepared by part-neutralisation of the acid phosphonate, so achieving compatibility with the core material. Thus, no formation damage was induced and retention of scale inhibitor by adsorption ensured the potential for long squeeze treatment lifetimes. The modified product has since been applied in the field and results from the laboratory qualification, chemical re-formulation and field treatments are presented in this paper. To date, 27 wells have been squeezed; the part-neutralized chemical targeted at susceptible wells and the acid chemical used elsewhere. Excellent are results in both formation damage and return lifetimes minimising the requirement for coil tubing scale removal treatments in this field.