Charge History Research Articles

Numerical Calculation of an Equilibrium Dust Grain Potential in Lunar Environment

The interaction of plasma particles with dust grains leads to their charging. An equilibrium grain potential depends on a plasma environment, as well as on the grain composition, size, shape, and charging history. We present results of calculations of the equilibrium potential of the grain immersed in the plasma simulating a lunar environment. In calculations, we apply a modified model of the secondary electron emission from dust grains, which takes into account grain sizes, their material, and surface roughness. Since this model describes the increase in the secondary emission yield caused by a finite dimension of the dust grain, the calculations provide a realistic estimation of the dust grain charge in the near-Earth environment. We show that the grain surface potential is a descending function of the grain size and this effect can even lead to opposite polarities of small and large grains.

Hydrocarbon charge history of the Tazhong Ordovician reservoirs, Tarim Basin as revealed from an integrated fluid inclusion study

Abstract This paper presents an integrated workflow for investigating hydrocarbon charge history using fluid inclusions using the Ordovician reservoirs from the Tazhong Oilfield, Tarim Basin as an example. The work flow involves the delineation of fluid inclusion assemblage (FIA) using fluid inclusion petrography and spectroscopy for microthermometric analysis. The interpretation of microthermometric data is based on data derived from synthetic inclusion experiments and takes consideration of the P-T re-equilibration of fluid inclusions in carbonate and over pressure effect on fluid inclusion trapping. The workflow also emphasizes on the requirements of adequate sample preparation, FIA identification, quantitative spectroscopic data (CIE), coeval petroleum and aqueous fluid inclusions, adequate number of microthermometric measurements and integrated interpretation using borehole temperature. In the study reservoirs in the Tazhong area, fluid inclusion spectroscopy reveals the presence of three groups of oil inclusions of near yellow, near blue and near white fluorescence colours. The fluid inclusion microthermometry data indicate the presence of at least two predominant hydrocarbon fluid inclusion assemblages including: homogenous liquid phase yellow fluorescence inclusions and liquid phase oil and condensate fluid inclusion assemblages with homogenous near blue, near white and near yellow fluorescence colours. The aqueous inclusions from the Ordovician reservoirs in the Tazhong area reveal the presence of low, moderate, high and very high salinities in the reservoirs. The extremely high salinity is believed to be caused by regional brine intrusions relating to regional structural movement and deformation.

Fluid inclusions and oil charge history in the reservoirs of the Yongjin oilfield in central Junggar Basin

In the Yongjin oilfield of southern Junggar Basin, many wells have been drilled to produce industrial oils. Based on the analysis of fluid inclusions in the reservoirs, in combination with the geological and thermal evolution, the charge history in this area has been studied. The results indicate that the Jurassic Formation and Cretaceous Formation reservoirs contain abundant oil and gas inclusions, and four types of fluid inclusions have been distinguished. According to the homogenization temperatures of the fluid inclusions, the hydrocarbons charged the Cretaceous Formation for two periods, one ranges from the Late Cretaceous period to the Eogene period, and the other ranges from the Neocene period to the present. The oil filling history is correlated with the oil source correlation analysis, which is controlled by the movement of the Che-Mo plaeo uplift. Overall, oil accumulation is characterized by the superposition of two sets of source rocks for two stages in the Shawan depression.

Ormen Lange Hydrodynamic-Aquifer Model

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 153507, ’Predicting Water in the Crest of a Giant Gas Field: Ormen Lange Hydrodynamic-Aquifer Model,’ by M. Boya Ferrero, S. Price, SPE, and J. Hognestad, Shell, prepared for the 2012 EAGE Conference & Exhibition/SPE Europec, Copenhagen, Denmark, 4-7 June. The paper has not been peer reviewed. Simulation showed that hydrodynamically tilted/stepping contacts depend on the rate of water flow across the aquifer, stratigraphic baffling and faulting, effective aquifer area, and reservoir quality. The role of sealing faults over geological time was downplayed in terms of justifying the fluid distribution. However, baffling during production is expected. At Ormen Lange, the hydrodynamic aquifer has pushed gas from the crest of the structure into the south of the field, leaving behind a northward-thickening prism of residual gas, which was imaged with a seismic direct hydrocarbon indicator (DHI). Confirmation of the hydrodynamic aquifer in this field was achieved after drilling an appraisal well in the north of the structure that corroborated fluids (water with residual gas) and pressures as predicted by the hydrodynamic-aquifer model. Introduction The Ormen Lange gas field was discovered in 1997, with first production in 2007. It is a large (8×40-km) deep-water reservoir 125 km offshore Norway at 700- to 1100-m water depth. Ormen Lange sands have excellent reservoir quality, with 26 to 30% average porosity and 500- to 1,000-md permeability. The field was developed with four subsea templates and 10 high-rate large-borehole wells. The initial field-development plan was based on a stratigraphic trap filled to spill point, with the gas accumulation being delineated by a seismic DHI, which was postulated to indicate perched water on the edges of the structure. The field-development plan was defined on the basis of information available from only four exploration and appraisal wells. The need to understand the field’s charge history became apparent when, in 2008, an appraisal well in the northern part of the field encountered only residual-gas saturations in the crest of the structure and in the middle of a high DHI. Therefore, the DHI could not be used as a proxy for the current free-water level (FWL) because seismic cannot distinguish between mobile-gas and residual-gas saturations. Subsequently, three additional appraisal wells confirmed elevated contacts, residual gas, and gas communication across the field.

Petroleum charging and leakage in the BZ25-1 field, Bohai Bay basin

This paper discusses origin and charging histories of the Bozhong (渤中) 25-1 field (BZ25-1) in the Bozhong sub-basin, Bohai (渤海) Bay basin. Petroleum is contained in both Paleogene and Neogene reservoirs in the BZ25-1 field. The origin of the field was studied using biomarker distributions for 61 source rock samples and 34 oil samples. Oil in the Paleogene reservoirs was derived from the third member (Es3, 43.0–38.0 Ma in age) of the Eocene Shahejie (沙河街) Formation, whereas oil in the Neogene reservoirs was a mixtures of oil generated from the third member and the first member (Es1, 35.8–32.8 Ma) of the Eocene Shahejie Formation. Charging of the shallow Neogene reservoirs was dynamic, probably ongoing, which was a combined result of the existence of active source rocks, the development of overpressure and the fault reactivation since about 5.1 Ma. On the contrary, the deep Paleogene reservoirs experienced intensive oil leakage as indicated by the high GOI (grains-containing-oil-inclusions) values (up to 30%) for samples below the present-day oil-water contact. Part of the oil that leaked from the Paleogene reservoirs re-accumulated in the shallow Neogene reservoirs. The variation of oil origins within the BZ25-1 field, and the dynamic petroleum charging into the shallow Neogene reservoirs and leakage from the deep Paleogene reservoirs have important implications for petroleum exploration.

Criminal Records and the Labor Market for Professional Athletes: The Case of the National Football League

This is the first paper to formally analyze character discrimination in the specific labor market for professional athletes. We observe all 1,273 players drafted into the National Football League between 2005-2009 to determine what effects character concerns, namely arrest records and team suspensions, have on draft status and performance in the NFL. Prospects that have a history of formal criminal charges or are suspended for team or university violations fall between 16-22 spots in the draft. The impacts of character concerns on performance depend on the nature of the issue. Players that have a history of suspension (non-criminal related) start and play in fewer games per season, but having an encounter with law enforcement does not negatively predict performance. This suggests that having a problem with coaches or fellow players is an indicator of future problems, but having a run in with the law does not adversely affect on the field performance. We also find some evidence that conditional on where players are picked in the draft, teams undervalue those with criminal records and overvalue those with other types of suspensions.

Simulation of the gallium nitride-based pulse mode X-ray detector for short-time applications

The purpose of this work is to simulate gallium nitride (GaN)-based X-ray pulse mode detector to study the capability of GaN for X-ray detection in short-time applications. The simulation was performed using Monte Carlo (MC) and finite-element methods. The history of charges created by X-photons inside the detector was obtained using the MC results, while the computation of electric field, steady-state and transient behavior of the detector was done using the finite-element method. Electrical properties of GaN were fully simulated. Moreover, unusual behavior of GaN under X-ray illumination was considered in the simulation. Response of the GaN-based detector to X-ray photons was simulated using analytical models and the results showed that the detector can be used in applications in which X-ray exposure time is short (as in the imaging systems). For the first time, a GaN-based X-ray detector was simulated and the capability of the GaN X-ray detector for applications with short-time X-ray exposure was analyzed.

Petroleum generation and charge history of the northern Dongying Depression, Bohai Bay Basin, China: Insight from integrated fluid inclusion analysis and basin modelling

The petroleum generation and charge history of the northern Dongying Depression, Bohai Bay Basin was investigated using an integrated fluid inclusion analysis workflow and geohistory modelling. One and two-dimensional basin modelling was performed to unravel the oil generation history of the Eocene Shahejie Formation (Es3 and Es4) source rocks based on the reconstruction of the burial, thermal and maturity history. Calibration of the model with thermal maturity and borehole temperature data using a rift basin heat flow model indicates that the upper interval of the Es4 source rocks began to generate oil at around 35 Ma, reached a maturity level of 0.7% Ro at 31–30 Ma and a peak hydrocarbon generation at 24–23 Ma. The lower interval of the Es3 source rocks began to generate oil at around 33–32 Ma and reached a maturity of 0.7% Ro at about 27–26 Ma. Oil generation from the lower Es3 and upper Es4 source rocks occurred in three phases with the first phase from approximately 30–20 Ma; the second phase from approximately 20–5 Ma; and the third phase from 5 Ma to the present day. The first and third phases were the two predominant phases of intense oil generation.Samples from the Es3 and Es4 reservoir intervals in 12 wells at depth intervals between 2677.7 m and 4323.0 m were investigated using an integrated fluid inclusion workflow including petrography, fluorescence spectroscopy and microthermometry to determine the petroleum charge history in the northern Dongying Depression. Abundant oil inclusions with a range of fluorescence colours from near yellow to near blue were observed and were interpreted to represent two episodes of hydrocarbon charge based on the fluid inclusion petrography, fluorescence spectroscopy and microthermometry data. Two episodes of oil charge were determined at 24–20 Ma and 4–3 Ma, respectively with the second episode being the predominant period for the oil accumulation in the northern Dongying Depression. The oil charge occurred during or immediately after the modelled intense oil generation and coincided with a regional uplift and a rapid subsidence, suggesting that the hydrocarbon migration from the already overpressured source rocks may have been triggered by the regional uplift and rapid subsidence. The expelled oil was then charged to the already established traps in the northern Dongying Depression. The proximal locations of the reservoirs to the generative kitchens and the short oil migration distance facilitate the intimate relationship between oil generation, migration and accumulation.

Spreading Controversy: The Story of Margarine in Quebec

If spices were pivotal to the earliest centuries of Western civilization, then another food substance has proved to be the focus of culinary (or perhaps, more accurately, chemical) creativity, contrivance, and competition during the past two centuries. Despite a charged history that involves inflated rhetoric reminiscent of liquor prohibition debates, some version of this product is likely to be found in many of our home refrigerators at this very moment, whether those fridges are in Canada, the United States, Europe, or Australia. Margarine, invented in 1869 in response to a challenge issued at the Paris World Exhibition of 1866, addressed the problem of rising costs of animal fats during rapid urbanization. By 1886, however, there were laws prohibiting its production and sale in seven U.S. states, followed soon after by taxation (in Russia and the United States) and various regulations concerning its identification (in Sweden, Holland, England, and Norway), coloration (Russia, Denmark, France, New Zealand, Australia, and South Africa, and 30 U.S. states), and storage (Russia, Denmark, Germany, and Holland). In Canada, restrictions were tougher still. With the exception of a temporary reprieve (1917–1922), margarine was banned entirely between 1886 and 1949. Quebec banned coloured additives through June 2008; and Ontario has allowed coloration only since 1995. In Quebec, debates continue to rage about the future of margarine and its appropriate classification.

Bitumen and heavy oil geochemistry: a tool for distinguishing barriers from baffles in oil sands reservoirs

Abstract To optimize SAGD well-pair placement and improve thermal recovery operations, geochemical bitumen composition logs are used to identify barriers and baffles to fluid flow, which may compartmentalize McMurray Formation reservoirs in the Athabasca Oil Sands. SAGD steam chamber growth and cumulative steam oil ratios are sensitive to both vertical permeability and bitumen viscosity variations, which are commonly encountered in the oil sands reservoirs. In the McMurray Formation, tidally influenced meandering channel deposits are commonly vertically stacked, forming reservoir columns up to 80 m thick. In many instances, inclined heterolithic strata (IHS), consisting of interbedded sand and silt deposited on point bars, comprise barriers to vertical steam chamber growth at multiple horizons of a reservoir. Thus, the identification, characterization, and delineation of IHS intervals is a critical step for evaluating the reservoir development potential, and designing an optimal reservoir development strategy. While siltstone beds are routinely identified in cores and geophysical logs, thin siltstone beds that can act as a barrier to fluid flow are not discernible in seismic reflection data and have proven difficult to correlate between adjacent delineation wells. In this study, geochemical bitumen analysis is used to determine the integrity and continuity of siltstone beds within IHS in order to assess their potential impact on SAGD steam chamber growth. First, high-resolution molecular composition profiles are obtained from gas chromatography–mass spectrometry analyses of bitumen extracted from cores. The continuity of biodegradation-susceptible aromatic hydrocarbon concentrations measured through vertical profiles of a reservoir were used to determine if siltstone-prone intervals observed in log and core data acted as barriers or baffles to fluid flow over geological time. Integration of the bitumen molecular composition data with geological cross-sections fosters predictions of the lateral extent of the identified barriers. Furthermore, inferences about reservoir charging and in-reservoir fluid mixing histories are also made. Geochemical log data indicate that thickness of a heterogeneous low permeability interval is not necessarily the critical attribute of a barrier to fluid flow. Integration of both sedimentological information and bitumen geochemical data is useful for the identification of barriers and baffles to fluid flow in oil sand reservoirs. The method can be applied prior to positioning of SAGD well-pairs and thus could represent an important step for development planning of heterogeneous reservoirs.

Laser ablation GC–MS analysis of oil-bearing fluid inclusions in petroleum reservoir rocks

The hydrocarbon composition of co-occurring blue and yellow fluorescing fluid inclusions (FIs) in Ordovician reservoirs of the Tarim Basin, NW China have been separately analyzed by laser microprobe gas chromatography–mass spectrometry (GC–MS) using a 193 nm excimer laser to drill through the host quartz. A newly designed GC inlet system enabled detection of C 4 C 30 hydrocarbons, extending the molecular weight significantly beyond the C 21 limit of previous online laser-based hydrocarbon analysis of oil inclusions. The blue fluorescing inclusions contain notably higher proportions of aliphatic hydrocarbons (e.g., n-alkanes, cycloalkanes) and gaseous range products, whereas the yellow fluorescing inclusions contain relatively more aromatic hydrocarbons (e.g., alkylnaphthalenes). Hydrocarbon-based parameters also indicate that the blue fluorescing inclusions are of higher thermal maturity than the yellow fluorescing inclusions, consistent with maturity estimates based on fluorescence colors. The compositional differences of the co-occurring inclusions are indicative of different oil types and charge events. This highlights the capacity of the new laser ablation technology to separately analyse specific inclusions amongst a mixture of inclusions of different fluorescing colors. In the future, integration of this new compositional detail with other inclusion and reservoir data will help reconstruct the oil charge history of the Tarim Basin.

Application of Fluid Inclusion Technology to the Study of Hydrocarbon Charge History in Upper Triassic Reservoir of Chuanxi Foreland Basin, China

Comprehensive application of fluid inclusions data from the Upper Triassic reservoir of Chuanxi foreland basin in China, integrated with burial history and thermal evolution, indicates that there are four episodes of hydrocarbon charge during geologic history: early thermo-genetic oil stage, middle thermo-genetic oil stage, late thermo-genetic gas stage, structural adjustment charge stage. In every phrase of charge, four types of fractures origin from inflexible compaction, acid dissolution, breaking by abnormal pressure and tectonic deformation played a essential role in migration and accumulation of hydrocabon in the Upper Triassic reservoir of Chuanxi foreland basin.

HIV Sexual and Drug-Use Risk in Drug-Dependent Pregnant Patients in Comprehensive Drug Treatment

This secondary analysis study investigated HIV sexual and drug-use risk in drug-dependent pregnant patients over the first month postrandomization to reinforcement-based treatment (RBT) (n = 47) or usual care (UC) (n = 42). Analysis of primary outcomes had indicated that RBT participants spent significantly longer time in treatment and recovery housing than UC participants. The present study examined the ability of 9 risk markers—age, race, estimated gestational age at treatment entry, lifetime substance abuse treatment episodes, history of prostitution charges, history of serious depression, current heroin injection status, current housing status, and current partner substance use—to predict changes in HIV risks. Sexual risk declined for participant subgroups with prostitution-charge histories and unstable housing. Drug-use risk declined for heroin injectors and nondepressed participants. A relationship was found between number of lifetime drug treatment episodes and sexual and drug-use risk. The role of risk markers in the response of drug-dependent pregnant women to drug treatment require attention.

Geochemical evidence for coal-derived hydrocarbons and their charge history in the Dabei Gas Field, Kuqa Thrust Belt, Tarim Basin, NW China

Large to middle-scale thrust structures are important reservoir plays for coal-derived hydrocarbons in the foreland basins of NW China, with both gas and some accompanying oil. In the Dabei Gas Field of the Kuqa Thrust, however, the oil and gas pools are vertically distributed in a quite unique way: (1) liquid oil and some dissolved gas are present in the Dawanqi Anticline with the reservoir at 300–700 m depth, forming the only oil field in the Kuqa Thrust; (2) gas and minor accompanying oil are found in the deep reservoir of the Dabei-1 and Dabei-2 thrust traps around 5000–6000 m depth; (3) an extremely dry gas pool is found in the Dabei-3 thrust trap where the depth of the reservoir is over 7000 m. Geochemical data suggest that the hydrocarbons in the Dawanqi Anticline and the Dabei thrust traps originated from a similar source, i.e. the underlying Jurassic coal measures, with some contribution from Jurassic lacustrine shales. The Jurassic source rocks did not start to generate oil until the Miocene (around the Kangcun Stage), and extended into the Pliocene (the Kuche Stage) with the main gas generation period in the Pliocene (the Kuche Stage) and the Quaternary. Because the traps formed relatively early, the Dabei-1 and Dabei-2 thrusts could trap some of the early generated oils, but most of the early charged oil was redistributed to the shallower Dawanqi Anticline during the Kuche Stage. The Dabei-3 thrust trap formed concurrently with major gas generation and thus could not trap liquid hydrocarbons. The difference in the vertical distribution of the hydrocarbon accumulations in the Dabei Gas Field resulted from a complex interplay of source variability, structural evolution of the basin and thermal maturation.

Hydrocarbon charge history of the Silurian bituminous sandstone reservoirs in the Tazhong uplift, Tarim Basin, China

The Tarim Basin is the largest inland basin in China. The hydrocarbon charge history of the Silurian bituminous sandstone reservoirs in the Tazhong uplift was investigated using an integrated approach, combining detailed petrographic analysis (thin section, scanning electron microscopy, and transmission electron microscopy), clay mineral x-ray diffraction characterization, and modeling of authigenic clay minerals and subsequent potassium-argon (K-Ar) dating of authigenic illite. The timing of the hydrocarbon charges of the reservoirs in the Tazhong uplift area is compared with that of the Kongquehe area within the basin. The authigenic illite ages in the Tazhong uplift area and the Kongquehe area range from 383 Ma to 204 Ma, indicating a unique age distribution pattern in the basin. The Silurian oil accumulations were primarily formed in the late Caledonian through the late Hercynian. The reservoirs within wells Qiao-1, Kongque-1, Longkou-1, and Yingnan-2, located in the western area and the eastern area of the basin, were charged around 383 to 271 Ma in the late Caledonian to the early Hercynian. The reservoirs in wells Tazhong-37, Tazhong-67, Tazhong-12, and Tazhong-32, located in the center of the basin, were charged at around 235 to 204 Ma in the late Hercynian. A correlation between the authigenic illite ages and the thickness of the Silurian bituminous sandstones suggests that the paleostructural framework is a key controlling factor. The paleo-oil pool located in and around the sedimentary centers, such as wells Qiao-1 and Kongque-1, was formed relatively early (383 Ma). The K-Ar dating results were consistent with the results of conventional hydrocarbon accumulation history analysis and highlight the differences in the accumulation timing between various oil pools in different parts of the basin.

Understanding the plumbing of the Gippsland Basin: new results on fluid migration and reservoir quality

Understanding the CO2 storage potential and petroleum prospectivity of the Gippsland Basin are critical to managing the resources of this region. Key controls on determining the prospectivity for CO2 storage and petroleum include understanding the fluid migration history and reservoir characteristics in the basin. Gippsland Basin hydrology, reservoir characteristics and petroleum systems are being studied to better understand how CO2 can be safely stored in the subsurface. Hydrocarbon migration pathways have been delineated using petroleum systems modelling. The latest hydrocarbon charge history data has been acquired to test the containment potential of individual structures along these migration pathways. The charge history results indicate the Golden Beach gas field has had a complex hydrocarbon fill history, and that early charge has migrated through the regional seal. The results also indicate that early oil charge was very common in the basin, including large structures that are now filled with gas (e.g. Barracouta). The results allow the regions with good CO2 containment potential to be delineated for further storage investigations. A new evaluation of the reservoir characteristics of the Latrobe Group—through porosity/permeability analysis and automated mineral analysis (AMA)—has provided insights into CO2 injectivity and capacity. The AMA results constrain the mineralogy and diagenetic history of the reservoirs and seals. In addition, the data highlights the presence of carbonates, glauconite and K-feldspar that are potentially reactive with injected CO2.

Different Hydrocarbon Accumulation Histories in the Kelasu‐Yiqikelike Structural Belt of the Kuqa Foreland Basin

Abstract:The Kuqa foreland basin is an important petroliferous basin where gas predominates. The Kela‐2 large natural gas reservoir and the Yinan‐2, Dabei‐1, Tuzi and Dina‐11 gas reservoirs have been discovered in the basin up to the present. Natural gases in the Kelasu district and the Yinan district are generated from different source rocks indicated by methane and ethane carbon isotopes. The former is derived from both Jurassic and Triassic source rocks, while the latter is mainly from the Jurassic. Based on its multistage evolution and superposition and the intense tectonic transformation in the basin, the hydrocarbon charging history can be divided into the early and middle Himalayan hydrocarbon accumulation and the late Himalayan redistribution and re‐enrichment. The heavier carbon isotope composition and the high natural gas ratio of C1/C1–4 indicate that the accumulated natural gas in the early Himalayan stage is destroyed and the present trapped natural gas was charged mainly in the middle and late Himalayan stages. Comparison and contrast of the oils produced in the Kelasu and Yinan regions indicate the hydrocarbon charging histories in the above two regions are complex and should be characterized by multistage hydrocarbon migration and accumulation.

Staying in the here‐and‐now: A pilot study on the use of dialectical behaviour therapy group skills training for forensic clients with intellectual disability

Dialectic behaviour therapy (DBT) has been widely used with individuals diagnosed with borderline personality disorder who exhibit severe emotional and behavioural dysregulation. There is a paucity of research in assessing the effectiveness of DBT with forensic clients with intellectual disability (ID). This pilot study aims to evaluate the effectiveness of the DBT group skills training programme adapted particularly for offenders with ID. Six participants completed the 13-week adapted DBT group skills training programme. All participants exhibited challenging behaviours and have a history of prior charges or convictions for violent crimes. The study conducted pre- and post-tests using instruments that measured dynamic risks, relative strengths, coping skills and global functioning. The study result showed improvement across all measures. A decrease in the level of risks, increase in relative strengths and general improvement in overall functioning were found significant. The results were promising particularly as a stand-alone adapted DBT group skills training programme for this client group.

Potential of palaeofluid analysis for understanding oil charge history

Geofluids (2010) 10, 73–82AbstractFluid inclusion data, particularly the distribution of hydrocarbon fluid inclusions and their chemistry, can provide insights into oil charge in a petroleum‐prospective region. Examples from the UK Atlantic margin show how we can understand thermal regime, timing and chemistry of oil charge. Data from the UK Atlantic margin based on fluid inclusion temperature profiles shows anomalously high temperatures which are highest at the top of the Triassic–Eocene sequence. This is interpreted as a product of hot fluid flow, probably reflecting hydrothermal activity related to intrusion of sills at depth. The preservation of high temperatures also implies rapid migration from depth through fracture systems. Ar–Ar analysis of oil‐bearing K‐feldspar cements, and petrographic studies of oil inclusion distribution help delimit timing and migration pathways for the hot fluid charge and later fluid migration events. Coupled with compositional data for oils measured destructively (organic geochemistry) or non‐destructively (fluorescence), these approaches allow the development of oil charge histories based on real data rather than theoretical modelling.

Effects of Charge Density and Thermal History on the Morphologies of Spontaneously Formed Unilamellar Vesicles

A phospholipid mixture consisting of dimyristoyl phosphatidylcholine (DMPC), dihexanoyl phosphatidylcholine (DHPC), and the negatively charged dimyristoyl phosphatidylglycerol (DMPG) lipid is found to spontaneously form uniform-size unilamellar vesicles (ULVs). Small angle neutron scattering (SANS) is used to examine ULV size as a function of net charge, dilution, and thermal history. It shows that ULVs only exist within a narrow window of charge densities, where larger size ULVs can be obtained at a lower charge density through slow temperature annealing. There is also a 6-fold change in the size of low polydispersity ULVs, confirming a previously proposed model for spontaneously forming ULVs [Nieh, M.-P. et al. Langmuir 2005, 21, 6656]. Finally, the stability of these ULVs was confirmed through a series of high temperature dilution experiments, further making the case that these nanoparticles can be used as carriers for drugs and contrast imaging agents.