Mechanisms and consequences of wettability alteration by crude oils

Reservoir wettability is controlled by crude oil/brine/rock interactions that have not been well understood. Studies using either model compounds or crude oil fractions have had only limited success in reproducing the wetting alteration that can occur in nature. In this study, the approach is first to identify the key features of interfacial activity unique to crude oils, then to design and conduct wetting alteration experiments—using both flat solids and porous media—that demonstrate the mechanisms by which alteration can occur. Components of crude oils that are interfacially active are found in the highest molecular weight, most polar fractions of the oil, the resins and asphaltenes. How these components affect wetting depends on the compositions of not only the oil, but also the mineral surfaces and the aqueous phase that is always present in oil reservoirs. Wettability altering interactions can occur by several mechanisms. In the absence of water, adsorption of polar species can create intermediately-wet surfaces. If the oil is a poor solvent for its asphaltene fraction, adsorption of large asphaltene aggregates can make surfaces fairly oil-wet. Adsorption can also occur because of ionic interactions between oppositely charged acidic and basic sites at the oil/water and solid/water interfaces. There may also be interactions between similarly charged sites, if ion binding can occur. All of these mechanisms have been documented for a range of crude oils with varying asphaltene fraction, solvency, acid number, and base number

Evaluation of Reservoir Wettability and Its Effect on Oil Recovery. Annual Report, February 1, 1996 to January 31, 1997

We report on the first year of the project, {open_quotes}Evaluation of Reservoir Wettability and its Effect on Oil Recovery.{close_quotes} The objectives of this five-year project are: (1) to achieve improved understanding of the surface and interfacial properties of crude oils and their interactions with mineral surfaces, (2) to apply the results of surface studies to improve predictions of oil production from laboratory measurements, and (3) to use the results of this research to recommend ways to improve oil recovery by waterflooding. During the first year of this project we have focused on understanding the interactions between crude oils and mineral surfaces that establish wetting in porous media. Mixed-wetting can occur in oil reservoirs as a consequence of the initial fluid distribution. Water existing as thick films on flat surfaces and as wedges in comers can prevent contact of oil and mineral. Water-wet pathways are thus preserved. Depending on the balance of surface forces-which depend on oil, solid, and brine compositions-thick water films can be either stable or unstable. Water film stability has important implications for subsequent alteration of wetting in a reservoir. On surfaces exposed to oil, the components that are likely to adsorb and alter wetting can divided into two main groups: those containing polar heteroatoms, especially organic acids and bases; and the asphaltenes, large molecules that aggregate in solution and precipitate upon addition of n-pentane and similar agents. In order to understand how crude oils interact with mineral surfaces, we must first gather information about both these classes of compounds in a crude oil. Test procedures used to assess the extent of wetting alteration include adhesion and adsorption on smooth surfaces and spontaneous imbibition into porous media. Part 1 of this project is devoted to determining the mechanisms by which crude oils alter wetting

Wettability and Prediction of Oil Recovery From Reservoirs Developed With Modern Drilling and Completion Fluids

Exposure to crude oil in the presence of an initial brine saturation can render rocks mixed-wet. Subsequent exposure to components of synthetic oil-based drilling fluids can alter the wetting toward less water-wet or more oil-wet conditions. Mixing of the non-aromatic base oils used in synthetic oil-based muds (SBM) with an asphaltic crude oil can destabilize asphaltenes and make cores less water-wet. Wetting changes can also occur due to contact with the surfactants used in SBM formulations to emulsify water and make the rock cuttings oil-wet. Reservoir cores drilled with SBMs, therefore, show wetting properties much different from the reservoir wetting conditions, invalidating laboratory core analysis using SBM contaminated cores. Core cleaning is required in order to remove all the drilling mud contaminants. In theory, core wettability can then be restored to reservoir wetting conditions by exposure to brine and crude oil. The efficiency of core cleaning of SBM contaminated cores has been explored in this study. A new core cleaning procedure was developed aimed to remove the adsorbed asphaltenes and emulsifiers from the contaminated Berea sandstone cores. Sodium hydroxide was introduced into the cleaning process in order to create a strongly alkaline condition. The high pH environment in the pore spaces changed the electrical charges of both basic and acidic functional groups, reducing the attractive interactions between adsorbing materials and the rock surface. In cores, flow-through and extraction methods were investigated. The effectiveness of the cleaning procedure was assessed by spontaneous imbibition tests and Amott wettability measurements. Test results indicating that introduction of sodium hydroxide played a key role in removing adsorbed materials were confirmed by contact angle measurements on similarly treated mica surfaces. Cleaning of the contaminated cores reversed their wettability from oil-wet to strongly water-wet as demonstrated by spontaneous imbibition rates and Amott wettability indices

What do they know? Mapping the knowledge, attitudes, and practices of dog owners in the United States regarding dog training.

It has been suggested that dog training that utilizes a reward-based approach can promote a healthy relationship between dogs and their owners, but that aversive-based dog training methods may harm dog welfare and the human-animal bond. This study aimed to explore the factors influencing dog owners' decisions regarding dog training methods in the United States. A questionnaire was designed and implemented to assess dog owners’ training knowledge, perceptions, and practices. A convenience sample of 385 dog owners residing in the United States completed a survey promoted on social media. Descriptive analysis was performed for all data. Most respondents planned to or had already participated in training classes with their dogs. Most participants reported knowing enough to educate their dogs but would reach out for help with behavioral problems, advanced training, and puppy classes. The owners considered the stressfulness and reliability of training methods to be more important than how quickly the results were achieved. Participants preferred less stressful training methods, and the specific method used was most important when choosing a dog trainer or school. Dog owners indicated that the most important behaviors for their dogs to learn were recall, being calm at home alone, and good manners around people and other dogs. This study is the first assessment of dog owners in the United States and their knowledge, perceptions, and practices regarding dog training

SCA2003-01: EFFECT OF CRUDE OIL COMPOSITION ON WETTABILITY OF MICA

ABSTRACT While many factors are recognized as influencing reservoir wetting, they do so primarily by controlling the fate of components of the crude oil. Surface mineralogy, brine composition, temperature, pressure, and history of fluid occupation all are important variables, but if the oil does not contain species capable of adsorbing or depositing, reservoir rocks, the majority of which are initially water-wet, would remain in their original water-wet condition, while minerals that are naturally oil-wet would also be unchanged. In this study we focus on specific features of the composition of produced oil samples and relate them to the extent to which these oils alter the wetting of mica surfaces under controlled conditions. Wetting alteration tests were designed to control water film stability. The extent of wetting alteration was quantified by measurements of probe fluid contact angles. Oil properties were selected on the basis of previous studies that indicated the importance of ionizable species and asphaltene stability in the produced oil samples. Statistical tests between single variables and contact angles show little evidence of correlation, but more significant relationships were found using linear multivariate analyses and non-linear artificial neural networks

Using codispersion analysis to quantify and understand spatial patterns in species-environment relationships

• The analysis of spatial patterns in species–environment relationships can provide new insights into the niche requirements and potential co-occurrence of species, but species abundance and environmental data are routinely collected at different spatial scales. Here, we investigate the use of codispersion analysis to measure and assess the scale, directionality and significance of complex relationships between plants and their environment in large forest plots. • We applied codispersion analysis to both simulated and field data on spatially located tree species basal area and environmental variables. The significance of the observed bivariate spatial associations between the basal area of key species and underlying environmental variables was tested using three null models. • Codispersion analysis reliably detected directionality (anisotropy) in bivariate species–environment relationships and identified relevant scales of effects. Null model-based significance tests applied to codispersion analyses of forest plot data enabled us to infer the extent to which environmental conditions, tree sizes and/or tree spatial positions underpinned the observed basal area–environment relationships, or whether relationships were a result of other unmeasured factors. • Codispersion analysis, combined with appropriate null models, can be used to infer hypothesized ecological processes from spatial patterns, allowing us to start disentangling the possible drivers of plant species–environment relationships

Embryonic exposure to the fungicide vinclozolin causes virilization of females and alteration of progesterone receptor expression in vivo: an experimental study in mice

BACKGROUND: Vinclozolin is a fungicide that has been reported to have anti-androgenic effects in rats. We have found that in utero exposure to natural or synthetic progesterones can induce hypospadias in mice, and that the synthetic progesterone medroxyprogesterone acetate (MPA) feminizes male and virilizes female genital tubercles. In the current work, we selected a relatively low dose of vinclozolin to examine its in utero effects on the development of the genital tubercle, both at the morphological and molecular levels. METHODS: We gave pregnant dams vinclozolin by oral gavage from gestational days 13 through 17. We assessed the fetal genital tubercles from exposed fetuses at E19 to determine location of the urethral opening. After determination of gonadal sex, either genital tubercles were harvested for mRNA quantitation, or urethras were injected with a plastic resin for casting. We analyzed quantified mRNA levels between treated and untreated animals for mRNA levels of estrogen receptors α and β, progesterone receptor, and androgen receptor using nonparametric tests or ANOVA. To determine effects on urethral length (males have long urethras compared to females), we measured the lengths of the casts and performed ANOVA analysis on these data. RESULTS: Our morphological results indicated that vinclozolin has morphological effects similar to those of MPA, feminizing males (hypospadias) and masculinizing females (longer urethras). Because these results reflected our MPA results, we investigated the effects of in utero vinclozolin exposure on the mRNA expression levels of androgen, estrogen α and β, and progesterone receptors. At the molecular level, vinclozolin down-regulated estrogen receptor α mRNA in females and up-regulated progesterone receptor mRNA. Vinclozolin-exposed males exhibited up-regulated estrogen receptor α and progesterone receptor mRNA, effects we have also seen with exposure to the synthetic estrogen, ethinyl estradiol. CONCLUSION: The results suggest that vinclozolin virilizes females and directly or indirectly affects progesterone receptor expression. It also affects estrogen receptor expression in a sex-based manner. We found no in vivo effect of vinclozolin on androgen receptor expression. We propose that vinclozolin, which has been designated an anti-androgen, may also exert its effects by involving additional steroid-signaling pathways

Ten years of major equestrian injury: are we addressing functional outcomes?

YesFunding provided by the Open Access Authors Fund

Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial

Background Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy