A Comparative Evaluation of Thermodynamic Models for Prediction of Wax Deposition

Wax deposition on inner surfaces of pipelines is a costly problem for the petroleum industry. This flow assurance problem is of particular interest during the production and transportation of waxy oils in cold environments. An understanding of known mechanisms and available thermodynamic models will be useful for the management and planning of mitigation strategies for wax deposition. This paper presents a critical review of wax prediction models used for estimation of wax deposition based on chemical hydrocarbon compositions and thermobaric condition. The comparative analysis is applied to highlight the effective mechanisms guiding the wax deposition, and how this knowledge can be used to model and provide solutions to reducing wax deposition issues. One group of thermodynamic models assume that the precipitated wax is a solid solution. These models are divided into two categories: ideal (Erickson and Pedersen models) and non-ideal solutions (Won and Coutinho models). In the other group of models, the wax phase consists of many solid phases (Lira-Galeana model). The authors summarized the limitations of the models, evaluated, and identified ways to represent the overview of existing thermodynamical models for predicting wax precipitation. Within the strong demand from industry, the results of this manuscript can aid to aspire engineers and researcher.

Reducing THI Injection and Gas Hydrate Agglomeration by Under-Inhibition of Crude Oil Systems

Gas hydrates constitute a serious flow assurance problem. Over the last decades, industry has faced this problem by using avoidance methods (e.g. injection of thermodynamic hydrate inhibitors) and management strategies (e.g. addition of hydrate anti-agglomerants). In the former, hydrates are completely avoided by shifting the hydrate boundary towards higher pressure and lower temperatures; in the latter, hydrates are allowed to form but their tendency to agglomerate is reduced. It should be noted that some crude oils are naturally able to avoid hydrate agglomeration, this non-plugging tendency may originate from the surfactant-like behavior of fractions like asphaltenes and acids. Recent works have shown that the natural non-plugging potential of certain oils can be affected by the addition of polar molecules like alcohols. There is another strategy for managing hydrate that consist of the addition of THIs at a concentration lower that the one required to full hydrate inhibition. In this case, hydrates are under-inhibited. Studies carried out on hydrate agglomerating systems have shown that under-inhibition might prevent hydrate agglomeration only in a specific range of THI concentrations and sub-cooling; however, work on non-plugging oils is scarce. In this paper, the hydrate agglomeration of two crude oils under-inhibited with methanol and MEG was evaluated through a visual rocking cell apparatus and a high-pressure rheometer. Results showed that THIs and the crude oil's natural surfactants were capable of acting synergistically in reducing hydrate agglomeration and improving the system flowability.

The inhibition of crystal growth of gypsum and barite scales in industrial water systems using green antiscalant

Mineral scale is a major flow assurance problem in industrial water systems. The antiscale properties of sunflower (Helianthus annuus) seed extract for CaSO4 and BaSO4 scales were investigated using NACE and conductivity tests, respectively. Comparative studies between the extract and 1-hydroxyethane-1,1-diphosphonic acid (HEDP), as commercial antiscalants, were done. The results revealed that the inhibition of CaSO4 scales using sunflower seed extract reached 100%, while HEDP achieved a maximum inhibition of 88%. Moreover, the maximum inhibition of BaSO4 scale in the presence of the extract was 84% compared with 86% in the presence of HEDP. Also microscopic examination showed that both inhibitors modified CaSO4 and BaSO4 crystals.

FLOW ASSURANCE IN KUMUJE WET-GAS PIPELINE: ANALYSIS OF PIGGING SOLUTION TO LIQUID ACCUMULATION

Liquid condensation in gas-condensate pipelines in a pronounced phenomenon in long transporting lines because of the composition of the gas which is highly sensitive to variations in temperature and pressure along the length of the pipeline. Hence, there is a resultant liquid accumulation in onshore wet-gas pipelines because of the pipeline profile. This accumulation which is a flow assurance problem can result to pressure loss, slugging and accelerated pipeline corrosion if not properly handled.

PUBLIC REASON'S CHAOS THEOREM

ABSTRACTCitizens in John Rawls's well-ordered society face an assurance dilemma. They wish to act justly only if they are reasonably sure their fellow citizens will also act justly. According to Rawls, this assurance problem is solved through public reasoning. This paper argues that public reason cannot serve this function. It begins by arguing that one kind of incompleteness public reason faces that most Rawlsians grant is ubiquitous but unproblematic from a normative standpoint is problematic from an assurance perspective: it makes it possible for citizens to argue for policy conclusions that are favored by their private interests, rather than justice. In response, perhaps the thing to do is structure deliberative democratic institutions such that citizens will always be incentivized to use public reasons to only argue for conclusions they believe are favored by justice. The paper proves that this is impossible by extending the Gibbard–Satterthwaite theorem.

Flow of Water-Oil Emulsion through an Orifice

The oil-in-water (O/W) and water-in-oil (W/O) emulsions are two common types of emulsions found in oil production industry. While stable O/W may be beneficial in transporting crude oil, stable W/O poses a flow assurance problem that leads to disruptions and losses in oil production line. This study examines the behaviour of both types of emulsion (40:60, 50:50 and 60:40 water-oil emulsion, vol. basis) subjected to 3/4D, 1/2D and 1/4D orifices within a pipeline. The study confirms that oil and water may form emulsion with only mechanical agitation and dynamic flow in the pipeline and without the presence of any emulsifying agent. The flow rate and the velocity of all emulsions were found to drop with the reduction of orifice diameter.

The Social Enterprise Trust Deficit

This chapter explains why social enterprises have more difficulty gaining access to capital than conventional businesses do. It begins with the insight that law lends both for-profits and nonprofits the stability they need to raise capital; legal doctrine and enforcement mechanisms combine to reassure donors and investors that their contributions to standard businesses and charities will be well spent. Using the tools of game theory, the chapter then describes the more challenging assurance problem faced by social enterprise founders and investors. For either an entrepreneur or investor to commit capital to the venture, each must trust the other to remain faithful to both of its dual missions—and particularly to be willing to trade more social good for lower financial returns. The chapter concludes by describing why neither traditional for-profit and nonprofit law nor the first-generation of social enterprise law satisfactorily bridge this trust deficit.

Private provision of public goods via crowdfunding

For various reasons, governments sometimes fail to provide public goods. Private provision of such goods might then be used if it succeeds in overcoming three main problems: high organization costs, the assurance problem, and the free-rider problem. We argue that technologies that enable crowdfunding – the method of funding projects by raising small amounts of money from a large number of people via the internet – have enabled these problems to be overcome more readily. Such technology has lowered organization costs and enabled the employment of more efficient mechanisms to reduce the assurance and free-rider problems. To illustrate these effects, we present two case studies of private provision of public goods via crowdfunding: police services in Rockridge in Oakland, California, and the Ukraine Army.

When Public Reason Fails Us: Convergence Discourse as Blood Oath

Public officials in John Rawls's well-ordered society face an assurance problem. They prefer to act in accordance with the political conception of justice, but only if they are assured that others will. On Paul Weithman's influential interpretation, Rawls attempts to solve this problem by claiming that public reason is an assurance mechanism. There are several problems with Rawls's solution: Public reason talk is too cheap to facilitate assurance, it is difficult to know when particular utterances express public reasons, and the requirements of public reason conflict with the fact of reasonable pluralism. We argue that convergence discourse—not public reason—solves the assurance problem by being a costly signal that indicates commitment to the political conception. This solution has none of Rawls's problems and has an interesting corollary: As diversity increases in society, so too does society's ability to solve the assurance problem. In short, the more diversity the better.