Liquid loading presents a formidable challenge for mature gas wells, often resulting in substantial economic losses. Traditional research has predominantly centered on the analysis of gas-liquid two-phase flow within the wellbore to predict critical gas velocity or rate, aiding in identifying the onset of liquid loading. This study introduces a fully coupled compositional wellbore-reservoir simulator designed to detect liquid loading in both vertical and inclined gas wells. Leveraging the drift-flux model to evaluate flow pattern transitions, this simulator employs pressure or rate constraints at the wellhead as boundary conditions. It comprehensively captures the flow dynamics in both the wellbore and reservoir, unveiling significant changes in gas production rate, water production rate, gas velocity, flow regime, and the reserved position of the liquid film under liquid-loaded conditions. Moreover, the accumulation of liquid at the bottom hole leads to increased reservoir pressure and gas saturation near the wellbore. The simulator predicts a typical unstable production period, emphasizing its crucial role in implementing effective strategies to mitigate liquid loading. This paper investigates the capability of the coupled wellbore-reservoir model to characterize transient liquid loading phenomena from a systematic perspective. The proposed model can function as a real-time tool for predicting the status of liquid loading in gas wells.
Kernel smoothing is a widely used nonparametric method in modern statistical analysis. The problem of efficiently conducting kernel smoothing for a massive dataset on a distributed system is a problem of great importance. In this work, we find that the popularly used one-shot type estimator is highly inefficient for prediction purposes. To this end, we propose a novel grid point approximation (GPA) method, which has the following advantages. First, the resulting GPA estimator is as statistically efficient as the global estimator under mild conditions. Second, it requires no communication and is extremely efficient in terms of computation for prediction. Third, it is applicable to the case where the data are not randomly distributed across different machines. To select a suitable bandwidth, two novel bandwidth selectors are further developed and theoretically supported. Extensive numerical studies are conducted to corroborate our theoretical findings. Two real data examples are also provided to demonstrate the usefulness of our GPA method.
This study assesses the health benefits of better air quality by examining the causal impact of China’s stringent “2+26” regional air pollution control policy on local air quality and population health. Employing a spatial regression discontinuity design that capitalizes on the policy’s location-specific features, we present compelling evidence that the 2+26 policy results in an average reduction of 12.2 units in the local Air Quality Index (AQI) and a 47.0% decrease in per capita medical expenditure from 2014 to 2018. A one-unit reduction in AQI corresponds to a 0.88% reduction in per capita annual medical spending, equivalent to RMB 30.2 (US$4.6). These health gains stem from reduced chronic disease prevalence and improved subjective well-being. Nationally, air quality improvement during 2014–2018 could save RMB 674billion (US$104billion) annually in national direct medical costs, constituting 11.6% of national medical expenditure in 2018. Our findings underscore the substantial health and welfare gains achievable through pollution controls in developing countries.
This paper considers the connectedness of the two ports-of-call of Amastris and Heraclea Pontica in the eparcheia of Pontus during the Roman principate. Stanford's ORBIS platform offers a heuristic model of connectedness. We find the two ports-of-call the most popular segments along the south for maritime traffic coming from eastern Pontus and the Bosporus.Where the two is most different concerns their connections with the interior. Heraclea Pontica connected Ancyra to the Pontic coast, while Amastris had none. ORBIS is understandably non- granular in the sense that it "restrict[s] coverage to the more important elements of the Roman communication system," but if this is the case, it means that Heraclea Pontica and Amastris were connected in other ways as well, and the Amastrian mountainous interior, which couldbe described as the "previously unconjoined, or at least the previously less well-connected" segment of Anatolia (Horden 2020: 204), could have also been connected with the wider ancient Mediterranean world. Low visibility of settlements beyond known the one known urbanized area in modern Amasra makes discussions of broader connectedness difficult, but at least from recent field survey results suggest that the number and vibrancy of settlements likely increased in the Roman period (Bes 2015: 288-289; Çam et al. 2019; Çam 2021). The question then is whether recent studies contribute to a new assessment of Amastrian connectedness, and how it compares with existing impressions of both Amastris and its peer poleis, with Heraclea Pontica serving as the primary example.Building upon Alexandru Avram's assumption that the aggregate of attestations of persons who have spent time in a city other than their homeland can serve as proxy for gauging their mobility (Avram 2013: 7-8), this paper uses the Prosopographia Ponti Euxini externa to test whether Amastrian connectedness reached currently unknown areas, particularly theinterior. Comparison between Amastrian data (n=136) and Heracleote specimens (n=1101)
may seem disproportionate, but this paper focuses on persons from the first to the third centuries CE and privileges locations instead of volumes so to visualize connectedness in the Roman world. The same concept is applied to persons of locales beyond the two subjects in question – foreigners who left records in Heracleote (n=5) and Amastrian territory (n=11) – and visualized together. In addition, though coins are a poor proxy as they may be transmitted in a variety of ways that do not reflect direct connections between Amastris and the cities that issued them, this paper considers coins from the Amasra Museum as published by Stanley Ireland and Soner Atesogullari (1996) to complement Amastris relatively poor prosopographical record and increase the potential to capture connections. The overall impression gleaned from this exercise is that Amastris could have played a comparable (though potentially less pronounced) role as that of Heraclea Pontica in terms of a hub-like node that connected interior land routes with maritime traffic, particularly for Hadrianopolis and Pompeiopolis (Corsten 2007; Ruscu 2017), but also potentially for centers such as Caesarea in Cappadocia.Bibliography:Avram, A. 2013. Prosopographia Ponti Euxini externa. Leuven.Bes, P. 2015. "The Cide-Şenpazar Region in the Roman Period," in Kinetic Landscapes. The Cide Archaeological Project: Surveying the Turkish Western Black Sea Region, Bleda Düring and Claudia Glatz, eds., Warsaw/Berlin, pp. 260-293.Çam, F. et al. 2019. "New Archaeological Expeditions in the Ancient City of Amastris,"Settlements and Necropoleis of the Black Sea and its Hinterland in Antiquity, Select Papers from the Third International Conference 'The Black Sea in Antiquity and Tekkeköy: An Ancient Settlement on the Southern Black Sea Coast', 27-29 October 2017, Tekkeköy, Samsun, Gocha Tsetskhladze and Sümer Atasoy, eds., Oxford, pp. 190-207.Çam, F. 2022. "Ancient Settlements in Bartin Province: 2017-2019 Research Results," in Bartın İli ve İlçeleri Yüzey Araştırması (Biya) İlk Tespitler ve Belgeler - Paphlagonia'dan Parthenios'a - I, Fatima Çam, ed., Istanbul, pp. 13-112.Corsten, T. 2007. "Prosoporaphische und Onomastische Notizen III," Gephyra 4, pp. 133-144. Horden, P. 2020. "Knitting Together the Unconjoined," Zeitschrift für Ethnologie 145.2 (2020)197-218.Irland, S. and Soner Atesogul. 1996. "The Ancient Coins in the Amasra Museum," in Studies in Ancient Coinage from Turkey, Richard Ashton, ed., London, pp. 115-137.Ruscu, L. 2017. "Über Sex. Vibius Gallus aus Amastris," Journal of Historical Researches 28, pp. 52-68.