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Experimental study on the discharging characteristics of pulsed high-voltage discharge technology in oil plug removal

Bingnan Y., Jing Z., Liang Z., Chongxin L., Meng F.

Journal of Power Technologies

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2016

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Vol. 96, nr 4

261--268

EN

Oil plugging of the downhole during oilfield development leads to a decline in well yield. A new plug removal method based on pulsed high-voltage discharge technology was proposed in this paper to solve this plugging problem. A low-carbon steel high-pressure sealed drum was developed to simulate a downhole operating environment with high static pressure. Four sealed contact pins were designed on the drum cover. These pins were used to insert the high-voltage cable into the drum body while ensuring the drum is leakproof. The maximum static pressure borne by the drum was 40 MPa. An experimental system of pulsed high-voltage discharge was designed based on the drum. A platform for the discharging experiment was established according to the system principle diagram. The effects of variation in static pressure on discharging voltage, discharging current, critical breakdown field strength, discharging time and its data discretization, and other parameters were determined with water and crude oil as the discharging media. Experimental results indicate that increasing static pressure increases discharging time, enhances pulsed discharging randomness, reduces the strength of impact waves generated in the discharging media, and weakens the fracture-generating effect on the cement tube. Increasing the working voltage achieves better plug removal. However, the requirements for size, texture, and insulativity of plug removal equipment are elevated accordingly. This study provides a basis for the application of pulsed high-voltage discharge technology in oil reservoir plug removal.

2

Roughness characterization of well-polished surfaces by measurements of light scattering distribution

Zhenrong Z., Jing Z., Peifu G.

Optica Applicata

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2010

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Vol. 40, nr 4

811--818

EN

According to vector scattering and scalar scattering theory, the relationship of BRDF (bidirectional reflectance distribution function) of light scattering from micro-rough surface with TIS (total integrated scattering) is analyzed. Roughness statistical characterization such as RMS (root mean square), PSD (power spectral density) function are deduced by TIS of polished surface. Based on the light scattering measurement theory, an automatic measure system of light scattering with one dimensional scanning method is built, BRDF of two kinds of polished surfaces (silica surface and Ag reflector) have been measured. PSD of two surfaces has been given by light scattering measurements, roughness characterization of two surfaces has been compared with the data tested by profile meter. The results show that the light scattering measurement method has great application prospects as regards nondestructive measurement for polishing surfaces.

3

The effects of protective enclosure on vegetation diversity, and productivity of degraded alpine Kobresia meadow (Qinghai-Tibetan Plateau)

Li S., Wang Q., Jing Z., Wang W.

Polish Journal of Ecology

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2009

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Vol. 57, nr 3

495-502

EN

Grassland degradation due to anthropogenic and natural factors and their interactions is one of the worldwide ecological and economic problems because it reduces grassland productivity and diversity and leads to desertification. The objective of this study was to assess the influence of protective enclosure on vegetation composition and diversity and plant biomass of an alpine degraded meadow. The experiment was conducted at center of Qinghai-Tibetan Plateau with two degraded (caused by overgrazing) alpine meadows: the lightly and severely degraded ones (LD and SD) and their enclosed areas with iron net (LDE and SDE, respectively). The areas 200 m x 150 m for each of four degraded alpine meadow treatments at average altitude 3,960 m a.s.l. were set for research. The lightly degraded plots were dominated by Scirpus distigmaticus (Kukenth.) Tang et Wang, Elymus nutans Griseb. and Oxytropis ochrocephala Bunge. The dominating plants in severely degraded plots were: Artemisia sieversiana Ehrhart ex Willd, Ajania tenuifolia (Jacq.) Tzvel, Lonicera minuta Batal. The results showed: (1) the vegetation cover of two degraded plots (LD and SD) has increased after taking the enclosure measures and the forbs dominated both plots. (2) Species richness has also increased in two enclosed degraded plots, respectively. There no significant differences in evenness and diversity between LD and LDE, and SD and SDE, respectively. (3) Enclosure may promote aboveground biomass, particularly grass and forb biomass in LD, and forb biomass in SD plots.