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

100%

Zhenrong Z. , Jing Z. , Peifu G.

tom Vol. 40, nr 4

811--818

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.

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

88%

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

tom Vol. 96, nr 4

261--268

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.