Water content in crude oil is very important in an oilfield production logging system. A non-contact optical method, called all-optical detection, was proposed for measuring the water content in the full range of 0−100% in crude oil by a non-contact laser source and receiver (adaptive laser interferometer). The laser-induced ultrasonic P-wave velocities of three series of an oil−water mixture accelerated significantly from 1289, 1342, and 1343 m/s, respectively, to 1458 m/s with the increase of the water content from 0 to 100%. The theoretical values of the effective medium model were agreement with the experimental results of three series of an oil−water mixture.

High-water-cut crude oil is currently the main form of underground oil in China. The high water content and the distribution of oil and water have an important impact on the rheological property and exploration efficiency. Terahertz (THz) waves are extremely sensitive to hydrogen bonds and intermolecular forces, and consequently, the responses of oil, water and air exhibit obvious differences. In this work, a series of crude oils with high water content were investigated by using THz timedomain spectroscopy (THz-TDS). Linear models were built between amplitudes of THz-TDS and the absorbance and water content from 50.05% to 100.00% with correlation coefficients (R) of 0.99 and >0.93, respectively. In addition, oil and water were determined to be distributed at different positions, based on THz signals in a series of oriented scans. Moreover, the transparent parts for visible light are identified by scanning the local points. The positions with low and high THz intensities refer to water and air regions, respectively. Therefore, THz technology is expected to act as a supplementary method to characterize highwater-cut crude oil, which will promote the efficiency and safe operation of pumping units and oil pipelines.

The photovoltaic effects of Nb-doped SrTiO 3 single crystals with different thicknesses were investigated under the illumination of ultraviolet pulsed lasers. The peak photovoltage increased and then decreased quickly with the decrease in crystal thickness, and a maximum photovoltage occurred for the 180 µm-thick crystal. The photovoltaic response time decreased monotonically with decreasing crystal thickness. The present results suggested the promising potential of reducing crystal thickness in high sensitivity detectors with fast response.

The oil yields of oil shales from the Longkou, Yaojie, and Barkol districts in China were characterized with laserinduced voltage, which was monitored by a voltage tester or a digital oscilloscope when oil shale was irradiated directly by a continuum solid-state laser with a wavelength of 532 nm without an applied bias or at a bias of 9 V. The laser-induced voltage strongly depends upon the properties of the oil shales and exhibits an increasing trend as the oil yield increases from ∼5.66, 9.05, to 14.16% for Barkol, Yaojie, and Longkou, respectively. In addition, the rise time constant increases with the decrease of the oil yield, while the fall time constant declines as the oil yield decreases. A possible mechanism was proposed by the comparative analysis of the experimental results. The experimental results provide useful optical information on oil shale, suggesting the laserinduced voltage can be used to characterize the oil yield of oil shale.

The laser ultrasonic technique was proposed to characterize the pyrolysis process of the oil shale. The ultrasonic velocity was produced by a noncontact all-optical method in the three regions of Barkol, Yaojie, and Longkou of China. It was found that the ultrasonic velocity was related with the pyrolysis temperature of the oil shale. The pyrolysis process was divided into three stages due to the ultrasonic propagation speed in the oil shale. The ultrasonic velocity had small changes from 20 to 320 °C in the first stage, a sharp decline between 320 and 470 °C in the second stage, and another small change above 470 °C in the third stage. The variation of the velocity was qualitatively explained, which was considered to be closely related with the characteristics of pyrolysis process in oil shale. An empirical equation of the velocity attenuation was proposed to estimate the beginning and the end of the decomposition of the kerogen. It is a new way to characterize the process of the pyrolysis of oil shale by using the laser ultrasonic technique.