The traditional downhole drilling vibration measurement methods which use cable or battery as power supplies increase the drilling costs and reduce the drilling efficiency. This paper proposes a spherical triboelectric nanogenerator, which shows the potential to collect the downhole vibration energy and measure the vibration frequency in a self-powered model. The power generation tests show that the output signal amplitude of the spherical triboelectric nanogenerator increases as the vibration frequency increases, and it can reach a maximum output voltage of 70 V, a maximum current of 3.3 × 10⁻⁵ A, and a maximum power of 10.9 × 10⁻⁹ W at 8 Hz when a 10-ohm resistor is connected. Therefore, if the power generation is stored for a certain period of time when numbers of the spherical triboelectric nanogenerators are connected in parallel, it may provide intermittent power for the low-power downhole measurement instruments. In addition, the sensing tests show that the measurement range is 0 to 8 Hz, the test error is less than 2%, the applicable working environment temperature is below 100 degrees Celsius, and the installation distance between the spherical triboelectric nanogenerator and the vibration source should be less than the critical value of 150 cm because the output signal amplitude is inversely proportional to the distance.

Drill string vibration is very critical to the drilling technology, which needs to be measured in real-time. This paper proposes a highly reliable pagoda-shaped triboelectric nanogenerator which can measure the downhole vibration frequency in self-powered model and harvest the downhole vibration energy to try to power other downhole instruments based on the Chinese pagoda. The designed pagoda-shaped triboelectric nanogenerator has seven layers, and charges are generated by floating contacts of two adjacent layers pasted with PMMA and Kapton, respectively. The sensing tests show that the measurement range is 0 to 5 Hz, the measurement error is less than 5%, and the minimum output signal amplitude difference is about 28 V while the maximum is about 155 V, which shows a higher signal-to-noise ratio. In addition, the pagoda-shaped triboelectric nanogenerator with seven layers can still work normally when the number of undamaged layers are two or more, which shows a higher reliability. The output power tests show that the maximum power is about 4090 × 10-10 W when all layers of the pagoda-shaped triboelectric nanogenerator are connected in series with a 470 k ohm resistance and the vibration frequency is about 3 Hz. Compared with the traditional downhole drill string measurement method, the multilayer structure of the pagoda-shaped triboelectric nanogenerator makes it has higher reliability, higher output power, and saves the radial dimension space, which are very suitable for actual drilling requirements of working conditions.

Gas drainage is carried out based on output from each coal bed throughout commingling production of coalbed methane (CBM). A reasonable drainage process should therefore initially guarantee main coal bed production and then enhance gas output from other beds. Permanent damage can result if this is not the case, especially with regard to fracture development in the main gas-producing coal bed and can greatly reduce single well output. Current theoretical models and measuring devices are inapplicable to commingled CBM drainage, however, and so large errors in predictive models cannot always be avoided. The most effective currently available method involves directly measuring gas output from each coal bed as well as determining the dominant gas-producing unit. A dynamic evaluation technique for gas output from each coal bed during commingling CBM production is therefore proposed in this study. This technique comprises a downhole measurement system combined with a theoretical calculation model. Gas output parameters (i.e., gas-phase flow rate, temperature, pressure) are measured in this approach via a downhole measurement system; substituting these parameters into a deduced theoretical calculation model then means that gas output from each seam can be calculated to determine the main gas-producing unit. Trends in gas output from a single well or each seam can therefore be predicted. The laboratory and field test results presented here demonstrate that calculation errors in CBM outputs can be controlled within a margin of 15% and therefore conform with field use requirements.

The rotating speed of the downhole motor is very important to the drilling process, so it is necessary to be measured in real-time. Here, a self-powered downhole motor rotating speed sensor, which designed as a double friction belts and a compressed friction contact structure, is proposed based on triboelectric nanogenerator. The double friction belts or any single friction belt of the sensor can be used as a self-powered rotating sensor alone, which shows a high reliability, and the compressed friction contact method increases the contact pressure of the two friction layers, thereby increasing the output signal amplitude. Test results show that the maximum output voltage and output current of the sensor with double friction belts working are respectively 15.8 V and 42.28 nA, and the maximum output power is 194.83×10-9 W when a 109 ohm resistance is connected in series, while the parameters of the sensor with single friction belt working are respectively 15.6 V and 24.17 nA, and the maximum output power is 52.22× 10-9 W when a 109 ohm resistance is connected in series. Further tests show that whether the sensor working with double belts or single belt, the measurement range is 0 to 910 r/min, the measurement error is less than 4%, and the working temperature range is 0 to 240 degrees Celsius, which shows that the sensor can meet the actual needs for the rotating speed measurement of downhole motor.

In order to improve the performance of surface plasmon resonance (SPR) biosensor, the structure based on two-dimensional (2D) of graphene and transition metal dichalcogenides (TMDCs) are proposed to greatly enhance the Goos-Hänchen (GH) shift. It is theoretically proved that GH shift can be significantly enhanced in SPR structure coated with gold (Au)-indium tin oxide (ITO)-TMDCs-graphene heterostructure. In order to realize high GH shifts, the number of TMDCs and graphene layer are optimized. The highest GH shift (−801.7 λ) is obtained by Au-ITO-MoSe₂-graphene hybrid structure with MoSe₂ monolayer and graphene bilayer, respectively. By analyzing the GH variation, the index sensitivity of such configuration can reach as high as 8.02 × 10⁵ λ/RIU, which is 293.24 times of the Au-ITO structure and 177.43 times of the Au-ITO-graphene structure. The proposed SPR biosensor can be widely used in the precision metrology and optical sensing.