Detecting Asphaltenes by A Miniaturized Electron Paramagnetic Resonance (EPR) Sensor

Asphaltenes precipitation has become a major issue in oil production. It can clog oil wells and increase the cost of production. The precipitation can occur in the near-wellbore region, inside the wellbore, in subsea flowlines, and in the separator. Currently, there is no effective solution for monitoring asphaltenes concentration and precipitation in real time. In this work, we propose a novel method for monitoring asphaltenes concentration in crude oil, utilizing the physical principle of Electron Paramagnetic Resonance (EPR). The phenomenon of EPR is based on the interaction of electron spins with electromagnetic fields in the presence of an external DC magnetic field. As asphaltenes have paramagnetic centers, they generate EPR signals that can be measured with our proprietary EPR sensor. The sensor is implemented in a 0.13μm SiGe BiCMOS process technology. The sensor chip can operate in both continuous wave (CW) and pulse modes. The frequency is tunable from 770MHz to 970MHz, corresponding to Zeeman magnetic fields from 28mT to 35mT for a free electron. The chip consists of a voltage-controlled oscillator, a power amplifier, a low-noise amplifier, a down-conversion mixer, baseband amplifiers, and a pulse generation block. The EPR sensor uses a loop-gap resonator built on a PCB board to interact with the sample. The measurement results of the asphaltenes samples are reported.