Abstract: Ultra-heavy oil is a strategic material for industry and national defense. Steam-assisted gravity drainage (SAGD) leakage is a critical problem to be solved urgently in the most advanced ultra-heavy oil development mode. The monitoring and characterization of the SAGD leakage channel are the most important. The three-dimensional electrical resistivity tomography is used to characterize the SAGD leakage channel. According to the resistivity change of oil and water in the leakage  channel after logging calibration, the resistivity of the leakage channel in the study area is lower than 3 Ω· m. The leakage channel is nearly north-south, narrow at the bottom, and wide at the top. Based on the geological and seismic data, it is considered that the SAGD leakage channel is a “cavity-crack” mode. There was no  leakage in the early stage of SAGD development. With the formation of the SAGD steam chamber, it gradually communicated with the upper stratum fracture zone during upward expansion, and the steam channeled up to the ground vertically along the fracture.

Key words: steam assisted gravity drainage, electrical resistivity tomography, leakage channels, “cavity-crack” mode, Junggar basin